Background Little is known about the impact of type 2 diabetes mellitus (DM) on coronary arteriole remodeling. The aim of this study was to determine the mechanisms that underlie coronary arteriole structural remodeling in type 2 diabetic (db/db) mice. Methods and Results Passive structural properties of septal coronary arterioles isolated from 12- and 16-wk-old diabetic db/db and control mice were assessed by pressure myography. Coronary arterioles from 12-wk-old db/db mice were structurally similar to age-matched controls. By 16-wks of age, coronary wall thickness was increased in db/db arterioles (p < 0.01), while luminal diameter was reduced (Control: 118±5μm; db/db: 102±4μm, p < 0.05), augmenting the wall-to-lumen ratio by 58% (Control: 5.9±0.6; db/db: 9.5±0.4, p < 0.001). Inward hypertrophic remodeling was accompanied by a 56% decrease in elastic modulus (p < 0.05, indicating decreased vessel coronary wall stiffness) and a ~30% reduction in coronary flow reserve in diabetic mice. Interestingly, aortic pulse wave velocity and femoral artery incremental modulus were increased (p < 0.05) in db/db mice, indicating macrovascular stiffness. Molecular tissue analysis revealed increased elastin-to-collagen ratio in diabetic coronaries when compared to control and a decrease in the same ratio in the diabetic aortas. Conclusions These data show that coronary arterioles isolated from type 2 diabetic mice undergo inward hypertrophic remodeling associated with decreased stiffness and increased elastin-to-collagen ratio which results in a decreased coronary flow reserve. This study suggests that coronary microvessels undergo a different pattern of remodeling from macrovessels in type 2 DM.

Traumatic brain injury (TBI) is an increasingly frequent and poorly understood condition lacking effective therapeutic strategies. Inflammation and oxidative stress (OS) are critical components of injury, and targeted interventions to reduce their contribution to injury should improve neurobehavioral recovery and outcomes. Recent evidence reveals potential protective, yet short-lived, effects of the endocannabinoids (ECs), 2-arachidonoyl glycerol (2-AG) and N-arachidonoylethanolamine (AEA), on neuroinflammatory and OS processes after TBI. The aim of this study was to determine whether EC degradation inhibition after TBI would improve neurobehavioral recovery by reducing inflammatory and oxidative damage. Adult male Sprague-Dawley rats underwent a 5-mm left lateral craniotomy, and TBI was induced by lateral fluid percussion. TBI produced apnea (17 -5 sec) and a delayed righting reflex (479 -21 sec). Thirty minutes post-TBI, rats were randomized to receive intraperitoneal injections of vehicle (alcohol, emulphor, and saline; 1:1:18) or a selective inhibitor of 2-AG ( JZL184, 16 mg/kg) or AEA (URB597, 0.3 mg/kg) degradation. At 24 h post-TBI, animals showed significant neurological and -behavioral impairment as well as disruption of blood-brain barrier (BBB) integrity. Improved neurological and -behavioral function was observed in JZL184-treated animals. BBB integrity was protected in both JZL184-and URB597-treated animals. No significant differences in ipsilateral cortex messenger RNA expression of interleukin (IL)-1b, IL-6, chemokine (C-C motif) ligand 2, tumor necrosis factor alpha, cyclooxygenase 2 (COX2), or nicotinamide adenine dinucleotide phosphate oxidase (NOX2) and protein expression of COX2 or NOX2 were observed across experimental groups. Astrocyte and microglia activation was significantly increased post-TBI, and treatment with JZL184 or URB597 blocked activation of both cell types. These findings suggest that EC degradation inhibition post-TBI exerts neuroprotective effects. Whether repeated dosing would achieve greater protection remains to be examined.

Objective Mitochondrial depolarization following ATP-sensitive potassium (mitoKATP) channel activation has been shown to induce cerebral vasodilation by the generation of ‘calcium sparks’ in smooth muscle. It is unclear, however, if mitochondrial depolarization in endothelial cells is capable of promoting vasodilation by releasing vasoactive factors. Therefore, we studied the effect of endothelial mitochondrial depolarization by mitoKATP channel activators, BMS-191095 (BMS) and diazoxide, on endothelium-dependent vasodilation. Methods and Results Diameter studies in isolated rat cerebral arteries showed BMS and diazoxide induced vasodilations that were diminished by endothelial denudation. Mitochondrial depolarization-induced vasodilation was reduced by inhibition of mitoKATP channels, phosphoinositide-3 kinase (PI3K) or nitric oxide synthase (NOS). Scavenging of reactive oxygen species (ROS), however, diminished vasodilation induced by diazoxide but not by BMS. Fluorescence studies in cultured rat brain microvascular endothelial cells (CMVECs) showed that BMS elicited mitochondrial depolarization, and enhanced nitric oxide (NO) production; diazoxide exhibited largely similar effects, but unlike BMS, increased mitochondrial ROS production. Measurements of intracellular calcium ([Ca2+]i) in CMVECs and arteries showed that both diazoxide and BMS increased endothelial [Ca2+]i. Western blot analyses revealed increased phosphorylation of Akt and endothelial NOS (eNOS) by BMS and diazoxide. Increased phosphorylation of eNOS by diazoxide was abolished by PI3K inhibition. Electron spin resonance spectroscopy confirmed vascular NO generation in response to diazoxide and BMS. Conclusions Pharmacological depolarization of endothelial mitochondria promotes activation of eNOS by dual pathways involving increased [Ca2+]i as well as by PI3K-Akt-induced eNOS phosphorylation. Both mitochondrial ROS-dependent and –independent mechanisms mediate activation of eNOS by endothelial mitochondrial depolarization.