Targeting JAK/STAT signaling pathways in treatment of inflammatory bowel disease.

Janus kinase/signal transduction and transcriptional activator (JAK/STAT) signaling pathway is a transport hub for cytokine secretion and exerts its effects. The activation of JAK/STAT signaling pathway is essential for the regulation of inflammatory responses. Inappropriate activation or deletion of JAK/STAT signaling pathway is the initiator of the inflammatory response. JAK/STAT signaling pathway has been demonstrated to be involved in the process of innate and adaptive immune response to inflammatory bowel disease (IBD). In this review, we discuss the role of the JAK/STAT signaling pathway in the regulation of different cells in IBD, as well as new findings on the involvement of the JAK/STAT signaling pathway in the regulation of the intestinal immune response. The current status of JAK inhibitors in the treatment of IBD is summarized as well. This review highlights natural remedies that can serve as potential JAK inhibitors. These phytochemicals may be useful in the identification of precursor compounds in the process of designing and developing novel JAK inhibitors.

Role of intracellular signaling pathways and their inhibitors in the treatment of inflammation.

Inflammation is not only a defense mechanism of the innate immune system against invaders, but it is also involved in the pathogenesis of many diseases such as atherosclerosis, thrombosis, diabetes, epilepsy, and many neurodegenerative disorders. The World Health Organization (WHO) reports worldwide estimates of people (9.6% in males and 18.0% in females) aged over 60 years, suffering from symptomatic osteoarthritis, and around 339 million suffering from asthma. Other chronic inflammatory diseases, such as ulcerative colitis and Crohn's disease are also highly prevalent. The existing anti-inflammatory agents, both non-steroidal and steroidal, are highly effective; however, their prolonged use is marred by the severity of associated side effects. A holistic approach to ensure patient compliance requires understanding the pathophysiology of inflammation and exploring new targets for drug development. In this regard, various intracellular cell signaling pathways and their signaling molecules have been identified to be associated with inflammation. Therefore, chemical inhibitors of these pathways may be potential candidates for novel anti-inflammatory drug approaches. This review focuses on the anti-inflammatory effect of these inhibitors (for JAK/STAT, MAPK, and mTOR pathways) describing their mechanism of action through literature search, current patents, and molecules under clinical trials.

Alopecia areata: a review on diagnosis, immunological etiopathogenesis and treatment options.

Patients suffering from alopecia areata (AA) can lose hair in focal regions, the complete scalp, including eyelashes and eyebrows, or even the entire body. The exact pathology is not yet known, but the most described theory is a collapse of the immune privilege system, which can be found in some specific regions of the body. Different treatment options, local and systemic, are available, but none of them have been proven to be effective in the long term as well for every treatment there should be considered for the possible side effects. In many cases, treated or non-treated, relapse often occurs. The prognosis is uncertain and is negatively influenced by the subtypes alopecia totalis and alopecia universalis and characteristics such as associated nail lesions, hair loss for more than 10 years and a positive familial history. The unpredictable course of the disease also makes it a mental struggle and AA patients are more often associated with depression and anxiety compared to the healthy population. Research into immunology and genetics, more particularly in the field of dendritic cells (DC), is recommended for AA as there is evidence of the possible role of DC in the treatment of other autoimmune diseases such as multiple Sclerosis and cancer. Promising therapies for the future treatment of AA are JAK-STAT inhibitors and PRP.

The Potential Inhibitory Effects of miR-19b on Ocular Inflammation are Mediated Upstream of the JAK/STAT Pathway in a Murine Model of Allergic Conjunctivitis.

Purpose: Thymic stromal lymphopoietin (TSLP) is a pro-allergic cytokine that initiates allergic inflammatory reaction between epithelial and dendritic cells (DCs). miR-19b was reported to suppress TSLP expression. The present study aimed to examine miR-19b expression, regulation, and function in allergic conjunctivitis (AC). Methods: A murine model of experimental AC was induced in BALB/c mice by short ragweed pollen. The serum, eye balls, conjunctiva, and cervical lymph nodes (CLN) were used for the study. Gene expression was determined by RT-PCR, whereas protein production and activation were evaluated by immunostaining, ELISA, and Western blotting. Results: In the murine AC model, miR-19b was aberrantly downregulated, whereas the levels of TSLP and p-STAT3, as well as the number of CD11c+ pSTAT3+ DCs were increased. Moreover, Th2 inflammatory cytokine expression was significantly increased. These severe phenotypes could be counteracted by either applying exogenous miR-19b mimic microRNAs or the JAK/STAT inhibitor CYT387. Moreover, overexpression of miR-19b repressed p-STAT3 expression and the number of CD11c+ cells in AC eye and CLN tissues. Conclusions: These findings suggested that miR-19b reduced ocular surface inflammation by inhibiting Stat3 signaling via TSLP downregulation in a murine AC model. Moreover, the present study further demonstrated the clinical potential of applying miR-19b and anti-JAK/STAT therapies in the treatment of AC.

Pyruvate Protects Against Intestinal Injury by Inhibiting the JAK/STAT Signaling Pathway in Rats With Hemorrhagic Shock.

BACKGROUND: This study aimed to investigate the role of Janus kinase/signal transducers and activators of transcription (JAK/STAT) signaling pathway in protection by peritoneal resuscitation (PR) using pyruvate-peritoneal dialysis solution (PY-PDS) against intestinal injury from hemorrhagic shock (HS) in rats. MATERIALS AND METHODS: Sixty-four rats were assigned to eight groups: group SHAM; group intravenous resuscitation (VR); groups NS, LA, and PY in which the rats were subjected to HS and PR with normal saline (NS), lactate-peritoneal dialysis solution (LA-PDS), and PY-PDS, respectively, combined with VR; and groups DMSO, RPM, and AG490 in which the rats were subjected to HS and VR with pretreatment of dimethyl sulfoxide (DMSO), rapamycin (RPM), and tyrphostin B42 (AG490). RESULTS: At 2 h after HS and resuscitation, the levels of diamine oxidase, 15-F2t-isoprostane, thromboxane B2, and endothelin-1, in the blood and the intestinal mucosal apoptotic index and caspase-3 were lower in groups PY, RPM, and AG490 than in groups VR, NS, LA, and DMSO. Group PY showed lower levels of malondialdehyde and myeloperoxidase and a higher level of superoxide dismutase than groups VR, NS, and LA. Phosphorylated JAK2 and phosphorylated STAT3 levels were lower in groups PY, RPM, AG490, and LA than in groups VR, NS, and DMSO. CONCLUSIONS: The protection mechanism of PR with PY-PDS combined with VR was related to the inhibition of the JAK/STAT signaling pathway during HS and resuscitation. The process might include suppression of oxidative stress, reduction of neutrophil infiltration, regulation of microcirculation, and inhibition of apoptosis.

Genkwanin ameliorates adjuvant-induced arthritis in rats through inhibiting JAK/STAT and NF-κB signaling pathways.

BACKGROUND: Genkwanin is a flavone isolated from the traditional Chinese herb Daphne genkwa. Our previous work proved that four flavonoids (including genkwanin) isolated from D. genkwa (FFD) significantly improved the symptoms of arthritis in rat models. Recent studies have revealed that genkwanin exhibited anti-inflammatory and immunomodulatory activities, both of which were closely related to the pathology of rheumatoid arthritis (RA). Therefore, studying the anti-RA effects and mechanisms of genkwanin may give us insight into FFD's therapeutic effects on RA. PURPOSE: This study aimed to investigate the anti-rheumatoid arthritis activity of genkwanin on adjuvant-induced arthritis (AIA) model in rats and explore the underlying mechanisms. METHODS: The anti-rheumatoid arthritis activity of genkwanin was evaluated on AIA rat model by determining the paw swelling degrees and arthritis index scores, along with histopathological analysis of joint tissues. The serum cytokine levels were measured by ELISA method, and serum NO levels were measured by Griess method. The expression and phosphorylation levels of proteins in JAK/STAT and NF-κB signaling pathways were determined by western blot analysis and immunohistochemistry analysis. RESULTS: Genkwanin significantly decreased the paw swelling and arthritis index in AIA rats and also decreased the inflammation and bone destruction in joint tissues. The serum TNF-α, IL-6, and NO concentrations were markedly reduced while the IL-10 concentration was markedly increased with the treatment of genkwanin. Genkwanin inhibited the activation of JAK/STAT and NF-κB signaling pathways in synovial tissues of AIA rats. CONCLUSION: Genkwanin exerted anti-rheumatoid arthritis effects on AIA rats through inhibiting the activation of JAK/STAT and NF-κB signaling pathways. The results obtained in this work lead us to suggest that Genkwanin could play a crucial role on the previously demonstrated anti-rheumatoid arthritis activity of flavonoid extract of D. genkwa (namely FFD).

Targeting STATs in neuroinflammation: The road less traveled!

JAK/STAT transduction pathway is a highly conserved pathway implicated in regulating cellular proliferation, differentiation, survival and apoptosis. Dysregulation of this pathway is involved in the onset of autoimmune, haematological, oncological, metabolic and neurological diseases. Over the last few years, the research of anti-neuroinflammatory agents has gained considerable attention. The ability to diminish the STAT-induced transcription of inflammatory genes is documented for both natural compounds (such as polyphenols) and chemical drugs. Among polyphenols, quercetin and curcumin directly inhibit STAT, while Berberis vulgaris L. and Sophora alopecuroides L extracts act indirectly. Also, the Food and Drug Administration has approved several JAK/STAT inhibitors (direct or indirect) for treating inflammatory diseases, indicating STAT can be considered as a therapeutic target for neuroinflammatory pathologies. Considering the encouraging data obtained so far, clinical trials are warranted to demonstrate the effectiveness and potential use in the clinical practice of STAT inhibitors to treat inflammation-associated neurodegenerative pathologies.

Preclinical characterization of the JAK/STAT inhibitor SGI-1252 on skeletal muscle function, morphology, and satellite cell content.

BACKGROUND: Recent studies have highlighted the JAK/STAT signaling pathway in the regulation of muscle satellite cell behavior. Herein we report preclinical studies designed to characterize the effects of a novel JAK/STAT inhibitor on plantar flexor skeletal muscle function, morphology, and satellite cell content. METHODS: The compound, SGI-1252, was administered orally (400mg/kg) in a 10% dextrose solution to wild type mice (n = 6) 3 times per week for 8 weeks. A control group (n = 6) received only the dextrose solution. RESULTS: SGI-1252 was well tolerated, as animals displayed similar weight gain over the 8-week treatment period. Following treatment, fatigue in the gastrocnemius-soleus-plantaris complex was greater in the SGI-1252 mice during a 300 second tetanic contraction bout (p = 0.035), though both the rate of fatigue and maximal force production were similar. SGI-1252 treated mice had increased type II myofiber cross-sectional area (1434.8 ± 225.4 vs 1754.7 ± 138.5 µm2), along with an increase in wet muscle mass (125.45 ± 5.46 vs 139.6 ± 12.34 mg, p = 0.032) of the gastrocnemius relative to vehicle treated mice. SGI-1252 treatment reduced gastrocnemius STAT3 phosphorylation 53% (94.79 ± 45.9 vs 44.5 ± 6.1 MFI) and significantly increased the concentration of Pax7+ satellite cells (2589.2 ± 105.5 vs 2859.4 ± 177.5 SC/mm3) in the gastrocnemius. SGI-1252 treatment suppressed MyoD (p = 0.013) and Myogenin (p<0.0001) expression in human primary myoblasts, resulting in reduced myogenic differentiation (p = 0.039). CONCLUSIONS: Orally delivered SGI-1252 was well tolerated, attenuates skeletal muscle STAT3 activity, and increases satellite cell content in mouse gastrocnemius muscle, likely by inhibiting myogenic progression.

Essential oil of Artemisia argyi suppresses inflammatory responses by inhibiting JAK/STATs activation.

ETHNOPHARMACOLOGICAL RELEVANCE: Artemisia argyi is a herbal medicine traditionally used in Asia for the treatment of bronchitis, dermatitis and arthritis. Recent studies revealed the anti-inflammatory effect of essential oil in this plant. However, the mechanisms underlying the therapeutic potential have not been well elucidated. The present study is aimed to verify its anti-inflammatory effect and investigate the probable mechanisms. MATERIALS AND METHODS: The essential oil from Artemisia argyi (AAEO) was initially tested against LPS-induced production of inflammatory mediators and cytokines in RAW264.7 macrophages. Protein and mRNA expressions of iNOS and COX-2 were determined by Western blotting and RT-PCR analysis, respectively. The effects on the activation of MAPK/NF-κB/AP-1 and JAK/STATs pathway were also investigated by western blot. Meanwhile, in vivo anti-inflammatory effect was examined by histologic and immunohistochemical analysis in TPA-induced mouse ear edema model. RESULTS: The results of in vitro experiments showed that AAEO dose-dependently suppressed the release of pro-inflammatory mediators (NO, PGE2 and ROS) and cytokines (TNF-α, IL-6, IFN-ß and MCP-1) in LPS-induced RAW264.7 macrophages. It down-regulated iNOS and COX-2 protein and mRNA expression but did not affect the activity of these two enzymes. AAEO significantly inhibited the phosphorylation of JAK2 and STAT1/3, but not the activation of MAPK and NF-κB cascades. In animal model, oral administration of AAEO significantly attenuated TPA-induced mouse ear edema and decreased the protein level of COX-2. CONCLUSION: AAEO suppresses inflammatory responses via down-regulation of the JAK/STATs signaling and ROS scavenging, which could contribute, at least in part, to the anti-inflammatory effect of AAEO.

Anti-inflammatory effects of the petasin phyto drug Ze339 are mediated by inhibition of the STAT pathway.

Ze339, an herbal extract from Petasites hybridus leaves is effective in treatment of allergic rhinitis by inhibition of a local production of IL-8 and eicosanoid LTB4 in allergen-challenged patients. However, the mechanism of action and anti-inflammatory potential in virally induced exacerbation of the upper airways is unknown. This study investigates the anti-inflammatory mechanisms of Ze339 on primary human nasal epithelial cells (HNECs) upon viral, bacterial and pro-inflammatory triggers. To investigate the influence of viral and bacterial infections on the airways, HNECs were stimulated with viral mimics, bacterial toll-like-receptor (TLR)-ligands or cytokines, in presence or absence of Ze339. The study uncovers Ze339 modulated changes in pro-inflammatory mediators and decreased neutrophil chemotaxis as well as a reduction of the nuclear translocation and phosphorylation of STAT molecules. Taken together, this study suggests that phyto drug Ze339 specifically targets STAT-signalling pathways in HNECs and has high potential as a broad anti-inflammatory drug that exceeds current indication. © 2016 BioFactors, 43(3):388-399, 2017.

Targeted inhibition of STATs and IRFs as a potential treatment strategy in cardiovascular disease.

Key factors contributing to early stages of atherosclerosis and plaque development include the pro-inflammatory cytokines Interferon (IFN)α, IFNγ and Interleukin (IL)-6 and Toll-like receptor 4 (TLR4) stimuli. Together, they trigger activation of Signal Transducer and Activator of Transcription (STAT) and Interferon Regulatory Factor (IRF) families. In particular, STAT1, 2 and 3; IRF1 and 8 have recently been recognized as prominent modulators of inflammation, especially in immune and vascular cells during atherosclerosis. Moreover, inflammation-mediated activation of these STATs and IRFs coordinates a platform for synergistic amplification leading to pro-atherogenic responses.Searches for STAT3-targeting compounds, exploring the pTyr-SH2 interaction area of STAT3, yielded many small molecules including natural products. Only a few inhibitors for other STATs, but none for IRFs, are described. Promising results for several STAT3 inhibitors in recent clinical trials predicts STAT3-inhibiting strategies may find their way to the clinic. However, many of these inhibitors do not seem STAT-specific, display toxicity and are not very potent. This illustrates the need for better models, and screening and validation tools for novel STAT and IRF inhibitors.This review presents a summary of these findings. It postulates STAT1, STAT2 and STAT3 and IRF1 and IRF8 as interesting therapeutic targets and targeted inhibition could be a potential treatment strategy in CVDs. In addition, it proposes a pipeline approach that combines comparative in silico docking of STAT-SH2 and IRF-DBD models with in vitro STAT and IRF activation inhibition validation, as a novel tool to screen multi-million compound libraries and identify specific inhibitors for STATs and IRFs.

Cyclovirobuxinum D suppresses lipopolysaccharide-induced inflammatory responses in murine macrophages in vitro by blocking JAK-STAT signaling pathway.

AIM: Cyclovirobuxinum D (CVB-D), an alkaloid isolated from the Chinese medicinal plant Buxus microphylla, has been found to be effective to treat cardiac insufficiency, arrhythmias and coronary heart disease. In the present study, we investigated the effects of CVB-D on the inflammatory responses in lipopolysaccharide (LPS)-stimulated murine macrophages in vitro and the underlying mechanisms. METHODS: Murine macrophage cell line RAW264.7 cells were incubated in the presence of LPS (0.1 µg/mL) for 24 h. The cell viability was measured using MTT assay. The release of NO and cytokines were detected using the Griess test and ELISA, respectively. The mRNA and protein levels were determined using RT-PCR and Western blot, respectively. Reporter gene assays were used to analyze the transcriptional activity of NF-κB. RESULTS: Treatment of RAW264.7 cells with CVB-D (25-300 µmol/L) did not affect the cell viability. Pretreatment with CVB-D (50, 100 and 200 µmol/L) concentration-dependently decreased NO release and iNOS expression in LPS-treated RAW264.7 cells (its IC50 value in inhibition of NO production was 144 µmol/L). CVB-D also concentration-dependently inhibited the secretion and mRNA expression of IL-1ß and IL-6 in LPS-treated RAW264.7 cells. Furthermore, CVB-D remarkably inhibited the phosphorylation of STAT1 and STAT3, as well as JAK2 in LPS-treated RAW264.7 cells, but did not affect the activation of NF-κB and MAPKs pathways. Pretreatment with the JAK2 specific inhibitor AG490 (30 µmol/L) produced similar effects on NO release and iNOS expression in LPS-treated RAW264.7 cells. CONCLUSION: CVB-D exerts anti-inflammatory effects in LPS-stimulated murine macrophages in vitro at least in part by blocking the JAK-STAT signaling pathway. The anti-inflammatory actions of CVB-D may contribute to its cardioprotection.

Forsythin inhibits lipopolysaccharide-induced inflammation by suppressing JAK-STAT and p38 MAPK signalings and ROS production.

OBJECTIVE: Forsythin (FOR) is an active ingredient extracted from the fruit of the medicinal plant Forsythia suspensa (Thunb.) Vahl. Here, we investigated the effect of FOR on LPS-induced inflammatory response and the underlying molecular mechanisms in RAW264.7 macrophages. MATERIALS AND METHODS: RAW264.7 cells were pre-treated with or without FOR and then stimulated with or without LPS. The productions of TNF-α, IL-1ß, IL-6, PGE2 and NO were determined by ELISA and nitrite analysis, respectively. The expressions of nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2) were measured by Western blotting and RT-PCR analysis. The activations of signaling molecules were detected by Western blotting using phosphorylation specific antibodies. Reactive oxygen species (ROS) production was determined by ROS assay. RESULTS: LPS-induced productions of IL-1ß, IL-6, TNF-α, NO and PGE2 were inhibited by FOR in a dose-dependent manner. FOR also suppressed the LPS-elevated expressions of iNOS and COX-2. Further investigations revealed that FOR significantly inhibited the LPS-induced activations of JAK-STATs and p38 MAPKs, but not of IKKα/ß in LPS-stimulated RAW264.7 cells. Additionally, FOR interfered with both JAK-STATs and p38 MAPKs signaling pathways to modulate the expressions of IL-1ß, IL-6, TNF-α, iNOS and COX-2. Furthermore, FOR reduced the LPS-induced ROS accumulation, validating that FOR serves as an antioxidant. CONCLUSIONS: Our data suggested that FOR exerts anti-inflammatory action, at least in part, via suppressing LPS-induced activation of JAK-STATs and p38 MAPKs signalings and production of ROS in macrophage cells.

Emerging topical treatments for psoriasis.

INTRODUCTION: Psoriasis is an immune-mediated chronic inflammatory skin disease which classically presents as erythematous, scaly plaques affecting extensor surfaces of the limbs, scalp and trunk. Approximately 80% of patients have a mild-to-moderate form routinely treated with topical medications, whereas phototherapy, systemic and biological therapies are typically reserved for treatment of moderate-to-severe psoriasis. AREAS COVERED: The major advances in psoriasis therapy in the past 15 years have been in new immunomodulatory and biological molecules, with a significant unmet need to have new, efficient and safe topical treatment options for the large percentage of patients for whom systemic therapy is not indicated. The available topical therapies (corticosteroids and vitamin D3 analogs) have remained relatively unchanged over the past several decades. This article reviews emerging topical drugs and formulations currently under evaluation in clinical trials. EXPERT OPINION: The time is right for a revolution in our topical therapy armamentarium. It has lagged significantly behind the systemic biological evolution of new drug development. Our large psoriasis population with mild-to-moderate psoriasis certainly deserves potent but safe and innovative topical agents with a new mode of action as well as with long-lasting clinical efficacy.

Parthenolide, a sesquiterpene lactone, expresses multiple anti-cancer and anti-inflammatory activities.

Parthenolide, a naturally occurring sesquiterpene lactone derived from feverfew (Tanacetum parthenium), exhibits exceptional anti-cancer and anti-inflammatory properties, making it a prominent candidate for further studies and drug development. In this review, we briefly investigate molecular events and cell-specific activities of this chemical in relation to cytochrome c, nuclear factor kappa-light-chain enhancer of activated B cells (NF-κB), signal transduction and activation of transcription (STAT), reactive oxygen species (ROS), TCP, HDACs, microtubules, and inflammasomes. This paper reports that parthenolide shows strong NF-κB- and STAT-inhibition-mediated transcriptional suppression of pro-apoptotic genes. This compound acts both at the transcriptional level and by direct inhibition of associated kinases (IKK-ß). Similarly, this review discusses parthenolide-induced ROS-mediated apoptosis of tumor cells via the intrinsic apoptotic signaling pathway. The unique ability of this compound to not harm normal cells but at the same time induce sensitization to extrinsic as well as intrinsic apoptosis signaling in cancer cells provides an important, novel therapeutic strategy for treatment of cancer and inflammation-related disorders.

Targeting silibinin in the antiproliferative pathway.

IMPORTANCE OF THE FIELD: Due to the failure and severe toxicity of cancer chemotherapy, silibinin, a natural flavonoid from the seeds of milk thistle, has recently received more attention for its potential anticancer and nontoxic roles in animals and humans. Silibinin has clearly demonstrated inhibition of multiple cancer cell signaling pathways, including growth inhibition, inhibition of angiogenesis, chemosensitization, and inhibition of invasion and metastasis. Cumulative evidence implicates that silibinin is a potential agent for cancer chemoprevention and chemotherapy. AREAS COVERED IN THIS REVIEW: Our aim is to discuss the recent progress of silibinin in regulating multiple anticancer proliferative signaling pathways; the review covers literature mainly from the past 3 - 5 years. WHAT THE READER WILL GAIN: One of the strategies for tumor therapy is eradication of cancer cells through targeting specific cell-proliferative pathways. This review highlights the current knowledge of silibinin in regulating multiple cellular proliferative pathways in cancer cells, including receptor tyrosine kinases, androgen receptor, STATs, NF-kappaB, cell cycle regulatory and apoptotic signaling pathways. TAKE HOME MESSAGE: The molecular mechanisms of silibinin-mediated antiproliferative effects are mainly via receptor tyrosine kinases, androgen receptor, STATs, NF-kappaB, cell cycle regulatory and apoptotic signaling pathways in various cancer cells. Targeting inhibition of proliferative pathways through silibinin treatment may provide a new approach for improving chemopreventive and chemotherapeutic effects.

American ginseng preferentially suppresses STAT/iNOS signaling in activated macrophages.

AIM OF THE STUDY: Ginseng has been used as general tonic for thousands of years in Asia and becomes a popular herbal medicine all over the world. However, the cellular and molecular mechanisms underlying its benefit effects are less explored. Thus, we investigated the effect of a crude extract from Panax quinquefolius (American ginseng) on suppression of pro-inflammatory responses in macrophages with a focus on signal transducer and activator of transcription (STAT) signaling. MATERIALS AND METHODS: The crude extract of American ginseng that was supplied by the National Research Council of Canada, Institute for National Measurement Standards (NRCC-INMS) was freshly solvated in Dulbecco's Modified Eagle Medium (DMEM) prior to each experiment. RAW264.7 cells, a murine macrophage cell line, were exposed to lipopolysaccharide (LPS) to induce inflammatory responses such as expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase 2 (COX2). Proteins were measured by Western blot and mRNA expression was determined by quantitative real-time PCR (Q-PCR). Activator protein 1 (AP-1)-, nuclear factor-kappaB (NF-kappaB)- and STAT-mediated transcriptional activities were investigated using luciferase reporter constructs. RESULTS: American ginseng inhibited LPS-induced iNOS expression; however, it did not affect LPS-induced COX2 expression. While American ginseng had no impact on LPS-induced activation of AP-1 or NF-kappaB pathways, it dramatically inhibited LPS-induced activation of STAT signaling. Moreover, American ginseng and AG490, an inhibitor of STAT cascade, synergistically suppressed the LPS-induced iNOS expression. CONCLUSION: American ginseng selectively inhibits the expression of iNOS via suppression of STAT cascade but not NF-kappaB and AP-1 pathways in inflamed macrophages. Such a preferential suppression of STAT/iNOS cascade by American ginseng might have therapeutic potential for inflammatory diseases with over-activation of iNOS.