title: Decrease of ATP by mitochondrial m-calpain inhibitory peptide in the rat retinas.
abstract: Activations of mitochondrial calpains cause apoptosis-inducing factor-dependent apoptosis of retinal photoreceptor cells in the Royal College of Surgeons (RCS) rat, an animal model of retinitis pigmentosa. In the present study, we attempted to develop specific inhibitors of mitochondrial calpains that would prevent the retinal degeneration. We examined the inhibitory potency of 20-mer peptides of the m-calpain for mitochondrial calpains activity, determined the inhibitory regions, and conjugated the cell-penetrating peptides (CPP). The cytotoxicity and delivery of the peptide was evaluated using mouse photoreceptor-derived 661W cells. After intravitreal injection of the peptide in RCS rats, we examined the peptide delivery to the retina, photoreceptor cell death numbers, responses of the electroretinogram (ERG), concentrations of intracellular ATP, and changes of retinal morphology. Results showed that one of the peptides inhibited the activity of the mitochondrial m-calpain. The HIV-1 tat-conjugated m-calpain peptide, HIV-Nm, could preserve the inhibitory potency of the mitochondrial m-calpain, and penetrate into the 661W cells. While intravitreal injection of HIV-Nm made it possible to deliver to the retina, it did not prevent photoreceptor cell death. Furthermore, it caused the ERG attenuation and the decrease in the intracellular ATP only a day after the injection. Although HIV-Nm did not cause histological change of the retina after 1 or 2 days of the administration, the morphological abnormality of the retina was observed after 3-14 days. Our results demonstrated that HIV-Nm failed to prevent the photoreceptor cell death, but rather caused the attenuation of ERG response and the decrease of ATP.
authors: Department of Biochemistry and Molecular Biology, Faculty of Agriculture and Life Science, Hirosaki University.
authors: Taku
authors: T
authors: Ozaki
authors: Mitsuru
authors: M
authors: Nakazawa
authors: Tetsuro
authors: T
authors: Yamashita
authors: Hiroshi
authors: H
authors: Tomita
authors: Yuichi
authors: Y
authors: Ebina
authors: Sei-ichi
authors: S
authors: Ishiguro
mesh_terms: D000255:Adenosine Triphosphate / Q000096:biosynthesis / Q000378:metabolism; D000595:Amino Acid Sequence; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D051033:Apoptosis Inducing Factor; D002154:Calpain / Q000037:antagonists & inhibitors* / Q000378:metabolism; D004596:Electroretinography; D006023:Glycoproteins / Q000494:pharmacology*; D008928:Mitochondria / Q000378:metabolism; D008969:Molecular Sequence Data; D010455:Peptides / Q000494:pharmacology; D020419:Photoreceptor Cells, Vertebrate / Q000378:metabolism*; D021381:Protein Transport; D051381:Rats; D017207:Rats, Sprague-Dawley; D055647:Rats, Transgenic; D012162:Retinal Degeneration / Q000378:metabolism; D012174:Retinitis Pigmentosa; D016415:Sequence Alignment; D054322:tat Gene Products, Human Immunodeficiency Virus / Q000378:metabolism
chemical_list: D051033:Apoptosis Inducing Factor; D006023:Glycoproteins; D010455:Peptides; C039304:calpain inhibitors; D054322:tat Gene Products, Human Immunodeficiency Virus; D000255:Adenosine Triphosphate; D002154:Calpain; C449000:m-calpain