The adipokine chemerin amplifies electrical field-stimulated contraction in the isolated rat superior mesenteric artery

Abstract

Darios ES, Winner BM, Charvat T, Krasinksi A, Punna S, Watts SW. The adipokine chemerin amplifies electrical field-stimulated contraction in the isolated rat superior mesenteric artery. Am J Physiol Heart Circ Physiol 311: H498 -H507, 2016. First published July 1, 2016; doi:10.1152/ajpheart.00998.2015.-The adipokine chemerin causes arterial contraction and is implicated in blood pressure regulation, especially in obese subjects with elevated levels of circulating chemerin. Because chemerin is expressed in the perivascular adipose tissue (PVAT) that surrounds the sympathetic innervation of the blood vessel, we tested the hypothesis that chemerin (endogenous and exogenous) amplifies the sympathetic nervous system in mediating electrical field-stimulated (EFS) contraction. The superior mesenteric artery, with or without PVAT and with endothelium and sympathetic nerve intact, was mounted into isolated tissue baths and used for isometric contraction and stimulation. Immunohistochemistry validated a robust expression of chemerin in the PVAT surrounding the superior mesenteric artery. EFS (0.3-20 Hz) caused a frequency-dependent contraction in isolated arteries that was reduced by the chemerin receptor ChemR23 antagonist CCX832 alone (100 nM; with, but not without, PVAT), but not by the inactive congener CCX826 (100 nM). Exogenous chemerin-9 (1 M)-amplified EFSinduced contraction in arteries (with and without PVAT) was blocked by CCX832 and the ␣-adrenergic receptor antagonist prazosin. CCX832 did not directly inhibit, nor did chemerin directly amplify, norepinephrine-induced contraction. Whole mount immunohistochemical experiments support colocalization of ChemR23 with the sympathetic nerve marker tyrosine hydroxylase in superior mesenteric PVAT and, to a lesser extent, in arteries and veins. These studies support the idea that exogenous chemerin modifies sympathetic nervemediated contraction through ChemR23 and that ChemR23 may be endogenously activated. This is significant because of the wellappreciated role of the sympathetic nervous system in blood pressure control. BECAUSE OF ITS LOCATION, the perivascular adipose tissue (PVAT) has the potential to affect the function of the blood vessels it encases. This can occur by secretion of adipokines that directly affect vascular tone, such as the relaxant adiponectin (25). We recently discovered the protein chemerin in PVAT and demonstrated that a shorter chemerin agonist, chemerin-9, caused direct arterial contraction through activation of the best-characterized chemerin receptor, ChemR23 (3,8,27,33,38,48). Chemerin is secreted from the liver and fat depots (10), functioning as an adipokine that regulates adipogenesis (12,31,32) and as an activator of inflammatory cells (13,50,52). Circulating levels of chemerin are positively associated with body mass index (1,4,9,16,36,37,40). Because of our long-term interest in understanding whether chemerin could play a role in obesity-associated hypertension, we turned our attention to a means by which arterial function could be m...

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“…These conclusions have been supported by other laboratories that noted the importance of the endothelium in protecting against chemerin-induced contraction (Neves et al, 2014). The normal SMA also has the ability to contract in a chemerin receptor-dependent manner when stimulated with an electrical field, a contraction that was dependent on PVAT and the sympathetic nervous system (Darios et al, 2016). We have identified the mechanism of vascular contraction in normal animals as an operation through the smooth muscle cells themselves that works in a calcium-dependent manner (Ferland et al, 2017).…”

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“…Moreover, these effects are exaggerated in thoracic aorta and mesenteric arteries with reduced endothelium‐dependent relaxation, a phenomenon often found in hypertension and obesity (Watts et al , ). A follow‐up study by the same group (Darios et al , ) has also shown that PVAT‐derived chemerin potentiates sympathetic contraction through its receptor, which is co‐localized with tyrosine hydrolase in sympathetic nerves of rat superior mesenteric artery. Direct application of chemerin to isolated aorta or mesenteric artery also augments agonist‐induced contraction in a manner dependent on endothelin ET A receptors and ERK activation (Lobato et al ., ) and increases systolic blood pressure in mice (Kunimoto et al ., ).…”

“…The expansion of PVAT is also likely to involve the generation of pre‐adipocytes from resident mesenchymal stem cells and maturation of pre‐adipocytes (Pellegrinelli et al ., ). Moreover, PVAT is also innervated by sympathetic nerves (Bulloch and Daly, ; Darios et al , ), which could stimulate the browning of PVAT. However, the interactions among perivascular adipocytes, immune cells and nerves in vascular regulation remain poorly defined.…”

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“…Furthermore, PVAT represents a source of so-called adipocytederived relaxing factor(s) (ADRF), that have potent relaxant or anticontractile properties [31,32] . Apart from these actions being demonstrated in blood vessels from experimental animals [37][38][39] , PVAT has been shown to possess anticontractile actions in isolated preparations of the human internal thoracic artery (ITA) [40] and SV [41] . Although specific ADRFs have not yet been identified, various candidates have been suggested, including NO [42] , leptin [32,43] , H2S [44] , adiponectin [45,46] , and prostaglandins [41,47] .…”