Requisite roles of LOX-1, JNK, and arginase in diabetes-induced endothelial vasodilator dysfunction of porcine coronary arterioles

Abstract

Diabetes is associated with cardiac inflammation and impaired endothelium-dependent coronary vasodilation, but molecular mechanisms involved in this dysfunction remain unclear. We examined contributions of inflammatory molecules lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), stress-activated kinases (c-Jun N-terminal kinase [JNK] and p38), arginase, and reactive oxygen species to coronary arteriolar dysfunction in a porcine model of type 1 diabetes. Coronary arterioles were isolated from streptozocin-induced diabetic pigs and control pigs for vasoreactivity and molecular/biochemical studies. Endothelium-dependent nitric oxide (NO)-mediated vasodilation to serotonin was diminished after 2 weeks of diabetes, without altering endotheliumindependent vasodilation to sodium nitroprusside. Superoxide scavenger TEMPOL, NO precursor L-arginine, arginase inhibitor nor-NOHA, anti-LOX-1 antibody or JNK inhibitors SP600125 and BI-78D3 improved dilation of diabetic vessels to serotonin. However, hydrogen peroxide scavenger catalase, anti-IgG antibody or p38 kinase inhibitor SB203580 had no effect. Combined inhibition of arginase and superoxide levels did not further improve vasodilation. Arginase-I mRNA expression, LOX-1 and JNK protein expression, and superoxide levels were elevated in diabetic arterioles. In conclusion, sequential activation of LOX-1, JNK, and L-arginine consuming enzyme arginase-I in diabetes elicits superoxide-dependent oxidative stress and impairs endothelial NO-mediated dilation in coronary arterioles. Therapeutic targeting of these adverse vascular molecules may improve coronary arteriolar function during diabetes.

Role of Arginase in Selective Impairment of Endothelium-Dependent Nitric Oxide Synthase-Mediated Dilation of Retinal Arterioles during Early Diabetes

“…38 We also performed functional studies with coronary and retinal arterioles isolated from the same diabetic pigs, but surprisingly found that TEMPOL only restored NOS-mediated dilation of coronary arterioles. 39 Our findings from this previous work with coronary arterioles also suggest that upregulation of arginase I in these vessels leads to the production of superoxide. These disparate results related to the roles of superoxide and arginase in retinal and coronary arterioles underscore the apparent heterogeneity in mechanisms of diabetes-induced endothelial vasodilator dysfunction in the microcirculation.…”

“…For some vessels, the relationship between NOS and arginase in the vasodilations to histamine and bradykinin was evaluated in the presence of L-NAME with or without the arginase inhibitor nor-NOHA (0.1 mmol/L intraluminal treatment for 90 minutes; Cayman Chemical; Ann Arbor, MI, USA). 28,39 To assess the involvement of arginase and superoxide in the diabetes-induced effect, the vasodilator responses were examined after intraluminal treatment of vessels with nor-NOHA (0.1 mM) 28,39 or superoxide dismutase mimetic TEMPOL (1 mmol/L), 38,39 respectively, for 90 minutes.…”

Activation of Coronary Arteriolar PKCβ2 Impairs Endothelial NO-Mediated Vasodilation: Role of JNK/Rho Kinase Signaling and Xanthine Oxidase Activation

“…This finding is consistent with a previous study showing that PKCβ2 activation links to the impairment of flow-induced vasodilation in a microvascular network by suppression of NO release from the endothelium [ 52 ]. Interestingly, inhibition of PKCβ2 preserves endothelium-dependent vasodilation [ 53 ] and reverses endothelial barrier dysfunction [ 54 ] in experimental models with hyperglycemia and diabetes, which are known to cause endothelial NO deficiency [ 14 , 23 , 52 , 55 ]. It should be noted that PKCβ2 is expressed abundantly in the coronary arteriolar wall, including endothelial cells, and is co-localized with eNOS ( Figure 5 ).…”

“…Moreover, inhibition of PKC has been shown to attenuate vascular superoxide production in various forms of cardiovascular stress in animals [14,17,18] and humans [14,19]. Interestingly, recent studies suggested a role of mitogen-activated protein kinases (MAPKs) or Rho kinase in superoxide production from coronary microvessels subjected to inflammatory insults [20][21][22] or harvested from animals with cardiovascular diseases [21,23,24]. However, it remains unclear whether direct activation of PKC signaling in the healthy vasculature can cause MAPK/Rho kinase activation and excessive superoxide production, with consequent vasomotor dysfunction.…”

The Role of PKC-MAPK Signalling Pathways in the Development of Hyperglycemia-Induced Cardiovascular Complications

“…In fact, only a few JNK inhibitors have been tested in clinical trials for various indications, yet none for the treatment of cardiovascular pathology. Preclinical studies on the use of JNK-specific inhibitors such as AS601245 and SP600125 have been found to exert cardiovascular protective effects by attenuating cardiac inflammation, endothelial dysfunction, as well as protecting against diabetic nephropathy progression [ 205 , 206 , 207 ].…”