Mitochondrial μ-
calpain and
apoptosis-inducing factor (AIF)-dependent photoreceptor cell death has been seen in several rat and mouse models of
retinitis pigmentosa (RP). Previously, we demonstrated that the specific
peptide inhibitor of mitochondrial μ-
calpain, Tat-µCL, protected against
retinal degeneration following
intravitreal injection or topical
eye-drop application in
Mertk gene-mutated Royal College of Surgeons rats, one of the animal models of RP. Because of the high rate of
rhodopsin mutations in RP patients, the present study was performed to confirm the protective effects of Tat-µCL against
retinal degeneration in
rhodopsin transgenic S334ter and P23H rats. We examined the effects of
intravitreal injection or topical application of the
peptide on
retinal degeneration in S334ter and P23H rats by
terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling (TUNEL) assay, electroretinogram (ERG), immunohistochemistry for AIF, and histological staining. In S334ter rats, we found that
intravitreal injection or topical application of the
peptide prevented photoreceptor cell death from postnatal (PN) 15 to 18 days, the time of early-stage
retinal degeneration. Topical application of the
peptide also delayed attenuation of ERG responses from PN 28 to 56 days. In P23H rats, topical application of the
peptide protected against photoreceptor cell death and nuclear translocation of AIF on PN 30, 40, and 50 days, as the primary stages of degeneration. We observed that topical application of the
peptide inhibited the thinning of the outer nuclear layer and delayed ERG attenuations from PN 30 to 90 days. Our results demonstrate that the mitochondrial μ-
calpain and AIF pathway is involved in early-stage
retinal degeneration in
rhodopsin transgenic S334ter and P23H rats, and inhibition of this pathway shows curative potential for
rhodopsin mutation-caused RP.