Mechanisms of tissue injury in lupus nephritis

Systemic lupus erythematosus is a prototypic autoimmune disease characterized by autoantibody production and immune complex formation/deposition in target organs such as the kidney. Resultant local inflammation then leads to organ damage. Nephritis, a major cause of morbidity and mortality in patients with lupus, occurs in approximately 50% of lupus patients. In the present review, we provide an overview of the current research and knowledge concerning mechanisms of renal injury in both lupus-prone mouse models and human lupus patients

Role of the transcription factor Fli-1 on the CXCL10/CXCR3 Axis*

The transcription factor Fli-1, a member of the ETS family of transcription factors, is implicated in the pathogenesis of lupus disease. Reduced Fli-1 expression in lupus mice leads to decreased renal Cxcl10 mRNA levels and renal infiltrating CXCR3+ T cells that parallels reduced renal inflammatory cell infiltration and renal damage. Inflammatory chemokine CXCL10 is critical for attracting inflammatory cells expressing the chemokine receptor CXCR3. The CXCL10/CXCR3 axis plays a role in the pathogenesis of various inflammatory diseases including lupus. Our data here demonstrate that renal CXCL10 protein levels are significantly lower in Fli-1 heterozygous MRL/lpr mice compared to wild-type MRL/lpr mice. Knockdown of Fli-1 significantly reduced CXCL10 secretion in mouse and human endothelial cells, and human mesangial cells, upon LPS or TNFα stimulation. The Fli-1 inhibitor, Camptothecin, significantly reduced CXCL10 production in human monocyte cells upon interferon stimulation. Four putative Ets binding sites in the Cxcl10 promoter showed significant enrichment for FLI-1; however, FLI-1 did not directly drive transcription from the human or mouse promoters, suggesting FLI-1 may regulate CXCL10 expression indirectly. Our results also suggest that the DNA binding domain of FLI-1 is necessary for regulation of human hCXCR3 promotor activity in human T cells and interactions with co-activators. Together, these results support a role for FLI-1 in modulating the CXCL10-CXCR3 axis by directly or indirectly regulating the expression of both genes to impact lupus disease development. Signaling pathways or drugs that reduce FLI-1 expression may offer novel approaches to lupus treatment

Identification of Novel Domains within Sox-2 and Sox-11 Involved in Autoinhibition of DNA Binding and Partnership Specificity

Sox transcription factors play key regulatory roles throughout development, binding DNA through a consensus (A/T)(A/T)CAA(A/T)G sequence. Although many different Sox proteins bind to this se-quence, it has been observed that gene regulatory elements are commonly responsive to only a small subset of the entire family, implying that regulatory mechanisms exist to permit selective DNA bind-ing and/or transactivation by Sox family members. To identify and explore the mechanisms modu-lating gene activation by Sox proteins further, we compared the function of Sox-2 and Sox-11. This led to the discovery that Sox proteins are regulated differentially at multiple levels, including trans-activation, protein partnerships with Pit-Oct-Unc (POU) transcription factors, and DNA binding au-toregulation. Specifically, we determined that Sox-11 activates transcription more strongly than Sox-2 and that the transactivation domain of Sox-11 is primarily responsible for this capability. Addition-ally, we demonstrate that the Sox-11 DNA binding domain is responsible for selective cooperation with the POU factor Brn-2. This requirement cannot be replaced by the DNA binding domain of Sox-2, indicating that the DNA binding domain of Sox proteins is critical for Sox-POU partnerships. In-terestingly, we have also determined that a conserved domain of Sox-11 has the novel capability of autoinhibiting its ability to bind DNA in vitro and to activate gene expression in vivo. Our findings suggest that the autoinhibitory domain can repress promiscuous binding of Sox-11 to DNA and plays an important role in regulating the recruitment of Sox-11 to specific genes

Identification of the Transactivation Domain of the Transcription Factor Sox-2 and an Associated Co-activator

The importance of interactions between Sox and POU transcription factors in the regulation of gene expression is becoming increasingly apparent. Recently, many examples of the involvement of Sox-POU partnerships in transcription have been discovered, including a partnership between Sox-2 and Oct-3. Little is known about the mechanisms by which these factors modulate transcription. To better understand the molecular interactions involved, we mapped the location of the transactivation do-main of Sox-2. This was done in the context of its interaction with Oct-3, as well as its ability to transactivate as a fusion protein linked to the DNA-binding domain of Gal4. Both approaches demonstrated that Sox-2 contains a transactivation domain in its C-terminal half, containing a serine-rich region and the C terminus. We also determined that the viral oncoprotein E1a inhibits the ability of the Gal4/Sox-2 fusion protein to transactivate, as well as the transcriptional activation mediated by the combined action of Sox-2 and Oct-3. In contrast, a mutant form of E1a, unable to bind p300, lacks both of these effects. Importantly, we determined that p300 overcomes the inhibitory effects of E1a in both assays. Together, these findings suggest that Sox-2 mediates its effects, at least in part, through the co-activator p300

Formal neurocognitive function and anti-N-methyl-D-aspartate receptor antibodies in paediatric lupus

Objective SLE is a chronic multisystem autoimmune inflammatory disease impacting a number of organs, including the central nervous system (CNS). The pathophysiology of CNS lupus is multifactorial, making diagnosis problematic. Neurocognitive (NC) testing and specific biomarkers to identify the development of neuropsychiatric (NP) symptoms in lupus are needed. Paediatric patients with SLE have high incidence of NP disease . While serum anti-N-methyl-D-aspartate receptor (NMDAR) antibodies have shown promise as a biomarker of NP in adults with SLE, much less is known with regard to paediatric patients with SLE.Methods We performed a cross-sectional study in paediatric patients with SLE. Serum NMDAR antibodies were measured and compared with levels in patients with juvenile idiopathic arthritis (JIA). Formal NC testing was performed in accordance with the Childhood Arthritis & Rheumatology Research Alliance neuropsychological core test battery. NC functioning was compared in the two groups and with NMDAR antibody levels.Results Serum NMDAR antibody levels were significantly higher in paediatric patients with SLE compared with patients with JIA. There were no significant correlations between NMDAR antibody levels and any measure of NC functioning. In an exploratory examination of anti-ribosomal P (RibP) antibody and NC functioning in a subset of patients with SLE, RibP antibody-positive patients exhibited worse scores for Verbal Memory Index and Design Fluency Test Switching compared with RibP antibody-negative patients. A globally significant association between disease status and NC functioning was observed. Specifically, patients with SLE had lower scores compared with patients with JIA for full-scale IQ, letter–word recognition, reading fluency and calculation skills after adjusting for multiple comparisons.Conclusion These collective results suggest that although serum NMDAR may serve as a biomarker, formal NC testing is superior in identifying paediatric patients with SLE with NP manifestations. RibP also may potentially serve as a biomarker of NP manifestations in paediatric patients with SLE. Additional and longitudinal studies are needed

The role of neuraminidase 1 (NEU1) in cytokine release by primary mouse mesangial cells and disease outcomes in murine lupus nephritis

The importance of altered glycosphingolipid (GSL) metabolism is increasingly gaining attention as a characteristic of multiple chronic kidney diseases. Previously, we reported elevated levels of GSLs and neuraminidase (NEU) enzyme activity/expression in the urine or kidney of lupus patients and lupus-prone mice, and demonstrated NEU activity mediates the production of cytokines by lupus-prone mouse primary mesangial cells. This mediation occurs in part through TLR4 and p38/ERK MAPK signalling in response to lipopolysaccharide (LPS) and lupus serum (LS). However, the precise role of NEU1, the most abundant NEU in the kidney, is incompletely known. In this study, we investigated the effect of genetically reduced Neu1 levels in vitro and in vivo. Mesangial cells from non-autoimmune prone Neu1+/− C57BL/6 mice had significantly reduced NEU activity, cytokine expression and cytokine secretion in response to LS and LPS, thereby suggesting reducing Neu1 expression may reduce the inflammatory response in lupus nephritis. Disease was assessed in female B6.SLE1/2/3 lupus-prone mice with genetically reduced levels (Neu1+/−) or wild-type levels (Neu1+/+) of Neu1 from 28 to 44 weeks of age along with aged-matched C57BL/6 controls. Renal disease was unexpectedly mild in all B6.SLE1/2/3 mice despite evidence of systemic disease. B6.SLE1/2/3 Neu1+/− mice exhibited significantly reduced levels of renal NEU1 expression and changes in renal α-2,6 linked sialylated N-glycans compared to the Neu1+/+ or healthy C57BL/6 mice, but measures of renal and systemic disease were similar between the B6.SLE1/2/3 Neu1+/+ and Neu1+/− mice. We conclude that NEU1 is the NEU largely responsible for mediating cytokine release by mesangial cells, at least in vitro, but may not be involved in modulating renal GSL levels in vivo or impact onset of nephritis in lupus-prone mice. However, the effect of reduced NEU1 levels on disease may not be appreciated in the mild disease expression in our colony of B6.SLE1/2/3 mice. The impact of the altered renal sialylated N-glycan levels and potential role of NEU1 with respect to established nephritis (late disease) in lupus-prone mice bears further investigation

Systemic lupus erythematosus and vitamin D deficiency are associated with shorter telomere length among African Americans: a case-control study.

Systemic lupus erythematosus (SLE) is a chronic systemic autoimmune disease that disproportionately affects African American females. The causes of SLE are unknown but postulated to be a combination of genetic predisposition and environmental triggers. Vitamin D deficiency is one of the possible environmental triggers. In this study we evaluated relationships between vitamin D status, cellular aging (telomere length) and anti-telomere antibodies among African American Gullah women with SLE. The study population included African American female SLE patients and unaffected controls from the Sea Island region of South Carolina. Serum 25-hydroxyvitamin D levels were measured using a nonchromatographic radioimmunoassay. Telomere length was measured in genomic DNA of peripheral blood mononuclear cells (PBMCs) by monochrome multiplex quantitative PCR. Anti-telomere antibody levels were measured by enzyme-linked immunosorbent assay (ELISA). Patients with SLE had significantly shorter telomeres and higher anti-telomere antibody titers compared to age- and gender-matched unaffected controls. There was a positive correlation between anti-telomere antibody levels and disease activity among patients and a significant correlation of shorter telomeres with lower 25-hydroxyvitamin D levels in both patients and controls. In follow-up examination of a subset of the patients, the patients who remained vitamin D deficient tended to have shorter telomeres than those patients whose 25-hydroxyvitamin D levels were repleted. Increasing 25-hydroxyvitamin D levels in African American patients with SLE may be beneficial in maintaining telomere length and preventing cellular aging. Moreover, anti-telomere antibody levels may be a promising biomarker of SLE status and disease activity

Glycosphingolipid Levels in Urine Extracellular Vesicles Enhance Prediction of Therapeutic Response in Lupus Nephritis

The development of nephritis increases the risk of morbidity and mortality in systemic lupus erythematosus (SLE) patients. While standard induction therapies, such as mycophenolate mofetil (MMF) induce clinical remission (i.e., complete response) in approximately 50% of SLE patients with nephritis, many patients fail to respond. Therapeutic response is often not assessed until 6–12 months after beginning treatment. Those patients that fail to respond to treatment continue to accumulate organ damage, thus, there is a critical need to predict which patients will fail therapy before beginning treatment, allowing physicians to optimize therapy. Our previous studies demonstrated elevated urine, but not serum, glycosphingolipids (GSLs) in SLE patients with nephritis compared to SLE patients without nephritis, suggesting the urine GSLs were derived from the kidney. In this study, we measured the GSLs hexosylceramide and lactosylceramide in extracellular vesicles isolated from longitudinal urine samples of LN patients that were treated with MMF for 12 months. GSL levels were significantly elevated in the baseline samples (prior to treatment) of non-responders compared to complete responders. While a few other proteins measured in the whole urine were higher in non-responders at baseline, only GSLs demonstrated a significant ability to discriminate treatment response in lupus nephritis patients

Vitamin D, telomere length and anti-telomere antibodies in SLEIGH patients and controls.

<p>A) 25(OH)D levels. B) Telomere length analysis. C) Anti-telomere antibody levels. Error, standard deviation by two-sample T-test with equal variance.</p