Long-Term Systemic Treatment With Methamphetamine Causes Retinal Damage in CD1 Mice

As a powerful psychostimulant with high potential for abuse, methamphetamine (Meth) could cause long-lasting abnormalities in retinas. The purpose of this study was to investigate the effects of systemic administration of Meth at low dose on retinal damage and understand the underlying mechanisms of pathology. CD1 mice were treated with 0.5 mg/kg or 1 mg/kg Meth by intraperitoneal injection daily for 2 months, mice treated with saline were used as negative control. Electroretinography (ERG) reflects the mass response of photoreceptor cells and was used to test the outer retinal function after Meth treatment. Toluidine blue staining was used to show the retinal morphology and evaluate the photoreceptor cell loss. Inflammatory factors were measured by enzyme-linked immunosorbent assay to show the inflammatory response. Terminal deoxynucleotidyl transferase dUTP Nick end labeling assay was used to detect the apoptosis-positive cells. Real-time polymerase chain reaction and Western blot were applied to measure the gene and protein change to explore the underlying mechanisms. Results demonstrated that retinal damage was caused by Meth treatment after 2 months, evidenced by loss of rod photoreceptor cells; decreased ERG amplitude; increased apoptotic photoreceptor cells, cytochrome-c release, caspase-3 activity, caspase-9 activity, and apoptosis-related protein expression; increased malondialdehyde level as well as nicotinamide adenine dinucleotide phosphate oxidase 4 protein expression; decreased anti-oxidative agents glutathione as well as superoxide dismutase levels; and increased production and gene expression of inflammatory factors. Our study indicated that systemic administration of Meth caused neurotoxic effects on CD1 mouse retinas, providing the potential mechanisms for the retina damage caused by Meth abuse.