Berberine ameliorates pulmonary inflammation in mice with influenza viral pneumonia by inhibiting NLRP3 inflammasome activation and gasdermin D-mediated pyroptosis.

Viral pneumonia is a common complication caused by Influenza A virus infection and is characterized by severe pulmonary inflammation. A previous study showed that berberine (BBR) significantly ameliorated the pulmonary inflammation in mice with influenza viral pneumonia but its underlying mechanism is not entirely understood. In this study, we reproduced the mouse model of influenza viral pneumonia through intranasal infection of A/Puerto Rico/8/34 (H1N1), to further investigate the anti-inflammatory mechanism of BBR based on nucleotide-binding oligomerization domain-like receptor protein (NLRP) 3 inflammasome activation and Gasdermin D (GSDMD)-mediated pyroptosis. Consistent with MCC950 (10 mg/kg, a specific NLRP3 inflammasome inhibitor), BBR (10 mg/kg) obviously improved the weight loss and survival rate of infected mice, alleviated their pulmonary inflammation, and suppressed the accumulation of tumor necrosis factor and interleukin (IL)-6 in lungs without obvious inhibition on viral multiplication (hemagglutinin titer and nucleoprotein messenger RNA). Moreover, BBR (10 mg/kg) reduced the expressions of NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and cysteinyl aspartate-specific proteinase (Caspase)1 (Caspase1 precursor [Pro-caspase1] + Caspase1p20 subunit) and the ratio of Caspase1p20 subunit to Caspase1, thus inhibiting the NLRP3 inflammasome activation and resulting in the decreased contents of mature IL-1β and IL-18 in lungs. The GSDMD expression (GSDMD precursor [Pro-GSDMD] + GSDMD-N terminal [NT]) and the ratio of GSDMD-NT to GSDMD were also declined by BBR (10 mg/kg). These evidence indicate that BBR may ameliorate pulmonary inflammation in mice with influenza viral pneumonia through inhibiting NLRP3 inflammasome activation, as well as depressing GSDMD-mediated pyroptosis via declining GSDMD expression and restraining NLRP3 inflammasome-mediated GSDMD activation.