Arterial Myocyte Pannexin 1 Channel Controls Vascular Reactivity in Diabetic Hyperglycemia

Diabetic hyperglycemia promotes vasoconstriction by activating an ATP-dependent P2Y_11L (P2Y₁₁-like receptor)/AC5 (adenylyl cyclase 5)/AKAP5 (A-kinase anchoring protein 5)/PKA (protein kinase A)/Ca_V1.2 (L-type voltage-dependent calcium channel 1.2) nanocomplex in arterial myocytes, but upstream mechanisms are unclear. We hypothesized that Panx1 (pannexin 1) channels, which facilitate ATP release, are associated with the complex in arterial myocytes and mediate its activation to induce vasoconstriction during diabetic hyperglycemia.

Multidisciplinary approach using extracellular ATP and cAMP biosensors, patch-clamp electrophysiology, super-resolution nanoscopy, proximity ligation assay, pressure myography, and laser speckle imaging to test premises in arterial myocytes and vessels from wild-type and genetically modified mice, including an inducible smooth muscle-specific Panx1 knockout and a global AKAP5 knockout.

We found that elevating extracellular glucose (eg, high glucose, hyperglycemia) triggered an increase in extracellular ATP levels, and this was reduced in the presence of the Panx1 inhibitor spironolactone, in inducible smooth muscle-specific Panx1 knockout cells, and by inhibiting glucose metabolism. Panx1 was found in complex with P2Y_11L, AC5, AKAP5, PKA, and Ca_V1.2 in arterial myocytes. The protein complex was strengthened in response to hyperglycemia, which required Panx1 and AKAP5. Hyperglycemia-induced cAMP production, Ca_V1.2 potentiation, sustained vasoconstriction, and in vivo changes in cerebral artery myogenic tone and blood flow were ameliorated by spironolactone and in inducible smooth muscle-specific Panx1 knockout samples. Panx1 expression was elevated in arterial lysates from a mouse model of type 1 diabetes (eg, streptozotocin), and increased Ca_V1.2 activity and enhanced ex vivo and in vivo myogenic tone were prevented in arterial myocytes and arteries from inducible smooth muscle-specific Panx1 knockout mice.

These results suggest a key role for Panx1 in controlling ATP signaling through the P2Y_11L/AC5/AKAP5/PKA/Ca_V1.2 axis in arterial myocytes. This Panx1-led complex modulates cAMP levels, Ca_V1.2 activity, and vascular reactivity in response to diabetic hyperglycemia. Thus, Panx1 could be a new therapeutic target to mitigate vascular complications during diabetes.