Nitric-oxide-induced necrosis and apoptosis in PC12 cells mediated by mitochondria

Recent advances in diverse nanosystems for nitric oxide delivery in cancer therapy

Gas therapy has been proven to be a promising and advantageous treatment option for cancers. Studies have shown that nitric oxide (NO) is one of the smallest structurally significant gas molecules with great potential to suppress cancer. However, there is controversy and concern about its use as it exhibits the opposite physiological effects based on its levels in the tumor. Therefore, the anti-cancer mechanism of NO is the key to cancer treatment, and rationally designed NO delivery systems are crucial to the success of NO biomedical applications. This review summarizes the endogenous production of NO, its physiological mechanisms of action, the application of NO in cancer treatment, and nano-delivery systems for delivering NO donors. Moreover, it briefly reviews challenges in delivering NO from different nanoparticles and the issues associated with its combination treatment strategies. The advantages and challenges of various NO delivery platforms are recapitulated for possible transformation into clinical applications.

CWHM-12, an Antagonist of Integrin-Mediated Transforming Growth Factor-Beta Activation Confers Protection During Early Mycobacterium tuberculosis Infection in Mice

Tuberculosis (TB) caused by the pathogenic bacterium Mycobacterium tuberculosis (Mtb) is one of the most lethal infectious diseases in the world. Presently, Bacillus Calmette-Guerin, the vaccine approved for use against TB, does not offer complete protection against the disease, which necessitates the development of new therapeutics to treat this infection. Overexpression of transforming growth factor beta (TGF-β) is associated with pulmonary profibrotic changes. The inactive TGF-β secreted is activated through its cleavage and release by αv integrins. Integrin-mediated regulation of TGF-β is considered as a master switch in the profibrotic process and a potential therapeutic target. Thus, in this study, we sought to determine if treatment with a broad range antagonist of integrins, CWHM-12, has the potency to inhibit pulmonary fibrosis and enhance Mtb control in a highly susceptible mouse model of Mtb infection, namely the C3Heb/FeJ (FeJ). CWHM-12 treatment at the early stages of Mtb infection was efficacious in reducing disease severity and inflammation associated with decreased iNOS, MIP-2, and IL-10 production without degradation of collagen. This suggests a potential for CWHM-12 targeting of TGF-β to be explored as an adjunct therapeutic for early Mtb infection.

Neoechinulins: Molecular, cellular, and functional attributes as promising therapeutics against cancer and other human diseases

Neoechinulins are fungal and plant-derived chemicals extracted from Microsporum sp., Eurotium rubrum, Aspergillus sp., etc. Two analogues of neoechinulin, i.e., A and B, exerted extensive pharmacological properties described in this review. Neoechinulin is an indole alkaloid and has a double bond between C8/C9, which tends to contribute to its cytoprotective nature. Neoechinulin A exhibits protection to PC12 cells against nitrosative stress via increasing NAD(P)H reserve capacity and decreasing cellular GSH levels. It also confers protection via rescuing PC12 cells from rotenone-induced stress by lowering LDH leakage. This compound has great positive potential against neurodegenerative diseases by inhibiting SIN-1 induced cell death in neuronal cells. Together with these, neoechinulin A tends to inhibit Aβ42-induced microglial activation and confers protection against neuroinflammation. Alongside, it also inhibits cervical cancer cells by caspase-dependent apoptosis and via upregulation of apoptosis inducing genes like Bax, it suppresses LPS-induced inflammation in RAW264.7 macrophages and acts as an antidepressant. Whereas, another analogue, Neoechinulin B tends to interfere with the cellular mechanism thereby, inhibiting the entry of influenza A virus and it targets Liver X receptor (LXR) and decreases the infection rate of Hepatitis C. The present review describes the pharmaceutical properties of neoechinulins with notes on their molecular, cellular, and functional basis and their therapeutic properties.

Neuroprotective Effects of Sodium Butyrate through Suppressing Neuroinflammation and Modulating Antioxidant Enzymes

The discovery of effective therapeutic agents against neurodegenerative diseases (NDDs) remains challenging. Neurotoxicity, inflammations, and oxidative stress are associating factors of NDDs. Sodium butyrate (NaB) is a short-chain fatty acid found in diet and produced in the gut that reportedly protects cancer, inflammation, obesity and so on. Previously, SH-SY5Y cells were studied as in vitro models of cerebral diseases. We have investigated the neuroprotective effects of NaB in SH-SY5Y cells stimulated with TNF-α. The expression of inflammatory mediators, including iNOS, COX-2, and mitogen-activated protein kinases (MAPK) and the apoptotic regulators, including P-53, Bcl-2 associated X (BAX) Protein, and caspase-3 were analyzed by western blot analysis. The anti-apoptotic gene Bcl-2 and the pro-apoptotic gene BAX translocation were also investigated. Our results showed that NaB attenuated cell death and inhibited the NO production and decreased the expression of iNOS and COX-2 in TNF-α-stimulated SH-SY5Y cells. NaB notably ameliorated apoptotic regulatory proteins p-53, Caspase-3 and caspase-1 level, and reversed phosphorylation of extracellular signal-regulated kinases and p-38 proteins. NaB ameliorated Glucocorticoid receptor and NLRP3 inflammasome expressions. NaB also suppressed the BAX nuclear translocation and modulated Nrf-2, HO-1 and MnSOD expression in neuroblastoma cells. In addition, NaB substantially reversed the reactive oxygen species in H₂O₂ induced SH-SY5Y cells. Altogether, our results suggest that sodium butyrate has potential therapeutic effects against NDDs.

Nitric oxide down-regulates voltage-gated Na+ channel in cardiomyocytes possibly through S-nitrosylation-mediated signaling

Nitric oxide (NO) is produced from endothelial cells and cardiomyocytes composing the myocardium and benefits cardiac function through both vascular-dependent and—independent effects. This study was purposed to investigate the possible adverse effect of NO focusing on the voltage-gated Na⁺ channel in cardiomyocytes. We carried out patch-clamp experiments on rat neonatal cardiomyocytes demonstrating that NOC-18, an NO donor, significantly reduced Na⁺ channel current in a dose-dependent manner by a long-term application for 24 h, accompanied by a reduction of Nav1.5-mRNA and the protein, and an increase of a transcription factor forkhead box protein O1 (FOXO1) in the nucleus. The effect of NOC-18 on the Na⁺ channel was blocked by an inhibitor of thiol oxidation N-ethylmaleimide, a disulfide reducing agent disulfide 1,4-Dithioerythritol, or a FOXO1 activator paclitaxel, suggesting that NO is a negative regulator of the voltage-gated Na⁺ channel through thiols in regulatory protein(s) for the channel transcription.

Nitric oxide and dopamine metabolism converge via mitochondrial dysfunction in the mechanisms of neurodegeneration in Parkinson's disease

The molecular mechanisms underlying the degeneration and neuronal death associated with Parkinson's disease (PD) are not clearly understood. Several pathways and models have been explored in an overwhelming number of studies. Overall, from these studies, mitochondrial dysfunction and nitroxidative stress have emerged as major contributors to degeneration of dopaminergic neurons in PD. In addition, an excessive or inappropriate production of nitric oxide (^•NO) and an abnormal metabolism of dopamine have been independently implicated in both processes. However, the participation of ^•NO in reactions with dopamine relevant to neurotoxicity strongly suggests that dopamine or its metabolites may be potential targets for ^•NO, affecting the physiological chemistry of both, ^•NO and dopamine. In this short review, we provide a critical and integrative appraisal of the nitric oxide-dopamine pathway we have previously suggested and that might be operative in PD. This pathway emphasizes a connection between abnormal dopamine and ^•NO metabolism, which may potentially converge in an integrated mechanism with toxic cellular outcomes. In particular, it encompasses the synergistic interaction of ^•NO with 3,4-dihydroxyphenylacetic acid (DOPAC), a major dopamine metabolite, leading to dopaminergic cell death via mechanisms that involve mitochondrial dysfunction, gluthathione depletion and nitroxidative stress.

Mitochondria-Specific Agents for Photodynamic Cancer Therapy: A Key Determinant to Boost the Efficacy

Mitochondria-targeted photodynamic therapy (Mt-PDT), which enables the photogenerated cytotoxic oxygen species with fatal oxidative damage to block mitochondrial functions, has been considered as a promising method to enhance the anticancer effectiveness. Aiming at the challenges of PDT, in the past few decades, numerous mitochondria-targeting molecular agents have been developed to boost the PDT efficacy via directly destroying the mitochondria or activating mitochondria-mediated cell death pathways. Herein, a review for recent advances of Mt-PDT is highlighted including: mitochondrial targeting design principles and strategies, therapeutic performance of mitochondria-targeted agents-mediated PDT as well as the agent-free Mt-PDT. In addition, it puts together the achievements of the combinatory mitochondria-anchoring PDT and other anticancer strategies, demonstrating the advantages provided by Mt-PDT. The existing challenges are discussed and future settlements for the development of mitochondria-specific agents are also forecasted.

Neuroprotective Effects of Chrysin on Diclofenac-Induced Apoptosis in SH-SY5Y Cells

Accumulating evidences demonstrated that Reactive Oxygen Species (ROS) may lead to serious damages to numerous cellular biomolecules, consequently resulting in the development of several neurological diseases. Diclofenac (Dic), the most widely preferred non-steroidal anti-inflammatory drug (NSAID) induces apoptosis by an alteration in function of mitochondria and creation of ROS. Chrysin (Chr) is a naturally active component that is found in numerous plants and bee products and retains strong neuroprotective and antioxidant properties. However its effect of Dic induced injury on SH-SY5Y neuron cells have not been investigated to date. The goal of present research was to study the molecular mechanisms of Chr protection from oxidative injury caused by Dic in SH-SY5Y cells. Dic induced significant toxicity on the cells and this effect was reversed by pre-treatment with Chr. Dic triggered a noteworthy increase in the cellular ROS and Lipid peroxidation (LPO) levels and decrease in Total antioxidant status (TAS) level while pre-treatment with Chr reversed these effects. Dic induction increased the Bax, cytochrome c, cas-3, cas-8 and p53 expression at gene transcription level. Elevated levels of these genes considerably decreased by Chr pre-treatment revealing the defensive effects of Chr. The results obviously presented that exposure of SH-SY5Y with Dic resulted in oxidative stress and apoptosis while pre-treatment of neuron cells with Chr protects the cells against apoptosis triggered by Dic induction.

The roles of reactive oxygen species and antioxidants in cryopreservation

Cryopreservation has facilitated advancement of biological research by allowing the storage of cells over prolonged periods of time. While cryopreservation at extremely low temperatures would render cells metabolically inactive, cells suffer insults during the freezing and thawing process. Among such insults, the generation of supra-physiological levels of reactive oxygen species (ROS) could impair cellular functions and survival. Antioxidants are potential additives that were reported to partially or completely reverse freeze-thaw stress-associated impairments. This review aims to discuss the potential sources of cryopreservation-induced ROS and the effectiveness of antioxidant administration when used individually or in combination.

Controlled Delivery of Nitric Oxide for Cancer Therapy

Nitric oxide (NO) is a short-lived, endogenously produced, signaling molecule which plays multiple roles in mammalian physiology. Underproduction of NO is associated with several pathological processes; hence a broad range of NO donors have emerged as potential therapeutics for cardiovascular and respiratory disorders, wound healing, the immune response to infection, and cancer. However, short half-lives, chemical reactivity, rapid systemic clearance, and cytotoxicity have hindered the clinical development of most low molecular weight NO donors. Hence, for controlled NO delivery, there has been extensive effort to design novel NO-releasing biomaterials for tumor targeting. This review covers the effects of NO in cancer biology, NO releasing moieties which can be used for NO delivery, and current advances in the design of NO releasing biomaterials focusing on their applications for tumor therapy.

Mahdy E, R. Youness E, Shafee N, S.S. Mowafy M, M. Mabrouk M. Effect of Co Enzyme Q10 Alone or in Combination with Vitamin C on Lipopolysaccharide-Induced Brain Injury in Rats

Our was to determine the impact of CoenzymeQ10 (Co Q10) and vitamin C alone or in combination on oxidative stress in brain tissue of rats during endotoxemia induced by single intraperitoneal dose of Lipopolysaccharide (LPS), 500µg/kg. Both CoQ10&vitamin C were given orally to rats with doses (200&100 mg/kg) respectively for 7successive days prior induction of endotoxemia .LPS injected, with Co Q10 with doses (100 &200 mg/kg) &vit. C (50&100 mg/kg).In addition CoQ10 and vitamin C together in doses (100&50 mg/kg) & (200&100 mg/kg) respectively were added to LPS-treated rats. Then euthanized 4 hours later. Histopathological assessment of brain tissue was done. Results: LPS injection induced oxidative stress in brain tissue, resulting in marked increase in malondiadehyde (MDA), nitrite (NO) and Amyloid beta (Aβ), while decreasing reduced glutathione (GSH), paraoxonase-1 (PON1) and brain derived neurotrophic factor (BDNF).CoQ10 and vit.C administration with doses(200&100 mg/ kg) before endotoxemia result in reduction of brain MDA, NO and Aβ, while increasing levels of GSH, PON1 and BDNF compared to controls. The addition of both Co Q10 &vit.C to LPS- treated rats lead to decrease of brain NO, MDA and Aβ, also increase of GSH, PON1 and BDNF. This effect was more obviouswith high doses, this due to the ameliorating effect of both CoQ10 and vit.C on oxidative stress of brain tissue during endotoxemia.This consisted with the histopathological results. Conclusion: this work focuses on the possible role of CoQ10 &vit.C as antioxidants in protecting brain tissue.

Cold atmospheric-pressure nitrogen plasma induces the production of reactive nitrogen species and cell death by increasing intracellular calcium in HEK293T cells

Cold atmospheric-pressure plasma (CAP) has been emerging as a promising tool for cancer therapy in recent times. In this study, we used a CAP device with nitrogen gas (N₂CAP) and investigated the effect of the N₂CAP on the viability of cultured cells. Moreover, we investigated whether N₂CAP-produced hydrogen peroxide (H₂O₂) in the medium is involved in N₂CAP-induced cell death. Here, we found that the N₂CAP irradiation inhibited cell proliferation in the human embryonic kidney cell line HEK293T and that the N₂CAP induced cell death in an irradiation time- and distance-dependent manner. Furthermore, the N₂CAP and H₂O₂ increased intracellular calcium levels and induced caspase-3/7 activation in HEK293T cells. The N₂CAP irradiation induced a time-dependent production of H₂O₂ and nitrite/nitrate in PBS or culture medium. However, the amount of H₂O₂ in the solution after N₂CAP irradiation was too low to induce cell death. Interestingly, carboxy-PTIO, a nitric oxide scavenger, or BAPTA-AM, a cell-permeable calcium chelator, inhibited N₂CAP-induced morphological change and cell death. These results suggest that the production of reactive nitrogen species and the increase in intracellular calcium were involved in the N₂CAP-induced cell death.

Neuronal Cell Death

Neuronal cell death occurs extensively during development and pathology, where it is especially important because of the limited capacity of adult neurons to proliferate or be replaced. The concept of cell death used to be simple as there were just two or three types, so we just had to work out which type was involved in our particular pathology and then block it. However, we now know that there are at least a dozen ways for neurons to die, that blocking a particular mechanism of cell death may not prevent the cell from dying, and that non-neuronal cells also contribute to neuronal death. We review here the mechanisms of neuronal death by intrinsic and extrinsic apoptosis, oncosis, necroptosis, parthanatos, ferroptosis, sarmoptosis, autophagic cell death, autosis, autolysis, paraptosis, pyroptosis, phagoptosis, and mitochondrial permeability transition. We next explore the mechanisms of neuronal death during development, and those induced by axotomy, aberrant cell-cycle reentry, glutamate (excitoxicity and oxytosis), loss of connected neurons, aggregated proteins and the unfolded protein response, oxidants, inflammation, and microglia. We then reassess which forms of cell death occur in stroke and Alzheimer's disease, two of the most important pathologies involving neuronal cell death. We also discuss why it has been so difficult to pinpoint the type of neuronal death involved, if and why the mechanism of neuronal death matters, the molecular overlap and interplay between death subroutines, and the therapeutic implications of these multiple overlapping forms of neuronal death.

Peroxynitrite dominates sodium nitroprusside-induced apoptosis in human hepatocellular carcinoma cells

This study aims to explore which radicals dominate sodium nitroprusside (SNP)-induced cytotoxicity in human hepatocellular carcinoma (HCC) cells (HepG2 and Hep3B). Exposure of SNP to cell medium produced abundant nitric oxide (NO), superoxide anion (O₂^·−), hydrogen peroxide (H₂O₂) and iron ions. SNP potently induced caspases activation, mitochondrial membrane permeabilization and apoptosis in HCC cells. In Hep3B cells, pretreatment with NO scavenger (PTIO) did not prevent SNP-induced cytotoxicity. However, in HepG2 cells, SNP-induced cytotoxicity was prevented significantly by pretreatment with PTIO and O₂^·− scavenger, and especially was almost completely blocked by pretreatment with FeTPPS (peroxynitrite scavenger). In contrast, although H₂O₂ scavenger potently scavenged SNP-induced H₂O₂ production, it did not prevent SNP-induced cytotoxicity in HepG2 cells. In addition, pretreatment with DFO (iron ions chelator) and iron-saturated DFO respectively completely prevented SNP-induced cytotoxicity in HepG2 cells. Collectively, peroxynitrite from the reaction between NO and O₂^·− elicited from SNP dominates the SNP-induced apoptosis of HepG2 cells, in which both iron ions and H₂O₂ are not involved.

SIRT1-mediated FoxOs pathways protect against apoptosis by promoting autophagy in osteoblast-like MC3T3-E1 cells exposed to sodium fluoride

Fluorine may result in damage to teeth, bones and other body tissues, and is a serious public health problem. SIRT1 deacetylates FOXOs, which brings about apoptosis and autophagy promotion or suppression. Fluorine may induce cell apoptosis, however, the role of autophagy in apoptosis induced by fluorine is still poorly understood, and the interaction between SIRT1 and FOXOs should be further illustrated. Therefore, this study investigated the mechanisms underlying the NaF- induced apoptosis and autophagy in osteoblast-like MC3T3-E1 cells in vitro through activating or inhibiting SIRT1. Via RT-PCR, western blot, flow cytometry assays, fluorescence and laser confocal microscopy, it was found that NaF induced both cell apoptosis and autophagy. Results also showed that NaF up-regulated SIRT1 expression in a dose-dependent manner. The autophagy of MC3T3-E1 was also up- regulated indirectly whilst apoptosis was significantly attenuated when incubated with the SIRT1 activator SRT1720. When SIRT1 inhibitor Ex-527 was used, the latter effects were reversed. Furthermore, SIRT1 increased deacetylation of FoxO1 and promoted the up-regulation of its target substrate Rab7, as well as increase of Bnip3 which was substrate of FoxO3, and we hypothesize that these pathways may cause an increase in autophagic flux and a reduction in apoptosis. In conclusion, SIRT1-induced autophagy enhancement protects against fluoride-induced apoptosis through autophagy induction in MC3T3-E1 cells, which may be associated with a SIRT1-FoxO1-Rab7 axis and a SIRT1-FoxO3-Binp3 axis. The role of SIRT1 in selecting between cell survival and death provides a potential therapeutic strategy in fluorosis.

Enhanced glycolysis contributes to the pathogenesis of experimental autoimmune neuritis

Background

With the recognition of the key roles of cellular metabolism in immunity, targeting metabolic pathway becomes a new strategy for autoimmune disease treatment. Guillain-Barré syndrome (GBS) is an acute immune-mediated inflammatory demyelinating disease of the peripheral nervous system, characterized by inflammatory cell infiltration. These inflammatory cells, including activated macrophages, Th1 cells, and Th17 cells, generally undergo metabolic reprogramming and rely mainly on glycolysis to exert functions. This study aimed to explore whether enhanced glycolysis contributed to the pathogenesis of experimental autoimmune neuritis (EAN), a classic model of GBS.

Methods

Preventive and therapeutic treatments with glycolysis inhibitor, 2-deoxy-d-glucose (2-DG), were applied to EAN rats. The effects of treatments were determined by clinical scoring, weighting, and tissue examination. Flow cytometry and ELISA were used to evaluate T cell differentiation, autoantibody level, and macrophage functions in vivo and in vitro.

Results

Glycolysis inhibition with 2-DG not only inhibited the initiation, but also prevented the progression of EAN, evidenced by the improved clinical scores, weight loss, inflammatory cell infiltration, and demyelination of sciatic nerves. 2-DG inhibited the differentiation of Th1, Th17, and Tfh cells but enhanced Treg cell development, accompanied with reduced autoantibody secretion. Further experiments in vitro proved glycolysis inhibition decreased the nitric oxide production and phagocytosis of macrophages and suppressed the maturation of dendritic cells (DC).

Conclusion

The effects of glycolysis inhibition on both innate and adaptive immune responses and the alleviation of animal clinical symptoms indicated that enhanced glycolysis contributed to the pathogenesis of EAN. Glycolysis inhibition may be a new therapy for GBS.

Vangl2 is essential for myocardial remodeling activated by Wnt/JNK signaling

The Wnt/JNK pathway, responsible for tissue polarity in cardiogenesis in vertebrates, has been shown to play numerous roles during differentiation and development of cardiac myocytes. Van Gogh-like-2 (Vangl2) is a core component that regulates the induction of polarized cellular and tissue morphology during animal development. However, little is known about Wnt/JNK signaling pathway in the process of myocardial remodeling. In present study, we found that activation of Wnt/JNK signaling by Wnt5a stimulates enlargement of cardiomyocyte surface area. The hypertrophic features were inhibited in Vangl2 depleted cells. Meanwhile, Wnt/JNK activation induced cytoskeleton rearrangement but failed to activate these effects in cells lacking Vangl2. Moreover, Wnt/JNK activation significantly increased the cell apoptosis by mediating the mitochondrial permeability transition pore (mPTP) dysfunction, whereas knockdown of Vangl2 partly reversed these effects. These results suggest that activation of Wnt/JNK signaling stimulates myocardial remodeling (cell morphological changes, apoptosis and mitochondrial dysfunction), in which Vangl2 may play an essential role.

Neuronal Nitric Oxide Synthase Negatively Regulates Zinc-Induced Nigrostriatal Dopaminergic Neurodegeneration

The study aimed to investigate the role of NO and neuronal NO synthase (nNOS) in Zn-induced neurodegeneration. Animals were treated with zinc sulfate (20 mg/kg), twice a week, for 2-12 weeks along with control. In a few sets, animals were also treated with/without a NO donor, sodium nitroprusside (SNP), or S-nitroso-N-acetyl penicillamine (SNAP) for 12 weeks. Moreover, human neuroblastoma (SH-SY-5Y) cells were also employed to investigate the role of nNOS in Zn-induced toxicity in in vitro in the presence/absence of nNOS inhibitor, 7-nitroindazole (7-NI). Zn caused time-dependent reduction in nitrite content and total/nNOS activity/expression. SNP/SNAP discernibly alleviated Zn-induced neurobehavioral impairments, dopaminergic neurodegeneration, tyrosine hydroxylase (TH) expression, and striatal dopamine depletion. NO donors also salvage from Zn-induced increase in lipid peroxidation (LPO), mitochondrial cytochrome c release, and caspase-3 activation. While Zn elevated LPO content, it attenuated nitrite content, nNOS activity, and glutathione level along with the expression of TH and nNOS in SH-SY-5Y cells. 7-NI further augmented Zn-induced changes in the cell viability, oxidative stress, and expression of TH and nNOS. The results obtained thus demonstrate that Zn inhibits nNOS that partially contributes to an increase in oxidative stress, which subsequently leads to the nigrostriatal dopaminergic neurodegeneration.

Methylmercury upregulates RE-1 silencing transcription factor (REST) in SH-SY5Y cells and mouse cerebellum

Methylmercury (MeHg) is a highly neurotoxic compound that, in adequate doses, can cause damage to the brain, including developmental defects and in severe cases cell death. The RE-1-silencing transcription factor (REST) has been found to be involved in the neurotoxic effects of environmental pollutants such as polychlorinated biphenyls (PCBs). In this study, we investigated the effects of MeHg treatment on REST expression and its role in MeHg-induced neurotoxicity in neuroblastoma SH-SY5Y cells. We found that MeHg exposure caused a dose- and time- dependent apoptotic cell death, as evidenced by the appearance of apoptotic hallmarks including caspase-3 processing and annexin V uptake. Moreover, MeHg increased REST gene and gene product expression. MeHg-induced apoptotic cell death was completely abolished by REST knockdown. Interestingly, MeHg (1μM/24h) increased the expression of REST Corepressor (Co-REST) and its binding with REST whereas the other REST cofactor mammalian SIN3 homolog A transcription regulator (mSin3A) was not modified. In addition, we demonstrated that the acetylation of histone protein H4 was reduced after MeHg treatment and was critical for MeHg-induced apoptosis. Accordingly, the pan-histone deacetylase inhibitor trichostatin-A (TSA) prevented MeHg-induced histone protein H4 deacetylation, thereby reverting MeHg-induced neurotoxic effect. Male mice subcutaneously injected with 10mg/kg of MeHg for 10 days showed an increase in REST expression in the granule cell layer of the cerebellum together with a decrease in histone H4 acetylation. Collectively, we demonstrated that methylmercury exposure can cause neurotoxicity by activating REST gene expression and H4 deacetylation.

Activated microglia cause reversible apoptosis of pheochromocytoma cells, inducing their cell death by phagocytosis

Some apoptotic processes, such as phosphatidylserine exposure, are potentially reversible and do not necessarily lead to cell death. However, phosphatidylserine exposure can induce phagocytosis of a cell, resulting in cell death by phagocytosis: phagoptosis. Phagoptosis of neurons by microglia might contribute to neuropathology, whereas phagoptosis of tumour cells by macrophages might limit cancer. Here, we examined the mechanisms by which BV-2 microglia killed co-cultured pheochromocytoma (PC12) cells that were either undifferentiated or differentiated into neuronal cells. We found that microglia activated by lipopolysaccharide rapidly phagocytosed PC12 cells. Activated microglia caused reversible phosphatidylserine exposure on and reversible caspase activation in PC12 cells, and caspase inhibition prevented phosphatidylserine exposur and decreased subsequent phagocytosis. Nitric oxide was necessary and sufficient to induce the reversible phosphatidylserine exposure and phagocytosis. The PC12 cells were not dead at the time they were phagocytised, and inhibition of their phagocytosis left viable cells. Cell loss was inhibited by blocking phagocytosis mediated by phosphatidylserine, MFG-E8, vitronectin receptors or P2Y6 receptors. Thus, activated microglia can induce reversible apoptosis of target cells, which is insufficient to cause apoptotic cell death, but sufficient to induce their phagocytosis and therefore cell death by phagoptosis.

Researching glutamate - induced cytotoxicity in different cell lines: a comparative/collective analysis/study

Although glutamate is one of the most important excitatory neurotransmitters of the central nervous system, its excessive extracellular concentration leads to uncontrolled continuous depolarization of neurons, a toxic process called, excitotoxicity. In excitotoxicity glutamate triggers the rise of intracellular Ca²⁺ levels, followed by up regulation of nNOS, dysfunction of mitochondria, ROS production, ER stress, and release of lysosomal enzymes. Excessive calcium concentration is the key mediator of glutamate toxicity through over activation of ionotropic and metabotropic receptors. In addition, glutamate accumulation can also inhibit cystine (CySS) uptake by reversing the action of the CySS/glutamate antiporter. Reversal of the antiporter action reinforces the aforementioned events by depleting neurons of cysteine and eventually glutathione’s reducing potential. Various cell lines have been employed in the pursuit to understand the mechanism(s) by which excitotoxicity affects the cells leading them ultimately to their demise. In some cell lines glutamate toxicity is exerted mainly through over activation of NMDA, AMPA, or kainate receptors whereas in other cell lines lacking such receptors, the toxicity is due to glutamate induced oxidative stress. However, in the greatest majority of the cell lines ionotropic glutamate receptors are present, co-existing to CySS/glutamate antiporters and metabotropic glutamate receptors, supporting the assumption that excitotoxicity effect in these cells is accumulative. Different cell lines differ in their responses when exposed to glutamate. In this review article the responses of PC12, SH-SY5Y, HT-22, NT-2, OLCs, C6, primary rat cortical neurons, RGC-5, and SCN2.2 cell systems are systematically collected and analyzed.

Curcumin-Protected PC12 Cells Against Glutamate-Induced Oxidative Toxicity

Glutamate is a major excitatory neurotransmitter present in the central nervous system. The glutamate/cystine antiporter system x c- connects the antioxidant defense with neurotransmission and behaviour. Overactivation of ionotropic glutamate receptors induces neuronal death, a pathway called excitotoxicity. Glutamate-induced oxidative stress is a major contributor to neurodegenerative diseases including cerebral ischemia, Alzheimer's and Huntington's disease. Curcuma has a wide spectrum of biological activities regarding neuroprotection and neurocognition. By reducing the oxidative damage, curcumin attenuates a spinal cord ischemia-reperfusion injury, seizures and hippocampal neuronal loss. The rat pheochromocytoma (PC12) cell line exhibits many characteristics useful for the study of the neuroprotection and neurocognition. This investigation was carried out to determine whether the neuroprotective effects of curcumin can be observed via the glutamate-PC12 cell model. Results indicate that glutamate (20 mM) upregulated glutathione peroxidase 1, glutathione disulphide, Ca2+ influx, nitric oxide production, cytochrome c release, Bax/Bcl-2 ratio, caspase-3 activity, lactate dehydrogenase release, reactive oxygen species, H 2 O 2 , and malondialdehyde; and downregulated glutathione, glutathione reductase, superoxide dismutase and catalase, resulting in enhanced cell apoptosis. Curcumin alleviates all these adverse effects. Conclusively, curcumin can effectively protect PC12 cells against the glutamate-induced oxidative toxicity. Its mode of action involves two pathways: the glutathione-dependent nitric oxide-reactive oxygen species pathway and the mitochondria-dependent nitric oxide-reactive oxygen species pathway.

Necrostatin-1 protects against reactive oxygen species (ROS)-induced hepatotoxicity in acetaminophen-induced acute liver failure

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RIPK-dependent necrosis is involved in acetaminophen (APAP)-induced hepatotoxicity.

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Necrostatin-1 (Nec-1) protects mice against APAP-induced acute liver damage.

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Nec-1 suppresses APAP-induced ROS generation in hepatocytes.

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Nec-1 promotes resistance to oxidative stress in hepatocytes.

Excessive acetaminophen (APAP) use is one of the most common causes of acute liver failure. Various types of cell death in the damaged liver are linked to APAP-induced hepatotoxicity, and, of these, necrotic cell death of hepatocytes has been shown to be involved in disease pathogenesis. Until recently, necrosis was commonly considered to be a random and unregulated form of cell death; however, recent studies have identified a previously unknown form of programmed necrosis called receptor-interacting protein kinase (RIPK)-dependent necrosis (or necroptosis), which is controlled by the kinases RIPK1 and RIPK3. Although RIPK-dependent necrosis has been implicated in a variety of disease states, including atherosclerosis, myocardial organ damage, stroke, ischemia–reperfusion injury, pancreatitis, and inflammatory bowel disease. However its involvement in APAP-induced hepatocyte necrosis remains elusive. Here, we showed that RIPK1 phosphorylation, which is a hallmark of RIPK-dependent necrosis, was induced by APAP, and the expression pattern of RIPK1 and RIPK3 in the liver overlapped with that of CYP2E1, whose activity around the central vein area has been demonstrated to be critical for the development of APAP-induced hepatic injury. Moreover, a RIPK1 inhibitor ameliorated APAP-induced hepatotoxicity in an animal model, which was underscored by significant suppression of the release of hepatic enzymes and cytokine expression levels. RIPK1 inhibition decreased reactive oxygen species levels produced in APAP-injured hepatocytes, whereas CYP2E1 expression and the depletion rate of total glutathione were unaffected. Of note, RIPK1 inhibition also conferred resistance to oxidative stress in hepatocytes. These data collectively demonstrated a RIPK-dependent necrotic mechanism operates in the APAP-injured liver and inhibition of this pathway may be beneficial for APAP-induced fulminant hepatic failure.

Protective effect of melittin against inflammation and apoptosis on Propionibacterium acnes-induced human THP-1 monocytic cell

Melittin is a cationic, hemolytic peptide that is the main toxic component in the venom of the honey bee (Apis mellifera). It has been used in treatment of various chronic inflammatory diseases. However, the cellular mechanism and the anti-apoptotic effect of melittin in Propionibactierium acnes (P. acnes)-induced THP-1 cells have not been explored. In the present study, we investigated the anti-inflammatory and anti-apoptotic mechanism by examining the effect of melittin on P. acnes-induced THP-1 monocytic cells. THP-1 monocytic cells were stimulated by heat-killed P. acnes in the presence of melittin. The expression levels of pro-inflammatory cytokines, NF-κB signaling, caspase family, and PARP signaling were measured by ELISA or Western blot analysis. The number of apoptotic cells and changes of cell morphology were examined using fluorescence microscopy and flow cytometry. Heat-killed P. acnes increased the secretion of pro-inflammatory cytokines and cleavage of caspase-3 and -8 in heat-killed P. acnes-induced THP-1 cells. However, treatment with melittin inhibited the pro-inflammatory cytokines and cleavage of the caspase-3 and -8. Moreover, the cleaved PARP appeared after 8h of heat-killed P. acnes treatment and its cleavage was reduced by melittin treatment. These results demonstrate that 1.0×10(7) CFU/ml of heat-killed P. acnes induces THP-1 cell apoptosis and secretion of inflammatory cytokines. Also, administration of melittin significantly decreases the expression of various inflammatory cytokines in heat-killed P. acnes-treated THP-1 monocytic cells. In particular, melittin exerts anti-apoptotic effects against 1.0×10(7) CFU/ml of heat-killed P. acnes injury to THP-1 cells.

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.

Protective effects of melittin on tumor necrosis factor-α induced hepatic damage through suppression of apoptotic pathway and nuclear factor-kappa B activation

Melittin, a major polypeptide in honeybee venom, have been used to treat inflammatory disease. Various studies have demonstrated the anti-bacterial, anti-viral, anti-inflammatory and anticancer effects of bee venom and melittin. However, the precise mechanism of melittin in liver disease is not yet known. Apoptosis contributes to liver inflammation and fibrosis. Knowledge of the apoptotic mechanisms is important to develop new and effective therapies for treatment of cirrhosis. In the present study, we investigated the anti-apoptotic effect of melittin on tumor necrosis factor (TNF)-α/actinomycin (Act) D-induced apoptosis in hepatocytes. Our results show significant protection from DNA damage by melittin treatment compared with corresponding TNF-α/Act D-treated hepatocytes without melittin. Melittin inhibited TNF-α/Act D-induced activation of the caspase, bcl-2 family of proteins and poly ADP-ribose polymerase (PARP)-1. Our results also indicate that melittin decreased nuclear factor-kappa B (NF-κB) by degradation of phosphorylation of IκB kinase (p-IKK) and NF-κB DNA binding activity in TNF-α/Act D-treated hepatocytes. These results suggest that melittin possesses a potent suppressive effect on apoptotic responses in TNF-α/Act D-treated hepatocytes via the NF-κB pathway.

Autophagy and metacaspase determine the mode of cell death in plants

Although animals eliminate apoptotic cells using macrophages, plants use cell corpses throughout development and disassemble cells in a cell-autonomous manner by vacuolar cell death. During vacuolar cell death, lytic vacuoles gradually engulf and digest the cytoplasmic content. On the other hand, acute stress triggers an alternative cell death, necrosis, which is characterized by mitochondrial dysfunction, early rupture of the plasma membrane, and disordered cell disassembly. How both types of cell death are regulated remains obscure. In this paper, we show that vacuolar death in the embryo suspensor of Norway spruce requires autophagy. In turn, activation of autophagy lies downstream of metacaspase mcII-Pa, a key protease essential for suspensor cell death. Genetic suppression of the metacaspase–autophagy pathway induced a switch from vacuolar to necrotic death, resulting in failure of suspensor differentiation and embryonic arrest. Our results establish metacaspase-dependent autophagy as a bona fide mechanism that is responsible for cell disassembly during vacuolar cell death and for inhibition of necrosis.

Adenovirus-mediated eNOS expression augments liver injury after ischemia/reperfusion in mice

Hepatic ischemia/reperfusion (l/R) injury continues to be a critical problem. The role of nitric oxide in liver I/R injury is still controversial. This study examines the effect of endothelial nitric oxide synthase (eNOS) over-expression on hepatic function following I/R. Adenovirus expressing human eNOS (Ad-eNOS) was administered by tail vein injection into C57BL/6 mice. Control mice received either adenovirus expressing LacZ or vehicle only. Sixty minutes of total hepatic ischemia was performed 3 days after adenovirus treatment, and mice were sacrificed after 6 or 24 hrs of reperfusion to assess hepatic injury. eNOS over expression caused increased liver injury as evidenced by elevated AST and ALT levels and decreased hepatic ATP content. While necrosis was not pervasive in any group, TUNEL demonstrated significantly increased apoptosis in Ad-eNOS infected livers. Western blotting demonstrated increased levels of protein nitration and upregulation of the pro-apoptotic proteins bax and p53. Our data suggest that over-expression of eNOS is detrimental in the setting of hepatic I/R.

Nitric oxide-induced apoptosis of human dental pulp cells is mediated by the mitochondria-dependent pathway

Nitric oxide (NO) is recognized as a mediator and regulator of inflammatory responses. NO is produced by nitric oxide synthase (NOS), and NOS is abundantly expressed in the human dental pulp cells (HDPCs). NO produced by NOS can be cytotoxic at higher concentrations to HDPCs. However, the mechanism by which this cytotoxic pathway is activated in cells exposed to NO is not known. The purpose of this study was to elucidate the NO-induced cytotoxic mechanism in HDPCs. Sodium nitroprusside (SNP), a NO donor, reduced the viability of HDPCs in a dose- and time-dependent manner. We investigated the in vitro effects of nitric oxide on apoptosis of cultured HDPCs. Cells showed typical apoptotic morphology after exposure to SNP. Besides, the number of Annexin V positive cells was increased among the SNP-treated HDPCs. SNP enhanced the production of reactive oxygen species (ROS), and N-acetylcysteine (NAC) ameliorated the decrement of cell viability induced by SNP. However, a soluble guanylate cyclase inhibitor (ODQ) did not inhibited the decrement of cell viability induced by SNP. SNP increased cytochrome c release from the mitochondria to the cytosol and the ratio of Bax/Bcl-2 expression levels. Moreover, SNP-treated HDPCs elevated activities of caspase-3 and caspase-9. While pretreatment with inhibitors of caspase (z-VAD-fmk, z-DEVD-fmk) reversed the NO-induced apoptosis of HDPCs. From these results, it can be suggested that NO induces apoptosis of HDPCs through the mitochondria-dependent pathway mediated by ROS and Bcl-2 family, but not by the cyclic GMP pathway.

CoCl2 induces apoptosis through the mitochondria- and death receptor-mediated pathway in the mouse embryonic stem cells

Embryonic hypoxia/ischemia is a major cause of a poor fetal outcome and future neonatal and adult handicaps. However, biochemical cellular events in mouse embryonic stem (mES) cells during hypoxia remains unclear. This study investigated the underlying mechanism of apoptosis in mES cells under CoCl2-induced hypoxic/ischemic conditions. CoCl2 enhanced the expression of hypoxia-inducible factor-1α (HIF-1α) and the accumulation of reactive oxygen species in mES cells. The CoCl2-treated mES cells showed a decrease in cell viability as well as typical apoptotic changes, cell shrinkage, chromatin condensation, and nuclear fragmentation and an extended G2/M phase of the cell cycle. CoCl2 augmented the release of cytochrome c into the cytosol from the mitochondria with a concomitant loss of the mitochondrial transmembrane potential (ΔΨm) and upregulated the voltage-dependent anion channel. In addition, CoCl2-induced caspase-3, -8, and -9 activation and upregulation of p53 level, whereas downregulated Bcl-2 and Bcl-xL, a member of the anti-apoptotic Bcl-2 family in mES cells. Furthermore, CoCl2 led to the upregulation of Fas and Fas-ligand, which are the death receptor assemblies, as well as the cleavage of Bid in mES cells. These results suggest that CoCl2 induces apoptosis through both mitochondria- and death receptor-mediated pathways that are regulated by the Bcl-2 family in mES cells.

The contribution of N₂O₃ to the cytotoxicity of the nitric oxide donor DETA/NO: an emerging role for S-nitrosylation

The relationship between the biological activity of NO and its chemistry is complex. The objectives of this study were to investigate the influence of oxygen tension on the cytotoxicity of the NO^• donor DETA/NO and to determine the effects of oxygen tension on the key RNS (reactive nitrogen species) responsible for any subsequent toxicity. The findings presented in this study indicate that the DETA/NO-mediated cytotoxic effects were enhanced under hypoxic conditions. Further investigations revealed that neither ONOO⁻ (peroxynitrite) nor nitroxyl was generated. Fluorimetric analysis in the presence of scavengers suggest for the first time that another RNS, dinitrogen trioxide may be responsible for the cytotoxicity with DETA/NO. Results showed destabilization of HIF (hypoxia inducible factor)-1α and depletion of GSH levels following the treatment with DETA/NO under hypoxia, which renders cells more susceptible to DETA/NO cytotoxicity, and could account for another mechanism of DETA/NO cytotoxicity under hypoxia. In addition, there was significant accumulation of nuclear p53, which showed that p53 itself might be a target for S-nitrosylation following the treatment with DETA/NO. Both the intrinsic apoptotic pathway and the Fas extrinsic apoptotic pathway were also activated. Finally, GAPDH (glyceraldehyde-3-phosphate dehydrogenase) is another important S-nitrosylated protein that may possibly play a key role in DETA/NO-mediated apoptosis and cytotoxicity. Therefore this study elucidates further mechanisms of DETA/NO mediated cytotoxicity with respect to S-nitrosylation that is emerging as a key player in the signalling and detection of DETA/NO-modified proteins in the tumour microenvironment.

The nitric oxide donor sodium nitroprusside requires the 18 kDa Translocator Protein to induce cell death

Various studies have shown that several lethal agents induce cell death via the mitochondrial 18 kDa Translocator Protein (TSPO). In this study we tested the possibility that nitric oxide (NO) is the signaling component inducing the TSPO to initiate cell death process. Cell viability assays included Trypan blue uptake, propidium iodide uptake, lactate dehydrogenase release, and DNA fragmentation. These assays showed that application of the specific TSPO ligand PK 11195 reduced these parameters for the lethal effects of the NO donor sodium nitroprusside (SNP) by 41, 27, 40, and 42 %, respectively. TSPO silencing by siRNA also reduced the measured lethal effects of SNP by 50 % for all of these four assays. With 2,3-bis[2-methoxy-4-nitro-5-sulphophenyl]-2H-tetrazolium-5-carboxyanilide (XTT) changes in metabolic activity were detected. PK 11195 and TSPO knockdown fully prevented the reductions in XTT signal otherwise induced by SNP. Collapse of the mitochondrial membrane potential was studied with the aid of JC-1 (5,5',6,6'-tetrachloro-1,1',3,3'-tetraethyl-benzimidazolylcarbocyanine chloride). PK 11195 and TSPO knockdown reduced, respectively by 36 and 100 %, the incidence of collapse of the mitochondrial membrane potential otherwise induced by SNP. 10-N-Nonyl-Acridine Orange (NAO) was used to detect mitochondrial reactive oxygen species generation due to SNP. PK 11195 and TSPO knockdown reduced this effect of SNP by 65 and 100 %, respectively. SNP did not affect TSPO protein expression and binding characteristics, and also did not cause TSPO S-nitrosylation. However, β-actin and various other proteins (not further defined) were S-nitrosylated. In conclusion, TSPO is required for the lethal and metabolic effects of the NO donor SNP, but TSPO itself is not S-nitrosylated.

Nitric oxide in neurodegeneration: potential benefits of non-steroidal anti-inflammatories

The cellular messenger nitric oxide (NO) has been linked to neurodegenerative disorders due to the increased expression of the enzymes that catalyze its synthesis in postmortem tissues derived from sufferers of these diseases. Nitrated proteins have also been detected in these samples, revealing that NO is biologically active in regions damaged during neurodegeneration. Modulation of NO levels has been reported not only in the neurons of the central nervous system, but also in the glial cells (microglia and astroglia) activated during the neuroinflammatory response. Neuroinflammation has been found in some neurodegenerative conditions, and inhibition of these neuroinflammatory signals has been shown to delay the progress of such disorders. Thus NO and the pathways triggering its release are emerging as an important research focus in the search for strategies to prevent, halt or cure neurodegenerative diseases.

The In Vitro and In Vivo Antitumour Activities of Nitrosyl Ruthenium Amine Complexes

Ruthenium compounds of the type trans-[Ru(NO)(NH3)4(L)]X3, L = N-heterocyclic ligands, P(OEt)3, SO32–, X = BF4– or PF6–, or [Ru(NO)Hedta], were tested for antitumour activity in vitro against murine melanoma and human tumour cells. The ruthenium complexes induced DNA fragmentation and morphological alterations suggestive of necrotic tumour cell death. The calculated IC50 values were lower than 100 μM. Complexes for which L = isn or imN were partially effective in vivo in a syngeneic model of murine melanoma B16F10, increasing animal survival. In addition, the same ruthenium complexes effectively inhibited angiogenesis of HUVEC cells in vitro. The results suggest that these nitrosyl complexes are a promising platform to be explored for the development of novel antitumour agents.

Neoechinulin a impedes the progression of rotenone-induced cytotoxicity in PC12 cells

Neoechinulin A, an indole alkaloid from marine fungi, can protect PC12 cells from the cytotoxicity of 1-methyl-4-phenylpyridinium (MPP(+)), a Parkinson disease-inducing neurotoxin, by ameliorating downstream events resulting from mitochondrial complex I inactivation. However, the cytoprotective mechanisms remained unclear. In this study, by using rotenone, another parkinsonian-inducing neurotoxin targeting mitochondrial complex I, we investigated the cytoprotective mechanism of neoechinulin A. Rotenone-induced cell death was associated with accelerated glucose consumption, and excess glucose supplementation in the culture medium almost completely suppressed cell death, suggesting that glucose deficiency in the medium is critical for triggering cell death in this model. Co-treatment with neoechinulin A, but not neoechinulin A pre-treatment before rotenone exposure, significantly impeded cell death by rotenone. Although the presence of neoechinulin A did not affect the accelerated glycolytic turnover in rotenone-treated cells, it paradoxically decreased ATP levels in the cells, suggesting increased ATP consumption. Although the link between the decreased ATP levels and cytoprotection is not clear at present, it suggests that neoechinulin A may ameliorate rotenone toxicity by activating a cytoprotective machinery that requires ATP.

Interferon gamma activated macrophages kill mycobacteria by nitric oxide induced apoptosis

Mycobacterium tuberculosis is an intracellular pathogen of macrophages and escapes the macrophages' bactericidal effectors by interfering with phagosome-lysosome fusion. IFN-γ activation renders the macrophages capable of killing intracellular mycobacteria by overcoming the phagosome maturation block, nutrient deprivation and exposure to microbicidal effectors including nitric oxide (NO). While the importance about NO for the control of mycobacterial infection in murine macrophages is well documented, the underlying mechanism has not been revealed yet. In this study we show that IFN-γ induced apoptosis in mycobacteria-infected macrophages, which was strictly dependent on NO. Subsequently, NO-mediated apoptosis resulted in the killing of intracellular mycobacteria independent of autophagy. In fact, killing of mycobacteria was susceptible to the autophagy inhibitor 3-methyladenine (3-MA). However, 3-MA also suppressed NO production, which is an important off-target effect to be considered in autophagy studies using 3-MA. Inhibition of caspase 3/7 activation, as well as NO production, abolished apoptosis and elimination of mycobacteria by IFN-γ activated macrophages. In line with the finding that drug-induced apoptosis kills intracellular mycobacteria in the absence of NO, we identified NO-mediated apoptosis as a new defense mechanism of activated macrophages against M. tuberculosis.

Differential susceptibility to nitric oxide-evoked apoptosis in human inflammatory cells

Apoptosis of neutrophils and their subsequent phagocytosis is critical to the successful resolution of inflammation. During inflammation, activated inflammatory cells generate reactive oxygen and nitrogen species, including nitric oxide (NO) and superoxide anion (O(2)(•-)), which rapidly combine to generate peroxynitrite (ONOO(-)). NO and ONOO(-) are proapoptotic in human neutrophils. This study examines the effects of NO and ONOO(-) on caspase activation and mitochondrial permeability in human neutrophils and determines the ability of these species to evoke apoptosis in human monocyte-derived macrophages (MDMs). NO or ONOO(-) release from donor compounds was characterized by electrochemistry and electron paramagnetic resonance. Neutrophils and MDMs isolated from the peripheral blood of healthy volunteers were exposed to NO or ONOO(-) before analysis of apoptosis by caspase activation, mitochondrial permeability, and annexin V binding. Both NO and ONOO(-) induced apoptosis via rapid activation of caspases 2 and 3 in neutrophils. In contrast, only ONOO(-) promoted apoptosis in MDMs, whereas a variety of NO donors were ineffective at inducing apoptosis in this cell type. We propose that human macrophages are refractory to NO-stimulated apoptosis in order that they persist long enough within the inflammatory focus to phagocytose apoptotic neutrophils, thereby ensuring successful resolution of inflammation.

Transcriptional regulation of inducible nitric oxide synthase gene therapy: targeting early stage and advanced prostate cancer

BACKGROUND

Using the tumour type specific human osteocalcin (hOC) promoter, we have previously reported strong promoter activation in hormone independent prostate cancer cells in vitro. In the present study, we present a comparative study of the tissue specific promoter prostate specific membrane antigen (PSMA), and the tumour-type specific hOC promoter driving the inducible nitric oxide synthase (iNOS) transgene using both in vitro and in vivo models.

METHODS

In vitro cytotoxicity was assessed by clonogenic assay. Quantification of nitric oxide expression was determined by the Griess test. In vivo anti-tumour efficacy was determined by tumour growth delay following direct intra-tumoural injection of the constructs into PC3 xenografts. In addition, tumours were dissected post mortem and examined for morphological differences as well as changes in apoptotic protein expression.

RESULTS

PSMA/iNOS produced cytotoxicity in both androgen dependant and independent cell lines. Nitric oxide quantification confirmed that increased cytotoxicity was directly associated with nitric oxide production. Tumour growth delays were observed in all groups treated with the iNOS-expressing constructs ranging from 10.7 days for the hOC/iNOS single dose treatment group to a maximum of 52.2 days for the hOC/iNOS multiple dose group. Intra-tumoural assessment of iNOS and cleaved poly (ADP-ribose) polymerase protein expression demonstrated a significant up-regulation of both proteins, indicating cytotoxicity mediated through the intrinsic apoptotic pathway.

CONCLUSIONS

Highly significant tumour growth delay coupled with no detrimental side-effects were observed following treatment with the PSMA/iNOS and hOC/iNOS constructs. We consider that these findings provide a basis for the development of systemically delivered PSMA/iNOS or hOC/iNOS targeting early stage and advanced prostate cancer.

The glycolipid sulfatide protects insulin-producing cells against cytokine-induced apoptosis, a possible role in diabetes

AIMS/HYPOTHESIS

Cytokine-induced apoptosis is recognised as a major cause of the decline in β-cell mass that ultimately leads to type 1 diabetes mellitus. Interleukin-1β, interferon-γ and tumour necrosis factor-α in conjunction initiate a series of events that lead to β-cell apoptosis; important among these is NO production. The glycosphingolipid sulfatide is present in β-cells in the secretory granules in varying amounts and is secreted together with insulin. We now investigate whether sulfatide is able to protect insulin-producing cells against the pro-apoptotic effect of interleukin-1β, interferon-γ and tumour necrosis factor-α.

METHODS

INS-1E cells and genuine rat islets were incubated for 24 h exposed to interleukin-1β, interferon-γ and tumour necrosis factor-α with or without sulfatide. The production of NO was monitored and the number of apoptotic cells was determined using terminal deoxynucleotidyl transferase-mediated dUTP Nick-End labelling and caspase-3/7 activity assays. In addition, the amount of iNOS mRNA was determined using real-time quantitative polymerase chain reaction.

RESULTS

Cytokine-induced apoptosis was reduced to 27% of cytokine-treated controls with 30 µmol/L sulfatide treatment (p < 0.01). Likewise, sulfatide in concentrations of 3-30 µmol/L decreased NO production in a dose-dependent manner to 19-40% of cytokine-treated controls (overall p = 0.0007). The level of iNOS mRNA after cytokine exposure was reduced to 55% of cytokine-treated controls with 30 µmol/L of sulfatide.

CONCLUSIONS/INTERPRETATION

In the present study, we report the ability of sulfatide to significantly reduce apoptosis, cellular leakage and NO production in insulin-producing cells. Data suggest this is not due to induction of β-cell rest. Our findings indicate a possible implication for sulfatide in the pathogenesis of diabetes.

The protective activities of water-soluble C(60) derivatives against nitric oxide-induced cytotoxicity in rat pheochromocytoma cells

In this study, the protective activities of water-soluble C(60) derivatives against nitric oxide (NO) induced cytotoxicity were investigated. To overcome C(60) insolubility in water, we modified C(60) with β-alanine, valine or folacin. The compounds were characterized by FT-IR, (1)H NMR, (13)C NMR, LC-MS, elemental analysis, light scattering and TEM. Investigation of the possible NO-scavenging activities of water-soluble C(60) derivatives demonstrated that they expressed direct scavenging activity toward NO liberated within solution of sodium nitroprusside (SNP). In parallel, following exposure of cells to SNP (1 mM), a marked decrease in mitochondrial membrane potential, cell viability, activities of superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px), as well as increased levels of intracellular NO accumulation and malondialdehyde (MDA) production were observed. Moreover, SNP caused significant elevation in intracellular caspase-3 activity, and induced apoptotic death as determined by flow cytometric assay. However, pretreatment of the cells with water-soluble C(60) derivatives prior to SNP exposure blocked these NO-induced cellular events noticeably. Experiments demonstrated that the aggregation morphology could impact the NO-scavenging abilities and protective effects on apoptosis of water-soluble C(60) derivatives. The results suggest that water-soluble C(60) derivatives have the potential to prevent NO-mediated cell death without evident toxicity.

The neuroprotective effects of tanshinone IIA on β-amyloid-induced toxicity in rat cortical neurons

Oxidative stress caused by amyloid β-peptide (Aβ) may play an important role in the pathogenesis of Alzheimer disease (AD). Aβ is known to be directly responsible for the production of reactive oxygen species (ROS) and induction of apoptosis. Tanshinone IIA (Tan IIA) is extracted from a traditional herbal medicine Salvia miltiorrhiza BUNGE, which has been shown to protect against oxidative stress and cell death. In this study, we investigated the neuroprotective effect of Tan IIA against Aβ₂₅₋₃₅-induced cell death in cultured cortical neurons. Exposure of cortical neurons to 30μM Aβ₂₅₋₃₅ caused a significant viability loss, cell apoptosis and decreased activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) as well as increased levels of malondialdehyde (MDA) production. In parallel, Aβ₂₅₋₃₅ significant increased the intracellular ROS elevation and decreased mitochondrial membrane potential (MMP). However, pretreatment of the cells with Tan IIA prior to Aβ₂₅₋₃₅ exposure suppressed these Aβ₂₅₋₃₅-induced cellular events noticeably. In addition, Tan IIA reduced the Aβ₂₅₋₃₅-induced increase of caspase-3 activity, and reduced cytochrome c translocation into the cytosol from mitochondria. Furthermore, Tan IIA also ameliorated the Aβ₂₅₋₃₅-induced Bcl-2/Bax ratio reduction in cortical neurons. Taken together, these data indicate that Tan IIA protected cultured cortical neurons against Aβ₂₅₋₃₅-induced neurotoxicity through its antioxidative potential. Our results strongly suggest that Tan IIA may be effective in treating AD associated with oxidative stress.

Ferulic acid inhibits nitric oxide-induced apoptosis by enhancing GABA(B1) receptor expression in transient focal cerebral ischemia in rats

AIM

Ferulic acid (4-hydroxy-3-methoxycinnamic acid, FA) provides neuroprotection against apoptosis in a transient middle cerebral artery occlusion (MCAo) model. This study was to further investigate the anti-apoptotic effect of FA during reperfusion after cerebral ischemia.

METHODS

Rats were subjected to 90 min of cerebral ischemia followed by 3 or 24 h of reperfusion after which they were sacrificed.

RESULTS

Intravenous FA (100 mg/kg) administered immediately after middle cerebral artery occlusion (MCAo) or 2 h after reperfusion effectively abrogated the elevation of postsynaptic density-95 (PSD-95), neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), nitrotyrosine, and cleaved caspase-3 levels as well as apoptosis in the ischemic cortex at 24 h of reperfusion. FA further inhibited Bax translocation, cytochrome c release, and p38 mitogen-activated protein (MAP) kinase phosphorylation. Moreover, FA enhanced the expression of gamma-aminobutyric acid type B receptor subunit 1 (GABA(B1)) in the ischemic cortex at 3 and 24 h of reperfusion. In addition, nitrotyrosine-positive cells colocalized with cleaved caspase-3-positive cells, and phospho-p38 MAP kinase-positive cells colocalized with nitrotyrosine- and Bax-positive cells, indicating a positive relationship among the expression of nitrotyrosine, phospho-p38 MAP kinase, Bax, and cleaved caspase-3. The mutually exclusive expression of GABA(B1) and nitrotyrosine revealed that there is a negative correlation between GABA(B1) and nitrotyrosine expression profiles. Additionally, pretreatment with saclofen, a GABA(B) receptor antagonist, abolished the neuroprotection of FA against nitric oxide (NO)-induced apoptosis.

CONCLUSION

FA significantly enhances GABA(B1) receptor expression at early reperfusion and thereby provides neuroprotection against p38 MAP kinase-mediated NO-induced apoptosis at 24 h of reperfusion.