Effects of methamphetamine in the hippocampus of cynomolgus monkeys according to age

Differential Gene Expression in the Hippocampi of Nonhuman Primates Chronically Exposed to Methamphetamine, Cocaine, or Heroin

OBJECTIVE

Methamphetamine (MA), cocaine, and heroin cause severe public health problems as well as impairments in neural plasticity and cognitive function in the hippocampus. This study aimed to identify the genes differentially expressed in the hippocampi of cynomolgus monkeys in response to these drugs.

METHODS

After the monkeys were chronically exposed to MA, cocaine, and heroin, we performed large-scale gene expression profiling of the hippocampus using RNA-Seq technology and functional annotation of genes differentially expressed. Some genes selected from RNA-Seq analysis data were validated with reverse transcription-quantitative polymerase chain reaction (RT-qPCR). And the expression changes of ADAM10 protein were assessed using immunohistochemistry.

RESULTS

The changes in genes related to axonal guidance (PTPRP and KAL1), the cell cycle (TLK2), and the regulation of potassium ions (DPP10) in the drug-treated groups compared to the control group were confirmed using RT-qPCR. Comparative analysis of all groups showed that among genes related to synaptic long-term potentiation, CREBBP and GRIN3A were downregulated in both the MA- and heroin-treated groups compared to the control group. In particular, the mRNA and protein expression levels of ADAM10 were decreased in the MA-treated group but increased in the cocaine-treated group compared to the control group.

CONCLUSION

These results provide insights into the genes that are upregulated and downregulated in the hippocampus by the chronic administration of MA, cocaine, or heroin and basic information for developing novel drugs for the treatment of hippocampal impairments caused by drug abuse.

Age-related Effects of Heroin on Gene Expression in the Hippocampus and Striatum of Cynomolgus Monkeys

Objective

The aim of this study was to investigate differentially expressed genes and their functions in the hippocampus and striatum after heroin administration in cynomolgus macaques of different ages.

Methods

Cynomolgus monkeys were divided by age as follows: 1 year (A1, n = 2); 3 to 4 years (A2, n = 2); 6 to 8 years (A3, n = 2); and older than 11 years (A4, n = 2). After heroin was injected intramuscularly into the monkeys (0.6 mg/kg), we performed large-scale transcriptome profiling in the hippocampus (H) and striatum (S) using RNA sequencing technology. Some genes were validated with real-time quantitative PCR.

Results

In the hippocampus, the gene expression of A1H was similar to that of A4H, while the gene expression of A2H was similar to that of A3H. Genes associated with the mitogen-activated protein kinase signaling pathway (STMN1, FGF14, and MAPT) and γ-aminobutyric acid-ergic synapses (GABBR2 and GAD1) were differentially expressed among control and heroin-treated animals. Differential gene expression between A1S and A4S was the least significant, while differential gene expression between A3S and A2S was the most significant. Genes associated with the neurotrophin signaling pathway (NTRK1 and NGFR), autophagy (ATG5), and dopaminergic synapses (AKT1) in the striatum were differentially expressed among control and heroin-treated animals.

Conclusion

These results suggest that even a single heroin exposure can cause differential gene expression in the hippocampus and striatum of nonhuman primates at different ages.