Time and region-dependent manner of increased brain derived neurotrophic factor and TrkB in rat brain after binge-like methamphetamine exposure

Time course of plasticity-related alterations following the first exposure to amphetamine in juvenile rats

In vulnerable consumers, the first drug exposure induces various neurobehavioral adaptations that may represent the starting point toward addiction. Elucidating the neuroplastic mechanisms underlying that first rewarding experience would contribute to understanding the transition from recreational to compulsive drug use. In a preclinical model with juvenile rats, we analyzed the time-dependent fluctuations in the expression of neuroplasticity-related genes like the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), the cAMP response element-binding protein (CREB), the microRNA-132, the Rho GTPase-activating protein 32 (p250GAP), the corticotropin-releasing factor (CRF), and the neurotransmitters contents in the nucleus accumbens (NAc) and the dorsal striatum (DS) 45, 90, and 180 min after an amphetamine (AMPH) injection. As expected, AMPH altered the concentration of norepinephrine, dopamine, DOPAC, and serotonin in a region- and time-dependent manner. Regarding gene expression, AMPH at 45 min upregulated BDNF and primiR-132 expression in NAc and downregulated TrkB expression in DS. At 90 min, AMPH upregulated TrkB, CREB, p250GAP, and primiR-132 expression in NAc and BDNF, primiR-132, and CRF in DS. At 180 min, only BNDF in NAc continued to be upregulated by AMPH. Based on the levels of AMPH-induced hyperactivity, we classified the rats as low and high AMPH responders. High AMPH responders characterized by overexpressing BDNF, CREB, p250GAP, and CRF in NAc and by showing lower levels of dopamine and serotonin metabolites and turnovers in both regions. Our findings demonstrated that a single AMPH administration is enough to induce neuroplastic adaptations, especially in the NAc of prone rats.

Regulation and bioinformatic analysis of circ_0015891/miR-129-1-3p axis in methamphetamine-induced dopaminergic apoptosis

Methamphetamine (METH) abuse can result in severe neurotoxicity, for which the mechanism is not yet clear. In the present study, we investigated the role of noncoding RNAs in METH-induced dopaminergic neurotoxicity, and analyzed the underlying mechanism using bioinformatic methods. We confirmed by flow cytometry that miR-129-1-3p is involved in promoting dopaminergic apoptosis under METH treatment and its role could be inhibited by a high concentration of circ_0015891. Also, we combined transcriptomic data with bioinformatics to explore the downstream mechanism of miR-129-1-3p regulation of METH-induced apoptosis, highlighted the potentially pivotal figure of response to nutrition. Further bioinformatic analysis of circ_0015891 was conducted as well and showed that circ_0015891 was the sponge of various microRNAs that effect apoptosis by different mechanisms. Collectively, we found a novel circ_0015891/miR-129-1-3p axis that may be a promising therapeutic target for METH-induced dopaminergic neurotoxicity.

Neuronal growth and synaptogenesis are inhibited by prenatal methamphetamine exposure leading to memory impairment in adolescent and adult mice

Synaptogenesis plays critical roles in learning and memory processes and is susceptible to substance abuse toxicity. The present study aimed to elucidate the long-lasting effects of prenatal methamphetamine exposure on synaptogenesis and learning and memory. The involvement of BDNF-TrkB signaling was also investigated. Pregnant mice (C57BL/6 JNc) were administered methamphetamine (5 mg/kg, s.c.) on gestation days 8-15. Primary hippocampal cultures were prepared from fetuses at gestational day 16.5 to study neuronal morphology and synaptogenesis. The expression of synaptic proteins, BDNF and TrkB receptor was determined in postnatal day 14 (PND14), adolescent and adult mice; memory tests were also conducted. MA exposure decreased axon length and diameter, and synaptic areas in the primary cultures. Presynaptic protein was decreased in the hippocampus of PND14 mice prenatally exposed to MA, while increases in postsynaptic protein (PSD-95) were found in MA-exposed adolescent and adult mice. BDNF expression was enhanced in the prefrontal cortex and striatum of MA-exposed PND14 mice. Memory impairment was observed in MA-exposed adolescent and adult mice compared to control mice. Prenatal MA exposure disrupted neuronal growth and synapse formation in the developing brain with only short-term interference of the BDNF-TrkB signaling pathway, resulting in the adaptation of postsynaptic neurons. Alterations in the developing brain and synaptogenesis lead to long-lasting learning and memory impairment.

Time-dependent changes in striatal monoamine levels and gene expression following single and repeated amphetamine administration in rats

As drug addiction may result from pathological usurpations of learning and memory's neural mechanisms, we focused on the amphetamine-induced time-dependent neurochemical changes associated with neural plasticity. We used juvenile rats as the risk for drug abuse is higher during adolescence. Experiment 1 served to define the appropriate amphetamine dose and the neurochemical effects of a single administration. In experiment 2, rats received seven amphetamine or saline injections in the open-field test throughout a twelve-day period. We measured the mRNA levels of the brain-derived neurotrophic factor (BDNF), its tropomyosin receptor kinase B (TrkB), the cAMP response element-binding protein (CREB), the microRNA-132, the Rho GTPase-activating protein 32 (p250GAP), the corticotropin-releasing factor (CRF), and monoamines and amino-acids contents in the nucleus accumbens and the dorsal striatum 45, 90, and 180 min after the last injection. We found that amphetamine changed gene expression only at certain time points and in a dose and region-dependent manner. Repeated but not single administrations upregulated accumbal and striatal BDNF (180 min) and striatal pri-miR-132 (90 min) expression, while downregulated accumbal CREB levels (90 min). As only some drug users develop addiction, we compared brain parameters between low and high amphetamine responders. Prone subjects characterized by having reduced striatal 5-HT metabolism, higher accumbal BDNF and TrkB expression, and lower levels of CREB in the dorsal striatum and p250GAP in both regions. Thus, individual differences in drug-induced changes in neurotransmission and gene expression in nigrostriatal and mesolimbic dopaminergic pathways may underlie the plasticity adaptations associated with behavioral sensitization to amphetamine.

Neuroprotective and neuro-survival properties of safinamide against methamphetamine-induced neurodegeneration: Hypothetic possible role of BDNF/TrkB/PGC-1α signaling pathway and mitochondrial uncoupling protein -2(UCP-2)

Methamphetamine is a behavioral psychostimulant that has a high potential for misuse and induction of neurotoxicity. Safinamide is a novel inhibitor of monoamine oxidase B (MAOB) with neuroprotective properties. Methamphetamine abuse causes dysfunction in the respiratory chain of the mitochondria, but the specific signaling mechanism and role of the uncoupling protein-2(UCP-2) remain unclear. As we know, some indirect evidence indicates that neurodegeneration can be caused by inhibition of the brain-derived neurotrophic factor (BDNF) receptor, TrkB and its downstream signaling pathway, such as the PGC-1α protein. Neuroprotective strategies and approaches to the management, treatment or prevention of methamphetamine-induced neurodegeneration by modulating BDNF / TrkB / PGC-1α-UCP-2 can be considered as novel therapeutic approaches to these psychostimulant neurochemical and neurobehavioral approaches. Previous studies have shown that safinamide, a monoamine oxidase-B (MAOB) inhibitor, can function as a neuroprotective agent and inhibit the neurodegenerative process especially in Parkinson's disease but its impact on other neurodegenerative processes and drug-induced neurotoxicity remain unclear. Although there is some evidence that BDNF / TrkB / PGC-1α-UCP-2 signaling pathway and mitochondrial UCP-2 mediated safinamide induced neuroprotection but it's exact and precise mechanism of action and neuroprotective effects in neurodegenerative disorder and the protective properties against methamphetamine induced neurodegeneration and the role of BDNF / TrkB / PGC-1α signaling pathway and role of mitochondrial UCP-2 in this process have not yet been clarified. Therefore, in subjects addicted to methamphetamine, we hypothesized that safinamide will provide neuroprotection against methamphetamine-prompted neurodegeneration, and it appears that BDNF / TrkB / PGC-1α signaling pathway and mitochondrial UCP-2 are likely to play a critical role.