Effect And Mechanism Of PGD₂/DP₁ Receptor Pathway On Endometrial Tissue Damage Of Bacterial Infected Dairy Cows

Dairy cows often suffer from different degrees of endometritis and other diseases after calving.PGD₂ plays an important role in inhibiting the development of lung inflammation and endometritis,but the mechanism of PGD₂ in bacterial cow endometritis is still unclear.In order to further study the regulation mechanism of PGD₂ on bacterial endometritis in dairy cows,this experiment used E.coli and S.aureus to infect cow’s endomerial tissue cultured in vitro as the research object.The expression and secretion of inflammatory factors interleukin IL-1β,IL-6,TNF-α,NOS-2,PAFR,MMP-2,and injury-related factor high mobility group box（HMGB）-1 were detected by RT-PCR,Western Blot and ELISA,after treatment with DP₁ receptor agonist,L-PGDS inhibitor and DP₁ receptor inhibitor.Immunofluorescence method was used to detect the expression of NOS-2,MMP-2 and HMGB-1 in the tissue,and the protein expression of PAFR and MMP-2 in the tissue was detected by immunohistochemical staining method.Finally,the H.E staining was used to observe the pathological changes of the endometrial tissue to evaluate whether the PGD₂/DP₁ receptor pathway mediates the endometrial tissue damage of dairy cows caused by E.coli and S.aureus.The results showed that the expression of inflammatory factors IL-1β,IL-6,TNF-a,NOS-2,MMP-2,PAFR and damage-related factors HMGB-1 was significantly up-regulated in endometrial tissue of cows when infected with E.coli and S.aureus comparing with the blank control group（P<0.05）;Notably,release of IL-6,IL-1β,TNF-αand the expression of NOS-2,PAFR,MMP-2 and HMGB-1 were suppressed after DP₁ receptor agonist treatment（P<0.05）;However,L-PGDS inhibitor and DP₁ receptor agonist significantly increased the expression of these factors in tissues（P<0.05）.The results of H.E staining showed that after the addition of DP₁ receptor agonist reducing the degree of tissue damage,endometrial epithelial cells were relatively intact and the outline of the glands was clear.Endometrial epithelial cells are completely shedding,necrosis,and disintegration.The structure of glands and blood vessels are also destroyed,and the outline of the glands is fused and unclear.Studies have shown that the PGD₂/DP₁ receptor pathway exerts anti-inflammatory effects and inhibits the expression of bacteria-induced inflammatory factors and injures-related factor HMGB-1,thereby reducing the damage of infected tissues.This study provided an important theoretical basis for understanding the pathophysiological role of PGD₂ in endometritis of dairy cows.