CAMP enriched EVs mediates hypoxic pulmonary hypertension

Abstract

Our lab reported the novel finding that stimulation of pulmonary endothelial cells with a beta-agonist and a phosphodiesterase inhibitor induced enrichment of cyclic adenosine monophosphate (cAMP) in EVs. cAMP protects the pulmonary vasculature by regulation of permeability, vasoreactivity and proliferation. Extracellular vesicles provide a protected environment for circulating cAMP. Thus, we hypothesized that administration of cAMP, in the protected environment of an EV, could deliver cAMP to improve outcomes in pulmonary hypertension. Briefly, male Sprague Dawley rats, maintained in normoxic or hypoxic conditions for 3 weeks, received 50 ug of cAMP-enriched EVs (cAMP-EVs) per day over 3 days via tail vein injection. cAMP-EV injections improved the Fulton index (non-injected hypoxia rat 0.37 ± 0.039 versus injected hypoxia rat 0.32 ± 0.019, p value 0.032 n = 5) and echocardiography revealed PH rats that received cAMP-EVs had a significant increase in PAAT/PAET ratio compared to those that did not (non-injected hypoxia rat 0.27 ± 0.056 versus injected hypoxia rat 0.32 ± 0.04, p value 0.04, n = 6). Using IVIS analysis of isolated tissues to detect PKH-labeled EVs we found that cAMP-enriched EVs accumulated in the lung but were not detectable in the heart. To confirm this was not strictly a vasoreactivity effect, we also examined PCNA, a marker of proliferation, in histological sections and found it was decreased in the presence of cAMP-EVs. Pulmonary arterial thickness was also significantly improved in the presence of cAMP-EVs. To understand the underlying mechanism for cAMP-EV based signaling, we studied the phosphorylation status of endothelial nitric oxide synthase (eNOS) in isolated paraffn fixed lung slices. We found increased phosphorylation of eNOS in PH rats which received cAMP EVs compared to non-injected PH or control rats. Combined these data suggest that cAMP-EVs may decrease right ventricular hypertrophy, improve pulmonary arterial function, and repair hypoxic vascular injury. Future investigations will determine whether the observed response is cAMP dependent and further evaluate the specificity of pulmonary vascular uptake of cAMP-EVs. 1R01HL133066-01A1 (Bauer). 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.