Defective Autophagy in T Cells Impairs the Development of Diet-Induced Hepatic Steatosis and Atherosclerosis

Macroautophagy (or autophagy) is a conserved cellular process in which cytoplasmic cargo is targeted for lysosomal degradation. Autophagy is crucial for the functional integrity of different subsets of T cells in various developmental stages. Since atherosclerosis is an inflammatory disease of the vessel wall which is partly characterized by T cell mediated autoimmunity, we investigated how advanced atherosclerotic lesions develop in mice with T cells that lack autophagy-related protein 7 (Atg7), a protein required for functional autophagy. Mice with a T cell-specific knock-out of Atg7 (Lck-Cre Atg7f/f) had a diminished naïve CD4+ and CD8+ T cell compartment in the spleen and mediastinal lymph node as compared to littermate controls (Atg7f/f). Lck-Cre Atg7f/f and Atg7f/f mice were injected intravenously with rAAV2/8-D377Y-mPCSK9 and fed a Western-type diet to induce atherosclerosis. While Lck-Cre Atg7f/f mice had equal serum Proprotein Convertase Subtilisin/Kexin type 9 levels as compared to Atg7f/f mice, serum cholesterol levels were significantly diminished in Lck-Cre Atg7f/f mice. Histological analysis of the liver revealed less steatosis, and liver gene expression profiling showed decreased expression of genes associated with hepatic steatosis in Lck-Cre Atg7f/f mice as compared to Atg7f/f mice. The level of hepatic CD4+ and CD8+ T cells was greatly diminished but both CD4+ and CD8+ T cells showed a relative increase in their IFNγ and IL-17 production upon Atg7 deficiency. Atg7 deficiency furthermore reduced the hepatic NKT cell population which was decreased to < 0.1% of the lymphocyte population. Interestingly, T cell-specific knock-out of Atg7 decreased the mean atherosclerotic lesion size in the tri-valve area by over 50%. Taken together, T cell-specific deficiency of Atg7 resulted in a decrease in hepatic steatosis and limited inflammatory potency in the (naïve) T cell compartment in peripheral lymphoid tissues, which was associated with a strong reduction in experimental atherosclerosis

Fluorescent small-molecule agonists as follicle-stimulating hormone receptor imaging tools

Fluorescent cell surface receptor agonists allow visualization of processes that are set in motion by receptor activation. This study describes the synthesis of two fluorescent, low molecular weight ligands for the follicle-stimulating hormone receptor (FSHR), based on a dihydropyridine (DHP) agonist. We show that both BODIPY- and Cy5-conjugated DHP (m-DHP-BDP and m-DHP-Cy5) are potent FSHR agonists, able to activate receptor signalling with nanomolar potencies and to effect receptor internalisation at higher concentrations. FSHR-dependent uptake of m-DHP-Cy5 is in stark contrast to the cellular uptake of m-DHP-BDP which was efficiently internalised also in the absence of FSHR. Our results comprise a first-in-class fluorescent low molecular weight ligand for in situ FSHR imaging and pertain the potential means for targeted delivery of drugs into the endolysosomal pathway of FSHR-expressing cells

Oxidized low-density lipoprotein-induced apoptotic dendritic cells as a novel therapy for atherosclerosis

Modulation of immune responses may form a powerful approach to treat atherosclerosis. It was shown that clearance of apoptotic cells results in tolerance induction to cleared Ags by dendritic cells (DCs); however, this seems impaired in atherosclerosis because Ag-specific tolerance is lacking. This could result, in part, from decreased emigration of DCs from atherosclerotic lesions because of the high-cholesterol environment. Nonetheless, local induction of anti-inflammatory responses by apoptotic cell clearance seems to dampen atherosclerosis, because inhibition of apoptotic cell clearance worsens atherosclerosis. In this study, we assessed whether i.v. administration of oxLDL-induced apoptotic DCs (apop(ox)-DCs) and, as a control, unpulsed apoptotic DCs could modulate atherosclerosis by inducing tolerance. Adoptive transfer of apop(ox)-DCs into low-density lipoprotein receptor knockout mice either before or during feeding of a Western-type diet resulted in increased numbers of CD103(+) tolerogenic splenic DCs, with a concomitant increase in regulatory T cells. Interestingly, both types of apoptotic DCs induced an immediate 40% decrease in Ly-6C(hi) monocyte numbers and a 50% decrease in circulating CCL2 levels, but only apop(ox)-DC treatment resulted in long-term effects on monocytes and CCL2 levels. Although initial lesion development was reduced by 40% in both treatment groups, only apop(ox)-DC treatment prevented lesion progression by 28%. Moreover, progressed lesions of apop(ox)-DC-treated mice showed a robust 45% increase in collagen content, indicating an enhanced stability of lesions. Our findings clearly show that apoptotic DC treatment significantly decreases lesion development, but only apop(ox)-DCs can positively modulate lesion progression and stability. These findings may translate into a safe treatment for patients with established cardiovascular diseases using patient-derived apop(ox)-DCs

Vaccination using oxidized low-density lipoprotein-pulsed dendritic cells reduces atherosclerosis in LDL receptor-deficient mice

Aims Modification of lipoproteins plays an important role in the development of atherosclerosis. Oxidatively modified low-density lipoprotein (oxLDL) has a number of pro-inflammatory effects, whereas immunization with various forms of oxLDL is able to reduce atherosclerosis. The uptake of modified LDL by dendritic cells (DCs) and the presentation of epitopes thereof may form an important step in the immunomodulatory effects of LDL. In this study, we transferred oxLDL-pulsed mature DCs (mDCs) to LDL receptor-null (LDLr-/-) mice and examined the effects on atherosclerosis. Methods and results Bone marrow-derived DCs were cultured for 10 days in the presence of granulocyte-macrophage colony-stimulating factor. Immature DCs were matured by lipopolysaccharide and pulsed with copper-oxidized LDL. These mDCs were transferred three times to LDLr-/- mice before the induction of atherosclerosis by Western-type diet feeding. The transfer of oxLDL-pulsed mDCs resulted in an 87% reduction in carotid artery lesion size (P < 0.001) with a concurrent increase in plaque stability, whereas treatment using mDCs pulsed with the atherosclerosis-irrelevant antigen, ovalbumin, did not influence lesion size or stability. Furthermore, the vaccination procedure resulted in the induction of oxLDL-specific T cells with a reduced Th1 profile and an increase in oxLDL-specific IgG levels, which contributed to a reduction in foam cell formation. Conclusion These data indicate that vaccination with oxLDL-pulsed mDCs provides a novel and powerful strategy for the immunomodulation of atherosclerosis.Pathophysiology and treatment of rheumatic disease

Agonistic anti-TIGIT treatment does not reduce more advanced atherosclerosis.

<p>Agonistic anti-TIGIT treatment (n = 12) and Armenian Hamster IgG treatment (n = 11) reduces atherosclerosis development in LDLr^−/− mice fed a Western-type diet for 8 weeks in comparison with PBS treatment (n = 12). Representative cross-sections of lesion formation in the three valves area of the aortic root stained with Oil-Red-O and hematoxylin are shown and lesion size was determined (A). Sections of the aortic root were stained for collagen using Masson’s trichrome staining. The percentage of collagen relative to the lesion size was determined (B). Furthermore, relative macrophage content was determined with a Moma-2 staining and quantified (C).</p

Agonistic anti-TIGIT treatment does not reduce initial atherosclerotic lesion development.

<p>No difference in atherosclerotic lesion size between agonistic anti-TIGIT, Armenian Hamster IgG and PBS treated LDLr^−/− mice fed a Western-type diet for 4 weeks. Representative cross-sections of lesion formation in the three valves area of the aortic root stained with Oil-Red-O and hematoxylin are shown and lesion size was determined (A). Sections of the aortic root were stained for collagen using Masson’s trichrome staining. The percentage of collagen relative to the lesion size was determined (B). Furthermore, relative macrophage content was determined with a Moma-2 staining and quantified (C).</p

Agonistic anti-TIGIT strongly inhibits T cell function.

<p>Splenocytes from Western-type diet fed mice (n = 3) were cultured for 72 hours with αCD3/αCD28 in the presence or absence of agonistic anti-TIGIT (0–30 µg/ml). Activated T cells (CD4⁺CD25⁺) were determined with flow cytometry (A). Proliferation was assessed by the amount of ³H-thymidine incorporation in dividing cells and is expressed as stimulation index (B) and by the amount of IL-2 produced by the splenocytes as determined with ELISA (C). Splenocytes of PBS, Armenian Hamster IgG and agonistic anti-TIGIT-treated mice (n = 5 per group) were cultured in the presence of αCD3/αCD28 stimulation and proliferation was assessed by the amount of 3H-thymidine incorporation expressed as stimulation index (D). *<i>P</i><0.05, **<i>P</i><0.01, ***<i>P</i><0.001.</p

Upregulation of TIGIT expression on CD4⁺ T cells under hypercholesterolemic conditions.

<p>Representative FACS dot plots of TIGIT surface expression on CD4⁺ T cells isolated from LDLr^−/− mice fed a Chow diet or a Western-type (WT) diet (A). Splenocytes from LDLr^−/− mice fed a Chow diet (n = 3) and Western-type diet (n = 3) were cultured for 48 hours in the presence or absence of anti-CD3/anti-CD28. Representative dot plots (B) and the mean percentage of TIGIT expressing CD4⁺ T cells in 4 different conditions (C) were obtained by flow cytometry. *<i>P</i><0.05.</p

Enhanced dendritic cell percentages and activation and decreased IL-10 expressing dendritic cells after agonistic anti-TIGIT treatment.

<p>At sacrifice, blood (A) and spleen (B) cells were isolated and stained for dendritic cells and activation markers and analyzed by flow cytometry (n = 5 per group). The effect of agonistic anti-TIGIT on IL-10 expression by DCs was determined by culturing splenocytes with increasing concentrations of agonistic anti-TIGIT (C). *<i>P</i><0.05, **<i>P</i><0.01.</p

Interruption of the OX40-OX40 Ligand Pathway in LDL Receptor-Deficient Mice Causes Regression of Atherosclerosis

Abstract Patients suffering from cardiovascular disease have well-established atherosclerotic lesions, rendering lesion regression of therapeutic interest. The OX40 (TNFRSF4)–OX40 ligand (OX40L; TNFSF4) pathway is important for the proliferation and survival of T cells, stimulates B cells, and is associated with cardiovascular disease. We hypothesized that interference with the OX40–OX40L pathway, in combination with decreases in cholesterol, may induce regression of atherosclerosis. LDLr−/− mice were fed a Western-type diet for 10 wk, after which they received chow diet and were treated with anti-OX40L or PBS for 10 wk. A significant regression of lesions was observed in the aorta and aortic arch of anti-OX40L–treated mice compared with control mice. Interference of the OX40–OX40L pathway reduced Th2 responses, as shown by decreases in GATA-3 and IL-4 levels. Also, IgE levels were decreased, as demonstrated by reduced mast cell presence and activation. Notably, IL-5 production by T and B1 cells was increased, thus enhancing atheroprotective oxidized low-density lipoprotein–specific IgM production. The increase in IL-5 production and IgM was mediated by IL-33 production by APCs upon OX40L blockade. We conclude that interruption of the OX40–OX40L signaling pathway, combined with decreases in dietary cholesterol, induces the regression of atherosclerosis through induction of IL-5–producing T cells and oxidized low-density lipoprotein–specific IgM and reductions in Th2 and mast cells.</jats:p