MDP-mediated chronic NOD2 stimulation confers protection against LPS challenge through M2b macrophage polarization

MANSILLA, FLORENCIA C.; MIRAGLIA, M. CRUZ; MAIDANA, SILVINA S.; CAPOZZO, ALEJANDRA V.

Kruger Park

Simposio; IVIS 2023 - 13th International veterinary immunology symposium; 2023

Innate immune cells show enhanced responsiveness to secondary challenges after an initial non-related stimulation (termed Trained Innate Immunity, TII). Acute NOD2 activation by Muramyl-Dipeptides (MDPs) promote TII inducing the secretion of pro-inflammatory mediators, while a sustained (chronic) MDP-stimulation can promote NOD2 degradation and down-regulate the inflammatory response, restoring both cross and self-tolerance. Chronic NOD2 stimulation has not been deeply explored although peripheral macrophages are continuously exposed to MDPs from microflora breakdown. Here we characterized in-vitro MDP-trained murine macrophages upon an experimental challenge with high concentrations of LPS in the context of chronic inflammation induced by a sustained stimulation of NOD2. Raw264.7 cells were trained with MDP (1μg/ml, 48h) and challenged with LPS (5μg/ml, 24h). Each determination was assessed in three experiments, three replicates each. ANOVA test was assessed, followed by Tukey Test for comparisons between treatments. Trained cells formed multinucleated giant cells with increased phagocytosis rates compared to untrained/challenged cells. They showed a reduced metabolic activity with evidence of a switch to aerobic glycolysis. LPS upregulated TNFα and NO with similar levels in both cultures (p>0.05) while IL10 was upregulated and IL12 downregulated in trained cells (p