Investigating the Role of the mPGES-PGE₂-EP4 Pathway in E. coli-Induced Mastitis in Dairy Cows: Insights for Non-antibiotic Therapeutic Strategie

Xiaolin Yang¹Xueqiang LI¹Lili Guo¹Pengfei Gong¹Yinghong Qian²Shuangyi Zhang¹Bo Liu¹Wenrui Guo¹Haixia Bao^1*Wei Mao^1*

• ¹Inner Mongolia Agricultural University, Hohhot, China
• ²Inner Mongolia Academy of Agricultural & Animal Husbandry Sciences, Zhaojun Road, Yu quan District, 010031, Hohhot, China

Escherichia coli (E. coli) is the primary causative agent of bovine mastitis. Currently, antibiotic therapy remains the cornerstone of mastitis treatment; necessitating the identification of alternative therapeutic options. This study employed in vitro cultured bovine bone marrow-derived macrophages (BMDMs) to systematically assess the potential of microsomal prostaglandin e synthase-1 (mPGES-1) inhibitors (MF63, MK886) and EP4 receptor inhibitor (Grapiprant) in modulating inflammatory responses and reducing tissue damage. Cells were pre-treated with mPGES-1 inhibitors and an EP4 receptor inhibitor before infection with E. coli. Following infection, extracellular bacteria were removed, and assays-including ELISA, Western blot, and qRT-PCR-were conducted to analyze inflammatory mediators, protein expression, and gene expression. E. coli infection significantly induced PGE₂ synthesis in BMDMs, which exacerbated the inflammatory response and tissue damage via NF-κB and MAPK signaling pathways, elevating TNF-α, IL-1β, IL-6, and IL-8.Treatment with MF63, MK886 and Grapiprant effectively reduced PGE₂ levels, inhibited NF-κB and MAPK signaling pathways, decreased inflammatory mediators, and enhanced macrophage bactericidal activity, thereby demonstrating potent anti-inflammatory and immunomodulatory effects.Moreover, inhibition of the mPGES-PGE₂-EP4 signaling pathway was found to reduce the expression of damage-associated molecular patterns (HMGB-1 and HABP-2), suggesting alleviation of E. coli-induced tissue damage. Based on the role of PGE₂ in mediating immune and inflammatory responses via the EP4 receptor, inhibiting the mPGES-1-PGE₂-EP4 signaling axis to reduce inflammation and tissue damage will facilitate further investigation into the regulatory mechanisms of the PGE₂ signaling axis in the pathogenesis of mastitis. This approach provides a theoretical foundation and experimental basis for the development of alternative anti-inflammatory therapies to replace antibiotics.