Epigallocatechin Gallate Slows Retinal Degeneration, Reduces Oxidative Damage, and Modifies Circadian Rhythms in P23H Rats

Abstract

Retinitis pigmentosa (RP) includes a group of genetic disorders that involve the loss of visual function due to mutations mainly in photoreceptors but also in other retinal cells. Apoptosis, retinal disorganization, and inflammation are common in the progression of the disease. Epigallocatechin gallate (EGCG) has been proved as beneficial in different eye diseases. Pigmented heterozygous P23H rat was used as an animal model of RP. Visual function was assessed by optomotor and electroretinogram (ERG) and circadian rhythms were evaluated by telemetry. Hepatic oxidative damage and antioxidant defenses were assessed using biochemical tests. The visual function of the EGCG P23H group was preserved, with a deterioration in the activity period and lower values in the interdaily stability parameter. Control rats treated with EGCG were less active than the sham group. EGCG increased antioxidant levels in P23H rats but reduced total hepatic antioxidant capacity by almost 42% in control rats compared to the sham group. We conclude that treatment with EGCG improves visual function and antioxidant status in P23H rats but diminishes antioxidant defenses in wild-type control animals, and slightly worsens activity circadian rhythms. Further studies are necessary to clarify the beneficial effects in disease conditions and in healthy organisms.

Flavonoids improve the stability and function of P23H rhodopsin slowing down the progression of retinitis pigmentosa in mice

“…Targeting the ER stress signaling to rescue photoreceptors in RP is one of the therapeutic strategies (Mostafa et al 2019; Lin et al 2007; Gupta et al 2019). Interestingly, flavonoids in addition to their opsin stabilizing effect can modulate the ER stress pathways (Mostafa et al 2019; Pandey et al 2019) and exhibit neuroprotective effects on retinal cells in the RP mouse models (Liu et al 2021; Perdices et al 2020; Piano et al 2019). Also, as we recently found, flavonoids prevent light‐induced retinal degeneration, likely due to their ability to stabilize the emerged ligand‐free opsin and inhibit the cellular events leading to photoreceptor death (Ortega et al 2021).…”

Effects of Daily Melatonin Supplementation on Visual Loss, Circadian Rhythms, and Hepatic Oxidative Damage in a Rodent Model of Retinitis Pigmentosa

“…Animals were killed by carbon dioxide asphyxiation when the treatment period ended (6 months). Whole liver tissue was removed and quickly homogenized, as described previously [ 28 ], in a 0.2 M phosphate buffer composed of Na 2 HPO 4 (Panreac, A1046, Barcelona, Spain NaH 2 PO 4 (Panreac, A3559, Barcelona, Spain) (pH = 7.4), 0.5% Triton X-100 (Panreac, A4975, Barcelona, Spain), 5 mM of β-mercaptoethanol (M6250, Sigma Aldrich, Madrid, Spain), and 0.1 mg/mL phenylmethylsulfonyl fluoride (P7626, Sigma Aldrich, Madrid, Spain). Aliquots were frozen at −80 °C for biochemical analyses.…”

Anti-inflammatory Effects of GTE in Eye Diseases

“…One of the widely used animal models, P23H rats, recapitulate the slow rod photoreceptor degeneration in human RP ( 76 ). A recent study reported that oral EGCG could help preserve the visual functions in the P23H rats ( 77 ). Visual acuity and b wave ERG amplitudes, but not a wave ERG amplitudes, were significantly higher in the EGCG treated P23H rats, compared to the sham treatment group.…”