Background-Although pharmacological studies suggest that the transient receptor potential vanilloid type 1 (TRPV1) channels expressed in sensory nerve fibers innervating the heart may exert a cardioprotective effect, definitive evidence supporting such a notion is lacking. In addition, function and regulation of sensory neuropeptides, namely, calcitonin gene-related peptide (CGRP) and substance P (SP), in the face of challenges induced by cardiac injury in the presence or absence of the TRPV1 are largely unknown. Methods and Results-The hearts of gene-targeted TRPV1-null mutant (TRPV1

Abstract-To determine the role of the transient receptor potential vanilloid type 1 (TRPV1) channels in development of hypertension in Dahl salt-sensitive (DS) rats fed a high-salt diet (HS), male DS and Dahl salt-resistant (DR) rats were maintained on a low-salt diet (LS) or HS for 3 weeks. HS significantly increased systolic blood pressure in DSϩHS rats compared with DSϩLS, DRϩHS, and DRϩLS rats. Intravenous bolus injection of capsazepine (3 mg/kg), a selective TRPV1 antagonist, significantly increased mean arterial pressure in conscious DRϩHS rats compared with DRϩLS, DSϮHS, and DSϮLS rats. In contrast, capsaicin (10 or 30 g/kg), a selective TRPV1 agonist, dose-dependently decreased mean arterial pressure in all of the groups with the most profound magnitude in DRϩHS rats compared with the other 3 groups. TRPV1 expression in mesenteric resistance arteries and the renal cortex and medulla, calcitonin gene-related peptide levels in dorsal root ganglia, and calcitonin gene-related peptide-positive sensory nerve density in mesenteric resistance arteries were significantly decreased in DSϩHS rats compared with DSϩLS, DRϩHS, and DRϩLS rats. Taken together, our data indicate that the TRPV1 receptor is activated and its expression upregulated during HS intake in DR rats, which acts to prevent salt-induced increases in blood pressure. In contrast, TRPV1 expression and function are impaired in DS rats, which renders DS rats sensitive to salt load in terms of blood pressure regulation. Key Words: peptides Ⅲ rats, Dahl Ⅲ hypertension, sodium-dependent Ⅲ blood pressure B oth clinical and experimental studies have shown a correlation of dietary salt intake and the prevalence and progression of hypertension. 1 Salt-sensitive hypertension is more prevalent in blacks and the elderly, who are accompanied by a decrease in sensory nerve function. 2 Studies in animals provide compelling evidence showing that sensory nerves play a key role in preventing salt-induced elevation in blood pressure, 3 suggesting that a defect in sensory nerve function may contribute to increased salt sensitivity in humans. Dahl salt-sensitive (DS) rats have been used as a model of human salt-sensitive hypertension given that salt load exaggerates the development of hypertension in this strain that is genetically predisposed to hypertension 4,5 and that these rats exhibit elevated insulin resistance, which mimics the black hypertensive population. 6 Thus, studies of DS rats may provide valuable clues to the pathogenesis of salt-sensitive hypertension and related traits in black patients.The transient receptor potential vanilloid type 1 (TRPV1) channel is a ligand-gated nonselective ion channel expressed primarily in sensory nerves of unmyelinated C-fibers or thinly myelinated A␦-fibers innervating cardiovascular tissues including the heart, kidney, and blood vessels. 2,7,8 The TRPV1 functions as a molecular integrator of multiple chemical and physical stimuli including capsaicin, lipid metabolites, proton, and noxious heat. 9 -12 Activation of the TRPV1...

Abstract-To test the hypothesis that activation of the vanilloid receptor (VR1) contributes to the anandamide-induced depressor effect in spontaneously hypertensive rats (SHR), we used a selective VR1 antagonist capsazepine (CAPZ) and a selective cannabinoid type 1 receptor antagonist SR141716A in conjunction with a VR1 agonist capsaicin in both SHR and Wistar-Kyoto rats (WKY 4 However, numerous studies indicate that the cardiovascular effect of anandamide is not solely mediated by the CB1 receptor. For example, it has been shown that the vasodilator actions of anandamide in the mesenteric arterial bed are independent of the CB1 receptor. 5 The potent CB1 agonist WIN55212-2 causes vasodilatation in the cat cerebral artery. 6 WIN55212-2 does not cause vasodilatation in the rat mesenteric arterial bed, whereas the endogenous ligand anandamide does cause vasodilatation in this same location. 7 Moreover, in CB1 knockout mice, as well as CB1/CB2 double-knockout mice, anandamide-induced mesenteric vasodilatation is intact. 8 Taken together, these data indicate that receptors distinctive from CB1 and CB2 receptors may mediate the vasodilatation and hypotensive effect of anandamide.One of the potential candidates is the vanilloid receptor 1 (VR1), a ligand-gated ion channel that integrates multiple stimuli, including capsaicin, proton, and heat. 9 -11 This receptor is expressed almost exclusively in primary sensory nerves. It has been demonstrated that VR1 mediates cardiovascular effects of capsaicin, anandamide, and other vanilloid compounds, including vasodilatation in a variety of vascular beds. 12,13 Activation of the VR1 receptor in primary sensory nerves by anandamide induces release of calcitonin generelated peptide (CGRP) from sensory nerve endings and causes vasodilatation. 13 These studies indicate that anandamide-induced activation of the VR1 receptor may play a significant role in blood pressure regulation.In spontaneously hypertensive rats (SHR), the pathogenesis of hypertension appears to be heterogeneous, including the central nervous system, neurohumoral, and renal abnormali-

Zhong B, Wang DH. TRPV1 gene knockout impairs preconditioning protection against myocardial injury in isolated perfused hearts in mice. Am J Physiol Heart Circ Physiol 293: H1791-H1798, 2007. First published June 22, 2007; doi:10.1152/ajpheart.00169.2007.-Although the transient receptor potential vanilloid type 1 (TRPV1)-containing afferent nerve fibers are widely distributed in the heart, the relationship between TRPV1 function and cardiac ischemic preconditioning (PC) has not been well defined. Using TRPV1 knockout mice (TRPV1 Ϫ/Ϫ ), we studied the role of TRPV1 in PC-induced myocardial protection. Hearts of gene-targeted TRPV1-null mutant (TRPV1 Ϫ/Ϫ ) or wild-type (WT) mice were Langendorffly perfused in the presence or absence of CGRP 8-37, a selective calcitonin generelated peptide (CGRP) receptor antagonist; or RP-67580, a selective neurokinin-1 receptor antagonist when hearts were subjected to three 5-min periods of ischemia PC followed by 30 min of global ischemia and 40 min of reperfusion (I/R). PC before I/R decreased left ventricular (LV) end-diastolic pressure and increased LV developed pressure, coronary flow (CF), peak-positive maximum rate of rise of LV pressure in WT mice (PC-WT) compared with PC-TRPV1 Ϫ/Ϫ , TRPV1 Ϫ/Ϫ , or WT hearts (P Ͻ 0.05), and PC also decreased LV end-diastolic pressure in PC-TRPV1 Ϫ/Ϫ compared with TRPV1 Ϫ/Ϫ . CGRP or RP-67580 abolished PC-induced protection in WT but not TRPV1Ϫ/Ϫ hearts (P Ͻ 0.05). Moreover, PC decreased lactate dehydrogenase release and infarct size in PC-WT compared with PC-TRPV1 Ϫ/Ϫ , TRPV1 Ϫ/Ϫ , or WT hearts, and it also lowered these parameters in PC-TRPV1 Ϫ/Ϫ compared with TRPV1 Ϫ/Ϫ hearts (P Ͻ 0.05). Radioimmunoassay showed that the release of substance P and CGRP after PC was higher in WT hearts than in TRPV1 Ϫ/Ϫ hearts (P Ͻ 0.05), which was attenuated by capsazepine in WT but not TRPV1 Ϫ/Ϫ hearts. Thus PC-induced protection of the heart was impaired in TRPV1 Ϫ/Ϫ hearts, indicating that TRPV1 contributes to the beneficial effects of preconditioning against I/R injury through release substance P and CGRP. transient receptor potential vanilloid type 1; ischemia-reperfusion; substance P; calcitonin gene-related peptide ISCHEMIC PRECONDITIONING (PC) confers a remarkable cardioprotection in a variety of species as well as in humans, which is triggered by repeated, no-lethal, brief episodes of myocardial ischemia and reperfusion, resulting in potent and immediate protection against subsequent injurious ischemia-reperfusion (I/R) (29, 32). The protective effect of ischemic PC has been shown to be attenuated in the diabetic (19) and aging hearts (40), whereas sensory nerve function is known to be impaired during these pathological processes. However, the relationship between sensory nerve function and ischemic PC has not been well defined.Capsaicin-sensitive sensory nerves are widely distributed in the cardiovascular system and can be activated by a variety of physical and chemical stimuli. The myocardium and the coronary vascular system possess dense cap...

N-oleoyldopamine (OLDA), a bioactive lipid originally found in the mammalian brain, is an endovanilloid that selectively activates the transient receptor potential vanilloid type 1 (TRPV1) channel. This study tests the hypothesis that OLDA protects the heart against ischemia and reperfusion (I/R) injury via activation of the TRPV1 in wild-type (WT) but not in gene-targeted TRPV1-null mutant (TRPV1(-/-)) mice. Hearts of WT or TRPV1(-/-) mice were Langendorffly perfused with OLDA (2 x 10(-9) M) in the presence or absence of CGRP8-37 (1 x 10(-6) M), a selective calcitonin gene-related peptide (CGRP) receptor antagonist; RP-67580 (1 x 10(-6) M), a selective neurokinin-1 receptor antagonist; chelerythrine (5 x 10(-6) M), a selective protein kinase C (PKC) antagonist; or tetrabutylammonium (TBA, 5 x 10(-4) M), a nonselective K(+) channel antagonist, followed by 35 min of global ischemia and 40 min of reperfusion (I/R). Left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDP), coronary flow (CF), and left ventricular peak positive dP/dt (+dP/dt) were evaluated after I/R. OLDA improved recovery of cardiac function after I/R in WT but not TRPV1(-/-) hearts by increasing LVDP, CF, and +dP/dt and by decreasing LVEDP. CGRP8-37, RP-67580, chelerythrine, or TBA abolished the protective effect of OLDA in WT hearts. Radioimmunoassay showed that the release of substance P (SP) and CGRP after OLDA treatment was higher in WT than in TRPV1(-/-) hearts, which was blocked by chelerythrine or TBA. Thus OLDA exerts a cardiac protective effect during I/R injury in WT hearts via CGRP and SP release, which is abolished by PKC or K(+) channel antagonists. The protective effect of OLDA is void in TRPV1(-/-) hearts, supporting the notion that TRPV1 mediates OLDA-induced protection against cardiac I/R injury.

Abstract-This study was designed to test the hypothesis that increased sensitivity of blood pressure to anandamide (AEA), an endocannabinoid compound, occurs during high-salt intake, which can be blocked by a selective vanilloid receptor 1(VR1) antagonist, capsazepine (CAPZ). Intravenous administration of a metabolically stable analog, methanandamide (MethA), dose-dependently decreased mean arterial pressure (MAP) in conscious rats fed a high-sodium diet (HS) for 3 weeks but it had a minimal effect in normal sodium (NS)-treated rats. The MethA-induced decrease in MAP was significantly attenuated but not abolished by CAPZ, or a selective cannabinoid receptor 1 (CB1) antagonist, SR141716A, administered separately in HS-treated rats. The MethA-induced depressor effect was prevented by the combined administration of CAPZ and SR141716A in HS-treated rats. Likewise, administration of capsaicin, a selective VR1 receptor agonist, dose-dependently decreased MAP in both HS-and NS-treated rats. The depressor effect of capsaicin was more profound in HS-treated rats, which was prevented by CAPZ. Western blot showed that expression of VR1 but not CB1 in mesenteric arteries was increased in HS-treated compared with NS-treated rats. Therefore, these data show that: (1) HS upregulates mesenteric VR1 expression; (2) HS increases sensitivity of blood pressure to AEA; and (3) HS-induced enhancement of the depressor effect of AEA can be prevented only when both VR1 and CB1 receptors are blocked. These results indicate that AEA contributes to the prevention of salt induced increases in blood pressure via, at least in part, activating the VR1 receptor. Key Words: high salt intake Ⅲ blood pressure Ⅲ sensory nerves Ⅲ neurotransmitters A nandamide, isolated from porcine brain in 1992, 1 is one of the endogenous ligands for the cannabinoid (CB) receptor. Cannabinoids are known to elicit neurobehavioral as well as cardiovascular effects. 2 The biological effects of cannabinoids are mediated by specific receptors, of which 2 subtypes have been identified by molecular cloning. The CB1 receptors express abundantly in both the central nervous system and peripheral tissues, 3 whereas CB2 receptor expression is essentially restricted to the immune system. 4 Given their profound cardiovascular effects in humans and animals, there is ever-increasing interest in endogenous cannabinoids. Recent evidence shows that anandamide and its analogs cause a prolonged hypotension and bradycardia in anesthetized normotensive or spontaneously hypertensive rats. 5,6 Although the hypotensive effect of anandamide may be mediated by the CB1 receptor in light of the fact that blood pressure response to anandamide can be blocked by the CB1 antagonist, SR141716A, 6 the mechanism underlying the anandamidemediated hypotension may be complex. We have shown that the methanandamide (MethA)-induced depressor effect in spontaneously hypertensive rats rats is attenuated by the vanilloid receptor 1 (VR1) antagonist, capsazepine (CAPZ), suggesting that activation of the VR1 rec...

Abstract-Enhanced vascular cell adhesion molecule-1 (VCAM-1) expression directly contributes to vascular dysfunction in hypertension. Decreased NO and/or increased superoxide are causative factors for such an event in the vessel wall. The present study was undertaken to determine whether gene transfer of endothelial NO synthase (eNOS) or manganese superoxide dismutase (MnSOD) affects VCAM-1 levels in arteries from hypertensive rats. Isolated carotid and femoral arteries from deoxycorticosterone acetate (DOCA)-salt hypertensive rats were transduced for 4 hours with adenoviral vectors encoding eNOS, MnSOD, or ␤-galactosidase reporter genes. Recombinant eNOS or MnSOD expression was evident morphologically and quantitatively 24 hours after gene transfer. Immunohistochemistry, ELISA, and Western blot techniques were used to determine VCAM-1 expression and levels. In addition, endogenous eNOS and MnSOD and in situ superoxide levels were analyzed by immunoblotting and fluorescence confocal microscopy, respectively. Arterial VCAM-1 expression was significantly higher in DOCA-salt hypertensive rats than in sham-operated rats; this expression was accompanied by decreased MnSOD but unaltered endogenous eNOS levels. VCAM-1 expression was significantly lower in MnSOD-and eNOS-transduced hypertensive arteries, with a concomitant reduction of superoxide level. These results suggest that gene transfer of MnSOD or eNOS suppresses arterial VCAM-1 expression in DOCA-salt hypertension by reducing the superoxide level. A lthough hypertension is one of the key risk factors for atherosclerosis, the underlying molecular and cellular mechanisms remain to be delineated. 1 Enhanced adhesion molecule expression is known to contribute directly to vascular dysfunction in hypertension. 2 Vascular cell adhesion molecule-1 (VCAM-1) is an early marker of endothelial activation and dysfunction, leukocyte infiltration, and vascular remodeling in the development of early atherosclerotic lesions (fatty streaks and fibrous plaques). 2-5 Although VCAM-1 is structurally similar to intercellular adhesion molecule-1 and other adhesion molecules, its pattern of expression is unique. It exhibits low to negligible expression under baseline conditions but is profoundly upregulated by proatherosclerotic conditions in animal models and in humans. [2][3][4][5] In addition, compared with other adhesion molecules whose expression often extends into uninvolved and/or lesion-protected regions of the vessel wall, VCAM-1 expression is largely restricted to atherosclerotic lesions and lesionpredisposed regions. 2-5 Consistent with these phenomena, a recent study has demonstrated that VCAM-1, but not intercellular adhesion molecule-1 (ICAM-1), plays a critical role in early atherogenesis. 6 Enhanced adhesion molecule expression has been ascribed to an imbalance between oxidative stress and antioxidant activity. Experimental evidence suggests that NO and superoxide are 2 key regulating factors for the expression of adhesion molecules, including VCAM-1. 7,8 In angiotensi...

Mammalian transient receptor potential (TRP) channels consist of six related protein sub‐families that are involved in a variety of pathophysiological function, and disease development. The TRPV1 channel, a member of the TRPV sub‐family, is identified by expression cloning using the “hot” pepper‐derived vanilloid compound capsaicin as a ligand. Therefore, TRPV1 is also referred as the vanilloid receptor (VR1) or the capsaicin receptor. VR1 is mainly expressed in a subpopulation of primary afferent neurons that project to cardiovascular and renal tissues. These capsaicin‐sensitive primary afferent neurons are not only involved in the perception of somatic and visceral pain, but also have a “sensory‐ effector” function. Regarding the latter, these neurons release stored neuropeptides through a calcium‐dependent mechanism via the binding of capsaicin to VR1. The most studied sensory neuropeptides are calcitonin gene‐related peptide (CGRP) and substance P (SP), which are potent vasodilators and natriuretic/diuretic factors. Recent evidence using the model of neonatal degeneration of capsaicin‐sensitive sensory nerves revealed novel mechanisms that underlie increased salt sensitivity and several experimental models of hypertension. These mechanisms include insufficient suppression of plasma renin activity and plasma aldosterone levels subsequent to salt loading, enhancement of sympathoexcitatory response in the face of a salt challenge, activation of the endothelin‐1 receptor, and impaired natriuretic response to salt loading in capsaicin‐pretreated rats. These data indicate that sensory nerves counterbalance the prohypertensive effects of several neurohormonal systems to maintain normal blood pressure when challenged with salt loading. The therapeutic utilities of vanilloid compounds, endogenous agonists, and sensory neuropeptides are also discussed.