Production of human elafin by genetically modified Lactococcus lactis: evaluation of its anti-inflammatory effects in a murine model of intestinal mucositis.

The aim of this study was to develop a recombinant strain of Lactococcus lactis designed to produce human elafin, a serine protease inhibitor, through a Stress-Inducible Controlled Expression (SICE) System, and to evaluate its anti-inflammatory potential both in vitro and in vivo. The impact of this recombinant strain on the efficacy of 5-Fluorouracil (5-FU) was evaluated by in vitro assays with Caco-2 (human colonic cancer cells) and IEC-18 (non-cancerous intestinal cells) exposed to 5-FU with or without the recombinant bacterium. In vivo, a mouse model of intestinal mucositis (IM) was induced by daily injections of 5-FU, followed by oral administration of the recombinant strain twice daily. Key assessments included the occurrence of diarrhea, small intestinal morphology and histopathology, and serum cytokines levels. In vitro results showed that the elafin-producing strain enhanced 5-FU cytotoxicity against Caco-2 cells, while preserving IEC-18 cell viability in the presence of 5-FU. In vivo, the strain significantly reduced the occurrence of diarrhea, improved the villus height/crypt depth ratio and attenuated intestinal inflammation. In addition, the recombinant strain reduced serum levels of the pro-inflammatory cytokines IL-6 and TNF-α, while significantly increasing the anti-inflammatory cytokine IL-10. Importantly, the strain did not compromise the anti-cancer efficacy of 5-FU on tumor cells and protected non-cancer cells. These results confirm the in vivo anti-inflammatory effects of this elafin-producing strain against IM.