Mechanical pressure-induced phosphorylation of p38 mitogen-activated protein kinase in epithelial cells via Src and protein kinase C

The aim of this study was to determine the impact of lentiviral transduction on primary murine B cells. Studying B cell activities in vivo or using them for tolerance induction requires that the cells remain unaltered in their biological behavior except for expression of the transgene. As we show here, murine B cells can efficiently be transduced by lentiviral, VSV-G-pseudotyped vectors without the necessity of prior activation. Culture with LPS gave enhanced transduction efficiencies but led to the upregulation of CD86 and proliferation of the cells. Transduction of naive B cells by lentiviral vectors was dependent on multiplicity of infection and did not lead to a concomitant activation. Furthermore, the transduced cells could be used for studies in the NOD mouse system without altering the onset of diabetes. We conclude that lentiviral gene transfer into naive B cells is a powerful tool for manipulation of B cells for therapeutic applications.     

Regulation of cartilage formation and maturation by mitogen-activated protein kinase signaling

The majority of bones comprising the adult vertebrate skeleton are generated from hyaline cartilage templates that form during embryonic development. A process known as endochondral ossification is responsible for the conversion of these transient cartilage anlagen into mature, calcified bone. Endochondral ossification is a highly regulated, multistep cell specification program involving the initial differentiation of prechondrogenic mesenchymal cells into hyaline chondrocytes, terminal differentiation of hyaline chondrocytes into hypertrophic chondrocytes, and finally, apoptosis of hypertrophic chondrocytes followed by bone matrix deposition. Recently, extensive research has been carried out describing roles for the three major mitogen-activated protein kinase (MAPK) signaling pathways, the extracellular signal-regulated kinase 1/2 (ERK1/2), p38, and c-jun N-terminal kinase (JNK) pathways, in the successive stages of chondrogenic differentiation. In this review, we survey this research examining the involvement of ERK1/2, p38, and JNK pathway signaling in all aspects of the chondrogenic differentiation program from embryonic through postnatal stages of development. In addition, we summarize evidence from in vitro studies examining MAPK function in immortalized chondrogenic cell lines and adult mesenchymal stem cells. We also provide suggestions for future studies that may help ameliorate existing confusion concerning the specific roles of MAPK signaling at different stages of chondrogenesis.     

Endothelin-1 activates p38 mitogen-activated protein kinase via endothelin-A receptor in rat myocardial cells

In myocardial cells (MCs), endothelin-1 (ET-1) exerts various effects such as hypertrophy, and causes cellular injury. Long-term treatment with an endothelin-A (ET_A) receptor antagonist improves the survival of rats with heart failure, suggesting that myocardial endothelin system contributes to the progression of heart failure. p38 mitogen-activated kinase (MAPK) is a member of the MAPK family and activated by several forms of environmental stresses. We show here the effect of ET-1 on p38 MAPK activation and the role of ET-1-activated p38 MAPK on morphological changes in MCs. ET-1-stimulated p38 MAPK phosphorylation was detectable within 2 min and maximal at 5 min and was concentration dependent. The maximum effect was obtained at 10 nM. An ET_A receptor antagonist, BQ-123, but not an endothelin-B receptor antagonist, BQ-788, inhibited these reactions. A p38 MAPK inhibitor, SB203580, failed to inhibit the morphological changes associated with ET-1-induced myocardial cell hypertrophy. These results indicate that p38 MAPK is activated by ET-1 but does not contribute to the development of ET-1-induced myocardial cell hypertrophy.     

皮质酮快速激活PC12细胞中p38丝列原激活的蛋白激酶

实验旨在研究糖皮质激素快速、非基因组作用的细胞内信号传导机制。Western分析研究结果表明,皮质酮可快速激活PC12细胞中p38丝列原激活的蛋白激酶（mitogen-activated protein kinase,MAPK）,时间、浓度曲线均为钟形,最大激活为10^-9mol/L和15min。糖皮质激素受体阻断剂RU38486不能阻断此作用,而小牛血清白蛋白耦联的皮质酮也能快速激活p38。受体酪氨酸激酶阻断剂genistein对此作用无影响,表明此快速作用不涉及受体酪氨酸激酶活性。此作用能被蛋白激酶C（protein kinase C,PKC）激动剂PMA模拟,而被PKC阻断剂Goe6976所阻断。结果表明,皮质酮可能通过推测的膜受体以PKC依赖的方式快速激活p38 MAPK。     

p38 mitogen-activated protein kinase (MAPK) promotes cholesterol ester accumulation in macrophages through inhibition of macroautophagy

p38 MAPK has been strongly implicated in the development of atherosclerosis, but its role in cholesterol ester accumulation in macrophages and formation of foam cells, an early step in the development of atherosclerosis, has not been investigated. We addressed this issue and made some brand new observations. First, elevated intracellular cholesterol level induced by the exposure to LDL-activated p38 MAPK and activation of p38 MAPK with anisomycin increased the ratio of cholesterol esters over free cholesterol, whereas inhibition of p38 MAPK with SB203580 or siRNA reduced the LDL loading-induced intracellular accumulation of free cholesterol and cholesterol esters in macrophages. Second, exposure to LDL cholesterol inhibited autophagy in macrophages, and inhibition of autophagy with 3-methyladenine increased intracellular accumulation of cholesterol (free cholesterol and cholesterol esters), whereas activation of autophagy with rapamycin decreased intracellular accumulation of free cholesterol and cholesterol esters induced by the exposure to LDL cholesterol. Third, LDL cholesterol loading-induced inhibition of autophagy was prevented by blockade of p38 MAPK with SB203580 or siRNA. Neutral cholesterol ester hydrolase was co-localized with autophagosomes. Finally, LDL cholesterol loading and p38 activation suppressed expression of the key autophagy gene, ulk1, in macrophages. Together, our results provide brand new insight about cholesterol ester accumulation in macrophages and foam cell formation.     

Involvement of p38 mitogen-activated protein kinase in gemcitabine-induced apoptosis in human pancreatic cancer cells

In this study, we investigated the involvement of Akt and members of the mitogen-activated protein kinase (MAPK) superfamily, including ERK, JNK, and p38 MAPK, in gemcitabine-induced cytotoxicity in human pancreatic cancer cells. We found that gemcitabine induces apoptosis in PK-1 and PCI-43 human pancreatic cancer cell lines. Gemcitabine specifically activated p38 MAPK in a dose- and time-dependent manner. A selective p38 MAPK inhibitor, SB203580, significantly inhibited gemcitabine-induced apoptosis in both cell lines, suggesting that phosphorylation of p38 MAPK may play a key role in gemcitabine-induced apoptosis in pancreatic cancer cells. A selective JNK inhibitor, SP600125, failed to inhibit gemcitabine-induced apoptosis in both cell lines. MKK3/6, an upstream activator of p38 MAPK, was phosphorylated by gemcitabine, indicating that the MKK3/6-p38 MAPK signaling pathway is indeed involved in gemcitabine-induced apoptosis. Furthermore, gemcitabine-induced cleavage of the caspase substrate poly(ADP-ribose) polymerase was inhibited by pretreatment with SB203580, suggesting that activation of p38 MAPK by gemcitabine induces apoptosis through caspase signaling. These results together suggest that gemcitabine-induced apoptosis in human pancreatic cancer cells is mediated by the MKK3/6-p38 MAPK-caspase signaling pathway. Further, these results lead us to suggest that p38 MAPK should be investigated as a novel molecular target for human pancreatic cancer therapies.     

Postconditioning attenuates cardiomyocyte apoptosis via inhibition of JNK and p38 mitogen-activated protein kinase signaling pathways

A sequence of intermittent interruptions of oxygen supply (i.e., postconditioning, Postcon) at reoxygenation reduces oxidant-induced cardiomyocyte loss. This study tested the hypothesis that prevention of cardiomyocyte apoptosis by Postcon is mediated by mitogen-activated protein kinases pathways. Primary cultured neonatal rat cardiomyocytes were exposed to 3 h hypoxia followed by 6 h of reoxygenation. Cardiomyocytes were postconditioned by three cycles each of 5 min reoxygenation and 5 min hypoxia after prolonged hypoxia. Relative to hypoxia alone, reoxygenation stimulated expression of JNKs and p38 kinases, corresponding to increased activity of JNKs (phospho-c-Jun) and p38 (phospho-ATF2). The level of TNFα in cell lysates, activity of cytosolic caspases-8, -3, expression of Bax and the number of apoptotic cardiomyocytes were increased while expression of Bcl-2 was decreased with reoxygenation. Consistent with an attenuation in generation of superoxide anions detected by lucigenin-enhanced chemiluminescence at early period of reoxygenation, treatment of cardiomyocytes with Postcon further reduced expression and activity of JNKs and p38 kinases, level of TNFα, the frequency of apoptotic cells and expression of Bax. However, the inhibitory effects of Postcon on these changes were lost when its application was delayed by 5 min after the start of reoxygenation. Addition of a JNK/p38 stimulator, anisomycin into cardiomyocytes at the beginning of reoxygenation eliminated protection by Postcon. These data suggest that 1) hypoxia/reoxygenation elicits cardiomyocyte apoptosis in conjunction with expression and activation of JNK and p38 kinases, release of TNFα, activation of caspases, and an increase in imbalance of pro-/anti-apoptotic proteins; 2) Postcon attenuates cardiomyocyte apoptosis, potentially mediated by inhibiting JNKs/p-38 signaling pathways and reducing TNFα release and caspase expression.     

Following in vitro activation of mitogen-activated protein kinases by mass spectrometry and tryptic peptide analysis: purifying fully activated p38 mitogen-activated protein kinase alpha

p38 mitogen-activated protein kinase alpha (MAPKalpha) belongs to the MAPK subfamily, which plays a pivotal role in cell signal transduction, where it mediates responses to cell stresses and, to a lesser extent, growth factors. Although its cellular function has been under intense scrutiny since its initial discovery, little progress has been made in understanding its kinetic mechanism. A contributory factor has been the lack of a fast and rigorous method for the purification of activated p38 MAPKalpha in sufficient quantity and purity for biophysical studies. Here we present a method for the preparation of milligram quantities of activated p38 MAPKalpha, specifically phosphorylated on Thr180 and Tyr182. Purification of the inactive (unphosphorylated) p38 MAPKalpha is facilitated by an N-terminal hexahistidine tag. Removal of this tag from His6-p38 MAPKalpha, prior to its activation, is essential to ensure preparation of high yields of homogeneous, dually phosphorylated enzyme. Activation is achieved on incubation with a glutathione S-transferase (GST) fusion of the constitutively active mutant of the upstream activator, MKK6b (GST-MKK6b S207E T211E), in the presence of MgATP2-. Notably, we show that specific formation of activated p38 MAPKalpha can be quantified by following the formation of the bis-phosphorylated tryptic peptide, 173-HTDDEMT*GY*VATR-186, using [gamma-32P]adenosine triphosphate (ATP) as the phosphate source and reverse-phase high-performance liquid chromatography (HPLC) to separate the phosphopeptides. This approach offers the only means to specifically determine both stoichiometry and specificity of p38 MAPKalpha phosphorylation.     

Calpain-2 protects against heat stress-induced cardiomyocyte apoptosis and heart dysfunction by blocking p38 mitogen-activated protein kinase activation

Cardiovascular dysfunction is a common complication among heatstroke patients, but its underlying mechanism is unclear. This study was designed to investigate the role of calpain-2 and its downstream signal pathway in heat stress-induced cardiomyocyte apoptosis and heart dysfunction. In cultured primary mouse neonatal cardiomyocytes (MNCs), heat stress (43°C for 2 hr) induced a heat-shock response, as indicated by upregulated heat-shock protein 27 (HSP27) expression and cellular apoptosis, as indicated by increased caspase-3 activity, DNA fragmentation and decreased cell viability. Meanwhile, heat stress decreased calpain activity, which was accompanied by downregulated calpain-2 expression and increased phosphorylation of p38, extraceIIuIar signaI-reguIated protein kinase (ERK1/2) and c-Jun N-terminaI kinase (JNK). Calpain-2 overexpression abrogated heat stress-induced apoptosis and phosphorylation of p38 and JNK, but not of ERK1/2. Blocking only p38 prevented heat stress-induced apoptosis in MNCs. In cardiac-specific calpain-2 overexpressing transgenic mice, p38 phosphorylation and cardiomyocyte apoptosis were decreased in the heart tissue of heatstroke mice, as revealed by western blot and terminal deoxynucleotidyl transferase dUTP nick end labelling assays, respectively. M-mode echocardiography also demonstrated that calpain-2 overexpression significantly improved heatstroke-induced decreases in ventricular end-diastolic volume and cardiac output. In conclusion, our study suggests that heat stress reduces calpain-2 expression, which then activates p38, leading to cardiomyocyte apoptosis and heart dysfunction.     

五灵胶囊对LPS诱导鼠枯否细胞p38MAPK信号转导通路的影响

目的:探讨五灵胶囊对脂多糖(LPS)诱导的大鼠枯否细胞(Kupffer cells,KC)p38MAPK信号转导通路的影响。方法:分离纯化KCs,60ng/ml LPS刺激建立LPS的肝细胞损伤模型;40只SD大鼠药物处理后,分离制备含药血清。实验分为四组:空白血清组、LPS+空白血清组、含药血清Ⅰ组(10.0g/kg)+LPS、含药血清Ⅱ组(6.25g/kg)+LPS。KCs产生促炎因子(I125放免法测定TNF-α、IL-6、IL-8,比色法测定NO生成量),采用Western blot法检测ERK、p-ERK、p38、p-p38、TNF-α和STAT3的蛋白水平。结果:1、空白血清+LPS组,TNF-α、IL-6、IL-8和NO浓度明显高于空白血清组;2、同空白血清+LPS组比较,含药血清Ⅰ、Ⅱ组TNF-α、IL-6、IL-8和NO水平明显降低;3、与空白血清组比较,空白血清+LPS组能上调KCs对p-ERK、P38、p-P38、STAT3和TNF-α表达(p<0.01,p<0.05),对ERK表达无影响(p>0.05)4、同空白血清+LPS组比较,含药血清Ⅰ+LPS、含药血清Ⅱ+LPS组p-p38、S...     

Hydrogen sulfide attenuates lipopolysaccharide-induced inflammation by inhibition of p38 mitogen-activated protein kinase in microglia

The present study attempts to investigate the effect of H(2)S on lipopolysaccharide (LPS)-induced inflammation in both primary cultured microglia and immortalized murine BV-2 microglial cells. We found that exogenous application of sodium hydrosulfide (NaHS) (a H(2)S donor, 10-300 micro mol/L) attenuated LPS-stimulated nitric oxide (NO) in a concentration-dependent manner. Stimulating endogenous H(2)S production decreased LPS-stimulated NO production, whereas lowering endogenous H(2)S level increased basal NO production. Western blot analysis showed that both exogenous and endogenous H(2)S significantly attenuated the stimulatory effect of LPS on inducible nitric oxide synthase expression, which is mimicked by SB 203580, a specific p38 mitogen-activated protein kinase (MAPK) inhibitor. Exogenously applied NaHS significantly attenuated LPS-induced p38 MAPK phosphorylation in BV-2 microglial cells. Moreover, both NaHS (300 micro mol/L) and SB 203580 (1 micro mol/L) significantly attenuated LPS-induced tumor necrosis factor-alpha secretion, another inflammatory indicator. In addition, NaHS (10-300 micro mol/L) dose-dependently decreased LPS-stimulated NO production in primary cultured astrocytes, suggesting that the anti-neuroinflammatory effect of H(2)S is not specific to microglial cells alone. Taken together, H(2)S produced an anti-inflammatory effect in LPS-stimulated microglia and astrocytes, which may be due to inhibition of inducible nitric oxide synthase and p38 MAPK signaling pathways. These findings may have important implications in the treatment of neuroinflammation-related diseases.     

1,2,4-Trisubstituted imidazolinones with dual carbonic anhydrase and p38 mitogen-activated protein kinase inhibitory activity

Various 1,2,4 trisubstituted imidazolin-5-one derivatives were synthesized and evaluated for their inhibitory activity against p38 mitogen-activated protein kinase (p38MAPK) and carbonic anhydrase (CA) enzymes aiming to explore potential dual inhibitors. Results revealed that compounds 3c, 3g, 3h, 4a, 6c and 6d were the most effective derivatives against p38αMAPK (IC₅₀ = 0.14, 0.14, 0.056, 0.14, 0.13 and 0.14 μM, respectively) compared to sorafenib (IC₅₀ = 1.58 μM) as standard drug. On the other hand, compound 4a revealed the best inhibitory activity against all the tested carbonic anhydrase isoforms CA I, II, IV and IX with K_i values of 95.0, 0.83, 6.90 and 12.4 nM, respectively compared to acetazolamide with K_i values 250, 12.1, 74 and 12.8 nM, respectively. Therefore, compound 4a can be considered as a potent dual p38αMAPK/CA inhibitor.     

p38 mitogen-activated protein kinase plays a key role in regulating MAPKAPK2 expression

One of three major families of the mitogen-activated kinases (MAPK), p38 as well as JNK, has been shown to transduce extracellular stress stimuli into cellular responses by phospho-relay cascades. Among p38 families, p38alpha is a widely characterized isoform and the biological phenomena are explained by its kinase activity regulating functions of its downstream substrates. However, its specific contributions to each phenomenon are yet not fully elucidated. For better understanding of the role of MAPKs, especially p38alpha, we utilized newly established mouse fibroblast cell lines originated from a p38alpha null mouse, namely, a parental cell line without p38alpha gene locus, knockout of p38alpha (KOP), Zeosin-resistant (ZKOP), revertant of p38alpha (RKOP), and Exip revertant (EKOP). EKOP is smaller in size but grows faster than the others. Although comparable amounts of ERK and JNK are expressed in each cell line, ERK is highly phosphorylated in EKOP even in normal culture conditions. Serum stimulation after serum starvation led to ERK phosphorylation in RKOP and ZKOP, but not in EKOP as much. On the contrary, relative phosphorylation level of JNK to total JNK in response to UV was low in RKOP. And its phosphorylation as well as total JNK is slightly lower in EKOP. RKOP is less sensitive to UV irradiation as judged by the survival rate. Stress response upon UV or sorbitol stimuli, leading to mitogen activate protein kinase activated kinase 2 (MAPKAPK2) phosphorylation, was only observed in RKOP. Further experiments reveal that MAPKAPK2 expression is largely suppressed in ZKOP and EKOP. Its expression was recovered by re-introduction of p38alpha. The loss of MAPKAPK2 expression accompanied by the defect of p38alpha is confirmed in an embryonic extract prepared from p38alpha null mice. These data demonstrate that p38 signal pathway is regulated not only by phosphorylation but also by modulation of the expression of its component. Together, we have established cell lines that can be used in analyzing the functions of MAPKs, especially p38alpha, and show that p38 is indispensable for MAPKAPK2 expression.     

beta-Amyloid peptide induces formation of actin stress fibers through p38 mitogen-activated protein kinase

Based on the critical role of actin in the maintenance of synaptic function, we examined whether expression of familial beta-amyloid precursor protein APP-V642I (IAPP) or mutant presenilin-1 L286V (mPS1) affects actin polymerization in rat septal neuronal cells. Expression of either IAPP or mPS1 but not wild-type amyloid precursor protein or presenilin-1induced formation of actin stress fibers in SN1 cells, a septal neuronal cell line. Treatment with beta-amyloid (Abeta) peptide also caused formation of actin stress fibers in SN1 cells and primary cultured hippocampal neurons. Treatment with a gamma-secretase inhibitor completely blocked formation of actin stress fibers, indicating that overproduction of Abeta peptide induces actin stress fibers. Because activation of the p38 mitogen-activated protein kinase (p38MAPK)-mitogen-associated protein kinase-associated protein kinase (MAPKAPK)-2-heat-shock protein 27 signaling pathway mediates actin polymerization, we explored whether Abeta peptide activates p38MAPK and MAPKAPK-2. Expression of IAPP or mPS1 induced activation of p38MAPK and MAPKAPK-2. Treatment with a p38MAPK inhibitor completely inhibited formation of actin stress fibers mediated by Abeta peptide, IAPP or mPS1. Moreover, treatment with a gamma-secretase inhibitor completely blocked activation of p38MAPK and MAPKAPK-2. In summary, our data suggest that overproduction of Abeta peptide induces formation of actin stress fibers through activation of the p38MAPK signaling pathway in septal neuronal cells.     

Cocaine up-regulation of the norepinephrine transporter requires threonine 30 phosphorylation by p38 mitogen-activated protein kinase

The norepinephrine (NE) transporter (NET) regulates NE signaling by rapidly clearing synaptic NE. Cocaine binds NET and modulates NE transport. These actions contribute to rewarding effects and abuse liability of cocaine. Activation of mitogen-activated protein kinase (MAPK) cascades is implicated in cocaine-induced neuroadaptations. However, the role of MAPK and the mechanisms involved in cocaine modulation of NET are not clear. Acute intra-peritoneal injections of cocaine (20 mg/kg body weight) to rats resulted in increased NE uptake by prefrontal cortex (PFC) synaptosomes with a parallel increase in the surface expression of endogenous NET. Cocaine also enhanced the immunoreactivity of phospho-p38 MAPK in the PFC synaptosomes without affecting the total p38 MAPK. In vitro cocaine (30-50 μM) treatment of rat PFC synaptosomes increased native NET function, surface expression, and phosphorylation in a manner sensitive to p38 MAPK inhibition by PD169316. We next examined cocaine-elicited effects on wild-type human NET (hNET) expressed heterologously in human placental trophoblast cells to gain more insights into the mechanisms involved. Cocaine treatment of hNET expressing human placental trophoblast cells up-regulated the function, surface expression, and phosphorylation of hNET in a PD169316-sensitive manner. In addition, cocaine inhibited constitutive endocytosis of hNET. Mutational analysis of serine and threonine residues revealed that substitution of threonine 30, located at the amino terminus of hNET with alanine (T30A-hNET), abolished cocaine-induced up-regulation of NET function, surface expression, and phosphorylation. Furthermore, cocaine did not alter T30A-hNET endocytosis. These studies identify a novel molecular mechanism that cocaine-activated p38 MAPK-mediated phosphorylation of NET-T30 dictates surface NET availability, and hence, NE transport.