Sevoflurane post-conditioning protects against myocardial reperfusion injury by activation of phosphatidylinositol-3-kinase signal transduction

The mechanisms underlying myocardial protection by sevoflurane post-conditioning are unclear. In the present study, we tested two hypotheses: (i) that sevoflurane post-conditioning produces cardioprotection via a phosphatidylinositol-3-kinase (PI3-K)-dependent pathway; and (ii) combining sevoflurane and ischaemic post-conditioning offers an additional benefit against reperfusion injury. Rat isolated perfused hearts were exposed to 25 min ischaemia followed by 90 min reperfusion. Sevoflurane post-conditioning was induced by administration of sevoflurane (3.0 vol%) for 15 min from the onset of reperfusion. In some groups, 15 micromol/L LY294002, a selective PI3-K inhibitor, was coadministrated with sevoflurane. Other groups of hearts were exposed to ischaemic post-conditioning or combined sevoflurane plus ischaemic post-conditioning in the presence and absence of LY294002. After 15 min reperfusion, phosphorylation of Akt and glycogen synthase kinase 3beta (GSK3beta) was determined by Western blot analysis. Infarct size was determined by 2,3,5-triphenyltetrazolium chloride staining and subsarcolemmal mitochondrial lesions were assessed by electron microscopy after 90 min reperfusion. Sevoflurane post-conditioning significantly decreased infarct size compared with control hearts (31 +/- 2 vs 42 +/- 3%, respectively; P < 0.05), diminished mitochondrial lesions and increased phosphorylation of Akt and GSK3beta, as did ischaemic post-conditioning. However, combined sevoflurane plus ischaemic post-conditioning did not further improve the cardioprotective effects compared with either intervention alone. Sevoflurane-mediated cardioprotection was abolished or inhibited by 15 micromol/L LY294002. In conclusion, sevoflurane acts during early reperfusion after ischaemia to salvage the myocardium by activating PI3-K. The combination of sevoflurane plus ischaemic post-conditioning does not offer any additional benefit over either intervention alone.     

Mu-opioid receptor activation prevents apoptosis following serum withdrawal in differentiated SH-SY5Y cells and cortical neurons via phosphatidylinositol 3-kinase

Opioid peptides and alkaloids exert their effects via G protein-coupled receptors (GPCRs). It has been shown that, in addition to trophic factors, some GPCRs are able to activate the phosphatidylinositol 3-kinase/Akt (PI 3-K/Akt) signal transduction pathway, thus leading to cell survival. The aim of this study was to test whether activation of mu-opioid receptors has protective effects on serum withdrawal-induced cell death and to study the possible implication of PI 3-K in this process. In SH-SY5Y neuroblastoma cells fully differentiated by exposure to retinoic acid for five days, the enkephalin derivative selective mu-agonist DAMGO (0.1-2 microM) and the alkaloid morphine (0.1-10 microM) promoted cell survival after serum deprivation (MTT and trypan blue exclusion assays), without inducing cell proliferation. These effects were fully reversed by naloxone, by the selective mu-antagonist beta-funaltrexamine (beta-FNA) and also by the specific PI 3-K inhibitor LY294002. The two agonists stimulated Akt phosphorylation and the effect was also abolished by beta-FNA and by LY294002. In mouse primary cortical neurons, DAMGO reduced the percentage of apoptosis after 6, 12, 24 and 48 h of serum withdrawal; as determined by Hoechst staining. This effect was blocked by beta-FNA, by pre-treatment with pertussis toxin and by LY294002. DAMGO also stimulated Akt phosphorylation via PI 3-K in this primary neuronal culture. Together, these results indicate that stimulation of the mu-opioid receptor promotes neuronal survival in a G(i/o)-linked, PI 3-K-dependent signaling cascade and suggest that Akt may be a key downstream kinase involved in this anti-apoptotic effect.     

The phosphatidylinositol 3-kinase/Akt pathway negatively regulates Nod2-mediated NF-kappaB pathway

Nucleotide-binding oligomerization domain containing proteins (Nods) are intracellular pattern recognition receptors (PRRs) that recognize conserved moieties of bacterial peptidoglycan and activate downstream signaling pathways, including NF-kappaB pathway. Here, we show that Nod2 agonist muramyldipeptide (MDP) induces Akt phosphorylation in time and dose-dependent manner. The pharmacological inhibitor of phosphatidylinositol 3-kinase (PI3K) (wortmannin) and dominant-negative forms of p85 (the regulatory subunit of PI3K) or Akt enhance, while constitutive active forms of p110 (the catalytic subunit of PI3K) or Akt inhibit, NF-kappaB activation and the target gene interleukin (IL)-8 induced by MDP. In addition, the pharmacological inhibitors of PI3K (wortmannin and LY294002) enhance phosphorylation of NF-kappaB p65 on Ser529 and Ser536 residues, which result in enhanced p65 transactivation activity. Furthermore, we show that the inhibition of PI3K by the pharmacological inhibitors prevent the inactivation of glycogen synthase kinase (GSK)-3beta, suggesting that the negative regulation of PI3K/Akt on MDP-induced NF-kappaB activation is at least in part mediated through inactivation of GSK-3beta. Taken together, our results demonstrate that PI3K/Akt pathway is activated by Nod2 agonist MDP and negatively regulates NF-kappaB pathway downstream of Nod2 activation. Our results suggest that PI3K/Akt pathway may involve in the resolution of inflammatory responses induced by Nod2 activation.     

诱导型HSP70过表达对低钾诱导的小脑颗粒神经元凋亡的保护作用

目的观察腺病毒介导的人诱导型HSP70过表达对低钾诱导的原代培养的大鼠小脑颗粒神经元(cerebellargranuleneurons,CGN)凋亡的影响。方法原代培养5d的CGN共感染含人诱导型HSP70和绿色荧光蛋白(GFP)的腺病毒(AdTR5/HSP70-GFP)和四环素调控的启动子(AdCMV/tTA),或共感染含GFP的腺病毒(AdTR5/GFP)和AdCMV/tTA(对照组)。48h后,采用细胞荧光免疫组织化学法、Westernblot法检测HSP70的表达,或者换成无血清含5mmol·L-1KCl的培养基以诱导神经元凋亡。24h后,采用相差显微镜观察细胞形态学变化,MTT法检测神经元存活率,Hoechst33258核染色和DNA琼脂糖凝胶电泳分析神经元凋亡,以观察HSP70过表达对低钾诱导的CGN凋亡的影响。结果共感染了AdCMV/tTA和AdTR5/HSP70-GFP的CGN过表达了HSP70,抑制了低钾诱导的CGN的凋亡:使神经元存活率由45·5%±5·2%提高至82·3%±5·2%(P<0·01),核固缩减少,DNA的片段化减轻。结论腺病毒介导的人诱导型HSP70的过表达抑制了低钾诱导的CGN凋亡。     

Brain-derived neurotrophic factor prevents phencyclidine-induced apoptosis in developing brain by parallel activation of both the ERK and PI-3K/Akt pathways

Phencyclidine is an N-methyl d-aspartate receptor (NMDAR) blocker that has been reported to induce neuronal apoptosis during development and schizophrenia-like behaviors in rats later in life. Brain-derived neurotrophic factor (BDNF) has been shown to prevent neuronal death caused by NMDAR blockade, but the precise mechanism is unknown. This study examined the role of the phosphatidylinositol-3 kinase (PI3K)/Akt and extracellular signal-regulated kinase (ERK) pathways in BDNF protection of PCP-induced apoptosis in corticostriatal organotypic cultures. It was observed that BDNF inhibited PCP-induced apoptosis in a concentration-dependent fashion. BDNF effectively prevented PCP-induced inhibition of the ERK and PI-3K/Akt pathways and suppressed GSK-3β activation. Blockade of either PI-3K/Akt or ERK activation abolished BDNF protection. Western blot analysis revealed that the PI-3K inhibitor LY294002 prevented the stimulating effect of BDNF on the PI-3K/Akt pathway, but had no effect on the ERK pathway. Similarly, the ERK inhibitor PD98059 prevented the stimulating effect of BDNF on the ERK pathway, but not the PI-3K/Akt pathway. Co-application of LY294002 and PD98059 had no additional effect on BDNF-evoked activation of Akt or ERK. However, concurrent exposure to PD98059 and LY294002 caused much greater inhibition of BDNF-evoked phosphorylation of GSK-3β at serine 9 than did LY294002 alone. Finally, either BDNF or GSK-3β inhibition prevented PCP-induced suppression of cyclic-AMP response element binding protein (CREB) phosphorylation. These data demonstrate that the protective effect of BDNF against PCP-induced apoptosis is mediated by parallel activation of the PI-3K/Akt and ERK pathways, most likely involves inhibition of GSK-3β and activation of CREB.     

Overexpressed Hsp70 alleviated formaldehyde‐induced apoptosis partly via PI3K/Akt signaling pathway in human bronchial epithelial cells

Formaldehyde (FA) is a ubiquitous environmental pollutant, which can induce apoptosis in lung cell and is related to the pathogenesis of asthma, pneumonia, and chronic obstructive pulmonary disease. Heat shock protein 70 (Hsp70) is an ATP‐dependent molecular chaperone and exhibits an anti‐apoptosis ability in a variety of cells. Previous studies reported that the expression of Hsp70 was induced when organisms were exposed to FA. Whether Hsp70 plays a role in the FA‐induced apoptosis and the involved cell signaling pathway remain largely unknown. In this study, human bronchial epithelial cells with overexpressed Hsp70 and the control were exposed to different concentrations of FA (0, 40, 80, and 160 μmol/L) for 24 hours. Apoptosis and the expression levels of PI3K, Akt, p‐Akt, MEK, p‐MEK, and GLI2 were detected by Annexin‐APC/7AAD double‐labeled flow cytometry and western blot. The results showed that overexpression of Hsp70 decreased the apoptosis induced by FA and alleviated the decline of PI3k and p‐Akt significantly. Inhibitor (LY 294002, a specific inhibitor of PI3K‐Akt) test result indicated that PI3K‐Akt signaling pathway was involved in the inhibition of FA‐induced apoptosis by Hsp70 overexpression and also active in the maintenance of GLI2 level. However, it also suggested that other signaling pathways activated by overexpressed Hsp70 participated in this process, which was needed to be elucidated in further research.     

Antioxidant effect of erythropoietin on 1-methyl-4-phenylpyridinium-induced neurotoxicity in PC12 cells

The neuroprotective effects of erythropoietin on 1-methyl-4-phenylpyridinium (MPP(+))-induced oxidative stress and apoptosis in cultured PC12 cells as well as the underlying mechanism were investigated. Treatment of PC12 cells with MPP(+) caused the loss of cell viability, which was associated with the elevation in apoptotic rate, the formation of reactive oxygen species and the disruption of mitochondrial transmembrane potential. It was also shown that MPP(+) significantly induced upregulation of Bax/Bcl-2 ratio and activation of caspase-3. In contrast, erythropoietin reversed these phenotypes and had its maximum protective effect at 1 U/ml. The effect of erythropoietin was mediated by the phosphatidylinositol 3-kinase (PI3K) signaling pathway since erythropoietin failed to rescue cells from MPP(+) insult in the presence of the PI3K inhibitor, LY 294002. In addition, the downstream effector of PI3K, Akt, was activated by erythropoietin, and Akt activation was inhibited by LY 294002. Furthermore, the effect of erythropoietin on reactive oxygen species levels was also blocked by LY 294002. These results show that erythropoietin may provide a useful therapeutic strategy for the treatment of oxidative stress-induced neurodegenerative diseases such as Parkinson disease.     

Inhibition of PI3K and calcineurin suppresses chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2)-dependent responses of Th2 lymphocytes to prostaglandin D(2)

Interaction of prostaglandin D2 (PGD2) with chemoattractant receptor-homologous molecule expressed on Th2 cells (CRTH2) triggers chemotaxis and pro-inflammatory cytokine production by Th2 lymphocytes. We have investigated the role of inhibitors of various cell-signalling pathways on the responses of human CRTH2+ CD4+ Th2 cells to PGD2. Phosphatidylinositol 3-kinase (PI3K) and Ca2+/calcineurin/nuclear factor of activated T cells (NFAT) pathways were activated by PGD2 in Th2 cells in a CRTH2-dependent manner. Inhibition of the PI3K pathway with LY294002 significantly reduced both PGD2-induced cell migration and cytokine (interleukin-4, interleukin-5 and interleukin-13) production. The inhibitory effect of LY294002 on cell migration is likely to be related to cytoskeleton reorganization as it showed a similar potency on PGD2-induced actin polymerization. The calcineurin inhibitors, tacrolimus (FK506) and cyclosporin A, had no effect on cell migration but completely blocked both cytokine production and the nuclear translocation of NFATc1 suggesting that Ca2+/calcineurin/NFAT is involved in CRTH2-dependent cytokine production but not chemotaxis. The promotion of NFAT nuclear location by PI3K activation may be mediated by negative regulation of glycogen synthase kinase-3beta (GSK3beta), since the PGD2-stimulated increase in phospho-GSK3beta was down-regulated by LY294002, and inhibition of GSK3beta by SB216763 enhanced PGD2-induced Th2 cytokine production and reversed the inhibitory effect of LY294002. These data suggest that PI3K and Ca2+/calcineurin/NFAT signalling pathways are critically involved in pro-inflammatory responses of Th2 cells to PGD2.     

IGF-1经PI3K/Akt依赖性途径保护苯妥英诱导的小脑颗粒神经元凋亡

目的　观察胰岛素样生长因子 1 (insulin likegrowfactor 1, IGF 1)对苯妥英(100μmol·L-1 )处理的大鼠小脑颗粒神经元 (cerebellargranularneurons, CGNs)存活率的影响,并探讨其与PI3K/Akt通路的关系。方法　体外培养 8的小脑颗粒神经元,同时给予 100μmol·L-1苯妥英和μmol·L-1 IGF 1, 48h后行凋亡分析,观察IGF 1对苯妥英诱导的小脑颗粒神经元的保护作用;采用PI3K/Akt通路特异性抑制剂LY294002(50μmol·L-1 )预先与小脑颗粒神经元孵育 30min,再加 1μmol·L-1 IGF 1和 100μmol·L-1苯妥英共孵育 48h,测定神经元存活率,观察IGF 1与PI3KAkt通路的关系;Westernblot法检测苯妥因处理不同时间小脑颗粒神经元内磷酸化Akt水平及总Akt的表达量,并观察IGF 1对磷酸化Akt水平的影响,进一步探讨IGF 1的作用是否经PI3K/Akt通路。结果　①1μmol·L-1 IGF 1可明显抑制 100μmol·L-1苯妥英引起的小脑颗粒神经元的凋亡明显提高小脑颗粒神经元的存活率,使其凋亡特征消失。②PI3K/Akt通路特异性抑制剂LY294002可取消IGF 1的保护作用。③苯妥英使小脑颗粒神经元内磷酸化Akt水平明显降低,但不影响总Akt表达量。④IGF 1可明显恢复被苯妥英抑制的磷酸化Akt的水平。结论　IGF 1保护苯妥英诱导的小脑颗粒神经元凋亡,这种     

The PI3K/Akt pathway mediates the protection of SO2 preconditioning against myocardial ischemia/reperfusion injury in rats

Aim:

To explore the mechanisms underlying the protection by SO₂ preconditioning against rat myocardial ischemia/reperfusion (I/R) injury.

Methods:

Male Wistar rats underwent 30-min left coronary artery ligation followed by 120-min reperfusion. An SO₂ donor (1 μmol/kg) was intravenously injected 10 min before the ischemia, while {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 (0.3 mg/kg) was intravenously injected 30 min before the ischemia. Plasma activities of LDH and CK were measured with an automatic enzyme analyzer. Myocardial infarct size was detected using Evans-TTC method. The activities of caspase-3 and -9 in myocardium were assayed using a commercial kit, and the levels of p-Akt, Akt, PI3K and p-PI3K were examined with Western blotting.

Results:

Pretreatment with SO₂ significantly reduced the myocardial infarct size and plasma LDH and CK activities, as well as myocardial caspase-3 and -9 activities in the rats. Furthermore, the pretreatment significantly increased the expression levels of myocardial p-Akt and p-PI3K p85. Administration of the PI3K inhibitor {"type":"entrez-nucleotide","attrs":{"text":"LY294002","term_id":"1257998346","term_text":"LY294002"}}LY294002 blocked all the effects induced by SO₂ pretreatment.

Conclusion:

The results suggest that the PI3K/Akt pathway mediates the protective effects of SO₂ preconditioning against myocardial I/R injury in rats.     

Rutaecarpine inhibits hypoxia/reoxygenation-induced apoptosis in rat hippocampal neurons

Our previous studies showed that rutaecarpine (Rut) protected against myocardial ischemia/reperfusion (I/R) injury, which was associated with activation of transient receptor potential vanilloid subtype 1 (TRPV1). Recently, TRPV1 activation was also reported to exert neuroprotective effects. The present study was to investigate the effect of Rut on hypoxia/reoxygenation (H/R)-induced apoptosis in primary rat hippocampal neurons. Three-hour hypoxia (1% O2) and consequent 24-h reoxygenation significantly increased the apoptotic death of hippocampal neurons as evidenced by increases in both TUNEL-positive cell number and caspase-3 activity. However, pretreatment with Rut (1-10microM) or caspase-3 specific inhibitor DEVD-CHO could markedly attenuate H/R-induced apoptosis in neurons. Rut markedly induced the phosphorylation of Akt and PI3K inhibitor LY294002 prevented the survival effect of Rut on neurons. Intracellular oxidative stress was significantly induced after H/R, which was inhibited by Rut and LY294002 as well as antioxidant PDTC. TRPV1 antagonist capsazepine or intracellular Ca2+ chelator BAPTA/AM could abolish these effects of Rut mentioned above. In summary, the present data suggest that Rut inhibits H/R-induced apoptosis of hippocampal neurons via TRPV1-[Ca2+]i-dependent and PI3K/Akt signaling pathway, which is related to inhibiting oxidative stress and caspase-3 activation.     

Gambogenic acid-induced time- and dose-dependent growth inhibition and apoptosis involving Akt pathway inactivation in U251 glioblastoma cells

Glioblastoma multiforme is the most common and aggressive type of primary brain tumor. Uncontrolled activation of the PI3K/Akt signaling pathway resulting from genetic alterations in phosphatase and tensin homolog deleted on chromosome 10 (PTEN) and epidermal growth factor receptor (EGFR) correlates with poor prognosis and resistance to chemotherapy and radiotherapy of glioblastomas. In this study, we found that gambogenic acid (GNA), a polyprenylated xanthone isolated from the traditional medicine gamboge, efficiently arrested the cell cycle at the G₀/G₁ phase by specifically repressing the expression of cyclin D1 and cyclin E, suppressed cell proliferation, colony formation and cell migration, and induced caspase-dependent apoptosis in U251 glioblastoma cells in a time- and dose-dependent manner. The pro-apoptotic effect of GNA on U251 cells was shown to be mediated through inactivation of the Akt pathway, because GNA efficiently suppressed the expression level of EGFR and reduced the phosphorylation of Akt (T308) and GSK3β (S9). Furthermore, the combined treatment with LY294002, a specific inhibitor of the PI3K/Akt kinase pathway, and GNA showed a synergistic or additive effect on the growth of U251 cells. Our results showed that GNA is a promising therapeutic agent for glioblastomas.     

Regulation of cellular growth, apoptosis, and Akt activity in human U251 glioma cells by a combination of cisplatin with CRM197

The aberrantly activated antiapoptotic phospatidyl-3-inositol-kinase (PI3K)/Akt signaling induced by cisplatin limits the effectiveness of chemotherapy; inhibition of this pathway may augment the sensitivity of tumor cells to cisplatin-induced toxicity and promote apoptosis. Cross-reacting material 197 (CRM197), the nontoxic mutant of diphtheria toxin, could act as an heparin-binding epidermal growth factor inhibitor and has been shown to have some anticancer effects, but the effect of CRM197 on glioma cells remains unclear. The aim of this study was to investigate the effects of a combination of cisplatin with CRM197 on the growth and apoptosis of human U251 glioma cells and the possible mechanism. In this study, we demonstrated that cisplatin or CRM197 induced a dose-dependent growth inhibition in U251 cells, but cisplatin at 5 μg/ml and CRM197 at 1 μg/ml did not affect the viability of human astrocytes. Cisplatin induced a time-dependent growth inhibition in U251 cells, whereas the growth-inhibitory effects induced by CRM197 alone or combined with cisplatin reached a peak at 24 h after treatment. Compared with the administration of cisplatin or CRM197 alone, CRM197 combined with cisplatin significantly enhanced U251 cell growth inhibition and apoptosis. Cisplatin induced sustained activation of Akt, whereas CRM197 markedly suppressed the Akt phosphorylation induced by cisplatin. The effects of growth inhibition and apoptosis were markedly enhanced after a combination of cisplatin with CRM197 plus the PI3K inhibitor LY294002 or wortmannin. Therefore, CRM197 combined with cisplatin could enhance growth inhibition and apoptosis of glioma cells by inhibiting the cisplatin-induced PI3K/Akt pathway.     

Pravastatin induces rat aortic endothelial cell proliferation and migration via activation of PI3K/Akt/mTOR/p70 S6 kinase signaling

The HMG-CoA reductase inhibitors (statins) have been shown to exert several vascular protective effects that are not related to changes in cholesterol profile, and these effects of statins are partly caused by the activation of angiogenesis. Endothelial cell (EC) proliferation and migration are crucial events for angiogenesis and statins are known to enhance these events. However, the molecular mechanism by which statins promote EC proliferation and migration is not fully understood. In this study, we show Akt and its downstream target mammalian target of rapamycin (mTOR) play an important role in pravastatin-induced EC proliferation and migration. We found that pravastatin significantly enhanced the proliferation and migration of rat aortic endothelial cells (rAECs). The addition of pravastatin to rAECs resulted in rapid phosphorylation of Akt and p70 S6 kinase (p70S6K). LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K), blocked both Akt and p70S6K phosphorylation, whereas rapamycin, a specific inhibitor of mTOR, suppressed only p70S6K phosphorylation induced by pravastatin. Furthermore, both LY294002 and rapamycin inhibited pravastatin-induced rAEC proliferation and migration. Taken together, our findings indicate that pravastatin activates PI3K/Akt/mTOR /p70S6K signaling in this sequential manner and this pathway contributes to pravastatin-induced rAEC proliferation and migration.     

PI3K/Akt信号通路活化在曲妥珠单抗耐药机制意义的研究

目的探讨磷脂酰肌醇-3-激酶/丝苏氨酸蛋白激酶(PI3K/Akt)信号转导通路激活是曲妥珠单抗耐药的重要靶点之一,为乳腺癌曲妥珠单抗耐药的靶向治疗提供理论基础。方法对人乳腺癌细胞株BT474连续处理建立了耐曲妥珠单抗的耐药亚株BT-HerR,FISH法对耐药细胞株BT-HerR做Her-2表型分析,MTT法检测曲妥珠单抗对BT474和BT-HerR细胞的体外增殖抑制情况,流式细胞仪检测曲妥珠单抗干预后细胞的凋亡变化,PI3K/Akt抑制剂LY294002干预细胞后Western blot检测p-Akt表达。结果耐药细胞株BT-HerR Her-2基因表达为强阳性;曲妥珠单抗干预细胞72 h后,细胞的体外增殖受到抑制且随着浓度的升高而增强;经曲妥珠单抗处理后比较BT474与BT-HerR细胞凋亡率,差异具有显著性(P<0.01);曲妥珠单抗仅能抑制BT474的Akt蛋白磷酸化,LY294002则能同时抑制BT474的BT-HerR Akt蛋白磷酸化。结论曲妥珠单抗耐药细胞Akt蛋白磷酸化活化,PI3K/Akt抑制剂LY294002能明显抑制曲妥珠单抗耐药细胞Akt蛋白磷酸化,PI3K/Akt信号转导通路与曲妥珠单抗耐药存在明确相关性。     

Dexmedetomidine attenuates propofol-induce neuroapoptosis partly via the activation of the PI3k/Akt/GSK3β pathway in the hippocampus of neonatal rats

Recent studies have demonstrated that propofol causes neurodegeneration in developing brains. Evidence has shown that dexmedetomidine has neuroprotective effects. However, whether dexmedetomidine can reduce propofol-induced neuroapoptosis and by what mechanisms it acts remain unclear. We investigated whether dexmedetomidine can attenuate propofol-induced neuroapoptosis by disturbing the PI3K/Akt/GSK3β pathway during brain development. Seven-day-old rats were randomly exposed to 100 mg/kg propofol and 100 mg/kg propofol plus different doses of dexmedetomidine or 100 mg/kg propofol and 75 μg/kg dexmedetomidine plus PI3K inhibitor LY294002 or GSK3β inhibitor TDZD-8. TEM and TUNEL were used to detect neuronal structure changes and apoptosis. The expression of phospho-Akt, phospho-GSK3β, Akt and GSK3β were quantified using western blots and immunofluorescence. Pretreatment with different doses of dexmedetomidine protected against propofol-induced neuroapoptosis. Furthermore, propofol decreased the levels of phospho-Akt and phospho-GSK3β, whereas dexmedetomidine partially reversed this inhibition. In addition, treatment with LY294002 inhibited the neuroprotection of dexmedetomidine, whereas TDZD-8 enhanced neuroprotection. Our results indicate that dexmedetomidine prevents propofol-induced neuroapoptosis by increasing the levels of phospho-Akt and phospho-GSK3β.     

Furazolidone induces apoptosis through activating reactive oxygen species-dependent mitochondrial signaling pathway and suppressing PI3K/Akt signaling pathway in HepG2 cells

Furazolidone (FZD), a synthetic nitrofuran with a broad spectrum of antimicrobial activities, has been shown to be genotoxic and potentially carcinogenic in several types of cells. However, the proper molecular mechanisms of FZD toxicity remain unclear. This study was aimed to explore the effect of FZD on apoptosis in HepG2 cells and uncover signaling pathway underlying the cytotoxicity of FZD. The results showed that FZD induced apoptosis in HepG2 cells in a dose-dependent manner characterized by nuclei morphology changes, cell membrane phosphatidylserine translocation, poly (ADP-ribose) polymerase (PARP) cleavage and a cascade activation of caspase-9 and -3. FZD could enhance reactive oxygen species (ROS) generation, up-regulate Bax/Bcl-2 ratio, disrupt mitochondrial membrane potential (MMP) and subsequently cause cytochrome c release. Both ROS scavenger (N-acetyl cysteine, NAC) and caspase inhibitors suppressed FZD-induced apoptosis. Furthermore, NAC attenuated FZD-induced ROS generation and mitochondrial dysfunction. Meanwhile, FZD treatment inhibited both the activation and expression of Akt, and PI3K/Akt inhibitor LY294002 promoted FZD-induced apoptosis. On the contrary, PI3K/Akt activator insulin-like growth factor-1 (IGF-1) attenuated lethality of FZD in HepG2 cells. In conclusion, it is first demonstrated that FZD-induced apoptosis in HepG2 cells might be mediated through ROS-dependent mitochondrial signaling pathway and involves PI3K/Akt signaling.