Brainstem adenosine A1 receptor signaling masks phosphorylated extracellular signal-regulated kinase 1/2-dependent hypotensive action of clonidine in conscious normotensive rats

Central adenosine A(1) and A(2A) receptors mediate pressor and depressor responses, respectively. The adenosine subtype A(2A) receptor (A(2A)R)-evoked enhancement of phosphorylated extracellular signal-regulated kinase (pERK) 1/2 production in the rostral ventrolateral medulla (RVLM), a major neuroanatomical target for clonidine, contributes to clonidine-evoked hypotension, which is evident in conscious aortic barodenervated (ABD) but not in conscious sham-operated (SO) normotensive rats. We conducted pharmacological and cellular studies to test the hypothesis that the adenosine A(2A)R-mediated (pERK1/2-dependent) hypotensive action of clonidine is not expressed in SO rats because it is counterbalanced by fully functional central adenosine subtype A(1) receptor (A(1)R) signaling. We first demonstrated an inverse relationship between A(1)R expression in RVLM and clonidine-evoked hypotension in ABD and SO rats. The functional (pharmacological) relevance of the reduced expression of RVLM A(1)R in ABD rats was verified by the smaller dose-dependent pressor responses elicited by the selective A(1)R agonist N(6)-cyclopentyladenosine in ABD versus SO rats. It is important that after selective blockade of central A(1)R with 8-cyclopentyl-1,3-dipropylxanthine in conscious SO rats, clonidine lowered blood pressure and significantly increased neuronal pERK1/2 in the RVLM. In contrast, central A(1)R blockade had no influence on the hypotensive response or the increase in RVLM pERK1/2 elicited by clonidine in ABD rats. These findings support the hypothesis that central adenosine A(1)R signaling opposes the adenosine A(2A)R-mediated (pERK1/2-dependent) hypotensive response and yield insight into a cellular mechanism that explains the absence of clonidine-evoked hypotension in conscious normotensive rats.     

Brainstem phosphorylated extracellular signal-regulated kinase 1/2-nitric-oxide synthase signaling mediates the adenosine A2A-dependent hypotensive action of clonidine in conscious aortic barodenervated rats

The cellular mechanisms that underlie the enhancement of clonidine-evoked hypotension in aortic barodenervated (ABD) rats and its dependence on central adenosine A(2A) receptor (A(2A)R) are not known. We tested the hypothesis that A(2A)R-mediated phosphorylation of extracellular signal-regulated kinase (pERK)1/2 in the rostral ventrolateral medulla (RVLM) and its downstream activation of nitric-oxide synthase (NOS)-NO signaling underlie the centrally (clonidine)-mediated hypotension. We first demonstrated an up-regulation of the molecular targets for clonidine [imidazoline I(1) and alpha(2A) adrenergic receptors (alpha(2A)R)] in the RVLM of ABD compared with sham-operated (SO) rats; this finding might explain the enhanced clonidine hypotension in ABD rats. A similar anatomical up-regulation of the RVLM A(2A)R was evident and was complemented with enhanced central A(2A)R [2-[4-[(2-carboxyethyl)phenyl]ethylamino]-5'-N-ethylcarboxamidoadenosine; CGS21680]-mediated hypotension in ABD rats. The hypotension produced by intracisternal CGS21680 or clonidine, in conscious ABD rats, was associated with a significant increase in pERK1/2 level in the RVLM. Whereas selective A(2A)R blockade [5-amino-7-(2-phenylethyl)-2-(2-furyl)-pyrazolo[4,3-epsilon]-1,2,4-triazolo[1,5-c]pyrimidine; SCH58261] or NOS inhibition (N(omega)-nitro-l-arginine methyl ester) virtually abolished clonidine-evoked hypotension, clonidine-evoked enhancement of RVLM pERK1/2 production was only abrogated by SCH58261 pretreatment. These findings suggest that interventions that act centrally to increase RVLM neuronal pERK1/2 production elicit hypotension via the activation of downstream NOS-NO signaling. The findings also yield insight into a cellular mechanism that might explain the dependence of centrally (clonidine)-mediated hypotension on central A(2A)R signaling in the ABD rat.     

Sulindac independently modulates extracellular signal-regulated kinase 1/2 and cyclic GMP-dependent protein kinase signaling pathways

Colorectal cancer is the second leading cause of cancer mortality in the United States. Substantial human and animal data support the ability of nonsteroidal anti-inflammatory drugs to cause regression of existing colon tumors and prevent new tumor formation. The mechanism by which the nonsteroidal anti-inflammatory drug sulindac prevents tumor growth is poorly understood and seems complex as sulindac can modulate several growth-related signaling pathways. Sulindac metabolites simultaneously (a) increase cellular cyclic GMP and subsequently activate cyclic GMP-dependent protein kinase (PKG); (b) activate c-jun NH2-terminal kinase (JNK); (c) inhibit extracellular signal-regulated kinase 1/2 (ERK1/2); and (d) decrease beta-catenin protein expression at times and doses consistent with apoptosis. The purpose of this study was to determine if PKG, ERK1/2, JNK, and beta-catenin are independent targets for sulindac in vitro. Pharmacologic activation of PKG with YC-1 increases JNK phosphorylation and induces apoptosis in colon cancer cells without modulating ERK1/2 phosphorylation or beta-catenin protein expression. Inhibition of ERK1/2 with U0126 induces apoptosis but fails to activate JNK phosphorylation or down-regulate beta-catenin protein expression. Cotreatment with U0126 and YC-1 synergistically increases apoptosis in colorectal cancer cells and recapitulates the effects of sulindac treatment on ERK1/2, JNK, and beta-catenin. These results indicate that sulindac metabolites modulate ERK1/2 and PKG pathways independently in colon cancer cells and suggest that the full apoptotic effect of sulindac is mediated by more than one pathway. Using similar combinatorial approaches in vivo may provide more effective, less toxic chemopreventive and chemotherapeutic strategies. Such therapies could dramatically reduce the incidence and death rate from colorectal cancer.     

Lithium protection of phencyclidine-induced neurotoxicity in developing brain: the role of phosphatidylinositol-3 kinase/Akt and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase signaling pathways

Phencyclidine (PCP) and other N-methyl-D-aspartate (NMDA) receptor antagonists have been shown to be neurotoxic to developing brains and to result in schizophrenia-like behaviors later in development. Prevention of both effects by antischizophrenic drugs suggests the validity of PCP neurodevelopmental toxicity as a heuristic model of schizophrenia. Lithium is used for the treatment of bipolar and schizoaffective disorders and has recently been shown to have neuroprotective properties. The present study used organotypic corticostriatal slices taken from postnatal day 2 rat pups to investigate the protective effect of lithium and the role of the phosphatidylinositol-3 kinase (PI-3K)/Akt and mitogen-activated protein kinase kinase/extracellular signal-regulated kinase (MEK/ERK) pathways in PCP-induced cell death. Lithium pretreatment dose-dependently reduced PCP-induced caspase-3 activation and DNA fragmentation in layers II to IV of the cortex. PCP elicited time-dependent inhibition of the MEK/ERK and PI-3K/Akt pathways, as indicated by dephosphorylation of ERK1/2 and Akt. The proapoptotic factor glycogen synthase kinase (GSK)-3beta was also dephosphorylated at serine 9 and thus activated. Lithium prevented PCP-induced inhibition of the two pathways and activation of GSK-3beta. Furthermore, blocking either PI-3K/Akt or MEK/ERK pathway abolished the protective effect of lithium, whereas inhibiting GSK-3beta activity mimicked the protective effect of lithium. However, no cross-talk between the two pathways was found. Finally, specific GSK-3beta inhibition did not prevent PCP-induced dephosphorylation of Akt and ERK. These data strongly suggest that the protective effect of lithium against PCP-induced neuroapoptosis is mediated through independent stimulation of the PI-3K/Akt and ERK pathways and suppression of GSK-3beta activity.     

Arachidonic acid epoxygenase metabolites stimulate endothelial cell growth and angiogenesis via mitogen-activated protein kinase and phosphatidylinositol 3-kinase/Akt signaling pathways

Cytochrome P450 arachidonic acid (AA) epoxygenase metabolites, the epoxyeicosatrienoic acids (EETs), dilate arteries via hyperpolarization of smooth muscle cells and also have nonvasodilatory effects within the vasculature. The present study investigated the angiogenic effects of endogenous and exogenous EETs and the relevant signaling mechanisms involved. Bovine aortic endothelial cells (BAECs) were incubated with synthetic EETs or infected with recombinant adeno-associated viruses (rAAVs) containing CYP2C11-NADPH-cytochrome P450 oxidoreductase (CYPOR), CYP2J2, or CYP102 F87V mutant to increase endogenous levels of EETs. The following endpoints were measured: BAEC proliferation, migration, capillary formation, and in vivo angiogenesis. The potential involvement of various signaling pathways was explored using selective inhibitors. The results showed that transfection with either rAAV-CYP2C11-CYPOR, rAAV-CYP2J2, or rAAV-CYP102 F87V, or incubation with EETs promoted BAEC proliferation, increased migration of BAECs as assessed by Transwell analysis and wound healing assays, and enhanced capillary tubule formation as determined by chicken embryo chorioallantoic membrane assays and tube formation tests on matrigel. The effects of EETs on proliferation, migration, and capillary tubule formation were attenuated by inhibitors of mitogen-activated protein kinase (MAPK) and phosphatidylinositol 3 (PI3)-kinase/Akt pathways and partially attenuated by an endothelial nitric-oxide synthase (eNOS) inhibitor but not by a protein kinase C inhibitor. In a rat ischemic hind limb model, rAAV-mediated AA epoxygenase transfection induced angiogenesis. We conclude that AA epoxygenase metabolites can promote angiogenesis, which may provide protection to ischemic tissues. The results also suggest that the angiogenic effects of EETs involve the MAPK and PI3-kinase/Akt signaling pathways, and to some extent, the eNOS pathway.     

Activation of phosphatidylinositol 3-kinase/Akt signaling pathway mediates acquired resistance to sorafenib in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is one of the most common potentially lethal human malignancies worldwide. Sorafenib, a tyrosine kinase inhibitor, was recently approved by the United States Food and Drug Administration for HCC. In this study, we established two sorafenib-resistant HCC cell lines from Huh7, a human HCC cell line, by long-term exposure of cells to sorafenib. Sorafenib induced significant apoptosis in Huh7 cells; however, Huh7-R1 and Huh7-R2 showed significant resistance to sorafenib-induced apoptosis at the clinical relevant concentrations (up to 10 μM). Thorough comparisons of the molecular changes between Huh7 and resistant cells showed that the phosphatidylinositol 3-kinase (PI3K)/Akt signaling pathway played a significant role in mediating acquired resistance to sorafenib in Huh7-R1 and Huh7-R2 cells. Phospho-Akt and p85 (a regulatory subunit of PI3K) were up-regulated, whereas tumor suppressor phosphatase and tensin homolog were down-regulated in these resistant cells. In addition, ectopic expression of constitutive Akt in Huh7 demonstrated similar resistance to sorafenib. The knockdown of Akt by RNA interference reversed resistance to sorafenib in Huh7-R1 cells, indicating the importance of Akt in drug sensitivity. Furthermore, the combination of 8-[4-(1-aminocyclobutyl)phenyl]-9-phenyl-1,2,4-triazolo[3,4-f][1,6]naphthyridin-3(2H)-one dihydrochloride (MK-2206), a novel allosteric Akt inhibitor, and sorafenib restored the sensitivity of resistant cells to sorafenib-induced apoptosis. In conclusion, activation of PI3K/Akt signaling pathway mediates acquired resistance to sorafenib in HCC, and the combination of sorafenib and MK-2206, an Akt inhibitor, overcomes the resistance at clinical achievable concentrations.     

依达拉奉对大鼠重型弥漫性脑创伤后细胞外信号调节激酶1/2信号通路的影响

目的 探讨依达拉奉对重型弥漫性脑创伤(TBI)的保护作用及其机制.方法 273只雄性SD大鼠按随机数字表法分为对照组(45只)、模型组(88只)及依达拉奉低剂量组(72只)、高剂量组(68只).采用重物撞击致大鼠TBI模型.伤后1、6、24、48和72 h,在光镜和电镜下观察脑组织病理变化;用蛋白质免疫印迹法(Western blotting)检测磷酸化细胞外信号调节激酶1/2(ERK1/2)表达;用免疫组化法和原位末端缺刻标记法(TUNEL)检测神经细胞凋亡情况.伤后7～10 d应用水迷宫对大鼠学习记忆能力进行评定.结果 与对照组比较,伤后6、24、48、72 h海马区部分神经细胞出现变性、坏死,1、6、24、48 h磷酸化ERK1/2表达水平(pg/U)显著增高(分别为:2.05±0.40、4.40±0.96、6.70±0.87、3.67±0.28比0.40±0.04、0.41±0.05、0.43±0.06、0.40±0.03),6、24、48、72 h神经细胞凋亡数(个)明显增多(分别为:9.60±2.69、12.68±2.99、16.94±3.92、25.82±4.61比2.42±0.38、2.58±0.57、2.74±0.56、2.61±0.58),7～10 d大鼠搜索安全岛潜伏期(s)延长(分别为:119.8±25.0、105.6±24.5、98.5±21.8、92.0±19.5比49.5±7.5、32.7±6.3、25.8±6.5、24.8±5.5,均P<0.05).应用依达拉奉干预后,脑组织损伤程度、磷酸化ERK1/2表达水平降低,神经细胞凋亡数回降,大鼠搜索安全岛潜伏期缩短(依达拉奉低剂量组磷酸化ERK1/2表达6、24、48 h分别为:2.46±0.22、4.00±0.84、2.38±0.32,高剂量组分别为:1.67±0.15、1.86±0.38、1.27±0.28;依达拉奉低剂量组凋亡细胞数6、24、48、72 h分别为:5.20±1.23、7.10±1.72、9.54±1.36、14.12±3.19,高剂量组分别为:3.40±0.49、4.39±0.73、5.02±1.12、8.78±2.16;依达拉奉低剂量组潜伏期7～10 d分别为:94.8±22.8、65.2±19.0、62.0±16.7、59.5±15.6,高剂量组分别为:81.5±20.7、55.4±18.5、40.0±12.3、32.2±11.0,均P<0.05);其中依达拉奉高剂量更为显著(均P<0.05).结论 依达拉奉对TBI有保护作用,其机制与对伤后ERK1/2、神经细胞凋亡通路的调控有关.     

Proline 326 in the C terminus of murine CX3CR1 prevents G-protein and phosphatidylinositol 3-kinase-dependent stimulation of Akt and extracellular signal-regulated kinase in Chinese hamster ovary cells

Naturally occurring single nucleotide polymorphisms have been identified in human CX3CR1, the chemokine receptor for fractalkine (FKN/CX3CL1). Individuals carrying the I249/M280 variant of CX3CR1 have a lower risk of cardiovascular disease compared with those homozygous for the common variant (V249/T280). The precise molecular basis for this phenotype is unclear, although differences in FKN binding, adhesive properties, and signaling efficiency between the CX3CR1 variants have been reported. FKN binding to CX3CR1 leads to an increase in intracellular calcium, actin rearrangement, and activation of the mitogen-activated protein kinase and phosphoinositide 3-kinase (PI3K) pathways. Regulation of these signaling pathways underlies the known roles for FKN in cell survival, proliferation, and migration. In the present study, we demonstrate that FKN stimulates phosphorylation of protein kinase B (Akt/PKB) in Chinese hamster ovary cells individually expressing the naturally occurring variants of human CX3CR1-, as well as rat CX3CR1-, but not in murine CX3CR1-expressing cells. Substitution of Pro326 in the C terminus of murine CX3CR1 with Ser (residue found in the analogous position of human CX3CR1) produced a mutant receptor that mimicked the human receptor in its ability to stimulate the phosphorylation of both Akt and extracellular signal-regulated kinase in a time-, PI3K-, and pertussis toxin-sensitive G-protein-dependent manner. These results identify a critical structural determinant of CX3CR1 important for activation of downstream signaling pathways.     

Insulin activation of the phosphatidylinositol 3-kinase/protein kinase B (Akt) pathway reduces lipopolysaccharide-induced inflammation in mice

Insulin is used to control pro-inflammatory hyperglycemia in critically ill patients. However, recent studies suggest that insulin-induced hypoglycemia may negate its beneficial effects in these patients. It is noteworthy that recent evidence indicates that insulin has anti-inflammatory effects that are independent of controlling hyperglycemia. To date, the mechanism by which insulin directly reduces inflammation has not been elucidated. It is well established that insulin activates phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) signaling in many cell types. We and others have shown that this pathway negatively regulates LPS-induced signaling and pro-inflammatory cytokine production in monocytic cells. We hypothesized that insulin inhibits inflammation during endotoxemia by activation of the PI3K/Akt pathway. We used a nonhyperglycemic mouse model of endotoxemia to determine the effect of continuous administration of a low dose of human insulin on inflammation and survival. It is noteworthy that insulin treatment induced phosphorylation of Akt in muscle and adipose tissues but did not exacerbate lipopolysaccharide (LPS)-induced hypoglycemia. Insulin decreased plasma levels of interleukin-6, tumor necrosis factor-alpha, monocyte chemotactic protein 1 (MCP1)/JE, and keratinocyte chemoattractant, and decreased mortality. The PI3K inhibitor wortmannin abolished the insulin-mediated activation of Akt and the reduction of chemokine and interleukin-6 levels. We conclude that insulin reduces LPS-induced inflammation in mice in a PI3K/Akt-dependent manner without affecting blood glucose levels.     

Combined inhibition of the phosphatidylinositol 3-kinase/Akt and Ras/mitogen-activated protein kinase pathways results in synergistic effects in glioblastoma cells

The present study uses cell-based screening assays to assess the anticancer effects of targeting phosphatidylinositol 3-kinase-regulated integrin-linked kinase (ILK) in combination with small-molecule inhibitors of Raf-1 or mitogen-activated protein kinase (MAPK)/extracellular signal-regulated kinase kinase (MEK). The objective was to determine if synergistic interactions are achievable through the use of agents targeting two key cell signaling pathways involved in regulating glioblastoma cancer. The phosphatidylinositol 3-kinase/protein kinase B (PKB)/Akt and the Ras/MAPK pathway were targeted for their involvement in cell survival and cell proliferation, respectively. The glioblastoma cell lines U87MG, SF-188, and U251MG were transiently transfected with an antisense oligonucleotide targeting ILK (ILKAS) alone or in combination with the Raf-1 inhibitor GW5074 or with the MEK inhibitor U0126. Dose and combination effects were analyzed by the Chou and Talalay median-effect method and indicated that combinations targeting ILK with either Raf-1 or MEK resulted in a synergistic interaction. Glioblastoma cells transfected with ILKAS exhibited reduced levels of ILK and phosphorylated PKB/Akt on Ser473 but not PKB/Akt on Thr308 as shown by immunoblot analysis. These results were confirmed using glioblastoma cells transfected with ILK small interfering RNA, which also suggested enhanced gene silencing when used in combination with U0126. U87MG glioblastoma cells showed a 90% (P < 0.05) reduction in colony formation in soft agar with exposure to ILKAS in combination with GW5074 compared with control colonies. A substantial increase in Annexin V-positive cells as determined by using fluorescence-activated cell sorting methods were seen in combinations that included ILKAS. Combinations targeting ILK and components of the Ras/MAPK pathway result in synergy and could potentially be more effective against glioblastoma cancer than monotherapy.     

狼疮肾炎外周血单个核细胞MAPKERK1/2信号通路活化的观察

目的目的观察有丝分裂原激活的蛋白激酶-细胞外调节激酶（MAPK^ERK1/2）细胞信号通路在系统性红斑狼疮（SLE）并肾炎（LN）患者外周血单个核细胞（PBMC）活化状态，探讨MAPK^ERK1/2通路在LN患者免疫异常中的作用及临床意义。方法26例LN患者和21例正常健康对照者进入研究，取外周血分离PBMC进行体外培养，利用蛋白印迹法（Western Blot）测定PBMC MAPK^ERK1/2蛋白磷酸化活化水平，比较LN与正常对照PBMC MAPK^ERK1/2活化水平的差异，并分析MAPK^ERK1/2。以活化水平与临床狼疮疾病活动的关系。结果LN患者PBMC中MAPK^ERK1/2信号通路呈高度活化状态，与正常健康对照有显著性差异（P〈0．05）；MAPK^ERK1/2蛋白磷酸化活化水平与狼疮疾病活动评分（SLEDAI）、血清抗双链DNA抗体呈正相关关系（P〈0．06）。结论LN患者PBMC MAPK^ERK1/2以信号通路异常活化，并与临床狼疮疾病活动密切相关。     

Effects of protein kinase C modulation by PEP005, a novel ingenol angelate, on mitogen-activated protein kinase and phosphatidylinositol 3-kinase signaling in cancer cells

PEP005 (ingenol-3-angelate) is a novel anticancer agent extracted from Euphorbia peplus that was previously shown to modulate protein kinase C (PKC), resulting in antiproliferative and proapoptotic effects in several human cancer cell lines. In Colo205 colon cancer cells, exposure to PEP005 induced a time- and concentration-dependent decrease of cells in S phase of cell cycle and apoptosis. In Colo205 cells exposed to PEP005, a variety of signaling pathways were activated as shown by increased phosphorylation of PKCdelta, Raf1, extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase (MAPK), c-Jun NH(2)-terminal kinase, p38 MAPK, and PTEN. PEP005-induced activation of PKCdelta was associated with its translocation from the cytosol to the nucleus and other cellular membranes. Interestingly, PEP005 treatment also resulted in reduced expression of PKCalpha and reduced levels of phosphorylated active form of AKT/protein kinase B. These data suggest that PEP005-induced activation of PKCdelta and reduced expression of PKCalpha resulted in apoptosis by mechanisms mediated by activation of Ras/Raf/MAPK and inhibition of the phosphatidylinositol 3-kinase/AKT signaling pathways. This study supports ongoing efforts targeting PKC isoforms in cancer therapy with PEP005 alone and in combination with other cytotoxic agents.     

Enhancement of rostral ventrolateral medulla neuronal nitric-oxide synthase-nitric-oxide signaling mediates the central cannabinoid receptor 1-evoked pressor response in conscious rats

Our recent studies implicated brainstem GABAergic signaling in the central cannabinoid receptor 1 (CB(1)R)-mediated pressor response in conscious rats. Given the well established link between neuronal nitric-oxide synthase (nNOS)/nitric oxide (NO) signaling and GABAergic transmission in brainstem cardiovascular regulating areas, we elucidated the role of nNOS-generated NO in the central CB(1)R-elicited pressor response. Compared with vehicle, intracisternal (i.c.) microinjection of the CB(1)R agonist (R)-(+)-[2,3-dihydro-5-methyl-3[(4-morpholinyl)methyl]pyrrolo[1,2,3-de]-1,4-benzoxazinyl]-(1-naphthalenyl) methanone mesylate (WIN55212-2) (15 μg/rat) significantly enhanced nNOS phosphorylation as well as the total nitrate and nitrite content in the rostral ventrolateral medulla (RVLM) at 5, 10, and 30 min, which paralleled the elicited pressor response. These findings were corroborated by: 1) the parallel dose-related increases in blood pressure and RVLM-NO levels, measured in real time by in vivo electrochemistry, elicited by intra-RVLM WIN55212-2 (100, 200, or 300 pmol /80 nl; n = 5) in conscious rats; and 2) the significantly higher phosphorylated nNOS (p-nNOS) levels in the WIN55212-2-injected RVLM compared with the contralateral RVLM. Subsequent neurochemical studies showed that WIN55212-2 (15 μg/rat i.c.) significantly increased the number and percentage of neurons immunostained for nNOS (nitroxidergic neurons) and c-Fos (marker of neuronal activity) within the RVLM. The increases in blood pressure and the neurochemical responses elicited by intracisternal WIN55212-2 were attenuated by prior central CB(1)R blockade by N-(piperidin-1-yl)-5-(4-iodophenyl)-1-(2,4-dichlorophenyl)-4-methyl-1H-pyrazole-3-carboxamide (AM251; 30 μg/rat i.c.) or selective nNOS inhibition by N(ω)-propyl-(L)-arginine (1 μg/rat i.c.). These findings implicate RVLM p-nNOS/NO signaling as a molecular mechanism in the central CB(1)R-evoked pressor effect in conscious rats.     

Resveratrol-caused apoptosis of human prostate carcinoma LNCaP cells is mediated via modulation of phosphatidylinositol 3'-kinase/Akt pathway and Bcl-2 family proteins

Prostate cancer is a major health problem in the U.S. and the available treatment and surgical options have proven to be inadequate in controlling the mortality and morbidity associated with this disease. It is therefore necessary to intensify our efforts to better understand this disease and develop novel approaches for its prevention and treatment. This study was conducted to evaluate the chemopreventive/antiproliferative potential of resveratrol (trans-3,4',5,-trihydroxystilbene) against prostate cancer and its mechanism of action. Treatment with resveratrol (0-50 micromol/L for 24 hours) resulted in a significant (a) decrease in cell viability, (b) decrease of clonogenic cell survival, (c) inhibition of androgen (R1881)-stimulated growth, and (d) induction of apoptosis in androgen-responsive human prostate carcinoma (LNCaP) cells. Interestingly, at similar concentrations, resveratrol treatment did not affect the viability or rate of apoptosis in normal human prostate epithelial cells. Furthermore, our data showed that resveratrol-treatment resulted in significant dose-dependent inhibition in the constitutive expression of phosphatidylinositol 3'-kinase and phosphorylated (active) Akt in LNCaP cells. Resveratrol treatment for LNCaP cells was also found to result in a significant (a) loss of mitochondrial membrane potential, (b) inhibition in the protein level of antiapoptotic Bcl-2, and (c) increase in proapoptotic members of the Bcl-2 family, i.e., Bax, Bak, Bid, and Bad. Taken together, our data suggested that resveratrol causes an inhibition of phosphatidylinositol 3'-kinase/Akt activation that, in turn, results in modulations in Bcl-2 family proteins in such a way that the apoptosis of LNCaP cells is promoted. Based on these studies, we suggest that resveratrol could be developed as an agent for the management of prostate cancer.     

电针干预自发性高血压大鼠主动脉丝裂原活化蛋白激酶磷酸酶1及磷酸化细胞外信号调节激酶1/2蛋白的表达

背景:近年来大量临床研究表明针刺风池、太冲、曲池等穴位能有效降低血压,可用于高血压,但对其治疗的分子机制尚未阐明.目的:观察针刺大鼠风池、太冲、曲池等穴位对丝裂原活化蛋白激酶信号转导调控系统的影响,从而探讨针刺治疗高血压的分子机制.方法:选取8月龄自发性高血压雄性Wistar大鼠14只,随机分为针刺组和模型组,每组7只;另选取同月龄正常血压雄性Wistar-Kyoto大鼠7只作为对照组.对针刺组大鼠采用电针针刺双侧风池、曲池和三阴交穴,毫针刺太溪和太冲穴.3周后采用RT-PCR方法检测各组大鼠主动脉组织丝裂原活化蛋白激酶磷酸酶1 mRAN的表达,Western blot方法检测丝裂原活化蛋白激酶磷酸酶1、磷酸化细胞外信号调节激酶1/2蛋白表达.结果与结论:与对照组比较,模型组主动脉组织磷酸化细胞外信号调节激酶1/2蛋白表达水平升高,丝裂原活化蛋白激酶磷酸酶1 mRNA及其蛋A表达水平降低(P<0.01);与模型组比较,针刺组主动脉组织磷酸化细胞外信号调节激酶1/2蛋白表达水平降低,丝裂原活化蛋白激酶磷酸酶1 mRNA及其蛋白表达水平升高(P<0.05).提示针刺治疗自发性高血压大鼠可能是通过调控丝裂原活化蛋白激酶信号转导途径,增强磷酸化细胞外信号调节激酶1/2蛋白表达,降低丝裂原活化蛋白激酶磷酸酶1蛋白表达,从而改善血管重塑,降低血压.     

阿托伐他汀对心肌梗死大鼠心肌纤维化和细胞外信号调节激酶表达的影响

目的观察阿托伐他汀对大鼠急性心肌梗死后心室重塑和心肌组织中细胞外信号调节激酶(ERK)1/2蛋白表达的影响。方法 20只雄性SD大鼠通过前降支动脉结扎法建立大鼠急性心肌梗死模型后随机分为心肌梗死组(AM I),心肌梗死阿托伐他汀组(ATV),另设假手术组(sham),每组n=10。阿托伐他汀组每天给予阿托伐他汀(10 mg/kg)灌胃,持续4周。假手术组和心肌梗死组每天给予同等量的0.9%氯化钠注射溶液灌胃。应用real-tim e PCR法检测梗死周边区心肌组织中Ⅰ型、Ⅲ型胶原mRNA表达,应用westernb lot方法检测p-ERK1/2、ERK1/2蛋白的表达。结果与假手术组比较,心肌梗死组和阿托伐他汀组中Ⅰ型、Ⅲ型胶原表达高于假手术组(P<0.01),阿托伐他汀组Ⅰ型、Ⅲ型胶原表达显著低于心肌梗死组(P<0.01)。心肌梗死组和阿托伐他汀组中p-ERK1/2表达高于假手术组(P<0.01),阿托伐他汀组p-ERK1/2表达低于心肌梗死组(P<0.01)。结论阿托伐他汀可以改善大鼠心肌梗死后心室重塑,其机制可能与下调心肌组织中p-ERK1/2表达有关。     

8-Amino-adenosine induces loss of phosphorylation of p38 mitogen-activated protein kinase, extracellular signal-regulated kinase 1/2, and Akt kinase: role in induction of apoptosis in multiple myeloma

Multiple myeloma is a slowly proliferating B-cell malignancy that accumulates apoptosis-resistant and replication-quiescent cell populations, posing a challenge for current chemotherapeutics that target rapidly replicating cells. Multiple myeloma remains an incurable disease in need of new therapeutic approaches. The purine nucleoside analogue, 8-amino-adenosine (8-NH2-Ado), exhibits potent activity in preclinical studies, inducing apoptosis in several multiple myeloma cell lines. This cytotoxic effect requires phosphorylation of 8-NH2-Ado to its triphosphate form, 8-amino-ATP, and results in a concomitant loss of endogenous ATP levels. Here, we show the novel effect of 8-NH2-Ado on the phosphorylation status of key cellular signaling molecules. Multiple myeloma cells treated with 8-NH2-Ado exhibit a dramatic loss of phosphorylation of several important signaling proteins, including extracellular signal-regulated kinase 1/2, p38 mitogen-activated protein kinase, and Akt kinase. Cells depleted of ATP independent of 8-NH2-Ado do not exhibit the same decrease in phosphorylation of vital cellular proteins. Therefore, the significant shifts in endogenous ATP pools caused by 8-NH2-Ado treatment cannot account for the changes in phosphorylation levels. Instead, 8-NH2-Ado may influence the activity of select regulatory protein kinases and/or phosphatases, with preliminary data suggesting that protein phophatase 2A activity is affected by 8-NH2-Ado. The distinctive effect of 8-NH2-Ado on the phosphorylation status of cellular proteins is a novel phenomenon for a nucleoside analogue drug and is unique to 8-NH2-Ado among this class of drugs. The kinetics of 8-NH2-Ado-mediated changes in phosphorylation levels of critical prosurvival and apoptosis-regulating proteins suggests that the modulation of these proteins by dephosphorylation at early time points may be an important mechanistic step in 8-NH2-Ado-induced apoptosis.     

Mechanisms linking adenosine A1 receptors and extracellular signal-regulated kinase 1/2 activation in human trabecular meshwork cells

This study was designed to evaluate the signaling pathways coupling adenosine A1 receptors and extracellular signal-regulated kinase (ERK) 1 and 2 in human trabecular meshwork (HTM) cells. Studies were conducted using cultures of primary HTM cells and the HTM-3 cell line. Activation of ERK1/2, location of protein kinase C (PKC) isoforms, and matrix metalloproteinase (MMP) secretion were determined by Western blotting. In primary HTM cells and the HTM-3 cell line, administration of the A1 agonist N6-cyclohexyladenosine (CHA) produced a concentration-dependent increase in ERK1/2 activation. This CHA-induced ERK activation was blocked by pretreatment with the A1 receptor antagonist 8-cyclopentyl-1,3-dimethylxanthine or pertussis toxin. Transfection with dominant negative N17 Ras produced only a small (31%) decline in CHA-induced ERK activation, and the response was not altered by pretreatment with the Src tyrosine kinase inhibitor, PP2 [3-(4-chlorophenyl)1-(1,1-dimethylethyl)-1H-pyrazolo[3,4-D] pyrimidin-4-amine], the phosphoinositide kinase-3 inhibitor, LY-294002 [2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one], or the A3 receptor antagonist, MRS-1191 [3-ethyl-5-benzyl-2-methyl-4-phenylethynyl-6-phenyl-1,4-(+/-)-dihydropyridine-3,5-dicarboxylate]. Administration of CHA also induced the translocation of PKCalpha from the cytosol to the membrane, and pretreatment with the phospholipase C (PLC) inhibitor, U73122 [1-[6-[[(17beta)-3-methoxyestra-1,3,5(10)-trien-17-yl]amino]-hexyl]-1H-pyrrole-2,5-dione], blocked ERK1/2 activation induced by CHA. Transfection of short interfering RNA targeting PKCalpha blocked the CHA-induced ERK1/2 activation and the secretion of MMP-2. These results confirm the existence of functional adenosine A1 receptors in the trabecular meshwork cells. These receptors are coupled to the activation of ERK1/2 through G(i/o) proteins and dependent upon the upstream activation of PLC and PKCalpha. These studies provide evidence that adenosine A1 receptor agonists increase outflow facility through sequential activation of G(i/o) > PLC > PKCalpha > c-Raf > mitogen-activated protein kinase kinase > ERK1/2, leading to secretion of MMP-2.     

Inhibition of nischarin expression attenuates rilmenidine-evoked hypotension and phosphorylated extracellular signal-regulated kinase 1/2 production in the rostral ventrolateral medulla of rats

Imidazoline (I(1))-evoked hypotension is linked to enhanced phosphorylated extracellular signal-regulated kinase (pERK)1/2 production in the rostral ventrolateral medulla (RVLM). Recent cell culture findings suggest that nischarin is a candidate for the I(1) receptor. In the present study, nischarin antisense oligodeoxynucleotide (ODN) (AS1 or AS2), designed according to nischarin cDNA sequence, was administered intracisternally (i.c., 2 nmol/rat for 2 days) to knockdown central nischarin expression; control rats received the corresponding mismatched ODN (MM1 or MM2) or artificial cerebrospinal fluid (aCSF). We investigated the effects of AS1 or AS2 on nischarin expression in the RVLM, and on the hypotension and RVLM pERK1/2 production elicited by the I(1)-selective agonist rilmenidine (25 mug/rat i.c.). Compared with aCSF, the mismatched ODN (MM1 or MM2) had no significant effect on RVLM nischarin expression or the cardiovascular and cellular (RVLM pERK1/2) responses elicited by rilmenidine. However, either antisense ODN substantially (>80%) reduced nischarin expression in the RVLM (AS1/MM1, 3 +/- 1 versus 32 +/- 2 positive cells; AS2/MM2, 4 +/- 1 versus 31 +/- 2 positive cells) and abrogated rilmenidine (I(1))-evoked hypotension (AS1/MM1, -4.1 +/- 0.9 versus -10.8 +/- 1.9 mm Hg; AS2/MM2, -2.1 +/- 1.1 versus -15.3 +/- 2.5 mm Hg) and ERK1/2 activation in the RVLM (AS1/MM1, 10 +/- 1 versus 15 +/- 2 positive cells; AS2/MM2, 9 +/- 1 versus 18 +/- 2 positive cells). Finally, pERK1/2 generated by central I(1) receptor activation is colocalized with nischarin in the RVLM neurons. This is the first evidence in vivo that nischarin plays a critical role in I(1) receptor-mediated pERK1/2 production in the RVLM and the subsequent hypotension.