Pulmonary Fibrosis Augments CGRP-Dependent Hyperpolarization and Vasodilation of Mouse Pulmonary Arteries

Abstract

Calcitonin gene related peptide (CGRP) hyperpolarizes membrane potential (Vm) of pulmonary arterial smooth muscle cells (SMCs) and endothelial cells (ECs) through PKA-dependent activation of KATP channels. CGRP can diminish the severity of pulmonary fibrosis (PF), however, the effects on vascular signaling were poorly defined. We hypothesized that hyperpolarization to CGRP would be augmented in a mouse model of PF. PF was induced by intratracheal delivery of bleomycin (3 wk), and saline was used as a control (sham). Pulmonary arteries (PAs; 100-150 μm diameter) from male C57BL/6J mice (age, ~5 mo), were cannulated, pressurized to 16 cmH2O, and studied at 37°C. Alternatively, intact endothelial tubes were studied at 32°C following dissociation of SMCs. Vm was recorded continuously using intracellular microelectrodes. At rest, Vm was similar for SMCs (bleomycin = -43±3 mV, sham = -44±3 mV; n = 5/group) and ECs (bleomycin = -45±4 mV, sham = -44±3 mV; n=5/group). Increasing concentrations of CGRP (10−10-10−6 M) evoked hyperpolarization of Vm with greater potency in SMCs (EC50: bleomycin = 2 nM, sham = 15 nM) and ECs (EC50: bleomycin = 3 nM, sham = 8 nM) from PF mice, without changing effcacy (SMCs: bleomycin ΔVm = -24±4 mV, sham ΔVm = -21±3 mV; ECs: bleomycin ΔVm = -26±2 mV, sham ΔVm=23±4 mV). Consistently, vasodilation to CGRP in PAs preconstricted with uridine triphosphate (UTP, 5 μM; EC50) was enhanced in PF (92±6% maximum dilation;) vs. sham (83±4% maximum dilation) mice (n=5/group). Greater vasodilation and hyperpolarization of SMCs to CGRP persisted in endothelium-disrupted PAs and during treatment with L-NAME (10−4 M) indicating that ECs are not required for greater responsiveness to CGRP in SMCs. With no effect on resting Vm, inhibition of KATP channels with 1 μM glibenclamide or PKA with protein kinase inhibitor [PKI-(14-22)-amide, myristoylated; 1 μM] significantly attenuated (p<0.05) hyperpolarization of SMCs and ECs (ΔVm ≤5 mV for all groups). Both glibenclamide and PKI attenuated vasodilation to CGRP in PAs and eliminated differences between groups. In a mouse model of PF, CGRP-dependent hyperpolarization of pulmonary arterial SMCs and ECs is augmented through increased PKA-dependent activation of KATP channels leading to increased vasodilator sensitivity. AHA CDA#931652. This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.