Amelioration of Functional, Metabolic, and Morphological Deterioration in the Retina following Retinal Detachment by Green Tea Extract

Retinal detachment (RD) can result in the loss of photoreceptors that cause vision impairment and potential blindness. This study explores the protective effects of the oral administration of green tea extract (GTE) in a rat model of RD. Various doses of GTE or epigallocatechin gallate (EGCG), the most active ingredient in green tea catechins, were administered to Sprague Dawley (SD) rats with experimentally induced retinal detachment. The rats received sub-retinal injections of hyaluronic acid (0.1%) to induce RD and were given different doses of GTE and EGCG twice daily for three days. Notably, a low dose of GTE (142.9 mg/kg) caused significantly higher signal amplitudes in electroretinograms (ERGs) compared to higher GTE doses and any doses of EGCG. After administration of a low dose of GTE, the outer nuclear layer thickness, following normalization, of the detached retina reduced to 82.4 ± 8.2% (Mean ± SEM, p p < 0.0001). This reduction was associated with the inhibition of apoptosis through decreased sphingomyelin levels and mitigation of oxidative stress shown by a lowered protein carbonyl level, which may involve suppression of HIF-1α pathways. Furthermore, GTE showed anti-inflammatory effects by reducing inflammatory cytokines and increasing resolving cytokines. In conclusion, low-dose GTE, but not EGCG, significantly alleviated RD-induced apoptosis, oxidative stress, inflammation, and energy insufficiency within a short period and without affecting energy metabolism. These findings suggest the potential of low-dose GTE as a protective agent for the retina in RD

Green tea extract treatment alleviates ocular inflammation in a rat model of endotoxin-induced uveitis.

Green tea extract (GTE) ingested by rats exerted anti-oxidative activities in various ocular tissues as shown in our previous studies. The present work investigated anti-inflammatory effects of GTE on endotoxin-induced uveitis (EIU). EIU was generated in adult rats by a footpad injection of 1 mg/kg lipopolysaccharide (LPS). Oral administration of GTE (550 mg/kg) was given one, two or four times after LPS injection. Twenty-four hours later, LPS produced severe hyperemia and edema in the iris. Immunocytochemical examinations showed an accumulation of infiltrating cells in the aqueous humor that were immunopositive for cluster of differentiation 43 (CD43) and CD68, markers for leucocytes and macrophages, respectively. Analyses of the aqueous humor showed an increase in pro-inflammatory mediators including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) and monocyte chemoattractant protein-1 (MCP-1). GTE treatments improved the clinical manifestations and reduced infiltrating cells and protein exudation in the aqueous humor, which were not observed under half dose of GTE (275 mg/kg). The number of CD68 positive macrophages residing in the iris and ciliary was also reduced. GTE suppressed production of TNF-α, IL-6 and MCP-1 in the aqueous humor, which was associated with a down-regulation of LPS receptor complex subunits, Toll-like receptor 4 (TLR-4) and CD14, and suppression of nuclear factor-kappa Bp65 (NF-κBp65) in the iris and ciliary body. Our findings show that GTE is a potent anti-inflammatory agent against the inflammation of EIU, and suggest a potential use in treatment of acute uveitis

Growth hormone releasing hormone signaling promotes Th17 cell differentiation and autoimmune inflammation

Abstract Dysregulation of Th17 cell differentiation and pathogenicity contributes to multiple autoimmune and inflammatory diseases. Previously growth hormone releasing hormone receptor (GHRH-R) deficient mice have been reported to be less susceptible to the induction of experimental autoimmune encephalomyelitis. Here, we show GHRH-R is an important regulator of Th17 cell differentiation in Th17 cell-mediated ocular and neural inflammation. We find that GHRH-R is not expressed in naïve CD4+ T cells, while its expression is induced throughout Th17 cell differentiation in vitro. Mechanistically, GHRH-R activates the JAK-STAT3 pathway, increases the phosphorylation of STAT3, enhances both non-pathogenic and pathogenic Th17 cell differentiation and promotes the gene expression signatures of pathogenic Th17 cells. Enhancing this signaling by GHRH agonist promotes, while inhibiting this signaling by GHRH antagonist or GHRH-R deficiency reduces, Th17 cell differentiation in vitro and Th17 cell-mediated ocular and neural inflammation in vivo. Thus, GHRH-R signaling functions as a critical factor that regulates Th17 cell differentiation and Th17 cell-mediated autoimmune ocular and neural inflammation

GTE treatment on cell infiltration and protein exudation in aqueous humor.

<p>(A) and (B): GTE caused a significant reduction in accumulation of cells (A) and protein exudation (B) in aqueous humor (***<i>p</i><0.01) when compared with LPS+water. The differences among the GTE treatment groups were, however, not significant (<i>p</i>>0.05). Saline+water, n = 3; LPS+water, n = 6; LPS+GTE1, n = 6; LPS+GTE2, n = 6; LPS+GTE4, n = 6; LPS+Dxm, n = 6; Saline+water, n = 3. (C) and (D): In another experiment, significant reduction in infiltrating cells (C) and protein content (D) in aqueous humor was observed only in rats treated with 550 mg/kg GTE (*<i>p</i><0.05), but not in those received half dose (275 mg/kg) of GTE. Saline+water, n = 5; n = 6 in LPS+water, LPS+GTE2 550 and LPS+GTE2 275. Data were shown as mean ± <i>SE</i>.</p

Effect of GTE on macrophages within iris and ciliary body.

<p>(A)–(D): Fluorescent micrographs showing some cells were immunopositive to CD68, a marker for macrophages (arrows, magnified in inserts) 24 hours after treatment with (A): saline+water, (B): LPS+water, (C): LPS+GTE4, (D): LPS+Dxm. (E): A significant reduction in number of macrophages presented in the stroma of iris and ciliary body was observed after treatment with GTE and dexamethasone (Dxm). n = 3 in each group. Data were shown as mean ± <i>SE</i>. **<i>p</i><0.05 compared with LPS+water. C: cornea; AC: anterior chamber; I: iris; PC: posterior chamber; L: lens; CB: ciliary body.</p

CD14 and TLR-4 mRNA expression in the iris and ciliary body and the retina by quantitative real-time PCR analyses.

<p>C_T: threshold cycle; Saline+water: saline injection and fed with water; LPS+water: LPS injection and fed with water; LPS+GTE1: GTE was fed once after LPS injection; LPS+GTE2: GTE was fed twice after LPS injection; LPS+GTE4: GTE was fed four times after LPS injection; LPS+Dxm: Dxm was fed once after LPS injection; Saline+GTE4: saline injection and fed as GTE4.</p

Clinical manifestations of ocular inflammation in rat eyes.

<p>Ocular inflammation was evaluated by slit lamp examination 24 hours after LPS injection. (A): No inflammatory feature was observed in normal control rats (saline+water). (B) and (C): Hyperemia (green arrow), edema (yellow arrow) and synachesia (purple arrow) occurred in the iris of LPS treated rats. (D) and (E): Inflammatory responses were subsided in rats treated with GTE1 (D) and GTE4 (E). (F): Inflammatory responses were also suppressed in rats treated with Dexamethasone (Dxm). (G): The scores of clinical features were reduced significantly after GTE and Dxm treatments (**<i>p<</i>0.05, when compared with LPS+water). Saline+water, n = 3; LPS+water, n = 6; LPS+GTE1, n = 6; LPS+GTE2, n = 6; LPS+GTE4, n = 6; LPS+Dxm, n = 6. Data were shown as mean ± <i>SE</i>. Scar bar = 2 mm.</p

Primer sequences used for quantitative real-time PCR detection of rat-CD14, TLR-4 and GAPDH.

<p>CD14: cluster of differentiation 14; TLR-4: toll-like receptor 4; GAPDH: glyceraldehyde-3-phosphate dehydrogenase.</p

TNF-α, IL-6 and MCP-1 concentration in the serum after different treatments.

<p>-: undetectable. Sensitivity of these assays is 5 pg/mL for TNF-α, 21 pg/mL for IL-6, less than 8.0 pg/mL for MCP-1.</p><p>Saline+water: saline injection and fed with water; LPS+water: LPS injection and fed with water; LPS+GTE1: GTE was fed once after LPS injection; LPS+GTE2: GTE was fed twice after LPS injection; LPS+GTE4: GTE was fed four times after LPS injection; LPS+Dxm: Dxm was fed once after LPS injection; Saline+GTE4: saline injection and fed as GTE4; **<i>p</i><0.05, compared with LPS+water.</p