MOLECULAR BASES OF METHAMPHETAMINE-INDUCED NEURODEGENERATION

Methamphetamine (METH) is a potent, addictive psychostimulant whose chronic use leads to persistent neuropsychiatric deficits, including impairments in attention, memory, and executive function. These clinical symptoms correlate with structural damage to the brain, specifically the loss of dopamine and serotonin transporters, as well as the death of neurons via apoptosis.

The neurotoxic cascade of METH is primarily initiated by the drug’s ability to enter nerve terminals, where it causes the release of dopamine into the cytoplasm and synaptic cleft. This leads to the formation of highly reactive dopamine quinones and superoxide radicals. The resulting oxidative stress damages lipids, proteins, and DNA, while also activating transcription factors like AP-1 and initiating apoptotic pathways. This toxicity is further compounded by the release of glutamate (excitotoxicity) and the production of nitric oxide (NO), which can react to form peroxynitrite, a potent neurotoxin.

Beyond oxidative stress, METH impacts specific cellular organelles. Dysregulation of calcium homeostasis in the endoplasmic reticulum (ER) triggers ER-dependent apoptotic pathways, characterized by the activation of calpains. Similarly, the mitochondrial death pathway is engaged, resulting in the release of cytochrome c and other pro-apoptotic factors. Simultaneously, the brain exhibits an immune response: microglia shift from a resting state to an activated morphology. While this is a typical defensive response, excessive microglial activation contributes to neurotoxicity by secreting pro-inflammatory cytokines and reactive oxygen species.

Research has identified several experimental strategies to attenuate these effects. These include the use of dopamine receptor antagonists, antioxidant supplementation, and neurotrophic factors (such as BDNF or GDNF), which aim to bolster survival pathways or inhibit the initial toxic cascades. These findings suggest that identifying specific molecular targets—particularly those involved in inflammatory signaling or apoptotic pathways—is essential for developing pharmacological treatments for METH abuse.