Elevated Lipocalin2 Expression In Vivo Protects Hosts Against Bacteria Infection

Lipocalin2, which also known as neutrophil gelatinase-associated lipocalin, is an essential component of the antimicrobial innate immune system. The aim of current study was to determine the distribution of lipocalin2, investigate the expression changes of lipocalin2 after bacterial challenge and further to explore the function of lipocalin2 during bacterial infection. Western blot, real-time quantitative PCR, immunohistochemistry (IHC) and enzyme-linked immunosorbent assay (ELISA) were employed to evaluate the temporospatial expression of lipocalin2. Normally, lipocalin2 could be detected mainly in liver, spleen, kidney, thymus and intestine. After E. coli K88 challenge, both mRNA and protein levels of lipocalin2 were significantly elevated in liver, spleen thymus and jejunum (p<0.05) either in piglets or in mice. Serum lipocalin2 exerted a continuous increase since 8 h after challenge and peaked by 32 h. In addition, we found that the bacterial burden in blood and liver tissues was significantly increased (p<0.05) in lipocalin2 deficient mice. Furthermore, our study revealed that in vitro lipocalin2 exerted obvious bacteriostatic activity, as the proliferation of E. coli K88 and S. typhimurium CMCC50013 was significantly inhibited (p<0.05) in a dose-dependent manner when treated with lipocalin2. The results suggested that the elevated lipocalin2 expression in vivo was presumed to contribute effectively protection to host innate immunity.