Phototoxicity of Indocyanine Green on Human Retinal Pigment Epithelium in Vitro and Its Reduction by Lutein¶

Complications of Macular Peeling

Macular peeling refers to the surgical technique for the removal of preretinal tissue or the internal limiting membrane (ILM) in the macula for several retinal disorders, ranging from epiretinal membranes (primary or secondary to diabetic retinopathy, retinal detachment…) to full-thickness macular holes, macular edema, foveal retinoschisis, and others. The technique has evolved in the last two decades, and the different instrumentations and adjuncts have progressively advanced turning into a safer, easier, and more useful tool for the vitreoretinal surgeon. Here, we describe the main milestones of macular peeling, drawing attention to its associated complications.

Lutein and zeaxanthin toxicity with and without brilliant blue in rabbits

PURPOSE

To evaluate the safety profile of solutions containing lutein and zeaxanthin alone or associated with brilliant blue (BB).

METHODS

Twenty-eight New Zealand rabbits were used to evaluate 4 concentrations of the various dye solutions: 0.5% lutein/zeaxanthin; 0.5% lutein/zeaxanthin associated with 0.0125% BB; 0.3% lutein/zeaxanthin associated with 0.025% BB; and 0.25% lutein/zeaxanthin associated with 0.05% BB. The pHs of the dye solutions ranged from 6.5 to 7.2 and the osmolarities from 280 to 320 mOsm/mL. Each rabbit had 0.1 mL of one of the dyeing solutions injected into the vitreous cavity of the right eye, while balanced salt solution (BSS) was injected into the left eye as the control. Scotopic electroretinography responses were recorded in all eyes at different time points. The animals were sacrificed at 1 and 7 days after injection; the eyes were analyzed by light and transmission electron microscopy.

RESULTS

No significant (P>0.05) differences were seen in the a- and b-wave amplitudes among groups at any given point in time. Light and electron microscopy findings showed no significant abnormalities either, and were similar to the histological findings after intravitreal BSS injection.

CONCLUSIONS

Lutein and zeaxanthin alone or in association with BB showed a good safety profile in this experimental model.

Retinoic acid suppresses the adhesion and migration of human retinal pigment epithelial cells

The study was designed to better understand how retinoic acid (RA) influenced the migration and invasion abilities of retinal pigment epithelial cells (RPE) in vitro and how the related genes of the extracellular matrix (ECM) were expressed. The inhibition effects of RA on proliferative vitreoretinopathy (PVR) formation induced by RPE cells were studied in rabbits. Wound healing and Boyden chamber assays were used to show the abilities of migration and invasion of RPE. Microarray, real-time quantitative PCR (qPCR) and Western blotting showed how RA regulated the ECM genes. RA (10(-5) M) significantly (P < 0.05) inhibited PVR membrane and traction retinal detachment formation (80%). Moreover, RA treatment significantly inhibited the migration (80%) and invasion (65%) behaviors of human RPE cells (P < 0.05) by wound healing and Boyden chamber assays, respectively. Microarray and q PCR analysis showed RA treatment did inhibit the motility of human RPE cells by inhibition of metalloproteinases (MMP) 1, 2, 9, fibronectin-1, transforming growth factor beta, thrombospondin-1, tenascin C, most collagen, integrin, laminin molecules and along enhancing E-cadherin and MMP3 genes expression. And Western blotting indicated the coincident results on protein level of MMP1, 2, 3, 9, 14; fibronectin-1; integrinαM, β2 and E-cadherin. In conclusions, RA is a vital drug to inhibit the abilities of migration and invasion of RPE and to hamper the PVR formation by regulating some genes expression of ECM.

Retinal photodamage by endogenous and xenobiotic agents

The human eye is constantly exposed to sunlight and artificial lighting. Light transmission through the eye is fundamental to its unique biological functions of directing vision and circadian rhythm and therefore light absorbed by the eye must be benign. However, exposure to the very intense ambient radiation can pose a hazard particularly if the recipient is over 40 years of age. There are age-related changes in the endogenous (natural) chromophores (lipofuscin, A2E and all-trans-retinal derivatives) in the human retina that makes it more susceptible to visible light damage. Intense visible light sources that do not filter short blue visible light (400-440 nm) used for phototherapy of circadian imbalance (i.e. seasonal affective disorder) increase the risk for age-related light damage to the retina. Moreover, many drugs, dietary supplements, nanoparticles and diagnostic dyes (xenobiotics) absorb ocular light and have the potential to induce photodamage to the retina, leading to transient or permanent blinding disorders. This article will review the underlying reasons why visible light in general and short blue visible light in particular dramatically raises the risk of photodamage to the human retina.

All-trans retinoic acid remodels extracellular matrix and suppresses laminin-enhanced contractility of cultured human retinal pigment epithelial cells

All-trans retinoic acid (atRA) has been reported to inhibit the proliferation of retinal pigment epithelial (RPE) cells and used in treatment of proliferative vitreoretinopathy (PVR) in animal model. This study aimed at examining the effectiveness of atRA in inhibiting the extracellular matrix (ECM) biosynthesis by RPE cells and the RPE cell-mediated collagen gel contraction. Cultured RPE cells were treated with atRA and the expression of four ECM proteins (collagen types I, III, IV and laminin beta1) was profiled. The results indicated that atRA treatment up-regulated de novo synthesis of collagen type I, but decreased that of laminin beta1 in a dose-dependent manner. Moreover, the effect of atRA on RPE cell contraction was evaluated by measuring the area of collagen gel where RPE cells populated. Treatment with atRA significantly inhibited RPE cell-mediated collagen gel contraction. Addition of exogenous laminin nonapeptide into gels promoted RPE cell contraction, while atRA reversed the laminin-enhanced contractility. atRA treatment significantly suppressed the gene expression of integrin beta3 but not alphaV subunit, and effectively inhibited the tyrosine phosphorylation of integrin beta3 at residue 747 in RPE cells grown on laminin-coated dish, suggesting that atRA may suppress the RPE contractility through either inhibiting integrin beta3 expression or abrogating the integrin beta3-mediated signaling. In conclusion, atRA pharmacologically possesses a tissue-remodeling capacity and inhibits contractility of RPE cells. Therefore, atRA might be potentially a therapeutic agent for certain ocular disorders such as PVR.