Molecular mechanism of diclofenac-induced apoptosis of promyelocytic leukemia: dependency on reactive oxygen species, Akt, Bid, cytochrome and caspase pathway

Manganese(II) complexes with the non-steroidal anti-inflammatory drug tolfenamic acid: structure and biological perspectives

Manganese(II) complexes with the non-steroidal anti-inflammatory drug tolfenamic acid (Htolf) with the nitrogen-donor heterocyclic ligands 1,10-phenanthroline (phen), pyridine (py), or 2,2'-bipyridylamine (bipyam) and/or the oxygen-donor ligands H2O or N,N-dimethylformamide (DMF) have been synthesized and characterized. The crystal structures of complexes [Mn(tolf-O)(tolf-O,O')(phen)(H2O)], [Mn2(μ2-tolf-O,O')2(tolf-O,O')2(bipyam)2], [Mn2(μ2-H2O)(μ2-tolf-O,O')2(tolf-O)2(py)4]·1.5MeOH·py, and [Mn(μ2-tolf-O,O')2(DMF)2]n have been determined by X-ray crystallography. The interaction of the complexes with serum albumin proteins was investigated, and relative high binding constant values were calculated. The ability of the compounds to scavenge 1,1-diphenyl-picrylhydrazyl, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid), and hydroxyl radicals was evaluated, and [Mn(tolf)2(phen)(H2O)] was the most active scavenger among the compounds. The compounds have also exhibited noteworthy in vitro inhibitory activity against soybean lipoxygenase. UV titration studies of the interaction of the complexes with calf-thymus (CT) DNA have proved the binding to CT DNA with [Mn(μ2-tolf)2(DMF)2]n exhibiting the highest DNA-binding constant (Kb = 5.21 (±0.35) × 10(5) M(-1)). The complexes bind to CT DNA probably via intercalation as suggested by DNA-viscosity measurements and competitive studies with ethidium bromide (EB), which revealed the ability of the complexes to displace the DNA-bound EB.

Antioxidant capacity and DNA-interaction studies of zinc complexes with a non-steroidal anti-inflammatory drug, mefenamic acid

Zinc(II) complexes of a non-steroidal anti-inflammatory drug, mefenamic acid(=Hmef) in the absence or presence of the nitrogen donor heterocyclic ligands 2,2'-bipyridine(=bipy), 2,2'-bipyridylamine(=bipyam), 2,2'-dipyridylketone oxime(=Hpko) or 1,10-phenanthroline(=phen) have been synthesized and characterized. The crystal structures of [Zn(mef-O,O')2(bipy)], 2, [Zn(mef-O)2(Hpko-N,N')2]·EtOH, 4 and [Zn(mef-O)(mef-O,O')(phen)(H2O)], 5, have been determined by X-ray crystallography showing distinct binding modes of mefenamato carboxylato group, bidentate in 2, monodentate in 4 or both in 5. Interaction studies of the complexes with calf-thymus DNA (CT DNA) have shown that complexes can bind to CT DNA with [Zn(mef-O)2(Hpko)2] exhibiting the highest binding constant to CT DNA (Kb = 1.93(±0.04) × 10(7) M(-1)). The complexes can bind to CT DNA via intercalation as concluded by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have shown that the complexes can displace the DNA-bound EB. The complexes exhibit good binding affinity to serum albumin proteins with [Zn(mef-O)2(H2O)4], 1 exhibiting the highest quenching ability (kq = 1.46 × 10(15) M(-1) s(-1) for human and 5.55 × 10(15) M(-1) s(-1) for bovine serum albumin). All compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase. The scavenging activity is low to moderate against 1,1-diphenyl-picrylhydrazyl (DPPH) radicals and high against hydroxyl and 2,2'-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS(+·)) radicals, with [Zn(mef-O)2(H2O)4], 1 (ABTS%, 0.1 mM: 94.75(±1.06)%; (·)OH%, 0.1mM: 96.69(±0.27)%; LOX: IC50 = 27.34(±0.90) μM) exhibiting the highest scavenging activity of the ABTS radical cation among the complexes. Additionally, the complexes exhibit higher scavenging and LOX inhibitory activity than free mefenamic acid (ABTS%, 0.1 mM: 66.32(±0.38)%; (·)OH%, 0.1 mM: 92.51(±0.44)%; LOX: IC50 = 48.52(±0.88) μM).

Role of apoptosis in mediating diclofenac-induced teratogenesis

Diclofenac (DCF) is among the most commonly used nonsteroidal anti-inflammatory drugs worldwide for the treatment of various conditions in postpubertal women. However, very limited information is available regarding its safety during pregnancy and teratogenecity. The present study was designed to elucidate the effects of DCF on the developing rat embryos during the major organogenesis period and investigate the critical role of apoptosis in bringing about these congenital anomalies. Embryos were exposed in vitro to various concentrations of DCF, that is, 0, 3.75, 7.5 and 15 µg/ml for 24 h, respectively, and examined for the growth and differentiation at the end of the culture period for the presence of any specific malformations. Growth and developmental parameters such as weight of embryos, crown–rump length and number of somites were found to be lower in the embryos exposed to high concentrations of DCF (7.5 and 15.0 μg/ml) when compared with the untreated control. However, no significant difference in growth parameters was found between embryos exposed to 3.75 µg/ml and the control group. In parallel to this, flow cytometric analysis and DNA quantitation of cultured rat embryos were performed to verify the involvement of apoptosis in mediating DCF-induced teratogenesis. A concentration-dependent increase in apoptosis in embryos suggests a possible engagement of apoptosis in the role of DCF as a teratogenic agent. A detailed analysis of the actual effect of DCF on cellular apoptotic machinery necessitates further evaluation.

Copper(II) interacting with the non-steroidal antiinflammatory drug flufenamic acid: structure, antioxidant activity and binding to DNA and albumins

Copper(II) complexes with the non-steroidal antiinflammatory drug flufenamic acid (Hfluf) in the presence of N,N-dimethylformamide (DMF) or nitrogen donor heterocyclic ligands (2,2'-bipyridylamine (bipyam), 1,10-phenanthroline (phen), 2,2'-bipyridine (bipy) or pyridine (py)) have been synthesized and characterized. The crystal structures of [Cu2(fluf)4(DMF)2], 1, and [Cu(fluf)(bipyam)Cl], 2, have been determined by X-ray crystallography. Density functional theory (DFT) (CAM-B3LYP/LANL2DZ/6-31G**) was employed to determine the structure of complex 2 and its analogues (complexes [Cu(fluf)(phen)Cl], 3, [Cu(fluf)(bipy)Cl], 4 and [Cu(fluf)2(py)2], 5). Time-dependent DFT calculations of doublet-doublet transitions show that the lowest-energy band in the absorption spectrum of 2-5 has a mixed d-d/LMCT character. UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA with [Cu(fluf)(bipy)Cl] exhibiting the highest binding constant to CT DNA. The complexes can bind to CT DNA via intercalation as concluded by studying the cyclic voltammograms of the complexes in the presence of CT DNA solution and by DNA solution viscosity measurements. Competitive studies with ethidium bromide (EB) have shown that the complexes can displace the DNA-bound EB suggesting strong competition with EB. Flufenamic acid and its Cu(II) complexes exhibit good binding affinity to human or bovine serum albumin protein with high binding constant values. All compounds have been tested for their antioxidant and free radical scavenging activity as well as for their in vitro inhibitory activity against soybean lipoxygenase showing significant activity with [Cu(fluf)(phen)Cl] being the most active.

Oxidative stress and lipid peroxidation products in cancer progression and therapy

The generation of reactive oxygen species (ROS) and an altered redox status are common biochemical aspects in cancer cells. ROS can react with the polyunsaturated fatty acids of lipid membranes and induce lipid peroxidation. The end products of lipid peroxidation, 4-hydroxynonenal (HNE), have been considered to be a second messenger of oxidative stress. Beyond ROS involvement in carcinogenesis, increased ROS level can inhibit tumor cell growth. Indeed, in tumors in advanced stages, a further increase of oxidative stress, such as that occurs when using several anticancer drugs and radiation therapy, can overcome the antioxidant defenses of cancer cells and drive them to apoptosis. High concentrations of HNE can also induce apoptosis in cancer cells. However, some cells escape the apoptosis induced by chemical or radiation therapy through the adaptation to intrinsic oxidative stress which confers drug resistance. This paper is focused on recent advances in the studies of the relation between oxidative stress, lipid peroxidation products, and cancer progression with particular attention to the pro-oxidant anticancer agents and the drug-resistant mechanisms, which could be modulated to obtain a better response to cancer therapy.

Diclofenac inhibits lactate formation and efficiently counteracts local immune suppression in a murine glioma model

Lactate formation in highly proliferative tumors such as malignant gliomas is associated with poor survival and contributes to the suppression of local immunity. Here, we report that diclofenac used at nontoxic concentrations significantly decreased lactate production in murine glioma cells and inhibited the expression of lactate dehydrogenase-A in vitro. Lactate reduction was accompanied by a dose-dependent inhibition of cell growth and a cell cycle arrest at the G2/M checkpoint. In the presence of diclofenac, murine bone marrow-derived dendritic cells (DCs) showed enhanced IL-12, but decreased IL-10 secretion on Toll-like receptor stimulation with R848 that correlated with reduced lactate levels in the glioma cell coculture and a blockade of signal transducers and activators of transcription 3 phosphorylation. In vivo, diclofenac treatment diminished intratumoral lactate levels and resulted in a significant delay of glioma growth. Ex vivo analyses revealed that tumor-infiltrating DCs regained their capacity to produce IL-12 on R848 stimulation. Moreover, diclofenac reduced the number of tumor-infiltrating regulatory T cells and impaired the upregulation of the Treg activation marker CD25. Nevertheless, a single intratumoral injection of R848 combined with diclofenac failed to induce an additional survival advantage in glioma-bearing mice. Further analyses illustrated that the presence of diclofenac during T-cell activation compromised INF-γ production and T-cell proliferation, indicating that immunotherapeutic approaches have to be carefully timed when combined with diclofenac. In summary, diclofenac appears as an attractive agent for targeting lactate production and counteracting local immune suppression in malignant gliomas.

Resveratrol suppresses constitutive activation of AKT via generation of ROS and induces apoptosis in diffuse large B cell lymphoma cell lines

Background

We have recently shown that deregulation PI3-kinase/AKT survival pathway plays an important role in pathogenesis of diffuse large B cell lymphoma (DLBCL). In an attempt to identify newer therapeutic agents, we investigated the role of Resveratrol (trans-3,4′, 5-trihydroxystilbene), a naturally occurring polyphenolic compound on a panel of diffuse large B-cell lymphoma (DLBCL) cells in causing inhibition of cell viability and inducing apoptosis.

Methodology/Principal Findings

We investigated the action of Resveratrol on DLBCL cells and found that Resveratrol inhibited cell viability and induced apoptosis by inhibition of constitutively activated AKT and its downstream targets via generation of reactive oxygen species (ROS). Simultaneously, Resveratrol treatment of DLBCL cell lines also caused ROS dependent upregulation of DR5; and interestingly, co-treatment of DLBCL with sub-toxic doses of TRAIL and Resveratrol synergistically induced apoptosis via utilizing DR5, on the other hand, gene silencing of DR5 abolished this effect.

Conclusion/Significance

Altogether, these data suggest that Resveratrol acts as a suppressor of AKT/PKB pathway leading to apoptosis via generation of ROS and at the same time primes DLBCL cells via up-regulation of DR5 to TRAIL-mediated apoptosis. These data raise the possibility that Resveratrol may have a future therapeutic role in DLBCL and possibly other malignancies with constitutive activation of the AKT/PKB pathway.

Induction of apoptosis by γ-tocotrienol in human cancer cell lines and leukemic blasts from patients: dependency on Bid, cytochrome c, and caspase pathway

Tocotrienols (Toc3) have been suggested to possess anticancer effects besides antioxidant and antiinflammatory effects. Previous studies have demonstrated that Toc3 induce apoptosis in epithelial carcinoma. However, the effects of Toc3 on malignant hematopoietic cells have not yet been thoroughly investigated. We investigated Toc3-induced apoptosis in human hematological cancer cell lines. α-, δ-, and γ-Toc3 induced concentration-dependent apoptosis, and γ-Toc3 demonstrated more effective induction than the other Toc3 derivatives in HL-60 cells. γ-Toc3 may have induced apoptosis by activation of the caspase cascade, cytochrome c (Cyt.c) release, Bid cleavage, and mitochondorial membrane depolarization in HL-60, NB-4, Raji, and SY-5Y cells. Furthermore, 10-30 μM γ-Toc3 showed cytotoxicity for leukemic cells from various patients regardless of lymphoblastic, myeloblastic, or relapsed leukemia, but the cytotoxic effect was weak in normal mononuclear cells, interestingly. γ-Toc3 may have a role in cancer prevention and potential for treating hematological malignancies.

Lactate is an ideal non-invasive marker for evaluating temporal alterations in cell stress and toxicity in repeat dose testing regimes

Technological developments are driving in vitro methods towards integrated "omic" strategies. However, there is still an over reliance on classical viability assays for dose range finding. Such assays are not readily suited to the investigation of subtle alterations in cell function and most require termination of the experiment, which makes it difficult to monitor temporal alterations in repeat-dose long term exposure experiments. To this end, we investigated the use of lactate production as a marker of cell stress in long term repeat dose experiments. We conducted daily exposures to eight compounds at five concentrations for 14 days on human renal proximal tubular cells (RPTEC/TERT1), human hepatoma cells (HepaRG) and mouse fibroblasts (BALB-3T3) cells. Compounds were chosen from a training set used in the 7th EU Framework project Predict-IV and consisted of amiodarone, diclofenac, troglitazone, cadmium chloride, cephaloridine, cidofovir, cyclosporine A and buflomedil. At days 1, 3, 7 and 14, lactate was measured in the supernatant medium. At day 14, cells were assayed for resazurin reduction capability and subsequently lysed in methanol for ATP determination. Compound-induced loss of viability was comparable across all cell lines. For all cell types, when cell viability was compromised at day 14, lactate production was induced during the treatment period. In some situations, lactate also fell below control values, indicating cell death. Thus, temporal alterations in supernatant lactate provides information on the time and concentration of stress induction and the time and concentration where cell death becomes the dominant factor. Supernatant lactate production is a simple, cheap and non-invasive parameter. Since many molecular pathways converge on the glycolytic pathway, enhanced lactate production may be considered as a global marker of sub-lethal injury and thus an ideal marker for investigating temporal alterations in long term repeat dose testing in vitro regimes.

Subunits Rip1p and Cox9p of the respiratory chain contribute to diclofenac-induced mitochondrial dysfunction

The widely used drug diclofenac can cause serious heart, liver and kidney injury, which may be related to its ability to cause mitochondrial dysfunction. Using Saccharomyces cerevisiae as a model system, we studied the mechanisms of diclofenac toxicity and the role of mitochondria therein. We found that diclofenac reduced cell growth and viability and increased levels of reactive oxygen species (ROS). Strains increasingly relying on respiration for their energy production showed enhanced sensitivity to diclofenac. Furthermore, oxygen consumption was inhibited by diclofenac, suggesting that the drug inhibits respiration. To identify the site of respiratory inhibition, we investigated the effects of deletion of respiratory chain subunits on diclofenac toxicity. Whereas deletion of most subunits had no effect, loss of either Rip1p of complex III or Cox9p of complex IV resulted in enhanced resistance to diclofenac. In these deletion strains, diclofenac did not increase ROS formation as severely as in the wild-type. Our data are consistent with a mechanism of toxicity in which diclofenac inhibits respiration by interfering with Rip1p and Cox9p in the respiratory chain, resulting in ROS production that causes cell death.

Interaction of copper(II) with the non-steroidal anti-inflammatory drugs naproxen and diclofenac: synthesis, structure, DNA- and albumin-binding

Copper(II) complexes with the non-steroidal anti-inflammatory drugs (NSAIDs) naproxen and diclofenac have been synthesized and characterized in the presence of nitrogen donor heterocyclic ligands (2,2'-bipyridine, 1,10-phenanthroline or pyridine). Naproxen and diclofenac act as deprotonated ligands coordinated to Cu(II) ion through carboxylato oxygens. The crystal structures of (2,2'-bipyridine)bis(naproxenato)copper(II), 1, (1,10-phenanthroline)bis(naproxenato)copper(II), 2 and bis(pyridine)bis(diclofenac)copper(II), 4 have been determined by X-ray crystallography. The UV study of the interaction of the complexes with calf-thymus DNA (CT DNA) has shown that the complexes can bind to CT DNA with (2,2'-bipyridine)bis(naproxenato)copper(II) exhibiting the highest binding constant to CT DNA. Competitive study with ethidium bromide (EB) indicates that the complexes can displace the DNA-bound EB suggesting strong competition with EB. The cyclic voltammograms of the complexes recorded in the presence of CT DNA have shown that the complexes can bind to CT DNA by the intercalative binding mode which has also been verified by DNA solution viscosity measurements. The NSAID ligands and their complexes exhibit good binding propensity to human or bovine serum albumin protein having relatively high binding constant values. The biological properties of the previously reported complexes [Cu(2)(naproxenato)(4)(H(2)O)(2)], [Cu(2)(diclofenac)(4)(H(2)O)(2)] and [Cu(naproxenato)(2)(pyridine)(2)(H(2)O)] have been also evaluated. The dinuclear complexes exhibit similar affinity for CT DNA as the 2,2'-bipyridine or 1,10-phenanthroline containing complexes. The pyridine containing complexes exhibit the lowest affinity for CT DNA and the lowest ability to displace EB from its EB-DNA complex.

Enhanced death ligand-induced apoptosis in cutaneous SCC cells by treatment with diclofenac/hyaluronic acid correlates with downregulation of c-FLIP

Actinic keratosis (AK) occurs on sun-exposed skin and may progress to invasive squamous cell carcinoma (SCC). As for its topical treatment, diclofenac/hyaluronic acid (HA) has been recently approved. The NSAID diclofenac is an inhibitor of COX-2; however, its mode of action in cutaneous epithelial cancer cells is largely unknown. Here, the effects of diclofenac/HA were investigated in relation to death ligand-mediated apoptosis (TNF-alpha, TRAIL, and CD95 activation). Whereas diclofenac/HA only moderately induced apoptosis by itself, it resulted in pronounced enhancement of death ligand-mediated apoptosis in sensitive SCC cell lines (3/4). Apoptosis was associated with activation of initiator caspases of the extrinsic pathway (caspase-8/caspase-10). Furthermore, death ligand and diclofenac/HA-mediated apoptosis were blocked by the same caspase inhibitors, indicating related pathways. The proapoptotic effects of diclofenac/HA appeared independent of the p53 pathway. Also, upregulation of death receptors appeared less important; however, strong downregulation of c-FLIP isoforms was seen after diclofenac/HA treatment. The crucial role of c-FLIP was proven through overexpression and knockdown experiments. Thus, induction of apoptosis appears to be highly characteristic of the mode of action of diclofenac/HA, and the therapeutic effect may be related to sensitization of neoplastic keratinocytes for death ligand-induced apoptosis.

Carbocisteine inhibits oxidant-induced apoptosis in cultured human airway epithelial cells

BACKGROUND AND OBJECTIVE

Increased oxidant levels have been associated with exacerbations of COPD, and L-carbocisteine, a mucolytic agent, reduces the frequency of exacerbations. The mechanisms underlying the inhibitory effects of L-carbocisteine on oxidant-induced COPD exacerbations were examined in an in vitro study of human airway epithelial cells.

METHODS

In order to examine the antioxidant effects of L-carbocisteine, human tracheal epithelial cells were treated with L-carbocisteine and exposed to hydrogen peroxide (H(2)O(2)). Cell apoptosis was assessed using a cell death detection ELISA, and the pathways leading to cell apoptosis were examined by measurement of caspase-3 and caspase-9 by western blot analysis with fluorescent detection.

RESULTS

The proportion of apoptotic cells in human tracheal epithelium was increased in a concentration- and time-dependent manner, following exposure to H(2)O(2). Treatment with L-carbocisteine reduced the proportion of apoptotic cells. In contrast, H(2)O(2) did not increase the concentration of LDH in supernatants of epithelial cells. Exposure to H(2)O(2) activated caspase-3 and caspase-9, and L-carbocisteine inhibited the H(2)O(2)-induced activation of these caspases. L-carbocisteine activated Akt phosphorylation, which modulates caspase activation, and the inhibitors of Akt, LY294002 and wortmannin, significantly reversed the inhibitory effects of L-carbocisteine on H(2)O(2)-induced cell apoptosis.

CONCLUSIONS

These findings suggest that in human airway epithelium, L-carbocisteine may inhibit cell damage induced by H(2)O(2) through the activation of Akt phosphorylation. L-carbocisteine may have antioxidant effects, as well as mucolytic activity, in inflamed airways.

Indomethacin causes renal epithelial cell injury involving Mcl-1 down-regulation

Nonsteroidal anti-inflammatory drugs (NSAIDs) exert anti-tumor action in a variety of cancer cells. However, several treatment side effects such as gastrointestinal injury, cardiovascular toxicity, and acute renal failure limit their clinical use. We found that indomethacin caused renal epithelial cell injury independently of cyclooxygenase inhibition. Indomethacin treatment was associated with the disruption of mitochondrial transmembrane potential, release of cytochrome c, down-regulation of Bcl-2 and Mcl-1, upregulation of Bax, and elevation of caspases activity. Enhanced Mcl-1 but not Bcl-2 expression alleviated indomethacin-increased caspase-3 activity. Down-regulation of Akt-related and signal transducer and activator of transcription (STAT-3)-related pathways was found in indomethacin-treated cells. Pharmacological and genetic studies revealed a potential mechanistic link between Akt/Mcl-1 and STAT-3/Mcl-1 signaling pathways and indomethacin-induced cytotoxicity. Mcl-1 is a determinant molecule for the induction of epithelial cell injury caused by indomethacin. Therefore, the maintenance of Mcl-1 levels is important for prevention of renal epithelial cell injury and apoptosis.

Pro-apoptotic effect of nonsteroidal anti-inflammatory drugs on synovial fibroblasts

Rheumatoid arthritis (RA) is a systemic inflammatory disease that mainly affects the articular synovial tissues. Although the etiology of RA has not yet been elucidated, physical and biochemical inhibition of synovial hyperplasia, which is the origin of articular destruction, may be an effective treatment for RA. Nonsteroidal anti-inflammatory drugs (NSAIDs) have long been used for the treatment of RA. The mechanism of action of NSAIDs generally involves the inhibition of cyclooxygenase (COX) at sites of inflammation. Thus, NSAIDs were not generally considered to have a so-called anti-rheumatic effect, including inhibition of progressive joint destruction and induction of remission. However, certain conventional NSAIDs and celecoxib, a selective COX-2 inhibitor, have been reported to inhibit synovial hyperplasia by inducing the apoptosis of human synovial fibroblasts. Therefore, it has been suggested that such NSAIDs may not only have an anti-inflammatory effect but also an anti-rheumatic effect. In this review, we summarize findings about the pro-apoptotic effect, in other words, anti-proliferative effect of NSAIDs on synovial fibroblasts from patients with RA.

The role of apoptosis in therapy and prophylaxis of epithelial tumours by nonsteroidal anti-inflammatory drugs (NSAIDs)

In addition to having anti-inflammatory activities, nonsteroidal anti-inflammatory drugs (NSAIDs) also inhibit neoplastic cell proliferation by inducing apoptosis. Diclofenac is the anti-neoplastic compound in diclofenac 3% gel (Solaraze) used for topical treatment of actinic keratosis (AK). Main target of NSAIDs seems to be the inhibition of cyclo-oxygenase-2 (COX-2), which is overexpressed in several epithelial tumours and catalyses the synthesis of prostaglandins. The precise mechanism of action of diclofenac in cutaneous cells is still unclear, but induction of apoptosis is a key effect of anti-neoplastic drugs, including NSAIDs. In this paper we give an overview of the anti-tumoural activities of NSAIDs with emphasis on induction of apoptosis. Cyclo-oxygenase-2-mediated synthesis of prostaglandin E(2) (PGE(2)) leads to activation of mitogen-activated protein kinase (MAPK), as well as phosphatidylinositol 3-kinase (PI3K)/Akt pathways. Induction of the anti-apoptotic Bcl-2 and Mcl-1, as well as activation of the caspase-8 inhibitor cFLIP have been reported. In addition, altered lipid concentrations in the cytoplasmic membrane may modulate death receptor activities. Downregulation of both the intrinsic mitochondrial and the extrinsic pathways have been reported. Our data demonstrate induced apoptosis and activation of the caspase cascade in three of four cutaneous squamous cell carcinoma (SCC) cell lines, after treatment with diclofenac plus hyaluronic acid and diclofenac alone; one cell line remained nonresponsive. The effects were less pronounced in normal keratinocytes and cytotoxic effects were not seen. Detailed analysis of apoptosis pathways employed by diclofenac in these cells may help to improve therapeutic strategies and to overcome possible mechanisms that are involved in nonresponsiveness.

Bax-mediated mitochondrial outer membrane permeabilization (MOMP), distinct from the mitochondrial permeability transition, is a key mechanism in diclofenac-induced hepatocyte injury: Multiple protective roles of cyclosporin A

Diclofenac, a widely used nonsteroidal anti-inflammatory drug, has been associated with rare but severe cases of clinical hepatotoxicity. Diclofenac causes concentration-dependent cell death in human hepatocytes (after 24-48 h) by mitochondrial permeabilization via poorly defined mechanisms. To explore whether the cyclophilin D (CyD)-dependent mitochondrial permeability transition (mPT) and/or the mitochondrial outer membrane permeabilization (MOMP) was primarily involved in mediating cell death, we exposed immortalized human hepatocytes (HC-04) to apoptogenic concentrations of diclofenac (>500 microM) in the presence or absence of inhibitors of upstream mediators. The CyD inhibitor, cyclosporin A (CsA, 2 microM) fully inhibited diclofenac-induced cell injury, suggesting that mPT was involved. However, CyD gene silencing using siRNA left the cells susceptible to diclofenac toxicity, and CsA still protected the CyD-negative cells from lethal injury. Diclofenac induced early (9 h) activation of Bax and Bak and caused mitochondrial translocation of Bax, indicating that MOMP was involved in cell death. Inhibition of Bax protein expression by using siRNA significantly protected HC-04 from diclofenac-induced cell injury. Diclofenac also induced early Bid activation (tBid formation, 6 h), which is an upstream mechanism that initiates Bax activation and mitochondrial translocation. Bid activation was sensitive to the Ca2+ chelator, BAPTA. In conclusion, we found that Bax/Bak-mediated MOMP is a key mechanism of diclofenac-induced lethal cell injury in human hepatocytes, and that CsA can prevent MOMP through inhibition of Bax activation. These data support our concept that the Ca2+-Bid-Bax-MOMP axis is a critical pathway in diclofenac (metabolite)-induced hepatocyte injury.

Modulation of dopaminergic neurotransmission in rat striatum upon in vitro and in vivo diclofenac treatment

Diclofenac (DCF) is a widely used non-steroidal anti-inflammatory drug, which also act as a mitochondrial toxin. As it is known that selective mitochondrial complex I inhibition combined with mild oxidative stress causes striatal dopaminergic dysfunction, we tested whether DCF also compromise dopaminergic function in the striatum. [³H]Dopamine ([³H]DA) release was measured from rat striatal slices after in vitro (2 h, 10–25 μmol/L) or in vivo (3 mg/kg i.v. for 28 days) DCF treatment. In vitro treatment significantly decreased [³H]DA uptake and dopamine (DA) content of the slices. H₂O₂ (0.1 mmol/L)-evoked DA release was enhanced. Intracellular reactive oxygen species production was not significantly changed in the presence of DCF. After in vivo DCF treatment no apparent decrease in striatal DA content was observed and the uptake of [³H]DA into slices was increased. The intensity of tyrosine hydroxylase immunoreactivity in the striatum was highly variable, and both decrease and increase were observed in individual rats. The H₂O₂-evoked [³H]DA release was significantly decreased and the effluent contained a significant amount of [³H]octopamine, [³H]tyramine, and [³H]β-phenylethylamine. The ATP content and adenylate energy charge were decreased. In conclusion, whereas in vitro DCF pre-treatment resembles the effect of the mitochondrial toxin rotenone, in vivo it rather counteracts than aggravates dopaminergic dysfunction.

J. Neurochem. (2008) 105, 360–368.

Mitochondrial abnormalities--a link to idiosyncratic drug hepatotoxicity?

Idiosyncratic drug-induced liver injury (DILI) is a major clinical problem and poses a considerable challenge for drug development as an increasing number of successfully launched drugs or new potential drugs have been implicated in causing DILI in susceptible patient subsets. Although the incidence for a particular drug is very low (yet grossly underestimated), the outcome of DILI can be serious. Unfortunately, prediction has remained poor (both for patients at risk and for new chemical entities). The underlying mechanisms and the determinants of susceptibility have largely remained ill-defined. The aim of this review is to provide both clinical and experimental evidence for a major role of mitochondria both as a target of drugs causing idiosyncratic DILI and as mediators of delayed liver injury. We develop a unifying hypothesis that involves underlying genetic or acquired mitochondrial abnormalities as a major determinant of susceptibility for a number of drugs that target mitochondria and cause DILI. The mitochondrial hypothesis, implying gradually accumulating and initially silent mitochondrial injury in heteroplasmic cells which reaches a critical threshold and abruptly triggers liver injury, is consistent with the findings that typically idiosyncratic DILI is delayed (by weeks or months), that increasing age and female gender are risk factors and that these drugs are targeted to the liver and clearly exhibit a mitochondrial hazard in vitro and in vivo. New animal models (e.g., the Sod2(+/-) mouse) provide supporting evidence for this concept. However, genetic analyses of DILI patient samples are needed to ultimately provide the proof-of-concept.

Critical role of free cytosolic calcium, but not uncoupling, in mitochondrial permeability transition and cell death induced by diclofenac oxidative metabolites in immortalized human hepatocytes

Diclofenac is a widely used nonsteroidal anti-inflammatory drug that has been associated with rare but serious hepatotoxicity. Experimental evidence indicates that diclofenac targets mitochondria and induces the permeability transition (mPT) which leads to apoptotic cell death in hepatocytes. While the downstream effector mechanisms have been well characterized, the more proximal pathways leading to the mPT are not known. The purpose of this study was to explore the role of free cytosolic calcium (Ca(2+)(c)) in diclofenac-induced cell injury in immortalized human hepatocytes. We show that exposure to diclofenac caused time- and concentration-dependent cell injury, which was prevented by the specific mPT inhibitor cyclosporin A (CsA, 5 microM). At 8 h, diclofenac caused increases in [Ca(2+)](c) (Fluo-4 fluorescence), which was unaffected by CsA. Combined exposure to diclofenac/BAPTA (Ca(2+) chelator) inhibited cell injury, indicating that Ca(2+) plays a critical role in precipitating mPT. Diclofenac decreased the mitochondrial membrane potential, DeltaPsi(m) (JC-1 fluorescence), even in the presence of CsA or BAPTA, indicating that mitochondrial depolarization was not a consequence of the mPT or elevated [Ca(2+)](c). The CYP2C9 inhibitor sulphaphenazole (10 microM) protected from diclofenac-induced cell injury and prevented increases in [Ca(2+)](c), while it had no effect on the dissipation of the DeltaPsi(m). Finally, diclofenac exposure greatly increased the mitochondria-selective superoxide levels secondary to the increases in [Ca(2+)](c). In conclusion, these data demonstrate that diclofenac has direct depolarizing effects on mitochondria which does not lead to cell injury, while CYP2C9-mediated bioactivation causes increases in [Ca(2+)](c), triggering the mPT and precipitating cell death.

Nitric oxide induces promyelocytic cell growth arrest and apoptosis through deactivation of Akt pathway

It is NO that mediates the inhibitory effect of IFN-gamma, MIP-1alpha and TNFalpha on hematopoiesis. However, the mechanism for NO effect on the hematopoietic system is likely to not clear. In the current work, we demonstrates that NO can directly suppress the colony formation of granulocyte/macrophage in vitro. Using a granulocyte/macrophage progenitor (GMP) model, HL-60 cell line, we show that NO inhibits the proliferation of HL-60 cells by inducing G0/G1 arrest and apoptosis in a dose- and time-dependent manner. Exposure of HL-60 cells to 1mM SNP for 2-48h results in marked decrease in Akt activation and Bad phosphorylation. Constitutively active Akt overexpression reduces NO-induced apoptosis and cell cycle arrest in HL-60 cells. A further investigation on apoptosis related protein shows that NO induces Bid cleavage and Bax expression but down-regulates the expression of Bcl-2 and Bcl-xL. We also demonstrate here that G0/G1 arrest is resulted from NO-induced disruption of cell cycle balance, which is mediated by up-regulation of p21(waf/cip1), p27(kip1) and down-regulation of cyclin D1, cyclin E. In brief, NO-induced apoptosis and G0/G1 arrest is mediated through regulation of apoptosis and cell cycle related protein, which may depend on Akt deactivation by NO, ultimately led to its inhibitory effect on hematopoiesis.

Cell-permeable cAMP analog suppresses 6-hydroxydopamine-induced apoptosis in PC12 cells through the activation of the Akt pathway

Although cAMP protects neuronal cells from various apoptotic stimulations, its mechanism is not fully elucidated. We report here the molecular mechanism of the 6-hydroxydopamine (6-OHDA)-induced apoptosis of pheochromocytoma PC12 cells and its suppression by 8-(4-chlorophenylthio)adenosine 3',5'-cyclic monophosphate (pCPT-cAMP), which is a membrane permeable cAMP analog. Treatment of PC12 cells with 6-OHDA resulted in the activation of caspases and apoptosis, as detected by chromatin condensation. 6-OHDA also induced superoxide generation, Bid cleavage and mitochondrial membrane depolarization. In addition, Akt phosphorylation that was favorable to cell survival was decreased and p38 MAPK phosphorylation was increased by 6-OHDA. PC12 cell apoptosis was inhibited by pCPT-cAMP, Z-VAD-fmk (a broad-range caspase inhibitor) and tiron (a superoxide scavenger), although PC12 cell apoptosis was not inhibited by cyclosporine A (an inhibitor of mitochondrial membrane permeability transition). Moreover, pCPT-cAMP promoted Akt phosphorylation, but it did not prevent superoxide generation and mitochondrial membrane depolarization. Conversely, LY294002, an inhibitor of Akt upstream molecule PI3-kinase, enhanced 6-OHDA-induced apoptosis. These results indicated that the 6-OHDA-induced apoptosis of PC12 cells was initiated by superoxide generation followed by caspase cascade activation, which was associated with the suppressed Akt phosphorylation and increased p38 phosphorylation. It is likely that pCPT-cAMP prevented the 6-OHDA-induced apoptosis via activation of the PI3-kinase/Akt pathway without any effect on superoxide generation or mitochondrial membrane depolarization.

Short-term and long-term effects of fatty acids in rat hepatoma AS-30D cells: The way to apoptosis

Arachidonic acid and, to a smaller extent, oleic acid at micromolar concentrations decreased the mitochondrial membrane potential within AS-30D rat hepatoma cells cultivated in vitro and increased cell respiration. The uncoupling effect of both fatty acids on cell respiration was partly prevented by cyclosporin A, blocker of the mitochondrial permeability transition pore. Arachidonic acid increased the rate of reactive oxygen species (ROS) production, while oleic acid decreased it. Both fatty acids induced apoptotic cell death of AS-30D cells, accompanied by the release of cytochrome c from mitochondria to the cytosol, activation of caspase-3 and association of proapoptotic Bax protein with mitochondria; arachidonic acid being a more potent inducer than oleic acid. Trolox, a potent antioxidant, prevented ROS increase induced by arachidonic acid and protected the cells against apoptosis produced by this fatty acid. It is concluded that arachidonic and oleic acids induce apoptosis of AS-30D hepatoma cells by the mitochondrial pathway but differ in the mechanism of their action: Arachidonic acid induces apoptosis mainly by stimulating ROS production, whereas oleic acid may contribute to programmed cell death by activation of the mitochondrial permeability transition pore.

Viscum album agglutinin-I (VAA-I) induces apoptosis and degradation of cytoskeletal proteins in human leukemia PLB-985 and X-CGD cells via caspases: Lamin B1 is a novel target of VAA-I

Viscum album agglutinin-I (VAA-I) is a potent inducer of cell apoptosis and possesses anti-tumoral activity. Using PLB-985 and chronic granulomatous disease (X-CGD) cells, which lack expression of gp91(phox), VAA-I was found to induce apoptosis in both cell lines as assessed by cytology, DNA laddering and degradation of the cytoskeletal protein gelsolin. Both cell lines expressed caspase-3 and -8 and VAA-I activated these caspases. We demonstrated that lamin B(1) is a novel target to VAA-I and its degradation was reversed by a pan-caspase inhibitor and by a caspase-6, but not a caspase-8, inhibitor.

Involvement of Ras/extracellular signal-regulated kinase, but not Akt pathway in risedronate-induced apoptosis of U937 cells and its suppression by cytochalasin B

Although risedronate, a nitrogen containing bisphosphonate (BPs), strongly inhibits bone resorption by enhanced apoptosis of osteoclasts, its mechanism remained unclear. In this study, we investigated the molecular mechanism of risedronate-induced apoptosis of U937 cells, with a focus on extracellular signal-regulated kinase 1/2 (ERK 1/2) and protein kinase B (Akt) pathways, mitochondria-mediated apoptosis, and the effect of disruption of the actin cytoskeleton. Risedronate facilitated the relocation of Ras from membrane to cytosol through inhibited isoprenylation. Accordingly, risedronate suppressed the phosphorylation of ERK 1/2, a downstream survival signaling kinase of Ras, affected the intracellular distribution of Bcl-xL, and induced the mitochondrial membrane depolarization, cytochrome c release, activated caspase cascade and DNA fragmentation. The risedronate-induced apoptosis was effectively suppressed with cyclosporine A plus trifluoperazine, potent inhibitors of mitochondrial membrane permeability transition (MPT). The risedronate-induced apoptosis was independent of Akt, another cAMP-dependent survival signaling kinase. Risedronate facilitated dephosphorylation of Bad at Ser112, an ERK phosphorylation site, but not at Ser136, an Akt phosphorylation site. All of these apoptosis-related changes induced by risedronate were strongly suppressed by cytochalasin B, an inhibitor of actin filament polymerization. These results indicate that risedronate-induced apoptosis in U937 cells involves Ras/ERK, but not Akt signaling pathway, and is dependent on MPT, and that disruption of the actin cytoskeleton inhibits the risedronate-induced apoptosis at its early step.