Aims PCSK9 is secreted into the circulation, mainly by the liver, and interacts with low-density lipoprotein receptor (LDLR) homologous and non-homologous receptors, including CD36, thus favouring their intracellular degradation. As PCSK9 deficiency increases the expression of lipids and lipoprotein receptors, thus contributing to cellular lipid accumulation, we investigated whether this could affect heart metabolism and function. Methods and results Wild-type (WT), Pcsk9 KO, Liver conditional Pcsk9 KO and Pcsk9/Ldlr double KO male mice were fed for 20 weeks with a standard fat diet and then exercise resistance, muscle strength, and heart characteristics were evaluated. Pcsk9 KO presented reduced running resistance coupled to echocardiographic abnormalities suggestive of heart failure with preserved ejection fraction (HFpEF). Heart mitochondrial activity, following maximal coupled and uncoupled respiration, was reduced in Pcsk9 KO mice compared to WT mice and was coupled to major changes in cardiac metabolism together with increased expression of LDLR and CD36 and with lipid accumulation. A similar phenotype was observed in Pcsk9/Ldlr DKO, thus excluding a contribution for LDLR to cardiac impairment observed in Pcsk9 KO mice. Heart function profiling of the liver selective Pcsk9 KO model further excluded the involvement of circulating PCSK9 in the development of HFpEF, pointing to a possible role locally produced PCSK9. Concordantly, carriers of the R46L loss-of-function variant for PCSK9 presented increased left ventricular mass but similar ejection fraction compared to matched control subjects. Conclusion PCSK9 deficiency impacts cardiac lipid metabolism in an LDLR independent manner and contributes to the development of HFpEF.

Protein glycosylation is a post-translational modification consisting of the enzymatic attachment of carbohydrate chains to specific residues of the protein sequence. Several types of glycosylation have been described, with N-glycosylation and O-glycosylation being the most common types impacting on crucial biological processes, such as protein synthesis, trafficking, localization, and function. Genetic defects in genes involved in protein glycosylation may result in altered production and activity of crucial proteins, with a broad range of clinical manifestations, including dyslipidemia and atherosclerosis. A large number of apolipoproteins, lipoprotein receptors, and other proteins involved in lipoprotein metabolism are glycosylated, and alterations in their glycosylation profile are associated with changes in their expression and/or function. Rare genetic diseases and population genetics have provided additional information linking protein glycosylation to the regulation of lipoprotein metabolism.

Aim Loss of immunosuppressive response supports inflammation during atherosclerosis. We tested whether adoptive cell therapy (ACT) with Tregulatory cells (Tregs) engineered to selectively migrate in the atherosclerotic plaque would dampen the immune-inflammatory response in the arterial wall in animal models of Familial Hypercholesterolemia (FH). Methods and Results FH patients presented a decreased Tregs suppressive function associated to an increased inflammatory burden. A similar phenotype was observed in Ldlr -/- mice accompanied by a selective increased expression of the chemokine CX3CL1 in the aorta but not in other districts (lymph nodes, spleen and liver). Treg overexpressing CX3CR1 were thus generated (CX3CR1+-Treg) to drive Treg selectively to the plaque. CX3CR1+-Treg were injected (i.v.) in Ldlr -/- fed high-cholesterol diet (WTD) for 8 weeks. CX3CR1+-Treg were detected in the aorta, but not in other tissues, of Ldlr -/- mice 24h after ACT, corroborating the efficacy of this approach. After 4 additional weeks of WTD, ACT with CX3CR1+-Treg resulted in reduced plaque progression and lipid deposition, ameliorated plaque stability by increasing collagen and smooth muscle cells content, while decreasing the number of pro-inflammatory macrophages. Shotgun proteomics of the aorta showed a metabolic rewiring in CX3CR1+-Treg treated Ldlr -/- mice compared to controls that was associated with the improvement of inflammation-resolving pathways and disease progression. Conclusion ACT with vasculotropic Treg appears as a promising strategy to selectively target immune activation in the atherosclerotic plaque. Translational relevance Improving pro-resolutive inflammatory response represents a promising therapeutic approach to control atherosclerosis progression. Meanwhile, selective immunosuppression at the atherosclerotic plaque looks critical to limit unspecific inhibition of inflammation in other tissues. Our work demonstrates that engineering of immunosuppressive T regulatory cells to be hijacked in the atherosclerotic plaque limits atherosclerosis progression by targeting local inflammation.

No abstract

Activation of T cells relies on the availability of intracellular cholesterol for an effective response after stimulation. We investigated the contribution of cholesterol derived from extracellular uptake by the low-density lipoprotein (LDL) receptor in the immunometabolic response of T cells. By combining proteomics, gene expression profiling, and immunophenotyping, we described a unique role for cholesterol provided by the LDLR pathway in CD8+ T cell activation. mRNA and protein expression of LDLR was significantly increased in activated CD8+ compared to CD4+ WT T cells, and this resulted in a significant reduction of proliferation and cytokine production (IFNγ, Granzyme B, and Perforin) of CD8+ but not CD4+ T cells from Ldlr −/− mice after in vitro and in vivo stimulation. This effect was the consequence of altered cholesterol routing to the lysosome resulting in a lower mTORC1 activation. Similarly, CD8+ T cells from humans affected by familial hypercholesterolemia (FH) carrying a mutation on the LDLR gene showed reduced activation after an immune challenge.