1
|
Aaen P, Kristensen KB, Antony A, Hansen SH, Cornett C, Pedersen SF, Boedtkjer E. Na +/H +-exchange inhibition by cariporide is compensated via Na +,HCO 3--cotransport and has no net growth consequences for ErbB2-driven breast carcinomas. Biochim Biophys Acta Mol Basis Dis 2024; 1870:167450. [PMID: 39111631 DOI: 10.1016/j.bbadis.2024.167450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2024] [Revised: 07/17/2024] [Accepted: 07/31/2024] [Indexed: 08/10/2024]
Abstract
Defense against intracellular acidification of breast cancer tissue depends on net acid extrusion via Na+,HCO3--cotransporter NBCn1/Slc4a7 and Na+/H+-exchanger NHE1/Slc9a1. NBCn1 is increasingly recognized as breast cancer susceptibility protein and promising therapeutic target, whereas evidence for targeting NHE1 is discordant. Currently, selective small molecule inhibitors exist against NHE1 but not NBCn1. Cellular assays-with some discrepancies-link NHE1 activity to proliferation, migration, and invasion; and disrupted NHE1 expression can reduce triple-negative breast cancer growth. Studies on human breast cancer tissue associate high NHE1 expression with reduced metastasis and-in some molecular subtypes-improved patient survival. Here, we evaluate Na+/H+-exchange and therapeutic potential of the NHE1 inhibitor cariporide/HOE-642 in murine ErbB2-driven breast cancer. Ex vivo, cariporide inhibits net acid extrusion in breast cancer tissue (IC50 = 0.18 μM) and causes small decreases in steady-state intracellular pH (pHi). In vivo, we deliver cariporide orally, by osmotic minipumps, and by intra- and peritumoral injections to address the low oral bioavailability and fast metabolism. Prolonged cariporide administration in vivo upregulates NBCn1 expression, shifts pHi regulation towards CO2/HCO3--dependent mechanisms, and shows no net effect on the growth rate of ErbB2-driven primary breast carcinomas. Cariporide also does not influence proliferation markers in breast cancer tissue. Oral, but not parenteral, cariporide elevates serum glucose by ∼1.5 mM. In conclusion, acute administration of cariporide ex vivo powerfully inhibits net acid extrusion from breast cancer tissue but lowers steady-state pHi minimally. Prolonged cariporide administration in vivo is compensated via NBCn1 and we observe no discernible effect on growth of ErbB2-driven breast carcinomas.
Collapse
Affiliation(s)
- Pernille Aaen
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | | | - Arththy Antony
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Steen H Hansen
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Claus Cornett
- Department of Pharmacy, University of Copenhagen, Copenhagen, Denmark
| | - Stine F Pedersen
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark.
| |
Collapse
|
2
|
Boedtkjer E, Ara T. Strengthening the basics: acids and bases influence vascular structure and function, tissue perfusion, blood pressure, and human cardiovascular disease. Pflugers Arch 2024; 476:623-637. [PMID: 38383822 DOI: 10.1007/s00424-024-02926-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2023] [Revised: 02/08/2024] [Accepted: 02/09/2024] [Indexed: 02/23/2024]
Abstract
Acids and their conjugate bases accumulate in or dissipate from the interstitial space when tissue perfusion does not match the metabolic demand. Extracellular acidosis dilates most arterial beds, but associated acid-base disturbances-e.g., intracellular acidification and decreases in HCO3- concentration-can also elicit pro-contractile influences that diminish vasodilation and even dominate in some vascular beds to cause vasoconstriction. The ensemble activities of the acid-base-sensitive reactions in vascular smooth muscle and endothelial cells optimize vascular resistance for blood pressure control and direct the perfusion towards active tissue. In this review, we describe the mechanisms of intracellular pH regulation in the vascular wall and discuss how vascular smooth muscle and endothelial cells sense acid-base disturbances. We further deliberate on the functional effects of local acid-base disturbances and their integrated cardiovascular consequences under physiological and pathophysiological conditions. Finally, we address how mutations and polymorphisms in the molecular machinery that regulates pH locally and senses acid-base disturbances in the vascular wall can result in cardiovascular disease. Based on the emerging molecular insight, we propose that targeting local pH-dependent effectors-rather than systemic acid-base disturbances-has therapeutic potential to interfere with the progression and reduce the severity of cardiovascular disease.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, DK-8000, Aarhus, Denmark.
| | - Tarannum Ara
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, DK-8000, Aarhus, Denmark
| |
Collapse
|
3
|
Rognant S, Baldwin SN, Pritchard HAT, Greenstein A, Calloe K, Aalkjaer C, Jepps TA. Acute, pro-contractile effects of prorenin on rat mesenteric arteries. FASEB J 2023; 37:e23282. [PMID: 37994700 DOI: 10.1096/fj.202301480] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2023] [Accepted: 10/16/2023] [Indexed: 11/24/2023]
Abstract
Prorenin and the prorenin receptor ((P)RR) are important, yet controversial, members of the renin-angiotensin-aldosterone system. The ((P)RR) is expressed throughout the body, including the vasculature, however, the direct effect of prorenin on arterial contractility is yet to be determined. Within rat mesenteric arteries, immunostaining and proximity ligation assays were used to determine the interacting partners of (P)RR in freshly isolated vascular smooth muscle cells (VSMCs). Wire myography examined the functional effect of prorenin. Simultaneous changes in [Ca2+ ]i and force were recorded in arteries loaded with Fura-2AM. Spontaneously transient outward currents were recorded via perforated whole-cell patch-clamp configuration in freshly isolated VSMCs. We found that the (P)RR is located within a distance of less than 40 nm from the V-ATPase, caveolin-1, ryanodine receptors, and large conductance Ca2+ -activated K+ channels (BKCa ) in VSMCs. [Ca2+ ]i imaging and isometric tension recordings indicate that 1 nM prorenin enhanced α1-adrenoreceptor-mediated contraction, associated with an increased number of Ca2+ waves, independent of voltage-gated Ca2+ channels activation. Incubation of VSMCs with 1 nM prorenin decreased the amplitude and frequency of spontaneously transient outward currents and attenuated BKCa -mediated relaxation. Inhibition of the V-ATPase with 100 nM bafilomycin prevented prorenin-mediated inhibition of BKCa -derived relaxation. Renin (1 nM) had no effect on BKCa -mediated relaxation. In conclusion, prorenin enhances arterial contractility by inhibition of BKCa and increasing intracellular Ca2+ release. It is likely that this effect is mediated through a local shift in pH upon activation of the (P)RR and stimulation of the V-ATPase.
Collapse
Affiliation(s)
- Salomé Rognant
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark
| | - Samuel N Baldwin
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark
| | - Harry A T Pritchard
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester University Teaching Hospitals NHS Foundation Trust, University of Manchester, Manchester, UK
- Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Foundation Trust, University of Manchester, Manchester, UK
| | - Adam Greenstein
- Division of Cardiovascular Sciences, Faculty of Biology, Medicine and Health, Manchester University Teaching Hospitals NHS Foundation Trust, University of Manchester, Manchester, UK
- Geoffrey Jefferson Brain Research Centre, The Manchester Academic Health Science Centre, Northern Care Alliance NHS Foundation Trust, University of Manchester, Manchester, UK
| | - Kirstine Calloe
- Section for Pathobiological Sciences, Department of Veterinary and Animal Sciences, University of Copenhagen, Frederiksberg C, Denmark
| | | | - Thomas A Jepps
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen N, Denmark
| |
Collapse
|
4
|
Kuo NC, Lin CH, Lin MC. Comparative effectiveness of two intravenous immunoglobulin products in children with Kawasaki disease, a nationwide cohort study. Sci Rep 2023; 13:18629. [PMID: 37903825 PMCID: PMC10616269 DOI: 10.1038/s41598-023-45092-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2023] [Accepted: 10/16/2023] [Indexed: 11/01/2023] Open
Abstract
Kawasaki Disease (KD) is the most common acquired pediatric heart disease in the developed world. Rapid infusion of high-dose intravenous immunoglobulin is the standard therapy. Different manufacturing processes of IVIG may influence their efficacy. This study aims to conduct a head to head comparison of two IVIGs, TBSF and Privigen, from a nationwide perspective. The main data source was the National Health Insurance Research Database (NHIRD) of Taiwan. A total of 3368 KD cases involving children under 2 years of age were enrolled from January 2015 to November 2020. The primary endpoint was IVIG resistance, which we defined as the total amount exceeding 26 g in one admission. The secondary endpoints encompassed two distinct criteria: coronary involvement, which was defined as the prolonged use of aspirin or anti-coagulation agents between 180 and 360 days after the index date, and recurrence, which was defined as readmission for IVIG therapy occurring more than 30 days after previous KD index day and continuing until the end of the follow-up period. Privigen demonstrated a lower IVIG resistance rate at 9.4% in comparison to TBSF, which exhibited a rate of 9.7% (odds ratio 0.72, 95% CI 0.52-0.99). Privigen had a lower odds of coronary involvement (odds ratio 0.38, 95% CI 0.18-0.82). There is no difference in recurrence rate (odds ratio 0.60, 95% CI 0.22-1.68). Privigen might have a lower rate of IVIG resistance and reduced coronary artery involvement. The discrepancy may be due to the concentration, the stabilizers, or the source of plasma. Further investigation is needed to compare the effectiveness of different IVIGs in the large randomized controlled clinical trial.
Collapse
Affiliation(s)
- Ni-Chun Kuo
- Children's Medical Center, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sec. 4, Taichung, 40705, Taiwan
| | - Ching-Heng Lin
- Department of Medical Research, Taichung Veterans General Hospital, Taichung, Taiwan
| | - Ming-Chih Lin
- Children's Medical Center, Taichung Veterans General Hospital, 1650 Taiwan Boulevard Sec. 4, Taichung, 40705, Taiwan.
- Department of Post-Baccalaureate Medicine, College of Medicine, National Chung Hsing University, Taichung, Taiwan.
- School of Medicine, National Yang Ming Chiao Tung University, Taipei, Taiwan.
- Department of Food and Nutrition, Providence University, Taichung, Taiwan.
- School of Medicine, Chung Shan Medical University, Taichung, Taiwan.
| |
Collapse
|
5
|
Lee S, Toft NJ, Axelsen TV, Espejo MS, Pedersen TM, Mele M, Pedersen HL, Balling E, Johansen T, Burton M, Thomassen M, Vahl P, Christiansen P, Boedtkjer E. Carbonic anhydrases reduce the acidity of the tumor microenvironment, promote immune infiltration, decelerate tumor growth, and improve survival in ErbB2/HER2-enriched breast cancer. Breast Cancer Res 2023; 25:46. [PMID: 37098526 PMCID: PMC10127511 DOI: 10.1186/s13058-023-01644-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2023] [Accepted: 03/30/2023] [Indexed: 04/27/2023] Open
Abstract
BACKGROUND Carbonic anhydrases catalyze CO2/HCO3- buffer reactions with implications for effective H+ mobility, pH dynamics, and cellular acid-base sensing. Yet, the integrated consequences of carbonic anhydrases for cancer and stromal cell functions, their interactions, and patient prognosis are not yet clear. METHODS We combine (a) bioinformatic analyses of human proteomic data and bulk and single-cell transcriptomic data coupled to clinicopathologic and prognostic information; (b) ex vivo experimental studies of gene expression in breast tissue based on quantitative reverse transcription and polymerase chain reactions, intracellular and extracellular pH recordings based on fluorescence confocal microscopy, and immunohistochemical protein identification in human and murine breast cancer biopsies; and (c) in vivo tumor size measurements, pH-sensitive microelectrode recordings, and microdialysis-based metabolite analyses in mice with experimentally induced breast carcinomas. RESULTS Carbonic anhydrases-particularly the extracellular isoforms CA4, CA6, CA9, CA12, and CA14-undergo potent expression changes during human and murine breast carcinogenesis. In patients with basal-like/triple-negative breast cancer, elevated expression of the extracellular carbonic anhydrases negatively predicts survival, whereas, surprisingly, the extracellular carbonic anhydrases positively predict patient survival in HER2/ErbB2-enriched breast cancer. Carbonic anhydrase inhibition attenuates cellular net acid extrusion and extracellular H+ elimination from diffusion-restricted to peripheral and well-perfused regions of human and murine breast cancer tissue. Supplied in vivo, the carbonic anhydrase inhibitor acetazolamide acidifies the microenvironment of ErbB2-induced murine breast carcinomas, limits tumor immune infiltration (CD3+ T cells, CD19+ B cells, F4/80+ macrophages), lowers inflammatory cytokine (Il1a, Il1b, Il6) and transcription factor (Nfkb1) expression, and accelerates tumor growth. Supporting the immunomodulatory influences of carbonic anhydrases, patient survival benefits associated with high extracellular carbonic anhydrase expression in HER2-enriched breast carcinomas depend on the tumor inflammatory profile. Acetazolamide lowers lactate levels in breast tissue and blood without influencing breast tumor perfusion, suggesting that carbonic anhydrase inhibition lowers fermentative glycolysis. CONCLUSIONS We conclude that carbonic anhydrases (a) elevate pH in breast carcinomas by accelerating net H+ elimination from cancer cells and across the interstitial space and (b) raise immune infiltration and inflammation in ErbB2/HER2-driven breast carcinomas, restricting tumor growth and improving patient survival.
Collapse
Affiliation(s)
- Soojung Lee
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Nicolai J Toft
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Trine V Axelsen
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Maria Sofia Espejo
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Tina M Pedersen
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark
| | - Marco Mele
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
| | - Helene L Pedersen
- Department of Pathology, Randers Regional Hospital, Randers, Denmark
| | - Eva Balling
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
| | - Tonje Johansen
- Department of Pathology, Randers Regional Hospital, Randers, Denmark
| | - Mark Burton
- Department of Clinical Genetics, University of Southern Denmark, Odense, Denmark
- Clinical Genome Center, University and Region of Southern Denmark, Odense, Denmark
- Department of Clinical Medicine, University of Southern Denmark, Odense, Denmark
| | - Mads Thomassen
- Department of Clinical Genetics, University of Southern Denmark, Odense, Denmark
- Clinical Genome Center, University and Region of Southern Denmark, Odense, Denmark
| | - Pernille Vahl
- Department of Pathology, Aarhus University Hospital, Aarhus, Denmark
| | - Peer Christiansen
- Department of Surgery, Randers Regional Hospital, Randers, Denmark
- Department of Plastic and Breast Surgery, Aarhus University Hospital, Aarhus, Denmark
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Hoegh-Guldbergs Gade 10, Building 1115, DK-8000, Aarhus C, Denmark.
| |
Collapse
|
6
|
Hammers DE, Donahue DL, Tucker Z, Ashfeld BL, Ploplis VA, Castellino FJ, Lee SW. Streptolysin S targets the sodium-bicarbonate cotransporter NBCn1 to induce inflammation and cytotoxicity in human keratinocytes during Group A Streptococcal infection. Front Cell Infect Microbiol 2022; 12:1002230. [PMID: 36389147 PMCID: PMC9663810 DOI: 10.3389/fcimb.2022.1002230] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2022] [Accepted: 09/29/2022] [Indexed: 11/30/2022] Open
Abstract
Group A <i>Streptococcus</i> (GAS, <i>Streptococcus pyogenes</i>) is a Gram-positive human pathogen that employs several secreted and surface-bound virulence factors to manipulate its environment, allowing it to cause a variety of disease outcomes. One such virulence factor is Streptolysin S (SLS), a ribosomally-produced peptide toxin that undergoes extensive post-translational modifications. The activity of SLS has been studied for over 100 years owing to its rapid and potent ability to lyse red blood cells, and the toxin has been shown to play a major role in GAS virulence <i>in vivo</i>. We have previously demonstrated that SLS induces hemolysis by targeting the chloride-bicarbonate exchanger Band 3 in erythrocytes, indicating that SLS is capable of targeting host proteins to promote cell lysis. However, the possibility that SLS has additional protein targets in other cell types, such as keratinocytes, has not been explored. Here, we use bioinformatics analysis and chemical inhibition studies to demonstrate that SLS targets the electroneutral sodium-bicarbonate cotransporter NBCn1 in keratinocytes during GAS infection. SLS induces NF-κB activation and host cytotoxicity in human keratinocytes, and these processes can be mitigated by treating keratinocytes with the sodium-bicarbonate cotransport inhibitor S0859. Furthermore, treating keratinocytes with SLS disrupts the ability of host cells to regulate their intracellular pH, and this can be monitored in real time using the pH-sensitive dye pHrodo Red AM in live imaging studies. These results demonstrate that SLS is a multifunctional bacterial toxin that GAS uses in numerous context-dependent ways to promote host cell cytotoxicity and increase disease severity. Studies to elucidate additional host targets of SLS have the potential to impact the development of therapeutics for severe GAS infections.
Collapse
Affiliation(s)
- Daniel E. Hammers
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States
| | - Deborah L. Donahue
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Zachary D. Tucker
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States
| | - Brandon L. Ashfeld
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States
| | - Victoria A. Ploplis
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Francis J. Castellino
- Department of Chemistry and Biochemistry, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States
| | - Shaun W. Lee
- Department of Biological Sciences, University of Notre Dame, Notre Dame, IN, United States,Eck Institute for Global Health, University of Notre Dame, Notre Dame, IN, United States,William Myron (W. M.) Keck Center for Transgene Research, University of Notre Dame, Notre Dame, IN, United States,*Correspondence: Shaun W. Lee,
| |
Collapse
|
7
|
Hansen KB, Staehr C, Rohde PD, Homilius C, Kim S, Nyegaard M, Matchkov VV, Boedtkjer E. PTPRG is an ischemia risk locus essential for HCO 3--dependent regulation of endothelial function and tissue perfusion. eLife 2020; 9:e57553. [PMID: 32955439 PMCID: PMC7541084 DOI: 10.7554/elife.57553] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2020] [Accepted: 09/18/2020] [Indexed: 12/22/2022] Open
Abstract
Acid-base conditions modify artery tone and tissue perfusion but the involved vascular-sensing mechanisms and disease consequences remain unclear. We experimentally investigated transgenic mice and performed genetic studies in a UK-based human cohort. We show that endothelial cells express the putative HCO3--sensor receptor-type tyrosine-protein phosphatase RPTPγ, which enhances endothelial intracellular Ca2+-responses in resistance arteries and facilitates endothelium-dependent vasorelaxation only when CO2/HCO3- is present. Consistent with waning RPTPγ-dependent vasorelaxation at low [HCO3-], RPTPγ limits increases in cerebral perfusion during neuronal activity and augments decreases in cerebral perfusion during hyperventilation. RPTPγ does not influence resting blood pressure but amplifies hyperventilation-induced blood pressure elevations. Loss-of-function variants in PTPRG, encoding RPTPγ, are associated with increased risk of cerebral infarction, heart attack, and reduced cardiac ejection fraction. We conclude that PTPRG is an ischemia susceptibility locus; and RPTPγ-dependent sensing of HCO3- adjusts endothelium-mediated vasorelaxation, microvascular perfusion, and blood pressure during acid-base disturbances and altered tissue metabolism.
Collapse
Affiliation(s)
| | | | - Palle D Rohde
- Department of Chemistry and Bioscience, Aalborg UniversityAalborgDenmark
| | | | - Sukhan Kim
- Department of Biomedicine, Aarhus UniversityAarhusDenmark
| | - Mette Nyegaard
- Department of Biomedicine, Aarhus UniversityAarhusDenmark
| | | | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus UniversityAarhusDenmark
| |
Collapse
|
8
|
Targeting the Acidic Tumor Microenvironment: Unexpected Pro-Neoplastic Effects of Oral NaHCO 3 Therapy in Murine Breast Tissue. Cancers (Basel) 2020; 12:cancers12040891. [PMID: 32268614 PMCID: PMC7226235 DOI: 10.3390/cancers12040891] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2020] [Revised: 03/31/2020] [Accepted: 03/31/2020] [Indexed: 11/16/2022] Open
Abstract
The acidic tumor microenvironment modifies malignant cell behavior. Here, we study consequences of the microenvironment in breast carcinomas. Beginning at carcinogen-based breast cancer induction, we supply either regular or NaHCO3-containing drinking water to female C57BL/6j mice. We evaluate urine and blood acid-base status, tumor metabolism (microdialysis sampling), and tumor pH (pH-sensitive microelectrodes) in vivo. Based on freshly isolated epithelial organoids from breast carcinomas and normal breast tissue, we assess protein expression (immunoblotting, mass spectrometry), intracellular pH (fluorescence microscopy), and cell proliferation (bromodeoxyuridine incorporation). Oral NaHCO3 therapy increases breast tumor pH in vivo from 6.68 ± 0.04 to 7.04 ± 0.09 and intracellular pH in breast epithelial organoids by ~0.15. Breast tumors develop with median latency of 85.5 ± 8.2 days in NaHCO3-treated mice vs. 82 ± 7.5 days in control mice. Oral NaHCO3 therapy does not affect tumor growth, histopathology or glycolytic metabolism. The capacity for cellular net acid extrusion is increased in NaHCO3-treated mice and correlates negatively with breast tumor latency. Oral NaHCO3 therapy elevates proliferative activity in organoids from breast carcinomas. Changes in protein expression patterns-observed by high-throughput proteomics analyses-between cancer and normal breast tissue and in response to oral NaHCO3 therapy reveal complex influences on metabolism, cytoskeleton, cell-cell and cell-matrix interaction, and cell signaling pathways. We conclude that oral NaHCO3 therapy neutralizes the microenvironment of breast carcinomas, elevates the cellular net acid extrusion capacity, and accelerates proliferation without net effect on breast cancer development or tumor growth. We demonstrate unexpected pro-neoplastic consequences of oral NaHCO3 therapy that in breast tissue cancel out previously reported anti-neoplastic effects.
Collapse
|
9
|
Upregulated Na +/H +-Exchange Protects Human Colon Cancer Tissue against Intracellular Acidification. BIOMED RESEARCH INTERNATIONAL 2019; 2019:3702783. [PMID: 30834261 PMCID: PMC6374860 DOI: 10.1155/2019/3702783] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/24/2018] [Revised: 01/03/2019] [Accepted: 01/17/2019] [Indexed: 11/17/2022]
Abstract
Increased metabolism accelerates local acid production in cancer tissue. The mechanisms eliminating acidic waste products from human colon cancer tissue represent promising therapeutic targets for pharmacological manipulation in order to improve prognosis for the increasing number of patients with colon cancer. We sampled biopsies of human colonic adenocarcinomas and matched normal colon tissue from patients undergoing colon cancer surgery. We measured steady-state intracellular pH and rates of net acid extrusion in freshly isolated human colonic crypts based on fluorescence microscopy. Net acid extrusion was almost entirely (>95%) Na+-dependent. The capacity for net acid extrusion was increased and steady-state intracellular pH elevated around 0.5 in crypts from colon cancer tissue compared with normal colon tissue irrespective of whether they were investigated in the presence or absence of CO2/HCO3–. The accelerated net acid extrusion from the human colon cancer tissue was sensitive to the Na+/H+-exchange inhibitor cariporide. We conclude that enhanced net acid extrusion via Na+/H+-exchange elevates intracellular pH in human colon cancer tissue.
Collapse
|
10
|
Artamonov MV, Sonkusare SK, Good ME, Momotani K, Eto M, Isakson BE, Le TH, Cope EL, Derewenda ZS, Derewenda U, Somlyo AV. RSK2 contributes to myogenic vasoconstriction of resistance arteries by activating smooth muscle myosin and the Na +/H + exchanger. Sci Signal 2018; 11:11/554/eaar3924. [PMID: 30377223 DOI: 10.1126/scisignal.aar3924] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022]
Abstract
Smooth muscle contraction is triggered when Ca2+/calmodulin-dependent myosin light chain kinase (MLCK) phosphorylates the regulatory light chain of myosin (RLC20). However, blood vessels from Mlck-deficient mouse embryos retain the ability to contract, suggesting the existence of additional regulatory mechanisms. We showed that the p90 ribosomal S6 kinase 2 (RSK2) also phosphorylated RLC20 to promote smooth muscle contractility. Active, phosphorylated RSK2 was present in mouse resistance arteries under normal basal tone, and phosphorylation of RSK2 increased with myogenic vasoconstriction or agonist stimulation. Resistance arteries from Rsk2-deficient mice were dilated and showed reduced myogenic tone and RLC20 phosphorylation. RSK2 phosphorylated Ser19 in RLC in vitro. In addition, RSK2 phosphorylated an activating site in the Na+/H+ exchanger (NHE-1), resulting in cytosolic alkalinization and an increase in intracellular Ca2+ that promotes vasoconstriction. NHE-1 activity increased upon myogenic constriction, and the increase in intracellular pH was suppressed in Rsk2-deficient mice. In pressured arteries, RSK2-dependent activation of NHE-1 was associated with increased intracellular Ca2+ transients, which would be expected to increase MLCK activity, thereby contributing to basal tone and myogenic responses. Accordingly, Rsk2-deficient mice had lower blood pressure than normal littermates. Thus, RSK2 mediates a procontractile signaling pathway that contributes to the regulation of basal vascular tone, myogenic vasoconstriction, and blood pressure and may be a potential therapeutic target in smooth muscle contractility disorders.
Collapse
Affiliation(s)
- Mykhaylo V Artamonov
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Swapnil K Sonkusare
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.,Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
| | - Miranda E Good
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
| | - Ko Momotani
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.,Faculty of Pharmaceutical Sciences, Sanyo-Onoda City University, 1-1-1 Daigaku-dori, Sanyo-Onoda-shi, Yamaguchi 756-0884, Japan
| | - Masumi Eto
- Department of Molecular Physiology and Biophysics, Sidney Kimmel Medical College at Thomas Jefferson University, Philadelphia, PA 19107, USA.,Faculty of Veterinary Medicine, Okayama University of Science, 1-13 Ikoinooka-oka, Imabari, Ehime 794-0085, Japan
| | - Brant E Isakson
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.,Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
| | - Thu H Le
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.,Department of Medicine, University of Virginia, Charlottesville, VA 22908, USA
| | - Eric L Cope
- Robert M. Berne Cardiovascular Research Center, University of Virginia, Charlottesville, VA 22908, USA
| | - Zygmunt S Derewenda
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Urszula Derewenda
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Avril V Somlyo
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA.
| |
Collapse
|
11
|
Boedtkjer E. Acid-base regulation and sensing: Accelerators and brakes in metabolic regulation of cerebrovascular tone. J Cereb Blood Flow Metab 2018; 38:588-602. [PMID: 28984162 PMCID: PMC5888856 DOI: 10.1177/0271678x17733868] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/08/2017] [Revised: 08/10/2017] [Accepted: 09/06/2017] [Indexed: 12/29/2022]
Abstract
Metabolic regulation of cerebrovascular tone directs blood flow to areas of increased neuronal activity and during disease states partially compensates for insufficient perfusion by enhancing blood flow in collateral blood vessels. Acid-base disturbances frequently occur as result of enhanced metabolism or insufficient blood supply, but despite definitive evidence that acid-base disturbances alter arterial tone, effects of individual acid-base equivalents and the underlying signaling mechanisms are still being debated. H+ is an important intra- and extracellular messenger that modifies cerebrovascular tone. In addition, low extracellular [HCO3-] promotes cerebrovascular contraction through an endothelium-dependent mechanism. CO2 alters arterial tone development via changes in intra- and extracellular pH but it is still controversial whether CO2 also has direct vasomotor effects. Vasocontractile responses to low extracellular [HCO3-] and acute CO2-induced decreases in intracellular pH can counteract H+-mediated vasorelaxation during metabolic and respiratory acidosis, respectively, and may thereby reduce the risk of capillary damage and cerebral edema that could be consequences of unopposed vasodilation. In this review, the signaling mechanisms for acid-base equivalents in cerebral arteries and the mechanisms of intracellular pH control in the arterial wall are discussed in the context of metabolic regulation of cerebrovascular tone and local perfusion.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
12
|
Rasmussen JK, Boedtkjer E. Carbonic anhydrase inhibitors modify intracellular pH transients and contractions of rat middle cerebral arteries during CO 2/HCO 3- fluctuations. J Cereb Blood Flow Metab 2018; 38:492-505. [PMID: 28318362 PMCID: PMC5851140 DOI: 10.1177/0271678x17699224] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The CO2/HCO3- buffer minimizes pH changes in response to acid-base loads, HCO3- provides substrate for Na+,HCO3--cotransporters and Cl-/HCO3--exchangers, and H+ and HCO3- modify vasomotor responses during acid-base disturbances. We show here that rat middle cerebral arteries express cytosolic, mitochondrial, extracellular, and secreted carbonic anhydrase isoforms that catalyze equilibration of the CO2/HCO3- buffer. Switching from CO2/HCO3--free to CO2/HCO3--containing extracellular solution results in initial intracellular acidification due to hydration of CO2 followed by gradual alkalinization due to cellular HCO3- uptake. Carbonic anhydrase inhibition decelerates the initial acidification and attenuates the associated transient vasoconstriction without affecting intracellular pH or artery tone at steady-state. Na+,HCO3--cotransport and Na+/H+-exchange activity after NH4+-prepulse-induced intracellular acidification are unaffected by carbonic anhydrase inhibition. Extracellular surface pH transients induced by transmembrane NH3 flux are evident under CO2/HCO3--free conditions but absent when the buffer capacity and apparent H+ mobility increase in the presence of CO2/HCO3- even after the inhibition of carbonic anhydrases. We conclude that (a) intracellular carbonic anhydrase activity accentuates pH transients and vasoconstriction in response to acute elevations of pCO2, (b) CO2/HCO3- minimizes extracellular surface pH transients without requiring carbonic anhydrase activity, and (c) carbonic anhydrases are not rate limiting for acid–base transport across cell membranes during recovery from intracellular acidification.
Collapse
Affiliation(s)
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| |
Collapse
|
13
|
Khammy MM, Kim S, Bentzen BH, Lee S, Choi I, Aalkjaer C, Jepps TA. 4-Aminopyridine: a pan voltage-gated potassium channel inhibitor that enhances K v 7.4 currents and inhibits noradrenaline-mediated contraction of rat mesenteric small arteries. Br J Pharmacol 2018; 175:501-516. [PMID: 29156097 DOI: 10.1111/bph.14097] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 11/01/2017] [Accepted: 11/08/2017] [Indexed: 01/14/2023] Open
Abstract
BACKGROUND AND PURPOSE Kv 7.4 and Kv 7.5 channels are regulators of vascular tone. 4-Aminopyridine (4-AP) is considered a broad inhibitor of voltage-gated potassium (KV ) channels, with little inhibitory effect on Kv 7 family members at mmol concentrations. However, the effect of 4-AP on Kv 7 channels has not been systematically studied. The aim of this study was to investigate the pharmacological activity of 4-AP on Kv 7.4 and Kv 7.5 channels and characterize the effect of 4-AP on rat resistance arteries. EXPERIMENTAL APPROACH Voltage clamp experiments were performed on Xenopus laevis oocytes injected with cRNA encoding KCNQ4 or KCNQ5, HEK cells expressing Kv 7.4 channels and on rat, freshly isolated mesenteric artery smooth muscle cells. The effect of 4-AP on tension, membrane potential, intracellular calcium and pH was assessed in rat mesenteric artery segments. KEY RESULTS 4-AP increased the Kv 7.4-mediated current in oocytes and HEK cells but did not affect Kv 7.5 current. 4-AP also enhanced native mesenteric artery myocyte K+ current at sub-mmol concentrations. When applied to NA-preconstricted mesenteric artery segments, 4-AP hyperpolarized the membrane, decreased [Ca2+ ]i and caused concentration-dependent relaxations that were independent of 4-AP-mediated changes in intracellular pH. Application of the Kv 7 channel blocker XE991 and BKCa channel blocker iberiotoxin attenuated 4-AP-mediated relaxation. 4-AP also inhibited the NA-mediated signal transduction to elicit a relaxation. CONCLUSIONS AND IMPLICATIONS These data show that 4-AP is able to relax NA-preconstricted rat mesenteric arteries by enhancing the activity of Kv 7.4 and BKCa channels and attenuating NA-mediated signalling.
Collapse
Affiliation(s)
- Makhala M Khammy
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Sukhan Kim
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Bo H Bentzen
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Soojung Lee
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA
| | - Inyeong Choi
- Department of Physiology, Emory University School of Medicine, Atlanta, GA, USA
| | - Christian Aalkjaer
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.,Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Thomas A Jepps
- Department of Biomedical Sciences, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
14
|
The crystal structure of the regulatory domain of the human sodium-driven chloride/bicarbonate exchanger. Sci Rep 2017; 7:12131. [PMID: 28935959 PMCID: PMC5608694 DOI: 10.1038/s41598-017-12409-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2017] [Accepted: 09/06/2017] [Indexed: 12/12/2022] Open
Abstract
The sodium-driven chloride/bicarbonate exchanger (NDCBE) is essential for maintaining homeostatic pH in neurons. The crystal structure at 2.8 Å resolution of the regulatory N-terminal domain of human NDCBE represents the first crystal structure of an electroneutral sodium-bicarbonate cotransporter. The crystal structure forms an equivalent dimeric interface as observed for the cytoplasmic domain of Band 3, and thus establishes that the consensus motif VTVLP is the key minimal dimerization motif. The VTVLP motif is highly conserved and likely to be the physiologically relevant interface for all other members of the SLC4 family. A novel conserved Zn2+-binding motif present in the N-terminal domain of NDCBE is identified and characterized in vitro. Cellular studies confirm the Zn2+ dependent transport of two electroneutral bicarbonate transporters, NCBE and NBCn1. The Zn2+ site is mapped to a cluster of histidines close to the conserved ETARWLKFEE motif and likely plays a role in the regulation of this important motif. The combined structural and bioinformatics analysis provides a model that predicts with additional confidence the physiologically relevant interface between the cytoplasmic domain and the transmembrane domain.
Collapse
|
15
|
Ng FL, Boedtkjer E, Witkowska K, Ren M, Zhang R, Tucker A, Aalkjær C, Caulfield MJ, Ye S. Increased NBCn1 expression, Na+/HCO3- co-transport and intracellular pH in human vascular smooth muscle cells with a risk allele for hypertension. Hum Mol Genet 2017; 26:989-1002. [PMID: 28087731 PMCID: PMC5409084 DOI: 10.1093/hmg/ddx015] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2016] [Revised: 12/21/2016] [Accepted: 12/30/2016] [Indexed: 02/05/2023] Open
Abstract
Genome-wide association studies have revealed an association between variation at the SLC4A7 locus and blood pressure. SLC4A7 encodes the electroneutral Na+/HCO3- co-transporter NBCn1 which regulates intracellular pH (pHi). We conducted a functional study of variants at this locus in primary cultures of vascular smooth muscle and endothelial cells. In both cell types, we found genotype-dependent differences for rs13082711 in DNA-nuclear protein interactions, where the risk allele is associated with increased SLC4A7 expression level, NBCn1 availability and function as reflected in elevated steady-state pHi and accelerated recovery from intracellular acidosis. However, in the presence of Na+/H+ exchange activity, the SLC4A7 genotypic effect on net base uptake and steady-state pHi persisted only in vascular smooth muscle cells but not endothelial cells. We found no discernable effect of the missense polymorphism resulting in the amino acid substitution Glu326Lys. The finding of a genotypic influence on SLC4A7 expression and pHi regulation in vascular smooth muscle cells provides an insight into the molecular mechanism underlying the association of variation at the SLC4A7 locus with blood pressure.
Collapse
Affiliation(s)
- Fu Liang Ng
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
| | - Kate Witkowska
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Meixia Ren
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Ruoxin Zhang
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Arthur Tucker
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
| | - Christian Aalkjær
- Department of Biomedicine, Aarhus University, Aarhus, Denmark
- Department of Biomedicine, University of Copenhagen, Copenhagen, Denmark
| | - Mark J. Caulfield
- Department of Clinical Pharmacology, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Queen Mary University of London, London, UK
- To whom correspondence should be addressed at: Heart Centre, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. Tel: +44 2078823403; Fax: +44 2078823408; (M.J.C.); Department of Cardiovascular Sciences, University of Leicester, BHF Cardiovascular Research Centre, Glenfield Hospital, Leicester LE3 9QP, UK. Tel: +44 1162044754; Fax: +44 1162875792; (S.Y.)
| | - Shu Ye
- Department of Cardiovascular Sciences, University of Leicester, Leicester, UK
- NIHR Biomedical Research Centre in Cardiovascular Disease, Leicester, UK
- Shantou University Medical College, Shantou, China
- To whom correspondence should be addressed at: Heart Centre, William Harvey Research Institute, Barts and The London School of Medicine and Dentistry, Charterhouse Square, London EC1M 6BQ, UK. Tel: +44 2078823403; Fax: +44 2078823408; (M.J.C.); Department of Cardiovascular Sciences, University of Leicester, BHF Cardiovascular Research Centre, Glenfield Hospital, Leicester LE3 9QP, UK. Tel: +44 1162044754; Fax: +44 1162875792; (S.Y.)
| |
Collapse
|
16
|
Walker J, Undem C, Yun X, Lade J, Jiang H, Shimoda LA. Role of Rho kinase and Na+/H+ exchange in hypoxia-induced pulmonary arterial smooth muscle cell proliferation and migration. Physiol Rep 2016; 4:4/6/e12702. [PMID: 27009277 PMCID: PMC4814889 DOI: 10.14814/phy2.12702] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2015] [Accepted: 01/17/2016] [Indexed: 12/21/2022] Open
Abstract
Abnormal proliferation and migration of pulmonary arterial smooth muscle cells (PASMCs) are hallmark characteristics of vascular remodeling in pulmonary hypertension induced by chronic hypoxia. In this study, we investigated the role of the Na+/H+ exchanger (NHE) and alterations in intracellular pH (pHi) homeostasis in meditating increased proliferation and migration in PASMCs isolated from resistance‐sized pulmonary arteries from chronically hypoxic rats or from normoxic rats that were exposed to hypoxia ex vivo (1% or 4% O2, 24–96 h). We found that PASMCs exposed to either in vivo or ex vivo hypoxia exhibited greater proliferative and migratory capacity, elevated pHi, and enhanced NHE activity. The NHE inhibitor, ethyl isopropyl amiloride (EIPA), normalized pHi in hypoxic PASMCs and reduced migration by 73% and 45% in cells exposed to in vivo and in vitro hypoxia, respectively. Similarly, EIPA reduced proliferation by 97% and 78% in cells exposed to in vivo and in vitro hypoxia, respectively. We previously demonstrated that NHE isoform 1 (NHE1) is the predominant isoform expressed in PASMCs. The development of hypoxia‐induced pulmonary hypertension and alterations in PASMC pHi homeostasis were prevented in mice deficient for NHE1. We found that short‐term (24 h) ex vivo hypoxic exposure did not alter the expression of NHE1, so we tested the role of Rho kinase (ROCK) as a possible means of increasing NHE activity. In the presence of the ROCK inhibitor, Y‐27632, we found that pHi and NHE activity were normalized and migration and proliferation were reduced in PASMCs exposed to either in vivo (by 68% for migration and 22% for proliferation) or ex vivo (by 43% for migration and 17% for proliferation) hypoxia. From these results, we conclude that during hypoxia, activation of ROCK enhances NHE activity and promotes PASMC migration and proliferation.
Collapse
Affiliation(s)
- Jasmine Walker
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Clark Undem
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Xin Yun
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Julie Lade
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Haiyang Jiang
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland
| |
Collapse
|
17
|
Boedtkjer E, Matchkov VV, Boedtkjer DMB, Aalkjaer C. Negative News: Cl− and HCO3− in the Vascular Wall. Physiology (Bethesda) 2016; 31:370-83. [DOI: 10.1152/physiol.00001.2016] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Cl− and HCO3− are the most prevalent membrane-permeable anions in the intra- and extracellular spaces of the vascular wall. Outwardly directed electrochemical gradients for Cl− and HCO3− permit anion channel opening to depolarize vascular smooth muscle and endothelial cells. Transporters and channels for Cl− and HCO3− also modify vascular contractility and structure independently of membrane potential. Transport of HCO3− regulates intracellular pH and thereby modifies the activity of enzymes, ion channels, and receptors. There is also evidence that Cl− and HCO3− transport proteins affect gene expression and protein trafficking. Considering the extensive implications of Cl− and HCO3− in the vascular wall, it is critical to understand how these ions are transported under physiological conditions and how disturbances in their transport can contribute to disease development. Recently, sensing mechanisms for Cl− and HCO3− have been identified in the vascular wall where they modify ion transport and vasomotor function, for instance, during metabolic disturbances. This review discusses current evidence that transport (e.g., via NKCC1, NBCn1, Ca2+-activated Cl− channels, volume-regulated anion channels, and CFTR) and sensing (e.g., via WNK and RPTPγ) of Cl− and HCO3− influence cardiovascular health and disease.
Collapse
Affiliation(s)
| | | | - Donna M. B. Boedtkjer
- Department of Biomedicine, Aarhus University, Denmark
- Department of Clinical Medicine, Aarhus University, Denmark; and
| | - Christian Aalkjaer
- Department of Biomedicine, Aarhus University, Denmark
- Department of Biomedical Sciences, University of Copenhagen, Copenhagen, Denmark
| |
Collapse
|
18
|
Boedtkjer E, Hansen KB, Boedtkjer DMB, Aalkjaer C, Boron WF. Extracellular HCO3- is sensed by mouse cerebral arteries: Regulation of tone by receptor protein tyrosine phosphatase γ. J Cereb Blood Flow Metab 2016; 36:965-80. [PMID: 26661205 PMCID: PMC4853837 DOI: 10.1177/0271678x15610787] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/27/2015] [Accepted: 09/15/2015] [Indexed: 11/15/2022]
Abstract
We investigate sensing and signaling mechanisms for H(+), [Formula: see text] and CO2 in basilar arteries using out-of-equilibrium solutions. Selectively varying pHo, [[Formula: see text]]o, or pCO2, we find: (a) lowering pHo attenuates vasoconstriction and vascular smooth muscle cell (VSMC) Ca(2+)-responses whereas raising pHo augments vasoconstriction independently of VSMC [Ca(2+)]i, (b) lowering [[Formula: see text]]o increases arterial agonist-sensitivity of tone development without affecting VSMC [Ca(2+)]i but c) no evidence that CO2 has direct net vasomotor effects. Receptor protein tyrosine phosphatase (RPTP)γ is transcribed in endothelial cells, and direct vasomotor effects of [Formula: see text] are absent in arteries from RPTPγ-knockout mice. At pHo 7.4, selective changes in [[Formula: see text]]o or pCO2 have little effect on pHi At pHo 7.1, decreased [[Formula: see text]]o or increased pCO2 causes intracellular acidification, which attenuates vasoconstriction. Under equilibrated conditions, anti-contractile effects of CO2/[Formula: see text] are endothelium-dependent and absent in arteries from RPTPγ-knockout mice. With CO2/[Formula: see text] present, contractile responses to agonist-stimulation are potentiated in arteries from RPTPγ-knockout compared to wild-type mice, and this difference is larger for respiratory than metabolic acidosis. In conclusion, decreased pHo and pHi inhibit vasoconstriction, whereas decreased [[Formula: see text]]o promotes vasoconstriction through RPTPγ-dependent changes in VSMC Ca(2+)-sensitivity. [Formula: see text] serves dual roles, providing substrate for pHi-regulating membrane transporters and modulating arterial responses to acid-base disturbances.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Donna M B Boedtkjer
- Department of Biomedicine, Aarhus University, Aarhus, Denmark Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| | | | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, OH, USA
| |
Collapse
|
19
|
Undem C, Luke T, Shimoda LA. Contribution of elevated intracellular calcium to pulmonary arterial myocyte alkalinization during chronic hypoxia. Pulm Circ 2016; 6:93-102. [PMID: 27076907 PMCID: PMC4809666 DOI: 10.1086/685053] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
In the lung, exposure to chronic hypoxia (CH) causes pulmonary hypertension, a debilitating disease. Development of this condition arises from increased muscularity and contraction of pulmonary vessels, associated with increases in pulmonary arterial smooth muscle cell (PASMC) intracellular pH (pHi) and Ca(2+) concentration ([Ca(2+)]i). In this study, we explored the interaction between pHi and [Ca(2+)]i in PASMCs from rats exposed to normoxia or CH (3 weeks, 10% O2). PASMC pHi and [Ca(2+)]i were measured with fluorescent microscopy and the dyes BCECF and Fura-2. Both pHi and [Ca(2+)]i levels were elevated in PASMCs from hypoxic rats. Exposure to KCl increased [Ca(2+)]i and pHi to a similar extent in normoxic and hypoxic PASMCs. Conversely, removal of extracellular Ca(2+) or blockade of Ca(2+) entry with NiCl2 or SKF 96365 decreased [Ca(2+)]i and pHi only in hypoxic cells. Neither increasing pHi with NH4Cl nor decreasing pHi by removal of bicarbonate impacted PASMC [Ca(2+)]i. We also examined the roles of Na(+)/Ca(2+) exchange (NCX) and Na(+)/H(+) exchange (NHE) in mediating the elevated basal [Ca(2+)]i and Ca(2+)-dependent changes in PASMC pHi. Bepridil, dichlorobenzamil, and KB-R7943, which are NCX inhibitors, decreased resting [Ca(2+)]i and pHi only in hypoxic PASMCs and blocked the changes in pHi induced by altering [Ca(2+)]i. Exposure to ethyl isopropyl amiloride, an NHE inhibitor, decreased resting pHi and prevented changes in pHi due to changing [Ca(2+)]i. Our findings indicate that, during CH, the elevation in basal [Ca(2+)]i may contribute to the alkaline shift in pHi in PASMCs, likely via mechanisms involving reverse-mode NCX and NHE.
Collapse
Affiliation(s)
- Clark Undem
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Trevor Luke
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, USA
| |
Collapse
|
20
|
Boedtkjer E, Bentzon JF, Dam VS, Aalkjaer C. Na+, HCO3--cotransporter NBCn1 increases pHi gradients, filopodia, and migration of smooth muscle cells and promotes arterial remodelling. Cardiovasc Res 2016; 111:227-39. [PMID: 27076468 DOI: 10.1093/cvr/cvw079] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Accepted: 03/17/2016] [Indexed: 12/19/2022] Open
Abstract
AIMS Arterial remodelling can cause luminal narrowing and obstruct blood flow. We tested the hypothesis that cellular acid-base transport facilitates proliferation and migration of vascular smooth muscle cells (VSMCs) and enhances remodelling of conduit arteries. METHODS AND RESULTS [Formula: see text]-cotransport via NBCn1 (Slc4a7) mediates net acid extrusion and controls steady-state intracellular pH (pHi) in VSMCs of mouse carotid arteries and primary aortic explants. Carotid arteries undergo hypertrophic inward remodelling in response to partial or complete ligation in vivo, but the increase in media area and thickness and reduction in lumen diameter are attenuated in arteries from NBCn1 knock-out compared with wild-type mice. With [Formula: see text] present, gradients for pHi (∼0.2 units magnitude) exist along the axis of VSMC migration in primary explants from wild-type but not NBCn1 knock-out mice. Knock-out or pharmacological inhibition of NBCn1 also reduces filopodia and lowers initial rates of VSMC migration after scratch-wound infliction. Interventions to reduce H(+)-buffer mobility (omission of [Formula: see text] or inhibition of carbonic anhydrases) re-establish axial pHi gradients, filopodia, and migration rates in explants from NBCn1 knock-out mice. The omission of [Formula: see text] also lowers global pHi and inhibits proliferation in primary explants. CONCLUSION Under physiological conditions (i.e. with [Formula: see text] present), NBCn1-mediated [Formula: see text] uptake raises VSMC pHi and promotes filopodia, VSMC migration, and hypertrophic inward remodelling. We propose that axial pHi gradients enhance VSMC migration whereas global acidification inhibits VSMC proliferation and media hypertrophy after carotid artery ligation. These findings support a key role of acid-base transport, particularly via NBCn1, for development of occlusive artery disease.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, Ole Worms Allé 3, Building 1170, DK-8000 Aarhus C, Denmark
| | - Jacob F Bentzon
- Department of Clinical Medicine, Aarhus University, Aarhus C, Denmark
| | - Vibeke S Dam
- Department of Biomedicine, Aarhus University, Ole Worms Allé 3, Building 1170, DK-8000 Aarhus C, Denmark
| | - Christian Aalkjaer
- Department of Biomedicine, Aarhus University, Ole Worms Allé 3, Building 1170, DK-8000 Aarhus C, Denmark
| |
Collapse
|
21
|
Abstract
Cation-coupled HCO3(-) transport was initially identified in the mid-1970s when pioneering studies showed that acid extrusion from cells is stimulated by CO2/HCO3(-) and associated with Na(+) and Cl(-) movement. The first Na(+)-coupled bicarbonate transporter (NCBT) was expression-cloned in the late 1990s. There are currently five mammalian NCBTs in the SLC4-family: the electrogenic Na,HCO3-cotransporters NBCe1 and NBCe2 (SLC4A4 and SLC4A5 gene products); the electroneutral Na,HCO3-cotransporter NBCn1 (SLC4A7 gene product); the Na(+)-driven Cl,HCO3-exchanger NDCBE (SLC4A8 gene product); and NBCn2/NCBE (SLC4A10 gene product), which has been characterized as an electroneutral Na,HCO3-cotransporter or a Na(+)-driven Cl,HCO3-exchanger. Despite the similarity in amino acid sequence and predicted structure among the NCBTs of the SLC4-family, they exhibit distinct differences in ion dependency, transport function, pharmacological properties, and interactions with other proteins. In epithelia, NCBTs are involved in transcellular movement of acid-base equivalents and intracellular pH control. In nonepithelial tissues, NCBTs contribute to intracellular pH regulation; and hence, they are crucial for diverse tissue functions including neuronal discharge, sensory neuron development, performance of the heart, and vascular tone regulation. The function and expression levels of the NCBTs are generally sensitive to intracellular and systemic pH. Animal models have revealed pathophysiological roles of the transporters in disease states including metabolic acidosis, hypertension, visual defects, and epileptic seizures. Studies are being conducted to understand the physiological consequences of genetic polymorphisms in the SLC4-members, which are associated with cancer, hypertension, and drug addiction. Here, we describe the current knowledge regarding the function, structure, and regulation of the mammalian cation-coupled HCO3(-) transporters of the SLC4-family.
Collapse
Affiliation(s)
- Christian Aalkjaer
- Department of Biomedicine, and the Water and Salt Research Center, Aarhus University, Aarhus, Denmark; Department of Physiology, Emory University School of Medicine, Atlanta, USA
| | | | | | | |
Collapse
|
22
|
Huetsch J, Shimoda LA. Na(+)/H(+) exchange and hypoxic pulmonary hypertension. Pulm Circ 2015; 5:228-43. [PMID: 26064449 DOI: 10.1086/680213] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/20/2014] [Accepted: 07/22/2014] [Indexed: 12/24/2022] Open
Abstract
Intracellular pH (pHi) homeostasis is key to the functioning of vascular smooth muscle cells, including pulmonary artery smooth muscle cells (PASMCs). Sodium-hydrogen exchange (NHE) is an important contributor to pHi control in PASMCs. In this review, we examine the role of NHE in PASMC function, in both physiologic and pathologic conditions. In particular, we focus on the contribution of NHE to the PASMC response to hypoxia, considering both acute hypoxic pulmonary vasoconstriction and the development of pulmonary vascular remodeling and pulmonary hypertension in response to chronic hypoxia. Hypoxic pulmonary hypertension remains a disease with limited therapeutic options. Thus, this review explores past efforts at disrupting NHE signaling and discusses the therapeutic potential that such efforts may have in the field of pulmonary hypertension.
Collapse
Affiliation(s)
- John Huetsch
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
| | - Larissa A Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, Maryland 21224, USA
| |
Collapse
|
23
|
El-Galaly A, Aalkjaer C, Kringelholt SK, Misfeldt MW, Bek T. Dorzolamide-induced relaxation of porcine retinal arterioles in vitro depends on nitric oxide but not on acidosis in vascular smooth muscle cells. Exp Eye Res 2014; 128:67-72. [PMID: 25251883 DOI: 10.1016/j.exer.2014.09.006] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2014] [Revised: 09/15/2014] [Accepted: 09/19/2014] [Indexed: 11/15/2022]
Abstract
The carbonic anhydrase inhibitor dorzolamide can induce relaxation of retinal arterioles with a consequent increase in blood flow and oxygenation of the retina. It has been shown that the mechanisms underlying this relaxation are independent of extracellular acidosis and CO2. The purpose of the present study was to investigate the possible involvement of nitric oxide (NO) and intracellular acidosis in dorzolamide-induced relaxation of retinal arterioles. Porcine retinal arterioles were mounted in a wire myograph and dorzolamide induced relaxation was studied after 1) the addition of the NO synthase inhibitor l-NAME (3 × 10(-4) M) or the guanylyl cyclase inhibitor ODQ (3 × 10(-6) M), and 2) after loading the smooth muscle cells with the pH sensitive fluorophore SNARF-1-AM and studying changes in vascular tone and intracellular fluorescence after the induction of hypoxia, addition of lactate (10(-2) M), and extracellular acidification (pH = 7.0) alone and in the presence of dorzolamide (10(-3) M). Dorzolamide significantly relaxed retinal arterioles (p < 0.03), and the effect was significantly higher in the presence of perivascular tissue than in isolated vessels at the highest concentration (p < 0.01). In the presence of perivascular tissue dorzolamide-induced relaxation could be reduced by NO inhibition (p < 0.02). Dorzolamide increased intracellular acidification (p < 0.02) during extracellular acidosis, but there was no relation between relaxation and intracellular acidosis. In conclusion, dorzolamide-induced vasorelaxation depends on NO and the perivascular retinal tissue, but is independent of acidification in the extracellular and the intracellular space of retinal vascular smooth muscle cells. Other factors than NO and acidification are involved in dorzolamide-induced relaxation of retinal arterioles.
Collapse
Affiliation(s)
- A El-Galaly
- Department of Ophthalmology, Aarhus University Hospital, 8000 Aarhus C, Denmark.
| | - C Aalkjaer
- Institute of Biomedicine (Physiology), Aarhus University, 8000 Aarhus C, Denmark
| | - S K Kringelholt
- Department of Ophthalmology, Aarhus University Hospital, 8000 Aarhus C, Denmark
| | - M W Misfeldt
- Department of Ophthalmology, Aarhus University Hospital, 8000 Aarhus C, Denmark
| | - T Bek
- Department of Ophthalmology, Aarhus University Hospital, 8000 Aarhus C, Denmark
| |
Collapse
|
24
|
Musa-Aziz R, Occhipinti R, Boron WF. Evidence from simultaneous intracellular- and surface-pH transients that carbonic anhydrase II enhances CO2 fluxes across Xenopus oocyte plasma membranes. Am J Physiol Cell Physiol 2014; 307:C791-813. [PMID: 24965587 DOI: 10.1152/ajpcell.00051.2014] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The α-carbonic anhydrases (CAs) are zinc-containing enzymes that catalyze the interconversion of CO2 and HCO3 (-). Here, we focus on human CA II (CA II), a ubiquitous cytoplasmic enzyme. In the second paper in this series, we examine CA IV at the extracellular surface. After microinjecting recombinant CA II in a Tris solution (or just Tris) into oocytes, we expose oocytes to 1.5% CO2/10 mM HCO3 (-)/pH 7.50 while using microelectrodes to monitor intracellular pH (pHi) and surface pH (pHS). CO2 influx causes the familiar sustained pHi fall as well as a transient pHS rise; CO2 efflux does the opposite. Both during CO2 addition and removal, CA II increases the magnitudes of the maximal rate of pHi change, (dpHi/dt)max, and the maximal change in pHS, ΔpHS. Preincubating oocytes with the inhibitor ethoxzolamide eliminates the effects of CA II. Compared with pHS, pHi begins to change only after a delay of ~9 s and its relaxation has a larger (i.e., slower) time constant (τpHi > τpHS ). Simultaneous measurements with two pHi electrodes, one superficial and one deep, suggest that impalement depth contributes to pHi delay and higher τpHi . Using higher CO2/HCO3 (-) levels, i.e., 5%/33 mM HCO3 (-) or 10%/66 mM HCO3 (-), increases (dpHi/dt)max and ΔpHS, though not in proportion to the increase in [CO2]. A reaction-diffusion mathematical model (described in the third paper in this series) accounts for the above general features and supports the conclusion that cytosolic CA-consuming entering CO2 or replenishing exiting CO2-increases CO2 fluxes across the cell membrane.
Collapse
Affiliation(s)
- Raif Musa-Aziz
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut; and Department of Physiology and Biophysics, University of Sao Paulo, Institute of Biomedical Sciences, Sao Paulo, Brazil
| | - Rossana Occhipinti
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio
| | - Walter F Boron
- Department of Physiology and Biophysics, Case Western Reserve University School of Medicine, Cleveland, Ohio; Department of Medicine, Case Western Reserve University School of Medicine, Cleveland, Ohio; Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, Connecticut; and
| |
Collapse
|
25
|
Comparative effectiveness of intravenous immunoglobulin for children with Kawasaki disease: a nationwide cohort study. PLoS One 2013; 8:e63399. [PMID: 23650564 PMCID: PMC3641142 DOI: 10.1371/journal.pone.0063399] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 04/01/2013] [Indexed: 02/07/2023] Open
Abstract
Introduction Different immunoglobulin manufacturing processes may influence its effectiveness for Kawasaki disease. However, nationwide studies with longitudinal follow-up are still lacking. The aim of this study was to evaluate the comparative effectiveness of immunoglobulin preparations from a nationwide perspective. Materials and Methods This is a nationwide retrospective cohort study with a new user design. Data came from the National Health Insurance Research Database of Taiwan. From 1997 to 2008, children under 2 years old who received immunoglobulin therapy for the first time under the main diagnosis of Kawasaki disease were enrolled. The manufacturing processes were divided into β-propiolactonation, acidification and those containing IgA. The endpoints were immunoglobulin non-responsiveness, acute aneurysm, prolonged use of anti-platelets or anti-coagulants, and recurrence. Results In total, 3830 children were enrolled. β-propiolactonation had a relative risk of 1.45 (95% CI 1.08∼1.94) of immunoglobulin non-responsiveness, however, the relative risks for acidification and containing IgA were non-significant. For acute aneurysms, acidification had a relative risk of 1.49 (95% CI 1.17∼1.90), however the relative risks for β-propiolactonation and containing IgA were non-significant. For prolonged use of anti-platelets or anti-coagulants, β-propiolactonation had a relative risk of 1.44 (95% CI 1.18∼1.76), and acidification protected against them both with a relative risk of 0.82 (95% CI 0.69∼0.97), whereas the relative risk for containing IgA was non-significant. For recurrence, all three factors were non-significant. Conclusions The effectiveness of immunoglobulin may differ among different manufacturing processes. β-propiolactonation had a higher risk of treatment failure and prolonged use of anti-platelets or anti-coagulants. Acidification may increase the risk of acute coronary aneurysms.
Collapse
|
26
|
Acid-base transporters modulate cell migration, growth and proliferation: Implications for structure development and remodeling of resistance arteries? Trends Cardiovasc Med 2012; 23:59-65. [PMID: 23266155 DOI: 10.1016/j.tcm.2012.09.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/31/2012] [Revised: 08/29/2012] [Accepted: 08/30/2012] [Indexed: 12/20/2022]
Abstract
Disturbed acid-base transport across the plasma membrane affects intracellular pH control and has been shown--primarily based on studies with non-vascular cells--to interfere with a number of fundamental cell functions including cell migration, growth and proliferation. Here, we evaluate the effects of acid-base transport and intracellular pH on the morphology of the resistance artery wall, which is altered in a number of physiological and pathological conditions and is an independent predictor of cardiovascular risk. The current evidence supports that disturbed function and/or expression of acid-base transporters can alter resistance artery morphology--and potentially atherosclerosis-prone conduit arteries--and hence should be considered as possible mechanistic components and targets for treatment in cardiovascular disease. More experimental evidence is required, however, to evaluate the cell biological effects of acid-base transport in vascular cells, the roles of specific acid-base transporters in artery remodeling, the relative mechanistic importance of acid-base transporters in the vascular wall compared to other organs, and the therapeutic potential of modifying acid-base transport activity pharmacologically or genetically.
Collapse
|
27
|
Undem C, Rios EJ, Maylor J, Shimoda LA. Endothelin-1 augments Na⁺/H⁺ exchange activity in murine pulmonary arterial smooth muscle cells via Rho kinase. PLoS One 2012; 7:e46303. [PMID: 23029469 PMCID: PMC3460862 DOI: 10.1371/journal.pone.0046303] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 08/29/2012] [Indexed: 12/20/2022] Open
Abstract
Excessive production of endothelin-1 (ET-1), a potent vasoconstrictor, occurs with several forms of pulmonary hypertension. In addition to modulating vasomotor tone, ET-1 can potentiate pulmonary arterial smooth muscle cell (PASMC) growth and migration, both of which contribute to the vascular remodeling that occurs during the development of pulmonary hypertension. It is well established that changes in cell proliferation and migration in PASMCs are associated with alkalinization of intracellular pH (pHi), typically due to activation of Na+/H+ exchange (NHE). In the systemic vasculature, ET-1 increases pHi, Na+/H+ exchange activity and stimulates cell growth via a mechanism dependent on protein kinase C (PKC). These results, coupled with data describing elevated levels of ET-1 in hypertensive animals/humans, suggest that ET-1 may play an important role in modulating pHi and smooth muscle growth in the lung; however, the effect of ET-1 on basal pHi and NHE activity has yet to be examined in PASMCs. Thus, we used fluorescent microscopy in transiently (3–5 days) cultured rat PASMCs and the pH-sensitive dye, BCECF-AM, to measure changes in basal pHi and NHE activity induced by increasing concentrations of ET-1 (10−10 to 10−8 M). We found that application of exogenous ET-1 increased pHi and NHE activity in PASMCs and that the ET-1-induced augmentation of NHE was prevented in PASMCs pretreated with an inhibitor of Rho kinase, but not inhibitors of PKC. Moreover, direct activation of PKC had no effect on pHi or NHE activity in PASMCs. Our results indicate that ET-1 can modulate pH homeostasis in PASMCs via a signaling pathway that includes Rho kinase and that, in contrast to systemic vascular smooth muscle, activation of PKC does not appear to be an important regulator of PASMC pHi.
Collapse
MESH Headings
- Animals
- Cells, Cultured
- Dose-Response Relationship, Drug
- Endothelin-1/pharmacology
- Enzyme Activation/drug effects
- Fluoresceins
- Fluorescent Dyes
- Hydrogen-Ion Concentration
- Male
- Mice
- Mice, Inbred C57BL
- Microscopy, Fluorescence
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/drug effects
- Muscle, Smooth, Vascular/enzymology
- Myocytes, Smooth Muscle/cytology
- Myocytes, Smooth Muscle/drug effects
- Myocytes, Smooth Muscle/enzymology
- Protein Kinase C/metabolism
- Protein Kinase Inhibitors/pharmacology
- Pulmonary Artery/cytology
- Pulmonary Artery/drug effects
- Pulmonary Artery/enzymology
- Signal Transduction/drug effects
- Sodium-Potassium-Exchanging ATPase/antagonists & inhibitors
- Sodium-Potassium-Exchanging ATPase/metabolism
- rho-Associated Kinases/antagonists & inhibitors
- rho-Associated Kinases/metabolism
Collapse
Affiliation(s)
- Clark Undem
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Eon J. Rios
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Julie Maylor
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
| | - Larissa A. Shimoda
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Johns Hopkins School of Medicine, Baltimore, Maryland, United States of America
- * E-mail:
| |
Collapse
|
28
|
Boedtkjer E, Moreira JMA, Mele M, Vahl P, Wielenga VT, Christiansen PM, Jensen VED, Pedersen SF, Aalkjaer C. Contribution of Na+,HCO3(-)-cotransport to cellular pH control in human breast cancer: a role for the breast cancer susceptibility locus NBCn1 (SLC4A7). Int J Cancer 2012; 132:1288-99. [PMID: 22907202 DOI: 10.1002/ijc.27782] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2012] [Accepted: 07/31/2012] [Indexed: 12/16/2022]
Abstract
Genome-wide association studies recently linked the locus for Na(+),HCO(3)(-)-cotransporter NBCn1 (SLC4A7) to breast cancer susceptibility, yet functional insights have been lacking. To determine whether NBCn1, by transporting HCO(3)(-) into cells, may dispose of acid produced during high metabolic activity, we studied the expression of NBCn1 and the functional impact of Na(+),HCO(3)(-)-cotransport in human breast cancer. We found that the plasmalemmal density of NBCn1 was 20-30% higher in primary breast carcinomas and metastases compared to matched normal breast tissue. The increase in NBCn1 density was similar in magnitude to that observed for Na(+)/H(+)-exchanger NHE1 (SLC9A1), a transporter previously implicated in cell migration, proliferation and malignancy. In primary breast carcinomas, the apparent molecular weight for NBCn1 was increased compared to normal tissue. Using pH-sensitive fluorophores, we showed that Na(+),HCO(3)(-)-cotransport is the predominant mechanism of acid extrusion and is inhibited 34 ± 9% by 200 μM 4,4'-diisothiocyanatostilbene-2,2'-disulfonic acid in human primary breast carcinomas. At intracellular pH (pH(i) ) levels >6.6, CO(2)/HCO(3)(-)-dependent mechanisms accounted for >90% of total net acid extrusion. Na(+)/H(+)-exchange activity was prominent only at lower pH(i) -values. Furthermore, steady-state pH(i) was 0.35 ± 0.06 units lower in the absence than in the presence of CO(2)/HCO(3)(-). In conclusion, expression of NBCn1 is upregulated in human primary breast carcinomas and metastases compared to normal breast tissue. Na(+),HCO(3)(-)-cotransport is a major determinant of pH(i) in breast cancer and the modest DIDS-sensitivity is consistent with NBCn1 being predominantly responsible. Hence, our results suggest a major pathophysiological role for NBCn1 that may be clinically relevant.
Collapse
|
29
|
Boedtkjer E, Aalkjaer C. Intracellular pH in the resistance vasculature: regulation and functional implications. J Vasc Res 2012; 49:479-96. [PMID: 22907294 DOI: 10.1159/000341235] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2012] [Accepted: 06/20/2012] [Indexed: 12/18/2022] Open
Abstract
Net acid extrusion from vascular smooth muscle (VSMCs) and endothelial cells (ECs) in the wall of resistance arteries is mediated by the Na(+),HCO(3)(-) cotransporter NBCn1 (SLC4A7) and the Na(+)/H(+) exchanger NHE1 (SLC9A1) and is essential for intracellular pH (pH(i)) control. Experimental evidence suggests that the pH(i) of VSMCs and ECs modulates both vasocontractile and vasodilatory functions in resistance arteries with implications for blood pressure regulation. The connection between disturbed pH(i) and altered cardiovascular function has been substantiated by a genome-wide association study showing a link between NBCn1 and human hypertension. On this basis, we here review the current evidence regarding (a) molecular mechanisms involved in pH(i) control in VSMCs and ECs of resistance arteries at rest and during contractions, (b) implications of disturbed pH(i) for resistance artery function, and (c) involvement of disturbed pH(i) in the pathogenesis of vascular disease. The current evidence clearly implies that pH(i) of VSMCs and ECs modulates vascular function and suggests that disturbed pH(i) either consequent to disturbed regulation or due to metabolic challenges needs to be taken into consideration as a mechanistic component of artery dysfunction and disturbed blood pressure regulation.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine and Water and Salt Research Center, Aarhus University, Aarhus, Denmark.
| | | |
Collapse
|
30
|
Boedtkjer E, Damkier HH, Aalkjaer C. NHE1 knockout reduces blood pressure and arterial media/lumen ratio with no effect on resting pH(i) in the vascular wall. J Physiol 2012; 590:1895-906. [PMID: 22351634 DOI: 10.1113/jphysiol.2011.227132] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Acid–base transport in the vascular wall remains incompletely understood. Here, we investigated (a) implications of Na(+)/H(+) exchanger NHE1 knockout for vascular smooth muscle (VSMC) and endothelial cell (EC) pH(i) regulation, mesenteric artery morphology, vasomotor function and blood pressure regulation, and (b) consequences of sustained EC and VSMC acidification for vasomotor function. Na(+)/H(+) exchange activity was abolished in VSMCs and ECs from NHE1 knockout mice, but with CO(2)/HCO(3)(−) present, steady-state pH(i) was unaffected. Active tension was 30% smaller in arteries from NHE1 knockout than wild-type mice, and media thickness equally reduced. Number of VSMCs per unit artery length was unchanged whereas volume and cross-sectional area of individual VSMCs were reduced. Media stress, force production per VSMC cross-sectional area and VSMC Ca(2+) responses were unaffected. Blood pressure was 25 mmHg lower in NHE1 knockout than wild-type mice. Omission of CO(2)/HCO(3)(−) caused VSMCs and ECs to acidify substantially more in NHE1 knockout (0.3–0.6 pH-units) than wild-type (0.02–0.1 pH units) mice. Removing CO(2)/HCO(3)(−) inhibited acetylcholine-induced NO-mediated relaxations in arteries from NHE1 knockout but not wild-type mice. Without CO(2)/HCO(3)(−), effects of NO synthase and rho kinase inhibition on noradrenaline-induced contractions were smaller in arteries from NHE1 knockout than wild-type mice whereas the EC Ca(2+) response to acetylcholine, VSMC Ca(2+) response to noradrenaline and vasorelaxation to S-nitroso-N-acetylpenicillamine were unaffected. In conclusion, NHE1 mediates the Na(+)/H(+) exchange in ECs and VSMCs. Under physiological conditions, CO(2)/HCO(3)(−)-dependent mechanisms mask the pH(i)-regulatory function of NHE1. NHE1 knockout causes hypotrophy of VSMCs, reduced artery tension and lower blood pressure. At acidic pH(i), NO-mediated vasorelaxation and rho kinase-dependent VSMC Ca(2+) sensitivity are reduced.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine and the Water and Salt Research Center, Aarhus University, Aarhus C, Denmark.
| | | | | |
Collapse
|
31
|
Boedtkjer E, Praetorius J, Matchkov VV, Stankevicius E, Mogensen S, Füchtbauer AC, Simonsen U, Füchtbauer EM, Aalkjaer C. Disruption of Na+,HCO₃⁻ cotransporter NBCn1 (slc4a7) inhibits NO-mediated vasorelaxation, smooth muscle Ca²⁺ sensitivity, and hypertension development in mice. Circulation 2011; 124:1819-29. [PMID: 21947296 DOI: 10.1161/circulationaha.110.015974] [Citation(s) in RCA: 109] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
BACKGROUND Disturbances in pH affect artery function, but the mechanistic background remains controversial. We investigated whether Na(+), HCO₃- transporter NBCn1, by regulating intracellular pH(pH₁), influences artery function and blood pressure regulation. METHODS AND RESULTS Knockout of NBCn1 in mice eliminated Na+, HCO₃⁻ cotransport and caused a lower steady-state pH(i) in mesenteric artery smooth muscle and endothelial cells in situ evaluated by fluorescence microscopy. Using myography, arteries from NBCn1 knockout mice showed reduced acetylcholine-induced NO-mediated relaxations and lower rho-kinase-dependent norepinephrine-stimulated smooth muscle Ca²⁺ sensitivity. Acetylcholine-stimulated NO levels (electrode measurements) and N-nitro-l-arginine methyl ester-sensitive l-arginine conversion (radioisotope measurements) were reduced in arteries from NBCn1 knockout mice, whereas relaxation to NO-donor S-nitroso-N-acetylpenicillamine, acetylcholine-induced endothelial Ca²⁺ responses (fluorescence microscopy), and total and Ser-1177 phosphorylated endothelial NO-synthase expression (Western blot analyses) were unaffected. Reduced NO-mediated relaxations in arteries from NBCn1 knockout mice were not rescued by superoxide scavenging. Phosphorylation of myosin phosphatase targeting subunit at Thr-850 was reduced in arteries from NBCn1 knockout mice. Evaluated by an in vitro assay, rho-kinase activity was reduced at low pH. Without CO₂/HCO₃⁻, no differences in pH(i), contraction or relaxation were observed between arteries from NBCn1 knockout and wild-type mice. Based on radiotelemetry and tail-cuff measurements, NBCn1 knockout mice were mildly hypertensive at rest, displayed attenuated blood pressure responses to NO-synthase and rho-kinase inhibition and were resistant to developing hypertension during angiotensin-II infusion. CONCLUSIONS Intracellular acidification of smooth muscle and endothelial cells after knockout of NBCn1 inhibits NO-mediated and rho-kinase-dependent signaling in isolated arteries and perturbs blood pressure regulation.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- Department of Biomedicine, Aarhus University, DK-8000 Aarhus C, Denmark.
| | | | | | | | | | | | | | | | | |
Collapse
|
32
|
Fenton RA, Praetorius J. Molecular Physiology of the Medullary Collecting Duct. Compr Physiol 2011; 1:1031-56. [DOI: 10.1002/cphy.c100064] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
|
33
|
Manlhiot C, Yeung RSM, Chahal N, McCrindle BW. Intravenous immunoglobulin preparation type: association with outcomes for patients with acute Kawasaki disease. Pediatr Allergy Immunol 2010; 21:515-21. [PMID: 20546528 DOI: 10.1111/j.1399-3038.2010.00987.x] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
To determine whether two different intravenous immunoglobulin (IVIG) preparations were equally efficacious in the treatment of Kawasaki disease (KD). Single centre retrospective review of all patients treated with IVIG for KD between January 1990 and April 2007. Comparison of IVIG (dose 2 g/kg) from two commercial preparations; Iveegam stabilized with sugar (lyophilized, 5 g/ml glucose, pH 6.4-7.2, IgA 10 microg/ml, 5% IgG/ml) and Gamimune stabilized through acidification (no sugar, pH 4.0-4.5, IgA 270 microg/ml, 5% 1990-1999, 10% 1999-2007 IgG/ml). Propensity-adjusted differences in duration of fever after treatment initiation, frequency of retreatment with IVIG, hospital stay and maximum coronary artery z-score. A total of 954 patients were included, 862 (90%) were treated with Iveegam and 92 (10%) were treated with Gamimune. Patients' demographic, clinical and laboratory characteristics were similar between the two groups. In propensity-adjusted models, Iveegam was found to be associated with higher probability of non-response to IVIG (12% vs. 5%, p = 0.05) and longer median duration of fever after IVIG [1 (1-27) vs. 1 (1-8) days, p = 0.02] than Gamimune. Nevertheless, Gamimune was found to be associated with longer median duration of hospital stay [5 (2-49) vs. 4 (2-76) days, p < 0.0001] and higher median maximum coronary artery z-score both at the end of the acute phase (+1.4 vs. +0.8, p < 0.0001) and 6-8 weeks after the acute phase (+0.7 vs. +0.4, p < 0.0001). IVIG preparations with lower IgA content and stabilized with glucose appear to be associated with improved coronary artery outcomes for patients with KD.
Collapse
Affiliation(s)
- Cedric Manlhiot
- University of Toronto, Labatt Family Heart Centre, The Hospital for Sick Children, Toronto, ON, Canada
| | | | | | | |
Collapse
|
34
|
Boedtkjer E, Aalkjaer C. Insulin inhibits Na+/H+ exchange in vascular smooth muscle and endothelial cells in situ: involvement of H2O2 and tyrosine phosphatase SHP-2. Am J Physiol Heart Circ Physiol 2009; 296:H247-55. [DOI: 10.1152/ajpheart.00725.2008] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Insulin signals through several intracellular pathways. Here, we tested the hypothesis that insulin modulates Na+/H+ exchange (NHE) activity in vascular cells through H2O2-mediated inhibition of tyrosine phosphatase Src homology 2 domain containing tyrosine phosphatase 2 (SHP-2). We measured intracellular pH (pHi) in isolated mouse mesenteric arteries using fluorescence confocal and wide-field microscopy. In the absence of CO2/HCO3−, removal of bath Na+ produced endothelial acidification (ΔpHi = −0.71 ± 0.12) inhibited by cariporide. Cariporide reduced endothelial steady-state pHi (ΔpHi=−0.28 ± 0.08). Insulin and H2O2 acidified endothelial cells 0.2–0.3 pH units and reduced the acidification upon Na+ removal by ∼65%. Cariporide abolished the effect of insulin and H2O2. In vascular smooth muscle cells, H2O2 produced intracellular acidification (ΔpHi = −0.48 ± 0.06) as did high concentrations of insulin (ΔpHi = −0.03 ± 0.01). NHE activity after an NH4+ prepulse was ∼80% attenuated by H2O2 and ∼40% by high insulin concentrations. H2O2 had no effect on Na+-HCO3− cotransport activity. NHE1 (slc9a1) was the only plasma membrane NHE isoform detected in mouse mesenteric arteries by RT-PCR analyses. In both cell types, polyethylene glycol catalase abolished the effect of insulin on pHi. Exposure to insulin increased the intracellular concentration of reactive oxygen species estimated with the fluorophore 5-(6)-chloromethyl-2′,7′-dichlorodihydrofluorescein. The SHP-2 selective inhibitor NSC-87877 and protein tyrosine phosphatase (PTP) inhibitor IV reduced steady-state pHi up to 0.3 pH units and inhibited NHE activity 60–80%; when applied in combination with insulin or H2O2, no further effect was obtained. We conclude that NHE contributes to pHi regulation in arterial endothelial and smooth muscle cells in situ and is inhibited by insulin and H2O2. We propose that insulin signaling involves H2O2 and inhibition of PTP SHP-2.
Collapse
|
35
|
Vasomotion has chloride-dependency in rat mesenteric small arteries. Pflugers Arch 2008; 457:389-404. [DOI: 10.1007/s00424-008-0532-3] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2008] [Revised: 04/22/2008] [Accepted: 05/13/2008] [Indexed: 10/22/2022]
|
36
|
Celotto A, Capellini V, Baldo C, Dalio M, Rodrigues A, Evora P. Effects of acid-base imbalance on vascular reactivity. Braz J Med Biol Res 2008; 41:439-45. [DOI: 10.1590/s0100-879x2008005000026] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2007] [Accepted: 05/29/2008] [Indexed: 11/22/2022] Open
|
37
|
Boedtkjer E, Praetorius J, Füchtbauer EM, Aalkjaer C. Antibody-independent localization of the electroneutral Na+-HCO3- cotransporter NBCn1 (slc4a7) in mice. Am J Physiol Cell Physiol 2007; 294:C591-603. [PMID: 18077606 DOI: 10.1152/ajpcell.00281.2007] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The expression pattern of the electroneutral Na(+)-HCO(3)(-)cotransporter NBCn1 (slc4a7) was investigated by beta-galactosidase staining of mice with a LacZ insertion into the NBCn1 gene. This method is of particular value because it is independent of immunoreactivity. We find that the NBCn1 promoter is active in a number of tissues where NBCn1 has previously been functionally or immunohistochemically identified, including a broad range of blood vessels (vascular smooth muscle cells and endothelial cells), kidney thick ascending limb and medullary collecting duct epithelial cells, the epithelial lining of the kidney pelvis, duodenal enterocytes, choroid plexus epithelial cells, hippocampus, and retina. Kidney corpuscles, colonic mucosa, and nonvascular smooth muscle cells (from the urinary bladder, trachea, gastrointestinal wall, and uterus) were novel areas of promoter activity. Atrial but not ventricular cardiomyocytes were stained. In the brain, distinct layers of the cerebral cortex and cerebellar Purkinje cells were stained as was the dentate nucleus. No staining of skeletal muscle or cortical collecting ducts was observed. RT-PCR analyses confirmed the expression of NBCn1 and beta-galactosidase in selected tissues. Disruption of the NBCn1 gene resulted in reduced NBCn1 expression, and in bladder smooth muscle cells, reduced amiloride-insensitive Na(+)-dependent HCO(3)(-) influx was observed. Furthermore, disruption of the NBCn1 gene resulted in a lower intracellular steady-state pH of bladder smooth muscle cells in the presence of CO(2)/HCO(3)(-) but not in its nominal absence. We conclude that NBCn1 has a broad expression profile, supporting previous findings based on immunoreactivity, and suggest several new tissues where NBCn1 may be important.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- The Water and Salt Research Center, University of Aarhus, Ole Worms Allé 1160, DK-8000 Aarhus C, Denmark.
| | | | | | | |
Collapse
|
38
|
Pedersen DB, Stefánsson E, Kiilgaard JF, Jensen PK, Eysteinsson T, Bang K, la Cour M. Optic nerve pH and PO2: the effects of carbonic anhydrase inhibition, and metabolic and respiratory acidosis. ACTA ACUST UNITED AC 2006; 84:475-80. [PMID: 16879567 DOI: 10.1111/j.1600-0420.2006.00709.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
PURPOSE Earlier studies have demonstrated that carbonic anhydrase inhibitors (CAIs) increase optic nerve oxygen tension (ONPO(2)) in pigs. We hypothesized that the mechanism of this effect was either a CO(2) increase or a pH decrease in tissue and blood. To test this hypothesis we investigated and compared how optic nerve pH (ONpH) and ONPO(2) are affected by: (1) carbonic anhydrase inhibition; (2) respiratory acidosis, and (3) metabolic acidosis. We measured ONpH with a glass pH electrode and ONPO(2) with a polarographic oxygen electrode. One of the electrodes was placed in the vitreous cavity 0.5 mm over the optic nerve in the eyes of domestic pigs. METHODS We measured ONpH during carbonic anhydrase inhibition and ONpH or ONPO(2) during NH(4)Cl-induced metabolic acidosis and during CO(2) breathing (respiratory acidosis). RESULTS Baseline ONpH was 0.12 +/- 0.06 lower than arterial pH (mean +/- SD, n = 10, p < 0.001). Optic nerve pH decreased with arterial pH during carbonic anhydrase inhibition, metabolic and respiratory acidosis. Optic nerve oxygen tension was not affected by metabolic acidosis but increased during CO(2) breathing, as it has been shown to do during carbonic anhydrase inhibition. CONCLUSIONS There is a close correlation between arterial blood pH and intraocular pH. Isolated ONpH changes do not affect ONPO(2), thus the ONPO(2) increase seen with carbonic anhydrase inhibition is probably not only due to pH changes in the blood and optic nerve. Accumulation of CO(2), either alone or in combination with a pH change, is likely to cause the ONPO(2) increase, but a direct vascular effect should also be considered.
Collapse
|
39
|
Wakabayashi I, Poteser M, Groschner K. Intracellular pH as a determinant of vascular smooth muscle function. J Vasc Res 2006; 43:238-50. [PMID: 16449818 DOI: 10.1159/000091235] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2005] [Accepted: 11/20/2005] [Indexed: 11/19/2022] Open
Abstract
Intracellular pH (pHi) is a physiological parameter that is intimately linked to contractility, growth and proliferation of vascular smooth muscle (VSM). Regarding contractility, no general unifying concept of pHi regulation but a rather complex relation between pHi signals and vascular tone has been revealed so far. The modulation of vasotone by pHi depends on the type of blood vessel as well as on the pattern of regulatory input signals. In addition, changes in pHi have been recognized as an important cellular signal to determine the fate of cells in terms of proliferation or apoptosis. Cellular sensors for pHi include a variety of ion transport systems which control intracellular Ca2+ gradients and are likely to serve as a link between pHi and cell functions. Here we provide an overview on the potential targets and mechanisms that transduce pHi signals in VSM. The role of pHi-sensing signaling complexes and localized pHi signaling as the basis of diversity of pHi regulation of VSM function is discussed.
Collapse
Affiliation(s)
- Ichiro Wakabayashi
- Department of Hygiene and Preventive Medicine, Yamagata University School of Medicine, Yamagata, Japan.
| | | | | |
Collapse
|
40
|
Boedtkjer E, Praetorius J, Aalkjaer C. NBCn1 (slc4a7) mediates the Na+-dependent bicarbonate transport important for regulation of intracellular pH in mouse vascular smooth muscle cells. Circ Res 2006; 98:515-23. [PMID: 16439691 DOI: 10.1161/01.res.0000204750.04971.76] [Citation(s) in RCA: 69] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
The contribution of sodium-dependent bicarbonate transport to intracellular pH (pH(i)) regulation in vascular smooth muscle cells is controversial, partly because the molecular identity of the transporter(s) responsible has not been identified. Here, using the pH-sensitive fluorophore 2',7'-bis-(2-carboxyethyl)-5-(and-6)-carboxyfluorescein (BCECF), we show that smooth muscle cells of intact mouse mesenteric, coronary, and cerebral small arteries all display a sodium- and bicarbonate-dependent pH(i) recovery after an NH4+-prepulse. The sodium-dependent bicarbonate flux was largely 4,4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS) sensitive (56% to 91%) and of a magnitude similar to the amiloride-sensitive flux. Additionally, steady-state pH(i) was lower (0.2 to 0.4 pH units magnitude) in all 3 vascular beds when CO2/bicarbonate was omitted. RT-PCR analyses showed that NBCn1 (slc4a7) is the only Na+-dependent bicarbonate transporter of the slc4 family detectable at the mRNA level in all 3 vascular beds investigated. Whole-mount immunolabeling and immunogold electron microscopy confirmed the presence of NBCn1 protein in the sarcolemma of mouse mesenteric small arterial smooth muscle cells. Intact mouse mesenteric small arteries were electropermeated to facilitate transfection with small interfering RNA targeting NBCn1, which resulted in an approximate 43% decrease in the ratio of NBCn1 to glyceraldehyde-3-phosphate dehydrogenase mRNA. After knock-down, we found a decreased steady-state pH(i) (0.21+/-0.08 pH units) as well as a 68+/-10% decrease in the net Na+-dependent, amiloride-insensitive base influx after acid load. Finally, omission of CO2/bicarbonate resulted in a decreased contractile response to norepinephrine after sustained exposure to the agonist, underlining the importance of CO2/bicarbonate for vascular contractility. We conclude that NBCn1 mediates the Na+-dependent bicarbonate transport important for pH(i) regulation in smooth muscle cells of mouse mesenteric, coronary, and cerebral small arteries.
Collapse
Affiliation(s)
- Ebbe Boedtkjer
- The Water and Salt Research Center, Department of Physiology, University of Aarhus, Denmark
| | | | | |
Collapse
|
41
|
Rohra DK, Saito SY, Ohizumi Y. Low Extracellular Cl – Environment Attenuates Changes in Intracellular pH and Contraction following Extracellular Acidosis in Wistar Kyoto Rat Aorta. Pharmacology 2005; 75:30-6. [PMID: 15942273 DOI: 10.1159/000086152] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2005] [Accepted: 04/07/2005] [Indexed: 11/19/2022]
Abstract
This study was conducted to investigate the influence of extracellular Cl- ([Cl-]o) on the intracellular pH (pHi) regulation and the contractile state of the isolated aorta from Wistar Kyoto (WKY) rats. Isometric tension recording and fluorometry techniques were utilized to measure contractile response and pHi in isolated aortic strips. Decreasing extracellular pH (pHo) from 7.4 to 6.5 produced a marked contraction, which was 75.8 +/- 5.6% of the 64.8 mmol/l KCl-induced contraction. The acidosis-induced contraction was significantly attenuated in low [Cl-]o solution, the magnitude of which was 56.0 +/- 3.0% of the 64.8 mmol/l KCl-induced contraction. Decreasing pHo of the normal solution to 6.5 rapidly decreased pHi in aortic smooth muscle cells and produced a corresponding contraction. When the pHo was decreased in low [Cl-]o solution, a rapid fall in pHi followed by reversal of pHi changes, in a time-dependent manner was observed, despite low pHo. Omission of HCO3- from the low [Cl-]o solution restored the contractile response to acidosis, which was comparable to that in normal solution. Similarly, following decrease in pHo to 6.5, no recovery of intracellular acidosis was observed. We conclude that low [Cl-]o environment causes activation of extracellular HCO3- -dependent pHi-regulating mechanism, that results in the rapid recovery of pHi following acidosis, and the attenuation of acidosis-induced contraction of WKY aorta.
Collapse
Affiliation(s)
- Dileep Kumar Rohra
- Department of Pharmaceutical Molecular Biology, Graduate School of Pharmaceutical Sciences, Tohoku University, Aoba, Aramaki, Sendai, Japan.
| | | | | |
Collapse
|
42
|
Damkier HH, Nielsen S, Praetorius J. An anti-NH2-terminal antibody localizes NBCn1 to heart endothelia and skeletal and vascular smooth muscle cells. Am J Physiol Heart Circ Physiol 2005; 290:H172-80. [PMID: 16126812 DOI: 10.1152/ajpheart.00713.2005] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
The electroneutral sodium bicarbonate cotransporter NBCn1 or NBC3 was originally cloned from rat aorta and from human skeletal muscle. NBCn1 (or NBC3) has been localized to the basolateral membrane of various epithelia, but thus far it has been impossible to detect the protein in these tissues by using anti-COOH-terminal antibodies. Hence an antibody was developed against the NH2-terminus of NBCn1 and was validated by peptide recognition and immunoblotting on positive control tissues and by binding of an approximately 180-kDa protein in the rat kidney, cerebrum, cerebellum, and duodenum. In addition, an approximately 180-kDa immunoreactive band appeared using samples from the aorta, heart ventricles and atria, mesenteric arteries, lung, spleen, liver, pancreas, and epididymis. Immunohistochemical analysis confirmed the previously described labeling in the kidney, duodenum, and the choroid plexus. The anti-NH2-terminal antibody localized NBCn1 to the plasma membrane domains of endothelia and smooth muscle cells in small mesenteric and renal arteries, as well as the capillaries of the heart ventricles, spleen, and salivary glands. NBCn1 was also detected in neuromuscular junctions and vasculature in skeletal muscle. Analysis of variable NBCn1 splicing by RT-PCR revealed that an NH2-terminal sequence, the cassette III, seems absent from cardiovascular NBCn1 and that both cassettes I and III are variable in most epithelia, whereas cassette II is absent from epithelial NBCn1. Thus the development of the NH2-terminal antibody allowed the localization of NBCn1 protein to major cardiovascular tissues where NBCn1 mRNA was previously detected. The NBCn1 is a likely candidate for mediating the reported electroneutral Na+-HCO3(-) cotransport in vascular smooth muscle.
Collapse
Affiliation(s)
- Helle Hasager Damkier
- Water and Salt Research Center, Institute of Anatomy, Univ. of Aarhus, Wilhelm Meyers Allé, Bldg. 234, 8000 Aarhus C, Denmark
| | | | | |
Collapse
|
43
|
Rios EJ, Fallon M, Wang J, Shimoda LA. Chronic hypoxia elevates intracellular pH and activates Na+/H+ exchange in pulmonary arterial smooth muscle cells. Am J Physiol Lung Cell Mol Physiol 2005; 289:L867-74. [PMID: 15964895 DOI: 10.1152/ajplung.00455.2004] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Chronic hypoxia (CH), caused by many lung diseases, results in pulmonary hypertension due, in part, to increased muscularity of small pulmonary vessels. Pulmonary arterial smooth muscle cell (PASMC) proliferation in response to growth factors requires increased intracellular pH (pHi) mediated by activation of Na+/H+ exchange (NHE); however, the effect of CH on PASMC pHi homeostasis is unknown. Thus we measured basal pHi and NHE activity and expression in PASMCs isolated from mice exposed to normoxia or CH (3 wk/10% O2). pHi was measured using the pH-sensitive fluorescent dye BCECF-AM. NHE activity was determined from Na+-dependent recovery from NH4-induced acidosis, and NHE expression was determined by RT-PCR and immunoblot. PASMCs from chronically hypoxic mice exhibited elevated basal pHi and increased NHE activity. NHE1 was the predominate isoform present in mouse PASMCs, and both gene and protein expression of NHE1 was increased following exposure to CH. Our findings indicate that exposure to CH caused increased pHi, NHE activity, and NHE1 expression, changes that may contribute to the development of pulmonary hypertension, in part, via pH-dependent induction of PASMC proliferation.
Collapse
MESH Headings
- Animals
- Base Sequence
- Cation Transport Proteins/genetics
- Cation Transport Proteins/metabolism
- Chronic Disease
- Gene Expression
- Hydrogen-Ion Concentration
- Hypertension, Pulmonary/genetics
- Hypertension, Pulmonary/metabolism
- Hypertension, Pulmonary/pathology
- Hypertrophy, Right Ventricular/genetics
- Hypertrophy, Right Ventricular/metabolism
- Hypertrophy, Right Ventricular/pathology
- Hypoxia/genetics
- Hypoxia/metabolism
- Hypoxia/pathology
- In Vitro Techniques
- Male
- Membrane Proteins/genetics
- Membrane Proteins/metabolism
- Mice
- Mice, Inbred C57BL
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/pathology
- Pulmonary Artery/metabolism
- Pulmonary Artery/pathology
- Sodium-Hydrogen Exchanger 1
- Sodium-Hydrogen Exchangers/genetics
- Sodium-Hydrogen Exchangers/metabolism
Collapse
Affiliation(s)
- Eon J Rios
- Division of Pulmonary and Critical Care Medicine, Johns Hopkins Univ., Baltimore, MD 21224, USA
| | | | | | | |
Collapse
|
44
|
Holmes ME, Mwanjewe J, Samson SE, Haist JV, Wilson JX, Dixon SJ, Karmazyn M, Grover AK. Dehydroascorbic acid uptake by coronary artery smooth muscle: effect of intracellular acidification. Biochem J 2002; 362:507-12. [PMID: 11853561 PMCID: PMC1222413 DOI: 10.1042/0264-6021:3620507] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
Dehydroascorbic acid (DHAA) enters cells via Na(+)-independent glucose transporters (GLUT) and is converted to ascorbate. However, we found that Na(+) removal inhibited [(14)C]DHAA uptake by smooth-muscle cells cultured from pig coronary artery. The uptake was examined for 2-12 min at 10-200 microM DHAA in either the presence of 134 mM Na(+) or in its absence (N-methyl D-glucamine, choline or sucrose replaced Na(+)). This inhibition of DHAA uptake by Na(+) removal was paradoxical because it was inhibited by 2-deoxyglucose and cytochalasin B, as expected of transport via the GLUT pathway. We tested the hypothesis that this paradox resulted from an inefficient intracellular reduction of [(14)C]DHAA into [(14)C]ascorbate upon intracellular acidosis caused by the Na(+) removal. Consistent with this hypothesis: (i) the Na(+)/H(+)-exchange inhibitors ethylisopropyl amiloride and cariporide also decreased the uptake, (ii) Na(+) removal and Na(+)/H(+)-exchange inhibitors lowered cytosolic pH, with the decrease being larger in 12 min than in 2 min, and (iii) less of the cellular (14)C was present as ascorbate (determined by HPLC) in cells in Na(+)-free buffer than in those in Na(+)-containing buffer. This inability to obtain ascorbate from extracellular DHAA may be detrimental to the coronary artery under hypoxia-induced acidosis during ischaemia/reperfusion.
Collapse
Affiliation(s)
- Melanie E Holmes
- Department of Medicine, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
| | | | | | | | | | | | | | | |
Collapse
|
45
|
Sandmann S, Yu M, Kaschina E, Blume A, Bouzinova E, Aalkjaer C, Unger T. Differential effects of angiotensin AT1 and AT2 receptors on the expression, translation and function of the Na+-H+ exchanger and Na+-HCO3- symporter in the rat heart after myocardial infarction. J Am Coll Cardiol 2001; 37:2154-65. [PMID: 11419902 DOI: 10.1016/s0735-1097(01)01287-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
Abstract
OBJECTIVES This study investigated the role of angiotensin receptor subtype 1 (AT1) and angiotensin receptor subtype 2 (AT2) in the regulation of Na+-H+ exchanger (NHE) and Na+-HCO3 symporter (NBC) in the infarcted myocardium. BACKGROUND The cardiac renin-angiotensin system is activated after myocardial infarction (MI), and both angiotensin AT1 and AT2 receptors are upregulated in the myocardium. METHODS Na+-H+ exchanger isoform-1 and NBC-1 gene expression were determined by reverse transcription polymerase chain reaction and Northern blot analysis; protein levels by Western blot analysis; and activity by measurement of H+ transport in left ventricular (LV) free wall, interventricular septum (IS) and right ventricle (RV) after induction of MI. Rats were treated with placebo, the angiotensin-converting enzyme inhibitor ramipril (1 mg/kg/day), the AT1 receptor antagonist valsartan (10 mg/kg/day) or the AT2 receptor antagonist PD 123319 (30 mg/kg/day). Treatment was started seven days before surgery. RESULTS Na+-H+ exchanger isoform-1 and NBC-1 messenger RNA (mRNA) expression and protein levels were increased twofold in the LV free wall after MI, whereas no changes were observed in the IS and RV. Na+-dependent H+ flux was increased in the LV free wall. Ramipril inhibited mRNA and protein upregulation of both transporters. Valsartan inhibited the upregulation of NHE-1 mRNA and protein but had no effect on NBC-1 mRNA expression and translation. In contrast, PD 123319 abolished the upregulation of NBC-1 mRNA and protein but had no effect on NHE-1 upregulation. Ramipril and valsartan prevented post-MI increase in NHE-1 activity, whereas ramipril and PD 123319 decreased NBC-1 activity. CONCLUSIONS Angiotensin II via its AT1 and AT2 receptors differentially controls transcriptional and translational regulation as well as the activity of NHE-1 and NBC-1 in the ischemic myocardium and contributes to the control of pH regulation in cardiac tissue.
Collapse
Affiliation(s)
- S Sandmann
- Institute of Pharmacology, University of Kiel, Germany
| | | | | | | | | | | | | |
Collapse
|
46
|
Lee VM, Halligan AW, Ng LL. Leucocyte intracellular pH and Na+/H+ exchanger isoform-1 activity in postpartum women with pre-eclampsia. BJOG 2001; 108:615-22. [PMID: 11426897 DOI: 10.1111/j.1471-0528.2001.00136.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To investigate leucocyte Na+/H+ exchanger isoform 1 activity in postpartum pre-eclamptics. DESIGN Exchanger isoform-1 activity and intracellular resting pH were established in leucocytes isolated from two study groups. SAMPLE Leucocytes isolated from 10 women who had had pre-eclamptic pregnancies more than five months postpartum, and from 10 age-matched normotensive women who were more than five months postpartum. SETTING Hypertension Clinic, Antenatal Assessment Area, Leicester Royal Infirmary. METHODS A well validated technique involving flurometry using a pH sensitive dye (BCECF-AM) was performed to determine exchanger isoform-1 activity and intracellular pH. Determination of exchanger isoform-1 protein abundance was performed by western blotting. Exchanger isoform-3 protein abundance was examined to rule out the possibility of activity due to this particular isoform. RESULTS Intracellular pH was significantly lower in the postpartum pre-eclamptic group (7.11 +/- 0.02), compared with the postpartum normotensive controls (7.33 +/- 0.04; P < 0.001). Exchanger isoform-1 efflux rate (in mmol/L/minute) was significantly higher in the postpartum pre-eclamptic group (35.91 +/- 3.1), compared with the postpartum normotensives (23.94 +/- 2.0; P = 0.005). Exchanger isoform-1 protein density was established to be similar among the two subject groups. No exchanger isoform-3 protein was identified by western blotting. CONCLUSION Our results suggest that elevated exchanger isoform-1 activity is an important finding in women who have suffered from pre-eclampsia. This increased activity is not due to an increase in exchanger isoform-1 protein abundance or the presence of exchanger isoform-3.
Collapse
Affiliation(s)
- V M Lee
- Department of Medicine and Therapeutics, Leicester Royal Infirmary, UK
| | | | | |
Collapse
|
47
|
Petkova-Kirova P, Gagov H, Krien U, Duridanova D, Noack T, Schubert R. 4-aminopyridine affects rat arterial smooth muscle BK(Ca) currents by changing intracellular pH. Br J Pharmacol 2000; 131:1643-50. [PMID: 11139442 PMCID: PMC1572501 DOI: 10.1038/sj.bjp.0703742] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
The hypothesis whether or not 4-AP can affect vascular smooth muscle BK(Ca) currents was tested using the patch-clamp technique, pH- and calcium-fluorimetry, and freshly isolated rat arterial smooth muscle cells. Application of 4-AP reversibly inhibited BK(Ca) currents at an intracellular calcium ([Ca](i)) of 250 nM with a half-block of 2. 5 mM at +50 mV. The presence of 2 microM thapsigargin, 10 microM heparin, and 10 microM ryanodine did not alter the effect of 4-AP on BK(Ca) currents at [Ca](i) 250 nM. At [Ca](i)<100 nM 4-AP did not inhibit BK(Ca) currents. Application of 4-AP to the intracellular or extracellular side of excised BK(Ca) channels did not alter channel activity or channel amplitude. Replacement of the pH-sensitive calcium buffer EGTA by the pH-insensitive calcium buffer BAPTA in the intracellular solution turned the 4-AP-induced inhibition of BK(Ca) currents into a stimulation at [Ca](i) 250 nM. Application of 4-AP to single cells increased intracellular pH, which was accompanied by a reduction of [Ca](i) in EGTA-loaded cells and a stable [Ca](i) in BAPTA-loaded cells. Thus, these results suggest that in isolated vascular smooth muscle cells at [Ca](i)>100 nM 4-AP affects BK(Ca) currents via an alteration of intracellular pH.
Collapse
Affiliation(s)
- Polina Petkova-Kirova
- Institute of Biophysics, Bulgarian Academy of Sciences, Acad. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Hristo Gagov
- Institute of Biophysics, Bulgarian Academy of Sciences, Acad. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Ulrike Krien
- University of Rostock, Institute of Physiology, PSF 100888, 18055 Rostock, Germany
| | - Dessislava Duridanova
- Institute of Biophysics, Bulgarian Academy of Sciences, Acad. Bonchev Str., Bl. 21, 1113 Sofia, Bulgaria
| | - Thomas Noack
- University of Rostock, Institute of Physiology, PSF 100888, 18055 Rostock, Germany
| | - Rudolf Schubert
- University of Rostock, Institute of Physiology, PSF 100888, 18055 Rostock, Germany
- Author for correspondence:
| |
Collapse
|
48
|
Ahmad S. Acetazolamide and enalapril combination offers complete protection from nitric oxide-deficient stroke in stroke-prone spontaneously hypertensive rats. Pharmacol Res 2000; 41:649-56. [PMID: 10816334 DOI: 10.1006/phrs.1999.0641] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Chronic oral administration of l -NAME precipitates stroke in stroke-prone spontaneously hypertensive rats (SHRSP). The present study investigated whether acetazolamide (an acidotic agent) given alone or in combination with an angiotensin blocker (enalapril maleate) offers any protection from NO-deficient stroke in SHRSP. We also examined whether protection from NO-deficient stroke involves activation of K(+)channels. Five-week-old SHRSP drank saline (group I), l -NAME (group II), l -NAME+enalapril (group III), l -NAME+acetazolamide (group IV), and l -NAME+enalapril+acetazolamide (group V). Within a few hours following onset of stroke, rats were attached to a blood pressure recorder. In subsequent experiments, to investigate the involvement of K(+)channels, glibenclamide and BaCl(2)(K(+)channel blockers) were included in the drinking solutions that were given to the SHRSP groups receiving l -NAME, acetazolamide and enalapril. Group I of SHRSP did not develop stroke. Group II, III and IV developed stroke in 12+/-2, 29+/-2 and 20+/-2 days, respectively. SHRSP from group V did not develop stroke. However, they died in 70+/-2 days. The glibenclamide and BaCl(2)administration failed to prevent this protection from stroke. In conclusion, concurrent administration of acetazolamide and enalapril prevents onset of NO-deficient stroke in SHRSP. These stroke-protective effects are independent of reductions in mean or systolic blood pressures and do not involve an activation of K(+)channels.
Collapse
Affiliation(s)
- S Ahmad
- Department of Pharmacology, Arnold and Marie Schwartz, College of Pharmacy, Long Island University, 75 Dekalb Avenue, Brooklyn, New York, NY 11201, USA
| |
Collapse
|
49
|
Rembold CM, O'Connor M. Caldesmon and heat shock protein 20 phosphorylation in nitroglycerin- and magnesium-induced relaxation of swine carotid artery. BIOCHIMICA ET BIOPHYSICA ACTA 2000; 1500:257-64. [PMID: 10699367 DOI: 10.1016/s0925-4439(99)00112-x] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Nitrovasodilators, high extracellular Mg(2+), and some other relaxing agents can cause smooth muscle relaxation without reductions in myosin regulatory light chain (MRLC) phosphorylation. Relaxations without MRLC dephosphorylation suggest that other regulatory systems, beyond MRLC phosphorylation, are present in smooth muscle. We tested whether changes in caldesmon phosphorylation, heat shock protein 20 (HSP20) phosphorylation, or intracellular pH (pH(i)) could be responsible for relaxation without MRLC dephosphorylation. In unstimulated tissues, caldesmon was phosphorylated 1.02+/-0.10 mol P(i)/mol caldesmon (mean+/-1 S.E.M.), HSP20 was phosphorylated 0.005+/-0.003 mol P(i)/mol HSP20, and estimated pH(i) was 7.21+/-0.07. Histamine stimulation induced a contraction, an intracellular acidosis, but did not significantly change caldesmon or HSP20 phosphorylation. Addition of nitroglycerin induced a relaxation, significantly increased HSP20 phosphorylation to 0.18+/-0.02 mol P(i)/mol HSP20, did not significantly change caldesmon phosphorylation, and pH(i) returned to near unstimulated values. Increase in extracellular Mg(2+) to 10 mM induced a relaxation, but did not significantly change HSP20 or caldesmon phosphorylation. These data suggest that changes in caldesmon phosphorylation, HSP20 phosphorylation, or pH(i) cannot be the sole explanation for relaxation without MRLC dephosphorylation. However, it is possible that HSP20 phosphorylation may be involved in nitroglycerin-induced relaxation without MRLC dephosphorylation.
Collapse
Affiliation(s)
- C M Rembold
- Cardiovascular Division, Departments of Internal Medicine and Physiology, University of Virginia Health System, Charlottesville, VA 22908, USA.
| | | |
Collapse
|
50
|
Abstract
Ca(2+) and H(+) ions can profoundly alter vascular tone. In many physiological and pathological processes, changes in the concentration of both ions occur. Thus, to understand the processes and mechanisms that modify force, it is necessary to understand what changes occur in these ions and, importantly, how they interact with each other. In this minireview, we highlight the quantitatively important mechanisms involved in the contractile responses of vascular tissues to pH change and discuss the cellular and molecular reasons underlying these responses.
Collapse
Affiliation(s)
- C Austin
- Department of Medicine, Manchester Royal Infirmary, Manchester, UK.
| | | |
Collapse
|