Effect of Pimecrolimus on apoptotic pathways in H₂O₂-treated neuron like differentiated-SH-SY5Y cells: a molecular...

Neurodegenerative diseases (NDs), including Alzheimer's and Parkinson's, are marked by progressive neuronal loss, driven largely by oxidative stress and apoptosis. Developing neuroprotective strategies to counteract these processes is critical for managing such disorders. This study explores the neuroprotective effects of pimecrolimus, a calcineurin inhibitor, in mitigating hydrogen peroxide (H₂O₂)-induced cytotoxicity in neuron-like differentiated SH-SY5Y (d-SH-SY5Y) cells. The investigation focuses on apoptosis modulation, cell viability, and molecular docking interactions with apoptotic proteins. SH-SY5Y cells were differentiated with retinoic acid and treated with H₂O₂ (250 μM) alone or in combination with pimecrolimus (0.01, 0.1, and 1 μM) for 24 h. Cell viability was assessed using lactate dehydrogenase (LDH) assays. Additionally, malondialdehyde (MDA) levels were measured to assess oxidative stress in SH-SY5Y cells following the treatment conditions. Molecular docking analyses evaluated pimecrolimus' interactions with bax, bcl-2, caspase-3 and caspase-8 proteins, using Venetoclax as a positive control. Apoptosis-related protein levels were analyzed via ELISA, qRT-PCR, and immunofluorescence staining (cleaved caspase-3 and DAPI). Molecular docking showed strong binding of pimecrolimus to bax, bcl-2, caspase-3 and caspase-8, with comparable binding energies to Venetoclax. LDH and MDA assays demonstrated significant reductions in H₂O₂-induced cytotoxicity with pimecrolimus. ELISA and qRT-PCR revealed that H₂O₂ increased pro-apoptotic bax, caspase-3 and caspase-8 levels while decreasing anti-apoptotic bcl-2 levels. Pimecrolimus co-treatment reversed these effects in a dose-dependent manner. Immunofluorescence confirmed reduced apoptosis and cell death with pimecrolimus. Pimecrolimus effectively mitigates oxidative stress and apoptosis in H₂O₂-treated d-SH-SY5Y cells. These findings suggest its potential as a neuroprotective agent for managing (NDs).