Physiological roles of mitogen-activated-protein-kinase-activated p38-regulated/activated protein kinase

Mitogen-activated protein kinases(MAPKs)are a family of proteins that constitute signaling pathways involved in processes that control gene expression,cell division, cell survival,apoptosis,metabolism,differentiation and motility.The MAPK pathways can be divided into conventional and atypical MAPK pathways.The first group converts a signal into a cellular response through a relay of three consecutive phosphorylation events exerted by MAPK kinase kinases,MAPK kinase,and MAPK.Atypical MAPK pathways are not organized into this three-tiered cascade.MAPK that belongs to both conventional and atypical MAPK pathways can phosphorylate both non-protein kinase substrates and other protein kinases.The latter are referred to as MAPK-activated protein kinases.This review focuses on one such MAPK-activated protein kinase,MAPK-activated protein kinase 5(MK5)or p38-regulated/activated protein kinase(PRAK).This protein is highly conserved throughout the animal kingdom and seems to be the target of both conventional and atypical MAPK pathways.Recent findings on the regulation of the activity and subcellular localization,bona fide interaction partners and physiological roles of MK5/PRAK are discussed.

Differential activation of mitogen-activated protein kinases by γ-irradi-ation in IEC-6 cells: Role of intracellular Ca^(2+)

Objective: To explore the effects of γ-irradiation on mitogen-activated protein kinases (MAPKs) and role of intracellular calcium in this event in intestinal epithelial cell line 6 (IEC-6 cells). Methods: After cultured rat IIEC-6 cells with or without the pretreatment of intracellular Ca2+ chelator were exposed to Y-ir-radiation of 6 Gy, the total and phosphorylated MAPKs in the cells were determined with Western blotting and apoptosis was examined with flow cytometry. Activities of Extracellular signal-regulated protein kinase (ERK) and p38 MAPK were determined by using immuoprecipitation followed by Western blotting. Results: In response to γ-irradiation, phosphorylation of ERK was not significantly observed, while the levels of phosphorylated c-Jun NH2-terminal kinase (JNK) and p38 MAPK were increased in 30 min and reached the peak 2 h after exposure to 6 Gy γ-irradiation, though the cell viability was significantly lowered 12 h. On the other hand, no obvious changes were seen in the total protein levels of ERK, JNK and p38 MAPK. Chelation of intracellular Ca2+ almost completely suppressed the JNK and p38 MAPK phosphorylation induced by γ-irradia-tion, but removal of external Ca2+ had no such effect. Activation of p38 MAPK, but not of ERK, was seen to have a correlation with γ-irradiation induced apoptosis. Conclusion: The results suggest that γ-irradiation is a potent activator for JNK and p38 MAPK, and Ca2+ mobilized from intracellular stores plays an important role in the activation of MAPKs and the induction of apoptosis in IEC-6 cells.

Effect of oxymatrine on the p38 mitogen-activated protein kinases signalling pathway in rats with CCl4 induced hepatic fibrosis

Background Recent studies have suggested that p38 mitogen-activated protein kinases （MAPK） signalling pathway plays an important role in hepatic fibrosis. This study explored the antifibrotic effect of oxymatrine on tetrachloromethane induced liver fibrosis in rats and its modulation on the p38 MAPK signalling pathway. Methods One hundred and twenty healthy male Sprague-Dawley rats were randomly assigned to six groups： normal （n=20）, induced fibrosis （n=20）, colchicine （n=20） and three treatment groups of oxymatrine （n=20x3）. We obesrved changes in deposition of collagen, hyaluronic acid （HA）, laminin （LN）, collagen type IV （CIV）, procollagen III （PCIll） and hydroxyproline （Hyp）, a-smooth muscle actin （α-SMA） and phosphor-p38 （pp38）. Results The relative indicators of changes in histopathology, HA, LN, CIV, PCIII, Hyp, a-SMA and pp38 were raised significantly in the induced fibrosis group （P〈0.01 vs normal group）. The semiquantitative hepatic fibrosis staging scores of middle dose group and high dose group were decreased （P 〈0.05 and P 〈0.01 respectively vs the induced fibrosis group）, as was the average area of collagen in rats＇ liver, the concentrations of serum HA, LN, CIV, PCIII and liver tissue homogenate Hyp. The gene expression of α-SMA mRNA was considerably decreased in the treated animals, as was the protein espression of pp38 protein. Conclusions Oxymatrine is effective in reducing the production and deposition of collagen in the liver tissue of experimental rats in ways which relate to modulating the fibrogenic signal transduction via p38 MAPK signalling pathway.

Down-regulation of HIV-1 Infection by Inhibition of the MAPK Signaling Pathway

The human immunodeficiency virus type 1 （HIV-1） can interact with and exploit the host cellular machinery to replicate and propagate itself. Numerous studies have shown that the Mitogen-activated protein kinase （MAPK） signal pathway can positively regulate the replication of HIV-1, but exactly how each MAPK pathway affects HIV-1 infection and replication is not understood. In this study, we used the Extracellular signal-regulated kinase （ERK） pathway inhibitor, PD98059, the Jun N-terminal kinase （JNK） pathway inhibitor, SP600125, and the p38 pathway inhibitor, SB203580, to investigate the roles of these pathways in HIV-1 replication. We found that application of PD98059 results in a strong VSV-G pseudotyped HIV-1NL4-3 luciferase reporter virus and HIV-1NL4-3 virus inhibition activity. In addition, SB203580 and SP600125 also elicited marked VSV-G pseudotyped HIV-INL4-3 luciferase reporter virus inhibition activity but no HIV-1NL4-3 virus inhibition activity. We also found that SB203580 and SP600125 can enhance the HIV-1 inhibition activity of PD98059 when cells were treated with all three MAPK pathway inhibitors in combination. Finally, we show that HIV-1 virus inhibition activity of the MAPK pathway inhibitors was the result of the negative regulation of HIV-1 LTR promoter activity.

The involvement of p38 MAPK in transforming growth factor β1-induced apoptosis in murine hepatocytes

We reported in this manuscript that TGF-beta1 induces apoptosis in AML12 murine hepatocytes, which is associated with the activation of p38 MAPK signaling pathway. SB202190, a specific inhibitor of p38 MAPK, strongly inhibited the TGF-beta1-induced apoptosis and PAI-1 promoter activity. Treatment of cells with TGF-beta1 activates p38. Furthermore, over-expression of dominant negative mutant p38 also reduced the TGF-beta1-induced apoptosis. The data indicate that the activation of p38 is involved in TGF-beta1-mediated gene expression and apoptosis.

The binding of actin to p38 MAPK and inhibiting its kinase activity in vitro

p38 MAP kinase mediates a signal pathway that is involved in many physiological and pathological processes such as inflammation, cellular stress, apoptosis, cell cycle and growth, ischemia/re-perfusion, and myocardium hypertrophy. To determine the molecular and regulative mechanism of p38 signal pathway, we used in vitro binding methods to screen the proteins that interact with p38. Here we report two proteins from mouse macrophage RAW264.7 strain treated with lipopolysaccharide (LPS) or ultraviolet radiation (UV), binding directly to p38. One of them is b-actin identified by peptide mass spectrum and ProFound program. Actin can inhibit the auto-phosphorylation of p38 and the phosphorylation of ATF by p38. It suggests that the binding of actin to p38 in vitro may represent a negative feedback to the kinase activity of p38, which leads to the regulation of p38 pathway and cellular function.

Dahuang Zhechong Pill Alleviates Liver Fibrosis Progression by Regulating p38 MAPK/NF-κB/TGF-β1 Pathway

Objective:To explore the effect and mechanism of Dahuang Zhechong Pill(DHZCP)on liver fibrosis.Methods:Liver fibrosis cell model was induced by transforming growth factor-β(TGF-β)in hepatic stellate cells(HSC-T6).DHZCP medicated serum(DMS)was prepared in rats.HSC-T6 cells were divided into the control(15%normal blank serum culture),TGF-β(15%normal blank serum+5 ng/mL TGF-β),DHZCP(15%DMS+5 ng/mL TGF-β),DHZCP+PDTC[15%DMS+4 mmol/L ammonium pyrrolidine dithiocarbamate(PDTC)+5 ng/mL TGF-β],and PDTC groups(4 mmol/L PDTC+5 ng/mL TGF-β).Cell activity was detected by cell counting kit 8 and levels of tumor necrosis factor-α(TNF-α),interleukin(IL)-1β,IL-6,aspartate aminotransferase(AST)and alanine aminotransferase(ALT)in the cell supernatant were determined by enzymelinked immunosorbnent assay.Western blot was used to measure the expressions of p38 mitogen-activated protein kinase/nuclear factor kappa B/transforming growth factor-β1(p38 MAPK/NF-κB/TGF-β1)pathway related proteins,and the localization and expressions of these proteins were observed by immunofluorescence staining.Results:DHZCP improved the viability of cells damaged by TGF-βand reduced inflammatory cytokines and ALT and AST levels in the supernatant of HSC-T6 cells induced with TGF-β(P<0.05 or P<0.01).Compared with the TGF-βgroup,NF-κB p65 levels in the DHZCP group were decreased(P<0.05).p38 MAPK and NF-κB p65 levels in the DHZCP+PDTC were also reduced(P<O.01).Compared with the TGF-βgroup,the protein expression of Smad2 showed a downward trend in the DHZCP,DHZCP+PDTC,and PDTC groups(all P<0.01),and the decreasing trend of Samd3 was statistically significant only in DHZCP+PDTC group(P<0.01),whereas Smad7 was increased(P<0.05 or P<0.01).Conclusion:DHZCP can inhibit the process of HSC-T6 cell fibrosis by down-regulating the expression of p38 MAPK/NF-κB/TGF-β1 pathway.

MAPKs represent novel therapeutic targets for gastrointestinal motility disorders

The number of patients suffering from symptoms associated with gastrointestinal(GI) motility disorders is on the rise. GI motility disorders are accompanied by alteration of gastrointestinal smooth muscle functions. Currently available drugs,which can directly affect gastrointestinal smooth muscle and restore altered smooth muscle contractility to normal,are not satisfactory for treating patients with GI motility disorders. We have recently shown that ERK1/2 and p38MAPK signaling pathways play an important role in the contractile response not only of normal intestinal smooth muscle but also of inflamed intestinal smooth muscle. Here we discuss the possibility that ERK1/2 and p38MAPK signaling pathways represent ideal targets for generation of novel therapeutics for patients with GI motility disorders.

Modified Sijunzi Granules Exhibit Hemostatic Effect by Activating Akt and Erk Signal Pathways via Regulating 5-HT and Its Receptors Levels

Objective:To investigate the hemostatic effect of modified Sijunzi Granules(MSG)in primary immune thrombocytopenia(ITP)zebrafish model and explore the potential mechanism.Methods:AB strain wild type zebrafish were treated with simvastatin(6μmol/L)for 24 h to establish the hemorrhage model(model control group).The zebrafish were treated with MSG at different doses(55.6,167,and 500μg/mL),respectively.The hemostatic effect was assessed by examining the intestinal bleeding and hemostatic rate.5-hydroxytryptamine(5-HT)content was determined using enzyme-linked immunosorbent assay(ELISA)assay.The expressions of5-HT2aR,5-HT2bR,and SERT genes were detected by quantitative real-time polymerase chain reaction(PCR).The protein expressions of protein kinase B(Akt),p-Akt,extracellular regulated protein kinases(Erk),and p-Erk were examined using Western blot analysis.Results:The intestinal bleeding rate was 37%,40%,and 80%in the55.6,167,and 500μg/mL dose of MSG,respectively,in which 55.6 and 167μg/mL MSG dose groups were associated with significantly decreased intestinal bleeding rate when compared with the model control group(70%,P<0.05).Significantly higher hemostatic rates were also observed in the 55.6μg/mL(54%)and 167μg/mL(52%)MSG dose groups(P<0.05).MSG increased the 5-HT content and mRNA expression levels of 5-HT2aR,5-HT2bR,and SERT(P<0.05).In addition,caspase3/7 activity was inhibited(P<0.05).Significant increase in p-Akt and p-Erk was also detected after treatment with MSG(P<0.05).Conclusions:MSG could reduce the incidence and severity of intestinal bleeding in zebrafish by activating MAPK/Erk and PI3K/Akt signal pathways through regulating the levels of 5-HT and its receptors,which may provide evidence for the treatment of ITP.

Anti-parkinsonian effects of octacosanol in 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine-treated mice

Our previous research showed that octacosanol exerted its protective effects in 6-hydroxydopamine-induced Parkinsonian rats. The goal of this study was to investigate whether octacosanol would attenuate neurotoxicity in 1-methyl-4-phenyl-l,2,3,6 tetrahydropyridine （MPTP）-treated C57BL/6N mice and its potential mechanism. Behavioral tests, tyrosine hydroxylase immunohistochemistry and western blot were used to investigate the effects of octacosanol in a mouse model of Parkinson＇s disease. Oral administration of octacosanol （100 mg/kg） significantly improved behavioral impairments Jn mice treated by MPTP and markedly ameliorated morphological appearances of tyrosine hydroxylase-positive neuronal cells in the substantia nigra. Furthermore, octacosanol blocked MPTP-induced phosphorylation of p38MAPK and JNK, but not ERK1/2. These findings implicated that the protective effects afforded by octacosanol might be mediated by blocking the phosphorylation of p38MAPK and JNK on the signa transduction in vivo. Considering its excellent tolerability, octacosanol might be considered as a candidate agent for clinical application in treating Parkinson＇s disease.

Exogenous nerve growth factor protects the hypoglossal nerve against crush injury

Studies have shown that sensory nerve damage can activate the p38 mitogen-activated protein kinase（MAPK）pathway,but whether the same type of nerve injury after exercise activates the p38MAPK pathway remains unclear.Several studies have demonstrated that nerve growth factor may play a role in the repair process after peripheral nerve injury,but there has been little research focusing on the hypoglossal nerve injury and repair.In this study,we designed and established rat models of hypoglossal nerve crush injury and gave intraperitoneal injections of exogenous nerve growth factor to rats for 14 days.p38MAPK activity in the damaged neurons was increased following hypoglossal nerve crush injury;exogenous nerve growth factor inhibited this increase in acitivity and increased the survival rate of motor neurons within the hypoglossal nucleus.Under transmission electron microscopy,we found that the injection of nerve growth factor contributed to the restoration of the morphology of hypoglossal nerve after crush injury.Our experimental findings indicate that exogenous nerve growth factor can protect damaged neurons and promote hypoglossal nerve regeneration following hypoglossal nerve crush injury.

Protective Effects of Sapindus Saponins in Spontaneously Hypertensive Rats

Objectives： To investigate the protective effects of Sapindus saponins in spontaneously hypertensive rats, and the possible cellular and molecular mechanisms. Methods： Thirty-two 16-week-old spontaneously hypertensive rats were randomly divided into four groups （8 in each group）： model group （placebo）, positive control group （27 mg/kg of Captopril Tablets）, Sapindus saponins groups （27 mg/kg and 108 mg/kg, respectively）. Another 8 healthy Wistar-Kyoto strain （WKY） rats were used as the normal group. The animals were treated for 8 weeks. Blood pressure of rats was determined by non-invasive blood pressure meter （BP-6）. Furthermore, the contents of angiotensin Ⅱ （Ang Ⅱ） in plasma and myocardial tissue were determined by enzyme-linked immunosorbent assay （ELISA）, the gene expression of receptor angiotensin type 1 （AT1R） in aorta was determined by quantitative real- time polymerase chain reaction （qRT-PCR）. The protein expression of transforming growth factor- β1 （TGF- 1β1） and AT1R in heart was determined by immunohistochemical staining. The protein expression of p-phosphorylation of p38 mitogen-activated protein kinase （p-p38MAPK） was determined by Western blotting. The contents of interleukin （IL）-1, IL-6 and tumor necrosis factor （TNF） in serum were determined by radioimmunoassay. And the histopathological and morphological changes of aorta and heart tissue samples were assessed semi-quantitatively by hematoxylin-eosin （HE） or Masson staining. Results： Thirty minutes after single or continuous treatment, systolic blood pressure （SBP） was reduced significantly in Sapindus saponins groups. And the contents of Ang 11, IL-1, IL-6 and TNF-α in serum, the expression of AT1R mRNA, p-p38MAPK and TGF- β1 were significantly suppressed dose-dependently （P〈0.05 or 1=〈0.01）. With the Sapindus saponins treatment, compared with those of the model group, the cardiac and aortic pathological changes were ameliorated significantly. Conclusions： Our findings suggest that Sapindus saponins might have protective effects in spontaneously hypertensive rats, the cellular and molecular mechanisms of which might be relevant to the regulation of inflammatory responses mediated by p-p38MAPK signal pathway based on activated Ang Ⅱ and AT1R.

Hydroxychavicol,a polyphenol from Piper betle leaf extract,induces cell cycle arrest and apoptosis in TP53-resistant HT-29 colon cancer cells

This study aims to elucidate the antiproliferative mechanism of hydroxychavicol(HC).Its effects on cell cycle,apoptosis,and the expression of c-Jun N-terminal kinase(JNK)and P38 mitogen-activated protein kinase(MAPK)in HT-29 colon cancer cells were investigated.HC was isolated from Piper betle leaf(PBL)and verified by high-performance liquid chromatography(HPLC),nuclear magnetic resonance(NMR),and gas chromatography-mass spectrometry(GC-MS).The cytotoxic effects of the standard drug 5-fluorouracil(5-FU),PBL water extract,and HC on HT-29 cells were measured after 24,48,and 72 h of treatment.Cell cycle and apoptosis modulation by 5-FU and HC treatments were investigated up to 30 h.Changes in phosphorylated JNK(pJNK)and P38(pP38)MAPK expression were observed up to 18 h.The half maximal inhibitory concentration(IC_(50))values of HC(30μg/mL)and PBL water extract(380μg/mL)were achieved at 24 h,whereas the IC_(50)of 5-FU(50μmol/L)was obtained at 72 h.Cell cycle arrest at the G0/G1 phase in HC-treated cells was observed from12 h onwards.Higher apoptotic cell death in HC-treated cells compared to 5-FU-treated cells(P<0.05)was observed.High expression of pJNK and pP38 MAPK was observed at 12 h in HC-treated cells,but not in 5-FU-treated HT-29 cells(P<0.05).It is concluded that HC induces cell cycle arrest and apoptosis of HT-29 cells,with these actions possibly mediated by JNK and P38 MAPK.