Organization and regulation of mitogen-activated protein kinase signaling pathways

P38 and ERK1/2 MAPKs act in opposition to regulate BMP9-induced osteogenic differentiation of mesenchymal progenitor cells

Although previous studies have demonstrated that BMP9 is highly capable of inducing osteogenic differentiation and bone formation, the precise molecular mechanism involved remains to be fully elucidated. In this current study, we explore the possible involvement and detail effects of p38 and ERK1/2 MAPKs on BMP9-indcued osteogenic differentiation of mesenchymal progenitor cell (MPCs). We find that BMP9 simultaneously stimulates the activation of p38 and ERK1/2 in MPCs. BMP9-induced early osteogenic marker, such as alkaline phosphatase (ALP), and late osteogenic markers, such as matrix mineralization and osteocalcin (OC) are inhibited by p38 inhibitor SB203580, whereas enhanced by ERK1/2 inhibitor PD98059. BMP9-induced activation of Runx2 and Smads signaling are reduced by SB203580, and yet increased by PD98059 in MPCs. The in vitro effects of inhibitors are reproduced with adenoviruses expressing siRNA targeted p38 and ERK1/2, respectively. Using mouse calvarial organ culture and subcutaneous MPCs implantation, we find that inhibition of p38 activity leads to significant decrease in BMP9-induced osteogenic differentiation and bone formation, however, blockage of ERK1/2 results in effective increase in BMP9-indcued osteogenic differentiation in vivo. Together, our results reveal that p38 and ERK1/2 MAPKs are activated in BMP9-induced osteogenic differentiation of MPCs. What is most noteworthy, however, is that p38 and ERK1/2 act in opposition to regulate BMP9-induced osteogenic differentiation of MPCs.

Infection with street strain rabies virus induces modulation of the microRNA profile of the mouse brain

Background

Rabies virus (RABV) causes a fatal infection of the central nervous systems (CNS) of warm-blooded animals. Once the clinical symptoms develop, rabies is almost invariably fatal. The mechanism of RABV pathogenesis remains poorly understood. Recent studies have shown that microRNA (miRNA) plays an important role in the pathogenesis of viral infections. Our recent findings have revealed that infection with laboratory-fixed rabies virus strain can induce modulation of the microRNA profile of mouse brains. However, no previous report has evaluated the miRNA expression profile of mouse brains infected with RABV street strain.

Results

The results of microarray analysis show that miRNA expression becomes modulated in the brains of mice infected with street RABV. Quantitative real-time PCR assay of the differentially expressed miRNAs confirmed the results of microarray assay. Functional analysis showed the differentially expressed miRNAs to be involved in many immune-related signaling pathways, such as the Jak-STAT signaling pathway, the MAPK signaling pathway, cytokine-cytokine receptor interactions, and Fc gamma R-mediated phagocytosis. The predicted expression levels of the target genes of these modulated miRNAs were found to be correlated with gene expression as measured by DNA microarray and qRT-PCR.

Conclusion

RABV causes significant changes in the miRNA expression profiles of infected mouse brains. Predicted target genes of the differentially expression miRNAs are associated with host immune response, which may provide important information for investigation of RABV pathogenesis and therapeutic method.

Conformational control of the Ste5 scaffold protein insulates against MAP kinase misactivation

Cells reuse signaling proteins in multiple pathways, raising the potential for improper cross talk. Scaffold proteins are thought to insulate against such miscommunication by sequestering proteins into distinct physical complexes. We show that the scaffold protein Ste5, which organizes the yeast mating mitogen-activated protein kinase (MAPK) pathway, does not use sequestration to prevent misactivation of the mating response. Instead, Ste5 appears to use a conformation mechanism: Under basal conditions, an intramolecular interaction of the pleckstrin homology (PH) domain with the von Willebrand type A (VWA) domain blocks the ability to coactivate the mating-specific MAPK Fus3. Pheromone-induced membrane binding of Ste5 triggers release of this autoinhibition. Thus, in addition to serving as a conduit guiding kinase communication, Ste5 directly receives input information to decide if and when signal can be transmitted to mating output.

A cytotoxic type III secretion effector of Vibrio parahaemolyticus targets vacuolar H+-ATPase subunit c and ruptures host cell lysosomes

Vibrio parahaemolyticus is one of the human pathogenic vibrios. During the infection of mammalian cells, this pathogen exhibits cytotoxicity that is dependent on its type III secretion system (T3SS1). VepA, an effector protein secreted via the T3SS1, plays a major role in the T3SS1-dependent cytotoxicity of V. parahaemolyticus. However, the mechanism by which VepA is involved in T3SS1-dependent cytotoxicity is unknown. Here, we found that protein transfection of VepA into HeLa cells resulted in cell death, indicating that VepA alone is cytotoxic. The ectopic expression of VepA in yeast Saccharomyces cerevisiae interferes with yeast growth, indicating that VepA is also toxic in yeast. A yeast genome-wide screen identified the yeast gene VMA3 as essential for the growth inhibition of yeast by VepA. Although VMA3 encodes subunit c of the vacuolar H⁺-ATPase (V-ATPase), the toxicity of VepA was independent of the function of V-ATPases. In HeLa cells, knockdown of V-ATPase subunit c decreased VepA-mediated cytotoxicity. We also demonstrated that VepA interacted with V-ATPase subunit c, whereas a carboxyl-terminally truncated mutant of VepA (VepAΔC), which does not show toxicity, did not. During infection, lysosomal contents leaked into the cytosol, revealing that lysosomal membrane permeabilization occurred prior to cell lysis. In a cell-free system, VepA was sufficient to induce the release of cathepsin D from isolated lysosomes. Therefore, our data suggest that the bacterial effector VepA targets subunit c of V-ATPase and induces the rupture of host cell lysosomes and subsequent cell death.

Vibrio parahaemolyticus is a bacterial pathogen that causes food-borne gastroenteritis and also wound infection and septicemia. It exhibits cytotoxicity that is dependent on its type III secretion system (T3SS1) during the infection of mammalian cells. Although an effector VepA plays a major role in the cytotoxicity, the mechanism was unknown. Here we show that VepA targets subunit c of the vacuolar H⁺-ATPase (V-ATPase) and induces the rupture of host cell lysosomes. We found that VepA alone is cytotoxic in HeLa cells and also toxic in yeast Saccharomyces cerevisiae. Using a yeast genome-wide screening, we identified yeast V-ATPase subunit c as essential for the toxicity of VepA to yeast. We also demonstrated that knockdown of V-ATPase subunit c decreased VepA-mediated cytotoxicity toward HeLa cells and that VepA interacted with subunit c of V-ATPase. During infection, lysosomal contents leaked into the cytosol prior to cell lysis, and VepA was necessary and sufficient for this leakage. Our data suggest that a bacterial effector VepA ruptures lysosomes, the “suicide bags” of host cells, by targeting the evolutionarily conserved V-ATPase, and elicits subsequent cell death.

Isofraxidin exhibited anti-inflammatory effects in vivo and inhibited TNF-α production in LPS-induced mouse peritoneal macrophages in vitro via the MAPK pathway

Isofraxidin (IF) is a Coumarin compound that can be isolated from medicinal plants, such as Sarcandra glabra (Thunb.). Nakai is widely used in Asian countries for the treatment of anti-bacterial, anti-inflammatory and anti-tumour action. The present investigation was designed to evaluate the effect of IF on inflammation and nociception. In addition, we investigated a potential novel mechanism to explain the anti-inflammatory properties of IF. In vivo, xylene-induced mouse ear edema, carrageenan-induced rat paw edema, LPS-induced mouse endotoxic shock, acetic acid-induced mice writhing and formalin-induced mouse pain models were used to evaluate the anti-inflammatory activity of IF. In vitro, we examined the effects of IF inhibition on TNF-α production and the regulation of ERK1/2 and p38 phosphorylation activity in LPS-induced mouse peritoneal macrophages. Our results demonstrated that IF can significantly decrease xylene-induced ear edema, carrageenan-induced paw edema, acetic acid-induced writhing and formalin-induced pain. Moreover, IF greatly inhibited the production of TNF-α in the serum of LPS-stimulated mice and peritoneal macrophages, and it decreased phospho-p38 and ERK1/2 protein expression in LPS-stimulated mouse peritoneal macrophages. Overall, our data suggest that IF possesses significant analgesic and anti-inflammatory activities that may be mediated through the regulation of pro-inflammatory cytokines, TNF-α and the phosphorylation of p38 and ERK1/2.

High-mobility group box 1 induces calcineurin-mediated cell hypertrophy in neonatal rat ventricular myocytes

Cardiac hypertrophy is an independent predictor of cardiovascular morbidity and mortality. In recent years, evidences suggest that high-mobility group box 1 (HMGB1) protein, an inflammatory cytokine, participates in cardiac remodeling; however, the involvement of HMGB1 in the pathogenesis of cardiac hypertrophy remains unknown. The aim of this study was to investigate whether HMGB1 is sufficient to induce cardiomyocyte hypertrophy and to identify the possible mechanisms underlying the hypertrophic response. Cardiomyocytes isolated from 1-day-old Sprague-Dawley rats were treated with recombinant HMGB1, at concentrations ranging from 50 ng/mL to 200 ng/mL. After 24 hours, cardiomyocytes were processed for the evaluation of atrial natriuretic peptide (ANP) and calcineurin A expression. Western blot and real-time RT-PCR was used to detect protein and mRNA expression levels, respectively. The activity of calcineurin was also evaluated using a biochemical enzyme assay. HMGB1 induced cardiomyocyte hypertrophy, characterized by enhanced expression of ANP, and increased protein synthesis. Meanwhile, increased calcineurin activity and calcineurin A protein expression were observed in cardiomyocytes preconditioned with HMGB1. Furthermore, cyclosporin A pretreatment partially inhibited the HMGB1-induced cardiomyocyte hypertrophy. Our findings suggest that HMGB1 leads to cardiac hypertrophy, at least in part through activating calcineurin.

Regulation of Proinflammatory Mediators via NF-κB and p38 MAPK-Dependent Mechanisms in RAW 264.7 Macrophages by Polyphenol Components Isolated from Korea Lonicera japonica THUNB

Lonicera japonica THUNB., which abundantly contains polyphenols, has been used as a traditional medicine for thousands of years in East Asian countries because of the anti-inflammation properties. This study aimed to investigate the anti-inflammatory mechanism of polyphenol components isolated from Korea L. japonica T. by nuclear factor-kappaB (NF-κB) and mitogen-activated protein kinases (MAPKs) pathway. Polyphenols significantly decreased lipopolysaccharide- (LPS-) induced mRNA and protein expression of inducible nitric oxide synthase and cyclooxygenase-2, as well as mRNA expression of tumor necrosis factor-alpha, interleukin- (IL-) 1β, and IL-6. Moreover, polyphenols inhibited nuclear translocation of NF-κB p65, phosphorylation/degradation of the inhibitor of κB, and phosphorylation of p38 MAPK, whereas the extracellular signal-regulated kinase and Janus N-terminal kinase were not affected. These results indicate that polyphenol components isolated from Korea L. japonica T. should have anti-inflammatory effect on LPS-stimulated RAW 264.7 cells through the decrease of proinflammatory mediators expression by suppressing NF-κB and p38 MAPK activity.

A non-Mendelian MAPK-generated hereditary unit controlled by a second MAPK pathway in Podospora anserina

The Podospora anserina PaMpk1 MAP kinase (MAPK) signaling pathway can generate a cytoplasmic and infectious element resembling prions. When present in the cells, this C element causes the crippled growth (CG) cell degeneration. CG results from the inappropriate autocatalytic activation of the PaMpk1 MAPK pathway during growth, whereas this cascade normally signals stationary phase. Little is known about the control of such prion-like hereditary units involved in regulatory inheritance. Here, we show that another MAPK pathway, PaMpk2, is crucial at every stage of the fungus life cycle, in particular those controlled by PaMpk1 during stationary phase, which includes the generation of C. Inactivation of the third P. anserina MAPK pathway, PaMpk3, has no effect on the development of the fungus. Mutants of MAPK, MAPK kinase, and MAPK kinase kinase of the PaMpk2 pathway are unable to present CG. This inability likely relies upon an incorrect activation of PaMpk1, although this MAPK is normally phosphorylated in the mutants. In PaMpk2 null mutants, hyphae are abnormal and PaMpk1 is mislocalized. Correspondingly, stationary phase differentiations controlled by PaMpk1 are defective in the mutants of the PaMpk2 cascade. Constitutive activation of the PaMpk2 pathway mimics in many ways its inactivation, including an effect on PaMpk1 localization. Analysis of double and triple mutants inactivated for two or all three MAPK genes undercover new growth and differentiation phenotypes, suggesting overlapping roles. Our data underscore the complex regulation of a prion-like element in a model organism.

Ginsenoside Rh1 suppresses matrix metalloproteinase-1 expression through inhibition of activator protein-1 and mitogen-activated protein kinase signaling pathway in human hepatocellular carcinoma cells

Invasion and metastasis are the major causes of treatment failure in patients with cancer. Here, we investigated the effects of ginsenoside Rh1 on tumor invasion and metastasis in human hepatocellular carcinoma HepG2 cells and its possible mechanism of action. Rh1 showed concentration- and time-dependent inhibition of HepG2 cell migration and invasion. Matrix metalloproteinase-1 (MMP-1) gene expression and its promoter activity were also concentration-dependently inhibited by Rh1 treatment. The inhibitory effect of Rh1 on MMP-1 expression was due to inactivation of the mitogen-activated protein kinases (MAPKs) ERK, JNK, and p38 MAPK. By transient transfection analysis with the MMP-1 promoter (-2846 to -29 nt) and AP-1 promoter, MMP-1 and AP-1 promoter activities were induced by phorbol myristate acetate (PMA) but were significantly inhibited by PD98059 (ERK1/2 inhibitor) or SP600125 (JNK inhibitor). The induction of MMP-1 and AP-1 promoters by PMA was attenuated by Rh1, and both promoter activities were synergistically inhibited by co-treatment with PD98059. To evaluate the effects of Rh1 on AP-1 dimers, expression analysis and electrophoretic mobility shift (EMSA) assay using radiolabeled AP-1-specific oligomers at proximal site (-73 nt) and distal site (-1600 nt) of the MMP-1 promoter were performed. The results showed that Rh1 inhibited the expression of c-Jun and c-Fos but did not affect the DNA binding ability of AP-1-specific oligomers. However, Rh1 attenuated the stability of c-Jun. Therefore, Rh1 has potential for development of novel chemotherapeutic agents for treatment of malignant cancers, including early hepatocellular carcinoma related to MMP-1 expression.

Syndecan-4 proteoliposomes enhance fibroblast growth factor-2 (FGF-2)-induced proliferation, migration, and neovascularization of ischemic muscle

Ischemia of the myocardium and lower limbs is a common consequence of arterial disease and a major source of morbidity and mortality in modernized countries. Inducing neovascularization for the treatment of ischemia is an appealing therapeutic strategy for patients for whom traditional treatment modalities cannot be performed or are ineffective. In the past, the stimulation of blood vessel growth was pursued using direct delivery of growth factors, angiogenic gene therapy, or cellular therapy. Although therapeutic angiogenesis holds great promise for treating patients with ischemia, current methods have not found success in clinical trials. Fibroblast growth factor-2 (FGF-2) was one of the first growth factors to be tested for use in therapeutic angiogenesis. Here, we present a method for improving the biological activity of FGF-2 by codelivering the growth factor with a liposomally embedded coreceptor, syndecan-4. This technique was shown to increase FGF-2 cellular signaling, uptake, and nuclear localization in comparison with FGF-2 alone. Delivery of syndecan-4 proteoliposomes also increased endothelial proliferation, migration, and angiogenic tube formation in response to FGF-2. Using an animal model of limb ischemia, syndecan-4 proteoliposomes markedly improved the neovascularization following femoral artery ligation and recovery of perfusion of the ischemic limb. Taken together, these results support liposomal delivery of syndecan-4 as an effective means to improving the potential of using growth factors to achieve therapeutic neovascularization of ischemic tissue.

Hypoxia promotes rabbit pulmonary artery smooth muscle cells proliferation through a 15-LOX-2 product 15(S)-hydroxyeicosatetraenoic acid

The initial event of hypoxic pulmonary hypertension is acute hypoxic pulmonary vasoconstriction followed by remodeling of pulmonary arteries. Although 15(S)-hydroxyeicosatetraenoic acid [15(S)-HETE] is found to be able to induce hypoxic pulmonary vasoconstriction, role of 15(S)-HETE in pulmonary artery smooth muscle cells (PASMCs) proliferation has been studied less. We sought evidence for a role of 15(S)-HETE in the development of hypoxia-induced pulmonary hypertension. We found that hypoxia enhances 15-lipoxygenase-2 (15-LOX-2) expression and stimulates cultured rabbit PASMCs proliferation. 15(S)-HETE at concentration 0.1 μM stimulated proliferation of PASMCs and induced ERK 1/ERK 2 phosphorylation but had no effect on p38 kinase expression as assessed by Western blotting. 15(S)-HETE-stimulated PASMC proliferation was blocked by the MEK inhibitors PD-98059. Hypoxia (3% O(2))-stimulated PASMC proliferation was blocked by U0126, a MEK inhibitor, as well as by NDGA and CDC, inhibitors of 15-LOX, but not by the p38 MAPK inhibitor SB-202190. We conclude that 15-LOX-2 and its product, 15(S)-HETE, are important intermediates in hypoxia-induced rabbit PASMC proliferation and may participate in hypoxia-induced pulmonary hypertension.

Sepsis

The health care provider faced with the management of a child with septic shock relies on a comprehensive understanding of the numerous disciplines embodied in the practice of pediatric critical care medicine. The child with septic shock may have simultaneous derangements in the function of virtually every system of the body including: cardiovascular, respiratory, immune, renal, coagulation, hepatic, metabolic and neurologic. The degree to which physiologic alterations are manifest in a given patient is variable and influenced by multiple host and non-host factors including: the developmental stage, the presence of co-morbidities, pathogen-related factors, and genetic influences on both the host inflammatory response as well as the response to pharmacologic agents, all combining to have a profound influence on outcome. The clinician must possess a systematic and multifaceted approach to these critically ill patients. The goal of this chapter is to provide a comprehensive description of the epidemiology, biology and pathophysiology (at both the cellular and organ level) of sepsis, as well as outlining the current principles of managing septic shock. It will be apparent that optimal management requires a strong working knowledge of cardiovascular physiology, infectious diseases, multiple organ interactions, immunity, coagulation, pharmacology, and the molecular biology of inflammation.

CDK11(p58) promotes rat astrocyte inflammatory response via activating p38 and JNK pathways induced by lipopolysaccharide

In response to a variety of neural damages in the CNS, quiescent astrocytes become reactive astrocytes. Astrocytes are the major glial subtype and are important effectors that participate in the pathogenesis of numerous neural disorders, including trauma, stroke, aging, and developmental, genetic, idiopathic or acquired neurodegenerative diseases. CDK11(p58) (Cyclin-dependent kinases 11 protein 58/PITSLRE) is a p34cdc2-related protein kinase that plays an important role in normal cell cycle progression. In the process of LPS stimulus, the expression of CDK11(p58) in astrocytes was increased. Induced CDK11(p58) was parallel to astrocyte inflammatory response. Knockdown of CDK11(p58) by small-interfering RNAs (siRNAs) reduced the LPS-induced astrocyte inflammatory response, while overexpression CDK11(p58) enhanced the process. CDK11(p58) exerted its functions via activating p38 and JNK MAPK pathways. This study delineates that CDK11(p58) may be a significant regulatory factor for host defenses in central nervous system (CNS) inflammation.

Macrophage-induced expression and release of matrix metalloproteinase 1 and 3 by human preadipocytes is mediated by IL-1β via activation of MAPK signaling

Obesity is associated with a chronic low-grade inflammation and increased macrophage infiltration in adipose tissue. Matrix metalloproteinases (MMPs) are involved in adipose tissue remodeling and inflammatory responses in obesity. This study investigated whether macrophage-derived factors modulate expression and secretion of MMP1 and MMP3 in human preadipocytes. The potential mediators and signaling pathways were also explored. MMP1 and MMP3 were primarily expressed and secreted by preadipocytes and dramatically reduced post-differentiation. Preadipocytes were incubated with RPMI 1640 medium (control) or THP-1 macrophage-conditioned (MC) medium (25% and 100%) for 24 h. MC medium markedly increased mRNA levels of MMP1 (up to 122-fold) and MMP3 (up to 59-fold), as well as protein release of MMP1 (up to 378-fold) and MMP3 (up to 10-fold) in a dose-dependent manner. Treatment with IL-1β or TNFα, the major products of macrophages, also induced MMP1 and MMP3 secretion by preadipocytes. Neutralizing IL-1β abolished the induction of MMP1 and MMP3 in preadipocytes by MC medium while the effects of TNFα neutralization were modest. Furthermore, MC medium or IL-1β led to the phosphorylation of p38, ERK and JNK MAPKs. Inhibition of p38, ERK and JNK reversed the stimulatory effects of MC or IL-1β on MMP1 and MMP3 production. MC medium and IL-1β also activated NF-κB p65 whereas reduced IκBα protein expression in preadipocytes. These results suggest that macrophage accumulation in adipose tissue has a central role in stimulating MMP1 and MMP3 production by preadipocytes, and this is partially mediated by IL-1β via activation of the MAPK and NF-κB signaling pathways.

The mechanism of MAP kinase activation under acidic condition in feline esophageal smooth muscle cells

Reflux esophagitis results from repeated exposure of the esophagus to acidic gastric juice or bile-containing duodenal contents. In Barrett's adenocarcinoma, acid increases proliferation via ERK and p38 MAPK activation. This study was focused on determination of the mechanism(s) underlying MAPKs (ERK 1/2, p38 MAPK, and JNK) activation induced by acidic medium at pH 4 in normal feline primary cultured esophageal smooth muscle cells (FESMCs). We detected ERK 1/2 and p38 MAPK phosphorylation after exposure to pH 4 or neutral media in the presence or absence of several inhibitors and quantified the MAPK levels using western blotting analysis and densitometry. Acidic medium markedly increased the phosphorylation of ERK 1/2 and p38 MAPK within 10 min. Acid-induced ERK 1/2 and p38 MAPK activation was inhibited by pertussis toxin (PTX-sensitive G(i/o) protein inhibitor), DEDA (phospholipase (PL) A(2) inhibitor), ρCMB (PLD inhibitor), GF109203X (protein kinase C (PKC) inhibitor) and D609 (phosphatidylcholine-specific PLC inhibitor). But, genistein (tyrosine kinase inhibitor), forskolin (adenylate cyclase activator) and U73122 (phosphatidylinositol-specific PLC inhibitor) had no effect on acid-induced ERK1/2 and p38 MAPK activation. These findings indicate that the activation of ERK 1/2 and p38 MAPK pathways by acidic conditions, at least in part, may be mediated by activation of the G(i/o) protein coupled receptors, PC-PLC, PLD, PLA(2), and PKC in FESMCs.

In situ kinase profiling reveals functionally relevant properties of native kinases

Protein kinases are intensely studied mediators of cellular signaling, yet important questions remain regarding their regulation and in vivo properties. Here, we use a probe-based chemoprotemics platform to profile several well studied kinase inhibitors against >200 kinases in native cell proteomes and reveal biological targets for some of these inhibitors. Several striking differences were identified between native and recombinant kinase inhibitory profiles, in particular, for the Raf kinases. The native kinase binding profiles presented here closely mirror the cellular activity of these inhibitors, even when the inhibition profiles differ dramatically from recombinant assay results. Additionally, Raf activation events could be detected on live cell treatment with inhibitors. These studies highlight the complexities of protein kinase behavior in the cellular context and demonstrate that profiling with only recombinant/purified enzymes can be misleading.

Mechanism of acute lung injury due to phosgene exposition and its protection by cafeic acid phenethyl ester in the rat

The mechanism of phosgene-induced acute lung injury (ALI) remains unclear and it is still lack of effective treatments. Previous study indicated that oxidative stress was involved in phosgene-induced ALI. Caffeic acid phenethyl ester (CAPE) has been proved to be an anti-inflammatory agent and a potent free radical scavenger. The purpose of this study was to investigate the protective effects of CAPE on phosgene-induced ALI and identify the mechanism, in which oxidative stress and inflammation were involved. The phosgene was used to induce ALI in rats. The results showed that after phosgene exposure, total protein content in BALF was not significantly changed. The increase of MDA level and SOD activity induced by phosgene was significantly reduced by CAPE administration, and the decrease of GSH level in BALF and lung were significantly reversed by CAPE. CAPE also partially blocked the translocation of NF-κB p65 to the nucleus, but it had little effect on the phosphorylation of p38 MAPK. In conclusion, CAPE showed protective effects on lung against phosgene-induced ALI, which may be related with a combination of the antioxidant and anti-inflammatory functions of CAPE.

Changes in microRNA expression induced by rabies virus infection in mouse brains

MicroRNAs (miRNAs) are small RNA (≈ 22 nt) molecules expressed endogenously in cells. They are involved in the regulation of gene expression. Recently, evidence has shown that cellular miRNAs have key regulatory roles in virus-host interactions. The rabies virus (RABV) causes a fatal infection of the central nervous systems (CNS) of warm-blooded animals, yet its pathogenesis remains poorly understood. To gain more insight into the pathogenesis of RABV, a miRNA microarray was performed as part of an investigation of changes in host miRNA expression in the brains of mice infected with RABV. The results showed that RABV infection induced modulation of the expression of sixteen miRNA molecules. These data were verified by real-time PCR. Functional analysis showed the differentially expressed miRNAs to be involved in many immune-related signaling pathways, such as the RIG-I-like receptor signaling pathway, JAK-STAT signaling pathway, chemokine signaling pathway, T-cell receptor signaling pathway, MAPK signaling pathway, leukocyte transendothelial migration, and natural killer cell mediated cytotoxicity. The predicted expression levels of the target genes of these modulated miRNAs correlated with measurements of gene expression measured by DNA microarray and qRT-PCR.

Infectious bursal disease virus-induced activation of JNK signaling pathway is required for virus replication and correlates with virus-induced apoptosis

The Jun NH2-terminal kinase (JNK) which serves as an important component of cellular signal transduction pathways has been shown to regulate many viral infections. The present study demonstrated for the first time that infectious bursal disease virus (IBDV), the causative agent of a highly contagious disease in chickens, can activate JNK1/2 pathway in IBDV-infected cells dependent upon viral replication. IBDV-induced JNK1/2 activation causes its downstream target c-Jun phosphorylation, which kinetically paralleled JNK1/2 activation. Investigations into the mechanism of JNK1/2 regulation revealed that inhibition of JNK1/2 activation leads to reduced viral progeny release, which is associated with decreased viral transcription and lower virus protein expression, and thereby limiting apoptotic cell death as evidenced by blockage of Bax activation, cytochrome c release, and caspase activation. These data suggest that the JNK pathway plays an important role in the IBDV replication and contributes to virus-mediated changes in host cells.

Domain orientation in the N-Terminal PDZ tandem from PSD-95 is maintained in the full-length protein

Tandem PDZ domains have been suggested to form structurally independent supramodules. However, dissimilarity between crystallography and NMR models emphasize their malleable conformation. Studies in full-length scaffold proteins are needed to examine the effect of tertiary interactions within their native context. Using single-molecule fluorescence to characterize the N-terminal PDZ tandem in PSD-95, we provide the first direct evidence that PDZ tandems can be structurally independent within a full-length scaffold protein. Molecular refinement using our data converged on a single structure with an antiparallel alignment of the ligand-binding sites. Devoid of interaction partners, single-molecule conditions captured PSD-95 in its unbound, ground state. Interactions between PDZ domains could not be detected while fluctuation correlation spectroscopy showed that other conformations are dynamically sampled. We conclude that ultra-weak interactions stabilize the conformation providing a "low-relief" energy landscape that allows the domain orientation to be flipped by environmental interactions.

Transforming growth factor beta signaling in adult cardiovascular diseases and repair

The majority of children with congenital heart disease now live into adulthood due to the remarkable surgical and medical advances that have taken place over the past half century. Because of this, adults now represent the largest age group with adult cardiovascular diseases. It includes patients with heart diseases that were not detected or not treated during childhood, those whose defects were surgically corrected but now need revision due to maladaptive responses to the procedure, those with exercise problems and those with age-related degenerative diseases. Because adult cardiovascular diseases in this population are relatively new, they are not well understood. It is therefore necessary to understand the molecular and physiological pathways involved if we are to improve treatments. Since there is a developmental basis to adult cardiovascular disease, transforming growth factor beta (TGFβ) signaling pathways that are essential for proper cardiovascular development may also play critical roles in the homeostatic, repair and stress response processes involved in adult cardiovascular diseases. Consequently, we have chosen to summarize the current information on a subset of TGFβ ligand and receptor genes and related effector genes that, when dysregulated, are known to lead to cardiovascular diseases and adult cardiovascular deficiencies and/or pathologies. A better understanding of the TGFβ signaling network in cardiovascular disease and repair will impact genetic and physiologic investigations of cardiovascular diseases in elderly patients and lead to an improvement in clinical interventions.

MAPK/AP-1 activation mediates TLR2 agonist-induced SPLUNC1 expression in human lung epithelial cells

BACKGROUND

Short Palate Lung and Nasal epithelium Clone 1 (SPLUNC1) is a newly described host defense protein, primarily expressed in large airway epithelial cells. Reduced SPLUNC1 has been reported in allergic and cigarette smoke-exposed airways. We found that Mycoplasma pneumoniae increases SPLUNC1 in airway epithelium in part via activating TLR2-NF-κB pathway. However, the contribution of additional signaling pathways to TLR2-mediated SPLUNC1 expression remains unclear. In the present study, we investigated if TLR2-induced mitogen-activated protein kinase (MAPK)/activator protein-1 (AP-1) signaling regulates SPLUNC1 expression in human lung epithelial cells.

METHODS

Human lung epithelial NCI-H292 cells were stimulated with a TLR2 agonist Palmitoyl (3)-Cys-Ser-Lys (4)-OH (Pam(3)CSK(4)). MAPK/AP-1 activation and its role in SPLUNC1 regulation were investigated by Western blot, c-Jun activation assay, chromatin immunoprecipitation (ChIP) and real-time PCR. SPLUNC1 promoter activity was assessed by a luciferase reporter assay.

RESULTS

Pam(3)CSK(4) increased SPLUNC1 expression in NCI-H292 cells in a dose- and time-dependent manner, and enhanced SPLUNC1 promoter activity. Pam(3)CSK(4)-treated cells demonstrated activated MAPK and c-Jun compared to untreated cells. ChIP assay indicated increased c-Jun binding to the SPLUNC1 promoter following Pam(3)CSK(4) stimulation. Inhibition of ERK1/2 significantly reduced Pam(3)CSK(4)-mediated c-Jun activation and SPLUNC1 expression.

CONCLUSIONS

Our results for the first time demonstrate that TLR2-mediated MAPK/AP-1 activation up-regulates lung epithelial SPLUNC1 expression at the transcriptional level. Understanding SPLUNC1 gene regulation should provide more specific therapeutic targets to restore deficient SPLUNC1 production in diseased airways.

Tyrosine kinase inhibitor, genistein, reduces renal inflammation and injury in streptozotocin-induced diabetic mice

Tyrosine kinase inhibition is known to reduce diabetes-induced end-organ damage but the mechanisms remain elusive. We hypothesized that inhibition of tyrosine kinase reduces renal inflammation and injury in streptozotocin-induced diabetes. Male C57BL/6 mice were given daily injections of streptozotocin (45 mg/kg/day, i.p. for 5 days); control animals received the vehicle (citrate buffer). Thereafter, streptozotocin-treated mice were treated with genistein (10 mg/kg, i.p three times a week for 10 weeks, n=8-10/group) or the vehicle (5% DMSO). The streptozotocin-treated mice displayed significant elevation in blood glucose level and decrease in plasma insulin level compared to their vehicle-treated controls. Treatment with genistein reduced blood glucose level (~15%; p<0.05) without a significant effect on plasma insulin level; however, blood glucose remained significantly higher than the control group. The development of diabetes was associated with significant increases in total protein, albumin, nephrin and collagen excretions compared to their controls. In addition, the diabetic mice displayed increased urinary MCP-1 excretion in association with increased renal ICAM-1 expression and apoptotic cells. Furthermore, renal gp91 expression levels and urinary Thio-Barbituric Acid Reactive Substances (TBARs) excretion, indices of oxidative stress, were also elevated in diabetic mice. These changes were associated with increased renal phospho-tyrosine expression and renal phospho-ERK/ERK ratio. Importantly, treatment with genistein reduced all these parameters towards control values. Collectively, the results suggest that the reno-protective effect of genistein likely relates to reduced renal inflammation, oxidative stress and apoptosis in diabetic mice.

Tryptase/Protease-activated receptor 2 interactions induce selective mitogen-activated protein kinase signaling and collagen synthesis by cardiac fibroblasts

The mast cell product, tryptase, has recently been implicated to mediate fibrosis in the hypertensive heart. Tryptase has been shown to mediate noncardiac fibroblast function via activation of protease-activated receptor 2 and subsequent activation of the mitogen-activated protein kinase pathway, including extracellular signal-regulated kinase 1/2. Therefore, we hypothesized that this pathway may be a mechanism leading to fibrosis in the hypertensive heart. Isolated adult cardiac fibroblasts were treated with tryptase, which induced activation of extracellular signal-regulated kinase 1/2 via protease-activated receptor 2. Blockade of protease activated receptor 2 with FSLLRY (10 μmol/L) and inhibition of the extracellular signal-regulated kinase pathway with PD98059 (10 μmol/L) prevented collagen synthesis in isolated cardiac fibroblasts stimulated with tryptase. In contrast, p38 mitogen-activated protein kinase and stress-activated protein/c-Jun N-terminal kinase were not activated by tryptase. Cardiac fibroblasts isolated from spontaneously hypertensive rats showed this same pattern of activation. Treatment of spontaneously hypertensive rats with FSLLRY prevented fibrosis in these animals, indicating the in vivo applicability of the cultured fibroblast findings. Also, tryptase induced a myofibroblastic phenotype indicated by elevations in α-smooth muscle actin and extra type III domain A (ED-A) fibronectin. Thus, the results from this study demonstrate the importance of tryptase for inducing a cardiac myofibroblastic phenotype, ultimately leading to the development of cardiac fibrosis. Specifically, tryptase causes cardiac fibroblasts to increase collagen synthesis via a mechanism involving activation of protease-activated receptor 2 and subsequent induction of extracellular signal-regulated kinase signaling.

Neutrophil Apoptosis in Neutropenic Patients With Hepatitis C Infection: Role of Caspases 3, 10, and GM-CSF

Patients with chronic HCV infection are prone to increased susceptibility bacterial infection due to neutropenia complicating the course of this disease. Neutropenia in those patients may stem from enhanced neutrophil apoptosis. However, the molecular mechanism of neutrophil apoptosis has not been clearly defined. Neutrophils harvested from 26 neutropenic patients with hepatitis C infection and nine age and sex-matched healthy control subjects were examined for the degree of apoptosis. Neutrophil apoptosis was quantified by flow cytometry through determination of annexin-V expression at 0 time (fresh neutrophil), and 24 h culture. Neutrophils from healthy subjects were also incubated with either 10% heterologous normal or neutropenic sera, with and without 10 µg GM-CSF. Caspases 3, 10 were assessed colormetrically in neutrophils at 0 times and after 24 h culture. At 0 time culture the neutrophil apoptosis of the HCV patients was in significantly higher as compared to that of normal control (P = 0.059). At 24 h culture patients neutrophils cultured with neutropenic patients own sera showed neutrophil apoptosis significantly increased as compared to that at 0 time culture and this effect was significantly attenuated in similar culture with addition of GM-CSF (P < 0.001). On the other hand patient's neutrophil cultured with normal sera showed insignificantly increased neutrophil apoptosis at 24 h culture as compared to that at 0 time culture. Caspases 3 and 10 activities were significantly higher in patients neutrophil after 24 h cultured with patients own sera as compared to 0 time culture (P < 0.001 for both). Addition of GM-CSF to the neutrophil culture down regulates the caspases 3 and 10 activities. The correlation study between annexin-V expression and caspases activities revealed a borderline positive correlation between annexin-V and caspase 3 (r = 0.376, P = 0.058), and significant positive correlation with caspase 10 activity (r = 0.494, P = 0.01). In conclusion, these findings suggest that enhanced neutrophil apoptosis demonstrated in neutropenic patients with HCV infection might be induced through activation of caspase 10 and is attenuated by GM-CSF.

Cysteinyl leukotrienes synthesis is involved in aristolochic acid I-induced apoptosis in renal proximal tubular epithelial cells

Aristolochic acid I (AAI) is a primary nephrotoxin and carcinogen that is found in some Chinese herbal medicines, and AAI is responsible for the progression of aristolochic acid nephropathy. The membrane associated proteins in the eicosanoid and glutathione metabolism (MAPEG) superfamily are associated with cysteinyl leukotrienes (cysLTs) synthesis. The present study investigated whether cysLTs synthesis was involved in AAI-induced renal proximal tubular epithelial cell injury in LLC-PK1 cells. Based on MAPEG and related molecular events, the potential mechanisms of AAI-induced LLC-PK1 cell injury were explored. AAI triggered the mitochondrial/caspase apoptotic pathway in LLC-PK1 cells, which was indicated by an enhanced Bax/Bcl-2 ratio, loss of mitochondrial membrane potential, cytochrome C release, and caspase 3 activation. In addition, AAI-induced cysLTs release was accompanied by selective upregulation of 5-lipoxygenase activating protein (FLAP) and microsomal glutathione S-transferase 3 (mGST3) in a concentration-dependent manner. The FLAP inhibitor MK866 significantly protected cells from AAI-induced apoptosis. Furthermore, activation of extracellular signal-regulated kinase (ERK) 1/2 and inhibition of phosphorylated p38-MAPK were demonstrated at the early phase of AAI treatment. Notably, the MEK/ERK inhibitor U0126 reversed AAI-induced apoptosis and reduced both FLAP, mGST3 and mitochondrial/caspase protein expression. Taken together, these findings suggest that cysLTs synthesis is involved in AAI-induced apoptosis via an ERK activation way.

The gsp oncogene disrupts Ras/ERK-dependent prolactin gene regulation in gsp inducible somatotroph cell line

The MAPK ERK1/2 cascade regulates all the critical cellular functions, and in many pathological situations, these regulatory processes are perturbed. It has been clearly established that this cascade is an integrative point in the control of the pituitary functions exerted by various extracellular signals. In particular, ERK1/2 cross talk with the cAMP pathway is determinant in the control of somatolactotroph hormonal secretion exerted via neuropeptide receptors. GH-secreting adenomas are characterized by frequent cAMP pathway alterations, such as constitutive activation of the α-subunit of the heterotrimeric Gs protein (the gsp oncogene), overexpression of Gsα, and changes in the protein kinase A regulatory subunits. However, it has not yet been established exactly how these alterations result in GH-secreting adenomas or how the ERK1/2 cascade contributes to the process of GH-secreting adenoma tumorigenesis. In this study on the conditional gsp-oncogene-expressing GH4C1 cell line, expression of the gsp oncogene, which was observed in up to 40% of GH-secreting adenomas, was found to induce sustained ERK1/2 activation, which required activation of the protein kinase A and the GTPases Ras and Rap1. All these signaling components contribute to the chronic activation of the human prolactin promoter. The data obtained here show that Ras plays a crucial role in these processes: in a physiopathological context, i.e. in the presence of the gsp oncogene, it switched from being a repressor of the cAMP/ protein kinase A ERK-sensitive prolactin gene control exerted by neuropeptides to an activator of the prolactin promoter.

Transforming growth factor-α attenuates hepatic fibrosis: possible involvement of matrix metalloproteinase-1

BACKGROUND

The effect of transforming growth factor (TGF)-α on fibrosis varies between cell types and the role of TGF-α in hepatic fibrosis has not been fully elucidated.

METHODS

We examined the effect of TGF-α on hepatic fibrosis using TGF-α-expressing transgenic mice fed a methionine- and choline-deficient (MCD) diet and human hepatic stellate cells (HSCs) line LX-2, rat and human primary HSCs.

RESULTS

Although the expression levels of the tissue inhibitor of metalloproteinases-1 and α1(I) collagen mRNA were unchanged, feeding the TGF-α transgenic mice the MCD diet resulted in greater expression of the murine functional analogue of matrix metalloproteinase-1 (MMP-1), MMP-13 mRNA and protein and attenuated hepatic fibrosis compared with wild-type mice. TGF-α overexpression did not affect the extent of the steatosis, oxidative stress and hepatic inflammation in the MCD diet-fed mice. The effect of TGF-α on the fibrogenic and anti-fibrogenic gene expressions varied between cell types in vitro. TGF-α increased MMP-1 mRNA expressions that were completely blocked by gefitinib in LX-2 cells. The extracellular signal-regulated kinase (ERK) 1/2, c-Jun N-terminal kinase and p38 pathways were involved in MMP-1 mRNA expression in LX-2 cells. Although TGF-α increased the phosphorylation of p38, the p38 inhibitor activated the RAS-ERK pathway and increased TGF-α-induced MMP-1 mRNA expression, which suggested that there may be a crosstalk between the RAS-ERK and the p38 pathways in LX-2 cells.

CONCLUSIONS

The TGF-α may attenuate hepatic fibrosis in part because of upregulation of the expression of MMP-1. The balance between fibrogenic and anti-fibrogenic gene expression and between the activity of the RAS-ERK and the p38 pathways may be crucial for the fibrotic process.

Cdc14: a highly conserved family of phosphatases with non-conserved functions?

CDC14 was originally identified by L. Hartwell in his famous screen for genes that regulate the budding yeast cell cycle. Subsequent work showed that Cdc14 belongs to a family of highly conserved dual-specificity phosphatases that are present in a wide range of organisms from yeast to human. Human CDC14B is even able to fulfill the essential functions of budding yeast Cdc14. In budding yeast, Cdc14 counteracts the activity of cyclin dependent kinase (Cdk1) at the end of mitosis and thus has important roles in the regulation of anaphase, mitotic exit and cytokinesis. On the basis of the functional conservation of other cell-cycle genes it seemed obvious to assume that Cdc14 phosphatases also have roles in late mitosis in mammalian cells and regulate similar targets to those found in yeast. However, analysis of the human Cdc14 proteins (CDC14A, CDC14B and CDC14C) by overexpression or by depletion using small interfering RNA (siRNA) has suggested functions that are quite different from those of ScCdc14. Recent studies in avian and human somatic cell lines in which the gene encoding either Cdc14A or Cdc14B had been deleted, have shown - surprisingly - that neither of the two phosphatases on its own is essential for viability, cell-cycle progression and checkpoint control. In this Commentary, we critically review the available data on the functions of yeast and vertebrate Cdc14 phosphatases, and discuss whether they indeed share common functions as generally assumed.

1,3,5-trihydroxy-4-prenylxanthone represses lipopolysaccharide-induced iNOS expression via impeding posttranslational modification of IRAK-1

Both high level of nitric oxide (NO) and its generating enzyme, inducible NO synthase (iNOS), play important roles in pathophysiological conditions such as inflammatory processes. We previously found that 1,3,5-trihydroxy-4-prenylxanthone (TH-4-PX) isolated from Cudrania cochinchinensis repressed lipopolysaccharide (LPS)-induced NO production in RAW264.7 macrophages. Here we further examined the underlying mechanisms using RT-PCR and Western blot analyses. Consistent with NO inhibition, suppression of LPS-induced iNOS expression by TH-4-PX through abolishing IκB kinase (IKK) phosphorylation, IκB degradation and nuclear factor-κB (NF-κB) nuclear translocation was observed. After LPS stimulation, the increased nuclear level of c-Fos and c-Jun (major components of activator protein-1, AP-1) and the phosphorylated level of upstream signal molecules, such as c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase, (ERK) were all significantly suppressed by TH-4-PX, while p38 remained unaffected. A further experiment revealed that TH-4-PX inhibited the phosphorylation of transforming growth factor-β (TGF-β)-activated kinase 1 (TAK1), an upstream signaling molecule required for IKK and mitogen-activated protein kinases (MAPKs) activation. Stimulation with LPS also triggered the modification (phosphorylation and ubiquitination) and eventually the proteasomal degradation of membrane-associated interleukin (IL)-1 receptor-associated serine/threonine kinase 1 (IRAK-1), an essential signaling component to toll-like receptor (TLR)-mediated TAK-1 activation. Interestingly, the modified pattern of IRAK-1 in the presence LPS was significantly attenuated by TH-4-PX treatment. In conclusion, TH-4-PX inhibited LPS-induced NF-κB and AP-1 activations by interfering with the posttranslational modification (phosphorylation and/or ubiquitinylation) of IRAK-1 in the cell membrane to impede TAK1-mediated activation of IKK and MAPKs signal transduction.

Rule-based modelling and simulation of biochemical systems with molecular finite automata

The authors propose a theoretical formalism, molecular finite automata (MFA), to describe individual proteins as rule-based computing machines. The MFA formalism provides a framework for modelling individual protein behaviours and systems-level dynamics via construction of programmable and executable machines. Models specified within this formalism explicitly represent the context-sensitive dynamics of individual proteins driven by external inputs and represent protein-protein interactions as synchronised machine reconfigurations. Both deterministic and stochastic simulations can be applied to quantitatively compute the dynamics of MFA models. They apply the MFA formalism to model and simulate a simple example of a signal-transduction system that involves an MAP kinase cascade and a scaffold protein.

Construction of a genetic multiplexer to toggle between chemosensory pathways in Escherichia coli

Many applications require cells to switch between discrete phenotypic states. Here, we harness the FimBE inversion switch to flip a promoter, allowing expression to be toggled between two genes oriented in opposite directions. The response characteristics of the switch are characterized using two-color cytometry. This switch is used to toggle between orthogonal chemosensory pathways by controlling the expression of CheW and CheW*, which interact with the Tar (aspartate) and Tsr* (serine) chemoreceptors, respectively. CheW* and Tsr* each contain a mutation at their protein-protein interface such that they interact with each other. The complete genetic program containing an arabinose-inducible FimE controlling CheW/CheW* (and constitutively expressed tar/tsr*) is transformed into an Escherichia coli strain lacking all native chemoreceptors. This program enables bacteria to swim toward serine or aspartate in the absence or in the presence of arabinose, respectively. Thus, the program functions as a multiplexer with arabinose as the selector. This demonstrates the ability of synthetic genetic circuits to connect to a natural signaling network to switch between phenotypes.

Vibrio parahaemolyticus infection induces modulation of IL-8 secretion through dual pathway via VP1680 in Caco-2 cells

BACKGROUND

Vibrio parahaemolyticus causes acute gastroenteritis and inflammations in humans. A variety of pathogenic bacteria can stimulate mitogen-activated protein kinases (MAPKs) in host cells. Phosphorylation of MAPKs leads to production of interleukin (IL)- 8 and subsequently causes inflammations. Thus, MAPK cascades were strong candidates for the main signaling pathway of V. parahaemolyticus-induced acute inflammation.

METHODS

To determine whether the signaling pathway on V. parahaemolyticus infection induces inflammation, we analyzed the secretion level of IL-8 and phosphorylation of MAPKs by use of intestinal epithelial Caco-2 cells.

RESULTS

V. parahaemolyticus infection of Caco-2 cells activated extracellular signal-regulated kinase (ERK) 1/2 and p38 MAPK signal pathways, leading to IL-8 secretion, whereas MAPK inhibitors, UO126 or SB203580, suppressed IL-8 secretion. A strain carrying a deletion of VP1680, a type three secretion system 1 (T3SS1) effector protein, failed to activate phosphorylation of ERK1/2 and p38 MAPK and secretion of IL-8. ERK1/2 pathway inhibitor, UO126, failed IL-8 promoter activity, whereas p38 MAPK inhibitor, SB203580, decreased the stabilization of IL-8 messenger RNA following V. parahaemolyticus infection.

CONCLUSIONS

We showed that V. parahaemolyticus infection of Caco-2 cells results in the secretion of IL-8, and that VP1680 plays a pivotal role in manipulating host cell signaling and is responsible for triggering IL-8 secretion.

Fluid shear stress-induced JNK activity leads to actin remodeling for cell alignment

Fluid shear stress (FSS) exerted on endothelial cell (EC) surfaces induces actin cytoskeleton remodeling through mechanotransduction. This study was designed to determine whether FSS activates Jun N-terminal kinase (JNK), to examine the spatial and temporal distribution of active JNK relative to the actin cytoskeleton in ECs exposed to different FSS conditions, and to evaluate the effects of active JNK on actin realignment. Exposure to 15 and 20 dyn/cm(2) FSS induced higher activity levels of JNK than the lower 2 and 4 dyn/cm(2) flow conditions. At the higher FSS treatments, JNK activity increased with increasing exposure time, peaking 30 min after flow onset with an eightfold activity increase compared to cells in static culture. FSS-induced phospho-JNK co-localized with actin filaments at cell peripheries, as well as with stress fibers. Pharmacologically blocking JNK activity altered FSS-induced actin structure and distribution as a response to FSS. Our results indicate that FSS-induced actin remodeling occurs in three phases, and that JNK plays a role in at least one, suggesting that this kinase activity is involved in mechanotransduction from the apical surface to the actin cytoskeleton in ECs.

Vascular endothelial growth factor receptor 2 and downstream p38 mitogen-activated protein kinase are possible candidate markers of intrinsic resistance to adjuvant endocrine treatment in steroid receptor positive breast cancer

A cross talk between tyrosine kinase receptors and mitogen-activated protein kinases (MAPKs) is proposed as involved in endocrine resistance. We wanted to investigate intratumoral levels of vascular endothelial growth factor receptor 2 (VEGFR2) and p38 MAPK in relation to relapse-free (RFS) and breast cancer corrected survival (BCCS) after adjuvant endocrine treatment, mainly tamoxifen for 2 or 5 years. We also wanted to investigate these markers in relation to early and late recurrences. VEGFR2 (n = 381) and p38 (n = 174) were determined by enzyme-linked immuno-sorbent assays in tumor homogenates from primary BC diagnosed 1993-1996. Wide ranges of VEGFR2 and p38 proteins were found; median 0.72 pg/μg DNA (range 0.0-11.66), and 0.04 pg/μg DNA (range 0.0-6.79), respectively. Detectable levels of p38 were registered in 65% and classified positive. Higher VEGFR2 were correlated to higher VEGF (P = 0.005), p38 MAPK (P = 0.018), negative ER (P = 0.008), larger tumors (P = 0.001), histopathological grade III (P = 0.018), distant metastasis (P = 0.044), shorter RFS (P = 0.013), and shorter BCCS (P = 0.017). Expression of p38 was significantly correlated with negative PgR (P = 0.044) and with early relapses (P = 0.021), while no difference was seen during the later follow-up period (P = 0.73). Higher VEGFR2 had a significant negative impact on both early (P = 0.029) and later recurrences (P = 0.018), while VEGF only predicted later relapses (P = 0.037). Our preliminary results suggest higher intratumoral levels of VEGFR2 and p38 MAPK as candidate markers of intrinsic resistance for adjuvant endocrine therapy.

Effects of sub-sonic vibration on the proliferation and maturation of 3T3-L1 cells

AIMS

Although low and high intensity sub-sonic vibrations (SSV) have been shown to facilitate wound healing, very few studies have investigated the effects of SSV on 3T3-L1 preadipocytes. Therefore, the present study was undertaken to investigate the influence of SSV on the proliferation and maturation of 3T3-L1 preadipocytes.

MAIN METHODS

To evaluate the effect of SSV on 3T3-L1 cell proliferation, the cells were maintained in an apparatus that administered SSV (0.5 V) for 3 days at a frequency of 10, 20, 30, or 40 Hz. In addition, to study the effect of SSV on 3T3-L1 cell maturation, the cells were stimulated with SSV for 6 days at a frequency of 10, 20, 30, or 45 Hz.

KEY FINDINGS

Sub-sonic vibrations inhibited the proliferation of 3T3-L1 preadipocytes at frequencies of 20 and 30 Hz. Triglyceride levels in cells subjected to SSV at frequencies ranging from 10 to 30 Hz increased compared with those measured in control cells. The expression of adipogenic genes, such as PPAR-γ and C/EBP-α, markedly increased in response to SSV at 20 Hz and 30 Hz during maturation.

SIGNIFICANCE

These results suggest that SSV affected adipogenic gene expression at 20 and 30 Hz.

Nucleoporin phosphorylation triggered by the encephalomyocarditis virus leader protein is mediated by mitogen-activated protein kinases

Cardioviruses disrupt nucleocytoplasmic transport through the activity of their leader (L) protein. We have shown that hyperphosphorylation of nuclear pore proteins (nucleoporins or Nups), including Nup62, Nup153, and Nup214, is central to this L protein function and requires one or more cytosolic kinases. In this study, potential cellular enzymes involved in encephalomyocarditis virus (EMCV) L-directed Nup phosphorylation were screened with a panel of specific, cell-permeating kinase inhibitors. Extracellular signal-regulated receptor kinase (ERK) and p38 mitogen-activated protein kinase inhibitors (U0126 and SB203580) were sufficient to block Nup hyperphosphorylation in EMCV-infected or L-expressing cells. Recombinant L alone, in the absence of infection, triggered activation of ERK and p38, independent of their upstream signaling cascades. Conserved residues within the L zinc finger (Cys(19)) and acidic domain (Asp(48),(51),(52),(55)) were essential for this activation and for the phosphorylation of Nups, suggesting that the phenomena are linked. Analysis of the hyperphosphorylated Nup species revealed only phosphoserine and phosphothreonine residues. The sizes of the tryptic phosphopeptides derived from Nup62 were compatible with sites in the Phe/Gly repeat domain which display common consensus sequences for ERK and p38 substrates. The results provide strong evidence that ERK and p38 are the probable effector kinases required for L-dependent inhibition of nuclear trafficking.

Dysregulation of p38 and MKP-1 in response to NOD1/TLR4 stimulation in sarcoid bronchoalveolar cells

RATIONALE

Sarcoidosis is a systemic inflammatory disorder characterized by distinct up-regulation of Th1 cytokines, such as tumor necrosis factor (TNF)-α and IL-12. The mechanism underlying this up-regulation remains unclear. Recognition of microbial moieties through Toll-like or Nod-like receptors evokes sequential activation of mitogen-activated protein kinases (MAPKs), which plays a role in Th1-immune response.

OBJECTIVES

To test the hypothesis that dysregulation in MAPK signaling in response to microbial stimulation is important in mediating Th1 response in sarcoidosis.

METHODS

Ex vivo cultured bronchoalveolar lavage (BAL) cells isolated from patients with sarcoidosis and control subjects were stimulated with low-dose Toll-like receptor 4 (TLR4) and nucleotide-binding oligomerization domain 1 (NOD1) ligands as a model of microbial stimulation, and MAPK signaling and inflammatory response were analyzed.

MEASUREMENTS AND MAIN RESULTS

BAL cells from patients with sarcoidosis exhibited higher basal p38 activity, greater p38 phosphorylation, and more robust production of TNF-α and IL-12/IL-23p40 on stimulation with NOD1 and TLR4 agonists than cells isolated from control subjects. In contrast, control BAL cells had greater basal extracellular signal-regulated kinase (ERK) activity and NOD1 and TLR4 agonists preferentially activated the ERK pathway. Inhibition of p38, but not ERK, attenuated production of both IL12/IL23p40 and TNF-α. Interestingly, stimulation of cells from patients with sarcoidosis with either NOD1 or TLR4 ligand failed to induce MAPK phosphatase 1 (MKP-1). Adenovirus-mediated overexpression of MKP-1 attenuated p38 activation and decreased the production of IL12/IL23p40 and TNF-α in sarcoid BAL cells.

CONCLUSIONS

Our results suggest that enhanced p38 signaling in response to microbial products is caused by abnormal regulation of MKP-1 and contributes to heightened inflammation in sarcoidosis.