Botanical Compounds: Effects on Major Eye Diseases

Botanical compounds have been widely used throughout history as cures for various diseases and ailments. Many of these compounds exhibit strong antioxidative, anti-inflammatory, and antiapoptotic properties. These are also common damaging mechanisms apparent in several ocular diseases, including age-related macular degeneration (AMD), glaucoma, diabetic retinopathy, cataract, and retinitis pigmentosa. In recent years, there have been many epidemiological and clinical studies that have demonstrated the beneficial effects of plant-derived compounds, such as curcumin, lutein and zeaxanthin, danshen, ginseng, and many more, on these ocular pathologies. Studies in cell cultures and animal models showed promising results for their uses in eye diseases. While there are many apparent significant correlations, further investigation is needed to uncover the mechanistic pathways of these botanical compounds in order to reach widespread pharmaceutical use and provide noninvasive alternatives for prevention and treatments of the major eye diseases

X-Box Binding Protein 1 Is Essential for the Anti-Oxidant Defense and Cell Survival in the Retinal Pigment Epithelium

Damage to the retinal pigment epithelium (RPE) is an early event in the pathogenesis of age-related macular degeneration (AMD). X-box binding protein 1 (XBP1) is a key transcription factor that regulates endoplasmic reticulum (ER) homeostasis and cell survival. This study aimed to delineate the role of endogenous XBP1 in the RPE. Our results show that in a rat model of light-induced retinal degeneration, XBP1 activation was suppressed in the RPE/choroid complex, accompanied by decreased anti-oxidant genes and increased oxidative stress. Knockdown of XBP1 by siRNA resulted in reduced expression of SOD1, SOD2, catalase, and glutathione synthase and sensitized RPE cells to oxidative damage. Using Cre/LoxP system, we generated a mouse line that lacks XBP1 only in RPE cells. Compared to wildtype littermates, RPE-XBP1 KO mice expressed less SOD1, SOD2, and catalase in the RPE, and had increased oxidative stress. At age 3 months and older, these mice exhibited apoptosis of RPE cells, decreased number of cone photoreceptors, shortened photoreceptor outer segment, reduced ONL thickness, and deficit in retinal function. Electron microscopy showed abnormal ultrastructure, Bruch's membrane thickening, and disrupted basal membrane infolding in XBP1-deficient RPE. These results indicate that XBP1 is an important gene involved in regulation of the anti-oxidant defense in the RPE, and that impaired activation of XBP1 may contribute to RPE dysfunction and cell death during retinal degeneration and AMD

Complement factor H: spatial and temporal expression and localization in the eye

PURPOSE. Complement factor H (CFH) is a component of the mammalian complement system, which regulates the alternative pathway of complement activation and protects the host cell from inappropriate complement activation. CFH is a key regulator of innate immunity, and CFH deficiency leads to membranoproliferative glomerulonephritis type II. A variation in human CFH, Y402H, has been shown to be associated with an increased risk for age-related macular degeneration. The authors describe studies on the spatial and temporal expression of the CFH gene and localization of this protein in ocular tissues to gain insight into its role in the eye. METHODS. CFH expression in human and mouse tissues was studied by quantitative RT-PCR and Western blot analysis, and localization of CFH was studied by immunohistochemical analysis followed by fluorescence microscopy. RESULTS. In human and mouse, CFH expression was found to be similar to the highest level of expression in the liver. In ocular tissue, CFH was detected in the distalmost optic nerve (3 mm) cut from the scleral surface of the eyeball, sclera, RPE-choroid, retina, lens, and ciliary body. In mouse, Cfh expression was observed from early embryonic stages, and in the eye its expression increased with age. CONCLUSIONS. A significant level of CFH expression is maintained in different ocular tissues during development and aging. Sustained high levels of CFH expression in eye tissues suggest that this protein may play a role in protecting these tissues from indiscriminate complement activation and inflammatory insult. (Invest Ophthalmol Vis Sci. 2006;47: 4091-4097

Hydroxychloroquine retinopathy: A review of imaging

Hydroxychloroquine (HCQ) retinopathy can result in permanent vision loss. In early stages of HCQ retinopathy, patients are usually asymptomatic with preservation of visual acuity. We aspire that our review, in conjunction with the American Academy of Ophthalmology screening guidelines, shall shed light on effective screening measures utilizing multimodal imaging techniques to detect early signs of HCQ retinopathy before advanced changes manifest clinically

Is Meibomian Gland Dysfunction One Disease? Heterogeneity Among Phenotypes

The purpose of this study was to examine ocular surface symptoms, tear metrics, and tear cytokines by Meibomian gland dysfunction (MGD) features.Symptom questionnaires and an ocular surface evaluation were performed on 40 individuals with varied MGD signs [Meibomian gland (MG) plugging, eyelid vascularity, meibum quality, and MG dropout]. Tear proteins were extracted off Schirmer strips and analyzed for 23 human inflammation-related proteins. Statistical analysis was performed to examine associations between dry eye metrics inflammatory proteins and MGD features.The study involved 40 South Florida veterans with a mean age of 61 ± 13 years; most individuals were male (95%), White (31%), and non-Hispanic (85%). MGD features differentially related to dry eye signs. Eyelid vascularity, meibum quality, and MG dropout, but not MG plugging, correlated with higher corneal staining and lower tear production. MGD features also differentially related to tear cytokines. Eyelid vascularity most closely related to inflammation with significant correlations for interferon-gamma-γ (r = 0.36, P = 0.02), interleukin-4 (IL-4) (r = 0.43, P = 0.006), IL-17A (r = 0.42, P = 0.007), matrix metalloproteinase-2 (r = 0.39, P = 0.01), C-X-C motif chemokine ligand 5 (Regulated upon Activation, Normal T-Cell Expressed and presumably Secreted [RANTES]) (r = 0.32, P = 0.04), and tumor necrosis factor α (r = 0.36, P = 0.02). The other 3 MGD signs were less related to inflammation. Multivariable models revealed IL-4 to be most closely related to eyelid vascularity (standardized β = 0.39, P < 0.0001).Eyelid vascularity was the MGD sign most closely related to inflammatory cytokines, suggesting that different MGD features may be driven by different pathophysiological mechanisms

Unravelling the interplay of sphingolipids and TGF-β signaling in the human corneal stroma

<div><p>Purpose</p><p>To delineate the role of Sphingolipids (SPLs) in the human cornea and their cross-talks with transforming growth factor beta (TGF-β) in order to develop novel, non-invasive therapies.</p><p>Methods</p><p>Human corneal fibroblasts (HCFs) were harvested from healthy donors, stimulated with Vitamin C to promote extracellular matrix assembly, treated with exogenous sphingosine-1-phosphate (S1P) or sphingosine kinase inhibitor 2 (SPHK I₂) and isolated after 4 weeks for further analysis.</p><p>Results</p><p>Data showed that S1P led to a significant decrease in cellular migration where SPHK I₂ just delayed it for 24h. Significant modulation of the sphingolipid pathway was also noted. Sphingosine kinase-1 (SphK1) was significantly downregulated upon exogenous stimulation with S1P at a concentration of 5μM and Sphingosine kinase-2 (SphK2) was also significantly downregulated at concentrations of 0.01μM, 0.1μM, and 5μM; whereas no effects were observed upon stimulation with SPHK I_2. S1PR3 was significantly downregulated by 0.1μM and 5μM S1P and upregulated by 5μM and 10μM SPHK I₂. Furthermore, both S1P and SPHK I₂ regulated corneal fibrosis markers such as alpha-smooth muscle actin, collagen I, III, and V. We also investigated the interplay between two TGF-β isoforms and S1P/SPHK I₂ treatments and found that TGF-β1 and TGF-β3 were both significantly upregulated with the 0.1μM S1P but were significantly downregulated with the 5μM S1P concentration. When TGF-β1 was compared directly to TGF-β3 expression, we observed that TGF-β3 was significantly downregulated compared to TGF-β1 in the 5μM concentration of S1P. No changes were observed upon SPHK I₂ treatment.</p><p>Conclusion</p><p>Our study delineates the role of sphingolipids in the human cornea and highlights their different activities based on the cell/tissue type.</p></div

Effects of S1P and SPHK I₂ on cellular migration/Scratch wound healing assay.

<p>(A-C) HCFs were scratched and the relative cell migration percentage was quantified at 0, 4, 24, and 48 hour time points. (D) Scratch assay quantification of S1P stimulated HCFs showing significant decrease (p ≤ 0.0001) in cell migration distance at 24 and 48 hour time points compared to controls (A). (E) Scratch assay quantification of SPHK I₂ stimulated HCFs showing significant decrease (p ≤ 0.001) in cell migration distance at the 24 hour time point compared to controls (A). (A-C) Dotted lines indicate cell fronts or origin location of scratch. A one-way ANOVA was performed and p ≤ 0.05 considered statistically significant. * represents p ≤ 0.05, ** represents p ≤ 0.01, *** represents p ≤ 0.001, **** represents p ≤ 0.0001.</p

S1P and SPHK I₂ signaling interactions with TGF-β isoforms/Quantification of western blots of HCF cell lysates following four week treatments with S1P or SPHK I₂.

<p>(A) Treatment with 0.1μM concentration of S1P on HCF 3D constructs led to significant upregulation (p ≤ 0.0001) of TGF-β1 when compared to controls, where 5μM concentration of S1P on HCF 3D constructs led to significant upregulation (p ≤ 0.0001) of TGF-β1 when compared to controls. (B) Treatment with 0.1μM concentration of S1P on HCF 3D constructs led to significant upregulation (p ≤ 0.05) of TGF-β3 when compared to controls, where 5μM concentration of S1P on HCF 3D constructs led to significant upregulation (p ≤ 0.0001) of TGF-β3 when compared to controls. A one-way ANOVA was performed and P ≤ 0.05 considered statistically significant. * represents p ≤ 0.05, ** represents p ≤ 0.01, *** represents p ≤ 0.001, **** represents p ≤ 0.0001.</p

Effects of S1P and SPHK I₂ on fibrosis (assembly)/Quantification of western blots of HCF cell lysates following four week treatments with S1P or SPHK I₂.

<p>(A) Treatment with 5μM concentration of S1P on HCF 3D constructs led to significant downregulation (p ≤ 0.0001) of Collagen I when compared to control HCFs. (B) Treatment with 2μM, 5μM, and 10μM concentrations of SPHK I₂ on HCF 3D constructs had no effect on Collagen I when compared to control HCFs. (C) Treatment with 5μM concentration of S1P on HCF 3D constructs led to significant downregulation (p ≤ 0.0001) of Collagen V when compared to control HCFs. (D) Treatment with 10μM concentration of SPHK I₂ on HCF 3D constructs led to significant upregulation (p ≤ 0.05) of Collagen V when compared to control HCFs. (E) Treatment with 0.01μM, 0.1μM, and 5μM concentrations of S1P on HCF 3D constructs had no effect on Collagen III when compared to control HCFs. (F) Treatment with 2μM, 5μM, and 10μM concentrations of SPHK I₂ on HCF 3D constructs led to significant upregulation (p ≤ 0.01, p ≤ 0.05, and p ≤ 0.05) of Collagen III when compared to control HCFs. A one-way ANOVA was performed and p ≤ 0.05 considered statistically significant. * represents p ≤ 0.05, ** represents p ≤ 0.01, *** represents p ≤ 0.001, **** represents p ≤ 0.0001.</p