Activation of integrin β1-focal adhesion kinase-RasGTP pathway plays a critical role in TGF beta1-induced podocyte injury

Integrin β4 as a Potential Diagnostic and Therapeutic Tumor Marker

Integrin β4 (ITGβ4) is a class of transmembrane adhesion molecules composed of hemidesmosomes (HDs). Its unique long intracellular domain provides intricate signal transduction functions. These signal transduction effects are especially prominent in tumors. Many recent studies have shown that integrin β4 is differentially expressed in various tumors, and it plays a vital role in tumor invasion, proliferation, epithelial–mesenchymal transition, and angiogenesis. Therefore, we categorize the research related to integrin β4, starting from its structure and function in tumor tissues, and provide a basic description. Based on its structure and function, we believe that integrin β4 can be used as a tumor marker. In clinical practice, it is described as a diagnostic marker for the targeted treatment of cancer and will be helpful in the clinical diagnosis and treatment of tumors.

Grb2 Induces Cardiorenal Syndrome Type 3: Roles of IL-6, Cardiomyocyte Bioenergetics, and Akt/mTOR Pathway

Cardiorenal syndrome type 3 (CRS-3) is damage to the heart following acute kidney injury (AKI). Although many experiments have found that inflammation, oxidative stress, and cardiomyocyte death are involved in cardiomyocyte pathophysiological alterations during CRS-3, they lack a non-bias analysis to figure out the primary mediator of cardiac dysfunction. Herein proteomic analysis was operated in CRS-3 and growth factor receptor-bound protein 2 (Grb2) was identified as a regulator involving AKI-related myocardial damage. Increased Grb2 was associated with cardiac diastolic dysfunction and mitochondrial bioenergetics impairment; these pathological changes could be reversed through the administration of a Grb2-specific inhibitor during AKI. Molecular investigation illustrated that augmented Grb2 promoted cardiomyocyte mitochondrial metabolism disorder through inhibiting the Akt/mTOR signaling pathway. Besides that, Mouse Inflammation Array Q1 further identified IL-6 as the upstream stimulator of Grb2 upregulation after AKI. Exogenous administration of IL-6 induced cardiomyocyte damage and mitochondrial bioenergetics impairment, whereas these effects were nullified in cardiomyocytes pretreated with Grb2 inhibitor. Our results altogether identify CRS-3 to be caused by the upregulations of IL-6/Grb2 which contribute to cardiac dysfunction through inhibiting the Akt/mTOR signaling pathway and inducing cardiomyocyte mitochondrial bioenergetics impairment. This finding provides a potential target for the clinical treatment of patients with CRS-3.

TXNIP deficiency mitigates podocyte apoptosis via restraining the activation of mTOR or p38 MAPK signaling in diabetic nephropathy

Thioredoxin-interacting protein (TXNIP), is identified as an inhibitor of the thiol oxidoreductase thioredoxin that acts endogenously, and is increased by high glucose (HG). In this study, we investigated the potential function of TXNIP on apoptosis of podocytes and its potential mechanism in vivo and in vitro in diabetic nephropathy (DN). TXNIP silencing attenuated HG-induced apoptosis and obliterated the activation of signaling pathways of mammalian target of rapamycin (mTOR) and p38 mitogen-activated protein kinase (MAPK) in conditionally immortalized mouse podocytes. Furthermore, the Raptor and Rictor shRNAs, mTOR specific inhibitor KU-0063794 and p38 MAPK inhibitor SB203580 were used to assess the role of mTOR or p38 MAPK pathway on podocyte apoptosis induced by HG. The Rictor and Raptor shRNAs and KU-0063794 appeared to reduce HG-induced apoptosis in podocytes. Simultaneously, SB203580 could also restrain HG-induced apoptosis in podocytes. Streptozotocin rendered equivalent diabetes in TXNIP-/- (TKO) and wild-type (WT) control mice. TXNIP deficiency mitigated renal injury in diabetic mice. Additionally, TXNIP deficiency also descended the apoptosis-related protein and Nox4 levels, the mTOR signaling activation and the p38 MAPK phosphorylation in podocytes of diabetic mice. All these data indicate that TXNIP deficiency may mitigate apoptosis of podocytes by inhibiting p38 MAPK or mTOR signaling pathway in DN, underlining TXNIP as a putative target for therapy.

Dendrobium candidum extract inhibits proliferation and induces apoptosis of liver cancer cells by inactivating Wnt/β-catenin signaling pathway

BACKGROUND

Dendrobium candidum extract (DCE) has been reported to have anti-tumor property. However, the effect of DCE on liver cancer has not been well explored. This study was aimed to evaluate the inhibitory effect of DCE on liver cancer cells.

METHODS

The effect of DCE on liver cancer cells was analyzed by detecting cell viability by MTT assay, detecting colony formation ability by colony formation assay, determining apoptotic cell rate, cell cycle distribution, active caspase-3 positive cells, Ki-67 positive cells, reactive oxygen species (ROS) level, and mitochondrial transmembrane potential (MMP) by flow cytometry analysis, and analyzing changes of expressions of cell cycle-, apoptosis-, and Wnt/β-catenin pathway-related proteins by Western blot.

RESULTS

DCE inhibited viability and promoted apoptosis of liver cancer cell lines SMMC-7721 and BEL-7404. DCE decreased colony formation, induced cell cycle arrest, and led to cell cycle-associated proteins' abnormal expressions in SMMC-7721 and BEL-7404 cells. DCE effectively suppressed viability and proliferation of primary liver cancer cells and also induced aberrant expressions of cell cycle- and apoptosis-related proteins. After DCE treatment, ROS level was increased and MMP level was decreased. DCE inhibited β-catenin level in the nucleus and regulated downstream genes of β-catenin and further blocked Wnt/β-catenin pathway in SMMC-7721 and BEL-7404 cells as well as primary liver cancer cells.

CONCLUSION

DCE suppressed liver cancer SMMC-7721 and BEL-7404 cells as well as primary liver cancer cells likely though activating mitochondria apoptosis pathway and inducing inhibition of Wnt/β-catenin pathway.

Dahuang Zexie Decoction Protects against High-Fat Diet-Induced NAFLD by Modulating Gut Microbiota-Mediated Toll-Like Receptor 4 Signaling Activation and Loss of Intestinal Barrier

Increasing evidence suggests that intestinal dysbiosis, intestinal barrier dysfunction, and activated Toll-like receptor 4 (TLR4) signaling play key roles in the pathogenesis of NAFLD. Dahuang Zexie Decoction (DZD) has been verified to be effective for treating NAFLD, but the mechanisms remain unclear. In this study, we investigated the effects of DZD on NAFLD rats and determined whether such effects were associated with change of the gut microbiota, downregulated activity of the TLR4 signaling pathway, and increased expressions of tight junction (TJ) proteins in the gut. Male Sprague Dawley rats were fed high-fat diet (HFD) for 16 weeks to induce NAFLD and then given DZD intervention for 4 weeks. We found that DZD reduced body and liver weights of NAFLD rats, improved serum lipid levels and liver function parameters, and relieved NAFLD. We further found that DZD changed intestinal bacterial communities, inhibited the intestinal TLR4 signaling pathway, and restored the expressions of TJ proteins in the gut. Meanwhile ten potential components of DZD had been identified. These findings suggest that DZD may protects against NAFLD by modulating gut microbiota-mediated TLR4 signaling activation and loss of intestinal barrier. However, further studies are needed to clarify the mechanism by which DZD treats NAFLD.

Nicotine Induces Podocyte Apoptosis through Increasing Oxidative Stress

Background

Cigarette smoking plays an important role in the progression of chronic kidney disease (CKD). Nicotine, one of the major components of cigarette smoking, has been demonstrated to increase proliferation of renal mesangial cells. In this study, we examined the effect of nicotine on podocyte injury.

Methods

To determine the expression of nicotinic acetylcholine receptors (nAChR subunits) in podocytes, cDNAs and cell lysate of cultured human podocytes were used for the expression of nAChR mRNAs and proteins, respectively; and mouse renal cortical sections were subjected to immunofluorescant staining. We also studied the effect of nicotine on podocyte nephrin expression, reactive oxygen species (ROS) generation (via DCFDA loading followed by fluorometric analysis), proliferation, and apoptosis (morphologic assays). We evaluated the effect of nicotine on podocyte downstream signaling including phosphorylation of ERK1/2, JNK, and p38 and established causal relationships by using respective inhibitors. We used nAChR antagonists to confirm the role of nicotine on podocyte injury.

Results

Human podocytes displayed robust mRNA and protein expression of nAChR in vitro studies. In vivo studies, mice renal cortical sections revealed co-localization of nAChRs along with synaptopodin. In vitro studies, nephrin expression in podocyte was decreased by nicotine. Nicotine stimulated podocyte ROS generation; nonetheless, antioxidants such as N-acetyl cysteine (NAC) and TEMPOL (superoxide dismutase mimetic agent) inhibited this effect of nicotine. Nicotine did not modulate proliferation but promoted apoptosis in podocytes. Nicotine enhanced podocyte phosphorylation of ERK1/2, JNK, and p38, and their specific inhibitors attenuated nicotine-induced apoptosis. nAChR antagonists significantly suppressed the effects of nicotine on podocyte.

Conclusions

Nicotine induces podocyte apoptosis through ROS generation and associated downstream MAPKs signaling. The present study provides insight into molecular mechanisms involved in smoking associated progression of chronic kidney disease.

Podocyte-actin dynamics in health and disease

Genetic studies of hereditary forms of nephrotic syndrome have identified several proteins that are involved in regulating the permselective properties of the glomerular filtration system. Further extensive research has elucidated the complex molecular basis of the glomerular filtration barrier and clearly established the pivotal role of podocytes in the pathophysiology of glomerular diseases. Podocyte architecture is centred on focal adhesions and slit diaphragms - multiprotein signalling hubs that regulate cell morphology and function. A highly interconnected actin cytoskeleton enables podocytes to adapt in order to accommodate environmental changes and maintain an intact glomerular filtration barrier. Actin-based endocytosis has now emerged as a regulator of podocyte integrity, providing an impetus for understanding the precise mechanisms that underlie the steady-state control of focal adhesion and slit diaphragm components. This Review outlines the role of actin dynamics and endocytosis in podocyte biology, and discusses how molecular heterogeneity in glomerular disorders could be exploited to deliver more rational therapeutic interventions, paving the way for targeted medicine in nephrology.

Distinct Dasatinib-Induced Mechanisms of Apoptotic Response and Exosome Release in Imatinib-Resistant Human Chronic Myeloid Leukemia Cells

Although dasatinib is effective in most imatinib mesylate (IMT)-resistant chronic myeloid leukemia (CML) patients, the underlying mechanism of its effectiveness in eliminating imatinib-resistant cells is only partially understood. This study investigated the effects of dasatinib on signaling mechanisms driving-resistance in imatinib-resistant CML cell line K562 (K562R^IMT). Compared with K562 control cells, exsomal release, the phosphoinositide 3-kinase (PI3K)/protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) signaling and autophagic activity were increased significantly in K562R^IMT cells and mTOR-independent beclin-1/Vps34 signaling was shown to be involved in exosomal release in these cells. We found that Notch1 activation-mediated reduction of phosphatase and tensin homolog (PTEN) was responsible for the increased Akt/mTOR activities in K562R^IMT cells and treatment with Notch1 γ-secretase inhibitor prevented activation of Akt/mTOR. In addition, suppression of mTOR activity by rapamycin decreased the level of activity of p70S6K, induced upregulation of p53 and caspase 3, and led to increase of apoptosis in K562R^IMT cells. Inhibition of autophagy by spautin-1 or beclin-1 knockdown decreased exosomal release, but did not affect apoptosis in K562R^IMT cells. In summary, in K562R^IMT cells dasatinib promoted apoptosis through downregulation of Akt/mTOR activities, while preventing exosomal release and inhibiting autophagy by downregulating expression of beclin-1 and Vps34. Our findings reveal distinct dasatinib-induced mechanisms of apoptotic response and exosomal release in imatinib-resistant CML cells.

Extracellular matrix as a contextual determinant of transforming growth factor-β signaling in epithelial-mesenchymal transition and in cancer

Extracellular matrix (ECM) provides both structural support and contextual information to cells within tissues and organs. The combination of biochemical and biomechanical signals from the ECM modulates responses to extracellular signals toward differentiation, proliferation, or apoptosis; alterations in the ECM are necessary for development and remodeling processes, but aberrations in the composition and organization of ECM are associated with disease pathology and can predispose to development of cancer. The primary cell surface sensors of the ECM are the integrins, which provide the physical connection between the ECM and the cytoskeleton and also convey biochemical information about the composition of the ECM. Transforming growth factor-β (TGF-β) is an extracellular signaling molecule that is a powerful controller of a variety of cellular functions, and that has been found to induce very different outcomes according to cell type and cellular context. It is becoming clear that ECM-mediated signaling through integrins is reciprocally influenced by TGF-β: integrin expression, activation, and responses are affected by cellular exposure to TGF-β, and TGF-β activation and cellular responses are in turn controlled by signaling from the ECM through integrins. Epithelial-mesenchymal transition (EMT), a physiological process that is activated by TGF-β in normal development and in cancer, is also affected by the composition and structure of the ECM. Here, we will outline how signaling from the ECM controls the contextual response to TGF-β, and how this response is selectively modulated during disease, with an emphasis on recent findings, current challenges, and future opportunities.

Modulation of sterol biosynthesis regulates viral replication and cytokine production in influenza A virus infected human alveolar epithelial cells

Highly pathogenic H5N1 viruses continue to transmit zoonotically, with mortality higher than 60%, and pose a pandemic threat. Antivirals remain the primary choice for treating H5N1 diseases and have their limitations. Encouraging findings highlight the beneficial effects of combined treatment of host targeting agents with immune-modulatory activities. This study evaluated the undefined roles of sterol metabolic pathway in viral replication and cytokine induction by H5N1 virus in human alveolar epithelial cells. The suppression of the sterol biosynthesis by Simvastatin in human alveolar epithelial cells led to reduction of virus replication and cytokine production by H5N1 virus. We further dissected the antiviral role of different regulators of the sterol metabolism, we showed that Zometa, FPT inhibitor III, but not GGTI-2133 had anti-viral activities against both H5N1 and H1N1 viruses. More importantly, FPT inhibitor III treatment significantly suppressed cytokine production by H5N1 virus infected alveolar epithelial cells. Since both viral replication itself and the effects of viral hyper-induction of cytokines contribute to the immunopathology of severe H5N1 disease, our findings highlights the therapeutic potential of FPT inhibitor III for severe human H5N1 diseases. Furthermore, our study is the first to dissect the roles of different steps in the sterol metabolic pathway in H5N1 virus replication and cytokine production.

EphB2 contributes to human naive B-cell activation and is regulated by miR-185

EphB2 is an important member of the receptor tyrosine kinases. Recently, EphB2 was shown to facilitate T-cell migration and monocyte activation. However, the effects of EphB2 on B cells remain unknown. In this study, the expression of EphB2 on B cells was tested by Western blot, and the roles of EphB2 in B-cell proliferation, cytokine secretion, and immunoglobulin (Ig) production were evaluated using EphB2 siRNA interference in human B cells from healthy volunteers. Our study revealed that EphB2 was distributed on naive B cells and was up-regulated on activated B cells. Moreover, B-cell proliferation (decreased by 22%, P<0.05), TNF-α secretion (decreased by 40%, P<0.01) and IgG production (decreased by 26%, P < 0.05) were depressed concordantly with the down-regulated EphB2 expression. Subsequently, we screened microRNAs that could regulate EphB2 expression in B cells, and discovered that miR-185 directly targeted to EphB2 mRNA and suppressed its expression. Furthermore, miR-185 overexpression inhibited B-cell activation, and the inhibitor of miR-185 enhanced B-cell activation. Moreover, abatement of EphB2 through miR-185 mimics or EphB2 siRNA attenuated the activation of Src-p65 and Notch1 signaling pathways in human B cells. Our study first suggested that EphB2 was involved in human naive B cell activation through Src-p65 and Notch1 signaling pathways and could be regulated by miR-185.

Role of caveolin-1 in asthma and chronic inflammatory respiratory diseases

Caveolin-1 (Cav-1) is the major protein present in invaginations of the plasma membrane of cells known as caveolae. Cav-1 is expressed in numerous resident and inflammatory cells implicated in the pathogenesis of asthma and chronic inflammatory respiratory diseases including chronic obstructive pulmonary disease. A remarkable repertoire of functions has been identified for Cav-1 and these extend to, and have relevance to, asthma and chronic inflammatory respiratory diseases. Important processes influenced by Cav-1 include inflammation, fibrosis, smooth muscle contractility, regulation of apoptosis and cell senescence as well as epithelial barrier function and homeostasis. A better understanding of Cav-1 may be useful in developing new therapies for chronic inflammatory respiratory diseases.