Acta Neuropathol Commun. 2025 Nov 14. 13(1):
234
Ikuko Miyazaki,
Nami Isooka,
Ryo Kikuoka,
Fuminori Imafuku,
Kaori Masai,
Kana Tomimoto,
Masakiyo Sakaguchi,
Chiharu Sogawa,
Norio Sogawa,
Yoshihisa Kitamura,
Masato Asanuma.
Exposure to pesticides, such as rotenone or paraquat, is an environmental factor that plays an important role in the pathogenesis of Parkinson's disease (PD). Rotenone induces PD-like pathology and is therefore used to develop parkinsonian animal models. Dopaminergic neurotoxicity caused by rotenone has been attributed to the inhibition of mitochondrial complex I, oxidative stress and neuroinflammation; however, the mechanisms underlying selective dopaminergic neurodegeneration by rotenone remain unclear. To resolve this, we focused on glial diversity and examined whether the brain region-specific glial response to rotenone could determine the vulnerability of dopaminergic neurons using primary cultured neurons, astrocytes and microglia from the midbrain and striatum of rat embryos and rotenone-injected PD model mice. Direct neuronal treatment with low-dose rotenone failed to damage dopaminergic neurons. Conversely, rotenone exposure in the presence of midbrain astrocyte and microglia or conditioned media from rotenone-treated midbrain glial cultures containing astrocytes and microglia produced dopaminergic neurotoxicity, but striatal glia did not. Surprisingly, conditioned media from rotenone-treated midbrain astrocytes or microglia monocultures did not affect neuronal survival. We also demonstrated that rotenone targeted midbrain astrocytes prior to microglia to induce dopaminergic neurotoxicity. Rotenone-treated astrocytes produced secreted protein acidic and rich in cysteine (SPARC) extracellularly, which induced microglial proliferation, increase in IL-1β and TNF-α, and NF-κB (p65) nuclear translocation in microglia, resulting in dopaminergic neurodegeneration. In addition, rotenone exposure caused the secretion of NFAT-related inflammatory cytokines and a reduction in the level of an antioxidant metallothionein (MT)-1 from midbrain glia. Furthermore, we observed microglial proliferation and a decrease in the number of MT-positive astrocytes in the substantia nigra, but not the striatum, of low-dose rotenone-injected PD model mice. Our data highlight that rotenone targets midbrain astrocytes, leading to SPARC secretion, which promotes the neurotoxic conversion of microglia and leads to glial dysfunction-mediated dopaminergic neurodegeneration.
Keywords: Astrocyte; Microglia; Parkinson's disease; Rotenone; SPARC