1
|
Olivares-Rubio HF, Espinosa-Aguirre JJ. Role of epoxyeicosatrienoic acids in the lung. Prostaglandins Other Lipid Mediat 2020; 149:106451. [PMID: 32294527 DOI: 10.1016/j.prostaglandins.2020.106451] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/01/2019] [Revised: 03/10/2020] [Accepted: 04/02/2020] [Indexed: 12/16/2022]
Abstract
Epoxyeicosatrienoic acids (EETs) are synthetized from arachidonic acid by the action of members of the CYP2C and CYP2J subfamilies of cytochrome P450 (CYPs). The effects of EETs on cardiovascular function, the nervous system, the kidney and metabolic disease have been reviewed. In the lungs, the presence of these CYPs and EETs has been documented. In general, EETs play a beneficial role in this essential tissue. Among the most important effects of EETs in the lungs are the induction of vasorelaxation in the bronchi, the stimulation of Ca2+-activated K+ channels, the induction of vasoconstriction of pulmonary arteries, anti-inflammatory effects induced by asthma, and protection against infection or exposure to chemical substances such as cigarette smoke. EETs also participate in tissue regeneration, but on the downside, they are possibly involved in the progression of lung cancer. More research is necessary to design therapies with EETs for the treatment of lung disease.
Collapse
Affiliation(s)
- Hugo F Olivares-Rubio
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ap. Postal 70-228, Ciudad de México, México.
| | - J J Espinosa-Aguirre
- Departamento de Medicina Genómica y Toxicología Ambiental, Instituto de Investigaciones Biomédicas, Universidad Nacional Autónoma de México, Ap. Postal 70-228, Ciudad de México, México.
| |
Collapse
|
2
|
Thakore P, Earley S. Transient Receptor Potential Channels and Endothelial Cell Calcium Signaling. Compr Physiol 2019; 9:1249-1277. [PMID: 31187891 DOI: 10.1002/cphy.c180034] [Citation(s) in RCA: 54] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The vascular endothelium is a broadly distributed and highly specialized organ. The endothelium has a number of functions including the control of blood vessels diameter through the production and release of potent vasoactive substances or direct electrical communication with underlying smooth muscle cells, regulates the permeability of the vascular barrier, stimulates the formation of new blood vessels, and influences inflammatory and thrombotic processes. Endothelial cells that make up the endothelium express a variety of cell-surface receptors and ion channels on the plasma membrane that are capable of detecting circulating hormones, neurotransmitters, oxygen tension, and shear stress across the vascular wall. Changes in these stimuli activate signaling cascades that initiate an appropriate physiological response. Increases in the global intracellular Ca2+ concentration and localized Ca2+ signals that occur within specialized subcellular microdomains are fundamentally important components of many signaling pathways in the endothelium. The transient receptor potential (TRP) channels are a superfamily of cation-permeable ion channels that act as a primary means of increasing cytosolic Ca2+ in endothelial cells. Consequently, TRP channels are vitally important for the major functions of the endothelium. In this review, we provide an in-depth discussion of Ca2+ -permeable TRP channels in the endothelium and their role in vascular regulation. © 2019 American Physiological Society. Compr Physiol 9:1249-1277, 2019.
Collapse
Affiliation(s)
- Pratish Thakore
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
| | - Scott Earley
- Department of Pharmacology, Center for Cardiovascular Research, University of Nevada, Reno School of Medicine, Reno, Nevada, USA
| |
Collapse
|
3
|
Hrdlička J, Neckář J, Papoušek F, Husková Z, Kikerlová S, Vaňourková Z, Vernerová Z, Akat F, Vašinová J, Hammock BD, Hwang SH, Imig JD, Falck JR, Červenka L, Kolář F. Epoxyeicosatrienoic Acid-Based Therapy Attenuates the Progression of Postischemic Heart Failure in Normotensive Sprague-Dawley but Not in Hypertensive Ren-2 Transgenic Rats. Front Pharmacol 2019; 10:159. [PMID: 30881303 PMCID: PMC6406051 DOI: 10.3389/fphar.2019.00159] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2018] [Accepted: 02/11/2019] [Indexed: 12/20/2022] Open
Abstract
Epoxyeicosatrienoic acids (EETs) and their analogs have been identified as potent antihypertensive compounds with cardio- and renoprotective actions. Here, we examined the effect of EET-A, an orally active EET analog, and c-AUCB, an inhibitor of the EETs degrading enzyme soluble epoxide hydrolase, on the progression of post-myocardial infarction (MI) heart failure (HF) in normotensive Hannover Sprague-Dawley (HanSD) and in heterozygous Ren-2 transgenic rats (TGR) with angiotensin II-dependent hypertension. Adult male rats (12 weeks old) were subjected to 60-min left anterior descending (LAD) coronary artery occlusion or sham (non-MI) operation. Animals were treated with EET-A and c-AUCB (10 and 1 mg/kg/day, respectively) in drinking water, given alone or combined for 5 weeks starting 24 h after MI induction. Left ventricle (LV) function and geometry were assessed by echocardiography before MI and during the progression of HF. At the end of the study, LV function was determined by catheterization and tissue samples were collected. Ischemic mortality due to the incidence of sustained ventricular fibrillation was significantly higher in TGR than in HanSD rats (35.4 and 17.7%, respectively). MI-induced HF markedly increased LV end-diastolic pressure (Ped) and reduced fractional shortening (FS) and the peak rate of pressure development [+(dP/dt)max] in untreated HanSD compared to sham (non-MI) group [Ped: 30.5 ± 3.3 vs. 9.7 ± 1.3 mmHg; FS: 11.1 ± 1.0 vs. 40.8 ± 0.5%; +(dP/dt)max: 3890 ± 291 vs. 5947 ± 309 mmHg/s]. EET-A and c-AUCB, given alone, tended to improve LV function parameters in HanSD rats. Their combination amplified the cardioprotective effect of single therapy and reached significant differences compared to untreated HanSD controls [Ped: 19.4 ± 2.2 mmHg; FS: 14.9 ± 1.0%; +(dP/dt)max: 5278 ± 255 mmHg/s]. In TGR, MI resulted in the impairment of LV function like HanSD rats. All treatments reduced the increased level of albuminuria in TGR compared to untreated MI group, but neither single nor combined EET-based therapy improved LV function. Our results indicate that EET-based therapy attenuates the progression of post-MI HF in HanSD, but not in TGR, even though they exhibited renoprotective action in TGR hypertensive rats.
Collapse
Affiliation(s)
- Jaroslav Hrdlička
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Department of Physiology, Faculty of Science, Charles University, Prague, Czechia
| | - Jan Neckář
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - František Papoušek
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Zuzana Husková
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - Soňa Kikerlová
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - Zdenka Vaňourková
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - Zdenka Vernerová
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - Firat Akat
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia.,Department of Physiology, Faculty of Medicine, Ankara University, Ankara, Turkey
| | - Jana Vašinová
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| | - Bruce D Hammock
- Department of Entomology and Nematology, UC Davis Comprehensive Cancer Center, University of California, Davis, Davis, CA, United States
| | - Sung Hee Hwang
- Department of Entomology and Nematology, UC Davis Comprehensive Cancer Center, University of California, Davis, Davis, CA, United States
| | - John D Imig
- Department of Pharmacology and Toxicology, Medical College of Wisconsin, Milwaukee, WI, United States
| | - John R Falck
- Department of Biochemistry, University of Texas Southwestern, Dallas, TX, United States
| | - Luděk Červenka
- Center for Experimental Medicine, Institute for Clinical and Experimental Medicine, Prague, Czechia
| | - František Kolář
- Institute of Physiology of the Czech Academy of Sciences, Prague, Czechia
| |
Collapse
|
4
|
Ning JZ, Li W, Cheng F, Yu WM, Rao T, Ruan Y, Yuan R, Zhang XB, Zhuo D, Du Y, Xiao CC. MiR-29a Suppresses Spermatogenic Cell Apoptosis in Testicular Ischemia-Reperfusion Injury by Targeting TRPV4 Channels. Front Physiol 2017; 8:966. [PMID: 29238305 PMCID: PMC5712590 DOI: 10.3389/fphys.2017.00966] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2017] [Accepted: 11/14/2017] [Indexed: 12/13/2022] Open
Abstract
Background: MicroRNAs (miRNAs) have emerged as gene expression regulators in the progression of ischemia-reperfusion injury (IRI). Accumulating evidences have indicated miR-29a play roles in myocardial and cerebral IRI. However, the role of miR-29a in testicular IRI has not been elucidated. Methods: Changes in expression of miR-29a and Transient Receptor Potential Vanilloid 4 (TRPV4) in animal samples and GC-1 spermatogenic cells were examined. The effects of miR-29a on spermatogenic cell apoptosis in testicular IRI were analyzed both in vitro and in vivo. Results: The expression of MiR-29a was negatively correlated with the expression of TRPV4 and significantly downregulated in animal samples and GC-1 cells as testicular IRI progressed. Further studies revealed TRPV4 as a downstream target of miR-29a. Inhibition of miR-29a expression increased the expression of TRPV4 and promoted spermatogenic cell apoptosis, whereas overexpression of miR-29a downregulated TRPV4 expression and suppressed spermatogenic cell apoptosis caused by testicular IRI in vitro and in vivo. Conclusion: Our results suggest that miR-29a suppresses apoptosis induced by testicular IRI by directly targeting TRPV4.
Collapse
Affiliation(s)
- Jin-Zhuo Ning
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Wei Li
- Department of Anesthesiology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Fan Cheng
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Wei-Min Yu
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Ting Rao
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Yuan Ruan
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Run Yuan
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Xiao-Bin Zhang
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Dong Zhuo
- Department of Urology, Wannan Medical College, Wuhu, China
| | - Yang Du
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| | - Cheng-Cheng Xiao
- Department of Urology, Renmin Hospital of Wuhan University, Wuhan, China
| |
Collapse
|
5
|
Sun C, Simon SI, Foster GA, Radecke CE, Hwang HV, Zhang X, Hammock BD, Chiamvimonvat N, Knowlton AA. 11,12-Epoxyecosatrienoic acids mitigate endothelial dysfunction associated with estrogen loss and aging: Role of membrane depolarization. J Mol Cell Cardiol 2016; 94:180-188. [PMID: 27079253 PMCID: PMC4972711 DOI: 10.1016/j.yjmcc.2016.03.019] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 12/08/2015] [Revised: 03/18/2016] [Accepted: 03/31/2016] [Indexed: 12/31/2022]
Abstract
OBJECTIVE Endothelial dysfunction, including upregulation of inflammatory adhesion molecules and impaired vasodilatation, is a key element in cardiovascular disease. Aging and estrogen withdrawal in women are associated with endothelial inflammation, vascular stiffness and increased cardiovascular disease. Epoxyecosatrienoic acids (EETs), the products of arachidonic acid metabolism mediated by cytochrome P450 (CYP) 2J, 2C and other isoforms, are regulated by soluble epoxide hydrolase (sEH)-catalyzed conversion into less active diols. We hypothesized that 11,12-EETs would reduce the endothelial dysfunction associated with aging and estrogen loss. APPROACH/RESULTS When stabilized by an sEH inhibitor (seHi), 11,12-EET at a physiologically low dose (0.1nM) reduced cytokine-stimulated upregulation of adhesion molecules on human aorta endothelial cells (HAEC) and monocyte adhesion under shear flow through marked depolarization of the HAEC when combined with TNFα. Mechanistically, neither 11,12-EETs nor 17β-estradiol (E2) at physiologic concentrations prevented activation of NFκB by TNFα. E2 at physiological concentrations reduced sEH expression in HAEC, but did not alter CYP expression, and when combined with TNFα depolarized the cell. We also examined vascular dysfunction in adult and aged ovariectomized Norway brown rats (with and without E2 replacement) using an ex-vivo model to analyze endothelial function in an intact segment of artery. sEHi and 11,12-EET with or without E2 attenuated phenylephrine induced constriction and increased endothelial-dependent dilation of aortic rings from ovariectomized rats. CONCLUSIONS Increasing 11,12-EETs through sEH inhibition effectively attenuates inflammation and may provide an effective strategy to preserve endothelial function and prevent atherosclerotic heart disease in postmenopausal women.
Collapse
Affiliation(s)
- Chongxiu Sun
- The Department of Veterans Affairs, Northern California VA, Sacramento, CA, United States; Molecular & Cellular Cardiology, Cardiovascular Division, Department of Medicine, University of California, Davis, Davis, CA, United States; Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
| | - Scott I Simon
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
| | - Greg A Foster
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
| | - Christopher E Radecke
- Department of Biomedical Engineering, University of California, Davis, Davis, CA, United States
| | - HyunTae V Hwang
- The Department of Veterans Affairs, Northern California VA, Sacramento, CA, United States; Molecular & Cellular Cardiology, Cardiovascular Division, Department of Medicine, University of California, Davis, Davis, CA, United States
| | - Xiaodong Zhang
- Molecular & Cellular Cardiology, Cardiovascular Division, Department of Medicine, University of California, Davis, Davis, CA, United States
| | - Bruce D Hammock
- Department of Entomology and Nematology, University of California, Davis, Davis, CA, United States; Comprehensive Cancer Center, University of California, Davis, Davis, CA, United States
| | - N Chiamvimonvat
- The Department of Veterans Affairs, Northern California VA, Sacramento, CA, United States; Molecular & Cellular Cardiology, Cardiovascular Division, Department of Medicine, University of California, Davis, Davis, CA, United States
| | - Anne A Knowlton
- The Department of Veterans Affairs, Northern California VA, Sacramento, CA, United States; Molecular & Cellular Cardiology, Cardiovascular Division, Department of Medicine, University of California, Davis, Davis, CA, United States; Department of Pharmacology, University of California, Davis, Davis, CA, United States.
| |
Collapse
|
6
|
Kodani SD, Hammock BD. The 2014 Bernard B. Brodie award lecture-epoxide hydrolases: drug metabolism to therapeutics for chronic pain. Drug Metab Dispos 2015; 43:788-802. [PMID: 25762541 PMCID: PMC4407705 DOI: 10.1124/dmd.115.063339] [Citation(s) in RCA: 62] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2015] [Accepted: 03/11/2015] [Indexed: 12/24/2022] Open
Abstract
Dr. Bernard Brodie's legacy is built on fundamental discoveries in pharmacology and drug metabolism that were then translated to the clinic to improve patient care. Similarly, the development of a novel class of therapeutics termed the soluble epoxide hydrolase (sEH) inhibitors was originally spurred by fundamental research exploring the biochemistry and physiology of the sEH. Here, we present an overview of the history and current state of research on epoxide hydrolases, specifically focusing on sEHs. In doing so, we start with the translational project studying the metabolism of the insect juvenile hormone mimic R-20458 [(E)-6,7-epoxy-1-(4-ethylphenoxy)-3,7-dimethyl-2-octene], which led to the identification of the mammalian sEH. Further investigation of this enzyme and its substrates, including the epoxyeicosatrienoic acids, led to insight into mechanisms of inflammation, chronic and neuropathic pain, angiogenesis, and other physiologic processes. This basic knowledge in turn led to the development of potent inhibitors of the sEH that are promising therapeutics for pain, hypertension, chronic obstructive pulmonary disorder, arthritis, and other disorders.
Collapse
Affiliation(s)
- Sean D Kodani
- Department of Entomology and Nematology, Comprehensive Cancer Center, University of California, Davis, California
| | - Bruce D Hammock
- Department of Entomology and Nematology, Comprehensive Cancer Center, University of California, Davis, California
| |
Collapse
|
7
|
Lu L, Xu K, Zhang LJ, Morelli J, Krazinski AW, Silverman JR, Schoepf UJ, Lu GM. Lung ischaemia-reperfusion injury in a canine model: dual-energy CT findings with pathophysiological correlation. Br J Radiol 2014; 87:20130716. [PMID: 24611753 DOI: 10.1259/bjr.20130716] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022] Open
Abstract
OBJECTIVE To evaluate dual-energy CT (DECT) findings of pulmonary ischaemic-reperfusion injury (PIRI) and its pathophysiological correlation in the canine model. METHODS A PIRI model was established in 11 canines, utilizing closed pectoral balloon occlusion. Two control canines were also included. For the PIRI model, the left pulmonary artery was occluded with a balloon, which was deflated and removed after 2 h. DECT was performed before, during occlusion and at 2, 3 and 4 h thereafter and was utilized to construct pulmonary perfusion maps. Immediately after the CT scan at the fourth hour post reperfusion, the canines were sacrificed, and lung specimens were harvested for pathological analysis. CT findings, pulmonary artery pressure and blood gas results were then analysed. RESULTS Data at every time point were available for 10 animals (experimental group, n = 8; control group, n = 2). Quantitative measurements from DECT pulmonary perfusion maps found iodine attenuation values of the left lung to be the lowest at 2 h post embolization and the highest at 1 h post reperfusion. In the contralateral lung, perfusion values also peaked at 1 h post reperfusion. Continuous hypoxia and acid-based disorders were observed during PIRI, and comprehensive analysis showed physiological changes to be worst at 3 h post reperfusion. CONCLUSION DECT pulmonary perfusion mapping demonstrated pulmonary perfusion of the bilateral lungs to be the greatest at 1 h post reperfusion. These CT findings corresponded with pathophysiological changes. ADVANCES IN KNOWLEDGE DECT pulmonary perfusion mapping can be used to evaluate lung ischaemia-reperfusion injury.
Collapse
Affiliation(s)
- L Lu
- Department of Medical Imaging, Jinling Hospital, Medical School of Nanjing University, Nanjing, China
| | | | | | | | | | | | | | | |
Collapse
|
8
|
Graves JP, Edin ML, Bradbury JA, Gruzdev A, Cheng J, Lih FB, Masinde TA, Qu W, Clayton NP, Morrison JP, Tomer KB, Zeldin DC. Characterization of four new mouse cytochrome P450 enzymes of the CYP2J subfamily. Drug Metab Dispos 2013; 41:763-73. [PMID: 23315644 DOI: 10.1124/dmd.112.049429] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
The cytochrome P450 superfamily encompasses a diverse group of enzymes that catalyze the oxidation of various substrates. The mouse CYP2J subfamily includes members that have wide tissue distribution and are active in the metabolism of arachidonic acid (AA), linoleic acid (LA), and other lipids and xenobiotics. The mouse Cyp2j locus contains seven genes and three pseudogenes located in a contiguous 0.62 megabase cluster on chromosome 4. We describe four new mouse CYP2J isoforms (designated CYP2J8, CYP2J11, CYP2J12, and CYP2J13). The four cDNAs contain open reading frames that encode polypeptides with 62-84% identity with the three previously identified mouse CYP2Js. All four new CYP2J proteins were expressed in Sf21 insect cells. Each recombinant protein metabolized AA and LA to epoxides and hydroxy derivatives. Specific antibodies, mRNA probes, and polymerase chain reaction primer sets were developed for each mouse CYP2J to examine their tissue distribution. CYP2J8 transcripts were found in the kidney, liver, and brain, and protein expression was confirmed in the kidney and brain (neuropil). CYP2J11 transcripts were most abundant in the kidney and heart, with protein detected primarily in the kidney (proximal convoluted tubules), liver, and heart (cardiomyocytes). CYP2J12 transcripts were prominently present in the brain, and CYP2J13 transcripts were detected in multiple tissues, with the highest expression in the kidney. CYP2J12 and CYP2J13 protein expression could not be determined because the antibodies developed were not immunospecific. We conclude that the four new CYP2J isoforms might be involved in the metabolism of AA and LA to bioactive lipids in mouse hepatic and extrahepatic tissues.
Collapse
Affiliation(s)
- Joan P Graves
- Laboratory of Respiratory Biology, National Institute of Environmental Health Sciences, National Institutes of Health, Research Triangle Park, North Carolina 27709, USA
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
9
|
Beneficial effects of n-3 PUFA on chronic airway inflammatory diseases. Prostaglandins Other Lipid Mediat 2012; 99:57-67. [DOI: 10.1016/j.prostaglandins.2012.09.006] [Citation(s) in RCA: 76] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2012] [Revised: 09/26/2012] [Accepted: 09/27/2012] [Indexed: 12/14/2022]
|
10
|
Cytochrome P450-derived epoxyeicosatrienoic acids and pulmonary hypertension: central role of transient receptor potential C6 channels. J Cardiovasc Pharmacol 2012; 57:140-7. [PMID: 20588188 DOI: 10.1097/fjc.0b013e3181ed088d] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Hypoxia induces the constriction of pulmonary resistance arteries, which results in the redistribution of blood from poor to better ventilated areas, thus optimizing its oxygenation. Many different oxygen-sensing mechanisms have been proposed to regulate this process, including cytochrome P450 enzymes. These enzymes, which convert substrates such as arachidonic acid into bioactive epoxides (the epoxyeicosatrienoic acids [EETs]), are highly expressed in the lung as is the soluble epoxide hydrolase which metabolizes the epoxides to their less active diols. The EETs play a well-documented role as endothelium-derived vasodilators in the systemic vasculature, but in the pulmonary circulation, they are generated in vascular smooth muscle cells and potentiate vasoconstriction. Preventing the breakdown of 11,12-EET by the inhibition or genetic deletion of the soluble epoxide hydrolase strongly augments the response to hypoxia. Mechanistically, 11,12-EET potentiates the contractile response by recruiting transient receptor potential C6 channels to caveolae. Indeed, neither 11,12-EET nor hypoxia is able to elicit pulmonary vasoconstriction in TRPC6 knockout mice. The cytochrome and soluble epoxide hydrolase enzymes are also implicated in the vascular remodeling associated with chronic hypoxia and pulmonary hypertension. Thus, targeting this pathway may be in an attractive new therapeutic approach to treat this incapacitating disease.
Collapse
|