Biochemical and Biophysical Research Communications, Vol.478, No.4, 1700-1705, 2016
The protection of rat retinal ganglion cells from ischemia/reperfusion injury by the inhibitory peptide of mitochondrial mu-calpain
Intracellular Ca2+-dependent cysteine proteases such as calpains have been suggested as critical factors in retinal ganglion cell (RGC) death. However, it is unknown whether mitochondrial calpains are involved in RGC death. The purpose of the present study was to determine whether the inhibition of mitochondrial mu-calpain activity protects against RGC death during ischemia/reperfusion (I/R) injury. This study used a well-established rat model of experimental acute glaucoma involving I/R injury. A specific peptide inhibitor of mitochondrial mu-calpain, Tat-mu CL, was topically applied to rats via eye drops three times a day for 5 days after I/R. RGC death was determined by the terminal deoxynucleotidyl transferase dUTP nick end labeling assay. The truncation of apoptosis-inducing factor (AIF) was determined by western blot analyses. Retinal morphology was determined after staining with hematoxyline and eosin. In addition, the number of Fluoro Gold-labeled RGCs in flat-mounted retinas was used to determine the percentage of surviving RGCs after I/R injury. After 1 day of I/R, RGC death was observed in the ganglion cell layer. Treatment with Tat-mu CL eye drops significantly prevented the death of RGCs and the truncation of AIF. After 5 days of I/R, RGC death decreased by approximately 40%. However, Tat-mu CL significantly inhibited the decrease in the retinal sections and flat-mounted retinas. The results suggested that mitochondrial mu-calpain is associated with RGC death during I/R injury via truncation of AIF. In addition, the inhibition of mitochondrial mu-calpain activity by Tat-mu CL had a neuroprotective effect against I/R-induced RGC death. (C) 2016 Elsevier Inc. All rights reserved.