Heat-killed <i>Lactococcus lactis</i> subsp. <i>lactis</i> L8 ameliorates dextran sulfate sodium-induced colitis in mice

<i>Lactococcus lactis</i> subsp. <i>lactis</i> (<i>L. lactis</i>) is a common species of lactic acid bacteria (LAB). There is increasing evidence that probiotic <i>L. lactis</i> ameliorates experimental colitis in mice, whereas few studies have revealed the effects of the paraprobiotics, i.e., inactivated forms of bacteria. <i>L. lactis</i> L8 strain is a newly identified plant-derived LAB. The present study aimed to investigate the effects of heat-killed <i>L. lactis</i> L8 on dextran sulfate sodium (DSS)-induced colitis in mice. C57BL/6J mice were orally administered <i>L. lactis</i> L8 for 12 days. Colitis was induced by adding 3.5% DSS to the drinking water for 7 days. Mice were euthanized on day 12, and colon tissues and fecal samples were collected. Results demonstrated that administration of <i>L. lactis</i> L8 alleviated the clinical score of the colitis and the histological abnormalities. Additionally, <i>L. lactis</i> L8 led to a significant reduction in the level of colon tumor necrosis factor (TNF)-α. Administration of <i>L. lactis</i> L8 did not affect the gut microbial structure, whereas it altered the relative abundance of <i>Clostridiaceae</i> and <i>Rikenellaceae</i> in colitis mice. Our findings suggest that paraprobiotic <i>L. lactis</i> L8 has an immunomodulatory effect on intestinal inflammation in mice, providing important insight into the biological function of <i>L. lactis</i> L8.