Immunopathogenesis of environmentally induced lupus in mice

Pristane cadmium chloride nanoemulsion accelerates the onset of systemic lupus erythematosus in a C57BL/6 mouse model

OBJECTIVE

To accelerate the onset of systemic lupus erythematosus in C57BL/6 mice by injecting cadmium chloride nanoemulsion and shorten the traditional modeling time.

METHODS

Pristane cadmium chloride nanoemulsion was prepared, and 66 C57BL/6 mice were randomly divided into four groups. The pristane group was intraperitoneally injected with 0.6 mL of pristane blank nanoemulsion, the model group was injected with 0.6 mL of pristane cadmium chloride nanoemulsion, the Cadmium chloride control group was injected with 0.6 mL of cadmium chloride nanoemulsion, and the control group was injected with the same amount of 0.9% sodium chloride solution. Urine protein content, anti-dsDNA antibody content, Th1 cell/Th2 cell ratio, and kidney staining were detected in each group.

RESULTS

The model group began to develop disease in the 4th week, the anti-dsDNA antibody level reached 566.71 ± 1.44 ng/L, and the proteinuria reached 245.38 ± 30.54 ng/mL. The model group showed an onset at least 5 weeks earlier than that in the pristane group. There was no significant difference in anti-dsDNA antibody content between Cadmium chloride control group and blank group. At the 12th week, the Th1/Th2 cell ratio in the model group significantly decreased, and the pathological changes in the kidneys were consistent with the typical manifestations of lupus in mouse models.

CONCLUSION

These results suggest that cadmium chloride promotes earlier onset of pristane-induced systemic lupus erythematosus in a C57BL/6 mouse model.

Chronic mineral oil administration increases hepatic inflammation in wild type mice compared to lipocalin 2 null mice

Lipocalin 2 (LCN2), an acute-phase protein produced during acute liver injury, plays an important role in the innate immune response against bacterial infection via iron scavenging. LCN2 further influences neutrophil development and physiology leading to increased inflammatory responses. We investigated the roles of LCN2 in chronic inflammation and fibrosis, using repeated carbon tetrachloride (CCl4) in mineral-oil injection. Surprisingly, mice treated with the mineral oil vehicle alone showed liver inflammation, evidenced by neutrophil and monocyte-macrophage infiltration. Fluorescence-activated cell sorting (FACS) of isolated liver leukocytes showed significantly high CD45+ leukocyte concentrations in CCl4 mice, but no difference of Ly6G+ neutrophils between mineral oil and CCl4 application. Liver CD11b+ F4/80+ cells counted higher in CCl4 mice, but the proportions of Gr1high, an indicator of inflammation, were significantly higher in mineral oil groups. Liver myeloperoxidase (MPO), expressed in neutrophils and monocytes, showed higher levels in wild type mice compared to Lcn2-/- in both mineral-oil and CCl4 treated groups. Hepatic and serum LCN2 levels were remarkably higher in the mineral oil-injected wild type group compared to the CCl4. Wild type animals receiving mineral oil showed significantly higher inflammatory cytokine- and chemokine mRNA levels compared to Lcn2-/- mice, with no differences in the CCl4 treated groups. RNA sequencing (RNA-Seq) confirmed significant downregulation of gene sets involved in myeloid cell activation and immune responses in Lcn2 null mice receiving chronic mineral oil versus wild-type. We observed significant upregulation of gene sets and proteins involved in cell cycle DNA replication, with downregulation of collagen-containing extracellular matrix genes in Lcn2-/- mice receiving CCl4, compared to the wild type. Consequently, the wild type mice developed slightly more liver fibrosis compared to Lcn2-/- mice, evidenced by higher levels of collagen type I in the CCl4 groups and no liver fibrosis in mineral oil-treated mice. Our findings indicate that serum and hepatic LCN2 levels correlate with hepatic inflammation rather than fibrosis.

The Immunomodulatory Effect of the Gut Microbiota in Kidney Disease

The human gut microbiota is a complex cluster composed of 100 trillion microorganisms, which holds a symbiotic relationship with the host under normal circumstances. Intestinal flora can facilitate the treatment of human metabolic dysfunctions and interact with the intestinal tract, which could influence intestinal tolerance, immunity, and sensitivity to inflammation. In recent years, significant interests have evolved on the association of intestinal microbiota and kidney diseases within the academic circle. Abnormal changes in intestinal microbiota, known as dysbiosis, can affect the integrity of the intestinal barrier, resulting in the bacterial translocation, production, and accumulation of dysbiotic gut-derived metabolites, such as urea, indoxyl sulfate (IS), and p-cresyl sulfate (PCS). These processes lead to the abnormal activation of immune cells; overproduction of antibodies, immune complexes, and inflammatory factors; and inflammatory cell infiltration that can directly or indirectly cause damage to the renal parenchyma. The aim of this review is to summarize the role of intestinal flora in the development and progression of several renal diseases, such as lupus nephritis, chronic kidney disease, diabetic nephropathy, and renal ischemia-reperfusion injury. Further research on these mechanisms should provide insights into the therapeutic potential of regulating intestinal flora and intervening related molecular targets for the abovementioned nephropathy.

Cognitive Impairment in SLE: Mechanisms and Therapeutic Approaches

A wide range of patients with systemic lupus erythematosus (SLE) suffer from cognitive dysfunction (CD) which severely impacts their quality of life. However, CD remains underdiagnosed and poorly understood. Here, we discuss current findings in patients and in animal models. Strong evidence suggests that CD pathogenesis involves known mechanisms of tissue injury in SLE. These mechanisms recruit brain resident cells, in particular microglia, into the pathological process. While systemic immune activation is critical to central nervous system injury, the current focus of therapy is the microglial cell and not the systemic immune perturbation. Further studies are critical to examine additional potential therapeutic targets and more specific treatments based on the cause and progress of the disease.

Lupus animal models and neuropsychiatric implications

Systemic lupus erythematosus (SLE) that involves neurological complications is known as neuropsychiatric systemic lupus erythematosus (NPSLE). Research in humans is difficult due to the disease's great heterogeneity. Animal models are a resource for new discoveries. In this review, we examine experimental models of lupus that present neuropsychiatric manifestations. Spontaneous animal models such as NZB/W F1 and MRL/lpr are commonly used in NPSLE research; these models present few SLE symptoms compared to induced animal models, such as pristane-induced lupus (PIL). The PIL model is known to present eight of the main clinical and laboratory manifestations of SLE described by the American College of Rheumatology. Many cytokines associated with NPSLE are expressed in the PIL model, such as IL-6, TNF-α, and IFN. However, to date, NPSLE manifestations have been poorly studied in the PIL model. In this review article, we discuss whether the PIL model can mimic neuropsychiatric manifestations of SLE. Key Points • PIL model have a strong interferon signature. • Animals with PIL express learning and memory deficit.

Protective effect of dihydroartemisinin in inhibiting senescence of myeloid-derived suppressor cells from lupus mice via Nrf2/HO-1 pathway

Systemic lupus erythematosus (SLE) is a chronic autoimmune inflammatory disease characterized by multi-organ injury. However, whether myeloid-derived suppressor cells (MDSCs) senescence exists and participates in SLE pathogenesis remains unclear. And whether dihydroartemisinin (DHA) attenuates the symptoms of SLE via relieving MDSCs senescence remains elusive. In the present study, we measured the senescence of MDSCs in SLE using SA-β-gal staining, senescence-associated secretory phenotype (SASP) and Western blot analysis of aging-related protein P21, P53 and P16. We identified that the MDSCs senescence promoted the SLE progress by adaptive transfer MDSCs assays. Meanwhile, we further showed DHA ameliorated the symptoms of pristane-induced lupus by histopathological detection, Western blot analysis, immunofluorescence, QPCR and flow cytometry analysis. DHA reversed MDSCs senescence by detecting SA-β-gal staining, senescence-associated secretory phenotype (SASP) and Western blot analysis of aging-related protein P21, P53 and P16. Furthermore, mechanistic analysis indicated that the inhibitory effect of DHA on MDSCs senescence was blocked by ML385, the specific antagonist of Nrf2, which revealed that the effect of DHA on MDSCs senescence was dependent on the induction of Nrf2/HO-1 pathway. Of note, we revealed that DHA inhibited MDSCs senescence to ameliorate the SLE development by adaptive transfer DHA-treated MDSCs assays. In conclusion, MDSCs senescence played a vital role in the pathogenesis of SLE, and DHA attenuated the symptoms of SLE via relieving MDSCs aging involved in the induction of Nrf2/HO-1 pathway.

Virgin olive oil and its phenol fraction modulate monocyte/macrophage functionality: a potential therapeutic strategy in the treatment of systemic lupus erythematosus

Monocytes and macrophages are critical effectors and regulators of inflammation and innate immune response, which appear altered in different autoimmune diseases such as systemic lupus erythematosus (SLE). Recent studies suggested that virgin olive oil (VOO) and particularly its phenol compounds might possess preventive effects on different immune-inflammatory diseases, including SLE. Here, we evaluated the effects of VOO (and sunflower oil) on lipopolysaccharide (LPS)-activated peritoneal macrophages from a model of pristane-induced SLE in BALB/c mice, as well as those of the phenol fraction (PF) from VOO on the immune-inflammatory activity and plasticity in monocytes and monocyte-derived macrophages from healthy volunteers. The release of nitrite and inflammatory cytokines was lower in LPS-treated peritoneal macrophages from pristane-SLE mice fed the VOO diet when compared with the sunflower oil diet. PF from VOO similarly decreased the secretion of nitrite and inflammatory cytokines and expression of inducible nitric oxide, PPARγ and Toll-like receptor 4 in LPS-treated human monocytes. PF from VOO also prevented the deregulation of human monocyte subset distribution by LPS and blocked the genetic signature of M1 macrophages while favouring the phenotype of M2 macrophages upon canonical polarisation of naïve human macrophages. For the first time, our study provides several lines of in vivo and in vitro evidence that VOO and PF from VOO target and counteract inflammatory pathways in the monocyte–macrophage lineage of mice with pristane-induced SLE and of healthy subjects, which is a meaningful foundation for further development and application in preclinical and clinical use of PF from VOO in patients with SLE.

Role of Lgals9 Deficiency in Attenuating Nephritis and Arthritis in BALB/c Mice in a Pristane-Induced Lupus Model

OBJECTIVE

In systemic lupus erythematosus (SLE), an autoimmune disease associated with multiple organ involvement, the development of lupus nephritis determines prognosis, and arthritis impairs quality of life. Galectin 9 (Gal-9, Lgals9) is a β-galactoside-binding lectin that has been used for clinical application in autoimmune diseases, since recombinant Gal-9, as a ligand for T cell immunoglobulin and mucin domain-containing protein 3 (TIM-3), induces apoptosis of activated CD4+TIM-3+ Th1 cells. This study was undertaken to investigate whether deficiency of Lgals9 has beneficial or deleterious effects on lupus in a murine model.

METHODS

Gal-9^+/+ and Gal-9^-/- female BALB/c mice were injected with pristane, and the severity of arthritis, proteinuria, and levels of autoantibody production were assessed at several time points immediately following injection. At 7 months after pristane injection, renal pathologic features, the severity of joint inflammation, and formation of lipogranulomas were evaluated. Subsets of inflammatory cells in the spleen and peritoneal lavage were characterized, and expression levels of cytokines from peritoneal macrophages were analyzed.

RESULTS

Lgals9 deficiency protected against the development of immune complex glomerulonephritis, arthritis, and peritoneal lipogranuloma formation in BALB/c mice in this murine model of pristane-induced lupus. The populations of T cell subsets and B cells in the spleen and peritoneum were not altered by Lgals9 deficiency in pristane-injected BALB/c mice. Furthermore, Lgals9 deficiency protected against pristane-induced lupus without altering the Toll-like receptor 7-type I interferon pathway.

CONCLUSION

Gal-9 is required for the induction and development of lupus nephritis and arthritis in this murine model of SLE. The results of the current investigation provide a potential new strategy in which antagonism of Gal-9 may be beneficial for the treatment of nephritis and arthritis in patients with SLE through targeting of activated macrophages.

C1q Modulates the Response to TLR7 Stimulation by Pristane-Primed Macrophages: Implications for Pristane-Induced Lupus

The complement component C1q is known to play a controversial role in the pathogenesis of systemic lupus erythematosus, but the underlying mechanisms remain poorly understood. Intraperitoneal injection of pristane induces a lupus-like syndrome whose pathogenesis implicates the secretion of type I IFN by CD11b(+) Ly6C(high) inflammatory monocytes in a TLR7-dependent fashion. C1q was also shown to influence the secretion of IFN-α. In this study, we explored whether C1q deficiency could affect pristane-induced lupus. Surprisingly, C1qa(-/-) mice developed lower titers of circulating Abs and milder arthritis compared with the controls. In keeping with the clinical scores, 2 wk after pristane injection the peritoneal recruitment of CD11b(+) Ly6C(high) inflammatory monocytes in C1qa(-/-) mice was impaired. Furthermore, C1q-deficient pristane-primed resident peritoneal macrophages secreted significantly less CCL3, CCL2, CXCL1, and IL-6 when stimulated in vitro with TLR7 ligand. Replenishing C1q in vivo during the pristane-priming phase rectified this defect. Conversely, pristane-primed macrophages from C3-deficient mice did not show impaired cytokine production. These findings demonstrate that C1q deficiency impairs the TLR7-dependent chemokine production by pristane-primed peritoneal macrophages and suggest that C1q, and not C3, is involved in the handling of pristane by phagocytic cells, which is required to trigger disease in this model.

Dietary extra virgin olive oil attenuates kidney injury in pristane-induced SLE model via activation of HO-1/Nrf-2 antioxidant pathway and suppression of JAK/STAT, NF-κB and MAPK activation

Systemic lupus erythematosus (SLE) is an autoimmune disease characterized by a widespread organ involvement. Recent studies have suggested that extra virgin olive oil (EVOO) might possess preventive effects on this immunoinflammation-related disease. However, its role in SLE remained unknown. In this work, we evaluated the effects of EVOO diet in a pristane-induced SLE model in mice. Three-month-old mice received an injection of pristane or saline solution and were fed with different experimental diets: sunflower oil diet or EVOO diet. After 24weeks, mice were sacrificed, spleens were collected and kidneys were removed for immunoinflammatory detections. The kidney expression of microsomal prostaglandin E synthase 1, heme oxygenase 1 (HO-1), nuclear factor E2-related factor 2 (Nrf-2), mitogen-activated protein kinases (MAPKs), Janus kinase/signal transducer and activator of transcription (JAK/STAT) and nuclear transcription factor-kappa B (NF-κB) pathways were studied by western blotting. In addition to macroscopic and histological analyses, serum matrix metalloproteinase 3 (MMP-3) levels and proinflammatory cytokines production in splenocytes were evaluated by enzyme-linked immunoassay. We have demonstrated that EVOO diet significantly reduced renal damage and decreased MMP-3 serum and PGE2 kidney levels as well as the proinflammatory cytokines production in splenocytes. Our data indicate that Nrf-2 and HO-1 protein expressions were up-regulated in those mice fed with EVOO and the activation of JAK/STAT, MAPK and NF-κB pathways were drastically ameliorated. These results support the interest of EVOO as a beneficial functional food exerting a preventive/palliative role in the management of SLE.

Toll-like receptor 2 is required for autoantibody production and development of renal disease in pristane-induced lupus

OBJECTIVE

The mechanisms involved in breaking immunologic tolerance against nuclear autoantigens in systemic lupus erythematosus (SLE) are not fully understood. Our recent studies in nonautoimmune mice provided evidence of an important role of Toll-like receptor 2 (TLR-2) in antichromatin autoantibody induction by high mobility group box chromosomal protein 1-nucleosome complexes derived from apoptotic cells. The objective of this study was to investigate whether TLR-2 signaling is required for the induction of autoantibodies and the development of SLE-like disease in murine pristane-induced lupus.

METHODS

Lupus-like disease in C57BL/6 and TLR-2(-/-) mice was induced by pristane injection. The numbers of immune cells and serum cytokine concentrations were determined by flow cytometry. Renal disease was assessed by quantification of proteinuria, histologic analyses, and enzyme-linked immunospot assay.

RESULTS

Pristane-injected TLR-2(-/-) mice generated reduced numbers of splenic CD138+/cytoplasmic κL/λL chain-positive plasma cells and displayed diminished IgG responses against double-stranded DNA, histones, nucleosomes, some extractable nuclear autoantigens, and cardiolipin when compared with wild- type controls. TLR-2 deficiency prevented the pristane-induced systemic release of interleukin-6 (IL-6) and IL-10. The absence of TLR-2 attenuated peritoneal recruitment of CD11c+ cells and formation of lipogranulomas. Importantly, the renal disease that developed in pristane-treated TLR-2(-/-) mice was less severe than that in control mice, as reflected by milder proteinuria, reduced glomerular deposition of IgG and complement, and decreased renal infiltration of autoantibody-secreting cells.

CONCLUSION

TLR-2 is required for the production of prototypical lupus autoantibodies and the development of renal disease in pristane-induced murine lupus. Interference with TLR-2 signaling may be a promising novel strategy for the treatment of SLE.

Prophylactic effect of Withania somnifera on inflammation in a non-autoimmune prone murine model of lupus

The immunosuppressive properties of an aqueous suspension of Withania somnifera (WS) root powder were investigated in a pristine induced female Balb/c model of a systemic lupus erythematosus (SLE) like disease. The course of disease is initiated by peritoneal inflammation caused by pristane which results in development of SLE like symptoms, i.e. autoantibody production, proteinuria, and nephritis within a period of five to six months. The model of SLE was established by injecting 0.5 mL of pristane intraperitoneally into female Balb/c mice (12-18 weeks old). WS root powder (500 mg and 1,000 mg per kg body weight) was administered orally from one month prior to disease induction and for the following 6 months. Parameters of inflammation like nitric oxide (NO), Interleukin 6 and tumour necrosis factor-α and reactive oxygen species (ROS) in serum and/or ascitic fluid were measured. Prophylactic administration of WS root powder (500 mg and 1,000 mg per kg body weight) potently inhibits the proinflammatory cytokines, NO, and ROS in the ascetic fluid as well as in serum. Therefore, our results indicate a preventive effect of WS root powder on the mouse model of lupus.

Role of Fc Receptors as a therapeutic target

It has been forty years since the discovery of Fc Receptors and their function. Fc Receptors include the IgG receptors (FcgammaR), high-affinity IgE receptor (FcepsilonRI), IgA and IgA/IgM receptors, and neonatal Fc receptor for IgG (FcRn). In particular, the FcgammaRs have been well known to play an important role in many biologic processes including those associated with the response to infection and cancer as well as in the pathogenesis of immune-mediated diseases. Both positive and negative regulatory function has ascribed to Fc receptors and FcgammaRs in particular which serve to establish a threshold for immune cell activation. In other cases, Fc receptors such as FcRn possess a novel structure and function by playing a major role in the transport of IgG across polarized epithelial barriers at mucosal surfaces and in the regulation of IgG half-life. These diverse functions highlight the potential effectiveness of targeting Fc receptors for therapeutic purposes. This review summarizes new information available in the therapeutic applications of this biology.

Subcutaneous and Intraperitoneal Lipogranulomas Following Subcutaneous Injection of Olive Oil in Sprague-Dawley Rats

Olive oil is commonly employed as a solubilizing agent for lipophilic materials in preclinical studies in rodents. Here we report that following subcutaneous (SC) injection of olive oil to Sprague-Dawley (SD) rats, local SC lipogranulomas formed, which were associated with an unusual location of the same changes in the peritoneum. Macroscopically, multifocal white spots were found over the liver and mesentery. Histologically, lipid granulomas were seen in the SC injection site, as well as on the capsular or serosal surface of the abdominal organs. No abnormal clinical signs were noted except for swelling at the injection site. The olive oil may have reached the peritoneal cavity from the SC tissue passively via the lymphatic vessels or actively after engulfment by antigen-presenting cells via the lymphatic or blood vessels. These findings are of particular importance for drug safety assessments, as the occurrence of lipogranulomas in locations distant from the site of administration may lead to misinterpretation of histological results. We suggest that these aberrations may be induced by the administration of olive oil as a vehicle.

FcgammaRII and multi-system autoimmune disease

The FcR are a crucial link in the immune response between humoral and cellular immunity and cell-based effector systems, mediating a wide variety of physiological and biochemical responses. The FcR for IgG (FcgammaR) and in particular the most widely expressed of these, FcgammaRII, are important in regulating adaptive immunity. Disruption of their function is a key factor in the development of autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA), which are characterized by chronic, multi-organ inflammation. Studies of the FcgammaRII include structure/function relationships, investigation of the associations between FcR polymorphisms and human disease and animal studies using knockout or transgenic mouse models. These investigations showed that the various forms of FcgammaRII interact with immune complexes to either initiate or inhibit inflammation. In conjunction with environmental antigens and genotype, the FcgammaRII activating and inhibitory receptors determine the nature and magnitude of response to antigens. In this review, the structure and function of the FcgammaRIIs and their role in immune complex-mediated auto-immunity are discussed.

Pristane-induced autoimmunity in germ-free mice

Hypergammaglobulinemia and autoantibodies are reduced in pristane-treated specific pathogen-free mice vs. conventionally housed controls, consistent with the role of microbial stimulation in this model. To determine whether microbial stimulation is required, BALB/c mice housed under germ-free conditions were treated i.p. with sterile PBS or pristane and examined 6 months later. As in conventional mice, pristane-treated germ-free mice developed peritoneal granulomas and hypergammaglobulinemia with increased IgG2a/IgG1 ratios. LPS stimulation induced more IL-6, IL-12, and TNF-alpha, and anti-CD3 induced more IFN-gamma and IL-4 by peritoneal cells from pristane-treated mice vs. control. Anti-nRNP/Sm and -Su autoantibodies were found in 40% and 43%, respectively, of pristane-treated germ-free mice by immunoprecipitation. Thus, bacterial stimulation was not required for lupus autoantibodies, peritoneal granuloma formation, hypergammaglobulinemia, or cytokine overproduction. Although microbial stimulation acts synergistically with pristane, these results clearly indicate that pristane does not act merely by increasing exposure to microbial products such as LPS.

Calculating the etiology of systemic lupus erythematosus

Objective was to clarify the etiology and pathogenesis of systemic lupus erythematosus (SLE). Drug-induced lupus (DIL) and SLE are both found in humans, are exacerbated by the same viruses or drugs, and they are both more common in slow acetylators. Thus, DIL can be used as a model for SLE and the Adhami equation of DIL can be applied to SLE. Polyamines are the only possible link between the viral and amine hypotheses of SLE pathogenesis. Based on the Adhami equation, polyamines can explain the actual annual incidence of SLE in the general population. Putrescine is a very weak SLE-causing agent, while spermine and spermidine contribute equally in triggering SLE. The positively charged polyamines bind to negatively charged internucleosomal DNA and change its conformation from B (non-immunogenic) to Z (immunogenic). This is the major contribution of polyamines in triggering SLE. The other effects of polyamines are only secondary. Apoptosis is a necessary step in SLE pathogenesis, because it causes the internucleosomal fragmentation of DNA and exposes Z-DNA to the immune system (due to cell death). The next step is the production of anti-DNA antibodies, followed by other SLE phenomena. Polyamines not only cause SLE, but they are also important in sustaining the disease. Other endogenous and exogenous amines have additive effects with polyamines and may contribute in exacerbating SLE. When SLE is in the active phase, polyamine levels are higher as compared to remissions. Fluctuations in polyamine levels due to diet, metabolic factors, infections, intestinal flora, etc. or the presence of other amines may explain the course of SLE, characterized by remissions and exacerbations. Acetylcysteine is a drug that can be completely metabolized to acetyl groups. As such, this drug is proposed as the ideal acetyl donor for the acetylation of polyamines and other SLE-triggering compounds. Clinical trials will be necessary to test the role of acetylcysteine in the etiologic treatment of SLE.

CONCLUSIONS

Changes in DNA conformation by polyamines are the first step in SLE pathogenesis. Many genetic and environmental factors may increase or decrease the effects or levels of polyamines, causing SLE exacerbations or remissions. Viruses and other infectious agents may cause SLE by producing polyamines or by increasing the levels of endogenous polyamines. The major autoimmune diseases are characterized by remissions and exacerbations and not by a continuously progressive course, as commonly believed. Consequently, they are not sustained by internal vicious cycles, but by the initial triggering agent(s). While the conventional treatment of autoimmune disorders is important in minimizing tissue damage, the neutralization of their etiology may be important in curing and preventing autoimmunity.