Protective effect of Juglans regia L. against ultraviolet B radiation induced inflammatory responses in human epidermal keratinocytes

Abstract

Background: Juglans regia L. has a history of traditional medicinal use for the treatment of various maladies and have been documented with significant antioxidant and antiinflammatory properties. Although all parts of the plant are medicinally important, but male the flower of the plant has not been yet investigated against the photo-damage.

Purpose: The present study, we sought to determine the photoprotective effect of the male flower of J. regia L. against ultraviolet-B radiation-induced inflammatory responses in human skin cells.

Methods: The profile of pharmacological active compounds present in the male flower of J. regia was analyzed by GC-MS. Then, the antioxidant property of methanolic extract of J. regia (MEJR) was analyzed by in vitro free radical scavenging assays. Further, we analyzed the sun protection factor of this extract by spectrophotometry. Moreover, we investigated the photoprotective effect of MEJR against UVB induced inflammatory signaling in human epidermal cells. Human skin epidermal keratinocytes (HaCaT) were pretreated with the MEJR (80 µg/ml), 30 min prior to UVB-irradiation at a dose of 20 mJ/cm² and were investigated for lipid peroxidation, enzymatic antioxidants activity, apoptosis and inflammatory markers expression level.

Results: The GC-MS results showed the presence of good amount of pharmacologically active compounds in the MEJR. We observed that the MEJR possess significant free radical scavenging activity and it was comparable with standard antioxidants. Further, the MEJR exhibits 8.8 sun-protection-factor (SPF) value. Pretreatment with MEJR, 30 min prior to UVB-irradiation, prevented ROS generation, lipid peroxidation and restored the activity of antioxidant status in HaCaT cells. Moreover, MEJR pretreatment significantly prevented UVB activated inflammatory markers like TNF-α, IL-1, IL-6, NF-κB, COX-2 in HaCaT.

Conclusion: The present findings suggest that MEJR exhibit photoprotective effects and hence it may be useful for the treatment of inflammation related responses. The pharmacological mechanism of MEJR partly associated with its UV absorbance, modulation of inflammatory signaling as well as due to its free radical scavenging capability.

Keywords: Antioxidant; Inflammation; J. regia L.; SPF; Skin cells; UVB radiation.