PINK1/Parkin-mediated mitophagy play a protective role in manganese induced apoptosis in SH-SY5Y cells

Manganese (Mn) as an environmental risk factor of Parkinson's disease (PD) is considered to cause manganism. Mitophagy is thought to play a key role in elimination the injured mitochondria. The goal of this paper was to explore whether the PINK1/Parkin-mediated mitophagy is activated and its role in Mn-induced mitochondrial dysfunction and cell death in SH-SY5Y cells. Here, we investigated effects of MnCl₂ on ROS generation, mitochondrial membrane potential (MMP/ΔΨ_m) and apoptosis by FACS and examined PINK1/Parkin-mediated mitophagy by western-blotting and the co-localization of mitochondria and acidic lysosomes. Further, we explore the role of mitophagy in Mn-induced apoptosis by inhibition the mitophagy by knockdown Parkin level. Results show that MnCl₂ dose-dependently caused ΔΨ_m decrease, ROS generation and apoptosis of dopaminergic SH-SY5Y cells. Moreover, Mn could induce mitophagy and PINK1/Parkin-mediated pathway was activated in SH-SY5Y cells. Transient transfection of Parkin siRNA knockdown the expressing level of parkin inhibited Mn-induced mitophagy and aggravated apoptosis of SH-SY5Y cells. In conclusion, our study demonstrated that Mn may induce PINK1/Parkin-mediated mitophagy, which may exert significant neuro-protective effect against Mn-induced dopaminergic neuronal cells apoptosis.     

Somatic and germline mutations in the tumor suppressor gene PARK2 impair PINK1/Parkin-mediated mitophagy in lung cancer cells

PARK2,which encodes Parkin,is a disease-causing gene for both neurodegenerative disorders and cancer.Parkin can function as a neuroprotector that plays a crucial role in the regulation of mitophagy,and germline mutations in PARK2 are associated with Parkinson’s disease(PD).Intriguingly,recent studies suggest that Parkin can also function as a tumor suppressor and that somatic and germline mutations in PARK2 are associated with various human cancers,including lung cancer.However,it is presently unknown how the tumor suppressor activity of Parkin is affected by these mutations and whether it is associated with mitophagy.Herein,we show that wild-type(WT)Parkin can rapidly translocate onto mitochondria following mitochondrial damage and that Parkin promotes mitophagic clearance of mitochondria in lung cancer cells.However,lung cancer-linked mutations inhibit the mitochondrial translocation and ubiquitin-associated activity of Parkin.Among all lung cancer-linked mutants that we tested,A46T Parkin failed to translocate onto mitochondria and could not recruit downstream mitophagic regulators,including optineurin(OPTN)and TFEB,whereas N254S and R275W Parkin displayed slower mitochondrial translocation than WT Parkin.Moreover,we found that deferiprone(DFP),an iron chelator that can induce mitophagy,greatly increased the death of A46T Parkin-expressing lung cancer cells.Taken together,our results reveal a novel mitophagic mechanism in lung cancer,suggesting that lung cancer-linked mutations in PARK2 are associated with impaired mitophagy and identifying DFP as a novel therapeutic agent for PARK2-linked lung cancer and possibly other types of cancers driven by mitophagic dysregulation.     

Blocking Parkin/PINK1-mediated mitophagy sensitizes hepatocellular carcinoma cells to sanguinarine-induced mitochondrial apoptosis

Hepatocellular carcinoma (HCC) remains a major clinical challenge. Although mitophagy is implicated in hepatocarcinogenesis, novel therapeutic options targeting mitophagy for HCC treatment still await further studies. Here, we demonstrate that sanguinarine induces cell death in HCC cell line MHCC-97H through the mitochondrial apoptosis pathway. Sanguinarine triggers mitochondrial dysfunction and PTEN-induced putative kinase 1 (PINK1)/Parkin upregulation and recruitment to mitochondria. Elevated levels of p62 and LC3-II/I ratios suggest that sanguinarine is both an inducer of autophagy and a blocker of autolysosome formation, which is further confirmed by LC3-II conversion levels in presence of autophagy and mitophagy inhibitors, as well as an autophagy activator. In addition, blocking autophagy promotes sanguinarine-induced cell death, indicating mitophagy plays a cytoprotective role in sanguinarine-treated cells. Our findings suggest that blocking mitophagy may contribute to sanguinarine-induced mitochondrial apoptosis through the prevention of damaged mitochondrial clearance.     

细胞外信号调节激酶蛋白参与雷帕霉素诱导的肺癌95D细胞凋亡的机制研究

目的观察雷帕霉素(Rapa)及联合多西紫杉醇(DTX)对肺癌95D细胞系凋亡的作用,并进一步探讨其对细胞外信号调节激酶蛋白(ERK1/2)表达的影响。方法流式细胞仪方法检测单独应用雷帕霉素和多西紫杉醇及两药联合应用对95D细胞凋亡的影响,Western Blot方法检测ERK1/2蛋白及p-ERK1/2蛋白的表达。结果雷帕霉素和多西紫杉醇单独处理组均能促进肺癌细胞的凋亡,且随着浓度的增加其促凋亡作用明显增加;联合应用雷帕霉素和多西紫杉醇促凋亡作用更强,并能显著降低p-ERK1/2蛋白的表达。结论雷帕霉素联合多西紫杉能进一步促进肺癌95D细胞凋亡,ERK1/2信号通路参与其诱导的肺癌95D细胞的凋亡过程。     

Hydroxysafflor yellow A induces apoptosis in activated hepatic stellate cells through ERK1/2 pathway in vitro

A key feature in the molecular pathogenesis of liver fibrosis requires maintenance of the activated hepatic stellate cells (HSCs) phenotype by inhibition of apoptosis. The induction of apoptosis in activated HSCs has been proposed as an antifibrotic treatment strategy. This study aims at evaluating the effect of hydroxysafflor yellow A (HSYA) on apoptosis of culture-activated HSCs and further elucidating the underlying mechanisms. Primary HSCs were isolated from rats. The analysis of the cell cycle be performed by flow cytometry, detection of apoptosis by Annexin V-FITC/ PI staining, and the results were confirmed by DNA fragmentation, and cleavage of caspase-3 and poly (ADP-ribose) polymerase (PARP). Real-time polymerase chain reaction and Western blotting were used to analyze the expression of genes. Our results revealed that HSYA significantly induced apoptosis in a dose- and time-dependent manner. HSYA suppresses the activation of ERK1/2 and ERK1/2-regulated gene expression, including Bcl-2, Cytochrome c, caspase-9, and caspase-3, leading to the enhancement of apoptosis. Pharmacological blockade of ERK1/2 kinase abrogation this action of HSYA. Our data provide a molecular basis for the anti-hepatic fibrosis activity of HSYA.     

Ablation of Akt2 and AMPKα2 rescues high fat diet-induced obesity and hepatic steatosis through Parkin-mediated mitophagy

Given the opposing effects of Akt and AMP-activated protein kinase (AMPK) on metabolic homeostasis, this study examined the effects of deletion of Akt2 and AMPKα2 on fat diet-induced hepatic steatosis. Akt2–Ampkα2 double knockout (DKO) mice were placed on high fat diet for 5 months. Glucose metabolism, energy homeostasis, cardiac function, lipid accumulation, and hepatic steatosis were examined. DKO mice were lean without anthropometric defects. High fat intake led to adiposity and decreased respiratory exchange ratio (RER) in wild-type (WT) mice, which were ablated in DKO but not Akt2^−/− and Ampkα2^−/− mice. High fat intake increased blood and hepatic triglycerides and cholesterol, promoted hepatic steatosis and injury in WT mice. These effects were eliminated in DKO but not Akt2^−/− and Ampkα2^−/− mice. Fat diet promoted fat accumulation, and enlarged adipocyte size, the effect was negated in DKO mice. Fat intake elevated fatty acid synthase (FAS), carbohydrate-responsive element-binding protein (CHREBP), sterol regulatory element-binding protein 1 (SREBP1), peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1α), peroxisome proliferator-activated receptor-α (PPARα), PPARγ, stearoyl-CoA desaturase 1 (SCD-1), phosphoenolpyruvate carboxykinase (PEPCK), glucose 6-phosphatase (G6Pase), and diglyceride O-acyltransferase 1 (DGAT1), the effect was absent in DKO but not Akt2^−/− and Ampkα2^−/− mice. Fat diet dampened mitophagy, promoted inflammation and phosphorylation of forkhead box protein O1 (FoxO1) and AMPKα1 (Ser⁴⁸⁵), the effects were eradicated by DKO. Deletion of Parkin effectively nullified DKO-induced metabolic benefits against high fat intake. Liver samples from obese humans displayed lowered microtubule-associated proteins 1A/1B light chain 3B (LC3B), Pink1, Parkin, as well as enhanced phosphorylation of Akt, AMPK (Ser⁴⁸⁵), and FoxO1, which were consolidated by RNA sequencing (RNAseq) and mass spectrometry analyses from rodent and human livers. These data suggest that concurrent deletion of Akt2 and AMPKα2 offers resilience to fat diet-induced obesity and hepatic steatosis, possibly through preservation of Parkin-mediated mitophagy and lipid metabolism.KEY WORDS: Akt2, AMPK, Parkin, High fat intake, Obesity, Steatosis, Mitophagy, FoxO1     

Kaempferol induces chondrogenesis in ATDC5 cells through activation of ERK/BMP-2 signaling pathway

Endochondral bone formation occurs when mesenchymal cells condense to differentiate into chondrocytes, the primary cell types of cartilage. The aim of the present study was to identify novel factors regulating chondrogenesis. We investigated whether kaempferol induces chondrogenic differentiation in clonal mouse chondrogenic ATDC5 cells. Kaempferol treatment stimulated the accumulation of cartilage nodules in a dose-dependent manner. Kaempferol-treated ATDC5 cells stained more intensely with alcian blue staining than control cells, suggesting greater synthesis of matrix proteoglycans in the kaempferol-treated cells. Similarly, kaempferol induced greater activation of alkaline phosphatase activity than control cells, and it enhanced the expression of chondrogenic marker genes, such as collagen type I, collagen type X, OCN, Runx2, and Sox9. Kaempferol induced an acute activation of extracellular signal-regulated kinase (ERK) but not c-jun N-terminal kinase or p38 MAP kinase. PD98059, an inhibitor of MAPK/ERK, decreased in stained cells treated with kaempferol. Furthermore, kaempferol greatly expressed the protein and mRNA levels of BMP-2, suggesting chondrogenesis was stimulated via a BMP-2 pathway. Taken together, our results suggest that kaempferol has chondromodulating effects via an ERK/BMP-2 signaling pathway and could potentially be used as a therapeutic agent for bone growth disorders.     

Fisetin induces apoptosis in human cervical cancer HeLa cells through ERK1/2-mediated activation of caspase-8-/caspase-3-dependent pathway

Fisetin is a naturally occurring flavonoid that has been reported to inhibit the proliferation and to induce apoptotic cell death in several tumor cells. However, the apoptosis-inducing effect of fisetin on tumor cell lines was investigated besides HeLa cells. In this study, we found that fisetin induced apoptosis of HeLa cells in a dose- and time-dependent manner, as evidenced by nuclear staining of 4′-6-Diamidino-2-phenylindole (DAPI), flow cytometry assay, and Annexin-V/PI double-labeling. In addition, fisetin triggered the activations of caspases-3 and -8 and the cleavages of poly (ADP-ribose) polymerase, resulting in apoptosis induction. Moreover, treatment of HeLa cells with fisetin induced a sustained activation of the phosphorylation of ERK1/2, and inhibition of ERK1/2 by PD98059 (MEK1/2 inhibitor) or transfection with the mutant ERK1/2 expression vector significantly abolished the fisetin-induced apoptosis through the activation of caspase-8/-3 pathway. The in vivo xenograft mice experiments revealed that fisetin significantly reduced tumor growth in mice with HeLa tumor xenografts. In conclusion, our results indicated that fisetin exhibited anti-cancer effect and induced apoptosis in HeLa cell lines both in vitro and in vivo.     

ERK1/2 activation attenuates TRAIL-induced apoptosis through the regulation of mitochondria-dependent pathway.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) functions as an extracellular signal, which triggers apoptosis in tumor cells. In order to characterize the molecular events involved in TRAIL cytotoxic signaling, we attempted to determine the role of extracellular signal-regulated kinase 1/2 (ERK1/2), as well as its downstream targets in TRAIL-treated HeLa cells. Here we demonstrate that TRAIL exposure resulted in the activation of ERK1/2, and the elevation of anti-apoptotic Bcl-2 protein levels. ERK1/2 inhibition with PD98059 promoted cell death via the down-regulation of Bcl-2 protein levels, together with increasing mitochondrial damage, including the collapse of mitochondrial membrane potential, the release of cytochrome c from mitochondria to cytoplasm and caspase activity. These results suggest that the ERK1/2 activation is a kind of survival mechanism to struggle against TRAIL-induced stress condition in early stage, via activating cellular defense mechanisms like as the up-regulation of the Bcl-2/Bax ratio, as well as several mitochondrial events.     

Bisdemethoxycurcumin promotes apoptosis in human platelets via activation of ERK signaling pathway

Curcumin, a major bioactive component of turmeric (Curcuma longa), is known for its multiple health benefits. Curcumin as such is a mixture of its analogs: bisdemethoxycurcumin (BDMC)-3%, and demethoxycurcumin (DMC)-17%. Although the effect of curcumin on platelets is documented, the effect of BDMC and DMC on platelets is less studied. Considering the indispensable role played by platelets in hemostasis, thrombosis, inflammation, and immunity, the present study evaluates the effect of curcumin, DMC and BDMC on platelet apoptosis. The components of curcumin were purified by silica-gel column chromatography. The purity and mass analysis of the purified curcuminoids was determined by RP-HPLC and LC-MS respectively. When analyzed for platelet apoptotic markers, only BDMC demonstrated increased incidence of platelet apoptotic markers including increase in intracellular Ca²⁺, decrease in ∆ψm, alteration in BCl-2 family proteins, the release of cytochrome c, caspase activation, and PS externalization via activation of ERK activation. ERK inhibitor PD98059 significantly alleviated BDMC induced decrease in ∆ψm, alteration in BCl-2, caspase-8 activation and PS externalization. Our results demonstrate that curcumin, DMC and BDMC differentially act on platelet in inducing apoptosis and the study highlights that the toxicity associated with curcumin therapy might be attributed to BDMC in the mammalian system.     

NADPH oxidase and ERK1/2 are involved in cadmium induced-STAT3 activation in HepG2 cells

The molecular mechanism of Cd-induced signal transduction is not well understood. The aims of this study were to determine the system that generates reactive oxygen species in response to Cd that contribute to intracellular signaling on the activation of the STAT3 pathway in HepG2 cells and to address the participation of STAT3 in the production of Hsp70. Cadmium induced a significant increase in STAT3 DNA-binding after 1 h treatment. Serine phosphorylation of STAT3 was observed as a result of cadmium treatment while no tyrosine phosphorylation was detected. Cells were pretreated with inhibitors for several ROS generating systems, only diphenylen iodonium, an inhibitor of NADPH oxidase, decreased STAT3 activation. Cd induced 2.6-fold NADPH oxidase activity. Antioxidant treatment with pegylated-catalase reduced STAT3 activation. Cells were pretreated with different MAPK's inhibitors. ERK contributes in approximately 60%, and JNK in a small proportion, while p38 does not contribute in STAT3 activation. Cells were pretreated with a specific STAT3 peptide inhibitor that decreased the Cd-induced Hsp70 expression. Data suggest that STAT3 is phosphorylated at serine 727 by a Cd stress-activated signaling pathway inducing NADPH oxidase activity which produced ROS, leading ERK activation. MAPK promotes STAT3 phosphorylation that could induce a protective mechanism against Cd toxicity.     

Down-regulation of the JAK2/PI3K-mediated signaling activation is involved in Taiwan cobra cardiotoxin III-induced apoptosis of human breast MDA-MB-231 cancer cells

Cardiotoxin III (CTX III), a basic polypeptide with 60 amino acid residues isolated from Naja naja atra venom, has been reported to have anticancer activity. Exposure of MDA-MB-231 cells with 0.03, 0.09, and 0.15 μM of CTX III for 18 h, CTX III-induced cell apoptosis, as evidenced by accumulation of sub-G1 population, externalization of phosphatidylserine, loss of mitochondrial membrane potential (ΔΨm) with subsequent release of cytochrome c, and activation of both capases-9 and caspase-3. This correlated with up-regulation in Bax and Bad, and down-regulation of various anti-apoptotic proteins, including Bcl-2, Bcl-X_L, and survivin in CTX III-treated cells. Mechanistic studies showed that CTX III suppressed the phosphorylation of JAK2, STAT3, Akt, and activation of PI3K. Moreover, the PI3K inhibitor wortmannin blocked activation of STAT3 and Akt without affecting the JAK2 activation, whereas JAK2 inhibitor AG490 suppressed the levels of phospho-STAT3, phospho-Akt, and PI3K, suggesting that PI3K activation occurs after JAK2 phosphorylation, and both PI3K and JAK2 kinases cooperate to mediate STAT3 and Akt phosphorylation. Both AG490 and wortmannin also led to up-regulation in Bax and Bad, and down-regulation of Bcl-2, Bcl-X_L, and survivin in MDA-MB-231 cells. Taken together, these results indicate that CTX III induces apoptosis in MDA-MB-231 cells via concomitant inactivation of the JAK2, STAT3, PI3K, and Akt signaling pathways.     

Nickel compounds induce apoptosis in human bronchial epithelial Beas-2B cells by activation of c-Myc through ERK pathway

Nickel compounds are carcinogenic to humans and have been shown to alter epigenetic homeostasis. The c-Myc protein controls 15% of human genes and it has been shown that fluctuations of c-Myc protein alter global epigenetic marks. Therefore, the regulation of c-Myc by nickel ions in immortalized but not tumorigenic human bronchial epithelial Beas-2B cells was examined in this study. It was found that c-Myc protein expression was increased by nickel ions in non-tumorigenic Beas-2B and human keratinocyte HaCaT cells. The results also indicated that nickel ions induced apoptosis in Beas-2B cells. Knockout of c-Myc and its restoration in a rat cell system confirmed the essential role of c-Myc in nickel ion-induced apoptosis. Further studies in Beas-2B cells showed that nickel ion increased the c-Myc mRNA level and c-Myc promoter activity, but did not increase c-Myc mRNA and protein stability. Moreover, nickel ion upregulated c-Myc in Beas-2B cells through the MEK/ERK pathway. Collectively, the results demonstrate that c-Myc induction by nickel ions occurs via an ERK-dependent pathway and plays a crucial role in nickel-induced apoptosis in Beas-2B cells.     

CCR10 activation stimulates the invasion and migration of breast cancer cells through the ERK1/2/MMP-7 signaling pathway

CCR10, a member of the chemokine receptor subfamily, is overexpressed in several tumors and play a crucial role in cancer development and progression. However, the functions of CCR10 in breast cancer are unknown. Here, we detected the protein levels of CCR10 in breast cancer cells by western blotting, and examined CCR10 expression in breast cancer tissues via immunohistochemical assay. The results showed that CCR10 expression was elevated in breast cancer MCF7, BT-474 and MDA-MB-231 cells. Further, 63 of 89 cases (70.8%) had positive CCR10 staining, and the CCR10 level was closely related to capsular invasion, lymph node metastasis and tumor stage. Moreover, CCL27, the ligand of CCR10, dose-dependently stimulated the invasion and migration of breast cancer cells, and promoted MMP-7 expression and ERK1/2 activation. CCR10 knockdown in breast cancer cells through siRNA transfection attenuated CCL27-induced cell invasiveness, and suppressed MMP-7 expression and ERK1/2 activation. Additionally, blocking the ERK1/2 pathway inhibited the CCL27/CCR10-promoted cell invasion of breast cancer cells. Together, these data suggest that CCL27/CCR10 interaction induces the ERK1/2 pathway, which then increases MMP-7 expresion and subsequently promotes breast cancer cell invasion and migration. Thus, CCR10 may be a key regulator in breast cancer cell invasion and migration.     

Induction of apoptosis by esculetin in human leukemia U937 cells through activation of JNK and ERK

Esculetin is a phenolic compound that is found in various natural plant products and induces apoptosis in several types of human cancer cells. However, the underlying mechanisms of its action are not completely understood. In the present study, we used human leukemia cells to gain further insight into the mechanism of esculetin-induced anti-proliferative action and apoptosis. It was found that esculetin inhibits cell viability by inducing apoptosis, as evidenced by the formation of apoptotic bodies, DNA fragmentation, and the accumulation of cells in the sub-G1 phase. Esculetin-induced apoptosis was correlated with mitochondrial dysfunction, leading to the release of cytochrome c from the mitochondria to the cytosol, as well as the proteolytic activation of caspases. The z-DEVD-fmk caspase-3 inhibitor and the ectopic expression of anti-apoptotic Bcl-2 significantly inhibited esculetin-induced apoptosis, demonstrating the important role of caspase-3 and mitochondrial proteins in the observed cytotoxic effect. Furthermore, esculetin selectively increased the phosphorylation of extracellular-regulated kinase (ERK) and c-Jun N-terminal kinase (JNK), but not that of other kinases such as Akt and p38 activation. In addition, an ERK-specific inhibitor, PD98059, and a JNK-specific inhibitor, SP600125, showed inhibited sub-G1 phase DNA content, DNA fragmentation, caspase activation, and mitochondrial dysfunction induced by esculetin treatment. These results indicated that the JNK and ERK pathways were key regulators of apoptosis in response to esculetin in human leukemia U937 cells.     

Cytochrome P450 omega-hydroxylase inhibition reduces cardiomyocyte apoptosis via activation of ERK1/2 signaling in rat myocardial ischemia-reperfusion

Cytochrome P450 (CYP) omega-hydroxylases and their arachidonic acid metabolites play important roles in myocardial ischemia-reperfusion injury. In this study we investigated the effects of several selective CYP omega-hydroxylase inhibitors on myocardial ischemia/reperfusion-induced myocardial apoptosis. Rats were subjected 30 min of ischemia and 2 h of reperfusion. Groups received either 17-octadecynoic acid (17-ODYA, 0.3 or 3 mg/kg), N-methylsulfonyl-12, 12-dibromododec-11-enamide (DDMS, 0.4 or 0.8 mg/kg), N-hydroxy-N'-(4-butyl-2-methylphenyl) formamidine (HET0016, 0.1 or 1 mg/kg) or vehicle 10 min prior to ischemia. To further assess the role of mitogen-activated protein kinases (MAPKs) in the CYP omega-hydroxylase inhibitor-induced anti-apoptotic effect, rats also received PD98059 (1 mg/kg), SB203580 (1 mg/kg) or SP600125 (6 mg/kg) 15 min prior to ischemia, with subsets of rats also receiving HET0016 10 min prior to ischemia. Compared with vehicle group, 17-ODYA, DDMS and HET0016 significantly inhibited myocardial apoptosis as evidenced by decreased DNA ladder formation, terminal dUTP deoxynucleotidyltransferase nick end-labeling (TUNEL) positive nuclear staining. They also decreased caspase-3 activity and Bax protein expression but up-regulated the expression of Bcl-2. Conversely, exogenous 20-HETE administration exerted opposite effects. Moreover, HET0016 increased the activity of extracellular signal-related protein kinases 1 and 2 (ERK1/2) but had no significant effect on p38 MAPK or c-Jun N-terminal kinase (JNK) during ischemia/reperfusion. Pretreatment with PD98059, the inhibitor of ERK1/2, but not SB203580 or SP600125, almost completely blocked the effect exerted by HET0016. Taken together, these data suggest that CYP omega-hydroxylase inhibition exerts significant anti-apoptosis effects, at least in part, by activation of ERK1/2 in ischemia/reperfusion heart.     

Involvement of mitochondrial and B-RAF/ERK signaling pathways in berberine-induced apoptosis in human melanoma cells

The natural isoquinoline alkaloid berberine exhibits a wide spectrum of biological activities including antitumor activity, but its mechanism of action remains to be fully elucidated. Here, we report that berberine induced apoptosis in human melanoma cells, through a process that involved mitochondria and caspase activation. Berberine-induced activation of a number of caspases, including caspases 3, 4, 7, 8, and 9. Pan-caspase inhibitor, z-VAD-fmk, and caspase-8 and caspase-9 inhibitors prevented apoptosis. Berberine also led to the generation of the p20 cleavage fragment of BAP31, involved in directing proapoptotic signals between the endoplasmic reticulum and the mitochondria. Treatment of SK-MEL-2 melanoma cells with berberine induced disruption of the mitochondrial transmembrane potential, release of cytochrome c and apoptosis-inducing factor from the mitochondria to the cytosol, generation of reactive oxygen species (ROS), and a decreased ATP/ADP ratio. Overexpression of bcl-xL by gene transfer prevented berberine-induced cell death, mitochondrial transmembrane potential loss, and cytochrome c and apoptosis-inducing factor release, but not ROS generation. N-acetyl-L-cysteine inhibited the production of ROS, but did not abrogate the berberine-induced apoptosis. Inhibition of extracellular signal-regulated kinase (ERK) phosphorylation, by using the mitogen-activated protein kinase/ERK kinase inhibitor PD98059, and reduction of B-RAF levels by silencing RNA induced cell death of SK-MEL-2 cells, and diminished the berberine concentration required to promote apoptosis. These data show that berberine-induced apoptosis in melanoma cells involves mitochondria and caspase activation, but ROS generation was not essential. Our results indicate that inhibition of B-RAF/ERK survival signaling facilitates the cell death response triggered by berberine.     

亚硒酸钠通过Keap1/Nrf2/ARE信号通路诱导人肺腺癌A549细胞凋亡

目的探究亚硒酸钠诱导人肺腺癌A549细胞凋亡的作用及可能的分子机制。方法 MTT法检测不同浓度亚硒酸钠对人肺腺癌A549细胞的抑制增殖率;倒置荧光显微镜观察细胞经亚硒酸钠处理后的形态学改变;流式细胞术检测细胞凋亡率;激光共聚焦观察活性氧荧光强度;多功能酶标仪测定氧化应激参数含量;Western blot检测Keap1/Nrf2/ARE信号通路蛋白的表达,以及Nrf2在细胞质和细胞核中的蛋白表达情况。结果亚硒酸钠剂量依赖性地抑制人肺腺癌A549细胞增殖,亚硒酸钠作用于人肺腺癌A549细胞24 h后,通过Hoechst 33342固定和流式细胞术分析,细胞凋亡率明显增加;亚硒酸钠可使活性氧和丙二醛水平明显升高,还原型谷胱甘肽和超氧化物歧化酶含量明显下降;同时亚硒酸钠能够下调Keap1、Nrf2和HO-1蛋白的表达,并且抑制Nrf2发生核位移。结论亚硒酸钠通过抑制人肺腺癌A549细胞增殖,诱导细胞凋亡,调节细胞内的氧化应激反应,调控Keap1/Nrf2/ARE抗氧化信号通路,从而促进肿瘤细胞凋亡。