The upstream regulation of p38 mitogen-activated protein kinase phosphorylation by arachidonic acid in rat neutrophils

The signal transduction pathways activated by arachidonic acid that lead to p38 mitogen‐activated protein kinase (MAPK) activation in neutrophils remains unclear. In this study, selective inhibitors of several signalling pathways were utilized to investigate the mechanisms of activation of p38 MAPK by arachidonic acid in rat neutrophils. Stimulation of p38 MAPK phosphorylation by arachidonic acid and its trifluoromethyl ketone analogue AACOCF₃ was transient, peaking at 1 min, and was concentration‐dependent. Arachidonic acid‐stimulated p38 MAPK phosphorylation was attenuated in cells pretreated with the G_i/o inhibitor (pertussis toxin), but not with the dual cyclooxygenase/lipoxygenase inhibitor (BW755C) or the leukotriene biosynthesis inhibitor (MK886). Tyrosine kinase inhibitor (genistein), but not the extracellular signal‐regulated kinase kinase inhibitors (PD98059 and U0126), attenuated the phosphorylation of p38 MAPK by arachidonic acid. Phosphoinositide 3‐kinase inhibitors (wortmannin and LY294002) did not affect the arachidonic acid‐induced response. After pretreatment of the cells with protein kinase C inhibitors (Gö6976, Gö6983 and GF109203X), only Gö6976 significantly attenuated the phosphorylation of p38 MAPK by arachidonic acid. In addition, phosphorylation of p38 MAPK by arachidonic acid was greatly attenuated by the phospholipase C inhibitor (U73122) and the Ca²⁺ chelator BAPTA ((1,2‐bis‐o‐amino‐phenoxy)‐ethane‐N,N,N′,N′‐tetraacetic acid), but not altered by the nitric oxide synthase inhibitor, N‐nitro‐l ‐arginine methyl ester. Arachidonic acid did not cause an increase in cellular cyclic GMP level. This study revealed the involvement of pertussis toxin‐sensitive G protein, non‐receptor tyrosine kinase, phospholipase C/Ca²⁺, and probably Ca²⁺‐dependent protein kinase C in arachidonic acid‐stimulated p38 MAPK activation.     

Structure-activity relationships of p38 mitogen-activated protein kinase inhibitors

Rheumatoid arthritis and other chronic inflammatory diseases constitute a major therapeutic challenge, usually not sufficiently met by the classical antiinflammatory medications. Recent research efforts provided new insights into the molecular basis of these pathologies and disclosed new opportunities for developing improved drugs directed to the chemical mediators of the disease. The enzyme p38 MAP kinase plays a central role in the signal transduction cascade that leads to the production of both the proinflammatory cytokines, TNF-alpha and IL-1 beta, thus representing an attractive therapeutic target for novel antiinflammatory therapies. A number of p38 inhibitors belonging to different structural families have been developed as potential antiinflammatory drugs, and some of them progressed into clinical trials. The initial pyridinyl imidazole inhibitors contributed to the identification and characterization of p38 MAP kinase as the molecular target of these new drugs, and were found to act as competitive inhibitors at the ATP binding site of the enzyme. A number of variations in the pyridine and imidazole rings were subsequently introduced. Other inhibitors structurally unrelated to the pyridinylimidazoles have also been developed, such as the pyridopyridazinones, diaryl ureas, aminobenzophenones and aromatic amides. One of these structural classes, the N,N'-diarylureas, has been found to interact with a distinct allosteric site of p38 MAP kinase and requires a deep conformational change prior to binding.     

Role of p38 mitogen-activated protein kinase in cardiac remodelling

BACKGROUND AND PURPOSE: Mitogen-activated protein kinases (MAPK) are centrally involved in several mechanisms important for heart failure such as apoptosis, activation of inflammatory responses and cell proliferation. We therefore evaluated the effect of the selective p38 MAPK inhibitor SB 239063 on progression of left ventricular remodelling after myocardial infarction (MI) in rats. EXPERIMENTAL APPROACH: Rats were treated for 9 weeks with placebo or SB 239063 by gavage (15 mg kg(-1)) twice daily starting 7 days after ligation of the left anterior descending artery. Serial transthoracic echocardiography was performed at days 7, 36 and 70. KEY RESULTS: Over the 9 weeks, mortality was not different between the groups. On echocardiography, animals after myocardial infarction exhibited significant left ventricular dilatation as expected (week 10, end-systolic diameter, placebo sham 5.21+/- 0.34 vs. placebo MI 8.44+/- 0.57 mm). However, there was no difference between placebo and SB 239063-treated rats (week 10, end-systolic diameter, SB MI 7.76+/- 0.74 mm, not significantly different from placebo MI). Haemodynamics changed accordingly. Moreover, SB 239063 had no effect on left ventricular hypertrophy. Treatment with SB 239063 significantly reduced cytokine expression of tumour necrosis factor and interleukin-1beta after myocardial infarction. However, collagen content was not influenced by the treatment. CONCLUSION: Despite a reduction of inflammation, treatment with the p38 inhibitor SB 239063 does not affect cardiac remodelling and cardiac function when treatment is started 7 days after myocardial infarction.     

p38 mitogen-activated protein kinase (MAPK) in rheumatoid arthritis

The importance of p38 MAPK inhibitors as new drug for rheumatoid arthritis is reflected by the large number of compounds that has been developed over the last years. In this review new insights such as non-stressful activation of p38 MAPK, and the role of p38 MAPK in regulation of NF-kappaB recruitment are also discussed.     

Potentiation of cyclic AMP and cyclic GMP accumulation by p38 mitogen-activated protein kinase (p38MAPK) inhibitors in rat pinealocytes.

The effects of p38 mitogen-activated protein kinase (p38MAPK) inhibitors on the adrenergic-stimulated cyclic nucleotide production in rat pinealocytes were investigated. Treatment with SB202190 [4-(4-fluorophenyl)-2-(4-hydroxyphenyl)-5-(4-pyridyl)IH-imidazole] and SB203580 [4-(4-fluoropheny)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)IH-imidazole] (1-100 microM), two pyridinyl imidazole compounds that inhibit p38MAPK, as well as SB202474 [4-(ethyl)-2-(4-methoxyphenyl)-5-(4-pyridyl)IH-imidazole], an inactive analog, was effective in potentiating norepinephrine- and isoproterenol-stimulated cyclic AMP (cAMP) and cyclic GMP (cGMP) accumulation in a concentration-dependent manner. All three compounds caused a greater increase in the cGMP than the cAMP response, with SB202474 being substantially more potent than the two active analogs. At 100 microM, SB202474 potentiated the isoproterenol-stimulated cAMP and cGMP accumulation by 65 and 500%, respectively. Pharmacological studies indicated that the potentiating effect of SB202474 was independent of protein kinase C activation, intracellular calcium elevation, or serine/threonine phosphatase inhibition, three pathways known to potentiate the beta-adrenergic-stimulated cyclic nucleotide responses in rat pinealocytes. In contrast, the potentiating effect of SB202474 was abolished in the presence of a phosphodiesterase inhibitor, isobutylmethylxanthine. At 100 microM, all three compounds inhibited cAMP- and cGMP-phosphodiesterase activities by 50 and 80%, respectively. These results suggest that the commonly used p38MAPK inhibitors can modulate cyclic nucleotide responses through phosphodiesterase inhibition, a mechanism that appears to be independent of p38MAPK inhibition.     

Mercury induces multidrug resistance-associated protein gene through p38 mitogen-activated protein kinase

The multidrug resistance-associated protein (MRP1) belongs to a drug efflux membrane pump that confers multidrug resistance to the cells. The MRP1 mediates the cellular efflux of various xenobiotics including heavy metals and mediates cellular resistance to heavy metals. Mercury is a well-known health hazard and an environmental contaminant. Recently, information about the uptake of the heavy metals such as mercury has been suggested. However, little is known regarding molecular mechanisms of exporting mercury. This study was designed to determine if mercury could be extruded by MRP1 in acute myeloid leukemia cells (AML-2). The MRP-1-overexpressing AML-2/DX100 cells showed a higher resistance to mercury than AML-2/WT. Probenecid, which is a specific MRP1 inhibitor, decreased the resistance to mercury. Exposing the AML-2 cells to mercury-induced MRP1 gene expression and production without altering the MRP1 activity. Mercury activated p38 mitogen-activated protein kinase (MAPK) and SB 203580, a specific p38 MAPK inhibitor, blocked the mercury-induced MRP1 production. These results suggest that MRP1 can control mercury and p38 MAPK mediates the mercury-induced MRP1 gene expression.     

Involvement of p38 mitogen-activated protein kinase in PLL-AGE-induced cyclooxgenase-2 expression

In the present study, murine RAW 264.7 macrophages were incubated with poly-L-lysine-derived advanced glycosylation end products (PLL-AGEs) to examine cyclooxygenase-2 protein expression. Treatment of RAW 264.7 cells with PLL-AGEs caused the dose-dependent expression of cylooxygenase-2 but not cylooxygenase-1 and an increase in cylooxygenase activity. Increased cylooxygenase-2 expression was seen at 6 h and reached a maximum at 24 h. The tyrosine kinase inhibitor, genistein, and the p38 mitogen-activated protein kinase (MAPK) inhibitor, [4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole] (SB 203580), inhibited PLL-AGE-induced cylooxygenase-2 expression, while the Ras inhibitor, FPT inhibitor II, and the MAP kinase kinase inhibitor, (2'-amino-3'-methoxyflavone) (PD 98059), had no effect on PLL-AGE-induced cylooxygenase-2 expression. Incubation of RAW 264.7 cells with PLL-AGEs resulted in activation of p38 MAPK, and this activation was suppressed by genistein and SB 203580. Taken together, our results suggest that activation of protein tyrosine kinase and p38 MAPK is involved in AGE-induced cyclooxygenase-2 expression in RAW 264.7 macrophages.     

p38 mitogen-activated protein kinase mediates sidestream cigarette smoke-induced endothelial permeability

Second-hand smoke is associated with increased risk of cardiovascular diseases. So far, little is known about the signaling mechanisms of second-hand smoke-induced vascular dysfunction. Endothelial junctions are fundamental structures important for maintaining endothelial barrier function. Our study showed that sidestream cigarette smoke (SCS), a major component of second-hand smoke, was able to disrupt endothelial junctions and increase endothelial permeability. Sidestream cigarette smoke stimulated the phosphorylation of p38 mitogen-activated protein kinase (MAPK) and myosin light chain (MLC). A selective inhibitor of p38 MAPK (SB203580) prevented SCS-induced loss of endothelial barrier integrity as evidenced by transendothelial resistance measurements. Resveratrol, an antioxidant that was able to inhibit SCS-induced p38 MAPK and MLC phosphorylation, also protected endothelial cells from the damage. Thus, p38 MAPK mediates SCS-induced endothelial permeability. Inhibition of p38 MAPK may have therapeutic potential for second-hand smoke-induced vascular injury.     

吡格列酮对脂多糖引起的大鼠海马有丝分裂原激活蛋白激酶p38信号传导通路的影响

<正>吡格列酮(pioglitazone,Pio)能抑制脂多糖诱导的原代培养的星形胶质细胞炎症因子的释放[1],对抗谷氨酸诱导的神经细胞损伤[2],也有研究显示Pio通过抑制p38MAPK信号传导通路抑制LPS诱导的小胶质细胞炎症反应[3]。但关于Pio对大鼠脑内炎症反应的抑制作用是否与p38MAPK信号传导通路有关目前尚未见报道,本研究通过大鼠脑室内注     

Activation of p38 mitogen-activated protein kinase by celecoxib oppositely regulates survivin and gamma-H2AX in human colorectal cancer cells

Cancer cells express survivin that facilitates tumorigenesis. Celecoxib has been shown to reduce human colorectal cancers. However, the role and regulation of survivin by celecoxib in colorectal carcinoma cells remain unclear. Treatment with 40-80 muM celecoxib for 24 h induced cytotoxicity and proliferation inhibition via a concentration-dependent manner in RKO colorectal carcinoma cells. Celecoxib blocked the survivin protein expression and increased the phosphorylation of H2AX at serine-193 (gamma-H2AX). The survivin gene knockdown by transfection with a survivin siRNA revealed that the loss of survivin correlated with the expression of gamma-H2AX. Meanwhile, celecoxib increased caspase-3 activation and apoptosis. Celecoxib activated the phosphorylation of p38 mitogen-activated protein (MAP) kinase. The phosphorylated proteins of p38 MAP kinase and gamma-H2AX were observed in the apoptotic cells. SB203580, a specific p38 MAP kinase inhibitor, protected the survivin protein expression and decreased the levels of gamma-H2AX and apoptosis in the celecoxib-exposed cells. The blockade of survivin expression increased the celecoxib-induced cytotoxicity; conversely, overexpression of survivin by transfection with a survivin-expressing vector raised the cancer cell proliferation and resisted the celecoxib-induced cell death. Our results provide for the first time that p38 MAP kinase participates in the down-regulation of survivin and subsequently induces the activation of gamma-H2AX for mediating apoptosis following treatment with celecoxib in human colorectal cancer cells.     

p38 mitogen-activated protein kinase contributes to angiotensin II-stimulated migration of rat aortic smooth muscle cells

In this study, we clarified the intracellular mechanism of angiotensin II (Ang II) in promoting migration in rat aortic smooth muscle cells (RASMCs). RASMC migration was measured with the Boyden chamber assay, and the result was confirmed with an aortic sprout assay. The activities of kinases were investigated by western blot analysis. Ang II enhanced RASMC migration, which was chemotaxis directed, and induced the phosphorylation of p38 mitogen-activated protein kinase (MAPK), extracellular signal-regulated kinase 1/2 (ERK1/2), and heat shock protein 27 (Hsp27). Ang II-enhanced cell migration was inhibited by SB203580 (a p38 MAPK inhibitor) and piceatannol (a spleen tyrosine kinase inhibitor), but only partially by PD98059 (an ERK inhibitor) and PP2 (a Src inhibitor). The Ang II-stimulated phosphorylation of p38 MAPK and Hsp27 in RASMCs was inhibited by piceatannol and SB203580. The phosphorylation of ERK1/2 stimulated by Ang II was suppressed by PD98059, piceatannol, and PP2. Ang II increased the sprout outgrowth from aortic rings and this response was attenuated by pretreatment with SB203580, PD98059, PP2, or piceatannol. These results suggest that p38 MAPK contributes to the regulation of the Ang II-induced chemotactic migration of vascular smooth muscle cells, which is mediated by Hsp27 phosphorylation.     

Role of p38 mitogen-activated protein kinase in ozone-induced airway hyperresponsiveness and inflammation

Ozone is a potent oxidant and causes airway hyperresponsiveness and neutrophilia. To determine the role of p38 mitogen-activated protein kinase (MAPK) activation, we studied the effect of a p38α inhibitor SD-282 (Scios Inc, Fremont, CA USA) on ozone-induced airway hyperresponsiveness and neutrophilia. Balb/c mice received SD-282 (30 or 90 mg/kg i.p) or vehicle 1 h before exposure to either ozone (3 ppm, 3 h) or air. Three hours after exposure, lungs were analysed for cytokine levels and bronchoalveolar lavage was performed. Another set of mice were dosed 6 h after exposure and 1 h before assessing airway hyperresponsiveness. SD-282 (90 mg/kg) significantly inhibited ozone-induced airway hyperresponsiveness (− LogPC₁₅₀: SD-282: − 1.73 ± 0.14 vs. vehicle: − 0.99 ± 0.15, P < 0.05). Bronchoalveolar lavage neutrophil numbers were time-dependently increased in vehicle-dosed, ozone-exposed mice, greatest at 20–24 h after exposure. SD-282 (30 and 90 mg/kg) significantly inhibited ozone induced neutrophil numbers at 3 h and 20–24 h after ozone SD-282 significantly inhibited ozone-induced increases in phosphorylated p38 MAPK expression, and in cyclooxygenase-2 (COX-2), interleukin-6 (IL-6) and IL-1β but not MIP-1α gene expression. We conclude that p38 MAPK is involved in ozone-induced airway hyperresponsiveness and lung neutrophilia. Inhibition of p38 MAPK with small molecule kinase inhibitors may be a means of reducing ozone-induced inflammation and airway hyperresponsiveness.     

Akt activation induced by lysophosphatidic acid and sphingosine-1-phosphate requires both mitogen-activated protein kinase kinase and p38 mitogen-activated protein kinase and is cell-line specific

The signaling pathways that lysophosphatidic acid (LPA) and sphingosine-1-phosphate (S1P) use to activate Akt in ovarian cancer cells are investigated here. We show for the first time, with the use of both pharmacological and genetic inhibitors, that the kinase activity and S473 phosphorylation of Akt induced by LPA and S1P requires both mitogen-activated protein (MAP) kinase kinase (MEK) and p38 MAP kinase, and MEK is likely to be upstream of p38, in HEY ovarian cancer cells. The requirement for both MEK and p38 is cell type- and stimulus-specific. Among 12 cell lines that we tested, 11 respond to LPA and S1P and all of the responsive cell lines require p38 but only nine of them require MEK. Among different stimuli tested, platelet-derived growth factor stimulates S473 phosphorylation of Akt in a MEK- and p38-dependent manner. However, epidermal growth factor, thrombin, and endothelin-1-stimulated Akt S473 phosphorylation require p38 but not MEK. Insulin, on the other hand, stimulates Akt S473 phosphorylation independent of both MEK and p38 in HEY cells. T308 phosphorylation stimulated by LPA/S1P requires MEK but not p38 activation. MEK and p38 activation were sufficient for Akt S473 but not T308 phosphorylation in HEY cells. In contrast to S1P and PDGF, LPA requires Rho for Akt S473 phosphorylation, and Rho is upstream of phosphatidylinositol 3-kinase (PI3-K). LPA/S1P-induced Akt activation may be involved in cell survival, because LPA and S1P treatment in HEY ovarian cancer cells results in a decrease in paclitaxel-induced caspase-3 activity in a PI3-K/MEK/p38-dependent manner.     

Inhibitors of p38 mitogen-activated protein kinase for the treatment of rheumatoid arthritis

The p38 mitogen-activated protein kinase pathway is involved in a number of cellular processes critical to the development of rheumatoid arthritis. The activation and infiltration of leukocytes as well as the production of inflammatory cytokines are p38-dependent processes. In addition, p38 regulates the differentiation of osteoclasts, which are directly involved in bone loss. Numerous inhibitors of p38 have demonstrated efficacy in animal models of arthritic disease and at least two p38 inhibitors are currently in phase II clinical trials for rheumatoid arthritis. Several other p38 inhibitors are currently undergoing phase I clinical trials.     

p38 mitogen-activated protein kinase inhibitors for the treatment of chronic cardiovascular disease

p38 Mitogen-activated protein kinase (MAPK) has been implicated in cardiovascular disease and is activated by various factors, including neurohormones (e.g., catecholamines, angiotensin II and endothelin), hypoxia and wall stress. Activation of p38 MAPK can cause cardiac hypertrophy, negative inotropy and endothelial dysfunction. All of these conditions lead to chronic cardiovascular disease, which is becoming an ever growing burden on society. p38 MAPK inhibition may therefore be an interesting therapeutic approach to the treatment of various cardiovascular diseases. However, in vitro and in vivo results are conflicting and caution must be applied in the translation of bench results to the clinic.