Acute toxicity, 28-day repeated-dose toxicity and toxicokinetic study of timosaponin BII in beagle dogs.

The safety evaluation of timosaponin BII (TBII) in beagle dogs with toxicokinetic study was performed. For the acute oral toxicity study, the minimum lethal dose (MLD) of TBII was more than 2000 mg/kg and suggested the characteristics of absorption saturation. For the 28-day repeated dose oral toxicity and toxicokinetic studies, there was no significant effect on all test parameters except for prolonged APTT in the 60 and 180 mg/kg groups, which recovered after withdrawal. The increase of drug exposure of 180 mg/kg group was not proportional to the increase of administration dose, showing the characteristics of absorption saturation.

Biotransformation of Timosaponin BII into Seven Characteristic Metabolites by the Gut Microbiota.

Timosaponin BII is one of the most abundant Anemarrhena saponins and is in a phase II clinical trial for the treatment of dementia. However, the pharmacological activity of timosaponin BII does not match its low bioavailability. In this study, we aimed to determine the effects of gut microbiota on timosaponin BII metabolism. We found that intestinal flora had a strong metabolic effect on timosaponin BII by HPLC-MS/MS. At the same time, seven potential metabolites (M1-M7) produced by rat intestinal flora were identified using HPLC/MS-Q-TOF. Among them, three structures identified are reported in gut microbiota for the first time. A comparison of rat liver homogenate and a rat liver microsome incubation system revealed that the metabolic behavior of timosaponin BII was unique to the gut microbiota system. Finally, a quantitative method for the three representative metabolites was established by HPLC-MS/MS, and the temporal relationship among the metabolites was initially clarified. In summary, it is suggested that the metabolic characteristics of gut microbiota may be an important indicator of the pharmacological activity of timosaponin BII, which can be applied to guide its application and clinical use in the future.

Naltrexone attenuates methamphetamine-induced behavioral sensitization and conditioned place preference in mice.

Methamphetamine addiction causes serious public health problems worldwide. However, there is no effective medication licensed for methamphetamine addiction. The endogenous opioid system is considered to be a common substrate in drug addiction due to its regulation of dopamine release. In recent clinical trials, (-)-naltrexone, an opioid receptors and Toll-like receptor 4 antagonist, has exhibited encouraging findings for treating methamphetamine addiction; however, the understanding of its pharmacological mechanisms remains insufficient. By using mice models of behavioral sensitization and conditioned place preference (CPP), the present study was performed to investigate the effects of naltrexone on the methamphetamine-associated properties of incentive salience and reward-related memory, the two crucial factors for the development of addictive process and relapse. We found that naltrexone reduced single methamphetamine-induced hyperlocomotion in mice. In the paradigm of methamphetamine-induced behavioral sensitization paired with contextual cues in mice, naltrexone suppressed the development and expression of locomotor sensitization, suggesting the decrease in incentive salience to methamphetamine and context. In the methamphetamine-induced CPP paradigm in mice, naltrexone attenuated both the expression and methamphetamine-priming reinstatement of CPP response, suggesting the impairment of either contextual cue- or drug-induced retrieval of methamphetamine-associated memory. After the establishment of methamphetamine-induced CPP in mice, naltrexone treatment during the extinction training produced conditioned place adverse response, suggesting that naltrexone facilitated negative affection-associated extinction learning. Taken together, these findings demonstrate that naltrexone could intervene in the properties of incentive salience and reward-related memory in methamphetamine addiction, which may contribute to its therapeutic effects on methamphetamine addicts in clinical studies.

Inhibition of naltrexone on relapse in methamphetamine self-administration and conditioned place preference in rats.

Methamphetamine (METH) addiction has been widely spread and caused severe problems both in society and public health in recent years, but there is a shortage of medication available. The naltrexone (NTX) as a non-selective opioid receptor antagonist has been widely applied to treat alcohol addiction and the relapse to opioid addiction after detoxification. In the present study, we investigated the potent pharmacotherapeutic effect of NTX in attenuating relapse to drug-seeking behavior in the METH self-administration and conditioned place preference (CPP) in rats. The results showed that acute intragastrical administration of NTX (40 mg/kg) significantly reduced cue-induced drug-seeking behavior after extinction training. The similar inhibition effect was observed in the CPP model, that the intragastrical administration of NTX (30 mg/kg) significantly disrupted the reactivation induced by intraperitoneal injection of METH (0.5 mg/kg) after the extinction training process. However, respective intragastrical administration of NTX (20 or 40 mg/kg) failed to alter the dose-response curve of METH under fixed ratio 2 program and intraperitoneal injection of METH (1.0 mg/kg)-induced reinstatement in rats self-administration. Overall, our findings suggest that NTX has the pharmacotherapeutic potential in reducing the relapse of METH addiction, which deserves further investigation as a promising medication for the treatment of METH addiction.