Death following recreational use of designer drug "bath salts" containing 3,4-Methylenedioxypyrovalerone (MDPV)

INTRODUCTION

3,4-Methylenedioxypyrovalerone (MDPV) is a designer stimulant drug that has gained popularity in the USA. Although adverse effects of MDPV have been described, to our knowledge, this is the first reported death.

CASE REPORT

We report the case of a 40-year-old male who injected and snorted "bath salts" containing MDPV and subsequently became agitated, aggressive, and experienced a cardiac arrest. He was resuscitated after his initial arrest; however, he developed hyperthermia, rhabdomyolysis, coagulopathy, acidosis, anoxic brain injury, and subsequently died.

DISCUSSION

This is the first case in the medical literature to report death due to isolated confirmed MDPV intoxication. The manner of death is also consistent with excited delirium syndrome.

Potent rewarding and reinforcing effects of the synthetic cathinone 3,4-methylenedioxypyrovalerone (MDPV)

Reports of abuse and toxic effects of synthetic cathinones, frequently sold as 'bath salts' or 'legal highs', have increased dramatically in recent years. One of the most widely used synthetic cathinones is 3,4-methylenedioxypyrovalerone (MDPV). The current study evaluated the abuse potential of MDPV by assessing its ability to support intravenous self-administration and to lower thresholds for intracranial self-stimulation (ICSS) in rats. In the first experiment, the rats were trained to intravenously self-administer MDPV in daily 2-hour sessions for 10 days at doses of 0.05, 0.1 or 0.2 mg/kg per infusion. The rats were then allowed to self-administer MDPV under a progressive ratio (PR) schedule of reinforcement. Next, the rats self-administered MDPV for an additional 10 days under short access (ShA; 2 hours/day) or long access (LgA; 6 hours/day) conditions to assess escalation of intake. A separate group of rats underwent the same procedures, with the exception of self-administering methamphetamine (0.05 mg/kg per infusion) instead of MDPV. In the second experiment, the effects of MDPV on ICSS thresholds following acute administration (0.1, 0.5, 1 and 2 mg/kg, i.p.) were assessed. MDPV maintained self-administration across all doses tested. A positive relationship between MDPV dose and breakpoints for reinforcement under PR conditions was observed. LgA conditions led to escalation of drug intake at 0.1 and 0.2 mg/kg doses, and rats self-administering methamphetamine showed similar patterns of escalation. Finally, MDPV significantly lowered ICSS thresholds at all doses tested. Together, these findings indicate that MDPV has reinforcing properties and activates brain reward circuitry, suggesting a potential for abuse and addiction in humans.

Studies on the metabolism of the α-pyrrolidinophenone designer drug methylenedioxy-pyrovalerone (MDPV) in rat and human urine and human liver microsomes using GC-MS and LC-high-resolution MS and its detectability in urine by GC-MS

Since the late 1990s, many derivatives of the α-pyrrolidinophenone (PPP) drug class appeared on the drugs of abuse market. The latest compound was described in 2009 to be a classic PPP carrying a methylenedioxy moiety remembering the classic entactogens (ecstasy). Besides Germany, 3,4-methylene-dioxypyrovalerone (MDPV) has appeared in many countries in Europe and Asia, indicating its worldwide importance for forensic and clinical toxicology. The aim of the presented work was to identify the phase I and II metabolites of MDPV and the human cytochrome-P450 (CYP) isoenzymes responsible for its main metabolic step(s). Finally, the detectability of MDPV in urine by the authors' systematic toxicological analysis (STA) should be studied. The urine samples were extracted after and without enzymatic cleavage of conjugates. The metabolites were separated and identified after work-up by GC-MS and liquid chromatography (LC)-high-resolution MS (LC-HR-MS). The studies revealed the following phase I main metabolic steps in rat and human: demethylenation followed by methylation, aromatic and side chain hydroxylation and oxidation of the pyrrolidine ring to the corresponding lactam as well as ring opening to the corresponding carboxylic acid. Using LC-HR-MS, most metabolite structures postulated according to GC-MS fragmentation could be confirmed and the phase II metabolites were identified. Finally, the formation of the initial metabolite demethylenyl-MDPV could be confirmed using incubation of human liver microsomes. Using recombinant human CYPs, CYP 2C19, CYP 2D6 and CYP 1A2 were found to catalyze this initial step. Finally, the STA allowed the detection of MDPV metabolites in the human urine samples.

Psychoactive "bath salts" intoxication with methylenedioxypyrovalerone

Abuse of the psychoactive "designer drug" methylenedioxypyrovalerone (MDPV) has become a serious international public health concern because of the severity of its physical and behavioral toxicities. MDPV is the primary ingredient in so-called "bath salts," labeled as such to avoid criminal prosecution and has only been classified recently as a controlled substance in the United States and some other countries. However, it remains a danger because of illegal sources, including the Internet. MDPV is a synthetic, cathinone-derivative, central nervous system stimulant and is taken to produce a cocaine- or methamphetamine-like high. Administered via oral ingestion, nasal insufflation, smoking, intravenous or intramuscular methods, or the rectum, the intoxication lasts 6 to 8 hours and has high addictive potential. Overdoses are characterized by profound toxicities, causing increased attention by emergency department and law enforcement personnel. Physical manifestations range from tachycardia, hypertension, arrhythmias, hyperthermia, sweating, rhabdomyolysis, and seizures to those as severe as stroke, cerebral edema, cardiorespiratory collapse, myocardial infarction, and death. Behavioral effects include panic attacks, anxiety, agitation, severe paranoia, hallucinations, psychosis, suicidal ideation, self-mutilation, and behavior that is aggressive, violent, and self-destructive. Treatment is principally supportive and focuses on counteracting the sympathetic overstimulation, including sedation with intravenous benzodiazepines, seizure-prevention measures, intravenous fluids, close (eg, intensive care unit) monitoring, and restraints to prevent harm to self or others. Clinical presentation is often complicated by coingestion of other psychoactive substances that may alter the treatment approach. Clinicians need to be especially vigilant in that MDPV is not detected by routine drug screens and overdoses can be life-threatening.

Toxicological determination and in vitro metabolism of the designer drug methylenedioxypyrovalerone (MDPV) by gas chromatography/mass spectrometry and liquid chromatography/quadrupole time-of-flight mass spectrometry

A method for the toxicological screening of the new designer drug methylenedioxypyrovalerone (MDPV) is described; with an emphasis on its application for anti-doping analysis. The metabolism of MDPV was evaluated in vitro using human liver microsomes and S9 cellular fractions for CYP450 phase I and uridine 5'-diphosphoglucuronosyltransferase (UGT) and sulfotransferase (SULT) phase II metabolism studies. The resulting metabolites were subsequently liquid/liquid extracted and analyzed using gas chromatography/mass spectrometry (GC/MS) as trimethylsilyl (TMS) derivatives. The structures of the metabolites were further confirmed by accurate mass measurement using a liquid chromatography/quadrupole time-of-flight (LC/QTOF) mass spectrometer. The studies demonstrated that the main metabolites of MDPV are catechol and methyl catechol pyrovalerone, which are in turn sulfated and glucuronated. The method for the determination of MDPV in urine has been fully validated by assessing the limits of detection and quantification, linearity, repeatability, and accuracy. This validation demonstrates the suitability for screening of this stimulant substance for anti-doping and forensic toxicology purposes.

The abuse-related effects of pyrrolidine-containing cathinones are related to their potency and selectivity to inhibit the dopamine transporter

Synthetic cathinones are common constituents of abused "bath salts" preparations and represent a large family of structurally related compounds that function as cocaine-like inhibitors or amphetamine-like substrates of dopamine (DAT), norepinephrine (NET), and serotonin (SERT) transporters. Preclinical evidence suggests that some cathinones (e.g., MDPV and α-PVP) are more effective reinforcers than prototypical stimulant drugs of abuse, such as cocaine or methamphetamine. Although the reinforcing potency of these cathinones is related to their potency to inhibit DAT, less is known about the pharmacological determinants of their unusually high reinforcing effectiveness. To this end, we tested the hypothesis that reinforcing effectiveness of cathinone stimulants is positively correlated with their selectivity for DAT relative to SERT. Uptake inhibition assays in rat brain synaptosomes were used to directly compare the potency of MDPV, MDPBP, MDPPP, α-PVP, α-PPP, and cocaine at DAT, NET, and SERT, whereas intravenous self-administration in rats was used to quantify relative reinforcing effectiveness of the drugs using progressive ratio (PR) and behavioral economic procedures. All cathinones were more potent at DAT than NET or SERT, with a rank order for selectivity at DAT over SERT of α-PVP > α-PPP > MDPV > MDPBP > MDPPP > cocaine. These synthetic cathinones were more effective reinforcers than cocaine, and the measures of reinforcing effectiveness determined by PR and demand curve analyses were highly correlated with selectivity for DAT over SERT. Together, these studies provide strong and convergent evidence that the abuse potential of stimulant drugs is mediated by uptake inhibition at DAT, with activity at SERT serving as a negative modulator of reinforcing effectiveness.

Psychosis from a bath salt product containing flephedrone and MDPV with serum, urine, and product quantification

INTRODUCTION

The use of designer drugs commonly marketed as bath salts or plant food has risen dramatically in recent years. Several different synthetic cathinones have been indentified in these products, including mephedrone, 3,4-methylenedioxypyrovalerone (MDPV), and 4-fluoromethcathinone (flephedrone). We report a case of bath salt intoxication with quantitative MDPV and flephedrone levels in a patient's serum and urine, and from the bath salt product.

CASE REPORT

A 23-year-old male with a prior psychiatric history arrived via EMS for bizarre behavior, suicidality, and hallucinations after reportedly insufflating a bath salt. He was found to have MDPV levels of 186 and 136 ng/mL in his serum and urine, respectively, and flephedrone levels of 346 and 257 ng/mL in the serum and urine, respectively. The white powder in question was found to contain 143 μg MDPV and 142 μg flephedrone per milligram powder. His psychosis and agitation resolved with lorazepam, droperidol, and observation in the emergency department.

DISCUSSION

Agitation, psychosis, movement disorders, tachycardia, and hypertension have all been attributed to the use of MDPV; there are no prior reports detailing clinical experience with flephedrone. Considering that our patient's serum flephedrone levels were twofold higher than his MDPV level, it is likely flephedrone contributed to his clinical toxicity. This case suggests the possibility that fluorinated cathinones, such as flephedrone, may have altered metabolism and/or elimination which may affect their course of clinical toxicity. This case highlights the evolving composition of synthetic cathinones found in bath salt products.

Stereoselective Effects of Abused "Bath Salt" Constituent 3,4-Methylenedioxypyrovalerone in Mice: Drug Discrimination, Locomotor Activity, and Thermoregulation

3,4-Methylenedioxypyrovalerone (MDPV) is a common constituent of illicit "bath salts" products. MDPV is a chiral molecule, but the contribution of each enantiomer to in vivo effects in mice has not been determined. To address this, mice were trained to discriminate 10 mg/kg cocaine from saline, and substitutions with racemic MDPV, S(+)-MDPV, and R(-)-MDPV were performed. Other mice were implanted with telemetry probes to monitor core temperature and locomotor responses elicited by racemic MDPV, S(+)-MDPV, and R(-)-MDPV under a warm (28°C) or cool (20°C) ambient temperature. Mice reliably discriminated the cocaine training dose from saline, and each form of MDPV fully substituted for cocaine, although marked potency differences were observed such that S(+)-MDPV was most potent, racemic MDPV was less potent than the S(+) enantiomer, and R(-)-MDPV was least potent. At both ambient temperatures, locomotor stimulant effects were observed after doses of S(+)-MDPV and racemic MDPV, but R(-)-MDPV did not elicit locomotor stimulant effects at any tested dose. Interestingly, significant increases in maximum core body temperature were only observed after administration of racemic MDPV in the warm ambient environment; neither MDPV enantiomer altered core temperature at any dose tested, at either ambient temperature. These studies suggest that all three forms of MDPV induce biologic effects, but R(-)-MDPV is less potent than S(+)-MDPV and racemic MDPV. Taken together, these data suggest that the S(+)-MDPV enantiomer is likely responsible for the majority of the biologic effects of the racemate and should be targeted in therapeutic efforts against MDPV overdose and abuse.

"Deconstruction" of the abused synthetic cathinone methylenedioxypyrovalerone (MDPV) and an examination of effects at the human dopamine transporter

Synthetic cathinones, β-keto analogues of amphetamine (or, more correctly, of phenylalkylamines), represent a new and growing class of abused substances. Several such analogues have been demonstrated to act as dopamine (DA) releasing agents. Methylenedioxypyrovalerone (MDPV) was the first synthetic cathinone shown to act as a cocaine-like DA reuptake inhibitor. MDPV and seven deconstructed analogues were examined to determine which of MDPV's structural features account(s) for uptake inhibition. In voltage-clamped (-60 mV) Xenopus oocytes transfected with the human DA transporter (hDAT), all analogues elicited inhibitor-like behavior shown as hDAT-mediated outward currents. Using hDAT-expressing mammalian cells we determined the affinities of MDPV and its analogues to inhibit uptake of [3H]DA by hDAT that varied over a broad range (IC50 values ca. 135 to >25,000 nM). The methylenedioxy group of MDPV made a minimal contribution to affinity, the carbonyl group and a tertiary amine are more important, and the extended α-alkyl group seems most important. Either a tertiary amine, or the extended α-alkyl group (but not both), are required for the potent nature of MDPV as an hDAT inhibitor.

Neurobiology of 3,4-methylenedioxypyrovalerone (MDPV) and α-pyrrolidinovalerophenone (α-PVP)

Synthetic cathinones are analogs of cathinone or β-ketoamphetamine - the major psychostimulant component of the shrub Catha edulis or khat. Cathinone analogs - though not termed as such - have been known for >100 years, but confusing chemical nomenclature often made the topic difficult to appreciate. In addition, many of the early analogs were prepared as synthetic precursors for the development of various other agents, and relatively few were pharmacologically evaluated. Cathinone is a close structural relative of amphetamine. Today, certain cathinone derivatives, synthetic cathinones, are known to produce central stimulant actions and represent a "new" class of drugs of abuse. Depending upon the nature of their terminal amine, α substituent, and aryl substituents, they seem to produce their effects via release or reuptake of various neurotansmitters including dopamine norepinephreine and/or serotonin. Two of the newest and most prominent members of the class are MDPV and its parent α-PVP ("flakka"). Both have been encountered on their own and in what might be constituents of what has been termed by a variety of names including psychoactive "bath salts". Here, we describe the nomenclature of synthetic cathinones, the mechanism(s) of action of MDPV and α-PVP, and their structure-activity relationships. In order to assist in forensic studies, and to identify novel substances requiring future pharmacological evaluation, the metabolism of these agents is also described. Finally, the preclinical behavioral actions of these two agents in a variety of behavioral assays, including rodent locomotor assays, self-administration studies, intracranial self-stimulation, conditioned place preference, and drug discrimination, is summarized. The results of these studies with MDPV and α-PVP are consistent with their acting as potent cocaine-like central stimulants with abuse liability.

Neuropharmacology of 3,4-Methylenedioxypyrovalerone (MDPV), Its Metabolites, and Related Analogs

3,4-Methylenedioxypyrovalerone (MDPV) is a psychoactive component of so-called bath salts products that has caused serious medical consequences in humans. In this chapter, we review the neuropharmacology of MDPV and related analogs, and supplement the discussion with new results from our preclinical experiments. MDPV acts as a potent uptake inhibitor at plasma membrane transporters for dopamine (DAT) and norepinephrine (NET) in nervous tissue. The MDPV formulation in bath salts is a racemic mixture, and the S isomer is much more potent than the R isomer at blocking DAT and producing abuse-related effects. Elevations in brain extracellular dopamine produced by MDPV are likely to underlie its locomotor stimulant and addictive properties. MDPV displays rapid pharmacokinetics when injected into rats (0.5-2.0 mg/kg), with peak plasma concentrations achieved by 10-20 min and declining quickly thereafter. MDPV is metabolized to 3,4-dihydroxypyrovalerone (3,4-catechol-PV) and 4-hydroxy-3-methoxypyrovalerone (4-OH-3-MeO-PV) in vivo, but motor activation produced by the drug is positively correlated with plasma concentrations of parent drug and not its metabolites. 3,4-Catechol-PV is a potent uptake blocker at DAT in vitro but has little activity after administration in vivo. 4-OH-3-MeO-PV is the main MDPV metabolite but is weak at DAT and NET. MDPV analogs, such as α-pyrrolidinovalerophenone (α-PVP), display similar ability to inhibit DAT and increase extracellular dopamine concentrations. Taken together, these findings demonstrate that MDPV and its analogs represent a unique class of transporter inhibitors with a high propensity for abuse and addiction.

Neurotoxicity of β-Keto Amphetamines: Deathly Mechanisms Elicited by Methylone and MDPV in Human Dopaminergic SH-SY5Y Cells

Synthetic cathinones (β-keto amphetamines) act as potent CNS stimulants similarly to classical amphetamines, which raise concerns about their potential neurotoxic effects. The present in vitro study aimed to explore and compare the mechanisms underlying the neurotoxicity of two commonly abused cathinone derivatives, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV), with those of 3,4-methylenedioxymethamphetamine (MDMA), using undifferentiated and differentiated SH-SY5Y cells. Following a 24 h exposure period, methylone and MDPV induced loss of cell viability in a concentration-dependent manner, in the following order of potency: MDPV ≈ MDMA > methylone. Dopaminergic differentiated cells evidenced higher sensitivity to the neurotoxic effects of both cathinones and MDMA than the undifferentiated ones, but this effect was not inhibited by the DAT inhibitor GBR 12909. Intracellular oxidative stress mediated by methylone and MDPV was demonstrated by the increase in reactive oxygen and nitrogen species (ROS and RNS) production, depletion of intracellular reduced glutathione and increased oxidized glutathione levels. All three drugs elicited mitochondrial impairment, characterized by the mitochondrial membrane potential (Δψm) dissipation and intracellular ATP depletion. Apoptosis was found to be a common mechanism of cell death induced by methylone and MDPV, with evident chromatin condensation and formation of pyknotic nuclei, and activation of caspases 3, 8, and 9. In conclusion, the present data shows that oxidative stress and mitochondrial dysfunction play a role in cathinones-induced neuronal damage, ultimately leading to cell death by apoptosis.

Excited delirium following use of synthetic cathinones (bath salts)

Synthetic analogs of the cathinone molecule have seen increasing recreational use as substitutes for cocaine, 3,4-methylenedioxymethamphetamine (ecstasy) and methamphetamine. Repeated use of these drugs is associated with a paranoid hallucinatory delirium. A subset of patients using these substances develops a syndrome of extreme agitation and violent behavior that has been reported following the use of other stimulant drugs that also produce rapid changes in brain monoamines. This syndrome, characterized as "excited delirium," presents to the acute care setting with a challenging combination of paranoia, severe agitation and violent behavior. These patients frequently suffer from dehydration, skeletal muscle damage and renal failure that may lead to multiorgan failure and death. Management of these individuals requires careful consideration of the consequences of interventions commonly implemented in medical settings to control dangerous aggressive behavior.

3,4-Methylenedioxypyrovalerone (MDPV): in vitro mechanisms of hepatotoxicity under normothermic and hyperthermic conditions

Synthetic cathinones have emerged in recreational drug markets as legal alternatives for classical amphetamines. Though currently banned in several countries, 3,4-methylenedioxypyrovalerone (MDPV) is one of the most commonly abused cathinone derivatives worldwide. We have recently reported the potential of MDPV to induce hepatocellular damage, but the underlying mechanisms responsible for such toxicity remain to be elucidated. Similar to amphetamines, a prominent toxic effect of acute intoxications by MDPV is hyperthermia. Therefore, the present in vitro study aimed to provide insights into cellular mechanisms involved in MDPV-induced hepatotoxicity and also evaluate the contribution of hyperthermia to the observed toxic effects. Primary cultures of rat hepatocytes were exposed to 0.2-1.6 mM MDPV for 48 h, at 37 or 40.5 °C, simulating the rise in body temperature that follows MDPV intake. Cell viability was measured through the MTT reduction and LDH leakage assays. Oxidative stress endpoints and cell death pathways were evaluated, namely the production of reactive oxygen and nitrogen species (ROS and RNS), intracellular levels of reduced (GSH) and oxidized (GSSG) glutathione, adenosine triphosphate (ATP) and free calcium (Ca(2+)), as well as the activities of caspases 3, 8 and 9, and nuclear morphological changes with Hoechst 33342/PI double staining. At 37 °C, MDPV induced a concentration-dependent loss of cell viability that was accompanied by GSH depletion, as one of the first signs of toxicity, observed already at low concentrations of MDPV, with negligible changes on GSSG levels, followed by accumulation of ROS and RNS, depletion of ATP contents and increases in intracellular Ca(2+) concentrations. Additionally, activation of caspases 3, 8, and 9 and apoptotic nuclear morphological changes were found in primary rat hepatocytes exposed to MDPV, indicating that this cathinone derivative activates both intrinsic and extrinsic apoptotic death pathways. The cytotoxic potential of MDPV and all the studied endpoints were markedly aggravated under hyperthermic conditions (40.5 °C). In conclusion, these data suggest that MDPV toxicity in primary rat hepatocytes is mediated by oxidative stress, subsequent to GSH depletion and increased ROS and RNS accumulation, mitochondrial dysfunction, and impairment of Ca(2+) homeostasis. Furthermore, the rise in body temperature subsequent to MDPV abuse greatly exacerbates its hepatotoxic potential.

Individual Differences in the Relative Reinforcing Effects of 3,4-Methylenedioxypyrovalerone under Fixed and Progressive Ratio Schedules of Reinforcement in Rats

The recreational use of designer drugs, including synthetic cathinones (bath salts), is associated with high levels of abuse and toxicity, and represents a growing threat to public health. 3,4-Methylenedioxypyrovalerone (MDPV) is a cocaine-like monoamine uptake inhibitor, and one of the most widely available and abused synthetic cathinones. The present study used male Sprague-Dawley rats to directly compare: (1) the acquisition of responding for MDPV and cocaine under a fixed ratio (FR) 1 schedule of reinforcement; (2) full dose-response curves for MDPV and cocaine under a FR5 schedule; and (3) progressive ratio (PR) schedules of reinforcement. Self-administration of MDPV and cocaine was acquired at comparable rates, and by a similar percentage of rats. Compared with cocaine, MDPV was ∼10-fold more potent and ∼3-fold more effective at maintaining responding (PR; final ratio completed). Unlike cocaine, for which little variability was observed among rats, the FR5 dose-response curve for MDPV was shifted ∼3-fold upward for a subset of rats (high-responders) relative to other rats with identical histories (low-responders). Compared with low-responding rats, high responders also self-administered more cocaine under the FR5 schedule, and earned significantly more MDPV, cocaine, and methamphetamine under a PR schedule of reinforcement. In addition to functioning as a significantly more effective reinforcer than either cocaine or methamphetamine, MDPV also appears to be unique in its capacity to establish an enduring phenotype in rats, characterized by unusually high levels of drug intake. Although the factors underlying this high-responder phenotype are unclear, they might be related to individual differences in human drug-taking behavior.

Label-Free, Visual Detection of Small Molecules Using Highly Target-Responsive Multimodule Split Aptamer Constructs

Colorimetric aptamer-based sensors offer a simple means of on-site or point-of-care analyte detection. However, these sensors are largely incapable of achieving naked-eye detection, because of the poor performance of the target-recognition and signal-reporting elements employed. To address this problem, we report a generalizable strategy for engineering novel multimodule split DNA constructs termed "CBSAzymes" that utilize a cooperative binding split aptamer (CBSA) as a highly target-responsive bioreceptor and a new, highly active split DNAzyme as an efficient signal reporter. CBSAzymes consist of two fragments that remain separate in the absence of target, but effectively assemble in the presence of the target to form a complex that catalyzes the oxidation of 2,2'-azino-bis(3-ethylbenzthiazoline)-6-sulfonic acid, developing a dark green color within 5 min. Such assay enables rapid, sensitive, and visual detection of small molecules, which has not been achieved with any previously reported split-aptamer-DNAzyme conjugates. In an initial demonstration, we generate a cocaine-binding CBSAzyme that enables naked-eye detection of cocaine at concentrations as low as 10 μM. Notably, CBSAzyme engineering is straightforward and generalizable. We demonstrate this by developing a methylenedioxypyrovalerone (MDPV)-binding CBSAzyme for visual detection of MDPV and 10 other synthetic cathinones at low micromolar concentrations, even in biological samples. Given that CBSAzyme-based assays are simple, label-free, rapid, robust, and instrument-free, we believe that such assays should be readily applicable for on-site visual detection of various important small molecules such as illicit drugs, medical biomarkers, and toxins in various sample matrices.

Methylone and MDPV activate autophagy in human dopaminergic SH-SY5Y cells: a new insight into the context of β-keto amphetamines-related neurotoxicity

Autophagy has an essential role in neuronal homeostasis and its dysregulation has been recently linked to neurotoxic effects of a growing list of psychoactive drugs, including amphetamines. However, the role of autophagy in β-keto amphetamine (β-KA) designer drugs-induced neurotoxicity has hitherto not been investigated. In the present study, we show that two commonly abused cathinone derivatives, 3,4-methylenedioxymethcathinone (methylone) and 3,4-methylenedioxypyrovalerone (MDPV), elicit morphological changes consistent with autophagy and neurodegeneration, including formation of autophagic vacuoles and neurite retraction in dopaminergic SH-SY5Y cells. Methylone and MDPV prompted the formation of acidic vesicular organelles (AVOs) and lead to increased expression of the autophagy-associated protein LC3-II in a concentration- and time-dependent manner. Electron microscopy confirmed the presence of autophagosomes with typical double membranes and autolysosomes in cells exposed to both β-KA. The autophagic flux was further confirmed using bafilomycin A1, a known inhibitor of the late phase of autophagy. Moreover, we showed that autophagy markers were activated before the triggering of cell death and caspase 3 activation, suggesting that β-KA-induced autophagy precedes apoptotic cell death. To address the role of oxidative stress in autophagy induction, we also investigated the effects of antioxidant treatment with N-acetyl-L-cysteine (NAC) on autophagy and apoptotic markers altered by these drugs. NAC significantly attenuated methylone- and MDPV-induced cell death by completely inhibiting the generation of reactive oxygen and nitrogen species, and hampering both apoptotic and autophagic activity, suggesting that oxidative stress plays an important role in mediating autophagy and apoptosis elicited by these drugs.

Acute Methylenedioxypyrovalerone Toxicity

The objective of this study was to characterize the acute clinical effects, laboratory findings, complications, and disposition of patients presenting to the hospital after abusing synthetic cathinone. We conducted a retrospective multicenter case series of patients with synthetic cathinone abuse by searching for the terms bath salts, MDPV, methylenedioxypyrovalerone, mephedrone, methcathinone, methylone, methedrone, and cathinone within the "agent" field of a national clinical toxicology database (ToxIC). The medical records of these patients were obtained and abstracted by investigators at each study site. Patients with confirmatory testing that identified a synthetic cathinone in either blood or urine were included in the series. Patients who had either an undetectable synthetic cathinone test or no confirmatory testing were excluded. A data abstraction sheet was used to obtain information on each patient. We entered data into an Excel spreadsheet and calculated descriptive statistics. We identified 23 patients with confirmed synthetic cathinone exposure--all were positive for methylenedioxyprovalerone (MDPV). Eighty-three percent were male and 74 % had recreational intent. The most common reported clinical effects were tachycardia (74 %), agitation (65 %), and sympathomimetic syndrome (65 %). Acidosis was the most common laboratory abnormality (43 %). Seventy-eight percent of patients were treated with benzodiazepines and 30 % were intubated. Ninety-six percent of patients were hospitalized and 87 % were admitted to the ICU. The majority (61 %) of patients was discharged home but 30 % required inpatient psychiatric care. There was one death in our series. The majority of patients presenting to the hospital after abusing MDPV have severe sympathomimetic findings requiring hospitalization. A number of these patients require inpatient psychiatric care after their acute presentation.

Occurrence of new psychoactive substances in wastewater of major Chinese cities

New psychoactive substances have become increasingly popular across the globe in recent years, which may cause certain public health issues. In this work, sewage-based epidemiology was applied to examine the use of two synthetic cathinones, mephedrone and methylenedioxypyrovalerone (MDPV), and three piperazines, benzylpiperazine (BZP), trifluoromethylphenylpiperazine (TFMPP), and 1-(3-Chlorophenyl)piperazine (mCPP), across China. Influent wastewater samples were collected from 36 sewage treatment plants (STPs) in 18 major cities that cover all the geographic regions of the country. Effluent samples were also collected from selected STPs to determine removal rates. Mephedrone, TFMPP, and mCPP were below detection limits in all the wastewater samples collected, indicating negligible use of these substances in China. MDPV was detected in wastewater at 13 STPs. However, its loads were <1mg/1000inh/d at most of these STPs, indicating low use of this substance. BZP was detected at all the STPs examined, with loads typically falling within the range of 3-10mg/1000inh/d. No clear geographic pattern in BZP occurrence in wastewater was identified. Since BZP in wastewater may also come from its legal sources, whether widespread occurrence of BZP means widespread abuse is yet to be confirmed. Apparent removal of MDPV by wastewater treatment was low (<25%), whereas removal of BZP was nearly complete (typically>95%).

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.

Neurotoxicology of Synthetic Cathinone Analogs

The present review briefly explores the neurotoxic properties of methcathinone, mephedrone, methylone, and methylenedioxypyrovalerone (MDPV), four synthetic cathinones most commonly found in "bath salts." Cathinones are β-keto analogs of the commonly abused amphetamines and display pharmacological effects resembling cocaine and amphetamines, but despite their commonalities in chemical structures, synthetic cathinones possess distinct neuropharmacological profiles and produce unique effects. Among the similarities of synthetic cathinones with their non-keto analogs are their targeting of monoamine systems, the release of neurotransmitters, and their stimulant properties. Most of the literature on synthetic cathinones has focused on describing their properties as psychostimulants, their behavioral effects on locomotion, memory, and potential for abuse, whereas descriptions of their neurotoxic properties are not abundant. The biochemical gauges of neurotoxicity induced by non-keto analogs are well studied in humans and experimental animals and include their ability to induce neuroinflammation, oxidative stress, excitotoxicity, temperature alterations as well as dysregulation of neurotransmitter systems and induce changes in monoamine transporters and receptors. These neurotoxicity gauges will serve as parameters to discuss the effects of the four previously mentioned synthetic cathinones alone or in combination with either another cathinone or with some of their non-keto analogs. Bath salts are not a defined combination of drugs and may consist of one synthetic cathinone compound or combinations of more cathinones. Furthermore, this review also presents some of the mechanisms that are thought to underlie this toxicity. A better understanding of the cellular and molecular mechanisms involved in the synthetic cathinones-induced neurotoxicity should contribute to generate modern therapeutic approaches to prevent or attenuate the adverse consequences of use of these drugs in humans.

3,4-Methylenedioxypyrovalerone (MDPV) and metabolites quantification in human and rat plasma by liquid chromatography-high resolution mass spectrometry

Synthetic cathinones are recreational drugs that mimic the effects of illicit stimulants like cocaine, amphetamine or Ecstasy. Among the available synthetic cathinones in the United States, 3,4-methylenedioxypyrovalerone (MDPV) is commonly abused and associated with dangerous side effects. MDPV is a dopamine transporter blocker 10-fold more potent than cocaine as a locomotor stimulant in rats. Previous in vitro and in vivo studies examining MDPV metabolism reported 3,4-dihydroxypyrovalerone (3,4-catechol-PV) and 4-hydroxy-3-methoxypyrovalerone (4-OH-3-MeO-PV) as the two primary metabolites. We developed and validated a liquid chromatography-high resolution mass spectrometry method to quantify MDPV and its primary metabolites in 100 μL human and rat plasma. Plasma hydrolysis was followed by protein precipitation before analysis. Limits of detection were 0.1 μg L(-1), with linear ranges from 0.25 to 1000 μg L(-1). Process efficiency, matrix effect, total imprecision (%CV) and accuracy (%target) were 36-93%, from -8 to 12%, 2.1 to 7.3% and 86 to 109%, respectively. MDPV and metabolites were stable at room temperature for 24 h, 4 °C for 72 h and after 3 freeze-thaw cycles with less than 10% variability. Human-rat plasma cross validation demonstrated that rat plasma could be accurately quantified against a human plasma calibration curve. As proof of this method, rat plasma specimens were analyzed after intraperitoneal and subcutaneous dosing with MDPV (0.5 mg kg(-1)). MDPV, 3,4-catechol-PV and 4-OH-3-MeO-PV concentrations ranged from not detected to 107.5 μg L(-1) prior to and up to 8h after dosing. This method provides a simultaneous quantification of MDPV and two metabolites in plasma with good selectivity and sensitivity.

Methamphetamine, 3,4-methylenedioxymethamphetamine (MDMA) and 3,4-methylenedioxypyrovalerone (MDPV) induce differential cytotoxic effects in bovine brain microvessel endothelial cells

Designer drugs such as synthetic psychostimulants are indicative of a worldwide problem of drug abuse and addiction. In addition to methamphetamine (METH), these drugs include 3,4-methylenedioxy-methamphetamine (MDMA) and commercial preparations of synthetic cathinones including 3,4-methylenedioxypyrovalerone (MDPV), typically referred to as "bath salts." These psychostimulants exert neurotoxic effects by altering monoamine systems in the brain. Additionally, METH and MDMA adversely affect the integrity of the blood-brain barrier (BBB): there are no current reports on the effects of MDPV on the BBB. The aim of this study was to compare the effects of METH, MDMA and MDPV on bovine brain microvessel endothelial cells (bBMVECs), an accepted in vitro model of the BBB. Confluent bBMVEC monolayers were treated with METH, MDMA and MDPV (0.5mM-2.5mM) for 24h. METH and MDMA increased lactate dehydrogenase release only at the highest concentration (2.5mM), whereas MDPV induced cytotoxicity at all concentrations. MDMA and METH decreased cellular proliferation only at 2.5mM, with similar effects observed after MDPV exposures starting at 1mM. Only MDPV increased reactive oxygen species production at all concentrations tested whereas all 3 drugs increased nitric oxide production. Morphological analysis revealed different patterns of compound-induced cell damage. METH induced vacuole formation at 1mM and disruption of the monolayer at 2.5mM. MDMA induced disruption of the endothelial monolayer from 1mM without vacuolization. On the other hand, MDPV induced monolayer disruption at doses ≥0.5mM without vacuole formation; at 2.5mM, the few remaining cells lacked endothelial morphology. These data suggest that even though these synthetic psychostimulants alter monoaminergic systems, they each induce BBB toxicity by different mechanisms with MDPV being the most toxic.

Studies on the microbial biotransformation of the novel psychoactive substance methylenedioxypyrovalerone (MDPV) in wastewater by means of liquid chromatography-high resolution mass spectrometry/mass spectrometry

Sewage profiling as a mean to estimate consumption of drugs of abuse is gaining increasing attention. However, only scarce data are available so far on the impact of microbial biotransformation on the presence and hence detectability of drugs of abuse and their metabolites in wastewater (WW) samples. The aim of this work was therefore to study the biotransformation pathways of the novel psychoactive substance 3,4-methylenedioxypyrovalerone (MPDV) in WW by incubating it, based on the OECD guideline 314 A. MDPV was incubated (100 μg/L) for 10d at 22 °C in WW from a local WW treatment plant. Furthermore, urine and feces collected from rats administered 20mg MDPV/kg BW were incubated correspondingly. Samples were worked-up either by centrifugation/filtration and solid-phase (HCX) extraction or QuEChERS. High resolution (HR) mass spectra (MS) were recorded using an Orbitrap mass spectrometer. All products were identified via their HR-MS(2) spectra and chromatographic properties. The observed biotransformations in WW were: demethylenation and subsequent O-methylation, hydroxylation at the phenyl part, hydroxylation at the pyrrolidine part with subsequent methylation or oxidation, N-demethylation, and hydroxylation at the alkyl part as well as combination of them. In total, 12 biotransformation products were identified after 10 days of incubation. Three of these biotransformation products were previously reported to be also rat and human metabolites. No additional MDPV biotransformation products could be found after incubating the rat urine and feces samples. Instead, the urinary phase II glucuronides were nearly completely cleaved after one day of WW incubation. The presented study indicates that demethylenyl-methyl MDPV, the most abundant metabolite in human urine, should be the best indicator in WW to estimate its use.