Methamphetamine Exposure in Adolescent Impairs Memory of Mice in Adulthood Accompanied by Changes in Neuroplasticity in the Dorsal Hippocampus

Methamphetamine-induced impairment of memory and fleeting neuroinflammation: Profiling mRNA changes in mouse hippocampus following short-term and long-term exposure

Methamphetamine (METH) has been implicated in inducing memory impairment, but the precise mechanisms underlying this effect remain unclear. Current research often limits itself to singular models or focuses on individual gene or protein functions, which hampers a comprehensive understanding of the underlying mechanisms. In this study, we established three METH mouse exposure models, extracted hippocampal nuclei, and utilized RNA sequencing to analyze changes in mRNA expression profiles. Our results indicate that METH significantly impairs the learning and memory capabilities of mice. Additionally, we observed that METH-induced inflammatory responses occur in the early phase and do not further exacerbate with repeated injections. However, RNA sequencing revealed the persistent enrichment of inflammatory pathway molecules, which correlated with worsened behaviors. This suggests that although METH-induced neuroinflammation plays a critical role in learning and memory impairment, the continued enrichment of inflammatory pathway molecules is associated with behavioral outcomes. These findings provide crucial evidence for the potential application of immune intervention in METH-related disorders.

Single-dose methamphetamine administration impairs ORM retrieval in mice via excessive DA-mediated inhibition of PrLGlu activity

Methamphetamine (METH), an abused psychostimulant, impairs cognition through prolonged or even single-dose exposure, but animal experiments have shown contradictory effects on memory deficits. In this study we investigated the effects and underlying mechanisms of single-dose METH administration on the retrieval of object recognition memory (ORM) in mice. We showed that single-dose METH administration (2 mg/kg, i.p.) significantly impaired ORM retrieval in mice. Fiber photometry recording in METH-treated mice revealed that the activity of prelimbic cortex glutamatergic neurons (PrLGlu) was significantly reduced during ORM retrieval. Chemogenetic activation of PrLGlu or glutamatergic projections from ventral CA1 to PrL (vCA1Glu-PrL) rescued ORM retrieval impairment. Fiber photometry recording revealed that dopamine (DA) levels in PrL of METH-treated mice were significantly increased, and micro-infusion of the D2 receptor (D2R) antagonist sulpiride (0.25 μg/side) into PrL rescued ORM retrieval impairment. Whole-cell recordings in brain slices containing the PrL revealed that PrLGlu intrinsic excitability and basal glutamatergic synaptic transmission were significantly reduced in METH-treated mice, and the decrease in intrinsic excitability was reversed by micro-infusion of Sulpiride into PrL in METH-treated mice. Thus, the impaired ORM retrieval caused by single-dose METH administration may be attributed to reduced PrLGlu activity, possibly due to excessive DA activity on D2R. Selective activation of PrLGlu or vCA1Glu-PrL may serve as a potential therapeutic strategy for METH-induced cognitive dysfunction.

Regional-specific changes in rat brain BDNF in a model of methamphetamine abuse

Brain-derived neurotrophic factor (BDNF), a member of the neurotrophin family, plays key roles in neuronal protection and synaptic plasticity. Changes in BDNF are associated with various pathological conditions, including methamphetamine (meth) addiction, although the effects of meth on BDNF expression are not always consistent. We have previously demonstrated region-specific effects of a chronic meth regime on BDNF methylation and expression in the rat brain. This study aims to determine the effect of chronic meth administration on the expression of BDNF protein using immunohistochemistry in the rat frontal cortex and hippocampus. Novel object recognition (NOR) as a measure of cognitive function was also determined. Male Sprague Dawley rats were administered a chronic escalating dose (0.1-4 mg/kg over 14 days) (ED) of meth or vehicle; a subgroup of animals receiving meth were also given an acute "binge" (4x6mg) dose on the final day before NOR testing. The results showed that hippocampal CA1 BDNF protein was significantly increased by 72 % above control values in the ED-binge rats, while other hippocampal regions and frontal cortex were not significantly affected. Meth-administered animals also demonstrated deficits in NOR after 24 h delay. No significant effect of the additional binge dose on BDNF protein or NOR findings was apparent. This finding is consistent with our previous results of reduced DNA methylation and increased expression of the BDNF gene in this region. The hippocampal BDNF increase may reflect an initial increase in a protective factor produced in response to elevated glutamate release resulting in neurodegenerative excitotoxicity.

Effects of exercise interventions on negative emotions, cognitive performance and drug craving in methamphetamine addiction

Introduction

Methamphetamine is currently one of the most commonly used addictive substances with strong addiction and a high relapse rate. This systematic review aims to examine the effectiveness of physical activity in improving negative emotions, cognitive impairment, and drug craving in people with methamphetamine use disorder (MUD).

Methods

A total of 17 studies out of 133 found from Embase and PubMed were identified, reporting results from 1836 participants from MUD populations. Original research using clearly described physical activity as interventions and reporting quantifiable outcomes of negative mood, cognitive function and drug craving level in people with MUD were eligible for inclusion. We included prospective studies, randomized controlled trials, or intervention studies, focusing on the neurological effects of physical activity on MUD.

Results

Taken together, the available clinical evidence showed that physical activity-based interventions may be effective in managing MUD-related withdrawal symptoms.

Discussion

Physical exercise may improve drug rehabilitation efficiency by improving negative emotions, cognitive behaviors, and drug cravings.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42024530359.

Gut Microbiota Taxon-Dependent Transformation of Microglial M1/M2 Phenotypes Underlying Mechanisms of Spatial Learning and Memory Impairment after Chronic Methamphetamine Exposure

Methamphetamine (METH) exposure may lead to cognitive impairment. Currently, evidence suggests that METH exposure alters the configuration of the gut microbiota. However, the role and mechanism of the gut microbiota in cognitive impairment after METH exposure are still largely unknown. Here, we investigated the impact of the gut microbiota on the phenotype status of microglia (microglial phenotypes M1 and microglial M2) and their secreting factors, the subsequent hippocampal neural processes, and the resulting influence on spatial learning and memory of chronically METH-exposed mice. We determined that gut microbiota perturbation triggered the transformation of microglial M2 to M1 and a subsequent change of pro-brain-derived neurotrophic factor (proBDNF)-p75NTR-mature BDNF (mBDNF)-TrkB signaling, which caused reduction of hippocampal neurogenesis and synaptic plasticity-related proteins (SYN, PSD95, and MAP2) and, consequently, deteriorated spatial learning and memory. More specifically, we found that Clostridia, Bacteroides, Lactobacillus, and Muribaculaceae might dramatically affect the homeostasis of microglial M1/M2 phenotypes and eventually contribute to spatial learning and memory decline after chronic METH exposure. Finally, we found that fecal microbial transplantation could protect against spatial learning and memory decline by restoring the microglial M1/M2 phenotype status and the subsequent proBDNF-p75NTR/mBDNF-TrkB signaling in the hippocampi of chronically METH-exposed mice. IMPORTANCE Our study indicated that the gut microbiota contributes to spatial learning and memory dysfunction after chronic METH exposure, in which microglial phenotype status plays an intermediary role. The elucidated "specific microbiota taxa-microglial M1/M2 phenotypes-spatial learning and memory impairment" pathway would provide a novel mechanism and elucidate potential gut microbiota taxon targets for the no-drug treatment of cognitive deterioration after chronic METH exposure.

Effects of glycogen synthase kinase-3β activity inhibition on cognitive, behavioral, and hippocampal ultrastructural deficits in adulthood associated with adolescent methamphetamine exposure

Objective

Glycogen synthase kinase-3β (GSK3β) has been implicated in the maintenance of synaptic plasticity, memory process, and psychostimulant-induced behavioral effects. Hyperactive GSK3β in the Cornu Ammonis 1 (CA1) subregion of the dorsal hippocampus (DHP) was associated with adolescent methamphetamine (METH) exposure-induced behavioral and cognitive deficits in adulthood. This study aimed to evaluate the possible therapeutic effects of GSK3β inhibition in adulthood on adolescent METH exposure-induced long-term neurobiological deficits.

Methods

Adolescent male mice were treated with METH from postnatal day (PND) 45-51. In adulthood, three intervention protocols (acute lithium chloride systemic administration, chronic lithium chloride systemic administration, and chronic SB216763 administration within CA1) were used for GSK3β activity inhibition. The effect of GSK3β intervention on cognition, behavior, and GSK3β activity and synaptic ultrastructure in the DHP CA1 subregion were detected in adulthood.

Results

In adulthood, all three interventions reduced adolescent METH exposure-induced hyperactivity (PND97), while only chronic systemic and chronic within CA1 administration ameliorated the induced impairments in spatial (PND99), social (PND101) and object (PND103) recognition memory. In addition, although three interventions reversed the aberrant GSK3β activity in the DHP CA1 subregion (PND104), only chronic systemic and chronic within CA1 administration rescued adolescent METH exposure-induced synaptic ultrastructure changes in the DHP CA1 subregion (PND104) in adulthood.

Conclusion

Rescuing synaptic ultrastructural abnormalities in the dHIP CA1 subregion by chronic administration of a GSK3β inhibitor may be a suitable therapeutic strategy for the treatment of behavioral and cognitive deficits in adulthood associated with adolescent METH abuse.

Progranulin from different gliocytes in the nucleus accumbens exerts distinct roles in FTD- and neuroinflammation-induced depression-like behaviors

BACKGROUND

Neuroinflammation in the nucleus accumbens (NAc) is well known to influence the progression of depression. However, the molecular mechanisms triggering NAc neuroinflammation in depression have not been fully elucidated. Progranulin (PGRN) is a multifunctional growth factor that is linked to the innate immune response and inflammation, and PGRN plays a key role in neurodegenerative diseases such as frontotemporal dementia (FTD). Here, the purpose of this study was to validate whether PGRN was involved in the NAc neuroinflammation-promoted depressive-like phenotype.

METHODS

A NAc neuroinflammation-relevant depression-like model was established using wild-type (WT) and PGRN-knockout (KO) mice after NAc injection with lipopolysaccharide (LPS), and various behavioral tests related to cognition, social recognition, depression and anxiety were performed with WT and PGRNKO mice with or without NAc immune challenge. RT‒PCR, ELISA, western blotting and immunofluorescence staining were used to determine the expression and function of PGRN in the neuroinflammatory reaction in the NAc after LPS challenge. The morphology of neurons in the NAc from WT and PGRNKO mice under conditions of NAc neuroinflammation was analyzed using Golgi-Cox staining, followed by Sholl analyses. The potential signaling pathways involved in NAc neuroinflammation in PGRNKO mice were investigated by western blotting.

RESULTS

Under normal conditions, PGRN deficiency induced FTD-like behaviors in mice and astrocyte activation in the NAc, promoted the release of the inflammatory cytokines interleukin (IL)-6 and IL-10 and increased dendritic complexity and synaptic protein BDNF levels in the NAc. However, NAc neuroinflammation enhanced PGRN expression, which was located in astrocytes and microglia within the NAc, and PGRN deficiency in mice alleviated NAc neuroinflammation-elicited depression-like behaviors, seemingly inhibiting astrocyte- and microglia-related inflammatory reactions and neuroplasticity complexity in the NAc via the p38 and nuclear factor of kappa (NF-κB) signaling pathways present in the NAc after neuroinflammation.

CONCLUSIONS

Our results suggest that PGRN exerts distinct function on different behaviors, showing protective roles in the FTD-like behavior and detrimental effects on the neuroinflammation-related depression-like behavior, resulting from mediating astrocyte and microglial functions from the NAc in different status.

Low and high dose methamphetamine differentially regulate synaptic structural plasticity in cortex and hippocampus

Psychostimulants, such as methamphetamine (METH) can induce structural remodeling of synapses by remodeling presynaptic and postsynaptic morphology. Escalating or long-lasting high dose METH accounts for neurodegeneration by targeting multiple neurotransmitters. However, the effects of low dose METH on synaptic structure and the modulation mechanism remain elusive. This study aims to assess the effects of low dose (2 mg/kg) and high dose (10 mg/kg) of METH on synaptic structure alternation in hippocampus and prefrontal cortex (PFC) and to reveal the underlying mechanism involved in the process. Low dose METH promoted spine formation, synaptic number increase, post-synaptic density length elongation, and memory function. High dose of METH induced synaptic degeneration, neuronal number loss and memory impairment. Moreover, high dose, but not low dose, of METH caused gliosis in PFC and hippocampus. Mechanism-wise, low dose METH inactivated ras-related C3 botulinum toxin substrate 1 (Rac1) and activated cell division control protein 42 homolog (Cdc42); whereas high dose METH inactivated Cdc42 and activated Rac1. We provided evidence that low and high doses of METH differentially regulate synaptic plasticity in cortex and hippocampus.

Microglial infiltration mediates cognitive dysfunction in rat models of hypothalamic obesity via a hypothalamic-hippocampal circuit involving the lateral hypothalamic area

This study aimed to explore the mechanism underlying cognitive dysfunction mediated by the lateral hypothalamic area (LHA) in a hypothalamic-hippocampal circuit in rats with lesion-induced hypothalamic obesity (HO). The HO model was established by electrically lesioning the hypothalamic nuclei. The open field (OP) test, Morris water maze (MWM), novel object recognition (NOR), and novel object location memory (NLM) tests were used to evaluate changes in cognition due to alterations in the hypothalamic-hippocampal circuit. Western blotting, immunohistochemical staining, and cholera toxin subunit B conjugated with Alexa Fluor 488 (CTB488) reverse tracer technology were used to determine synaptophysin (SYN), postsynaptic density protein 95 (PSD95), ionized calcium binding adaptor molecule 1 (Iba1), neuronal nuclear protein (NeuN), and Caspase3 expression levels and the hypothalamic-hippocampal circuit. In HO rats, severe obesity was associated with cognitive dysfunction after the lesion of the hypothalamus. Furthermore, neuronal apoptosis and activated microglia in the downstream of the lesion area (the LHA) induced microglial infiltration into the intact hippocampus via the LHA-hippocampal circuit, and the synapses engulfment in the hippocampus may be the underlying mechanism by which the remodeled microglial mediates memory impairments in HO rats. The HO rats exhibited microglial infiltration and synapse loss into the hippocampus from the lesioned LHA via the hypothalamic-hippocampal circuit. The underlying mechanisms of memory function may be related to the circuit.