Regulation Of Signal Transducer And Activator Of Transcription 3 Research Articles

STAT3 Protein-Protein Interaction Analysis Finds P300 as a Regulator of STAT3 and Histone 3 Lysine 27 Acetylation in Pericytes.

Signal transducer and activator of transcription 3 (STAT3) is a member of the cytoplasmic inducible transcription factors and plays an important role in mediating signals from cytokines, chemokines, and growth factors. We and others have found that STAT3 directly regulates pro-fibrotic signaling in the kidney. The STAT3 protein-protein interaction plays an important role in activating its transcriptional activity. It is necessary to identify these interactions to investigate their function in kidney disease. Here, we investigated the protein-protein interaction among three species to find crucial interactions that can be targeted to alleviate kidney disease. In this study, we examined common protein-protein interactions leading to the activation or downregulation of STAT3 among three different species: humans (Homo sapiens), mice (Mus musculus), and rabbits (Oryctolagus cuniculus). Further, we chose to investigate the P300 and STAT3 interaction and performed studies of the activation of STAT3 using IL-6 and inhibition of the P300 by its specific inhibitor A-485 in pericytes. Next, we performed immunoprecipitation to confirm whether A-485 inhibits the binding of P300 to STAT3. Using the STRING application from ExPASy, we found that six proteins, including PIAS3, JAK1, JAK2, EGFR, SRC, and EP300, showed highly confident interactions with STAT3 in humans, mice, and rabbits. We also found that IL-6 treatment increased the acetylation of STAT3 and increased histone 3 lysine acetylation (H3K27ac). Furthermore, we found that the disruption of STAT3 and P300 interaction by the P300 inhibitor A-485 decreased STAT3 acetylation and H3K27ac. Finally, we confirmed that the P300 inhibitor A-485 inhibited the binding of STAT3 with P300, which inhibited its transcriptional activity by reducing the expression of Ccnd1 (Cyclin D1). Targeting the P300 protein interaction with STAT3 may alleviate STAT3-mediated fibrotic signaling in humans and other species.

Regulation of STAT3 and NF-κB signaling pathways by trans-Anethole in testicular ischemia-reperfusion injury and its gonadoprotective effect.

Testicular ischemia reperfusion (I/R) injury is a significant urological problem where clinical interventions may be inadequate, and the antioxidants might be potential co-treatment modalities. This study examined the gonadoprotective effect of trans-Anethole in testicular I/R injury. Twenty-eight male rats were divided into four groups. Rats in the I/R, I/R + t100, I/R + t200 groups underwent bilateral testicular I/R injury. The I/R + t100 and I/R + t200 groups received 100 or 200 mg/kg trans-Anethole at the 2nd hour of ischemia. Microscopic evaluations demonstrated that testicular I/R injury leads to severe testicular degeneration. Tissue oxidative stress, pro-apoptotic Bcl-2 associated X (Bax) and Caspase 3, pro-inflammatory Tumor necrosis factor-alpha (TNF-α), Interleukin-1 beta (IL-1β) and Interleukin 6 (IL-6) cytokines levels were significantly (p < 0.05) upregulated when compared to the Control group. Additionally, transcription factors Signal transducer and activator of transcription 3 (STAT3) and Nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) levels increased significantly (p < 0.05) compared to the Control group. Tissue disrupted parameters in the I/R + t200 group were significantly different (p < 0.05) from the I/R group, contrasting with the slight improvement in the I/R + t100 group. The STAT3 and NF-κB expression levels in the I/R + t200 group were significantly suppressed (p < 0.05) compared to the I/R group. In conclusion, our study indicates that trans-Anethole could enhance gonadoprotective activity in testicular I/R injury, potentially involving transcription factors STAT3 and NF-κB. However, before the consumption of trans-Anethole-containing natural or manufactured goods, the potential benefits and side effects should be carefully evaluated.

Renal epithelial-derived miR-17~92 inhibits STAT3 signaling, serving a sex-specific and renoprotective role in the development of AKI

Prerenal acute kidney injury (AKI) is a sudden loss of kidney excretory function from reduced blood flow to the kidney. Sex differences in the degree of injury have been recognized, the causes of which are ill-defined. While a role for miRs (microRNAs) in AKI has been recognized, there are no reports of sex differences in miR regulation after injury. Here we investigated sex differences in miR regulation in proximal tubular epithelial cells during AKI with IRI (ischemia reperfusion injury) in vivo and miR regulation of signal transducer and activator of transcription 3 (STAT3) signaling in vitro. We hypothesize that sex-differentially expressed miR-17~92 serves as a negative regulator of STAT3 signaling, repressing proinflammatory signaling in tubular epithelium during AKI. We recapitulated the phenotype that males have a higher level of injury compared to females with proportional intensity and duration of IRI in a murine AKI model. C57BL/6J mice underwent 25 minutes of unilateral IRI with a contralateral nephrectomy and sacrificed 18 hours post-reperfusion. Injured male tubules showed a significant increase in Kidney injury molecule-1 (Kim-1) expression (n³3, fold change=75.28 ± 35.92) whereas injured females showed no change, confirming that injured males experience a higher level of tubular injury than females with a matched degree of ischemia. Control female tubules showed significantly higher baseline expression of miR-17~92 compared to control males (n ³ 5, difference between means ± SEM: miR-17a, 2.337 ± 0.6322; miR-18a, 5.841 ± 2.008; miR-19a, 5.041 ± 1.232; miR- 19b, 3.826 ± 0.9791; miR-20a, 3.826 ± 1.053; miR-92a, 5.627 ± 1.588). MiR-17~92 expression in injured male tubules significantly increased compared to male controls. Even after this increase, miR-17~92 expression in male tubules was lower compared to miR-17~92 in injured females. Mir-17~92 is predicted to target STAT3 and components of the interleukin-6 (IL6)/STAT3 pathway. qPCR showed a significant increase in Stat3 expression after IRI in both sexes, but only a significant increase in IL6 and heme oxygenase-1 in injured males. To investigate miR regulation of STAT3 in vitro, we used a human proximal tubule cell line (HK2) model. Recombinant IL6 induced STAT3 protein expression and phosphorylation, and increased miR-17~92 expression. By altering miR-17~92 expression in HK2 cells we demonstrated that expression of STAT3 in response to IL6 is regulated, in part, by these miRs. These data provide the first example of sex-differential miR regulation in response to IRI. The elevated baseline expression of miR-17~92 in the female mice may provide a novel mechanism to account for sex-differences in IRI-AKI and may form part of the mechanism to protect female kidney epithelia from IRI and AKI. This work is supported by the NIH (DK102843 to MBB), (NIH R01DK102843-08S1 to AS), NIH (DK137419 and DK125015 to JH) and NIH (5R01DK131991 and 5R01DK064005 to RT). This is the full abstract presented at the American Physiology Summit 2024 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Inhibition of STAT3 alleviates LPS-induced apoptosis and inflammation in renal tubular epithelial cells by transcriptionally down-regulating TASL

BackgroundSystemic lupus erythematosus (SLE) is a common autoimmune disease that impacts various organs. Lupus nephritis (LN) significantly contributes to death in children with SLE. Toll-like receptor (TLR) adaptor interacting with SLC15A4 on the lysosome (TASL) acts as an innate immune adaptor for TLR and is implicated in the pathogenesis of SLE. A transcription factor known as signal transducer and activator of transcription 3 (STAT3), which is known to be linked to autoimmune diseases, is also involved in the development of SLE.MethodsBioinformatics and real-time quantitative PCR (qRT-PCR) was used to detect the expression of STAT3 and TASL in peripheral blood of SLE patients and their correlation. Bioinformatics analysis, qRT-PCR, luciferase assay and chromatin immunoprecipitation (ChIP) were used to verify the regulation of transcription factor STAT3 on TASL. The expression levels of STAT3, TASL and apoptosis-related genes in LPS-induced HK2 cells were detected by qRT-PCR and Western blot. TUNEL staining were used to detect the apoptosis of HK2 cells after LPS stimulation. ELISA and qRT-PCR were used to detect the levels of inflammatory cytokines in the cell culture supernatant. TASL knockdown in HK2 cells was used to detect the changes in apoptosis-related genes and inflammatory factors. The expression level of TASL in LPS-stimulated HK2 cells and its effect on cell apoptosis and inflammatory factors were observed by knocking down and overexpressing STAT3, respectively. It was also verified in a rescue experiment.ResultsThe expressions of STAT3 and TASL were higher in SLE than in healthy children, and the expression of STAT3 was positively correlated with TASL. Transcription factor STAT3 can directly and positively regulate the expression of TASL through the promoter region binding site. The expression of STAT3, TASL and inflammatory cytokines was elevated, and the change of apoptosis was up-regulated in LPS-stimulated HK2 cells. Inhibition of STAT3 alleviates LPS-stimulated apoptosis and inflammatory response in HK2 cells through transcriptional regulation of TASL.ConclusionsThese findings provide new insights into the transcriptional regulation of TASL and provide new evidence of a direct regulatory relationship between signaling nodes in the lupus signaling network.Graphical

SENP3 affects the expression of PYCR1 to promote bladder cancer proliferation and EMT transformation by deSUMOylation of STAT3.

Abnormal activation of signal transducer and activator of transcription 3 (STAT3) has been found in various types of human cancers, including bladder cancer (BC). In our study, we examined the regulation of STAT3 post-translational modifications (PTMs) and found that SENP3 is high in bladder cancer. Sentrin/SUMO-specific protease3 (SENP3) and STAT3 were highly expressed in BC tissues when compared with tissue adjacent to carcinoma. SENP3 induced STAT3 protein level and p-STAT3 translocating into nuclear through deSUMOylation of STAT3. Further, nuclear STAT3, as a transcriptional activity factor, promoted pyrroline-5-carboxylate reductase 1 PYCR1 gene and protein level by interacting with the promoter of (PYCR1). Next, we found that knockdown of PYCR1 inhibited Epithelial to mesenchymal transition of bladder cancer, and simultaneously mitigated the carcinogenic effects of STAT3. In vitro, STAT3 knockdown in bladder cancer cells inhibited cell proliferation, migration, and invasion. In contrast, SENP3 overexpression reversed these effects. In all, results lend novel insights into the regulation of STAT3, which has key roles in bladder cancer progression.

The crosstalk between STAT3 and microRNA in cardiac diseases and protection

Signal transducer and activator of transcription 3 (STAT3), an important transcription factor and signaling molecule, play an important role in cardiac disease and protection. As a transcription factor, STAT3 upregulates anti-oxidative and anti-apoptotic genes but suppresses anti-inflammatory and anti-fibrotic genes in cardiac disease and protection. As a signaling molecule, STAT3 is the downstream or upstream of other molecules for signaling transduction, also activated in cardiac disease and protection. MicroRNAs (miRNAs) are endogenous short non-coding RNAs that regulate mRNA expression at the transcriptional level and prevent protein translation. Recently, STAT3 is reported to be not only the target of miRNA but also the inhibitor or inducer of miRNA to modify the mRNA expression profiles in cardiomyocytes resulting in different effects on cardiac disease and protection. We summarize the current knowledge on STAT3 regulation of individual miRNAs and the modulation of STAT3 by miRNAs in cardiac diseases and protection.

STAT3 and p63 in the Regulation of Cancer Stemness.

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor with many important functions in normal and transformed cells. STAT3 regulatory activities are highly complex as they are involved in various signaling pathways in different cell types under different conditions. Biologically, STAT3 is a regulative factor for normal and cancer stem cells (CSCs). Tumor protein p63 (p63), a member of the p53 protein family, is involved in these biological processes and is also physically and functionally associated with STAT3. STAT3 activation occurs during various aspects of carcinogenesis, including regulation of CSCs properties. In combination with p63, STAT3 is a possible biological marker of CSCs and a major regulator of maintenance of stemness in CSCs. We summarized the STAT3 functions and regulation and its role in CSC properties and highlight how these are affected by its associations with p63.

Prognostic significance of STAT3 gene expression in patients with glioblastoma tumors: a study from Western India

ObjectiveGlioblastoma Multiforme (GBM), a devastating the most common primary malignant intracranial brain tumors. In India, the incidence of this malignancy is escalating, however, there are very few studies on this tumor entity from Indian population. The present study sought to investigate the prevalence and prognostic significance of Signal Transducer and Activator of Transcription 3 (STAT3) gene expression in GBM patients from Western India.MethodSTAT3 gene expression using real-time PCR was detected in total 55 GBM patients. The impact of STAT3 aberrant expression on progression-free survival (PFS) and overall (OS) was analysed using univariate and multivariate survival analysis. The data were analysed using SPSS statistical software and p value ≤0.05 was considered as significant.ResultsThe aberrant STAT3 expression was found in 85% (47/55) of patients with -1.12 fold change down-regulation in 49% (23/47) and 3.36 fold change up-regulation was noted in 51% (24/47) of patients. In wild type IDH tumors (n=30), down regulation and up regulation of STAT3 was noted in 63% and 27% of patients, respectively, whereas, for IDH mutant GBM tumors (n=25), the incidence of low expression and high expression of STAT3 was noted in 16% and 68% of patients, respectively. Thus, we found that incidence of STAT3 down regulation was significantly high in patients with IDH wild type tumors, whereas, in IDH mutant GBM tumors, the incidence of up-regulated STAT3 was significantly high (P=0.021, χ2=12.81, r=+0.310). In Kaplan-Meier univariate survival analysis, a part from age (P=0.006), tumor location (P=0.025), and KPS score (P=0.002), co-detection of STAT3 up regulation and presence of IDH mutation (P=0.030) remained significant prognostic factors for PFS and OS. In multivariate survival analysis also, co-detection of STAT3 high expression and presence of IDH mutation remained independent prognosticators for PFS (HR=6.45, 95% CI=1.32-31.40, P=0.021) and OS (HR=8.69, 95% CI=1.66-45.51, P=0.010).ConclusionFor GBM tumors, STAT3 up-regulation and presence of IDH mutations together predicts better survival. This reflects unique molecular etiology for GBM patients. Therefore, they would be useful in the future for targeted therapy and for clinicians they would be useful for better patient management. However, study on a larger sample size is required for validation.

Abstract 92: tGLI1 and IL-6/IL-6R/GP130/STAT3 pathways cooperate to promote breast cancer stem cells and are co-activated in HER2-enriched and triple-negative breast cancers

Abstract Breast cancer is the most frequently diagnosed cancer and second leading cause of cancer-related deaths in women; 30% of primary breast cancer cases will develop distant metastases. The majority (90%) of breast cancer-related deaths are due to distant metastases. HER2-enriched breast cancer and triple-negative breast cancer (TNBC) have the highest propensity to metastasize and have limited to no treatment options. Metastatic HER2-enriched breast cancer and TNBC patients commonly develop therapeutic resistance and, therefore, lack efficacious therapies. Due to dismal prognoses in metastatic HER2-enriched breast cancer and TNBC patients, there remains an urgent need to identify novel molecular pathways for actionable therapeutic targets. Truncated glioma-associated oncogene homolog 1 (tGLI1), an alternatively spliced variant of GLI1, is a gain-of-function tumor-specific terminal effector in the Hedgehog pathway. tGLI1 promotes breast cancer growth and circulating tumor cells to the brain. More recently, our lab has reported tGLI1 physically interacts with Signal Transducer and Activator of Transcription 3 (STAT3); tGLI1 and STAT3 are co-overexpressed in node-positive HER2-enriched and triple-negative breast carcinomas. The Interleukin-6 (IL-6) signaling axis is a primary regulator of STAT3 and is frequently dysregulated and hyperactivated in multiple cancers, including breast cancer. IL-6 functions through a hexameric receptor complex comprised of IL-6 receptor α (IL-6R) and glycoprotein 130 (GP130) to recruit Janus tyrosine kinases (JAK). In turn, JAKs phosphorylate STAT3 resulting in homodimerization, nuclear translocation, and transcriptional activity. Independently, tGLI1 and IL-6/IL-6R/GP130/STAT3 pathways have been previously investigated as mediators for breast cancer metastases; however, whether they cooperate to promote breast cancer progression remains unknown. Herein, we report tGLI1 and IL-6/IL-6R/GP130/STAT3 pathways to be frequently co-expressed and co-activated in HER2-enriched breast cancer and TNBC tumors and that the co-activation is associated with a shortened metastasis-free survival (MFS). Additionally, when stratified by metastatic site, breast tumors with high tGLI1 and IL-6/IL-6R/GP130/STAT3 co-activation are associated with a worse bone, brain, and lung MFS compared to tumors with low co-activation. Ectopic co-overexpression of tGLI1 and GP130 upregulates mRNA expression of stemness genes, Nanog, Sox2, and Oct4, leading to the subsequent promotion of the breast cancer stem cell (CSC) subpopulation in vitro. Taken together, our findings revealed a novel crosstalk between tGLI1 and the IL-6/IL-6R/GP130/STAT3 signaling axis to enhance the CSC subpopulation, suggesting the importance of the crosstalk in mediating metastasis of HER2-enriched breast cancer and TNBC. Citation Format: Sara G. Manore, Daniel L. Doheny, Dongqin Zhu, Grace L. Wong, Angelina T. Regua, Austin Arrigo, Calvin J. Wagner, Mariana Najjar, Hui-Wen Lo. tGLI1 and IL-6/IL-6R/GP130/STAT3 pathways cooperate to promote breast cancer stem cells and are co-activated in HER2-enriched and triple-negative breast cancers [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 92.

The Core Mechanism of Yiqi Yangjing Decoction Inhibiting Nonsmall-Cell Lung Cancer.

Background Yiqi Yangjing prescription (YQYJ) is a traditional Chinese medicine prescription used for treating lung cancer. It has a significant effect on enhancing efficacy, reducing toxic symptoms, and improving patients' physical well-being. The effective inhibitory effect on nonsmall-cell lung cancer (NSCLC) has been demonstrated in vitro and in vivo. However, the mechanism of action and the material basis still remain unclear. Methods In this study, we explored this mechanism using network pharmacology, after which we explored the pharmacodynamics and the action mechanism of YQYJ using cell viability evaluation, plate clone formation assay, flow cytometry, real-time quantitative PCR, and Western blot. Results The enrichment results showed that there were 50 active components and 68 core targets related to YQYJ inhibiting NSCLC, including quercetin, luteolin, gamatin, kaempferol, heat shock protein HSP 90-alpha (HSP90AA1), cyclin-dependent kinase 2 (CDK2), epidermal growth factor receptor (EGFR), signal transducer and activator of transcription 3 (STAT3), and others. Among them, quercetin and kaempferol revealed the best binding effect with core targets. Most importantly, YQYJ promoted A549 cells from the quiescent phase into the proliferative phase to enhance the sensitivity of A549 cells to YQYJ and inhibited the proliferation of A549 cells significantly (P < 0.05). The A549 cells were blocked in both S and G2/M phases while the apoptosis ratio was increased. The proliferation score of A549 cells treated with YQYJ was significantly reduced compared to A549 cells in the proliferative phase (P < 0.05). This regulatory effect was related to the expression regulation of HSP90AA1, CDK2, STAT3, and phosphor-STAT3 (p-STAT3) by YQYJ, kaempferol, and quercetin. Conclusion Our results suggested that the inhibition of NSCLC via YQYJ had multicomponent and multitarget characteristics. Its core mechanism is related to the regulation of the cell cycle, proliferation, and apoptosis of NSCLC. This study provides a direction and scientific basis for exploring the future mechanism of YQYJ for the treatment of NSCLC.

STAT3 pathway in cancers: Past, present, and future.

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, discovered in the cytoplasm of almost all types of mammalian cells, plays a significant role in biological functions. The duration of STAT3 activation in normal tissues is a transient event and is strictly regulated. However, in cancer tissues, STAT3 is activated in an aberrant manner and is induced by certain cytokines. The continuous activation of STAT3 regulates the expression of downstream proteins associated with the formation, progression, and metastasis of cancers. Thus, elucidating the mechanisms of STAT3 regulation and designing inhibitors targeting the STAT3 pathway are considered promising strategies for cancer treatment. This review aims to introduce the history, research advances, and prospects concerning the STAT3 pathway in cancer. We review the mechanisms of STAT3 pathway regulation and the consequent cancer hallmarks associated with tumor biology that are induced by the STAT3 pathway. Moreover, we summarize the emerging development of inhibitors that target the STAT3 pathway and novel drug delivery systems for delivering these inhibitors. The barriers against targeting the STAT3 pathway, the focus of future research on promising targets in the STAT3 pathway, and our perspective on the overall utility of STAT3 pathway inhibitors in cancer treatment are also discussed.

Antitumor Activity of Pulvomycin via Targeting Activated-STAT3 Signaling in Docetaxel-Resistant Triple-Negative Breast Cancer Cells.

Although docetaxel-based regimens are common and effective for early-stage triple-negative breast cancer (TNBC) treatment, acquired drug resistance frequently occurs. Therefore, a novel therapeutic strategy for docetaxel-resistant TNBC is urgently required. Signal transducer and activator of transcription 3 (STAT3) plays a pivotal role in the tumorigenesis and metastasis of numerous cancers, and STAT3 signaling is aberrantly activated in TNBC cells. In this study, a docetaxel-resistant TNBC cell line (MDA-MB-231-DTR) was established, and mechanisms for the antitumor activity of pulvomycin, a novel STAT3 inhibitor isolated from marine-derived actinomycete, were investigated. Levels of activated STAT3 (p-STAT3 (Y705)) increased in docetaxel-resistant cells, and knockdown of STAT3 recovered the sensitivity to docetaxel in MDA-MB-231-DTR cells. Pulvomycin effectively inhibited the proliferation of both cell lines. In addition, pulvomycin suppressed the activation of STAT3 and subsequently induced G0/G1 cell cycle arrest and apoptosis. Pulvomycin also significantly inhibited the invasion and migration of MDA-MB-231-DTR cells through the modulation of epithelial-mesenchymal transition markers. In an MDA-MB-231-DTR-bearing xenograft mouse model, the combination of pulvomycin and docetaxel effectively inhibited tumor growth through STAT3 regulation. Thus, our findings demonstrate that the combination of docetaxel and STAT3 inhibitors is an effective strategy for overcoming docetaxel resistance in TNBC.

Mitochondrial STAT3 regulates antioxidant gene expression through complex I-derived NAD in triple negative breast cancer.

Signal transducer and activator of transcription 3 (STAT3) is a transcription factor with roles in inflammation and tumorigenicity. A fraction of STAT3 localizes in mitochondria, where it augments tumorigenesis via regulation of mitochondrial functions, including modulation of respiration and redox status. We show a novel mechanism for mitochondrial STAT3 regulation of redox homeostasis in triple‐negative breast cancer cells. Loss of STAT3 diminished complex I dehydrogenase activity and impaired NAD+ regeneration, leading to impaired expression of glutathione biosynthetic genes and other antioxidant genes. Expressing mitochondrially restricted STAT3 or replenishment of the cellular NAD pool restored antioxidant gene expression, as did complementation of the NADH dehydrogenase activity by expression of the STAT3‐independent yeast dehydrogenase, NDI1. These NAD‐regulated processes contributed to malignant phenotypes by promoting clonal cell growth and migration. Proximity interaction and protein pull‐down assays identified three components of complex I that associated with mitochondrial STAT3, providing a potential mechanistic basis for how mitochondrial STAT3 affects complex I activity. Our data document a novel mechanism through which mitochondrial STAT3 indirectly controls antioxidant gene regulation through a retrograde NAD+ signal that is modulated by complex I dehydrogenase activity.

The Neuroprotective Mechanism of Spinal Cord Stimulation in Spinal Cord Ischemia/Reperfusion Injury

Spinal cord ischemia/reperfusion (I/R) injury following thoracoabdominal aneurysm surgery can lead to severe lower limb neurologic defect. The preliminary result of our study suggested that spinal cord stimulation (SCS) postconditioning effectively protected spinal cord from I/R injury on rabbits. But the mechanism is unknown. In this study, we further investigated the mechanism of SCS postconditioning. New Zealand white rabbits were randomly divided into sham, I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group (n = 24/group). Transient spinal cord ischemia was induced by infrarenal aortic balloon occlusion and performed on all rabbits except rabbits of sham group. Rabbits of I/R group received no further intervention. Rabbits of I/R + 2 Hz SCS and I/R + 50 Hz SCS group received 2 Hz or 50 Hz SCS for 30 min at the onset of reperfusion and then daily. The expression of Akt (serine-threonine kinase)/p-Akt, STAT3 (signal transducer and activator of transcription 3)/p-STAT3 and GSK-3β (glycogen synthase kinase)/p-GSK-3β of spinal cord were measured by Western blot analysis at 8 h, 1 day, 3 day, and 7 day of reperfusion. The Akt expressions of sham, I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group were not significantly different at all prescribed time points, while the p-Akt expression of I/R + 2 Hz SCS group was significantly higher than that of I/R group and sham group at all prescribed time points; The STAT3 and p-STAT3 expression of I/R, I/R + 2 Hz SCS, and I/R + 50 Hz SCS group were not significantly different at all prescribed time points except that at 1day of reperfusion the p-STAT3 expression of I/R + 50 Hz SCS group was significantly lower than I/R group. The GSK-3β and p-GSK-3β expressions of I/R, I/R + 2 Hz SCS and I/R + 50 Hz SCS group were not significantly different at all prescribed time points. The neuroprotective effect of 2 Hz SCS postconditioning in spinal cord I/R injury is related to Akt activation but not regulation of STAT3 and GSK-3β phosphorylation.

The pleiotropic role of transcription factor STAT3 in oncogenesis and its targeting through natural products for cancer prevention and therapy.

Signal transducer and activator of transcription 3 (STAT3) is one of the crucial transcription factors, responsible for regulating cellular proliferation, cellular differentiation, migration, programmed cell death, inflammatory response, angiogenesis, and immune activation. In this review, we have discussed the classical regulation of STAT3 via diverse growth factors, cytokines, G-protein-coupled receptors, as well as toll-like receptors. We have also highlighted the potential role of noncoding RNAs in regulating STAT3 signaling. However, the deregulation of STAT3 signaling has been found to be associated with the initiation and progression of both solid and hematological malignancies. Additionally, hyperactivation of STAT3 signaling can maintain the cancer stem cell phenotype by modulating the tumor microenvironment, cellular metabolism, and immune responses to favor drug resistance and metastasis. Finally, we have also discussed several plausible ways to target oncogenic STAT3 signaling using various small molecules derived from natural products.

Long non-coding RNA XIST binding to let-7c-5p contributes to rheumatoid arthritis through its effects on proliferation and differentiation of osteoblasts via regulation of STAT3.

BackgroundRheumatoid arthritis (RA), a chronic autoimmune disease, affects around 1% population worldwide, with the life quality of patients severely reduced. In this study, it is intended to explore the role of long non‐coding RNA X‐inactive specific transcript (lncRNA XIST) in RA and the underlying mechanisms associated with let‐7c‐5p and signal transducer and activator of transcription 3 (STAT3).MethodsLncRNA XIST, let‐7c‐5p, and STAT3 expressions were determined in RA and normal cartilage tissues, and their relationship was analyzed in osteoblasts. The regulatory effects of lncRNA XIST in RA were investigated when XIST expression was upregulated or downregulated in osteoblasts. TNF‐α, IL‐2, IL‐6, alkaline phosphatase (ALP), osteocalcin, TGF‐β1, and IGF1 were measured in vivo in RA rats.ResultsLncRNA XIST and STAT3 were expressed at high levels and let‐7c‐5p expressed at a low level in RA cartilage tissues. LncRNA XIST silencing or let‐7c‐5p enhancement led to decreased levels of TNF‐α, IL‐2, and IL‐6, suggestive of suppressed inflammatory response, and increased levels of ALP, osteocalcin, TGF‐β1, and IGF‐1 as well as reduced damage in cartilage tissues.ConclusionLncRNA XIST downregulation could promote proliferation and differentiation of osteoblasts in RA, serving as a future therapeutic target for RA.

The loss of STAT3 in mature osteoclasts has detrimental effects on bone structure.

Signal Transducer and Activator of Transcription 3 (STAT3) has recently been shown to be involved in bone development and has been implicated in bone diseases, such as Job’s Syndrome. Bone growth and changes have been known for many years to differ between sexes with male bones tending to have higher bone mass than female bones and older females tending to lose bone mass at faster rates than older males. Previous studies using conditional knock mice with Stat3 specifically deleted from the osteoblasts showed both sexes exhibited decreased bone mineral density (BMD) and strength. Using the Cre-Lox system with Cathepsin K promotor driving Cre to target the deletion of the Stat3 gene in mature osteoclasts (STAT3-cKO mice), we observed that 8-week old STAT3-cKO female femurs exhibited significantly lower BMD and bone mineral content (BMC) compared to littermate control (CN) females. There were no differences in BMD and BMC observed between male knock-out and male CN femurs. However, micro-computed tomography (μCT) analysis showed that both male and female STAT3-cKO mice had significant decreases in bone volume/tissue volume (BV/TV). Bone histomorphometry analysis of the distal femur, further revealed a decrease in bone formation rate and mineralizing surface/bone surface (MS/BS) with a significant decrease in osteoclast surface in female, but not male, STAT3-cKO mice. Profiling gene expression in an osteoclastic cell line with a knockdown of STAT3 showed an upregulation of a number of genes that are directly regulated by estrogen receptors. These data collectively suggest that regulation of STAT3 differs in male and female osteoclasts and that inactivation of STAT3 in osteoclasts affects bone turnover more in females than males, demonstrating the complicated nature of STAT3 signaling pathways in osteoclastogenesis. Drugs targeting the STAT3 pathway may be used for treatment of diseases such as Job’s Syndrome and osteoporosis.

Regulation of signal transducer and activator of transcription 3 activation by dual-specificity phosphatase 3

Since cancer is the leading cause of death worldwide, there is an urgent need to understand the mechanisms underlying cancer progression and the development of cancer inhibitors. Signal transducer and activator of transcription 3 (STAT3) is a major transcription factor that regulates the proliferation and survival of various cancer cells. Here, dual-specificity phosphatase 3 (DUSP3) was identified as a regulator of STAT3 based on an interaction screening performed using the protein tyrosine phosphatase library. DUSP3 interacted with the C-terminal domain of STAT3 and dephosphorylated p-Y705 of STAT3. In vitro dephosphorylation assay revealed that DUSP3 directly dephosphorylated p-STAT3. The suppressive effects of DUSP3 on STAT3 were evaluated by a decreased STAT3-specific promoter activity, which in turn reduced the expression of the downstream target genes of STAT3. In summary, DUSP3 downregulated the transcriptional activity of STAT3 via dephosphorylation at Y705 and also suppressed the migratory activity of cancer cells. This study demonstrated that DUSP3 inhibits interleukin 6 (IL-6)/STAT3 signaling and is expected to regulate cancer development. Novel functions of DUSP3 discovered in IL-6/STAT3 signaling regulation would help expand the understanding of cancer development mechanisms.

STAT3 Pathway in Gastric Cancer: Signaling, Therapeutic Targeting and Future Prospects.

Molecular signaling pathways play a significant role in the regulation of biological mechanisms, and their abnormal expression can provide the conditions for cancer development. The signal transducer and activator of transcription 3 (STAT3) is a key member of the STAT proteins and its oncogene role in cancer has been shown. STAT3 is able to promote the proliferation and invasion of cancer cells and induces chemoresistance. Different downstream targets of STAT3 have been identified in cancer and it has also been shown that microRNA (miR), long non-coding RNA (lncRNA) and other molecular pathways are able to function as upstream mediators of STAT3 in cancer. In the present review, we focus on the role and regulation of STAT3 in gastric cancer (GC). miRs and lncRNAs are considered as potential upstream mediators of STAT3 and they are able to affect STAT3 expression in exerting their oncogene or onco-suppressor role in GC cells. Anti-tumor compounds suppress the STAT3 signaling pathway to restrict the proliferation and malignant behavior of GC cells. Other molecular pathways, such as sirtuin, stathmin and so on, can act as upstream mediators of STAT3 in GC. Notably, the components of the tumor microenvironment that are capable of targeting STAT3 in GC, such as fibroblasts and macrophages, are discussed in this review. Finally, we demonstrate that STAT3 can target oncogene factors to enhance the proliferation and metastasis of GC cells.

Heme oxygenase-1 alleviates eosinophilic inflammation by inhibiting STAT3-SOCS3 signaling.

Airway inflammation of eosinophilic asthma (EA) attributes to Th2 response, leaving the role of Th17 response unknown. Signal transducer and activator of transcription 3 (STAT3) induce both suppressors of cytokine signaling 3 (SOCS3) and retinoic acid receptor-related orphan nuclear receptor γ (RORγt) to initiate Th17 cell differentiation which is inhibited by SOCS3, a negative feedback regulator of STAT3. Heme oxygenase-1 (HO-1) is a stress-responsive, cytoprotective, and immunoregulatory molecular. Two other isoforms of the enzyme includes HO-2 and HO-3. Because HO-2 does not exhibit stress-related upregulation and distributes mainly in nervous system and HO-3 shows a low enzymatic activity, we tested a hypothesized anti-inflammatory role for HO-1 in EA by inhibiting STAT3-SOCS3 signaling. Animal model was established with Ovalbumin in wild type Balb/C mice. Hemin or SNPP was intraperitoneally (IP) injected ahead of the animal model to induce or inhibit HO-1 expression. Airway inflammation was evaluated by bronchoalveolar lavage, hematoxyline and eosin staining, enzyme-linked immunosorbent assay, and Western blot analysis. In vivo results showed that HO-1 induction inhibited phosphorylation of STAT3 and expression of SOCS3 and RORγt, decreased Th2 and Th17 immune responses, and alleviated airway inflammation. In vitro results revealed that HO-1 inhibited phosphorylation of STAT3 and expression of SOCS3 in naive CD4+ T cells. These findings identify HO-1 induction as a potential therapeutic strategy for EA treatment by reducing STAT3 phosphorylation, STAT3-SOCS3-mediated Th2/Th17 immune responses, and ultimate allergic airway inflammation.