Interphotoreceptor retinoid-binding protein (IRBP), which is critical to photoreceptor survival and function, is comprised of homologous tandem modules each ~300 amino acids, and contains 10 cysteines, possibly 8 as free thiols. Purification of IRBP has historically been difficult due to aggregation, denaturation and precipitation. Our observation that reducing agent 1,4-dithiothreitol dramatically prevents aggregation prompted investigation of possible functions for IRBP’s free thiols. Bovine IRBP (bIRBP) was purified from retina saline washes by a combination of concanavalin A, ion exchange and size exclusion chromatography. Antioxidant activity of the purified protein was measured by its ability to inhibit oxidation of 2,2'-azinobis [3-ethylbenzothiazoline-6-sulfonate] by metmyoglobin. Homology modeling predicted the relationship of the retinoid binding sites to cysteine residues. As a free radical scanvenger, bIRBP was more active than ovalbumin, thioredoxin, and vitamin E analog Trolox. Alkylation of free cysteines by N-ethylmaleimide inhibited bIRBP’s antioxidant activity, but not its ability to bind all-trans retinol. Structural modeling predicted that Cys 1051 is at the mouth of the module 4 hydrophobic ligand-binding site. Its free radical scavenging activity points to a new function for IRBP in defining the redox environment in the subretinal space.

Retinol degrades rapidly in light into a variety of photoproducts. It is remarkable that visual cycle retinoids can evade photodegradation as they are exchanged between the photoreceptors, retinal pigment epithelium and Müller glia. Within the interphotoreceptor matrix, all-trans retinol, 11-cis retinol and retinal are bound by interphotoreceptor retinoid-binding protein (IRBP). Apart from its role in retinoid trafficking and targeting, could IRBP have a photoprotective function? HPLC was used to evaluate the ability of IRBP to protect all-trans and 11-cis retinols from photodegradation when exposed to incandescent light (0 to 8,842 μW/cm2); time periods of 0 – 60 min, and bIRBP: retinol molar ratios of 1:1 to 1:5. bIRBP afforded a significant prevention of both all-trans and 11-cis retinol to rapid photodegradation. The effect was significant over the entire light intensity range tested, and extended to the bIRBP: retinol ratio 1:5. In view of the continual exposure of the retina to light, and the high oxidative stress in the outer retina, our results suggest IRBP may have an important protective role in the visual cycle by reducing photodegradation of all-trans and 11-cis retinols. This role of IRBP is particularly relevant in the high flux conditions of the cone visual cycle.

BackgroundOcular sebaceous carcinoma can masquerade as benign lesions resulting in delay of diagnosis. Early recognition is even more difficult in young patients where the disease rarely occurs. Here, we provide a clinicopathological correlation of ocular sebaceous carcinoma in a young individual lacking history of hereditary cancer or immunosuppression.FindingsA detailed histopathological study including p53 DNA sequencing was performed on an aggressive sebaceous carcinoma presenting in a healthy 32 year-old Caucasian woman. She had no history of retinoblastoma, evidence for a hereditary cancer syndrome, or radiation therapy. However, she potentially was at risk for excessive UV light exposure. A detailed review of the literature is also provided.A moderately well differentiated sebaceous carcinoma was established histopathologically arising from the meibomian gland of the upper eyelid. In most areas, the cytoplasm contained small but distinct Oil-red-O positive vacuoles. Direct sequencing of p53 identified a G:C→A:T mutation at a dipyrimidine site. The mutation results in substitution of arginine for the highly conserved glycine at residue 199 located at the p53 dimer-dimer interface. Energy minimization structural modeling predicts that G199R will neutralize negative charges contributed by nearby inter- and intramonomeric glutamate residues.DiscussionThis study points to the importance of recognizing that sebaceous carcinoma can occur in young patients with no evidence for hereditary cancer risk or radiation therapy. The G199R substitution is anticipated to alter the stability of the p53 tetrameric complex. The role of UV light in the etiology of sebaceous carcinoma deserves further study. Our findings, taken together with those of others, suggest that different environmental factors could lead to the development of sebaceous carcinoma in different patients.

This study was performed to investigate the effect of regular aerobic exercise on the representative markers of cardiovascular inflammatory diseases. Biomarkers of cardiovascular disease were measured in 89 healthy elderly males (age range; 47-88) living in Seoul, Korea. Questionnaires were used to assess the status of the regular exercise participants. Various factors associated with chronic cardiovascular diseases, including total cholesterol, triglyceride, phospholipid, platelet, and C-reactive protein were lowered in regular exercise participants (pϽ0.05). In contrast, serum albumin concentration was higher in the exercised group compared with a non-exercised group (pϽ0.05). Therefore it was concluded that participation in regular exercise reduces cardiovascular inflammation and offers protection against chronic cardiovascular disease in elderly Korean men.