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Hyperlipidemia elicits an atypical, Th1 like CD4+ T cell response: a key role for VLDL

ABSTRACT: Hyperlipidemia and T cell driven inflammation are important drivers of atherosclerosis, the principal underlying cause of cardiovascular disease. Here, we applied an in-depth multi-omics approach to detail the effects of hyperlipidemia on T cells. In vitro, exposure of CD4+ T cells to very low-density lipoprotein (VLDL), but not to low-density lipoprotein (LDL) resulted in upregulation of Th1 associated pathways, suggesting that VLDL serves as the main lipid component driving hyperlipidemia induced T cell activation. To further detail this response in vivo, T-cells of ldlr-/- fed a normal cholesterol or high cholesterol diet, which develop a strong increase in VLDL cholesterol and triglyceride levels, were investigated. CD4+ T cells of hyperlipidemic ldlr-/- mice exhibited an increased expression of CXC-chemokine receptor 3 (CXCR3) and produced more TNFα and interferon-γ (IFN-γ). Gene set enrichment analysis identified IFN-γ-mediated signaling as the most upregulated pathway in hyperlipidemic T cells. However, the classical Th1 associated transcription factor profile with strong upregulation of Tbet and downregulation of Gata3 was not observed. Hyperlipidemia did not affect levels of the CD4+ T-cell’s metabolites involved in glycolysis or other canonical metabolic pathways but enhanced amino acids levels. However, CD4+ T-cells of hyperlipidemic mice showed increased cellular cholesterol accumulation and an increased arachidonic acid (AA) to docosahexaenoic acid (DHA) ratio, which was associated with T cell activation and IFN-γ-mediated signaling. In conclusion, hyperlipidemia, and especially its VLDL component induces an atypicial Th1 response in CD4+ T-cells.

ORGANISM(S): Homo sapiens

PROVIDER: GSE201598 | GEO | 2023/04/03

REPOSITORIES: GEO

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Project description:Background: Regulatory T cells (Tregs) are protective in atherosclerosis but reduced during disease progression due to cell death and loss of stability. However, the mechanisms of Treg dysfunction remain unknown. Oxidized phospholipids (oxPLs) are abundant in atherosclerosis and can activate innate immune cells, but little is known regarding their impact on T cells. Given Treg loss during atherosclerosis progression and oxPL levels in the plaque microenvironment, we investigated whether oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (oxPAPC), an oxPL associated with atherosclerotic plaques, alters Treg differentiation and function. Methods: CD4+ T cells were polarized to Treg, Th1, and Th17 cells with or without oxPAPC and assessed by flow cytometry. Gene expression in oxPAPC-treated Tregs was analyzed by bulk RNA sequencing. Functional studies of oxPAPC-induced Tregs were performed by co-culturing Tregs with CTV-labeled cells in vitro, and by adoptively transferring Tregs to hyperlipidemic Ldlr-/- mice to measure atherosclerosis progression. Results: Compared to controls, oxPAPC-treated Tregs were less viable, but surviving cells expressed higher levels of the Th1-associated markers T-bet, CXCR3, and IFN-. Th1 and Th17 skewing cultures were unaltered by oxPAPC. IFN- is linked to Treg instability, thus Treg polarization experiments were repeated using Ifngr1-/- CD4+ T cells. IFNR1 deficiency did not improve cell viability in oxPAPC-treated Tregs, however, T-bet and IFN- expression was not increased in surviving cells suggesting a role for IFN-signaling. OxPAPC-treated Tregs were less suppressive in vitro, and adoptive transfer studies in hyperlipidemic Ldlr-/- mice showed that oxPAPC-induced Tregs possessed altered tissue homing and were insufficient to inhibit atherosclerosis progression. Conclusions: OxPAPC elicits Treg-specific changes altering Treg differentiation and inducing a Th1-like phenotype in surviving cells partially through IFN- signaling. This is biologically relevant as oxPAPC-treated Tregs do not reduce atherosclerosis progression in Ldlr-/- mice. This study supports the role for oxPLs in negatively impacting Treg differentiation and atheroprotective function.

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Hyperlipidemia elicits an atypical, Th1 like CD4+ T cell response: a key role for VLDL

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