Iguratimod is a novel synthetic, small-molecule immunosuppressive agent used to treat rheumatoid arthritis. Through ongoing exploration of its role and mechanisms of action, iguratimod has been observed to have antifibrotic effects in the lung and skin; however, its effect on renal fibrosis remains unknown. This study aimed to investigate whether iguratimod could affect renal fibrosis progression. Three different concentrations of iguratimod (30 mg/kg/day, 10 mg/kg/day, and 3 mg/kg/day) were used to intervene in unilateral ureteral obstruction (UUO) model mice. Iguratimod at 10 mg/kg/day was observed to be effective in slowing UUO-mediated renal fibrosis. In addition, stimulating bone marrow-derived macrophages with IL-4 and/or iguratimod, or with TGF-beta and iguratimod or SRC inhibitors in vitro, suggested that iguratimod mitigates the progression of renal fibrosis in UUO mice, at least in part, by inhibiting the IL-4/STAT6 signaling pathway to attenuate renal M2 macrophage infiltration, as well as by impeding SRC activation to reduce macrophage-myofibroblast transition. These findings reveal the potential of iguratimod as a treatment for renal disease.

The molecular mechanisms underlying lupus nephritis (LN) pathogenesis are not fully understood. Hydrogen sulfide (H2S) is involved in many pathological and physiological processes. We sought to investigate the roles of H2S in LN pathogenesis. H2S synthase cystathionine-lyase (CSE) and cystathionine-synthetase (CBS) expression was downregulated in renal tissues of patients with LN and their levels were associated with LN's prognosis using the Nephroseq database. Reduced CSE and CBS protein expression in kidney tissues of LN patients and MRL/lpr mice were confirmed by immunohistochemistry. CSE and CBS mRNA levels were reduced in MRL/lpr and pristine- and R848-induced lupus mice. Given that H2S exerts an anti-inflammatory role partly via regulating inflammatory transcription factors (TFs), we analyzed hub TFs by using a bioinformatics approach. It showed that STAT1, RELA, and T-cell-related signaling pathways were enriched in LN. Increased STAT1 and RELA expression were confirmed in renal tissues of LN patients. Treatment of MRL/lpr and pristine mice with H2S donors alleviated systemic lupus erythematosus (SLE) phenotypes and renal injury. H2S donors inhibited RELA level and T-cell infiltration in the kidneys of MRL/lpr and pristine mice. Our data indicated that CSE/CBS/H2S contributes to LN pathogenesis. Supplementation of H2S would be a potential therapeutic strategy for LN.

Fibrosis is a common pathology in renal disease. Hypertensive nephropathy (HN) is one of the most common secondary nephropathies that often progresses to severe renal fibrosis with limited treatment options beyond hypertension control. Bromodomain-containing protein 4 (Brd4) was recently recognized as a target in signaling pathways that underlie the pathologies of inflammatory diseases and tumors. A recently developed inhibitor of Brd4, JQ1, has been shown to exert antifibrotic effects and is being clinically explored as an anti-inflammatory and antitumor drug. Here, using human kidney biopsies and Angiotensin II-induced mouse fibrotic kidney samples, we show that Brd4 was upregulated in renal tissue from HN patients and hypertensive mouse models. In mice, JQ1 alleviated Angiotensin II-induced kidney fibrosis and blocked epithelial-mesenchymal transition (EMT) by altering the expression of EMT-related proteins. Using an in vitro model of HK2 cells exposed to Angiotensin II, we also demonstrated that JQ1 suppressed the protein expression of fibrotic genes in these cells. These results further implicate Brd4 in the fibrotic response in HN and reveal that Brd4 is a potential antifibrotic target. BET inhibitors are currently being investigated in clinical trials as antitumor agents and show potent pharmacological effects. Our findings suggest that BET inhibitors may also be potential translational therapies for HN.

Renal fibrosis is a key pathological feature in chronic kidney diseases (CKDs). Dysregulation of hydrogen sulfide (H2S) homeostasis is implicated in the pathogenesis of CKDs. Here, C57/BL6 mice were allocated to Sham and unilateral ureteral obstruction (UUO) groups, which were treated with NaHS or NLRP3 inflammasome inhibitor 16673-34-0 for 3–14 days. UUO mice displayed downregulation of H2S production and increased macrophage infiltration in obstructed kidneys. H2S donor NaHS treatment attenuated renal damage and fibrosis and inhibited M1 and M2 macrophage infiltration. NLPR3 inflammasome was activated and levels of phosphorylated nuclear factor κB (NF-κB) p65 subunit, phosphorylated signal transducer and activator of transcription 6 (STAT6) and interleukin (IL)-4 protein were increased in the kidneys after UUO. NLRP3 inhibitor inactivated NF-κB and IL-4/STAT6 signaling, suppressed M1 and M2 macrophage infiltration and attenuated renal damage and fibrosis in UUO mice. NaHS treatment also suppressed NLRP3, NF-κB and IL-4/STAT6 activation in the obstructed kidneys. In conclusion, the therapeutic effects of H2S on UUO-induced renal injury and fibrosis are at least in part by inhibition of M1 and M2 macrophage infiltration. H2S suppresses NLRP3 activation and subsequently inactivates NF-κB and IL-4/STAT6 signaling, which may contribute to the anti-inflammatory and anti-fibrotic effects of H2S.

OBJECTIVES:Lupus nephritis (LN) is an immune-complex mediated nephritis with complicated pathogenesis. The aims of the present study were to investigate whether inflammasomes are activated in the renal pathology of LN patients and analyse the association of inflammasome activation in different classes of LN renal tissues with the disease activity.METHODS:A total of 86 patients with renal biopsy-proven chronic kidney disease admitted in Xiangya Hospital from January 2015 to August 2018 were enrolled in the present study. Immunofluorescence analysis was applied to examine NLRP1, NLRP3 and AIM3 expression in renal tissues.RESULTS:AIM2 was mainly expressed in glomerular cells of LN class II. No obvious positive staining of AIM2 in renal tissues was found in other LN classes. NLRP1 and NLRP3 were mainly localised in tubular cells. NLRP1 was mainly expressed in tubular cells of LN class II and class IV while NLRP3 was expressed in tubular cells of LN class IV. Moreover, NLRP3 expression level was positive correlated with the activity index (AI) score in patients with LN.CONCLUSIONS:NLRP3, NLRP1 and AIM2 activation are involved in the progress of LN. NLRP3 activation has a positive correlation with the AI score of LN.

Objective To investigate the correlation between neutrophil-lymphocyte ratio (NLR) and disease activity of systemic lupus erythematosus (SLE),and the changes of NLR in different organ involvement of SLE patients.Methods A total of 155 SLE patients and 135 healthy controls from the Rheumatology Department of Xiangya Hospital were enrolled in this study from 2010 to 2018.Patients with SLE were divided into lupus nephritis group (LN group) and non-lupus nephritis group (non-LN group),serositis group and non-serositis group,according to whether they had kidney involvement or serositis.According to the SLE disease activity index 2000(SLEDAI-2000),the patients were divided into mild to moderate disease activity group (SLEDAI score ＜ 15) and severe disease activity group (SLEDAI score≥ 15).The NLR values of the above groups were compared.Spearman's correlation analysis was used to analyze the correlation between NLR and SLE patients' laboratory indexes.Multiple linear regression model was used to analyze the relationship between NLR and SLE disease activity.Receiver operating characteristic curve (ROC) was used to evaluate the value of NLR in SLE diagnosis and activity assessment.Results (1)The NLR value of SLE patients was significantly higher than that of healthy control group,and the difference was statistically significant (P ＜ 0.01).(2)The NLR value of SLE patients in the LN group was higher than that in the non-LN group,and the NLR value of SLE patients with serositis was higher than that in the group without serositis,with statistically significant differences (both P ＜ 0.05).(3)The NLR value of SLE patients in the severe disease activity group was higher than that in the mild and moderate disease activity group,and the difference was statistically significant (P ＜ 0.01).(4)NLR of SLE patients was positively correlated with CRP (rs=0.188,P=0.019),SLEDAI score (rs=0.264,P=0.001),and negatively correlated with total serum protein (rs=-0.250,P=0.002) and serum albumin (rs=-0.329,P ＜ 0.001),respectively.(5) Multiple linear regression showed that NLR was independently associated with SLE disease activity (B=0.351,95％CI 0.012-0.690,t=2.047,P=0.042).(6) According to ROC curve,the optimal cut-off value of NLR for SLE diagnosis was 2.17 (sensitivity 60.0％,specificity 83.1％,AUC=0.744),and the best cut-off value for predicting the activity of severe disease activity in SLE patients was 3.28 (sensitivity 58.5％,specificity 78.1％,AUC=0.700).Conclusion NLR is closely related to renal involvement,serositis and disease activity in SLE patients,which indicates that NLR,as a new inflammatory indicator,is of great significance for the assessment of SLE disease activity and organ involvement.