Barry Ripley

IL-6 blockade inhibits the induction of myelin antigen-specific Th17 cells and Th1 cells in experimental autoimmune encephalomyelitis

The development of Th17 cells is a key event in the pathogenesis of experimental autoimmune encephalomyelitis (EAE), a murine model of human multiple sclerosis (MS). Previous studies have demonstrated that an IL-6-dependent pathway is involved in the differentiation of Th17 cells from naïve CD4-positive T cells in vitro. However, the role of IL-6 in vivo in the development of Th17 cells in EAE has remained unclear. In the present study, we found that IL-6 blockade by treatment with an anti-IL-6 receptor monoclonal antibody (anti-IL-6R mAb) inhibited the development of EAE and inhibited the induction of myelin oligodendrocyte glycoprotein (MOG) peptide-specific CD4-positive, CD8-positive, and Th17 T cells, in inguinal lymph nodes. Thus, the protective effect of IL-6 blockade in EAE is likely to be mediated via the inhibition of the development of MOG-peptide-specific Th17 cells and Th1 cells, which in turn leads to reduced infiltration of T cells into the CNS. These findings indicate that anti-IL-6R mAb treatment might represent a novel therapy for human MS.

Interleukin-6 blockade suppresses autoimmune arthritis in mice by the inhibition of inflammatory Th17 responses

OBJECTIVE To investigate the mechanism of interleukin-6 (IL-6) blockade in autoimmune arthritis, by comparing the effect of anti-IL-6 receptor (anti-IL-6R) monoclonal antibody (mAb) treatment with the effect of soluble tumor necrosis factor (sTNFR)-Fc fusion protein treatment on T helper cell differentiation in collagen-induced arthritis (CIA). METHODS DBA/1 mice were immunized with type II collagen (CII) to induce arthritis and were left untreated or were treated with anti-IL-6R mAb or TNFR-Fc. T helper cell differentiation and cytokine expression during the development of arthritis in these mice were analyzed. RESULTS Immunization with CII predominantly increased the frequency of Th17 cells rather than Th1 cells. The frequency of FoxP3+ Treg cells was also increased after immunization. Treatment of mice with CIA with anti-IL-6R mAb on day 0 markedly suppressed the induction of Th17 cells and arthritis development, but treatment with this antibody on day 14 failed to suppress both Th17 differentiation and arthritis. In contrast, treatment of mice with CIA with TNFR-Fc from day 0 to day 14 suppressed neither Th17 differentiation nor arthritis, but treatment from day 21 to day 35 successfully ameliorated arthritis without inhibiting Th17 induction. Neither antibody treatment increased the frequency of Treg cells. CONCLUSION Our results indicate that the protective effect of IL-6 blockade, but not tumor necrosis factor (TNF) blockade, in CIA correlates with the inhibition of Th17 differentiation. Our findings suggest that IL-6 blockade in rheumatoid arthritis in human is also likely to involve a therapeutic mechanism distinct from that of TNF blockade and thus may represent an alternative therapy for patients in whom the disease is refractory to TNF blockade.

The Influence of Excessive IL-6 Production In Vivo on the Development and Function of Foxp3+ Regulatory T Cells

IL-6 is a proinflammatory cytokine and its overproduction is implicated in a variety of inflammatory disorders. Recent in vitro analyses suggest that IL-6 is a key cytokine that determines the balance between Foxp3+ regulatory T cells (Tregs) and Th17 cells. However, it remains unclear whether excessive IL-6 production in vivo alters the development and function of Foxp3+ Tregs. In this study, we analyzed IL-6 transgenic (Tg) mice in which serum IL-6 levels are constitutively elevated. Interestingly, in IL-6 Tg mice, whereas peripheral lymphoid organs were enlarged, and T cells exhibited activated phenotype, Tregs were not reduced but rather increased compared with wild-type mice. In addition, Tregs from Tg mice normally suppressed proliferation of naive T cells in vitro. Furthermore, Tregs cotransferred with naive CD4 T cells into SCID–IL-6 Tg mice inhibited colitis as successfully as those transferred into control SCID mice. These results indicate that overproduction of IL-6 does not inhibit development or function of Foxp3+ Tregs in vivo. However, when naive CD4 T cells alone were transferred, Foxp3+ Tregs retrieved from SCID–IL-6 Tg mice were reduced compared with SCID mice. Moreover, the Helios− subpopulation of Foxp3+ Tregs, recently defined as extrathymic Tregs, was significantly reduced in IL-6 Tg mice compared with wild-type mice. Collectively, these results suggest that IL-6 overproduced in vivo inhibits inducible Treg generation from naive T cells, but does not affect the development and function of natural Tregs.

Arid5a controls IL-6 mRNA stability, which contributes to elevation of IL-6 level in vivo

Posttranscriptional regulation of IL-6 has been largely uncharacterized, with the exception of the ribonuclease Regnase-1, which prevents autoimmunity by destabilizing IL-6 mRNA. Here, we identified AT-rich interactive domain-containing protein 5A (Arid5a) as a unique RNA binding protein, which stabilizes IL-6 but not TNF-α mRNA through binding to the 3′ untranslated region of IL-6 mRNA. Arid5a was enhanced in macrophages in response to LPS, IL-1β, and IL-6. Arid5a deficiency inhibited elevation of IL-6 serum level in LPS-treated mice and suppressed IL-6 levels and the development of TH17 cells in experimental autoimmune encephalomyelitis. Importantly, Arid5a inhibited the destabilizing effect of Regnase-1 on IL-6 mRNA. These results indicate that Arid5a plays an important role in promotion of inflammatory processes and autoimmune diseases.

Enhanced expression of Annexin A4 in clear cell carcinoma of the ovary and its association with chemoresistance to carboplatin

Clear cell carcinoma (CCC) of the ovary is known to be highly resistant to platinum‐based chemotherapy. The purpose of our study was to identify a candidate protein that is associated with chemoresistance of CCC and to investigate the specific mechanism of chemoresistance conferred by the identified protein. Enhanced expression of Annexin A4 (Anx A4) was identified in ovarian CCC cells using 2‐D differential gel electrophoresis (2D‐DIGE) and mass spectrometry. Anx A4 levels were elevated in CCC cells compared with non‐CCC cells as determined by real‐time RT‐PCR and Western blot analysis. Immunohistochemical analysis of Anx A4 was performed in 126 epithelial ovarian cancer tissue samples and demonstrated significantly elevated levels of Anx A4 protein levels in ovarian CCC tumors compared with ovarian serous and endometrioid tumors (p < 0.01). Anx A4‐transfected ovarian non‐CCC cells were more resistant to carboplatin (IC50 = 42 μM) compared with control cells (IC50 = 23 μM) as determined by modified MTT assay. Intracellular platinum levels were significantly lower in Anx A4‐transfected cells compared with control cells after carboplatin treatment (p = 0.0020) and after an additional 360 min of carboplatin‐free incubation (p = 0.0004), as measured by atomic absorption spectrophotometry. Expression of Anx A4 is elevated in ovarian CCC tumors and is associated with chemoresistance in cultured ovarian cancer cells. These results demonstrate that Anx A4 confers chemoresistance in ovarian cancer cells in part by enhancing drug efflux. Thus, Anx A4 may represent a novel therapeutic target of chemoresistance in patients with ovarian CCC.

Overexpression of SOCS3 exhibits preclinical antitumor activity against malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis for which an effective therapy remains to be established. Our study investigated the therapeutic potential of the suppressor of cytokine signaling 3 (SOCS3), an endogenous inhibitor of intracellular signaling pathways, for treatment of MPM. We infected MPM cells (H226, EHMES‐1, MESO‐1 and MESO‐4) with an adenovirus‐expressing SOCS3 (AdSOCS3) to examine the effect of SOCS3 overexpression on MPM cells. SOCS3 overexpression reduced MPM proliferation and induced apoptosis and partial G0/G1 arrest. SOCS3 also inhibited the proliferation of MPM cells via multiple signaling pathways including Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3), extracellular signal‐regulated kinase (ERK), focal adhesion kinase (FAK) and p53 pathways. Notably, AdSOCS3 treatment inhibited tumor growth in an MPM pleural xenograft model. These findings demonstrate that overexpression of SOCS3 has a potent antitumor effect against MPM both in vitro and in vivo and indicate the potential for clinical use of SOCS3 for MPM treatment.

The aryl hydrocarbon receptor/microRNA-212/132 axis in T cells regulates IL-10 production to maintain intestinal homeostasis

Aryl hydrocarbon receptor (Ahr), a transcription factor, plays a critical role in autoimmune inflammation of the intestine. In addition, microRNAs (miRNAs), small non-coding oligonucleotides, mediate pathogenesis of inflammatory bowel diseases (IBD). However, the precise mechanism and interactions of these molecules in IBD pathogenesis have not yet been investigated. We analyzed the role of Ahr and Ahr-regulated miRNAs in colonic inflammation. Our results show that deficiency of Ahr in intestinal epithelial cells in mice exacerbated inflammation in dextran sodium sulfate-induced colitis. Deletion of Ahr in T cells attenuated colitis, which was manifested by suppressed Th17 cell infiltration into the lamina propria. Candidate miRNA analysis showed that induction of colitis elevated expression of the miR-212/132 cluster in the colon of wild-type mice, whereas in Ahr (-/-) mice, expression was clearly lower. Furthermore, miR-212/132(-/-) mice were highly resistant to colitis and had reduced levels of Th17 cells and elevated levels of IL-10-producing CD4(+) cells. In vitro analyses revealed that induction of type 1 regulatory T (Tr1) cells was significantly elevated in miR-212/132(-/-) T cells with increased c-Maf expression. Our findings emphasize the vital role of Ahr in intestinal homeostasis and suggest that inhibition of miR-212/132 represents a viable therapeutic strategy for treating colitis.

Arid5a regulates naive CD4+ T cell fate through selective stabilization of Stat3 mRNA

Masuda et al. show that Arid5a regulates the fate of naive CD4+ T cells to pro- or antiinflammatory T cells through selective stabilization of Stat3 mRNA under Th17-polarizing conditions.

Green tea polyphenol epigallocatechin gallate inhibits cell signaling by inducing SOCS1 gene expression

Therapeutic effects of green tea involve an inhibitory function of its constituent polyphenol epigallocatechin gallate (EGCG) on cell signaling. The specificity and mechanism(s) by which EGCG inhibits cell signaling have remained unclear. Here, we demonstrate that green tea and EGCG induce suppressor of cytokine signaling 1 (SOCS1) gene expression, a negative regulator of specific cell signaling pathways. In mouse immune cells, EGCG induces SOCS1 expression via an oxidative (superoxide) pathway and activation of the signal transducer and activator of transcription 5 transcription factor. EGCG inhibited SOCS1-regulated cell signaling, but this inhibitory effect was abrogated in cells deficient in SOCS1. These findings identify a mechanism by which EGCG inhibits cell signaling with specificity, mediated by induction of the negative regulator SOCS1.

SOCS‐1 gene delivery cooperates with cisplatin plus pemetrexed to exhibit preclinical antitumor activity against malignant pleural mesothelioma

Malignant pleural mesothelioma (MPM) is an aggressive tumor with poor prognosis for which an effective therapy remains to be established. This study investigated the therapeutic potential of gene delivery using suppressor of cytokine signaling 1 (SOCS‐1), an endogenous inhibitor of intracellular signaling pathways, for the treatment of MPM. We infected MPM cells (MESO‐4, H28 and H226) with adenovirus‐expressing SOCS‐1 vector to examine the effect of SOCS‐1 overexpression on MPM cells. We evaluated the antitumor effect of SOCS‐1 gene delivery combined with cisplatin plus pemetrexed by cell proliferation, apoptosis and invasion assay. We also investigated the regulation of NF‐κB and STAT3 signaling related to apoptotic pathways. Furthermore, we evaluated the inhibition of tumor growth by SOCS‐1 gene delivery combined with cisplatin plus pemetrexed in vivo. SOCS‐1 gene delivery cooperated with cisplatin plus pemetrexed to inhibit cell proliferation, invasiveness and induction of apoptosis in MPM cells. SOCS‐1 regulated NF‐κB and STAT3 signaling to induce apoptosis in MESO‐4 and H226 cells. Furthermore, SOCS‐1 gene delivery cooperated with cisplatin plus pemetrexed to regulate NF‐κB signaling and significantly inhibit tumor growth of MPM in vivo. These results suggest that SOCS‐1 gene delivery has a potent antitumor effect against MPM and a potential for clinical use in combination with cisplatin plus pemetrexed.