Pleiotropic vascular effects of ivabradine in streptozotocin-induced diabetes

Area of Science:

• Cardiovascular Pharmacology
• Endocrinology
• Molecular Biology

Background:

• Ivabradine (IVA) primarily inhibits hyperpolarization-activated cyclic nucleotide-gated (HCN) channels to reduce heart rate.
• Emerging evidence suggests IVA possesses cardiovascular benefits beyond heart rate reduction, including antioxidant and endothelial protective effects.
• HCN channels are expressed in various tissues, with altered expression patterns in pathologies like hypertension and hypertrophy.

Purpose of the Study:

• To investigate the mechanism of Ivabradine's effect on streptozotocin (STZ)-induced cardiovascular damage.
• To assess the direct effects of IVA on thoracic aorta function and its potential to prevent vascular dysfunction in diabetes.
• To explore the role of HCN channels in mediating IVA's vascular effects in a diabetic setting.

Main Methods:

• Vascular function was assessed in control and STZ-diabetic rats, with and without IVA treatment.
• Plasma levels of adhesion molecules (p-selectin, VCAM-1) and aortic nitric oxide content were measured.
• Isolated thoracic aorta relaxations to IVA were evaluated, with and without L-NAME pre-incubation, and HCN protein expression was analyzed.

Main Results:

• IVA treatment normalized increased plasma p-selectin and VCAM-1 levels and restored nitric oxide content in diabetic rats.
• IVA induced concentration-dependent relaxations in isolated thoracic aorta, partly mediated by nitric oxide.
• Both diabetes and IVA treatment modulated the expression patterns of all HCN channel isoforms.

Conclusions:

• Ivabradine significantly improves vascular function in diabetic conditions.
• HCN channels play a crucial role in maintaining vascular activity against diabetes-induced damage.
• IVA offers potential as a therapeutic agent to prevent diabetic cardiovascular complications through mechanisms independent of its heart rate-reducing action.