Dynamin-independent Ca1.2 and K1.1 channels regulation and vascular tone modulation by the mitochondrial fission inhibitors dynasore and dyngo-4a.

A role for mitochondrial fission in vascular contraction has been proposed based on the vasorelaxant activity of the dynamin (and mitochondrial fission) inhibitors mdivi-1 and dynasore. However, mdivi-1 is capable to inhibit Ba currents through Ca1.2 channels (I), stimulate K1.1 channel currents (I), and modulate pathways key to the maintenance of vessel active tone in a dynamin-independent manner. Using a multidisciplinary approach, the present study demonstrates that dynasore, like mdivi-1, is a bi-functional vasodilator, blocking I and stimulating I in rat tail artery myocytes, as well as promoting relaxation of rat aorta rings pre-contracted by either high K or phenylephrine. Conversely, its analogue dyngo-4a, though inhibiting mitochondrial fission triggered by phenylephrine and stimulating I, did not affect I but potentiated both high K- and phenylephrine-induced contractions. Docking and molecular dynamics simulations identified the molecular basis supporting the different activity of dynasore and dyngo-4a at Ca1.2 and K1.1 channels. Mito-tempol only partially counteracted the effects of dynasore and dyngo-4a on phenylephrine-induced tone. In conclusion, the present data, along with previous observations (Ahmed et al., 2022) rise caution for the use of dynasore, mdivi-1, and dyngo-4a as tools to investigate the role of mitochondrial fission in vascular contraction: to this end, a selective dynamin inhibitor and/or a different experimental approach are needed.