RIPK1 inhibition attenuates experimental autoimmune arthritis via suppression of osteoclastogenesis.

BACKGROUND: Rheumatoid arthritis (RA) is a chronic and systemic inflammatory disease characterized by upregulation of inflammatory cell death and osteoclastogenesis. Necrostatin (NST)-1s is a chemical inhibitor of receptor-interacting serine/threonine-protein kinase (RIPK)1, which plays a role in necroptosis. METHODS: We investigated whether NST-1s decreases inflammatory cell death and inflammatory responses in a mouse model of collagen-induced arthritis (CIA). RESULTS: NST-1s decreased the progression of CIA and the synovial expression of proinflammatory cytokines. Moreover, NST-1s treatment decreased the expression of necroptosis mediators such as RIPK1, RIPK3, and mixed lineage kinase domain-like (MLKL). In addition, NST-1s decreased osteoclastogenesis in vitro and in vivo. NST-1s downregulated T helper (Th)1 and Th17 cell expression, but promoted Th2 and regulatory T (Treg) cell expression in CIA mice. CONCLUSIONS: These results suggest that NST-1s attenuates CIA progression via the inhibition of osteoclastogenesis and might be a potential therapeutic agent for RA therapy.

Correction: The anti-arthritis effect of sulforaphane, an activator of Nrf2, is associated with inhibition of both B cell differentiation and the production of inflammatory cytokines.

[This corrects the article DOI: 10.1371/journal.pone.0245986.].

The anti-arthritis effect of sulforaphane, an activator of Nrf2, is associated with inhibition of both B cell differentiation and the production of inflammatory cytokines.

Nuclear factor (erythroid-derived 2)-like 2 (Nrf2) is an important transcription factor that plays a pivotal role in cellular defense against oxidative injury. Nrf2 signaling is involved in attenuating autoimmune disorders such as rheumatoid arthritis (RA). B cells play several roles in the pathogenesis of RA, such as in autoantibody production, antigen presentation, and T-cell activation. We investigated the anti-arthritic mechanisms of sulforaphane, an activator of Nrf2, in terms of its effect on B cells. To investigate the effect of sulforaphane on collagen-induced arthritis (CIA), sulforaphane was administered intraperitoneally after CIA induction. Hematoxylin and eosin-stained sections were scored for inflammation, pannus invasion, and bone and cartilage damage. We assessed the expression levels of inflammation-related factors by real-time PCR and the levels of various IgG subclasses by enzyme-linked immunosorbent assay. Sulforaphane treatment reduced the arthritis score and the severity of histologic inflammation in CIA mice. The joints from sulforaphane-treated CIA mice showed decreased expression of interleukin (IL)-6, IL-17, tumor necrosis factor (TNF)-α, receptor activator of NF-κB ligand, and tartrate-resistant acid phosphatase. Sulforaphane-treated mice showed lower circulating levels of type-II-collagen-specific IgG, IgG1, and IgG2a. In vitro, sulforaphane treatment significantly reduced the differentiation of lipopolysaccharide-stimulated murine splenocytes into plasma B cells and germinal-center B cells. Finally, sulforaphane significantly inhibited the production of IL-6, TNF-α, and IL-17 by human peripheral blood mononuclear cells stimulated with an anti-CD3 monoclonal antibody in a dose-dependent manner. Inhibition of differentiation into plasma B and Germinal Center B cells may be the mechanism underlying the anti-arthritic effect of sulforaphane.

Combinatmarion treatment with Lactobacillus acidophilus LA-1, vitamin B, and curcumin ameliorates the progression of osteoarthritis by inhibiting the pro-inflammatory mediators.

Disease-modifying osteoarthritis (OA) therapy is not yet available. Several adjuvant therapies have demonstrated promising results in the treatment of OA. The present study aimed to investigate the therapeutic effects and underlying mechanisms of a combination of Lactobacillus acidophilus, vitamin B, and curcumin in the treatment of OA. Monosodium iodoacetate (MIA)-induced arthritis of the knee joint in rat was used as an animal model of human OA. The combination of L. acidophilus LA-1, vitamin B, and curcumin or a saline solution was given orally. Pain was measured according to the paw withdrawal latency, and paw withdrawal threshold. Cartilage destruction was analyzed using histomorphological techniques and the Mankin scoring system. Protein expression in the joint was examined using immunohistochemistry. The effects of the combination of L. acidophilus LA-1, vitamin B, and curcumin on mRNA levels in chondrocytes stimulated with interleukin (IL)-1ß were analyzed using real-time polymerase chain reaction. The combination of L. acidophilus, vitamin B, and curcumin effectively downregulated Th17 cells and the related cytokine IL-17, thereby maintained the Treg population, and increased the expression of the Treg-related cytokine IL-10 in human peripheral blood mononuclear cells. The OA animal model exhibited reduced pain and preservation of cartilage in response to the combination treatment. The expression levels of pro-inflammatory cytokines and the catabolic, matrix metalloproteinase-13 (MMP-13), were decreased, whereas the expression of the anabolic tissue inhibitors of metalloproteinases (TIMPs) were upregulated in response to the drug combination. The combination of L. acidophilus, vitamin B, and curcumin was beneficial in OA treatment, controlling the inflammatory response via regulation of the Th17/Treg population and reducing the expression of pro-inflammatory cytokines in human peripheral blood mononuclear cells. The combination treatment also preserved cartilage, suppressed osteoclastogenesis, and regulated the anabolic/catabolic imbalance. These findings indicate the therapeutic potential of combination use of L. acidophilus, vitamin B, and curcumin in patients with OA.

Interferon-gamma regulates inflammatory cell death by targeting necroptosis in experimental autoimmune arthritis.

Interferon γ (IFN-γ) induces an inflammatory response and apoptotic cell death. Rheumatoid arthritis (RA) is a systemic inflammatory disease associated with increased levels of inflammatory mediators, including tumour necrosis factor α (TNF-α) and T helper (Th) 17 cells, and downregulation of apoptosis of inflammatory cells. We hypothesized that IFN-γ would reduce inflammatory cell death in vitro and that loss of IFN-γ would aggravate inflammation in vivo. IFN-γ downregulated necroptosis and the expression of cellular FLICE-like inhibitory protein (cFLIPL) and mixed lineage kinase domain-like (MLKL). However, loss of IFN-γ promoted the production of cFLIPL and MLKL, and necroptosis. IFN-γ deficiency increased Th17 cell number and upregulated the expression of IL-17 and TNF-α. Expression of MLKL, receptor interacting protein kinase (RIPK)1, and RIPK3 was increased in the joints of mice with collagen-induced arthritis (CIA). Compared with wild-type mice with CIA, IFN-γ-/- CIA mice showed exacerbation of cartilage damage and joint inflammation, and acceleration of MLKL, RIPK1, and RIPK3 production in the joints. IFN-γ deficiency induced the activation of signal transducer and activator of transcription 3. These results suggest that IFN-γ regulates inflammatory cell death and may have potential for use in the treatment of RA.

IL-17 axis accelerates the inflammatory progression of obese in mice via TBK1 and IKBKE pathway.

Obesity mediates immune inflammatory response and induces IL-17 expression. Adipgenesis can be regulated by IL-17 and it causes TBK1 activation. The inhibition of TBK1 and the inhibition of I IKBKE reduces inflammatory response and improves obesity. It is hypothesized that IL-17 deficiency inhibits obesity progression and inflammation. 3T3-L1 preadipocytes were differentiated in vitro and treated with IL-17. RAW264.7 cells and differentiated 3T3-L1 were pretreated with TBK1 inhibitor and then stimulated with IL-17. Wild-type and IL-17 knock out mice were fed with high-fat diet. IL-17 inhibits adipocyte differentiation from mouse-derived 3T3-L1 preadipocytes and reduces mRNA expression of proadipogenic transcription factors and adipokines in adipocyte cells. IL-17 also showed up-regulation of mRNA levels of inflammatory cytokines in RAW cells. The inhibitor of TBK1 and IKBKE attenuates the effect of IL-17. Loss of IL-17 deficiency improves diet-induced obesity, fatty liver, glucose and lipid metabolism in mice. The expression of TBK1 and IKBKE decreased in the spleen and liver of IL-17 deficiency mice. Moreover, the inflammatory response within the visceral adipose tissue and Th1 cells were inhibited, however, M2 macrophage and Th2 cells increased in IL-17 deficiency mice. IL-17 inhibits adipogenesis where a lack of IL-17 ameliorates glucose metabolism. As well, the inhibition of TBK1 reduces inflammation induced by IL-17. Therefore, IL-17 may be involved in the development of obesity and metabolic dysfunction in a TBK1-dependent manner.

Ssu72 attenuates autoimmune arthritis via targeting of STAT3 signaling and Th17 activation.

Signal transducer and activator of transcription 3 (STAT3) orchestrates the differentiation of several cell types, including interleukin-17 (IL-17)-releasing Th17 cells. Dysregulation of Th17 cells results in chronic inflammatory responses. Ssu72 is a C-terminal domain phosphatase required for transcriptional regulation. However, the mechanism by which Ssu72 affects STAT3 activation and Th17 cell differentiation is unclear. Here, we found that Ssu72 overexpression suppresses STAT3 activation and Th17 cell responses in vitro. A systemic infusion of Ssu72 attenuates experimental autoimmune arthritis by reducing STAT3 activity and the differentiation of Th17 cells. It also reduces joint destruction, serum immunoglobulin concentrations and osteoclastogenesis but increases the number of marginal zone B cells and B10 cells. These effects are associated with reduced p-STAT3 levels and the suppression of Th17 cell formation in vivo. Based on these data, Ssu72 is related to STAT3 activation and the inflammatory response; and Ssu72 overexpression in T-cell-mediated immunity has potential utility for the treatment of autoimmune arthritis.