Proteomic Insights into Heroin Use: Links to Neurodegeneration

Abstract Due to a lack of information related to molecular changes in heroin use, we aimed to examine heroin-dependent alterations in different regions of the post-mortem human brain. Tissues were obtained from males (n = 24 heroin users, n = 24 controls) through the Turkish Forensic Medicine Institute after structured verbal interviews with the relatives of the deceased to gather history of substance use. Following toxicological confirmation of heroin use, the hippocampus, putamen, and caudate nucleus were dissected from the left hemispheres. Proteomic analyses were performed using a high-resolution liquid chromatography-electrospray ionization-tandem mass spectrometry (LC–ESI–MS/MS) system. Label-free quantitative analysis revealed significant differential expression of 87 proteins in the hippocampus, 121 proteins in the putamen, and 80 proteins in the caudate nucleus compared to controls. These differentially expressed proteins (DEPs) were subsequently used to construct protein–protein interaction (PPI) networks using the STRING database, revealing significantly enriched and highly interconnected interaction networks in all three regions. Gene Ontology (GO) enrichment analysis of DEPs consistently identified extracellular exosome, extracellular space, and vesicle as the top three cellular components. Molecular function enrichment further indicated alterations in signaling, binding, and stress-related processes. The expression of TST, RYR2, ACTBL2, and RPS27 decreased, whereas the expression of COL4A2, OGN, PMP2, and MAP2K6 increased in the hippocampus. In the putamen, the most prominent increases were observed in DNM2 and MADD expression. In the caudate nucleus, the expressions of RPS6KA2, TMED10, and NBEA proteins decreased, whereas HPX protein expression increased. Overall, these alterations promote oxidative stress and molecular changes linked to neurodegeneration, which likely contribute to impaired neuronal function and synaptic plasticity.