Cocaine-induced liver injury in mice is mediated by nitric oxide and reactive oxygen species

Essential Involvement of Neutrophil Elastase in Acute Acetaminophen Hepatotoxicity Using BALB/c Mice

Intense neutrophil infiltration into the liver is a characteristic of acetaminophen-induced acute liver injury. Neutrophil elastase is released by neutrophils during inflammation. To elucidate the involvement of neutrophil elastase in acetaminophen-induced liver injury, we investigated the efficacy of a potent and specific neutrophil elastase inhibitor, sivelestat, in mice with acetaminophen-induced acute liver injury. Intraperitoneal administration of 750 mg/kg of acetaminophen caused severe liver damage, such as elevated serum transaminase levels, centrilobular hepatic necrosis, and neutrophil infiltration, with approximately 50% mortality in BALB/c mice within 48 h of administration. However, in mice treated with sivelestat 30 min after the acetaminophen challenge, all mice survived, with reduced serum transaminase elevation and diminished hepatic necrosis. In addition, mice treated with sivelestat had reduced NOS-II expression and hepatic neutrophil infiltration after the acetaminophen challenge. Furthermore, treatment with sivelestat at 3 h after the acetaminophen challenge significantly improved survival. These findings indicate a new clinical application for sivelestat in the treatment of acetaminophen-induced liver failure through mechanisms involving the regulation of neutrophil migration and NO production.

Could Alcohol Abuse and Dependence on Junk Foods Inducing Obesity and/or Illicit Drug Use Represent Danger to Liver in Young People with Altered Psychological/Relational Spheres or Emotional Problems?

Recent data show that young people, mainly due to the pressure of some risk factors or due to disrupted interpersonal relationships, utilise greater reward value and display greater sensitivity to the reinforcing properties of “pleasurable stimuli”, specifically in those situations in which an enhanced dopamine release is present. Alcoholic beverages, foods rich in sugar and fat, and illicit drug use are pleasurable feelings associated with rewards. Research shows that there is a link between substance abuse and obesity in brain functioning. Still, alcohol excess is central in leading to obesity and obesity-related morbidities, such as hepatic steatosis, mainly when associated with illicit drug dependence and negative eating behaviours in young people. It is ascertained that long-term drinking causes mental damage, similarly to drug abuse, but also affects liver function. Indeed, beyond the pharmacokinetic interactions of alcohol with drugs, occurring in the liver due to the same metabolic enzymes, there are also pharmacodynamic interactions of both substances in the CNS. To complicate matters, an important noxious effect of junk foods consists of inducing obesity and obesity-related NAFLD. In this review, we focus on some key mechanisms underlying the impact of these addictions on the liver, as well as those on the CNS.

Metabolic phenotyping of opioid and psychostimulant addiction: A novel approach for biomarker discovery and biochemical understanding of the disorder

Despite the progress in characterising the pharmacological profile of drugs of abuse, their precise biochemical impact remains unclear. The metabolome reflects the multifaceted biochemical processes occurring within a biological system. This includes those encoded in the genome but also those arising from environmental/exogenous exposures and interactions between the two. Using metabolomics, the biochemical derangements associated with substance abuse can be determined as the individual transitions from recreational drug to chronic use (dependence). By understanding the biomolecular perturbations along this time course and how they vary across individuals, metabolomics can elucidate biochemical mechanisms of the addiction cycle (dependence/withdrawal/relapse) and predict prognosis (recovery/relapse). In this review, we summarise human and animal metabolomic studies in the field of opioid and psychostimulant addiction. We highlight the importance of metabolomics as a powerful approach for biomarker discovery and its potential to guide personalised pharmacotherapeutic strategies for addiction targeted towards the individual's metabolome.

Protein kinase Cδ knockout mice are protected from cocaine-induced hepatotoxicity

We investigated whether protein kinase Cδ (PKCδ) mediates cocaine-induced hepatotoxicity in mice. Cocaine treatment (60 mg/kg, i.p.) significantly increased cleaved PKCδ expression in the liver of wild-type (WT) mice, and led to significant increases in oxidative parameters (i.e., reactive oxygen species, 4-hydroxylnonenal and protein carbonyl). These cocaine-induced oxidative burdens were attenuated by pharmacological (i.e., rottlerin) or genetic depletion of PKCδ. We also demonstrated that treatment with cocaine resulted in significant increases in nuclear factor erythroid-2-related factor 2 (Nrf-2) nuclear translocation and increased Nrf-2 DNA-binding activity in wild-type (WT) mice. These increases were more pronounced in the rottlerin-treated WT or PKCδ knockout mice than in the saline-treated WT mice. Although cocaine treatment increased Nrf-2 nuclear translocation, DNA binding activity, and γ-glutamyl cysteine ligases (i.e., GCLc and GCLm) mRNA expressions, while it reduced the glutathione level and GSH/GSSG ratio. These decreases were attenuated by PKCδ depletion. Cocaine treatment significantly increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the serum of WT mice signifying the hepatic damage. These increases were also attenuated by PKCδ depletion. In addition, cocaine-induced hepatic degeneration in WT mice was evident 1 d post-cocaine. At that time, cocaine treatment decreased Bcl-2 and Bcl-xL levels, and increased Bax, cytosolic cytochrome c, and cleaved caspase-3 levels. Pharmacological or genetic depletion of PKCδ significantly ameliorated the pro-apoptotic properties and hepatic degeneration. Therefore, our results suggest that inhibition of PKCδ, as well as activation of Nrf-2, is important for protecting against hepatotoxicity induced by cocaine.

Environmental concentrations of cocaine and its main metabolites modulated antioxidant response and caused cyto-genotoxic effects in zebrafish embryo cells

Illicit drugs have been recently identified as a serious environmental problem because of the growing evidence regarding their occurrence in aquatic environment and potential toxicity towards non-target organisms. Among them, cocaine (COC) and its main metabolites, namely benzoylecgonine (BE) and ecgonine methyl ester (EME), are commonly measured in freshwaters worldwide at levels that might cause diverse sub-lethal effects to aquatic organisms. Thus, the present study was aimed at investigating the potential adverse effects induced by the exposure to environmental concentrations (0.04, 0.4, 4 and 40 nM) of COC, BE, and EME on zebrafish (Danio rerio) embryos at 96 h post fertilization. Cytotoxicity was assessed by the Trypan Blue exclusion method, while primary and fixed genetic damages were evaluated by the Single Cell Gel Electrophoresis (SCGE) assay, and the DNA diffusion assay together with the Micronucleus test, respectively. The involvement of oxidative stress in the mechanism of action (MoA) of all tested drugs was assessed by measuring the activity of defense enzymes (SOD, CAT, GPx, and GST) and the expression of their encoding genes. Exposure to COC and both metabolites significantly reduced cell viability, increased DNA fragmentation and promoted the onset of apoptotic cells and micronuclei in zebrafish embryos. Results from oxidative stress-related endpoints and gene expression suggested that the observed genotoxicity may be caused by an overproduction of free radicals that imbalanced the oxidative status of embryos. The integration of biomarker responses into a synthetic index showed that at each tested concentration, BE and EME had a similar toxicity and were both more toxic than COC. Our data confirmed the potential toxicity of environmental concentrations of COC, BE, and EME, suggesting the need of further in-depth studies to shed light on their MoA and long-term toxicity towards non-target aquatic species.

Investigation on the combined effect of cocaine and ethanol administration through a liquid chromatography-mass spectrometry metabolomics approach

Alcohol is the most widely consumed legal drug, whereas cocaine is the illicit psychostimulant most commonly used in Europe. The combined use of alcohol and cocaine is frequent among drug-abuse consumers and leads to further exacerbation of health consequences compared to individual consumption. The pharmacokinetic and metabolic interactions leading to an increase in their combined toxicity still remains poorly understood. Here, the first metabolomics study of combined cocaine and ethanol chronic exposure effects is reported. A Liquid Chromatography strategy based on sample derivatization with 9-fluorenylmethyloxycarbonyl chloride and using a C18 column coupled to high resolution Mass Spectrometry (time of flight analyzer) was employed to analyze plasma from rats exposed intravenously to these drugs in a 52-min analysis. Using a combination of non-supervised and supervised multivariate analysis the metabolic differences between our experimental groups were explored and unraveled. A comparative analysis of the individual models and their variable importance in the projection values have shown that every experiment intervention includes a subset of specific metabolites. Eleven of these metabolites were annotated, where eight were unequivocally identified using standards and three were tentatively identified by matching the MS/MS spectra to libraries. The results demonstrated that the affected metabolic pathways were mainly those related to the metabolism of different amino acids.

Global cocaine intoxication research trends during 1975-2015: a bibliometric analysis of Web of Science publications

BACKGROUND

Cocaine is subject to recreational abuse as a stimulant and psychoactive agent, which poses a major worldwide health problem. The aim of the present study was to perform a bibliometric analysis of publication related to cocaine intoxication an insight of the research trends at a global level to enable recommendations for future research strategies in this field.

METHODS

Publications about cocaine intoxication were retrieved from the Web of Science (WoS) Core Collection database on December 28, 2016, and analysed regarding the following bibliometric indicators: research trends, document types, languages, countries/territories with their h-index, collaboration patterns, journals with their impact factors (IF), and institutions.

RESULTS

In total, 2,902 scientific publications from 1975 to 2015 were retrieved from the WoS database. The annual number of publications related to cocaine toxicity increased slightly after 1990 and reached a peak of 148 in 1992, with an average of 103 publications per year. The USA outranked other countries/territories with 2,089 publications, of which 1,927 arose exclusively from the USA and 162 involved international collaborations. The h-index for all publications related to cocaine was 212, and the h-index for all publications related to cocaine intoxication was 99. Moreover, the USA had the highest h-index of 95, followed by Spain with h-index of 24, and Canada with h-index of 24. The main research topics were consistently reproductive toxicity, clinical management of acute cocaine exposure, laboratory methods for detection of exposure to cocaine, cocaine metabolism, and cocaine toxicity in animals.

CONCLUSIONS

This is the first bibliometric approach to examining research related to cocaine toxicity and shows that research activity has become more global and extensive since 1990. The USA remains the leading country regarding published literature, the highest h-index, and greatest role in international collaborations.

Differential Patterns of Cocaine-Induced Organ Toxicity in Murine Heart versus Liver

To determine cocaine's toxicity in different organs, BALB/c mice were intraperitoneally injected daily for 15 days with either saline or cocaine: 10 mg/kg, 30 mg/kg, or 60 mg/kg. Cardiac function, hepatic pathophysiology, heart and liver apoptosis, and tumor necrosis factor (TNF-α) levels were analyzed. After administration of cocaine, cardiac function decreased. Inflammatory cell infiltration and eosinophilic contraction bands were visible in the hearts of mice treated with 60mg/kg cocaine. Moreover, histopathology demonstrated that cocaine caused hepatic necrosis. TdT-mediated dUTP nick end-labeling (TUNEL) staining and DNA ladder analysis indicated that cocaine caused apoptosis in both the heart and liver. Moreover, immunoassay showed that TNF-α levels significantly increased in the heart and liver with cocaine administration. However, our RT-PCR study showed that there was no significant difference in either the heart or liver in the levels of mRNA for TNF-α between cocaine-treated and saline control mice. The present study demonstrated that cocaine is toxic to multiple organs, and at low dose can induce hepatic damage without gross pathological injury to the heart. The results suggest that the liver is more sensitive than the heart to cocaine toxicity, and induction of apoptosis or TNF-α elevation may be a common mechanism responsible for cocaines toxicity.

Cardiovascular and Hepatic Toxicity of Cocaine: Potential Beneficial Effects of Modulators of Oxidative Stress

Oxidative stress (OS) is thought to play an important role in the pharmacological and toxic effects of various drugs of abuse. Herein we review the literature on the mechanisms responsible for the cardiovascular and hepatic toxicity of cocaine with special focus on OS-related mechanisms. We also review the preclinical and clinical literature concerning the putative therapeutic effects of OS modulators (such as N-acetylcysteine, superoxide dismutase mimetics, nitroxides and nitrones, NADPH oxidase inhibitors, xanthine oxidase inhibitors, and mitochondriotropic antioxidants) for the treatment of cocaine toxicity. We conclude that available OS modulators do not appear to have clinical efficacy.

Drugs of abuse and addiction: A slippery slope toward liver injury

Substances of abuse induce alteration in neurobehavioral symptoms, which can lead to simultaneous exacerbation of liver injury. The biochemical changes of liver are significantly observed in the abused group of people using illicit drugs or drugs that are abused. A huge amount of work has been carried out by scientists for validation experiments using animal models to assess hepatotoxicity in cases of drugs of abuse. The risk of hepatotoxicity from these psychostimulants has been determined by different research groups. Hepatotoxicity of these drugs has been recently highlighted and isolated case reports always have been documented in relation to misuse of the drugs. These drugs induce liver toxicity on acute or chronic dose dependent process, which ultimately lead to liver damage, acute fatty infiltration, cholestatic jaundice, liver granulomas, hepatitis, liver cirrhosis etc. Considering the importance of drug-induced hepatotoxicity as a major cause of liver damage, this review emphasizes on various drugs of abuse and addiction which induce hepatotoxicity along with their mechanism of liver damage in clinical aspect as well as in vitro and in vivo approach. However, the mechanisms of drug-induced hepatotoxicity is dependent on reactive metabolite formation via metabolism, modification of covalent bonding between cellular components with drug and its metabolites, reactive oxygen species generation inside and outside of hepatocytes, activation of signal transduction pathways that alter cell death or survival mechanism, and cellular mitochondrial damage, which leads to alteration in ATP generation have been notified here. Moreover, how the cytokines are modulated by these drugs has been mentioned here.

Regulation by resveratrol of the cellular factors mediating liver damage and regeneration after acute toxic liver injury

BACKGROUND AND AIM

Acute liver injury is manifested by different degree of hepatocyte necrosis and may recover via the process of hepatocyte regeneration once the injury is discontinued. Most of the liver injury is associating with inflammatory cytokines. Resveratrol (RSV) is a natural phytoalexin with powerful anti-inflammatory effects.

AIM

The effects of RSV on cellular factors mediating liver damage and regeneration in acute carbon tetrachloride (CCl4 ) liver injury were investigated.

RESULTS

RSV decreased alanine aminotransferase, aspartate aminotransferase, necrosis, and 4-hydroxynonenal in the CCl4 -injured liver. RSV decreased hepatocyte apoptosis by reducing caspase 8 and caspase 3 but not Bax and Bcl-xL. RSV reduced Kupffer cells recruitment, the expressions of tumor necrosis factor-α and interleukin-6, but not interleukin-10. RSV lowered the numbers of anti-5-bromon-2'-deoxyuridine and anti-Ki67-positive hepatocytes. Hepatic hepatocyte growth factor, c-Met and transforming growth factor-α expressions were reduced by RSV, while transforming growth factor-β1 and hepatic stellate cells activation were not changed. RSV reduced the injury-induced CXCL10 elevations in serum and liver in vivo. Besides, RSV inhibited CXCL10 release from CCl4 -injured hepatocytes in vitro. In contrast, recombinant CXCL10 improved the viability of CCl4 -injured hepatocytes.

CONCLUSIONS

RSV therapy can be beneficial for acute toxic liver injury. RSV reduced hepatocyte apoptosis but limited hepatocyte regeneration possibly through reducing the hepatomitogenic signaling and the release of CXCL10.

A review on renal toxicity profile of common abusive drugs

Drug abuse has become a major social problem of the modern world and majority of these abusive drugs or their metabolites are excreted through the kidneys and, thus, the renal complications of these drugs are very common. Morphine, heroin, cocaine, nicotine and alcohol are the most commonly abused drugs, and their use is associated with various types of renal toxicity. The renal complications include a wide range of glomerular, interstitial and vascular diseases leading to acute or chronic renal failure. The present review discusses the renal toxicity profile and possible mechanisms of commonly abused drugs including morphine, heroin, cocaine, nicotine, caffeine and alcohol.

Hepatoprotective effects of saponarin, isolated from Gypsophila trichotoma Wend. on cocaine-induced oxidative stress in rats

The antioxidant effect of saponarin, which is the main flavone isolated from Gypsophila trichotoma Wend., and its protection against cocaine hepatotoxicity were investigated in male Wistar rats. The animals were treated with cocaine (40 mg/kg i.p.) alone and also after 3 consecutive days of pretreatment with saponarin (80 mg/kg p.o.). After 18 hours the rats were sacrificed by decapitation. The production of thiobarbituric acid reactive substances, reduced glutathione (GSH) and the activity of the following antioxidant enzymes: catalase, superoxide dismutase, glutathione peroxidase, glutathione reductase, and glutathione-S-transferase were assessed in liver homogenate. Administered alone, cocaine induced significant hepatotoxicity manifested with GSH depletion and reduced antioxidant defences. Saponarin pretreatment, however, decreased cocaine toxicity both by increasing GSH levels and antioxidant enzyme activities. The results of this study proved the antioxidant activity of saponarin and its protective effect against cocaine-induced oxidative stress and hepatotoxicity.

Cocaine-induced kidney toxicity: an in vitro study using primary cultured human proximal tubular epithelial cells

Renal failure resulting from cocaine abuse has been well documented, although the underlying mechanisms remain to be investigated. In the present study, primary cultured human proximal tubular epithelial cells (HPTECs) of the kidney were used to investigate its ability to metabolize cocaine, as well as the cytotoxicity induced by cocaine and its metabolites benzoylecgonine (BE), ecgonine methyl ester (EME) and norcocaine (NCOC). Gas chromatography/ion trap-mass spectrometry (GC/IT-MS) analysis of HPTECs exposed to cocaine (1 mM) for 72 h confirmed its metabolism into EME and NCOC, but not BE. EME levels increased along the exposure time to cocaine, while NCOC concentration diminished after reaching a maximum at 6 h, indicating a possible secondary metabolism for this metabolite. Cocaine promoted a concentration-dependent loss of cell viability, whereas BE and EME were found to be non-toxic to HPTECs at the tested conditions. In contrast, NCOC revealed to have higher intrinsic nephrotoxicity than the parent compound. Moreover, cocaine-induced cell death was partially reversed in the presence of ketoconazole (KTZ), a potent CYP3A inhibitor, supporting the hypothesis that NCOC may play a role in cocaine-induced nephrotoxicity. Cocaine-induced cytotoxicity was found to involve intracellular glutathione depletion at low concentrations and to induce mitochondrial damage at higher concentrations. Under the present experimental conditions, HPTECs death pathway followed an apoptotic pattern, which was evident for concentrations as low as 0.1 mM.

Beneficial role of aminoguanidine on acute cardiomyopathy related to doxorubicin-treatment

Doxorubicin (DOX) is a broad-spectrum anthracycline antibiotic that has cardiotoxicity as a major side effect. One mechanism of this toxicity is believed to involve the reactive oxygen radical species (ROS); these agents likely account for the pathophysiology of DOX-induced cardiomyopathy. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against ROS formation. We investigated the effects of AG on DOX-induced changes in thiobarbituric acid reactive substances (TBARS) and reduced glutathione (GSH) content. The rats were divided into four groups:1) Control; 2) DOX group; injected intraperitoneally (i.p.) with DOX 20 mg/kg in a single dose 3) AG-treated group; injected i.p. in single dose of 20 mg/kg DOX plus 100 mg/kg AG 1 h before the DOX for 3 days, 4) AG group; injected i.p. with AG 100 mg/kg for 3 days. DOX administration to control rats increased TBARS and decreased GSH levels. AG administration before DOX injection caused significant decrease in TBARS and increase in GSH levels in the heart tissue when compared with DOX only. Morphological changes, including severe myocardial fibrosis and inflammatory cell infiltration were clearly observed in the DOX-treated heart. AG reversed the DOX-induced heart damage. Therefore AG could protect the heart tissue against free radical injury. The application of AG during cancer chemotherapy may attenuate tissue damage and improve the therapeutic index of DOX.

Therapeutic effects of xanthine oxidase inhibitors: renaissance half a century after the discovery of allopurinol

The prototypical xanthine oxidase (XO) inhibitor allopurinol, has been the cornerstone of the clinical management of gout and conditions associated with hyperuricemia for several decades. More recent data indicate that XO also plays an important role in various forms of ischemic and other types of tissue and vascular injuries, inflammatory diseases, and chronic heart failure. Allopurinol and its active metabolite oxypurinol showed considerable promise in the treatment of these conditions both in experimental animals and in small-scale human clinical trials. Although some of the beneficial effects of these compounds may be unrelated to the inhibition of the XO, the encouraging findings rekindled significant interest in the development of additional, novel series of XO inhibitors for various therapeutic indications. Here we present a critical overview of the effects of XO inhibitors in various pathophysiological conditions and also review the various emerging therapeutic strategies offered by this approach.

A GSTP1 functional variant associated with cocaine dependence in a Brazilian population

Cocaine dependence aetiology is complex and genetically influenced. We hypothesize that, for many users, efficient metabolism of cocaine and its toxic byproducts aids persistent cocaine use, such as that leading to dependence. The glutathione-S-transferases - in particular, GST-Pi - may be important in preventing cocaine and alcohol-induced oxidative damage. We genotyped a GST-Pi functional polymorphism (Ile105Val) in 654 male cocaine users and 572 controls from Brazil. Genotype and allele frequencies of Ile105Val differed significantly (chi = 6.74; P=0.03 and chi = 6.54; P = 0.01, respectively). Ile/Ile cocaine dependents had an OR = 1.31 (95%CI: 1.04-1.65), and Ile/Ile dependents consuming >50 units alcohol weekly an OR of 1.44 (95% CI:1.06-1.96). Population stratification was assessed and did not affect the results. These data require replication but do suggest that the high activity Ile105 GST-Pi allele may influence the aetiology and development of cocaine dependence.

Protective effect of aminoguanidine against nephrotoxicity induced by amikacin in rats

Aminoglycoside antibiotics have long been used in antibacterial therapy. Despite their beneficial effects, aminoglycosides have considerable nephrotoxic and ototoxic side effects. It has been reported that reactive oxygen radical species (ROS) play role in the pathophysiology of aminoglycosides-induced nephrotoxicity. Aminoguanidine (AG) is an effective antioxidant and free radical scavenger which has long been known to protect against nephrotoxicity. We investigated the effects of AG on amikacin (AK)-induced changes of renal malondialdehyde (MDA), glutathione (GSH), blood urea nitrogen (BUN), serum creatinine (Cr) and albumin (Alb) which are used to monitor the development of renal tubular damage. Morphological changes in the kidney were also examined using light microscopy. A total of 21 rats were equally divided into three groups which were: (1) injected with saline, (2) injected with AK, and (3) injected with AK + AG, respectively. AK administration to control rats increased renal MDA and decreased GSH levels. AG administration before AK injection caused significant decreases in MDA and increases in GSH levels in kidneys compared to rats treated with AK alone. The serum BUN level increased slightly, Cr and serum Alb did not change as a result of any treatment. AG tended to decrease the level of serum BUN and did not cause any change in Alb or Cr levels. Morphological changes, including glomerular, tubular epithelial alterations and interstitial edema, were clearly observed in AK-treated rats. In addition, AG reversed the morphological damage to the kidney induced by AK. The results show that AG has a protective effect on nephrotoxicity induced by AK and may therefore improve the therapeutic index of AK.

Endotoxin potentiates cocaine-mediated hepatotoxicity by nitric oxide and reactive oxygen species

Exposure to small, noninjurious doses of the inflammagen, bacterial endotoxin (lipopolysaccharide, LPS) augments the toxicity of certain hepatotoxicants, including cocaine. The mechanism of this interaction has not been clearly elucidated, but it seems that aspects of the inflammatory response initiated by exposure to LPS may be responsible. In particular, this study examined the role of Kupffer cells and the modulating effects of nitric oxide (NO) and reactive oxygen species (ROS) on the LPS potentiation of cocaine-mediated hepatotoxicity (CMH). Mice were administered oral cocaine hydrochloride for 5 consecutive days at a dose of 20 mg/kg with and without 12 x 10(6) EU LPS/kg given intraperitoneally (IP) 4 hours after the last cocaine injection. Pretreatment regimens consisted of administration of 300 mg/kg, IP, of aminoguanidine (AM) or 1,3-dimethylthiourea (DMU) at 1 hour or 15 minutes, respectively, before each cocaine administration. In another group, mice were pretreated with saline using the same cocaine and LPS treatment protocol, but received a single pretreatment of 7 mg gadolinium chloride (GdCl(3))/kg intravenously (IV), or sterile saline 24 hours prior to the LPS administration. The GdCl(3) (Kupffer cell inhibitor) pretreatment inhibited the LPS potentiation of CMH, but did not reverse the effects of cocaine alone. On the other hand, AM (NO synthase inhibitor), decreased the synthesis of NO as observed by the decrease in the plasma nitrate/nitrite level and completely reversed the hepatotoxic effects of cocaine and LPS alone and in combination. Moreover, DMU (hydroxyl free radical scavenger) ameliorated the effects of cocaine and significantly reduced the hepatotoxicity observed with the cocaine and LPS administration. These data suggest that cocaine sensitizes the liver and subsequent activation of Kupffer cells by LPS leads to the formation of increased levels of NO, which can promote oxidant stress and thus provide an environment favoring the generation of more reactive species such as the hydroxyl free radical.

Glutathione depletion increases nitric oxide-induced oxidative stress in primary rat hepatocyte cultures: involvement of low-molecular-weight iron

Various drugs and chemicals can cause a glutathione (GSH) depletion in the liver. Moreover, nitric oxide (NO) can be generated in response to physiological and pathological situations such as inflammation. The aim of this study was to estimate oxidative stress when primary rat hepatocytes were exposed to GSH depletion after NO production. For this purpose, cells were preincubated with lipopolysaccharide (LPS) and gamma-interferon (IFN) for 18 h in order to induce NO production by NO synthase and then L-buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, was added for 5 h. In hepatocyte cultures preincubated with LPS and IFN before BSO addition, an increase in lipid peroxidation was noted. In those cells, an elevation of iron-bound NO and a decrease in free NO led us to suggest the involvement of low-molecular-weight iron (LMW iron) in the enhancement of oxidative stress. Indeed, addition of deferiprone, a chelator of LMW iron, reduced iron-bound NO levels and the extent of oxidative stress. Moreover, an important elevation of LMW iron levels was also observed. As both, N-acetylcysteine, a GSH precursor, and N(G)-monomethyl-L-arginine, a NO synthase inhibitor, totally inhibited the elevation of LMW iron and oxidative stress, a cooperative role could be attributed to NO production and GSH depletion.

A comparison of hepatoprotective activities of aminoguanidine and N-acetylcysteine in rat against the toxic damage induced by azathioprine

Azathioprine (AZA) is an important drug used in the therapy of autoimmune system disorders. It induces hepatotoxicity that restricts its use. The rationale behind this study was the proven efficacy of N-acetylcysteine (NAC; a replenisher of sulfhydryls) and reports on the antioxidant potential of aminoguanidine (AG; an iNOS inhibitor), that might be useful to protect against the toxic implications of AZA. AG (100 mg/kg; i.p.) or NAC (100 mg/kg; i.p.) were administered to the Wistar male rats for 7 days and after that AZA (15 mg/kg, i.p.) was given as a single dose. This caused an increase in the activity of hepatic aminotransferases (AST and ALT) in the serum 24 h after AZA treatment. AZA (7.5 or 15 mg/kg, i.p.) also caused an increase in rat liver lipid peroxides and a lowering of reduced glutathione (GSH) contents. In the other part of experiment, protective effects of AG and NAC were observed on AZA induced hepatotoxicity. NAC significantly protected against the toxic effects produced by AZA. Pretreatment with NAC prevented any change in the activities of both the aminotransferases after AZA. This pretreatment also resulted in a significant decline in the contents of lipid peroxides and a significant elevation in GSH level was evident after AZA treatment. In the group with AG pretreatment the activities of AST and ALT did not increase significantly after AZA when compared to control. However, the lipid peroxides and GSH levels did not have any significant difference when compared to AZA group. These observations also indicate that the improvement in the GSH levels by NAC is the most significant protective mechanism rather than any other mechanistic profile. The protective effect of AG against the enzyme leakage seems to be through the liver cell membrane permeability restoration and is independent of any effects on liver GSH contents.

Immunosuppression and oxidative stress induced by acute and chronic exposure to cocaine in rat

The objective of the present study was to verify if immunosuppression caused by cocaine (CO) can be mediated, at least in part, by increased formation of oxidative metabolites and reactive oxygen species (ROS) in rat. Pharmacokinetics of cocaine and its metabolites, cell-mediated immune function and cytokines production, biomarkers of cell redox state maintenance and lipidic peroxidation, and variations of activity in the enzymatic systems involved in cell antioxidant defence were measured in spleen of Wistar rats acutely and chronically treated with cocaine.C(max), AUC, and t(1/2) of norcocaine (NC) significantly increased after chronic exposure to cocaine while kinetic parameters of benzoylecgonine (BE) significantly decreased. A decrease in cultured T-lymphocytes proliferation and natural killer (NK) cell activity, a high increase of immunosuppressive cytokines and a switch from Th1-type cytokines to Th2-type cytokines together with an unbalance toward anti-inflammatory cytokines recovered within 4 h after acute treatment while subsisted for 14 days after chronic treatment. A significant increase in ascorbic acid (AA), reduced glutathione and glutathione reductase (GR) with a simultaneous decrease in oxidized glutathione were observed in the first hours after acute administration. Conversely, the increase in oxidized glutathione and malondialdehyde (MDA) production and the simultaneous depletion of reduced glutathione and ascorbic acid persisted at least 24 h after chronic cocaine treatment as well as the increase in the activities of glutathione reductase, glutathione peroxidase (GPx) and superoxide dismutase (SOD). The results suggest that chronic cocaine administration affects cellular enzyme and non-enzyme-mediated antioxidant defence systems and promotes immunotoxicity in rat. Cocaine N-oxidative metabolism may be an indirect contributor, via oxidative stress.

N-acetylcysteine pretreatment decreases cocaine and endotoxin-induced hepatotoxicity

Cocaine produces hepatotoxicity by a mechanism that remains undefined but has been linked to its oxidative metabolism. Endotoxin (lipopolysaccharide, LPS) is also a well-known cause of hepatic damage, and exposure to noninjurious doses of LPS increases the toxicity of certain hepatotoxins. Previously it was demonstrated that exposure to noninjurious doses of LPS dramatically increases cocaine-mediated hepatotoxicity (CMH). This study was conducted to investigate whether pretreatment with N-acetylcysteine (NAC), a glutathione (GSH) precursor and an antioxidant agent, inhibits LPS potentiation of CMH. For 5 consecutive days, male CF-1 mice were administered daily oral NAC (200 mg/kg) or sterile saline followed an hour later by cocaine (20 mg/kg) or sterile saline. Four hours following the last cocaine or saline treatment, the mice were administered 12 x 10(6) EU LPS/kg or sterile saline. For the cocaine alone and cocaine and LPS groups, NAC pretreatment significantly decreased serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities with absence of necrotic hepatic lesions, indicating a reduction of liver injury. In addition, in all groups pretreated with NAC, hepatic GSH concentration was significantly increased, as were hepatic and blood glutathione peroxidase (GPx) and catalase (CAT) activities. In conclusion, the results demonstrate that NAC pretreatment exerted a protective effect against LPS potentia-tion of CMH.

Abrogation of bleomycin-induced lung fibrosis by nitric oxide synthase inhibitor, aminoguanidine in mice

The effects of aminoguanidine (AG), a specific inhibitor of inducible nitric oxide synthase, on the bleomycin (BL)-induced lung fibrosis was evaluated in mice. The animals were placed into five groups: saline (SA)-instilled drinking water (SA+H(2)O), saline-instilled drinking water containing 0.5%AG (SA+0.5%AG), BL-instilled drinking water (BL+H(2)O), BL-instilled drinking water containing 0.2%AG (BL+0.2%AG), and BL-instilled drinking water containing 0.5%AG (BL+0.5%AG). The mice had free access to H(2)O or H(2)O containing AG and lab chow ad lib 2 days prior to intratracheal (IT) instillation of BL (0.07U/mouse/100 microL) or an equivalent volume of sterile isotonic saline. The mice in the SA+0.5%AG group consumed the greatest amount of AG without any ill effects than the mice in any other group. There were no differences in any of the measured biochemical determinants between the SA+H(2)O and SA+0.5%AG control groups. The IT instillation of BL in the BL+H(2)O group caused significant increases in the lipid peroxidation, hydroxyproline content, and prolyl hydroxylase activity of lungs and influx of inflammatory cells in the broncheoalveolar lavage fluid (BALF) as compared to both control groups. The intake of aminoguanidine by mice in the BL+0.5%AG group caused significant reductions in the BL-induced increases in all measured biochemical indices of lung fibrosis without any effects on the influx of inflammatory cells in the BALF. In fact, AG in both BL-treated groups additionally increased the total cell counts in the BALF from mice in the BL+0.2%AG and BL+0.5%AG groups as compared to the BL+H(2)O group. Histopathological evaluation of the lungs revealed that the mice in the BL+0.5%AG group had markedly fewer fibrotic lesions than mice in the BL+H(2)O group. These results demonstrate that aminoguanidine minimizes the BL-induced lung fibrosis at both the biochemical and the morphological level and support our earlier hypothesis that the production of nitric oxide plays a significant role in the pathogenesis lung fibrosis caused by BL.

Protective effect of aminoguanidine against nephrotoxicity induced by cisplatin in normal rats

The effect of aminoguanidine (AG) on nephrotoxicity induced by cisplatin (CDDP) was investigated. A single dose of CDDP (7.5 mg/kg i.p.) induced nephrotoxicity, manifested biochemically by a significant elevation in serum urea, creatinine and a severe decrease in serum albumin. Moreover, marked increases in kidney weight, urine volume and urinary excretion of albumin were observed. Nephrotoxicity was further confirmed by a significant decrease in glutathione-S-transferase (GST, E.C. 2.5.1.18), glutathione peroxidase (GSH-Px, E.C. 1.11.1.9) and catalase (E.C. 1.11.1.6) and a significant increase in lipid peroxides measured as malondialdhyde (MDA) in kidney homogenates. Administration of AG (100 mg/kg per day p.o.) in drinking water 5 days before and 5 days after CDDP injection produced a significant protection against nephrotoxicity induced by CDDP. The amelioration of nephrotoxicity was evidenced by significant reductions in serum urea and creatinine concentrations. In addition, AG tended to normalize decreased levels of serum albumin. Urine volume, urinary excretions of albumin and GST and kidney weight were significantly decreased. Moreover, AG prevented the rise of MDA and the reduction of GST and GSH-Px activities in the kidney. These results suggest that AG has a protective effect on nephrotoxicity induced by CDDP and it may therefore improve the therapeutic index of CDDP.

Protective effect of L-arginine against nephrotoxicity induced by cyclosporine in normal rats

Effects of L-arginine (L-arg) and aminoguanidine (AG) on the nephrotoxicity induced by cyclosporine (CsA) were investigated. After injection of CsA (15 mg kg(-1) day (-1)i.p. for 10 days), it induced nephrotoxicity, manifested biochemically by a significant elevation of serum urea and creatinine. In addition, a marked increase in lipid peroxides measured as malondialdehyde (MDA) as well as a significant decrease in glutathione peroxidase (GSH-Px) activity (EC.1.11.1.9) and reduced glutathione content (GSH) in kidney tissues homogenate were observed. Nephrotoxicity was further confirmed by histopathological investigation. Oral administration of L-arg (300 mg kg (-1)day(-1) orally) for 5 days before and 10 days concomitant with CsA injection produced a significant protection against nephrotoxity induced by CsA. The amelioration of nephrotoxicity was evidenced by significant reductions in serum urea and creatinine concentrations. In addition, L-arg prevented the rise of MDA as well as reduction of GSH-Px activity and reduced GSH content in kidney tissue. The protective effects of L-arg against CsA-induced nephrotoxicity were further confirmed by histopathological examination. However, oral supplementation of AG (100 mg kg (-1)day(-1) p.o.) did not protect the kidney from the damaging effects of CsA. These results suggest that L-arg can ameliorate kidney dysfunction induced by CsA via a mechanism(s) which involves the production of nitric oxide. In addition, L-arg may therefore be a beneficial remedy for CsA nephrotoxicity and can be used to improve the therapeutic index of CsA.

Nitric oxide in liver diseases: friend, foe, or just passerby?

Research on the free radical gas, nitric oxide (NO), during the past twenty years is one of the most rapid growing areas in biology. NO seems to play a part in almost every organ and tissue. However, there is considerable controversy and confusion in understanding its role. The liver is one organ that is clearly influenced by NO. Acute versus chronic exposure to NO has been associated with distinct patterns of liver disease. In this paper we review and discuss the involvement of NO in various liver diseases collated from observations by various researchers. Overall, the important factors in determining the beneficial versus harmful effects of NO are the amount, duration, and site of NO production. A low dose of NO serves to maximize blood perfusion, prevent platelet aggregation and thrombosis, and neutralize toxic oxygen radicals in the liver during acute sepsis and reperfusion events. NO also demonstrates antimicrobial and antiapoptosis properties during acute hepatitis infection and other inflammatory processes. However, in the setting of chronic liver inflammation, when a large sustained amount of NO is present, NO might become genotoxic and lead to the development of liver cancer. Additionally, during prolonged ischemia, high levels of NO may have cytotoxic effects leading to severe liver injury. In view of the various possible roles that NO plays, the pharmacologic modulation of NO synthesis is promising in the future treatment of liver diseases, especially with the emergence of selective NO synthase inhibitors and cell-specific NO donors.

Beneficial effect of nitric oxide synthase inhibitor on hepatotoxicity induced by allyl alcohol

The effect of aminoguanidine (a selective inhibitor of inducible nitric oxide synthase) on allyl alcohol-induced liver injury was assessed by the measurement of serum ALT and AST activities and histopathological examination. When aminoguanidine (50-300 mg/kg, i.p.) was administered to mice 30 min before a toxic dose of allyl alcohol (75 microL/kg, i.p.), significant changes related to liver injury were observed. In the presence of aminoguanidine the level of ALT and AST enzymes were significantly decreased. All symptoms of liver necrosis produced by allyl alcohol toxicity almost completely disappeared when animals were pretreated with aminoguanidine at 300 mg/kg. Depletion of hepatic glutathione as a consequence of allyl alcohol metabolism was minimal in mice pretreated with aminoguanidine at 300 mg/kg. It was found that the inhibition of toxicity was not due to alteration in allyl alcohol metabolism since aminoguanidine did not effect alcohol dehydrogenase activity both in vivo and in vitro.

Induction of cardiac cytochrome p450 in cocaine-treated mice

Cytochrome P450 (P450) is a ubiquitous family of enzymes responsible for the metabolism of a wide variety of drugs and their metabolites, including cocaine. To investigate the effects of cocaine on myocardial injuries and cardiac P450 expression, BALB/c mice were injected daily intraperitoneally with cocaine (30 mg/kg) or cocaine plus pretreatment of P450 inhibitors for 14 days. Tumor necrosis factor-alpha (TNF-alpha) content and creatine phosphokinase (CPK) activity in mice hearts and serums were significantly increased after long-term treatment with cocaine. Pretreatment with the P450 inhibitor, cimetidine (Cime, 50 mg/kg) or metyrapone (Mety, 40 mg/kg) abolished or significantly attenuated the effects of cocaine on TNF-alpha and CPK activity. Western blot analysis shows that mouse cardiac tissues express the P450 isoforms CYP1A1, CYP1A2, and CYP2J2. The protein levels normalized with cyclophilin A were 1.20 plus minus 0.07, 0.67 plus minus 0.03, and 1.48 plus minus 0.01 for CYP1A1, CYP1A2, and CYP 2J2, respectively. After cocaine administration, CYP2J2 increased by 43.6% and CYP1A1 increased by 108.5%, but CYP1A2 was not significantly altered. However, the cytochrome P450 inhibitors Cime and Mety suppressed the cocaine-induced increase in CYP1A1 and CYP2J2 expression. Moreover, application of Cime or Mety alone did not alter the level of cardiac TNF-alpha or the expression of P450. Our results demonstrate that long-term exposure to cocaine causes an increase in cardiac CYP1A1 and CYP2J2 concentration. We speculate that induction of P450 isoforms may cause cardiac injury due to cocaine metabolites locally catalyzed by P450 or the increase in P450 expression itself.

Oral cocaine produces dose-related hepatotoxicity in male mice

Cocaine remains a widely abused substance. While most addicts take cocaine intranasally, a considerable number abuse cocaine by mouth. It has been assumed that after oral exposure cocaine is hydrolyzed in the stomach rendering it ineffective. This study investigated the effect of orally administered cocaine on liver function and integrity as well as its effect on liver and blood antioxidative enzymes. Male CF-1 mice were orally administered either 0, 5, 10 or 20 mg cocaine/kg body weight and sacrificed 24 h after the last treatment. Serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were measured as markers of liver injury. Blood and liver glutathione (GSH) levels were determined as well as the activities of glutathione peroxidase (GPx) and catalase (CAT). In addition, the activity of liver glutathione reductase (GRx) was also measured. The results demonstrated that oral cocaine caused hepatotoxicity in a dose dependent manner. Serum ALT and AST were elevated while blood GSH concentration decreased in all cocaine treated animals. In addition, there was a significant dose dependent decrease in the activities of GPx and CAT in blood and liver of cocaine treated animals. However, hepatic GSH content and GRx activity manifested a significant increase, particularly in the group, which received 20 mg/kg cocaine. This study is the first to demonstrate that cocaine-induced hepatotoxicity results following the oral route of administration.

The effects of phencyclidine pretreatment on cocaine-mediated hepatotoxicity in mice

Cocaine-mediated hepatotoxicity (CMH) requires cocaine (CCN) bioactivation by microsomal monooxygenase enzymes that results in cell death. Proposed mechanisms of toxicity involve reactive metabolites that covalently bind to hepatocellular proteins, depletion of cellular reducing equivalents through redox cycling, and/or the generation of reactive oxygen and nitrogen species that alter lipids and proteins. We have previously shown that phencyclidine (PCP) pretreatment potentiated CMH in CF-1 mice without increasing in vitro N-demethylation or N-hydroxylation of CCN. We have now further characterized PCP-potentiated CMH and determined that it is a dose- and time-dependent process, with PCP doses as low as 2.5 mg/kg for 3 days significantly increasing CMH. Immunohistochemistry and histology of livers from mice pretreated with PCP before CCN administration revealed a marked correlation between the regions of CCN metabolite binding and that of necrosis, whereas there was little binding or necrosis in vehicle-pretreated mice. Although hepatic GSH levels were not altered after repetitive PCP treatment alone, a sustained decrease (at least 6 h) in these levels was observed following CCN administration. Inhibitors of inducible nitric oxide synthase (NOS) abrogated PCP-potentiated CMH, although repetitive PCP treatment alone did not increase nitric oxide synthesis systemically or locally in hepatic tissue nor did lipopolysaccharide induction of NOS (without PCP) directly potentiate CMH. The precise mechanisms of PCP potentiation of CMH and involvement of NOS in CMH remain unclear, however, sustained depletion of GSH levels and increased hepatocellular binding of reactive cocaine metabolites have been demonstrated.

Effects of cocaine and its oxidative metabolites on mitochondrial respiration and generation of reactive oxygen species

Cocaine is capable of producing severe hepatocellular necrosis in laboratory animals and humans. The mechanism of cocaine hepatotoxicity is not well understood, but appears to result from the actions of one or more N-oxidative metabolites of cocaine. Mitochondria have been proposed as critical cellular targets for cocaine toxicity, and previous studies have found depressed mitochondrial respiration and increased mitochondrial generation of reactive oxygen species (ROS) in animals treated with cocaine. To examine the potential role of cocaine N-oxidative metabolites in these effects, mitochondrial respiration and ROS generation were examined in isolated mouse mitochondria treated with cocaine and its N-oxidative metabolites-norcocaine, N-hydroxynorcocaine, and norcocaine nitroxide. Cocaine, in concentrations of 0.25 or 0.5 mM, had no effect on state 3 respiration, state 4 respiration, respiratory control ratio (RCR), or ADP/O ratio. Norcocaine (0.5 mM) inhibited state 3 respiration, and N-hydroxynorcocaine (0.5 mM) inhibited both state 3 and state 4 respiration. Norcocaine nitroxide had the greatest effect on mitochondrial respiration; the lower concentration (0.25 mM) completely inhibited both state 3 and state 4 respiration. Preincubation of mitochondria with cocaine or metabolites increased the inhibitory effect of norcocaine and N-hydroxynorcocaine, but not cocaine. Cocaine, norcocaine, and N-hydroxynorcocaine (0.1 mM) had no effect on ROS generation during state 3 respiration, and cocaine and norcocaine decreased ROS generation under state 4 conditions. Norcocaine nitroxide interfered with the fluorescence ROS assay and could not be assessed. The results suggest that the effects of cocaine on mitochondrial respiration are due to its N-oxidative metabolites. Inhibition of mitochondrial respiration by the N-oxidative metabolites of cocaine may be the underlying cause for observed ATP depletion and subsequent cell death.

Protective effect of aminoguanidine, a nitric oxide synthase inhibitor, against carbon tetrachloride induced hepatotoxicity in mice

The present study was undertaken to evaluate the effect of aminoguanidine (AG) on carbon tetrachloride (CCl4)-induced hepatotoxicity. Treatment of mice with CCl4 (20 microl/kg, i.p.) resulted in damage to centrilobular regions of the liver, increase in serum aminotransferase and rise in lipid peroxides level 24 hours after CCl4 administration. Pretreatment of mice with AG (50 mg/kg, i.p.) 30 minutes before CCl4 was found to protect mice from the CCl4-induced hepatic toxicity. This protection was evident from the significant reduction in serum aminotransferase, inhibition of lipid peroxidation and prevention of CCl4-induced hepatic necrosis revealed by histopathology. Aminoguanidine, a relatively specific inhibitor of inducible nitric oxide synthase, did not inhibit the in vitro lipid peroxidation. Taken together, these data suggest a potential role of nitric oxide as an important mediator of CCl4-induced hepatotoxicity.

The role of stimulated lipid peroxidation and impaired calcium sequestration in the enhancement of cocaine induced hepatotoxicity by ethanol

The purpose of this study was to investigate possible mechanism of cocaine-induced hepatotoxicity and its potentiation by ethanol in mice. Ethanol (2 g/kg) and/or cocaine (25 mg/kg) injections were given as binge model (five injections in 3 days). Cocaine administration with or without ethanol caused an increase in lipid peroxidation in liver homogenate and its subcellular fractions. The greatest increases were observed in mitochondrial fraction following cocaine plus ethanol treatment. Also, glutathione (GSH) levels were increased in liver homogenate and its mitochondrial fractions after cocaine and cocaine plus ethanol treatment. Microsomal calcium sequestration was found to decrease in all treatments. These results suggest that increased lipid peroxidation and decreased microsomal calcium sequestration in the liver may play a possible role cocaine-induced hepatotoxicity and its potentiation by ethanol.