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Articles by C. J Diehl
Total Records ( 2 ) for C. J Diehl
  J Sun , K Hartvigsen , M. Y Chou , Y Zhang , G. K Sukhova , J Zhang , M Lopez Ilasaca , C. J Diehl , N Yakov , D Harats , J George , J. L Witztum , P Libby , H Ploegh and G. P. Shi

Background— Adaptive immunity and innate immunity play important roles in atherogenesis. Invariant chain (CD74) mediates antigen-presenting cell antigen presentation and T-cell activation. This study tested the hypothesis that CD74-deficient mice have reduced numbers of active T cells and resist atherogenesis.

Methods and Results— In low-density lipoprotein receptor–deficient (Ldlr–/–) mice, CD74 deficiency (Ldlr–/–Cd74–/–) significantly reduced atherosclerosis and CD25+-activated T cells in the atheromata. Although Ldlr–/–Cd74–/– mice had decreased levels of plasma immunoglobulin (Ig) G1, IgG2b, and IgG2c against malondialdehyde-modified LDL (MDA-LDL), presumably as a result of impaired antigen-presenting cell function, Ldlr–/–Cd74–/– mice showed higher levels of anti–MDA-LDL IgM and IgG3. After immunization with MDA-LDL, Ldlr–/–Cd74–/– mice had lower levels of all anti–MDA-LDL Ig isotypes compared with Ldlr–/– mice. As anticipated, only Ldlr–/– splenocytes responded to in vitro stimulation with MDA-LDL, producing Th1/Th2 cytokines. Heat shock protein-65 immunization enhanced atherogenesis in Ldlr–/– mice, but Ldlr–/– Cd74–/– mice remained protected. Compared with Ldlr–/– mice, Ldlr–/–Cd74–/– mice had higher anti–MDA-LDL autoantibody titers, fewer lesion CD25+-activated T cells, impaired release of Th1/Th2 cytokines from antigen-presenting cells after heat shock protein-65 stimulation, and reduced levels of all plasma anti–heat shock protein-65 Ig isotypes. Cytofluorimetry of splenocytes and peritoneal cavity cells of MDA-LDL– or heat shock protein-65–immunized mice showed increased percentages of autoantibody-producing marginal zone B and B-1 cells in Ldlr–/–Cd74–/– mice compared with Ldlr–/– mice.

Conclusions— Invariant chain deficiency in Ldlr–/– mice reduced atherosclerosis. This finding was associated with an impaired adaptive immune response to disease-specific antigens. Concomitantly, an unexpected increase in the number of innate-like peripheral B-1 cell populations occurred, resulting in increased IgM/IgG3 titers to the oxidation-specific epitopes.

  P Wiesner , S. H Choi , F Almazan , C Benner , W Huang , C. J Diehl , A Gonen , S Butler , J. L Witztum , C. K Glass and Y. I. Miller

Rationale: Oxidized low-density lipoprotein (LDL) is an important determinant of inflammation in atherosclerotic lesions. It has also been documented that certain chronic infectious diseases, such as periodontitis and chlamydial infection, exacerbate clinical manifestations of atherosclerosis. In addition, low-level but persistent metabolic endotoxemia is often found in diabetic and obese subjects and is induced in mice fed a high-fat diet.

Objective: In this study, we examined cooperative macrophage activation by low levels of bacterial lipopolysaccharide (LPS) and by minimally oxidized LDL (mmLDL), as a model for subclinical endotoxemia-complicated atherosclerosis.

Methods and Results: We found that both in vitro and in vivo, mmLDL and LPS (Kdo2-LipidA) cooperatively activated macrophages to express proinflammatory cytokines Cxcl2 (MIP-2), Ccl3 (MIP-1), and Ccl4 (MIP-1β). Importantly, the mmLDL and LPS cooperative effects were evident at a threshold LPS concentration (1 ng/mL) at which LPS alone induced only a limited macrophage response. Analyzing microarray data with a de novo motif discovery algorithm, we found that genes transcribed by promoters containing an activator protein (AP)-1 binding site were significantly upregulated by costimulation with mmLDL and LPS. In a nuclear factor–DNA binding assay, the cooperative effect of mmLDL and LPS costimulation on c-Jun and c-Fos DNA binding, but not on p65 or p50, was dependent on mmLDL-induced activation of extracellular signal-regulated kinase (ERK) 1/2. In addition, mmLDL induced c-Jun N-terminal kinase (JNK)-dependent derepression of AP-1 by removing nuclear receptor corepressor (NCoR) from the chemokine promoters.

Conclusions: The cooperative engagement of AP-1 and nuclear factor (NF)-B by mmLDL and LPS may constitute a mechanism of increased transcription of inflammatory cytokines within atherosclerotic lesions.

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