Baicalin Alleviates ADAM17/EGFR Axis-Induced Peritonitis in Weaned Piglets Infected by Glaesserella parasuis

Glaesserella parasuis (GPS) is a Gram-negative, pathogenic bacterium that colonizes the upper respiratory tract of piglets and causes Glässer's disease with peritonitis under stress conditions. The mechanism underlying GPS-induced peritonitis in piglets remains unclear. Baicalin is one of the main active ingredients of Huangqin (Scutellaria baicalensis), which has a significant anti-inflammatory effect on inflammatory diseases. Therefore, this study aimed to elucidate the molecular mechanism by which baicalin alleviates GPS-induced peritonitis in piglets, specifically focusing on the role of the ADAM17/EGFR signaling axis. We investigated the effects of baicalin in vitro using porcine peritoneal mesothelial cells (PPMCs) and in vivo in GPS-infected piglets. Our results showed that baicalin reduced the expression of the pro-inflammatory cytokines tumor necrosis factor alpha (TNF-α), interleukin-1 beta (IL-1β), and interleukin-6 (IL-6) in PPMCs and the peritoneum of piglets after GPS infection. Concurrently, baicalin significantly reduced the upregulation of disintegrin and metalloproteinase 17 (ADAM17), phosphorylated epidermal growth factor receptor (p-EGFR)/EGFR, and phosphorylated extracellular signal-regulated kinase (p-ERK)/ERK induced by GPS infection in PPMCs and the peritoneum of piglets. Crucially, in vitro mechanistic investigations revealed that baicalin can significantly reduce the upregulation of ADAM17, p-EGFR/EGFR, p-ERK/ERK, TNF-α, IL-1β, and IL-6 induced by ADAM17 overexpression in PPMCs. Furthermore, ADAM17 small interfering RNA can significantly reduce the upregulation of ADAM17, p-EGFR/EGFR, p-ERK/ERK, TNF-α, IL-1β, and IL-6 induced by GPS infection in PPMCs. These findings demonstrate that baicalin can inhibit the expression of inflammatory factors TNF-α, IL-1β, and IL-6 through the ADAM17/EGFR axis, and then alleviate the peritonitis caused by GPS in piglets. This provides a theoretical basis for developing novel non-antibiotic strategies, including phytochemical therapeutics and feed additives, for preventing and controlling GPS.