Isoliensinine promotes vasorelaxation and inhibits constriction by regulating the calcium channel in hypertension: In vitro and in vivo approaches

Isoliensinine, a bioactive alkaloid derived from Nelumbo nucifera Gaertn , has antihypertension effects. This study investigated its antihypertensive effect and molecular mechanism. Spontaneously hypertensive rats (SHRs) and Wistar Kyoto rats (n=6 per group) were treated with 2.5, 5 or 10 mg/kg isoliensinine or 7 mg/kg valsartan for 10 weeks. Ultrasonography, histology, immunohistochemistry, RNA-sequencing analysis, vascular tension, calcium imaging, and virtual docking were performed. Isoliensinine effectively attenuated the elevation of blood pressure, pulse wave velocity, and medial thickness of the abdominal aortas in SHRs. It reversed 253-upregulated and 161-downregulated differentially expressed transcripts in the abdominal aorta of SHRs, with enrichment in vascular smooth muscle contraction and calcium signaling pathways. Isoliensinine significantly attenuated the vasoconstriction induced by angiotensin II (Ang II), norepinephrine (NE), or potassium chloride (KCl) and maintained its inhibitory effects across increasing calcium concentrations. It promotes vasodilation in the abdominal aorta rings induced by NE or KCl independent of the endothelium and potassium ion channels but is associated with the modulation of L-type calcium channels. Isoliensinine also suppressed calcium release in vascular smooth muscle cells after KCl, Ang II, or NE stimulation. Isoliensinine upregulated the expression of MLCP but downregulated that of p-MLC2 in the abdominal aorta of SHRs. Virtual docking analysis revealed lower binding energy values for isoliensinine with MLCP, suggesting a potential interaction. Isoliensinine lowers blood pressure by regulating vascular smooth muscle contraction and relaxation, and its effects are potentially mediated by regulating calcium signaling pathways. Graphical presentation of the antihypertensive effects of isoliensinine via the regulation of calcium channels Calcium channels including voltage-, receptor-, and store-operated channels (voltage-dependent calcium channels, receptor-operated channels, and store-operated channels, respectively) were associated with vascular contraction. Activated calcium channels increased intracellular Ca 2+ levels in VSMCs, triggering the phosphorylation of myosin light chain 2 (MLC2) and resulting in rapid vasoconstriction. In this study, isoliensinine effectively lowered BP by regulating MLCP activity, thereby promoting the dephosphorylation of p-MLC2. This mechanism facilitates vascular relaxation and inhibits vasoconstriction, highlighting the effect of isoliensinine in antihypertension.