Downregulation of the gene expression of Cyp2c29 and Cyp3a11 by cecal ligation and puncture-induced sepsis is associated with interleukin-6

Sepsis is a pathological condition that affects the metabolism of administered drugs, leading to changes in the duration and intensity of their intended efficacies. Proinflammatory cytokines downregulate the expression of cytochrome P450s (P450s). The effects of P450 expression under inflammatory conditions have been studied using prophlogistic substances such as lipopolysaccharide; however, few studies have focused on clinical models of sepsis. Here, we show that cecal ligation and puncture (CLP), an approach for the study of human polymicrobial sepsis, leads to the expression of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor α (TNFα) at 24 h after the CLP operation. Following CLP, IL-6^-/- mice exhibited markedly lower survival than WT mice. In addition, CLP led to the significant downregulation of Cyp2c29 and Cyp3a11 gene expression in IL-1α^-/-/β^-/- (IL-1^-/-) and TNFα^-/- mice as well as in WT mice. In contrast, CLP elicited no significant effect on Cyp3a11 expression in IL-6^-/- mice. Although CLP reduced the Cyp2c29 expression level in IL-6^-/- mice, the expression of Cyp2c29 was lower in CLP-operated WT mice than in CLP-operated IL-6^-/- mice. The reduction in the respective P450 protein levels and activities due to CLP-induced sepsis, reflected in the mRNA expression levels, was abolished by IL-6 depletion. Thus, CLP-induced sepsis downregulates P450 gene expression, particularly Cyp2c expression, and this effect is associated with IL-6 without affecting resistance to CLP-induced sepsis. These findings demonstrate the usefulness of CLP for studying the regulation of P450s and highlight IL-6 as a potential indicator of drug-metabolizing capacity under septic conditions.

Auranofin and Pharmacologic Ascorbate as Radiomodulators in the Treatment of Pancreatic Cancer

Pancreatic cancer accounts for nearly one fourth of all new cancers worldwide. Little progress in the development of novel or adjuvant therapies has been made over the past few decades and new approaches to the treatment of pancreatic cancer are desperately needed. Pharmacologic ascorbate (P-AscH⁻, high-dose, intravenous vitamin C) is being investigated in clinical trials as an adjunct to standard-of-care chemoradiation treatments. In vitro, P-AscH⁻ has been shown to sensitize cancer cells to ionizing radiation in a manner that is dependent on the generation of H₂O₂ while simultaneously protecting normal tissue from radiation damage. There is renewed interest in Auranofin (Au), an FDA-approved medication utilized in the treatment of rheumatoid arthritis, as an anti-cancer agent. Au inhibits the thioredoxin antioxidant system, thus increasing the overall peroxide burden on cancer cells. In support of current literature demonstrating Au’s effectiveness in breast, colon, lung, and ovarian cancer, we offer additional data that demonstrate the effectiveness of Au alone and in combination with P-AscH⁻ and ionizing radiation in pancreatic cancer treatment. Combining P-AscH⁻ and Au in the treatment of pancreatic cancer may confer multiple mechanisms to increase H₂O₂-dependent toxicity amongst cancer cells and provide a promising translatable avenue by which to enhance radiation effectiveness and improve patient outcomes.

Nrf2 Antioxidative System is Involved in Cytochrome P450 Gene Expression and Activity: A Delay in Pentobarbital Metabolism in Nrf2-Deficient Mice

NF-E2-related factor 2 (Nrf2) is a transcriptional regulator of biologic defense proteins, such as antioxidant proteins and phase II detoxification enzymes. Cytochrome P450 (P450) enzymes have been shown to regulate phase I metabolism of various drugs and are partially regulated by Nrf2; however, the influence of Nrf2 on drug pharmacokinetics is not known. Here, we showed that Nrf2 depletion prolonged the effect of pentobarbital, a sleep-promoting drug. Pretreatment with phenobarbital, a P450 inducer, shortens the sleeping time associated with pentobarbital-induced sedation in wild-type (WT) mice; however, this effect was not observed in Nrf2^-/- mice. Furthermore, the blood pentobarbital concentration was higher in Nrf2^-/- mice than in WT mice at 30-60 minutes, and the phenobarbital-induced enhancement of its clearance was attenuated in Nrf2^-/- mice compared with WT mice. Total P450 content was decreased in Nrf2^-/- mouse livers, and the phenobarbital-induced increase in P450 content was lower in Nrf2^-/- mice than WT mice. Cyp1a2, Cyp2a5, Cyp2c29, and Cyp2e1 gene expression levels under physiologic conditions and Cyp1a2, Cyp2a5, and Cyp2b10 gene expression levels under phenobarbital-treated conditions were lower in Nrf2^-/- mice compared with WT mice. Additionally, pentobarbital metabolism in liver microsomes was attenuated by Nrf2 depletion. Taken together, these findings suggested that Nrf2 influenced pentobarbital pharmacokinetics through the regulation of drug metabolism and P450 gene expression. Thus, Nrf2-mediated regulation of P450 may contribute to the biologic defense against increased reactive oxygen species production. SIGNIFICANCE STATEMENT: NF-E2-related factor 2 (Nrf2) plays a critical role in the cellular defense against oxidative stress. Nrf2^-/- mice with reduced ability to eliminate reactive oxygen species (ROS) showed a significant delay in emergence from pentobarbital-induced sleep, which was associated with decreased P450 activities and gene expression. Our findings provide that Nrf2 dysfunction or ROS that exceed a threshold level of the eliminating ability of the Nrf2 system may reduce P450 activity.

Genetic depletion of p53 attenuates cocaine-induced hepatotoxicity in mice

Cocaine, an addictive drug, is known to induce hepatotoxicity via oxidative damage and proapoptosis. Since p53, a tumor suppressor gene, plays a major role in inducing oxidative stress and apoptosis, we examined the role of p53 inhibition against cocaine-induced hepatotoxicity. Cocaine treatment significantly increased oxidative parameters (i.e., reactive oxygen species, 4-hydroxylnonenal, and protein carbonyl) in the liver of wild type (WT) mice. We found that the pharmacological (i.e. pifithrin-α) and genetic (i.e. p53 knockout) inhibition of p53 significantly attenuates cocaine-induced hepatotoxicity. Cocaine treatment increased alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels in the serum of mice, signifying hepatic damage. Consistently, these increases were attenuated by inhibition of p53, implying protection against cocaine-induced hepatic damage. In addition, cocaine treatment significantly increased PKCδ, cleaved PKCδ and p53 levels in the liver of WT mice. These increases were followed by the interaction between p53 and PKCδ, and pro-apoptotic consequences (i.e., cytosolic release of cytochrome c, activation of caspase-3, increase in Bax level and decreases in Bcl-2 and Bcl-xL levels). These changes were attenuated by p53 depletion, reflecting that the critical role of PKCδ in p53-mediated apoptotic potentials. Combined, our results suggest that the inhibition of p53 is important for protection against oxidative burdens, pro-apoptotic events, and hepatic degeneration induced by cocaine.

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.

Evaluating New Compounds to Treat Burkholderia pseudomallei Infections

Burkholderia pseudomallei is the causative agent of melioidosis, a disease that requires long-term treatment regimens with no assurance of bacterial clearance. Clinical isolates are intrinsically resistant to most antibiotics and in recent years, isolates have been collected that display resistance to frontline drugs. With the expanding global burden of B. pseudomallei, there is a need to identify new compounds or improve current treatments to reduce risk of relapse. Using the Pathogen Box generated by Medicines for Malaria Venture, we screened a library of 400 compounds for bacteriostatic or bactericidal activity against B. pseudomallei K96243 and identified seven compounds that exhibited inhibitory effects. New compounds found to have function against B. pseudomallei were auranofin, rifampicin, miltefosine, MMV688179, and MMV688271. An additional two compounds currently used to treat melioidosis, doxycycline and levofloxacin, were also identified in the screen. We determined that the minimal inhibitory concentrations (MIC) for levofloxacin, doxycycline, and MMV688271 were below 12 μg/ml for 5 strains of B. pseudomallei. To assess persister frequency, bacteria were exposed to 100x MIC of each compound. Auranofin, MMV688179, and MMV688271 reduced the bacterial population to an average of 4.53 × 10⁻⁶% compared to ceftazidime, which corresponds to 25.1% survival. Overall, our data demonstrates that auranofin, MMV688197, and MMV688271 have the potential to become repurposed drugs for treating melioidosis infections and the first evidence that alternative therapeutics can reduce B. pseudomallei persistence.

Date fruits inhibit hepatocyte apoptosis and modulate the expression of hepatocyte growth factor, cytochrome P450 2E1 and heme oxygenase-1 in carbon tetrachloride-induced liver fibrosis

CONTEXT

Date fruits have protective effects against liver fibrosis; however their anti-apoptotic effects have not been investigated.

OBJECTIVE

To investigate the modulating effects of date fruits on pro- and anti-apoptotic markers, cytochrome P450 2E1 (CYP2E1) and hepatocyte growth factor (HGF) in liver fibrosis.

MATERIALS AND METHODS

Liver fibrosis was induced by injection of carbon tetrachloride (CCl₄) for eight weeks. Date flesh extract (DFE) and pits extract (DPE) were taken daily concomitant with CCl₄. Hepatocyte apoptosis was determined by measuring the expression of Fas, caspase-3, Bax, Bcl2 and hemeoxygenase-1 (HO-1). Hepatic levels of HGF and CYP2E1 were determined.

RESULTS

Treatment with DFE and DPE significantly attenuated the elevated levels of Fas, caspase 3, Bax and CYP2E1 induced by CCl₄. In addition, they alleviated the reduction in Bcl2, HGF and HO-1, the cytoprotective and anti-apoptotic factors in liver. Conclusions DFE and DPE treatment can ameliorate liver fibrosis by inhibiting hepatocyte apoptosis.

Expression of the thioredoxin system in an in vivo-like cancer cell environment upon auranofin treatment

As essential elements of the tumor microenvironment, the variable oxygenation state of the tumor tissue, the extracellular matrix (ECM) and different cell types are important determinants of carcinogenesis. These elements may also influence how tumor cells respond to therapeutic treatments. In the present study, we assessed the anti-cancer activity of auranofin and its effect on the thioredoxin (Trx) system under conditions that closely resemble the in vivo tumor microenvironment with respect to the oxygen levels and tissue architecture. We utilised an oxygen scheme involving growth of cancer cells under normoxia (20%) and hypoxia (0.1%). We also preconditioned cells with intermittent hypoxia (IH) prior to a prolonged hypoxic incubation. This oxygen scheme did not affect the cytotoxicity of auranofin; however, IH preconditioned cells were less sensitive towards the inhibition of thioredoxin reductase (TrxR) specific activity upon treatment with auranofin. IH preconditioning also upregulated Trx protein levels in auranofin treated cells. We also compared the activity of auranofin against cancer cells cultured in 2D monolayer and 3D spheroid-based culture models. Auranofin was less potent against cells grown under a more in vivo-like 3D environment. The results presented in this paper implicate the importance of the tumor oxygen environment and tissue architecture in influencing the response of cancer cells towards auranofin.

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.

TrxR1 as a potent regulator of the Nrf2-Keap1 response system

SIGNIFICANCE

All cells must maintain a balance between oxidants and reductants, while allowing for fluctuations in redox states triggered by signaling, altered metabolic flow, or extracellular stimuli. Furthermore, they must be able to rapidly sense and react to various challenges that would disrupt the redox homeostasis.

RECENT ADVANCES

Many studies have identified Keap1 as a key sensor for oxidative or electrophilic stress, with modification of Keap1 by oxidation or electrophiles triggering Nrf2-mediated transcriptional induction of enzymes supporting reductive and detoxification pathways. However, additional mechanisms for Nrf2 regulation are likely to exist upstream of, or in parallel with, Keap1.

CRITICAL ISSUES

Here, we propose that the mammalian selenoprotein thioredoxin reductase 1 (TrxR1) is a potent regulator of Nrf2. A high chemical reactivity of TrxR1 and its vital role for the thioredoxin (Trx) system distinguishes TrxR1 as a prime target for electrophilic challenges. Chemical modification of the selenocysteine (Sec) in TrxR1 by electrophiles leads to rapid inhibition of thioredoxin disulfide reductase activity, often combined with induction of NADPH oxidase activity of the derivatized enzyme, thereby affecting many downstream redox pathways. The notion of TrxR1 as a regulator of Nrf2 is supported by many publications on effects in human cells of selenium deficiency, oxidative stress or electrophile exposure, as well as the phenotypes of genetic mouse models.

FUTURE DIRECTIONS

Investigation of the role of TrxR1 as a regulator of Nrf2 activation will facilitate further studies of redox control in diverse cells and tissues of mammals, and possibly also in animals of other classes.

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.

Anti-rheumatic agent auranofin induced apoptosis in chronic myeloid leukemia cells resistant to imatinib through both Bcr/Abl-dependent and -independent mechanisms

Resistance to Imatinib mesylate (IM) is an emerging problem for patients with chronic myelogenous leukemia (CML). T315I mutation in the Bcr-Abl is the predominant mechanism of the acquired resistance to IM and second generation tyrosine kinase inhibitors (TKI). Therefore it is urgent to search for new measures to overcome TKI-resistance. Auranofin (AF), clinically used to treat rheumatic arthritis, was recently approved by US Food and Drug Administration for Phase II clinical trial to treat cancer. In contrast to the reports that AF induces apoptosis by increasing intracellular reactive oxygen species (ROS) levels via inhibiting thioredoxin reductase, our recent study revealed that AF-induced apoptosis depends on inhibition of proteasomal deubiquitinases (UCHL5 and USP14). Here we report that (i) AF induces apoptosis in both Bcr-Abl wild-type cells and Bcr-Abl-T315I mutation cells and inhibits the growth of IM-resistant Bcr-Abl-T315I xenografts in vivo; (ii) AF inhibits Bcr-Abl through both downregulation of Bcr-Abl gene expression and Bcr-Abl cleavage mediated by proteasome inhibition-induced caspase activation; (iii) proteasome inhibition but not ROS is required for AF-induced caspase activation and apoptosis. These findings support that AF overcomes IM resistance through both Bcr/Abl-dependent and -independent mechanisms, providing great clinical significance for cancer treatment.

Inhibitory effect of synthetic cannabinoids on CYP1A activity in mouse liver microsomes

Synthetic cannabinoids developed by chemical modification are believed to bind to cannabinoid receptors and cause neurological effects similar to cannabis; however, their effects on drug metabolizing enzymes are unknown. This study aimed to elucidate the effect of synthetic cannabinoids on cytochrome P450 1A activity. Naphthoylindole, a basic structure of the major synthetic cannabinoids, strongly inhibited CYP1A activity in a competitive manner; the apparent Ki value was 0.40 μM. The N-Alkylated derivatives of naphthoylindole, MAM-2201 and JWH-019, also inhibited CYP1A activity in a concentration-dependent manner; however, their inhibitory effects were weaker than naphthoylindole. An adamantylamidoindole derivative, STS-135, showed inhibition of CYP1A activity in a concentrationdependent manner, but the adamantoylindole derivatives, AB-001 and AM-1248, did not. A tetramethylcyclopropanoylindole derivative, UR-144, showed a weak inhibition of CYP1A activity at high concentrations. These results suggest that synthetic cannabinoids and their basic molecules are capable of inhibiting CYP1A enzymatic activity.

Homocysteine downregulates gene expression of heme oxygenase-1 in hepatocytes

Background

Hyperhomocysteinemia (HHcy) is an independent risk factor for liver diseases, such as fatty liver and hepatic fibrosis. However, the mechanisms underlying this pro-oxidative effect of homocysteine (Hcy) in hepatocytes remain largely unknown. Thus, we investigated the effect of Hcy on the gene expression of heme oxygenase-1 (HO-1), the primary rate-limiting enzyme in heme catabolism and a key anti-oxidant detoxification enzyme in maintaining cellular redox homeostasis.

Methods

In vivo, twenty male C57BL/6 mice at 8 weeks of age were randomly divided into two groups. One group was fed a chow diet (chow group; n = 10), the other group of mice was fed a methionine-supplemented diet (Met group, 1 mg kg⁻¹ day⁻¹ L-methionine in drinking water; n = 10) for 4 weeks. In vitro, HepG2 cells were stimulated with different doses of homocysteine (Hcy).

Results

Four weeks’ methionine supplementation caused a significant increase of plasma Hcy concentration and a decrease of HO-1 expression in the liver of C57BL/6 mice than mice received chow diet. Besides, SOD enzyme activities were impaired and the level of oxidative stress markers, such as malondialdehyde (MDA) were elevated in the liver from mice supplemented with methionine compared with control mice. In cultured hepatocytes, Hcy treatment reduced both the mRNA and protein levels of HO-1 dose-dependently. However, Hcy had no effect on the gene expression of Nrf2, the major transcriptional regulator of HO-1. Instead, Hcy induced the expression of Bach1, a transcriptional repressor of HO-1. In addition, Hcy stimulated the nuclear localization of Bach1 but prevented that of Nrf2. Furthermore, we found that knockdown of Bach1 attenuated the suppression of the HO-1 expression by Hcy.

Conclusions

Collectively, our results demonstrated that Bach1 plays an important role in Hcy-triggered ROS generations through inhibiting HO-1 expression, likely, resulting from the disturbed interplay between Bach1 and Nrf2.

Electronic supplementary material

The online version of this article (doi:10.1186/1743-7075-11-55) contains supplementary material, which is available to authorized users.

Benzyl-substituted metallocarbene antibiotics and anticancer drugs

Benzyl-substituted metallocarbene compounds synthesised by our group and others during the past 5 years give a new perspective on their activity as antibiotic and antitumoral drugs. N-heterocyclic carbenes containing an imidazole core were functionalised and their transition metal complexes (M = Ag, Au, Cu, Ru) have shown promising antibacterial as well as anticancer activity in vitro and in vivo. IC50 values in the nanomolar region or antibacterial activity comparable to conventional antibiotics lead the way towards novel drug candidates.

The biological activity of auranofin: implications for novel treatment of diseases

More than 30 years ago, auranofin was developed for the treatment of rheumatoid arthritis as a substitution for the injectable gold compounds aurothiomalate and aurothioglucose. Both the ease of oral administration over intramuscular injections and more potent anti-inflammatory effects in vitro made auranofin seem like an excellent substitute for the traditional injectable gold compounds. Despite efficacy in the treatment of both rheumatoid arthritis and psoriasis, currently, auranofin is seldom used as a treatment for patients with rheumatoid arthritis as more novel anti-rheumatic medications have become available. Despite the decline in its clinical applications, research on auranofin has continued as it shows promise in the treatment of several different diseases. In recent years, advances in technology have allowed researchers to use molecular techniques to identify novel mechanisms of action of auranofin. Additionally, researchers are discovering potential new applications of auranofin. Dual inhibition of inflammatory pathways and thiol redox enzymes by auranofin makes it a new candidate for cancer therapy and treating microbial infections. This review will summarize recently obtained data on the mechanisms of action of auranofin, and potential new applications of auranofin in the treatment of various diseases, including several types of leukaemia, carcinomas, and parasitic, bacterial, and viral infections.