The contribution of nitric oxide and vasodilatory prostanoids to bradykinin-mediated vasodilation in Type 1 diabetes

Roles and current applications of S-nitrosoglutathione in anti-infective biomaterials

Bacterial infections can compromise the physical and biological functionalities of humans and pose a huge economical and psychological burden on infected patients. Nitric oxide (NO) is a broad-spectrum antimicrobial agent, whose mechanism of action is not affected by bacterial resistance. S-nitrosoglutathione (GSNO), an endogenous donor and carrier of NO, has gained increasing attention because of its potent antibacterial activity and efficient biocompatibility. Significant breakthroughs have been made in the application of GSNO in biomaterials. This review is based on the existing evidence that comprehensively summarizes the progress of antimicrobial GSNO applications focusing on their anti-infective performance, underlying antibacterial mechanisms, and application in anti-infective biomaterials. We provide an accurate overview of the roles and applications of GSNO in antibacterial biomaterials and shed new light on the avenues for future studies.

Early Endothelial Dysfunction in Type 1 Diabetes Is Accompanied by an Impairment of Vascular Smooth Muscle Function: A Meta-Analysis

Background: A large yet heterogeneous body of literature exists suggesting that endothelial dysfunction appears early in type 1 diabetes, due to hyperglycemia-induced oxidative stress. The latter may also affect vascular smooth muscles (VSM) function, a layer albeit less frequently considered in that pathology. This meta-analysis aims at evaluating the extent, and the contributing risk factors, of early endothelial dysfunction, and of the possible concomitant VSM dysfunction, in type 1 diabetes. Methods: PubMed, Web of Sciences, Cochrane Library databases were screened from their respective inceptions until October 2019. We included studies comparing vasodilatory capacity depending or not on endothelium (i.e., endothelial function or VSM function, respectively) in patients with uncomplicated type 1 diabetes and healthy controls. Results: Fifty-eight articles studying endothelium-dependent function, among which 21 studies also assessed VSM, were included. Global analyses revealed an impairment of standardized mean difference (SMD) (Cohen's d) of endothelial function: -0.61 (95% CI: -0.79, -0.44) but also of VSM SMD: -0.32 (95% CI: -0.57, -0.07). The type of stimuli used (i.e., exercise, occlusion-reperfusion, pharmacological substances, heat) did not influence the impairment of the vasodilatory capacity. Endothelial dysfunction appeared more pronounced within macrovascular than microvascular beds. The latter was particularly altered in cases of poor glycemic control [HbA_1c > 67 mmol/mol (8.3%)]. Conclusions: This meta-analysis not only corroborates the presence of an early impairment of endothelial function, even in response to physiological stimuli like exercise, but also highlights a VSM dysfunction in children and adults with type 1 diabetes. Endothelial dysfunction seems to be more pronounced in large than small vessels, fostering the debate on their relative temporal appearance.

Type 1 diabetes modulates cyclooxygenase- and nitric oxide-dependent mechanisms governing sweating but not cutaneous vasodilation during exercise in the heat

Both cyclooxygenase (COX) and nitric oxide synthase (NOS) contribute to sweating, whereas NOS alone contributes to cutaneous vasodilation during exercise in the heat. Here, we evaluated if Type 1 diabetes mellitus (T1DM) modulates these responses. Adults with (n = 11, 25 ± 5 yr) and without (n = 12, 24 ± 4 yr) T1DM performed two bouts of 30-min cycling at a fixed rate of heat production of 400 W in the heat (35°C); each followed by a 20- and 40-min recovery period, respectively. Sweat rate and cutaneous vascular conductance (CVC) were measured at four intradermal microdialysis sites treated with either 1) lactated Ringer (vehicle control site), 2) 10 mM ketorolac (nonselective COX inhibitor), 3) 10 mM N^G-nitro-l-arginine methyl ester (nonselective NOS inhibitor), or 4) a combination of both inhibitors. In nondiabetic adults, separate and combined inhibition of COX and NOS reduced exercise sweat rate (P ≤ 0.05), and the magnitude of reductions were similar across sites. In individuals with T1DM, inhibition of COX resulted in an increase in sweat rate of 0.10 ± 0.09 and 0.09 ± 0.08 mg ·: min^-1 ·: cm^-2 for the first and second exercise bouts, respectively, relative to vehicle control site (P ≤ 0.05), whereas NOS inhibition had no effect on sweating. In both groups, NOS inhibition reduced CVC during exercise (P ≤ 0.05), although the magnitude of reduction did not differ between the nondiabetic and T1DM groups (exercise 1: -28 ± 10 vs. -23 ± 8% max, P = 0.51; exercise 2: -31 ± 12 vs. -24 ± 10% max, P = 0.38). We show that in individuals with T1DM performing moderate intensity exercise in the heat, NOS-dependent sweating but not cutaneous vasodilation is attenuated, whereas COX inhibition increases sweating.

Pharmacology and therapeutic role of inorganic nitrite and nitrate in vasodilatation

Nitrite has emerged as an important bioactive molecule that can be biotransformed to nitric oxide (NO) related metabolites in normoxia and reduced to NO under hypoxic and acidic conditions to exert vasodilatory effects and confer a variety of other benefits to the cardiovascular system. Abundant research is currently underway to understand the mechanisms involved and define the role of nitrite in health and disease. In this review we discuss the impact of nitrite and dietary nitrate on vascular function and the potential therapeutic role of nitrite in acute heart failure.

Vasoconstrictor prostanoids

In cardiovascular diseases and during aging, endothelial dysfunction is due in part to the release of endothelium-derived contracting factors that counteract the vasodilator effect of the nitric oxide. Endothelium-dependent contractions involve the activation of endothelial cyclooxygenases and the release of various prostanoids, which activate thromboxane prostanoid (TP) receptors of the underlying vascular smooth muscle. The stimulation of TP receptors elicits not only the contraction and the proliferation of vascular smooth muscle cells but also diverse physiological/pathophysiological reactions, including platelet aggregation and activation of endothelial inflammatory responses. TP receptor antagonists curtail endothelial dysfunction in diseases such as hypertension and diabetes, are potent antithrombotic agents, and prevent vascular inflammation.

Hypoxic modulation of exogenous nitrite-induced vasodilation in humans

BACKGROUND

It has been proposed that under hypoxic conditions, nitrite may release nitric oxide, which causes potent vasodilation. We hypothesized that nitrite would have a greater dilator effect in capacitance than in resistance vessels because of lower oxygen tension and that resistance-vessel dilation should become more pronounced during hypoxemia. The effect of intra-arterial infusion of nitrite on forearm blood flow and forearm venous volumes was assessed during normoxia and hypoxia.

METHODS AND RESULTS

Forty healthy volunteers were studied. After baseline infusion of 0.9% saline, sodium nitrite was infused at incremental doses from 40 nmol/min to 7.84 mumol/min. At each stage, forearm blood flow was measured by strain-gauge plethysmography. Forearm venous volume was assessed by radionuclide plethysmography. Changes in forearm blood flow and forearm venous volume in the infused arm were corrected for those in the control arm. The peak percentage of venodilation during normoxia was 35.8+/-3.4% (mean+/-SEM) at 7.84 micromol/min (P<0.001) and was similar during hypoxia. In normoxia, arterial blood flow, assessed by the forearm blood flow ratio, increased from 1.04+/-0.09 (baseline) to 1.62+/-0.18 (nitrite; P<0.05) versus 1.07+/-0.09 (baseline) to 2.37+/-0.15 (nitrite; P<0.005) during hypoxia. This result was recapitulated in vitro in vascular rings.

CONCLUSIONS

Nitrite is a potent venodilator in normoxia and hypoxia. Arteries are modestly affected in normoxia but potently dilated in hypoxia, which suggests the important phenomenon of hypoxic augmentation of nitrite-mediated vasodilation in vivo. The use of nitrite as a selective arterial vasodilator in ischemic territories and as a potent venodilator in heart failure has therapeutic implications.