Involvement of PGE₂ in intestinal immunity of heat-stressed broilers with a potential link to the brain-gut axis

Heat stress severely impairs broiler intestinal health and production, and prostaglandin E2 (PGE₂) plays a crucial role in body thermoregulation. However, the regulatory mechanism linking PGE₂ to intestinal inflammation through the brain-gut axis has not been fully elucidated in broilers. Here, we integrated in vivo and in vitro experiments to explore how PGE₂ mediates heat stress-induced intestinal immune dysfunction in broilers. Heat stress increased brain and rectal temperatures while suppressing growth performance (P < 0.05). It activated the transient receptor potential melastatin 2 (TRPM2) channel and elevated cyclooxygenase-2 (COX-2, PGE₂ synthase) content and PGE₂ concentration in the hypothalamus (P < 0.05), and intracerebroventricular inhibition confirmed the role of TRPM2. Heat stress triggered intestinal barrier disruption, characterized by reduced tight junction protein expression (P < 0.05), particularly in the jejunum; In vitro PGE₂ treatment of intestinal epithelial cells recapitulated this observation. Mechanistically, both in vivo heat stress and in vitro PGE₂ treatment upregulated intestinal EP₄ (PGE₂ receptor), inositol 1,4,5-trisphosphate (IP₃), transient receptor potential vanilloid 4 (TRPV4), the nuclear factor-κB (NF-κB) signaling pathway, and pro-inflammatory cytokine production (P < 0.05); In vitro blockade of EP₄, IP₃ or TRPV4 attenuated PGE₂ -induced intestinal epithelial inflammation (P < 0.05). We therefore infer that hypothalamic TRPM2, together with intestinal EP₄, IP₃ and TRPV4, may contribute to PGE₂-mediated intestinal inflammation under heat stress. Intestinal interleukin-6 (IL-6) was elevated under heat stress in vivo and in PGE₂-treated intestinal epithelial cells; IL-6 stimulation of hypothalamic neurons enhanced PGE₂ synthesis (P < 0.05), implying a potential intestine-to-hypothalamus feedback loop. Collectively, these findings indicate that PGE₂ participates in heat stress-triggered intestinal inflammation, potentially through the brain-gut axis. This study provides a novel immunological insight and theoretical basis for understanding heat stress-related intestinal disorders and optimizing broiler health management under high-temperature conditions.