Extracellular Nucleotide Signaling Stimulates Vascular L‐Type Ca 2+ Channel Activity And Vasoconstriction During Diabetic Hyperglycemia

Elevated extracellular glucose (i.e. hyperglycemia; HG) is a hallmark metabolic abnormality in diabetes and a major risk factor of vascular complications such as hypertension, stroke, and end organ damage. We recently discovered that HG amplifies intracellular Ca 2+ concentration ([Ca 2+ ] i ) in vascular smooth muscle via PKA‐mediated potentiation of L‐type Ca 2+ channels (LTCCs). Whereas elevation of [Ca 2+ ] i by HG is prevented by ectonucleotidase activity, in this study, we tested the hypothesis that extracellular nucleotide signaling is required for PKA‐dependent potentiation of LTCC and vasoconstriction in response to HG. Using patch clamp electrophysiology and pressurized cerebral arterial diameter measurements, we found that HG‐potentiated LTCC current and endothelium‐independent vasoconstriction was associated with enhanced phosphorylation of Ca V 1.2 serine 1928 (S1928), a putative PKA target site in LTCCs. Consistent with our hypothesis, the increase in S1928 phosphorylation, vascular LTCC activity and vasoconstriction in the presence of HG was prevented by apyrase and a PKA inhibitory peptide, suggesting a mechanism involving the release of extracellular nucleotides and activation of PKA. Inhibition of the G q ‐coupled purinergic receptor P2Y 6 , which has been implicated in HG‐mediated increase in [Ca 2+ ] i , failed to prevent the HG effects on S1928 phosphorylation, LTCC activity and vasoconstriction in response to HG. Altogether, our results indicate that extracellular nucleotide and PKA signaling is responsible for Ca V 1.2 S1928 phosphorylation, LTCC potentiation and vasoconstriction in HG. Considering our findings, we propose a potential functional association between PKA‐coupled purinergic receptors promoting LTCC activation and vasoconstriction in HG. Support or Funding Information This work was supported by grants NIH HL098200 and HL121059, and AHA‐14GRNT18730054 to MFN.