Mouse study: Fermented paprika may protect against retinal degeneration

Diseases of the outer retina, including age-related macular degeneration (AMD), are major causes of permanent visual damage. The pathogenesis of AMD involves oxidative stress and damage of the retinal pigment epithelium. 

Capsicum annuum L. (paprika) fruits have been known as a source of vitamins, carotenoids, phenolic compounds, and metabolites with a well-known antioxidant activity, which have positive effects on human health and protection against AMD and cataracts.

Studies have reported that Capsicum annuum L. exhibit a range of bioactivities​ including antioxidant​, antimicrobial, antiviral, anti-inflammatory, and anticancer​ properties. Health-linked functionality improves by fermentation of nutrients, which is useful technology for enhancing antioxidative​ and biological activity​. L. plantarum​ is a lactic acid species that improves the content of phenolic compounds and subsequently enhanced antioxidant capacity during fermentation​.

Recently, fermentation has been reported as one of the effective means to improve the antioxidant properties of plants​.However, studies on the beneficial effects of fermentation to improve biological efficacy have been reported using various materials, but there is no research on fermented paprika.

In the current study, researchers investigated whether paprika (fermented (FP), yellow, and orange colored) fermented with Lactobacillus (L.) plantarum​ could increase the protective effect of retinal degeneration using in vitro and in vivo models.

FP significantly increased cell survival and reduced levels of lactate dehydrogenase as well as intracellular reactive oxygen species (ROS) increase in SI (sodium iodate, NaIO3)-treated human retinal pigment epithelial (ARPE-19) cells.

Researchers developed a model of retinal damage in mice using SI (30 mg/kg) via intraperitoneal injection. Seven days after SI administration, deformation and a decrease in thickness were observed in the outer nuclear layer, but improved by FP treatment.

They found that FP administration protected the SI-mediated reduction of superoxide dismutase and glutathione levels in the serum and ocular tissues of mice.

The overproduction of cleaved poly(ADP-Ribose) Polymerase (PARP)1, caspase-3 and -8 proteins were significantly protected by FP in SI-treated cells and ocular tissues. In addition, we evaluated the potentiating effects of FP on antioxidants and their underlying mechanisms in RAW 264.7 cells. Lipopolysaccharide (LPS)-induced nitrite increase was markedly blocked by FP treatment in RAW 264.7 cells.

Furthermore, FP reduced LPS-induced inducible nitric oxide synthase and cyclooxygenase-2 activation. The FP also enhanced the inhibitory effects on mitogen activated kinase signaling protein activation in ARPE-19 and RAW 264.7 cells and ocular tissues.

There was no significant difference in total phenol and flavonoid content in paprika by fermentation, but the vitamin C content was increased in orange colored paprika, and protective effect against oxidative stress-mediated retinal damage was enhanced after fermentation.

The researchers therefore conclude these results suggest that FP may be a potential candidate to protect against retinal degenerative diseases through the regulation of oxidative stress.

Source: Nutrients​

Kim. S. Y., et al

"Protective Effects of Fermented Paprika (Capsicum Annuum L.) on Sodium Iodate-Induced Retinal Damage"​

https://doi.org/10.3390/nu13010025