Xuanbai Chengqi decoction targets sphingolipid metabolism: A novel strategy to preserve pulmonary endothelial barrier integrity in severe viral pneumonia.

Abstract

ETHNOPHARMACOLOGICAL RELEVANCE: The disruption of the pulmonary endothelial barrier is an important pathological feature of severe pneumonia. While our prior research has confirmed the therapeutic efficacy of the herbal formulation Xuanbai Chengqi Decoction (XBCQ) against severe pneumonia, the underlying molecular mechanisms remain elusive. AIM OF THE STUDY: This study was designed to elucidate the mechanism of XBCQ in preserving pulmonary endothelial integrity through sphingolipid metabolism modulation during severe influenza pneumonia. MATERIALS AND METHODS: This study employed an H1N1 influenza murine model (4 × LD) to evaluate the therapeutic efficacy of XBCQ against viral pulmonary injury. Air-blood barrier protection was systematically assessed through quantitative analysis of surfactant protein expression and glycocalyx integrity in lung. Lipidomic perturbations and transcriptional profiles were characterized using high-resolution mass spectrometry and Illumina NovaSeq 6000 sequencing. The mechanism of XBCQ in regulating Smpd3 and downstream signaling was delineated through integrated in vivo and in vitro investigations. Furthermore, pulmonary endothelial preservation via nSMase2/S1PR2 modulation was validated using selective pharmacological inhibitors in both experimental systems. RESULTS: XBCQ treatment significantly ameliorated lung injury and preserved pulmonary endothelial integrity. Integrated transcriptomic and untargeted lipidomic analyses identified Smpd3 as the key gene responsible for orchestrating sphingolipid metabolic dysregulation in H1N1-infected mice. Administration of XBCQ rectified the sphingolipid imbalance, suppressed Smpd3 expression, and consequently modulated the S1PR2/eNOS signaling axis. Furthermore, pharmacological inhibition of nSMase2 and S1PR2 enhanced lung endothelial barrier integrity both in vivo and in vitro. Collectively, these findings substantiate the mechanism whereby XBCQ mitigates barrier dysfunction via the regulation of the Smpd3/S1PR2 pathway. CONCLUSIONS: This study demonstrates that XBCQ exerts its therapeutic effects by correcting sphingolipid metabolic dysregulation and regulating the S1PR2/eNOS signaling pathway. These results validate the potential therapeutic value of targeting Smpd3 and S1PR2 in the management of severe pneumonia.