Dual L/T calcium channel blocker exerts both antihypertensive and renoprotective effects in L-NAME-induced hypertension model

Renal hypertension, a common form of secondary hypertension, results from kidney disease. It arises due to the narrowing of arteries connected to the kidneys, often caused by atherosclerosis. Over time, this condition can lead to kidney failure. Therapeutics for kidney protection are currently limited, prompting continual search for new renoprotective agents in the context of hypertension. Dual blockage of both L-type and T-type calcium channels has shown promise in the treatment of hypertension when compared to selective calcium channel blockers. Toddaculin has been proven to be a potent inhibitor of the T-type channel. Conserved amino acid sequence comparison, electrophysiological recordings, and Flex Station were used to evaluate and compare toddaculin effect on the Ca_V3.1 and Ca_V1.2 channels and their respective residues, transiently expressed in HEK293T cells. Intracellular Ca²⁺ was assessed using the molecular probe fluo-4-AM. They specifically investigated the impact of toddaculin on vascular smooth muscle cells (VSMCs). Toddaculin's myogenic effects were assessed using aortic rings isolated from rats within an organ bath system. In an in vivo context, a mouse model with L-NAME-induced hypertension was employed to investigate toddaculin's anti-hypertensive and renoprotective properties. We found that L1047A in Ca_V1.2, and L1456A in Ca_V3.1 are potential key binding sites for toddaculin, and that toddaculin inhibited Ca_V3.1 and Ca_V1.2 equally and dose-dependently. Toddaculin-induced decline of [Ca²⁺]_i cultured VSMCs under a laser scanning confocal microscopy. Aortic rings exposed to toddaculin demonstrated dose-dependent relaxation following KCl-induced contraction. Moreover, toddaculin exhibited significant blood pressure reduction and renoprotective effects against L-NAME-induced renal injury in mice. This finding provides an evident therapeutic potential of toddaculin as an antihypertensive drug candidate with a renoprotective effect.