A novel JAK-STAT inhibitor, 2-[(3-Carbamoyl-2-thienyl)amino]-2-oxoethyl(2,6-dichlorophenyl)acetate, suppresses helper T cell differentiation in vitro and collagen-induced arthritis in vivo.

Th17 cells, which have been implicated in autoimmune diseases including rheumatoid arthritis (RA), require the JAK-STAT3 pathway for their differentiation and functions. Recently, JAK inhibitors have been developed as a therapeutic drug for RA. However, the current JAK inhibitors are not optimized to STAT3 compared with other STATs. In this study, we found a new lead compound of a small molecule JAK-STAT inhibitor, 2-[(3-Carbamoyl-2-thienyl)amino]-2-oxoethyl (2,6-dichlorophenyl)acetate, which inhibits STAT3 as efficiently as other STATs. This compound, named JI069, was selected by STAT3 reporter assay in combination with an in silico docking model. JI069 inhibited gp130 signaling by inducing dissociation between gp130 and JAK1. In HEK293T cells and primary T cells, JI069 suppressed STAT3 activation as efficiently as other STATs, including STAT1, STAT5, and STAT6. JI069 effectively suppressed Th1, Th2, and Th17 differentiation while strongly promoted iTreg differentiation. JI069 suppressed symptoms of the collagen-induced arthritis (CIA) model in mice, and inhibited the cytokine production from T cells as well as the STAT3 phosphorylation of synovial cells. These data suggest that JI069 is a new type of JAK inhibitor which has potential for the treatment of immunological disorders.

CDK inhibitors suppress Th17 and promote iTreg differentiation, and ameliorate experimental autoimmune encephalomyelitis in mice.

Th17 cells, which have been implicated in autoimmune diseases, require IL-6 and TGF-ß for early differentiation. Several Smad-independent pathways including the JNK and the RhoA-ROCK pathways have been implicated in the induction of RORγt, the master regulator of Th17, however, molecular mechanisms underlying Smad-independent pathway remain largely unknown. To identify novel pathways involved in Th17 differentiation, we screened 285 chemical inhibitors for known signaling pathways. Among them, we found that Kenpaullone, a GSK3-ß and CDK inhibitor, efficiently suppressed TGF-ß-mediated RORγt induction and enhanced Foxp3 induction in primary T cells. Another CDK inhibitor, Roscovitine, but not other GSK3-ß inhibitors, suppressed Th17 differentiation and enhanced iTreg development. Kenpaullone and Roscovitine suppressed experimental autoimmune encephalomyelitis (EAE), a typical Th17-mediated autoimmune disease model. These two compounds enhanced STAT5 phosphorylation and restored IL-2 production in the presence of TGF-ß. These data suggest that CDK inhibitors modulate TGF-ß-signaling pathways, which restore TGF-ß-mediated suppression of IL-2 production, thereby modifying the Th17/iTreg balance.

SOCS1 is essential for regulatory T cell functions by preventing loss of Foxp3 expression as well as IFN-{gamma} and IL-17A production.

Regulatory T cells (T(reg) cells) maintain immune homeostasis by limiting inflammatory responses. SOCS1 (suppressor of cytokine signaling 1), a negative regulator of cytokine signaling, is necessary for the suppressor functions of T(reg) cells in vivo, yet detailed mechanisms remain to be clarified. We found that Socs1(-/-) T(reg) cells produced high levels of IFN-γ and rapidly lost Foxp3 when transferred into Rag2(-/-) mice or cultured in vitro, even though the CNS2 (conserved noncoding DNA sequence 2) in the Foxp3 enhancer region was fully demethylated. Socs1(-/-) T(reg) cells showed hyperactivation of STAT1 and STAT3. Because Foxp3 expression was stable and STAT1 activation was at normal levels in Ifnγ(-/-)Socs1(-/-) T(reg) cells, the restriction of IFN-γ-STAT1 signaling by SOCS1 is suggested to be necessary for stable Foxp3 expression. However, Ifnγ(-/-)Socs1(-/-) T(reg) cells had hyperactivated STAT3 and higher IL-17A (IL-17) production compared with Ifnγ(-/-)Socs1(+/+) T(reg) cells and could not suppress colitis induced by naive T cells in Rag2(-/-) mice. In vitro experiments suggested that cytokines produced by Socs1(-/-) T(reg) cells and Ifnγ(-/-)Socs1(-/-) T(reg) cells modulated antigen-presenting cells for preferential Th1 and Th17 induction, respectively. We propose that SOCS1 plays important roles in T(reg) cell integrity and function by maintaining Foxp3 expression and by suppressing IFN-γ and IL-17 production driven by STAT1 and STAT3, respectively.

Pyridone 6, a pan-JAK inhibitor, ameliorates allergic skin inflammation of NC/Nga mice via suppression of Th2 and enhancement of Th17.

Atopic dermatitis (AD) is a common pruritic inflammatory disease triggered by a defective skin barrier and immunodysregulation. AD has been considered a typical example of a Th2 response associated with allergic disease. In the early phases of the disease, symptoms include IgE hyperproduction, eosinophil accumulation, and mast cell activation; in the chronic phase, a Th1-dominant immune response is also observed at the sites of AD skin lesions. The role of IL-17-producing Th (Th17) cells in AD has not been established. In the current study, we found that pyridone 6 (P6), a pan-JAK inhibitor, delayed the onset and reduced the magnitude of skin disease in an AD-like skin-disease model of NC/Nga mice. P6 reduced IFN-γ and IL-13, whereas it enhanced IL-17 and IL-22 expression. In vitro, P6 also inhibited both Th1 and Th2 development, whereas it promoted Th17 differentiation from naive T cells when present within a certain range of concentrations. This was probably because P6 strongly inhibited STAT1, STAT5, and STAT6 phosphorylation, whereas STAT3 phosphorylation was less efficiently suppressed by P6 at the same concentration. Furthermore, IL-22 protects keratinocytes from apoptosis induced by IFN-γ, and administration of IL-17 and IL-22 partially ameliorated skin diseases in NC/Nga mice. These results suggested that the JAK inhibitor P6 is therapeutic for AD by modulating the balance of Th2 and Th17.

Smad2 and Smad3 are redundantly essential for the TGF-beta-mediated regulation of regulatory T plasticity and Th1 development.

Although it has been well established that TGF-beta plays a pivotal role in immune regulation, the roles of its downstream transcription factors, Smad2 and Smad3, have not been fully clarified. Specifically, the function of Smad2 in the immune system has not been investigated because of the embryonic lethality of Smad2-deficient mice. In this study, we generated T cell-specific Smad2 conditional knockout (KO) mice and unexpectedly found that Smad2 and Smad3 were redundantly essential for TGF-beta-mediated induction of Foxp3-expressing regulatory T cells and suppression of IFN-gamma production in CD4(+) T cells. Consistent with these observations, Smad2/Smad3-double KO mice, but not single KO mice, developed fatal inflammatory diseases with higher IFN-gamma production and reduced Foxp3 expression in CD4(+) T cells at the periphery. Although it has been suggested that Foxp3 induction might underlie TGF-beta-mediated immunosuppression, TGF-beta still can suppress Th1 cell development in Foxp3-deficient T cells, suggesting that the Smad2/3 pathway inhibits Th1 cell development with Foxp3-independent mechanisms. We also found that Th17 cell development was reduced in Smad-deficient CD4(+) T cells because of higher production of Th17-inhibitory cytokines from these T cells. However, TGF-beta-mediated induction of RORgamma t, a master regulator of Th17 cell, was independent of both Smad2 and Smad3, suggesting that TGF-beta regulates Th17 development through Smad2/3-dependent and -independent mechanisms.

Tyrosine kinase inhibitor, methyl 2,5-dihydromethylcinnimate, induces PML nuclear body formation and apoptosis in tumor cells.

Promyelocytic leukemia (PML) nuclear bodies (PML-NBs) are the nuclear structure consisting of various proteins such as PML, SUMO-1, and p53. PML-NBs are implicated in the regulation of tumor suppression, antiviral responses, and apoptosis. In this study, we searched for bioactive metabolites that would promote the formation of PML-NBs in tumor cells. As a result, methyl 2,5-dihydromethylcinnimate (2,5-MeC), a tyrosine kinase inhibitor, enhanced expression and/or stability of PML proteins and induced PML-NB formation in p53 null H1299 cells established from non-small cell lung cancer (NSCLC) and wild-type p53-expressing U2OS cells derived from osteosarcoma. Furthermore, it enhanced apoptosis by exogenously expressed wild type p53 and the expression of p53-responsive genes, such as PUMA and p21, in H1299 cells. 2,5-MeC also activated endogenous p53 and induced apoptosis in U2OS cells. The results suggest that 2,5-MeC is likely to be a promising candidate drug for the clinical treatment of terminal cancer-expressing wild-type p53.