The risky cocktail: what combination effects can we expect between ecstasy and other amphetamines?

Microbiota-Derived Short-Chain Fatty Acids: New Road in Colorectal Cancer Therapy

The colon microbiota is an important player in colorectal cancer (CRC) development, which is responsible for most of the cancer-related deaths worldwide. During carcinogenesis, the colon microbiota composition changes from a normobiosis profile to dysbiosis, interfering with the production of short-chain fatty acids (SCFAs). Each SCFA is known to play a role in several biological processes but, despite their reported individual effects, colon cells are exposed to these compounds simultaneously and the combined effect of SCFAs in colon cells is still unknown. Our aim was to explore the effects of SCFAs, alone or in combination, unveiling their biological impact on CRC cell phenotypes. We used a mathematical model for the prediction of the expected SCFA mixture effects and found that, when in mixture, SCFAs exhibit a concentration addition behavior. All SCFAs, alone or combined at the physiological proportions founded in the human colon, revealed to have a selective and anticancer effect by inhibiting colony formation and cell proliferation, increasing apoptosis, disturbing the energetic metabolism, inducing lysosomal membrane permeabilization, and decreasing cytosolic pH. We showed for the first time that SCFAs are specific towards colon cancer cells, showing promising therapeutic effects. These findings open a new road for the development of alternatives for CRC therapy based on the increase in SCFA levels through the modulation of the colon microbiota composition.

Toxicity of pesticides widely applied on soybean cultivation: Synergistic effects of fipronil, glyphosate and imidacloprid in HepG2 cells

The transgenic soy monoculture demands supplementation with pesticides. The aim of this study was to evaluate the individual and mixture effects of fipronil, glyphosate and imidacloprid in human HepG2 cells. Cytotoxicity was evaluated after 48-h incubations through MTT reduction and neutral red uptake assays. Free radicals production, mitochondrial membrane potential, DNA damage, and release of liver enzymes were also evaluated. Data obtained for individual agents were used to compute the additivity expectations for two mixtures of definite composition (one equipotent mixture, based in the EC₅₀ values achieved in the MTT assay; the other one based in the acceptable daily intake of each pesticide), using the models of concentration addition and independent action. The EC₅₀ values for fipronil, glyphosate and imidacloprid were 37.59, 41.13, and 663.66 mg/L, respectively. The mixtures of pesticides elicited significant synergistic effects (p < 0.05), which were greater than the expected by both addictive predictions. Decreased in mitochondrial membrane potential and increased in the transaminases enzymatic activities were observed. As they occur simultaneously, interactions between pesticides, even at non-effective single levels, can reverberate in significant deleterious effects, justifying the need for a more realistic approach in safety evaluations to better predict the effects to human health.

4-Fluoromethamphetamine (4-FMA) induces in vitro hepatotoxicity mediated by CYP2E1, CYP2D6, and CYP3A4 metabolism

4-Fluoromethamphetamine (4-FMA) is an amphetamine-like psychoactive substance with recognized entactogenic and stimulant effects, but hitherto unclear toxicological mechanisms. Taking into consideration that the vast majority of 4-FMA users consume this substance through oral route, the liver is expected to be highly exposed. The aim of this work was to determine the hepatotoxic potential of 4-FMA using in vitro hepatocellular models: primary rat hepatocytes (PRH), human hepatoma cell lines HepaRG and HepG2, and resorting to concentrations ranging from 37 μM to 30 mM, during a 24-h exposure. EC₅₀ values, estimated from the MTT viability assay data, were 2.21 mM, 5.59 mM and 9.57 mM, for each model, respectively. The most sensitive model, PRH, was then co-exposed to 4-FMA and cytochrome P450 (CYP) inhibitors to investigate the influence of metabolism on the toxicity of 4-FMA. Results show that CYP2E1, CYP3A4 and CYP2D6 have major roles in 4-FMA cytotoxicity. Inhibition of CYP2D6 and CYP3A4 led to left-geared shifts in the concentration-response curves of 4-FMA, hinting at a role of these metabolic enzymes for detoxifying 4-FMA, while CYP2E1 inhibition pointed towards a toxifying role of this enzyme in 4-FMA metabolism at physiologically-relevant concentrations. The drug also destabilised mitochondrial membrane potential and decreased ATP levels, increased the production of reactive oxygen and nitrogen species and compromised thiol antioxidant defences. 4-FMA further affected PRH integrity by interfering with the machinery of apoptosis and necrosis, increasing the activity of initiator and effector caspases, and causing loss of cell membrane integrity. Potential for autophagy was also observed. This research contributes to the growing body of evidence regarding the toxicity of new psychoactive substances, in particular regarding their hepatotoxic effects; the apparent influence of metabolism over the resulting cytotoxicity of 4-FMA shows that there is a substantial degree of unpredictability of the consequences for users that could be independent of the dose.

Emerging club drugs: 5-(2-aminopropyl)benzofuran (5-APB) is more toxic than its isomer 6-(2-aminopropyl)benzofuran (6-APB) in hepatocyte cellular models

New phenylethylamine derivatives are among the most commonly abused new psychoactive substances. They are synthesized and marketed in lieu of classical amphetaminic stimulants, with no previous safety testing. Our study aimed to determine the in vitro hepatotoxicity of two benzofurans [6-(2-aminopropyl)benzofuran (6-APB) and 5-(2-aminopropyl)benzofuran (5-APB)] that have been misused as 'legal highs'. Cellular viability was assessed through the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) reduction assay, following 24-h drug exposure of human hepatoma HepaRG cells (EC₅₀ 2.62 mM 5-APB; 6.02 mM 6-APB), HepG2 cells (EC₅₀ 3.79 mM 5-APB; 8.18 mM 6-APB) and primary rat hepatocytes (EC₅₀ 964 μM 5-APB; 1.94 mM 6-APB). Co-incubation of primary hepatocytes, the most sensitive in vitro model, with CYP450 inhibitors revealed a role of metabolism, in particular by CYP3A4, in the toxic effects of both benzofurans. Also, 6-APB and 5-APB concentration-dependently enhanced oxidative stress (significantly increased reactive species and oxidized glutathione, and decreased reduced glutathione levels) and unsettled mitochondrial homeostasis, with disruption of mitochondrial membrane potential and decline of intracellular ATP. Evaluation of cell death mechanisms showed increased caspase-8, -9, and -3 activation, and nuclear morphological changes consistent with apoptosis; at concentrations higher than 2 mM, however, necrosis prevailed. Concentration-dependent formation of acidic vesicular organelles typical of autophagy was also observed for both drugs. Overall, 5-APB displayed higher hepatotoxicity than its 6-isomer. Our findings provide new insights into the potential hepatotoxicity of these so-called 'safe drugs' and highlight the putative risks associated with their use as psychostimulants.

Insights on the relationship between structure vs. toxicological activity of antibacterial rhodamine-labelled 3-hydroxy-4-pyridinone iron(III) chelators in HepG2 cells

In the present study we investigated the in vitro hepatotoxicity of a set of rhodamine-labelled 3-hydroxy-4-pyridinones (3,4-HPO) that had previously demonstrated significant inhibitory effect in the intramacrophagic growth of Mycobacterium avium. Our aim was to establish a correspondence between the molecular structure and the in vitro toxicological activity of these compounds.

The impact of a set of bidentate (MRB2, MRB7, MRB8, and MRB9) and hexadentate (MRH7, MRH8, and MRH10) chelators on cellular metabolic competence and membrane integrity was investigated in HepG2 cells.

Our findings indicate that: a) hexadentate chelators are more cytotoxic than parent bidentate ligands; b) disruption of cell membrane and metabolic competence only occurred after 5 days, at the highest concentrations tested; c) strict correlation between bacteriostatic activity and in vitro toxicity was observed, which seems to be directly dependent on the size of the molecule and on the hydrophilic/lipophilic balance; d) among the set of bidentate ligands, carboxyrhodamine derivatives (amide linker) presented lower detrimental effects, when compared with rhodamine B isothiocyanate chelators (thiourea linker); e) contrarily, for the hexadentate series, rhodamine B isothiocyanate derivatives are less cytotoxic to HepG2 cells than carboxyrhodamine molecules; and f) for all compounds tested, when the substituents of the nitrogen atom were switched from ethyl to methyl, an increment of toxicity was observed.

Overall, all chelators seem to display suitable in vitro toxicological potential to combat fast grow bacteria. According to their in vitro pharmacological: toxicological potential ratio, MRH7 and MRH8 may be considered as the most suitable compounds to undergo further pre-clinical development studies.

Ethanol addictively enhances the in vitro cardiotoxicity of cocaine through oxidative damage, energetic deregulation, and apoptosis

Cocaine (COC) is frequently consumed in polydrug abuse settings, and ethanol (EtOH) is the most prominent co-abused substance. Clinical data and experimental evidence suggest that the co-administration of COC with EtOH can be more cardiotoxic than EtOH or COC alone, but information on the molecular pathways involved is scarce. Since these data are crucial to potentiate the identification of therapeutic targets to treat intoxications, we sought to (i) elucidate the type of interaction that occurs between both substances, and (ii) assess the mechanisms implicated in the cardiotoxic effects elicited by COC combined with EtOH. For this purpose, H9c2 cardiomyocytes were exposed to COC (104 µM-6.5 mM) and EtOH (977 µM-4 M), individually or combined at a molar ratio based on blood concentrations of intoxicated abusers (COC 1: EtOH 9; 206 µM-110 mM). After 24 h, cell metabolic viability was recorded by the MTT assay and mixture toxicity expectations were calculated using the independent action (IA) and concentration addition (CA) models. EtOH (EC₅₀ 305.26 mM) proved to act additively with COC (EC₅₀ 2.60 mM) to significantly increase the drug in vitro cardiotoxicity, even when both substances were combined at individually non-cytotoxic concentrations. Experimental mixture testing (EC₅₀ 19.18 ± 3.36 mM) demonstrated that the cardiotoxicity was fairly similar to that predicted by IA (EC₅₀ 22.95 mM) and CA (EC₅₀ 21.75 mM), supporting additivity. Concentration-dependent increases of intracellular ROS/RNS and GSSG, depletion of GSH and ATP, along with mitochondrial hyperpolarization and activation of intrinsic, extrinsic, and common apoptosis pathways were observed both for single and combined exposures. In general, the mixture exhibited a toxicological profile that mechanistically did not deviate from the single drugs, suggesting that interventions such as antioxidant administration might aid in the clinical treatment of this type of polydrug intoxication. In a clinical perspective, the observed additive mixture effect may reflect the increased hazards at which users of this combination are exposed to in recreational settings.

Mechanisms of hepatocellular toxicity associated with new psychoactive synthetic cathinones

Synthetic cathinones are a new class of psychostimulant substances. Rarely, they can cause liver injury but associated mechanisms are not completely elucidated. In order to increase our knowledge about mechanisms of hepatotoxicity, we investigated the effect of five frequently used cathinones on two human cell lines. Bupropion was included as structurally related drug used therapeutically. In HepG2 cells, bupropion, MDPV, mephedrone and naphyrone depleted the cellular ATP content at lower concentrations (0.2-1mM) than cytotoxicity occurred (0.5-2mM), suggesting mitochondrial toxicity. In comparison, methedrone and methylone depleted the cellular ATP pool and induced cytotoxicity at similar concentrations (≥2mM). In HepaRG cells, cytotoxicity and ATP depletion could also be demonstrated, but cytochrome P450 induction did not increase the toxicity of the compounds investigated. The mitochondrial membrane potential was decreased in HepG2 cells by bupropion, MDPV and naphyrone, confirming mitochondrial toxicity. Bupropion, but not the other compounds, uncoupled oxidative phosphorylation. Bupropion, MDPV, mephedrone and naphyrone inhibited complex I and II of the electron transport chain, naphyrone also complex III. All four mitochondrial toxicants were associated with increased mitochondrial ROS and increased lactate production, which was accompanied by a decrease in the cellular total GSH pool for naphyrone and MDPV. In conclusion, bupropion, MDPV, mephedrone and naphyrone are mitochondrial toxicants impairing the function of the electron transport chain and depleting cellular ATP stores. Since liver injury is rare in users of these drugs, affected persons must have susceptibility factors rendering them more sensitive for these drugs.

In vitro hepatotoxicity of 'Legal X': the combination of 1-benzylpiperazine (BZP) and 1-(m-trifluoromethylphenyl)piperazine (TFMPP) triggers oxidative stress, mitochondrial impairment and apoptosis

N-Benzylpiperazine (BZP) and 1-(3-trifluoromethylphenyl)piperazine (TFMPP) are two synthetic phenylpiperazine analogues that have been frequently commercialized in combination as an alternative to ecstasy ('Legal X'). Despite reports of several clinical complications following the use of these drugs in association, few studies have been conducted so far to elucidate their combined toxicity. The present study was aimed at clarifying the cytotoxic effects of mixtures of BZP and TFMPP in vitro. Human-derived HepaRG cells and primary rat hepatocytes were exposed to the drugs, individually or combined at different mixture ratios, and cytotoxicity was assessed by the MTT assay. Mixture additivity expectations were calculated by the independent action and the concentration addition (CA) models and compared with the experimental outcomes. To delineate the mechanisms underlying the elicited effects, a range of stress endpoints was evaluated, including oxidative stress, energetic imbalance, and metabolic interactions. It was observed that primary rat hepatocytes are more sensitive than HepaRG cells to the toxicity of BZP (EC₅₀ 2.20 and 6.60 mM, respectively) and TFMPP (EC₅₀ 0.14 and 0.45 mM, respectively). For all BZP-TFMPP combinations tested, CA was the most appropriate model to predict the mixture effects. TFMPP proved to act additively with BZP to produce significant hepatotoxicity (p < 0.01). Remarkably, substantial mixture effects were observed even when each drug was present at concentrations that were harmless individually. In primary hepatocytes, a small deviation from additivity (antagonism) was observed toward the upper range of the concentration-response curve. GC/MS data suggest that a metabolic interaction may be at a play, as the mixture favors the metabolism of both substances, to a significant extent in the case of BZP (p < 0.05). Also, our results demonstrate the influence of oxidative stress and energetic imbalance on these effects (increase in RNS and ROS production, decrease in intracellular GSH/GSSG, ATP depletion and mitochondrial Δψm disruption). The present work clearly demonstrates that potentially harmful interactions among BZP and TFMPP are expected when these drugs are taken concomitantly.

Hepatotoxicity of piperazine designer drugs: Comparison of different in vitro models

Piperazine derived drugs emerged on the drug market in the last decade. The aim of this study was to investigate in vitro the potential hepatotoxicity of the designer drugs N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl)piperazine (TFMPP), 1-(4-methoxyphenyl)piperazine (MeOPP) and 1-(3,4-methylenedioxybenzyl)piperazine (MDBP) in two human hepatic cell lines (HepaRG and HepG2) and in primary rat hepatocytes. Cell death was evaluated by the MTT assay, after 24 h-incubations. Among the tested drugs, TFMPP was the most cytotoxic. HepaRG cells and primary hepatocytes revealed to be the most and the least resistant cellular models, respectively. To ascertain whether the CYP450 metabolism could explain their higher susceptibility, primary hepatocytes were co-incubated with the piperazines and the CYP450 inhibitors metyrapone and quinidine, showing that CYP450-mediated metabolism contributes to the detoxification of these drugs. Additionally, the intracellular contents of reactive species, ATP, reduced (GSH) and oxidized (GSSG) glutathione, changes in mitochondrial membrane potential (Δψm) and caspase-3 activation were further evaluated in primary cells. Overall, an increase in reactive species formation, followed by intracellular GSH and ATP depletion, loss of Δψm and caspase-3 activation was observed for all piperazines, in a concentration-dependent manner. In conclusion, piperazine designer drugs produce hepatic detrimental effects that can vary in magnitude among the different analogues.

Piperazine designer drugs induce toxicity in cardiomyoblast h9c2 cells through mitochondrial impairment

Abuse of synthetic drugs is widespread among young people worldwide. In this context, piperazine derived drugs recently appeared in the recreational drug market. Clinical studies and case-reports describe sympathomimetic effects including hypertension, tachycardia, and increased heart rate. Our aim was to investigate the cytotoxicity of N-benzylpiperazine (BZP), 1-(3-trifluoromethylphenyl) piperazine (TFMPP), 1-(4-methoxyphenyl) piperazine (MeOPP), and 1-(3,4-methylenedioxybenzyl) piperazine (MDBP) in the H9c2 rat cardiac cell line. Complete cytotoxicity curves were obtained at a 0-20 mM concentration range after 24 h incubations with each drug. The EC50 values (μM) were 343.9, 59.6, 570.1, and 702.5 for BZP, TFMPP, MeOPP, and MDBP, respectively. There was no change in oxidative stress markers. However, a decrease in total GSH content was noted for MDBP, probably due to metabolic conjugation reactions. All drugs caused significant decreases in intracellular ATP, accompanied by increased intracellular calcium levels and a decrease in mitochondrial membrane potential that seems to involve the mitochondrial permeability transition pore. The cell death mode revealed early apoptotic cells and high number of cells undergoing secondary necrosis. Among the tested drugs, TFMPP seems to be the most potent cytotoxic compound. Overall, piperazine designer drugs are potentially cardiotoxic and support concerns on risks associated with the intake of these drugs.

Raising awareness of new psychoactive substances: chemical analysis and in vitro toxicity screening of 'legal high' packages containing synthetic cathinones

The world's status quo on recreational drugs has dramatically changed in recent years due to the rapid emergence of new psychoactive substances (NPS), represented by new narcotic or psychotropic drugs, in pure form or in preparation, which are not controlled by international conventions, but that may pose a public health threat comparable with that posed by substances listed in these conventions. These NPS, also known as 'legal highs' or 'smart drugs', are typically sold via Internet or 'smartshops' as legal alternatives to controlled substances, being announced as 'bath salts' and 'plant feeders' and is often sought after for consumption especially among young people. Although NPS have the biased reputation of being safe, the vast majority has hitherto not been tested and several fatal cases have been reported, namely for synthetic cathinones, with pathological patterns comparable with amphetamines. Additionally, the unprecedented speed of appearance and distribution of the NPS worldwide brings technical difficulties in the development of analytical procedures and risk assessment in real time. In this study, 27 products commercialized as 'plant feeders' were chemically characterized by gas chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy. It was also evaluated, for the first time, the in vitro hepatotoxic effects of individual synthetic cathinones, namely methylone, pentedrone, 4-methylethcathinone (4-MEC) and 3,4-methylenedioxypyrovalerone (MDPV). Two commercial mixtures ('Bloom' and 'Blow') containing mainly cathinone derivatives were also tested, and 3,4-methylenedioxymethamphetamine (MDMA) was used as the reference drug. The study allowed the identification of 19 compounds, showing that synthetic cathinones are the main active compounds present in these products. Qualitative and quantitative variability was found in products sold with the same trade name in matching or different 'smartshops'. In the toxicity studies performed in primary cultured rat hepatocytes, pentedrone and MDPV proved to be the most potent individual agents, with EC50 values of 0.664 and 0.742 mM, respectively, followed by MDMA (EC50 = 0.754 mM). 4-MEC and methylone were the least potent substances, with EC50 values significantly higher (1.29 and 1.18 mM, respectively; p < 0.05 vs. MDMA). 'Bloom' and 'Blow' showed hepatotoxic effects similar to MDMA (EC50 = 0.788 and 0.870 mM, respectively), with cathinones present in these mixtures contributing additively to the overall toxicological effect. Our results show a miscellany of psychoactive compounds present in 'legal high' products with evident hepatotoxic effects. These data contribute to increase the awareness on the real composition of 'legal high' packages and unveil the health risks posed by NPS.

An insight into the hepatocellular death induced by amphetamines, individually and in combination: the involvement of necrosis and apoptosis

The liver is a vulnerable target for amphetamine toxicity, but the mechanisms involved in the drug's hepatotoxicity remain poorly understood. The purpose of the current research was to characterize the mode of death elicited by four amphetamines and to evaluate whether their combination triggered similar mechanisms in immortalized human HepG2 cells. The obtained data revealed a time- and temperature-dependent mortality of HepG2 cells exposed to 3,4-methylenedioxymethamphetamine (MDMA, ecstasy; 1.3 mM), methamphetamine (3 mM), 4-methylthioamphetamine (0.5 mM) and D-amphetamine (1.7 mM), alone or combined (1.6 mM mixture). At physiological temperature (37 °C), 24-h exposures caused HepG2 death preferentially by apoptosis, while a rise to 40.5 °C favoured necrosis. ATP levels remained unaltered when the drugs where tested at normothermia, but incubation at 40.5 °C provoked marked ATP depletion for all treatments. Further investigations on the apoptotic mechanisms triggered by the drugs (alone or combined) showed a decline in BCL-2 and BCL- XL mRNA levels, with concurrent upregulation of BAX, BIM, PUMA and BID genes. Elevation of Bax, cleaved Bid, Puma, Bak and Bim protein levels was also seen. To the best of our knowledge, Puma, Bim and Bak have never been linked with the toxicity induced by amphetamines. Time-dependent caspase-3/-7 activation, but not mitochondrial membrane potential (∆ψm) disruption, also mediated amphetamine-induced apoptosis. The cell dismantling was confirmed by poly(ADP-ribose)polymerase proteolysis. Overall, for all evaluated parameters, no relevant differences were detected between individual amphetamines and the mixture (all tested at equieffective cytotoxic concentrations), suggesting that the mode of action of the amphetamines in combination does not deviate from the mode of action of the drugs individually, when eliciting HepG2 cell death.

Combination effects of amphetamines under hyperthermia - the role played by oxidative stress

Rise in body temperature is a life-threatening consequence of 3,4-methylenedioxymethamphetamine (MDMA, ecstasy) abuse. We evaluated the impact of hyperthermia on the cytotoxicity of combinations of MDMA and three other amphetamines, often co-ingested. For this, Hep G2 cells were exposed to MDMA, d-amphetamine, methamphetamine and 4-methylthioamphetamine, individually or combined, at 40.5 °C. The results were compared with normothermia data (37.0 °C). Mixture additivity expectations were calculated by independent action and concentration addition (CA) models. To delineate the mechanism(s) underlying the elicited effects, a range of stress endpoints was evaluated, including quantification of reactive oxygen/nitrogen species (ROS/RNS), lipid peroxidation, reduced/oxidized glutathione (GSH/GSSG), ATP and mitochondrial membrane potential (Δψm) changes. Our data show that, in hyperthermia, amphetamines acted additively and mixture effects were accurately predicted by CA. At 40.5 °C, even slight increases in the concentrations of each drug/mixture promoted significant rises in cytotoxicity, which quickly shifted from roughly undetectable to maximal mortality. Additionally, the increase of RNS/ROS production, decrease of GSH, ATP depletion and mitochondrial impairment were exacerbated under hyperthermia. Importantly, when equieffective cytotoxic concentrations of the mixture and individual amphetamines were compared for all tested stress endpoints, mixture effects did not deviate from those elicited by individual treatments, suggesting that these amphetamines have a similar mode of action, which is not altered in combination. Concluding, our data indicate that amphetamine mixtures produce deleterious effects, even when individual drugs are combined at negligible concentrations. These effects are strongly exacerbated in hyperthermia, emphasizing the potential increased risks of ecstasy intake, especially when hyperthermia occurs concurrently with polydrug abuse.