Beneficial effect of Crocus sativus stigma extract in amyloid-beta degradation by monocytes from sporadic Alzheimer's disease patients

Alzheimer’s disease (AD), the most common form of dementia in the elderly, is characterized by neurofibrillary tangles, extracellular amyloid-beta (Abeta) plaques, and neuroinflammation. The accumulation of Abeta in the brain of patients with sporadic Alzheimer’s disease (SAD) seems to reflect a defective clearance. In this process, cells of monocytes-macrophage lineage exert a relevant role. Saffron, the dried stigma of Crocus sativusL., is a naturally derived plant product with several biological properties such as anti-inflammatory and antioxidant activity. The present study investigates the possible reversal effects of saffron in the reduced amyloid-beta degradation by monocytes of SAD patients. Crocus sativusL. was collected from Umbria (Central Italy) and kindly provided by the Associazione dello Zafferano di Cascia–Zafferano Purissimo dell’Umbria. Cytotoxicity of saffron extract was first assessed, and then amyloid-beta (1–42) HiLyte FluorTM 488–labeled (FITC-Abeta42) degradation rate by monocytes after saffron treatment was analyzed by flow cytometry (Beckman Coulter EPICS XL). Monocytes from SAD subjects pre-treated with low concentration of saffron extract (5microM referred to trans crocine amount) showed an improved ability to degrade FITC-Abeta42 and an increased level of lysosomal protease Cathepsin B, one of the key Abeta42 degrading enzyme. Even though more studies are needed to identify the active molecules, or their combinations, responsible for the enhanced Ab42 degradation, these data suggest a potential beneficial effect of saffron on AD patients in terms of Ab42 increased clearance.