Introduction: The molecular mechanisms underlying chemotherapy-associated hippocampal neurodegeneration, particularly following exposure to alkylating agents, remain poorly understood. This study investigated the association between melphalan- and chlorambucil-induced hippocampal injury and alterations in apoptosis-, autophagy-, and miR-204-related pathways.
Methods: Adult male Wistar rats were treated daily for 30 days with saline (control), Mel, or Chl. Hippocampal tissue was analyzed using histological assessment of dark neurons and qRT-PCR analysis of apoptosis-related genes (Bax, Bcl-2, Caspase-3), autophagy-related genes (LC3β and Beclin-1), and miR-204 expression.
Results: Both Mel and Chl significantly increased the density of dark neurons in the hippocampus compared with the control group. Molecular analysis revealed increased expression of the pro-apoptotic genes BAX and Caspase-3 together with reduced expression of the anti-apoptotic gene BCL2. In addition, the expression levels of the autophagy-related genes LC3β and Beclin-1 were significantly decreased following treatment. Furthermore, miR-204 expression was significantly upregulated in both Mel and Chl groups and was associated with hippocampal neurodegeneration, increased expression of apoptosis-related genes, and reduced expression of autophagy-related genes.
Conclusion: These findings indicate that systemic exposure to melphalan and chlorambucil is associated with hippocampal neurodegenerative changes accompanied by altered expression of apoptosis- and autophagy-related genes. The consistent upregulation of miR-204 suggests that this microRNA may contribute to alkylating agent-associated hippocampal neurodegeneration; however, further functional studies are required to determine its mechanistic role and therapeutic relevance in chemotherapy-related cognitive impairment.