Mechanism Of MIF Regulation On The Inflammatory Responses Of Astrocytes

Objective The excessive inflammatory responses induced by CNS damage often cause secondary injury,which exaggerates the output of the injured nerves.The injury-associated signals trigger the inflammatory responses by acting on the inflammatory cells.Whether the proliferating astrocyte is involved in such inflammatory response is not clear.Here,we are going to study the relationship between MIF and its roles on the astrocyte production of inflammatory cytokines following spinal cord injury,as well as the underlying mechanisms.Methods The spinal cord of adult male SD rats(Sprague Dawley)at T8-T10 was injured with weight drop;the injured segments were perfused and collected at 0d,1d,4d and 7d,repectively;Western blot and immunofluorescence were performed to examine the expression of MIF expression in the collected tissues;the primary cultured astrocytes from the newborn SD rats at postnatal 1 days were treated with the recombinant MIF protein,and the expression changes of cytokines including TNF-α and IL-1β were detected by Real-time PCR;by using siRNA interference for MIF receptor CD74,the transcriptome sequencing was performed to analyze the differentially expressed genes,which are associated with the inflammatory responses of astrocytes.Results 1.The expression of MIF was strongly upregulated at 4d following the injury of spinal cord,and showing a decrease at 7d;2.The expression of TNF-α,IL-1β and NF-κB was upregulated following MIF treatment of the astrocytes,whereas they showed a decrease after interference of CD74 siRNA.3.The expression level of p-Erk has shown an increase after treatment of MIF recombinant protein for 24 h,but decreased following CD74 siRNA interference.4.Analysis of transcriptome sequencing demonstrated that ch25 h and pla2g2 a were under regulation of the MIF/CD74 axis in astrocytes;5.EdU assay has shown that MIF promotes the proliferation of astrocytes in a dose-dependent manner.Conclusions 1.MIF is able to upregulate the expression of inflammatory cytokines through MIF/CD74 axis in the astrocytes;2.MIF activates Erk pathway intracellularly;3.MIF promotes the proliferation of astrocytes...