Image_1_Role of Phosphatidylinositol 3-Kinase (PI3K), Mitogen-Activated Protein Kinase (MAPK), and Protein Kinase C (PKC) in Calcium Signaling Pathways Linked to the α1-Adrenoceptor in Resistance Arteries.JPEG GutiérrezAlejandro ContrerasCristina SánchezAna PrietoDolores 2019 <p>Insulin resistance plays a key role in the pathogenesis of type 2 diabetes and is also related to other health problems like obesity, hypertension, and metabolic syndrome. Imbalance between insulin vascular actions via the phosphatidylinositol 3-Kinase (PI3K) and the mitogen activated protein kinase (MAPK) signaling pathways during insulin resistant states results in impaired endothelial PI3K/eNOS- and augmented MAPK/endothelin 1 pathways leading to endothelial dysfunction and abnormal vasoconstriction. The role of PI3K, MAPK, and protein kinase C (PKC) in Ca<sup>2+</sup> handling of resistance arteries involved in blood pressure regulation is poorly understood. Therefore, we assessed here whether PI3K, MAPK, and PKC play a role in the Ca<sup>2+</sup> signaling pathways linked to adrenergic vasoconstriction in resistance arteries. Simultaneous measurements of intracellular calcium concentration ([Ca<sup>2+</sup>]<sub>i</sub>) in vascular smooth muscle (VSM) and tension were performed in endothelium-denuded branches of mesenteric arteries from Wistar rats mounted in a microvascular myographs. Responses to CaCl<sub>2</sub> were assessed in arteries activated with phenylephrine (PE) and kept in Ca<sup>2+</sup>-free solution, in the absence and presence of the selective antagonist of L-type Ca<sup>2+</sup> channels nifedipine, cyclopiazonic acid (CPA) to block sarcoplasmic reticulum (SR) intracellular Ca<sup>2+</sup> release or specific inhibitors of PI3K, ERK-MAPK, or PKC. Activation of α<sub>1</sub>-adrenoceptors with PE stimulated both intracellular Ca<sup>2+</sup> mobilization and Ca<sup>2+</sup> entry along with contraction in resistance arteries. Both [Ca<sup>2+</sup>]<sub>i</sub> and contractile responses were inhibited by nifedipine while CPA abolished intracellular Ca<sup>2+</sup> mobilization and modestly reduced Ca<sup>2+</sup> entry suggesting that α<sub>1</sub>-adrenergic vasoconstriction is largely dependent Ca<sup>2+</sup> influx through L-type Ca<sup>2+</sup> channel and to a lesser extent through store-operated Ca<sup>2+</sup> channels. Inhibition of ERK-MAPK did not alter intracellular Ca<sup>2+</sup> mobilization but largely reduced L-type Ca<sup>2+</sup> entry elicited by PE without altering vasoconstriction. The PI3K blocker LY-294002 moderately reduced intracellular Ca<sup>2+</sup> release, Ca<sup>2+</sup> entry and contraction induced by the α<sub>1</sub>-adrenoceptor agonist, while PKC inhibition decreased PE-elicited Ca<sup>2+</sup> entry and to a lesser extent contraction without affecting intracellular Ca<sup>2+</sup> mobilization. Under conditions of ryanodine receptor (RyR) blockade to inhibit Ca<sup>2+</sup>-induced Ca<sup>2+</sup>-release (CICR), inhibitors of PI3K, ERK-MAPK, or PKC significantly reduced [Ca<sup>2+</sup>]<sub>i</sub> increases but not contraction elicited by high K<sup>+</sup> depolarization suggesting an activation of L-type Ca<sup>2+</sup> entry in VSM independent of RyR. In summary, our results demonstrate that PI3K, ERK-MAPK, and PKC regulate Ca<sup>2+</sup> handling coupled to the α<sub>1</sub>-adrenoceptor in VSM of resistance arteries and related to both contractile and non-contractile functions. These kinases represent potential pharmacological targets in pathologies associated to vascular dysfunction and abnormal Ca<sup>2+</sup> handling such as obesity, hypertension and diabetes mellitus, in which these signaling pathways are profoundly impaired.</p>