Orally administered betaine reduces photodamage caused by UVB irradiation through the regulation of matrix metalloproteinase-9 activity in hairless mice

Abstract

Betaine is widely distributed in plants, microorganisms, in several types of food and in medical herbs, including Lycium chinense. The administration of 100 mg betaine/kg body weight/day is an effective strategy for preventing ultraviolet irradiation-induced skin damage. The present study aimed to determine the preventive effects of betaine on ultraviolet B (UVB) irradiation-induced skin damage in hairless mice. The mice were divided into three groups: Control (n=5), UVB-treated vehicle (n=5) and UVB-treated betaine (n=5) groups. The level of irradiation was progressively increased between 60 mJ/cm2 per exposure at week 1 (one minimal erythematous dose = 60 mJ/cm2) and 90 mJ/cm2 per exposure at week 7. The formation of wrinkles significantly increased following UVB exposure in the UVB-treated vehicle group. However, treatment with betaine suppressed UVB-induced wrinkle formation, as determined by the mean length, mean depth, number, epidermal thickness and collagen damage. Furthermore, oral administration of betaine also inhibited the UVB-induced expression of mitogen-activated protein kinase kinase (MEK), extracellular signal-regulated kinase (ERK), and matrix metalloproteinase-9 (MMP-9). These findings suggested that betaine inhibits UVB-induced skin damage by suppressing increased expression of MMP-9 through the inhibition of MEK and ERK.