Activin B promotes epithelial wound healing in vivo through RhoA-JNK signaling pathway

Background

Activin B has been reported to promote the proliferation and migration of keratinocytes in vitro via the RhoA-JNK signaling pathway, whereas its in vivo role and mechanism in wound healing process has not yet been elucidated.

Principal Findings

In this study, we explored the potential mechanism by which activin B induces epithelial wound healing in mice. Recombinant lentiviral plasmids, with RhoA (N19) and RhoA (L63) were used to infect wounded KM mice. The wound healing process was monitored after different treatments. Activin B-induced cell proliferation on the wounded skin was visualized by electron microscopy and analyzed by 5′-bromodeoxyuridine (BrdU) incorporation assay. Protein expression of p-JNK or p-cJun was determined by immunohistochemical staining and immunoblotting analysis. Activin B efficiently stimulated the proliferation of keratinocytes and hair follicle cells at the wound area and promoted wound closure. RhoA positively regulated activin B-induced wound healing by up-regulating the expression of p-JNK and p-cJun. Moreover, suppression of RhoA activation delayed activin B-induced wound healing, while JNK inhibition recapitulated phenotypes of RhoA inhibition on wound healing.

Conclusion

These results demonstrate that activin B promotes epithelial wound closure in vivo through the RhoA-Rock-JNK-cJun signaling pathway, providing novel insight into the essential role of activin B in the therapy of wound repair.     

Metabolic patterns and biotransformation activities of resveratrol in human glioblastoma cells: relevance with therapeutic efficacies

Background

Trans-resveratrol rather than its biotransformed monosulfate metabolite exerts anti-medulloblastoma effects by suppressing STAT3 activation. Nevertheless, its effects on human glioblastoma cells are variable due to certain unknown reason(s).

Methodology/Principal Findings

Citing resveratrol-sensitive UW228-3 medulloblastoma cell line and primarily cultured rat brain cells/PBCs as controls, the effect of resveratrol on LN-18 human glioblastoma cells and its relevance with metabolic pattern(s), brain-associated sulfotransferase/SULT expression and the statuses of STAT3 signaling and protein inhibitor of activated STAT3 (PIAS3) were elucidated by multiple experimental approaches. Meanwhile, the expression patterns of three SULTs (SULT1A1, 1C2 and 4A1) in human glioblastoma tumors were profiled immunohistochemically. The results revealed that 100 µM resveratrol-treated LN-18 generated the same metabolites as UW228-3 cells, while additional metabolite in molecular weight of 403.0992 in negative ion mode was found in PBCs. Neither growth arrest nor apoptosis was found in resveratrol-treated LN-18 and PBC cells. Upon resveratrol treatment, the levels of SULT1A1, 1C2 and 4A1 expression in LN-18 cells were more up-regulated than that expressed in UW228-3 cells and close to the levels in PBCs. Immunohistochemical staining showed that 42.0%, 27.1% and 19.6% of 149 glioblastoma cases produced similar SULT1A1, 1C2 and 4A1 levels as that of tumor-surrounding tissues. Unlike the situation in UW228-3 cells, STAT3 signaling remained activated and its protein inhibitor PIAS3 was restricted in the cytosol of resveratrol-treated LN-18 cells. No nuclear translocation of STAT3 and PIAS3 was observed in resveratrol-treated PBCs. Treatment with STAT3 chemical inhibitor, AG490, committed majority of LN-18 and UW228-3 cells but not PBCs to apoptosis within 48 hours.

Conclusions/Significance

LN-18 glioblastoma cells are insensitive to resveratrol due to the more inducible brain-associated SULT expression, insufficiency of resveratrol to suppress activated STAT3 signaling and the lack of PIAS3 nuclear translocation. The findings from PBCs suggest that an effective anticancer dose of resveratrol exerts little side effect on normal brain cells.     

NOP14 regulates the growth,migration, and invasion of colorectal cancer cells by modulating the NRIP1/GSK-3β/β-catenin signaling pathway

Colorectal cancer (CRC) is the third most common cancer diagnosed worldwide. Recently, nucleolar complex protein 14 (NOP14) has been discovered to play a critical role in cancer development and progression, but the mechanisms of action of NOP14 in colorectal cancer remain to be elucidated. In this study, we used collected colorectal cancer tissues and cultured colorectal cancer cell lines (SW480, HT29, HCT116, DLD1, Lovo), and measured the mRNA and protein expression levels of NOP14 in colorectal cancer cells using qPCR and Western blotting. GFP-NOP14 was constructed and siRNA fragments against NOP14 were synthesized to investigate the importance of NOP14 for the development of colorectal cells. Transwell migration assays were used to measure cell invasion and migration, CCK-8 kits were used to measure cell activity, and flow cytometry was applied to the observation of apoptosis. We found that both the mRNA and protein levels of NOP14 were significantly upregulated in CRC tissues and cell lines. Overexpression of GFP-NOP14 markedly promoted the growth, migration, and invasion of the CRC cells HT19 and SW480, while genetic knockdown of NOP14 inhibited these behaviors. Overexpression of NOP14 promoted the expression of NRIP1 and phosphorylated inactivation of GSK-3β, leading to the upregulation of β-catenin. Genetic knockdown of NOP14 had the opposite effect on NRIP1/GSK-3/β-catenin signals. NOP14 therefore appears to be overexpressed in clinical samples and cell lines of colorectal cancer, and promotes the proliferation, growth, and metastasis of colorectal cancer cells by modulating the NRIP1/GSK-3β/β-catenin signaling pathway.Key words: Colorectal cancer, NOP14, proliferation, migration, invasion     

Differential susceptibility epidemic models

We formulate compartmental differential susceptibility (DS) susceptible-infective-removed (SIR) models by dividing the susceptible population into multiple subgroups according to the susceptibility of individuals in each group. We analyze the impact of disease-induced mortality in the situations where the number of contacts per individual is either constant or proportional to the total population. We derive an explicit formula for the reproductive number of infection for each model by investigating the local stability of the infection-free equilibrium. We further prove that the infection-free equilibrium of each model is globally asymptotically stable by qualitative analysis of the dynamics of the model system and by utilizing an appropriately chosen Liapunov function. We show that if the reproductive number is greater than one, then there exists a unique endemic equilibrium for all of the DS models studied in this paper. We prove that the endemic equilibrium is locally asymptotically stable for the models with no disease-induced mortality and the models with contact numbers proportional to the total population. We also provide sufficient conditions for the stability of the endemic equilibrium for other situations. We briefly discuss applications of the DS models to optimal vaccine strategies and the connections between the DS models and predator-prey models with multiple prey populations or host-parasitic interaction models with multiple hosts are also given.This research was partially supported by the Department of Energy under contracts W-7405-ENG-36 and the Applied Mathematical Sciences Program KC-07-01-01.     

Hypertrophy, increased ejection fraction, and reduced Na-K-ATPase activity in phospholemman-deficient mice

Phospholemman (FXYD1), a 72-amino acid transmembrane protein abundantly expressed in the heart and skeletal muscle, is a major substrate for phosphorylation in the cardiomyocyte sarcolemma. Biochemical, cellular, and electrophysiological studies have suggested a number of possible roles for this protein, including ion channel modulator, taurine-release channel, Na(+)/Ca(2+) exchanger modulator, and Na-K-ATPase-associated subunit. We have generated a phospholemman-deficient mouse. The adult null mice exhibited increased cardiac mass, larger cardiomyocytes, and ejection fractions that were 9% higher by magnetic resonance imaging compared with wild-type animals. Notably, this occurred in the absence of hypertension. Total Na-K-ATPase activity was 50% lower in the phospholemman-deficient hearts. Expression (per unit of membrane protein) of total Na-K-ATPase was only slightly diminished, but expression of the minor alpha(2)-isoform, which has been specifically implicated in the control of contractility, was reduced by 60%. The absence of phospholemman thus results in a complex response, including a surprisingly large reduction in intrinsic Na-K-ATPase activity, changes in Na-K-ATPase isoform expression, increase in ejection fraction, and increase in cardiac mass. We hypothesize that a primary effect of phospholemman is to modulate the Na-K-ATPase and that its reduced activity initiates compensatory responses.     

A biochemical and functional characterization of diet-induced brain insulin resistance

While considerable research has examined diminished insulin responses within peripheral tissues, comparatively little has been done to examine the effects of this metabolic disruption upon the CNS. The present study employed biochemical and electrophysiological assays of acutely prepared brain slices to determine whether neural insulin resistance is a component of the metabolic syndrome observed within the fructose-fed (FF) hamster. The tyrosine phosphorylation levels of the insulin receptor (IR) and insulin receptor substrate 1 (IRS-1) in response to insulin were significantly reduced within FF hamsters. Also, insulin-mediated phosphorylation of both residues necessary for activation of the serine-threonine kinase Akt/PKB, a key effector of insulin signaling, was markedly decreased. Elevated levels of the protein tyrosine phosphatase 1B, which dephosphorylates the IR and IRS-1, were also observed within the cerebral cortex and hippocampus of FF hamsters. Examination of whether a nutritionally induced compromise of neural insulin signaling altered synaptic function revealed a significant attenuation of insulin-induced long-term depression, but no effect upon either paired-pulse facilitation or electrically induced long-term potentiation. Collectively, our results demonstrate, for the first time, that nutritionally induced insulin resistance significantly affects the neural insulin signaling pathway, and suggest that brain insulin resistance may contribute to cognitive impairment.     

Murine gammaherpesvirus 68 open reading frame 45 plays an essential role during the immediate-early phase of viral replication

Murine gammaherpesvirus 68 (MHV-68) has been developed as a model for the human gammaherpesviruses Epstein-Barr virus and human herpesvirus 8/Kaposi's sarcoma-associated herpesvirus (HHV-8/KSHV), which are associated with several types of human diseases. Open reading frame 45 (ORF45) is conserved among the members of the Gammaherpesvirinae subfamily and has been suggested to be a virion tegument protein. The repression of ORF45 expression by small interfering RNAs inhibits MHV-68 viral replication. However, the gene product of MHV-68 ORF45 and its function have not yet been well characterized. In this report, we show that MHV-68 ORF45 is a phosphorylated nuclear protein. We constructed an ORF45-null MHV-68 mutant virus (45STOP) by the insertion of translation termination codons into the portion of the gene encoding the N terminus of ORF45. We demonstrated that the ORF45 protein is essential for viral gene expression immediately after the viral genome enters the nucleus. These defects in viral replication were rescued by providing ORF45 in trans or in an ORF45-null revertant (45STOP.R) virus. Using a transcomplementation assay, we showed that the function of ORF45 in viral replication is conserved with that of its KSHV homologue. Finally, we found that the C-terminal 23 amino acids that are highly conserved among the Gammaherpesvirinae subfamily are critical for the function of ORF45 in viral replication.