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Samir H, El-Sherbiny HR, Ahmed AE, Ahmad Sindi R, Al Syaad KM, Abdelnaby EA. Administration of Estradiol Benzoate Enhances Ovarian and Uterine Hemodynamics in Postpartum Dairy Buffaloes. Animals (Basel) 2023; 13:2340. [PMID: 37508117 PMCID: PMC10376374 DOI: 10.3390/ani13142340] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2023] [Revised: 06/29/2023] [Accepted: 07/04/2023] [Indexed: 07/30/2023] Open
Abstract
The postpartum (PP) period is a crucial stage for the resumption of reproductive performance and ovarian cyclicity in dairy buffaloes. The present study aimed, for the first time, to assess the effect of the administration of estradiol benzoate (EB) on ovarian and uterine hemodynamics in PP dairy buffaloes. Eight pluriparous acyclic domestic buffaloes were enrolled in the present experiment and received a dose of 10 mg of estradiol benzoate (EB) intramuscularly 4 weeks after parturition. All animals were examined two times before EB administration (days -3, and -1) and on the day of EB administration (day 0), followed by examinations on days 1, 3, 5, 7, and 9 post-EB administration. The middle uterine artery (MUA) and ovarian artery (OA) blood flow patterns were assessed using a color Doppler ultrasound device. The reproductive parameters were (1) the cross-sectional diameters (cm) of the OA and MUA, (2) cranial uterine horn thickness (UHT; cm), and (3) hemodynamic changes within the MUA on both the ipsi- and contra-lateral sides of the previous pregnant horn and within the OA corresponding to the ovarian tissues. The examined blood flow parameters were the pulsatility index (PI), resistance index (RI), peak systolic/end-diastolic ratio (S/D), time-averaged maximum velocity (TAV; cm/s), uterine blood flow rate (BFR; bpm), and uterine blood flow volume (BFV; mL/min). Concomitantly, blood samples were collected from the coccygeal vein, and the sera were stored at -18 °C for use in estradiol (E2-17β) and nitric oxide (NO) assays. The results revealed increases in both OA and MUA cross-sectional diameter (cm) on the ipsi-lateral and contra-lateral (p < 0.05) sides within 24 h until day 9 post-treatment. The values of the RI and PI of blood flow within the OA and MUA on the ipsi-lateral and contra-lateral sides of the previous pregnancy were obviously lower (p < 0.05) at 24 h after the administration of EB, and then, started to gradually elevate, reaching the pre-treatment values on day 9 after EB administration. Both the BFR and BFV in the OA and MUA significantly increased from 24 h to 72 h after EB administration on both the ipsi-lateral and contra-lateral sides (p < 0.05); then, their values started to decrease to reach the pretreatment value on day 9 after EB administration. Both E2 and NO concentrations significantly increased (p < 0.05) from 24 h until day 3 after EB injection and then started to decline after that, reaching the pre-treatment value on day 9. In conclusion, the administration of EB enhances the ovarian and uterine blood flow concomitantly with increased levels of NO in PP dairy buffaloes.
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Affiliation(s)
- Haney Samir
- Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt
| | - Hossam R El-Sherbiny
- Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt
| | - Ahmed Ezzat Ahmed
- Biology Department, College of Science, King Khalid University, Abha 61413, Saudi Arabia
| | - Ramya Ahmad Sindi
- Department of Laboratory Medicine, Faculty of Applied Medical Sciences, Umm Al-Qura University, Makkah Al-Mukarramah 24382, Saudi Arabia
| | - Khalid M Al Syaad
- Biology Department, College of Science, King Khalid University, Abha 61413, Saudi Arabia
| | - Elshymaa A Abdelnaby
- Theriogenology Department, Faculty of Veterinary Medicine, Cairo University, Giza 12211, Egypt
- Department of Clinical Sciences, College of Veterinary Medicine, King Faisal University, Alahsa 31982, Saudi Arabia
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2
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Giles GI, Erickson JR, Bussey CT. Photoactivation of tDodSNO induces localized vasodilation in rats: Metabolically stable S-nitrosothiols can act as targeted nitric oxide donors in vivo. Nitric Oxide 2022; 129:53-62. [DOI: 10.1016/j.niox.2022.10.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2022] [Revised: 10/03/2022] [Accepted: 10/04/2022] [Indexed: 11/06/2022]
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3
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Daniele A, Lucas SJE, Rendeiro C. Detrimental effects of physical inactivity on peripheral and brain vasculature in humans: Insights into mechanisms, long-term health consequences and protective strategies. Front Physiol 2022; 13:998380. [PMID: 36237532 PMCID: PMC9553009 DOI: 10.3389/fphys.2022.998380] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2022] [Accepted: 08/25/2022] [Indexed: 11/13/2022] Open
Abstract
The growing prevalence of physical inactivity in the population highlights the urgent need for a more comprehensive understanding of how sedentary behaviour affects health, the mechanisms involved and what strategies are effective in counteracting its negative effects. Physical inactivity is an independent risk factor for different pathologies including atherosclerosis, hypertension and cardiovascular disease. It is known to progressively lead to reduced life expectancy and quality of life, and it is the fourth leading risk factor for mortality worldwide. Recent evidence indicates that uninterrupted prolonged sitting and short-term inactivity periods impair endothelial function (measured by flow-mediated dilation) and induce arterial structural alterations, predominantly in the lower body vasculature. Similar effects may occur in the cerebral vasculature, with recent evidence showing impairments in cerebral blood flow following prolonged sitting. The precise molecular and physiological mechanisms underlying inactivity-induced vascular dysfunction in humans are yet to be fully established, although evidence to date indicates that it may involve modulation of shear stress, inflammatory and vascular biomarkers. Despite the steady increase in sedentarism in our societies, only a few intervention strategies have been investigated for their efficacy in counteracting the associated vascular impairments. The current review provides a comprehensive overview of the evidence linking acute and short-term physical inactivity to detrimental effects on peripheral, central and cerebral vascular health in humans. We further examine the underlying molecular and physiological mechanisms and attempt to link these to long-term consequences for cardiovascular health. Finally, we summarize and discuss the efficacy of lifestyle interventions in offsetting the negative consequences of physical inactivity.
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Affiliation(s)
- Alessio Daniele
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
| | - Samuel J. E. Lucas
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
- Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom
| | - Catarina Rendeiro
- School of Sport, Exercise and Rehabilitation Sciences, University of Birmingham, Birmingham, United Kingdom
- Centre for Human Brain Health, University of Birmingham, Birmingham, United Kingdom
- *Correspondence: Catarina Rendeiro,
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4
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King DR, Hardin KM, Hoeker GS, Poelzing S. Re-evaluating methods reporting practices to improve reproducibility: an analysis of methodological rigor for the Langendorff whole-heart technique. Am J Physiol Heart Circ Physiol 2022; 323:H363-H377. [PMID: 35749719 PMCID: PMC9359653 DOI: 10.1152/ajpheart.00164.2022] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In recent decades, the scientific community has seen an increased interest in rigor and reproducibility. In 2017, concerns of methodological thoroughness and reporting practices were implicated as significant barriers to reproducibility within the preclinical cardiovascular literature, particularly in studies employing animal research. The Langendorff, whole-heart technique has proven to be an invaluable research tool, being modified in a myriad of ways to probe questions across the spectrum of physio- and pathophysiologic function of the heart. As a result, significant variability in the application of the Langendorff technique exists. This literature review quantifies the different methods employed in the implementation of the Langendorff technique and provides brief examples of how individual parametric differences can impact the outcomes and interpretation of studies. From 2017-2020, significant variability of animal models, anesthesia, cannulation time, and perfusate composition, pH, and temperature demonstrate that the technique has diversified to meet new challenges and answer different scientific questions. The review also reveals which individual methods are most frequently reported, even if there is no explicit agreement upon which parameters should be reported. The analysis of methods related to the Langendorff technique suggests a framework for considering methodological approach when interpreting seemingly contradictory results, rather than concluding that results are irreproducible.
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Affiliation(s)
- D Ryan King
- Translational Biology, Medicine, and Health Graduate Program. Virginia Polytechnic Institute and State University. Blacksburg, Virginia.,Dorothy M. Davis Heart and Lunch Research Institute, College of Medicine, The Ohio State University Wexner Medical Center. Columbus, Ohio
| | - Kathryn M Hardin
- Virginia Tech Carilion School of Medicine. Roanoke, Virginia.,Center for Heart and Reparative Medicine Research. Fralin Biomedical Research Institute at Virginia Tech Carilion. Roanoke, Virginia
| | - Gregory S Hoeker
- Center for Heart and Reparative Medicine Research. Fralin Biomedical Research Institute at Virginia Tech Carilion. Roanoke, Virginia
| | - Steven Poelzing
- Virginia Tech Carilion School of Medicine. Roanoke, Virginia.,Center for Heart and Reparative Medicine Research. Fralin Biomedical Research Institute at Virginia Tech Carilion. Roanoke, Virginia.,Department of Biomedical Engineering and Mechanics. Virginia Polytechnic Institute and State University. Blacksburg, Virginia
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5
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Advanced Glycations End Products in the Skin as Biomarkers of Cardiovascular Risk in Type 2 Diabetes. Int J Mol Sci 2022; 23:ijms23116234. [PMID: 35682915 PMCID: PMC9181586 DOI: 10.3390/ijms23116234] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Revised: 05/31/2022] [Accepted: 05/31/2022] [Indexed: 02/01/2023] Open
Abstract
The incidence and prevalence of diabetes are increasing worldwide, and cardiovascular disease (CVD) is the leading cause of death among subjects with type 2 diabetes (T2D). The assessment and stratification of cardiovascular risk in subjects with T2D is a challenge. Advanced glycation end products are heterogeneous molecules produced by non-enzymatic glycation of proteins, lipids, or nucleic acids. Accumulation of advanced glycation end products is increased in subjects with T2D and is considered to be one of the major pathogenic mechanism in developing complications in diabetes. Skin AGEs could be assessed by skin autofluorescence. This method has been validated and related to the presence of micro and macroangiopathy in individuals with type 2 diabetes. In this context, the aim of this review is to critically summarize current knowledge and scientific evidence on the relationship between skin AGEs and CVD in subjects with type 2 diabetes, with a brief reference to other diabetes-related complications.
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6
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Nanda SK. New-onset seizure at high altitude among healthy males. Seizure 2022; 97:82-87. [DOI: 10.1016/j.seizure.2022.03.006] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2021] [Revised: 03/05/2022] [Accepted: 03/07/2022] [Indexed: 11/25/2022] Open
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7
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Alimoradi H, Thomas A, Lyth DDB, Barzegar-Fallah A, Matikonda SS, Gamble AB, Giles GI. SMA-BmobaSNO: an intelligent photoresponsive nitric oxide releasing polymer for drug nanoencapsulation and targeted delivery. NANOTECHNOLOGY 2022; 33:195101. [PMID: 35078165 DOI: 10.1088/1361-6528/ac4eb0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 01/25/2022] [Indexed: 06/14/2023]
Abstract
Nitric oxide (NO) is an important biological signalling molecule that acts to vasodilate blood vessels and change the permeability of the blood vessel wall. Due to these cardiovascular actions, co-administering NO with a therapeutic could enhance drug uptake. However current NO donors are not suitable for targeted drug delivery as they systemically release NO. To overcome this limitation we report the development of a smart polymer, SMA-BmobaSNO, designed to release NO in response to a photostimulus. The polymer's NO releasing functionality is an S-nitrosothiol group that, at 10 mg ml-1, is highly resistant to both thermal (t1/216 d) and metabolic (t1/232 h) decomposition, but rapidly brakes down under photoactivation (2700 W m-2, halogen source) to release NO (t1/225 min). Photoresponsive NO release from SMA-BmobaSNO was confirmed in a cardiovascular preparation, where irradiation resulted in a 12-fold decrease in vasorelaxation EC50(from 5.2μM to 420 nM). To demonstrate the polymer's utility for drug delivery we then used SMA-BmobaSNO to fabricate a nanoparticle containing the probe Nile Red (NR). The resulting SMA-BmobaSNO-NR nanoparticle exhibited spherical morphology (180 nm diameter) and sustained NR release (≈20% over 5 d). Targeted delivery was characterised in an abdominal preparation, where photoactivation (450 W m-2) caused localized increases in vasodilation and blood vessel permeability, resulting in a 3-fold increase in NR uptake into photoactivated tissue. Nanoparticles fabricated from SMA-BmobaSNO therefore display highly photoresponsive NO release and can apply the Trojan Horse paradigm by using endogenous NO signalling pathways to smuggle a therapeutic cargo into target tissue.
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Affiliation(s)
- Houman Alimoradi
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Ansa Thomas
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | - Daniel D B Lyth
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
| | | | | | - Allan B Gamble
- School of Pharmacy, University of Otago, Dunedin, New Zealand
| | - Gregory I Giles
- Department of Pharmacology and Toxicology, School of Biomedical Sciences, University of Otago, Dunedin, New Zealand
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8
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Luo Y, Zhu Y, Basang W, Wang X, Li C, Zhou X. Roles of Nitric Oxide in the Regulation of Reproduction: A Review. Front Endocrinol (Lausanne) 2021; 12:752410. [PMID: 34867795 PMCID: PMC8640491 DOI: 10.3389/fendo.2021.752410] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/03/2021] [Accepted: 10/25/2021] [Indexed: 12/11/2022] Open
Abstract
Nitric oxide (NO) has attracted significant attention as a stellar molecule. Presently, the study of NO has penetrated every field of life science, and NO is widely distributed in various tissues and organs. This review demonstrates the importance of NO in both male and female reproductive processes in numerous ways, such as in neuromodulation, follicular and oocyte maturation, ovulation, corpus luteum degeneration, fertilization, implantation, pregnancy maintenance, labor and menstrual cycle regulation, spermatogenesis, sperm maturation, and reproduction. However, the mechanism of action of some NO is still unknown, and understanding its mechanism may contribute to the clinical treatment of some reproductive diseases.
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Affiliation(s)
- Yuxin Luo
- College of Animal Science, Jilin University, Changchun, China
| | - Yanbin Zhu
- State Key Laboratory of Hulless Barley and Yak Germplasm Resources and Genetic Improvement, Lhasa, China
| | - Wangdui Basang
- State Key Laboratory of Hulless Barley and Yak Germplasm Resources and Genetic Improvement, Lhasa, China
| | - Xin Wang
- College of Animal Science, Jilin University, Changchun, China
| | - Chunjin Li
- College of Animal Science, Jilin University, Changchun, China
| | - Xu Zhou
- College of Animal Science, Jilin University, Changchun, China
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9
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Pantan R, Tocharus J, Nakaew A, Suksamrarn A, Tocharus C. Ethyl Rosmarinate Prevents the Impairment of Vascular Function and Morphological Changes in L-NAME-Induced Hypertensive Rats. MEDICINA (KAUNAS, LITHUANIA) 2019; 55:E777. [PMID: 31817916 PMCID: PMC6956334 DOI: 10.3390/medicina55120777] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/14/2019] [Revised: 12/01/2019] [Accepted: 12/05/2019] [Indexed: 11/16/2022]
Abstract
Background and Objectives: The potent, endothelium-independent, vasorelaxant effect of ethyl rosmarinate, an ester derivative of rosmarinic acid, makes it of interest as an alternative therapeutic agent for use in hypertension. This study was designed to investigate the effect of ethyl rosmarinate on Nω-nitro-L-arginine methyl ester (L-NAME)-induced hypertensive rats. Materials and Methods: L-NAME was given orally to male Wistar rats for 6 weeks to induce hypertension concurrently with treatment of ethyl rosmarinate at 5, 15, or 30 mg/kgor enalapril at 10 mg/kg Systolic blood pressure (SBP), heart rate, and body weight of all experimental groups were recorded weekly, while the vascular sensitivity and histological changes of the aorta were evaluated at the end of the experiment. Results: For all treatment groups, the data indicated that ethyl rosmarinate significantly attenuated the SBP in hypertensive rats induced by L-NAME, with no significant differences in heart rate and body weight. In addition, the response of vascular sensitivity to acetylcholine (ACh) was improved but there was no significant difference in the response to sodium nitroprusside (SNP). Furthermore, the sensitivity of the aorta to phenylephrine (PE) was significantly decreased. The thickness of the aortic wall did not differ between groups but the expression of endothelial nitric oxide synthase (eNOS) was increased in ethyl rosmarinate- and enalapril-treated groups compared with the hypertensive group. Conclusions: Ethyl rosmarinate is an interesting candidate as an alternative treatment for hypertension due to its ability to improve vascular function and to increase the expression of eNOS similar to enalapril which is a drug commonly used in hypertension.
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Affiliation(s)
- Rungusa Pantan
- Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand;
| | - Jiraporn Tocharus
- Department of Physiology, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand
| | - Archawin Nakaew
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand
| | - Apichart Suksamrarn
- Department of Chemistry and Center of Excellence for Innovation in Chemistry, Faculty of Science, Ramkhamhaeng University, Bangkok 10240, Thailand
| | - Chainarong Tocharus
- Department of Anatomy, Faculty of Medicine, Chiang Mai University, Chiang Mai 50200, Thailand;
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10
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Cavero-Redondo I, Soriano-Cano A, Álvarez-Bueno C, Cunha PG, Martínez-Hortelano JA, Garrido-Miguel M, Berlanga-Macías C, Martínez-Vizcaíno V. Skin Autofluorescence-Indicated Advanced Glycation End Products as Predictors of Cardiovascular and All-Cause Mortality in High-Risk Subjects: A Systematic Review and Meta-analysis. J Am Heart Assoc 2019; 7:e009833. [PMID: 30371199 PMCID: PMC6222966 DOI: 10.1161/jaha.118.009833] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Background Chronic deposits of advanced glycation end products produced by enzymatic glycation have been suggested as predictors of atherosclerotic‐related disorders. This study aimed to estimate the relationship between advanced glycation end products indicated by skin autofluorescence levels and the risk of cardiovascular and all‐cause mortality based on data from observational studies. Methods and Results We systematically searched Medline, Embase, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and the Web of Science databases from their inceptions until November 2017 for observational studies addressing the association of advanced glycation end products by skin autofluorescence levels with cardiovascular and all‐cause mortality. The DerSimonian and Laird random‐effects method was used to compute pooled estimates of hazard ratios and their respective 95% confidence intervals for the risk of cardiovascular and all‐cause mortality associated with levels of advanced glycation end products by skin autofluorescence. Ten published studies were included in the systematic review and meta‐analysis. Higher skin autofluorescence levels were significantly associated with a higher pooled risk estimate for cardiovascular mortality (hazard ratio: 2.06; 95% confidence interval, 1.58–2.67), which might not be important to moderate heterogeneity (I2=34.7%; P=0.163), and for all‐cause mortality (hazard ratio: 1.91; 95% confidence interval, 1.42–2.56) with substantial heterogeneity (I2=60.8%; P=0.0.18). Conclusions Our data suggest that skin autofluorescence levels could be considered predictors of all‐cause mortality and cardiovascular mortality in patients at high and very high risk.
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Affiliation(s)
- Ivan Cavero-Redondo
- 1 Universidad de Castilla-La Mancha Health and Social Research Center Cuenca Spain
| | - Alba Soriano-Cano
- 1 Universidad de Castilla-La Mancha Health and Social Research Center Cuenca Spain
| | - Celia Álvarez-Bueno
- 1 Universidad de Castilla-La Mancha Health and Social Research Center Cuenca Spain
| | - Pedro G Cunha
- 2 Center for the Research and Treatment of Arterial Hypertension and Cardiovascular Risk Internal Medicine Department Guimarães Portugal.,3 School of Medicine Minho University Braga Portugal.,4 Life and Health Science Research Institute (ICVS)/3B's PT Government Associate Laboratory Braga/Guimarães Portugal
| | | | | | | | - Vicente Martínez-Vizcaíno
- 1 Universidad de Castilla-La Mancha Health and Social Research Center Cuenca Spain.,5 Universidad Autónoma de Chile Facultad de Ciencias de la Salud Talca Chile
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11
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Alimoradi H, Barzegar-Fallah A, Sammut IA, Greish K, Giles GI. Encapsulation of tDodSNO generates a photoactivated nitric oxide releasing nanoparticle for localized control of vasodilation and vascular hyperpermeability. Free Radic Biol Med 2019; 130:297-305. [PMID: 30367997 DOI: 10.1016/j.freeradbiomed.2018.10.433] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/14/2018] [Revised: 10/07/2018] [Accepted: 10/18/2018] [Indexed: 11/25/2022]
Abstract
We report the synthesis and characterization of a photoactive nitric oxide (NO) releasing nanoparticle (NP) by encapsulation of the NO donor tert-dodecane S-nitrosothiol (tDodSNO) into a co-polymer of styrene and maleic anhydride (SMA) to afford SMA-tDodSNO. Encapsulation did not affect tDodSNO's stability or NO release profile, but imparted water solubility and protection from degradation reactions with glutathione. Under photoactivation the NP acted as a potent NO donor, with photoactivation acting as a switch to induce localized vasodilation in aortic rings (EC50* 660 nM at 2700 W/m2) and cause vascular hyperpermeability in mesenteric beds (8-fold increase in dye uptake at 1 µM SMA-tDodSNO with 460 W/m2 photoactivation). The NP was markedly superior as a photoactive NO donor in comparison to the S-nitrosothiols GSNO and SNAP, which are commonly used in experimental studies, as well as sodium nitroprusside, a clinically used vasodilator. Future development of this NP may find wide ranging therapeutic applications for treating cardiovascular disease and other disorders related to NO signaling, as well as enhancing macromolecular drug delivery to target organs through selective hyperpermeability. Supporting information describing the biophysical characterization of SMA-tDodSNO is supplied in an accompanying Data in Brief article (Alimoradi et al., doi: 10.1016/j.dib.2018.10.149).
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Affiliation(s)
- Houman Alimoradi
- Department of Pharmacology and Toxicology, University of Otago, Dunedin, New Zealand
| | - Anita Barzegar-Fallah
- Department of Pharmacology and Toxicology, University of Otago, Dunedin, New Zealand
| | - Ivan A Sammut
- Department of Pharmacology and Toxicology, University of Otago, Dunedin, New Zealand
| | - Khaled Greish
- College of Medicine and Medical Sciences, Department of Molecular Medicine, Nanomedicine Unit, Princess Al-Jawhara Center for Molecular Medicine and Inherited Disorders, Arabian Gulf University, Manama, Bahrain
| | - Gregory I Giles
- Department of Pharmacology and Toxicology, University of Otago, Dunedin, New Zealand.
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12
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Komatsu S, Kitazawa T, Ikebe M. Visualization of stimulus-specific heterogeneous activation of individual vascular smooth muscle cells in aortic tissues. J Cell Physiol 2018; 233:434-446. [PMID: 28295256 PMCID: PMC5741290 DOI: 10.1002/jcp.25903] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2017] [Accepted: 03/09/2017] [Indexed: 11/11/2022]
Abstract
Intercellular communication among autonomic nerves, endothelial cells (ECs), and vascular smooth muscle cells (VSMCs) plays a central role in an uninterrupted regulation of blood flow through vascular contractile machinery. Impairment of this communication is linked to development of vascular diseases such as hypertension, cerebral/coronary vasospasms, aortic aneurism, and erectile dysfunction. Although the basic concept of the communication as a whole has been studied, the spatiotemporal correlation of ECs/VSMCs in tissues at the cellular level is unknown. Here, we show a unique VSMC response to ECs during contraction and relaxation of isolated aorta tissues through visualization of spatiotemporal activation patterns of smooth muscle myosin II. ECs in the intimal layer dictate the stimulus-specific heterogeneous activation pattern of myosin II in VSMCs within distinct medial layers. Myosin light chain (MLC) phosphorylation (active form of myosin II) gradually increases towards outer layers (approximately threefold higher MLC phosphorylation at the outermost layer than that of the innermost layer), presumably by release of an intercellular messenger, nitric oxide (NO). Our study also demonstrates that the MLC phosphorylation at the outermost layer in spontaneously hypertensive rats (SHR) during NO-induced relaxation is quite high and approximately 10-fold higher than that of its counterpart, the Wister-Kyoto rats (WKY), suggesting that the distinct pattern of myosin II activation within tissues is important for vascular protection against elevated blood pressure.
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MESH Headings
- Animals
- Aorta, Thoracic/metabolism
- Aorta, Thoracic/physiology
- Biomarkers
- Cell Communication
- Disease Models, Animal
- Endothelial Cells/metabolism
- Endothelial Cells/physiology
- Fluorescent Antibody Technique
- Hypertension/metabolism
- Hypertension/physiopathology
- In Vitro Techniques
- Microscopy, Fluorescence
- Muscle, Smooth, Vascular/metabolism
- Muscle, Smooth, Vascular/physiology
- Myocytes, Smooth Muscle/metabolism
- Myocytes, Smooth Muscle/physiology
- Myosin Light Chains/metabolism
- Myosin Type II/metabolism
- Nitric Oxide/metabolism
- Phosphorylation
- Rats, Inbred SHR
- Rats, Inbred WKY
- Time Factors
- Vasoconstriction
- Vasodilation
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Affiliation(s)
- Satoshi Komatsu
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Toshio Kitazawa
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
| | - Mitsuo Ikebe
- Department of Cellular and Molecular Biology, The University of Texas Health Science Center at Tyler, Tyler, Texas
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13
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Contreras GF, Castillo K, Enrique N, Carrasquel-Ursulaez W, Castillo JP, Milesi V, Neely A, Alvarez O, Ferreira G, González C, Latorre R. A BK (Slo1) channel journey from molecule to physiology. Channels (Austin) 2013; 7:442-58. [PMID: 24025517 DOI: 10.4161/chan.26242] [Citation(s) in RCA: 121] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Calcium and voltage-activated potassium (BK) channels are key actors in cell physiology, both in neuronal and non-neuronal cells and tissues. Through negative feedback between intracellular Ca (2+) and membrane voltage, BK channels provide a damping mechanism for excitatory signals. Molecular modulation of these channels by alternative splicing, auxiliary subunits and post-translational modifications showed that these channels are subjected to many mechanisms that add diversity to the BK channel α subunit gene. This complexity of interactions modulates BK channel gating, modifying the energetic barrier of voltage sensor domain activation and channel opening. Regions for voltage as well as Ca (2+) sensitivity have been identified, and the crystal structure generated by the 2 RCK domains contained in the C-terminal of the channel has been described. The linkage of these channels to many intracellular metabolites and pathways, as well as their modulation by extracellular natural agents, has been found to be relevant in many physiological processes. This review includes the hallmarks of BK channel biophysics and its physiological impact on specific cells and tissues, highlighting its relationship with auxiliary subunit expression.
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Affiliation(s)
- Gustavo F Contreras
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile; Doctorado en Ciencias mención Neurociencia; Universidad de Valparaíso; Valparaíso, Chile
| | - Karen Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile
| | - Nicolás Enrique
- Grupo de Investigación en Fisiología Vascular (GINFIV); Universidad Nacional de la Plata; La Plata, Argentina
| | - Willy Carrasquel-Ursulaez
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile; Doctorado en Ciencias mención Neurociencia; Universidad de Valparaíso; Valparaíso, Chile
| | - Juan Pablo Castillo
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile; Facultad de Ciencias; Universidad de Chile; Santiago, Chile
| | - Verónica Milesi
- Grupo de Investigación en Fisiología Vascular (GINFIV); Universidad Nacional de la Plata; La Plata, Argentina
| | - Alan Neely
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile
| | | | - Gonzalo Ferreira
- Laboratorio de Canales Iónicos; Departamento de Biofísica; Facultad de Medicina; Universidad de la República; Montevideo, Uruguay
| | - Carlos González
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile
| | - Ramón Latorre
- Centro Interdisciplinario de Neurociencia de Valparaíso; Facultad de Ciencias; Universidad de Valparaíso; Valparaíso, Chile
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14
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The promise of inhibition of smooth muscle tone as a treatment for erectile dysfunction: where are we now? Int J Impot Res 2011; 24:49-60. [PMID: 21975566 DOI: 10.1038/ijir.2011.49] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Ten years ago, the inhibition of Rho kinase by intracavernosal injection of Y-27632 was found to induce an erectile response. This effect did not require activation of nitric oxide-mediated signaling, introducing a novel target pathway for the treatment of erectile dysfunction (ED), with potential added benefit in cases where nitric oxide bioavailability is attenuated (and thus phosphodiesterase type 5 (PDE5) inhibitors are less efficacious). Rho-kinase antagonists are currently being developed and tested for a wide range of potential uses. The inhibition of this calcium-sensitizing pathway results in blood vessel relaxation. It is also possible that blockade of additional smooth muscle contractile signaling mechanisms may have the same effect. In this review, we conducted an extensive search of pertinent literature using PUBMED. We have outlined the various pathways involved in the maintenance of penile smooth muscle tone and discussed the current potential benefit for the pharmacological inhibition of these targets for the treatment of ED.
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15
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Blain AM, Straub VW. δ-Sarcoglycan-deficient muscular dystrophy: from discovery to therapeutic approaches. Skelet Muscle 2011; 1:13. [PMID: 21798091 PMCID: PMC3156636 DOI: 10.1186/2044-5040-1-13] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2010] [Accepted: 03/17/2011] [Indexed: 11/10/2022] Open
Abstract
Mutations in the δ-sarcoglycan gene cause limb-girdle muscular dystrophy 2F (LGMD2F), an autosomal recessive disease that causes progressive weakness and wasting of the proximal limb muscles and often has cardiac involvement. Here we review the clinical implications of LGMD2F and discuss the current understanding of the putative mechanisms underlying its pathogenesis. Preclinical research has benefited enormously from various animal models of δ-sarcoglycan deficiency, which have helped researchers to explore therapeutic approaches for both muscular dystrophy and cardiomyopathy.
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Affiliation(s)
- Alison M Blain
- Institute of Genetic Medicine, Newcastle University, International Centre for Life, Central Parkway, Newcastle upon Tyne, NE1 3BZ, UK
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16
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TRC4186, a Novel AGE-breaker, Improves Diabetic Cardiomyopathy and Nephropathy in Ob-ZSF1 Model of Type 2 Diabetes. J Cardiovasc Pharmacol 2009; 54:72-81. [DOI: 10.1097/fjc.0b013e3181ac3a34] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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17
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Abstract
Cellular hypoxia is the common final pathway of brain injury that occurs not just after asphyxia, but also when cerebral perfusion is impaired directly (eg, embolic stroke) or indirectly (eg, raised intracranial pressure after head injury). We Review recent advances in the understanding of neurological clinical syndromes that occur on exposure to high altitudes, including high altitude headache (HAH), acute mountain sickness (AMS), and high altitude cerebral oedema (HACE), and the genetics, molecular mechanisms, and physiology that underpin them. We also present the vasogenic and cytotoxic bases for HACE and explore venous hypertension as a possible contributory factor. Although the factors that control susceptibility to HACE are poorly understood, the effects of exposure to altitude (and thus hypobaric hypoxia) might provide a reproducible model for the study of cerebral cellular hypoxia in healthy individuals. The effects of hypobaric hypoxia might also provide new insights into the understanding of hypoxia in the clinical setting.
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Affiliation(s)
- Mark H Wilson
- Centre for Altitude, Space and Extreme Environment Medicine, University College London, London, UK.
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18
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Hartog JWL, Voors AA, Bakker SJL, Smit AJ, van Veldhuisen DJ. Advanced glycation end-products (AGEs) and heart failure: pathophysiology and clinical implications. Eur J Heart Fail 2008; 9:1146-55. [PMID: 18023248 DOI: 10.1016/j.ejheart.2007.09.009] [Citation(s) in RCA: 194] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/19/2007] [Revised: 08/01/2007] [Accepted: 09/26/2007] [Indexed: 12/29/2022] Open
Abstract
Advanced glycation end-products (AGEs) are molecules formed during a non-enzymatic reaction between proteins and sugar residues, called the Maillard reaction. AGEs accumulate in the human body with age, and accumulation is accelerated in the presence of diabetes mellitus. In patients with diabetes, AGE accumulation is associated with the development of cardiac dysfunction. Enhanced AGE accumulation is not restricted to patients with diabetes, but can also occur in renal failure, enhanced states of oxidative stress, and by an increased intake of AGEs. Several lines of evidence suggest that AGEs are related to the development and progression of heart failure in non-diabetic patients as well. Preliminary small intervention studies with AGE cross-link breakers in heart failure patients have shown promising results. In this review, the role of AGEs in the development of heart failure and the role of AGE intervention as a possible treatment for heart failure are discussed.
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Affiliation(s)
- Jasper W L Hartog
- Department of Cardiology, Thoraxcenter, University Medical Center Groningen and University of Groningen, Hanzeplein 1, 9700 RB, Groningen, The Netherlands.
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19
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Brugniaux JV, Hodges ANH, Hanly PJ, Poulin MJ. Cerebrovascular responses to altitude. Respir Physiol Neurobiol 2007; 158:212-23. [PMID: 17544954 DOI: 10.1016/j.resp.2007.04.008] [Citation(s) in RCA: 85] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2007] [Revised: 04/17/2007] [Accepted: 04/19/2007] [Indexed: 10/23/2022]
Abstract
The regulation of cerebral blood flow (CBF) is a complex process that is altered significantly with altitude exposure. Acute exposure produces a marked increase in CBF, in proportion to the severity of the hypoxia and mitigated by hyperventilation-induced hypocapnia when CO(2) is uncontrolled. A number of mediators contribute to the hypoxia-induced cerebral vasodilation, including adenosine, potassium channels, substance P, prostaglandins, and NO. Upon acclimatization to altitude, CBF returns towards normal sea-level values in subsequent days and weeks, mediated by a progressive increase in PO2, first through hyperventilation followed by erythropoiesis. With long-term altitude exposure, a number of mechanisms play a role in regulating CBF, including acid-base balance, hematological modifications, and angiogenesis. Finally, several cerebrovascular disorders are associated with altitude exposure. Existing gaps in our knowledge of CBF and altitude, and areas of future investigation include effects of longer exposures, intermittent hypoxia, and gender differences in the CBF responses to altitude.
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Affiliation(s)
- Julien V Brugniaux
- Department of Physiology & Biophysics, University of Calgary, Calgary, Alberta T2N 4N1, Canada
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20
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Fryer RM, Segreti JA, Widomski DL, Franklin PH, Banfor PN, Koch KA, Nakane M, Wu-Wong JR, Cox BF, Reinhart GA. Systemic activation of the calcium sensing receptor produces acute effects on vascular tone and circulatory function in uremic and normal rats: focus on central versus peripheral control of vascular tone and blood pressure by cinacalcet. J Pharmacol Exp Ther 2007; 323:217-26. [PMID: 17636005 DOI: 10.1124/jpet.107.123901] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Calcium-sensing receptor (CaR) activation decreases serum parathyroid hormone (PTH) and Ca2+ and, despite long-term reductions in mean arterial blood pressure (MAP), may produce acute hypertension in rats, an effect we hypothesized was mediated by constriction of multiple vascular beds. Rats were subjected to 5/6 nephrectomy (NX) or no surgery (Normal); at 7 to 8 weeks, uremia animals were anesthetized and instrumented to record MAP and regional blood flow (carotid, mesenteric, and hindlimb). Cinacalcet [N-(1-naphthalen-1-ylethyl)-3-[3-(trifluoromethyl)phenyl]-propan-1-amine; 1, 3, and 10 mg/kg; 30 min/dose] was infused over 90 min. In NX rats, cinacalcet dose-dependently decreased ionized calcium (iCa2+), elicited a 90% reduction in PTH, and produced dose-dependent self-limiting increases in MAP (from 119 +/- 6 to 129 +/- 5, 142 +/- 4, and 145 +/- 3 mm Hg at the end of each infusion). At 1 mg/kg, carotid vascular resistance (CVR) and mesenteric vascular resistance (MVR) increased to 16 +/- 6 and 18 +/- 6% above baseline, respectively. Hindlimb vascular resistance (HVR) also trended upward (13 +/- 8%). At 3 mg/kg, increases in CVR (38 +/- 10%), MVR (40 +/- 8%), and HVR (39 +/- 14%) were exacerbated; at 10 mg/kg, values remained at or near these levels. The effects of cinacalcet in Normal rats were similar to NX and were attenuated by ganglionic blockade with hexamethonium at low doses but remained significantly elevated at higher doses. Thus, CaR activation acutely increases MAP in uremic and nonuremic rats, responses that occur in parallel to vasoconstriction in multiple vascular beds through both a central and peripheral mechanism of action. Moreover, subsequent mechanistic studies suggest that increases in MAP produced by cinacalcet may be mediated by reduced tonic NO synthase-dependent NO production subsequent to reductions in blood iCa2+.
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Affiliation(s)
- Ryan M Fryer
- Integrative Pharmacology, Global Pharmaceutical Research and Development, Abbott Laboratories, 100 Abbott Park Road, Abbott Park, IL 60064-6119, USA.
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21
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Affiliation(s)
- Paul McDonough
- Department of Internal Medicine, University of Texas Southwestern Medical CenterDallas, TX 75390, USA
| | - Andrew M Jones
- School of Sport and Health Sciences, University of ExeterExeter EX1 2LU, UK
| | - David C Poole
- Departments of Kinesiology, Anatomy and Physiology, Kansas State UniversityManhattan, KS 66506-5802, USA
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22
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Møllerløkken A, Berge VJ, Jørgensen A, Wisløff U, Brubakk AO. Effect of a short-acting NO donor on bubble formation from a saturation dive in pigs. J Appl Physiol (1985) 2006; 101:1541-5. [PMID: 16857861 DOI: 10.1152/japplphysiol.01191.2005] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
It has previously been reported that a nitric oxide (NO) donor reduces bubble formation from an air dive and that blocking NO production increases bubble formation. The present study was initiated to see whether a short-acting NO donor (glycerol trinitrate, 5 mg/ml; Nycomed Pharma) given immediately before start of decompression would affect the amount of vascular bubbles during and after decompression from a saturation dive in pigs. A total of 14 pigs (Sus scrofa domestica of the strain Norsk landsvin) were randomly divided into an experimental (n = 7) and a control group (n = 7). The pigs were anesthetized with ketamine and alpha-chloralose and compressed in a hyperbaric chamber to 500 kPa (40 m of seawater) in 2 min, and they had 3-h bottom time while breathing nitrox (35 kPa O(2)). The pigs were all decompressed to the surface (100 kPa) at a rate of 200 kPa/h. During decompression, the inspired Po(2) of the breathing gas was kept at 100 kPa. Thirty minutes before decompression, the experimental group received a short-acting NO donor intravenously, while the control group were given equal amounts of saline. The average number of bubbles seen during the observation period decreased from 0.2 to 0.02 bubbles/cm(2) (P < 0.0001) in the experimental group compared with the controls. The present study gives further support to the role of NO in preventing vascular bubble formation after decompression.
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Affiliation(s)
- A Møllerløkken
- Department of Circulation and Medical Imaging, Faculty of Medicine, Norwegian University of Science and Technology, Olav Kyrres gt. 3, N-7489 Trondheim, Norway.
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23
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Kim NN, Stankovic M, Cushman TT, Goldstein I, Munarriz R, Traish AM. Streptozotocin-induced diabetes in the rat is associated with changes in vaginal hemodynamics, morphology and biochemical markers. BMC PHYSIOLOGY 2006; 6:4. [PMID: 16734901 PMCID: PMC1481539 DOI: 10.1186/1472-6793-6-4] [Citation(s) in RCA: 57] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2006] [Accepted: 05/30/2006] [Indexed: 12/26/2022]
Abstract
Background Diabetes is associated with declining sexual function in women. However, the effects of diabetes on genital tissue structure, innervation and function remains poorly characterized. In control and streptozotocin-treated female rats, we investigated the effects of diabetes on vaginal blood flow, tissue morphology, and expression of arginase I, endothelial nitric oxide synthase (eNOS) and cGMP-dependent protein kinase (PKG), key enzymes that regulate smooth muscle relaxation. We further related these changes with estrogen receptor alpha (ERα) and androgen receptor (AR) expression. Results In addition to significantly elevated blood glucose levels, diabetic rats had decreased mean body weight, lower levels of plasma estradiol, and higher plasma testosterone concentration, compared to age-matched controls. Eight weeks after administration of buffer (control) or 65 mg/kg of streptozotocin (diabetic), the vaginal blood flow response to pelvic nerve stimulation was significantly reduced in diabetic rats. Histological examination of vaginal tissue from diabetic animals showed reduced epithelial thickness and atrophy of the muscularis layer. Diabetic animals also had reduced vaginal levels of eNOS and arginase I, but elevated levels of PKG, as assessed by Western blot analyses. These alterations were accompanied by a reduction in both ERα and AR in nuclear extracts of vaginal tissue from diabetic animals. Conclusion In ovariectomized (estrogen deficient) animals, previous reports from our lab and others have documented changes in blood flow, tissue structure, ERα, arginase I and eNOS that parallel those observed in diabetic rats. We hypothesize that diabetes may lead to multiple disruptions in sex steroid hormone synthesis, metabolism and action. These pathological events may cause dramatic changes in tissue structure and key enzymes that regulate cell growth and smooth muscle contractility, ultimately affecting the genital response during sexual arousal.
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Affiliation(s)
- Noel N Kim
- Institute for Sexual Medicine, Department of Urology, Boston University School of Medicine, Boston, USA
| | - Miljan Stankovic
- Institute for Sexual Medicine, Department of Urology, Boston University School of Medicine, Boston, USA
| | - Tulay T Cushman
- Department of Anatomy and Neurobiology, Boston University School of Medicine, Boston, USA
| | - Irwin Goldstein
- Institute for Sexual Medicine, Department of Urology, Boston University School of Medicine, Boston, USA
| | - Ricardo Munarriz
- Institute for Sexual Medicine, Department of Urology, Boston University School of Medicine, Boston, USA
| | - Abdulmaged M Traish
- Institute for Sexual Medicine, Department of Urology, Boston University School of Medicine, Boston, USA
- Department of Biochemistry, Boston University School of Medicine, Boston, USA
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24
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Scipioni A, Stefanini S, Santone R, Giorgi M. Immunohistochemical localisation of PDE5 in Leydig and myoid cells of prepuberal and adult rat testis. Histochem Cell Biol 2005; 124:401-7. [PMID: 16163485 DOI: 10.1007/s00418-005-0057-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/03/2005] [Indexed: 10/25/2022]
Abstract
Expression of phosphodiesterase 5 (PDE5) in the rat testis at several pre and postnatal developmental stages was investigated by immunohistochemistry. The enzyme was localised in vascular smooth muscle cells, as well as in Leydig and peritubular cells. The latter were identified as myoid, based on their immunoreactivity to desmin and alpha-smooth muscle actin. The presence of PDE5 in myoid cells was confirmed by Western blot analysis and immunohistochemistry performed on highly purified cell fractions, obtained from 16-day-old rats. The expression of PDE5 in these somatic cells of rat testis is discussed in view of the roles played by cGMP signal transduction pathways in the mammalian male reproductive function.
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MESH Headings
- 3',5'-Cyclic-GMP Phosphodiesterases/metabolism
- Actins/metabolism
- Animals
- Animals, Newborn
- Biomarkers/metabolism
- Blotting, Western
- Cell Fractionation
- Cyclic Nucleotide Phosphodiesterases, Type 5
- Fetal Development/physiology
- Fluorescent Antibody Technique, Indirect
- Gestational Age
- Immunoenzyme Techniques
- Leydig Cells/cytology
- Leydig Cells/enzymology
- Male
- Muscle, Smooth, Vascular/cytology
- Muscle, Smooth, Vascular/enzymology
- Rats
- Rats, Wistar
- Seminiferous Tubules/cytology
- Seminiferous Tubules/metabolism
- Testis/embryology
- Testis/enzymology
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Affiliation(s)
- Angela Scipioni
- Department of Cellular and Developmental Biology, University La Sapienza, Piazzale Aldo Moro 5, Rome, 00185, Italy
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25
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de Miranda Cará A, Fregonesi A, Antunes E, De Nucci G, Rodrigues Netto N. Role of adenosine triphosphate-dependent potassium channels in canine penile erection. Urology 2005; 64:603-7. [PMID: 15351617 DOI: 10.1016/j.urology.2004.04.044] [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: 02/05/2004] [Accepted: 04/23/2004] [Indexed: 10/26/2022]
Abstract
OBJECTIVES To define the physiologic role and hemodynamic features of nitric oxide (NO) and the adenosine triphosphate (ATP)-dependent K(+) (K(ATP)) channel in canine penile erection. METHODS Mongrel dogs were anesthetized, and penile erection was induced by electrical stimulation of the pelvic nerve. Changes in the intracavernous pressure (ICP) were measured with a transducer. RESULTS The basal ICP was 12.8 +/- 5.0 mm Hg. Pelvic nerve stimulation (5 to 20 V, 5 to 15 Hz, for 1-minute intervals) significantly increased the ICP to 86.2 +/- 11.4 mm Hg (n = 5, P <0.05). Treatment with the NO synthase inhibitor N(omega)-nitro-L-arginine methyl ester (10 mg/kg intravenously) abolished this increase (15.4 +/- 5.0 mm Hg, n = 5). Intracavernous injection of the K(ATP) channel opener cromakalim (3 and 10 microg) increased the ICP (103 +/- 14.4 mm Hg and 106 +/- 12.1 mm Hg, respectively; n = 4). This response was abolished by the prior intracavernous injection of the selective K(ATP) channel-specific blocker glibenclamide (10 mg). Glibenclamide did not affect the increase in ICP induced by electric stimulation of the pelvic nerve (88 +/- 24.2 mm Hg). CONCLUSIONS Our results indicate that relaxation of canine cavernous smooth muscle and penile tumescence are mediated by NO. The failure of glibenclamide to affect the increase in ICP induced by pelvic nerve stimulation suggests that ATP-dependent K(+) channels probably do not play a physiologic role in canine penile erection.
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Affiliation(s)
- Alister de Miranda Cará
- Discipline of Urology, State University of Campinas Faculty of Medical Sciences, Campinas, São Paulo, Brazil
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26
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Linder AE, McCluskey LP, Cole KR, Lanning KM, Webb RC. Dynamic association of nitric oxide downstream signaling molecules with endothelial caveolin-1 in rat aorta. J Pharmacol Exp Ther 2005; 314:9-15. [PMID: 15778264 DOI: 10.1124/jpet.105.083634] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Classically, nitric oxide (NO) formed by endothelial NO synthase (eNOS) freely diffuses from its generation site to smooth muscle cells where it activates soluble guanylyl cyclase (sGC), producing cGMP. Subsequently, cGMP activates both cGMP- and cAMP-dependent protein kinases [cGMP-dependent protein kinase (PKG) and cAMP-dependent protein kinase (PKA), respectively], leading to smooth muscle relaxation. In endothelial cells, eNOS has been localized to caveolae, small invaginations of the plasma membrane rich in cholesterol. Membrane cholesterol depletion impairs acetylcholine (ACh)-induced relaxation due to alteration in caveolar structure. Given the nature of NO to be more soluble in a hydrophobic environment than in water, and assuming that colocalization of components in a signal transduction cascade seems to be a critical determinant of signaling efficiency by eNOS activation, we hypothesize that sGC, PKA, and PKG activation may occur at the plasma membrane caveolae. In endothelium-intact rat aortic rings, the relaxation induced by ACh, by the sGC activator 3-(5'-hydroxymethyl-2'furyl)-1-benzyl indazole (YC-1), and by 8-bromo-cGMP was impaired in the presence of methyl-beta-cyclodextrin, a drug that disassembles caveolae by sequestering cholesterol from the membrane. sGC, PKG, and PKA were colocalized with caveolin-1 in aortic endothelium, and this colocalization was abolished by methyl-beta-cyclodextrin. Methyl-beta-cyclodextrin efficiently disassembled caveolae in endothelium. In summary, our results provide evidence of compartmentalization of sGC, PKG, and PKA in endothelial caveolae contributing to NO signaling cascade, giving new insights by which the endothelium mediates vascular smooth muscle relaxation.
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Affiliation(s)
- A Elizabeth Linder
- Medical College of Georgia, Department of Physiology (CA-3101), 1120 Fifteenth St., Augusta, GA 30912-3000, USA.
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27
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de Laforcade AM, Freeman LM, Rush JE. Serum nitrate and nitrite in dogs with spontaneous cardiac disease. J Vet Intern Med 2003; 17:315-8. [PMID: 12774972 DOI: 10.1111/j.1939-1676.2003.tb02454.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
The purpose of this study was to determine whether nitric oxide (NO) concentrations are high in dogs with chronic valvular disease (CVD) and dilated cardiomyopathy (DCM) compared to healthy controls and to determine whether NO concentrations are correlated with type of cardiac disease, disease severity, medical therapy, or serum tumor necrosis factor (TNF) and interleukin-1 (IL-1). Blood was collected from 32 dogs with DCM, from 10 dogs with CVD, and from 10 healthy controls. Indirect determination of NO concentrations was performed by a commercial photoabsorbance assay that uses a Greiss reagent to measure the concentration of nitrite and nitrate (NN), end products of NO metabolism. TNF and IL-1 activities were measured by bioassay. Mean NN concentrations were significantly higher in dogs with heart disease (median, 4.57 microM; range, 0.00-31.05 microM) than in controls (median, 0.00 microM; range, 0.00-6.16 microM; P = .04). NN concentrations in dogs with cardiac disease were not correlated with type or severity of cardiac disease, medication type, or TNF and IL-1 concentrations. NN concentrations were inversely correlated with fractional shortening. The results of this study suggest that metabolites of NO are increased in some dogs with cardiac disease, but these increases appear to be independent of disease severity, TNF and IL-1 concentrations, and type of pharmacologic intervention.
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Affiliation(s)
- Armelle M de Laforcade
- Department of Clinical Sciences, Tufts University School of Veterinary Medicine, North Grafton, MA 01536, USA.
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28
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Chitaley K, Webb RC, Mills TM. The ups and downs of Rho-kinase and penile erection: upstream regulators and downstream substrates of rho-kinase and their potential role in the erectile response. Int J Impot Res 2003; 15:105-9. [PMID: 12789389 DOI: 10.1038/sj.ijir.3900964] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the absence of arousal stimuli, the activity of the Rho-kinase-mediated signaling pathway promotes vasoconstriction of the cavernosal arterioles and sinuses, keeping the penis in the nonerect state. Upon sexual arousal or during nocturnal tumescence, nitric oxide (NO), released from nonadrenergic/noncholinergic nerves or from local endothelial cells, induces cavernosal vasodilation, resulting in an elevation in blood flow and intracavernosal pressure to initiate the erectile response. Although NO is thought to be the principal stimulator of penile erection, the signaling mechanism(s) of NO-mediated cavernosal vasodilation is unknown. In this article, we will consider the novel hypothesis that NO induces penile erection through the inhibition of endogenous Rho-kinase-mediated vasoconstriction. Additionally, we will look downstream of Rho-kinase, introducing a potential role for various substrates in the mechanism of Rho-kinase-mediated constriction in the cavernosal vasculature.
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Affiliation(s)
- K Chitaley
- Department of Physiology, University of Michigan, Ann Arbor, Michigan, USA.
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29
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Abstract
Pulmonary involvement is common in patients with portal hypertension and can manifest in diverse manners. Changes in pulmonary arterial resistance, manifesting either as the hepatopulmonary syndrome or portopulmonary hypertension (PPHTN), have been increasingly recognized in these patients in recent years. This review summarizes the clinicopathologic features, diagnostic criteria, as well as the latest concepts in the pathogenesis and management of PPHTN, which is defined as an elevated pulmonary artery pressure in the setting of an increased pulmonary vascular resistance and a normal wedge pressure in a patient with portal hypertension.
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Affiliation(s)
- Rohit Budhiraja
- Pulmonary and Critical Care Division, Department of Medicine, Tufts-New England Medical Center, Tufts University School of Medicine, Boston, MA, USA
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30
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DeFeudis FV. Effects ofGinkgo biloba extract (EGb 761) on gene expression: Possible relevance to neurological disorders and age-associated cognitive impairment. Drug Dev Res 2003. [DOI: 10.1002/ddr.10151] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
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31
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Abstract
nNOS, anchored to the sarcolemma through its interactions with the dystrophin-glycoprotein complex, is dramatically reduced in dystrophin-deficient mdx mice and Duchenne muscular dystrophy patients. Recent evidence suggests that loss of nNOS in dystrophin-deficient muscle may contribute significantly to the progression of muscle pathology through a variety of mechanisms. To investigate whether nNOS plays a role in other forms of muscular dystrophy, we analyzed protein expression of nNOS in several sarcoglycan-deficient animal models of muscular dystrophy as well as patients with primary mutations in the sarcoglycan genes. Primary mutations in alpha-, beta-, delta-, and gamma-sarcoglycan result in autosomal recessive limb girdle muscular dystrophy (AR-LGMD). We report that loss of the sarcoglycan-sarcospan complex in muscle causes a dramatic reduction in the levels of nNOS expression at the membrane, even in the presence of normal dystrophin and syntrophin expression. Furthermore, we show that expression of three out of four sarcoglycans is not sufficient to maintain nNOS at the sarcolemma. Our data suggest that loss of nNOS may contribute to muscle pathology in AR-LGMD with primary mutations in the sarcoglycans.
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Affiliation(s)
- Rachelle H Crosbie
- Howard Hughes Medical Institute, Department of Physiology and Biophysics, University of Iowa College of Medicine, Iowa City, Iowa 52242, USA
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Xian M, Fujiwara N, Wen Z, Cai T, Kazuma S, Janczuk AJ, Tang X, Telyatnikov VV, Zhang Y, Chen X, Miyamoto Y, Taniguchi N, Wang PG. Novel substrates for nitric oxide synthases. Bioorg Med Chem 2002; 10:3049-55. [PMID: 12110328 DOI: 10.1016/s0968-0896(02)00155-4] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Enzymatic generation of nitric oxide (NO) by nitric oxide synthase (NOS) consists of two oxidation steps. The first step converts L-arginine to N(G)-hydroxy-L-arginine (NOHA), a key intermediate, and the second step converts NOHA to NO and L-citrulline. To fully probe the substrate specificity of the second enzymatic step, an extensive structural screening was carried out using a series of N-alkyl (and N-aryl) substituted-N'-hydroxyguanidines (1-14). Among the eleven N-alkyl-N'-hydroxyguanidines evaluated, N-n-propyl (2), N-iso-propyl (3), N-n-butyl (4), N-s-butyl (5), N-iso-butyl (6), N-pentyl (8) and N-iso-pentyl (9) derivatives were efficiently oxidized by the three isoenzymes of NOS (nNOS, iNOS and eNOS) to generate NO. N-Butyl-N'-hydroxyguanidine (4) was the best substrate for iNOS (K(m)=33 microM) and N-iso-propyl-N'-hydroxyguanidine (3) was the best substrate for nNOS (K(m)=56 microM). When the alkyl substituents were too small (such as ethyl 1) or too large (such as hexyl 10 and cyclohexyl 11), the activity decreased significantly. This suggests that the van der Waals interaction between the alkyl group and the hydrophobic cavity in the NOS active site contributes significantly to the relative reactivity of compounds 3-11. Moreover, five N-aryl-N'-hydroxyguanidines were found to be good substrates for iNOS, but not substrates for eNOS and nNOS. N-phenyl-N'-hydroxyguanidine was the best substrate among them (K(m)=243 microM). This work demonstrates that N-alkyl substituted hydroxyguanidine compounds are novel NOS substrates which 'short-circuit' the first oxidation step of NOS, and N-aryl substituted hydroxyguanidine compounds are isoform selective NOS substrate.
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Affiliation(s)
- Ming Xian
- Department of Chemistry, Wayne State University, Detroit, MI 48202, USA
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Abstract
Acute administration of cadmium (Cd) to rats results in hepatotoxicity. Recent reports indicate that Kupffer cells, the resident macrophages of the liver, participate in the manifestation of Cd-induced hepatotoxicity. Nitric oxide (NO) is a reactive nitrogen radical produced by activated Kupffer cells via the induction of inducible nitric oxide synthase (iNOS). Nitric oxide can combine with superoxide to form peroxynitrite, a molecule that may participate in the toxic mechanisms of hepatotoxins, such as acetaminophen and bacterial endotoxin. It has been speculated that Cd also may exert its hepatotoxicity, in part, via the production of NO by iNOS. Therefore, this study was undertaken to determine whether iNOS contributes to Cd-induced hepatotoxicity. Wild-type (WT) mice were administered selective iNOS inhibitors (AMT and 1400W) concurrently and 3 h after administration of a hepatotoxic dose of Cd (4.0 mg Cd/mg). Additionally, WT and iNOS-null (iNOS-KO) mice were dosed iv with saline or 2.0, 2.5, 3.0, 3.5 or 4.0 mg Cd/kg. Serum alanine aminotransferase (ALT) and sorbitol dehydrogenase (SDH) activities were quantified to assess liver injury. Administration of iNOS inhibitors failed to prevent Cd-induced hepatotoxicity. Also, Cd caused a dose-dependent increase in liver injury in both WT and iNOS-KO mice. The liver injury produced by Cd in the iNOS-KO mice was not different from that in WT at any dose. These data indicate that iNOS does not appear to mediate Cd-induced hepatotoxicity.
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Affiliation(s)
- Eric B Harstad
- Department of Pharmacology, Toxicology, and Therapeutics, University of Kansas Medical Center, 3901 Rainbow Blvd., Kansas City, KS 66160-7417, USA
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Leong SK, Ruan RS, Zhang Z. A critical assessment of the neurodestructive and neuroprotective effects of nitric oxide. Ann N Y Acad Sci 2002; 962:161-81. [PMID: 12076973 DOI: 10.1111/j.1749-6632.2002.tb04066.x] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Whether nitric oxide is cytodestructive or cytoprotective is of obvious clinical importance. The debate on this subject in the past decade has generated much "heat and light". This paper focuses on the actions of NO on the nervous system and reexamines the controversial issue and the contribution of the authors and their colleagues in the light of recent findings. We also report new findings, critically assesses previous experimental data, and share perspectives on this important subject.
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Affiliation(s)
- Seng-Kee Leong
- Department of Anatomy, National University of Singapore, Singapore.
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Chitaley K, Webb RC. Nitric oxide induces dilation of rat aorta via inhibition of rho-kinase signaling. Hypertension 2002; 39:438-42. [PMID: 11882586 DOI: 10.1161/hy02t2.102960] [Citation(s) in RCA: 115] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
NO induces vasodilation through cGMP-dependent protein kinase--dependent and --independent mechanisms. A recent study demonstrated that recombinant cGMP-dependent protein kinase can phosphorylate the small G protein, RhoA, thus inhibiting its activity. Additionally, sodium nitroprusside was found to reverse the phenylephrine-induced translocation of RhoA, which is further indicative of the inhibition of RhoA activity. RhoA is known to be involved in the Ca(2+) sensitization of vascular smooth muscle through the actions of one of its downstream effectors, Rho-kinase. This study examined whether NO endogenously induces the relaxation of intact rat aorta via the inhibition of the Rho-kinase--mediated Ca(2+)-sensitizing pathway. Endogenous Rho-kinase inhibitor activity was inhibited by the selective compound Y-27632. Treatment of endothelium-intact rat aorta with Y-27632 (1 micromol/L) resulted in an attenuation of maximal force generated in response to phenylephrine. In endothelium-denuded rings, however, 1 micromol/L Y-27632 was ineffective at inhibiting the phenylephrine-induced contraction. Additionally, 1 micromol/L Y-27632 was significantly less effective at inhibiting the phenylephrine-induced contraction of endothelium-intact rings in the presence of inhibitors of NO synthase or guanylate cyclase (N(omega)-nitro-L-arginine and 1H-[1,2,4]oxadiazolo-[4,3-a]quinoxalin-1-one, respectively). Interestingly, sodium nitroprusside restored the ability of 1 micromol/L Y-27632 to attenuate phenylephrine-induced contraction. Rho-kinase inhibition was also found to increase the sensitivity of the endothelium-denuded aorta to sodium nitroprusside. These data demonstrate that NO inhibits Rho-kinase activity in the intact rat aorta, supporting the hypothesis that endogenous NO-mediated vasodilation occurs through the inhibition of Rho-kinase constrictor activity in the intact rat aorta.
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Affiliation(s)
- Kanchan Chitaley
- Department of Physiology, Medical College of Georgia, Augusta 30912-3000, USA.
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Tilton RG, Brock TA, Dixon RA. Therapeutic potential of endothelin receptor antagonists and nitric oxide donors in pulmonary hypertension. Expert Opin Investig Drugs 2001; 10:1291-308. [PMID: 11772252 DOI: 10.1517/13543784.10.7.1291] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
Pulmonary hypertension can occur idiopathically as a primary disorder of the pulmonary circulation or more commonly, it can exist as a haemodynamic manifestation of a wide variety of pulmonary and cardiovascular diseases, including acute lung injury, chronic obstructive lung disease, congenital heart disease, mitral stenosis, chronic left-sided congestive heart failure and connective tissue diseases such as scleroderma. Pulmonary hypertension is associated with changes in vascular tone as well as vascular structure, with the relative contribution of each dependent upon the aetiology of the increased pulmonary vascular resistance. Most currently available treatments utilise anticoagulants as well as vasodilator drugs that only attenuate the vasoconstrictive component of the disease. The latter category includes oral calcium channel blockers, iv. and aerosolised prostacyclin analogues and inhaled nitric oxide but all three classes of vasodilators have disadvantages and limitations. Treatment with vasodilators is often ineffective in patients with longstanding pulmonary hypertension in which structural changes contribute significantly to the pulmonary hypertension, blood flow obstruction and right heart failure. In view of the immense clinical need, new therapies are being developed by pharmaceutical companies to treat pulmonary hypertension. This update will focus on the current development status of endothelin receptor antagonists and nitric oxide donors for the treatment of pulmonary hypertension.
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Affiliation(s)
- R G Tilton
- Department of Pharmacology, Texas Biotechnology Corporation, Houston, Texas, TX 77030, USA.
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Tang XD, Daggett H, Hanner M, Garcia ML, McManus OB, Brot N, Weissbach H, Heinemann SH, Hoshi T. Oxidative regulation of large conductance calcium-activated potassium channels. J Gen Physiol 2001; 117:253-74. [PMID: 11222629 PMCID: PMC2225619 DOI: 10.1085/jgp.117.3.253] [Citation(s) in RCA: 114] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Reactive oxygen/nitrogen species are readily generated in vivo, playing roles in many physiological and pathological conditions, such as Alzheimer's disease and Parkinson's disease, by oxidatively modifying various proteins. Previous studies indicate that large conductance Ca(2+)-activated K(+) channels (BK(Ca) or Slo) are subject to redox regulation. However, conflicting results exist whether oxidation increases or decreases the channel activity. We used chloramine-T, which preferentially oxidizes methionine, to examine the functional consequences of methionine oxidation in the cloned human Slo (hSlo) channel expressed in mammalian cells. In the virtual absence of Ca(2+), the oxidant shifted the steady-state macroscopic conductance to a more negative direction and slowed deactivation. The results obtained suggest that oxidation enhances specific voltage-dependent opening transitions and slows the rate-limiting closing transition. Enhancement of the hSlo activity was partially reversed by the enzyme peptide methionine sulfoxide reductase, suggesting that the upregulation is mediated by methionine oxidation. In contrast, hydrogen peroxide and cysteine-specific reagents, DTNB, MTSEA, and PCMB, decreased the channel activity. Chloramine-T was much less effective when concurrently applied with the K(+) channel blocker TEA, which is consistent with the possibility that the target methionine lies within the channel pore. Regulation of the Slo channel by methionine oxidation may represent an important link between cellular electrical excitability and metabolism.
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Affiliation(s)
- Xiang D. Tang
- Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242
| | - Heather Daggett
- Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242
| | - Markus Hanner
- Merck Research Laboratories, Rahway, New Jersey 07065
| | | | | | - Nathan Brot
- Hospital for Special Surgery, Cornell University Medical Center, New York, New York 10021
| | - Herbert Weissbach
- Center for Molecular Biology and Biotechnology, Florida Atlantic University, Boca Raton, Florida 33431
| | - Stefan H. Heinemann
- AG Molekulare und Zelluläre Biophysik am Klinikum der Universitat Jena, D-07447 Jena, Germany
| | - Toshinori Hoshi
- Department of Physiology and Biophysics, The University of Iowa, Iowa City, Iowa 52242
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