Investigation of neuroprotective and antiapoptotic effects of rosmarinic acid in an in vitro Alzheimer's disease model.

OBJECTIVES: Rosmarinic acid (RA) exhibits anti-oxidant, anti-aging, and anti-inflammatory properties. This study aimed to investigate the effects of RA on amyloid beta (Aβ), phosphorylated tau (p-tau), α-synuclein (α-syn), Abelson tyrosine kinase (Abl), and apoptotic markers in an in vitro Alzheimer's disease (AD) model. MATERIALS AND METHODS: SH-SY5Y cells were differentiated into cholinergic neurons by all-trans retinoic acid (ATRA). CCK-8 assay was performed to determine the concentrations of Aβ, RA, and Aβ+RA on differentiated cells (D-cholinergic neurons). Then, control (D), D+Aβ, pretreatment (D+Aβ+RA), and D+RA groups were formed. Gene expression levels of apoptotic biomarkers were evaluated using qRT-PCR. Aβ, α-syn, Abl, p-tau, caspase-7 (CASP7), BAX, and cytochrome c (CYCS) protein levels were determined by ELISA. RESULTS: CCK-8 assay showed that RA (0.5-5 µM) was non-toxic to differentiated cells, and the IC₄₀ of Aβ₁₋₄₂ was 20 µM. Pretreatment with 1.5 µM RA protected cells from Aβ-induced toxicity. Gene expression analysis revealed that apoptotic markers (BAX, BLC2, CYCS, CASP3, CASP7, FAS, FADD) were significantly increased in the D+Aβ group compared to the control, whereas their levels were markedly reduced in the D+Aβ+RA group relative to the D+Aβ group. ELISA results corroborated qRT-PCR findings for CASP7, BAX, and CYCS. Additionally, RA decreased Aβ, α-syn, and p-tau protein levels, while Abl levels increased only in the D+RA group. CONCLUSION: RA exhibits neuroprotective and antiapoptotic effects by modulating apoptotic markers and reducing pathological proteins in an in vitro AD model.