S-adenosylmethionine Decarboxylase 1 Participates in PM2.5 Exposure Induced Neuronal Apoptosis via Mitochondria-Mediated Pathway

Abstract

Background: Fine particle (Particulate matter 2.5, PM2.5), as the primary ambient pollutant, is considered harmful to some neurodegenerative diseases, while the specific biochemical mechanism underlying is still unrevealed. Neuronal apoptosis is believed the crucial event in neurodegenerative pathogenesis, but evidence supporting neuronal apoptosis as PM2.5 induced neuronal injury is insufficient. S-adenosylmethionine decarboxylase 1 (AMD1) and its related spermidine synthesis have been shown to participate in cellular apoptosis, but its role in PM2.5 exposure induced neuronal apoptosis was rarely reported. To better understand contribution of AMD1 activity and spermidine in PM2.5 exposure induced neuronal apoptosis, may provide novel therapeutic and preventive targets for air pollution associated neurodegenerative diseases.Methods: In the current work, sixteen C57BL/6 male mice were randomly divided into ambient PM2.5 chamber or filtered air chamber, and the mouse model of whole-body ambient PM2.5 chronic exposure was established. Behavioral and cognitive ability, together with corresponding biomedical index were recorded and tested to evaluated neurotoxicity by PM2.5 exposure in mice. In parallel, PC12 cells and primary hippocampal neurons were applied for PM2.5 treatment to explore the possible cellular and molecular mechanism which may be critically involved in the process. AMD1 activity and cellular spermidine content were modulated by pharmacological approach to examine their participation in PM2.5 triggered neuronal apoptosis, followed by better examination of typical index for mitochondrial membrane potential and mitochondrial-mediated apoptosis pathway signaling.Results: Chronic ambient PM2.5 exposure attenuated spatial learning and memory ability, and triggered neuronal apoptosis together with increased expression of apoptosis-related Bax/Bcl-2 and cleaved caspase-3. PM2.5 exposure impaired AMD1 expression and spermidine synthesis. AMD1 inhibition could mimick PM2.5 exposure induced neuronal apoptosis. Spermidine supplementation rescued against neurotoxicity and inhibited PM2.5 induced apoptosis, in which mitochondrial pathway signaling.Conclusions: Chronic real-time exposure to ambient PM2.5 led to the reduced the ability of spatial learning and memory in mice. Neuronal apoptosis was the key event in the process of neurodegenerative development induced by PM2.5 exposure. AMD1 and spermidine participated in neuronal apoptosis induced by PM2.5 exposure, which was at least partially dependent on mitochondria mediated pathway.