Galectin-3 Regulates Smooth Muscle Contraction and Blood Pressure by Modulating Ca_V1.2 Channel Function

Fine-tuning of Ca_V1.2 calcium channel activity by binding proteins represents a novel mechanism for regulating smooth muscle contraction and blood pressure (BP). This study aimed to elucidate the role of Gal-3 (galectin-3), a newly identified Ca_V1.2-binding protein, in the pathogenesis of hypertension.

In vitro, ex vivo, and in vivo experiments involving molecular and biochemical assays, in silico prediction, patch-clamp electrophysiologic recordings, immunohistochemistry, pressure myography, and tail-cuff BP measurements were used to evaluate the molecular mechanisms by which Gal-3 binds to and elevates membrane insertion of Ca_V1.2 channels. The experiments were performed in transfected HEK 293 cells, isolated smooth muscle cells, and arteries from smooth muscle-specific Gal-3 knockout mice and their wild-type littermates; spontaneously hypertensive rats; or human patients. In vivo experiments involving delivery of the blocking iGal3BP (inhibitory galectin-3-binding peptide) into spontaneously hypertensive rats were performed to investigate its effect on BP.

We identified Gal-3 as a novel binding partner and unexpected positive modulator of the Ca_V1.2 channel through binding to the intracellular II-III loop. Gal-3 increased total and surface expression, current density, and open probability of Ca_V1.2 channels. Both Ca_V1.2 and Gal-3 were upregulated in hypertensive rat aortas and human pulmonary arteries. Conditional deletion of Gal-3 in smooth muscle significantly lowered Ca_V1.2 protein and BP in mice. With specific binding sites identified within both Gal-3 and the Ca_V1.2 II-III loop, the peptide iGal3BP, designed to block Ca_V1.2-Gal-3 interaction, significantly reduced BP in spontaneously hypertensive rats by decreasing Ca_V1.2 protein expression. Repeated iGal3BP administration resulted in cumulative peptide accumulation in mesenteric arteries and produced a sustained reduction in BP, which demonstrated greater long-lasting antihypertensive efficacy compared with amlodipine and losartan. Administration of iGal3BP in combination with a negative modulatory Gal-1 mimetic peptide that mimics Gal-1-Ca_V1.2 interaction returned systolic BP to normotensive levels within 4 hours and lowered BP in hypertensive rats in a sustained manner for 35 days.

These results provide strong evidence that Gal-based Ca_V1.2 channel modulators are novel therapeutic pathways for normalizing BP.