Mitochondrial Ferritin Is a Hypoxia-Inducible Factor 1α-Inducible Gene That Protects from Hypoxia-Induced Cell Death in Brain.

Aims: Mitochondrial ferritin (protein [FtMt]) is preferentially expressed in cell types of high metabolic activity and oxygen consumption, which is consistent with its role of sequestering iron and preventing oxygen-derived redox damage. As of yet, the mechanisms of FtMt regulation and the protection FtMt affords remain largely unknown. Results: Here, we report that hypoxia-inducible factor 1α (HIF-1α) can upregulate FtMt expression. We verify one functional hypoxia-response element (HRE) in the positive regulatory region and two HREs possessing HIF-1α binding activity in the minimal promoter region of the human FTMT gene. We also demonstrate that FtMt can alleviate hypoxia-induced brain cell death by sequestering uncommitted iron, whose levels increase with hypoxia in these cells. Innovation: In the absence of FtMt, this catalytic metal excess catalyzes the production of cytotoxic reactive oxygen species. Conclusion: Thus, the cell ability to increase expression of FtMt during hypoxia may be a skill to avoid tissue damage derived from oxygen limitation.

Mitochondrial Ferritin Protects Hydrogen Peroxide-Induced Neuronal Cell Damage.

Oxidative stress and iron accumulation are tightly associated with neurodegenerative diseases. Mitochondrial ferritin (FtMt) is identified as an iron-storage protein located in the mitochondria, and its role in regulation of iron hemeostasis in neurodegenerative diseases has been reported. However, the role of FtMt in hydrogen peroxide (H2O2)-induced oxidative stress and iron accumulation in neuronal cells has not been studied. Here, we overexpressed FtMt in neuroblastoma SH-SY5Y cells and induced oxidative stress by treating with extracellular H2O2. We found that overexpression of FtMt significantly prevented cell death induced by H2O2, particularly the apoptosis-dependent cell death. The protective effects involved inhibiting the generation of cellular reactive oxygen species, sustaining mitochondrial membrane potential, maintaining the level of anti-apoptotic protein Bcl-2, and inhibiting the activation of pro-apoptotic protein caspase 3. We further explored the mechanism of these protective effects and found that FtMt expression markedly altered iron homeostasis of the H2O2 treated cells as compared to that of controls. The FtMt overexpression significantly reduced cellular labile iron pool (LIP) and protected H2O2-induced elevation on LIP. While in H2O2 treated SH-SY5Y cells, the increased iron uptake and reduced iron release, in correlation with levels of DMT1(-IRE) and ferroportin 1, resulted in heavy iron accumulation, the FtMt overexpressing cells didn't show any significant changes in levels of iron transport proteins and in the level of LIP. These results implicate a neuroprotective role of FtMt on H2O2-induced oxidative stress, which may provide insights into the treatment of iron accumulation associated neurodegenerative diseases.

Mitochondrial ferritin suppresses MPTP-induced cell damage by regulating iron metabolism and attenuating oxidative stress.

Our previous work showed that mitochondrial ferritin (MtFt) played an important role in preventing neuronal damage in 6-OHDA-induced Parkinson's disease (PD). However, the role of MtFt in a PD model induced by MPTP is not clear. Here, we found that methyl-4-phenyl-1, 2, 3, 6-tetra-pyridine (MPTP) significantly upregulated MtFt in the mouse hippocampus, substantia nigra (SN) and striatum. To explore the effect of MtFt upregulation on the MPTP-mediated injury to neural cells, MtFt-/- mice and MtFt-overexpressing cells were used to construct models of PD induced by MPTP. Our results showed that MPTP dramatically downregulated expression of transferrin receptor 1 (TfR1) and tyrosine hydroxylase and upregulated L-ferritin expression in the mouse striatum and SN. Interestingly, MPTP induced high levels of MtFt in these tissues, indicating that MtFt was involved in iron metabolism and influenced dopamine synthesis induced by MPTP. Meanwhile, the Bcl2/Bax ratio was decreased significantly by MPTP in the striatum and SN of MtFt knockout (MtFt-/-) mice compared with controls. Overexpression of MtFt increased TfR1 and decreased ferroportin 1 induced by 1-methyl-4-phenylpyridinium ions (MPP+). MtFt strongly inhibited mitochondrial damage through maintaining the mitochondrial membrane potential and protecting the integrity of the mitochondrial membrane. It also suppressed the increase of the labile iron pool, decreased production of reactive oxygen species and dramatically rescued the apoptosis induced by MPP+. In conclusion, this study demonstrates that MtFt plays an important role in preventing neuronal damage in the MPTP-induced parkinsonian phenotype by inhibiting cellular iron accumulation and subsequent oxidative stress.

Mitochondrial ferritin, a new target for inhibiting neuronal tumor cell proliferation.

Mitochondrial ferritin (FtMt) has a significant effect on the regulation of cytosolic and mitochondrial iron levels. However, because of the deficiency of iron regulatory elements (IRE) in FtMt's gene sequence, the exact function of FtMt remains unclear. In the present study, we found that FtMt dramatically inhibited SH-SY5Y cell proliferation and tumor growth in nude mice. Interestingly, excess FtMt did not adversely affect the development of drosophila. Additionally, we found that the expression of FtMt in human normal brain tissue was significantly higher than that of neuroblastoma, but not higher than that of neurospongioma. However, the expression of transferrin receptor 1 is completely opposite. We therefore hypothesized that increased expression of FtMt may negatively affect the vitality of neuronal tumor cells. Therefore, we further investigated the underlying mechanisms of FtMt's inhibitory effects on neuronal tumor cell proliferation. As expected, FtMt overexpression disturbed the iron homeostasis of tumor cells and significantly downregulated the expression of proliferating cell nuclear antigen. Moreover, FtMt affected cell cycle, causing G1/S arrest by modifying the expression of cyclinD1, cyclinE, Cdk2, Cdk4 and p21. Remarkably, FtMt strongly upregulated the expression of the tumor suppressors, p53 and N-myc downstream-regulated gene-1 (NDRG1), but dramatically decreased C-myc, N-myc and p-Rb levels. This study demonstrates for the first time a new role and mechanism for FtMt in the regulation of cell cycle. We thus propose FtMt as a new candidate target for inhibiting neuronal tumor cell proliferation. Appropriate regulation of FtMt expression may prevent tumor cell growth. Our study may provide a new strategy for neuronal cancer therapy.

Hypoxia-triggered m-calpain activation evokes endoplasmic reticulum stress and neuropathogenesis in a transgenic mouse model of Alzheimer's disease.

BACKGROUND: Previous studies have demonstrated that endoplasmic reticulum (ER) stress is activated in Alzheimer's disease (AD) brains. ER stress-triggered unfolded protein response (UPR) leads to tau phosphorylation and neuronal death. AIMS: In this study, we tested the hypothesis that hypoxia-induced m-calpain activation is involved in ER stress-mediated AD pathogenesis. METHOD: We employed a hypoxic exposure in APP/PS1 transgenic mice and SH-SY5Y cells overexpressing human Swedish mutation APP (APPswe). RESULTS: We observed that hypoxia impaired spatial learning and memory in the APP/PS1 mouse. In the transgenic mouse brain, hypoxia increased the UPR, upregulated apoptotic signaling, enhanced the activation of calpain and glycogen synthase kinase-3ß (GSK3ß), and increased tau hyperphosphorylation and ß-amyloid deposition. In APPswe cells, m-calpain silencing reduced hypoxia-induced cellular dysfunction and resulted in suppression of GSK3ß activation, ER stress and tau hyperphosphorylation reduction as well as caspase pathway suppression. CONCLUSION: These findings demonstrate that hypoxia-induced abnormal calpain activation may increase ER stress-induced apoptosis in AD pathogenesis. In contrast, a reduction in the expression of the m-calpain isoform reduces ER stress-linked apoptosis that is triggered by hypoxia. These findings suggest that hypoxia-triggered m-calpain activation is involved in ER stress-mediated AD pathogenesis. m-calpain is a potential target for AD therapeutics.

Trientine reduces BACE1 activity and mitigates amyloidosis via the AGE/RAGE/NF-κB pathway in a transgenic mouse model of Alzheimer's disease.

AIMS: There is mounting evidence that the transition metal copper may play an important role in the pathophysiology of Alzheimer's disease (AD). Triethylene tetramine dihydrochloride (trientine), a CuII-selective chelator, is a commonly used treatment for Wilson's disease to decrease accumulated copper, and thereby decreases oxidative stress. In the present study, we evaluated the effects of a 3-month treatment course of trientine (Trien) on amyloidosis in 7-month-old ß-amyloid (Aß) precursor protein and presenilin-1 (APP/PS1) double transgenic (Tg) AD model mice. RESULTS: We observed that Trien reduced the level of advanced glycation end products (AGEs), and decreased Aß deposition and synapse loss in brain of APP/PS1 mice. Importantly, we found that Trien blocked the receptor for AGEs (RAGE), downregulated ß-site APP cleaving enzyme 1 (BACE1), inhibited amyloidogenic APP cleavage, and subsequently reduced Aß levels. In vitro, in SH-SY5Y cells overexpressing Swedish mutant APP, Trien-mediated downregulation of BACE1 occurred via inhibition of the NF-κB signaling pathway. INNOVATION: In this study, we demonstrated for the first time that Trien inhibited amyloidogenic pathway including targeting the downregulation of RAGE and NF-κB. CONCLUSION: Trien might mitigate amyloidosis in AD by inhibiting the RAGE/NF-κB/BACE1 pathway. Our study demonstrates that Trien may be a viable therapeutic strategy for the intervention and treatment of AD and other AD-like pathologies.

Mitochondrial ferritin attenuates ß-amyloid-induced neurotoxicity: reduction in oxidative damage through the Erk/P38 mitogen-activated protein kinase pathways.

AIMS: Mitochondrial ferritin (MtFt), which was recently discovered, plays an important role in preventing neuronal damage in 6-hydroxydopamine-induced Parkinsonism by maintaining mitochondrial iron homeostasis. Disruption of iron regulation also plays a key role in the etiology of Alzheimer's disease (AD). To explore the potential neuroprotective roles of MtFt, rats and cells were treated with Aß(25-35) to establish an AD model. RESULTS: We report that knockdown of MtFt expression significantly enhanced Aß(25-35)-induced neurotoxicity as shown by dysregulation of iron homeostasis, enhanced oxidative stress, and increased cell apoptosis. Opposite results were obtained when MtFt was overexpressed in SH-SY5Y cells prior to treatment with Aß(25-35). Further, MtFt inhibited Aß(25-35)-induced P38 mitogen-activated protein kinase and activated extracellular signal-regulated kinase (Erk) signaling. INNOVATION: MtFt attenuated Aß(25-35)-induced neurotoxicity and reduced oxidative damage through Erk/P38 kinase signaling. CONCLUSION: Our results show a protective role of MtFt in AD and suggest that regulation of MtFt expression in neuronal cells may provide a new neuroprotective strategy for AD.

Huperzine A activates Wnt/ß-catenin signaling and enhances the nonamyloidogenic pathway in an Alzheimer transgenic mouse model.

Huperzine A (HupA) is a reversible and selective inhibitor of acetylcholinesterase (AChE), and it has multiple targets when used for Alzheimer's disease (AD) therapy. In this study, we searched for new mechanisms by which HupA could activate Wnt signaling and reduce amyloidosis in AD brain. A nasal gel containing HupA was prepared. No obvious toxicity of intranasal administration of HupA was found in mice. HupA was administered intranasally to ß-amyloid (Aß) precursor protein and presenilin-1 double-transgenic mice for 4 months. We observed an increase in ADAM10 and a decrease in BACE1 and APP695 protein levels and, subsequently, a reduction in Aß levels and Aß burden were present in HupA-treated mouse brain, suggesting that HupA enhances the nonamyloidogenic APP cleavage pathway. Importantly, our results further showed that HupA inhibited GSK3α/ß activity, and enhanced the ß-catenin level in the transgenic mouse brain and in SH-SY5Y cells overexpressing Swedish mutation APP, suggesting that the neuroprotective effect of HupA is not related simply to its AChE inhibition and antioxidation, but also involves other mechanisms, including targeting of the Wnt/ß-catenin signaling pathway in AD brain.

Zinc overload enhances APP cleavage and Aß deposition in the Alzheimer mouse brain.

BACKGROUND: Abnormal zinc homeostasis is involved in ß-amyloid (Aß) plaque formation and, therefore, the zinc load is a contributing factor in Alzheimer's disease (AD). However, the involvement of zinc in amyloid precursor protein (APP) processing and Aß deposition has not been well established in AD animal models in vivo. METHODOLOGY/PRINCIPAL FINDINGS: In the present study, APP and presenilin 1 (PS1) double transgenic mice were treated with a high dose of zinc (20 mg/ml ZnSO4 in drinking water). This zinc treatment increased APP expression, enhanced amyloidogenic APP cleavage and Aß deposition, and impaired spatial learning and memory in the transgenic mice. We further examined the effects of zinc overload on APP processing in SHSY-5Y cells overexpressing human APPsw. The zinc enhancement of APP expression and cleavage was further confirmed in vitro. CONCLUSIONS/SIGNIFICANCE: The present data indicate that excess zinc exposure could be a risk factor for AD pathological processes, and alteration of zinc homeostasis is a potential strategy for the prevention and treatment of AD.

R492X mutation in PTEN-induced putative kinase 1 induced cellular mitochondrial dysfunction and oxidative stress.

The identification of rare monogenic forms of Parkinson's disease (PD) has provided tremendous insights into the molecular pathogenesis of the disorder. Mitochondrial dysfunction and oxidative stress are thought to play a prominent role in the pathogenesis of PD, but how the monogenic mutation gene causes the disease onset or progression is largely unknown. In this study we investigated the effects of wild-type and R492X mutation in the PTEN-induced putative kinase 1 (PINK1). Cell cultures show that R492X PINK1 mutation induces the generation of cellular reactive oxidative species (ROS), degrades cell membrane potential, causes cytochrome C (Cyt.C) release from mitochondrial to cytoplasm, attenuates mitochondrial complex I activity, and lastly, causes changes in mitochondrial numbers and morphology; especially when cells are treated with 1-Methyl-4-phenylpyridinium ion (MPP(+)). Our results suggest that the R492X mutation can cause mitochondrial dysfunction and oxidative stress and can associate with MPP(+) to induce mitochondrial dysfunction and oxidative stress.

Neuroprotective mechanism of mitochondrial ferritin on 6-hydroxydopamine-induced dopaminergic cell damage: implication for neuroprotection in Parkinson's disease.

Neuronal iron homeostasis disruption and oxidative stress are closely related to the pathogenesis of Parkinson's disease (PD). Adult iron-regulatory protein 2 knockout (Ireb2(-/-)) mice develop iron accumulation in white matter tracts and nuclei in different brain area and display severe neurodegeneration in Purkinje cells of the cerebrum. Mitochondrial ferritin (MtFt), a newly discovered ferritin, specifically expresses in high energy-consuming cells, including neurons of brain and spinal cord. Interestingly, the decreased expression of MtFt in cerebrum, but not in striatum, matches the differential neurodegeneration pattern in these Ireb2(-/-) mice. To explore its effect on neurodegeneration, the effects of MtFt expression on 6-hydrodopamine (6-OHDA)-induced neuronal damage was examined. The overexpression of MtFt led to a cytosolic iron deficiency in the neuronal cells and significantly prevented the alteration of iron redistribution induced by 6-OHDA. Importantly, MtFt strongly inhibited mitochondrial damage, decreased production of the reactive oxygen species and lipid peroxidation, and dramatically rescued apoptosis by regulating Bcl-2, Bax and caspase-3 pathways. In conclusion, this study demonstrates that MtFt plays an important role in preventing neuronal damage in an 6-OHDA-induced parkinsonian phenotype by maintaining iron homeostasis. Regulation of MtFt expression in neuronal cells may provide a new neuroprotective strategy for PD.

Nitric oxide mediates stretch-induced Ca2+ release via activation of phosphatidylinositol 3-kinase-Akt pathway in smooth muscle.

BACKGROUND: Hollow smooth muscle organs such as the bladder undergo significant changes in wall tension associated with filling and distension, with attendant changes in muscle tone. Our previous study indicated that stretch induces Ca(2+) release occurs in the form of Ca(2+) sparks and Ca(2+) waves in urinary bladder myocytes. While, the mechanism underlying stretch-induced Ca2+ release in smooth muscle is unknown. METHODOLOGY/PRINCIPAL FINDINGS: We examined the transduction mechanism linking cell stretch to Ca(2+) release. The probability and frequency of Ca(2+) sparks induced by stretch were closely related to the extent of cell extension and the time that the stretch was maintained. Experiments in tissues and single myocytes indicated that mechanical stretch significantly increases the production of nitric oxide (NO) and the amplitude and duration of muscle contraction. Stretch-induced Ca(2+) sparks and contractility increases were abrogated by the NO inhibitor L-NAME and were also absent in eNOS knockout mice. Furthermore, exposure of eNOS null mice to exogenously generated NO induced Ca(2+) sparks. The soluble guanylyl cyclase inhibitor ODQ did not inhibit SICR, but this process was effectively blocked by the PI3 kinase inhibitors LY494002 and wortmannin; the phosphorylation of Akt and eNOS were up-regulated by 204+/-28.6% and 258+/-36.8% by stretch, respectively. Moreover, stretch significantly increased the eNOS protein expression level. CONCLUSIONS/SIGNIFICANCE: Taking together, these results suggest that stretch-induced Ca2+ release is NO dependent, resulting from the activation of PI3K/Akt pathway in smooth muscle.

Nicotine attenuates beta-amyloid-induced neurotoxicity by regulating metal homeostasis.

Nicotine reduces beta-amyloidosis and has a beneficial effect against Alzheimer's disease (AD), but the underlying mechanism is not clear. The abnormal interactions of beta-amyloid (Abeta) with metal ions such as copper and zinc are implicated in the process of Abeta deposition in AD brains. In the present study, we investigated the effect of nicotine on metal homeostasis in the hippocampus and cortex of APP(V717I) (London mutant form of APP) transgenic mice. A significant reduction in the metal contents of copper and zinc in senile plaques and neuropil is observed after nicotine treatment. The densities of copper and zinc distributions in a subfield of the hippocampus CA1 region are also reduced after nicotine treatment. We further studied the mechanism of nicotine-mediated effect on metal homeostasis by using SH-SY5Y cells overexpressing the Swedish mutant form of human APP (APPsw). Nicotine treatment decreases the intracellular copper concentration and attenuates Abeta-mediated neurotoxicity facilitated by the addition of copper, and these effects are independent of the activation of nicotinic acetylcholine-receptor. These data suggest that the effect of nicotine on reducing beta-amyloidosis is partly mediated by regulating metal homeostasis.

Investigating the receptor-independent neuroprotective mechanisms of nicotine in mitochondria.

Although nicotine has been associated with a decreased risk of developing Parkinson disease, the underlying mechanisms are still unclear. By using isolated brain mitochondria, we found that nicotine inhibited N-methyl-4-phenylpyridine (MPP(+)) and calcium-induced mitochondria high amplitude swelling and cytochrome c release from intact mitochondria. Intra-mitochondria redox state was also maintained by nicotine, which could be attributed to an attenuation of mitochondria permeability transition. Further investigation revealed that nicotine did not prevent MPP(+)- or calcium-induced mitochondria membrane potential loss, but instead decreased the electron leak at the site of respiratory chain complex I. In the presence of mecamylamine hydrochloride, a nonselective nicotinic acetylcholine receptor inhibitor, nicotine significantly postponed mitochondria swelling and cytochrome c release induced by a mixture of neurotoxins (MPP(+) and 6-hydroxydopamine) in SH-SY5Y cells, suggesting that there is a receptor-independent nicotine-mediated neuroprotective effect of nicotine. These results show that interaction of nicotine with mitochondria respiratory chain together with its antioxidant effects should be considered in the neuroprotective effects of nicotine.

The effects of meso-2,3-dimercaptosuccinic acid and oligomeric procyanidins on acute lead neurotoxicity in rat hippocampus.

Oxidative stress is considered to be a mechanism involved in lead neurotoxicity. Apoptosis is also thought to relate to lead neurotoxicity. The present study, focused on the hippocampus, was designed to investigate the two possible mechanisms involved in lead neurotoxicity and the potential protective effects of 2,3-dimercaptosuccinic acid (DMSA) and oligomeric procyanidins (OPC). It was proved that reactive oxygen species and oxidative damage were implicated in the induction of apoptosis induced by lead in the hippocampus. Administration of DMSA attenuated the oxidative stress and apoptosis in addition to having strong chelating and lead-removing capacity. OPC alone had antioxidant protective effects in the hippocampus but no removing capacity for lead in vivo despite showing higher affinity and stronger chelating ability for Pb(2+) than DMSA in vitro. It is suggested that OPC chelates Pb(2+) but does not discharge it from the body and even accumulates Pb(2+) in some organs. At the same time, a reasonable deduction can also be made that the complex of OPC-Pb(2+) prevents or at least weakens the neurotoxicity of Pb(2+). Whether this complex displays toxicity over a long time span should be studied further.

Oral administration of Crataegus flavonoids protects against ischemia/reperfusion brain damage in gerbils.

Stroke is the third leading cause of death as dementia is a main symptom of Alzheimer's disease. One of the important mechanisms in the pathogeny of stroke is free radical production during the reperfusion period, therefore the effects of a type of natural antioxidant, i.e. Crataegus flavonoids (CF), on brain ischemic insults were investigated in Mongolian gerbil stroke model. Results showed that pretreatment of the animals with CF decreased reactive oxygen species (ROS) production, thiobarbituric acid reactive substances content, and nitrite/nitrate concentration in brain homogenate, increased the brain homogenate-associated antioxidant level in a dose-dependent manner. CF pretreatment increased the amount of biologically available NO by scavenging of superoxide anion produced during reperfusion. At same time, in the process of ischemia/reperfusion brain damage, the content of nitrite/nitrate (the end product of NO) increased, and of NO detected by ESR decreased. Oral pretreatment with CF decreased the nitrite/nitrate content in the brain homogenate and increased the biologically available NO concentration in a dose-dependent manner. The increasing effect of antioxidant on NO might be due to its scavenging effect on superoxide anion, which could react with NO into peroxynitrite. iNOS was implied in delayed neuron death after brain ischemic damage and it was found that pretreatment with CF could decrease the protein level of tumor necrosis factor (TNF)-alpha and nuclear factor-kappa B (NF-kappaB), and increase the mRNA level of NOS estimated by western blotting and RT-PCR. More neurons survived and fewer cells suffered apoptosis in the hippocampal CA1 region of CF treated animal brain. These results suggest that oral administration of this antioxidant increases the antioxidant level in the brain and protects the brain against delayed cell death caused by ischemia/reperfusion injury.

Detection of nitric oxide in plants by electron spin resonance.

ABSTRACT Three methods to detect nitric oxide (NO()) are reported here. The first method was determining NO() in extracted plant tissue. NO() was trapped by spin trapping reagent containing diethyldithiocarbamate (DETC) and FeSO(4), extracted by ethyl acetate, and determined with an electron spin resonance (ESR) spectrometer. The second method was indirectly determining NO() in live wheat leaves. Seedlings were cultured in a medium containing FeSO(4), and the leaves were brushed by DETC. Then, the leaves were ground and the complex of (DETC)(2)-Fe(2+)-NO was extracted and determined with an ESR spectrometer. The third method was directly determining NO* in live wheat leaves. After treating plant materials as in the second method, part of the water in leaves was transpired, and the leaf disks were inserted directly into quartz tubes to determine NO() with an ESR spectrometer. The NO() scavenger 2-phenyl-4,4,5,5,-tetramethylimidazoline- 1-oxyl 3-oxide (PTIO) decreased NO() signal detected either by an indirect or a direct method. This result indicates that both methods could detect NO() in the live plant. Using the first methods, we detected NO() change in wheat infected by Puccinia striiformis race CY22-2 pathogen (incompatible interaction) at different inoculation times, and it was found that the NO() content dramatically increased at 24 h postinoculation, quickly decreased at 48 h, and increased again at 96 h.

[The effects of nitric oxide on cardiac apoptosis and function during myocardial/reperfusion injury].

AIM: The observation of the relationship between the level of NO detected by ESR in the blood and the myocardial apoptosis and function caused by the recurrent, reversible myocardial ischemia/reperfusion injury. METHODS: Fifteen New Zealand white rabbits were randomly divided into three groups (n = 5): (1) control group, (2) L-Arg group, (3) L-NNA group. The rabbits were anesthetized with intravenous pentobarbital. A suture ligature was passed around the left anterior descending coronary artery (LAD), so it could be snare occluded and reperfused. The LAD was occluded for 10 min three times, the first and second occlusions were followed by 10 min of reflow, after the third occlusion, the reperfusion was 120 min. RESULTS: In all groups dp/dt(max) began to decrease at 5 min after the first ischemia. But compared with control group at 5 min after first reperfusion: in L-Arg group NO and apoptosis level were elevated but dp/dt(max) decreased significantly. In L-NNA group NO and apoptosis decreased significantly, dp/dt(max) improved significantly. CONCLUSION: The fact that the level of NO and apoptosis elevated suggested that they had taken part in the process of myocardial stunning.

Protective effects of green tea polyphenols on human HepG2 cells against oxidative damage of fenofibrate.

The aim of this work was to investigate the protective effects of green tea polyphenols on the cytotoxic effects of hypolipidemic agent fenofibrate (FF), a peroxisome proliferator (PP), in human HepG2 cells. The results showed that high concentrations of FF induced human HepG2 cell death through a mechanism involving an increase of reactive oxygen species (ROS) and intracellular reduced glutathione (GSH) depletion. These effects were partially prevented by antioxidant green tea polyphenols. The elevated expression of PP-activated receptors alpha (PPARalpha) in HepG2 cells induced by FF was also decreased by treatment with green tea polyphenols. In conclusion, this result demonstrates that oxidative stress and PPARalpha are involved in FF cytotoxicity and green tea polyphenols have a protective effect against FF-induced cellular injury. It may be beneficial for the hyperlipidemic patients who were administered the hypolipidemic drug fenofibrate to drink tea or use green tea polyphenols synchronously during their treatment.

Cytotoxic effect of peroxisome proliferator fenofibrate on human HepG2 hepatoma cell line and relevant mechanisms.

The aim of this work was to investigate the effects of hypolipidemic agent fenofibrate (FF), a peroxisome proliferator (PP), on human HepG2 cells and to characterize the intracellular events involved. The results showed that, in contrast to the tumor-promoting effects in rodents, high FF concentrations induced human HepG2 cell death through a mechanism involving an increase in the levels of reactive oxygen species (ROS) and intracellular GSH depletion, which led, through mitochondrial dysfunction and perturbation of intracellular Ca(2+) homeostasis, to cell death. The nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR(alpha)) was expressed following FF treatment. The results suggest that, although long-term administration of PPs causes liver cancer in susceptible species (e.g., rodents), FF inhibits the growth of human HepG2 cells in a dose-related manner and oxidative stress was involved in this effect.