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bioRxiv · 10.1101/2025.01.31.635924

Enterococcus faecalis-derived lactic acid facilitates persistent and polymicrobial wound infections by suppressing macrophage activation

da Silva, R. A. G.·Tien, B. Y. Q.·Kao, P. H. N.·Celik, C.·Tan, A. Z. C.·Ismail, M. H.·Hu, G.·Chong, K. K. L.·Thibault, G.·Chen, J.·Kline, K. A.
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Abstract

Macrophage activation is essential for innate immunity, and its suppression enables pathogen persistence. We show that Enterococcus faecalis suppresses macrophage activation through lactic acid-mediated extracellular acidification. Mutants lacking lactate dehydrogenase (ldh), and thus unable to acidify the environment, fail to inhibit NF-{kappa}B. E. faecalis-derived lactic acid acts via MCT-1 and GPR81 through two distinct but complementary mechanisms that culminate in the reduction of NF-{kappa}B activity. Lactic acid acts through MCT-1 to inhibit ERK and STAT3 phosphorylation, leading to reduced STAT3 binding to the Myd88 promoter, and reduced MyD88 protein levels. Lactic acid signaling to GPR81 mediates the phosphorylation of the transcriptional factor YAP, ultimately attenuating NF-{kappa}B signaling. In a murine wound infection model, this lactic acid-driven immunosuppressive niche enables prolonged E. faecalis persistence and enhances the fitness of co-infecting bacteria such as Escherichia coli. These findings reveal how bacterial lactic acid subverts innate immunity to support chronic and polymicrobial infections. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=140 SRC="FIGDIR/small/635924v2_ufig1.gif" ALT="Figure 1"> View larger version (34K): org.highwire.dtl.DTLVardef@2e1565org.highwire.dtl.DTLVardef@17eaf85org.highwire.dtl.DTLVardef@356139org.highwire.dtl.DTLVardef@821581_HPS_FORMAT_FIGEXP M_FIG C_FIG Highlights- E. faecalis lactate dehydrogenase mutants fail to acidify the environment and cannot suppress NF-{kappa}B signaling. - Lactic acid is necessary and sufficient to drive NF-{kappa}B suppression in macrophages. - Lactic acid NF-{kappa}B suppression is relayed through two complementary routes: MCT- 1 transport and the lactate sensor GPR81. - MCT-1-dependent signaling blunts ERK/STAT3 phosphorylation, lowering MyD88 levels; whereas GPR81 drives YAP phosphorylation, reducing NF-{kappa}B activation. - E. faecalis-derived lactic acid drives immunosuppression, potentiates persistence, and promotes multi-species wound infection in vivo.

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da Silva, R. A. G., Tien, B. Y. Q., Kao, P. H. N., Celik, C., Tan, A. Z. C., Ismail, M. H., Hu, G., Chong, K. K. L., Thibault, G., Chen, J., Kline, K. A.. 2025-01-31. Enterococcus faecalis-derived lactic acid facilitates persistent and polymicrobial wound infections by suppressing macrophage activation. https://doi.org/10.1101/2025.01.31.635924

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