PPARgamma antagonists reverse the inhibition of neural antigen-specific Th1 response and experimental allergic encephalomyelitis by Ciglitazone and 15-deoxy-Delta12,14-prostaglandin J2.

Peroxisome proliferator-activated receptor-gamma is a nuclear receptor transcription factor that regulates cell growth, differentiation and homeostasis. PPARgamma agonists have been used to treat obesity, diabetes, cancer and inflammation and recent studies have shown the protective effects of PPARgamma agonists on experimental allergic encephalomyelitis (EAE), a Th1 cell-mediated autoimmune disease model of multiple sclerosis (MS). Our studies have further demonstrated that the PPARgamma agonists, 15d-PGJ2 and Ciglitazone, inhibit EAE through blocking IL-12 signaling leading to Th1 differentiation and the PPARgamma deficient heterozygous mice (PPARgamma+/-) or those treated with PPARgamma antagonists develop an exacerbated EAE in association with an augmented Th1 response. In this study, we show that the PPARgamma antagonists, Bisphenol A diglycidyl ether (BADGE) and 2-chloro-5-nitro-N-(4-pyridyl)benzamide (T0070907), reverse the inhibition of EAE by the PPARgamma agonists, Ciglitazone and 15-Deoxy-Delta(12,14)-Prostaglandin J2, in C57BL/6 wild-type and PPARgamma+/- mice. The reversal of EAE by BADGE and T0070907 was associated with restoration of neural antigen-induced T cell proliferation, IFNgamma production and Th1 differentiation inhibited by Ciglitazone and 15d-PGJ2. These results suggest that Ciglitazone and 15d-PGJ2 ameliorate EAE through PPARgamma-dependent mechanisms and further confirm a physiological role for PPARgamma in the regulation of CNS inflammation and demyelination in EAE.

Connecting the innate and adaptive immune responses in mouse choroidal neovascularization via the anaphylatoxin C5a and γδT-cells.

Neovascular age-related macular degeneration (AMD) is characterized by choroidal neovascularization (CNV). An overactive complement system is associated with AMD pathogenesis, and serum pro-inflammatory cytokines, including IL-17, are elevated in AMD patients. IL-17 is produced by complement C5a-receptor-expressing T-cells. In murine CNV, infiltrating γδT- rather than Th17-cells produce the IL-17 measurable in lesioned eyes. Here we asked whether C5a generated locally in response to CNV recruits IL-17-producing T-cells to the eye. CNV lesions were generated using laser photocoagulation and quantified by imaging; T-lymphocytes were characterized by QRT-PCR. CNV resulted in an increase in splenic IL-17-producing γδT- and Th17-cells; yet in the CNV eye, only elevated levels of γδT-cells were observed. Systemic administration of anti-C5- or anti-C5a-blocking antibodies blunted the CNV-induced production of splenic Th17- and γδT-cells, reduced CNV size and eliminated ocular γδT-cell infiltration. In ARPE-19 cell monolayers, IL-17 triggered a pro-inflammatory state; and splenocyte proliferation was elevated in response to ocular proteins. Thus, we demonstrated that CNV lesions trigger a systemic immune response, augmenting local ocular inflammation via the infiltration of IL-17-producing γδT-cells, which are presumably recruited to the eye in a C5a-dependent manner. Understanding the complexity of complement-mediated pathological mechanisms will aid in the development of an AMD treatment.

PPARgamma antagonists exacerbate neural antigen-specific Th1 response and experimental allergic encephalomyelitis.

Peroxisome proliferator-activated receptor-gamma is a nuclear receptor transcription factor that regulates cell growth, differentiation and homeostasis. PPARgamma agonists have been used in the treatment of obesity, diabetes, cancer and inflammation. We and others have shown recently that PPARgamma agonists ameliorate experimental allergic encephalomyelitis (EAE), a Th1 cell-mediated autoimmune disease model of multiple sclerosis (MS). We have further shown that PPARgamma agonists inhibit EAE through blocking IL-12 signaling leading to Th1 differentiation and the PPARgamma-deficient heterozygous mice (PPARgamma(+/-)) develop an exacerbated EAE. In this study, we show that in vivo treatment (i.p.) with 100 mug PPARgamma antagonists, Bisphenol A diglycidyl ether (BADGE) or 2-Chloro-5-nitro-N-(4-pyridyl)benzamide (T0070907), on every other day from day 0 to 30, increased the severity and duration of EAE in C57BL/6 wild-type and PPARgamma(+/-) mice. The exacerbation of EAE by PPARgamma antagonists associates with an augmented neural antigen-induced T cell proliferation, IFNgamma production or Th1 differentiation. These results further suggest that PPARgamma is a critical physiological regulator of CNS inflammation and demyelination in EAE.

1,25 Dihydroxyvitamin-D3 modulates JAK-STAT pathway in IL-12/IFNgamma axis leading to Th1 response in experimental allergic encephalomyelitis.

Experimental allergic encephalomyelitis (EAE) is a Th1 cell-mediated autoimmune disease model of multiple sclerosis (MS). Vitamin D deficiency is commonly observed in MS patients and vitamin D supplements reduce the clinical symptoms of EAE and MS. Earlier studies have shown that in vivo treatment with vitamin D analogs ameliorates EAE in association with the inhibition of IL-12 production and Th1 differentiation. The mechanisms in the regulation of Th1 response by vitamin D in EAE/MS are, however, not known. We show that in vivo treatment of C57BL/6 and SJL/J mice (i.p.) with 100 ng of 1,25 dihydroxyvitamin D3, on every other day from Day 0-30, ameliorates EAE in association with the inhibition of IL-12 production and neural antigen-specific Th1 response. In vitro treatment with 1,25(OH)2D3 inhibited IFNgamma-induced tyrosine phosphorylation of STAT1, without affecting JAK2, in EOC-20 microglial cells. Treatment of activated T cells with 1,25(OH)2D3 also inhibited the IL-12-induced tyrosine phosphorylation of JAK2, TYK2, STAT3, and STAT4 in association with a decrease in T cell proliferation in vitro. These findings highlight the fact that vitamin D modulates JAK-STAT signaling pathway in IL-12/IFNgamma axis leading to Th1 differentiation and further suggest its use in the treatment of MS and other Th1 cell-mediated autoimmune diseases.

Curcumin induces growth-arrest and apoptosis in association with the inhibition of constitutively active JAK-STAT pathway in T cell leukemia.

Adult T cell leukemia is an aggressive and frequently fatal malignancy that expressess constitutively activated growth-signaling pathways in association with deregulated growth and resistance to apoptosis. Curcumin (diferuloylmethane) is a naturally occurring yellow pigment, isolated from the rhizomes of the plant Curcuma longa that has traditionally been used in the treatment of injury and inflammation. But the effect and mechanism of action of curcumin on T cell leukemia is not known. To investigate the antitumor activity of curcumin in T cell leukemia, we examined its effect on constitutive phosphorylation of JAK and STAT proteins, proliferation, and apoptosis in HTLV-I-transformed T cell lines. HTLV-I-transformed T cell leukemia lines, MT-2, HuT-102, and SLB-1, express constitutively phosphorylated JAK3, TYK2, STAT3, and STAT5 signaling proteins. In vitro treatment with curcumin induced a dose-dependent decrease in JAK and STAT phosphorylation resulting in the induction of growth-arrest and apoptosis in T cell leukemia. The induction of growth-arrest and apoptosis in association with the blockade of constitutively active JAK-STAT pathway suggests this be a mechanism by which curcumin induces antitumor activity in T cell leukemia.

COX-2 inhibitors modulate IL-12 signaling through JAK-STAT pathway leading to Th1 response in experimental allergic encephalomyelitis.

Experimental allergic encephalomyelitis (EAE) is a Th1 cell-mediated autoimmune disease model of multiple sclerosis (MS). IL-12 plays a crucial role in the pathogenesis of EAE/MS and inhibition of IL-12 production or IL-12 signaling was effective in preventing EAE. Cyclooxygenase (COX-2) is a key enzyme promoting inflammation in rheumatoid arthritis and tumor induced angiogenesis. Recent studies have shown that COX-2 inhibitors prevent EAE, however, their mechanism of action is not fully understood. In this study, we show that in vivo treatment (i.p.) with 100 mug COX-2 selective inhibitors (LM01, LM08, LM11, and NS398), on every other day from day 0 to 30, significantly reduced the incidence and severity of EAE in SJL/J and C57BL/6 mice. Further analyses showed that the COX-2 inhibitors reduced neural antigen-induced IL-12 production, T cell proliferation and Th1 differentiation ex vivo and in vitro. The COX-2 inhibitors also decreased IL-12-induced T cell responses through blocking tyrosine phosphorylation of JAK2, TYK2, STAT3, and STAT4 proteins in T cells. These results demonstrate that COX-2 inhibitors ameliorate EAE in association with the modulation of IL-12 signaling through JAK-STAT pathway leading to Th1 differentiation and suggest their use in the treatment of MS and other Th1 cell-mediated autoimmune diseases.