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Inhibitory peptide of mitochondrial ?-calpain protects against photoreceptor degeneration in rhodopsin transgenic S334ter and P23H rats.

ABSTRACT: Mitochondrial ?-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 ?-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 ?-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.

SUBMITTER: Ozaki T

PROVIDER: S-EPMC3739725 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Inhibitory peptide of mitochondrial μ-calpain protects against photoreceptor degeneration in rhodopsin transgenic S334ter and P23H rats.

Ozaki Taku T Ishiguro Sei-ichi S Hirano Satoshi S Baba Ayaka A Yamashita Tetsuro T Tomita Hiroshi H Nakazawa Mitsuru M

PloS one 20130809 8

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 ...[more]

PMID: 23951212

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Project description:PurposeTo characterize the optical coherence tomography (OCT) appearances of photoreceptor degeneration in the rhodopsin P23H transgenic rat (line 2) in relation to the histological, ultrastructural, and electroretinography (ERG) findings.Materials and methodsHomozygous rhodopsin P23H transgenic albino rats (line 2, very-slow degeneration model) were employed. Using OCT (Micron IV®; Phoenix Research Labs, Pleasanton, CA, USA), the natural course of photoreceptor degeneration was recorded from postnatal day (P) 15 to P 287. The OCT images were qualitatively observed by comparing them to histological and ultrastructural findings at P 62 and P 169. In addition, each retinal layer was quantitatively analyzed longitudinally during degeneration, compared it to that observed in wild type Sprague-Dawley (SD) rats. The relationships between the ERG (full-field combined rod-cone response, 3.0 cds/m2 stimulation) findings and OCT images were also analyzed.ResultsIn the qualitative study, the two layers presumably corresponding to the photoreceptor inner segment ellipsoid zone (EZ) and interdigitation zone (IZ) were identified in the P23H rat until PN day 32. However, the photoreceptor inner and outer segment (IS/OS) layer became diffusely hyperreflective on OCT after P 46, and the EZ and IZ zones could no longer be identified on OCT. In contrast, in the SD rats, the EZ and IZ were clearly distinguished until at least P 247. The ultrastructural study showed partial disarrangements of the photoreceptor outer segment discs in the P23H rats at P 62, although a light-microscopic histological study detected almost no abnormality in the outer segment. In the quantitative study, the outer retinal layer including the outer plexiform layer (OPL) and the outer nuclear layer (ONL) became significantly thinner in the P23H rats than in the SD rats after P 71. The thickness of the IS/OS layer was maintained in the P23H rats until P 130, and it became statistically thinner than in the SD rats at P 237. The longitudinal attenuation in the amplitude of the a- and b-waves of ERG was significantly correlated with the thickness of the combined OPL and ONL but not with that of the IS/OS layer.ConclusionOCT showed the degenerated photoreceptor IS/OS layer in rhodopsin P23H transgenic rats (line 2) as a diffuse hyperreflective zone, even in the early stage, with the partially disarranged and destabilized OS discs recognizable by ultrastructural assessment but not by a histological study. The amplitude of the a- and b-waves mainly depends on the thickness of the OPL and ONL layer rather than the thickness of the photoreceptor IS/OS layer in P23H rats.

Dataset Information

Inhibitory peptide of mitochondrial ?-calpain protects against photoreceptor degeneration in rhodopsin transgenic S334ter and P23H rats.

Publications

Inhibitory peptide of mitochondrial μ-calpain protects against photoreceptor degeneration in rhodopsin transgenic S334ter and P23H rats.

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