Caspase inhibition restores dopaminergic identity through the PKA–CREB–BDNF axis in Parkinson’s disease neurons

The progressive loss of dopaminergic identity in midbrain neurons is a hallmark of Parkinson’s disease (PD), contributing to synaptic dysfunction and neurodegeneration. While a subset of PD cases is linked to genetic mutations, the majority are sporadic (sPD) and of unknown etiology. Current therapies offer only symptomatic relief and do not prevent neurodegeneration, underscoring the urgent need for disease-modifying strategies targeting actionable molecular pathways. Here, we used human induced pluripotent stem cell (hiPSC)-derived midbrain dopaminergic neurons (mDAs) from sporadic PD patients to investigate early alterations in neuronal identity, plasticity, and survival. We found that PD-derived mDAs exhibit upregulation of phosphorylated α-synuclein, marked reductions in dopaminergic markers (TH, NURR1), deficient dopamine handling, and impaired synaptogenesis. Transcriptomic and protein analyses revealed sustained activation of apoptotic caspases (caspase-3, -7) and downregulation of the PKA–CREB–BDNF signaling axis, which underpins dopaminergic differentiation and synaptic maturation. Pharmacological inhibition of caspases with Q-VD-OPh restored pCREB, BDNF, and downstream dopaminergic markers, leading to morphological recovery and functional synaptic rescue. Inhibition of PKA with H89 abrogated these effects, positioning the caspase–PKA–CREB cascade as a critical regulator of dopaminergic identity in PD neurons. These findings define a novel non-apoptotic role for caspases in disrupting the transcriptional program of mDAs and identify a druggable pathway capable of rescuing key aspects of dopaminergic function in a patient-derived cellular model. This work provides a mechanistic rationale for targeting caspase signaling in early-stage PD.