Haoyang Zhuang

Monocyte surface expression of Fcγ receptor RI (CD64), a biomarker reflecting type-I interferon levels in systemic lupus erythematosus

IntroductionMore than half of systemic lupus erythematosus (SLE) patients show evidence of excess type I interferon (IFN-I) production, a phenotype associated with renal disease and certain autoantibodies. However, detection of IFN-I proteins in serum is unreliable, and the measurement of interferon-stimulated gene (ISG) expression is expensive and time consuming. The aim of this study was to identify a surrogate marker for IFN-I activity in clinical samples for monitoring disease activity and response to therapy.MethodsMonocyte surface expression of Fcγ receptors (FcγRs), chemokine receptors, and activation markers were analyzed with flow cytometry in whole blood from patients with SLE and healthy controls. FcγR expression also was measured in peripheral blood mononuclear cells (PBMCs) from healthy controls cultured with Toll-like receptor (TLR) agonists, cytokines, or serum from SLE patients. Expression of ISGs was analyzed with real-time PCR.ResultsCirculating CD14+ monocytes from SLE patients showed increased surface expression of FcγRI (CD64). The mean fluorescent intensity of CD64 staining correlated highly with the ISG expression (MX1, IFI44, and Ly6E). In vitro, IFN-I as well as TLR7 and TLR9 agonists, induced CD64 expression on monocytes from healthy controls. Exposure of monocytes from healthy controls to SLE sera also upregulated the expression of CD64 in an IFN-I-dependent manner. Decreased CD64 expression was observed concomitant with the reduction of ISG expression after high-dose corticosteroid therapy.ConclusionsExpression of CD64 on circulating monocytes is IFN-I inducible and highly correlated with ISG expression. Flow-cytometry analysis of CD64 expression on circulating monocytes is a convenient and rapid approach for estimating IFN-I levels in SLE patients.

Pleiotropic IFN-Dependent and -Independent Effects of IRF5 on the Pathogenesis of Experimental Lupus

Genetic polymorphisms of IFN regulatory factor 5 (IRF5) are associated with an increased risk of lupus in humans. In this study, we examined the role of IRF5 in the pathogenesis of pristane-induced lupus in mice. The pathological response to pristane in IRF5−/− mice shared many features with type I IFN receptor (IFNAR)−/− and TLR7−/− mice: production of anti-Sm/RNP autoantibodies, glomerulonephritis, generation of Ly6Chi monocytes, and IFN-I production all were greatly attenuated. Lymphocyte activation following pristane injection was greatly diminished in IRF5−/− mice, and Th cell differentiation was deviated from Th1 in wild-type mice toward Th2 in IRF5−/− mice. Th cell development was skewed similarly in TLR7−/− or IFNAR−/− mice, suggesting that IRF5 alters T cell activation and differentiation by affecting cytokine production. Indeed, production of IFN-I, IL-12, and IL-23 in response to pristane was markedly decreased, whereas IL-4 increased. Unexpectedly, plasmacytoid dendritic cells (pDC) were not recruited to the site of inflammation in IRF5−/− or MyD88−/− mice, but were recruited normally in IFNAR−/− and TLR7−/− mice. In striking contrast to wild-type mice, pristane did not stimulate local expression of CCL19 and CCL21 in IRF5−/− mice, suggesting that IRF5 regulates chemokine-mediated pDC migration independently of its effects on IFN-I. Collectively, these data indicate that altered production of IFN-I and other cytokines in IRF5−/− mice prevents pristane from inducing lupus pathology by broadly affecting T and B lymphocyte activation/differentiation. Additionally, we uncovered a new, IFN-I–independent role of IRF5 in regulating chemokines involved in the homing of pDCs and certain lymphocyte subsets.

Toll-like receptor 7-stimulated tumor necrosis factor α causes bone marrow damage in systemic lupus erythematosus.

To define the pathogenesis of bone marrow (BM) involvement in systemic lupus erythematosus (SLE).

Irisin Controls Growth, Intracellular Ca2+ Signals, and Mitochondrial Thermogenesis in Cardiomyoblasts.

Exercise offers short-term and long-term health benefits, including an increased metabolic rate and energy expenditure in myocardium. The newly-discovered exercise-induced myokine, irisin, stimulates conversion of white into brown adipocytes as well as increased mitochondrial biogenesis and energy expenditure. Remarkably, irisin is highly expressed in myocardium, but its physiological effects in the heart are unknown. The objective of this work is to investigate irisin’s potential multifaceted effects on cardiomyoblasts and myocardium. For this purpose, H9C2 cells were treated with recombinant irisin produced in yeast cells (r-irisin) and in HEK293 cells (hr-irisin) for examining its effects on cell proliferation by MTT [3-(4, 5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay and on gene transcription profiles by qRT-PCR. R-irisin and hr-irisin both inhibited cell proliferation and activated genes related to cardiomyocyte metabolic function and differentiation, including myocardin, follistatin, smooth muscle actin, and nuclear respiratory factor-1. Signal transduction pathways affected by r-irisin in H9C2 cells and C57BL/6 mice were examined by detecting phosphorylation of PI3K-AKT, p38, ERK or STAT3. We also measured intracellular Ca2+ signaling and mitochondrial thermogenesis and energy expenditure in r-irisin-treated H9C2 cells. The results showed that r-irisin, in a certain concentration rage, could activate PI3K-AKT and intracellular Ca2+ signaling and increase cellular oxygen consumption in H9C2 cells. Our study also suggests the existence of irisin-specific receptor on the membrane of H9C2 cells. In conclusion, irisin in a certain concentration rage increased myocardial cell metabolism, inhibited cell proliferation and promoted cell differentiation. These effects might be mediated through PI3K-AKT and Ca2+ signaling, which are known to activate expression of exercise-related genes such as follistatin and myocardin. This work supports the value of exercise, which promotes irisin release.

Animal Models of Interferon Signature Positive Lupus

Human lupus is strongly associated with a gene expression signature characterized by over-expression of Type I interferon-regulated genes. A strong interferon signature generally is not seen in the standard mouse models of lupus, despite considerable evidence for the involvement of toll-like receptor-driven interferon production. In contrast, pristane-induced lupus exhibits a prominent TLR7-dependent interferon signature. Importantly, genetic disorders with dysregulated interferon production in both human beings and mice cause severe autoinflammatory diseases but not the typical manifestations of lupus, suggesting that interferon over-production is insufficient to cause systemic lupus erythematosus itself. Single-gene models in mice suggest that lupus-like disease may result from abnormalities in B-cell activation and the clearance of dead cells. Pristane may mimic human systemic lupus erythematosus by causing synergistic abnormalities in interferon production along with defective clearance of apoptotic cells and over-active B-cell signaling.

Mechanisms of Autoantibody Production in Systemic Lupus Erythematosus

Autoantibodies against a panoply of self-antigens are seen in systemic lupus erythematosus, but only a few (anti-Sm/RNP, anti-Ro/La, anti-dsDNA) are common. The common lupus autoantigens are nucleic acid complexes and levels of autoantibodies can be extraordinarily high. We explore why that is the case. Lupus is associated with impaired central or peripheral B-cell tolerance and increased circulating autoreactive B cells. However, terminal differentiation is necessary for autoantibody production. Nucleic acid components of the major lupus autoantigens are immunostimulatory ligands for toll-like receptor (TLR)7 or TLR9 that promote plasma cell differentiation. We show that the levels of autoantibodies against the U1A protein (part of a ribonucleoprotein) are markedly higher than autoantibodies against other antigens, including dsDNA and the non-nucleic acid-associated autoantigens insulin and thyroglobulin. In addition to driving autoantibody production, TLR7 engagement is likely to contribute to the pathogenesis of inflammatory disease in lupus.

Endogenous type-I interferon activity is not associated with depression or fatigue in systemic lupus erythematosus

Patients with systemic lupus erythematosus (SLE) often suffer from depression and fatigue in addition to the physical manifestations of the autoimmune disease. Elevated production of type-I interferons (IFN-I) has been found in lupus patients and IFN-I can precipitate a variety of neuropsychiatric side effects. This study was conducted to evaluate the relationship between dysregulated IFN-I production and the presence of depression or fatigue in lupus patients. Through cross-sectional and longitudinal analysis we found no significant correlation between abnormal IFN-I levels (as measured by peripheral blood expression of IFN-I-stimulated genes) and neuropsychiatric manifestations. Elevation of endogenous serum IFN-I levels is unlikely to account for the depression and fatigue associated with SLE.

A Novel Mechanism for Generating the Interferon Signature in Lupus: Opsonization of Dead Cells by Complement and IgM

In vitro studies suggest that the type I interferon (IFN) signature seen in most lupus patients results from Fcγ receptor–mediated uptake of nucleic acid–containing immune complexes by plasmacytoid dendritic cells and engagement of endosomal Toll‐like receptors. The aim of this study was to reexamine the pathogenesis of the IFN signature in vivo.

Pathogenesis of Diffuse Alveolar Hemorrhage in Murine Lupus

Diffuse alveolar hemorrhage (DAH) in lupus patients confers >50% mortality, and the cause is unknown. We undertook this study to examine the pathogenesis of DAH in C57BL/6 mice with pristane‐induced lupus, a model of human lupus‐associated DAH.

Maintenance of autoantibody production in pristane-induced murine lupus

BackgroundPristane-treated mice chronically produce high levels of anti-ribonucleoprotein/Smith (anti-Sm/RNP) and other lupus autoantibodies. The present study addressed how these autoantibody levels are maintained over time.MethodsLupus was induced in BALB/c mice using pristane. Naïve B cells, switched memory B cells, switched plasmablasts, and plasma cells were flow-sorted and total IgG and anti-U1A (RNP) autoantibodies were determined with ELISA.ResultsB cells with a switched “memory-like” (CD19+CD138−IgM−IgD−) (sMB) phenotype were increased in pristane-treated mice and expressed higher levels of Toll like receptor 7 (Tlr7) than cells with this phenotype from untreated mice. Flow-sorted sMB cells from pristane-treated mice did not secrete IgG spontaneously, but were hyper-responsive to both synthetic (R848) and natural (apoptotic cells) TLR7 ligands, resulting in increased IgG production in vitro. The flow-sorted sMB cells also could be driven by R848 to produce IgG anti-U1A autoantibodies. Production of IgG was strongly inhibited by both JSH-23 and SB203580, suggesting that the canonical NFκB and p38 MAPK pathways, respectively, contribute to the TLR7 ligand hyper-responsiveness of sMB from pristane-treated mice.ConclusionsThe switched memory B cell subset from pristane-treated mice is expanded and shows an increased propensity to undergo terminal (plasma cell) differentiation in response to synthetic and natural TLR7 ligands. The data suggest that the decreased clearance of apoptotic cells characteristic of pristane-treated mice might help maintain high serum levels of anti-RNP/Sm autoantibodies.