N-Propargyl caffeamide (PACA) ameliorates MPTP-induced dopaminergic neurodegeneration and motor impairments via activating Keap1-Nrf2 pathway and inducing NGF expression

Abstract

Insufficient production of neurotrophic factors is implicated in various neurodegenerative disorders. We recently synthesized a novel caffeic acid derivative N-propargyl caffeamide (PACA) and discovered the neuroprotective and neuritogenic activities of PACA in cell culture system (Yang CB et al ACS Chem Neurosci 2015 Sep 16;6(9):1560-9). The aim of the present study was to evaluate the potential of PACA in the treatment of MPTP-induced dopaminergic neurodegeneration and motor impairments and the underlying mechanism. was discovered that PACA not only potentiated NGF-induced neurite outgrowth but also attenuated 6-hydroxydopamine (6-OHDA) neurotoxicity in dopaminergic PC12 cells and primary rat midbrain neurons. To identify the PACA-binding proteins, a biotin tag was introduced to the covalent PACA-protein adducts via “Click chemistry” alkyne-azido cycloaddition. As a result, kelch-like ECH-associated protein 1 (Keap1) was isolated as the predominant protein from PACA treated PC12 cells. It was demonstrated that the formation of PACA-Keap1 conjugates induced the nuclear translocation of transcription factor Nrf2 and the expression of antioxidant heme oxygenase-1 (HO-1). Importantly, specific HO-1 inhibitor SnPP diminished the neuroprotective and neuritogenic activities of PACA. Moreover, PACA attenuated 6-OHDA-induced production of neurotoxic reactive oxygen species and reactive nitrogen species. PACA also preserved mitochondrial membrane integrity and enhanced the cellular resistance against 6-OHDA neurotoxicity. These results suggest that PACA exhibits neuroprotective and neuritogenic activities via activating the Nrf2/HO-1 antioxidant pathway.