Moslea Herba flavonoids alleviated influenza A virus-induced pulmonary endothelial barrier disruption via suppressing NOX4/NF-κB/MLCK pathway

Moslae Herba, a common traditional Chinese herb with special flavor, has potential for treating respiratory and gastrointestinal diseases.

Lung endothelial barrier dysfunction (LEBD) accelerates the pathogenesis of influenza A virus (IAV)-induced secondary acute lung injury. New strategies against LEBD provide benefits in prevention and treatment of IAV. Previous studies showed that flavonoids (MHF), main bioactivity fraction derived from M. Herba, exerted anti-inflammatory and antiviral activities, but the underlying protection of MHF against IAV-induced acute lung injury remained obscure. The present study was to investigate the protection of MHF against IAV-induced LEBD in vivo and in vitro.

Mice were intranasally challenged with IAV and orally administered with MHF for 5 days. The pulmonary hyperpermeability of infected mice was evaluated by Evans Blue staining and in vivo imaging. Serum levels of inflammatory cytokines and mediators were detected by ELISA assay. The transepithelial electrical resistance (TER) of human pulmonary microvascular endothelial cells (HPMVECs) was measured by using TER meter. The expressions of key proteins in NOX4-mediated NF-κB/MLCK pathways were determined by western blotting.

MHF treatment reduced lung index, W/D ratios, and serum levels of inflammatory factors (IL-6, TNF-α, IL-1β, PLA₂, LBT₄ and ICAM-1) in IAV-infected mice. Evans blue staining and in vivo imaging results revealed that MHF alleviated IAV-induced barrier dysfunction and pulmonary hyperpermeability. Moreover, luteolin and kaempferol, the main activity compounds in MHF, significantly inhibited TNF-α-induced HPMVEC apoptosis, and downregulated NF-κB/MLCK pathway by targeting NOX4.

MHF attenuated IAV-induced barrier dysfunction by suppressing NOX4/NF-κB/MLCK pathway and may serve as a potential agent for the prevention of LEBD and IAV.