Chemerin Connects Fat to Arterial Contraction

Abstract

Objective-Obesity and hypertension are comorbid in epidemic proportion, yet their biological connection is largely a mystery. The peptide chemerin is a candidate for connecting fat deposits around the blood vessel (perivascular adipose tissue) to arterial contraction. We presently tested the hypothesis that chemerin is expressed in perivascular adipose tissue and is vasoactive, supporting the existence of a chemerin axis in the vasculature. Approach and Results-Real-time polymerase chain reaction, immunohistochemistry, and Western analyses supported the synthesis and expression of chemerin in perivascular adipose tissue, whereas the primary chemerin receptor ChemR23 was expressed both in the tunica media and endothelial layer. The ChemR23 agonist chemerin-9 caused receptor, concentration-dependent contraction in the isolated rat thoracic aorta, superior mesenteric artery, and mesenteric resistance artery, and contraction was significantly amplified (more than 100%) when nitric oxide synthase was inhibited and the endothelial cell mechanically removed or tone was placed on the arteries. The novel ChemR23 antagonist CCX832 inhibited phenylephrine-induced and prostaglandin F2α-induced contraction (+perivascular adipose tissue), suggesting that endogenous chemerin contributes to contraction. Arteries from animals with dysfunctional endothelium (obese or hypertensive) demonstrated a pronounced contraction to chemerin-9. Finally, mesenteric arteries from obese humans demonstrate amplified contraction to chemerin-9. Conclusions-These Watts et al Chemerin as a Vasoconstrictor 1321also play a role in obesity. Additionally, chemerin regulates adipocyte differentiation [18][19][20] and production of several proinflammatory cytokines. We hypothesized that a chemerin axis exists in blood vessels. We propose that chemerin and the primary receptor for chemerin, ChemR23, are present and mediate contraction in the vasculature. Materials and MethodsMaterials and Methods are available in the online-only Supplement. Results Arterial Chemerin AxisIsolated rat arteries express chemerin protein in the PVAT ( Figure 1A). Real-time polymerase chain reaction supports the expression of chemerin (RARRES2) mRNA in the rat thoracic aortic PVAT (whole PVAT; threshold cycle [C T ] =22.78±0.35; β2-microglobulin as control = 19.32±0.27; n=6). Chemerin signal does not wholly derive from resident mast cells because there was negligible CD68 staining in PVAT ( Figure 1B, + control below), and staining for chemerin was, in many places, not punctate. Positive staining was observed within the cytoplasm of the fat cell, outside the rounded lipid droplet. The predominant receptor for chemerin, ChemR23, is expressed in the tunica media and endothelial cell layer ( Figure 1C) and is observed as 3 dominant bands in homogenates (−PVAT) of the thoracic aorta and superior mesenteric artery cleaned of PVAT ( Figure 1D and 1E). Two bands (at arrows) are consistent with that observed in a JAR (choriocarcinoma) positive control and were 42 kDa (expected size for...

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

“…Figure 1 shows the immunohistochemical staining of the PVAT surrounding the superior mesenteric artery with an antibody against chemerin in the presence of the primary antibody (left) and without the primary antibody in the reaction (right). The cytosol of the adipose cells stained robustly for chemerin, which indicates that PVAT is an endogenous source of chemerin to the artery and confirms previous findings (48).…”

“…Chemerin-9 itself did not cause a leftward or an upward shift in the NE concentration-response curve, and the ChemR23 antagonist CCX832 did not result in a rightward or a downward shift in NE-induced contraction. We previously reported that addition of an adrenergic agonist (PE) would amplify contraction to chemerin-9 (48). In this previous experiment, a half-maximal contraction to PE was established and then chemerin-9 was added.…”

“…This particular fat is important to study, because it directly surrounds the artery and, thus, is a source of chemerin in close proximity to the artery. CCX832, which was first reported in 2013 as an original small-molecule ChemR23 antagonist (48), allows us to examine if there is endogenous activation of ChemR23. CCX826 provided a structure control for CCX832.…”

“…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).…”

Development by Genetic Immunization of Monovalent Antibodies (Nanobodies) Behaving as Antagonists of the Human ChemR23 Receptor

“…Only one antagonist of ChemR23 has been developed: the small molecule CCX832. It was described as an inhibitor of chemerin signaling through ChemR23 across multiple species (human, mouse, and rat) using radioligand-binding and calciummobilization assays (41). No antagonist of GPR1 or CCRL2 has been described.…”