Effect of high glucose on cytokine production by human peripheral blood immune cells and type I interferon signaling in monocytes: Implications for the role of hyperglycemia in the diabetes inflammatory process and host defense against infection.

The major metabolic feature of diabetes is hyperglycemia which has been linked to the diabetes inflammatory processes, and diabetes-related vulnerability to infection. In the present study, we assessed how glucose affected PBMCs in type I interferon (IFN) production and subsequent signaling. We found that the moderately elevated glucose promoted, and high glucose suppressed type I IFN production, respectively. Pre-exposure to high glucose rendered monocytes more sensitive to IFN-α stimulation with heightened signaling, whereas, instantaneous addition of high glucose did not exhibit such effect. Consistent with this finding, the mRNA levels of IFN-α-induced IRF-7 in PBMCs were positively correlated with HbA1c levels of diabetes patients. Additionally, we found that high glucose promoted the production of other proinflammatory cytokines/chemokines. This study suggests that hyperglycemia may affect the inflammatory process in diabetes via promoting proinflammatory cytokines, as well as the host defense against microbial infections through impeding type I IFN production and signaling.

Pre-B cell leukemia homeobox 1 is associated with lupus susceptibility in mice and humans.

Sle1a.1 is part of the Sle1 susceptibility locus, which has the strongest association with lupus nephritis in the NZM2410 mouse model. In this study, we show that Sle1a.1 results in the production of activated and autoreactive CD4(+) T cells. Additionally, Sle1a.1 expression reduces the peripheral regulatory T cell pool, as well as induces a defective response of CD4(+) T cells to the retinoic acid expansion of TGF-ß-induced regulatory T cells. At the molecular level, Sle1a.1 corresponds to an increased expression of a novel splice isoform of Pbx1, Pbx1-d. Pbx1-d overexpression is sufficient to induce an activated/inflammatory phenotype in Jurkat T cells and to decrease their apoptotic response to retinoic acid. PBX1-d is expressed more frequently in the CD4(+) T cells from lupus patients than from healthy controls, and its presence correlates with an increased central memory T cell population. These findings indicate that Pbx1 is a novel lupus susceptibility gene that regulates T cell activation and tolerance.

Type I interferon modulates monocyte recruitment and maturation in chronic inflammation.

Chronic inflammation is characterized by continuous recruitment and activation of immune cells such as monocytes in response to a persistent stimulus. Production of proinflammatory mediators by monocytes leads to tissue damage and perpetuates the inflammatory response. However, the mechanism(s) responsible for the sustained influx of monocytes in chronic inflammation are not well defined. In chronic peritonitis induced by pristane, the persistent recruitment of Ly6C(hi) inflammatory monocytes into the peritoneum was abolished in type I interferon (IFN-I) receptor-deficient mice but was unaffected by the absence of IFN-gamma, tumor necrosis factor-alpha, interleukin-6, or interleukin-1. IFN-I signaling stimulated the production of chemokines (CCL2, CCL7, and CCL12) that recruited Ly6C(hi) monocytes via interactions with the chemokine receptor CCR2. Interestingly, after 2,6,10,14-tetramethylpentadecane treatment, the rapid turnover of inflammatory monocytes in the inflamed peritoneum was associated with a lack of differentiation into Ly6C(lo) monocytes/macrophages, a more mature subset with enhanced phagocytic capacity. In contrast, Ly6C(hi) monocytes differentiated normally into Ly6C(lo) cells in IFN-I receptor-deficient mice. The effects of IFN-I were specific for monocytes as granulocyte migration was unaffected in the absence of IFN-I signaling. Taken together, our findings reveal a novel role of IFN-I in promoting the recruitment of inflammatory monocytes via the chemokine receptor CCR2. Continuous monocyte recruitment and the lack of terminal differentiation induced by IFN-I may help sustain the chronic inflammatory response.

Comparison of chlordecone and estradiol effects on splenic T-cells in (NZBxNZW)F(1) mice.

Previous studies have shown that treatment of ovariectomized females with 17-beta estradiol (E2) accelerates the development of autoimmunity in the (NZBxNZW)F(1) murine lupus model. Treatment with estrogenic organochlorine pesticides (OCPs) such as chlordecone produces a similar effect. Although it is reasonable to postulate that the effects of chlordecone and related OCPs on autoimmunity are due to their estrogenic effects, this has not been clearly demonstrated. The objective of this study was to compare effects of chlordecone and E2 on splenic T lymphocyte parameters plausibly related to autoimmunity; specifically, on T-cell phenotype and functions. Ovariectomized (NZBxNZW)F(1) mice were treated for 6 weeks with implanted sustained-release pellets containing chlordecone or E2 at dosing rates shown previously to significantly shorten time to onset of disease. E2, but not chlordecone, increased the percentage of activated and memory CD4 T-cells, and reduced naive CD4 T-cells. E2 also elevated CD25 and glucocorticoid-induced TNF receptor (GITR) levels in CD4 T-cells, an effect not shared by chlordecone. On the other hand, both chlordecone and E2 increased Bcl-2 expression in CD4 T-cells and reduced CD4 T-cell apoptosis without affecting their proliferation. Although both treatments increased TNF-alpha and IL-2 secretion by CD4 T-cells, only chlordecone increased secretion of IFN-gamma and GM-CSF. E2, but not chlordecone, increased IL-10 secretion. These observations indicate that although it is considered an estrogenic OCP, chlordecone exerts effects on splenic T-cells that are different in a number of ways from E2.

A novel type I IFN-producing cell subset in murine lupus.

Excess type I IFNs (IFN-I) have been linked to the pathogenesis of systemic lupus erythematosus (SLE). Therapeutic use of IFN-I can trigger the onset of SLE and most lupus patients display up-regulation of a group of IFN-stimulated genes (ISGs). Although this "IFN signature" has been linked with disease activity, kidney involvement, and autoantibody production, the source of IFN-I production in SLE remains unclear. 2,6,10,14-Tetramethylpentadecane-induced lupus is at present the only model of SLE associated with excess IFN-I production and ISG expression. In this study, we demonstrate that tetramethylpentadecane treatment induces an accumulation of immature Ly6C(high) monocytes, which are a major source of IFN-I in this lupus model. Importantly, they were distinct from IFN-producing dendritic cells (DCs). The expression of IFN-I and ISGs was rapidly abolished by monocyte depletion whereas systemic ablation of DCs had little effect. In addition, there was a striking correlation between the numbers of Ly6C(high) monocytes and the production of lupus autoantibodies. Therefore, immature monocytes rather than DCs appear to be the primary source of IFN-I in this model of IFN-I-dependent lupus.

Diminished prolactin from chlordecone treatment in ovariectomized (NZBxNZW)F(1) mice.

In murine models of systemic lupus erythematosus (SLE), administration of either prolactin or estradiol (E2) increases autoimmunity, and there is evidence that elevated prolactin in response to E2 administration may contribute substantially to E2 effects. Hormonal influence on SLE can extend to environmental agents, as demonstrated by the ability of estrogenic organochlorine pesticides such as chlordecone to accelerate the development of lupus in female (NZBxNZW)F(1) mice. In order to evaluate a potential role for prolactin in chlordecone effects on SLE, it was necessary to first determine whether treatment with chlordecone, like E2, results in elevated prolactin levels. Ovariectomized (NZBxNZW)F(1) mice were treated for 5-6 weeks with chlordecone or E2 in doses shown previously to significantly shorten the time to onset of SLE. At the end of the treatment period, serum prolactin levels were increased 10- to 20-fold in E2-treated mice compared to untreated controls, but decreased in an apparent dose-dependent manner in mice treated with chlordecone. Prolactin receptor in purified splenic B and CD4 T cells from treated animals, assessed through measurement of mRNA using quantitative real-time PCR, was increased by E2 treatment but unchanged in response to chlordecone. These observations suggest that the role of prolactin in eliciting autoimmunity in E2-treated animals is absent in the case of chlordecone, and by implication, that chlordecone possesses other actions that can replace the contribution of prolactin to development of SLE.

Type I interferon as a novel risk factor for endothelial progenitor cell depletion and endothelial dysfunction in systemic lupus erythematosus.

OBJECTIVE: The premature atherosclerosis seen in patients with systemic lupus erythematosus (SLE) is not explained by traditional risk factors. SLE disease activity, such as renal involvement and presence of autoantibodies, is associated with elevated serum levels of type I interferon (IFN-I), a family of cytokines with potent antiviral and antiproliferative effects. This study was undertaken to test the hypothesis that elevated IFN-I levels could lead to endothelial dysfunction, a surrogate for cardiovascular disease, by causing a reduction in the number of endothelial progenitor cells (EPCs), bone marrow-derived cells that participate in endothelial repair. METHODS: EPCs were enumerated in the peripheral blood of SLE patients (n = 70) and healthy controls (n = 31), using a colony-forming assay. Serum IFN-I levels were quantified by real-time polymerase chain reaction measurement of the expression of the IFN-I-inducible gene MX1. Endothelial function was determined by peripheral arterial plethysmography. RESULTS: SLE patients had markedly reduced levels of EPC colony-forming units compared with controls (median 5.7/ml peripheral blood [interquartile range 1.9-12.8] versus 28.5/ml peripheral blood [14.7-47.3]; P < 0.0001), and the depletion of EPCs was more dramatic in patients with elevated levels of IFN-I. Stepwise multiple regression analysis showed that MX1 expression and serum levels of C-reactive protein were independently associated with the reduction of EPCs. Importantly, high IFN-I levels were associated with impaired endothelial function in patients with SLE. CONCLUSION: These data support the novel hypothesis that depletion of EPCs caused by excessive IFN-I may be linked to endothelial dysfunction and increased cardiovascular risk in SLE.

Acceleration of autoimmunity by organochlorine pesticides: a comparison of splenic B-cell effects of chlordecone and estradiol in (NZBxNZW)F1 mice.

The weakly estrogenic organochlorine pesticide chlordecone can accelerate the development of systemic lupus erythematosus (SLE) in ovariectomized (NZBxNZW)F1 mice, with a shortened time to appearance of autoantibodies and disease similar to that produced by treatment with the sex hormone 17beta-estradiol (E2). It is unclear whether chlordecone and E2 share the same pathways in mediating this effect. The effects of chlordecone and E2 treatment on splenic germinal center (GC) and marginal zone B cells were examined. Both chlordecone and E2 activated splenic B cells and enhanced GC reactions, as shown by upregulated protein expression of GL7, CXCR5, and CXCR4. Both treatments increased B-cell bcl-2 and shp-1 gene expression and enhanced ICAM-1 and VCAM-1 protein levels in GC B cells. Chlordecone reduced total B cell and GC B-cell apoptosis without affecting proliferation, another feature shared by E2 treatment. However, chlordecone treatment did not alter the composition of splenic B-cell subsets in marked contrast to the decrease in transitional B cells and increase in marginal zone B cells seen in E2-treated mice. The differences in effects between chlordecone and E2 indicate that chlordecone is not functioning simply as an estrogen mimic with respect to effects on the immune system. Similarities in the effects of chlordecone and E2 on specific immune functions, such as diminished apoptosis in GC B cells, may provide valuable clues regarding key events in the acceleration of autoimmunity by E2, chlordecone, and other agents.

Comparison of chlordecone effects on autoimmunity in (NZBxNZW) F(1) and BALB/c mice.

It has been shown previously that chronic treatment with relatively low doses of chlordecone accelerates the development of systemic lupus erythematosus (SLE) in ovariectomized female (NZBxNZW) F(1) mice. In this study, the effect of chronic chlordecone treatment on SLE was evaluated in ovary-intact female (NZBxNZW) F(1) mice, as well as in female mice from a strain that is not lupus-prone, BALB/c. Chlordecone was administered chronically via implanted sustained-release pellets, and mice were monitored over time for the appearance of elevated autoantibodies (anti-dsDNA and anti-chromatin) and for the development of renal impairment, both indicators of SLE. Chlordecone treatment in (NZBxNZW) F(1) mice shortened significantly the time to onset of elevated autoantibody titers and renal disease in a dose-related manner. The doses required to produce this effect were similar to those observed previously to accelerate SLE development in ovariectomized females. Treatment of female BALB/c mice with chlordecone for up to one year did not produce elevated autoantibody titers or renal disease, suggesting an inability of chlordecone to cause a break in tolerance in this strain. These observations confirm the ability of chronic chlordecone to influence SLE, but demonstrate the importance of genetic background for this effect.

Genetic dissection of systemic lupus erythematosus pathogenesis: partial functional complementation between Sle1 and Sle3/5 demonstrates requirement for intracellular coexpression for full phenotypic expression of lupus.

Sle1 on chromosome 1 and Sle3/5 on chromosome 7 are two of the most critical lupus susceptibility loci of the New Zealand Black/White-derived NZM2410 mouse strain. In contrast to C57BL/6 mice congenic for either Sle1 (B6.Sle1) or Sle3/5 (B6.Sle3/5), strains that express only a modest lupus-related phenotype, the bicongenic B6.Sle1.Sle3/5 strain has a robust phenotype, suggesting a critical role for epistatic interactions in lupus pathogenesis. Mixed chimera experiments indicated that the two loci are functionally expressed by different cell populations and predicted that phenotypic expression of the phenotypic features of the B6.Sle1.Sle3/5 strain could be fully reproduced with a combination of B6.Sle1 and B6.Sle3/5 bone marrow. Contrary to our expectations, there was only a partial functional complementation in these mixed chimeras. Spleen enlargement, CD4:CD8 ratio elevation, and epitope spreading of autoantibodies were fully developed in B6+B6.Sle1.Sle3/5 but not in B6.Sle1+B6.Sle3/5 mixed chimeras. This study is the first to present evidence that the pathways mediated by two critical lupus susceptibility loci derived from the New Zealand White strain must be integrated intracellularly for epistatic interactions to occur. Our mixed chimera approach continues to provide novel insights into the functional genetic pathways underlying this important murine model of systemic autoimmunity.

Acceleration of autoimmunity by organochlorine pesticides in (NZB x NZW)F1 mice.

Systemic lupus erythematosus (SLE) is an autoimmune disorder that affects women more frequently than men. In the (NZB times NZW)F1 mouse, a murine SLE model, the presence or absence of estrogen markedly influences the rate of progression of disease. Three organochlorine pesticides with estrogenic effects were administered chronically to ovariectomized female (NZB times NZW)F1 mice, and we measured the time to development of renal disease, the principal clinical manifestation of lupus in this model. Treatment with chlordecone, methoxychlor, or o,p -dichlorodiphenyltrichloroethane (o,p -DDT) significantly decreased the time to onset of renal impairment, as did treatment with 17ss-estradiol used as a positive control. In an expanded study of chlordecone, we found a dose-related early appearance of elevated anti-double-strand DNA autoantibody titers that corresponded with subsequent development of glomerulonephritis. Immunohistofluorescence confirmed early deposition of immune complexes in kidneys of mice treated with chlordecone. These observations are consistent with an effect of these organochlorine pesticides to accelerate the natural course of SLE in the (NZB times NZW)F1 mouse. Although we originally hypothesized that the effect on progression of autoimmunity was due to estrogenic properties of the pesticides, autoimmune effects and estrogenicity, assessed through measurement of uterine hypertrophy, were not well correlated. This may indicate that uterine hypertrophy is a poor indicator of comparative estrogenic effects of organochlorine pesticides on the immune system, or that the pesticides are influencing autoimmunity through a mode of action unrelated to their estrogenicity.

Genetic dissection of lupus pathogenesis: Sle3/5 impacts IgH CDR3 sequences, somatic mutations, and receptor editing.

Sle3/5 is a lupus susceptibility locus identified on mouse chromosome 7 of the New Zealand Black/New Zealand White (NZB/NZW)-derived NZM2410 strain. Based on previous observations, this locus appears to contribute to lupus pathogenesis through its impact on diversification of immune responses. To understand how Sle3/5 affects somatic diversification of humoral responses, we analyzed IgH rearrangements preferentially encoding hapten-reactive IgG1 repertoires after immunization and assessed peripheral IgH VDJ recombination activities in C57BL/6 (B6) mice congenic for Sle3/5 (B6.Sle3/5). In addition to altered somatic V(H) mutation profiles, sequences from B6.Sle3/5 mice exhibited atypical IgH CDR3 structures characteristic of autoreactive B cells and consistent with peripheral B cells bearing putatively edited receptors. Significant expression of Rag genes and circular V(H)D gene excision products were detected in splenic mature B cells of B6.Sle3/5 but not B6 mice, showing that peripheral IgH rearrangements occurred beyond allelic exclusion. Taken together, on the nonautoimmune background, Sle3/5 affected V(H)DJ(H) junctional diversity and V(H) mutational diversity and led to recombinational activation of allelically excluded IgH genes in the periphery. Such impact on somatic IgH diversification may contribute to the development of autoreactive B cell repertoires. This is the first report to present evidence for significant association of a lupus susceptibility locus, which has been mapped to a chromosomal region in which no Ig genes have been identified, with somatic IgH sequence diversity and peripheral H chain receptor editing or revision without relying upon Ig transgene strategies.

Mechanisms of peritoneal B-1a cells accumulation induced by murine lupus susceptibility locus Sle2.

The abundance of B-1a cells found in the peritoneal cavity of mice is under genetic control. The lupus-prone mouse New Zealand Black and New Zealand White (NZB x NZW)F(1) and its derivative NZM2410 are among the strains with the highest numbers of peritoneal B1-a cells. We have previously identified an NZM2410 genetic locus, Sle2, which is associated with the production of large numbers of B-1a cells. In this paper, we examined the mechanisms responsible for this phenotype by comparing congenic C57BL/6 mice with or without Sle2. Fetal livers generated more B-1a cells in B6.Sle2 mice, providing them with a greater starting number of B-1a cells early in life. Sle2-expressing B1-a cells proliferated significantly more in vivo than their B6 counterparts, and reciprocal adoptive transfers showed that this phenotype is intrinsic to Sle2 peritoneal B cells. The rate of apoptosis detected was significantly lower in B6.Sle2 peritoneal cavity B-1a cells than in B6, with or without exogenous B cell receptor cross-linking. Increased proliferation and decreased apoptosis did not affect Sle2 peritoneal B-2 cells. In addition, a significant number of peritoneal cavity B-1a cells were recovered in lethally irradiated B6.Sle2 mice reconstituted with B6.Igh(a) bone marrow, showing radiation resistance in Sle2 B-1a cells or its precursors. Finally, B6.Sle2 adult bone marrow and spleen were a significant source of peritoneal B-1a cells when transferred into B6.Rag2(-/-) mice. This suggests that peritoneal B-1a cells are replenished throughout the animal life span in B6.Sle2 mice. These results show that Sle2 regulates the size of the B-1a cell compartment at multiple developmental checkpoints.