Proliferation Enhanced By NGF-NTRK1 Signaling Makes Pancreatic Cancer Cells More Sensitive To 2DG-Induced Apoptosis

Rapidly proliferating cancer cells rely on increased glucose consumption for survival. The glucose analog 2-deoxy-D-glucose (2DG) cannot complete glycolysis and inhibits the growth of many types of cancers. It is unknown whether reduced glycolysis inhibits the growth of pancreatic cancer. Activation of nerve growth factor (NGF)-neurotrophic tyrosine kinase receptor type 1 (NTRK1) signaling leads to enhanced proliferation of these cells. We investigated the effect of 2DG treatment on the viability of NTRK1-transfected pancreatic cancer cells. After treatment with 2DG, the viability of pancreatic cancer cells was evaluated by MTT assay. SB203580 (a specific inhibitor of the p38-MAPK pathway) and PD98059 (an MAP2K1 [mitogen-activated protein kinase kinase 1, previously, MEK1] inhibitor) were used to inhibit p38-MAPK and ERKs, respectively. The percentage of apoptotic cells was determined by flow cytometry. Overexpression of NTRK1 in pancreatic cancer cells resulted in increased cell proliferation, which was reduced by PD98059-mediated inhibition of ERKs but not by suppression of p38-MAPK with SB203580. After treatment with 2DG, the percentage of apoptotic cells was greater in those with high expression of NTRK1 than in cells with low NTRK1 expression. Blocking the p38-MAPK pathway with SB203580 effectively abolished the apoptosis induced by 2DG. We conclude that pancreatic cancer cells with a high expression of NTRK1 are more sensitive to 2DG-induced apoptosis, through the p38-MAPK pathway.     

Continuous intrathecal infusion of SB203580, a selective inhibitor of p38 mitogen-activated protein kinase, reduces the damage of hind-limb function after thoracic spinal cord injury in rat

P38 mitogen-activated protein kinase (MAPK) is one of the key enzymes in apoptosis induction pathways. We tested continuous intrathecal infusion of SB203580, a selective inhibitor of p38-MAPK, after spinal cord compression injury by a 20 g weight for 40 min at the 11th vertebra level-thoracic spinal cord. SB203580 (1 microg/day) was infused for 1 week after the compression. Hind-limb function was evaluated by measuring the frequency of 'standing' posture; raising fore limbs and sustaining body weight with hind-limbs. One-week after the compression, frequency of standing spinal cord injured rat was decreased to about half of that in sham operated animals which underwent laminectomy without compression. The frequency of standing in rats infused SB203580 recovered 2-3 weeks after the spinal cord injury, on the other hand, vehicle animals infused with saline did not recover. Myelin staining by Luxol fast blue showed severe myelin degradation in vehicle animals in lateral and dorsal funiculi. Apoptotic cells, detected by TUNEL staining, appeared in lateral funiculi of spinal cord injured rats. The application of SB203580 decreased the number of apoptotic cells. The SB203580-treated animals showed no significant degeneration of myelin structure. These results suggest that inhibition of p38-MAPK is one candidate for therapeutic agents against neurological deficits after spinal cord injury.     

Advanced glycation end products promote proliferation of cardiac fibroblasts by upregulation of KCa3.1 channels

The present study was designed to investigate whether advanced glycation end products (AGEs) would regulate K_Ca3.1 channels in cardiac fibroblasts and participate in cell proliferation. Cultured adult rat cardiac fibroblasts were employed to investigate the regulation of K_Ca3.1 channels by advanced glycation end products?Cbovine serum albumin (AGE?CBSA) and the role of K_Ca3.1 channels in cell proliferation using approaches of molecular biology. K_Ca3.1 channel mRNA and protein levels were greatly enhanced in cardiac fibroblasts treated with 200???g/ml AGE?CBSA, and the effects were countered by anti-RAGE antibody or the ERK1/2 inhibitor PD98059, the p38-MAPK inhibitor SB203580, and the PI3K/Akt inhibitor LY294002. In addition, AGE?CBSA stimulated cell proliferation and collagen production in cultured cardiac fibroblasts, and the effects were reversed by K_Ca3.1 blocker TRAM-34, anti-RAGE antibody, or signal inhibitors PD98059, SB203580, and LY294002. These results demonstrate for the first time that AGEs increase the expression of K_Ca3.1 channels in a RAGE-dependent manner and promote cardiac fibroblast proliferation and collagen production, which is mediated by phosphorylation of ERK1/2, p38-MAPK, and PI3K/Akt signals.     

基于p38-MAPK信号通路探讨和厚朴酚对结直肠癌细胞增殖、凋亡的影响

目的基于p38-丝裂原活化蛋白激酶(p38-mitogen activated protein kinases,p38-MAPK)探讨和厚朴酚(honokiol,HNK)对结直肠癌细胞增殖和凋亡的影响.方法将体外培养HCT116细胞分为对照组(0 μmol/L)、HNK低剂量(20 μmol/L)、中剂量(40 μmol/L)和高剂量组(80μmol/L)。采用CCK-8法和克隆形成试验检测细胞增殖,流式细胞仪检测细胞凋亡,Western印迹检测p38、p-P38、细胞增殖指数67(cell proliferation index 67,Ki67)、B细胞淋巴瘤/白血病-2(B-cell lymphoma-2,Bcl-2)、BCL2相关X蛋内(B-cell lymphoma-2 associated X protein,Bax)和裂解的半胱氨酸天冬氨酸蛋内酶3(cleaved Caspase-3)蛋白表达。将HCT116细胞分为空内对照组(0μmol/L)、HNK组(80μmol/L)、SB203580组(10 μmoL/L)和SB203580+HNK组(SB203580 10μmol/L+HNK 80 μmol/L),检测SB203580对各组细胞增殖、凋亡以及Ki67、cleaved Caspase3蛋白表达的影响。结果与对照组比较,HNK中高剂量组HCT116细胞的相对增殖率和克隆形成率明显降低,细胞凋亡率明显升高,Ki-67、Bcl-2蛋白表达明显下降,p-p38/p38、Bax和cleaved Caspase-3蛋白表达明显升高(P<0.05),且随着HNK剂量增加,其作用明显增加(P<0.05)。与空白对照组比较,SB203580组细胞相对增殖率明显升高,细胞凋亡率明显下降,Ki67蛋内表达明显升高,cleaved Caspase-3蛋白表达明显下降(P<0.05);与SB203580组比较,SB203580+HNK组细胞相对增殖率明显下降,细胞凋亡率明显升高,Ki67蛋白表达明显下降,cleaved Caspase-3蛋白表达明显升高(P<0.05)。结论HNK可以激活p38-MAPK信号通路,抑制HCT116细胞增殖,诱导细胞凋亡。     

CP-64131, an aminobenzazepine with cytokine-like properties, stimulates human neutrophil functions through the p38-MAPK pathway

CP-64131 (CP), an aminobenzazepine with cytokine-like, physiologic effects similar to granulocyte-colony stimulating factor (G-CSF) and granulocyte macrophage (GM)-CSF, increases the number of neutrophils and stimulates marrow recovery after doxirubicin ablation. CP can also function as a neutrophil agonist, like formyl-Met-leu-Phe (fMLP). In these studies, we show that CP is unique in that it stimulates the p38-mitogen-activated protein kinase (MAPK) pathway but not extracellular signal-regulated kinase (ERK)1/2 or c-jun N-terminal kinase MAPKs in human neutrophils from peripheral blood. This is in contrast to other neutrophil agonists such as fMLP, interleukin (IL)-8, or GM-CSF, which stimulate multiple MAPK pathways. Like fMLP and IL-8, CP is capable of stimulating superoxide (O2-) production, CD11b expression, and cell polarization in human neutrophils. CP-stimulated O2- production is completely dependent on p38-MAPK activation, as determined by sensitivity to the p38-MAPK inhibitor SB203580. In contrast, SB203580 only partially inhibits expression of CD11b and has no effect on cell polarization stimulated by CP. Therefore, CP treatment of neutrophils activates p38-MAPK but has effects independent of p38-MAPK activation. In human embryonic kidney 293 cells, a human kidney epithelial cell line CP stimulates p38-MAPK and modestly activates ERK1/2. The findings define CP as a novel, small molecule, which has little cellular toxicity in vitro. CP has the ability to activate specific MAPK pathways in different cell types and should prove to be an effective agonist in combination with inhibitors to study biological responses regulated by MAPKs.     

ET-1介导损伤气道上皮诱导成纤维细胞活化的信号机制

目的： 探讨p38丝裂原活化蛋白激酶(MAPK)、磷脂酰肌醇3-激酶(PI3K/Akt)在内皮素(ET)-1介导损伤气道上皮诱导上皮下成纤维细胞活化过程中的作用及对白细胞介素(IL)-6的影响。方法：将正常或经多聚左旋精氨酸(PLA)刺激的人气道上皮细胞与原代气道成纤维细胞共培养并分别加入p38 MAPK、PI3K特异性抑制剂SB203580、LY294002或ET受体A阻断剂BQ123,应用免疫组化、免疫印迹技术或ELISA检测成纤维细胞α-平滑肌肌动蛋白（α-SMA）表达、p38 MAPK、Akt的活化及成纤维细胞上清IL-6水平;制备成纤维细胞胶原凝胶并与不同方法处理的上皮细胞共培养,测量各组凝胶面积变化以了解上皮细胞对成纤维细胞收缩反应的诱导及其上述处理因素的影响。结果：与损伤上皮细胞共培养的成纤维细胞上清中ET-1、IL-6水平［（13.69±1.36） ng/L、(56.7±10.7) ng/L］明显高于与正常上皮细胞共培养的成纤维细胞上清［（3.79±0.64） ng/L、（15.5±3.2）ng/L］,BQ123、SB203580或LY294002皆不同程度减弱损伤上皮细胞诱导的IL-6释放［分别为(27.2±3.1) ng/L、(31.5±3.6) ng/L、(41.3±3.2) ng/L］;成纤维细胞与损伤气道上皮细胞共培养后p38 MAPK、Akt先后激活,BQ123减弱磷酸化p38 MAPK、Akt水平,SB203580浓度依赖性减弱Akt磷酸化水平,而LY294002对磷酸化p38 MAPK水平影响很小。与损伤气道上皮细胞共培养后成纤维细胞α-SMA表达增加,并且胶原收缩百分比明显大于与正常气道上皮共培养的成纤维细胞［(61.2±2.7)% vs (15.4±7.3)%］;BQ123、SB203580及LY294002皆不同程度减弱成纤维细胞α-SMA表达与凝胶收缩且BQ123、SB203580抑制凝胶收缩作用较LY294002更明显。结论：ET-1通过激活p38 MAPK、PI3K/Akt信号通路并促进IL-6分泌在损伤气道上皮诱导成纤维细胞活化过程中发挥关键作用。     

p38 MAPK在顺铂诱导肾小管上皮细胞凋亡中的作用

目的:探讨p38 MAPK在顺铂诱导大鼠近端肾小管上皮细胞(RPTC)凋亡中的作用。方法:首先采用Western blot实验检测0、5、10和20μmol/L顺铂处理24 h对细胞凋亡的影响,确定最佳处理剂量;而后采用20μmol/L顺铂联合50 mg/L p38 MAPK抑制剂SB203580刺激RPTC,实验分为对照组、顺铂组及顺铂+SB203580(加入SB203580处理RPTC 1 h后再给予顺铂处理24 h)。采用相差荧光显微镜观察和流式细胞术分析顺铂处理后RPTC的凋亡情况;采用Ac-DEVD-AFC试剂盒检测RPTC裂解液中的caspase活性;Western blot实验检测p38、磷酸化p38、cleaved PARP和cleaved caspase-3等的蛋白水平;pH计检测顺铂处理后RPTC外环境pH值改变。结果:20μmol/L顺铂处理RPTC 24 h,可以明显诱导细胞凋亡;顺铂处理15 min后RPTC中p38 MAPK开始磷酸化并达到高峰。顺铂处理后12.08%的RPTC呈凋亡形态,具有增强的caspase活性,并且cleaved PARP和cleaved caspase-3水平明显升高(P0.05);p38 MAPK抑制剂SB203580可抑制p38的磷酸化,降低RPTC的凋亡率和caspase活性,并减少cleaved PARP和cleaved caspase-3的蛋白水平。同时,SB203580可逆转顺铂诱导的RPTC培养基pH值的改变。结论:p38 MAPK的磷酸化在顺铂诱导的RPTC凋亡中发挥作用。顺铂诱导RPTC凋亡后,可改变细胞外酸性环境,并可被p38 MAPK抑制剂SB203580所抑制。     

周期性张应力诱导成纤维细胞凋亡中p38MAPK信号通路的作用

背景：当牙齿受异常咬合力时会导致牙体吸收、牙周组织的大量破坏。 目的：研究牙周膜成纤维细胞在受到周期性张应力刺激后是否发生凋亡及p38MAPK信号通路是否参与该凋亡过程。 方法：取4~7代成纤维细胞,同步化后随机分为对照组、加力组和SB203580组。加力组和SB203580组细胞加载力值为12%表面应变率,加力频率为6个循环/min,即5 s拉伸,5 s松弛。SB203580组细胞在加力前1 h加入终浓度为20 mmol/L的p38MAPK抑制剂SB203580。分别在加力6,12,24 h,取各组细胞,流式细胞仪检测细胞凋亡,RT-PCR检测细胞凋亡基因bax mRNA的表达。 结果与结论：与对照组比较,加力后成纤维细胞凋亡率及bax mRNA表达增加 (P < 0.05),且随着加力时间的延长而增强,12 h达高峰,之后逐渐下降。与加力组比较,SB203580组对应时间点细胞凋亡减少 (P < 0.05),bax mRNA表达降低。说明细胞受到力学刺激会发生凋亡,而丝裂原活化蛋白激酶p38MAPK信号通路参与了该凋亡过程。     

Reactive oxygen species and p38 phosphorylation regulate the protective effect of Delta9-tetrahydrocannabinol in the apoptotic response to NMDA

NMDA causes oxidative stress in neurons, and produces cell death involving elements of both necrosis and apoptosis. To examine the neuroprotective mechanism of Delta9-tetrahydrocannabinol (THC) in NMDA-induced death of AF5 cells, we measured reactive oxygen species (ROS) formation after exposure to NMDA. ROS generation was increased by NMDA, and NMDA-induced ROS generation was significantly decreased by THC. Western blotting revealed an increase in phosphorylated p38 MAPK after NMDA treatment, which was also blocked by pretreatment with THC. The time course of ROS generation and activation of MAPK signaling pathways were similar. SB203580, a p38 inhibitor, partially blocked glutamate excitotoxicity in AF5 cells. The present data suggest that THC protects against NMDA-induced apoptosis in AF5 cells by blocking ROS generation and inhibiting the activation of p38-MAPK.     

Stimulation of TNFα expression by hyperosmotic stress

Hyperosmotic stress is known to induce apoptotic cell death, an effect previously attributed to seemingly ligand-independent clustering of tumour necrosis factor alpha (TNF alpha) receptors. An alternative explanation for the clustering of TNF alpha receptors may be stimulation of TNF alpha production, with subsequent autocrine or paracrine stimulation of the receptors. The present study was performed to test for an effect of exposure to hyperosmotic extracellular fluid on cellular TNF alpha production. In both the macrophage cell line U937 and the B lymphocyte cell line LCL721, an increase of extracellular osmolarity to 500 mosmol/l indeed increased TNF alpha expression, an effect reversed by the p38 kinase inhibitor SB203580. In both cell types hyperosmotic stress triggered apoptosis, which in U937 cells was significantly inhibited by neutralizing antibodies against TNF alpha and by SB203580 and was similarly elicited by exogenous addition of TNF alpha. In contrast, osmotically induced apoptosis of LCL721 cells was only slightly blunted by anti-TNF alpha antibodies and rather increased by SB203580. In conclusion, through activation of p38 kinase hyperosmotic stress stimulates the expression of TNF alpha which at least in U937 macrophages may participate in the triggering of subsequent apoptotic cell death. However, the observations in LCL721 cells point to other, TNF alpha-independent, mechanisms mediating apoptotic cell death following an excessive increase of extracellular osmolarity.     

Inhibition of the p38 mitogen-activated protein kinase (MAPK) pathway attenuates cerebral vasospasm following experimental subarachnoid hemorrhage in rabbits

The p38 mitogen-activated protein kinase (MAPK) plays an important role in apoptosis and is also involved in the development of cerebral vasospasm after subarachnoid hemorrhage (SAH). Here, we sought to examine whether inhibition of p38 MAPK could attenuate cerebral vasospasm and investigate the underlying mechanisms in a rabbit SAH model. SAH was established in rabbits (n=12/group) using the double-hemorrhage method. We observed apparent vasospasm in the basilar arteries of rabbits with SAH, which was significantly attenuated by SB203580, a selective p38MAPK inhibitor. Immunoblotting assays showed enhanced phosphorylation of p38 MAPK and ATF2 and increased caspase-3 cleavage following SAH, which were, however, markedly suppressed by SB203580. TUNEL staining further revealed significant apoptosis in the basilar arteries of rabbits with SAH, which was scantly present in rabbits treated with SB203580. Our results demonstrated that p38 MAPK was activated in cerebral vasospasm and associated with increased apoptosis in the basilar arteries and p38 MAPK inhibition suppressed apoptosis, suggesting that p38 MAPK could be a novel therapeutic target for cerebral vasospasm.     

Regulation of p38 MAPK phosphorylation inhibits chondrocyte apoptosis in response to heat stress or mechanical stress

Activation of p38 MAPK has been associated with a stress response and with apoptotic processes. However, the function of p38 MAPK in chondrocytes is not clearly understood. In this study, we analyzed the expression of p38 MAPK in chondrocytes and investigated the function of p38 MAPK in response to heat stress and mechanical stress. Chondrocytes were isolated from human cartilage and cultured. Expression of p38 and phosphorylated p38 in cartilage of patients with osteoarthritis (OA) was compared to those in normal cartilage by immunohistochemistry and Western blotting. Human knee chondrocytes were exposed to heat stress or mechanical stress. Normal knee chondrocytes were pre-treated with SB203580 or p38 small interfering RNA (siRNA) before induction of heat stress or mechanical stress. Chondrocyte apoptosis was detected by TUNEL staining and Western blotting of cleaved caspases. OA and normal chondrocytes expressed p38; however, OA chondrocytes showed much higher phosphorylated p38 compared to normal chondrocytes. Heat stress or mechanical stress induced apoptosis and increased phosphorylated p38 in normal chondrocytes. The TUNEL positive cells and expression levels of phosphorylated p38 in response to stress decreased when chondrocytes were incubated with SB203580 or transfected with siRNA against p38. In conclusion, we have demonstrated that heat stress or mechanical stress increased chondrocyte apoptosis via phosphorylation of p38. Stress-induced chondrocyte apoptosis decreased due to inhibition of p38 MAPK activation. In contrast, the phosphorylation of p38 MAPK increased in OA chondrocytes. Our results show that down-regulation of p38 MAPK activation inhibits chondrocyte death induced by heat stress or mechanical stress.     

Effects of FPL 55712, ETYA and aminophylline upon Ascaris-induced bronchoconstriction in cynomolgus monkeys

Dose-related impairment of pulmonary functions was induced in artificially respired, anesthetized cynomolgus monkeys by inhalation of aerosolized Ascaris antigen (AA) in ascending doses. The effects of pharmacologic agents were assessed by increases in threshold Ascaris dose (TAD). TAD were defined as the doses of AA needed for 20% increase in pulmonary resistance and 15% decrease in compliance. Inhaled FPL 55712, an SRS-A antagonist (1.24 mg through-the-valve dose; TTVD), and 5,8,11,14-eicosatetraynoic acid (ETYA), an inhibitor of lipoxygenase and cyclooxygenase (1.0 mg TTVD) resulted in significant increases in the geometric means of TAD for changes in compliance (p less than 0.01). The effects of both agents upon resistance were of borderline significance. Orally administered aminophylline (30 mg/kg) had no significant effect upon mean TAD for resistance or compliance. The activities of FPL 55712 and ETYA suggest that spasmogenic leukotrienes are involved in the pulmonary allergic reactions in cynomolgus monkeys.     

Secreted beta-amyloid precursor protein activates microglia via JNK and p38-MAPK

Reactive microglia are thought to play a role in the pathogenesis of Alzheimer's disease (AD) and are localized to the senile plaques that are associated with cognitive decline. The beta-amyloid precursor protein (betaAPP) is over-expressed in the dystrophic neurites near such plaques, and secreted forms of betaAPP (sAPPalpha) activate inflammatory responses in microglia. To characterize the mechanisms by which sAPPalpha activates microglia, we assayed its effects on MAP kinases, including c-Jun N-terminal kinases (JNK), extracellular signal-regulated protein kinases (ERK), and p38-MAPK. sAPPalpha was found to rapidly activate JNKs, ERKs and p38-MAPK in a dose-dependent manner. The JNK inhibitor SP600125 and the p38 inhibitor SB203580 independently reduced both nitrite accumulation and induction of inflammatory nitric oxide synthase (iNOS). By contrast, inhibition of the ERK pathway with U0126 did not appreciably affect either outcome measure. These findings suggest that sAPP activates the ERK, JNK and p38 classes of MAP kinases but that only JNK and p38-MAPK are critical for activation of microglia by sAPPalpha, a process that compromises neuronal function and survival.     

p38 MAP kinase regulates RANTES production by TNF-alpha-stimulated human pulmonary vascular endothelial cells

BACKGROUND: RANTES plays an important role in the production of allergic inflammation of the airway through its chemotactic activity for eosinophils. However, the intracellular signal regulating RANTES expression in human pulmonary vascular endothelial cells has not been determined. In the present study, therefore, we examined the role of p38 mitogen-activated protein (MAP) kinase in RANTES production by tumor necrosis factor (TNF)-alpha-stimulated pulmonary vascular endothelial cells in order to clarify the signal transduction pathway regulating RANTES production by pulmonary vascular endothelial cells. METHODS: We examined p38 MAP kinase activation, and the effect of SB 203580, as the specific inhibitor for p38 MAP kinase, on p38 MAP kinase activity and RANTES production by TNF-alpha-stimulated human pulmonary vascular endothelial cells. RESULTS: The results showed that TNF-alpha induced RANTES production and p38 MAP kinase activity in human pulmonary vascular endothelial cells. Abrogation of p38 MAP kinase activity by SB 203580 repressed TNF-alpha-induced p38 MAP kinase activity and RANTES production. CONCLUSIONS: These results indicate that p38 MAP kinase plays an important role in the TNF-alpha-activated signaling pathway which regulates RANTES production by human pulmonary vascular endothelial cells.     

p38MAPK参与高糖刺激大鼠肾小管上皮细胞产生细胞外基质胶原Ⅲ

目的：探讨p38MAPK信号通路在高糖刺激大鼠肾小管上皮细胞产生细胞外基质胶原Ⅲ中的作用。 方法： 采用体外培养和Western blotting等方法，以不同浓度D-葡萄糖、p38MAPK信号通路特异性阻断剂SB203580以及用不同时间刺激正常大鼠肾小管上皮细胞NRK52E，分别检NRK52E细胞p38MAPK磷酸化水平和细胞外基质胶原Ⅲ的表达。 结果： 随D-葡萄糖浓度增加，p38MAPK磷酸化水平、胶原Ⅲ的产生也增加，SB203580可有效阻断高糖引起p38MAPK磷酸化水平的升高和细胞外基质胶原Ⅲ的表达的增高。 结论： 高糖引起p38MAPK磷酸化水平的升高可能在糖尿病肾病的肾间质纤维化中发挥重要作用。SB203580有潜在的糖尿病肾病防治的临床应用价值。     

The p38 mitogen-activated protein kinases can have opposing roles in the antigen-dependent or endotoxin-stimulated production of IL-12 and IFN-gamma.

The p38 mitogen-activated protein kinases (p38 MAPK) are activated in lymphocytes and acessory cells during innate and antigen-specific responses. We show that an inhibitor of two isoforms of p38 MAPK, SB 203580, inhibited the antigen-initiated production of IL-12, and IFN-gamma by cultures of splenic APC and naive CD4(+) T cells. Paradoxically, SB 203580 enhanced the LPS plus IFN-gamma-initiated production of IL-12 by peritoneal exudate macrophages, and the LPS-initiated of the production of both IL-12 and IFN-gamma by non-T non-B (scid) splenocytes. The enhancing effect of SB 203580 on the production of IL-12 by peritoneal exudate macrophages stimulated by LPS and IFN-gamma was dose dependent (EC(50) 0.3 microM), was only seen at lower concentrations of IFN-gamma and was due, at least in part, to a dose-dependent (IC(50) 0.3 microM) inhibition of the production of IL-10. These results indicate first, that p38 MAP kinase activity is required for the production of IL-10, as well as that of proinflammatory cytokines such as IL-12 and IFN-gamma, and, second, that the net effects of SB 203580 on the production of IL-12 and IFN-gamma can be positive or negative, depending on stimuli, cell populations, and levels of cytokines such as IFN-gamma and IL-10.     

Redox-sensitive events in Fas-induced apoptosis in human NK cells include ceramide generation and protein tyrosine dephosphorylation

We previously reported that intracellular oxidation-reduction (redox) regulates NK cell functions and that IL-2-activated NK cells undergo apoptosis upon contact with NK-sensitive target cells. We now report that apoptosis in activated human NK cells is also regulated by redox. Thiol deprivation increased apoptosis in NK cells induced by anti-Fas mAb or Fas ligand-transfected cells, and pretreatment of cells with N- acetyl cysteine, which increased intracellular glutathione, partially inhibited the apoptosis and reversed the effect of thiol-deficient medium, suggesting that Fas-induced apoptosis in NK cells is also redox sensitive. Thiol deprivation did not alter cell surface Fas expression, but did increase ceramide generation following Fas engagement. Although exogenous ceramides induced apoptosis of NK cells, thiol depletion had no effect on this apoptosis. Thiol deprivation increased CPP32 activation induced by Fas engagement, but not by ceramides. These findings suggest that, if ceramide is required for Fas-induced apoptosis, thiol deprivation affects the Fas-mediated signaling pathway at the generation of ceramide and/or upstream thereof. Though tyrosine phosphorylation following Fas engagement was not significantly affected by thiol deprivation, tyrosine dephosphorylation was delayed, suggesting that tyrosine phosphatases may also be redox sensitive. The notion that dephosphorylation is important in the Fas signaling pathway is supported by the finding that tyrosine phosphatase inhibitors significantly enhanced both CPP32 activity and apoptosis following Fas ligation. We conclude that events downstream of tyrosine phosphorylation and upstream of CPP32 activation, including tyrosine dephosphorylation and possibly ceramide generation, are sensitive to regulation by redox in human NK cells, requiring a reducing environment for optimal protection from apoptosis induced by Fas ligation.