No abstract

The transient receptor potential type V1 channel (vanilloid receptor 1, TRPV1) is a Ca 2ϩ -permeable nonspecific cation channel activated by various painful stimuli including ischemia. We hypothesized that TRPV1 is expressed in the arterioles and is involved in the regulation of microvascular tone. We found that TRPV1 stimulation by capsaicin (intra-arterial administration) of the isolated, perfused right hind limb of the rat increased vascular resistance (by 98 Ϯ 21 mm Hg at 10 g) in association with decreased skeletal muscle perfusion and elevation of skin perfusion (detected by dual-channel laser Doppler flowmetry). Denervation of the hind limb did not affect capsaicin-evoked changes in vascular resistance and tissue perfusion in the hind limb but reduced the elevation of perfusion in the skin. In isolated, pressurized skeletal (musculus gracilis) muscle arterioles (diameter, 147 Ϯ 35 m), capsaicin had biphasic effects: at lower concentrations, capsaicin (up to 10 nM) evoked dilations (maximum, 32 Ϯ 13%), whereas higher concentrations (0.1-1 M) elicited substantial constrictions (maximum, 66 Ϯ 7%). Endothelium removal or inhibition of nitric-oxide synthase abolished capsaicin-induced dilations but did not affect arteriolar constriction. Expression of TRPV1 was detected by reverse transcriptase-polymerase chain reaction in the aorta and in cultured rat aortic vascular smooth muscle cells (A7r5). Immunohistochemistry revealed expression primarily in the smooth muscle layers of the gracilis arteriole. These data demonstrate the functional expression of TRPV1 in vascular smooth muscle cells mediating vasoconstriction of the resistance arteries. Because of the dual effects of TRPV1 stimulation on the arteriolar diameter (dilation in skin, constriction in skeletal muscle), we propose that TRPV1 ligands represent drug candidates for tissue-specific modulation of blood distribution.The transient receptor potential type V1 channel (vanilloid receptor-1, TRPV1) is a nonselective cation channel, structurally belonging to the transient receptor potential family of ion channels. TRPV1 is found in sensory C and A-␦ fibers (Caterina et al., 1997) and functions as a ligand-, proton-, and heat-activated molecular integrator of nociceptive stimuli in the periphery (Szallasi and Blumberg, 1999;

BackgroundGrowing evidence exists for soluble Angiotensin Converting Enzyme-2 (sACE2) as a biomarker in definitive heart failure (HF), but there is little information about changes in sACE2 activity in hypertension with imminent heart failure and in reverse remodeling.Methods, FindingsPatients with systolic HF (NYHAII-IV, enrolled for cardiac resynchronisation therapy, CRT, n = 100) were compared to hypertensive patients (n = 239) and to a healthy cohort (n = 45) with preserved ejection fraction (EF>50%) in a single center prospective clinical study. The status of the heart failure patients were checked before and after CRT. Biochemical (ACE and sACE2 activity, ACE concentration) and echocardiographic parameters (EF, left ventricular end-diastolic (EDD) and end-systolic diameter (ESD) and dP/dt) were measured.sACE2 activity negatively correlated with EF and positively with ESD and EDD in all patient's populations, while it was independent in the healthy cohort. sACE2 activity was already increased in the hypertensive group, where signs for imminent heart failure (slightly decreased EF and barely increased NT-proBNP levels) were detected. sACE2 activities further increased in patients with definitive heart failure (EF<50%), while sACE2 activities decreased with the improvement of the heart failure after CRT (reverse remodeling). Serum angiotensin converting enzyme (ACE) concentrations were lower in the diseased populations, but did not show a strong correlation with the echocardiographic parameters.ConclusionsSoluble ACE2 activity appears to be biomarker in heart failure, and in hypertension, where heart failure may be imminent. Our data suggest that sACE2 is involved in the pathomechanism of hypertension and HF.

It has been proposed that activation of vanilloid receptor-1 (TRPV1) affects the vasotone of resistance arteries. One of the endogenous activators of TRPV1 is anandamide. The effects of anandamide on TRPV1 responsiveness were tested on isolated, pressurized (80 mm Hg) skeletal muscle (m. gracilis) arterioles (179 Ϯ 33 m in diameter). We found that the TRPV1 agonist capsaicin (1 M) elicited a substantial constriction in isolated arterioles (51 Ϯ 12%). In contrast, anandamide (0 -100 M) did not affect arteriolar diameter significantly (3 Ϯ 5%). Isolated vessels were also preincubated with anandamide (30 M for 20 min). This anandamide pretreatment completely blocked capsaicin-induced arteriolar constriction (response decreased to 1 Ϯ 0.6%), and this inhibition was reversed by a protein phosphatase-2B inhibitor (cyclosporin-A; 100 nM, 5 min) treatment (constriction, 31 Ϯ 1%). An exogenous TRPV1-expressing cell line [Chinese hamster ovary (CHO)-TRPV1] was used to specifically evaluate TRPV1-mediated effects of anandamide. The efficacy of anandamide in this system, as determined by 45 Ca 2ϩ uptake, was 65 Ϯ 8% of that of capsaicin. Upon treatment of the cells with cyclosporin-A or the protein kinase C activator phorbol 12-myristate 13-acetate (PMA), anandamide was transformed to a full agonist. Anandamide treatment caused an acute desensitization in these cells as measured by intracellular Ca 2ϩ imaging. Application of cyclosporin-A or PMA reversed this desensitization. Our data suggest that anandamide may cause a complete (albeit phosphorylation-dependent) desensitization of TRPV1 in skeletal muscle arterioles and in CHO-TRPV1 cells, which apparently transforms the ligand-gated TRPV1 into a phosphorylationgated channel. This property of anandamide may provide a new therapeutic strategy to manipulate TRPV1 activity.The vanilloid receptor 1 (TRPV1) is a nonselective cation channel, the structure of which places it in the transient receptor potential family of ion channels. In the periphery, TRPV1 is primarily expressed in sensory C and A-␦ fibers (Caterina et al., 1997) and acts as a ligand-, proton-, and heat-activated molecular integrator of nociceptive stimuli Di Marzo et al., 2002a,b;Ross, 2003). Activation of TRPV1 leads to central (pain) and to local "sensory-efferent" effects (Szolcsanyi, 2000). These include the release of vasoactive agents (such as calcitonin gene-related peptide) and subsequent vasorelaxation (Zygmunt et al., 1999).Compared with the well characterized effects of TRPV1 upon stimulation by exogenous substances , relatively little is known about its endogenous ligands. So far, anandamide (N-arachidonoyl-ethanolamide) (Zygmunt et al., 1999), N-arachidonoyl-dopamine (NADA) (Huang et al., 2002), and different lipoxygenase products (Hwang et al., 2000) have been identified as endogenous agonists of TRPV1. Among them, anandamide was originally identified as an endocannabinoid activating the

It was shown recently that angiotensin-converting enzyme activity is limited by endogenous inhibition in vivo, highlighting the importance of angiotensin II (ACE2) elimination. The potential contribution of the ACE2 to cardiovascular disease progression was addressed. Serum ACE2 activities were measured in different clinical states (healthy, n=45; hypertensive, n=239; heart failure (HF) with reduced ejection fraction (HFrEF) n=141 and HF with preserved ejection fraction (HFpEF) n=47). ACE2 activity was significantly higher in hypertensive patients (24.8±0.8 U/ml) than that in healthy volunteers (16.2±0.8 U/ml, p=0.01). ACE2 activity further increased in HFrEF patients (43.9±2.1 U/ml, p=0.001) but not in HFpEF patients (24.6±1.9 U/ml) when compared with hypertensive patients. Serum ACE2 activity negatively correlated with left ventricular systolic function in HFrEF, but not in hypertensive, HFpEF or healthy populations. Serum ACE2 activity had a fair diagnostic value to differentiate HFpEF from HFrEF patients in this study. Serum ACE2 activity correlates with cardiovascular disease development: it increases when hypertension develops and further increases when the cardiovascular disease further progresses to systolic dysfunction, suggesting that ACE2 metabolism plays a role in these processes. In contrast, serum ACE2 activity does not change when hypertension progresses to HFpEF, suggesting a different pathomechanism for HFpEF, and proposing a biomarker-based identification of these HF forms.