Protective effect of oat bran extracts on human dermal fibroblast injury induced by hydrogen peroxide

Abstract

Oat contains different components that possess antioxidant properties; no study to date has addressed the antioxidant effect of the extract of oat bran on the cellular level. Therefore, the present study focuses on the investigation of the protective effect of oat bran extract by enzymatic hydrolysates on human dermal fibroblast injury induced by hydrogen peroxide (H(2)O(2)). Kjeldahl determination, phenol-sulfuric acid method, and high-performance liquid chromatography (HPLC) analysis indicated that the enzymatic products of oat bran contain a protein amount of 71.93%, of which 97.43% are peptides with a molecular range from 438.56 to 1301.01 Da. Assays for 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity indicate that oat peptide-rich extract has a direct and concentration-dependent antioxidant activity. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) colorimetric assay and the TdT-mediated digoxigenin-dUTP nick-end labeling (TUNEL) assay for apoptosis showed that administration of H(2)O(2) in human dermal fibroblasts caused cell damage and apoptosis. Pre-incubation of human dermal fibroblasts with the Oatp for 24 h markedly inhibited human dermal fibroblast injury induced by H(2)O(2), but application oat peptides with H(2)O(2) at same time did not. Pre-treatment of human dermal fibroblasts with Oatp significantly reversed the H(2)O(2)-induced decrease of superoxide dismutase (SOD) and the inhibition of malondialdehyde (MDA). The results demonstrate that oat peptides possess antioxidant activity and are effective against H(2)O(2)-induced human dermal fibroblast injury by the enhanced activity of SOD and decrease in MDA level. Our results suggest that oat bran will have the potential to be further explored as an antioxidant functional food in the prevention of aging-related skin injury.

Fig. 1

HPLC chromatogram of the molecular weight distribution in Oatps Two major peaks with estimated molecular weights of 1 301.01 and 921.82 Da were observed

Fig. 2

Antioxidant activity of oat bran extracts detected by a DPPH radical scavenging assay (a) Oatp significantly increased the scavenged DPPH radicals in a concentration-dependent manner. (b) EGCG that exhibited certain antioxidant activity in previous research was used as the positive control. ^* P(0.05 when comparing different concentrations of Oatp or EGCG by one-way ANOVA. Data are presented as the mean±SEM obtained from three independent experiments

Fig. 3

Oxidation damage to human dermal fibroblast induced by different concentrations of H₂O₂ (a) Cell viability and damaged cell nuclei detected by PI staining and TUNEL assay after exposure of human dermal fibroblasts to different concentrations of H₂O₂. (b, c) The statistical analyses of the reduced survival rates and TUNEL-positive cells were resulting from treatments with different concentrations of H₂O₂. (d) Statistical analysis of cell death rate measured by an MTT colorimetric assay with different concentrations of H₂O₂ and treatment time. ^* P<0.05 according to one-way ANOVA. Data (mean±SEM) are obtained from five independent experiments

Fig. 4

Effect of oat bran extracts on H₂O₂-induced dermal fibroblast injury (a–d) Statistical analyses of the effect of oat bran extracts on viability rates of human dermal fibroblasts undergoing pre-incubation time of 0–24 h before H₂O₂ injury. The viability rates were measured with an MTT colorimetric assay. ^* P<0.05; ^** P(0.01 according to the Student’s t-test, compared with H₂O₂ alone. Data (mean±SEM) are obtained from five independent experiments. (e) Effect of oat bran extracts on H₂O₂-induced apoptosis detected by the TUNEL assay. (f) Statistical analysis of the effect of oat bran extracts on the apoptotic rate induced by H₂O₂. ^* P<0.05 according to Student’s t-test, compared with H₂O₂ alone

Fig. 5

Effect of oat bran extracts on antioxidant enzymes SOD and GSH-Px, and production of lipid peroxidation MDA (a) The statistical analyses of the effect of oat bran extracts on antioxidant enzymes SOD of human dermal fibroblasts undergoing pre-incubation time of 0–24 h or no pre-incubation before H₂O₂ injury. (b) The statistical analyses of the effect of oat bran extracts on the production of lipid peroxidation MDA of human dermal fibroblasts undergoing pre-incubation time of 0–24 h or no pre-incubation before H₂O₂ injury. (c) The statistical analyses of the effect of oat bran extracts on antioxidant enzymes GSH-Px of human dermal fibroblasts undergoing pre-incubation time of 0–24 h or no pre-incubation before H₂O₂ injury. The data (mean±SEM) for this statistical analysis were obtained from four independent experiments. ^* P<0.05 by Student’s t-test, compared with H₂O₂ alone