Mechanisms involved in the increased sensitivity of the rabbit basilar artery to atrial natriuretic peptide in diabetes

Rutin ameliorates nitrergic and endothelial dysfunction on vessels and corpora cavernosa of diabetic animals

Endothelial dysfunction is an early complication of diabetes and it is related to both micro- and macroangiopathies. In addition, >70% of diabetic patients develop autonomic neuropathies. Increased oxidative stress has a major role in the development of both nitrergic and endothelial dysfunction. The aim of this work is to evaluate whether rutin, a potent antioxidant, could ameliorate nitrergic and/or endothelial dysfunction in diabetic animals. Primary and secondary treatment protocols with rutin were investigated on rat aortic rings and the mesenteric arteriolar bed, and on rabbit aortic rings and corpora cavernosa (RbCC) from both euglycemic and alloxan-diabetic animals. Acetylcholine endothelium-dependent and sodium nitroprusside endothelium-independent relaxations were compared in tissues from euglycemic or diabetic animals. Electrical field stimulation (EFS)-induced relaxation was performed only in the RbCC. Endothelial-dependent relaxations were blunted by 40% in vessels and neuronal relaxation was blunted by 50% in RbCC taken from diabetic animals when compared to euglycemic animals. Pre-treatment with rutin restored both neuronal and endothelial dependent relaxations in diabetic animals towards the values achieved in control euglycemic tissues. Rutin was able to ameliorate both endothelial dysfunction and nitrergic neuropathy in animal experimental models. Rutin could be a lead compound in the primary or secondary preventive ancillary treatment of endothelial and nitrergic dysfunction in the course of diabetes.

Higher Prevalence of Diabetes in Pontine Infarction than in Other Posterior Circulation Strokes

BACKGROUND

Pontine infarction is the major subtype of posterior circulation stroke, and diabetes is more common in pontine infarction patients than in anterior circulation stroke patients. Whether the prevalence of diabetes remains homogenous within the posterior circulation stroke population is unclear. The present study is aimed at investigating the prevalence of diabetes in pontine infarction and comparing it to other subtypes of posterior circulation stroke.

METHODS

We conducted a multicenter case-control study. Patients with posterior circulation stroke were screened. The subjects were divided into pontine infarction and nonpontine infarction groups.

RESULTS

From November 1, 2018, to February 28, 2021, a total of 6145 stroke patients were screened and 2627 patients had posterior circulation strokes. After excluding cardioembolic stroke, as well as its other determined and undetermined causes, 1549 patients with 754 pontine infarctions were included in the analysis. The prevalence of diabetes in the pontine infarction group was higher than that in the nonpontine infarction group (42.7% vs. 31.4%, P < 0.05). After adjusting for confounding factors, diabetes was an independent risk factor for pontine infarction (OR 1.63, 95% CI 1.27-2.09, P < 0.05). For small vessel occlusion, diabetes was also more common in the pontine infarction group (43.2% vs. 30.0%, P < 0.05). Multivariate analysis also showed that diabetes was an independent risk factor for pontine infarction (OR 1.80, 95% CI 1.32-2.46, P < 0.05).

CONCLUSION

In comparison with the nonpontine infarction subtype of posterior circulation stroke, patients with pontine infarction had a higher prevalence of diabetes, and diabetes was an independent risk factor for pontine infarction.

Potassium channels contribute to the increased sensitivity of the rabbit carotid artery to hydrogen sulfide in diabetes

Hydrogen sulfide (H₂S) is a potential endothelium-derived hyperpolarizing factor (EDHF) and adventitium- or adipocyte-derived relaxing factor (ADRF) which vasorelaxant action is mediated by potassium channels. H₂S could also play an important role in the pathophysiology of diabetic cardiovascular complications. The present study has investigated the influence of alloxan-induced diabetes on the role of potassium channels mediating the relaxant response of the rabbit carotid artery to NaHS, a donor of H₂S. NaHS (10^-8-3 × 10^-5 M) relaxed phenylephrine-precontracted carotid arteries, with higher potency in diabetic than in control rabbits. The selective blockers of potassium channels charybdotoxin, 4-amynopiridine and glibenclamide significantly inhibited the relaxant action of NaHS in diabetic rabbits, but not in control rabbits. When compared to control rabbits, carotid arteries from diabetic rabbits showed significantly reduced expression of big conductance Ca⁺²-activated potassium channels (BK_Ca), significantly enhanced expression of intermediate conductance Ca⁺²-activated potassium channels (IK_Ca) and not significant different expression of voltage-sensitive potassium channels (K_V) and ATP-sensitive potassium channels (K_ATP). These results suggest that an enhanced role of IK_Ca, K_V and K_ATP potassium channels could be involved in the increased sensitivity of the rabbit carotid artery to H₂S in diabetes.

Molecular mechanisms underlying the neuroprotective role of atrial natriuretic peptide in experimental acute ischemic stroke

Along with its role in regulating blood pressure and fluid homeostasis, the natriuretic peptide system could be also part of an endogenous protective mechanism against brain damage. We aimed to assess the possibility that exogenous atrial natriuretic peptide (ANP) could protect against acute ischemic stroke, as well as the molecular mechanisms involved. Three groups of rats subjected to transient middle cerebral artery occlusion (tMCAO, intraluminal filament technique, 60 min) received intracerebroventricular vehicle, low-dose ANP (0.5 nmol) or high-dose ANP (2.5 nmol), at 30 min reperfusion. Neurofunctional condition, and brain infarct and edema volumes were measured at 24 h after tMCAO. Apoptotic cell death and expression of natriuretic peptide receptors (NPR-A and NPR-C), K⁺ channels (K_ATP, K_V and BK_Ca), and PI3K/Akt and MAPK/ERK1/2 signaling pathways were analyzed. Significant improvement in neurofunctional status, associated to reduction in infarct and edema volumes, was shown in the high-dose ANP group. As to the molecular mechanisms analyzed, high-dose ANP: 1) reduced caspase-3-mediated apoptosis; 2) did not modify the expression of NPR-A and NPR-C, which had been downregulated by the ischemic insult; 3) induced a significant reversion of ischemia-downregulated K_ATP channel expression; and 4) induced a significant reversion of ischemia-upregulated pERK2/ERK2 expression ratio. In conclusion, ANP exerts a significant protective role in terms of both improvement of neurofunctional status and reduction in infarct volume. Modulation of ANP on some molecular mechanisms involved in ischemia-induced apoptotic cell death (K_ATP channels and MAPK/ERK1/2 signaling pathway) could account, at least in part, for its beneficial effect. Therefore, ANP should be considered as a potential adjunctive neuroprotective agent improving stroke outcome after successful reperfusion interventions.