Exosomal Transfer of DNA Methyl-Transferase mRNA Induces an Immunosuppressive Phenotype in Human Monocytes

Abstract

Survivors of sepsis exhibit persistent immunosuppression. Epigenetic events may be responsible for some of these immunosuppressive changes. During sepsis circulating exosomes contain large quantities of DNA methyltransferase (DNMT) mRNAs. We hypothesized that exosomes directly transfer DNMTmRNAs to recipient monocytes with resultant methylation events and immunosuppression. Methods: Exosomes containing DNMT mRNA were generated by stimulating monocytes with LPS. Confocal microscopy was used to determine uptake kinetics in the presence of pharmacologic inhibition. Expression and packaging of specific DNMT mRNA was controlled using DNMT siRNAs. Whole genome and gene specific methylation was assessed using bisulfite sequencing. Ingenuity pathway analysis was performed to determine the biological function of significance of differentially methylated regions. Results: Exosomes effectively transferred DNMT mRNA to recipient monocytes. Pharmacologic inhibition of exosome uptake prevented this increase in DNMT mRNA expression. Recipient monocytes exhibited hypermethylation changes and gene suppression. siRNAs decreased the packaging of DNMT mRNAs and prevented TNFa gene suppression, restoring immunocompetence. Conclusion: These data support a role for exosome-mediated transfer of DNMT mRNA with resultant methylation and gene silencing. Pharmacologic uptake inhibition or targeted siRNA mediated DNMT gene silencing prevented DNMT mRNA transfer and maintained the cell's ability to express TNFa in response to LPS. This highlights the potential therapeutic value of targeting these exosome-mediated epigenetic events to maintain the host immune response during sepsis.

Surviving Sepsis Campaign Research Priorities 2023

“…While studies support a role for genetic (243)(244)(245)(246)(247)(248) and epigenetic (249)(250)(251)(252)(253)(254)(255) factors in sepsis, the topic remains relatively unexplored. Despite years of research in this domain, we do not yet fully understand the link between genetic factors and susceptibility, severity and evolution of sepsis.…”

“…Some cohort data or post hoc analyses of intervention studies suggest a link between genetic or metabolomic factors and response to therapy (206,219,(256)(257)(258). Epigenetic factors play a crucial role in various processes in sepsis from the coordination of the response to infection to inflammatory response (259,260) but also particularly contributes to the induction of immunoparalysis (249,250,252,261). The pattern (predominantly affecting immune state, coagulation or other genes) may vary on a daily basis after admission, suggesting that repeated measurements may be required (257).…”

Chromatin modifiers in human disease: from functional roles to regulatory mechanisms

“…By comparing multiple HDAC inhibitors, HDAC3 could inhibit the secretion of cytokines such as TNFα and IL-6 in monocytes and M1 macrophages induced by Lipopolysaccharides, and also reduced the tolerance of M1 macrophages to Lipopolysaccharides [ 115 ]. Sepsis can recruit a large number of monocyte exosomes to induce DNMT aggregation and induce immunosuppression [ 116 ]. Dysregulation of the inflammatory response is inseparable from the disrupting action of inflammasomes (complexes of platform proteins, adaptor proteins and effector proteins) [ 117 ].…”

Untitled

“…According to J. Wisler et al (2022), excessive levels of IL-1 destroy intercellular interactions, causing infertility, due to the excessive development of the endometrial inflammatory response during the stage of excitation. The results of studies obtained by M. Segura-Benítez et al (2022) indicate that physiological zygote nidulation is possible under conditions of a balance between the immunomodulatory and immunosuppressive effects of the endometrium, in the implementation of which components of the cytokine system are directly involved.…”