Sequential activation of inflammatory signaling pathways during graft-versus-host disease (GVHD): early role for STAT1 and STAT3

The aim of this study was to delineate the temporal and spatial sequence of STAT1 and STAT3 activation during development of GVHD following fully Major Histocompatibility Complex (MHC)-mismatched allogeneic Bone Marrow Transplantation (BMT). Activation of inflammatory signaling pathways in GVHD target organs was assessed by western blotting, phospho-flow cytometry and electromobility shift assays (EMSA). Development of GVHD was associated with significant expansion of phospho[p]-STAT1 and p-STAT3 expressing CD4⁺ T cells and CD8⁺ T cells. GVHD-specific STAT3/STAT1 activation preceded activation of Nuclear Factor-κB (NF-κB) and Mitogen Activated Protein Kinase (MAPK) and was associated with subsequent induction of STAT1 or STAT3-dependent inflammatory gene-expression programs (e.g. expression of IRF-1, SOCS1, IL-17). Our studies may help to establish a functional hierarchy of the signaling events leading to the development of GVHD and could be helpful in designing new molecularly targeted treatment approaches for GVHD.     

WNT signaling in atrial fibrillation

The Wnt signaling pathway regulates physiological processes such as cell proliferation and differentiation, cell fate decisions, and stem cell maintenance and, thus, plays essential roles in embryonic development, but also in adult tissue homeostasis and repair. The Wnt signaling pathway has been associated with heart development and repair and has been shown to be crucially involved in proliferation and differentiation of progenitor cells into cardiomyocytes. The investigation of the role of the Wnt signaling pathway and the regulation of its expression/activity in atrial fibrillation has only just begun. The present minireview (I) provides original data regarding the expression of Wnt signaling components in atrial tissue of patients with atrial fibrillation or sinus rhythm and (II) summarizes the current state of knowledge of the regulation of Wnt signaling components’ expression/activity and the contribution of the various levels of the Wnt signal transduction pathway to the processes of the development, maintenance, and progression of atrial fibrillation.     

Commensal microbe-derived SCFA alleviates atrial fibrillation via GPR43/NLRP3 signaling

Rationale: Dysbiotic gut microbiota (GM) and NLRP3 inflammasome are proarrhythmic factors in atrial fibrillation (AF). Herein, whether short-chain fatty acid (SCFA) produced from GM fermentation of dietary fiber serving as invisible mediators is yet unclear. Thus, the current study aimed to determine whether SCFA alleviated from NLRP3 signaling-mediated atrial remodeling protects AF development.Methods: First, a cross-sectional study based on the GC-MS metabolomics was performed to explore the association between fecal SCFA levels and AF traits in a cohort consisted of 48 individuals. Then, a well-established mice model fed diet deficient or enriched in dietary fiber was established to elucidate the pathophysiological role of SCFA involved in AF susceptibility, atrial remodeling, and G-protein-coupled receptor 43 (GPR43)/NLRP3 signaling. Finally, the effects of SCFA were verified on HL-1 cells.Results: Fecal SCFA levels were remarkably reduced in AF patients with a declining trend from paroxysmal to persistent AF. Prolonged P wave duration based on surface ECG and increased left atrial diameter gained from echocardiography was identified in low-fiber diet mice but lost in SCFA-supplemented group. Lack of dietary fiber enhanced susceptibility to AF under burst pacing, whereas SCFA might exert a protective effect. The supplementation of SCFA prevented dietary fiber deficiency-upregulated phosphorylation of calmodulin-dependent protein kinase II and ryanodine receptor 2, the disarray fibrosis, collagen expression, and NLRP3 inflammasome activation in atrial tissue. Finally, the AF protective roles of SCFA were identified through GPR43 mediated deactivation of NLRP3 by GPR43 knockdown in HL-1 cells.Conclusions: SCFA derived from dietary fiber fermentation by gut commensals alleviates AF development via GPR43/NLRP3 signaling.     

TRIM72 contributes to cardiac fibrosis via regulating STAT3/Notch-1 signaling

Cardiac fibrosis is a pathophysiological process characterized by excessive deposition of extracellular matrix. We developed a cardiac hypertrophy model using transverse aortic constriction (TAC) to uncover mechanisms relevant to excessive deposition of extracellular matrix in mouse myocardial cells. TAC caused upregulation of Tripartite motif protein 72 (TRIM72), a tripartite motif-containing protein that is critical for proliferation and migration. Importantly, in vivo silencing of TRIM72 reversed TAC-induced cardiac fibrosis, as indicated by markedly increased left ventricular systolic pressure and decreased left ventricular end-diastolic pressure. TRIM72 knockdown also attenuated deposition of fibrosis marker collagen type I and α-smooth muscle actin (α-SMA). In an in vitro study, TRIM72 was similarly upregulated in cardiac fibroblasts. Knockdown of TRIM72 markedly suppressed collagen type I and α-SMA expression and significantly decreased the proliferation and migration of cardiac fibroblasts. However, TRIM72 overexpression markedly increased collagen type I and α-SMA expression and increased the proliferation and migration of cardiac fibroblasts. Further study demonstrated that TRIM72 increased phosphorylated STAT3 in cardiac fibroblasts. TRIM72 knockdown in cardiac fibroblasts resulted in increased expression of Notch ligand Jagged-1 and its downstream gene and Notch-1 intracellular domain. Inhibition of Notch-1 abrogated sh-TRIM72-induced cardiac fibrosis. Together, our results support a novel role for TRIM72 in maintaining fibroblast-to-myofibroblast transition and suppressing fibroblast growth by regulating the STAT3/Notch-1 pathway.     

bFGF and LIF signaling activates STAT3 in proliferating myoblasts

Different mitogens elicit similar effects on growth and differentiation of skeletal muscle, suggesting that potential overlap exists in the signaling cascades activated by such factors. To investigate this possibility, we examined the status of STAT and ERK proteins in C2C12 myoblasts and myotubes following stimulation with bFGF or LIF. Both STAT1 and STAT3 as well as ERK1 and ERK2 proteins were detectable in extracts of myoblasts. LIF stimulation of myoblasts lead to rapid phosphorylation on tyrosine of STAT3 and of ERKs 1 and 2. Similarly, bFGF stimulation of myoblasts resulted in the tyrosine phosphorylation of STAT3. However, unlike LIF, the bFGF induced tyrosine phosphorylation of STAT3 appeared cyclical, with recurrent peaks of phosphorylation even after prolonged exposure. By contrast, STAT1 remained unphosphorylated in myoblasts treated with bFGF or LIF. In differentiated myotubes, LIF treatment resulted in the tyrosine phosphorylation of both STAT3 and STAT1, but ERK phosphorylation was not detectable, and bFGF treatment did not lead to STAT1 or STAT3 tyrosine phosphorylation. Therefore these observations suggest that disparate mitogens can activate similar downstream effectors in proliferating myoblasts. © 1996 Wiley-Liss, Inc.     

Tumor-derived lactate induces M2 macrophage polarization via the activation of the ERK/STAT3 signaling pathway in breast cancer

Tumor-associated macrophages (TAM) are prominent components of tumor microenvironment (TME) and capable of promoting cancer progression. However, the mechanisms for the formation of M2-like TAMs remain enigmatic. Here, we show that lactate is a pivotal oncometabolite in the TME that drives macrophage M2-polarization to promote breast cancer proliferation, migration, and angiogenesis. In addition, we identified that the activation of ERK/STAT3, major signaling molecules in the lactate signaling pathway, deepens our molecular understanding of how lactate educates TAMs. Moreover, suppression of ERK/STAT3 signaling diminished tumor growth and angiogenesis by abolishing lactate-induced M2 macrophage polarization. Finally, research data of the natural compound withanolide D provide evidence for ERK/STAT3 signaling as a potential therapeutic strategy for the prevention and treatment of breast cancer. These findings suggest that the lactate-ERK/STAT3 signaling pathway is a driver of breast cancer progression by stimulating macrophage M2-like polarization and reveal potential new therapeutic targets for breast cancer treatment.     

Angoline: A selective IL-6/STAT3 signaling pathway inhibitor isolated from Zanthoxylum nitidum

STAT3 signaling pathway is an important target for human cancer therapy. Thus, the identification of small-molecules that target STAT3 signaling will be of great interests in the development of anticancer agents. The aim of this study was to identify novel inhibitors of STAT3 pathway from the roots of Zanthoxylum nitidum (Roxb.) DC. The bioassay-guided fractionation of MeOH extract of Z. nitidum using a STAT3-responsive gene reporter assay led to the isolation of angoline (1) as a potent and selective inhibitor of the STAT3 signaling pathway (IC₅₀ = 11.56 μM). Angoline inhibited STAT3 phosphorylation and its target gene expression and consequently induced growth inhibition of human cancer cells with constitutively activated STAT3 (IC₅₀ = 3.14–4.72 μM). This work provided a novel lead for the development of anti-cancer agents targeting the STAT3 signaling pathway.     

Growth arrest-specific 5 attenuates cisplatin-induced apoptosis in cervical cancer by regulating STAT3 signaling via miR-21

Cervical cancer is the most common cause of female cancer-related mortality worldwide. Decreased expression of long noncoding RNA growth arrest-specific 5 (GAS5) is found in human cervical cancer tissues and associated with poor prognosis. However, the studies on associations between GAS5 level and malignant phenotypes, as well as sensitivity to chemotherapeutic drug in cervical cancer cells are limited. In this study, overexpression of GAS5 in cervical cancer cells resulted in prohibited cell proliferation and colony formation, which were promoted by siGAS5. Enhanced GAS5 increased cell percentage in the G0/G1 phase and decreased cells percentage in the S phase, whereas reduced expression did not. The malignant behaviors of cervical cancer cells, manifested by cell migration and invasion, could be weakened by the GAS5 overexpression and enhanced by siGAS5. Furthermore, in cisplatin-induced cell, overexpression of GAS5 reduced cells viability and enhanced apoptosis, whereas in cells transfected with siGAS5, apoptosis eliminated. We have reported the upregulation of microRNA-21 (miR-21) and its oncogenetic roles in cervical cancer previously. In this study, we found the negative relationship between the GAS5 and miR-21. Moreover, the decrease of miR-21 associated proteins phosphorylated STAT3 and E2F3 was seen in GAS5 overexpressed cells, both of which could be increased by siGAS5. The GAS5 deficiency also reduced miR-21 target proteins TIMP3 and PDCD4 expressions. Taken together, the GAS5 expression level is inversely associated with malignancy, but positively associated with sensitivity to cisplatin-induced apoptosis, suggesting that GAS5 could be a biomarker of cisplatin-resistance in clinical therapy of human cervical cancer.     

miRNA-21 inhibition enhances RANTES and IP-10 release in MCF-7 via PIAS3 and STAT3 signalling and causes increased lymphocyte migration

MicroRNAs (miRNAs) are a class of small endogenous gene regulators that have been implicated in various developmental and pathological processes. However, the precise identities and functions of miRNAs involved in antitumor immunity are not yet well understood. miRNA-21 is an oncogenic miRNA that can be detected in various tumours. In this study, we report that a miRNA-21 inhibitor enhances the release of chemoattractants RANTES and IP-10 in the MCF-7 breast cancer cell line and results in increased lymphocyte migration. Thus, miRNA-21 is a potential therapeutic target for cancer immunotherapy. We further demonstrated that PIAS3, a protein inhibitor of activated STAT3, is a target of miRNA-21 in MCF-7. Thus, miRNA-21 is a novel miRNA regulating immune cell recruitment, which acts at least in part via its inhibition of PIAS3 expression and oncogenic STAT3 signalling in tumour cells.