Mitogen-activated Protein Kinase Signal Transduction Research Articles

Oxidized Hemoglobin Is an Endogenous Proinflammatory Agonist That Targets Vascular Endothelial Cells

Several pathologic conditions are associated with hemolysis, i.e. release of ferrous (Fe(II)) hemoglobin from red blood cells. Oxidation of cell-free hemoglobin produces (Fe(III)) methemoglobin. More extensive oxidation produces (Fe(III)/Fe(IV) O) ferryl hemoglobin. Both cell-free methemoglobin and ferryl hemoglobin are thought to contribute to the pathogenesis of hemolytic disorders. We show hereby that ferryl hemoglobin, but not hemoglobin or methemoglobin, acts as a potent proinflammatory agonist that induces vascular endothelial cells in vitro to rearrange the actin cytoskeleton, forming intercellular gaps and disrupting the integrity of the endothelial cell monolayer. Furthermore, ferryl hemoglobin induces the expression of proinflammatory genes in endothelial cells in vitro, e.g. E-selectin, Icam-1, and Vcam-1, through the activation of the nuclear factor kappaB family of transcription factors. This proinflammatory effect, which requires actin polymerization, involves the activation of the c-Jun N-terminal kinase and the p38 mitogen-activated protein kinase signal transduction pathways. When administered to naïve mice, ferryl hemoglobin induces the recruitment of polymorphonuclear cells, demonstrating that it acts as a proinflammatory agonist in vivo. In conclusion, oxidized hemoglobin, i.e. ferryl hemoglobin, acts as a proinflammatory agonist that targets vascular endothelial cells.

Cardiac sympathovagal balance shift and left ventricular systolic dysfunction in alcoholic rats

Objective: Statins have been shown to reduce the cardiac remodeling independent of their well-known lipid lowering effect. Considering the importance of transforming growth factor-beta1 (TGF-β1) overproduction in heart failure, the effect of atorvastatin on TGF-β1 expression and p44/42 mitogen-activated protein kinases (p44/42 MAPK) signal transduction passway in cardiac fibroblasts was examined. Design andmethods: The cardiac fibroblasts of neonatal rat were culturedby trypsinogen anddifferent speed adherence. The level of TGFβ1 in conditioned medium was measured by EIA. Intracellular TGF-β1, p44/42 MAPK and phospho-p44/42 MAPK levels were evaluated by Western blot, and the expression of TGF-β1 mRNA was detected using RT-PCR. Results: The cardiac fibroblasts, treated with aldosterone at 1×10−7mol/L, significantly up-regulated TGF-β1 mRNA expression (P<0.01), as well as TGF-β1 synthesis (P<0.01) and release (P<0.01). Atorvastatin (1×10−6, 10−5, 10−4mol/L) dose-dependently blocked TGF-β1 mRNA expression (P<0.01, respectively), as well as TGF-β1 synthesis (P<0.01, respectively) and release (P=0.113, P<0.01, P<0.01, respectively). In contrast, atorvastatin-induced inhibitory effects were reversed in the presence of mevalonate. Similarly, phospho-p44/42 MAPK was significantly up-regulated by aldosterone (P<0.01). The increased level of phospho-p44/42 MAPK was reduced when the cells were pretreated with atorvastatin (P<0.01). Our data also showed the recovery of phospho-p44/42 MAPK expression in the presence of mevalonate (P<0.01). Pre-incubation with PD 98059, an antagonist for p44/42 MAPK, abolished aldosterone-induced TGF-β1 secretion (P<0.01). Conclusion: Atorvastatin down-regulated TGF-β1 expression inducedbyaldosterone in aprocess specifically related tomevalonate and p44/42 MAPK pathway in cultured neonatal rat cardiac fibroblasts. Thus, itwas indicated that atorvastatinmight exert therapeutic effects bya new possible mechanism in patients with heart failure.

Effects of atorvastatin on TGF-β1 expression and p44/42 MAPK signal transduction passway in cardiac fibroblasts

Objective: Statins have been shown to reduce the cardiac remodeling independent of their well-known lipid lowering effect. Considering the importance of transforming growth factor-beta1 (TGF-β1) overproduction in heart failure, the effect of atorvastatin on TGF-β1 expression and p44/42 mitogen-activated protein kinases (p44/42 MAPK) signal transduction passway in cardiac fibroblasts was examined. Design andmethods: The cardiac fibroblasts of neonatal rat were culturedby trypsinogen anddifferent speed adherence. The level of TGFβ1 in conditioned medium was measured by EIA. Intracellular TGF-β1, p44/42 MAPK and phospho-p44/42 MAPK levels were evaluated by Western blot, and the expression of TGF-β1 mRNA was detected using RT-PCR. Results: The cardiac fibroblasts, treated with aldosterone at 1×10−7mol/L, significantly up-regulated TGF-β1 mRNA expression (P<0.01), as well as TGF-β1 synthesis (P<0.01) and release (P<0.01). Atorvastatin (1×10−6, 10−5, 10−4mol/L) dose-dependently blocked TGF-β1 mRNA expression (P<0.01, respectively), as well as TGF-β1 synthesis (P<0.01, respectively) and release (P=0.113, P<0.01, P<0.01, respectively). In contrast, atorvastatin-induced inhibitory effects were reversed in the presence of mevalonate. Similarly, phospho-p44/42 MAPK was significantly up-regulated by aldosterone (P<0.01). The increased level of phospho-p44/42 MAPK was reduced when the cells were pretreated with atorvastatin (P<0.01). Our data also showed the recovery of phospho-p44/42 MAPK expression in the presence of mevalonate (P<0.01). Pre-incubation with PD 98059, an antagonist for p44/42 MAPK, abolished aldosterone-induced TGF-β1 secretion (P<0.01). Conclusion: Atorvastatin down-regulated TGF-β1 expression inducedbyaldosterone in aprocess specifically related tomevalonate and p44/42 MAPK pathway in cultured neonatal rat cardiac fibroblasts. Thus, itwas indicated that atorvastatinmight exert therapeutic effects bya new possible mechanism in patients with heart failure.

Inhibition of extracellular signal-regulated kinase 1 by adenovirus mediated small interfering RNA attenuates hepatic fibrosis in rats #

Extracellular signal-regulated kinase 1 (ERK1) is a critical part of the mitogen-activated protein kinase signal transduction pathway, which is involved in hepatic fibrosis. However, the effect of down-regulation of ERK1 on hepatic fibrosis has not been reported. Here, we induced hepatic fibrosis in rats with dimethylnitrosamine administration or bile duct ligation. An adenovirus carrying small interfering RNA targeting ERK1 (AdshERK1) was constructed to determine its effect on hepatic fibrosis, as evaluated by histological and immunohistochemical examination. Our results demonstrated that AdshERK1 significantly reduced the expression of ERK1 and suppressed proliferation and levels of fibrosis-related genes in hepatic stellate cells in vitro. More importantly, selective inhibition of ERK1 remarkably attenuated the deposition of the extracellular matrix in fibrotic liver in both fibrosis models. In addition, both hepatocytes and biliary epithelial cells were proven to exert the ability to generate the myofibroblasts depending on the insults of the liver, which were remarkably reduced by AdshERK1. Furthermore, up-regulation of ERK1 paralleled the increased expression of transforming growth factor beta1 (TGF-beta1), vimentin, snail, platelet-derived growth factor-BB (PDGF-BB), bone morphogenetic protein 4 (BMP4), and small mothers against decapentaplegic-1 (p-Smad1), and was in reverse correlation with E-cadherin in the fibrotic liver. Nevertheless, inhibition of ERK1 resulted in the increased level of E-cadherin in parallel with suppression of TGF-beta1, vimentin, snail, PDGF-BB, BMP4, and p-Smad1. Interestingly, AdshERK1 treatment promoted hepatocellular proliferation. Our study provides the first evidence for AdshERK1 suppression of hepatic fibrosis through the reversal of epithelial-mesenchymal transition of both hepatocytes and biliary epithelial cells without interference of hepatocellular proliferation. This suggests that ERK1 is implicated in hepatic fibrogenesis and selective inhibition of ERK1 by small interfering RNA may present a novel option for hepatic fibrosis treatment.

Oxidative stress of silica nanoparticles in human bronchial epithelial cell, Beas-2B

In this study, the potentially harmful effect of the exposure to fumed and porous silicon dioxide (silica) nanoparticles was investigated using human bronchial epithelial cell, Beas-2B, with a focus on the involvement of oxidative stress as the toxic mechanism. Silica nanoparticles-induced oxidative stress was assessed by examining the formation of reactive oxygen species (ROS) and induction of antioxidant enzymes, such as superoxide dismutase (SOD) and heme oxygenase-1 (HO-1). Subsequently, to understand the mechanism of nanoparticles-induced oxidative stress, the involvement of oxidative stress-responding transcription factors, such as, nuclear factor-kappaB (NF-κB) and nuclear factor-E2-related factor-2 (Nrf-2), as well as the mitogen-activated protein (MAP) kinase signal transduction pathway were investigated. From the overall results, silica nanoparticles exerted toxicity via oxidative stress, which lead to the induction of HO-1 via the Nrf-2–ERK MAP kinase signaling pathway; cells exposed to porous silica nanoparticles showed a more sensitive response than those exposed to fumed silica. Nevertheless, the parameters tested were rather limited in terms of gaining a full understanding of the oxidative stress and cellular response due to exposure to silica nanoparticles. Further studies on the mechanism by which silica nanoparticles induce the Nrf-2–ERK MAP kinase pathway, to more clearly elucidate the silica-induced oxidative stress, as well as on the relationship between the physico-chemical properties of nanoparticles and their cytotoxicity are warranted to gain an understanding of the phenomenon of different sensitivities between porous and fumed silica.

Effects of hydroxyethyl starch 130/0.4 on P38 mitogen-activated protein kinases signal transduction pathway

To observe the effect of hydroxyethyl starch 130/0.4 (voluven) on P38 mitogen-activated protein kinases (MAPK) signal transduction pathway, with the aim of investigating the mechanism of its protective effect on acute lung injury (ALI) due to infection. Thirty male Sprague-Dawley (SD) rats were randomly divided into control group, lipopolysaccharide (LPS 10 mg/kg) group, voluven groups (LPS 10 mg/kg, and hydroxyethyl starch 130/0.4 15 ml/kg or 30 ml/kg) and alone voluven group (hydroxyethyl starch 130/0.4 30 ml/kg), with 6 rats in each group. Rats were sacrificed at 6 hours, the lungs were harvested for observation of pathological changes. The expression of p-P38, P38, p-P44/42 and P44/42 were detected with Western blotting. Activating protein-1 (AP-1) activation was measured with electrophoretic mobility shift assay (EMSA). Compared with control, p-P38, p-P44/42 and AP-1 were significantly higher in LPS group (P<0.05 or P<0.01). The expressions of p-P38 and AP-1 activation were significantly reduced in both voluven groups (all P<0.05). But there was no statistically significant difference between voluven 15 ml/kg and 30 ml/kg groups (all P>0.05). Hydroxyethyl starch 130/0.4 can inhibit LPS-induced ALI by depressing expression of p-P38 and AP-1 activation in lung.

Regulation of apoptosis in tumor cells by p38 mitogen-activated protein kinases signal transduction

p38 mitogen- activated protein kinases signaling pathway is an important way of Mitogen- ac-tivated protein kinases( MAPK) superfamily ,which can be activated by diverse extracellular stimuli and plays a central role in cell apoptosis process. p38MAPK is involved in apoptosis of malignant tumor by activating caspase family members,regulating activities of Bel-2 family members,activating p53,participating in Fas/FasL pathway and so on. This paper provides a brief review of p38MAPK,including structural characteristics,activity regulation and it' s role in apoptosis of malignant tumor. Key words: Neoplasms; Apoptosis; p38MAPK

Characterization of a Novel Mitogen-Activated Protein Kinase Kinase 1/2 Inhibitor with a Unique Mechanism of Action for Cancer Therapy

The mitogen-activated protein kinase (MAPK) signal transduction pathway plays a central role in regulating tumor cell growth, survival, differentiation, and angiogenesis. The key components of the Ras/Raf/MEK/ERK signal module are frequently altered in human cancers. Targeting this pathway represents a promising anticancer strategy. Small molecule inhibitors targeting MEK1/2 have shown promise in the clinic; however, ultimate clinical proof-of-concept remains elusive. Here, we report a potent and highly selective non-ATP-competitive MEK1/2 inhibitor, RO4927350, with a novel chemical structure and unique mechanism of action. It selectively blocks the MAPK pathway signaling both in vitro and in vivo, which results in significant antitumor efficacy in a broad spectrum of tumor models. Compared with previously reported MEK inhibitors, RO4927350 inhibits not only ERK1/2 but also MEK1/2 phosphorylation. In cancer cells, high basal levels of phospho-MEK1/2 rather than phospho-ERK1/2 seem to correlate with greater sensitivity to RO4927350. Furthermore, RO4927350 prevents a feedback increase in MEK phosphorylation, which has been observed with other MEK inhibitors. We show that B-Raf rather than C-Raf plays a critical role in the feedback regulation. The unique MAPK signaling blockade mediated by RO4927350 in cancer may reduce the risk of developing drug resistance. Thus, RO4927350 represents a novel therapeutic modality in cancers with aberrant MAPK pathway activation.

Ultra-low dose naloxone restores the antinociceptive effect of morphine in pertussis toxin–treated rats and prevents glutamate transporter downregulation by suppressing the p38 mitogen-activated protein kinase signaling pathway

We previously demonstrated that ultra-low dose naloxone restores the antinociceptive effect of morphine in rats with pertussis toxin (PTX)–induced thermal hyperalgesia by reversing the downregulation of glutamate transporter (GT) expression and suppressing spinal neuroinflammation. In the present study, we examined the underlying mechanisms of this anti-inflammatory effect in PTX-treated rats, particularly on the expression of GTs. Male Wistar rats were implanted with an intrathecal catheter and, in some cases, with a microdialysis probe. All rats were injected intrathecally with saline (5 μl) or PTX (1 μg), then, 4 days later, were randomly assigned to receive a single injection of saline, ultra-low dose naloxone (15 ng), or the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 (5 μg), followed by morphine injection (10 μg) 30 min later. Our results showed that PTX injection induced activation of microglia and a significant increase in P-p38 MAPK expression in the spinal cord. Ultra-low dose naloxone plus morphine significantly inhibited the effect of PTX on P-p38 MAPK expression in the spinal cord, while the p38 MAPK inhibitor SB203580 attenuated the PTX-induced mechanical allodynia, thermal hyperalgesia, increase in spinal cerebrospinal fluid excitatory amino acids, and downregulation of GTs. These results show that the restoration of the antinociceptive effect of morphine and GT expression in PTX-treated rats by ultra-low dose naloxone involves suppression of the p38 MAPK signal transduction cascade.

Preclinical Activity of Eltrombopag (SB-497115), an Oral, Nonpeptide Thrombopoietin Receptor Agonist

Eltrombopag is a first-in-class, orally bioavailable, small-molecule, nonpeptide agonist of the thrombopoietin receptor (TpoR), which is being developed as a treatment for thrombocytopenia of various etiologies. In vitro studies have demonstrated that the activity of eltrombopag is dependent on expression of TpoR, which activates the signaling transducers and activators of transcription (STAT) and mitogen-activated protein kinase signal transduction pathways. The objective of this preclinical study is to determine if eltrombopag interacts selectively with the TpoR to facilitate megakaryocyte differentiation in platelets. Functional thrombopoietic activity was demonstrated by the proliferation and differentiation of primary human CD34+ bone marrow cells into CD41+ megakaryocytes. Measurements in platelets in several species indicated that eltrombopag specifically activates only the human and chimpanzee STAT pathways. The in vivo activity of eltrombopag was demonstrated by an increase of up to 100% in platelet numbers when administered orally (10 mg/kg per day for 5 days) to chimpanzees. In conclusion, eltrombopag interacts selectively with the TpoR without competing with Tpo, leading to the increased proliferation and differentiation of human bone marrow progenitor cells into megakaryocytes and increased platelet production. These results suggest that eltrombopag and Tpo may be able to act additively to increase platelet production.

Computational prediction and analysis of impact of the cross-talks between JNK and P38 kinase cascades.

Signal transduction is a complex protein signaling process with a rich network of multifunctional interactions that occur in a non-linear fashion. Mitogen-activated protein kinase (MAPK) signal transduction pathways regulate diverse cellular processes ranging from proliferation and differentiation to apoptosis. In mammals, out of five, there are three well characterized subfamilies of MAPKs - ERKs (Extracellular signal-regulated kinases), JNKs (c-Jun N-terminal kinases), and P38 kinases, and their activators, are implicated in human diseases and are targets for drug development. Kinase cascades in MAPK pathways mediate the sensing and processing of stimuli. To understand how cells makes decisions, the dynamic interactions of components of signaling cascades are important rather than just creating static maps. Based on enzyme kinetic reactions, we have developed a mathematical model to analyze the impact of the cross-talks between JNK and P38 kinase cascades. Cross-talks between JNK and P38 kinase cascades influence the activities of P38 kinases. Responses of the signals should be studied for network of kinase cascades by considering cross-talks.

Signal transduction pathways in liver and the influence of hepatitis C virus infection on their activities

In liver, the most intensively studied transmembrane and intracellular signal transduction pathways are the Janus kinase signal transduction pathway, the mitogen-activated protein kinases signal transduction pathway, the transforming growth factor beta signal transduction pathway, the tumor necrosis factor alpha signal transduction pathway and the recently discovered sphingolipid signal transduction pathway. All of them are activated by many different cytokines and growth factors. They regulate specific cell mechanisms such as hepatocytes proliferation, growth, differentiation, adhesion, apoptosis, and synthesis and degradation of the extracellular matrix. The replication cycle of hepatitis C virus (HCV) is intracellular and requires signal transduction to the nucleus to regulate transcription of its genes. Moreover, HCV itself, by its structural and non-structural proteins, could influence the activity of the second signal messengers. Thus, the inhibition of the transmembrane and intracellular signal transduction pathways could be a new therapeutic target in chronic hepatitis C treatment.

Allicin, a major component of garlic, inhibits apoptosis in vital organs in rats with trauma/hemorrhagic shock*

Allicin is believed to be the main component responsible for the biological activity of garlic. The regulation of cell apoptosis may have therapeutic potential for trauma/hemorrhagic shock, and previous studies have demonstrated that allicin exerts protective effects against tissue ischemia-reperfusion injury. Therefore, this study examined the effects of allicin on apoptosis-related organ damage, induced by trauma/hemorrhagic shock. Studies were performed on an in vivo model of spontaneously breathing rats with induced trauma/hemorrhagic shock; the left lower lobe of the lungs, left kidney, and intestine were resected, and the rats were subjected to femur fracture, ischemia for 30 mins, and reperfusion for 20 mins. Allicin (30 microg/kg) was administered during reperfusion. Allicin administered during reperfusion markedly attenuated injury and apoptosis of the lungs, kidneys, and intestine and decreased the concentrations of lactic acid and creatinine, the number of in situ TdT-mediated dUTP nick-end labeling-positive cells, and the activity and expression of caspase-3 and -9 (as determined by Western blot). Furthermore, immunohistochemistry and Western blot performed 24 hrs after reperfusion revealed increases in the levels of nuclear factor kappaB, phosphorylated p38, and extracellular signal-regulated kinase 1 mitogen-activated protein kinase in the allicin-untreated group when compared with the sham rats. Allicin treatment downregulated the levels of nuclear factor kappaB and phosphorylated p38 mitogen-activated protein kinase but did not modify those of phosphorylated extracellular signal-regulated kinase 1 mitogen-activated protein kinase. Allicin attenuates tissue injury and inhibits trauma/hemorrhagic shock- and reperfusion-induced apoptosis in several important organs via the p38 mitogen-activated protein kinase signal transduction pathway that functions to stimulate the activation of nuclear factor-kappaB, caspase-3 and -9, but not of extracellular signal-regulated kinase 1 mitogen-activated protein kinase.

Cdc25A Protein Phosphatase: A Therapeutic Target for Liver Cancer Therapies

Cdc25A, a dual specificity protein phosphatase, is well-recognized as a critical regulator for cell cycle progression. We recently found that it also regulates mitogen-activated protein kinase (MAPK) signal transduction pathway. Inhibition of Cdc25A activity by a K vitamin analog Compound 5 (Cpd 5) can induce a strong and prolonged activation of epidermal growth factor receptor (EGFR)-MAPK pathway, which leads to suppression of transcription factors CREB and c-Myc, resulting in decreased expression of Cdc25A and cyclin D1 levels. Our investigations suggest that Cdc25A plays a central role in regulating and linking cell cycle progression and MAPK signal transduction pathways. Several other recently synthesized K vitamin analogs also affect this pathway, including the non-quinone PM20 and fluoro-Cpd 5. Thus, searching for new and efficient small molecules to inhibit Cdc25A activity may provide new means to control cancers of the liver and other sites.

Role of the Caenorhabditis elegans Shc Adaptor Protein in the c-Jun N-Terminal Kinase Signaling Pathway

Mitogen-activated protein kinases (MAPKs) are integral to the mechanisms by which cells respond to physiological stimuli and a wide variety of environmental stresses. In Caenorhabditis elegans, the stress response is controlled by a c-Jun N-terminal kinase (JNK)-like mitogen-activated protein kinase (MAPK) signaling pathway, which is regulated by MLK-1 MAPK kinase kinase (MAPKKK), MEK-1 MAPK kinase (MAPKK), and KGB-1 JNK-like MAPK. In this study, we identify the shc-1 gene, which encodes a C. elegans homolog of Shc, as a factor that specifically interacts with MEK-1. The shc-1 loss-of-function mutation is defective in activation of KGB-1, resulting in hypersensitivity to heavy metals. A specific tyrosine residue in the NPXY motif of MLK-1 creates a docking site for SHC-1 with the phosphotyrosine binding (PTB) domain. Introduction of a mutation that perturbs binding to the PTB domain or the NPXY motif abolishes the function of SHC-1 or MLK-1, respectively, thereby abolishing the resistance to heavy metal stress. These results suggest that SHC-1 acts as a scaffold to link MAPKKK to MAPKK activation in the KGB-1 MAPK signal transduction pathway.

Differential Roles of Peripheral Mitogen-Activated Protein Kinase Signal Transduction Pathways in Bee Venom–Induced Nociception and Inflammation in Conscious Rats

Intraplantar injection of bee venom (BV) produces persistent spontaneous nociception (PSN) and hyperalgesia, as well as obvious inflammatory swelling, in the paws of injected rats. The present study was designed to determine the peripheral roles of mitogen-activated protein kinase (MAPK) signal transduction pathways in BV-induced nociception and inflammation. We examined the effect of intraplantar injection of an ERK1/2 inhibitor, PD98059, and a p38 inhibitor, SB202190, on BV-induced PSN, mechanical hyperalgesia, and inflammatory swelling. We found that (1) pretreatment with SB202190 (0.1 to 10 microg) had no effect on BV-induced PSN, whereas pretreatment with PD98059 (0.1 to 100 microg) produced a significant and dose-dependent inhibition of BV-induced PSN; (2) pretreatment with PD98059 (0.1 to 100 microg) had no effect on BV-induced decreases in paw withdrawal mechanical threshold (PWMT), while pretreatment with SB202190 (0.1 to 10 microg) produced an obvious prevention of the BV-induced decrease in PWMT; and (3) pretreatment with PD98059 (0.1 to 100 microg) had no effect on BV-induced increase in paw volume (PV), whereas pretreatment with SB202190 (0.1 to 10 microg) produced a dose-related inhibition of BV-induced increases in PV. No contralateral drug treatments, even at the highest dose, had any effect on BV-induced PSN, PWMT or PV, ruling out the systemic effect of these drugs. These results suggest that peripheral MAPK signal transduction pathways may play differential roles in bee venom-induced nociception and inflammation. Targeting specific peripheral MAPKs might prove effective in the treatment of persistent pain and inflammation. The present article showed that intraplantar injection of different MAPK inhibitors produced differential effects on bee venom-induced nociception and inflammation, suggesting that the peripheral MAPK signal transduction pathways have differential roles. Targeting specific peripheral MAPKs might prove effective in the treatment of persistent pain and inflammation.

Specific and overlapping sphingosine-1-phosphate receptor functions in human synoviocytes: impact of TNF-α

Sphingosine-1-phosphate (S1P), via interaction with its G protein-coupled receptors, regulates various physiological and pathological responses. The present study investigated the role of S1P/S1P receptor signaling in several functional responses of human fibroblast-like synoviocytes (FLSs) that may contribute to the pathogenesis of rheumatoid arthritis (RA). We report that FLSs express the S1P(1), S1P(2), and S1P(3) receptors. Moreover, exogenously applied S1P induces FLS 1) migration, 2) secretion of inflammatory cytokines/chemokines, and 3) protection from apoptosis. Using specific S1P receptor agonists/antagonists, we determined that S1P stimulates FLS migration through S1P(1) and S1P(3), induces cytokine/chemokine secretion through S1P(2) and S1P(3), and protects from cell apoptosis via S1P(1). The S1P-mediated cell motility and cytokine/chemokine secretion seem to be regulated by the p38 mitogen-activated protein kinase (MAPK), p42/44 MAPK, and Rho kinase signal transduction pathways. Interestingly, treatment of FLSs with tumor necrosis factor-alpha increases S1P(3) expression and correlates with the enhancement of S1P-induced cytokine/chemokine production. Our data suggest that S1P(1), S1P(2), and S1P(3) play essential roles in the pathogenesis of RA by modulating FLS migration, cytokine/chemokine production, and cell survival. Moreover, the cytokine-rich environment of the inflamed synovium may synergize with S1P signaling to exacerbate the clinical manifestations of this autoimmune disease.

Albumin resuscitation protects against traumatic/hemorrhagic shock-induced lung apoptosis in rats

To determine the effects of albumin administration on lung injury and apoptosis in traumatic/hemorrhagic shock (T/HS) rats. Studies were performed on an in vivo model of spontaneously breathing rats with induced T/HS; the rats were subjected to femur fracture, ischemia for 30 min, and reperfusion for 20 min with Ringer's lactate solution (RS) or 5% (w/v) albumin (ALB), and the left lower lobes of the lungs were resected. Albumin administered during reperfusion markedly attenuated injury of the lung and decreased the concentration of lactic acid and the number of in situ TdT-mediated dUTP nick-end labelling (TUNEL)-positive cells. Moreover, immunohistochemistry performed 24 h after reperfusion revealed increases in the level of nuclear factor kappaB (NF-kappaB), and phosphorylated p38 mitogen-activated protein kinase (MAPK) in the albumin-untreated group was down-regulated by albumin treatment when compared with the sham rats. Resuscitation with albumin attenuates tissue injury and inhibits T/HS-induced apoptosis in the lung via the p38 MAPK signal transduction pathway that functions to stimulate the activation of NF-kappaB.

Different Na+K+-ATPase signal pathways was involved in the increase of [Ca2+]i induced by strophanthidin in normal and failing isolated guinea pig ventricular myocytes

To determine whether different Na+/K+-ATPase signal transduction pathways have positive inotropic effects on normal ventricular myocytes (NC) and failing ventricular myocytes (FC), and are involved in an increase of [Ca2+]i induced by strophanthidin (Str). A guinea pig model of congestive heart failure was made by constricting descending aorta. The left ventricular myocytes were enzymatically isolated. The effects of 25 micromol/L Str with different signal-transducing inhibitors on contractility and the calcium transient of NC or FC from guinea pigs were simultaneously assessed and compared with those in the 25 micromol/L Str-only group by a video-based, motion-edge detection system. Str at 1, 10, and 25 micromol/L in NC and Str at 0.1, 1, 10, and 25 micromol/L) in FC elevated the calcium transient amplitude and increased the positive inotropic effects in a concentration-dependent manner, respectively. At the same concentration, the effects of Str were more potent in FC than in NC. In FC, both the mitogen-activated protein kinase (MAPK) and reactive oxygen species (ROS) signal transduction pathway of Na+/K+-ATPase were involved in the increase of the calcium transient induced by Str, but only activation of the MAPK pathway increased the calcium transient in NC. However, only the ROS pathway was involved in positive inotropic effects both in NC and FC. The present study suggests that Na+/K+-ATPase signaling pathways involved in the inotropic effects of Str in NC and FC are consistent, and Na+/K+-ATPase signaling pathways involved in the increase of [Ca2+]i by Str in NC and FC are different.

Urotensin II is an autocrine/paracrine growth factor for aortic adventitia of rat

Urotensin II (UII) is a potent vasoconstrictive peptide; however, its significance in vascular adventitia has not been clearly elucidated. In this study, rat aortic adventitia showed mRNA expression and immunoreactivity of UII and its receptor (UT). Moreover, radioligand-binding assay showed that maximum binding capacity (Bmax) of [ 125I]-UII was higher in adventitia than in media (28.60 ± 1.94 vs. 20.21 ± 1.11 fmol/mg, P < 0.01), with no difference in binding affinity (dissociation constant [Kd] 4.27 ± 0.49 vs. 4.60 ± 0.40 nM, P > 0.05). Furthermore, in cultured adventitial fibroblasts, UII stimulated DNA synthesis, collagen synthesis and secretion in a concentration-dependent manner. These effects were inhibited by the UII receptor antagonist urantide (10 − 6 mol/l), Ca 2+ channel blocker nicardipine (10 − 5 mol/l), protein kinase C inhibitor H7 (10 − 6 mol/l), and mitogen-activated protein kinase inhibitor PD98059 (10 − 6 mol/l) but not the phosphatidyl inositol-3 kinase inhibitor wortmannin (10 − 7 mol/l). UII may act as an autocrine/paracrine factor through its receptor and the Ca 2+ channel, protein kinase C, and mitogen-activated protein kinase signal transduction pathways, in the pathogenesis of vascular remodeling by activating vascular adventitia.