C6orf120 gene knockout in rats mitigates concanavalin A­induced autoimmune hepatitis via regulating NKT cells.

OBJECTIVE: To elucidate the role of the functional unknown gene C6orf120 in the pathogenesis of AIH and its mechanism of action, using C6orf120 knockout rats. METHODS: An autoimmune hepatitis model was established with 35 mg/kg intravenous injection of concanavalin A (Con A) in C6orf120-knockout (C6orf120-/-) and wild-type (WT) rats. Rats were sacrificed after administering Con A for 0, 12, and 24 h. The peripheral blood, liver, spleen, and mesenteric lymph nodes were collected for follow-up studies. RESULTS: C6orf120 knockout significantly decreased the serum levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and improved the histological damage in Con A-induced autoimmune liver injury.Loss of C6orf120 function significantly increased the frequency of CD3+ CD161+ NKT cells in the peripheral blood, liver, and spleen; downregulated the expression of CD314 (NKG2D) in the liver, spleen, and mesenteric lymph nodes; reduced the expression of inflammatory cytokines and chemokines; and suppressed the mRNA and protein expression of Fas and FasL in the liver. Additionally, C6orf120 knockout significantly downregulated the expression of p-JAK1, p-JAK2, p-STAT1, and p-STAT3 in liver tissue. CONCLUSION: The protective effect of C6orf120 knockout against Con A-induced hepatitis may be due to the inhibition of NKT cell activation, restriction of cytokine and chemokine activities, inhibition of JAK-STAT and Fas/FasL signaling pathway activation, and reduction in liver inflammation and hepatocyte apoptosis.

Cytokine signaling pathway in cystic fibrosis: expression of SOCS and STATs genes in different clinical phenotypes of the disease.

This was an observational cross-sectional study which was done to assess the expression profile of STATs and SOCS genes in cystic fibrosis. The mRNA was isolated from peripheral blood mononuclear cells of CF patients in exacerbation, colonization and post exacerbation phases of the disease. The relative gene expression level for SOCS 1, -3, -5 and STAT 1, -3,-4,-6 genes was quantified by Real-time PCR. The levels of IL-6 were also measured in the serum by ELISA. The expression of the Th1 pathway associated genes (SOCS1, SOCS5, STAT4 and STAT1) was downregulated while the expression of Th2/Th17 pathway genes (SOCS3, STAT3, STAT6) was upregulated in both exacerbation and colonization phases as compared to healthy controls. The serum levels of IL-6 were also elevated in both the disease groups. After antibiotic treatment, the expression of SOCS5 and STAT4 was increased while the expression of rest of the genes showed downregulation which shows a shift in immune response from Th2/Th17 to Th1. Our results suggest that infection alters the cytokine signaling pathway through modulation of STATs and SOCS genes which is not able to regulate the overstimulation of cytokine signaling further leading to chronic inflammation in CF.

Insights into the impact of Ivermectin on some protein aspects linked to Culex pipiens digestion and immunity.

In developing countries, low-cost control and treatment programs that offer combined approaches against diseases and their vectors are certainly needed. Ivermectin (IVM) has been well known for its role in the treatment of parasitic diseases, due to its effect on glutamate-gated chloride channels. These same channels are also present in the mosquito vector, and thus, research has focused on the insecticidal effects of this drug. Possible alternative mechanisms of IVM on the physiology of mosquitoes, however, have not been sufficiently elaborated. We assessed the protease activity, lipid peroxidation, and local expression of STAT, p53, caspase-3, and Bax markers to study the effect of this antibiotic on digestion and immunity in Culex pipiens. Sugar- and blood-feeding assays were employed to investigate the potential influence of blood feeding on the dynamics of these parameters. IVM was found to have an effect on protease activity, lipid peroxidation as well as the expression of different markers investigated in this work. The focus on the detailed effect of this drug certainly opens the gate to broadening the spectrum of IVM and expanding its health and economic benefit, especially that it is relatively more affordable than other antibiotics on the market.

Effects of 9-cis-retinoic acid on the proliferation and apoptosis of cutaneous T-cell lymphoma cells.

The vitamin A derivative 9-cis-retinoic acid (9-cis-RA) has been used for the treatment and prevention of cutaneous T-cell lymphoma (CTCL). However, the precise mechanism by which 9-cis-RA treatment ameliorates CTCL remains elusive. Our research shows that 9-cis-RA inhibits proliferation and induces apoptosis in CTCL cells in a dose-dependent and time-dependent manner. 9-Cis-RA also induced G0/G1 cell cycle arrest by downregulation of cyclin D1. We confirmed that 9-cis-RA significantly decreased phosphorylation of JAK1, STAT3, and STAT5 and downregulated Bcl-xL and cyclin D1, indicating that 9-cis-RA inhibited the activation of JAK/STAT signaling. Meanwhile, 9-cis-RA also activated classical RA-mediated transcription by retinoic acid receptors (RAR) and/or retinoid X receptors (RXR) in a CTCL cell line. Thus, 9-cis-RA may be effective for chemotherapy and may prevent human CTCL by inhibiting proliferation and inducing apoptosis by inhibition of the JAK/STAT pathway and activation of the RAR/RXR pathway.

Utility of Combined EZH2, p-ERK1/2, p-STAT, and MYC Expression in the Differential Diagnosis of EZH2-positive Hodgkin Lymphomas and Related Large B-Cell Lymphomas.

EZH2 is a methyltransferase that plays an important tumorigenic role in various neoplasms. We previously found that EZH2 is expressed in a range of aggressive B-cell lymphomas (ABCLs), T-cell lymphomas, and histiocytic neoplasms, with differential expression of intracellular signaling molecules p-ERK, MYC, and p-STAT3, potential regulators of EZH2 expression. We studied EZH2 expression in nodular lymphocyte predominant Hodgkin lymphoma (NLPHL), classic Hodgkin lymphoma (cHL), T-cell/histiocyte-rich large B-cell lymphoma (THRLBCL), and B-cell Lymphoma, unclassifiable, with features intermediate between diffuse large B-cell lymphomas and classic Hodgkin lymphoma (BCLu-DLBCL/cHL), as well as the coexpression of p-ERK, MYC, and p-STAT3 in these neoplasms. The neoplastic LP cells of NLPHL and Hodgkin/Reed-Sternberg cells of cHL were strongly positive for EZH2, as were the neoplastic cells in THRLBCL and BCLu-DLBCL/cHL. EZH2 expression correlated with proliferation rate, as assessed by Ki-67 staining. LP cells in NLPHL and Hodgkin/Reed-Sternberg cells in cHL were strongly positive for p-ERK, p-STAT3, and MYC, as were the neoplastic cells in THRLBCL and BCLu-DLBCL/cHL, in contrast to the differential expression of these molecules seen in ABCLs. These findings suggest that combined expression of p-ERK, MYC, and p-STAT3 is a useful immunohistochemical pattern for the diagnosis of EZH2-positive Hodgkin lymphomas and related lymphomas, in contrast to ABCLs. Furthermore, the overexpression of EZH2, in association with coexpression of tumorigenic signaling molecules, suggests an oncogenic role for this molecule in the development of Hodgkin lymphomas and related lymphomas. THRLBCL and BCLu-DLBCL/cHL appear to have a mechanism for the regulation of EZH2 expression that is similar to NLPHL and cHL and different from that of ABCLs. In addition, EZH2 and associated signaling cascades may serve as therapeutic targets for the treatment of Hodgkin lymphomas and related lymphomas.

Interferon Independent Non-Canonical STAT Activation and Virus Induced Inflammation.

Interferons (IFNs) are a group of secreted proteins that play critical roles in antiviral immunity, antitumor activity, activation of cytotoxic T cells, and modulation of host immune responses. IFNs are cytokines, and bind receptors on cell surfaces to trigger signal transduction. The major signaling pathway activated by IFNs is the JAK/STAT (Janus kinase/signal transducer and activator of transcription) pathway, a complex pathway involved in both viral and host survival strategies. On the one hand, viruses have evolved strategies to escape from antiviral host defenses evoked by IFN-activated JAK/STAT signaling. On the other hand, viruses have also evolved to exploit the JAK/STAT pathway to evoke activation of certain STATs that somehow promote viral pathogenesis. In this review, recent progress in our understanding of the virus-induced IFN-independent STAT signaling and its potential roles in viral induced inflammation and pathogenesis are summarized in detail, and perspectives are provided.

Nickel Sulfate Promotes IL-17A Producing CD4+ T Cells by an IL-23-Dependent Mechanism Regulated by TLR4 and Jak-STAT Pathways.

Allergic contact dermatitis, caused by nickel, is a delayed-type hypersensitivity reaction, and 14.5% of the general population may be affected in Europe. Among a wide range of cytokines, the IL-12 family has unique structural and immunological characteristics. Whereas IL-12p70 promotes T helper (Th) 1 cell polarization, IL-23 promotes Th17 cell development and both have been isolated from nickel-allergic patients. In this work, we were interested in understanding the mechanism behind nickel-induced Th17 cell development. We showed that nickel induced an early production of IL-23 in human monocyte-derived dendritic cells along with an increase in the expression of il-23p19 and il-12p40 mRNA. However, the production of a significant level of IL-12p70 required an additional signal such as IFN-γ. Moreover, nickel-treated monocyte-derived dendritic cells induced an increase in the percentage of IL-17A+ CD4+ T cells, an effect reduced by IL-23 neutralization. We then investigated the molecular mechanism of IL-23 production. Our results showed that toll-like receptor 4, p38 mitogen-activated protein kinase, and NF-κB were involved in IL-23 production induced by nickel. However, Jak-signal transducer and activator of transcription activation seems to maintain the IL-23/IL-12p70 balance by limiting IL-23 production and promoting Th1 polarization. These results indicate that nickel-induced Th17 cell development is dependent on the production of IL-23 by human monocyte-derived dendritic cells via toll-like receptor 4, p38 mitogen-activated protein kinase, NF-κB, and Jak-signal transducer and activator of transcription pathways.

Interleukin-17 upregulates vascular endothelial growth factor by activating the JAK/STAT pathway in nucleus pulposus cells.

OBJECTIVES: Intervertebral disc (IVD) related diseases and age-related IVD degeneration are responsible for significant morbidity. Inflammatory mediators and pro-inflammatory cytokines, including interleukin (IL)-17, show elevated expression in degenerated disc tissue. IL-17 is reported to transduce signals across the cell membrane predominantly via the Janus kinase/signal transducer and activator of transcription (JAK/STAT) signal transduction pathway, leading to transcriptional activation of target genes. METHODS: In this study, we investigated whether the JAK/STAT pathway plays a role in IL-17-mediated signaling in the nucleus pulposus (NP) cells of IVDs. Vascular endothelial growth factor (VEGF) and IL-17 were found to be highly expressed in human degenerated NP tissue. In isolated rat NP cells, IL-17-induced VEGF expression in a time- and dose-dependent manner. Rat NP cells were co-transfected with VEGF promoter plasmid along with constitutively active STAT1, STAT3 or JAK2 plasmid. VEGF promoter activity was found to be increased by STAT1, STAT3 and JAK2 in IL-17-treated cells. Transfection of cultured rat NP cells with STAT1 or STAT3 lentiviral short hairpin RNAs or treatment with the JAK2 inhibitor AG490 significantly reduced IL-17-stimulated VEGF expression. CONCLUSIONS: IL-17 upregulated VEGF expression in rat NP cells mediated by the JAK/STAT pathway, and elevated levels of IL-17 and VEGF are present in human degenerated NP tissue. These findings provide new insight into the pathology of IVD degeneration.

Eriobotrya japonica Water Extract Characterization: An Inducer of Interferon-Gamma Production Mainly by the JAK-STAT Pathway.

Eriobotrya japonica (Thunb.) Lindl. (Loquat) (EJ) has been used as a medicinal plant to treat chronic bronchitis, coughs, phlegm, high fever and gastro-enteric disorders. Since the traditional use of EJ is related to modulating inflammation processes, our earlier studies on EJ leaves were performed on the water extract to investigate specific cytokines' modulation. These earlier studies, however, have shown that EJ leaf water extract (WE) and the water phase (WP) induce cytokines' production in in vitro and in vivo models. Therefore, the aim of this study was to specify the group(s) of compounds in EJ leaves that have this immunomodulatory activity and their mechanism of action. WE was obtained from boiling the leaves followed by butanol extraction, yielding a butanol-water phase (WP). WP was then subjected to methanol:acetone fractionation, yielding upper (MAU) and lower (MAL) phases. For further fractionation, MAU was subjected to column chromatography followed by elution with ethanol:water (EW), methanol:ethanol (ME) and, lastly, acetone:water (AW), respectively, to reveal three sub-fractions; MAU-EW, MAU-ME and MAU-AW. MAU-AW significantly increased IFN-γ production from unstimulated and stimulated mouse spleen cells, as well as CD3+ T cells and natural killer cells. Furthermore, the fold increase of IFN-γ production by MAU-AW was concentration dependent, higher than the parent extract or any of the other sub-fractions, and such an IFN-γ increase was reversed by two JAK-STAT inhibitors. In addition, MALDI-TOF-MS analysis of the extracts and sub-fractions showed compounds with molecular weights of >500 Daltons. The MAU-AW sub-fraction contained more polar compounds, such as flavonol and caffeic glycosides. In conclusion, these polar compounds in the EJ extract are responsible for inducing IFN-γ production. Further chemical elucidation is warranted to lead to a specific IFN-γ inducer and an immunomodulator in polarizing immune cells and balancing immune responses in certain diseases.

Honokiol inhibits sphere formation and xenograft growth of oral cancer side population cells accompanied with JAK/STAT signaling pathway suppression and apoptosis induction.

BACKGROUND: Eliminating cancer stem cells (CSCs) has been suggested for prevention of tumor recurrence and metastasis. Honokiol, an active compound of Magnolia officinalis, had been proposed to be a potential candidate drug for cancer treatment. We explored its effects on the elimination of oral CSCs both in vitro and in vivo. METHODS: By using the Hoechst side population (SP) technique, CSCs-like SP cells were isolated from human oral squamous cell carcinoma (OSCC) cell lines, SAS and OECM-1. Effects of honokiol on the apoptosis and signaling pathways of SP-derived spheres were examined by Annexin V/Propidium iodide staining and Western blotting, respectively. The in vivo effectiveness was examined by xenograft mouse model and immunohistochemical tissue staining. RESULTS: The SP cells possessed higher stemness marker expression (ABCG2, Ep-CAM, Oct-4 and Nestin), clonogenicity, sphere formation capacity as well as tumorigenicity when compared to the parental cells. Treatment of these SP-derived spheres with honokiol resulted in apoptosis induction via Bax/Bcl-2 and caspase-3-dependent pathway. This apoptosis induction was associated with marked suppression of JAK2/STAT3, Akt and Erk signaling pathways in honokiol-treated SAS spheres. Consistent with its effect on JAK2/STAT3 suppression, honokiol also markedly inhibited IL-6-mediated migration of SAS cells. Accordingly, honokiol dose-dependently inhibited the growth of SAS SP xenograft and markedly reduced the immunohistochemical staining of PCNA and endothelial marker CD31 in the xenograft tumor. CONCLUSIONS: Honokiol suppressed the sphere formation and xenograft growth of oral CSC-like cells in association with apoptosis induction and inhibition of survival/proliferation signaling pathways as well as angiogenesis. These results suggest its potential as an integrative medicine for combating oral cancer through targeting on CSCs.

Decreased expression of pSTAT, IRF-1 and DAP10 signalling molecules in peripheral blood lymphocytes of patients with metastatic melanoma.

AIMS: As numerous signalling molecules regulate effector functions of peripheral blood lymphocytes (PBLs) that have an important anti-tumour activity, the aim of this study was to analyse their level in patients with metastatic melanoma (MM) compared with healthy controls (HCs). METHODS: Peripheral blood mononuclear cells (PBMCs) of 36 MMs and 28 HCs were analysed for the level of perforin, interferon-regulating transcription factor-1 (IRF-1), DAP10 and Src homology 2 domain-containing tyrosine phosphatase-1 by reverse transcriptase PCR, level of phosphorylated signal transducers and activators of transcription (pSTAT)-1, pSTAT-4, pSTAT-5 by western blot and interferon (IFN)-γ production by ELISA. The expression of activating NKG2D and inhibitory killer immunoglobulin-like receptors (KIR), CD158a and CD158b, on PBL, CD3-CD56+ natural killer (NK) cells and CD3+CD8+ cytotoxic T lymphocytes (CTLs), as well as the percentage of CD14+HLA-DR- cells in PBMC were estimated by flow cytometry. RESULTS: Patients with MM, compared with HCs, had significantly lower level of cytotoxic molecule perforin and decreased IFN-γ production, as well as lower level of pSTAT-1, pSTAT-4, pSTAT-5 and IRF-1 signalling molecules in PBMC. Furthermore, MM had decreased expression of activating NKG2D receptor on PBL and NK cells and low level of its DAP10 signalling molecule contrary to no changes in KIR expression on all investigated cells. These results could be associated with increased percentage of immunosuppressive CD14+HLA-DR- myeloid-derived suppressor cells detected in patients with MM. CONCLUSIONS: The altered signalling molecules of PBL could represent biomarkers of impaired cytotoxic and immunoregulatory function of these cells, indicating melanoma-associated immunosuppression that facilitates tumour progression.

The overexpression of Thioredoxin-1 suppressing inflammation induced by methamphetamine in spleen.

BACKGROUND: Methamphetamine (METH) is an addictive psychostimulant and has been shown to induce oxidative stress and inflammation in various tissues. Thioredoxin-1 (Trx-1) plays the roles in regulating redox and inhibiting inflammation. Whether Trx-1 is involved in METH-induced inflammation is still unknown. METHODS: The present study was designed to investigate inflammatory factors in spleen of wild type and Trx-1 overexpression transgenic mice after METH treatment. RESULTS: We found the mRNA level of Trx-1 was decreased and mRNA level of Trx-1 binding protein-2 (TBP-2) was increased. The mRNA levels of tumor necrosis factor-α (TNF-α), interferon-γ(IFN-γ), interleukin-2 (IL-2), T-bet and signal transducer and activators of transcription 4 (STAT 4) were increased and the mRNA levels of IL-10, GA-TA-binding protein-3 (GATA-3) and STAT 6 were decreased. Overexpression of Trx-1 reversed the above effects induced by METH. CONCLUSION: The present study showed for the first time that Trx-1 overexpression suppressed the inflammation induced by METH.

Retinoic acid amide inhibits JAK/STAT pathway in lung cancer which leads to apoptosis.

Small cell lung cancer (SCLC) accounts for 12 to 16% of lung neoplasms and has a high rate of metastasis. The present study demonstrates the antiproliferative effect of retinoic acid amide in vitro and in vivo against human lung cancer cells. The results from MTT assay showed a significant growth inhibition of six tested lung cancer cell lines and inhibition of clonogenic growth at 30 µM. Retinoic acid amide also leads to G2/M-phase cell cycle arrest and apoptosis of lung cancer cells. It caused inhibition of JAK2, STAT3, and STAT5, increased the level of p21WAF1, and decreased cyclin A, cyclin B1, and Bcl-XL expression. Retinoic acid amide exhibited a synergistic effect on antiproliferative effects of methotrexate in lung cancer cells. In lung tumor xenografts, the tumor volume was decreased by 82.4% compared to controls. The retinoic acid amide-treated tumors showed inhibition of JAK2/STAT3 activation and Bcl-XL expression. There was also increase in expression of caspase-3 and caspase-9 in tumors on treatment with retinoic acid amide. Thus, retinoic acid amide exhibits promising antiproliferative effects against human lung cancer cells in vitro and in vivo and enhances the antiproliferative effect of methotrexate.

Coordinate regulation of stem cell competition by Slit-Robo and JAK-STAT signaling in the Drosophila testis.

Stem cells in tissues reside in and receive signals from local microenvironments called niches. Understanding how multiple signals within niches integrate to control stem cell function is challenging. The Drosophila testis stem cell niche consists of somatic hub cells that maintain both germline stem cells and somatic cyst stem cells (CySCs). Here, we show a role for the axon guidance pathway Slit-Roundabout (Robo) in the testis niche. The ligand Slit is expressed specifically in hub cells while its receptor, Roundabout 2 (Robo2), is required in CySCs in order for them to compete for occupancy in the niche. CySCs also require the Slit-Robo effector Abelson tyrosine kinase (Abl) to prevent over-adhesion of CySCs to the niche, and CySCs mutant for Abl outcompete wild type CySCs for niche occupancy. Both Robo2 and Abl phenotypes can be rescued through modulation of adherens junction components, suggesting that the two work together to balance CySC adhesion levels. Interestingly, expression of Robo2 requires JAK-STAT signaling, an important maintenance pathway for both germline and cyst stem cells in the testis. Our work indicates that Slit-Robo signaling affects stem cell function downstream of the JAK-STAT pathway by controlling the ability of stem cells to compete for occupancy in their niche.

Rabaptin-5 and Rabex-5 are neoplastic tumour suppressor genes that interact to modulate Rab5 dynamics in Drosophila melanogaster.

Endocytosis plays an important role in the regulation of tumour growth and metastasis. In Drosophila, a number of endocytic neoplastic tumour suppressor genes have been identified that when mutated cause epithelial disruption and over-proliferation. Here we characterise the Drosophila homologue of the Rab5 effector Rabaptin-5, and show that it is a novel neoplastic tumour suppressor. Its ability to bind Rab5 and modulate early endosomal dynamics is conserved in Drosophila, as is its interaction with the Rab5 GEF Rabex5, for which we also demonstrate neoplastic tumour suppressor characteristics. Surprisingly, we do not observe disruption of apico-basal polarity in Rabaptin-5 and Rabex-5 mutant tissues; instead the tumour phenotype is associated with upregulation of Jun N-terminal Kinase (JNK) and Janus Kinase (JAK)/Signal Transducer and Activator of Transcription (STAT) signalling.

ß-Escin sodium inhibits inducible nitric oxide synthase expression via downregulation of the JAK/STAT pathway in A549 cells.

ß-escin, a triterpene saponin, is one of the major active compounds extracted from horse chestnut (Aesculus hippocastanum) seed. Previous work has found that ß-escin sodium has antiinflammatory and antitumor effects. In the present study, we investigated its effect on cell proliferation and inducible nitric-oxide synthase (iNOS) expression in human lung carcinoma A549 cells. ß-escin sodium (5-40 µg/mL) inhibited cytokine mixture (CM)-induced nitric oxide (NO) production in A549 cells by reducing the expression of iNOS. ß-escin sodium suppressed phosphorylation and nuclear translocation of STAT1 (Tyr701) and STAT3 (Tyr705) induced by CM but did not affect the activation of c-Jun and NF-κB. ß-escin sodium inhibited the activation of protein tyrosine kinase JAK2. Pervanadate treatment reversed the ß-escin sodium-induced downregulation of STAT3 and STAT1. ß-escin sodium treatment enhanced an activating phosphorylation of the phosphatase SHP2. Small interfering RNA-mediated knockdown of SHP2 inhibited ß-escin sodium-induced phospho-STAT dephosphorylation. Moreover ß-escin sodium reduced the activation of p38 MAPK. Finally, ß-escin sodium inhibited the proliferation of A549 cells, did not change the cell membrane's permeability, nuclear morphology and size and the mitochondria's transmembrane potential of A549 cells. Taken together, these results demonstrate that ß-escin sodium could downregulate iNOS expression through inhibiting JAK/STAT signaling and p38 MAPK activation in A549 cells. ß-escin sodium has a marked antiproliferative effect on A549 cells at least in part by inhibiting the JAK/STAT signaling pathway, but not by a cytotoxic effect. ß-escin sodium would be useful as a chemopreventive agent or a therapeutic against inflammatory-associated tumor. © 2011 Wiley Periodicals, Inc.

HCV structural proteins interfere with interferon-alpha Jak/STAT signalling pathway.

Hepatitis C virus (HCV) is remarkably efficient at establishing persistent infection. The current treatment with IFN-alpha given alone or in combination with ribavirin is ineffective in eliminating the virus in a large proportion of individuals with chronic hepatitis C. Recent data suggest that HCV blocks IFN-alpha signalling, an effect that facilitates viral persistence. We have used the HCV genomic and subgenomic replicon system to analyze the effect of structural and non-structural viral proteins on the activation of the Jak/STAT pathway and induction of antiviral activity by IFN-alpha. Our results show that IFN-alpha-mediated STAT activation (but not IFN-gamma-stimulated STAT phosphorylation) is blocked in Huh7 cell line containing the genomic replicon, while this is not observed in cells with the subgenomic replicon. In agreement with these findings, the transcriptional activity and the antiviral effect of IFN-alpha were significantly lower in cells harboring the genomic replicon than in cells with the subgenomic replicon. These results indicate that HCV structural proteins play an important role in the escape of HCV from the interferon system.

Constitutive and induced activation of JAK/Stat pathway in leukemogenic and asymptomatic human T-cell lymphoptropic virus type 1 (HTLV-1) transformed rabbit cell lines.

We have shown that Vav and C-cbl are activated in the leukemogenic HTLV-I transformed rabbit T cell line RH/K34 but not in the asymptomatic one RH/K30. We extended these observations and investigated the activation of JAKs (Janus Kinase) and the STATs (signal transducers and activators of transcription) pathway in these cell lines. We found that Tyk2 and Stat3 are constitutively tyrosine phosphorylated in the leukemogenic cell line. Phosphorylation of Tyk2 can be induced in RH/K30 by treatment with IL-10, interferon alpha (INFalpha) and by the supernatant of RH/K34 which contain both these cytokines. Stat3 tyrosine phosphorylation can be induced in RH/K30 by treatment with IL-10. Transfection of RL-5, a rabbit T-cell line, with the RH/K34 viral clone transiently increased the expression of serine/threonine phosphorylated Stat3. Differences were also observed on induced Stat5 phosphorylation. These results highlight the relation between the virulence of HTLV-I and the activation of the Jak/Stat pathway.

Key gravity-sensitive signaling pathways drive T cell activation.

Returning astronauts have experienced altered immune function and increased vulnerability to infection during spaceflights dating back to Apollo and Skylab. Lack of immune response in microgravity occurs at the cellular level. We analyzed differential gene expression to find gravity-dependent genes and pathways. We found inhibited induction of 91 genes in the simulated freefall environment of the random positioning machine. Altered induction of 10 genes regulated by key signaling pathways was verified using real-time RT-PCR. We discovered that impaired induction of early genes regulated primarily by transcription factors NF-kappaB, CREB, ELK, AP-1, and STAT after crosslinking the T-cell receptor contributes to T-cell dysfunction in altered gravity environments. We have previously shown that PKA and PKC are key early regulators in T-cell activation. Since the majority of the genes were regulated by NF-kappaB, CREB, and AP-1, we studied the pathways that regulated these transcription factors. We found that the PKA pathway was down-regulated in vg. In contrast, PI3-K, PKC, and its upstream regulator pLAT were not significantly down-regulated by vectorless gravity. Since NF-kappaB, AP-1, and CREB are all regulated by PKA and are transcription factors predicted by microarray analysis to be involved in the altered gene expression in vectorless gravity, the data suggest that PKA is a key player in the loss of T-cell activation in altered gravity.