L-type calcium channels link oxidative stress to calcium signaling pathway and membrane excitability: Insights from computational modeling of dopaminergic neurons
Dopamine neurons, which are critical in movement, cognition, and reward learning, are vulnerable to oxidative stress during aging, drugs of abuse, and viral infection and can lead to neurodegeneration. Previous work used computational modeling to study dopamine neuron function based on experimental findings from rodent brain slices containing dopamine neurons. Here we show for the first time the feasibility and utility of applying such computational models of DA neurons to the analysis of experimental findings from in-vitro cultured cells. We used DCFH-DA (and DHE) and time-lapse, Fura-2 ratiometric imaging to measure changes in ROS levels and changes in intracellular calcium (Ca2+) levels, respectively, in two dopaminergic cell models: differentiated SH-SY5Y and differentiated human neural progenitor cells. We investigated how peroxide-dependent changes in the behavior of the L-type channel might alter the excitability of the dopaminergic cell. We found that L-type channels mediated clusters of calcium spikes (or oscillations) and that our model suggested that such increased excitability could be explained by changes in the voltage-dependence of activation of the L-type channels in response to exogenous peroxide. Our findings suggested that L-type channels link oxidative stress responses to modulation of excitability. We conclude that the Ca2+ channel blocker nicardipine may help disrupt this link by reducing oxidative stress and preventing channel activation at more hyperpolarized potentials, thus reducing plasma membrane excitability.