Oxidized phospholipid oxPAPC induces a Th1-like phenotype in regulatory T cells and inhibits their protective function in atherosclerosis

Abstract

AbstractBackgroundRegulatory T cells (Tregs) are protective in atherosclerosis but reduced during disease progression due to cell death and loss of stability. However, the mechanisms of Tregdysfunction remain unknown. Oxidized phospholipids (oxPLs) are abundant in atherosclerosis and can activate innate immune cells, but there is limited information regarding their impact on T cells. Given Tregloss during atherosclerosis progression and oxPL levels in the plaque microenvironment, we sought to determine whether oxidized 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine (oxPAPC), an oxPL associated with atherosclerotic plaques, alters Tregdifferentiation and function.MethodsNaïve CD4+T cells were cultured under Treg,Th1, and Th17 polarizing conditions with or without oxPAPC and assessed by flow cytometry. Gene expression in oxPAPC-treated Tregswas analyzed by bulk RNA sequencing. Functional studies of oxPAPC-induced Tregswere performed by co-culturing Tregswith CTV-labeled CD8+cellsin vitro. In vivosuppression of atherosclerosis was evaluated by adoptively transferring control or oxPAPC-treated Tregsto hyperlipidemicLdlr-/-mice.ResultsCompared to controls, oxPAPC-treated Tregswere less viable but expressed higher levels of the Th1-associated markers T-bet, CXCR3, and IFN-γ. Th1 and Th17 skewing cultures were unaltered by oxPAPC. IFN-γ is linked to Treginstability, thus Tregpolarization experiments were repeated usingIfngr1-/-CD4+T cells. IFNγR1 deficiency did not improve cell viability in oxPAPC-treated Tregs, however, T-bet and IFN-γ expression was not increased suggesting a role for IFN-γ signaling. OxPAPC-treated Tregswere less suppressivein vitro, and adoptive transfer studies in hyperlipidemicLdlr-/-mice showed that oxPAPC-induced Tregspossessed altered tissue homing and were insufficient to inhibit atherosclerosis progression.ConclusionsOxPAPC elicits Treg-specific changes that induce a Th1-like phenotype dependent on IFN-γ signaling. This is biologically relevant as oxPAPC-treated Tregsare unable to reduce atherosclerosis progression inLdlr-/-mice. This study supports a role for oxPLs in negatively impacting Tregdifferentiation and atheroprotective function.