A new functional role of Ca2+ sensitization mechanisms in the regulation of vascular smooth muscle contraction

Resumen

Introduction: Cardiovascular diseases related to sustained arterial contraction are an important cause of mortality andmorbidity in humans. Although the increase in [Ca2+]i can cause contraction of smooth muscle, arterial contraction canbe regulated even if the concentration of this ion remains constant. This mechanism, called "Ca2+ sensitization",participates in the maintenance of arterial contraction through the inhibition of the activity of myosin light chain phosphatase (MLCP). Although RhoA/Rho kinase (ROCK) and PKC can both inhibit MLCP, these two pathways not only work in parallel, but they can also interact. We have studied the role of both, PKC and RhoA/ROCK, sensitization pathways in PDButreated arteries. Materials and Methods: Isometric force was measured in rat femoral arterial rings. Immunofluorescence experiments were performed on isolated myocytes. PKC and RhoA were analyzed by Western blot and G-LISA in arterial rings precontracted with PDBu, a PKC activator. Results: PDBu induced the activation and translocation of PKCα to the plasma membrane. PDBu also evoked an increase in cytosolic RhoA, suggesting its inhibition. Simultaneous application of ROCK and PKCα inhibitors induced a synergistic, non-additive, vasorelaxant effect on sustained contraction in PDBu-treated arteries. Discussion: Here we describe a new form of crosstalk between PKCα and RhoA pathways. As PKCα negatively regulates RhoA activity, PKCα inhibitors could facilitate the vasorelaxant effect of ROCK inhibitors. Simultaneous treatment with ROCK and PKCα inhibitors could provide a new strategy to optimize the therapeutic treatment of pathological processes that mediates arterial vasospasm.