Basolateral Amygdala Serotonin 2C Receptor Regulates Emotional Disorder-Related Symptoms Induced by Chronic Methamphetamine Administration

Aerobic Exercise Improves Methamphetamine-Induced Olfactory Dysfunction Through α-Synuclein Intervention in Male Mice

Methamphetamine (Meth) is a predominantly abused neurostimulant, and its abuse is often associated with multiple neurological symptoms. Olfaction, the sense of smell, is a highly neurotransmission-dependent physiological process; however, the effect of Meth on olfactory function and its underlying mechanisms remain largely unknown. This study aimed to explore the impact of Meth abuse on the olfactory system and the potential mechanisms. Chronic Meth abuse was induced by daily administration of Meth in male mice for 4 weeks, and we then systematically examined olfactory performance. Behavioral tests found that Meth-treated animals showed increased olfactory threshold, decreased olfactory sensitivity, reduced olfactory-dependent discrimination, and difficulty in seeking buried food. Notably, the increased deposition of α-synuclein (α-syn) in the olfactory bulb was detected. Adeno-associated virus (AAV)-mediated α-syn intervention therapy in the olfactory bulb significantly alleviated Meth-induced olfactory function impairment, and 8 weeks of aerobic exercise showed similar effects through the same principle of α-syn intervention. Notably, exercise-mediated reduction of α-syn inhibited abnormal firing activity and restored the inhibitory synaptic regulation of mitral cells in the olfactory bulb. These findings suggest the involvement of α-syn in the pathogenic mechanisms of Meth-induced olfactory dysfunction and shed light on the possible therapeutic applications of aerobic exercise in Meth-induced olfactory dysfunction.

Icariside II Attenuates Methamphetamine-Induced Neurotoxicity and Behavioral Impairments via Activating the Keap1-Nrf2 Pathway

Chronic and long-term methamphetamine (METH) abuse is bound to cause damages to multiple organs and systems, especially the central nervous system (CNS). Icariside II (ICS), a type of flavonoid and one of the main active ingredients of the traditional Chinese medicine Epimedium, exhibits a variety of biological and pharmacological properties such as anti-inflammatory, antioxidant, and anticancer activities. However, whether ICS could protect against METH-induced neurotoxicity remains unknown. Based on a chronic METH abuse mouse model, we detected the neurotoxicity after METH exposure and determined the intervention effect of ICS and the potential mechanism of action. Here, we found that METH could trigger neurotoxicity, which was characterized by loss of dopaminergic neurons, depletion of dopamine (DA), activation of glial cells, upregulation of α-synuclein (α-syn), abnormal dendritic spine plasticity, and dysfunction of motor coordination and balance. ICS treatment, however, alleviated the above-mentioned neurotoxicity elicited by METH. Our data also indicated that when ICS combated METH-induced neurotoxicity, it was accompanied by partial correction of the abnormal Kelch 2 like ECH2 associated protein 1 (Keap1)-nuclear factor erythroid-2-related factor 2 (Nrf2) pathway and oxidative stress response. In the presence of ML385, an inhibitor of Nrf2, ICS failed to activate the Nrf2-related protein expression and reduce the oxidative stress response. More importantly, ICS could not attenuate METH-induced dopaminergic neurotoxicity and behavioral damage when the Nrf2 was inhibited, suggesting that the neuroprotective effect of ICS on METH-induced neurotoxicity was dependent on activating the Keap1-Nrf2 pathway. Although further research is needed to dig deeper into the actual molecular targets of ICS, it is undeniable that the current results imply the potential value of ICS to reduce the neurotoxicity of METH abusers.

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.