Fig. 2.

Microglial activation and dopaminergic neuron death induced by LPS and MPTP: different pathways and common outcomes. Microglial activation can be categorized into two types: (1) direct microglial phenotypic and functional activation by LPS and (2) delayed reactive microgliosis secondary to MPTP-induced dopaminergic neuron death. LPS can be specifically recognized by microglial TLR4 and then proceeds to activate downstream pro-inflammatory pathways, resulting in neuroinflammation-induced dopaminergic neuron death and amplified microglial activation. In comparison, MPTP is primitively metabolized into MPP⁺ by astrocytes and then taken up into dopaminergic neurons via DAT, ultimately leading to mitochondrial damage, reactive microgliosis, and neuronal death