Abstract Introduction Schistosomiasis-associated pulmonary hypertension (Sch-PH) affects 1 million people worldwide; however, there are no specific therapeutic targets. Recently, our group observed gut-lung dysbiosis and increased extracellular vesicle (EV) shedding in the preclinical model, potentially dependent on activation of the death-associated P2X7 receptor (P2X7R) in lung endothelial cells (ECs). Cell death is highly regulated by members of the Inhibitors of Apoptosis family (IAPs), but their role in Sch-PH is unknown. Hypothesis: Lung dysbiosis may contribute to P2X7R-mediated endothelial c-IAP2-EV shedding and immune cell survival in the preclinical Sch-PH model. Materials/Methods Control and Cdh5cre-ERT2;cIAP1-/-;cIAP2fl/fl (male/female) mice +/- S. mansoni eggs were used to quantify right ventricular systolic pressure (RVSP), hypertrophy (RVH), and function by echocardiograph. Western blot, ELISA, and immunohistochemistry (IHC) were used to assess protein expression, while microbial composition was analyzed via metagenomics. Additionally, P2X7R was inhibited by Brilliant Blue G (BBG; 45.5 mg/kg) prior to egg injections, and human lung microvessel ECs (HMVEC-L) were exposed to S. mansoni eggs for a time-dependent evaluation of P2X7R and c-IAP2 expression. Results/Discussion The validated pre-clinical Sch-PH model exhibited elevated levels of extracellular ATP and overactivation of the canonical P2X7R-NLRP3-mediated signaling in lung microvascular ECs, which was associated with increased EVs, EC apoptosis, and potentially c-IAP2 shedding into the plasma. In vitro, P2X7R inhibition prevented ATP-mediated lung microvascular EC death, and in vivo, it ameliorated pulmonary vascular injury/remodeling, preventing increased EV shedding and RVSP but not RVH in female egg-exposed mice. Endothelial-specific cIAP2fl/fl mice exhibited a spontaneous increase in lung P2X7R expression, and females exhibited a lower pulmonary acceleration time and pulmonary ejection time ratio (PAT/PET) and a higher right ventricular free wall thickness (RVFWT) than males during echocardiograph, indicating sex- linked differences in this model. Finally, whereas c-IAP2 was increased in the plasma of egg-exposed animals, preliminary IHC analysis revealed c-IAP2 expression accumulated in lung CD45+ cells, which could be a result of the uptake of circulating c-IAP2, contributing to their prolonged survival. Conclusion Our data indicate that lung dysbiosis may exacerbate P2X7R function and suppress c-IAP2 expression via EV shedding, contributing to immune cell survival. This abstract is funded by: NIH
Villarreal et al. (Fri,) studied this question.