Hematopoietic Fas deficiency does not affect experimental atherosclerotic lesion formation despite inducing a proatherogenic state

A Novel Subset of CD95+ Pro-Inflammatory Macrophages Overcome miR155 Deficiency and May Serve as a Switch From Metabolically Healthy Obesity to Metabolically Unhealthy Obesity

Metabolically healthy obesity (MHO) accounts for roughly 35% of all obese patients. There is no clear consensus that has been reached on whether MHO is a stable condition or merely a transitory period between metabolically healthy lean and metabolically unhealthy obesity (MUO). Additionally, the mechanisms underlying MHO and any transition to MUO are not clear. Macrophages are the most common immune cells in adipose tissues and have a significant presence in atherosclerosis. Fas (or CD95), which is highly expressed on macrophages, is classically recognized as a pro-apoptotic cell surface receptor. However, Fas also plays a significant role as a pro-inflammatory molecule. Previously, we established a mouse model (ApoE-/-/miR155-/-; DKO mouse) of MHO, based on the criteria of not having metabolic syndrome (MetS) and insulin resistance (IR). In our current study, we hypothesized that MHO is a transition phase toward MUO, and that inflammation driven by our newly classified CD95+CD86- macrophages is a novel mechanism for this transition. We found that, with extended (24 weeks) high-fat diet feeding (HFD), MHO mice became MUO, shown by increased atherosclerosis. Mechanistically, we found the following: 1) at the MHO stage, DKO mice exhibited increased pro-inflammatory markers in adipose tissue, including CD95, and serum; 2) total adipose tissue macrophages (ATMs) increased; 3) CD95+CD86- subset of ATMs also increased; and 4) human aortic endothelial cells (HAECs) were activated (as determined by upregulated ICAM1 expression) when incubated with conditioned media from CD95+-containing DKO ATMs and human peripheral blood mononuclear cells-derived macrophages in comparison to respective controls. These results suggest that extended HFD in MHO mice promotes vascular inflammation and atherosclerosis via increasing CD95+ pro-inflammatory ATMs. In conclusion, we have identified a novel molecular mechanism underlying MHO transition to MUO with HFD. We have also found a previously unappreciated role of CD95+ macrophages as a potentially novel subset that may be utilized to assess pro-inflammatory characteristics of macrophages, specifically in adipose tissue in the absence of pro-inflammatory miR-155. These findings have provided novel insights on MHO transition to MUO and new therapeutic targets for the future treatment of MUO, MetS, other obese diseases, and type II diabetes.

CD8+ T-cells contribute to lesion stabilization in advanced atherosclerosis by limiting macrophage content and CD4+ T-cell responses

AIMS

T lymphocytes play an important role in atherosclerosis development, but the role of the CD8+ T-cell remains debated, especially in the clinically relevant advanced stages of atherosclerosis development. Here, we set out to determine the role of CD8+ T-cells in advanced atherosclerosis.

METHODS AND RESULTS

Human endarterectomy samples analysed by flow cytometry showed a negative correlation between the percentage of CD8+ T-cells and macrophages, suggesting a possible protective role for these cells in lesion development. To further test this hypothesis, LDLr-/- mice were fed a western-type diet (WTD) for 10 weeks to induce atherosclerosis, after which they received CD8α-depleting or isotype control antibody for 6 weeks. Depletion of CD8+ T-cells in advanced atherosclerosis resulted in less stable lesions, with significantly reduced collagen content in the trivalve area, increased macrophage content and increased necrotic core area compared with controls. Mechanistically, we observed that CD8 depletion specifically increased the fraction of Th1 CD4+ T-cells in the lesions. Treatment of WTD-fed LDLr-/- mice with a FasL-neutralizing antibody resulted in similar changes in macrophages and CD4+ T-cell skewing as CD8+ T-cell depletion.

CONCLUSION

These findings demonstrate for the first time a local, protective role for CD8+ T-cells in advanced atherosclerosis, through limiting accumulation of Th1 cells and macrophages, identifying a novel regulatory mechanism for these cells in atherosclerosis.

DNA methylation patterns are associated with n-3 fatty acid intake in Yup'ik people

A large body of evidence links a high dietary intake of n-3 (ω-3) polyunsaturated fatty acids (PUFAs) with improved cardiometabolic outcomes. Recent studies suggested that the biologic processes underlying the observed associations may involve epigenetic changes, specifically DNA methylation. To evaluate changes in methylation associated with n-3 PUFA intake, we conducted an epigenome-wide methylation association study of long-chain n-3 PUFA intake and tested associations between the diabetes- and cardiovascular disease-related traits. We assessed DNA methylation at ∼470,000 cytosine-phosphate-guanine (CpG) sites in a cross-sectional study of 185 Yup'ik Alaska Native individuals representing the top and bottom deciles of PUFA intake. Linear regression models were used to test for the associations of interest, adjusting for age, sex, and community group. We identified 27 differentially methylated CpG sites at biologically relevant regions that reached epigenome-wide significance (P < 1 × 10⁻⁷). Specifically, regions on chromosomes 3 (helicase-like transcription factor), 10 (actin α 2 smooth muscle/Fas cell surface death receptor), and 16 (protease serine 36/C16 open reading frame 67) each harbored 2 significant correlates of n-3 PUFA intake. In conclusion, we present promising evidence of association between several biologically relevant epigenetic markers and long-term intake of marine-derived n-3 PUFAs.