C5a-C5aR1 axis controls mitochondrial fission to promote podocyte injury in lupus nephritis.

Podocytes are essential to maintaining the integrity of the glomerular filtration barrier, but they are frequently affected in lupus nephritis (LN). Here, we show that the significant upregulation of Drp1S616 phosphorylation in podocytes promotes mitochondrial fission, leading to mitochondrial dysfunction and podocyte injury in LN. Inhibition or knockdown of Drp1 promotes mitochondrial fusion and protects podocytes from injury induced by LN serum. In vivo, pharmacological inhibition of Drp1 reduces the phosphorylation of Drp1S616 in podocytes in lupus-prone mice. Podocyte injury is reversed when Drp1 is inhibited, resulting in the alleviation of proteinuria. Mechanistically, complement component C5a (C5a) upregulates the phosphorylation of Drp1S616 and promotes mitochondrial fission in podocytes. Moreover, the expression of C5a receptor 1 (C5aR1) is notably upregulated in podocytes in LN. C5a-C5aR1 axis-controlled phosphorylation of Drp1S616 and mitochondrial fission are substantially suppressed when C5aR1 is knocked down by siRNA. Moreover, lupus-prone mice treated with C5aR inhibitor show reduced phosphorylation of Drp1S616 in podocytes, resulting in significantly less podocyte damage. Together, this study uncovers a novel mechanism by which the C5a-C5aR1 axis promotes podocyte injury by enhancing Drp1-mediated mitochondrial fission, which could have significant implications for the treatment of LN.

NAMPT is a metabolic checkpoint of IFNγ-producing CD4+ T cells in lupus nephritis.

Interferon γ (IFNγ) produced by T cells represents the featured cytokine and is central to the pathogenesis of lupus nephritis (LN). Here, we identified nicotinamide phosphoribosyltransferase (NAMPT), the rate-limiting enzyme in the salvage NAD+ biosynthetic pathway, as playing a key role in controlling IFNγ production by CD4+ T cells in LN. Our data revealed that CD4+ T cells from LN showed an enhanced NAMPT-mediated NAD+ biosynthetic process, which was positively correlated with IFNγ production in CD4+ T cells. NAMPT promoted aerobic glycolysis and mitochondrial respiration in CD4+ T cells from patients with LN or MRL/lpr mice through the production of NAD+. By orchestrating metabolic fitness, NAMPT promoted translational efficiency of Ifng in CD4+ T cells. In vivo, knockdown of NAMPT by small interfering RNA (siRNA) or pharmacological inhibition of NAMPT by FK866 suppressed IFNγ production in CD4+ T cells, leading to reduced inflammatory infiltrates and ameliorated kidney damage in lupus mice. Taken together, this study uncovers a metabolic checkpoint of IFNγ-producing CD4+ T cells in LN in which therapeutically targeting NAMPT has the potential to normalize metabolic competence and blunt pathogenicity of CD4+ T cells in LN.

Efficacy and safety of tripterygium wilfordii Hook F plus TNF inhibitor for active rheumatoid arthritis: A multicentre, randomized, double-blind, triple-dummy controlled trial.

An investigator-initiated, multicentre, randomized, double-blind, triple-dummy, controlled trial was conducted at 14 tertiary rheumatology centers in China to evaluate the efficacy and safety of Tripterygium wilfordii Hook F (TwHF) with recombinant human TNF receptor IgGFc fusion protein (rhTNFR-Fc) in active Rheumatoid Arthritis (RA). Primary endpoint was the proportion of patients achieved a 50% improvement of American College of Rheumatology criteria (ACR50) in TwHF+rhTNFR-Fc vs. methotrexate (MTX) group at week 12. ACR50 was achieved in 57.1% (72/126), 41.3% (52/126), 23.0% (29/126), and 26.2% (33/126) patients receiving TwHF+rhTNFR-Fc, MTX + rhTNFR-Fc, TwHF and MTX monotherapy, respectively, at week 12 (TwHF+rhTNFR-Fc vs. other three groups, all p < 0.05). No statistical difference in serious adverse events or adverse events leading to discontinuation of study across all groups was documented. TwHF+rhTNFR-Fc was superior to MTX for active RA, and was more effective than MTX + rhTNFR-Fc on ACR50, with a similar safety profile. Trial registration:ClinicalTrials.govNCT03589833.

Tfh cells with NLRP3 inflammasome activation are essential for high-affinity antibody generation, germinal centre formation and autoimmunity.

OBJECTIVE: NLRP3 inflammasome regulates T cell responses. This study examined the roles of NLRP3 inflammasome activation in the regulation of T follicular helper (Tfh) cells during humoral response to T dependent antigens and in systemic lupus erythematosus (SLE). METHODS: NLRP3 inflammasome activation of Tfh cells was studied in B6, MRL/lpr and NZM2328 mice and in SLE patients and healthy controls using a fluorescence-labelled caspase-1 inhibitor probe. MCC950, a selective inhibitor of NLRP3, was used to investigate the relation between NLRP3 inflammasome activation and germinal centre (GC) reaction, Ab responses to immunisation, and autoantibody production. RESULTS: NLRP3 inflammasome activation in Tfh cells after immunisation was identified in B6 mice. MCC950 inhibited humoral responses to sheep red blood cell and NP-CGG with reduction of the GC reaction. B6 mice with lymphoid cell-specific deletion of NLRP3 or Casp1 mounted suboptimal humoral responses with impaired GC formation and defective affinity maturation. In MRL/lpr and NZM2328 mice, inhibition of NLRP3 activation suppressed NLRP3 activated Tfh cell expansion as well as attenuated lupus-like phenotypes. Tfh cells with activated NLRP3 inflammasome exhibited increased expression of molecules for Tfh cell function and differentiation, and had greater ability to activate B cells. In SLE patients, disease activity was positively correlated with an increase in the activated NLRP3+ Tfh population and this population was markedly reduced in response to therapy. CONCLUSIONS: The activation of NLRP3 inflammasome in Tfh cells is an integral part of responses to immunisation. The activated NLRP3+ Tfh population is essential for optimal humoral responses, GC formation and autoimmunity.

Activation of necroptosis pathway in podocyte contributes to the pathogenesis of focal segmental glomerular sclerosis.

BACKGROUND: Focal segmental glomerulosclerosis (FSGS) is characterized by podocyte damage and severe proteinuria. The exact mechanism of podocyte damage and loss remains unclear. Necroptosis, a lytic form of programmed cell death mediated by RIP3 and MLKL, has emerged as an important cell death pattern in multiple tissues and cell types. Necroptosis in FSGS has not been investigated. METHODS: Public GEO data regarding podocyte treated with vehicle or adriamycin (ADR) was identified and analyzed. Cultured human podocytes were used to explore the activation of necroptosis upon ADR stimulation. The expression of necroptosis pathway molecules, p-RIP3 and p-MLKL, was examined in the glomeruli and defoliated urinary podocytes of patients with FSGS. The effect of necroptosis inhibition was assessed in ADR-induced glomerulopathy mice using GSK872. RESULTS: Publicly available RNA-sequencing data analysis showed that both necroptosis and NLRP3 inflammasome pathway were up-regulated in ADR-injured podocyte. Immunofluorescent staining showed increased expression of p-RIP3 and p-MLKL, the active forms of RIP3 and MLKL, in podocytes of FSGS patients and ADR-induced glomerulopathy mice but not in the normal control. GSK872, an RIP3 kinase inhibitor, significantly inhibited the expression of p-RIP3, p-MLKL and activation of NLRP3 in cultured podocytes treated with ADR. GSK872 treatment of mice with ADR-induced nephropathy resulted in the reduced expression of p-RIP3, p-MLKL, NLRP3 and caspase-1 p20. GSK872 also significantly inhibited the expression of p-MLKL in the podocytes of ADR-induced nephropathy, resulting in the attenuation of proteinuria and renal histological lesions. CONCLUSION: Necroptosis pathway might be a valuable target for the treatment of FSGS.

Circulating TFH cells is correlated with disease activity in anti-MDA5 antibody positive idiopathic inflammatory myopathies.

OBJECTIVES: Idiopathic inflammatory myopathies (IIM) are a group of disorders characterised by the production of autoantibodies and inflammatory infiltrates in the skeletal muscles. Follicular T helper (TFH) cells are known to be crucial for B cell differentiation and autoantibody production in autoimmune diseases. The aim of this study was to investigate the involvement of TFH cells in IIM. METHODS: Circulating TFH cells in 44 IIM patients or 11 age- and gender-matched healthy controls (HCs) were measured by flow cytometry. ICOS, PD-1, active caspase-1 and Ki-67 expression in TFH cells was examined. The correlations between the frequency of TFH cells and clinical disease activities were also analysed. RESULTS: The frequency of TFH cells was 16.6% in IIM patients with anti-melanoma differentiation-associated gene (MDA5) antibody compared to 10.6% and 12.9% in anti-MDA5 negative patients or HCs, respectively (both p<0.05). The frequency of TFH cells was positively correlated with clinical disease activities: patient/parent's assessment VAS (r=0.51, p<0.05), physician's assessment VAS (r=0.59, p<0.05) and MYOACT scores (total systems: r=0.62, p<0.05; extramuscular system: r=0.56, p<0.05; pulmonary system, r=0.55, p<0.05). The percentage of PD-1highICOShigh TFH cells was 3.68% in anti-MDA5 positive patients compared to 2.70% and 1.96% in anti-MDA5 negative patients or HCs, respectively (both p<0.05). The percentage of Ki-67 positive TFH cells was 3.50% in anti-MDA5 positive patients compared to 2.36% and 1.76% in anti-MDA5 negative patients or HCs, respectively (p<0.05). Interestingly, active caspase-1 was significantly increased in TFH cells in anti-MDA5 positive patients compared to the patients without anti-MDA5 or HCs (3.30% vs. 1.67% and 3.30% vs. 1.02%, both p<0.001). CONCLUSIONS: These data suggest a role for TFH cells in the pathogenesis of anti-MDA5 positive IIM and TFH cells might serve as a disease biomarker for this subset of patients.

JAK/STAT signaling controls the fate of CD8+CD103+ tissue-resident memory T cell in lupus nephritis.

Autoimmune mediated inflammation and renal damage in lupus nephritis (LN) depends partly on the infiltration of lymphocytes in glomeruli and renal interstitium. Here we identified a population of CD8+ T cells with a CD103+-phenotype in the healthy kidneys of human and mouse. These cells were typically CD69+CD103+ tissue-resident memory T cells (TRM) in the kidney. CD8+ TRM cells were expanded in the kidneys of patients with LN or MRL/lpr mice. The expansion of renal CD8+ TRM cells correlated significantly with kidney disease activity. These cells were active in producing cytokines, perforin and granzyme B in the kidney of MRL/lpr mice. Importantly, renal CD8+ TRM cells underwent proliferation and self-renewal to maintain a stable TRM pool in the kidney of MRL/lpr mice, contributing to renal inflammation and damage. JAK/STAT signaling in the MRL/lpr mice was required for renal TRM self-renewal as well as maintenance of effector functions. Targeting JAK/STAT signaling by tofacitinib effectively suppressed effector functions and impaired the survival of renal TRM cells in the kidney, contributing to improved kidney function in MRL/lpr mice. These results provided evidences that renal CD8+ TRM cells play a role in the pathogenesis of LN. They could serve as a therapeutic target for LN.

Innate lymphoid cell disturbance with increase in ILC1 in systemic lupus erythematosus.

The innate lymphoid cell (ILC) is a group of effector cells with diverse important cellular functions in both health and disease states. In comparison with healthy controls, there were increases in circulating ILC in SLE patients. The proportion of ILC1 significantly increased with significant decreases of ILC2 in SLE patients and ILC3 in SLE patients with moderate to severe activity. IL-12, IL-18, IL-25, IL-33, IL-23, IL-1ß and IFN-γ were significantly increased in SLE patients. Moreover, IL-12, IL-18 and IL-1ß but not IFN-γ correlated significantly with SLEDAI. Successful treatments rapidly reduced them and with certain normalization of the ILC subsets. In addition to increases in ILC1 numbers, ~ 80% of the ILC1 in SLE patients were positive for synthesis of IFN-γ. Plasma from SLE patients were shown to be potent in inducing ILC1. Thus, increased circulating ILC1 might contribute to the pathogenesis of SLE through mounting type 1 immune response.

Pathogenesis of lupus nephritis: RIP3 dependent necroptosis and NLRP3 inflammasome activation.

RIP3 activation leads to activation of necroptosis and the NLRP3 inflammasome pathways. The activation of RIP3 in lupus nephritis (LN) has not been investigated. In this study, RIP3 and necroptosis pathway activations were demonstrated in podocytes in renal biopsies from patients with class IV LN and in the diseased kidneys from lupus-prone NZM2328 and MRL/lpr mice. RIP3 activation was accompanied with the activation of MLKL, the effector molecule of the necroptosis pathway, and activation of caspase-1, the effector of the NLRP3 inflammasome pathway. Podocyte activation of RIP3 was detected readily with the development of LN in NZM2328 mice, suggesting this activation may play a significant role in the pathogenesis of LN. GSK872, a RIP3 specific inhibitor, inhibited the development of LN in MRL/lpr mice with down-regulation of RIP3 activation in podocytes, decreased the splenic sizes and weights and anti-dsDNA antibody titers. IgG from pooled sera of diseased NZM2328 mice succumbing to LN induced both the necroptosis pathway and NLRP3 inflammasome activation in a podocyte cell line and this activation was specifically blocked by GSK872. These results indicate that the necroptosis pathway and the RIP3 dependent NLRP3 inflammasome pathway are activated in podocytes during LN. Inhibition of RIP3 kinase may be a novel therapeutic approach to treat LN and systemic lupus erythematosus (SLE).

RIP3 dependent NLRP3 inflammasome activation is implicated in acute lung injury in mice.

BACKGROUND: NLRP3 inflammasome is involved in the inflammatory responses during acute lung injury (ALI). RIP3 triggered NLRP3 inflammasome activation independent of necroptosis induction has recently been documented. In this study, the role of RIP3 in the activation of NLRP3 inflammasome in the development of ALI was investigated. METHODS: A selective RIP3 inhibitor GSK872 was used to investigate the roles of RIP3 in NLRP3 inflammasome activation in the lipopolysaccharide (LPS) induced ALI mouse model. The mechanism of NLRP3 inflammasome activation was investigated in the human monocytic cell line THP-1. NLRP3 inflammasome and necroptosis were measured by flow cytometry or western blot. RIP3-NLRP3 interaction was interrogated using immunoprecipitation and the Duolink® In situ detection. RESULTS: Significant upregulation of both necroptosis and NLRP3 inflammasome pathways were observed in the lungs of mice with LPS induced ALI. GSK872 significantly suppressed the activation of necroptosis and NLRP3 activation with reduction of IL-1ß and IL-18 production and inflammatory cells infiltration, resulting in a significant amelioration of lung injury. These two processes were shown to be active in interstitial macrophages and CD11b+ monocyte-macrophages/dendritic cells. In THP-1 cells, RIP3 and NLRP3 interaction was enhanced by LPS/ATP stimulation resulting in IL-1ß and IL-18 production. This RIP3-NLRP3 interaction was significantly inhibited by GSK872. CONCLUSION: Taking together, these results show that RIP3 participates in the NLRP3 inflammasome activation in infiltrating macrophages in ALI induced by LPS. This process plays a significant pathogenic role in LPS-induced lung injury.

The ratio of circulating follicular T helper cell to follicular T regulatory cell is correlated with disease activity in systemic lupus erythematosus.

Follicular T regulatory (Tfr) cells inhibit follicular T helper (Tfh) cells mediated B cell responses. Tfh cells are involved in the pathogenesis of systemic lupus erythematosus (SLE). However, the role of Tfr cells in SLE remains unclear. The frequency of circulating Tfr and Tfh cells were examined in SLE patients and healthy controls. The frequency of circulating Tfr cell decreased and Tfh/Tfr ratio increased in SLE patients. Serum anti-dsDNA antibody level positively correlated with frequency of Tfh cells and Tfh/Tfr ratios but negatively correlated with the frequency of Tfr cells. Moreover, the frequency of Tfr and Tfh/Tfr ratio but not that of Tfh was correlated with diseases activity. In addition, increase in Tfr cell numbers and decrease in the Tfh/Tfr ratios were observed with successful treatments. Thus, Tfr cells should be considered as a biomarker for SLE and their role in the pathogenesis of SLE warrants further investigation.

Anti-dsDNA antibodies bind to TLR4 and activate NLRP3 inflammasome in lupus monocytes/macrophages.

BACKGROUND: NLRP3 inflammasome has been implicated in the pathogenesis of systemic lupus erythematosus (SLE). The activation of NLRP3 inflammasome results in the production of IL-1ß and the subsequent inflammation. Anti-dsDNA antibodies (anti-dsDNA Abs) play critical roles in the development and progression of SLE. However, the mechanism of NLRP3 inflammasome activation in SLE is still not known. This study investigated the activation of NLRP3 inflammasome stimulated by anti-dsDNA Abs in monocytes/macrophages from SLE patients. METHODS: Monocytes/macrophages from SLE patients or healthy controls were stimulated with anti-dsDNA Ab-positive serum or purified anti-dsDNA Abs. Activation of inflammasome was measured by flow cytometry or Western blot. Anti-dsDNA Abs isolated from active SLE patients were injected into female (NZB × NZW) F1 mice and the activation of NLRP3 inflammasome and the frequencies of Th17 and Treg were examined. RESULTS: The activity of caspase-1 was significantly increased in active SLE patients and was correlated with serum levels of anti-dsDNA Abs and disease activities. The concentrations of IL-1ß and IL-17A were also significantly higher in SLE patients compared to healthy controls. Anti-dsDNA Ab-positive serum rather than healthy serum or RF (rheumatoid factor)-positive serum stimulated the activation of caspase-1 in monocytes. Anti-dsDNA Abs bound to TLR4 on macrophages and induced the production of ROS. Mitochondria-targeting antioxidant Mito-TEMPO, IκB kinase inhibitor peptide or TLR4 siRNA inhibited the activation of NLRP3 inflammasome and the secretion of IL-1ß induced by anti-dsDNA Abs. Injection of anti-dsDNA Abs into (NZB × NZW) F1 mice resulted in increased caspase-1 activation and production of IL-1ß and IL-17A. The Th17/Treg cell ratio also significantly increased following anti-dsDNA Ab injection. CONCLUSIONS: Anti-dsDNA Abs activated NLRP3 inflammasome in monocytes/macrophages from SLE patients by binding to TLR4 and inducing the production of mitochondrial ROS.

Myeloid-derived suppressor cells are proinflammatory and regulate collagen-induced arthritis through manipulating Th17 cell differentiation.

Myeloid-derived suppressor cells (MDSC) and Th17 cells were found to expand in collagen-induced arthritis (CIA) significantly. Two subsets of MDSC, polymorphonuclear (PMN) and mononuclear (MO), were detected and their ratios varied during the development of CIA. The depletion of MDSC in vivo resulted in suppression of T-cell proliferation and decreased IL-17A and IL-1ß production. The adoptive transfer of MDSC restored the severity of arthritis and Th17 cell differentiation. The depletion of MDSCs on day 35 resulted in arthritis amelioration without reaching a significant difference. Furthermore, MDSCs from CIA mice had higher production of IL-1ß and promoted Th17 cell differentiation. The expansion of MDSCs in the peripheral blood of rheumatoid arthritis (RA) patients was in correlation with increased Th17 cells and disease activity DAS28. These results support the hypothesis that MDSC may play a significant proinflammatory role in the pathogenesis of CIA and RA by inducing Th17 development in an IL-1ß-dependent manner.

Anti-dsDNA antibodies induce inflammation via endoplasmic reticulum stress in human mesangial cells.

BACKGROUND: Anti-dsDNA antibodies play an important role in the pathogenesis of lupus nephritis (LN). Endoplasmic reticulum (ER) stress is a physical reaction under stressful condition and can cause inflammation when stimulation is sustained. This study investigated the roles of ER stress in anti-dsDNA antibody-induced inflammation response in human mesangial cells (HMCs). METHOD: Anti-dsDNA antibodies isolated from LN patients were used to stimulate HMCs. The expression of GRP78, PERK, p-PERK, p-eIF2α, ATF4, p-IRE1α, ATF6 and CHOP in HMCs was measured by western blot. NF-κB activation was detected by examining nuclear translocation of NF-κB p65. The expression and production of IL-1ß, TNF-α and MCP-1 were examined by qPCR and ELISA. RESULTS: Flow cytometry and cellular ELISA showed that anti-dsDNA antibodies can bind to HMCs. The binding was not inhibited by blockage of Fc receptor. Anti-dsDNA antibody stimulation significantly enhanced the expression of GRP78, p-PERK, p-eIF2α and ATF4 in HMCs. However, no significant increase in the expression of p-IRE1α and ATF6 was found. In addition, anti-dsDNA antibodies also significantly increased the activation of NF-κB and upregulated the expression of IL-1ß, TNF-α and MCP-1, which were suppressed by pretreatment of HMCs with chemical ER stress inhibitor 4-PBA. Transfection of specific ATF4 siRNA also significantly reduced the activation of NF-κB and expression of proinflammatory cytokines. CONCLUSION: Anti-dsDNA antibodies induce NF-κB activation and inflammation in HMCs via PERK-eIF2α-ATF4 ER stress pathway.

Myeloid-derived suppressor cells contribute to bone erosion in collagen-induced arthritis by differentiating to osteoclasts.

Bone erosion is a sign of severe rheumatoid arthritis and osteoclasts play a major role in the bone resorption. Recently, myeloid-derived suppressor cells (MDSC) has been reported to be increased in collagen-induced arthritis (CIA). The number of circulating MDSCs is shown to correlate with rheumatoid arthritis. These findings suggest that MDSCs are precursor cells involved in bone erosion. In this study, MDSCs isolated from mice with CIA stimulated with M-CSF and RANKL in vitro expressed osteoclast markers and acquired osteoclast bone resorption function. MDSCs sorted from CIA mice were transferred into the tibia of normal DBA/1J mice and bones were subjected to histological and Micro CT analyses. The transferred CIA-MDSCs were shown to differentiate into TRAP(+) osteoclasts that were capable of bone resorption in vivo. MDSCs isolated from normal mice had more potent suppressor activity and much less capability to differentiate to osteoclast. Additional experiments showed that NF-κB inhibitor Bay 11-7082 or IκB inhibitor peptide blocked the differentiation of MDSCs to osteoclast and bone resorption. IL-1Ra also blocked this differentiation. In contrast, the addition of IL-1α further enhanced osteoclast differentiation and bone resorption. These results suggest that MDSCs are a source of osteoclast precursors and inflammatory cytokines such as IL-1, contributing significantly to erosive changes seen in rheumatoid arthritis and related disorders.

P2X7 blockade attenuates murine lupus nephritis by inhibiting activation of the NLRP3/ASC/caspase 1 pathway.

OBJECTIVE: The NLRP3 inflammasome plays key roles in inflammation and autoimmunity, and purinergic receptor P2X7 has been proposed to be upstream of NLRP3 activation. The aim of the present study, using murine models, was to investigate whether the P2X7 /NLRP3 inflammasome pathway contributes to the pathogenesis of lupus nephritis (LN). METHODS: MRL/lpr mice were treated with the selective P2X7 antagonist brilliant blue G (BBG) for 8 weeks. Following treatment, the severity of renal lesions, production of anti-double-stranded DNA (anti-dsDNA) antibodies, rate of survival, activation of the NLRP3/ASC/caspase 1 inflammasome pathway, and ratio of Th17 cells to Treg cells were evaluated. P2X7 -targeted small interfering RNA (siRNA) was also used for in vivo intervention. Similar evaluations were carried out in NZM2328 mice, a model of LN in which the disease was accelerated by administration of adenovirus-expressing interferon-α (AdIFNα). RESULTS: Significant up-regulation of P2X7 /NLRP3 inflammasome signaling molecules was detected in the kidneys of MLR/lpr mice as compared with normal control mice. Blockade of P2X7 activation by BBG suppressed NLRP3/ASC/caspase 1 assembly and the subsequent release of interleukin-1ß (IL-1ß), resulting in a significant reduction in the severity of nephritis and circulating anti-dsDNA antibodies. The lifespan of the treated mice was significantly prolonged. BBG treatment reduced the serum levels of IL-1ß and IL-17 and the Th17:Treg cell ratio. Similar results were obtained by specific siRNA silencing of P2X7 in vivo. The effectiveness of BBG treatment in modulating LN was confirmed in NZM2328 mice with AdIFNα-accelerated disease. CONCLUSION: Activation of the P2X7 signaling pathway accelerates murine LN by activating the NLRP3/ASC/caspase 1 inflammasome, resulting in increased IL-1ß production and enhanced Th17 cell polarization. Thus, targeting of the P2X7 /NLRP3 pathway should be considered as a novel therapeutic strategy in patients with lupus.

Serum procalcitonin and C-reactive protein for differentiating bacterial infection from disease activity in patients with systemic lupus erythematosus.

OBJECTIVE: To study the clinical value of procalcitonin (PCT) and C-reactive protein (CRP) in differentiating bacterial infection from disease activity in systemic lupus erythematosus (SLE) patients. METHOD: PCT and CRP in active SLE patients complicated with and without bacterial infection were retrospectively studied. Bacterial infection was diagnosed by positive culture results or typical symptoms and signs combined with positive response to antibiotics. Disease activity of SLE was assessed by systemic lupus erythematosus disease activity index (SLEDAI). RESULT: One hundred and fourteen active SLE patients were recruited, 47 of which were with bacterial infection and 67 were non-infected. PCT and CRP levels were significantly elevated in patients with bacterial infection (P < 0.05). The ideal cutoff value for PCT was 0.38 ng/ml, at which the sensitivity (74.5%) and specificity (95.5%) combined the best. The negative predictive value and positive predictive value to detect bacterial infection were 84.2% and 92.1%, respectively. PCT but not the CRP level in the septic patients was significantly higher than that of non-septic ones. Meanwhile, in patients with SLEDAI score of > 10, both PCT and CRP levels were higher in patients with bacterial infection, but the difference was only statistically significant for PCT (P < 0.05). PCT was significantly reduced after anti-bacterial treatment. CONCLUSION: PCT test is superior to CRP test in detecting superimposed bacterial infection in active SLE patients. The levels of PCT are correlated with the severity of bacterial infection and can be used to monitor the response to antibiotic treatment.

Metabolic dysregulation of lymphocytes in autoimmune diseases.

Lymphocytes are crucial for protective immunity against infection and cancers; however, immune dysregulation can lead to autoimmune diseases such as systemic lupus erythematosus (SLE) and rheumatoid arthritis (RA). Metabolic adaptation controls lymphocyte fate; thus, metabolic reprogramming can contribute to the pathogenesis of autoimmune diseases. Here, we summarize recent advances on how metabolic reprogramming determines the autoreactive and proinflammatory nature of lymphocytes in SLE and RA, unraveling molecular mechanisms and providing therapeutic targets for human autoimmune diseases.

VISTA Deficiency Exacerbates the Development of Pulmonary Fibrosis by Promoting Th17 Differentiation.

Background: Interstitial lung disease (ILD), characterized by pulmonary fibrosis (PF), represents the end-stage of various ILDs. The immune system plays an important role in the pathogenesis of PF. V-domain immunoglobulin suppressor of T-cell activation (VISTA) is an immune checkpoint with immune suppressive functions. However, its specific role in the development of PF and the underlying mechanisms remain to be elucidated. Methods: We assessed the expression of VISTA in CD4 T cells from patients with connective tissue disease-related interstitial lung disease (CTD-ILD). Spleen cells from wild-type (WT) or Vsir -/- mice were isolated and induced for cell differentiation in vitro. Additionally, primary lung fibroblasts were isolated and treated with interleukin-17A (IL-17A). Mice were challenged with bleomycin (BLM) following VISTA blockade or Vsir knockout. Moreover, WT or Vsir -/- CD4 T cells were transferred into Rag1 -/- mice, which were then challenged with BLM. Results: VISTA expression was decreased in CD4 T cells from patients with CTD-ILD. Vsir deficiency augmented T-helper 17 (Th17) cell differentiation in vitro. Furthermore, IL-17A enhanced the production of inflammatory cytokines, as well as the differentiation and migration of lung fibroblasts. Both VISTA blockade and knockout of Vsir increased the percentage of IL-17A-producing Th17 cells and promoted BLM-induced PF. In addition, mice receiving Vsir -/- CD4 T cells exhibited a higher percentage of Th17 cells and more severe PF compared to those receiving WT CD4 T cells. Conclusion: These findings demonstrate the significant role of VISTA in modulating the development of PF by controlling Th17 cell differentiation. These insights suggest that targeting VISTA could be a promising therapeutic strategy for PF.

TIGIT regulates CD4+ T cell immunity against polymicrobial sepsis.

Background: Sepsis is one of the major causes of death and increased health care burden in modern intensive care units. Immune checkpoints have been prompted to be key modulators of T cell activation, T cell tolerance and T cell exhaustion. This study was designed to investigate the role of the negative immune checkpoint, T cell immunoglobulin and ITIM domain (TIGIT), in the early stage of sepsis. Method: An experimental murine model of sepsis was developed by cecal ligation and puncture (CLP). TIGIT and CD155 expression in splenocytes at different time points were assessed using flow cytometry. And the phenotypes of TIGIT-deficient (TIGIT-/-) and wild-type (WT) mice were evaluated to explore the engagement of TIGIT in the acute phase of sepsis. In addition, the characteristics were also evaluated in the WT septic mice pretreated with anti-TIGIT antibody. TIGIT and CD155 expression in tissues was measured using real-time quantitative PCR and immunofluorescence staining. Proliferation and effector function of splenic immune cells were evaluated by flow cytometry. Clinical severity and tissue injury were scored to evaluate the function of TIGIT on sepsis. Additionally, tissue injury biomarkers in peripheral blood, as well as bacterial load in peritoneal lavage fluid and liver were also measured. Results: The expression of TIGIT in splenic T cells and NK cells was significantly elevated at 24 hours post CLP.TIGIT and CD155 mRNA levels were upregulated in sepsis-involved organs when mice were challenged with CLP. In CLP-induced sepsis, CD4+ T cells from TIGIT-/- mice shown increased proliferation potency and cytokine production when compared with that from WT mice. Meanwhile, innate immune system was mobilized in TIGIT-/- mice as indicated by increased proportion of neutrophils and macrophages with potent effector function. In addition, tissue injury and bacteria burden in the peritoneal cavity and liver was reduced in TIGIT-/- mice with CLP induced sepsis. Similar results were observed in mice treated with anti-TIGIT antibody. Conclusion: TIGIT modulates CD4+ T cell response against polymicrobial sepsis, suggesting that TIGIT could serve as a potential therapeutic target for sepsis.