Protein nanoparticle-induced osmotic pressure gradients modify pulmonary edema through hyperpermeability in acute respiratory distress syndrome.

Acute respiratory distress syndrome (ARDS), caused by noncardiogenic pulmonary edema (PE), contributes significantly to Coronavirus 2019 (COVID-19)-associated morbidity and mortality. We explored the effect of transmembrane osmotic pressure (OP) gradients in PE using a fluorescence resonance energy transfer-based Intermediate filament (IF) tension optical probe. Angiotensin-II- and bradykinin-induced increases in intracellular protein nanoparticle (PN)-OP were associated with inflammasome production and cytoskeletal depolymerization. Intracellular protein nanoparticle production also resulted in cytomembrane hyperpolarization and L-VGCC-induced calcium signals, which differed from diacylglycerol-induced calcium increment via TRPC6 activation. Both pathways involve voltage-dependent cation influx and OP upregulation via SUR1-TRPM4 channels. Meanwhile, intra/extracellular PN-induced OP gradients across membranes upregulated pulmonary endothelial and alveolar barrier permeability. Attenuation of intracellular PN, calcium signals, and cation influx by drug combinations effectively relieved intracellular OP and pulmonary endothelial nonselective permeability, and improved epithelial fluid absorption and PE. Thus, PN-OP is pivotal in pulmonary edema in ARDS and COVID-19, and transmembrane OP recovery could be used to treat pulmonary edema and develop new drug targets in pulmonary injury.

Aristolochic acid I aggravates renal injury by activating the C3a/C3aR complement system.

Previous studies have reported that the complement system is unconventionally activated in many kinds of glomerulonephritis. Multiple complement components participate in the pathogenic process by triggering immune response or other intracellular signaling pathways. Here, we have investigated the role of C3a and its receptor C3aR in aristolochic acid nephropathy (AAN), which, is featured with progressive interstitial fibrosis. Over release of C3a and increased expression of C3aR parallels to the up-regulation of α-SMA and TGF-ß1 in AAN, which appeared to promote epithelial-mesenchymal-transition (EMT). To identify the role of complement activation in AAN, we used an inhibitor of C3aR (C3aRA) to block the coupling of C3a to its receptor. Our results confirmed from decreased EMT, the protective effect of C3aRA in cell apoptosis and inflammatory response induced by aristolochic acid I. These results showed that C3a and its receptor C3aR played pathogenic roles in AAN, and renal tubular epithelial cells were potentially pivotal targets of complement activation that could cause pro-fibrotic effects.