CD8 T cell-derived perforin regulates macrophage-mediated inflammation in a murine model of gout.

OBJECTIVES: Gout is characterized by hyperuricemia and recurrent inflammatory episodes caused by intra-articular crystal deposition of monosodium urate (MSU). There is a clear relationship between gout and metabolic syndrome. Recent evidence indicates that perforin plays a role in regulating glucose homeostasis and provides protection in diet-induced non-alcoholic steatohepatitis models. However, the impact of perforin on immune inflammation in gout remains unclear. METHODS: We induced acute gout models in both wild-type (WT) mice and Prf1null mice by administering intra-articular injections of MSU crystals. We compared the ankle joint swelling and the histological score between the two groups. Furthermore, we investigated underlying mechanisms through in vitro co-culture experiments involving CD8 T cells and macrophages. RESULTS: In this study, Prf1null mice showed significantly more pronounced ankle swelling with increased inflammatory cell infiltrations compared with WT mice 24 h after local MSU injection. Moreover, MSU-induced Prf1null mice exhibited increased accumulation of CD8 T cells but not NK cells. Perforin-deficient CD8 T cells displayed reduced cytotoxicity towards bone marrow-derived M0 and M1 macrophages and promoted TNF-α secretion from macrophage. CONCLUSIONS: Perforin from CD8 T cells limits joint inflammation in mice with acute gout by downregulating macrophage-mediated inflammation. Key Points • Perforin deficiency increased swelling in the ankle joints of mice upon MSU injection. • Perforin deficiency is associated with increased immune cell recruitment and severe joint damage in gout. • Perforin regulated CD8 T cell accumulation in gout and promoted CD8 T cell cytotoxicity towards M0 and M1 macrophages. • CD8 T cell-derived perforin regulated pro-inflammatory cytokine secretion of macrophage.

Reduction of excessive unfolded protein response by 4-phenylbutyric acid may mitigate procymidone-induced testicular damage in mice by changing the levels of circRNA Scar and circZc3h4.

Procymidone (PCM) exposure below the no-observed-effect level triggers changes in circRNA Scar and circZc3h4 and overactivation of the unfolded protein response (UPR) in mice, culminating in testicular injury. The 4-phenyl butyric acid (4-PBA) is known to stabilize proteins and reduce the UPR. This study employed an in vitro system in which mouse testes were cultured with 1 × 10-5 M PCM and varying concentrations (0, 20, 40, and 80 mM) of 4-PBA; 4-week-old male mice were subsequently treated with 100 mg/kg/d PCM (suspended in corn oil) and/or 100 mg/kg/d 4-PBA for 21 d, consecutively. The treatments were as follows: the negative control (NC) group was orally administered corn oil; the positive control (PC) group was orally administered PCM; the 4-PBA group was intraperitoneally injected with 4-PBA; the 4-PBA-I group was orally administered PCM and 4-PBA simultaneously; the 4-PBA-II group received daily administration of 4-PBA 24 h prior to PCM; and the 4-PBA-III group was intraperitoneally injected with 4-PBA for 7 d after 21 d of PCM administration. However, the 4-PBA intervention groups showed no considerable changes in the overall or testicular appearance of mice. In vitro, 4-PBA inhibited the PCM-induced testicular injury, with the most significant effect observed at 80 mM. In vivo, the 4-PBA-III group exhibited the best in vivo effects. Our findings indicate that 4-PBA conferred testicular protection by decreasing PCM-induced circRNA Scar, elevating circZc3h4, and suppressing UPR both in vitro and in vivo. It has been hypothesized that 4-PBA mitigates testicular damage by reducing excessive UPR levels.

4-Phenylbutyric acid may prevent mouse ovarian and uterine damage due to procymidone-induced alteration of circRNA Scar and circZc3h4 levels by controlling excessive unfolded protein response.

Procymidone (PCM) below the no-observed-adverse-effect-level (NOAEL) has previously been proven to induce ovarian and uterine damage in adolescent mice due to its raised circRNA Scar, decreased circZc3h4, and overactivated unfolded protein response (UPR). Also, 4-phenylbutyric acid (4-PBA) inhibits histone deacetylase and endoplasmic reticulum stress, reduces UPR, improves metabolism, and ensures homeostasis within the endoplasmic reticulum. In this study, 20, 40 and 80 mM of 4-PBA were utilized respectively to intervene the damage caused by 1.0 × 10-5 M PCM to ovaries and uterus in vitro culture. Besides, 100 mg/kg /d 4-PBA was intraperitoneally injected to female adolescent mice before, during and after oral administration of 100 mg/kg /d PCM for prevention and cure to observe tissue changes in the ovaries and uteri, and levels of circRNA Scar, circZc3h4 and UPR members. Our findings demonstrated that in vitro experiments, all doses of 4-PBA could inhibit ovarian and uterine damage caused by PCM, and the effect of 80 mM was especially noticeable. In the in vivo experiments, the best results were obtained when PCM was given with simultaneous 4-PBA intervention, i.e., minimal ovarian and uterine damage. Both in vivo and in vitro, 4-PBA in the ovary and uterus resulted in decreased circRNA Scar levels, increased circZc3h4 abundance, and moderately elevated levels of UPR members. So, it is suggested that 4-PBA moderately activates UPR, partially or completely antagonizing the elevated circRNA Scar and decreased circZc3h4 and consequently preventing PCM-induced ovarian and uterine damage effectively in adolescent mice.

Impaired regulatory function of granzyme B-producing B cells against T cell inflammatory responses in lupus mice.

OBJECTIVE: Recently, a new subtype of granzyme B (GrB)-producing Breg cells has been identified, which was proven to be involved in autoimmune disease. Our recent report demonstrated that GrB-producing Breg cells were correlated with clinical and immunological features of SLE. However, the effect of GrB-producing Breg cells in lupus mice is unclear. METHODS: GrB expression in naïve and lupus mouse B cells was analysed using flow cytometry, PCR, ELISA and ELISpot assays. To study the role of GrB-producing B cells in a lupus model, GrB knockout (KO) and wild-type (WT) mice were intraperitoneally injected with monoclonal cells from the mutant mouse strain B6.C-H-2bm12 (bm12) for 2 weeks. In addition, the function of GrB-producing Breg cells in naïve and lupus mice was further explored using in vitro B cells-CD4+CD25- T cell co-culture assays with GrB blockade/KO of B cells. RESULTS: B cells from the spleens of WT C57BL/6 (B6) mice could express and secret GrB (p<0.001). GrB-producing Breg cells from WT mice showed their regulatory functions on CD4+CD25- T cell. While the frequency of GrB-producing Breg cells was significantly decreased (p=0.001) in lupus mice (p<0.001). Moreover, GrB-producing Breg cells in lupus mice failed to suppress T cell-mediated proinflammatory responses, partially due to the impaired capacity of downregulating the T cell receptor-zeta chain and inducing CD4+CD25- T cell apoptosis. CONCLUSION: This study further revealed the function and mechanism of GrB-producing Breg cells in regulating T cell homeostasis in lupus mice and highlighted GrB-producing Breg cells as a therapeutic target in SLE.

Clinical profiles differ in IgG4-related disease with and without allergy: a large case-control study in China.

OBJECTIVES: This study aimed to elucidate different clinical profiles in IgG4-related disease (IgG4-RD) with and without allergy. METHODS: Four hundred and thirty-four patients diagnosed with IgG4-RD at Peking University People's Hospital were included. Clinical and treatment options-based relapse data were collected and compared between IgG4-RD patients with and without allergy. RESULTS: Among these patients, 214 (49.3%) had allergic diseases. Most of the IgG4-RD patients with allergy had initial involved organs directly exposed to ambient air and their allergic symptoms occurred mostly before or at IgG4-RD disease onset. Compared with IgG4-RD patients without allergy, allergic patients had almost equal sex ratio, more organ involvement, earlier ages of disease onset and diagnosis, longer disease duration, higher incidence of dacryoadenitis, sialadenitis, lymphadenopathy, paranasal sinus and lung lesions. Higher serum IgG4, IgE and IgG4/IgG ratio, lower serum C3 complement 3 (C3) and C4, and higher incidence of eosinophilia were also found in IgG4-RD patients with allergy. Furthermore, allergy may increase relapse rate and shorten relapse-free survival time in IgG4-RD patients treated with glucocorticoids only, whereas combination therapy of glucocorticoids and immunosuppressants could improve treatment outcome. CONCLUSIONS: Allergy leads to disparities in clinical profiles in IgG4-RD patients. Allergy could result in higher relapse rate and shorten relapse-free survival time in patients receiving glucocorticoids only.

Decreased perforin-producing B cells correlate with systemic lupus erythematosus.

OBJECTIVES: It has been proved that B cells play indispensable roles in immunity via producing cytokines and secreting antibodies. Aberrant B cells are considered as the major participants in the pathogenesis of systemic lupus erythematosus (SLE). Recently, perforin (PFP)-producing B cell has been identified, serving as a new type of potential anti-tumour effector cells. However, the roles and characteristics of the PFP-producing B cells in SLE remain unclear. METHODS: The frequencies of PFP-producing B cells in peripheral blood of heathy controls (HC) and SLE patients were detected by flow cytometry, and their correlation with the patient clinical and immunological features were analysed. The capacities of these cells in producing PFP were also compared between HC and SLE by RT-qPCR and ELISpot analyses. RESULTS: In this study, we demonstrated that B cells could produce PFP and was further enhanced upon anti-BCR and IL-21 stimulation. In patients with SLE, the frequencies of these PFP-producing B cells were decreased and negatively correlated with the clinical characteristics. Further analysis revealed that SLE patients with vasculitis and pleurisy showed even lower frequencies of PFP-producing B cells. CONCLUSIONS: These findings revealed that B cells could produce PFP, and a decrease in these cells was associated with SLE pathogenesis.

Elevated expression of TAM receptor tyrosine kinase in synovial fluid and synovial tissue of rheumatoid arthritis.

To investigate the expression and roles of TAM (Tyro3/Axl/Mer) receptor tyrosine kinases (TK) in synovial fluid and synovial tissue of patients with rheumatoid arthritis (RA). The expression of TAM TKs in the synovial fluid and synovial tissues of RA and osteoarthritis (OA) patients was measured by ELISA and immunohistochemistry. The relationships between soluble TAM TKs (sTAM TKs) levels and the clinical features, laboratory parameters and disease activity were analyzed in RA. The concentrations of sTAM TK in the synovial fluids of RA patients were increased in comparison to those of OA patients. Compared with OA patients, the expression of membrane Tyro3 TK (mTyro3 TK) and mMer TK in RA patient synovial tissue were significantly increased, which may partly explain the possible mechanism of elevated levels of sTAM TK in RA patient synovial fluid. sAxl TK levels were decreased in RA patients under sulfasalazine treatment and elevated in patients under Iguratimod treatment. Furthermore, sTyro3 TK levels were positively correlated with erythrocyte sedimentation rate (ESR) and negatively correlated with white blood cells (WBCs), red blood cells (RBCs), and hemoglobin (HB) in RA patients. The levels of sMer TK were positively associated with disease duration and rheumatoid factor (RF) and negatively correlated with HB, complement 3 (C3), and C4. Taken together, TAM TKs might be involved in RA synovial tissue inflammation.

SR-A neutralizing antibody: potential drug candidate for ameliorating osteoclastogenesis in rheumatoid arthritis.

Rheumatoid arthritis (RA) is an autoimmune disease characterized by proliferative synovitis with deterioration of cartilage and bone. Osteoclasts (OCs) are the active participants in the bone destruction of RA. Although with great advances, most current therapeutic strategies for RA have limited effects on bone destruction. Macrophage scavenger receptor A (SR-A) is a class of pattern recognition receptors (PRRs) involved in bone metabolism and OC differentiation. More recently, our study revealed the critical role of SR-A in RA diagnosis and pathogenesis. Here, we further demonstrated that serum SR-A levels were positively correlated with bone destruction in patients with RA. Anti-SR-A neutralizing antibodies significantly inhibited OC differentiation and bone absorption in vitro in patients with RA, but not in healthy individuals, dampening the expression of OC-specific genes such as tartrate-resistant acid phosphatase (TRAP), cathepsin K (CTSK), and matrix metalloproteinase-9 (MMP-9). Similar results were also seen in collagen-induced arthritis (CIA) mice in vitro. Moreover, the anti-SR-A neutralizing antibody could further ameliorate osteoclastogenesis in vivo and ex vivo in CIA mice, accompanied by decreased serum levels of C-terminal telopeptide and IL-6, exhibiting potential protective effects. These results suggest that blockade of SR-A using anti-SR-A neutralizing antibodies might provide a promising therapeutic strategy for bone destruction in the RA.

Impaired granzyme B-producing regulatory B cells in systemic lupus erythematosus.

Granzyme B (GrB)-producing B cells are proposed to be a kind of regulatory B cells (Bregs) and have been revealed to be implicated in the pathogenesis of autoimmune diseases. Nevertheless, their role in SLE remains elusive. In this study, the frequencies of GrB-producing Bregs in peripheral blood of heathy control (HC) and systemic lupus erythematosus (SLE) were evaluated by flow cytometry, and their correlation with SLE patient clinical and immunological features were analyzed. The expression of GrB in HC and SLE B cells were also further detected by RT-qPCR analysis and ELISpot. The function of GrB-producing Bregs in HC and SLE patients was further investigated by in vitro CD4+ effector T cells-B cells co-culture assays with GrB blockade. We found that GrB-producing Bregs were significantly decreased in SLE patients and correlated with the clinical and immunological features. Moreover, these cells were functionally impaired under SLE circumstance. The negative correlation between GrB-producing Bregs and CD4+ T cells observed in healthy individuals disappeared in SLE patients. In vitro cell co-culture assay further showed that GrB-producing Bregs from SLE patients failed to suppress the Th1, Th2 and Th17 cell inflammatory responses, partially due to the dampened capacity of down-regulating TCR zeta and inducing T cell apoptosis. Taken together, these results revealed the disturbance of GrB-producing Bregs in SLE that might contribute to the disease initiation and progression.

Endoplasmic reticulum stress perpetuated toll-like receptor signalling-mediated inflammation in rheumatoid arthritis via X-box-binding protein-1.

OBJECTIVES: Multiple physiological and pathological conditions interfere with the function of the endoplasmic reticulum (ER). However, much remains unknown regarding the impact of ER stress on toll-like receptors (TLRs) -induced inflammatory responses in rheumatoid arthritis (RA). The aim of this study was to reveal the effects of ER stress and its regulator, X-box-binding protein-1 (XBP-1), on the inflammatory response of RA synovial fibroblasts (RASF) to different TLRs ligands. METHODS: ER stress was induced in RASF by incubating with thapsigargin (Tg). TLR2 ligand Pam3CSK4, TLR3 ligand PolyIC, TLR4 ligand LPS were used to stimulate the cells. Effects of ER stress on TLRs-induced inflammatory mediators were determined by using RT-PCR, qPCR and ELISA analysis. Western blots analysis was used to detected the signalling pathways in this process. For gene silencing experiment, control scrambled or XBP-1 specific siRNA were transfected into RASF. T helper (Th)1/Th17 cells expansion was determined by flow cytometry analysis, and IFN-γ/IL-17A production in supernatants were collected for ELISA assay. RESULTS: ER stress potentiated the expression of inflammatory cytokines, MMPs and VEGF in RASF stimulated by different TLRs ligands, which was companied with enhanced the activation of NF-κB and MAPKs signalling pathways. Silencing XBP-1 in RASF could dampen TLRs signalling-simulated inflammatory response under ER stress. Moreover, blockade of XBP-1 reduced the generation of Th1 and Th17 cells mediated by RASF, and suppressed the production of IFN-γ and IL-17A. CONCLUSIONS: Our findings suggest that ER stress and XBP-1 may function in conjunction with TLRs to drive the inflammation of RASF, and this pathway may serve as a therapeutic target for the disease.

CD14+CD16- monocytes are the main precursors of osteoclasts in rheumatoid arthritis via expressing Tyro3TK.

BACKGROUND: Monocytes as precursors of osteoclasts in rheumatoid arthritis (RA) are well demonstrated, while monocyte subsets in osteoclast formation are still controversial. Tyro3 tyrosine kinase (Tyro3TK) is a member of the receptor tyrosine kinase family involved in immune homeostasis, the role of which in osteoclast differentiation was reported recently. This study aimed to compare the osteoclastic capacity of CD14+CD16+ and CD14+CD16- monocytes in RA and determine the potential involvement of Tyro3TK in their osteoclastogenesis. METHODS: Osteoclasts were induced from CD14+CD16+ and CD14+CD16- monocyte subsets isolated from healthy control (HC) and RA patients in vitro and evaluated by tartrate-resistant acid phosphatase (TRAP) staining. Then, the expression of Tyro3TK on CD14+CD16+ and CD14+CD16- monocyte subsets in the peripheral blood of RA, osteoarthritis (OA) patients, and HC were evaluated by flow cytometry and qPCR, and their correlation with RA patient clinical and immunological features was analyzed. The role of Tyro3TK in CD14+CD16- monocyte-mediated osteoclastogenesis was further investigated by osteoclast differentiation assay with Tyro3TK blockade. RESULTS: The results revealed that CD14+CD16- monocytes were the primary source of osteoclasts. Compared with HC and OA patients, the expression of Tyro3TK on CD14+CD16- monocytes in RA patients was significantly upregulated and positively correlated with the disease manifestations, such as IgM level, tender joint count, and the disease activity score. Moreover, anti-Tyro3TK antibody could inhibit Gas6-mediated osteoclast differentiation from CD14+CD16- monocytes in a dose-dependent manner. CONCLUSIONS: These findings indicate that elevated Tyro3TK on CD14+CD16- monocytes serves as a critical signal for osteoclast differentiation in RA.

Scavenger receptor-A is a biomarker and effector of rheumatoid arthritis: A large-scale multicenter study.

Early diagnosis is critical to improve outcomes in rheumatoid arthritis (RA), but current diagnostic tools have limited sensitivity. Here we report a large-scale multicenter study involving training and validation cohorts of 3,262 participants. We show that serum levels of soluble scavenger receptor-A (sSR-A) are increased in patients with RA and correlate positively with clinical and immunological features of the disease. This discriminatory capacity of sSR-A is clinically valuable and complements the diagnosis for early stage and seronegative RA. sSR-A also has 15.97% prevalence in undifferentiated arthritis patients. Furthermore, administration of SR-A accelerates the onset of experimental arthritis in mice, whereas inhibition of SR-A ameliorates the disease pathogenesis. Together, these data identify sSR-A as a potential biomarker in diagnosis of RA, and targeting SR-A might be a therapeutic strategy.