Macrophage fumarate hydratase restrains mtRNA-mediated interferon production.

Metabolic rewiring underlies the effector functions of macrophages1-3, but the mechanisms involved remain incompletely defined. Here, using unbiased metabolomics and stable isotope-assisted tracing, we show that an inflammatory aspartate-argininosuccinate shunt is induced following lipopolysaccharide stimulation. The shunt, supported by increased argininosuccinate synthase (ASS1) expression, also leads to increased cytosolic fumarate levels and fumarate-mediated protein succination. Pharmacological inhibition and genetic ablation of the tricarboxylic acid cycle enzyme fumarate hydratase (FH) further increases intracellular fumarate levels. Mitochondrial respiration is also suppressed and mitochondrial membrane potential increased. RNA sequencing and proteomics analyses demonstrate that there are strong inflammatory effects resulting from FH inhibition. Notably, acute FH inhibition suppresses interleukin-10 expression, which leads to increased tumour necrosis factor secretion, an effect recapitulated by fumarate esters. Moreover, FH inhibition, but not fumarate esters, increases interferon-ß production through mechanisms that are driven by mitochondrial RNA (mtRNA) release and activation of the RNA sensors TLR7, RIG-I and MDA5. This effect is recapitulated endogenously when FH is suppressed following prolonged lipopolysaccharide stimulation. Furthermore, cells from patients with systemic lupus erythematosus also exhibit FH suppression, which indicates a potential pathogenic role for this process in human disease. We therefore identify a protective role for FH in maintaining appropriate macrophage cytokine and interferon responses.

SMS2 deficiency impairs PKCδ-regulated B cell tolerance in the germinal center.

B cell tolerance prevents autoimmunity by deleting or deactivating autoreactive B cells that otherwise may cause autoantibody-driven disorders, including systemic lupus erythematosus (lupus). Lupus is characterized by immunoglobulin Gs carrying a double-stranded (ds)-DNA autospecificity derived mainly from somatic hypermutation in the germinal center (GC), pointing to a checkpoint breach of GC B cell tolerance that leads to lupus. However, tolerance mechanisms in the GC remain poorly understood. Here, we show that upregulated sphingomyelin synthase 2 (SMS2) in anti-dsDNA GC B cells induces apoptosis by directly activating protein kinase C δ (PKCδ)'s pro-apoptotic activity. This tolerance mechanism prevents lupus autoimmunity in C57/BL6 mice and can be stimulated pharmacologically to inhibit lupus pathogenesis in lupus-prone NZBWF1 mice. Patients with lupus consistently have substantially reduced SMS2 expression in B cells and to an even greater extent in autoimmune-prone, age-associated B cells, suggesting that patients with lupus have insufficient SMS2-regulated B cell tolerance.

DNA glycosylase deficiency leads to decreased severity of lupus in the Polb-Y265C mouse model.

The Polb gene encodes DNA polymerase beta (Pol ß), a DNA polymerase that functions in base excision repair (BER) and microhomology-mediated end-joining. The Pol ß-Y265C protein exhibits low catalytic activity and fidelity, and is also deficient in microhomology-mediated end-joining. We have previously shown that the PolbY265C/+ and PolbY265C/C mice develop lupus. These mice exhibit high levels of antinuclear antibodies and severe glomerulonephritis. We also demonstrated that the low catalytic activity of the Pol ß-Y265C protein resulted in accumulation of BER intermediates that lead to cell death. Debris released from dying cells in our mice could drive development of lupus. We hypothesized that deletion of the Neil1 and Ogg1 DNA glycosylases that act upstream of Pol ß during BER would result in accumulation of fewer BER intermediates, resulting in less severe lupus. We found that high levels of antinuclear antibodies are present in the sera of PolbY265C/+ mice deleted of Ogg1 and Neil1 DNA glycosylases. However, these mice develop significantly less severe renal disease, most likely due to high levels of IgM in their sera.

Sustained high expression of multiple APOBEC3 cytidine deaminases in systemic lupus erythematosus.

APOBEC3 (A3) enzymes are best known for their role as antiviral restriction factors and as mutagens in cancer. Although four of them, A3A, A3B, A3F and A3G, are induced by type-1-interferon (IFN-I), their role in inflammatory conditions is unknown. We thus investigated the expression of A3, and particularly A3A and A3B because of their ability to edit cellular DNA, in Systemic Lupus Erythematosus (SLE), a chronic inflammatory disease characterized by high IFN-α serum levels. In a cohort of 57 SLE patients, A3A and A3B, but also A3C and A3G, were upregulated ~ 10 to 15-fold (> 1000-fold for A3B) compared to healthy controls, particularly in patients with flares and elevated serum IFN-α levels. Hydroxychloroquine, corticosteroids and immunosuppressive treatment did not reverse A3 levels. The A3AΔ3B polymorphism, which potentiates A3A, was detected in 14.9% of patients and in 10% of controls, and was associated with higher A3A mRNA expression. A3A and A3B mRNA levels, but not A3C or A3G, were correlated positively with dsDNA breaks and negatively with lymphopenia. Exposure of SLE PBMCs to IFN-α in culture induced massive and sustained A3A levels by 4 h and led to massive cell death. Furthermore, the rs2853669 A > G polymorphism in the telomerase reverse transcriptase (TERT) promoter, which disrupts an Ets-TCF-binding site and influences certain cancers, was highly prevalent in SLE patients, possibly contributing to lymphopenia. Taken together, these findings suggest that high baseline A3A and A3B levels may contribute to cell frailty, lymphopenia and to the generation of neoantigens in SLE patients. Targeting A3 expression could be a strategy to reverse cell death and the generation of neoantigens.

Dysregulated CD38 Expression on Peripheral Blood Immune Cell Subsets in SLE.

Given its uniformly high expression on plasma cells, CD38 has been considered as a therapeutic target in patients with systemic lupus erythematosus (SLE). Herein, we investigate the distribution of CD38 expression by peripheral blood leukocyte lineages to evaluate the potential therapeutic effect of CD38-targeting antibodies on these immune cell subsets and to delineate the use of CD38 as a biomarker in SLE. We analyzed the expression of CD38 on peripheral blood leukocyte subsets by flow and mass cytometry in two different cohorts, comprising a total of 56 SLE patients. The CD38 expression levels were subsequently correlated across immune cell lineages and subsets, and with clinical and serologic disease parameters of SLE. Compared to healthy controls (HC), CD38 expression levels in SLE were significantly increased on circulating plasmacytoid dendritic cells, CD14++CD16+ monocytes, CD56+ CD16dim natural killer cells, marginal zone-like IgD+CD27+ B cells, and on CD4+ and CD8+ memory T cells. Correlation analyses revealed coordinated CD38 expression between individual innate and memory T cell subsets in SLE but not HC. However, CD38 expression levels were heterogeneous across patients, and no correlation was found between CD38 expression on immune cell subsets and the disease activity index SLEDAI-2K or established serologic and immunological markers of disease activity. In conclusion, we identified widespread changes in CD38 expression on SLE immune cells that highly correlated over different leukocyte subsets within individual patients, but was heterogenous within the population of SLE patients, regardless of disease severity or clinical manifestations. As anti-CD38 treatment is being investigated in SLE, our results may have important implications for the personalized targeting of pathogenic leukocytes by anti-CD38 monoclonal antibodies.

A novel JAK/ROCK inhibitor, CPL409116, demonstrates potent efficacy in the mouse model of systemic lupus erythematosus.

Systemic lupus erythematosus is a chronic inflammatory disease, in which treatment is still limited due to suboptimal efficacy and toxicities associated with the available therapies. JAK kinases are well known to play an important role in systemic lupus erythematous. There is growing evidence that ROCK kinases are also important in disease development. In this paper, we present the results of the development of CPL409116, a dual JAK and ROCK inhibitor. The studies we performed demonstrate that this molecule is an effective JAK and ROCK inhibitor which efficiently blocks disease progression in NZBWF1/J mouse models of systemic lupus erythematous.

Mesenchymal Stem Cells Activate the MEK/ERK Signaling Pathway and Enhance DNA Methylation via DNMT1 in PBMC from Systemic Lupus Erythematosus.

The defective MEK/ERK signaling pathway and downstream hypomethylation pattern of lymphocytes are crucial for the pathogenesis of systemic lupus erythematosus (SLE). However, the role that the mesenchymal stem cells play in the MEK/ERK signaling pathway and DNA methylation of peripheral blood mononuclear cells (PBMC) from SLE patients remains unknown. In this study, we found that the MEK/ERK signaling pathway of PBMC from SLE patients was activated after the coculture with bone marrow-derived mesenchymal stem cells (BM-MSC) compared with that from the control group. In addition, the expression level of DNA methyltransferase 1 (DNMT1) increased while the levels of CD70, integrin, alpha L (ITGAL), selectin-l, and IL-13 were reduced in PBMC from SLE patients. However, no obvious effect of BM-MSC on PBMC from healthy controls was observed. These findings revealed that BM-MSC might downregulate the expression of methylation-sensitive genes and then suppress the autoactivated PBMC via the MEK/ERK signaling pathway. And it may be one of the mechanisms that BM-MSC ameliorated SLE.

Plasma DNA Profile Associated with DNASE1L3 Gene Mutations: Clinical Observations, Relationships to Nuclease Substrate Preference, and In Vivo Correction.

Plasma DNA fragmentomics is an emerging area in cell-free DNA diagnostics and research. In murine models, it has been shown that the extracellular DNase, DNASE1L3, plays a role in the fragmentation of plasma DNA. In humans, DNASE1L3 deficiency causes familial monogenic systemic lupus erythematosus with childhood onset and anti-dsDNA reactivity. In this study, we found that human patients with DNASE1L3 disease-associated gene variations showed aberrations in size and a reduction of a "CC" end motif of plasma DNA. Furthermore, we demonstrated that DNA from DNASE1L3-digested cell nuclei showed a median length of 153 bp with CC motif frequencies resembling plasma DNA from healthy individuals. Adeno-associated virus-based transduction of Dnase1l3 into Dnase1l3-deficient mice restored the end motif profiles to those seen in the plasma DNA of wild-type mice. Our findings demonstrate that DNASE1L3 is an important player in the fragmentation of plasma DNA, which appears to act in a cell-extrinsic manner to regulate plasma DNA size and motif frequency.

Glycosphingolipid-associated ß-1,4 galactosyltransferase is elevated in patients with systemic lupus erythematosus.

OBJECTIVE: ß-1,4 galactosyltransferase-V (ß-1,4 GalT-V) is an enzyme that synthesises a glycosphingolipid known as lactosylceramide, which has been implicated in general inflammation and atherosclerosis. We asked if ß-1,4 GalT-V was present at elevated levels in patients with SLE, a disease which is associated with increased risk of atherosclerosis. METHODS: In this case-control observational study, serum samples were obtained from patients with SLE who are part of the Johns Hopkins Lupus Cohort. Control serum samples were obtained from healthy adult community members recruited from the Baltimore area. All serum samples (n=50 in the SLE group and n=50 in the healthy control group) were analysed with enzyme-linked immunoassays. These assays used antibodies raised against antigens that enabled us to measure the absorbance of oxidised phosphocholines per apolipoprotein B-100 (ox-PC/apoB) and the concentration of lipoprotein(a) (Lp(a)) and ß-1,4 GalT-V. RESULTS: Absorbance of ox-PC/apoB and concentrations of Lp(a) and ß-1,4 GalT-V were significantly higher in the SLE serum samples as compared with the control serum (p<0.0001). CONCLUSIONS: We conclude that patients with SLE have elevated levels of ß-1,4 GalT-V and ox-PC, which have previously been recognised as risk factors for atherosclerosis.

Serine/threonine phosphatase PP2A is essential for optimal B cell function.

Protein phosphatase 2A (PP2A), a serine/threonine phosphatase, has been shown to control T cell function. We found that in vitro-activated B cells and B cells from various lupus-prone mice and patients with systemic lupus erythematosus display increased PP2A activity. To understand the contribution of PP2A to B cell function, we generated a Cd19CrePpp2r1afl/fl (flox/flox) mouse which lacks functional PP2A only in B cells. Flox/flox mice displayed reduced spontaneous germinal center formation and decreased responses to T cell-dependent and T-independent antigens, while their B cells responded poorly in vitro to stimulation with an anti-CD40 antibody or CpG in the presence of IL-4. Transcriptome and metabolome studies revealed altered nicotinamide adenine dinucleotide (NAD) and purine/pyrimidine metabolism and increased expression of purine nucleoside phosphorylase in PP2A-deficient B cells. Our results demonstrate that PP2A is required for optimal B cell function and may contribute to increased B cell activity in systemic autoimmunity.

Systemic lupus erythematosus: Possible localization of trypsin-like and metalloprotease active centers in the protein sequence of the monoclonal light chain (NGTA2-Me-pro-Tr).

It was previously shown that several monoclonal light chains corresponding to the phagemid library of recombinant peripheral blood lymphocyte immunoglobulin light chains of patients with systemic lupus erythematosus specifically hydrolyze only myelin basic protein (MBP). Canonical enzymes usually have only one active site catalyzing some kind of chemical reaction. It was shown previously that in contrast to classical enzymes, preparations of one of the light chains (NGTA2-Me-pro-Tr) showed two optimal pH values, two optimal concentrations of metal ions, and two Km values for MBP. One protease active site of NGTA2-Me-pro-Tr was trypsin like, whereas second one was metal dependent. In this article, a search for protein sequences of NGTA2-Me-pro-Tr responsible for catalytic functions was carried out. We performed, for the first time, analysis of the homology of the protein sequence of NGTA2-Me-pro-Tr with those of several classical Zn2+ - and Ca2+ -dependent, as well as human serine, proteases. The analysis allowed us to identify the protein sequences of NGTA2-Me-pro-Tr responsible for serine-like activity, the binding of MBP, and chelation of metal ions and catalysis directly. The data obtained are summarized using hypothetical models of the structure of the two active centers of a very unusual light chain of antibodies (Abs). The findings obtained may be very important for understanding possible structure of active centers of very unusual light chain of Abs possessing several enzymatic activities.

JAK2 and PTPRC mRNA expression in peripheral blood mononuclear cells from patients with systemic lupus erythematosus.

In this study, we aimed to explore the expression levels of JAK2 and PTPRC in peripheral blood mononuclear cells (PBMCs) from SLE patients and controls, detect the effects of SLE activity on genes mRNA expression, and find the association between genes mRNA expression and clinical manifestations of patients. We performed quantitative real-time PCR (qRT-PCR) to test differences in the expression levels of JAK2 and PTPRC in PBMCs extracted from 135 patients with SLE and 130 healthy controls. Furthermore, we detected the regulatory effect of SNPs on gene expression by expression quantitative trait loci (eQTL). We also tested whether the genes mRNA expression was affected with the SLE activity and analyzed the relationship between genes mRNA expression and clinical manifestations of patients. The mRNA expression levels of JAK2 in SLE patients were significantly higher than those in healthy controls (P = 0.005), and PTPRC mRNA expression levels were significantly decreased (P < 0.001). However, no other statistical significance was detected. We found that the elevated JAK2 mRNA expression and the decreased PTPRC mRNA expression may play suggestive roles in the pathogenesis of SLE.Key Points• The JAK2 mRNA expression levels in SLE patients were significantly higher than those in healthy controls.• The PTPRC mRNA expression levels in SLE were decreased.• JAK2 and PTPRC mRNA expression may play suggestive roles in the pathogenesis of SLE.

Alpha-hydroxybutyrate dehydrogenase as a biomarker for predicting systemic lupus erythematosus with liver injury.

PURPOSE: To explore potential biomarkers for identifying systemic lupus erythematosus (SLE) with liver injury. METHODS: This retrospective study examined the records of 158 SLE cases. The Apriori algorithm of association rules was employed to identify laboratory indexes related to liver injury in SLE patients. RESULTS: The ratio of albumin to globulin; levels of alpha-hydroxybutyrate dehydrogenase (α-HBDH), calcium, hemoglobin, urine protein, total cholesterol; absolute value of lymphocytes; red cell distribution width and hematocrit were identified by the Apriori algorithm from SLE-related liver injury patients. α-HBDH was identified as an independent risk factor for SLE-related liver injury. There were more SLE patients with liver injury in high-α-HBDH group than in low-α-HBDH group (64.63% vs. 21.05%; P < 0.001). In high-α-HBDH group, levels of aspartate aminotransferase (AST), alanine aminotransferase (ALT), lactate dehydrogenase (LDH), and gamma-glutamyl transpeptidase (GGT), and the AST/ALT ratio were significantly higher, and albumin and complement 3 (C3) were markedly lower. Moreover, α-HBDH level was significantly higher in the SLE-related liver injury patients than in the non-SLE-related liver injury patients. In addition, α-HBDH was positively correlated with levels of AST and LDH, the AST/ALT ratio, and the SLE Disease Activity Index 2000, and it was negatively correlated with albumin and C3. The optimal cutoff value of α-HBDH for distinguishing SLE patients with and without liver injury was 258.50 U/L, which provided a 60.94% sensitivity and a 94.67% specificity. CONCLUSION: α-HBDH could be used to evaluate the disease activity of SLE-related liver injury, and it may be a potential biomarker for diagnosing SLE-related liver injury.

Associations between paraoxonase-1 and systemic lupus erythematosus.

OBJECTIVE: The objective of this analysis was to explore associations between paraoxonase-1 levels, gene polymorphisms and systemic lupus erythematosus. METHODS: Meta-analyses of paraoxonase-1 levels and Q192R and L55M and polymorphisms in systemic lupus erythematosus were conducted. RESULTS: Nine articles were incorporated in our meta-analysis, which uncovered that the paraoxonase-1 level was decreased in systemic lupus erythematosus compared to control (standard mean difference = -1.626, 95% confidence interval = -2.829--0.424, p = 0.008). Ethnicity-specific meta-analysis demonstrated a relation tendency between decreased paraoxonase-1 activity and lupus in Europeans (standard mean difference = -1.236, 95% confidence interval = -2.634-0.163, p = 0.083). Paraoxonase-1 activity was reduced in systemic lupus erythematosus in a single Arab and African population. Decreased paraoxonase-1 activity was found in a small sample of systemic lupus erythematosus patients (standard mean difference = -1.642, 95% confidence interval = -3.076--0.247, p = 0.021). Ethnicity-specific analysis indicated a relationship between the paraoxonase-1 55 M allele in the Arab systemic lupus erythematosus population. However, a lack of association with systemic lupus erythematosus and the paraoxonase-1 192 R allele was observed. CONCLUSIONS: Meta-analyses revealed reduced paraoxonase-1 activity in patients with systemic lupus erythematosus and found possible associations between systemic lupus erythematosus and paraoxonase-1 L55M polymorphism in a specific ethnic group.

Association between Serum Matrix Metalloproteinase- (MMP-) 3 Levels and Systemic Lupus Erythematosus: A Meta-analysis.

INTRODUCTION: Matrix metalloproteinase (MMP) is an emerging disease marker in rheumatic diseases. This is a meta-analysis aimed at systematically reviewing association between serum MMP-3 levels and systematic lupus erythematosus (SLE) activity, which sought to raise interest in MMP-3 as a putative biomarker. METHODS: We conducted a meta-analysis of serum MMP-3 levels in patients with SLE and controls. We performed a PubMed search, EMBASE search, and forward search of the retrieved articles published until Oct. 1, 2018. In addition to this, we included data from a case-control study on a national pediatric SLE cohort, in which serum MMP-3 levels were measured in 11 SLE patients and 9 controls (unpublished). Subgroup analyses based on gender and disease activity were performed. RESULTS: A total of 662 cases and 771 controls including 651 patients and 762 controls from 11 publications were studied. We observed significantly higher MMP-3 levels in SLE patients compared to healthy controls (P < 0.001, Hedges' g: 2.104, 95% CI 1.426-2.782). In subgroup analyses, we found a significant elevation of MMP-3 in the patients with nephritis compared to those without (P = 0.006, Hedges' g: 0.611, 95% CI 0.611-1.704). This finding was consistent between patients with persistent proteinuria and those without (P = 0.023, Hedges' g: 1.535, 95% CI 0.207-2.862). Meta-analysis showed no association between MMP-3 levels and gender or anti-double strand DNA antibody titer. CONCLUSIONS: Our meta-analysis demonstrated significantly higher MMP-3 levels in SLE patients than in controls and in patients with renal involvement than in those without.

Increased CD14+HLA-DR-/low Myeloid-Derived Suppressor Cells Correlate With Disease Severity in Systemic Lupus Erythematosus Patients in an iNOS-Dependent Manner.

Myeloid-derived suppressor cells (MDSCs) comprise of a population of cells, which suppress the innate and adaptive immune system via different mechanisms. MDSCs are accumulated under pathological conditions. The present study aimed to clarify the pathological role of MDSCs in systemic lupus erythematosus (SLE) patients. Consequently, the level of circulating M-MDSCs was significantly increased in newly diagnosed SLE patients as compared to healthy controls. An elevated level of M-MDSCs was positively correlated with the disease severity in SLE patients and an immunosuppressive role was exerted in an iNOS-dependent manner. The decrease in the number of M-MDSCs after therapy rendered them as an indicator for the efficacy of treatment. These results demonstrated that M-MDSCs participated in the pathological progress in SLE patients. Thus, MDSCs are attractive biomarkers and therapeutic targets for SLE patients.

Efficacy and Pharmacodynamic Modeling of the BTK Inhibitor Evobrutinib in Autoimmune Disease Models.

Because of its role in mediating both B cell and Fc receptor signaling, Bruton's tyrosine kinase (BTK) is a promising target for the treatment of autoimmune diseases such as rheumatoid arthritis (RA) and systemic lupus erythematosus (SLE). Evobrutinib is a novel, highly selective, irreversible BTK inhibitor that potently inhibits BCR- and Fc receptor-mediated signaling and, thus, subsequent activation and function of human B cells and innate immune cells such as monocytes and basophils. We evaluated evobrutinib in preclinical models of RA and SLE and characterized the relationship between BTK occupancy and inhibition of disease activity. In mouse models of RA and SLE, orally administered evobrutinib displayed robust efficacy, as demonstrated by reduction of disease severity and histological damage. In the SLE model, evobrutinib inhibited B cell activation, reduced autoantibody production and plasma cell numbers, and normalized B and T cell subsets. In the RA model, efficacy was achieved despite failure to reduce autoantibodies. Pharmacokinetic/pharmacodynamic modeling showed that mean BTK occupancy in blood cells of 80% was linked to near-complete disease inhibition in both RA and SLE mouse models. In addition, evobrutinib inhibited mast cell activation in a passive cutaneous anaphylaxis model. Thus, evobrutinib achieves efficacy by acting both on B cells and innate immune cells. Taken together, our data show that evobrutinib is a promising molecule for the chronic treatment of B cell-driven autoimmune disorders.

Season Dependent Changes in the Expression of Protein Kinase C Isoenzymes in a Female Patient with Systemic Lupus Erythematosus.

We aimed to answer the question whether the decreased expression of protein kinase C (PKC) isoenzymes in the peripheral blood mononuclear cells (PBMC) of patients with systemic lupus erythematosus (SLE) is inherited or not. For this reason we examined the expression of PKC isoenzymes in a European white girl with acute SLE and in her healthy mother and father simultaneously in summer and winter during one year using western blotting and densitometry. We found that in the father the expression of PKC isoenzymes did not differ from that of eight healthy controls included women and men. However, in the "SLE-free" mother and in the patient arrived in July with acute symptoms of lupus, the expression of PKC isoenzymes showed a season dependent undulation in parallel. Namely, in summer the expression values were significantly lower, in winter they were significantly higher than those in the controls. Thus, the decreased expression of PKC isoenzymes in the PBMC of SLE patient is not a disease specific marker; it appears also in her lupus free mother. This phenomenon may be due to a season dependent female genetic background. However, the low PKC levels in summer can still decrease further the low production of IL-2 in T cells of lupus patients augmenting the existing AP-1 defects. This is the first report on the season and female dependent inherited changing of PKC expression in a European white patient with SLE and her mother. Further studies are needed to confirm these findings in other populations.

LRRK2 is involved in the pathogenesis of system lupus erythematosus through promoting pathogenic antibody production.

BACKGROUND: Systemic lupus erythematosus (SLE) is a prototypic autoimmune disease characterized by the presence of pathogenic autoantibodies associated with polyclonal B cell hyperreactivity. Previous study reported that autophagy-related gene Leucine-rich repeat kinase 2 (LRRK2) was likely a susceptible gene for SLE. However, the pathogenic function of LRRK2 in SLE is undefined. METHODS: Using quantitative PCR, we compared the expression levels of LRRK2 in B cells between SLE patients and healthy controls. The expression levels of LRRK2 in in vitro induced CD19hi B cells and naïve B cells were compared as well based on RNA-seq assay. A pristane-induced lupus-like mouse model was used to explore the effects of LRRK2 on the development of SLE. IgG level, B cell subsets in the spleens and bone marrows and pathological features in the kidneys were compared between wildtype (WT) and Lrrk2-/- littermates. RESULTS: It was obvious that LRRK2 expression was dramatically up-regulated in primary B cells from SLE patients compared to those from healthy controls, as well as in activated CD19hi B cells. More significantly, LRRK2 expression in B cells was positively correlated with system lupus erythematosus disease activity index (SLEDAI), an indicator for disease severity, and serum IgG levels in SLE patients. Negative correlations were observed between LRRK2 expression and serum C3 or C4 levels, two clinical features associated with SLE-related nephritis. LRRK2 deficiency reduced the death rate of pristane treated mice. Decreased levels of total IgG and autoantibody were detected in the serum with less deposition of immune complexes and attenuated pathological symptoms in the kidneys of Lrrk2-/- mice. Consistent with the reduction in IgG production, the percentages of germinal center B cells and plasma cells decreased significantly as well with LRRK2 deficiency. CONCLUSIONS: Our study demonstrates that LRRK2 expression is upregulated in B cells from SLE patients with strong correlations to disease severity. LRRK2 deficiency largely attenuates the pathogenic progress of lupus-like features in pristane-induced mice. This is probably achieved through affecting B cell terminal differentiation and subsequent immunoglobulin production.