Signal Transducer And Activator Of Transcription 3 Phosphorylation Research Articles

The Induction of Drug Uptake Transporter Organic Anion Transporting Polypeptide 1A2 by Radiation Is Mediated by the Nonreceptor Tyrosine Kinase v-YES-1 Yamaguchi Sarcoma Viral Oncogene Homolog 1.

Organic anion transporting polypeptides (OATP, gene symbol SLCO) are well-recognized key determinants for the absorption, distribution, and excretion of a wide spectrum of endogenous and exogenous compounds including many antineoplastic agents. It was therefore proposed as a potential drug target for cancer therapy. In our previous study, it was found that low-dose X-ray and carbon ion irradiation both upregulated the expression of OATP family member OATP1A2 and in turn, led to a more dramatic killing effect when cancer cells were cotreated with antitumor drugs such as methotrexate. In the present study, the underlying mechanism of the phenomenon was explored in breast cancer cell line MCF-7. It was found that the nonreceptor tyrosine kinase v-YES-1 Yamaguchi sarcoma viral oncogene homolog 1 (YES-1) was temporally coordinated with the change of OATP1A2 after irradiation. The overexpression of YES-1 significantly increased OATP1A2 both at the mRNA and protein level. The signal transducer and activator of transcription 3 (STAT3) pathway is likely the downstream target of YES-1 because phosphorylation and nuclear accumulation of STAT3 were both enhanced after overexpressing YES-1 in MCF-7 cells. Further investigation revealed that there are two possible binding sites of STAT3 localized at the upstream sequence of SLCO1A2, the encoding gene of OATP1A2. Electrophoretic mobility shift assay and chromatin immunoprecipitation analysis suggested that these two sites bound to STAT3 specifically and the overexpression of YES-1 significantly increased the association of the transcription factor with the putative binding sites. Finally, inhibition or knockdown of YES-1 attenuated the induction effect of radiation on the expression of OATP1A2. SIGNIFICANCE STATEMENT: The present study found that the effect of X-rays on v-YES-1 Yamaguchi sarcoma viral oncogene homolog 1 (YES-1) and organic anion transporting polypeptides (OATP)1A2 was temporally coordinated. YES-1 phosphorylates and increases the nuclear accumulation of signal transducer and activator of transcription 3, which in turn binds to the upstream regulatory sequences of SLCO1A2, the coding gene for OATP1A2. Hence, inhibitors of YES-1 may suppress the radiation induction effect on OATP1A2.

Interleukin 31 mediates pruritus in horses.

This study investigated the effects of recombinant equine IL-31 (eIL-31) in vivo and in vitro. Equine IL-31 mRNA sequences were verified by sequencing. Recombinant eIL-31 was produced using mammalian and bacterial expression systems. From November 2019 through February 2021, 12 normal horses, 6 to 10 years old with no history or clinical signs consistent with allergic skin disease, were injected ID with eIL-31 and saline in 2 challenge studies. Pruritus-associated behaviors were recorded for a minimum of 15 minutes preinjection and 4 hours postinjection. Adherent monocytes from 3 pruritic horses, exhibiting insect bite hypersensitivity and/or atopic dermatitis, were stimulated with bacterial eIL-31, and subsequent phosphorylation of signal transducer and activator of transcription 3 (STAT3) was measured by western blot and AlphaLISA. The bacterial eIL-31 was produced with greater purity than the mammalian eIL-31 (> 95% vs 70%). Pruritus was elicited by both recombinant proteins. The mammalian eIL-31 induced mild pruritus (cumulative seconds spent itching postinjection ranged from 6 to 313). The bacterial eIL-31 induced marked pruritus in some horses (a cumulative maximum of 5,529 seconds spent itching in 1 horse) and a milder response in others (range of cumulative seconds spent itching, 17 to 2,313). Most pruritus occurred after 2 hours and subsided by 4 hours postinjection. Bacterial eIL-31 induced STAT3 phosphorylation in adherent monocytes from allergic horses. In this proof-of-concept study, IL-31 was found to mediate pruritus and was associated with STAT3 phosphorylation in horses as in other species. Interleukin 31 is a promising therapeutic target for equine allergic pruritus.

Morinda officinalis iridoid glycosides, as an inhibitor of GSK-3β, alleviates rheumatoid arthritis through inhibition of NF-κB and JAK2/STAT3 pathway.

Morinda officinalis iridoid glycosides (MOIG) showed potential benefits in the treatment of rheumatoid arthritis (RA), but their exact mechanism has yet to be explored. To evaluate the effects of MOIG on RA, and explore the potential targets and molecular mechanism of MOIG in RA. The collagen-induced arthritis (CIA) rats were used to evaluate the effects of MOIG on RA. The proliferation, migration and invasion of fibroblast-like synoviocytes (FLSs) stimulated with or without tumor necrosis factor (TNF)-α were examined by CCK-8, wound healing and transwell assays, respectively. IF and WB were applied to investigate related mechanism in FLSs. The molecular docking, molecular dynamics simulation, CETSA and siRNA were used to analyze the interaction of MOIG with target. Finally, the adjuvant-induced arthritis (AA) mice model with gene knockdown was used to confirm the effect of MOIG on glycogen synthase kinase-3β (GSK-3β). MOIG significantly alleviated the paw swelling and synovial hyperplasia in CIA rats. Moreover, MOIG suppressed proliferation, migration and invasion, the secretion of inflammatory factors, and the expression of adhesion related proteins in TNF-α-stimulated FLSs. MOIG also inhibited the activation of Janus activating kinase 2 (JAK2)/signal transducer and activator of transcription 3 (STAT3) and nuclear factor kappa-B (NF-κB) signaling pathway in FLSs. Interestingly, the plant metabolites in MOIG had a good affinity with GSK-3β, and inhibition of GSK-3β attenuated the effects of MOIG on FLSs. Knockdown GSK-3β gene could inhibit the paw swelling and inflammatory indicators, decrease the arthritis score and synovial hyperplasia, reduce the phosphorylation of p65 and STAT3 in AA mice, thereby suppressing the NF-κB and STAT3 signaling activation, and MOIG treatment had no significant effects on AA mice with si-GSK-3β. MOIG alleviates joint inflammation in RA through inhibition NF-κB and JAK2/STAT3 pathway via suppression of GSK-3β in FLSs, which provides supports for MOIG as a promising therapeutic agent of RA.

Pancreatic STAT5 activation promotes KrasG12D-induced and inflammation-induced acinar-to-ductal metaplasia and pancreatic cancer

ObjectivePancreatic ductal adenocarcinoma (PDAC) is a highly lethal malignancy because it is often diagnosed at a late-stage. Signal transducer and activator of transcription 5 (STAT5) is a transcription factor implicated...

Visible light accelerates skin wound healing and alleviates scar formation in mice by adjusting STAT3 signaling

During the wound healing process, the activation of signal transducer and activator of transcription 3 (STAT3) is considered crucial for the migration and proliferation of epithelial cells, as well as for establishing the inflammatory environment. However, an excessive STAT3 activation aggravates scar formation. Here we show that 450 nm blue light and 630 nm red light can differentially regulate the phosphorylation of STAT3 (p-STAT3) and its downstream cytokines in keratinocytes. Further mechanistic studies reveal that red light promotes wound healing by activating the PI3 kinase p110 beta (PI3Kβ)/STAT3 signaling axis, while blue light inhibits p-STAT3 at the wound site by modulating cytochrome c-P450 (CYT-P450) activity and reactive oxygen species (ROS) generation. In a mouse scar model, skin wound healing can be significantly accelerated with red light followed by blue light to reduce scar formation. In summary, our study presents a potential strategy for regulating epithelial cell p-STAT3 through visible light to address skin scarring issues and elucidates the underlying mechanisms.

Biological evaluation of signal transducer and activator of transcription 3 (STAT3) targeting by phaeosphaeride A and its analogs

The inhibitory activities of phaeosphaeride A (PPA), phaeosphaeride B, and four synthetic derivatives against phosphorylation of signal transducer and activator of transcription 3 (STAT3) and cell proliferation in cervical (HeLa) and breast (MDA-MB-231) cancer cells were evaluated. PPA inhibited IL-6-induced STAT3 phosphorylation and cell proliferation at similar concentrations. The structure–activity relationship studies revealed that the enantiomer of PPA was the most potent of the evaluated phaeosphaerides in both inhibiting STAT3 phosphorylation and cell growth. PPA clearly inhibited the IL-6-activated STAT3 signaling pathway. However, the presence or absence of activation of the STAT3 signaling pathway in cells showed no relationship to the antiproliferative activity. Notably, the possible covalent bond-forming ability of PPA was critical for its biological activities.

STAT6 blockade ameliorates thyroid function in Graves' disease via downregulation of the sodium/iodide symporter.

Signal transducer and activator of transcription 6 (STAT6) is an important nuclear transcription factor. Previous study demonstrated that blockading STAT6 can ameliorate thyroid function by reducing serum T3 and T4. Sodium/iodide symporter (NIS) is a key protein that mediates active iodine uptake and plays an important role in regulating thyroid function. This study explored the interaction between STAT6 and NIS. Immunohistochemical staining was performed for detecting the expression of NIS in different tissues. Reverse transcription-polymerase chain reaction (RT-PCR) was performed for evaluating the mRNA level of NIS when Nthy-ori 3-1cells were incubated with IL4, TSH (Thyroid stimulating hormone) or monoclonal TSAb (thyroid-specific stimulatory autoantibody) for 24h. Quantitative RT-PCR,Western blot and immunofluorescence analysis were performed for detecting NIS expression after inhibiting STAT6 phosphorylation by AS1517499. Finally, we used Luciferase reporter assays to explore the ability of STAT6 to regulate the promoter activity of the NIS-coding gene. NIS was highly expressed in thyroid epithelial cells of EAGD mice or Graves' disease (GD) patients and TSAb increased the expression of NIS. We show that STAT6 phosphorylation inhibitor can attenuate the effect of TSAb on increasing NIS protein and mRNA levels. Finally, we confirm that transcription factor STAT6 can mediate NIS transcription and co-activator P100 protein can enhance STAT6-dependent transcriptional activation. In Graves' disease, TSAb induces STAT6 signaling to upregulate NIS expression and STAT6 blockade ameliorates thyroid function via downregulation of the sodium/iodide symporter. Our study furthers understanding of the effects of STAT6 on thyroid function and reveals new avenues for GD treatment.

Inhibition of STAT3 by 2-Methoxyestradiol suppresses M2 polarization and protumoral functions of macrophages in breast cancer

BackgroundBreast cancer metastasis remains the leading cause of cancer-related deaths in women worldwide. Infiltration of tumor-associated macrophages (TAMs) in the tumor stroma is known to be correlated with reduced overall survival. The inhibitors of TAMs are sought after for reprogramming the tumor microenvironment. Signal transducer and activator of transcription 3 (STAT3) is well known to contribute in pro-tumoral properties of TAMs. 2-Methoxyestradiol (2ME2), a potent anticancer and antiangiogenic agent, has been in clinical trials for treatment of breast cancer. Here, we investigated the potential of 2ME2 in modulating the pro-tumoral effects of TAMs in breast cancer.MethodsTHP-1-derived macrophages were polarized to macrophages with or without 2ME2. The effect of 2ME2 on macrophage surface markers and anti-inflammatory genes was determined by Western blotting, flow cytometry, immunofluorescence, qRT‒PCR. The concentration of cytokines secreted by cells was monitored by ELISA. The effect of M2 macrophages on malignant properties of breast cancer cells was determined using colony formation, wound healing, transwell, and gelatin zymography assays. An orthotopic model of breast cancer was used to determine the effect of 2ME2 on macrophage polarization and metastasis in vivo.ResultsFirst, our study found that polarization of monocytes to alternatively activated M2 macrophages is associated with the reorganization of the microtubule cytoskeleton. At lower concentrations, 2ME2 treatment depolymerized microtubules and reduced the expression of CD206 and CD163, suggesting that it inhibits the polarization of macrophages to M2 phenotype. However, the M1 polarization was not significantly affected at these concentrations. Importantly, 2ME2 inhibited the expression of several anti-inflammatory cytokines and growth factors, including CCL18, TGF-β, IL-10, FNT, arginase, CXCL12, MMP9, and VEGF-A, and hindered the metastasis-promoting effects of M2 macrophages. Concurrently, 2ME2 treatment reduced the expression of CD163 in tumors and inhibited lung metastasis in the orthotopic breast cancer model. Mechanistically, 2ME2 treatment reduced the phosphorylation and nuclear translocation of STAT3, an effect which was abrogated by colivelin.ConclusionsOur study presents novel findings on mechanism of 2ME2 from the perspective of its effects on the polarization of the TAMs via the STAT3 signaling in breast cancer. Altogether, the data supports further clinical investigation of 2ME2 and its derivatives as therapeutic agents to modulate the tumor microenvironment and immune response in breast carcinoma.

The Atypical Dual Specificity Phosphatase DUSP15 Regulates Jak1-Mediated STAT3 Activation.

The signal transducer and activator of transcription 3 (STAT3) protein is a key regulator of cell differentiation, proliferation, and survival in hematopoiesis, immune responses, and other biological systems. STAT3 transcriptional activity is strictly regulated through various mechanisms, such as phosphorylation and dephosphorylation. In this study, we attempted to identify novel phosphatases which regulate STAT3 activity in response to cytokine stimulations. To this end, leukemia inhibitory factor (LIF)/STAT3 dependent phosphatase induction was evaluated in the mouse hepatoma cell line Hepa1-6. After LIF stimulation, the expression of several atypical dual specific phosphatases (aDUSPs) was upregulated in Hepa1-6 cells. Among the LIF-induced aDUSPs, we focused on DUSP15 and clarified its functions in LIF/STAT3 signaling using RNA interference. DUSP15 knockdown decreased LIF-induced Socs3 mRNA expression and STAT3 translocation. Furthermore, loss of DUSP15 reduced the phosphorylation of STAT3 at Tyr705 and Janus family tyrosine kinase 1 (Jak1) at Tyr1034/1035 in response to LIF. The interaction between Jak1 and DUSP15 was observed in LIF-stimulated Hepa1-6 cells. We also demonstrated the suppression of granulocyte colony-stimulating factor (G-CSF)-mediated gp130/STAT3-dependent cell growth of Ba/F-G133 cells via DUSP15 knockdown. Therefore, DUSP15 functions as a positive feedback regulator in the Jak1/STAT3 signaling cascade.

Geniposide attenuates influenza virus-induced pneumonia by regulating inflammatory cytokines production. Evidences to elucidate the followed pathway

BackgroundInfluenza virus-induced pneumonia (IVP) is an infectious pulmonary disease characterized by exacerbated pulmonary inflammation caused by invasion of the influenza virus. IVP continues to threaten public health due to its high morbidity and mortality rates. Geniposide is one of the major bioactive constituents of G. jasminoides, which exerts antiviral and anti-inflammatory effects on influenza A virus (IAV) infection. PurposeTo investigate therapeutic effects and comprehensive mechanisms of geniposide on IAV infection and subsequent pneumonia. MethodsICR mice were infected intranasally with H1N1 (A/FM/1/47) to detect the anti-IAV activity of geniposide. Proteomics combined with function-integrated analysis were conducted to gain insight into the comprehensive mechanisms of geniposide. Subsequently, western blot was used to detect the phosphorylation of signal transducer and activator of transcription 1 (STAT1), signal transducer and activator of transcription 2 (STAT2), Interferon regulatory factor 9 (IRF9) and Janus kinase 1 (JAK1) in Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway in lung tissue. Finally, RT-qPCR was used to detect the levels of interleukin 6 (IL-6), interleukin 17 (IL-17), interferon-γ (IFN-γ) and the STAT1 inhibitor (fludarabine) was used to verify the targeting between STAT1 and geniposide in RAW cells. ResultsGeniposide could significantly reduce the lung index, diminish lung pathology, decrease the virus loads and the inflammatory cytokines expression induced by IAV infection. A total of 411 differentially expressed proteins were identified among control, model, and geniposide-treated group in proteomic analysis. According to function-integrated analysis, 15 KEGG pathways were enriched and divided into 9 groups (modules), including influenza A, NOD-like receptor signaling, RIG-I-like receptor signaling, and so on. Among these modules, the most intensely interacting module pair was the NOD-like receptor signaling and influenza A, in which STAT1 and STAT2 acted as hubs with critical bridgeness role in the target network of geniposide. This indicated that geniposide may mitigate inflammation and alleviate IVP by JAK/STAT signaling pathways. Moreover, validation experiments confirmed that geniposide can significantly inhibit STAT1 and STAT2 phosphorylation as well as down-regulated expression of IL-6, IFN-γ and IL-17 in lung. Furthermore, when RAW cells were treated with the STAT1 inhibitor (fludarabine), the inhibitory effect of geniposide on IFN-γ and IL-6 was attenuated significantly. ConclusionsGeniposide can attenuate IAV-induced pneumonia by regulating inflammatory cytokines production through the JAK/STAT pathway.

Patient-derived acellular ascites fluid affects drug responses in ovarian cancer cell lines through the activation of key signalling pathways.

Malignant ascites is commonly produced in advanced epithelial ovarian cancer (EOC) and serves as unique microenvironment for tumour cells. Acellular ascites fluid (AAF) is rich in signalling molecules and has been proposed to play a role in the induction of chemoresistance. Through in vitro testing of drug sensitivity and by assessing intracellular phosphorylation status in response to mono- and combination treatment of five EOC cell lines after incubation with AAFs derived from 20 different patients, we investigated the chemoresistance-inducing potential of ascites. We show that the addition of AAFs to the culture media of EOC cell lines has the potential to induce resistance to standard-of-care drugs (SCDs). We also show that AAFs induce time- and concentration-dependent activation of downstream signalling to signal transducer and activator of transcription 3 (STAT3), and concomitantly altered phosphorylation of mitogen-activated protein kinase kinase (MEK), phosphoinositide 3-kinase (PI3K)-protein kinase B (AKT) and nuclear factor NF-kappa-B (NFκB). Antibodies targeting the interleukin-6 receptor (IL6R) effectively blocked phosphorylation of STAT3 and STAT1. Treatments with SCDs were effective in reducing cell viability in only a third of 30 clinically relevant conditions examined, defined as combinations of drugs, different cell lines and AAFs. Combinations of SCDs and novel therapeutics such as trametinib, fludarabine or rapamycin were superior in another third. Notably, we could nominate effective treatment combinations in almost all conditions except in 4 out of 30 conditions, in which trametinib or fludarabine showed higher efficacy alone. Taken together, our study underscores the importance of the molecular characterisation of individual patients' AAFs and the impact on treatment resistance as providing clinically meaningful information for future precision treatment approaches in EOC.

STAT3 Increases CVB3 Replication and Acute Pancreatitis and Myocarditis Pathology via Impeding Nuclear Translocation of STAT1 and Interferon-Stimulated Gene Expression.

Acute pancreatitis (AP) is an inflammatory disease initiated by the death of exocrine acinar cells, but its pathogenesis remains unclear. Signal transducer and activator of transcription 3 (STAT3) is a multifunctional factor that regulates immunity and the inflammatory response. The protective role of STAT3 is reported in Coxsackievirus B3 (CVB3)-induced cardiac fibrosis, yet the exact role of STAT3 in modulating viral-induced STAT1 activation and type I interferon (IFN)-stimulated gene (ISG) transcription in the pancreas remains unclarified. In this study, we tested whether STAT3 regulated viral-induced STAT1 translocation. We found that CVB3, particularly capsid VP1 protein, markedly upregulated the phosphorylation and nuclear import of STAT3 (p-STAT3) while it significantly impeded the nuclear translocation of p-STAT1 in the pancreases and hearts of mice on day 3 postinfection (p.i.). Immunoblotting and an immunofluorescent assay demonstrated the increased expression and nuclear translocation of p-STAT3 but a blunted p-STAT1 nuclear translocation in CVB3-infected acinar 266-6 cells. STAT3 shRNA knockdown or STAT3 inhibitors reduced viral replication via the rescue of STAT1 nuclear translocation and increasing the ISRE activity and ISG transcription in vitro. The knockdown of STAT1 blocked the antiviral effect of the STAT3 inhibitor. STAT3 inhibits STAT1 activation by virally inducing a potent inhibitor of IFN signaling, the suppressor of cytokine signaling-3 ((SOCS)-3). Sustained pSTAT1 and the elevated expression of ISGs were induced in SOCS3 knockdown cells. The in vivo administration of HJC0152, a pharmaceutical STAT3 inhibitor, mitigated the viral-induced AP and myocarditis pathology via increasing the IFNβ as well as ISG expression on day 3 p.i. and reducing the viral load in multi-organs. These findings define STAT3 as a negative regulator of the type I IFN response via impeding the nuclear STAT1 translocation that otherwise triggers ISG induction in infected pancreases and hearts. Our findings identify STAT3 as an antagonizing factor of the IFN-STAT1 signaling pathway and provide a potential therapeutic target for viral-induced AP and myocarditis.

Malvidin From Malva sylvestris L. Ameliorates Allergic Responses in Ovalbumin-Induced Allergic Rhinitis Mouse Model via the STAT6/GATA3 Pathway.

Malva sylvestris L. (commonly known as mallow) has been widely used in traditional Tibetan formulations to treat allergic rhinitis (AR), and malvidin is a key anti-inflammation constituent of this plant. The present study aimed to evaluate the potential therapeutic effect and mechanism of malvidin in an AR mouse model. Malvidin's efficacy was evaluated in an AR mouse model induced by ovalbumin (OVA) sensitization and challenge. The factors, such as nasal symptoms, serum OVA-specific immunoglobulin E (IgE) levels, histological changes in the nasal mucosa, and expressions of Th1, Th2, Th17, and Tregs and their cytokines, were assessed. Western blotting was used to analyze the effect of malvidin on signal transducer and activator of transcription 6 (STAT6) and GATA3 expression levels. Malvidin reduced the allergic symptoms and serum levels of OVA-specific IgE in the AR model. Histological analysis indicated that malvidin alleviates nasal mucosal edema, eosinophil infiltration, and goblet cell proliferation. In addition, it altered the expression of Th1/Th2/Th17-related cytokines, enhanced the Treg population, and reduced Th2-mediated immunity by suppressing the phosphorylation of STAT6 and expression of the GATA3 protein. Malvidin significantly improved allergic symptoms in an OVA-induced AR mouse model by modulating Th1/Th2 immune responses and suppressing the STAT6/GATA3 pathway, indicating its potential as a naturally sourced agent for AR management.

Alantolactone alleviates epithelial-mesenchymal transition by regulating the TGF-β/STAT3 signaling pathway in renal fibrosis

ObjectiveThe epithelial-to-mesenchymal transition (EMT) of renal tubular epithelial cells (RTECs) plays a crucial role in renal interstitial fibrosis and inflammation, which are key components of chronic kidney disease (CKD). Alantolactone, a selective inhibitor of signal transducer and activator of transcription 3 (STAT3), is used in Chinese herbal medicine. Despite its use, the effects of alnatolactone on EMT of RTECs has not been fully elucidated. MethodsIn this study, we investigated the potential of alantolactone to EMT in vivo and in vitro. Our experiments were performed using a unilateral ureteral obstruction (UUO) models and HK-2 cells, RTECs, treated with transforming growth factor (TGF-β). ResultsAlantolactone decreased tubular injury and reduced the expression of vimentin, a key EMT marker, while increasing E-cadherin expression in UUO kidneys. Similarly, in RTECs, alantolactone inhibited TGF-β-induced EMT and its markers. Furthermore, alantolactone attenuated UUO- and TGF-β-induced STAT3 phosphorylation both in vivo and in vitro, and inhibited the expression of TWIST, an EMT transcription factor, in both models. ConclusionAlantolactone improves EMT in RTECs by inhibiting STAT3 phosphorylation and Twist expression, suggesting its potential as a therapeutic agent for kidney fibrosis.

Spore Oil enhances the effect of cyclophosphamide inhibiting programmed death-1 and prolongs the survival of H22 tumor-bearing mice.

To investigate the effect of Ganoderma Lucidum Spore Oil (GLSO) on the tumor growth and survival of H22 tumor-bearing mice treated with cyclophosphamide (CTX), and explore the underlying mechanism. Allograft H22 hepatocellular carcinoma mouse model was applied to investigate the effect of GLSO on the tumor growth and survival of animals, and Kaplan-Meier survival analysis was used to analyze the life span. Plasma biochemical examination was used to determine the levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), urea (UREA) and creatinine (CRE). Western blot analysis was performed to detect Programmed Death-1 (PD-1), Programmed Death Ligand 1 (PD-L1), Janus Kinase 2 (JAK2), phosphorylated Signal Transducer and Activator of Transcription 3 (p-STAT3), and Signal Transducer and Activator of Transcription 3 (STAT3) expression. GLSO increased the anti-tumor effect of CTX and prolonged the survival of H22 tumor-bearing mice treated with CTX. Meanwhile, GLSO increased the thymus index and showed no obvious toxicity to liver functions of animals. GLSO also decreased the level of UREA in H22 tumor-bearing mice treated with CTX. Furthermore, GLSO could inhibit the expression of PD-1 in spleen, which was independent of JAK2 expression and STAT3 phosphorylation. However, GLSO did not affect the expression of PD-L1, JAK2, and p-STAT3 in tumor tissue. GLSO could strengthen the anti-tumor effect of CTX and prolong the life span of H22 tumor-bearing mice, while the underlying mechanism might be relevant to the amelioration effect of thymus function and inhibition of PD-1 expression in spleen. Furthermore, these findings implied the promising role of GLSO in combination with CTX to extend the survival of patients in clinical chemotherapy of hepatocellular carcinoma.

RBP4 promotes denervation-induced muscle atrophy through STRA6-dependent pathway.

Fat infiltration of skeletal muscle has been recognized as a common feature of many degenerative muscle disorders. Retinol binding protein 4 (RBP4) is an adipokine that has been demonstrated to be correlated with the presence and severity of sarcopenia in the elderly. However, the exact role and the underlying mechanism of RBP4 in muscle atrophy remains unclear. Denervation-induced muscle atrophy model was constructed in wild-type and RBP4 knockout mice. To modify the expression of RBP4, mice were received intramuscular injection of retinol-free RBP4 (apo-RBP4), retinol-bound RBP4 (holo-RBP4) or oral gavage of RBP4 inhibitor A1120. Holo-RBP4-stimulated C2C12 myotubes were treated with siRNAs or specific inhibitors targeting signalling receptor and transporter of retinol 6 (STRA6)/Janus kinase 2 (JAK2)/Signal transducer and activator of transcription 3 (STAT3) pathway. Fat accumulation, myofibre cross-sectional area, myotube diameter and the expression of muscle atrophy markers and myogenesis markers were analysed. The expression levels of RBP4 in skeletal muscles were significantly up-regulated more than 2-fold from 7days and sustained for 28days after denervation. Immunofluorescence analysis indicated that increased RBP4 was localized in the infiltrated fatty region in denervated skeletal muscles. Knockout of RBP4 alleviated denervation-induced fatty infiltration and muscle atrophy together with decreased expression of atrophy marker Atrogin-1 and MuRF1 as well as increased expression of myogenesis regulators MyoD and MyoG. By contrast, injection of retinol-bound holo-RBP4 aggregated denervation-induced ectopic fat accumulation and muscle atrophy. Consistently, holo-RBP4 stimulation also had a dose-dependent effect on the reduction of C2C12 myotube diameter and myofibre cross-sectional area, as well as on the increase of Atrogin-1and MuRF1 expression and decrease of MyoD and MyoG expression. Mechanistically, holo-RBP4 treatment increased the expression of its membrane receptor STRA6 (>3-fold) and promoted the phosphorylation of downstream JAK2 and STAT3. Inhibition of STRA6/JAK2/STAT3 pathway either by specific siRNAs or inhibitors could decrease the expression of Atrogin-1 and MuRF1 (>50%) and decrease the expression of MyoD and MyoG (>3-fold) in holo-RBP4-treated C2C12 myotube. RBP4 specific pharmacological antagonist A1120 significantly inhibited the activation of STRA6/JAK2/STAT3 pathway, ameliorated ectopic fat infiltration and protected against denervation-induced muscle atrophy (30% increased myofibre cross-sectional area) in mice. In conclusion, our data reveal that RBP4 promotes fat infiltration and muscle atrophy through a STRA6-dependent and JAK2/STAT3 pathway-mediated mechanism in denervated skeletal muscle. Our results suggest that lowering RBP4 levels might serve as a promising therapeutic approach for prevention and treatment of muscle atrophy.

Isoliquiritigenin diminishes invasiveness of human nasopharyngeal carcinoma cells associating with inhibition of MMP-2 expression and STAT3 signalling.

Nasopharyngeal carcinoma (NPC) is prevalent in Asia and exhibits highly metastatic characteristics, leading to uncontrolled disease progression. Isoliquiritigenin (ISL) have attracted attention due to their diverse biological and pharmacological properties, including anticancer activities. However, the impact of ISL on the invasive and migratory ability of NPC remains poorly understood. Hence, this study aimed to investigate the invitro anti-metastatic effects of ISL on NPC cells and elucidate the underlying signalling pathways. Human NPC cell NPC-39 and NPC-BM were utilized as cell models. Migratory and invasive capabilities were evaluated through wound healing and invasion assays, respectively. Gelatin zymography was employed to demonstrate matrix metalloproteinase-2 (MMP-2) activity, while western blotting was conducted to analyse protein expression levels and explore signalling cascades. Overexpression of signal transducer and activator of transcription 3 (STAT3) was carried out by transduction of STAT3-expressing vector. Our findings revealed that ISL effectively suppressed the migration and invasion of NPC cells. Gelatin zymography and Western blotting assays demonstrated that ISL treatment led to a reduction in MMP-2 enzyme activity and protein expression. Investigation of signalling cascades revealed that ISL treatment resulted in the inhibition of STAT3 phosphorylation. Moreover, overexpression of STAT3 restored the migratory ability of NPC cells in the presence of ISL. Collectively, these findings indicate that ISL inhibits the migration and invasion of NPC cells associating with MMP-2 downregulation through suppressing STAT3 activation. This suggests that ISL has an anti-metastatic effect on NPC cells and has potential therapeutic benefit for NPC treatment.

Evaluation of STAT3 Inhibition by Cancer Chemopreventive Trichothecenes Derived from Metabolites of Trichothecium roseum.

This study evaluated the ability of isolated or semisynthesized trichothecene sesquiterpenes to prevent cancer emergence and proliferation and inhibit signal transducer and activator of transcription-3 (STAT3) phosphorylation through in vitro assays. Trichothecinol A (TTC-A), which bears a hydroxy group at C3, exhibited greater cancer prevention, antiproliferation, and STAT3 phosphorylation inhibition effects than trichothecin (TTC), which lacks a hydroxy group at C3. Furthermore, trichothecinol B (TTC-B), which is a reduced derivative of TTC and has similar cytotoxic effect, showed substantially weaker chemoprotection and STAT3 phosphorylation inhibition effects than TTC. These results clearly indicate that the hydroxy group at C3 and carbonyl group at C8 are crucial for inducing both potent chemoprevention and STAT3 phosphorylation inhibition.

JAK2/STAT3 signaling pathway mediates methylmercury toxicity in mouse astrocyte neuronal C8-D1A cell line.

Methylmercury (MeHg) is an environmental pollutant. Consumption of contaminated fish is the main exposure route in humans, leading to severe neurological disorders. Upon ingestion MeHg reaches the brain and selectively accumulates in astrocytes disrupting glutamate and calcium homeostasis and increasing oxidative stress. Despite extensive research, the molecular mechanisms underlying MeHg neurotoxicity remain incompletely understood. The induction of nuclear factor erythroid 2-related factor 2 (Nrf2) and its role activating antioxidant responses during MeHg-induced oxidative injury have garnered significant attention as a potential therapeutic target against MeHg toxicity. However, recent studies indicate that the Nrf2 signaling pathway alone may not be sufficient to mitigate MeHg-induced damage, suggesting the existence of other protective mechanisms. The signal transducer and activator of transcription 3 (STAT3) plays a crucial role in cell growth and survival. Several studies have also highlighted its involvement in regulating redox homeostasis, thereby preventing oxidative stress through mechanisms that involve modulation of nuclear genes that encode electron transport complexes (ETC) and antioxidant enzymes. These characteristics suggest that STAT3 could serve as a viable mechanism to mitigate MeHg toxicity, either in conjunction with or as an alternative to Nrf2 signaling. Our previous findings demonstrated that MeHg activates the STAT3 signaling pathway in the GT1-7 hypothalamic neuronal cell line, suggesting its potential role in promoting neuroprotection. Here, to elucidate the role of the STAT3 signaling pathway in MeHg neurotoxicity, we pharmacologically inhibited STAT3 using AG490 in the C8D1A astrocytic cell line exposed to 10 µM MeHg. Our data demonstrated that pharmacological inhibition of STAT3 phosphorylation exacerbates MeHg-induced mortality, antioxidant responses, and ROS production, suggesting that STAT3 may contribute to neuroprotection against MeHg exposure in astrocytes.

Selective STAT3 inhibitor STX-0119 alleviates osteoarthritis progression by modulating the STAT3/PPARγ signaling pathway

Osteoarthritis (OA), characterized by chronic pain, significantly affects the quality of life of affected individuals. Key factors in OA pathogenesis include cartilage degradation and inflammation. Signal transducer and activator of transcription 3 (STAT3), a member of the STAT protein family, plays a pivotal role in mediating inflammation. STX-0119 has been verified as a small molecular compound that can specifically inhibit STAT3. However, the efficacy of STX-0119 in the treatment of OA remains to be evaluated. Therefore, the aim of this study was to explore the therapeutic effects and molecular mechanisms of STX-0119 in the treatment of OA. We found that the expression of phosphorylated STAT3 is upregulated in human OA cartilage as well as in the cartilage of a mouse model of OA. In vivo, joint injection of STX-0119 into OA mice alleviated cartilage degeneration without affecting the subchondral bone. Additionally, STX-0119 could inhibit the phosphorylation of STAT3 in the cartilage. In vitro, STX-0119 suppressed inflammatory responses in chondrocytes and promoted anabolic metabolism in an interleukin-1β-induced chondrocyte inflammation model. Additionally, the results of transcriptome sequencing and lentiviral infection assays demonstrated that in chondrocytes, STX-0119 induces the upregulation of peroxisome proliferators-activated receptor gamma (PPARγ) expression by inhibiting STAT3 phosphorylation. Finally, in ex vivo cultures of human cartilage samples, STX-0119 was reaffirmed to inhibit cartilage degeneration via the STAT3/PPARγ signaling pathway. Together, our findings support the potential of STX-0119 for development as a therapeutic agent targeting STAT3 for the treatment of OA.