The cytotoxicity of tumor necrosis factor depends on induction of the mitochondrial permeability transition

Diazepam diminishes temozolomide efficacy in the treatment of U87 glioblastoma cell line

AIMS

Many patients with glioblastoma (GBM) suffer from comorbid neurological/psychiatric disorders and, therefore, are treated with psychopharmacological agents. Diazepam (DIA) is widely adopted to treat status epilepticus, alleviate anxiety, and inhibit chemotherapy-associated delayed emesis in GBM patients. Even though temozolomide (TMZ) and DIA could be found as possible combination therapy in clinical practice, there are no reports of their combined effects in GBM. Hence, it may be of interest to investigate whether DIA enhances the antitumor efficacy of TMZ in GBM cells.

METHODS

U87 human GBM was used to examine the effects of combined TMZ and DIA on cell viability, and the oxygen consumption within the cells, in order to evaluate mitochondrial bioenergetic response upon the treatment.

RESULTS

The cooperative index showed the presence of antagonism between TMZ and DIA, which was confirmed on long-term observation. Moreover, the level of apoptosis after the TMZ treatment was significantly decreased when administered with DIA (p < 0.001). Concomitant use of TMZ and DIA increased the basal cell respiration rate, the oxidative phosphorylation rate, and maximal capacity of mitochondrial electron transport chain, as well as the activities of complexes I and II, vs. TMZ alone (p < 0.001).

CONCLUSION

Comparing our results with data reported that DIA elicits cell cycle arrest in the G0/G1 phase and favors senescence reveals that DIA diminishes TMZ efficacy in concomitant use in the treatment of GBM. However, due to its great potency to hinder GBM proliferation and metabolism, it could be considered using DIA as maintenance therapy after TMZ cycles.

Non-Alcoholic Fatty Liver Disease and Cardiovascular Comorbidities: Pathophysiological Links, Diagnosis, and Therapeutic Management

Non-alcoholic fatty liver disease (NAFLD) has a growing prevalence in recent years. Its association with cardiovascular disease has been intensively studied, and certain correlations have been identified. The connection between these two entities has lately aroused interest regarding therapeutic management. In order to find the best therapeutic options, a detailed understanding of the pathophysiology that links (NAFLD) to cardiovascular comorbidities is needed. This review focuses on the pathogenic mechanisms that are behind these two diseases and on the therapeutic management available at this time.

The Role of Ceramides in Diabetes and Cardiovascular Disease Regulation of Ceramides by Adipokines

Metabolic dysfunction is intertwined with the pathophysiology of both diabetes and cardiovascular disease. Recently, one particular lipid class has been shown to influence the development and sustainment of these diseases: ceramides. As a subtype of sphingolipids, these species are particularly central to many sphingolipid pathways. Increased levels of ceramides are known to correlate with impaired cardiovascular and metabolic health. Furthermore, the interaction between ceramides and adipokines, most notably adiponectin and leptin, appears to play a role in the pathophysiology of these conditions. Adiponectin appears to counteract the detrimental effects of elevated ceramides, largely through activation of the ceramidase activity of its receptors. Elevated ceramides appear to worsen leptin resistance, which is an important phenomenon in the pathophysiology of obesity and metabolic syndrome.

Neuroprotection: A versatile approach to combat glaucoma

In most retinal diseases, neuronal loss is the main cause of vision loss. Neuroprotection is the alteration of neurons and/or their environment to encourage the survival and function of the neurons, especially in environments that are deleterious to the neuronal health. The area of neuroprotection progresses with a therapeutically-based hope of improving vision and clinical outcomes for patients through the developments in neurotrophic therapy, antioxidative therapy, anti-excitotoxic, anti-ischemic, anti-inflammatory, and anti-apoptotic care. In this review, we summarize the various neuroprotection strategies for the treatment of glaucoma, genetics of glaucoma and the role of various nanoplatforms in the treatment of glaucoma.

Amelioration of High Fructose-Induced Cardiac Hypertrophy by Naringin

Heart failure is a frequent unfavorable outcome of pathological cardiac hypertrophy. Recent increase in dietary fructose consumption mirrors the rise in prevalence of cardiovascular diseases such as cardiac hypertrophy leading to concerns raised by public health experts. Mitochondria, comprising 30% of cardiomyocyte volume, play a central role in modulating redox-dependent cellular processes such as metabolism and apoptosis. Furthermore, mitochondrial dysfunction is a key cause of pathogenesis of fructose-induced cardiac hypertrophy. Naringin, a major flavanone glycoside in citrus species, has displayed strong antioxidant potential in models of oxidative stress. In this study, we evaluated protective effects of naringin against fructose-induced cardiac hypertrophy and associated mechanisms of action, using in vitro and in vivo models. We found that naringin suppressed mitochondrial ROS production and mitochondrial dysfunction in cardiomyocytes exposed to fructose and consequently reduced cardiomyocyte hypertrophy by regulating AMPK-mTOR signaling axis. Furthermore, naringin counteracted fructose-induced cardiomyocyte apoptosis, and this function of naringin was linked to its ability to inhibit ROS-dependent ATM-mediated p53 signaling. This result was supported by observations in in vivo mouse model of cardiac hypertrophy. These findings indicate a novel role for naringin in protecting against fructose-induced cardiac hypertrophy and suggest unique therapeutic strategies for prevention of cardiovascular diseases.

IDH2 deficiency accelerates skin pigmentation in mice via enhancing melanogenesis

Melanogenesis is a complex biosynthetic pathway regulated by multiple agents, which are involved in the production, transport, and release of melanin. Melanin has diverse roles, including determination of visible skin color and photoprotection. Studies indicate that melanin synthesis is tightly linked to the interaction between melanocytes and keratinocytes. α-melanocyte-stimulating hormone (α-MSH) is known as a trigger that enhances melanin biosynthesis in melanocytes through paracrine effects. Accumulated reactive oxygen species (ROS) in skin affects both keratinocytes and melanocytes by causing DNA damage, which eventually leads to the stimulation of α-MSH production. Mitochondria are one of the main sources of ROS in the skin and play a central role in modulating redox-dependent cellular processes such as metabolism and apoptosis. Therefore, mitochondrial dysfunction may serve as a key for the pathogenesis of skin melanogenesis. Mitochondrial NADP⁺-dependent isocitrate dehydrogenase (IDH2) is a key enzyme that regulates mitochondrial redox balance and reduces oxidative stress-induced cell injury through the generation of NADPH. Downregulation of IDH2 expression resulted in an increase in oxidative DNA damage in mice skin through ROS-dependent ATM-mediated p53 signaling. IDH2 deficiency also promoted pigmentation on the dorsal skin of mice, as evident from the elevated levels of melanin synthesis markers. Furthermore, pretreatment with mitochondria-targeted antioxidant mito-TEMPO alleviated oxidative DNA damage and melanogenesis induced by IDH2 deficiency both in vitro and in vivo. Together, our findings highlight the role of IDH2 in skin melanogenesis in association with mitochondrial ROS and suggest unique therapeutic strategies for the prevention of skin pigmentation.

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Melanogenesis is associated with the production of ROS.

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IDH2 is an essential enzyme in the mitochondrial antioxidant system.

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Downregulation of IDH2 induces ROS-dependent ATM-mediated p53 signaling.

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IDH2 deficiency promotes skin pigmentation.

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mito-TEMPO alleviates melanogenesis caused by IDH2 deficiency.

Recurrent Hypoglycemia Exacerbates Cerebral Ischemic Damage in Diabetic Rats via Enhanced Post-Ischemic Mitochondrial Dysfunction

Diabetes significantly increases the risk of stroke and post-stroke mortality. Recurrent hypoglycemia (RH) is common among diabetes patients owing to glucose-lowering therapies. Earlier, we showed that RH in a rat model of insulin-dependent diabetes exacerbates cerebral ischemic damage. Impaired mitochondrial function has been implicated as a central player in the development of cerebral ischemic damage. Hypoglycemia is also known to affect mitochondrial functioning. The present study tested the hypothesis that prior exposure of insulin-treated diabetic (ITD) rats to RH exacerbates brain damage via enhanced post-ischemic mitochondrial dysfunction. In a rat model of streptozotocin-induced diabetes, we evaluated post-ischemic mitochondrial function in RH-exposed ITD rats. Rats were exposed to five episodes of moderate hypoglycemia prior to the induction of cerebral ischemia. We also evaluated the impact of RH, both alone and in combination with cerebral ischemia, on cognitive function using the Barnes circular platform maze test. We observed that RH exposure to ITD rats leads to increased cerebral ischemic damage and decreased mitochondrial complex I activity. Exposure of ITD rats to RH impaired spatial learning and memory. Our results demonstrate that RH exposure to ITD rats potentially increases post-ischemic damage via enhanced post-ischemic mitochondrial dysfunction.

Clinical importance of nonsteroidal anti-inflammatory drug enteropathy: the relevance of tumor necrosis factor as a promising target

The pathogenesis of nonsteroidal anti-inflammatory drug (NSAID) enteropathy is still unclear, and consequently, there is no approved therapeutic strategy for ameliorating such damage. On the other hand, molecular treatment strategies targeting tumor necrosis factor (TNF) exerts beneficial effects on NSAID-induced intestinal lesions in rodents and rheumatoid arthritis patients. Thus, TNF appears to be a potential therapeutic target for both the prevention and treatment of NSAID enteropathy. However, the causative relationship between TNF and NSAID enteropathy is largely unknown. Currently approved anti-TNF agents are highly expensive and exhibit numerous side effects. Hence, in this review, the pivotal role of TNF in NSAID enteropathy has been summarized and plant-derived polyphenols have been suggested as useful alternative anti-TNF agents because of their ability to suppress TNF activated inflammatory pathways both in vitro and in vivo.

Blocking mPTP on Neural Stem Cells and Activating the Nicotinic Acetylcholine Receptor α7 Subunit on Microglia Attenuate Aβ-Induced Neurotoxicity on Neural Stem Cells

β-Amyloid (Aβ) can stimulate microglia to release a variety of proinflammatory cytokines and induce neurotoxicity. Nicotine has been reported to inhibit TNF-α, IL-1, and ROS production in microglia. Mitochondrial permeability transition pore (mPTP) plays an important role in neurotoxicity as well. Here, we investigated whether activating the microglial α7-nAChR has a neuroprotective role on neural stem cells (NSCs) and the function of mPTP in NSCs in this process. The expression of α7-nAChR in rat NSCs was detected by immunocytochemistry and RT-PCR. The viability of microglia and NSCs was examined by MTT assay. The mitochondrial membrane potential (ΔΨm) and morphological characteristics of NSCs was measured by JC-1 staining and transmission electron microscopy respectively. The distribution of cytochrome c in the subcellular regions of NSCs was visualized by confocal laser scanning microscopy, and the expression levels of cyclophilin D and cleaved caspase-3 were assayed by western blot. The apoptotic rate of NSCs was measured by flow cytometry. The expression of α7-nAChR was detected in microglial cells, but no expression was found in NSCs. The viability of rat microglial cells and NSCs was not affected by reagents or coculture itself. Aβ1-42-mediated microglial activation impaired the morphology and the ΔΨm of mitochondria of NSCs as well as increased cell apoptosis. However, the damage was attenuated when the α7-nAChRs on microglial cells were activated or the mPTPs on NSCs were blocked. Blockade of mPTPs on NSCs and activation of α7-nAChRs on microglia exhibit neuroprotective roles in Aβ-induced neurotoxicity of NSCs.

The 18 kDa translocator protein, microglia and neuroinflammation

The 18 kDa translocator protein (TSPO), previously known as the peripheral benzodiazepine receptor, is expressed in the injured brain. It has become known as an imaging marker of "neuroinflammation" indicating active disease, and is best interpreted as a nondiagnostic biomarker and disease staging tool that refers to histopathology rather than disease etiology. The therapeutic potential of TSPO as a drug target is mostly based on the understanding that it is an outer mitochondrial membrane protein required for the translocation of cholesterol, which thus regulates the rate of steroid synthesis. This pivotal role together with the evolutionary conservation of TSPO has underpinned the belief that any loss or mutation of TSPO should be associated with significant physiological deficits or be outright incompatible with life. However, against prediction, full Tspo knockout mice are viable and across their lifespan do not show the phenotype expected if cholesterol transport and steroid synthesis were significantly impaired. Thus, the "translocation" function of TSPO remains to be better substantiated. Here, we discuss the literature before and after the introduction of the new nomenclature for TSPO and review some of the newer findings. In light of the controversy surrounding the function of TSPO, we emphasize the continued importance of identifying compounds with confirmed selectivity and suggest that TSPO expression is analyzed within specific disease contexts rather than merely equated with the reified concept of "neuroinflammation."

Aristolochic acid induced suicidal erythrocyte death

BACKGROUND/AIMS

Aristolochic Acid, a component of Aristolochia plants, has been shown to cause acute kidney injury, renal aristolochic acid nephropathy, Balkan endemic nephropathy, and urothelial carcinoma. Aristolochic acid nephropathy may be associated with severe anemia. The anemia could theoretically be due to stimulation of eryptosis, the suicidal death of erythrocytes characterized by cell shrinkage and cell membrane scrambling with translocation of phosphatidylserine to the erythrocyte cell membrane surface. Signalling involved in the stimulation of eryptosis include increase of cytosolic Ca(2+)-activity ([Ca(2+)]i) and formation of ceramide.

METHODS

Cell volume was estimated from forward scatter, phosphatidylserine-exposure from annexin V binding, [Ca(2+)]i from Fluo3 fluorescence, and ceramide abundance from binding of fluorescent antibodies in flow cytometry.

RESULTS

A 48 hours exposure to Aristolochic Acid (≥ 75 µg/ml) was followed by a significant decrease of forward scatter and increase of annexin-V-binding. The effects were paralleled by a significant increase of [Ca(2+)]i and significantly blunted, but not abrogated by removal of extracellular Ca(2+). Aristolochic Acid further significantly increased ceramide abundance.

CONCLUSIONS

Aristolochic Acid triggers eryptosis, an effect at least in part due to entry of extracellular Ca(2+) and ceramide formation.

Hexokinase II binding to mitochondria is necessary for Kupffer cell activation and is potentiated by ethanol exposure

Ethanol exposure promotes the development of steatohepatitis, which can progress to end stage liver disease. Kupffer cells have been documented to play a key role in the genesis and progression of alcoholic liver disease with ethanol exposure enhancing Kupffer cell activation. In the present study, we identified the binding of hexokinase II to the mitochondria as a requirement for LPS-induced activation of Kupffer cells and its potentiation by ethanol. LPS and ethanol exposure induced a reduction in sirtuin-3 activity. In turn, the decline of sirtuin-3 activity led to the activation of cyclophilin-D, which mediated an increased binding of hexokinase II to the mitochondria. Suppression of cyclophilin-D expression or enforced detachment of hexokinase II from the mitochondria abrogated the LPS- and ethanol-induced stimulation of Kupffer cells, preventing NADPH oxidase and inflammasome activation. Moreover, activation of AMP-activated protein kinase restored sirtuin-3 activity, thereby preventing LPS and ethanol from stimulating the binding of hexokinase II to the mitochondria and precluding NADPH oxidase and inflammasome activation.

Mitochondrial channels: ion fluxes and more

The field of mitochondrial ion channels has recently seen substantial progress, including the molecular identification of some of the channels. An integrative approach using genetics, electrophysiology, pharmacology, and cell biology to clarify the roles of these channels has thus become possible. It is by now clear that many of these channels are important for energy supply by the mitochondria and have a major impact on the fate of the entire cell as well. The purpose of this review is to provide an up-to-date overview of the electrophysiological properties, molecular identity, and pathophysiological functions of the mitochondrial ion channels studied so far and to highlight possible therapeutic perspectives based on current information.

Sulfite disrupts brain mitochondrial energy homeostasis and induces mitochondrial permeability transition pore opening via thiol group modification

Sulfite oxidase (SO) deficiency is biochemically characterized by the accumulation of sulfite, thiosulfate and S-sulfocysteine in tissues and biological fluids of the affected patients. The main clinical symptoms include severe neurological dysfunction and brain abnormalities, whose pathophysiology is still unknown. The present study investigated the in vitro effects of sulfite and thiosulfate on mitochondrial homeostasis in rat brain mitochondria. It was verified that sulfite per se, but not thiosulfate, decreased state 3, CCCP-stimulated state and respiratory control ratio in mitochondria respiring with glutamate plus malate. In line with this, we found that sulfite inhibited the activities of glutamate and malate (MDH) dehydrogenases. In addition, sulfite decreased the activity of a commercial solution of MDH, that was prevented by antioxidants and dithiothreitol. Sulfite also induced mitochondrial swelling and reduced mitochondrial membrane potential, Ca(2+) retention capacity, NAD(P)H pool and cytochrome c immunocontent when Ca(2+) was present in the medium. These alterations were prevented by ruthenium red, cyclosporine A (CsA) and ADP, supporting the involvement of mitochondrial permeability transition (MPT) in these effects. We further observed that N-ethylmaleimide prevented the sulfite-elicited swelling and that sulfite decreased free thiol group content in brain mitochondria. These findings indicate that sulfite acts directly on MPT pore containing thiol groups. Finally, we verified that sulfite reduced cell viability in cerebral cortex slices and that this effect was prevented by CsA. Therefore, it may be presumed that disturbance of mitochondrial energy homeostasis and MPT induced by sulfite could be involved in the neuronal damage characteristic of SO deficiency.

Therapeutic mechanisms of single Chinese medicine herb or their extracts for extrahepatic obstructive jaundice

Obstructive jaundice (OJ) is classified as extrahepatic OJ or intrahepatic OJ. Extrahepatic OJ is attributed to a variety of intricate etiological factors. Research has begun with Chinese medicine (CM), which can be used as an adjunctive therapy for extrahepatic OJ. Particular attention has been paid to the therapeutic effects and their mechanisms of single CM herb and relevant extracts. The roles of single CM or their extracts during adjunctive therapy for extrahepatic OJ have been described briefly. This review focuses on the effects and their mechanisms of relevant herbal medicines.

Oxyphenisatin acetate (NSC 59687) triggers a cell starvation response leading to autophagy, mitochondrial dysfunction, and autocrine TNFα-mediated apoptosis

Oxyphenisatin (3,3-bis(4-hydroxyphenyl)-1H-indol-2-one) and several structurally related molecules have been shown to have in vitro and in vivo antiproliferative activity. This study aims to confirm and extend mechanistic studies by focusing on oxyphenisatin acetate (OXY, NSC 59687), the pro-drug of oxyphenisatin. Results confirm that OXY inhibits the growth of the breast cancer cell lines MCF7, T47D, HS578T, and MDA-MB-468. This effect is associated with selective inhibition of translation accompanied by rapid phosphorylation of the nutrient sensing eukaryotic translation initiation factor 2α (eIF2α) kinases, GCN2 and PERK. This effect was paralleled by activation of AMP-activated protein kinase (AMPK) combined with reduced phosphorylation of the mammalian target of rapamycin (mTOR) substrates p70S6K and 4E-BP1. Microarray analysis highlighted activation of pathways involved in apoptosis induction, autophagy, RNA/protein metabolism, starvation responses, and solute transport. Pathway inhibitor combination studies suggested a role for AMPK/mTOR signaling, de novo transcription and translation, reactive oxygen species (ROS)/glutathione metabolism, calcium homeostasis and plasma membrane Na(+) /K(+) /Ca(2+) transport in activity. Further examination confirmed that OXY treatment was associated with autophagy, mitochondrial dysfunction, and ROS generation. Additionally, treatment was associated with activation of both intrinsic and extrinsic apoptotic pathways. In the estrogen receptor (ER) positive MCF7 and T47D cells, OXY induced TNFα expression and TNFR1 degradation, indicating autocrine receptor-mediated apoptosis in these lines. Lastly, in an MCF7 xenograft model, OXY delivered intraperitoneally inhibited tumor growth, accompanied by phosphorylation of eIF2α and degradation of TNFR1. These data suggest that OXY induces a multifaceted cell starvation response, which ultimately induces programmed cell death.

Physiological roles of the permeability transition pore

Mitochondria are implicated in many important cellular functions covering the whole life cycle from mitochondrial biogenesis to cell death. Mitochondrial homeostasis is tightly regulated, and mitochondrial dysfunction is frequently associated with severe human pathologies (eg, cardiovascular diseases, cancer, and neurodegeneration). The permeability transition pore (PTP) is an unselective voltage-dependent mitochondrial channel. Despite the extensive use of electrophysiology, biochemistry, pharmacology, and genetic invalidation in mice, the molecular identity of PTP is still unknown. Nevertheless, PTP is central to mitochondrial vital functions and can play a lethal role in many pathophysiological conditions. This review recapitulates the current knowledge of the various modes of conductance of the PTP channel and discusses their implication in the physiological roles of PTP and their regulation. Based on its involvement in normal physiology and human pathology, a better understanding of this channel and its roles remains a major goal for basic scientists and clinicians.

Sirtuin-4 modulates sensitivity to induction of the mitochondrial permeability transition pore

The sustained opening of the mitochondrial permeability transition pore (PTP) is a decisive event in the onset of irreversible cell injury. The PTP is modulated by numerous exogenous and endogenous effectors, including mitochondrial membrane potential, ions and metabolites. Mitochondrial sirtuins have recently emerged as pivotal mediators of mitochondrial metabolism. In the present study, we demonstrate that sirt-4 modulates sensitivity to PTP onset induced by calcium and the oxidative cross linking reagent phenylarsine oxide, and PTP dependent cytotoxicity brought about by TNF or doxorubicin. Moreover, the ability of sirt-4 to modulate onset of the PTP is dependent on the expression of glutamate dehydrogenase-1.

Protective Effect of Rehmannia glutinosa on the UV-Induced Apoptosis in U937 Cells

Ultraviolet (UV) radiation has been shown to generate reactive oxygen species (ROS), such as singlet oxygen, superoxide radicals, hydroxyl radicals and hydrogen peroxide in a variety of cells. These ROS have the potential to damage critical cellular components such as DNA, proteins, and lipids and eventually result in physical and chemical damage to tissues that may lead to cell death. The steamed root of Rehmannia glutinosa (Saeng Jihuang, SJH) is reported to have an antioxidant activity. We investigated the effect of SJH on UV-induced apoptosis in U937 cells. Upon exposure to UV, there was a distinct difference between untreated cells and cells pre-treated with 0.5–2 mg/ml SJH for 12 hours in regard to cellular redox status and morphological change to cells. SJH pre-treated cells showed significant suppression of apoptotic features such as DNA fragmentation, damage to mitochondrial function, and modulation of apoptotic marker proteins upon exposure to UV. This study indicates that SJH may play an important role in regulating the apoptosis induced by UV presumably through scavenging of reactive oxygen species.

Sensitization of ionizing radiation-induced apoptosis by ursolic acid

Radiation therapy has been widely used for treating human cancers. However, cancer cells develop radioresistant phenotypes that decrease the efficacy of radiotherapy. Ionizing radiation (IR) induces the production of reactive oxygen species, which play an important role in apoptotic cell death. Therefore, radiation therapy combined with a sensitizer, which modulates cellular redox status, has the potential to enhance therapeutic efficacy in a variety of human cancers. Here, we investigated the radiosensitizing effects of ursolic acid (UA), a pentacyclic triterpenoid found in rosemary and holy basil. IR-induced apoptosis in cancer cell lines such as DU145, CT26 and B16F10 was significantly enhanced by UA, as reflected by DNA fragmentation, cellular redox status, mitochondrial dysfunction and modulation of apoptotic marker proteins. Additionally, UA combined with IR was also effective for inhibiting tumorigenesis in B16F10 melanoma cells implanted into mice. Taken together, these results suggest that applying UA together with IR may be an effective combination modality for treating cancer.

Mitochondria and redox signaling in steatohepatitis

Alcoholic and nonalcoholic fatty liver diseases are potentially pathological conditions that can progress to steatohepatitis, fibrosis, and cirrhosis. These conditions affect millions of people throughout the world in part through poor lifestyle choices of excess alcohol consumption, overnutrition, and lack of regular physical activity. Abnormal mitochondrial and cellular redox homeostasis has been documented in steatohepatitis and results in alterations of multiple redox-sensitive signaling cascades. Ultimately, these changes in signaling lead to altered enzyme function and transcriptional activities of proteins critical to mitochondrial and cellular function. In this article, we review the current hypotheses linking mitochondrial redox state to the overall pathophysiology of alcoholic and nonalcoholic steatohepatitis and briefly discuss the current therapeutic options under investigation.

Metaxin deficiency alters mitochondrial membrane permeability and leads to resistance to TNF-induced cell killing

Metaxin, a mitochondrial outer membrane protein, is critical for TNF-induced cell death in L929 cells. Its deficiency, caused by retroviral insertion-mediated mutagenesis, renders L929 cells resistance to TNF killing. In this study, we further characterized metaxin deficiency-caused TNF resistance in parallel with Bcl-X(L) overexpression-mediated death resistance. We did not find obvious change in mitochondria membrane potential in metaxin-deficient (Met(mut)) and Bcl-X(L)-overexpressing cells, but we did find an increase in the release rate of the mitochondrial membrane potential probe rhodamine 123 (Rh123) that was preloaded into mitochondria. In addition, overexpression of a function-interfering mutant of metaxin (MetaΔTM/C) or Bcl-X(L) in MCF-7.3.28 cells also resulted in an acquired resistance to TNF killing and a faster rate of Rh123 release, indicating a close correlation between TNF resistance and higher rates of the dye release from the mitochondria. The release of Rh123 can be controlled by the mitochondrial membrane permeability transition (PT) pore, as targeting an inner membrane component of the PT pore by cyclosporin A (CsA) inhibited Rh123 release. However, metaxin deficiency and Bcl-X(L) overexpression apparently affect Rh123 release from a site(s) different from that of CsA, as CsA can overcome their effect. Though both metaxin and Bcl-X(L) appear to function on the outer mitochondrial membrane, they do not interact with each other. They may use different mechanisms to increase the permeability of Rh123, since previous studies have suggested that metaxin may influence certain outer membrane porins while Bcl-X(L) may form pores on the outer membrane. The alteration of the mitochondrial outer membrane properties by metaxin deficiency and Bcl-X(L) overexpression, as indicated by a quicker Rh123 release, may be helpful in maintaining mitochondrial integrity.

Mitochondrial disorders in NSAIDs-induced small bowel injury

Recent studies using small bowel endoscopy revealed that non-steroidal anti-inflammatory drugs including low-dose aspirin, can often induce small bowel injury. Non-steroidal anti-inflammatory drugs-induced small bowel mucosal injury involves various factors such as enterobacteria, cytokines, and bile. Experimental studies demonstrate that both mitochondrial disorders and inhibition of cyclooxygenases are required for development of non-steroidal anti-inflammatory drugs-induced small bowel injury. Mitochondrion is an organelle playing a central role in energy production in organisms. Many non-steroidal anti-inflammatory drugs directly cause mitochondrial disorders, which are attributable to uncoupling of oxidative phosphorylation induced by opening of the mega channel called mitochondrial permeability transition pore on the mitochondrial membrane by non-steroidal anti-inflammatory drugs. Bile acids and tumor necrosis factor-α also can open the permeability transition pore. The permeability transition pore opening induces the release of cytochrome c from mitochondrial matrix into the cytosol, which triggers a cascade of events that will lead to cell death. Therefore these mitochondrial disorders may cause disturbance of the mucosal barrier function and elevation of the small bowel permeability, and play particularly important roles in early processes of non-steroidal anti-inflammatory drugs-induced small bowel injury. Although no valid means of preventing or treating non-steroidal anti-inflammatory drugs-induced small bowel injury has been established, advances in mitochondrial studies may bring about innovation in the prevention and treatment of this kind of injury.

Knockdown of sensitive to apoptosis gene by small interfering RNA enhances the sensitivity of PC3 cells toward actinomycin D and etoposide

Actinomycin D and etoposide induce the production of reactive oxygen species, which play an important causative role in apoptotic cell death. Sensitive to apoptosis gene (SAG) protein, a redox inducible zinc RING finger protein that protects mammalian cells from apoptosis by redox reagents, is a metal chelator and a potential reactive oxygen species scavenger. The present report show that knockdown of SAG expression in PC3 cells greatly enhances apoptosis induced by actinomycin D and etoposide. Transfection of human prostate cancer PC3 cells with SAG small interfering RNA (siRNA) markedly decreased the expression of SAG, enhancing the susceptibility of actinomycin D- and etoposide-induced apoptosis reflected by DNA fragmentation, cellular redox status and the modulation of apoptotic marker proteins. These results indicate that SAG may play an important role in regulating the apoptosis induced by actinomycin D and etoposide and the sensitizing effect of SAG siRNA on the apoptotic cell death of PC3 cells offers the possibility of developing a modifier of cancer chemotherapy.

Ethanol sensitizes mitochondria to the permeability transition by inhibiting deacetylation of cyclophilin-D mediated by sirtuin-3

Ethanol increases the vulnerability of mitochondria to induction of the mitochondrial permeability transition (MPT). Cyclophilin-D activity enhances the potential for the permeability transition pore (PTP) to open. In the present study, we demonstrate that ethanol and its metabolism sensitize the PTP to opening, in part by increasing the acetylation and activity of cyclophilin-D. This effect of ethanol is mediated by inhibiting the activity of sirtuin-3, an NAD(+) dependent deacetylase that is localized to the mitochondrial matrix. The ethanol-enhanced acetylation of cyclophilin-D also increases the interaction of cyclophilin-D with the adenine nucleotide translocator-1 (ANT-1) and is dependent on ethanol metabolism. Moreover, activation of AMPK, a known positive modulator of sirtuin activity, prevented the ethanol-induced suppression of sirtuin-3 activity and the attendant increase of cyclophilin-D acetylation, activity and association with ANT-1. Additionally, AMPK reactivation of sirtuin-3 prevented the sensitization to the MPT and the enhancement of cell killing by TNF in cells exposed to ethanol.

Suppression of mitochondrial NADP(+)-dependent isocitrate dehydrogenase activity enhances curcumin-induced apoptosis in HCT116 cells

Curcumin is a polyphenol derived from the plant Curcuma longa that induces apoptotic cell death in malignant cancer cell lines. It has been shown previously that mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm) plays an essential role in defense against oxidative stress by supplying NADPH for antioxidant systems. This study demonstrates that curcumin decreased the activity of IDPm, both as a purified enzyme and in cultured cells. It also shows that curcumin-induced apoptosis in the colon cancer cell line HCT116 is significantly enhanced by suppression of IDPm activity. Transfection of HCT116 cells with an IDPm small interfering RNA (siRNA) markedly decreased activity of IDPm, enhancing cellular susceptibility to curcumin-induced apoptosis, as reflected by DNA fragmentation, cellular redox status, mitochondria dysfunction and modulation of apoptotic marker proteins. Together, these results suggest that application of curcumin together with IDPm siRNA may be an effective combination modality in the treatment of cancer.

Effects of different doses and schedules of diazepam treatment on lymphocyte parameters in rats

Benzodiazepines (BZD) are widely used for the treatment of anxiety. They enhance GABA-ergic neurotransmission through the binding on specific BDZ recognition sites, within the GABA(A) receptor-ion channel complex. However, recent studies showed that BZD also act on peripheral benzodiazepine receptor sites (PBR) or translocator protein 18 kDa (TSPO). Evidence for a direct immunomodulatory action for BZD emerged from studies that demonstrated the presence of TSPO on immune/inflammatory cells. The present study was designed to analyze the effects of diazepam on rat lymphocyte parameters, specifically on phenotype, cell proliferation and cell death. The effects of both acute and long-term (21 days) diazepam (1 and 10 mg/kg/day) administrations were evaluated. Results showed that diazepam (1 mg/kg) treatment did not change the immune parameters analyzed. However, both diazepam (10 mg/kg) acute and long-term treatments decreased the number of apoptotic cells; they also increased the percentage of T cytotoxic cells; decreased the percentage of B cells and increased the corticosterone serum levels. The induction of functional tolerance was suggested for the highest dose of diazepam (10 mg/kg), but not for the smaller dose (1 mg/kg) used, at least for diazepam effects on corticosterone serum levels. Diazepam effects were discussed as being related to the number of TSPO sites present on immune cells and/or to the increased levels of serum corticosterone observed after the treatments used.

Neuroprotection in glaucoma - Is there a future role?

In glaucoma, the major cause of global irreversible blindness, there is an urgent need for treatment modalities that directly target the RGCs. The discovery of an alternative therapeutic approach, independent of IOP reduction, is highly sought after, due to the indirect nature and limited effectiveness of IOP lowering therapy in preventing RGC loss. Several mechanisms have been implicated in initiating the apoptotic cascade in glaucomatous retinopathy and numerous drugs have been shown to be neuroprotective in animal models of glaucoma. These mechanisms and their potential treatment include excitotoxicity, protein misfolding, mitochondrial dysfunction, oxidative stress, inflammation and neurotrophin deprivation. All of these mechanisms ultimately lead to programmed cell death with loss of RGCs. In this article we summarize the mechanisms involved in glaucomatous disease, highlight the rationale for neuroprotection in glaucoma management and review current potential neuroprotective strategies targeting RGCs from the laboratory to the clinic.

Mitochondrial involvement in drug-induced liver injury

Mitochondrial dysfunction is a major mechanism of liver injury. A parent drug or its reactive metabolite can trigger outer mitochondrial membrane permeabilization or rupture due to mitochondrial permeability transition. The latter can severely deplete ATP and cause liver cell necrosis, or it can instead lead to apoptosis by releasing cytochrome c, which activates caspases in the cytosol. Necrosis and apoptosis can trigger cytolytic hepatitis resulting in lethal fulminant hepatitis in some patients. Other drugs severely inhibit mitochondrial function and trigger extensive microvesicular steatosis, hypoglycaemia, coma, and death. Milder and more prolonged forms of drug-induced mitochondrial dysfunction can also cause macrovacuolar steatosis. Although this is a benign liver lesion in the short-term, it can progress to steatohepatitis and then to cirrhosis. Patient susceptibility to drug-induced mitochondrial dysfunction and liver injury can sometimes be explained by genetic or acquired variations in drug metabolism and/or elimination that increase the concentration of the toxic species (parent drug or metabolite). Susceptibility may also be increased by the presence of another condition, which also impairs mitochondrial function, such as an inborn mitochondrial cytopathy, beta-oxidation defect, certain viral infections, pregnancy, or the obesity-associated metabolic syndrome. Liver injury due to mitochondrial dysfunction can have important consequences for pharmaceutical companies. It has led to the interruption of clinical trials, the recall of several drugs after marketing, or the introduction of severe black box warnings by drug agencies. Pharmaceutical companies should systematically investigate mitochondrial effects during lead selection or preclinical safety studies.

Effect of salvia miltiorrhizae on pulmonary apoptosis of rats with severe acute pancreatitis or obstructive jaundice

To investigate the effect of apoptosis about Salvia miltiorrhizae injection on the lungs of SAP and OJ rats. Total 288 rats were used for SAP-associated experiments and OJ-associated experiments, respectively. The rats were randomly divided into sham-operated, model control and treated group. According to the difference of time points after operation, the SAP rats in each group were subdivided into 3, 6 and 12 h groups while the OJ rats were divided into 7, 14, 21 and 28 days groups. The pathological changes, expression levels of Bax protein and apoptotic indexes in the lungs of SAP or OJ rats were observed, and the mortality rates of SAP or OJ rats were recorded, respectively. The numbers of dead SAP and OJ rats in treated groups declined. The pathological changes in the lungs of SAP or OJ rats in treated groups were relieved to varying degrees. There was no marked difference in pathological severity scores and the positive staining intensity of Bax protein between treated groups and model control groups (all P > 0.05). Salvia miltiorrhizae has some protective effect on the lungs of rats with SAP or OJ which may be related apoptosis although our results can not find significant difference between treated groups and model control groups.

Silencing of cytosolic NADP(+)-dependent isocitrate dehydrogenase by small interfering RNA enhances the sensitivity of HeLa cells toward staurosporine

Staurosporine induces the production of reactive oxygen species, which play an important causative role in apoptotic cell death. Recently, it was demonstrated that the control of cellular redox balance and the defense against oxidative damage is one of the primary functions of cytosolic NADP(+)-dependent isocitrate dehydrogenase (IDPc) by supplying NADPH for antioxidant systems. The present report shows that silencing of IDPc expression in HeLa cells greatly enhances apoptosis induced by staurosporine. Transfection of HeLa cells with an IDPc small interfering RNA (siRNA) markedly decreased activity of IDPc, enhancing the susceptibility of staurosporine-induced apoptosis reflected by DNA fragmentation, cellular redox status and the modulation of apoptotic marker proteins. These results indicate that IDPc may play an important role in regulating the apoptosis induced by staurosporine and the sensitizing effect of IDPc siRNA on the apoptotic cell death of HeLa cells offers the possibility of developing a modifier of cancer chemotherapy.

Ceramide and mitochondria in ischemia/reperfusion

A hallmark of tissue injury in various models of ischemia/reperfusion (IR) is mitochondrial dysfunction and the release of mitochondrial proapoptotic proteins leading to cell death. Although IR-induced mitochondrial injury has been extensively studied and key mitochondrial functions affected by IR are chiefly characterized, the nature of the molecule that causes loss of mitochondrial integrity and function remains obscure. It has become increasingly clear that ceramide, a membrane sphingolipid and a key mediator of cell stress responses, could play a critical role in IR-induced mitochondrial damage. Emerging data point to excessive ceramide accumulation in tissue and, specifically, in mitochondria after IR. Exogenously added to isolated mitochondria, ceramide could mimic some of the mitochondrial dysfunctions occurring in IR. The recent identification and characterization of major enzymes in ceramide synthesis is expected to contribute to the understanding of molecular mechanisms of ceramide involvement in mitochondrial damage in IR. This review will examine the experimental evidence supporting the important role of ceramide in mitochondrial dysfunction in IR to highlight potential targets for pharmacological manipulation of ceramide levels.

Impact of TNF-R1 and CD95 internalization on apoptotic and antiapoptotic signaling

Internalization of cell surface receptors has long been regarded as a pure means to terminate signaling via receptor degradation. A growing body of information points to the fact that many internalized receptors are still in their active state and that signaling continues along the endocytic pathway. Thus endocytosis orchestrates cell signaling by coupling and integrating different cascades on the surface of endocytic vesicles to control the quality, duration, intensity, and distribution of signaling events. The death receptors tumor necrosis factor-receptor 1 (TNF-R1) and CD95 (Fas, APO-1) are known not only to signal for cell death via apoptosis but are also capable of inducing antiapoptotic signals via transcription factor NF-kappaB induction or activation of the proliferative mitogen-activated protein kinase (MAPK)/ERK (extracellular signal-regulated kinase) protein kinase cascades, resulting in cell protection and tissue regeneration. A clue to the understanding of these contradictory biological phenomena may arise from recent findings which reveal a regulatory role of receptor internalization and intracellular receptor trafficking in selectively transmitting signals, which lead either to apoptosis or to the survival of the cell. In this chapter, we discuss the dichotomy of pro- and antiapoptotic signaling of the death receptors TNF-R1 and CD95. First, we will address the role of lipid rafts and post-translational modifications of death receptors in regulating the formation of receptor complexes. Then, we will discuss the role of internalization in determining the fate of the receptors and subsequently the specificity of signaling events. We propose that fusion of internalized TNF-receptosomes with trans-Golgi vesicles should be recognized as a novel mechanism to transduce death signals along the endocytic route. Finally, the lessons learnt from the strategy of adenovirus to escape apoptosis by targeting death receptor internalization demonstrate the biological significance of TNF receptor compartmentalization for immunosurveillance.

Oligomeric BAX induces mitochondrial permeability transition and complete cytochrome c release without oxidative stress

In the present study, we investigated the mechanism of cytochrome c release from isolated brain mitochondria induced by recombinant oligomeric BAX (BAX(oligo)). We found that BAX(oligo) caused a complete release of cytochrome c in a concentration- and time-dependent manner. The release was similar to those induced by alamethicin, which causes maximal mitochondrial swelling and eliminates barrier properties of the OMM. BAX(oligo) also produced large amplitude mitochondrial swelling as judged by light scattering assay and transmission electron microscopy. In addition, BAX(oligo) resulted in a strong mitochondrial depolarization. ATP or a combination of cyclosporin A and ADP, inhibitors of the mPT, suppressed BAX(oligo)-induced mitochondrial swelling and depolarization as well as cytochrome c release but did not influence BAX(oligo) insertion into the OMM. Both BAX(oligo)- and alamethicin-induced cytochrome c releases were accompanied by inhibition of ROS generation, which was assessed by measuring mitochondrial H(2)O(2) release with an Amplex Red assay. The mPT inhibitors antagonized suppression of ROS generation caused by BAX(oligo) but not by alamethicin. Thus, BAX(oligo) resulted in a complete cytochrome c release from isolated brain mitochondria in the mPT-dependent manner without involvement of oxidative stress by the mechanism requiring mitochondrial remodeling and permeabilization of the OMM.

Sepsis: links between pathogen sensing and organ damage

The host's inflammatory response to sepsis can be divided into two phases, the initial detection and response to the pathogen initiated by the innate immune response, and the persistent inflammatory state characterized by multiple organ dysfunction syndrome (MODS). New therapies aimed at pathogen recognition receptors (PRRs) particularly the TLRs and the NOD-like receptors offer hope to suppress the initial inflammatory response in early sepsis and to bolster this response in late sepsis. The persistence of MODS after the initial inflammatory surge can also be a determining factor to host survival. MODS is due to the cellular damage and death induced by sepsis. The mechanism of this cell death depends in part upon mitochondrial dysfunction. Damaged mitochondria have increased membrane permeability prompting their autophagic removal if few mitochondria are involved but apoptotic cell death may occur if the mitochondrial losses are more extensive. In addition. severe loss of mitochondria results in low cell energy stores, necrotic cell death, and increased inflammation driven by the release of cell components such as HMGB1. Therapies, which aim at improving cellular energy reserves such as the promotion of mitochondrial biogenesis by insulin, may have a role in future sepsis therapies. Finally, both the inflammatory responses and the susceptibility to organ failure may be modulated by nutritional status and micronutrients, such as zinc, Therapies aimed at micronutrient repletion may further augment approaches targeting PRR function and mitochondrial viability.

Long-chain ceramide is a potent inhibitor of the mitochondrial permeability transition pore

The sphingolipid ceramide has been implicated in mediating cell death that is accompanied by mitochondrial functional alterations. Moreover, ceramide has been shown to accumulate in mitochondria upon induction of apoptotic processes. In this study, we sought to evaluate the effects of natural, highly hydrophobic long-chain ceramides on mitochondrial function in vitro. Ceramide in a dodecane/ethanol delivery system inhibited the opening of the mitochondrial permeability transition pore (PTP) induced by either oxidative stress, SH group cross-linking, or high Ca2+ load, suggesting that the inhibitory point is at a level at which major PTP regulatory pathways converge. Moreover, ceramide had no effect on well known mitochondrial components that modulate PTP activity, such as cyclophilin D, voltage-dependent anion channel, adenine nucleotide transporter, and ATP synthase. The inhibitory effect of ceramide on PTP was not stereospecific, nor was there a preference for ceramide over dihydroceramide. However, the effect of ceramide on PTP was significantly influenced by the fatty acid moiety chain length. These studies are the first to show that long-chain ceramide can influence PTP at physiologically relevant concentrations, suggesting that it is the only known potent natural inhibitor of PTP. These results suggest a novel mechanism of ceramide regulation of mitochondrial function.

Inactivation of mitochondrial NADP+-dependent isocitrate dehydrogenase by hypochlorous acid

Myeoloperoxidase catalyses the formation of hypochlorous acid (HOCl) via reaction of H(2)O(2) with Cl(-) ion. Although HOCl is known to play a major role in the human immune system by killing bacteria and other invading pathogens, excessive generation of this oxidant is known to cause damage to tissue. Recently, it was demonstrated that the control of mitochondrial redox balance and oxidative damage is one of the primary functions of mitochondrial NADP(+)-dependent isocitrate dehydrogenase (IDPm) to supply NADPH for antioxidant systems. This study investigated whether the IDPm would be a vulnerable target of HOCl as a purified enzyme and in intact cells. Loss of enzyme activity was observed and the inactivation of IDPm was reversed by thiols. Transfection of HeLa cells with an IDPm small interfering RNA (siRNA) markedly enhanced HOCl-induced oxidative damage to cells. The HOCl-mediated damage to IDPm may result in the perturbation of the cellular antioxidant defense mechanisms and subsequently lead to a pro-oxidant condition.

Hypochlorous acid-induced modulation of cellular redox status in HeLa cells

Myeloperoxidase catalyzes the formation of hypochlorous acid (HOCI) via reaction of H2O2 with CI(-) ions. Although HOCI plays a major role in the human immune system by killing bacteria and other invading pathogens, excessive generation of this oxidant causes damage to tissues. Exposure of HeLa cells to HOCI decreased viability, inactivated antioxidant enzymes, damaged mitochondria, and modulated cellular redox status. HOCI also induced significant increases in cellular oxidative damage reflected by lipid peroxidation, protein oxidation, and DNA damage. HOCI-mediated oxidative damage to HeLa cells may perturb the cellular antioxidant defense mechanisms and subsequently lead to a pro-oxidant state.

Regulation of heat shock-induced apoptosis by sensitive to apoptosis gene protein

Heat shock may increase oxidative stress due to increased production of reactive oxygen species and/or the promotion of cellular oxidation events. Sensitive to apoptosis gene (SAG) protein, a novel zinc RING finger protein that protects mammalian cells from apoptosis by redox reagents, is a metal chelator and a potential reactive oxygen species scavenger, but its antioxidant properties have not been completely defined. In this report, we demonstrate that modulation of SAG expression in U937 cells regulates heat shock-induced apoptosis. When we examined the protective role of SAG against heat shock-induced apoptosis with U937 cells transfected with the cDNA for SAG, a clear inverse relationship was observed between the amount of SAG expressed in target cells and their susceptibility to apoptosis. We also observed a significant decrease in the endogenous production of reactive oxygen species and oxidative DNA damage in SAG-overexpressed cells compared to control cells on exposure to heat shock. In addition, transfection of PC3 cells with SAG small interfering RNA markedly decreased the expression of SAG, enhancing the susceptibility of heat shock-induced apoptosis. Taken together, these results indicate that SAG may play an important role in regulating the apoptosis induced by heat shock presumably through maintaining the cellular redox status.

Regulation of TNFR1 and CD95 signalling by receptor compartmentalization

The death receptors tumour-necrosis factor receptor-1 (TNFR1) and CD95 (also known as FAS and APO-1) transduce signals that promote cell death by apoptosis. However, these receptors are also capable of inducing anti-apoptotic signals through the activation of the transcription factor nuclear factor-kappaB (NF-kappaB) or through activation of the proliferative mitogen-activated protein kinase (MAPK) cascade. Recent findings reveal a role for receptor internalization and endosomal trafficking in selectively transmitting the signals that lead either to apoptosis or to the survival of the cell.

Bcl-xL prevents staurosporine-induced hepatocyte apoptosis by restoring protein kinase B/mitogen-activated protein kinase activity and mitochondria integrity

Our study reports that staurosporine induces apoptosis in cultured rat hepatocytes in a dose- and time-dependent fashion. Staurosporine induced apparent cleavage of caspase-8, caspase-9, and caspase-3. The release of cytochrome c from mitochondria, and Bid activation were also detected in staurosporine-treated primary hepatocytes. These results suggest that mitochondria-mediated cell death signaling may be involved in staurosporine-induced hepatocyte apoptosis. Bcl-x(L) overexpression protected from "loss of" mitochondrial transmembrane potential and prevented staurosporine-induced caspase-3 and caspase-8 cleavage. Overexpression of constitutively active ERK and PKB inhibited staurosporine-induced caspase-3 activation and hepatocyte death. PI3K inhibitor (LY294002) and ERK inhibitor (PD98059) significantly reversed the protective effects of Bcl-x(L) on staurosporine-induced hepatocyte death. Our data suggest that Bcl-x(L) prevents staurosporine-induced hepatocyte apoptosis by modulating protein kinase B and p44/42 mitogen-activated protein kinase activity and disrupts mitochondria death signaling.