Critical role of cytochrome P450 2E1 (CYP2E1) in the development of high fat-induced non-alcoholic steatohepatitis.

BACKGROUND & AIMS: Ethanol-inducible cytochrome P450 2E1 (CYP2E1) activity contributes to oxidative stress. However, CYP2E1 may have an important role in the pathogenesis of high-fat mediated non-alcoholic steatohepatitis (NASH). Thus, the role of CYP2E1 in high-fat mediated NASH development was evaluated. METHODS: Male wild type (WT) and Cyp2e1-null mice were fed a low-fat diet (LFD, 10% energy-derived) or a high-fat diet (HFD, 60% energy-derived) for 10 weeks. Liver histology and tissue homogenates were examined for various parameters of oxidative stress and inflammation. RESULTS: Liver histology showed that only WT mice fed a HFD developed NASH despite the presence of increased steatosis in both WT and Cyp2e1-null mice fed HFD. Markers of oxidative stress such as elevated CYP2E1 activity and protein amounts, lipid peroxidation, protein carbonylation, nitration, and glycation with increased phospho-JNK were all markedly elevated only in the livers of HFD-fed WT mice. Furthermore, while the levels of inflammation markers osteopontin and F4/80 were higher in HFD-fed WT mice, TNFα and MCP-1 levels were lower compared to the corresponding LFD-fed WT. Finally, only HFD-fed WT mice exhibited increased insulin resistance and impaired glucose tolerance. CONCLUSIONS: These data suggest that CYP2E1 is critically important in NASH development by promoting oxidative/nitrosative stress, protein modifications, inflammation, and insulin resistance.

The influence of estrogen on hepatobiliary osteopontin (SPP1) expression in a female rodent model of alcoholic steatohepatitis.

Our recent studies suggest that higher neutrophil infiltration in females correlates with increased hepatobiliary expression of osteopontin (OPN) in alcoholic steatohepatitis (ASH). The objective of this study was to understand the role of alcohol in altering estrogen levels in females by examining the effect of ethanol (EtOH) on the estrous cycle and then investigate the potential relationship between estradiol (E2) and hepatobiliary OPN expression in a female rat ASH model. Ovariectomized (OVX) and E2-implanted OVX rats in the ASH group were evaluated for OPN mRNA and protein expression. Low doses of E2 resulted in significant down-regulation of OPN protein and mRNA as compared to the OVX group. However, with increasing doses of E2, there was up-regulation of both OPN mRNA and protein. Osteopontin was localized primarily to the biliary epithelium. Liver injury assessed by serum ALT and histopathology revealed a pattern similar to OPN expression. In all groups, hepatic neutrophilic infiltration correlated positively with OPN expression. Based on these data, we conclude that in our ASH model, low doses of E2 appear to be hepatoprotective, whereas the protective effect appears to diminish with increasing doses of E2, although additional cause and effect studies are needed for confirmation.

N-acetylcysteineamide (NACA) prevents inflammation and oxidative stress in animals exposed to diesel engine exhaust.

Diesel exhaust particles (DEPs), a by-product of diesel engine exhaust (DEE), are one of the major components of air borne particulate matter (PM) in the urban environment. DEPs are composed of soot, polycyclic aromatic hydrocarbons (PAHs), redox active semi-quinones, and transition metals, which are known to produce pro-oxidative and pro-inflammatory effects, thereby leading to oxidative stress-induced damage in the lungs. The objective of this study was to determine if N-acetylcysteineamide (NACA), a novel thiol antioxidant, confers protection to animals exposed to DEPs from oxidative stress-induced damage to the lung. To study this, male C57BL/6 mice, pretreated with either NACA (250mg/kg body weight) or saline, were exposed to DEPs (15mg/m(3)) or filtered air (1.5-3h/day) for nine consecutive days. The animals were sacrificed 24h after the last exposure. NACA-treated animals exposed to DEP had significant decreases in the number of macrophages and the amount of mucus plug formation in the lungs, as compared to the DEP-only exposed animals. In addition, DEP-exposed animals, pretreated with NACA, also experienced significantly lower oxidative stress than the untreated group, as indicated by the glutathione (GSH), and malondialdehyde (MDA) levels and catalase (CAT) activity. Further, DEP-induced toxicity in the lungs was reversed in NACA-treated animals, as indicated by the lactate dehydrogenase levels. Taken together, these data suggest that the thiol-antioxidant, NACA, can protect the lungs from DEP-induced inflammation and oxidative stress related damage.

Identification of proteins to predict the molecular basis for the observed gender susceptibility in a rat model of alcoholic steatohepatitis by 2-D gel proteomics.

Females are reported to be highly susceptible to alcoholic steatohepatitis (ASH) compared to the males. Although a variety of mechanisms have been proposed to explain this higher sensitivity of females, the precise mechanism is not well understood. The objective of this study was to identify changes in global protein expression in liver tissues of male and female rats with pathologically evident ASH by 2-DE (dimensional electrophoresis). ASH was induced in the SD (Sprague-Dawley) rats by feeding ethanol (EtOH) containing Lieber-DeCarli diet for 6 wk followed by a single injection of lipopolysaccharide (LPS, 10 mg/kg, i.p.). Higher liver injury in females in the ASH group as compared to the males was confirmed by HE stained liver sections. As identified by 2-DE, 22 protein-spots were differentially expressed in the females in the ASH group as compared to the males. Following identification of these proteins by MALDI-MS, they were mainly categorized into metabolism and oxidative stress-related proteins. The expression pattern of a few of these oxidative stress-related proteins like Ferritin Heavy chain (Ferritin-H chain), ER stress protein 60 (ER 60) and Heat-shock protein-60 (HSP 60) were verified by Western blotting. To conclude, the current study has identified a set of proteins that highlights potential novel mechanisms associated with higher liver injury noted in the female rat ASH model.

Interaction of osteopontin with neutrophil alpha(4)beta(1) and alpha(9)beta(1) integrins in a rodent model of alcoholic liver disease.

Previous studies from our laboratory have reported that osteopontin (OPN) mediated higher hepatic neutrophil infiltration makes female rats more susceptible to alcoholic steatohepatitis (ASH) than their male counterparts. The objective of the current work was to investigate the patho-mechanism by which OPN attracts the hepatic neutrophils in ASH. We hypothesized that OPN-mediated hepatic neutrophil infiltration is a result of signaling by N-terminal integrin binding motif (SLAYGLR) of OPN through its receptor alpha(9)beta(1) (VLA9) and alpha(4)beta(1) (VLA4) integrins on neutrophils. Compared to the males, females in the ASH group exhibited higher expression of alpha(4)beta(1) and alpha(9)beta(1) protein and mRNA and a significant decrease in the expression of these integrins was observed in rats treated with neutralizing OPN antibody. Immunoprecipitation experiments suggested the binding of OPN to alpha(4)beta(1) and alpha(9)beta(1) integrins. OPN-mediated neutrophil infiltration was also confirmed using Boyden chamber assays, and antibodies directed against alpha(4) and beta(1) integrins was found to significantly inhibit neutrophilic migration in vitro. In conclusion, these data suggest that SLAYGLR-mediated alpha(4)beta(1) and alpha(9)beta(1) integrin signaling may be responsible for higher hepatic neutrophil infiltration and higher liver injury in the rat ASH model.

Cytochrome P450-2E1 promotes fast food-mediated hepatic fibrosis.

Cytochrome P450-2E1 (CYP2E1) increases oxidative stress. High hepatic cholesterol causes non-alcoholic steatohepatitis (NASH) and fibrosis. Thus, we aimed to study the role of CYP2E1 in promoting liver fibrosis by high cholesterol-containing fast-food (FF). Male wild-type (WT) and Cyp2e1-null mice were fed standard chow or FF for 2, 12, and 24 weeks. Various parameters of liver fibrosis and potential mechanisms such as oxidative and endoplasmic reticulum (ER) stress, inflammation, and insulin resistance (IR) were studied. Indirect calorimetry was also used to determine metabolic parameters. Liver histology showed that only WT fed FF (WT-FF) developed NASH and fibrosis. Hepatic levels of fibrosis protein markers were significantly increased in WT-FF. The nitroxidative stress marker iNOS, but not CYP2E1, was significantly elevated only in FF-fed WT. Serum endotoxin, TLR-4 levels, and inflammatory markers were highest in WT-FF. FAS, PPAR-α, PPAR-γ, and CB1-R were markedly altered in WT-FF. Electron microscopy and immunoblot analyses showed significantly higher levels of ER stress in FF-fed WT. Indirect calorimetry showed that Cyp2e1-null-mice fed FF exhibited consistently higher total energy expenditure (TEE) than their corresponding WT. These results demonstrate that CYP2E1 is important in fast food-mediated liver fibrosis by promoting nitroxidative and ER stress, endotoxemia, inflammation, IR, and low TEE.

Increased Sensitivity to Binge Alcohol-Induced Gut Leakiness and Inflammatory Liver Disease in HIV Transgenic Rats.

The mechanisms of alcohol-mediated advanced liver injury in HIV-infected individuals are poorly understood. Thus, this study was aimed to investigate the effect of binge alcohol on the inflammatory liver disease in HIV transgenic rats as a model for simulating human conditions. Female wild-type (WT) or HIV transgenic rats were treated with three consecutive doses of binge ethanol (EtOH) (3.5 g/kg/dose oral gavages at 12-h intervals) or dextrose (Control). Blood and liver tissues were collected at 1 or 6-h following the last dose of ethanol or dextrose for the measurements of serum endotoxin and liver pathology, respectively. Compared to the WT, the HIV rats showed increased sensitivity to alcohol-mediated gut leakiness, hepatic steatosis and inflammation, as evidenced with the significantly elevated levels of serum endotoxin, hepatic triglycerides, histological fat accumulation and F4/80 staining. Real-time PCR analysis revealed that hepatic levels of toll-like receptor-4 (TLR4), leptin and the downstream target monocyte chemoattractant protein-1 (MCP-1) were significantly up-regulated in the HIV-EtOH rats, compared to all other groups. Subsequent experiments with primary cultured cells showed that both hepatocytes and hepatic Kupffer cells were the sources of the elevated MCP-1 in HIV-EtOH rats. Further, TLR4 and MCP-1 were found to be upregulated by leptin. Collectively, these results show that HIV rats, similar to HIV-infected people being treated with the highly active anti-retroviral therapy (HAART), are more susceptible to binge alcohol-induced gut leakiness and inflammatory liver disease than the corresponding WT, possibly due to additive or synergistic interaction between binge alcohol exposure and HIV infection. Based on these results, HIV transgenic rats can be used as a surrogate model to study the molecular mechanisms of many disease states caused by heavy alcohol intake in HIV-infected people on HAART.

Critical role of c-jun N-terminal protein kinase in promoting mitochondrial dysfunction and acute liver injury.

The mechanism by which c-Jun N-terminal protein kinase (JNK) promotes tissue injury is poorly understood. Thus we aimed at studying the roles of JNK and its phospho-target proteins in mouse models of acute liver injury. Young male mice were exposed to a single dose of CCl4 (50mg/kg, IP) and euthanized at different time points. Liver histology, blood alanine aminotransferase, and other enzyme activities were measured in CCl4-exposed mice without or with the highly-specific JNK inhibitors. Phosphoproteins were purified from control or CCl4-exposed mice and analyzed by differential mass-spectrometry followed by further characterizations of immunoprecipitation and activity measurements. JNK was activated within 1h while liver damage was maximal at 24h post-CCl4 injection. Markedly increased phosphorylation of many mitochondrial proteins was observed between 1 and 8h following CCl4 exposure. Pretreatment with the selective JNK inhibitor SU3327 or the mitochondria-targeted antioxidant mito-TEMPO markedly reduced the levels of p-JNK, mitochondrial phosphoproteins and liver damage in CCl4-exposed mice. Differential proteomic analysis identified many phosphorylated mitochondrial proteins involved in anti-oxidant defense, electron transfer, energy supply, fatty acid oxidation, etc. Aldehyde dehydrogenase, NADH-ubiquinone oxidoreductase, and α-ketoglutarate dehydrogenase were phosphorylated in CCl4-exposed mice but dephosphorylated after SU3327 pretreatment. Consistently, the suppressed activities of these enzymes were restored by SU3327 pretreatment in CCl4-exposed mice. These data provide a novel mechanism by which JNK, rapidly activated by CCl4, promotes mitochondrial dysfunction and acute hepatotoxicity through robust phosphorylation of numerous mitochondrial proteins.

Acute and subacute pulmonary toxicity and mortality in mice after intratracheal instillation of ZnO nanoparticles in three laboratories.

Inhalation is the main pathway of ZnO exposure in the occupational environment but only few studies have addressed toxic effects after pulmonary exposure to ZnO nanoparticles (NP). Here we present results from three studies of pulmonary exposure and toxicity of ZnO NP in mice. The studies were prematurely terminated because interim results unexpectedly showed severe pulmonary toxicity. High bolus doses of ZnO NP (25 up to 100 µg; ≥1.4 mg/kg) were clearly associated with a dose dependent mortality in the mice. Lower doses (≥6 µg; ≥0.3 mg/kg) elicited acute toxicity in terms of reduced weight gain, desquamation of epithelial cells with concomitantly increased barrier permeability of the alveolar/blood as well as DNA damage. Oxidative stress was shown via a strong increase in lipid peroxidation and reduced glutathione in the pulmonary tissue. Two months post-exposure revealed no obvious toxicity for 12.5 and 25 µg on a range of parameters. However, mice that survived a high dose (50 µg; 2.7 mg/kg) had an increased pulmonary collagen accumulation (fibrosis) at a similar level as a high bolus dose of crystalline silica. The recovery from these toxicological effects appeared dose-dependent. The results indicate that alveolar deposition of ZnO NP may cause significant adverse health effects.

Binge alcohol promotes hypoxic liver injury through a CYP2E1-HIF-1α-dependent apoptosis pathway in mice and humans.

Binge drinking, a common pattern of alcohol ingestion, is known to potentiate liver injury caused by chronic alcohol abuse. This study was aimed at investigating the effects of acute binge alcohol on hypoxia-inducible factor-1α (HIF-1α)-mediated liver injury and the roles of alcohol-metabolizing enzymes in alcohol-induced hypoxia and hepatotoxicity. Mice and human specimens assigned to binge or nonbinge groups were analyzed for blood alcohol concentration (BAC), alcohol-metabolizing enzymes, HIF-1α-related protein nitration, and apoptosis. Binge alcohol promoted acute liver injury in mice with elevated levels of ethanol-inducible cytochrome P450 2E1 (CYP2E1) and hypoxia, both of which were colocalized in the centrilobular areas. We observed positive correlations among elevated BAC, CYP2E1, and HIF-1α in mice and humans exposed to binge alcohol. The CYP2E1 protein levels (r = 0.629, p = 0.001) and activity (r = 0.641, p = 0.001) showed a significantly positive correlation with BAC in human livers. HIF-1α levels were also positively correlated with BAC (r = 0.745, p < 0.001) or CYP2E1 activity (r = 0.792, p < 0.001) in humans. Binge alcohol promoted protein nitration and apoptosis with significant correlations observed between inducible nitric oxide synthase and BAC, CYP2E1, or HIF-1α in human specimens. Binge-alcohol-induced HIF-1α activation and subsequent protein nitration or apoptosis seen in wild type were significantly alleviated in the corresponding Cyp2e1-null mice, whereas pretreatment with an HIF-1α inhibitor, PX-478, prevented HIF-1α elevation with a trend of decreased levels of 3-nitrotyrosine and apoptosis, supporting the roles of CYP2E1 and HIF-1α in binge-alcohol-mediated protein nitration and hepatotoxicity. Thus binge alcohol promotes acute liver injury in mice and humans at least partly through a CYP2E1-HIF-1α-dependent apoptosis pathway.

Zidovudine (AZT) and hepatic lipid accumulation: implication of inflammation, oxidative and endoplasmic reticulum stress mediators.

The clinical effectiveness of Zidovudine (AZT) is constrained due to its side-effects including hepatic steatosis and toxicity. However, the mechanism(s) of hepatic lipid accumulation in AZT-treated individuals is unknown. We hypothesized that AZT-mediated oxidative and endoplasmic reticulum (ER) stress may play a role in the AZT-induced hepatic lipid accumulation. AZT treatment of C57BL/6J female mice (400 mg/day/kg body weight, i.p.) for 10 consecutive days significantly increased hepatic triglyceride levels and inflammation. Markers of oxidative stress such as protein oxidation, nitration, glycation and lipid peroxidation were significantly higher in the AZT-treated mice compared to vehicle controls. Further, the levels of ER stress marker proteins like GRP78, p-PERK, and p-eIF2α were significantly elevated in AZT-treated mice. The level of nuclear SREBP-1c, a transcription factor involved in fat synthesis, was increased while significantly decreased protein levels of phospho-acetyl-CoA carboxylase, phospho-AMP kinase and PPARα as well as inactivation of 3-keto-acyl-CoA thiolase in the mitochondrial fatty acid ß-oxidation pathway were observed in AZT-exposed mice compared to those in control animals. Collectively, these data suggest that elevated oxidative and ER stress plays a key role, at least partially, in lipid accumulation, inflammation and hepatotoxicity in AZT-treated mice.

Robust protein nitration contributes to acetaminophen-induced mitochondrial dysfunction and acute liver injury.

Acetaminophen (APAP), a widely used analgesic/antipyretic agent, can cause liver injury through increased nitrative stress, leading to protein nitration. However, the identities of nitrated proteins and their roles in hepatotoxicity are poorly understood. Thus, we aimed at studying the mechanism of APAP-induced hepatotoxicity by systematic identification and characterization of nitrated proteins in the absence or presence of an antioxidant, N-acetylcysteine (NAC). The levels of nitrated proteins markedly increased at 2h in mice exposed to a single APAP dose (350mg/kg ip), which caused severe liver necrosis at 24h. Protein nitration and liver necrosis were minimal in mice exposed to nontoxic 3-hydroxyacetanilide or animals co-treated with APAP and NAC. Mass-spectral analysis of the affinity-purified nitrated proteins identified numerous mitochondrial and cytosolic proteins, including mitochondrial aldehyde dehydrogenase, Mn-superoxide dismutase, glutathione peroxidase, ATP synthase, and 3-ketoacyl-CoA thiolase, involved in antioxidant defense, energy supply, or fatty acid metabolism. Immunoprecipitation followed by immunoblot with anti-3-nitrotyrosine antibody confirmed that the aforementioned proteins were nitrated in APAP-exposed mice but not in NAC-cotreated mice. Consistently, NAC cotreatment significantly restored the suppressed activity of these enzymes. Thus, we demonstrate a new mechanism by which many nitrated proteins with concomitantly suppressed activity promotes APAP-induced mitochondrial dysfunction and hepatotoxicity.

CYP2E1 potentiates binge alcohol-induced gut leakiness, steatohepatitis, and apoptosis.

Ethanol-inducible cytochrome P450 2E1 (CYP2E1) contributes to increased oxidative stress and steatosis in chronic alcohol-exposure models. However, its role in binge ethanol-induced gut leakiness and hepatic injury is unclear. This study was aimed at investigating the role of CYP2E1 in binge alcohol-induced gut leakiness and the mechanisms of steatohepatitis. Female wild-type (WT) and Cyp2e1-null mice were treated with three doses of binge ethanol (WT-EtOH or Cyp2e1-null-EtOH) (6g/kg oral gavage at 12-h intervals) or dextrose (negative control). Intestinal histology of only WT-EtOH exhibited epithelial alteration and blebbing of lamina propria, and liver histology obtained at 6h after the last ethanol dose showed elevated steatosis with scattered inflammatory foci. These were accompanied by increased levels of serum endotoxin, hepatic enterobacteria, and triglycerides. All these changes, including the intestinal histology and hepatic apoptosis, determined by TUNEL assay, were significantly reversed when WT-EtOH mice were treated with the specific inhibitor of CYP2E1 chlormethiazole and the antioxidant N-acetylcysteine, both of which suppressed oxidative markers including intestinal CYP2E1. WT-EtOH also exhibited elevated amounts of serum TNF-α, hepatic cytokines, CYP2E1, and lipid peroxidation, with decreased levels of mitochondrial superoxide dismutase and suppressed aldehyde dehydrogenase 2 activity. Increased hepatocyte apoptosis with elevated levels of proapoptotic proteins and decreased levels of active (phosphorylated) p-AKT, p-AMPK, and peroxisome proliferator-activated receptor-α, all of which are involved in fat metabolism and inflammation, were observed in WT-EtOH. These changes were significantly attenuated in the corresponding Cyp2e1-null-EtOH mice. These data indicate that both intestinal and hepatic CYP2E1 induced by binge alcohol seems critical in binge alcohol-mediated increased nitroxidative stress, gut leakage, and endotoxemia; altered fat metabolism; and inflammation contributing to hepatic apoptosis and steatohepatitis.

Pulmonary DWCNT exposure causes sustained local and low-level systemic inflammatory changes in mice.

Carbon nanotubes (CNTs) represent promising vectors to facilitate cellular drug delivery and to overcome biological barriers, but some types may also elicit persistent pulmonary inflammation based on their fibre characteristics. Here, we show the pulmonary response to aqueous suspensions of block copolymer dispersed, double-walled carbon nanotubes (DWCNT, length 1-10 µm) in mice by bronchoalveolar lavage (BAL) analysis, and BAL and blood cytokine and lung antioxidant profiling. The intratracheally instilled dose of 50 µg DWCNT caused significant pulmonary inflammation that was not resolved during a 7-day observation period. Light microscopy investigation of the uptake of DWCNT agglomerates revealed no particle ingestion for granulocytes, but only for macrophages. Accumulating macrophage, multinucleated macrophage and lymphocyte numbers in the alveolar region further indicated ineffective resolution with chronification of the inflammation. The local inflammatory impairment of the lung was accompanied by pulmonary antioxidant depletion and haematological signs of systemic inflammation. While the observed inflammation during its acute phase was dominated by neutrophils and neutrophil recruiting cytokines, the contribution of macrophages and lymphocytes with related cytokines became more significant after day 3 of exposure. This study confirms that acute pulmonary toxicity can occur on exposure of high doses of DWCNT agglomerates and offers further insight for improved nanotube design parameters to avoid potential long-term toxicity.

Highly active antiretroviral therapy drug combination induces oxidative stress and mitochondrial dysfunction in immortalized human blood-brain barrier endothelial cells.

The era of highly active antiretroviral therapy (HAART) has controlled AIDS and its related disorders considerably; however, the prevalence of HIV-1-associated neurocognitive disorders has been on the rise in the post-HAART era. In view of these developments, we investigated whether a HAART drug combination of 3'-azido-2',3'-deoxythymidine (AZT) and indinavir (IDV) can alter the functionality of the blood-brain barrier (BBB) endothelial cells, thereby exacerbating this condition. The viability of hCMEC/D3 cells (in vitro model of BBB) that were exposed to these drugs was significantly reduced after 72h treatment, in a dose-dependent manner. Reactive oxygen species were highly elevated after the exposure, indicating that mechanisms that induce oxidative stress were involved. Measures of oxidative stress parameters, such as glutathione and malondialdehyde, were altered in the treated groups. Loss of mitochondrial membrane potential, as assessed by fluorescence microscopy and decreased levels of ATP, indicated that cytotoxicity was mediated through mitochondrial dysfunction. Furthermore, AZT+IDV treatment caused apoptosis in endothelial cells, as assessed by the expression of cytochrome c and procaspase-3 proteins. Pretreatment with the thiol antioxidant N-acetylcysteine amide reversed some of the pro-oxidant effects of AZT+IDV. Results from our in vitro studies indicate that the AZT+IDV combination may affect the BBB in HIV-infected individuals treated with HAART drugs.

Inflammatory responses to pulmonary application of PEI-based siRNA nanocarriers in mice.

Polymeric non-viral vector systems for pulmonary application of siRNA are promising carriers, but have failed to enter clinical trials because of safety and efficiency problems. Therefore, improving their transfection efficiency, as well as their toxicological profile, is the subject of intensive research efforts. Six different poly(ethylene imine) (PEI)-based nanocarriers, with hydrophilic and hydrophobic PEG modifications, were toxicologically evaluated for pulmonary application in mice. Nanocarriers were intratracheally instilled to determine their toxicological profile, with particular focus on the inflammatory response in the lungs. Nanocarriers from both groups caused an acute inflammatory response in the lungs, albeit with different resolution kinetics and cytotoxicity. Hydrophobic modifications caused a severe inflammatory response with increased epithelial barrier permeability, accompanied by an acute antioxidant response. Hydrophilic modifications, with high PEG-grafting degrees, induced less proinflammatory effects without depleting macrophages and disrupting the epithelial/endothelial barrier in the lungs, while showing only a minor oxidative stress response. For pulmonary applications, local proinflammatory effects should be optimized by further development of nanocarriers with highly grafted PEG-PEI-based carriers or Jeffamine-modified hydrophobic PEI modifications.

HIV proteins (gp120 and Tat) and methamphetamine in oxidative stress-induced damage in the brain: potential role of the thiol antioxidant N-acetylcysteine amide.

An increased risk of HIV-1 associated dementia (HAD) has been observed in patients abusing methamphetamine (METH). Since both HIV viral proteins (gp120, Tat) and METH induce oxidative stress, drug abusing patients are at a greater risk of oxidative stress-induced damage. The objective of this study was to determine if N-acetylcysteine amide (NACA) protects the blood brain barrier (BBB) from oxidative stress-induced damage in animals exposed to gp120, Tat and METH. To study this, CD-1 mice pre-treated with NACA/saline, received injections of gp120, Tat, gp120+Tat or saline for 5days, followed by three injections of METH/saline on the fifth day, and sacrificed 24h after the final injection. Various oxidative stress parameters were measured, and animals treated with gp120+Tat+Meth were found to be the most challenged group, as indicated by their GSH and MDA levels. Treatment with NACA significantly rescued the animals from oxidative stress. Further, NACA-treated animals had significantly higher expression of TJ proteins and BBB permeability as compared to the group treated with gp120+Tat+METH alone, indicating that NACA can protect the BBB from oxidative stress-induced damage in gp120, Tat and METH exposed animals, and thus could be a viable therapeutic option for patients with HAD.

N-Acetylcysteine amide protects against methamphetamine-induced oxidative stress and neurotoxicity in immortalized human brain endothelial cells.

Oxidative stress plays an important role in neurodegenerative disorders such as Parkinson's disease and Alzheimer's disease. Methamphetamine (METH) is an amphetamine analog that causes degeneration of the dopaminergic system in mammals and subsequent oxidative stress. In our present study, we have used immortalized human brain microvascular endothelial (HBMVEC) cells to test whether N-acetylcysteine amide (NACA), a novel antioxidant, prevents METH-induced oxidative stress in vitro. Our studies showed that NACA protects against METH-induced oxidative stress in HBMVEC cells. NACA significantly protected the integrity of our blood brain barrier (BBB) model, as shown by permeability and trans-endothelial electrical resistance (TEER) studies. NACA also significantly increased the levels of intracellular glutathione (GSH) and glutathione peroxidase (GPx). Malondialdehyde (MDA) levels increased dramatically after METH exposure, but this increase was almost completely prevented when the cells were treated with NACA. Generation of reactive oxygen species (ROS) also increased after METH exposure, but was reduced to control levels with NACA treatment, as measured by dichlorofluorescin (DCF). These results suggest that NACA protects the BBB integrity in vitro, which could prevent oxidative stress-induced damage; therefore, the effectiveness of this antioxidant should be evaluated for the treatment of neurodegenerative diseases in the future.

Potential relationship between hepatobiliary osteopontin and peroxisome proliferator-activated receptor alpha expression following ethanol-associated hepatic injury in vivo and in vitro.

Osteopontin (OPN) up-regulation is known to mediate hepatic inflammation in a rodent model of alcoholic liver disease (ALD) and alcohol ingestion is reported to inhibit hepatic peroxisome proliferator-activated receptor-alpha (PPAR-alpha) activity leading to hepatic steatosis and inflammation. Therefore, the objective of this study was to investigate the potential relationship between the anti-inflammatory PPAR-alpha and proinflammatory OPN in rats and mice livers, and cell cultures of hepatocytes and biliary epithelium. Experiments were designed to evaluate the influence of ethanol (EtOH), lipopolysaccharide (LPS), and acetaldehyde (ACA) on OPN and PPAR-alpha expression levels in vivo (rats and mice) and in vitro (hepatocytes and biliary epithelium). Adult Sprague-Dawley rats and C57BL6 mice were fed EtOH-containing Lieber-DeCarli liquid diet for 6 weeks and injected with a single dose of LPS. A combination of EtOH and LPS treated rats and mice showed significant induction of hepatic OPN expression compared with the controls. Similarly, cells exposed to physiological doses of EtOH, LPS, a combination of EtOH and LPS, and ACA resulted in increased OPN protein and mRNA expression. Rats and mice in ALD model and cells treated with EtOH and ACA showed downregulation of PPAR-alpha mRNA. Also, DNA binding activity of PPAR-alpha to PPAR response element was significantly reduced following treatment. Overexpression of PPAR-alpha rescued the reduced PPAR-alpha activity and PPAR-alpha agonist, bezafibrate, elevated PPAR-alpha activity after treatment of EtOH, LPS, and ACA when cells were exposed by bezafibrate. To further delineate the potential relationship between OPN and PPAR-alpha, OPN(-/-) mice showed no change of PPAR-alpha mRNA level although wild-type mice showed downregulation of PPAR-alpha mRNA after EtOH treatment. In conclusion, the current study suggests that OPN is induced by EtOH and its metabolite ACA and opposite relationship likely exist between PPAR-alpha and OPN expression within the liver during ALD.