Abstract Body (Do not enter title and authors here): Background: Several pro-inflammatory signals, including microbial cell components such as β-glucan or metabolites produced during western-diet feeding, function as initial “triggers” that train macrophages to respond more robustly to a later secondary inflammatory challenge. This crude “memory” response in innate immune cells is termed as “trained immunity." This memory response is mediated, at least in part, through epigenomic changes to the chromatin landscape.
Aim: Role of SETDB2 in trained immunity and atherosclerosis.
Results: Our preliminary findings suggest that SETDB2, a putative epigenomic enzyme that is a member of the KMT1 family of lysine methyltransferases, is induced by β-glucan training in macrophages, and knocking out SETDB2 in myeloid cells (SETDB2mKO) altered the magnitude of the secondary pro-inflammatory response in the two-step training protocol described in Background. RNA sequencing revealed a dynamic profile of transcripts that were altered in SETDB2mKO with different gene clusters, consistent with SETDB2 positively regulating some genes while negatively regulating others. We also developed SETDB2 knock-in (SETDB2KI) mice that crippled its potential enzymatic function. Interestingly, SETDB2KI data suggested that SETDB2’s enzyme activity is essential for its role in negatively regulating genes, while positively regulated genes require SETDB2 but not its enzyme activity. Several metabolic and inflammatory pathway genes were regulated by SETDB2, as were several genes known to be involved in immune cell infiltration. Bone marrow transplantation from global SETDB2-deficient mice into LDLRKO resulted in more severe atherosclerotic plaques following western diet feeding, and single-cell RNA sequencing revealed increased neutrophil and reduced CD4+ T-cell populations in lesions from the SETDB2-deficient plaques. When combined together, the positive and negative regulation of different gene clusters by SETDB2 in the in-vitro training study and the more severe atherosclerosis with altered immune profiles in the SETDB2-deficient plaques in vivo suggest that SETDB2 positively and negatively regulates CD4+ T cell and neutrophil recruitment to atherosclerotic plaques, respectively.
Conclusion: Our preliminary findings show that SETDB2 regulates immuno-metabolic pathway genes via two different mechanisms, which might also influence the immune cell inflammatory landscape and severity of atherosclerosis.