Up-regulation Of Gga-mir-1306-5p And Gga-mir-155 Negatively Modulates Tollip Involved In Host Responses To Salmonella Enteritidis In Chickens

Salmonella enteritidis(SE)is currently the only Salmonella serotype that causes frequent human illness related to meat or egg contaminations.The on-farm environment of chickens is a rich source of plentiful Salmonella serotypes,which demonstrates its severe threat to food safety.Although,SE contaminations can be effectively controlled through various measures in poultry industry,there was still a considerable increase in reported SE cases.The resistance of SE to multiple antimicrobials has been a great challenge in treatment of animal and human disease.Therefore,developing novel preventive and therapeutic strategies for SE infection is quite urgent.Innate immunity is the first line of host defense barriers against invading infectious pathogens.The recognition of microbial pathogens is an essential step for activation of the host innate immune responses,which relies on several kinds of germline-encoded pattern recognition receptors(PRRs).As is well-known that TLRs are the most extensively studied PRRs and crucial players required for hosts to eliminate invading microbial pathogens.The Toll interacting protein(Tollip),one TLR-associated signaling protein,represents an endogenous regulator in TLR signaling pathway.Increasing evidences have drawn a conclusion that Tollip is required to maintain immune homeostasis and control the MyD88-dependent NF-?B activation pathways during inflammation via suppression of IRAK-1's activity,confirming a modulatory role of Tollip in immune responses.The miRNA is a group of small and non-coding RNA molecules(18-25 nucleotides in length),which could regulate a variety of biological processes by reducing gene expression at the post-transcriptional level.As reported previously,up to 60%of all protein-coding genes have been predicted to be regulated by miRNAs to a certain extent.And miRNAs could induce mRNA degradation or protein translation repression mainly through binding to the 3'-untranslated region(3'-UTR)of the target mRNAs.In present study,our data showed that Gallus gallus microRNA-1306-5p(gga-miR-1306-5p)was increased in not only various tissues following SE infection but also HD11 cells stimulated by lipopolysaccharides(LPS).And subsequently,molecular study confirmed that gga-miR-1306-5p targets Tollip and the highly expressed gga-miR-1306-5p could significantly block the expression of Tollip.Furthermore,the overexpression of gga-miR-1306-5p uprgulated the release of pro-inflammatory cytokines including NF-?B,TNF-?,IL-6,and IL-1?,which ultimately produced effects similar to those of Tollip silence.Taken together,gga-miR-1306-5p induced by the pathogen or LPS,regulates immune responses through the inhibition of Tollip,and whereafter activates the production of inflammatory cytokines.Our data may not only specifically enhance the information available on the roles of miRNAs during the development of SE infection but also provide new insights into the defence mechanisms of chickens in the innate signaling pathway.