Interleukin-18 induces angiogenic factors in rheumatoid arthritis synovial tissue fibroblasts via distinct signaling pathways

Objective Interleukin-18 (IL-18) is a proinflammatory cytokine implicated in the pathogenesis of rheumatoid arthritis (RA). This study was undertaken to examine the role of IL-18 in up-regulating secretion of the angiogenic factors stromal cell–derived factor 1Α (SDF-1Α)/CXCL12, monocyte chemoattractant protein 1 (MCP-1)/CCL2, and vascular endothelial growth factor (VEGF) in RA synovial tissue (ST) fibroblasts, and the underlying signaling mechanisms involved. Methods We used enzyme-linked immunosorbent assays, Western blotting, and chemical inhibitors/antisense oligodeoxynucleotides to signaling intermediates to assess the role of IL-18. Results IL-18 significantly enhanced the production of SDF-1Α/CXCL12, MCP-1/CCL2, and VEGF in RA ST fibroblasts, in a time- and concentration-dependent manner. IL-18–induced SDF-1Α/CXCL12 up-regulation was dependent on JNK, p38 MAPK, phosphatidylinositol 3-kinase (PI3K), and NFΚB. While IL-18–induced production of SDF-1Α/CXCL12 was also dependent on protein kinase CΔ (PKCΔ), production of MCP-1/CCL2 was dependent on PKCΑ, not PKCΔ. Additionally, RA ST fibroblast IL-18–induced MCP-1/CCL2 production was mediated by JNK, PI3K, and NFΚB. In contrast, IL-18 did not induce secretion of RA ST fibroblast MCP-1/CCL2 or VEGF via p38 MAPK. IL-18–induced RA ST fibroblast production of VEGF was mediated mainly by JNK-2, PKCΑ, and NFΚB. IL-18 induced phosphorylation of JNK, PKCΔ, p38 MAPK, and activating transcription factor 2 (ATF-2) in RA ST fibroblasts in a time-dependent manner, with JNK-2 being upstream of PKCΔ, ATF-2, and NFΚB. Conclusion These data support the notion that IL-18 has a unique role in inducing the secretion of angiogenic SDF-1Α/CXCL12, MCP-1/CCL2, and VEGF in RA ST fibroblasts, via distinct signaling intermediates.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/56041/1/22705_ftp.pd

Macrophage migration inhibitory factor: a mediator of matrix metalloproteinase-2 production in rheumatoid arthritis

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by destruction of bone and cartilage, which is mediated, in part, by synovial fibroblasts. Matrix metalloproteinases (MMPs) are a large family of proteolytic enzymes responsible for matrix degradation. Macrophage migration inhibitory factor (MIF) is a cytokine that induces the production of a large number of proinflammatory molecules and has an important role in the pathogenesis of RA by promoting inflammation and angiogenesis. In the present study, we determined the role of MIF in RA synovial fibroblast MMP production and the underlying signaling mechanisms. We found that MIF induces RA synovial fibroblast MMP-2 expression in a time-dependent and concentration-dependent manner. To elucidate the role of MIF in MMP-2 production, we produced zymosan-induced arthritis (ZIA) in MIF gene-deficient and wild-type mice. We found that MMP-2 protein levels were significantly decreased in MIF gene-deficient compared with wild-type mice joint homogenates. The expression of MMP-2 in ZIA was evaluated by immunohistochemistry (IHC). IHC revealed that MMP-2 is highly expressed in wild-type compared with MIF gene-deficient mice ZIA joints. Interestingly, synovial lining cells, endothelial cells, and sublining nonlymphoid mononuclear cells expressed MMP-2 in the ZIA synovium. Consistent with these results, in methylated BSA (mBSA) antigen-induced arthritis (AIA), a model of RA, enhanced MMP-2 expression was also observed in wild-type compared with MIF gene-deficient mice joints. To elucidate the signaling mechanisms in MIF-induced MMP-2 upregulation, RA synovial fibroblasts were stimulated with MIF in the presence of signaling inhibitors. We found that MIF-induced RA synovial fibroblast MMP-2 upregulation required the protein kinase C (PKC), c-jun N-terminal kinase (JNK), and Src signaling pathways. We studied the expression of MMP-2 in the presence of PKC isoform-specific inhibitors and found that the PKCδ inhibitor rottlerin inhibits MIF-induced RA synovial fibroblast MMP-2 production. Consistent with these results, MIF induced phosphorylation of JNK, PKCδ, and c-jun. These results indicate a potential novel role for MIF in tissue destruction in RA

Regulation of interleukin-1Β–induced chemokine production and matrix metalloproteinase 2 activation by epigallocatechin-3-gallate in rheumatoid arthritis synovial fibroblasts

Objective To evaluate the efficacy of epigallocatechin-3-gallate (EGCG), a potent antiinflammatory molecule, in regulating interleukin-1Β (IL-1Β)–induced production of the chemokines RANTES (CCL5), monocyte chemoattractant protein 1 (MCP-1/CCL2), epithelial neutrophil–activating peptide 78 (ENA-78/CXCL5), growth-regulated oncogene Α (GROΑ/CXCL1), and matrix metalloproteinase 2 (MMP-2) activity in rheumatoid arthritis (RA) synovial fibroblasts. Methods Fibroblasts obtained from RA synovium were grown, and conditioned medium was obtained. Cell viability was determined by MTT assay. RANTES, MCP-1, ENA-78, and GROΑ produced in culture supernatants were measured by enzyme-linked immunosorbent assay. MMP-2 activity was analyzed by gelatin zymography. Western blotting was used to study the phosphorylation of protein kinase C (PKC) isoforms and nuclear translocation of NF-ΚB. Results EGCG was nontoxic to RA synovial fibroblasts. Treatment with EGCG at 10 Μ M or 20 Μ M significantly inhibited IL-1Β–induced ENA-78, RANTES, and GROΑ, but not MCP-1 production in a concentration-dependent manner. EGCG at 50 Μ M caused a complete block of IL-1Β–induced production of RANTES, ENA-78, and GROΑ, and reduced production of MCP-1 by 48% ( P < 0.05). Zymography showed that EGCG blocked constitutive, IL-1Β–induced, and chemokine-mediated MMP-2 activity. Evaluation of signaling events revealed that EGCG preferentially blocked the phosphorylation of PKCΔ and inhibited the activation and nuclear translocation of NF-ΚB in IL-1Β–treated RA synovial fibroblasts. Conclusion These results suggest that EGCG may be of potential therapeutic value in inhibiting joint destruction in RA.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/55807/1/22023_ftp.pd

Systematic Review and the External Validity of Randomized Controlled Trials in Lupus Nephritis

Randomized controlled trials (RCTs) are considered the gold standard for assessing treatment efficacy. However, sampling bias can affect the generalization of results to routine clinical practice. Here we assessed whether patients with lupus nephritis (LN) seen in routine clinical practice would have satisfied entry criteria to the major published RCTs in LN. Methods: A systematic literature search from January 1974 to May 2015 was carried out, identifying all RCTs investigating LN induction treatment. Patients diagnosed with proliferative or membranous LN between 1995 and 2013 were identified from the Barts Lupus Centre database; baseline characteristics were compared with each RCT’s entry criteria to assess hypothetical inclusion or exclusion. Results: Of 363 articles, 33 RCTs met inclusion criteria. Of 137 patients newly diagnosed with LN (111 with proliferative/mixed proliferative and 26 with pure membranous LN), 32% would have been excluded from RCT entry (range 8%–73%). The main reasons for exclusion would have been too severe disease, too mild disease, or prior immunosuppressant use, which were exclusion criteria in 26, 20, and 22 RCTs, respectively. A total of 27 patients with LN (20%) were re-biopsied due to flare; 68% of these would have been ineligible to enter RCTs. Conclusion: Published RCTs do not truly reflect the heterogeneity of patients with LN in routine practice at our lupus center. The external validity of RCTs could be improved by including more representative patient cohorts. RCTs should be used as a guide but consideration should be given to similarities between individual patients and the characteristics of the trial cohorts before treatment decisions being made