The Phagocytosis of Lacticaseibacillus casei and Its Immunomodulatory Properties on Human Monocyte-Derived Dendritic Cells Depend on the Expression of Lc-p75, a Bacterial Peptidoglycan Hydrolase

• Published in: International journal of molecular sciences Vol. 23; no. 14; p. 7620
• Main Authors: Tóth, Márta, Muzsai, Szabolcs, Regulski, Krzysztof, Szendi-Szatmári, Tímea, Czimmerer, Zsolt, Rajnavölgyi, Éva, Chapot-Chartier, Marie-Pierre, Bácsi, Attila
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.07.2022; MDPI
• Subjects: Antigen presentation; Bacteria; Cell division; Cell walls; Chemokines; Cytokines; Cytology; Dendritic cells; Enzymes; Gastrointestinal system; Gastrointestinal tract; Helper cells; Hydrolase; Immunomodulation; Inflammation; Internalization; Lactobacilli; lactobacillus; Life Sciences; Lymphocytes; Lymphocytes T; Monocytes; Morphology; Mutation; Pathogens; Peptidoglycan hydrolase; Phagocytosis; Probiotics; lactobacillus; phagocytosis; immunomodulation; dendritic cells
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms23147620

The human gut symbiont Lacticaseibacillus (L.) casei (previously Lactobacillus casei) is under intense research due to its wide range of immunomodulatory effects on the human host. Dendritic cells (DCs) are crucial players in the direct and indirect communication with lactobacilli in the gastrointestinal tract. Here, we demonstrate that human monocyte-derived DCs (moDCs) are able to engulf L. casei BL23, in which the intact bacterial cell wall and morphology have a key role. The absence of the bacterial cell-wall-degrading enzyme, Lc-p75, in L. casei cells causes remarkable morphological changes, which have important consequences in the phagocytosis of L. casei by moDCs. Our results showed that the Lc-p75 mutation induced defective internalization and impaired proinflammatory and T-cell-polarizing cytokine secretion by bacteria-exposed moDCs. The T helper (Th) 1 and Th17 cell activating capacity of moDCs induced by the mutant L. casei was consequently reduced. Moreover, inhibition of the phagocytosis of wild-type bacteria showed similar results. Taken together, these data suggested that formation of short bacterial chains helps to exert the potent immunomodulatory properties of L. casei BL23.