Characterization of DJ-1 mutation in mouse astrocytes
Date
2008
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Abstract
Mutations in DJ-1 cause early-onset Parkinson's disease (PD), a progressive, irreversible neurodegenerative condition. Currently, the only known cause of PD is mutation of certain genes including DJ-1, however these mutations account for only 5-10% of overall PD cases. The initial studies attempt to discern if expression of VEGF and HIF1α, factors thought to contribute to both PD as well as carcinogenesis were altered as a result of DJ-1 mutation. In fact, VEGF expression decreased in the brain of DJ-1-/- mice, and increased in lung tissue. As PD is a complex, multi-factorial condition, our studies are designed to incorporate mutation of the PD gene DJ-1 in our target cell type, astrocytes, which are exposed to toxic agents. Overall our results indicate that DJ-1-/- astrocytes do not have an exaggerated phenotype compared to DJ-1+/+ counterparts, however subtle alterations in cell function are observed in mitochondrial membrane potential, expression of proinflammatory mediators, as well as intracellular calcium (Ca2+) dynamics. First, DJ-1-/- astrocytes' resting mitochondrial membrane potential is significantly lower than that of DJ-1+/+ cells. Following treatment with 10μg/mL lipopolysaccharide (LPS), expression of COX2, and NOS2 were similar in both genotypes, however expression of TNFα was significantly lower in DJ-1-/- astrocytes. Finally, a delay in return to baseline intracellular Ca2+ levels following treatment with 1μM ATP was observed in DJ-1-/- cells. Interestingly, expression and secretion of TNFα were decreased in our DJ-1-/- astrocytes following LPS exposure, while expression of COX2 and NOS2 were similar. In conclusion, these changes, though modest, indicate basal dysfunction in astrocyte homeostasis induced by mutation of DJ-1. Secretion of TNFα may be the most significant finding, as it may predispose neurons to degeneration due to lack of sufficient protection against early neurotoxic insults that secreted TNFα may provide. These specific indicators are significant because mitochondrial dysfunction, altered neuroinflammation, and reactive gliosis are all implicated in PD. While altering astrocyte cellular function may not be the primary cause of DJ-1-linked PD, it is possible that changes in this cell type may contribute the progression of parkinsonism.
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Subject
astrocytes
DJ-1
Parkinson's disease
neurosciences