Leptin receptors are expressed in coronary arteries, and hyperleptinemia causes significant coronary endothelial dysfunction

Obesity is associated with marked increases in plasma leptin concentration, and hyperleptinemia is an independent risk factor for coronary artery disease. As a result, the purpose of this investigation was to test the following hypotheses: 1) leptin receptors are expressed in coronary endothelial cells; and 2) hyperleptinemia induces coronary endothelial dysfunction. RT-PCR analysis revealed that the leptin receptor gene is expressed in canine coronary arteries and human coronary endothelium. Furthermore, immunocytochemistry demonstrated that the long-form leptin receptor protein (ObRb) is present in human coronary endothelium. The functional effects of leptin were determined using pressurized coronary arterioles (<130 microm) isolated from Wistar rats, Zucker rats, and mongrel dogs. Leptin induced pharmacological vasodilation that was abolished by denudation and the nitric oxide synthase inhibitor N(omega)-nitro-l-arginine methyl ester and was absent in obese Zucker rats. Intracoronary leptin dose-response experiments were conducted in anesthetized dogs. Normal and obese concentrations of leptin (0.1-3.0 microg/min ic) did not significantly change coronary blood flow or myocardial oxygen consumption; however, obese concentrations of leptin significantly attenuated the dilation to graded intracoronary doses of acetylcholine (0.3-30.0 microg/min). Additional experiments were performed in canine coronary rings, and relaxation to acetylcholine (6.25 nmol/l-6.25 micromol/l) was significantly attenuated by obese concentrations of leptin (625 pmol/l) but not by physiological concentrations of leptin (250 pmol/l). The major findings of this investigation were as follows: 1) the ObRb is present in coronary arteries and coupled to pharmacological, nitric oxide-dependent vasodilation; and 2) hyperleptinemia produces significant coronary endothelial dysfunction.     

Rosuvastatin provides pleiotropic protection against pulmonary hypertension, right ventricular hypertrophy, and coronary endothelial dysfunction in rats

We recently reported that increased vascular endothelial nitric oxide production could protect against the development of monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) and right ventricular hypertrophy (RVH) in rats (32). The present study investigated whether the pleiotropic action of 3-hydroxy-3-methylglutaryl-CoA reductase inhibitors in upregulating endothelial function could also protect against the MCT-induced end-organ damages. Rosuvastatin (2 mg kg(-1) day(-1) via oral gavage) or placebo was initiated 1 wk before or 1 wk after MCT (60 mg/kg ip) administration. One month after MCT, significant PAH developed in the placebo rats, which were accompanied by histological evidence of pulmonary vascular thickening and right ventricular hypertrophy. The coronary endothelial vasodilatory function, assessed with endothelial/nitric oxide-dependent responses to acetylcholine and N(G)-nitro-L-arginine methyl ester (L-NAME), was depressed, while the constrictory responses to known coronary constrictors was enhanced. In rats that received rosuvastatin treatment 1 wk before MCT administration, a significantly reduced PAH and RVH was observed, as well as reduced pulmonary vascular and right ventricular remodelings. Rosuvastatin 1-wk posttreatment had no effect on PAH, but inhibited RVH. Right coronary endothelial dysfunction, which was shown in placebo rats, was effectively prevented by both pre- and postrosuvastatin treatment, while this effect was more dramatic in the pretreated group. Left coronary endothelial function, which was not affected by MCT, also showed an upregulation by rosuvastatin. Taken together, our results demonstrated the pleiotropic protection of rosuvastatin against the development of PAH and RVH and confirmed our previous finding that the targeted preservation of coronary endothelial function and vasoactivity may provide a novel approach to protect against cardiac remodeling.     

Accelerated endothelial dysfunction in mild prediabetic insulin resistance: the early role of reactive oxygen species

Insulin resistance is well established as an independent risk factor for the development of type 2 diabetes and cardiovascular atherosclerosis. Most studies have examined atherogenesis in models of severe insulin resistance or diabetes. However, by the time of diagnosis, individuals with type 2 diabetes already demonstrate a significant atheroma burden. Furthermore, recent studies suggest that, even in adolescence, insulin resistance is a progressive disorder that increases cardiovascular risk. In the present report, we studied early mechanisms of reduction in the bioavailability of the antiatheroscerotic molecule nitric oxide (NO) in very mild insulin resistance. Mice with haploinsufficiency for the insulin receptor (IRKO) are a model of mild insulin resistance with preserved glycemic control. We previously demonstrated that 2-mo-old (Young) IRKO mice have preserved vasorelaxation responses to ACh. This remained the case at 4 mo of age. However, by 6 mo, despite no significant deterioration in glucose homeostasis (Adult), IRKO mice had marked blunting of ACh-mediated vasorelaxation [IRKO maximum contraction response (E(max)) 66 +/- 5% vs. wild type 87 +/- 4%, P < 0.01]. Despite the endothelial dysfunction demonstrated, aortic endothelial nitric oxide synthase (eNOS) mRNA levels were similar in Adult IRKO and wild-type mice, and, interestingly, aortic eNOS protein levels were increased, suggesting a compensatory upregulation in the IRKO. We then examined the potential role of reactive oxygen species in mediating early endothelial dysfunction. The superoxide dismutase mimetic Mn(III)tetrakis(1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP) restored ACh relaxation responses in the Adult IRKO (E(max) to ACh with MnTMPyP 85 +/- 5%). Dihydroethidium fluorescence of aortas and isolated coronary microvascular endothelial cells confirmed a substantial increase in endothelium-derived reactive oxygen species in IRKO mice. These data demonstrate that mild insulin resistance is a potent substrate for accelerated endothelial dysfunction and support a role for endothelial cell superoxide production as a mechanism underlying the early reduction in NO bioavailability.     

Peroxynitrite triggers a delayed resistance of coronary endothelial cells against ischemia-reperfusion injury

Experiments were designed to test whether nitric oxide (NO) and peroxynitrite trigger delayed coronary endothelial protection induced by preconditioning (PC) in rats. Prolonged ischemia reperfusion markedly reduced the response of isolated coronary arteries to acetylcholine, and this was prevented by PC performed 24 h earlier. The NO synthase (NOS) inhibitor N(G)-nitro-L-arginine methyl ester (L-NAME) administered during PC abolished its delayed endothelial protective effect, whereas the inducible NOS inhibitor N-(3(aminomethyl)benzyl)acetaminide had no effect. Delayed endothelial PC was also abolished by the peroxynitrite scavengers selenomethionine or uric acid given during PC. In parallel, the NO/peroxynitrite donor S-morpholinosydnonimine and authentic peroxynitrite, administered 24 h before prolonged ischemia-reperfusion mimicked endothelial PC, whereas the NO donor S-nitroso-N-acetylpencillamine had no effect. This suggests that peroxynitrite is an essential trigger of the delayed coronary endothelial protection induced by PC in rat hearts.     

Allicin in garlic protects against coronary endothelial dysfunction and right heart hypertrophy in pulmonary hypertensive rats

We recently reported that coronary endothelial cell (CEC) dysfunction may contribute to the development of right ventricular (RV) hypertrophy (RVH) in monocrotaline (MCT)-induced pulmonary hypertensive rats. This present study investigated whether preservation of CEC function with garlic and its active metabolite allicin could abrogate RVH. Rats were fed with 1% raw garlic (RG)-supplemented diet 1 day or 3 wk before and 1 day after MCT injection, and changes in RV pressure (RVP), RVH, and CEC function were assessed 3 wk after MCT administration. In all cases, RG feeding significantly inhibited the development of RVP and RVH in these MCT rats. However, similar treatments with either boiled garlic (BG) or aged garlic (AG), which do not contain the active allicin metabolite, were ineffective. CEC function, assessed with acetylcholine-induced dilation as well as N(omega)-nitro-l-arginine methyl ester-induced constriction, revealed marked attenuation in right, but not left, coronary arteries of the MCT rats. This is consistent with our earlier report. Feeding of RG, but not BG or AG, preserved the CEC function and prevented the exaggerated vasoconstrictory responses of the MCT coronary arteries. There was no change in the coronary dilatory responses to a nitric oxide donor sodium nitroprusside. Further testings of vasoactivity to garlic extracts showed that only RG, but not BG or AG, elicited a potent, dose-dependent dilation on the isolated coronaries. Taken together, these findings show that the protective effect of garlic against the development of RVP and RVH in MCT-treated rats is probably mediated via its active metabolite allicin action on coronary endothelial function and vasoreactivity.     

Mg-Gluconate provides superior protection against postischemic dysfunction and oxidative injury compared to Mg-sulfate

Cardioprotection by Mg Sulfate (MgSO4) during ischemia/reperfusion (I/R) is attributed largely to the Mg2+ cation. However, Mg-gluconate (MgGl2) may provide added benefit, possibly through its anion's antioxidant properties. Protective effects of both Mg-salts and their anions during 30 min global I and 50 min R were assessed in Langendorff-perfused (Krebs-Henseleit buffer) rat hearts. Recovery of function was compared between untreated hearts and those receiving supplement (2.4 mM MgGl2, MgSO4, or Na2SO4, or 4.8 mM NaGI) for 5 min prior to I and during the initial 30 min R. The final 20 min R was conducted without supplement. End diastolic pressure (EDP, mmHg) of the 50 min reperfused MgGl2 group (2.6) was lower than MgSO4 (16.2) and untreated (35.6) groups, and the NaGI group (25.2) was considerably lower than Na2SO4 (38.8). Recovery of developed pressure (% preischemic DP) at the onset of R for MgGl2 (74.9) was greater than MgSO4 (37.9) and untreated (33.2). After 50 min, MgGl2 (77.9) and MgSO4 (66.9) provided protection compared to untreated (51.8). In separate studies, ESR spin trapping with alpha-phenyl-N-tert-butylnitrone (3 mM PBN) showed that I/R alkoxyl radical production was reduced with MgGl2 (0.0 vs. 2.4 vs. 3.6 mM: 184 vs. 97 vs. 54.8 nM/g tissue x min) to a greater extent than seen with MgSO4 (3.6 mM: 108). Additional studies suggest that Gl(1-), unlike SO4(2-), may scavenge hydroxyl radicals, accounting for the added protection. MgGl2 treated hearts exhibited less postischemic dysfunction and oxidative injury compared to MgSO4, suggesting the contribution of Gl(1-) to cardioprotection.     

Maximum coronary blood flow and minimum coronary resistance in exercise-trained dogs

Exercise training has been found to increase coronary vascularity of the heart in experimental animals. Maximum coronary flow and minimum coronary resistance were determined in 16 dogs with the injection of microspheres (15 micron) into the left atrium at rest and during the intravenous infusion of adenosine (0.7 mg X min-1 X kg-1). Heart rate was paced at 150 beats/min. Dogs were divided into three groups with microsphere injections made before and after 4-5 wk of daily exercise (group 1); before and after 8-10 wk of daily exercise (group II); and before and after 8-10 wk of cage rest (group III). Results of average left ventricular maximum myocardial flow before and after daily exercise were 4.08 +/- 0.34 and 4.89 +/- 0.33 ml X min-1 X g-1 for group I, 5.13 +/- 0.32 and 5.55 +/- 0.56 ml X min-1 X g-1 for group II, and 5.24 +/- 0.43 and 4.34 +/- 0.55 ml X min-1 X g-1 for group III. Arterial pressure, maximum coronary flow, and minimum coronary resistance were not significantly different before and after any condition in all three groups of dogs. Peak reactive hyperemia coronary flow was not altered by daily exercise. These results indicate that maximum coronary flow and minimum coronary resistance were not altered by either 4-5 or 8-10 wk of exercise training.     

Serum amyloid A induces endothelial dysfunction in porcine coronary arteries and human coronary artery endothelial cells

The objective of this study was to determine the effects and mechanisms of serum amyloid A (SAA) on coronary endothelial function. Porcine coronary arteries and human coronary arterial endothelial cells (HCAECs) were treated with SAA (0, 1, 10, or 25 microg/ml). Vasomotor reactivity was studied using a myograph tension system. SAA significantly reduced endothelium-dependent vasorelaxation of porcine coronary arteries in response to bradykinin in a concentration-dependent manner. SAA significantly decreased endothelial nitric oxide (NO) synthase (eNOS) mRNA and protein levels as well as NO bioavailability, whereas it increased ROS in both artery rings and HCAECs. In addition, the activities of internal antioxidant enzymes catalase and SOD were decreased in SAA-treated HCAECs. Bio-plex immunoassay analysis showed the activation of JNK, ERK2, and IkappaB-alpha after SAA treatment. Consequently, the antioxidants seleno-l-methionine and Mn(III) tetrakis-(4-benzoic acid)porphyrin and specific inhibitors for JNK and ERK1/2 effectively blocked the SAA-induced eNOS mRNA decrease and SAA-induced decrease in endothelium-dependent vasorelaxation in porcine coronary arteries. Thus, SAA at clinically relevant concentrations causes endothelial dysfunction in both porcine coronary arteries and HCAECs through molecular mechanisms involving eNOS downregulation, oxidative stress, and activation of JNK and ERK1/2 as well as NF-kappaB. These findings suggest that SAA may contribute to the progress of coronary artery disease.     

Hypothyroidism provides resistance to kidney mitochondria against the injury induced by renal ischemia-reperfusion

Massive Ca(2+) accumulation in mitochondria, plus the stimulating effect of an inducing agent, i.e., oxidative stress, induces the so-called permeability transition, which is characterized by the opening of a nonspecific pore. This work was aimed at studying the influence of thyroid hormone on the opening of such a nonspecific pore in kidney mitochondria, as induced by an oxidative stress. To meet this objective, membrane permeability transition was examined in mitochondria isolated from kidney of euthyroid and hypothyroid rats, after a period of ischemia/reperfusion. It was found that mitochondria from hypothyroid rats were able to retain accumulated Ca(2+) to sustain a transmembrane potential after Ca(2+) addition, as well as to maintain matrix NAD(+) and membrane cytochrome c content. The protective effect of hypothyroidism was clearly opposed to that occurring in ischemic reperfused mitochondria from euthyroid rats. Our findings demonstrate that these mitochondria were unable to preserve selective membrane permeability, except when cyclosporin A was added. It is proposed that the protection is conferred by the low content of cardiolipin found in the inner membrane. This phospholipid is required to switch adenine nucleotide translocase from specific carrier to a non-specific pore.     

Protection of calcitonin gene-related peptide-mediated preconditioning against coronary endothelial dysfunction induced by reperfusion in the isolated rat heart

This study was designed to explore the protective effect of ischemic preconditioning on reperfusion-induced coronary endothelial dysfunction, with a focus on the role of calcitonin gene-related peptide (CGRP) in this effect, in the isolated perfused rat heart. Thirty minutes of global ischemia and 30 min of reperfusion significantly decreased heart rate, left ventricular pressure, and its first derivative and impaired vasodilator responses to acetylcholine. Ischemia-reperfusion did not affect vasodilator responses to sodium nitroprusside. Preconditioning induced by three cycles of 5 min of ischemia and 5 min of reperfusion produced a significant improvement in cardiac function concomitantly with an amelioration of vasodilator responses to acetylcholine. The protective effects of ischemic preconditioning were abolished by CGRP(8-37) (10(-7) M) , the selective CGRP receptor antagonist. After pretreatment with capsaicin (50 mg x kg(-1), s.c.) to deplete endogenous CGRP, the preconditioning effect was absent. Pretreatment with exogenous CGRP (5 x 10(-9) M) for 5 min induced a preconditioning-like protection. The present study suggests that the cardioprotection of ischemic preconditioning is related to the preservation of the coronary endothelial cell, and that the protective effect of preconditioning is mediated by endogenous CGRP in the isolated perfused rat heart.     

Increased susceptibility to hypoxic pulmonary hypertension in Bmpr2 mutant mice is associated with endothelial dysfunction in the pulmonary vasculature

Patients with familial pulmonary arterial hypertension inherit heterozygous mutations of the type 2 bone morphogenetic protein (BMP) receptor BMPR2. To explore the cellular mechanisms of this disease, we evaluated the pulmonary vascular responses to chronic hypoxia in mice carrying heterozygous hypomorphic Bmpr2 mutations (Bmpr2 delta Ex2/+). These mice develop more severe pulmonary hypertension after prolonged exposure to hypoxia without an associated increase in pulmonary vascular remodeling or proliferation compared with wild-type mice. This is associated with defective endothelial-dependent vasodilatation and enhanced vasoconstriction in isolated intrapulmonary artery preparations. In addition, there is a selective decrease in hypoxia-induced, BMP-dependent, endothelial nitric oxide synthase expression and Smad signaling in the intact lungs and in cultured pulmonary microvascular endothelial cells from Bmpr2 delta Ex2/+ mutant mice. These findings indicate that the pulmonary endothelium is a target of abnormal BMP signaling in Bmpr2 delta Ex2/+ mutant mice and suggest that endothelial dysfunction contributes to their increased susceptibility to hypoxic pulmonary hypertension.     

The roles of hyperglycaemia and oxidative stress in the rise and collapse of the natural protective mechanism against vascular endothelial cell dysfunction in diabetes

Vascular endothelial cell (VEC) dysfunction in diabetes has been associated with hyperglycaemia-induced intra- and extracellular glycation of proteins and to overproduction of glucose-derived free radicals. VEC protect their intracellular environment against an increased influx of glucose in face of hyperglycaemia by reducing the expression and plasma membrane abundance of their glucose transporter-1 (GLUT-1). We investigated the hypothesis that glucose-derived free radicals induce this down-regulatory mechanism in VEC, but proved the contrary. In fact, pro-oxidants significantly increased the expression and plasma membrane abundance of GLUT-1 and the rate of glucose transport in VEC while abolishing high-glucose-induced down-regulation of the hexose transport system. The resulting uncontrolled influx of glucose followed by overproduction of glucose-derived ROS further up-regulates the rate of glucose transport, and vice versa. This perpetuating glycoxidative stress finally leads to the collapse of the auto-regulatory protective mechanism and accelerates the development of dysfunctional endothelium in blood vessels.     

Protective effects of epoxyeicosatrienoic acids on human endothelial cells from the pulmonary and coronary vasculature

Epoxyeicosatrienoic acids (EETs) are cytochrome P-450 (CYP) metabolites synthesized from the essential fatty acid arachidonic acid to generate four regioisomers, 14,15-, 11,12-, 8,9-, and 5,6-EET. Cultured human coronary artery endothelial cells (HCAECs) contain endogenous EETs that are increased by stimulation with physiological agonists such as bradykinin. Because EETs are known to modulate a number of vascular functions, including angiogenesis, we tested each of the four regioisomers to characterize their effects on survival and apoptosis of HCAECs and cultured human lung microvascular endothelial cells (HLMVECs). A single application of physiologically relevant concentration of 14,15-, 11,12-, and 8,9-EET but not 5,6-EET (0.75-300 nM) promoted concentration-dependent increase in cell survival of HLMVECs and HCAECs after removal of serum. The lipids also protected the same cells from death via the intrinsic, as well as extrinsic, pathways of apoptosis. EETs did not increase intracellular calcium concentration ([Ca2+]i) or phosphorylate mitogen-activated protein kinase p44/42 when applied to these cells, and their protective action was attenuated by the phosphotidylinositol-3 kinase inhibitor wortmannin (10 microM) but not the cyclooxygenase inhibitor indomethacin (20 microM). Our results demonstrate for the first time the capacity of EETs to enhance human endothelial cell survival by inhibiting both the intrinsic, as well as extrinsic, pathways of apoptosis, an important underlying mechanism that may promote angiogenesis and endothelial survival during atherosclerosis and related cardiovascular ailments.     

Ceramide-induced activation of NADPH oxidase and endothelial dysfunction in small coronary arteries

We tested the hypothesis that ceramide induces endothelial dysfunction in small coronary arteries via NADPH oxidase-mediated superoxide and resulting peroxynitrite formation. With the use of dihydroethidium as a superoxide indicator, C(2)-ceramide was found to increase superoxide production in the endothelial cells of small coronary arteries, which was inhibited by the NADPH oxidase inhibitors N-vanillylnonanamide, apocynin, and diphenylene iodonium. NADPH oxidase expression was confirmed in endothelial cells, as indicated by the immunoblotting of its subunits gp91(phox) and p47(phox). C(2)-ceramide increased NADPH oxidase activity by 52%, which was blocked by NADPH oxidase inhibitors but not by inhibitors of NO synthase, xanthine oxidase, and mitochondrial electron transport chain enzymes. By Western blot analysis, ceramide-induced NADPH oxidase activation was found to be associated with the translocation of p47(phox) to the membrane. In isolated and pressurized small coronary arteries, N-vanillylnonanamide, apocynin, or uric acid, a peroxynitrite scavenger, largely restored the inhibitory effects of ceramide on bradykinin- and A-23187-induced vasorelaxation. With the use of nitrotyrosine as a marker, C(2)-ceramide was found to increase peroxynitrite in small coronary arteries, which could be blocked by uric acid. We conclude that NADPH oxidase-mediated superoxide production and subsequent peroxynitrite formation mediate ceramide-induced endothelial dysfunction in small coronary arteries.     

Acidic reoxygenation protects against endothelial dysfunction in rat aortic rings submitted to simulated ischemia

Ischemia-reperfusion causes endothelial dysfunction. Prolongation of acidosis during initial cardiac reperfusion limits infarct size in animal models, but the effects of acidic reperfusion on vascular function are unknown. The present work analyzes the effects of acidic reoxygenation on vascular responses to different agonists in rat aortic rings. Arterial rings obtained from Sprague-Dawley rat aorta were placed in organ baths containing a Krebs solution oxygenated at 37 degrees C (pH 7.4). After equilibration (30 mN, 1 h), the effects of acidosis (pH 6.4) on aortic responses to acetylcholine and norepinephrine were initially assessed under normoxic conditions. Thereafter, the effects of acidosis during hypoxia (1 h) or reoxygenation on aortic responses to acetylcholine, norepinephrine, or sodium nitroprusside were analyzed and compared with those observed in control rings. Acidosis did not modify aortic responses to acetylcholine or adrenaline during normoxia. In contrast, rings submitted to hypoxia and reoxygenated at pH 7.4 showed a reduction in vasodilator responses to acetylcholine and in contractions to norepinephrine with no change in responses to sodium nitroprusside. Reoxygenation at pH 6.4 did not modify the depressed response to norepinephrine but enhanced the recovery of acetylcholine-induced vasorelaxation. Cumulative concentration-response curves to acetylcholine showed an increased responsiveness to this drug in rings reoxygenated at a low pH. This functional improvement was associated with the preservation of aortic cGMP content after stimulation of reoxygenated rings with acetylcholine. In conclusion, acidic reoxygenation preserves endothelial function in arterial rings submitted to simulated ischemia, likely through the preservation of cGMP signaling.     

CRISPR--a widespread system that provides acquired resistance against phages in bacteria and archaea

Arrays of clustered, regularly interspaced short palindromic repeats (CRISPRs) are widespread in the genomes of many bacteria and almost all archaea. These arrays are composed of direct repeats that are separated by similarly sized non-repetitive spacers. CRISPR arrays, together with a group of associated proteins, confer resistance to phages, possibly by an RNA-interference-like mechanism. This Progress discusses the structure and function of this newly recognized antiviral mechanism.     

Insulin resistance and endothelial dysfunction in smokers: effects of vitamin C

Cigarette smoking impairs endothelial function and is one of the major risk factors for atherosclerosis and coronary heart disease. Insulin resistance is associated with major risk factors for atherosclerosis. We examined the effects of vitamin C on insulin sensitivity and endothelial function by measuring steady-state plasma glucose (SSPG) and flow-mediated dilation (FMD) of the brachial artery. We studied 16 current smokers with normal glucose tolerance, 15 nonsmokers with impaired glucose tolerance (IGT), and 17 nonsmokers with normal glucose tolerance as controls. Both SSPG and FMD were blunted in smokers and nonsmokers with IGT compared with controls. In smokers, vitamin C decreased SSPG (P < 0.01 by ANOVA) with decreasing plasma thiobarbituric acid-reactive substances (TBARS) (P < 0.05 by ANOVA) and improved FMD (P < 0.05 by ANOVA). Furthermore, vitamin C improved both SSPG (P < 0.005 by ANOVA) and FMD (P < 0.05 by ANOVA) in nonsmokers with IGT. SSPG, FMD, or TBARS in controls did not change after vitamin C infusion. There was a significant correlation between SSPG and FMD both in smokers and nonsmokers with IGT, whereas no correlation was observed in controls. In conclusion, both insulin sensitivity and endothelial function were impaired in smokers and nonsmokers with IGT and were improved by vitamin C. Thus increased reactive oxygen species play an important role in the pathogenesis of insulin resistance as well as endothelial dysfunction in smokers and nonsmokers with IGT.     

11,12-EET increases porto-sinusoidal resistance and may play a role in endothelial dysfunction of portal hypertension

CYP450-dependent epoxyeicosatrienoic acids (EETs) are potent arterial vasodilators, while 20-hydroxyeicosatatraenoic acid (20-HETE) is a vasoconstrictor. We evaluated their role in the control of portal circulation in normal and cirrhotic (CCl(4) induced) isolated perfused rat liver. Phenylephrine (PE) and endothelin-1 (ET-1) increased portal perfusion pressure, as did arachidonic acid (AA), 20-HETE, and 11,12-EET. Inhibition of 20-HETE with 12,12-dibromododecenoic acid (DBDD) did not affect basal pressure nor the responses to PE, ET-1, or AA. However, inhibition of epoxygenase with miconazole caused a significant reduction in the response to ET-1 and to AA, without affecting neither basal pressure nor the response to PE. Hepatic vein EETs concentration increased in response to ET-1, and was increased in cirrhotic, compared to control, livers. 20HETE levels were non-measurable. Miconazole decreased portal perfusion pressure in cirrhotic livers. In conclusion, 20HETE and EETs increase portal resistance; EETs, but not 20-HETE, mediate in part the pressure response to ET-1 in the portal circulation and may be involved in pathophysiology of portal hypertension.