Genetically modified Lactococcus lactis producing a green fluorescent protein–bovine lactoferrin fusion protein suppresses proinflammatory cytokine expression in lipopolysaccharide-stimulated RAW 264.7 cells

Abstract

Lactoferrin (LF), an iron-binding glycoprotein distributed widely in the biological fluids of mammals, is believed to play an important role in host defenses against infection. Previous studies in animal models and humans demonstrated that combined administration of LF and probiotic lactic acid bacteria (LAB) can prevent sepsis. In this study, we genetically engineered a probiotic LAB strain, Lactococcus lactis, to produce recombinant bovine LF based on the green fluorescent protein (GFP)-fused expression system. Western blotting confirmed that the genetically modified L. lactis strain (designated NZ-GFP-bLF) produced a protein corresponding to a fusion of GFP and bLF in the presence of nisin, an inducer of target gene expression. The protein synthesized by NZ-GFP-bLF was fluorescent and thus we monitored the time-dependent change in the production level of the recombinant protein using fluorometric analysis. The utility of NZ-GFP-bLF in preventing sepsis was determined by investigating its anti-inflammatory property in lipopolysaccharide (LPS)-stimulated mouse macrophage RAW 264.7 cells. Pretreatment of RAW 264.7 cells with NZ-GFP-bLF significantly attenuated the LPS-induced mRNA expression and protein production of 3 proinflammatory cytokines (IL-1α, IL-6, and tumor necrosis factor-α) compared with pretreatment with a vector control strain of L. lactis. Our results suggest that NZ-GFP-bLF holds promise for the development of a new prophylaxis for sepsis.