Novel small molecule inhibitor of GPR68 attenuates endothelial dysfunction and lung injury caused by bacterial lipopolysaccharide

The treatment of acute respiratory distress syndrome (ARDS) associated with high mortality remains a major global clinical challenge. Role of pulmonary endothelial dysfunction in uncontrolled lung inflammation and alveolar flooding is increasingly recognized. GPR68 is a member of proton-sensing G protein-coupled receptor family and highly expressed in pulmonary vascular endothelial cells (EC). Although GPR68 has been implicated in flow-induced, EC-dependent vasodilation, its role in endothelial dysfunction caused by ARDS-related insults remains unknown. Herein, we assessed the role of a first-in-class GPR68 inhibitor ogremorphin (OGM-8345) discovered by our group in modulating pulmonary EC dysfunction and lung injury in mice caused by bacterial lipopolysaccharide LPS. GPCR activation Tango assay showed that LPS-induced EC barrier failure was associated with increased GPR68 activity and was suppressed by OGM-8345. OGM-8345, but not GPR4 inhibitor NE52-QQ57, strongly attenuated LPS-induced paracellular gap formation, adherence junction disassembly and EC hyper-permeability, suppressed activation of the NF-kB pathway, and blocked LPS-induced protein expression of EC adhesion molecules ICAM-1 and VCAM-1 and transcriptional activation of cytokines and chemokines. Beneficial effects of OGM-8345 were also observed in the clinically relevant post-treatment model of EC dysfunction caused by LPS or synthetic TLR4 activator, CRX-527. Protective effects of OGM-8345 were observed in lung EC from both macrovascular and microvascular beds. In vivo, OGM-8345 ameliorated vascular leak and inflammation in mouse lungs exposed to LPS, as determined by Evans blue extravasation assay, total cell and protein content in bronchoalveolar lavage samples, and mRNA levels of inflammatory marker genes in lung tissue. Taken together, these findings uncover a role of GPR68 in propagation of EC barrier compromise and inflammation caused by bacterial agents and suggest a therapeutic potential of GPR68-selective inhibitor in improving EC dysfunction and lung injury.