cytochrome-c-t and Retinitis-Pigmentosa

As an inherited disorder caused by initial death of rod photoreceptors, retinitis pigmentosa is currently untreatable and usually leads to partial or complete blindness. (2R, 3S)-Pinobanksin-3-cinnamate (PC) is a new flavonone isolated from the seed of Alpinia galanga Willd, and has been reported to exert neuroprotective effects by upregulating endogenous antioxidant enzymes. In this study, the anti-oxidative and neuroprotective activity of PC against photoreceptor apoptosis in rd10 mouse model of retinitis pigmentosa was explored. PC showed to produce significant improvement in histology and function in rd10 mice through reducing oxidative stress. For the first time, the protective effects of PC were demonstrated against retina degeneration in rd10 mice and our study provides scientific rationale on using PC as the supplementary treatment to the outer retina diseases, including retinitis pigmentosa, in which oxidative stress is thought to contribute to disease progression.

Topics: Animals; Antioxidants; Apoptosis; Caspase 3; Caspase 9; Cytochromes c; Disease Models, Animal; DNA Fragmentation; Electroretinography; Glutathione; Malondialdehyde; Mice, Inbred C57BL; Neuroprotective Agents; Photoreceptor Cells; Reactive Oxygen Species; Retinitis Pigmentosa; Superoxide Dismutase

We previously reported activation of the unfolded protein response (UPR) in P23H rhodopsin (RHO) retinas with autosomal dominant retinitis pigmentosa (ADRP). Knowing that the UPR can trigger Ca(2+) release from the endoplasmic reticulum and regulate cellular signaling we examined the level of Ca(2+)-regulated proteins. We also looked for changes in the expression of Bcl2 family proteins, autophagy proteins and the mTOR/AKT pathways, as well as for the induction of mitochondria-associated apoptosis in the P23H RHO retina. Our data demonstrated that the elevation of calpain and caspase-12 activity was concomitantly observed with a decrease in the BCL2-XL/BAX ratio and an increase in mTor levels in the P23H-3 RHO retina suggesting a vulnerability of P23H RHO photoreceptors to apoptosis. The translocation of BAX to the mitochondria, as well as the release of cytochrome C and AIF into the cytosol supports this conclusion and indicates the involvement of mitochondria-induced apoptosis in the progression of ADRP. The level of autophagy proteins in general was found to be decreased in the P21-P30 P23H RHO retina. Injections of rapamycin, however, protected the P23H RHO rod photoreceptors from experiencing physiological decline. Despite this fact, the downregulation of mTOR did not alter the level of autophagy proteins. Our results imply that in addition to activation of the UPR during ADRP progression, photoreceptors also experience alterations in major proapoptotic pathways.

Topics: Animals; Apoptosis; Apoptosis Inducing Factor; bcl-2-Associated X Protein; Calcium; Calpain; Caspase 12; Cytochromes c; Humans; Mitochondria; Proto-Oncogene Proteins c-akt; Proto-Oncogene Proteins c-bcl-2; Rats; Retinal Rod Photoreceptor Cells; Retinitis Pigmentosa; Rhodopsin; Signal Transduction; TOR Serine-Threonine Kinases; Up-Regulation

Sildenafil, the active ingredient in Viagra, has been reported to cause transient visual disturbance from inhibition of phosphodiesterase 6 (PDE6), a key enzyme in the visual phototransduction pathway. This study investigated the effects of sildenafil on the rd1(+/-) mouse, a model for carriers of Retinitis Pigmentosa which exhibit normal vision but may have a lower threshold for cellular stress caused by sildenafil due to a heterozygous mutation in PDE6. Sildenafil caused a dose-dependent decrease in electroretinogram (ERG) responses of normal mice which mostly recovered two days post administration. In contrast, rd1(+/-) mice exhibited a significantly reduced photoreceptor and a supernormal bipolar cell response to sildenafil within 1 h of treatment. Carrier mice retinae took two weeks to return to baseline levels suggesting sildenafil has direct effects on both the inner and outer retina and these effects differ significantly between normal and carrier mice. Anatomically, an increase in expression of the early apoptotic marker, cytochrome C in rd1(+/-) mice indicated that the effects of sildenafil on visual function may lead to degeneration. The results of this study are significant considering approximately 1 in 50 people are likely to be carriers of recessive traits leading to retinal degeneration.

Topics: Animals; Cytochromes c; Disease Models, Animal; Dose-Response Relationship, Drug; Electroretinography; Female; Fluorescent Antibody Technique, Indirect; Glial Fibrillary Acidic Protein; Heterozygote; In Situ Nick-End Labeling; Male; Mice; Mice, Inbred C57BL; Phosphodiesterase 5 Inhibitors; Photoreceptor Cells, Vertebrate; Piperazines; Purines; Retina; Retinal Bipolar Cells; Retinitis Pigmentosa; Sildenafil Citrate; Sulfones

The importance of mitochondrial biogenesis in the pathogenesis of mitochondrial diseases has been widely recognised but little is known about it with regard to NARP (Neuropathy, Ataxia and Retinitis Pigmentosa) syndrome. Since such knowledge would contribute to the understanding of the pathogenesis of this disease, we designed a study to provide comprehensive overview of mitochondrial biogenesis in cybrid cells harboring NARP mutation (8993T>G). We also used Rho0 cells with the same nuclear background to show that distinct mtDNA defects lead to distinct cellular responses irrespective of nuclear genome. Mitochondrial biogenesis is regulated by mitochondria-to-nucleus (retrograde) communication which depends on intracellular signaling pathways sensitive to ROS. Since we previously found that selenite lowered ROS in NARP cybrids, we hypothesised that selenite could also modulate mitochondrial biogenesis in these cells. Although the mitochondrial mass was not changed in NARP cybrids, we showed the compensatory upregulation of respiratory chain subunits which prompted us to investigate the transcription factors that regulate their expression such as PGC-1α, NRFs, and TFAM. Selenite supplementation increased the level of NRF1 and nuclear accumulation of NRF2, but we did not detect any major changes in the levels of investigated respiratory chain proteins. These subtle changes in mitochondrial biogenesis in response to selenite treatment support the hypothesis that selenite could be considered as a potential therapeutic agent of NARP syndrome due to its antioxidant properties. Moreover, it could also be tested with regard to other mitochondrial disorders associated with ROS overproduction.

Topics: Cell Line, Tumor; Cells, Cultured; Cytochromes c; Dietary Supplements; DNA-Binding Proteins; DNA, Mitochondrial; Fibroblasts; Heat-Shock Proteins; HSP70 Heat-Shock Proteins; Humans; Immunohistochemistry; Ion Channels; Mitochondria; Mitochondrial Myopathies; Mitochondrial Proteins; Mutation; Peroxisome Proliferator-Activated Receptor Gamma Coactivator 1-alpha; Phosphorylation; Retinitis Pigmentosa; Sodium Selenite; Transcription Factors; Uncoupling Protein 3