Mitochondrial nitric oxide synthase, oxidative stress and apoptosis

Effects of tetrahydroxy stilbene glycoside derivatives on free radical damage and apoptosis in APP695V717I transgenic mice

Mitochondrial dysfunction leading to overproduction of oxygen free radicals is an important event in the development of Alzheimer's disease. Tetrahydroxy stilbene glycoside (TSG) is one of the main effective components of Polygonum multiflorum and has a certain free radical scavenging effect. We synthesized tetrahydroxy stilbene glycoside derivatives (Mito-TSGs) that can cross the mitochondrial membrane and may provide effective protection against Alzheimer's disease. This experiment investigates the protective mechanism of tetrahydroxy stilbene glycoside derivatives against mitochondrial free radical damage and apoptosis in APP695V717I transgenic model mice. The experimental subjects were healthy 3-month-old APP695V717I transgenic model mice, while C57BL/6J mice of the same age and genetic background served as controls. The results demonstrated that the tetrahydroxy stilbene glycoside derivatives significantly improved mouse behavioral performance. It also led to a decrease in the levels of H2O2, NO, MDA, and LD, along with an increase in LDH activity and in the antioxidant enzyme activity of SOD, CAT, and GSH-Px. Moreover, it elevated the mitochondrial membrane potential, decreased the gene and protein expression of Caspase-3 and Bax, and increased the gene and protein expression of Bcl-2. Notably, the effectiveness of tetrahydroxy stilbene glycoside derivatives was superior to that of traditional tetrahydroxy stilbene glycoside.

Crosstalk between Sirtuins and Nrf2: SIRT1 activators as emerging treatment for diabetic neuropathy

About 50% of the diabetic patients worldwide suffer from Diabetic peripheral neuropathy (DPN) which is characterized by chronic pain and loss of sensation, frequent foot ulcerations, and risk for amputation. Numerous factors like hyperglycemia, oxidative stress (OS), impaired glucose signaling, inflammatory responses, neuronal cell death are known to be the various mechanisms underlying DACD and DPN. Development of tolerance, insufficient and inadequate relief and potential toxicity of classical antinociceptives still remains a challenge in the clinical setting. Therefore, there is an emerging need for novel treatments which are both without any potential side effects as well as which focus more on the pathophysiological mechanisms underlying the disease. Also, sirtuins are known to deacetylate Nrf2 and contribute to its action of reducing ROS by generation of anti-oxidant enzymes. Therefore, targeting sirtuins could be a favourable therapeutic strategy to treat diabetic neuropathy by reducing ROS and thereby alleviating OS in DPN. In the present review, we outline the potential use of SIRT1 activators as therapeutic alternatives in treating DPN. We have tried to highlight how sirtuins are interlinked with Nrf2 and NF-κB and put forth how SIRT activators could serve as potential therapy for DPN.

Revisiting Excitotoxicity in Traumatic Brain Injury: From Bench to Bedside

Traumatic brain injury (TBI) is one of the leading causes of morbidity and mortality. Consequences vary from mild cognitive impairment to death and, no matter the severity of subsequent sequelae, it represents a high burden for affected patients and for the health care system. Brain trauma can cause neuronal death through mechanical forces that disrupt cell architecture, and other secondary consequences through mechanisms such as inflammation, oxidative stress, programmed cell death, and, most importantly, excitotoxicity. This review aims to provide a comprehensive understanding of the many classical and novel pathways implicated in tissue damage following TBI. We summarize the preclinical evidence of potential therapeutic interventions and describe the available clinical evaluation of novel drug targets such as vitamin B12 and ifenprodil, among others.

A review on the mechanisms of the effect of silymarin in milk thistle (Silybum marianum) on some laboratory animals

One of the most valuable medicinal plants is milk thistle (Silybum marianum) or martighal. An annual or biennial plant of the Asteraceae family and English name Milk thistle, a Matte green colour and prickly plant with a standing stem that can be thick, simple, or slightly branched (ramified). Its seeds contain about 70%-80% of the flavonolignans of silymarin and about 20%-30% of polymeric and oxidized polyphenolic compounds (such as tannins). Traditionally, the plant has been used to increase milk secretion, relieve menstrual cramps, lessen depression, decrease gallstones, and jaundice as well as improve functions of the liver, spleen, and kidney. This review reviews studies on the effects of adding milk thistle to quail diet. Consumption (0.5% and 1%) of milk thistle powder in the diet of Japanese quail significantly increased feed intake, body weight, and improved carcass components. Blood constituents including total protein and albumin were improved along with decreased HDL, ALT, and AST. The use of milk thistle levels (0.5% and 1.5%) significantly improved the antioxidant total of plasma. Consumption of silymarin in quail diet increased the number of white blood cells, calcium, vitamin D3, and albumin. Silymarin also decreased the relative weights of bursa of Fabricius and spleen. This review indicates that milk thistle can improve growth performance, feed conversion ratio, and immune system in quail.

Extracellular Inorganic Phosphate-Induced Release of Reactive Oxygen Species: Roles in Physiological Processes and Disease Development

Inorganic phosphate (Pi) is an essential nutrient for living organisms and is maintained in equilibrium in the range of 0.8-1.4 mM Pi. Pi is a source of organic constituents for DNA, RNA, and phospholipids and is essential for ATP formation mainly through energy metabolism or cellular signalling modulators. In mitochondria isolated from the brain, liver, and heart, Pi has been shown to induce mitochondrial reactive oxygen species (ROS) release. Therefore, the purpose of this review article was to gather relevant experimental records of the production of Pi-induced reactive species, mainly ROS, to examine their essential roles in physiological processes, such as the development of bone and cartilage and the development of diseases, such as cardiovascular disease, diabetes, muscle atrophy, and male reproductive system impairment. Interestingly, in the presence of different antioxidants or inhibitors of cytoplasmic and mitochondrial Pi transporters, Pi-induced ROS production can be reversed and may be a possible pharmacological target.

The antagonistic effect of bisphenol A and nonylphenol on liver and kidney injury in rats

OBJECTIVE

Bisphenol A (BPA) and nonylphenol (NP) are widely distributed endocrine-disrupting compounds. We aimed to estimate the combined toxicity of BPA and NP at a clinically safe dose (100 μg/kg) in rats.

MATERIALS AND METHODS

Liver and kidney functions were evaluated by detecting the relevant indicators. Hematoxylin and Eosin (HE) staining was performed to examine the injury in the tissue. TUNEL assay and Western blot were used to detect cell apoptosis and expressions of target factors, respectively.

RESULTS

The body weight of rats in the BPA + NP group was lighter than that in the BPA or NP group. BPA or NP weakened liver function through increasing levels of aspartate aminotransferase (AST), alkaline phosphatase (ALP), alanine aminotransferase (ALT), cholesterol (CHOL), triglyceride TG, globulin (GLOB), treponemiapallidum (TP), and total bilirubin (TBIL). BPA and NP could induce kidney damage by elevating the levels of serum creatinine (Scr) and blood urea nitrogen (BUN). Moreover, the malondialdehyde (MDA) content was increased, whereas the activities of superoxide dismutase (SOD), glutathione (GSH), glutathione peroxidase (GSH-PX), glutathione sulfotransferase (GSH-ST), catalase (CAT), and peroxidase (POD) were reduced in those groups exposed to BPA or NP. HE staining exhibited injuries of the liver and kidney. Furthermore, the apoptosis of liver and kidney cells was enhanced by exposure to BPA or NP. Additionally, the expressions of CYP2D6, CYP1A1, and CYP2E1 were triggered by the treatment of BPA or NP. The combined effect of BPA and NP seemed to be antagonistic at a low dose.

CONCLUSION

BPA and NP may have potential interactions.

Effects of Individual and Coexisting Diabetes and Cardiomyopathy on Diastolic Function in Rats (Rattus norvegicus domestica)

The goal of this study was to evaluate diastolic intraventricular pressure gradients (IVPG) and 2-dimensional tissue tracking (2DTT) patterns during diabetes and cardiomyopathy. Rats (n = 60) were induced to become diabetic (DM group, n = 15) by using streptozotocin, to become cardiomyopathic (CM group, n = 15) by using isoproterenol, and to become both diabetic and cardiomyopathic (DMCM group, n = 15); control rats (CT group, n = 15) were injected with saline. Two months after induction, all rats underwent conventional echocardiography, IVPG, and 2DTT and then were euthanized for microscopic examination of cardiac fibrosis. Compared with the controls, all 3 treated groups showed diastolic dysfunction and delayed cardiac relaxation. DMCM rats showed the most pronounced cardiac abnormalities. In addition, CM and DMCM groups had showed decreased middle IVPG, whereas DMCM rats had decreased midapical IVPG. Although the overall IVPG of the CM group was normal, the middle segment was significantly decreased. 2DTT results showed that the DMCM group had a delay in relaxation compared with other groups. IVPG and 2DTT can be used to overcome the limitation of conventional echocardiographic methods and reveal diastolic dysfunction. DM worsened diastolic function during cardiac disease.

Dexamethasone induces osteoblast apoptosis through ROS-PI3K/AKT/GSK3β signaling pathway

BACKGROUND

Osteoblasts play important roles in the process of osteogenesis and prevention of osteonecrosis. Dexamethasone (Dex), a type of glucocorticoids (GCs), induces apoptosis of osteoblasts and leads to the occurrence of non-traumatic osteonecrosis. This study aimed to explore the effects of phosphatidylinositol 3-kinase/Protein kinase 3 (PI3K/AKT) and glycogen synthase kinase 3β (GSK3β) on Dex-induced osteoblasts apoptosis.

METHODS

Viabilities, proliferation, and apoptosis of primary osteoblasts and pre-osteoblast MC3T3-E1 cells after Dex treatment were detected using cell counting kit-8 (CCK-8) assay, 5-bromo-2'-deoxyuridine (BrdU) incorporation assay, FITC-Annexin V/PI staining and western blotting, respectively. 2',7'-Dichlorodihydrofluorescein diacetate (DCFH-DA) staining was performed to measure the intracellular reactive oxygen species (ROS) levels after Dex treatment. N-acetyl-l-cysteine (NAC) was used as ROS scavenger in this research. The expressions of PI3K/AKT and GSK3β in osteoblasts and MC3T3-E1 cells after Dex treatment were analyzed using western blotting and qRT-PCR, respectively. Then the effects of GSK3β knockdown on Dex-induced apoptosis of osteoblasts were explored. Alkaline phosphatase (ALP) activity assay was used to detect the role of Dex in regulating ALP activity.

RESULTS

Dex remarkably inhibited proliferation and induced apoptosis of osteoblasts and MC3T3-E1 cells. Dex potentially attenuated the osteoblast differentiation. The intracellular ROS levels were significantly increased after Dex treatment. Dex suppressed the activation of PI3K/AKT pathway in osteoblasts and MC3T3-E1 cells by down-regulating the expressions of p-PI3K and p-AKT. The expressions of GSK3β in osteoblasts and MC3T3-E1 cells were obviously up-regulated after Dex treatment. Knockdown of GSK3β alleviated Dex-induced osteoblast and MC3T3-E1 cell apoptosis by decreasing the expressions of Bax, cleaved-caspase 3, cleaved-caspase 9 and increasing the expression of Bcl-2.

CONCLUSION

Our research verified that Dex induced osteoblasts apoptosis by ROS-PI3K/AKT/GSK3β signaling pathway.

Recent advances in understanding the role of oxidative stress in diabetic neuropathy

Diabetic neuropathy (DN) is one of the most common and severe manifestations of diabetes mellitus. The mechanisms underlying the structural, functional and metabolic changes in diabetic neuropathy have been under study for a long time. In this review the biochemistry and implications of the four pathways responsible for the development of DN, polyol pathway; increased AGEs (advanced glycation end-products) formation; activation of PKC (protein kinase C) and hexosamine pathway have been discussed. Experimental and clinical evidences suggest a close link between neurodegeneration and oxidative stress which serves as a unifying mechanism, thus linking the four pathways. Recent studies indicate that oxidative stress mediated DNA damage causes poly(ADP-ribose) polymerase (PARP) overactivation and reduced activity of glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a factor common to all the four pathways. The exact mechanism of PARP mediated cell death in DN needs further investigation. Based on current studies neuroprotective and antioxidant therapy have been suggested as potential treatment and preventive solutions for DN.

Reactive nitrogen species contribute to the rapid onset of redox changes induced by acute immobilization stress in rats

Acute stress leads to the rapid secretion of glucocorticoids, which accelerates cellular metabolism, resulting in increased reactive oxygen and nitrogen species generation. Although the nitrergic system has been implicated in numerous stress-related diseases, the time course and extent of nitrosative changes during acute stress have not been characterized. Outbred male Wistar rats were randomly allocated into control (n = 9) or 120 min acute immobilization stress (n = 9) groups. Serial blood samples were collected at 0 (baseline), 60, 90, and 120 min. Plasma corticosterone concentrations increased by approximately 350% at 60, 90, and 120 (p < 0.001) min of stress. The production of nitric oxide, measured as the benzotriazole form of 4-amino-5-methylamino-2',7'-difluorofluorescein, increased during stress exposure by approximately 5%, 10%, and 15% at 60 (p < 0.05), 90 (p < 0.01) and 120 (p < 0.001) min, respectively, compared to controls. Nitric oxide metabolism, measured as the stable metabolites nitrite and nitrate, showed a 40-60% increase at 60, 90, and 120 (p < 0.001) min of stress. The oxidative status of 2',7'-dichlorofluorescein in plasma was significantly elevated at 60 (p < 0.01), 90, and 120 (p < 0.001) min. A delayed decrease of approximately 25% in the glutathione redox ratio at 120 min (p < 0.001) also indicates stress-induced cellular oxidative stress. The peroxidation of plasma lipids increased by approximately 10% at 90 (p < 0.05) and 15% at 120 (p < 0.001) min, indicative of oxidative damage. It was concluded that a single episode of stress causes early and marked changes of both oxidative and nitrosative status sufficient to induce oxidative damage in peripheral tissues.

Protective effect of short-term treatment with parathyroid hormone 1-34 on oxidative stress is involved in insulin-like growth factor-I and nuclear factor erythroid 2-related factor 2 in rat bone marrow derived mesenchymal stem cells

Bone marrow-derived mesenchymal stem cell (MSC)-mediated regeneration is a promising treatment for degenerative disease and traumatic injuries. MSCs can be isolated from rats using magnetic-activated cell sorting with CD105 antibody. We investigated the relationships between the expression of endogenous insulin-like growth factor-I (IGF-I) and nuclear factor erythroid 2-related factor 2 (Nrf-2) during short-term treatment with parathyroid hormone (PTH) 1-34-induced protective response in MSCs. PTH 1-34 (10(-9)M) decreased reactive oxygen species (ROS) generation but increased cell viability and endogenous IGF-I (p<0.01). Suppression of IGF-I and Nrf-2 using specific small interfering RNA (siRNA) blocked the effects of PTH 1-34. Furthermore, increasing cell viability of PTH against hydrogen peroxide (H2O2) was suppressed by treatment with siRNA to IGF-I and Nr-2 (p<0.05). Exogenous IGF-I (10(-9)M) also increased endogenous IGF-I, cell viability, and Nrf-2 expression. These incremental increases were lessened by Nrf-2 siRNA (p<0.05). Exogenous IGF-I also inhibited the increase of H2O2-induced ROS generation, and the decrease of PTH 1-34-induced ROS generation in the presence of IGF-I and Nrf-2 siRNA. The increase of PTH 1-34-induced Nrf-2 expression was more significant in the nucleus than in the cytosol (p<0.05). PTH 1-34 also inhibited H2O2-induced inducible nitric oxide synthase expression, but increased the expression of heme oxygenase 1/2. The results implicate PTH 1-34, Nrf-2, and IGF-I signaling pathways in the response to oxidative stress. These factors could influence IGF-I regulation of metabolic fate and survival in MSCs.

Differential S-nitrosylation of proteins in Alzheimer's disease

Numerous studies have provided evidence regarding the involvement of protein S-nitrosylation in the progression of Alzheimer's disease (AD) pathology and its implication in the formation and accumulation of misfolded protein aggregates. The identification of S-nitrosylated proteins can be a major step toward the understanding of mechanisms leading to neuronal degeneration. The present study targeted S-nitrosylated proteins in AD hippocampus, substantia nigra and cortex using the following work-flow that combines S-nitrosothiol-specific antibody detection, classical biotin switch method labeled with fluorescence dye followed by electrospray ionization quadrupole time of flight tandem MS (ESI-QTOF MS/MS) identification. Endogenous nitrosocysteines were identified in 45 proteins, mainly involved in metabolism, signaling pathways, apoptosis and redox regulation as assigned by REACTOME and KEGG pathway database analysis. Superoxide dismutase (SOD2) [Mn], fructose-bisphosphate aldolase C (ALDOC) and voltage-dependent anion-selective channel protein 2 (VDAC2) showed differential S-nitrosylation signal, not previously reported in AD regions. Extensive neuronal atrophy with increased protein S-nitrosylation in AD regions is also evident from immunofluorescence studies using S-nitrosocysteine antibody. A number of plausible cysteine modification sites were predicted via Group-based Prediction System-S-nitrosothiols (GPS-SNO) 1.0 while STRING 8.3 analysis revealed functional annotations in the modified proteins. The findings are helpful in characterization of functional abnormalities and may facilitate the understanding of molecular mechanisms and biological function of S-nitrosylation in AD pathology.

Excitotoxicity: bridge to various triggers in neurodegenerative disorders

Glutamate is one of the most prominent neurotransmitter in the body, present in over 50% of nervous tissue and plays an important role in neuronal excitation. This neuronal excitation is short-lived and is followed by depression. Multiple abnormal triggers such as energy deficiency, oxidative stress, mitochondrial dysfunction, calcium overload, etc can lead to aberration in neuronal excitation process. Such an aberration, serves as a common pool or bridge between abnormal triggers and deleterious signaling processes with which central neurons cannot cope up, leading to death. Excitotoxicity is the pathological process by which nerve cells are damaged and killed by excessive stimulation by neurotransmitters such as glutamate and similar substances. Such excitotoxic neuronal death has been implicated in spinal cord injury, stroke, traumatic brain injury, hearing loss and in neurodegenerative diseases of the central nervous system such as stroke, epilepsy, multiple sclerosis, Alzheimer disease, Amyltropic lateral sclerosis, Parkinson's disease, Huntington disease and alcohol withdrawal. This review mainly emphasizes the triggering events which sustain neuronal excitation, role of calcium, mitochondrial dysfunction, ROS, NO, chloride homeostasis and eicosanoids pathways. Further, a brief introduction about the recent research occurring in the treatment of various neurodegenerative diseases, including a summary of the presumed physiologic mechanisms behind the pharmacology of these disorders.

Curcumin protects against hepatic and renal injuries mediated by inducible nitric oxide synthase during selenium-induced toxicity in Wistar rats

The aim of this study is to evaluate the effect of curcumin in protecting against selenium-induced toxicity in liver and kidney of Wistar rats. Light microscopy evaluation of selenium alone administered rats showed liver to be infiltrated with mononuclear cells, vacuolation, necrosis, and pronounced degeneration. Control liver sections showed a regular morphology of parenchymal cells with intact hepatocytes and sinusoids. Kidney from selenium alone administered rats showed vacuolar degeneration changes in the epithelial cells, cellular proliferation with fibrosis, thickening of capillary walls, and glomerular tuft atrophy. Such changes were also observed in rats administered with selenium and curcumin simultaneously and rats administered first with selenium and then curcumin 24 h later. Interestingly, such degenerative changes observed in liver and kidney induced by selenium were not seen in rats that were administered with curcumin first and selenium 24 h later. This clearly suggests the protective nature of curcumin against selenium toxicity. To understand the probable mechanism of action of curcumin, we analyzed inducible nitric oxide synthase (iNOS) expression by immunohistochemistry, and the results showed an increased iNOS expression in selenium-alone induced liver and kidney. Such high iNOS levels were inhibited in liver and kidney of rats pretreated with curcumin and then with selenium 24 h later. Based on the histological results, it can be concluded that curcumin functions as a protective agent against selenium-induced toxicity in liver as well as kidney, and this action is probably by the regulatory role of curcumin on iNOS expression.

Potential therapeutic applications of tetrahydrobiopterin: from inherited hyperphenylalaninemia to mitochondrial diseases

Tetrahydrobiopterin (BH(4)) is an essential enzymatic cofactor in the formation of key neurotransmitters and nitric oxide (NO). It also has a cellular protective role as an antioxidant and scavenger of reactive nitrogen or oxygen species. Inherited hyperphenylalaninemia, which is caused by mutations in converting enzymes responsible for BH(4) synthesis, was the first reported disease implicating BH(4). Oxidative stress can also cause decreased BH(4) levels, leading to uncoupling of BH(4)-nitric oxide synthase (NOS) and diminished NO, further aggravating numerous pathologies. BH(4) deficiency is found in cardiovascular, neurodegenerative, and metabolic diseases and is also involved in aging and mitochondrial dysfunction. BH(4) supplementation successfully prevents the development or progression of these diseases and thus has valuable clinical potential.

Diminution of free radical induced DNA damage by extracts/fractions from bark of Schleichera oleosa (Lour.) Oken

The present study was undertaken to investigate the effect of extracts of Schleichera oleosa (Sapindaceae) for its cytotoxic and hydroxyl radical-scavenging activities. The bark of the tree was used to prepare extracts with different solvents (i.e., hexane, chloroform, ethyl acetate, methanol, and water). The extracts were initially assessed for their in vitro cytotoxicity potential in the sulforhodamine B dye assay against cell lines, such as 502713 (colon), SW-620 (colon), HCT-15 (colon), A-549 (lung), HEP-2 (liver), SK-NS-H (central nervous system), and IMR-32 (neuroblastoma). It was observed that the water extract was effective against all the three colon cancer cell lines, while only methanol and water extracts were effective against A-549 (lung) and HEP-2 (liver), respectively. As DNA damage is one of the hallmarks of cell death, so the extracts were assessed for their ability to scavenge hydroxyl radicals, in the deoxyribose degradation assay (site- and nonsite specific) as well as their protective effect against the hydroxyl radical-induced DNA damage in the plasmid nicking assay, using pBR322. It was observed that all the extracts, except chloroform and hexane, exhibited relatively greater antioxidant activity in the nonsite-specific than in the site-specific assay. Similarly, the extracts were also found to be effective in inhibiting the hydroxyl radical-induced unwinding of supercoiled DNA, which further confirmed the hydroxyl radical-scavenging ability of the extracts in the deoxyribose degradation method.

Anti-cataractogenic effect of curcumin and aminoguanidine against selenium-induced oxidative stress in the eye lens of Wistar rat pups: An in vitro study using isolated lens

The aim of this study was to investigate whether curcumin and aminoguanidine (AG) prevent selenium-induced cataractogenesis in vitro. On postpartum day 8, transparent isolated lens were incubated in 24 well plates containing Dulbecco's Modified Eagle Medium (DMEM). Isolated lens of group I were incubated with DMEM medium alone. Group II: lenses incubated in DMEM containing 100microM sodium selenite; group III: lenses incubated in DMEM containing 100microM sodium selenite and 100microM curcumin; group IV: lenses incubated in DMEM containing 100microM sodium selenite and 200microM curcumin; group V: lenses incubated in DMEM containing 100microM sodium selenite and 100microM AG; group V: lenses incubated in DMEM containing 100microM sodium selenite and 200microM AG. On day 12, cataract development was graded using an inverted microscope and the lenses were analyzed for enzymic as well as non-enzymic antioxidants, lipid peroxidation (LPO), nitric oxide (NO), superoxide anion (O(2)(-)) and hydroxyl radical generation (OH) and inducible nitric oxide synthase (iNOS) activity by Western blotting and RT-PCR. All control lenses in group I were clear (0). In groups II and III, all isolated lenses developed cataract with variation in levels (+++ or ++), whereas isolated lenses from groups IV, V and VI were clear (0). In agreement to this, a decrease in antioxidants and increased free radical generation and also iNOS expression were observed in selenium exposed lenses when compared to other groups. AG (100microM) was found to be more effective in anti-cataractogenic effect than curcumin (200microM). Curcumin and AG suppressed selenium-induced oxidative stress and cataract formation in isolated lens from Wistar rat pups, possibly by inhibiting depletion of enzymic as well as non-enzymic antioxidants, and preventing uncontrolled generation of free radicals and also by inhibiting iNOS expression. Our results implicate a major role for curcumin and AG in preventing cataractogenesis in selenite-exposed lenses, wherein AG was found to be more potent.

Lipid rafts and caveolae and their role in compartmentation of redox signaling

Membrane (lipid) rafts and caveolae, a subset of rafts, are cellular domains that concentrate plasma membrane proteins and lipids involved in the regulation of cell function. In addition to providing signaling platforms for G-protein-coupled receptors and certain tyrosine kinase receptors, rafts/caveolae can influence redox signaling. This review discusses molecular characteristics of and methods to study rafts/caveolae, determinants that contribute to the localization of molecules in these entities, an overview of signaling molecules that show such localization, and the contribution of rafts/caveolae to redox signaling. Of particular note is the evidence that endothelial nitric oxide synthase (eNOS), NADPH oxygenase, and heme oxygenase, along with other less well-studied redox systems, localize in rafts and caveolae. The precise basis for this localization and the contribution of raft/caveolae-localized redox components to physiology and disease are important issues for future studies.

Effects of hyaluronic acid on mitochondrial function and mitochondria-driven apoptosis following oxidative stress in human chondrocytes

Hyaluronic acid is widely used in the treatment of osteoarthritis and exerts significant chondroprotective effects. The exact mechanisms of its chondroprotective action are not yet fully elucidated. Human articular chondrocytes actively produce reactive oxygen and nitrogen species capable of causing cellular dysfunction and death. A growing body of evidence indicates that mitochondrial dysfunction and mitochondrial DNA damage play a causal role in disorders linked to excessive generation of oxygen free radicals. We hypothesized that the chondroprotective effects of hyaluronic acid on oxidatively stressed chondrocytes are due to preservation of mitochondrial function and amelioration of mitochondria-driven apoptosis. When primary human chondrocyte cultures were exposed to reactive oxygen or nitrogen species generators, mitochondrial DNA damage along with mitochondrial dysfunction and mitochondria-driven apoptosis accumulated as a consequence. In addition, cytokine-treated primary human chondrocytes showed increased levels of mitochondrial DNA damage. Pretreatment of chondrocytes with hyaluronic acid caused a decrease of mitochondrial DNA damage, enhanced mitochondrial DNA repair capacity and cell viability, preservation of ATP levels, and amelioration of apoptosis. The results of these studies demonstrate that enhanced chondrocyte survival and improved mitochondrial function under conditions of oxidative injury are probably important therapeutic mechanisms for the actions of hyaluronic acid in osteoarthritis.

Immune modulation and apoptosis induction: Two sides of antitumoural activity of a standardised herbal formulation of Withania somnifera

Deregulated apoptosis and suppressed tumour reactive immunity render tumour cells to grow amok in the host body. Traditionally used botanicals may offer potential anticancer chemo-immunotherapeutic leads. We report in this study a chemically standardised herbal formulation (WSF) of Withania somnifera possessing anticancer and Th1 immune up-regulatory activities. WSF produced cytotoxicity in a panel of human cancer cell lines in vitro. The molecular mechanism of cell cytotoxicity, IC(50) 48h approximately 20mug/ml, was investigated in HL-60, where it induced apoptosis by activating both intrinsic and extrinsic signalling pathways. It induced early generation of reactive nitrogen and oxygen species (RNOS), thus producing oxidative stress mediated mitochondrial membrane potential (MMP) loss leading to the release of cytochrome c, the translocation of Bax to mitochondria and apoptosis-inducing factor to the nuclei. These events paralleled the activation of caspase-9, -3 and PARP cleavage. WSF also activated caspase-8 through enhanced expression of TNF-R1 and DR-4, suggesting also the involvement of extrinsic pathway of apoptosis. WSF at 150mg/kg, i.p., inhibited >50% tumour growth in the mouse tumour models. In tumour-bearing mice, WSF inhibited the expression of pStat-3, with a selective stimulation of Th1 immunity as evidenced by enhanced secretion of IFN-gamma and IL-2. In parallel, it enhanced the proliferation of CD4(+)/CD8(+) and NK cells along with an increased expression of CD40/CD40L/CD80. In addition, WSF also enhanced T cell activation in camptothecin treated tumour-bearing mice. WSF being safe when given orally up to 1500mg/kg to rats for 6 months may be found useful in the management of malignancy by targeting at multiple pathways.

Studies on cytotoxic, hydroxyl radical scavenging and topoisomerase inhibitory activities of extracts of Tabernaemontana divaricata (L.) R.Br. ex Roem. and Schult

In the present investigation, the cytotoxic, hydroxyl radical scavenging and topoisomerase inhibition activities of Tabernaemontana divaricata (Apocynaceae) were evaluated. The extracts from leaves of the plant were prepared with different solvents viz. chloroform, methanol, ethyl acetate and hexane. In, in vitro cytotoxicity assay, with cell lines viz HCT-15 (Colon), HT-29 (Colon), 502713 (Colon), MCF-7 (Breast), PC- 3 (Prostrate), it was observed that the ethyl acetate extract was effective against only one colon cell line (502713) at the lowest dose i.e. 10 micro g/ml, whereas the chloroform extract was effective against all the three colon cancer cell lines, at 30 microg/ ml. In order to evaluate the mechanism of cytotoxicity of these extracts, they were assessed for their ability to scavenge hydroxyl radicals in plasmid nicking assay with pBR322. It was observed that all the extracts effectively inhibited the unwinding of supercoiled DNA except hexane extract, which showed the least effect. Since the expression of topo enzymes is linked with cell proliferation so the extracts were also checked for topo I and topo II inhibitory activities. It was noticed that ethyl acetate extract selectively showed inhibition of topo II in topoisomerase II relaxation assay.

A triterpenediol from Boswellia serrata induces apoptosis through both the intrinsic and extrinsic apoptotic pathways in human leukemia HL-60 cells

A triterpenediol (TPD) comprising of isomeric mixture of 3alpha, 24-dihydroxyurs-12-ene and 3alpha, 24-dihydroxyolean-12-ene from Boswellia serrata induces apoptosis in cancer cells. An attempt was made in this study to investigate the mechanism of cell death by TPD in human leukemia HL-60 cells. It inhibited cell proliferation with IC50 approximately 12 microg/ml and produced apoptosis as measured by various biological end points e.g. increased sub-G0 DNA fraction, DNA ladder formation, enhanced AnnexinV-FITC binding of the cells. Further, initial events involved massive reactive oxygen species (ROS) and nitric oxide (NO) formation, which were significantly inhibited by their respective inhibitors. Persistent high levels of NO and ROS caused Bcl-2 cleavage and translocation of Bax to mitochondria, which lead to loss of mitochondrial membrane potential (Deltapsim) and release of cytochrome c, AIF, Smac/DIABLO to the cytosol. These events were associated with decreased expression of survivin and ICAD with attendant activation of caspases leading to PARP cleavage. Furthermore, TPD up regulated the expression of cell death receptors DR4 and TNF-R1 level, leading to caspase-8 activation. These studies thus demonstrate that TPD produces oxidative stress in cancer cells that triggers self-demise by ROS and NO regulated activation of both the intrinsic and extrinsic signaling cascades.

Inflammation: a way to understanding the evolution of portal hypertension

BACKGROUND

Portal hypertension is a clinical syndrome that manifests as ascites, portosystemic encephalopathy and variceal hemorrhage, and these alterations often lead to death.

HYPOTHESIS

Splanchnic and/or systemic responses to portal hypertension could have pathophysiological mechanisms similar to those involved in the post-traumatic inflammatory response.The splanchnic and systemic impairments produced throughout the evolution of experimental prehepatic portal hypertension could be considered to have an inflammatory origin. In portal vein ligated rats, portal hypertensive enteropathy, hepatic steatosis and portal hypertensive encephalopathy show phenotypes during their development that can be considered inflammatory, such as: ischemia-reperfusion (vasodilatory response), infiltration by inflammatory cells (mast cells) and bacteria (intestinal translocation of endotoxins and bacteria) and lastly, angiogenesis. Similar inflammatory phenotypes, worsened by chronic liver disease (with anti-oxidant and anti-enzymatic ability reduction) characterize the evolution of portal hypertension and its complications (hepatorenal syndrome, ascites and esophageal variceal hemorrhage) in humans.

CONCLUSION

Low-grade inflammation, related to prehepatic portal hypertension, switches to high-grade inflammation with the development of severe and life-threatening complications when associated with chronic liver disease.

Parthenolide induces significant apoptosis and production of reactive oxygen species in high-risk pre-B leukemia cells

We investigated whether parthenolide, the principal bioactive component of the herb feverfew (Tanacetum parthenium) induced apoptosis in pre-B acute lymphoblastic leukemia (ALL) lines, including cells carrying the t(4;11)(q21;q23) chromosomal translocation. Parthenolide induced rapid apoptotic cell death distinguished by loss of nuclear DNA, externalization of cell membrane phosphatidylserine, and depolarization of mitochondrial membranes at concentrations ranging from 5 to 100 microM. Using reactive oxygen species (ROS)-specific dyes, an increase in nitric oxide and superoxide anion was detected in the cells by 4 h after exposure to parthenolide. Parthenolide-induced elevation of hypochlorite anion was observed only in the two t(4;11) lines. These data suggest parthenolide may have potential as a potent and novel therapeutic agent against pre-B ALLs.

Nitric Oxide Synthase 3-Mediated Neurodegeneration After Intracerebral Gene Delivery

In Alzheimer disease (AD), increased nitric oxide synthase 3 (NOS3) expression correlates with apoptosis in cortical neurons and colocalizes with amyloid precursor protein (APP)-amyloid beta (Abeta) deposits in the brain. In the present study we examined the potential role of NOS3 in relation to AD-type neurodegeneration using an in vivo model of gene delivery. Long Evans rat pups were given a single intracerebral injection of recombinant plasmid DNA containing the human NOS3 cDNA (p-hNOS3) or the luciferase (p-Luc) gene as a negative control, and complexed with polyamine reagent. Overexpression of NOS3 in the brain increased the levels of APP, APP-Abeta, p53, Tau, glial fibrillary acidic protein, and peroxisome proliferator activated receptors (PPAR) delta and gamma and decreased the levels of Hu (neuronal marker) mRNA, phosphorylated glycogen synthase kinase 3beta, ATP synthase, and choline acetyltransferase expression as demonstrated by real-time quantitative reverse-transcribed polymerase chain reaction, Western blot analysis, or immunohistochemical staining. These effects of NOS3 overexpression were accompanied by increased single-stranded DNA immunoreactivity, reflecting DNA damage. The results suggest that increased cerebral expression of NOS3 causes several molecular abnormalities related to AD-type neurodegeneration, including oxidative stress, mitochondrial dysfunction, and impaired acetylcholine homeostasis. The coexisting increases in PPAR-delta and -gamma expression suggest that the adverse effects of NOS3 overexpression may be abated by PPAR agonist treatment.

Induction of apoptosis by the Lactuca indica L. in human leukemia cell line and its active components

Lactuca indica L. (Compositae family) is used as a folk medicine in anti-inflammatory, antibacterial, antidiabetic, and other medications in Asia. The objectives of this study were to evaluate the antiproliferative effect of ethanol extracts of Lactuca indica L. (EEL) on human leukemic HL-60 cell lines and its active components. The results showed that EEL exhibited strong cytotoxic effects against HL-60 cells; the IC50 value was 313 microg/mL. Flow cytometric analysis of the externalization of phosphatidylserine (PS) using the annexin V/PI method on EEL-treated HL-60 cells showed a concentration-dependent increase of apoptosis. Moreover, EEL could induce typical DNA fragmentation in a concentration- and time-dependent manner as determined by electrophoresis and TUNEL assays. The treatment of HL-60 cells with EEL induced significant accumulation of cells in the G0/G1 phase, indicating that EEL is a cell-cycle-dependent anticancer agent. Our results also indicate that EEL-induced apoptosis in HL-60 cells is associated with the loss of mitochondrial membrane potential (delta psi m). EEL contains 5% phenolic compounds, such as quercetin, caffeic acid, rutin, and chlorogenic acid. Among the four active phenolic compounds, quercetin was found to be the most effective in inhibition against cell viability and in alteration of mitochondrial function. Our results suggest that the induction of apoptosis by EEL might offer a pivotal mechanism for its chemopreventive action.

Tamoxifen induces oxidative stress and mitochondrial apoptosis via stimulating mitochondrial nitric oxide synthase

Tamoxifen is an anticancer drug that induces oxidative stress and apoptosis via mitochondria-dependent and nitric oxide (NO)-dependent pathways. The present report shows that tamoxifen increases intramitochondrial ionized Ca(2+) concentration and stimulates mitochondrial NO synthase (mtNOS) activity in the mitochondria from rat liver and human breast cancer MCF-7 cells. By stimulating mtNOS, tamoxifen hampers mitochondrial respiration, releases cytochrome c, elevates mitochondrial lipid peroxidation, increases protein tyrosine nitration of certain mitochondrial proteins, decreases the catalytic activity of succinyl-CoA:3-oxoacid CoA-transferase, and induces aggregation of mitochondria. The present report suggests a critical role for mtNOS in apoptosis induced by tamoxifen.

Diabetic neuropathy and oxidative stress

This review will focus on the impact of hyperglycemia-induced oxidative stress in the development of diabetes-related neural dysfunction. Oxidative stress occurs when the balance between the production of reactive oxygen species (ROS) and the ability of cells or tissues to detoxify the free radicals produced during metabolic activity is tilted in the favor of the former. Although hyperglycemia plays a key role in inducing oxidative stress in the diabetic nerve, the contribution of other factors, such as endoneurial hypoxia, transition metal imbalances, and hyperlipidemia have been also suggested. The possible sources for the overproduction of ROS in diabetes are widespread and include enzymatic pathways, auto-oxidation of glucose, and mitochondrial superoxide production. Increase in oxidative stress has clearly been shown to contribute to the pathology of neural and vascular dysfunction in diabetes. Potential therapies for preventing increased oxidative stress in diabetic nerve dysfunction will be discussed.

Complex-1 activity and 18F-DOPA uptake in genetically engineered mouse model of Parkinson's disease and the neuroprotective role of coenzyme Q10

Regional distribution of coenzyme Q10 and mitochondrial complex-1 activity were estimated in the brains of control-(C57BL/6), metallothionein knock out-, metallothionein transgenic-, and homozygous weaver mutant mice; and human dopaminergic (SK-N-SH) cells with a primary objective to determine the neuroprotective potential of coenzyme Q10 in Parkinson's disease. Complex-1 activity as well as coenzyme Q10 were significantly higher in the cerebral cortex as compared to the striatum in all the genotypes examined. Complex-1 activity and coenzyme Q10 were significantly reduced in weaver mutant mice and metallothionein knock out mice, but were significantly increased in metallothionein transgenic mice. The reduced complex-1 activity and 18F-DOPA uptake occurred concomitantly with negligible differences in the coenzyme Q10 between in the cerebral cortex and striatum of weaver mutant mice. Administration of coenzyme Q10 increased complex-1 activity and partially improved motoric performance in weaver mutant mice. Direct exposure of rotenone also reduced coenzyme Q10, complex-1 activity, and mitochondrial membrane potential in SK-N-SH cells. Rotenone-induced down-regulation of complex-1 activity was attenuated by coenzyme Q10 treatment, suggesting that complex-1 may be down regulated due to depletion of coenzyme Q10 in the brain. Therefore, metallothionein-induced coenzyme Q10 synthesis may provide neuroprotection by augmenting mitochondrial complex-1 activity in Parkinson's disease.

Nitric oxide synthase expression and nitric oxide toxicity in oligodendrocytes

Oligodendrocytes (OLG) have more complex interactions with nitric oxide (NO) than initially suspected. Historically, OLG were seen only as targets of high NO levels released from other cells. Expression of nitric oxide synthase type II (NOS-2) in primary cultures of OLGs stimulated by cytokines led to controversy due to the presence of small numbers of microglia, cells also inducible for NOS-2 expression. The present review summarizes the findings that immature OLG express NOS-2, but that they do not in their most mature stage in culture as membrane sheet-bearing cells. This raises questions about the regulation of NOS-2 expression in OLG. Additionally, novel data are presented on NOS-3 expression in cultured OLG. If confirmed in vivo, this finding suggests that constitutive NOS-3 expression may play a key role in OLG injury due to its activation by calcium, in interaction with pathways mediating glutamate toxicity. The authors discuss in vivo NO levels to place in vitro findings in context, and compare OLG sensitivity to NO with that of other brain cells. Lastly, the multiple interactions of NO are considered with regard to glutamate cytotoxicity, the antioxidant glutathione, mitochondrial function, and myelin architecture.

Role of nitric oxide-induced mtDNA damage in mitochondrial dysfunction and apoptosis

An increasing body of evidence suggests that nitric oxide (NO) can be cytotoxic and induce apoptosis. NO can also be genotoxic and cause DNA damage and mutations. It has been shown that NO damages mitochondrial DNA (mtDNA) to a greater extent than nuclear DNA. Previously, we reported that conditional targeting of the DNA repair protein hOGG1 into mitochondria using a mitochondria targeting sequence (MTS) augmented mtDNA repair of oxidative damage and enhanced cellular survival. To determine whether enhanced repair resulting from augmented expression of hOGG1 could also protect against the deleterious effects of NO, we used HeLa TetOff/MTS-OGG1-transfected cells to conditionally express hOGG1 in mitochondria. The effects of additional hOGG1 expression on repair of NO-induced mtDNA damage and cell survival were evaluated. These cells, along with vector transfectants, in either the presence or absence of doxycycline (Dox), were exposed to NO produced by the rapid decomposition of 1-propanamine, 3-(2-hydroxy-2-nitroso-1-propylhydrazino) (PAPA NONOate). Functional studies revealed that cells expressing recombinant hOGG1 were more proficient at repairing NO-induced mtDNA damage, which led to increased cellular survival following NO exposure. Moreover, the results described here show that conditional expression of hOGG1 in mitochondria decreases NO-induced inhibition of ATP production and protects cells from NO-induced apoptosis.

A novel lignan composition from Cedrus deodara induces apoptosis and early nitric oxide generation in human leukemia Molt-4 and HL-60 cells

AP9-cd, a standardized lignan composition from Cedrus deodara consisting of (-)-wikstromal, (-)-matairesinol, and dibenzyl butyrolactol, showed cytotoxicity in several human cancer cell lines reported earlier. An attempt was made in this study to investigate the mechanism of cell death in human leukemia Molt-4 and HL-60 cells. It inhibited Molt-4 cell proliferation with 48-h IC(50) of approximately 15 microg/ml, increased sub-G0 cell fraction with no mitotic block, produced apoptotic bodies and induced DNA ladder formation. Flow cytometric analysis of annexinV-FITC/PI-stained cells showed time-related increase in apoptosis and post-apoptotic necrosis. All these biological end-points indicated cell death by apoptosis. Further, initial events involved massive nitric oxide (NO) formation within 4 h with subsequent late appearance of peroxides in cells; measured by flow cytometry using specific fluorescent probes. Persistently high levels of NO and peroxide appeared to decrease mitochondrial membrane potential (Psi(mt)) which was recovered by cyclosporin A in Molt-4 cells. AP9-cd caused 2-fold activation of caspase-3 in Molt-4 and 5-fold activation in HL-60 cells. Also caspases-8 and -9 were activated in HL-60 cells. Ascorbate suppressed the enhanced caspases activities indicating a pro-oxidant effect of AP9-cd. Further, caspase-3 activation correlated with NO generation that was partially impaired by nitric oxide synthase (NOS) inhibitors and ascorbate suggesting a role of pro-oxidant species in caspase-3 activation. AP9-cd produced no cytotoxicity in primary rat hepatocyte culture at the concentrations used. The studies indicated that AP9-cd mediated early NO formation leads to caspases activation, peroxide generation, and mitochondrial depolarization which may be responsible for mitochondrial-dependent and -independent apoptotic pathways involved in the killing of leukemia cells by AP9-cd.

Effects of nitric oxide donors on cybrids harbouring the mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes (MELAS) A3243G mitochondrial DNA mutation

Reactive nitrogen and oxygen species (O2*-, H2O2, NO* and ONOO-) have been strongly implicated in the pathophysiology of neurodegenerative and mitochondrial diseases. In the present study, we examined the effects of nitrosative and/or nitrative stress generated by DETA-NO {(Z)-1-[2-aminoethyl-N-(2-ammonioethyl)amino]diazen-1-ium-1,2-diolate}, SIN-1 (3-morpholinosydnonimine hydrochloride) and SNP (sodium nitroprusside) on U87MG glioblastoma cybrids carrying wt (wild-type) and mutant [A3243G (Ala3243-->Gly)] mtDNA (mitochondrial genome) from a patient suffering from MELAS (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes). The mutant cybrids had reduced activity of cytochrome c oxidase, significantly lower ATP level and decreased mitochondrial membrane potential. However, endogenous levels of reactive oxygen species were very similar in all cybrids regardless of whether they carried the mtDNA defects or not. Furthermore, the cybrids were insensitive to the nitrosative and/or nitrative stress produced by either DETA-NO or SIN-1 alone. Cytotoxicity, however, was observed in response to SNP treatment and a combination of SIN-1 and glucose-deprivation. The mutant cybrids were significantly more sensitive to these insults compared with the wt controls. Ultrastructural examination of dying cells revealed several characteristic features of autophagic cell death. We concluded that nitrosative and/or nitrative stress alone were insufficient to trigger cytotoxicity in these cells, but cell death was observed with a combination of metabolic and nitrative stress. The vulnerability of the cybrids to these types of injury correlated with the cellular energy status, which were compromised by the MELAS mutation.

Determination of mitochondrial nitric oxide synthase activity

The main biological targets of nitric oxide (NO) are hemoproteins, thiols, and superoxide anion (O2-). Mitochondria possess several hemoproteins, thiol-containing molecules, and they are one of the prime cellular producers of O2-. Thus, these organelles remain one of the main biological targets for NO. Reports on the existence of a Ca2+-sensitive mitochondrial NO synthase (mtNOS) have opened a new window in the field of NO and mitochondria research (Ghafourifar and Richter, 1997). mtNOS-derived NO reversibly decreases the activity of the mitochondrial hemoprotein, cytochrome c oxidase. This function of mtNOS regulates mitochondrial respiration and transmembrane potential (Deltapsi). The NO generated by mtNOS reacts with mitochondrial thiol-containing proteins including caspase-3. Because the S-nitrosated caspase-3 remains apoptotically silent as long as it is located within the mitochondria, this function of mtNOS portrays an anti-apoptotic property for mtNOS. mtNOS-derived NO also reacts with O2- to generate peroxynitrite. mtNOS-derived peroxynitrite induces oxidative stress and releases cytochrome c from the mitochondria, which represents a pro-apoptotic role for mtNOS. How mitochondria harmonize the reversible functions of mtNOS for mitochondrial respiration, its anti-apoptotic actions via S-nitrosation of caspase-3, versus the pro-apoptotic properties of peroxynitrite remains to be fully understood. However, intramitochondrial ionized Ca2+ concentration ([Ca2+]m) and the status of mitochondrial reducing defense barriers seem to play crucial roles in orchestrating the functions of mtNOS for mitochondria and cells (Ghafourifar and Cadenas, 2005).

Tumor necrosis factor-alpha, interleukin-1beta and nitric oxide: induction of liver megamitochondria in prehepatic portal hypertensive rats

It has been shown that portal hypertension in the rat causes microvesicular hepatocytic fatty infiltration. Formation of megamitochondria (MG) is one of the most prominent alterations in steatosis. Because nitric oxide (NO), tumor necrosis factor-alpha (TNFalpha), and interleukin-1beta (IL-1beta) impair mitochondrial function, these mediators have been studied in prehepatic portal hypertensive rats to verify their coexistence with MG and therefore with steatosis. Male Wistar rats were divided into two groups: a control group (n = 7) and a group with partial portal vein hgation (n = 19) at 6 weeks of evolution. TNFalpha and IL-1beta were quantified in liver by enzyme-linked immunosorbent assay, and NO was measured in the portal vein, suprahepatic inferior vena cava, and infrahepatic inferior vena cava by the Griess reaction. In portal hypertensive rats, the serum concentration of NO of hepatic origin increases (132.10 +/- 34.72 vs. 52.44 +/- 11.32 nmol/ml; p < 0.001), as do TNFalpha (2.02 +/- 0.20 vs. 1.12 +/- 0.43 micromol/mg protein) and IL-1beta (18.95 +/- 2.59 vs. 5.48 +/- 1.70 micromol/mg protein) (p = 0.005) in the liver. The most frequent hepatic histologic findings are the presence of MG (p < 0.001), steatosis, and hyperplasia. An increase in hepatic release of NO, TNFalpha and IL-1beta with MG formation is produced in rats with portal hypertension. Therefore these proinflammatory mediators and this morphologic mitochondrial alteration could both be involved in the etiopathogenesis of steatosis.

Functional characterization of brain mitochondrial nitric oxide synthase during hypertension and aging

Nitric oxide (NO*) plays an important role in various physiological processes. The aim of the present study was to investigate if brain mitochondrial nitric oxide synthase (mtNOS) is active and functional during hypertension. L-citrulline production, an indicator of nitric oxide synthesis, was concentration-dependent on L-arginine in all strains and all ages tested, and was inhibited by 7-Nitroindazole (7-NI). Brain mitochondria of 1 month-old (prehypertensive) spontaneously hypertensive rats (SHR) exhibited a significantly (p < 0.05) low basal L-citrulline content as compared to age-matched Wistar (W) and Wistar-Kyoto (WKY) rats. L-citrulline synthesis in SHR rats showed a significant (p < 0.01) low response to L-arginine in 3 and 7 months-old rats. Respiratory rates in states 3 and 4 increased with low L-arginine concentration in all strains and all ages. The results suggest that in rat brain mitochondria, L-citrulline synthesis is constant once age-related hypertension is installed and NO* does not regulate oxidative phosphorylation.

Nitric oxide is synthesized in acute leukemia cells after exposure to phenolic antioxidants and initially protects against mitochondrial membrane depolarization

We investigated the early events involved in loss of mitochondrial membrane potential (DeltaPsi(mt)) leading to apoptosis in cells derived from patients with acute lymphocytic leukemia after exposure to phenolic antioxidants. Using the nitric oxide binding dye diaminofluorescein-FM diacetate, we found that intracellular nitric oxide (NO) levels increased significantly within 4h after exposure to the antioxidants curcumin, carnosol, and quercetin. Inhibition of nitric oxide synthetase (NOS) activity with mercaptoethylguanidine increased the percentage of leukemia cells with depolarized mitochondria membranes after antioxidant treatment. These data suggest that NO production in the leukemia-derived cells may be a protective response to maintain DeltaPsi(mt) after antioxidant exposure and inhibition of NOS increases the disruption of mitochondrial homeostasis induced by the antioxidants.

Oxidative stress in the pathogenesis of diabetic neuropathy

Oxidative stress results from a cell or tissue failing to detoxify the free radicals that are produced during metabolic activity. Diabetes is characterized by chronic hyperglycemia that produces dysregulation of cellular metabolism. This review explores the concept that diabetes overloads glucose metabolic pathways, resulting in excess free radical production and oxidative stress. Evidence is presented to support the idea that both chronic and acute hyperglycemia cause oxidative stress in the peripheral nervous system that can promote the development of diabetic neuropathy. Proteins that are damaged by oxidative stress have decreased biological activity leading to loss of energy metabolism, cell signaling, transport, and, ultimately, to cell death. Examination of the data from animal and cell culture models of diabetes, as well as clinical trials of antioxidants, strongly implicates hyperglycemia-induced oxidative stress in diabetic neuropathy. We conclude that striving for superior antioxidative therapies remains essential for the prevention of neuropathy in diabetic patients.

Effect of inhibiting nitric oxide production on mouse preimplantation embryo development and metabolism

Nitric oxide (NO) is a free radical that functions as a cell signaling molecule but at high concentrations can be toxic. It is formed from arginine, which is consumed by the mouse blastocyst, but its effect on early embryo development has been little studied. In this study, the role of NO in mouse preimplantation development has been examined in terms of developmental rate and oxidative metabolism. Zygotes were cultured in one of four media; potassium simplex optimization medium (KSOM), KSOM with amino acids (KSOMaa), KSOM without glutamine (KSOM-glut), or KSOM with 0.5 mM arginine (KSOMarg) +/- l-NAME (a specific inhibitor of NO production). End points were Day 4 blastocyst rates, cell counts determined using bisbenzimide and oxygen consumption. In KSOM and KSOM-glut, the blastocyst rate was decreased by 1 mM l-NAME from 50.2% +/- 3.1% and 37.4% +/- 4.5% to 6% +/- 3% and 0%, respectively. In KSOMaa, cavitation rates were unaltered but the blastocysts contained fewer cells (P < 0.001). Blastocysts cultured in KSOM and KSOM-glut consumed significantly more oxygen than those cultured in KSOMaa (P < 0.001 and P < 0.05, respectively). However, the addition of 0.1 mM or 1 mM l-NAME to KSOMaa significantly increased the amount of oxygen consumed (P < 0.05 and P < 0.001, respectively). The data suggest a physiological role for NO in mouse preimplantation metabolism and development. One possibility is that NO may limit oxygen consumption at the blastocyst stage at the level of mitochondrial cytochrome c oxidase.

Docking of endothelial nitric oxide synthase (eNOS) to the mitochondrial outer membrane: a pentabasic amino acid sequence in the autoinhibitory domain of eNOS targets a proteinase K-cleavable peptide on the cytoplasmic face of mitochondria

Despite growing evidence for a mitochondrial localization of nitric oxide (NO) synthase and a broadening spectrum of NO actions on mitochondrial respiration and apoptosis, the basis for interaction between the enzyme and the organelle remain obscure. Here we investigated mitochondrial localization of endothelial nitric oxide synthase (eNOS) in human umbilical vein endothelial cells and human embryonic kidney cells transfected or infected with eNOS expression vectors. Copurification of eNOS with mitochondria was observed in both human umbilical vein endothelial cells and eNOS-expressing human embryonic kidney cells. Immunodetectable eNOS was cleaved from mitochondria by proteinase K treatment, suggesting eNOS association with the outer mitochondrial membrane. Localization of eNOS to a proteinase K-cleavable site on the cytoplasmic face of the outer membrane was confirmed by immunogold labeling of non-permeabilized mitochondria. Markers for mitochondrial subfractions ruled out the possibility of eNOS association with an intramitochondrial site or inverted mitochondrial particles. Denaturation of eNOS did not attenuate association with mitochondria. Mutant eNOS lacking a pentabasic amino acid sequence within the autoinhibitory domain (residues 628-632 of the bovine eNOS) showed dramatically reduced binding to the mitochondrial but not to the plasma membrane, which was associated with increased oxygen consumption. Collectively, these findings argue in favor of eNOS localization to the outer mitochondrial membrane in endothelial cells and identify elements of a novel anchoring mechanism.

Expression of nitric oxide, peroxynitrite, and apoptosis in loose total hip replacements

Nitric oxide (NO) is an effector molecule associated with inflammation, immune function, bone metabolism, and the induction of apoptosis. This study examined the role of NO, peroxynitrite (ONOO(-)), and apoptosis in cases of revision total hip replacements (THRs). We hypothesized that apoptosis and excess production of NO contribute to the inflammatory reaction to orthopedic biomaterial wear debris that is associated with loosening and osteolysis. Periprosthetic membranous specimens were collected from revised cemented acetabular components with simple loosening and ballooning osteolysis. Synovial samples from patients undergoing primary THR were used as controls. The presence of macrophages (CD68(+)) and levels of inducible nitric oxide synthase (INOS), endothelial nitric oxide synthase (EcNOS), ONOO(-) (Nitro, assayed by the amount of nitrated tyrosine residues), and apoptosis (TUNEL staining) were examined using immunohistochemistry. Increased expression for INOS, EcNOS, and ONOO(-) in both the loose/osteolytic and the loose/non-osteolytic groups was observed when compared to the synovium group. There were no significant differences between the loose/osteolytic group and loose/non-osteolytic group for these biologic markers. TUNEL staining showed a significant increase in apoptosis in the loose/osteolytic group compared to the loose/non-osteolytic group and synovial tissues. These findings suggest that NO and NO-derived molecules, such as ONOO(-), may be involved in sustaining the foreign-body reaction to wear debris. NO and ONOO(-) may prove to be useful markers of prosthetic loosening whereas apoptosis may be a marker distinguishing ballooning from simple osteolysis.