The state of the STATs: recent developments in the study of signal transduction to the nucleus

Obesity Arrhythmias: Role of IL-6 Trans-Signaling

Obesity is a chronic disease that is rapidly increasing in prevalence and affects more than 600 million adults worldwide, and this figure is estimated to increase by at least double by 2030. In the United States, more than one-third of the adult population is either overweight or obese. The global obesity epidemic is a major risk factor for the development of life-threatening arrhythmias occurring in patients with long QT, particularly in conditions where multiple heart-rate-corrected QT-interval-prolonging mechanisms are simultaneously present. In obesity, excess dietary fat in adipose tissue stimulates the release of immunomodulatory cytokines such as interleukin (IL)-6, leading to a state of chronic inflammation in patients. Over the last decade, increasing evidence has been found to support IL-6 signaling as a powerful predictor of the severity of heart diseases and increased risk for ventricular arrhythmias. IL-6's pro-inflammatory effects are mediated via trans-signaling and may represent a novel arrhythmogenic risk factor in obese hearts. The first selective inhibitor of IL-6 trans-signaling, olamkicept, has shown encouraging results in phase II clinical studies for inflammatory bowel disease. Nevertheless, the connection between IL-6 trans-signaling and obesity-linked ventricular arrhythmias remains unexplored. Therefore, understanding how IL-6 trans-signaling elicits a cellular pro-arrhythmic phenotype and its use as an anti-arrhythmic target in a model of obesity remain unmet clinical needs.

STAT4 Mediates IL-6 Trans-Signaling Arrhythmias in High Fat Diet Guinea Pig Heart

Obesity is a major risk factor for the development of life-threatening malignant ventricular tachyarrhythmias (VT) and sudden cardiac death (SCD). Risks may be highest for patients with high levels of the proinflammatory cytokine interleukin (IL)-6. We used our guinea pig model of high-fat diet (HFD)-induced arrhythmias that exhibit a heightened proinflammatory-like pathology, which is also observed in human obesity arrhythmias, as well as immunofluorescence and confocal microscopy approaches to evaluate the pathological IL-6 trans-signaling function and explore the underlying mechanisms. Using blind-stick and electrocardiogram (ECG) techniques, we tested the hypothesis that heightened IL-6 trans-signaling would exhibit increased ventricular arrhythmia/SCD incidence and underlying arrhythmia substrates. Remarkably, compared to low-fat diet (LFD)-fed controls, HFD promoted phosphorylation of the IL-6 signal transducer and activator of transcription 4 (STAT4), leading to its activation and enhanced nuclear translocation of pSTAT4/STAT4 compared to LFD controls and pSTAT3/STAT3 nuclear expression. Overactivation of IL-6 trans-signaling in guinea pigs prolonged the QT interval, which resulted in greater susceptibility to arrhythmias/SCD with isoproterenol challenge, as also observed with the downstream Janus kinase (JAK) 2 activator. These findings may have potentially profound implications for more effective arrhythmia therapy in the vulnerable obese patient population.

Exposure to the environmental pollutant chlorpyrifos induces hepatic toxicity through activation of the JAK/STAT and MAPK pathways

Chlorpyrifos (CHP) is an inexpensive highly effective organophosphate insecticide used worldwide. The unguided and excessive use of CHP by farmers has led to its significant accumulation in crops as well as contamination of water sources, causing health problems for humans and animals. Therefore, this study evaluated the toxicological effects of exposure to the environmental pollutant CHP at low, medium, and high (2.5, 5, and 10 mg·kg-1 BW) levels on rat liver by examining antioxidant levels, inflammation, and apoptosis based on the no observed adverse effect levels (NOAEL) (1 mg·kg-1 BW) and the CHP dose that does not cause any visual symptoms (5 mg·kg-1 BW). Furthermore, the involvement of the JAK/STAT and MAPK pathways in CHP-induced toxic effects was identified. The relationship between the expression levels of key proteins (p-JAK/JAK, p-STAT/STAT, p-JNK/JNK, p-P38/P38, and p-ERK/ERK) in the pathways and changes in the expression of markers associated with inflammation [inflammatory factors (IL-1β, IL-6, IL-10, TNF-α), chemokines (GCLC and GCLM), and inflammatory signaling pathways (NF-кB, TLR2, TLR4, NLRP3, ASC, MyD88, IFN-γ, and iNOS)] and apoptosis [Bad, Bax, Bcl-2, Caspase3, Caspase9, and the cleavage substrate of Caspase PARP1] were also determined. The results suggest that CHP exposure disrupts liver function and activates the JAK/STAT and MAPK pathways via oxidative stress, exacerbating inflammation and apoptosis. Meanwhile, the JAK/STAT and MAPK pathways are involved in CHP-induced hepatotoxicity. These findings provide a novel direction for effective prevention and amelioration of health problems caused by CHP abuse in agriculture and households.

Immune regulation mediated by JAK/STAT signaling pathway in hemocytes of Pacific white shrimps, Litopenaeus vannamei stimulated by lipopolysaccharide

To understand the regulatory mechanism of Janus kinase/Signal Transducers and Activators of Transcription (JAK/STAT) signaling pathway on the immune system of the Pacific white shrimp, Litopenaeus vannamei, RNA interference technique was used to investigate the effects of JAK/STAT signaling pathway on the immune response of hemocyte in Litopenaeus vannamei stimulated by lipopolysaccharide (LPS). The results showed that 1) after 6 h of LPS stimulation, the expression levels of immune genes in hemocyte were significantly up-regulated (P < 0.05), the immune defense ability (hemocyte number, phagocytosis rate, hemagglutination activity, bacteriolytic activity, antibacterial activity, prophenoloxidase system activity) and the hemocyte antioxidant ability were significantly higher than the control group, especially at 12 h. 2) After 48 h of STAT gene interference, the expression levels of immune genes in hemocytes were significantly down-regulated, and the immune defense ability (hemocyte count, phagocytosis rate, plasma agglutination activity, lysozyme activity, antibacterial activity, proPO system activity) and the antioxidant ability were reduced and significantly lower than control. Concurrently, after LPS stimulation, the immune indexes were significantly up-regulated at 12 h to the maximum but was still lower the undisturbed LPS group. These results indicate that JAK/STAT signaling pathway is involved in the immune regulation mechanism of L. vannamei against LPS stimulation through positive regulation of cellular immune and humoral immune. These results provide a basis for further research on the role and status of JAK/STAT signaling pathway in the immune defense of crustaceans.

Blockade of STAT3 signaling alleviates progression of acute kidney injury-to-chronic kidney disease through anti-apoptosis

Signal transducer and activator of transcription 3 (STAT3) is a pivotal mediator of IL-6-type cytokine signaling. However, the roles of its full-length and truncated isoforms in acute kidney injury (AKI) and its transition to chronic kidney disease (CKD) remain elusive. Herein, the role of STAT3 isoforms in AKI-to-CKD transition was characterized using an ischemia-reperfusion injury (IRI) mouse model. IRI was induced in C57BL/6 mice. Stattic^®, a STAT3 inhibitor, was administered to the mice 3 h prior to IRI. Intrarenal cytokine expression was quantified using real-time PCR, and FACS analysis was performed. The effect of Stattic^® on human tubular epithelial cells (TECs) cultured under hypoxic conditions was also evaluated. Phosphorylated STAT3 isoforms were detected by western blotting. Stattic^® treatment attenuated IRI-induced tubular damage and inflammatory cytokine/chemokine expression, while decreasing macrophage infiltration and fibrosis in mouse unilateral IRI and UUO models. Similarly, in vitro STAT3 inhibition downregulated fibrosis and apoptosis in 72-h hypoxia-induced human TECs and reduced pSTAT3α-mediated inflammation. Moreover, pSTAT3 expression was increased in human acute tubular necrosis and CKD tissues. STAT3 activation is associated with IRI progression, and STAT3-α may be a significant contributor. Hence, STAT3 may affect AKI-to-CKD transition, suggesting a novel strategy for AKI management with STAT3 inhibitors.

SOCS Proteins in Immunity, Inflammatory Diseases, and Immune-Related Cancer

Cytokine signaling represents one of the cornerstones of the immune system, mediating the complex responses required to facilitate appropriate immune cell development and function that supports robust immunity. It is crucial that these signals be tightly regulated, with dysregulation underpinning immune defects, including excessive inflammation, as well as contributing to various immune-related malignancies. A specialized family of proteins called suppressors of cytokine signaling (SOCS) participate in negative feedback regulation of cytokine signaling, ensuring it is appropriately restrained. The eight SOCS proteins identified regulate cytokine and other signaling pathways in unique ways. SOCS1–3 and CISH are most closely involved in the regulation of immune-related signaling, influencing processes such polarization of lymphocytes and the activation of myeloid cells by controlling signaling downstream of essential cytokines such as IL-4, IL-6, and IFN-γ. SOCS protein perturbation disrupts these processes resulting in the development of inflammatory and autoimmune conditions as well as malignancies. As a consequence, SOCS proteins are garnering increased interest as a unique avenue to treat these disorders.

Bombyx mori Apolipophorin-III inhibits Beauveria bassiana directly and through regulating expression of genes relevant to immune signaling pathways

Insect Apolipophorin-III is a multifunctional protein and also plays an important role in insect innate immunity. Early transcriptome and proteome studies indicated that the gene expression level of Bombyx mori Apolipophorin-III (BmApoLp-III) in silkworm larvae infected with Beauveria bassiana was significantly up-regulated. In this study, BmApoLp-III gene was cloned, its expression patterns in different larval tissues investigated, the BmApoLp-III protein was successfully expressed with prokaryotic expression system and its antifungal effect was verified. The results showed that the BmApoLp-III gene was expressed in all the tested tissues of the 5th instar larvae infected by B. bassiana, with the highest expression in fat body. The fungistatic zone test showed that the recombinant BmApoLp-III has a significant antifungal effect on B. bassiana. Injecting purified BmApoLp-III to the larvae delayed the onset and death of the infected larvae. Conversely, silencing BmApoLp-III gene by RNAi resulted in early morbidity and death of the infected larvae. At the same time, injecting BmApoLp-III up-regulated the expression of genes including BmβGRP4 and BmMyd88 in the Toll signaling pathway, BmCTL5 and BmHOP in the Jak/STAT signaling pathway, serine proteinase inhibitor BmSerpin5, and antimicrobial peptide BmCecA, but down-regulated the expression of BmTak1 of Imd signaling pathway; while silencing BmApoLp-III gene down-regulated the expression of BmβGRP1 and BmSpaetzle, BmCTL5 and BmHOP, BmSerpin2 and BmSerpin5, BmBAEE and BmPPO2 of relevant pathways and BmCecA, but up-regulated the expression of BmPGRP-Lc and BmTak1 of Imd pathway. These results indicate that the BmApoLp-III could not only directly inhibit B. bassiana, but also participate in regulation of the expression of immune signaling pathway related genes, promote the expression of immune effectors, and indirectly inhibit the reproduction of B. bassiana in the silkworm.

Alprazolam Prompts HIV-1 Transcriptional Reactivation and Enhances CTL Response Through RUNX1 Inhibition and STAT5 Activation

The HIV-1 pandemic is a significant challenge to the field of medicine. Despite advancements in antiretroviral (ART) development, 38 million people worldwide still live with this disease without a cure. A significant barrier to the eradication of HIV-1 lies in the persistently latent pool that establishes early in the infection. The “shock and kill” strategy relies on the discovery of a latency-reversing agent (LRA) that can robustly reactivate the latent pool and not limit immune clearance. We have found that a benzodiazepine (BDZ), that is commonly prescribed for panic and anxiety disorder, to be an ideal candidate for latency reversal. The BDZ Alprazolam functions as an inhibitor of the transcription factor RUNX1, which negatively regulates HIV-1 transcription. In addition to the displacement of RUNX1 from the HIV-1 5′LTR, Alprazolam potentiates the activation of STAT5 and its recruitment to the viral promoter. The activation of STAT5 in cytotoxic T cells may enable immune activation which is independent of the IL-2 receptor. These findings have significance for the potential use of Alprazolam in a curative strategy and to addressing the neuroinflammation associated with neuroHIV-1.

Cancer immunotherapy from biology to nanomedicine

With the significant drawbacks of conventional cancer chemotherapeutics, cancer immunotherapy has demonstrated the ability to eradicate cancer cells and circumvent multidrug resistance (MDR) with fewer side effects than traditional cytotoxic therapies. Various immunotherapeutic agents have been investigated for that purpose including checkpoint inhibitors, cytokines, monoclonal antibodies and cancer vaccines. All these agents aid immune cells to recognize and engage tumor cells by acting on tumor-specific pathways, antigens or cellular targets. However, immunotherapeutics are still associated with some concerns such as off-target side effects and poor pharmacokinetics. Nanomedicine may resolve some limitations of current immunotherapeutics such as localizing delivery, controlling release and enhancing the pharmacokinetic profile. Herein, we discuss recent advances of immunotherapeutic agents with respect to their development and biological mechanisms of action, along with the advantages that nanomedicine strategies lend to immunotherapeutics by possibly improving therapeutic outcomes and minimizing side effects.

Urinary biomarkers in lupus nephritis

Systemic lupus erythematosus (SLE) is the prototypical autoimmune disease that can affect any organ of the body. Multiple mechanisms may contribute to the pathophysiology of systemic lupus, including failure to remove apoptotic bodies, hyperactivity of self-reactive B and T lymphocytes, abnormal exposure to autoantigens, and increased levels of B-cell stimulatory cytokines. The involvement of the kidney, called lupus nephritis (LN), during the course of the disease affects between 30% and 60% of adult SLE patients, and up to 70% of children. LN is an immune-mediated glomerulonephritis that is a common and serious finding in patients with SLE. Nowadays, renal biopsy is considered the gold standard for classifying LN, besides its degree of activity or chronicity. Nevertheless, renal biopsy lacks the ability to predict which patients will respond to immunosuppressive therapy and is a costly and risky procedure that is not practical in the monitoring of LN because serial repetitions would be necessary. Consequently, many serum and urinary biomarkers have been studied in SLE patients for the complementary study of LN, existing conventional biomarkers like proteinuria, protein/creatinine ratio in spot urine, 24 ​h urine proteinuria, creatinine clearance, among others and non-conventional biomarkers, like Monocyte chemoattractant protein-1 (MCP-1), have been correlated with the histological findings of the different types of LN. In this article, we review the advances in lupus nephritis urinary biomarkers. Such markers ideally should be capable of predicting early sub-clinical flares and could be used to follow response to therapy. In addition, some of these markers have been found to be involved in the pathogenesis of lupus nephritis.

Type I interferon-dependent CCL4 is induced by a cGAS/STING pathway that bypasses viral inhibition and protects infected tissue, independent of viral burden

Type I interferons (T1-IFN) are critical in the innate immune response, acting upon infected and uninfected cells to initiate an antiviral state by expressing genes that inhibit multiple stages of the lifecycle of many viruses. T1-IFN triggers the production of Interferon-Stimulated Genes (ISGs), activating an antiviral program that reduces virus replication. The importance of the T1-IFN response is highlighted by the evolution of viral evasion strategies to inhibit the production or action of T1-IFN in virus-infected cells. T1-IFN is produced via activation of pathogen sensors within infected cells, a process that is targeted by virus-encoded immunomodulatory molecules. This is probably best exemplified by the prototypic poxvirus, Vaccinia virus (VACV), which uses at least 6 different mechanisms to completely block the production of T1-IFN within infected cells in vitro. Yet, mice lacking aspects of T1-IFN signaling are often more susceptible to infection with many viruses, including VACV, than wild-type mice. How can these opposing findings be rationalized? The cytosolic DNA sensor cGAS has been implicated in immunity to VACV, but has yet to be linked to the production of T1-IFN in response to VACV infection. Indeed, there are two VACV-encoded proteins that effectively prevent cGAS-mediated activation of T1-IFN. We find that the majority of VACV-infected cells in vivo do not produce T1-IFN, but that a small subset of VACV-infected cells in vivo utilize cGAS to sense VACV and produce T1-IFN to protect infected mice. The protective effect of T1-IFN is not mediated via ISG-mediated control of virus replication. Rather, T1-IFN drives increased expression of CCL4, which recruits inflammatory monocytes that constrain the VACV lesion in a virus replication-independent manner by limiting spread within the tissue. Our findings have broad implications in our understanding of pathogen detection and viral evasion in vivo, and highlight a novel immune strategy to protect infected tissue.

Atiprimod induce apoptosis in pituitary adenoma: Endoplasmic reticulum stress and autophagy pathways

Pituitary adenoma is the most common tumor with a high recurrence rate due to a hormone-dependent JAK/signal transducer and activator of transcriptions (STAT) signaling. Atiprimod, a novel compound belonging to the azaspirane class of cationic amphiphilic drugs, has antiproliferative, anticarcinogenic effects in multiple myeloma, breast, and hepatocellular carcinoma by blocking STAT3 activation. Therapeutic agents' efficiency depends on endoplasmic reticulum (ER) stress-autophagy regulation during drug-mediated apoptotic cell death decision. However, the molecular machinery of dose-dependent atiprimod treatment regarding ER stress-autophagy has not been investigated yet. Thus, our aim is to investigate the ER stress-autophagy axis in atiprimod-mediated apoptotic cell death in GH-secreting rat cell line (GH3) pituitary adenoma cells. Dose-dependent atiprimod treatment decreased GH3 cell viability, inhibited cell growth, and colony formation. Upregulation of Atg5, Atg12, Beclin-1 expressions, cleavage of LC-3II and formation of autophagy vacuoles were determined only after 1 µM atiprimod exposure. In addition, atiprimod-triggered ER stress was evaluated by BiP, C/EBP-homologous protein (CHOP), p-PERK upregulation, and Ca⁺² release after 1 µM atiprimod exposure. Concomitantly, increasing concentration of atiprimod induced caspase-dependent apoptotic cell death via modulating Bcl₂ family members. Moreover, by N-acetyl cycteinc pretreatment, atiprimod triggered reactive oxygen species generation and prevented apoptotic induction. Concomitantly, dose-dependent atiprimod treatment decreased both GH and STAT3 expression in GH3 cells. In addition, overexpression of STAT3 increased atiprimod-mediated cell viability loss and apoptotic cell death through suppressing autophagy and ER stress key molecules expression profile. In conclusion, a low dose of atiprimod exposure triggers autophagy and mild-ER stress as a survival mechanism, but increased atiprimod dose induced caspase-dependent apoptotic cell death by targeting STAT3 in GH3 pituitary adenoma cells.

Ex vivo immunomodulatory effect of ethanolic extract of propolis during Celiac Disease: involvement of nitric oxide pathway

Celiac Disease (CeD) is a chronic immune-mediated enteropathy, in which dietary gluten induces an inflammatory reaction, predominantly in the duodenum. Propolis is a resinous hive product, collected by honeybees from various plant sources. Propolis is well-known for its anti-inflammatory, anti-oxidant and immunomodulatory effects, due to its major compounds, polyphenols and flavonoids. The aim of our study was to assess the ex vivo effect of ethanolic extract of propolis (EEP) upon the activity and expression of iNOS, along with IFN-γ and IL-10 production in Algerian Celiac patients. In this context, PBMCs isolated from peripheral blood of Celiac patients and healthy controls were cultured with different concentrations of EEP. NO production was measured using the Griess method, whereas quantitation of IFN-γ and IL-10 levels was performed by ELISA. Inducible nitric oxide synthase (iNOS) expression, NFκB and pSTAT-3 activity were analyzed by immunofluorescence assay. Our results showed that PBMCs from Celiac patients produced high levels of NO and IFN-γ compared with healthy controls (HC). Interestingly, EEP reduced significantly, NO and IFN-γ levels and significantly increased IL-10 levels at a concentration of 50 µg/mL. Importantly, EEP downmodulated the iNOS expression as well as the activity of NFκB and pSTAT-3 transcription factors. Altogether, our results highlight the immunomodulatory effect of propolis on NO pathway and on pro-inflammatory cytokines. Therefore, we suggest that propolis may constitute a potential candidate to modulate inflammation during Celiac Disease and has a potential therapeutic value.

TYK2-induced phosphorylation of Y640 suppresses STAT3 transcriptional activity

STAT3 is a pleiotropic transcription factor involved in homeostatic and host defense processes in the human body. It is activated by numerous cytokines and growth factors and generates a series of cellular effects. Of the STAT-mediated signal transduction pathways, STAT3 transcriptional control is best understood. Jak kinase dependent activation of STAT3 relies on Y705 phosphorylation triggering a conformational switch that is stabilized by intermolecular interactions between SH2 domains and the pY705 motif. We here show that a second tyrosine phosphorylation within the SH2 domain at position Y640, induced by Tyk2, negatively controls STAT3 activity. The Y640F mutation leads to stabilization of activated STAT3 homodimers, accelerated nuclear translocation and superior transcriptional activity following IL-6 and LIF stimulation. Moreover, it unlocks type I IFN-dependent STAT3 signalling in cells that are normally refractory to STAT3 transcriptional activation.

Virus infection drives IL-2 antibody complexes into pro-inflammatory agonists in mice

The use of IL-2/JES6-1 Ab complex (IL-2 Ab Cx) has been considered as a potential therapeutic for inflammatory diseases due to its selective expansion of regulatory T cells (Tregs) in mice. Here, IL-2 Ab Cx was explored as a therapeutic agent to reduce joint inflammation induced by chikungunya virus, an alphavirus causing debilitating joint disease globally. Virus-infected mice treated with IL-2 Ab Cx exhibited exacerbated joint inflammation due to infiltration of highly activated CD4+ effector T cells (Teffs). Virus infection led to upregulation of CD25 on the Teffs, rendering them sensitive towards IL2 Ab Cx. Ready responsiveness of Teffs to IL-2 was further demonstrated in healthy human donors, suggesting that the use of IL-2 Ab Cx in humans is not suitable. Changes in IL-2 sensitivity during active virus infection could change the responsive pattern towards the IL-2 Ab Cx, resulting in the expansion of pro-inflammatory rather than anti-inflammatory responses.

STAT4 contributes to adipose tissue inflammation and atherosclerosis

Adipose tissue (AT) inflammation is an emerging factor contributing to cardiovascular disease. STAT4 is a transcription factor expressed in adipocytes and in immune cells and contributes to AT inflammation and insulin resistance in obesity. The objective of this study was to determine the effect of STAT4 deficiency on visceral and peri-aortic AT inflammation in a model of atherosclerosis without obesity. Stat4(-/-)Apoe(-/-) mice and Apoe(-/-) controls were kept either on chow or Western diet for 12 weeks. Visceral and peri-aortic AT were collected and analyzed for immune composition by flow cytometry and for cytokine/chemokine expression by real-time PCR. Stat4(-/-)Apoe(-/-) and Apoe(-/-) mice had similar body weight, plasma glucose, and lipids. Western diet significantly increased macrophage, CD4+, CD8+, and NK cells in peri-aortic and visceral fat in Apoe(-/-) mice. In contrast, in Stat4(-/-)Apoe(-/-) mice, a Western diet failed to increase the percentage of immune cells infiltrating the AT. Also, IL12p40, TNFa, CCL5, CXCL10, and CX3CL1 were significantly reduced in the peri-aortic fat in Stat4(-/-)Apoe(-/-) mice. Importantly, Stat4(-/-)Apoe(-/-) mice on a Western diet had significantly reduced plaque burden vs Apoe(-/-) controls. In conclusion, STAT4 deletion reduces inflammation in peri-vascular and visceral AT and this may contribute via direct or indirect effects to reduced atheroma formation.

STAT3 induces anoikis resistance, promotes cell invasion and metastatic potential in pancreatic cancer cells

Tumor cells need to attain anoikis resistance to survive prior to metastasis making it a vital trait of malignancy. The mechanism by which pancreatic cancer cells resist anoikis and metastasize is not well established. Significant proportion of pancreatic cancer cells resisted anoikis when grown under anchorage-independent conditions. The cells that resisted anoikis showed higher migratory and invasive characteristics than the cells that were cultured under anchorage-dependent condition. Interestingly, anoikis-resistant cells exhibited significantly increased expression and phosphorylation of signal transducer and activation of transcription 3 (STAT3) at Tyr 705, as compared to adherent cells. AG 490 and piplartine (PL) induced significant anoikis in anoikis-resistant pancreatic cancer cells. Silencing STAT3 not only reduced the capacity of pancreatic cancer cells to resist anoikis but also reversed its invasive characteristics. Interleukin-6 treatment and overexpression of STAT3 enhanced anoikis resistance and protected the cells from PL-induced anoikis. PL-treated cells completely failed to develop tumors when injected subcutaneously in immune-compromised mice. Moreover, these cells also failed to metastasize when injected intravenously. On the other hand, untreated anoikis-resistant cells not only formed aggressive tumors but also metastasized substantially to lungs and liver when injected intravenously. Metastatic nodules formed by untreated anoikis-resistant cells in lungs exhibited significant phosphorylation of STAT3 at Tyr705. Taken together, our results established the critical involvement of STAT3 in conferring anoikis resistance to pancreatic cancer cells and increased metastasis.

Critical role of STAT3 in melanoma metastasis through anoikis resistance

Anoikis is an anchorage-independent cell death. Resistance to anoikis is one of the key features of metastatic cells. Here, we analyzed the role of STAT3 in anoikis resistance in melanoma cells leading to metastasis. When grown under anchorage-independent conditions, significant proportion of cells resisted anoikis and these resistant cells had higher rate of migration and invasion as compared to the cells grown under anchorage-dependent conditions. The anoikis resistant cells also had significantly higher expression and phosphorylation of STAT3 at Y705 than the cells that were attached to the basement membrane. STAT3 inhibitors, AG 490 and piplartine (PL) induced anoikis in a concentration-dependent manner in anoikis resistant cells. Over-expression of STAT3 or treatment with IL-6 not only increased anoikis resistance, but also protected the cancer cells from PL-induced anoikis. On the other hand, silencing STAT3 decreased the potential of cancer cells to resist anoikis and to migrate. STAT3 knock-down cells and PL treated cells did not form tumors as well as failed to metastasize in SCID-NSG mice as compared to untreated anchorage-independent cells, which formed big tumors and extensively metastasized. In summary, our results for the first time establish STAT3 as a critical player that renders anoikis resistance to melanoma cells and enhance their metastatic potential.

Role of the JAK-STAT signal pathway in the development and progression of liver cancer

Primary liver cancer is a kind of malignant tumor that occurs in liver cells and bile duct epithelial cells. There is a great difference in the incidence of liver cancer among different countries and regions. In China, liver cancer is one of the most common malignant tumors and has the third highest mortality rate. About 110 thousand people die of liver cancer in China each year, accounting for 45% of worldwide deaths caused by liver cancer. The research on the biological behavior of liver cancer has been widely carried out, and the relationship between the janus kinase-signal transducers and activators of transcription (JAK-STAT) signal pathway, which is activated in many types of human malignant tumors and involved in the occurrence and development of tumors, and liver cancer has attracted wide attention. In this paper we will discuss the relationship between the JAK-STAT signal pathway and biological behavior of liver cancer.

Cucurbitacins - a promising target for cancer therapy

During the last decades a large number of cucurbitacins have been isolated from various plant species belonging to other plant families than Cucurbitaceae. Although the roots and the fruits of plant belong to these Cucurbitaceae species are very bitter, they have been used as folk medicines in some countries because of their wide spectrum of pharmacological activities such as anti-inflammation and anticancer effects. In the last ten years, cucurbitacins had been shown to inhibit proliferation and induced apoptosis utilizing a long array of in vitro and in vivo cancer cell models. Several molecular targets for cucurbitacins have been discovered, such as fibrous-actin, signal transducer and activator of transcription (STAT), cyclooxygenase-2, etc. This review aimed at elucidating the natural sources of some cucurbitacin compounds, their chemical structure and derivatives, physical properties, biological activities and mechanism by which they reduce the proliferation human cancer cells. This widens our armaments against a devastating disease that we are failing to face.

Regulation of STAT signaling by acetylation

Signal transducers and activators of transcription (STAT) belong to a family of latent cytoplasmic factors that can be activated by tyrosine phosphorylation by the members of the Jak tyrosine kinase family in response to a variety of cytokines and growth factors. Activated STATs form dimers and translocate into nucleus to induce expression of critical genes essential for normal cellular events. In the past several years, significant progress has been made in the characterization of STAT acetylation, which is dependent on the balance between histone deacetylases (HDACs) and histone acetyltransferases (HATs) such as CBP/p300. Acetylation of STAT1, STAT2, STAT3, STAT5b and STAT6 has been identified. This review will highlight acetylation on the modulation of STAT activation.

Cucurbitacins: potential candidates targeting mitogen-activated protein kinase pathway for treatment of melanoma

Cucurbitacins (Cucs) have been classified as signal transducer and activator of transcription 3 inhibitors. Kinase inhibition has been a validated drug target in multiple types of malignancies. B-RAF mutations are highly expressed in the melanoma. Our hypothesis is the Cucs can be a potential candidate to inhibit the signaling kinase pathway. The research presented is the evaluation of Cucs, as B-RAF and MEK1 kinase inhibitors. Virtual screening methods were employed to identify lead compounds. The hypothesis was tested on mutant B-RAF cell lines, A-375 and Sk-Mel-28 cell lines to determine the activity toward melanoma. A series of natural Cucs show an improved activity toward Sk-Mel-28 and A-375 cell lines. Cucs show potential inhibition for the total and phosphorylated ERK using ELISA kits. Cucs could be potential candidate for inhibiting cell growth.

HSV-2 inhibits type-I interferon signaling via multiple complementary and compensatory STAT2-associated mechanisms

Type-I interferon (IFN)-mediated responses are a crucial first line of defense against viral infections and are critical for generating both innate and adaptive immunity. Therefore, viruses have necessarily evolved mechanisms to impede the IFN response. HSV-2 was found to completely abolish type-1 IFN-mediated signaling via multiple STAT2-associated mechanisms. Although the extent and kinetics of this inactivation were indistinguishable between the various cell-lines examined, there were distinct differences in the mechanisms HSV-2 employed to subvert IFN-signaling among the cell-lines. These mechanistic differences could be segregated into two categories dependent on the phase of the HSV replicative cycle that was responsible for this inhibition: (1) early phase-inhibited cells which exhibited abrogation of IFN-signaling prior to viral DNA replication; (2) late phase-inhibited cells where early phase inhibition mechanisms were not functional, but viral functions expressed following DNA replication compensated for their ineffectiveness. In early phase-inhibited cells, HSV-2 infection targeted STAT2 protein for proteosomal degradation and prevented de novo expression of STAT2 by degrading its mRNA. In contrast, HSV-2 infected late phase-inhibited cells exhibited no apparent changes in STAT2 transcript or protein levels. However, in these cells STAT2 was not activated by phosphorylation and failed to translocate to the cell nucleus, thereby preventing transactivation of antiviral genes. In primary human fibroblasts, HSV-2 failed to fully degrade STAT2 and therefore, both early and late phase mechanisms functioned cooperatively to subvert IFN-mediated antiviral gene expression. Taken together, these results indicate the importance that HSV-2 has assigned to STAT2, investing significant genomic currency throughout its replicative lifecycle for continuous targeted destruction and inhibition of this protein.

Sarcophine-diol, a skin cancer chemopreventive agent, inhibits proliferation and stimulates apoptosis in mouse melanoma B₁₆F₁₀ cell line

Sarcodiol (SD) is a semi-synthetic derivative of sarcophine, a marine natural product. In our previous work, we reported the significant chemopreventive effects of SD against non-melanoma skin cancer both in vitro and in vivo mouse models. In this investigation, we extended this work to study the effect of sarcodiol on melanoma development, the more deadly form of skin cancer, using the mouse melanoma B₁₆F₁₀ cell line. In this study we report that SD inhibits the de novo DNA synthesis and enhances fragmentation of DNA. We also evaluated the antitumor effect of SD on melanoma cell viability using several biomarkers for cell proliferation and apoptosis. SD inhibits the expression levels of signal transducers and activators of transcription protein (STAT-3) and cyclin D1, an activator of cyclin-dependent kinase 4 (Cdk4). SD treatment also enhances cellular level of tumor suppressor protein 53 (p53) and stimulates cleavage of the nuclear poly (ADP-ribose) polymerase (cleaved-PARP). SD also enhances cellular levels of cleaved Caspase-3, -8, -9 and stimulates enzymatic activities of Caspase-3, -8 and -9. These results, in addition to inhibition of cell viability, suggest that SD inhibits melanoma cell proliferation by arresting the cell-division cycle in a Go quiescent phase and activates programmed cell death (apoptosis) via extrinsic and intrinsic pathways. Finally, these studies demonstrate that SD shows a very promising chemopreventive effect in melanoma B₁₆F₁₀ tumor cells.

JAK3 in clear cell renal cell carcinoma: mutational screening and clinical implications

OBJECTIVES

Janus Kinase 3 (JAK3) mediates cytokine signaling and T-cell activation. We hypothesized that JAK3 mutations may contribute to the development and progression of clear cell renal cell carcinoma (ccRCC). To test this hypothesis, we performed mutational screening and functional studies.

PATIENTS AND METHODS

This hospital-based case-control study included 50 patients with ccRCC and 100 age- and gender-matched controls. Both genomic and tumor DNA were extracted. All 23 JAK3 exons were amplified by PCR and analyzed by denaturing high-performance liquid chromatography and automatic sequencing. Effects of JAK3 mutations on interleukin-2-stimulated peripheral T-cells were analyzed by confocal laser-scanning microscopy and immunoprecipitation.

RESULTS

Four different JAK3 germline missense mutations (p.Gln13Lys; p.Arg925Ser; p.Ala677Thr, p.Val722Ile) were found in a total of 7 ccRCC patients (14%), but in none of the controls (P = 0.0006). All germline mutations were similarly detected in the tumors. An additional somatic missense mutation (p.Tyr238Cys) was found in a patient who had a germline mutation. Four of the mutations have not been previously described (p.Gln13Lys; p.Arg925Ser; p.Ala677Thr, p.Tyr238Cys). Patients with JAK3 mutations more frequently presented with metastases (3 out of 4 [75%] vs. 4 out of 46 [9%]; P = 0.004) and had poorer survival (P = 0.049). In p.Arg925Ser and p.Ala677Thr/p.Val722Ile, functional analyses showed abnormal JAK3 and STAT5 tyrosine phosphorylation and a reduction of JAK3/STAT5 interaction.

CONCLUSIONS

JAK3 mutations are found in a subset of ccRCC patients and may be associated with ccRCC development and a greater risk of metastases. JAK3 function is compromised in p.Arg925Ser and p.Ala677Thr/p.Val722Ile. Future studies with a larger number of patients need to confirm these findings.

New curcumin analogues exhibit enhanced growth-suppressive activity and inhibit AKT and signal transducer and activator of transcription 3 phosphorylation in breast and prostate cancer cells

Curcumin, the active component of turmeric, has been shown to protect against carcinogenesis and prevent tumor development in cancer. To enhance its potency, we tested the efficacy of synthetic curcumin analogues, known as FLLL11 and FLLL12, in cancer cells. We examined the impact of FLLL11 and FLLL12 on cell viability in eight different breast and prostate cancer cell lines. FLLL11 and FLLL12 (IC(50) values 0.3-5.7 and 0.3-3.8 micromol/L, respectively) were substantially more potent than curcumin (IC(50) values between 14.4-50 micromol/L). FLLL11 and FLLL12 were also found to inhibit AKT phosphorylation and downregulate the expression of HER2/neu. In addition, we demonstrate for the first time that FLLL11 and FLLL12 inhibit phosphorylation of signal transducer and activator of transcription (STAT) 3, an oncogene frequently found to be persistently active in many cancer types. The inhibition of STAT3 signaling was confirmed by the inhibition of STAT3 DNA binding and STAT3 transcriptional activity. Furthermore, FLLL11 and FLLL12 were more effective than curcumin in inhibiting cell migration and colony formation in soft agar as well as inducing apoptosis in cancer cells. These results indicate that FLLL11 and FLLL12 exhibit more potent activities than curcumin on the inhibition of STAT3, AKT, and HER-2/neu, as well as inhibit cancer cell growth and migration, and may thus have translational potential as chemopreventive or therapeutic agents for breast and prostate cancers.

Activation of the Jak3 pathway and myeloid differentiation

Although the role of Jak3 in lymphoid development has been well-characterized, increasing evidence demonstrates that activation of the Jak3 pathway plays an important role in myeloid differentiation as well. Overexpression of Jak3 in murine myeloid 32Dcl3 cells has been shown to result in an acceleration of granulocytic differentiation induced by G-CSF. Early onset of G1 cell cycle arrest along with upregulation of the cyclin dependent kinase inhibitor p27Kip1 and downregulation of Cdk2, Cdk4, Cdk6, and Cyclin E has also been observed in Jak3-overexpressing 32Dcl3 cells. In addition, Jak3 overexpression in normal mouse bone marrow cells results in accelerated granulocytic and monocytic differentiation in response to GM-CSF, while pharmacological inhibition of Jak3 results in a block to GM-CSF-induced colony formation in normal mouse bone marrow cells. Jak3 is unique among the members of the Jak kinase family in that it is inducibly expressed and is a target for regulation at the level of transcription. Recent studies have demonstrated that upregulation of Jak3 during myeloid differentiation is achieved through the cooperative action of Sp1 and STAT3, consistent with evidence indicative of a crucial role for STAT3 in myeloid differentiation. These results suggest that cytokine-inducible activation of Jak3 plays a critical role in integrating the processes of growth arrest and differentiation of myeloid cells.

STAT3 regulation of glioblastoma pathogenesis

Malignant gliomas are the most common primary brain tumors. Despite efforts to find effective treatments, these tumors remain incurable. The failure of malignant gliomas to respond to conventional cancer therapies may reflect the unique biology of these tumors, underscoring the need for new approaches in their investigation. Recently, progress has been made in characterization of the molecular pathogenesis of glioblastoma using a developmental neurobiological perspective, by exploring the role of signaling pathways that control the differentiation of neural stem cells along the glial lineage. The transcription factor STAT3, which has an established function in neural stem cell and astrocyte development, has been found to play dual tumor suppressive and oncogenic roles in glial malignancy depending on the mutational profile of the tumor. These findings establish a novel developmental paradigm in the study of glioblastoma pathogenesis and provide the rationale for patient-tailored therapy in the treatment of this devastating disease.

Pyridone 6, a pan-Janus-activated kinase inhibitor, suppresses osteoclast formation and bone resorption through down-regulation of receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL)-induced c-Fos and nuclear factor of activated T cells (NFAT) c1 expression

It has been reported that Janus tyrosine kinase (JAK)-dependent signaling pathways play a critical role in the pathogenesis of numerous malignancies and immune reactions, and inhibition of JAK has been implicated in cell growth inhibition. The role which JAK has on osteoclast differentiation and anti-bone resorptive activity is not well understood. In this study, we investigated the effects of a pan-JAK inhibitor, pyridone 6, on osteoclast differentiation and bone-resorption in vitro and ex vivo. Pyridone 6 inhibited osteoclast differentiation in mouse bone marrow macrophage (BMM) cultures stimulated by the receptor activator of nuclear factor-kappaB (NF-kappaB) ligand (RANKL) and co-cultures of bone marrow cells and osteoblasts. Pyridone 6 suppressed the expression of c-Fos and nuclear factor of activated T cells (NFAT) c1 in BMMs. It also inhibited the bone resorptive activity of mature osteoclasts that was accompanied by disruption of actin rings. Pyridone 6 also suppressed I-kappaB degradation and extracellular signal-regulated kinase (ERK) in mature osteoclasts, suggesting that these are the key molecules that pyridone 6 targets in the inhibition of osteoclast function. These results demonstrate inhibition of JAK may be useful for the treatment of bone-resorptive diseases, such as osteoporosis.

The role of STAT-3 in the induction of apoptosis in pancreatic cancer cells by benzyl isothiocyanate

BACKGROUND

Benzyl isothiocyanate (BITC), a compound found in cruciferous vegetables, has been reported to have anticancer properties, but the mechanism whereby it inhibits growth of human pancreatic cancer cells is incompletely understood.

METHODS

Human pancreatic cancer cells (BxPC-3, AsPC-1, Capan-2, MiaPaCa-2, and Panc-1) and immortalized human pancreatic cells (HPDE-6) were treated with vehicle or with BITC at 5-40 microM, cell survival was evaluated by sulforhodamine B assay, and apoptosis by caspase-3 and poly-ADP ribose polymerase cleavage or by a commercial assay for cell death. Total and activated signal transducer and activator of transcription-3 (STAT-3) protein expression in the cells were examined by western blotting, STAT-3 mRNA levels by reverse transcription-polymerase chain reaction, and STAT-3 DNA-binding and transcriptional activity by commercially available binding and reporter assays. The effects of BITC treatment on tumor growth, apoptosis, and STAT-3 protein expression in vivo were studied in xenografts of BxPC-3 pancreatic tumor cells in athymic nude mice. All statistical tests were two-sided.

RESULTS

BITC treatment reduced cell survival and induced apoptosis in BxPC-3, AsPC-1, Capan-2, and MiaPaCa-2 cells, and to a much lesser extent in Panc-1 cells, but not in HPDE-6 cells. It also reduced levels of activated and total STAT-3 protein, and as a result, STAT-3 DNA-binding and transcriptional activities. Overexpression of STAT-3 in BxPC-3 cells inhibited BITC-induced apoptosis and restored STAT-3 activity. In mice that were fed BITC (60 micromol/wk, five mice, 10 tumors per group), growth of BxPC-3 pancreatic tumor xenografts was suppressed compared with control mice (at 6 weeks, mean tumor volume of control vs BITC-treated mice = 334 vs 172 mm3, difference =162 mm3, 95% confidence interval = 118 to 204 mm3; P = .008) and tumors had increased apoptosis and reduced STAT-3 protein expression.

CONCLUSION

BITC induces apoptosis in some types of pancreatic cancer cells by inhibiting the STAT-3 signaling pathway.

Pivotal Advance: Th-1 cytokines inhibit, and Th-2 cytokines promote fibrocyte differentiation

CD14+ peripheral blood monocytes can differentiate into fibroblast-like cells called fibrocytes, which are associated with and are at least partially responsible for wound healing and fibrosis in multiple organ systems. Signals regulating fibrocyte differentiation are poorly understood. In this study, we find that when added to human PBMCs cultured in serum-free medium, the profibrotic cytokines IL-4 and IL-13 promote fibrocyte differentiation without inducing fibrocyte or fibrocyte precursor proliferation. We also find that the potent, antifibrotic cytokines IFN-gamma and IL-12 inhibit fibrocyte differentiation. In our culture system, IL-1beta, IL-3, IL-6, IL-7, IL-16, GM-CSF, M-CSF, fetal liver tyrosine kinase 3, insulin growth factor 1, vascular endothelial growth factor, and TNF-alpha had no significant effect on fibrocyte differentiation. IL-4, IL-13, and IFN-gamma act directly on monocytes to regulate fibrocyte differentiation, and IL-12 acts indirectly, possibly through CD16-positive NK cells. We previously identified the plasma protein serum amyloid P (SAP) as a potent inhibitor of fibrocyte differentiation. When added together, the fibrocyte-inhibitory activity of SAP dominates the profibrocyte activities of IL-4 and IL-13. The profibrocyte activities of IL-4 and IL-13 and the fibrocyte-inhibitory activities of IFN-gamma and IL-12 counteract each other in a concentration-dependent manner. These results indicate that the complex mix of cytokines and plasma proteins present in inflammatory lesions, wounds, and fibrosis will influence fibrocyte differentiation.

Angiotensin II Signaling in Vascular Physiology and Pathophysiology

Initially recognized as a physiologic regulator of blood pressure and body fluid homeostasis, angiotensin (Ang) II has now been shown in innumerable experiments and clinical studies to contribute to the development and maintenance of cardiovascular disease. Dissection of its signaling mechanisms over the past decades has led to the discovery of several novel concepts, such as tissue-specific metabolism of Ang peptides. Identification and cloning of the various receptors through which Ang II acts on almost all tissues has led to the development of specific pharmacologic inhibitors with proven clinical benefit in patients with cardiovascular disorders. Work on the G-protein-coupled Ang II Type 1 receptor has demonstrated that different receptors interact through oligomerization, compartmentalization, and transactivation, and may explain how Ang II can activate G-protein-independent pathways. Unraveling the downstream effects of Ang II in specific cell types corroborates the importance of the cellular redox state on certain signaling pathways. Finally, the effects of Ang II on cell function and phenotype, such as the expression of inflammatory cytokines and receptors promoting the recruitment of inflammatory cells into vascular tissues, have indicated its role in local inflammation as a general pathogenetic basis of cardiovascular disease. The recognition of Ang II as a contributor to such fundamental pathophysiologic mechanisms, which are believed to be a common pathway for diverse cardiovascular risk factors like hypertension and diabetes, has greatly advanced our knowledge of pathologic signaling in vascular tissues and may help to eventually define novel targets for pharmacologic interventions.

Activation of the signal transducer and activator of transcription-1 in diffuse proliferative lupus nephritis

Difuse proliferative lupus nephritis (DPLN) is the most common and severe form of lupus nephritis. A predominance of IFN-gamma-producing T cells in both peripheral and renal tissues of patients with DPLN has been identified which suggests an important role for cell-mediated immunity in the pathogenesis of this complication in SLE. The biological effects of IFN-gamma rely mainly on the activity of the transcription factor called signal transducer and activator of transcription (STAT)-1. To assess the IFN-gamma/STAT-1 pathway in DPLN, we examined the expression of STAT-1 in renal biopsies from 15 DPLN patients by immunohistochemical staining with an anti-STAT-1 antibody. The expression of STAT-1 in renal tissues was correlated with several clinical and laboratory findings in these DNPN patients.STAT-1 was activated in the tubular cells in all DPLN patients. Seven of 15 DPLN biopsies (46.7%) showed positive cells in glomeruli. Five of these seven DPLN biopsies (71.4%) with positive glomerular cells showed a serum creatinine >1.5 mg/mL at the time the biopsy was carried out whereas only one of eight DPLN biopsy specimens (12.5%) without positive glomerular cells, showed a serum creatinine >1.5 mg/mL (P = 0.041). Moreover, the percentage of DPLN patients with a worse renal outcome in those who showed expression of STAT-1 in glomerulari were higher in comparison to those without STAT-1 expression (P = 0.041). Our results show that STAT-1 is activated in DPLN suggesting that biological effects of IFN-gamma in renal tissues depend, at least in part, on the activation of STAT-1.

Small molecule signal transduction inhibitors for the treatment of solid tumors

A greater understanding of the pathogenesis of malignancy has led to the development of novel therapies designed to target aberrant molecular pathways that characterize and distinguish cancer cells from normal tissue. Small molecules are being designed to interfere with specific steps along the deregulated signaling cascade from the cytoplasmic membrane to the nucleus. Viable targets include growth factor receptors and their downstream second messengers, modulators of the cell cycle or apoptosis, regulators of protein trafficking and degradation, and transcription regulators. This review will discuss the small molecule signal transduction inhibitors in various stages of development and address the strategic issues relating to clinical trial design with these novel targeted agents.

Physiologically achievable concentrations of genistein enhance telomerase activity in prostate cancer cells via the activation of STAT3

Telomerase contributes to the infinite replicative potential of cancer cells by conferring proliferation and survival through the regulation of growth factors and apoptotic proteins. Although it is generally known that the phytoestrogen, genistein, has telomerase-repressing and anti-proliferative effects on various cancer cells at pharmacological concentrations, we report here that physiologically achievable concentrations of genistein enhance telomerase activity, the proliferation of human prostate cancer cells and tumor growth in the transgenic adenocarcinoma mouse prostate model. In determining the mechanism for enhanced telomerase activity, we observed that physiological concentrations of genistein activated signal transducers and activators of transcription 3 (STAT3) both in vitro and in vivo and increased STAT3 binding to the telomerase reverse transcriptase promoter in human prostate cancer cells. These results demonstrate for the first time that physiologically achievable concentrations of genistein enhance telomerase reverse transcriptase transcriptional activity in prostate cancer cells via the activation of STAT3. Consequently, these concentrations of genistein will augment the growth of prostate cancer cells that could be detrimental to individuals with prostate cancer and therefore, caution should be exercised when genistein is considered for chemotherapeutic purposes.

Possible drug targets for celiac disease

Celiac disease (CD) is an intestinal disorder caused by an altered immune response against wheat gluten, a common dietary antigen, and related cereal proteins. Both CD4+ and CD8+ T cells have a role in inducing the intestinal damage, although recent studies have also pinpointed the involvement of the innate immune response in CD pathogenesis. So far, the only available treatment for CD is the strict avoidance of gluten in the diet, but the poor compliance and the associated complications demand alternative therapies. During the last decade, the knowledge of genetic, molecular and cellular mechanisms leading to CD pathogenesis made great progress. The improved understanding of gluten peptides activating either adaptive or innate immune response, of HLA restriction molecules, as well as of cytokines that mediate most of the inflammatory reactions, opens several new promising perspectives for therapeutic intervention. This review discusses both molecular and cellular strategies to treat CD, including the use of proteolytic enzymes active on gluten peptides, antibodies neutralising IL-15 and IFN-gamma, drugs targeting HLA, regulatory cytokines and T cells.

Alpha-synuclein activates stress signaling protein kinases in THP-1 cells and microglia

Here we show that alpha-synuclein, a major constituent of Lewy bodies, induces inflammation in human microglial and human THP-1 cells. Secretions from such stimulated THP-1 cells contain increased levels of IL-1beta and TNF-alpha. When stimulated by alpha-synuclein in combination with IFN-gamma, secretions from the cells also become toxic towards SH-SY5Y neuroblastoma cells. The A30P, E46K and A53T alpha-synuclein mutations, which induce Parkinson's disease, are more potent than normal alpha-synuclein in the induction of such cytotoxicity. To investigate the signaling mechanisms evoked, protein phosphorylation profiling was applied. At least 81 target phospho-sites were identified. Large increases were induced in the three major mitogen-activated protein (MAP) kinase pathways: p38 MAP kinase, extracellular regulated protein-serine kinase (ERK)1/2 and c-Jun-N-terminal kinase (JNK). Upregulation occurred within minutes following exposure to alpha-synuclein, which is consistent with a receptor-mediated effect. These findings demonstrate that alpha-synuclein acts as a potent inflammatory stimulator of microglial cells, and that inhibitors of such stimulation might be beneficial in the treatment of Parkinson's disease and other synucleinopathies.

Inhibition of Smad7 with a specific antisense oligonucleotide facilitates TGF-beta1-mediated suppression of colitis

BACKGROUND & AIMS

Defective transforming growth factor (TGF)-beta1 signaling due to high levels of Smad7 is a feature of inflammatory bowel disease (IBD). In this study, we analyzed the effect of reducing Smad7 levels with antisense oligonucleotide on mouse models of colitis.

METHODS

Mucosal samples taken from colitic tissue of mice with colitis due to either haptenating reagents (trinitrobenzene sulfonic acid [TNBS] or oxazolone) or to transfer of T cells (SCID transfer colitis) were analyzed for Smad3 and/or Smad7 expression by Western blotting and, in some cases, content of TGF-beta1 by enzyme-linked immunosorbent assay. The effect of oral Smad7 antisense oligonucleotide on mucosal inflammation was assessed.

RESULTS

TGF-beta1 levels were increased in the inflamed tissues of mice with colitis induced by either TNBS or oxazolone. Nevertheless, TGF-beta1 did not exert a regulatory effect, probably because TGF-beta1 signaling was blocked, as indicated by the presence of reduced Smad3 phosphorylation and high levels of Smad7. Oral administration of Smad7 antisense oligonucleotide to colitic mice restored TGF-beta1 signaling via Smad3 and ameliorated inflammation in hapten-induced colitis. In addition, Smad7 antisense oligonucleotide had a therapeutic effect on relapsing TNBS-induced colitis but not on cell-transfer colitis.

CONCLUSIONS

These data suggest that colitis models associated with high endogenous TGF-beta1 levels and defective TGF-beta1 signaling due to high levels of Smad7 can be ameliorated by down-regulation of Smad7 and by oral administration of Smad7 antisense oligonucleotide. This may represent a new approach to the control of IBD, particularly during active phases when its Smad7 profile resembles that of hapten-induced colitis.

Both integrated and differential regulation of components of the IL-2/IL-2 receptor system

Interleukin-2 was discovered in 1976 as a T-cell growth factor. It was the first type I cytokine cloned and the first for which a receptor component was cloned. Its importance includes its multiple actions, therapeutic potential, and lessons for receptor biology, with three components differentially combining to form high, intermediate, and low-affinity receptors. IL-2Ralpha and IL-2Rbeta, respectively, are markers for double-negative thymocytes and regulatory T-cells versus memory cells. gamma(c), which is shared by six cytokines, is mutated in patients with X-linked severe-combined immunodeficiency. We now cover an under-reviewed area-the regulation of genes encoding IL-2 and IL-2R components, with an effort to integrate/explain this knowledge.

STAT4 and the proliferation of artery smooth muscle cells in atherosclerosis

Artery smooth muscle cell proliferation is of key importance in the development of atherosclerosis and restenosis following PTCA. In order to understand gene regulation involved in these processes, vascular smooth muscle cells (VSMCs) from atherosclerosis-susceptible White Carneau (WC) and atherosclerosis-resistant Show Racer (SR) pigeons were used to identify transcription factors involved in the enhanced proliferation of WC VSMCs. With protein/DNA array, signal transducer and activator of transcription 4 (STAT4) was found to have over a 10-fold increase in expression in WC compared to SR VSMCs. The difference was confirmed with electrophoretic-mobility shift assay (EMSA) and Western blot. Cells cultured under low serum had 5-fold higher levels of STAT4 in WC compared to SR. By Western analysis, aortic tissue from newly hatched WC pigeons had 1.7-2.0 times greater STAT4 expression than in SR pigeons. A pathway whereby enhanced STAT4 may be associated with enhanced proliferation was identified following IL-12 stimulation of WC VSMCs where 3-fold increases in proliferation and 2-fold higher expression of STAT4 were measured. The findings suggest STAT4 may play a role in VSMC proliferation and describe a unique pigeon model system in which to study STAT4 as a gene target for atherosclerosis therapy.

BIG news in alcohol addiction: new findings on growth factor pathways BDNF, insulin, and GDNF

In recent years, it has become clear that growth factors are not only critical for the development of the central nervous system (CNS) but may also be important contributors to other neuronal functions in the adult brain. This symposium, presented at the 2005 RSA meeting, discussed evidence to support the hypothesis that alterations in growth factor pathways produce dramatic changes in the effects of alcohol on the CNS. The 4 speakers showed that the behavioral effects of alcohol in the adult are regulated by 3 growth factors, insulin, glial cell line-derived neurotrophic factor (GDNF), and brain-derived neurotrophic factor (BDNF). Dr. Wolf from the Heberlein laboratory presented findings obtained from genetic manipulations in Drosophila melanogaster, demonstrating that the insulin pathway controls sensitivity to the intoxicating effects of alcohol. Marian Logrip from the Ron and Janak laboratories presented evidence obtained in rodents that low concentrations of alcohol increase the expression of BDNF in the brain to regulate alcohol consumption. Dr. Pandey showed that amygdalar BDNF regulates alcohol's anxiolytic effects and preference. Finally, Dr. Janak presented evidence that increases in the expression of GDNF in the midbrain reduce alcohol self-administration in rats.

NFkappaB negatively regulates interferon-induced gene expression and anti-influenza activity

Interferons (IFNs) are antiviral cytokines that selectively regulate gene expression through several signaling pathways including nuclear factor kappaB(NFkappaB). To investigate the specific role of NFkappaB in IFN signaling, we performed gene expression profiling after IFN treatment of embryonic fibroblasts derived from normal mice or mice with targeted deletion of NFkappaB p50 and p65 genes. Interestingly, several antiviral and immunomodulatory genes were induced higher by IFN in NFkappaB knock-out cells. Chromatin immunoprecipitation experiments demonstrated that NFkappaB was basally bound to the promoters of these genes, while IFN treatment resulted in the recruitment of STAT1 and STAT2 to these promoters. However, in NFkappaB knock-out cells IFN induced STAT binding as well as the binding of the IFN regulatory factor-1 (IRF1) to the IFN-stimulated gene (ISG) promoters. IRF1 binding closely correlated with enhanced gene induction. Moreover, NFkappaB suppressed both antiviral and immunomodulatory actions of IFN against influenza virus. Our results identify a novel negative regulatory role of NFkappaB in IFN-induced gene expression and biological activities and suggest that modulating NFkappaB activity may provide a new avenue for enhancing the therapeutic effectiveness of IFN.

The Inhibitory Effects of Interleukin‐1 on Growth Hormone Action During Catabolic Illness

Growth hormone (GH) induces the expression of the anabolic genes responsible for growth, metabolism, and differentiation. Normally, GH stimulates the synthesis of circulating insulin-like growth factor-I (IGF-I) by liver, which upregulates protein synthesis in many tissues. The development of GH resistance during catabolic illness or inflammation contributes to loss of body protein, resulting in multiple complications that prolong recovery and cause death. In septic patients, increased levels of proinflammatory cytokines and GH resistance are commonly observed together. Numerous studies have provided evidence that the inhibitory effects of cytokines on skeletal muscle protein synthesis during sepsis and inflammation are mediated indirectly by changes in the GH/IGF-I system. Interleukin (IL)-1, a member of the family of proinflammatory cytokines, interacts with most cell types and is an important mediator of the inflammatory response. Infusion of a specific IL-1 receptor antagonist (IL-1Ra) ameliorates protein catabolism and GH resistance during systemic infection. This suggests that IL-1 is an important mediator of GH resistance during systemic infection or inflammation. Consequently, a better understanding of the interaction between GH, IL-1, and the regulation of protein metabolism is of great importance for the care of the patient.

SLIM trims STATs: ubiquitin E3 ligases provide insights for specificity in the regulation of cytokine signaling

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) pathway has evolved to serve highly specialized functions in the regulation of hematopoiesis, cell metabolism, and immune responses. The duration, strength, and specificity of cytokine signaling are controlled by several mechanisms, including the ubiquitin-proteasome pathway, which modulates the turnover of cytokine receptors and activated JAKs. The specificity of the ubiquitin pathway is achieved through various E3 ligase complexes that recognize and interact with distinct target proteins, often in a phosphorylation-dependent manner. Intriguing new information about the ubiquitin pathway came with the identification of an E3 ubiquitin ligase, SLIM, that specifically interacts with activated STAT1 and STAT4 and induces their ubiquitination and degradation. These findings, together with the evidence from paramyxoviruses about the role of ubiquitination as a highly specific STAT inhibition mechanism, highlight the role of E3 ubiquitin ligases as specificity determinants in the regulation of STAT activation, and open the field for investigation of additional E3s that target other STAT proteins.

Type IV collagen induces STAT5 activation in MCF7 human breast cancer cells

A rapid increase in the tyrosine phosphorylation of signal transducer and activators of transcription (STAT) proteins has been extensively documented in cells stimulated with cytokines and growth factors, but virtually nothing is known about the regulation of STAT5 activation in breast cancer cells stimulated with basement membrane (BM) components. Stimulation of MCF7 cells with type IV collagen (Col-IV) promoted a striking increase in the phosphorylation of STAT5 at Tyr-694, as revealed by site-specific antibodies that recognized the phosphorylated state of this residue. In addition, Col-IV also stimulated STAT5 nuclear translocation and an increased in STAT5 DNA binding activity. Treatment with the selective Src family inhibitor pyrazolopyrimidine PP-2 prevented STAT5 phosphorylation at Tyr-694, nuclear translocation of STAT5 and the STAT5-DNA complex formation. Our results demonstrate, for the first time, that stimulation with Col-IV induces STAT5 phosphorylation of endogenous STAT5 at Tyr-694, nuclear translocation of STAT5 and increases in STAT5 DNA binding activity via a Src-dependent pathway in MCF7 cells.