Israel Gotsman

Interferon-γ, a Th1 Cytokine, Regulates Fat Inflammation. A Role for Adaptive Immunity in Obesity

Adipose tissue (AT) can accumulate macrophages and secrete several inflammatory mediators. Despite its pivotal role in the progression of chronic inflammatory processes such as atherosclerosis, the adaptive role of immunity in obesity remains poorly explored. Visceral AT of diet-induced obese C57BL/6 mice had higher numbers of both CD4+ and CD8+ T cells than lean controls, monitored by flow cytometry. When stimulated in vitro, T cells from obese AT produced more interferon (IFN)&ggr; than those from controls. AT from obese animals also had more cells expressing I-Ab, a mouse class II histocompatibility marker implicated in antigen presentation, as determined by immunostaining. Differentiated 3T3-L1 cells stimulated with recombinant IFN&ggr; or T-helper 1–derived supernatant produced several chemokines and their mRNAs. Obese IFN&ggr;-deficient animals had significantly reduced AT expression of mRNA-encoding inflammatory genes such as tumor necrosis factor-&agr; and monocyte chemoattractant protein-1, decreased AT inflammatory cell accumulation, and better glucose tolerance than control animals consuming the same diet. Obese mice doubly deficient for IFN&ggr; receptor and apolipoprotein (Apo)E on a mixed 129SvEv/C57BL/6 (129/B6) genetic background, despite exhibiting similar AT mRNA levels of tumor necrosis factor-&agr; and monocyte chemoattractant protein-1 as 129/B6-ApoE−/− controls, had decreased expression of important T cell–related genes, such as IFN&ggr;-inducible protein-10 and I-Ab, and lower plasma triglycerides and glucose. These results indicate a role for T cells and IFN&ggr;, a prototypical T-helper 1 cytokine, in regulation of the inflammatory response that accompanies obesity.

Impaired Regulatory T-Cell Response and Enhanced Atherosclerosis in the Absence of Inducible Costimulatory Molecule

Background— T-cell–mediated immunity contributes to the pathogenesis of atherosclerosis, but little is known about how these responses are regulated. We explored the influence of the inducible costimulatory molecule (ICOS) on atherosclerosis and associated immune responses. Methods and Results— Bone morrow chimeras were generated by transplanting ICOS-deficient or wild-type bone marrow into irradiated atherosclerosis-prone, LDR receptor–deficient mice, and the chimeric mice were fed a high-cholesterol diet for 8 weeks. Compared with controls, mice transplanted with ICOS-deficient marrow had a 43% increase in the atherosclerotic burden, and importantly, their lesions had a 3-fold increase in CD4+ T cells, as well as increased macrophage, smooth muscle cell, and collagen content. CD4+ T cells from ICOS-deficient chimeras proliferated more and secreted more interferon-γ and tumor necrosis factor-α than T cells from control mice, which suggests a lack of regulation. FoxP3+ regulatory T cells (Treg) were found to constitutively express high ICOS levels, which suggests a role for ICOS in Treg function. ICOS-deficient mice had decreased numbers of FoxP3+ Treg and impaired in vitro Treg suppressive function compared with control mice. Conclusions— ICOS has a key role in regulation of atherosclerosis, through its effect on regulatory T-cell responses.

T-Cell Costimulation and Coinhibition in Atherosclerosis

Evidence from many human and rodent studies has established that T lymphocytes enhance inflammation in atherosclerotic plaques and contribute to lesion progression and remodeling. Recent work also indicates that regulatory T cells are important in limiting proatherogenic T-cell responses. Given the important role of T cells in atherosclerosis, there is a need to fully understand how proatherogenic T cells are activated and regulated. Antigen-dependent activation of naïve T cells, leading to clonal expansion and effector T-cell differentiation, and effector and memory T cells, is enhanced by signals provided by costimulatory molecules expressed by antigen presenting cells, which bind to receptors on the T cells. In addition, T-cell responses to antigen are negatively regulated by coinhibitory molecules expressed by antigen-presenting cells, which bind to receptors on T cells. Two major families of costimulatory molecules include the B7 and the tumor necrosis factor (TNF) families. These molecules bind to receptors on T cells belonging to the CD28 or TNF receptor families, respectively. The best-defined coinhibitors and their receptors belong to the B7 and CD28 families. Recent work has begun to define how these T-cell costimulatory and coinhibitory pathways influence atherosclerosis, largely in mouse models of the disease. Profound effects are attributable to molecules in both the B7/CD28 (B7-1/2, ICOS, and PDL-1/2) and the TNF/TNF receptor (CD40, OX40, and CD137) families. One emerging theme is that both pathogenic effector T-cell responses and regulatory T cells are influenced by overlapping sets of costimulators and coinhibitors. These complexities must be considered as immunotherapeutic approaches for atherosclerotic disease are developed.

Vitamin D deficiency is a predictor of reduced survival in patients with heart failure; vitamin D supplementation improves outcome

Vitamin D deficiency is a highly prevalent, global phenomenon. The prevalence in heart failure (HF) patients and its effect on outcome are less clear. We evaluated vitamin D levels and vitamin D supplementation in patients with HF and its effect on mortality.

Endothelial Programmed Death-1 Ligand 1 (PD-L1) Regulates CD8+ T-Cell–Mediated Injury in the Heart

Background— PD-L1 and PD-L2 are ligands for the inhibitory receptor programmed death-1 (PD-1), which is an important regulator of immune responses. PD-L1 is induced on cardiac endothelial cells under inflammatory conditions, but little is known about its role in regulating immune injury in the heart. Methods and Results— Cytotoxic T-lymphocyte–mediated myocarditis was induced in mice, and the influence of PD-L1 signaling was studied with PD-L1/L2–deficient mice and blocking antibodies. During cytotoxic T-lymphocyte–induced myocarditis, the upregulation of PD-L1 on cardiac endothelia was dependent on T-cell–derived interferon-γ, and blocking of interferon-γ signaling worsened disease. Genetic deletion of both PD-1 ligands [PD-L1/2(−/−)], as well as treatment with PD-L1 blocking antibody, transformed transient myocarditis to lethal disease, in association with widespread polymorphonuclear leukocyte–rich microabscesses but without change in cytotoxic T-lymphocyte recruitment. PD-L1/2(−/−) mice reconstituted with bone marrow from wild-type mice remained susceptible to severe disease, which demonstrates that PD-L1 on non–bone marrow–derived cells confers the protective effect. Finally, depletion of polymorphonuclear leukocytes reversed the enhanced susceptibility to lethal myocarditis attributable to PD-L1 deficiency. Conclusions— Myocardial PD-L1, mainly localized on endothelium, is critical for control of immune-mediated cardiac injury and polymorphonuclear leukocyte inflammation.

Proatherogenic immune responses are regulated by the PD-1/PD-L pathway in mice

T lymphocyte responses promote proatherogenic inflammatory events, which are influenced by costimulatory molecules of the B7 family. Effects of negative regulatory members of the B7 family on atherosclerosis have not been described. Programmed death-ligand 1 (PD-L1) and PD-L2 are B7 family members expressed on several cell types, which inhibit T cell activation via binding to programmed death-1 (PD-1) on T cells. In order to test whether the PD-1/PD-L pathway regulates proatherogenic T cell responses, we compared atherosclerotic lesion burden and phenotype in hypercholesterolemic PD-L1/2(-/-)LDLR(-/-) mice and LDLR(-/-) controls. PD-L1/2 deficiency led to significantly increased atherosclerotic burden throughout the aorta and increased numbers of lesional CD4(+) and CD8(+) T cells. Compared with controls, PD-L1/2(-/-)LDLR(-/-) mice had iliac lymphadenopathy and increased numbers of activated CD4(+) T cells. Serum levels of TNF-alpha were higher in PD-L1/2(-/-)LDLR(-/-) mice than in controls. PD-L1/2-deficient APCs were more effective than control APCs in activating CD4(+) T cells in vitro, with or without cholesterol loading. Freshly isolated APCs from hypercholesterolemic PD-L1/2(-/-)LDLR(-/-) mice stimulated greater T cell responses than did APCs from hypercholesterolemic controls. Our findings indicate that the PD-1/PD-L pathway has an important role in downregulating proatherogenic T cell response and atherosclerosis by limiting APC-dependent T cell activation.

CD11c+ Dendritic Cells Maintain Antigen Processing, Presentation Capabilities, and CD4+ T-Cell Priming Efficacy Under Hypercholesterolemic Conditions Associated With Atherosclerosis

Recent reports suggest dyslipidemia impairs dendritic cell (DC) function and adaptive immunity. This study aimed to characterize the effect of hypercholesterolemia on antigen-presenting cell function of DCs and DC-dependent CD4+ T-cell responses. DCs incubated in vitro with acetylated low-density lipoprotein cholesterol with or without an acyl-coenzyme A:cholesterol acyl-transferase inhibitor maintained their ability to prime CD4+ T cells. Analysis of T-cell proliferation and interferon-γ and tumor necrosis factor-α production after ex vivo coculture of naïve CD4+ T cells with splenic, inguinal, or iliac DCs from low-density lipoprotein receptor–deficient (LDLR−/−) or apolipoprotein E–deficient (ApoE−/−) mice fed an atherogenic diet highlighted DC efficacy in effector T-cell generation under hypercholesterolemic conditions. Adoptive transfer of carboxyfluorescein diacetate, succinimidyl ester (CFSE)-labeled naïve CD4+ T cells in LDLR−/− recipients and subsequent immunization demonstrated effective priming of naïve T cells in hypercholesterolemic mice. CFSE dilution analyses revealed that hypercholesterolemic DCs were equipotent in naïve CD4+ T-cell priming efficacy with normocholesterolemic DCs. Quantitative real-time PCR and flow cytometric analyses demonstrated that DC expression of multiple molecules involved in antigen processing, presentation, and T-cell stimulation remained unaltered by dyslipidemia. Finally, endogenous antigen-primed CD4+ T cells responded equivalently to a secondary ex vivo antigenic challenge, regardless of whether they were primed in vivo under hypercholesterolemic or control conditions, demonstrating that all essential steps in CD4+ T-cell responses remain intact under atherogenic conditions. This study affirms that the adaptive immune response prevails under the hypercholesterolemic conditions present in atherosclerosis. In particular, DCs remain functional antigen-presenting cells and maintain their ability to prime CD4+ T cells even when cholesterol-loaded.

The Influence of the Regulatory T Lymphocytes on Atherosclerosis

Atherosclerosis is complex inflammatory disease of the arterial wall, in which T lymphocytes play a significant role.1 Since the recognition that T lymphocytes are present in human atherosclerotic plaque nearly 2 decades ago,2 research has focused on the functional importance of these cells in the atherosclerotic process. The majority of T lymphocytes in atherosclerotic lesions are CD4+ T-helper cells with a phenotype characteristic of the proinflammatory T-helper 1 (Th1) subset. These cells recognize specifically antigens that are produced in relative abundance in hypercholesterolemic individuals or in plaques including oxidatively modified LDL (Ox-LDL) and HSP60/65. The T cells are activated when macrophage or dendritic cells present these antigens to the T cells in plaques or lymphoid tissues. The Th1 cells produce inflammatory cytokines IFN-γ, tumor necrosis factor (TNF)-α, and membrane CD40-ligand, which amplify the immune response through activation of macrophages, vascular smooth muscle cells, and endothelial cells.1 See page 2691 Many mechanisms have evolved to maintain immunologic self-tolerance and to limit responses to foreign antigens. One of these mechanisms involves regulatory T cells (Treg) that actively suppress responses of effector T cells. The best- characterized Treg are the natural CD4+CD25+ Treg that mature in the thymus and comprise 5% to 10% of peripheral CD4+ T cells.3 Other surface markers expressed by Treg include CTLA-4 and GITR. FoxP3, a forkhead family transcription factor, is a lineage specification factor for Treg and plays a crucial role in their suppressive function.4 Natural Treg are generated during thymic development, but Treg are also induced in peripheral tissues during immune responses. Treg express antigen receptors typical of effector T cells and are presumably activated by peptide antigens presented by APCs. They also require interleukin (IL)-2 for development and survival. Once activated, Treg may suppress other T …

The significance of serum urea and renal function in patients with heart failure.

Renal function and urea are frequently abnormal in patients with heart failure (HF) and are predictive of increased mortality. The relative importance of each parameter is less clear. We prospectively compared the predictive value of renal function and serum urea on clinical outcome in patients with HF. Patients hospitalized with definite clinical diagnosis of HF (n = 355) were followed for short-term (1 yr) and long-term (mean, 6.5 yr) survival and HF rehospitalization. Increasing tertiles of discharge estimated glomerular filtration rate (eGFR) were an independent predictor of increased long-term survival (hazard ratio [HR], 0.65; 95% confidence interval [CI], 0.47-0.91; p = 0.01) but not short-term survival. Admission and discharge serum urea and blood urea nitrogen (BUN)/creatinine ratio were predictors of reduced short- and long-term survival on multivariate Cox regression analysis. Increasing tertiles of discharge urea were a predictor of reduced 1-year survival (HR, 2.13; 95% CI, 1.21-3.73; p = 0.009) and long-term survival (HR, 1.93; 95% CI, 1.37-2.71; p < 0.0001). Multivariate analysis including discharge eGFR and serum urea demonstrated that only serum urea remained a significant predictor of long-term survival; however, eGFR and BUN/creatinine ratio were both independently predictive of survival. Urea was more discriminative than eGFR in predicting long-term survival by area under the receiver operating characteristic curve (0.803 vs. 0.787; p = 0.01). Increasing tertiles of discharge serum urea and BUN/creatinine were independent predictors of HF rehospitalization and combined death and HF rehospitalization. This study suggests that serum urea is a more powerful predictor of survival than eGFR in patients with HF. This may be due to ureas relation to key biological parameters including renal, hemodynamic, and neurohormonal parameters pertaining to the overall clinical status of the patient with chronic HF. Abbreviations: ADHF = acute decompensated heart failure, AUC = area under the curve, BUN = blood urea nitrogen, CI = confidence interval, eGFR = estimated glomerular filtration rate, HF = heart failure, HR = hazard ratio, MDRD = Modification of Diet in Renal Disease, ROC = receiver operating characteristic.

Clinical Outcome of Patients with Heart Failure and Preserved Left Ventricular Function

BACKGROUND Patients with heart failure have a poor prognosis. However, it has been presumed that patients with heart failure and preserved left ventricular function (LVF) may have a more benign prognosis. OBJECTIVES We evaluated the clinical outcome of patients with heart failure and preserved LVF compared with patients with reduced function and the factors affecting prognosis. METHODS We prospectively evaluated 289 consecutive patients hospitalized with a definite clinical diagnosis of heart failure based on typical symptoms and signs. They were divided into 2 subsets based on echocardiographic LVF. Patients were followed clinically for a period of 1 year. RESULTS Echocardiography showed that more than one third (36%) of the patients had preserved systolic LVF. These patients were more likely to be older and female and have less ischemic heart disease. The survival at 1 year in this group was poor and not significantly different from patients with reduced LVF (75% vs 71%, respectively). The adjusted survival by Cox regression analysis was not significantly different (P=.25). However, patients with preserved LVF had fewer rehospitalizations for heart failure (25% vs 35%, P<.05). Predictors of mortality in the whole group by multivariate analysis were age, diabetes, chronic renal failure, atrial fibrillation, residence in a nursing home, and serum sodium < or = 135 mEq/L. CONCLUSION The prognosis of patients with clinical heart failure with or without preserved LVF is poor. Better treatment modalities are needed in both subsets.