Vitamin C as an antioxidant
Recently, the use of vitamin C after sun exposure is becoming popular. This is due to its action on UV-induced reactive oxygen species (ROS). Vitamin C was shown to delay carcinogenesis after UV exposure in mice. Topical application of vitamin C was found to provide photoprotection. Histologically, topical ascorbic acid helped reduced the number of sunburn cells (sunburn cells refer to apoptosis of basal kertatinocytes induced by irreversible DNA damage). Researchers have found that topical vitamin C drastically reduced erythema and the vitamin C level decreased after sun exposure. A recent study found that a sunblock added with vitamin C provided better protection against UV compared to sunblock alone. Combination of vitamin C and E markedly strengthens the UV blocking action.
Many studies in mice have shown that topical vitamin C reduces the redness of the skin, sunburn cells and cancer after sun exposure. On top of being a powerful antioxidant by itself, vitamin C restores vitamin E’s antioxidant action.
Vitamin C in collagenesis and elastin generation.
Ascorbate works as a cofactor of prolyl hydroxylase, an important process in collagenesis. Deficiency of ascorbic acid leads to poor collagenesis and scurvy. Elastin contains hydroxyproline but prolyl hydroxylation is not needed in elastin generation and the role of vitamin C in this regard is still unclear.
Ascorbic acid increases the transcription rate of procollagen genes in fibroblasts. It was also found to increase procollagen mRNA levels to promote collagenesis.
Ascorbic acid promotes collagenesis but it works as an antagonist for elastin. Bergethon et al. reported that elastin accumulation was markedly reduced in cell culture treated with vitamin C. Adding ascorbic acid to fibroblast culture increases collagen. The mechanism through which it reduces elastin is unknown.
A study examining the effect of topical vitamin C on wrinkles reported wrinkle reduction after three months of topical vitamin C therapy. This was accompanied with serious skin irritation but there was drastic improvement of wrinkles in treated areas compared to the control. The mechanism in which vitamin C reduces wrinkles is not clearly understood yet. One can presume that vitamin C can improve wrinkles through inflammation, irritation or promoting collagenesis.
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A study examined the effects of topical vitamin C in healthy women with signs of photoaging. Topical cream with 5% vitamin C used over 6 months resulted in statistically significant improvement in water content, wrinkles, glow and blemishes. It also resulted in improved skin density and smoothed deep wrinkles. The increased MMP-1 inhibitor level prevented UV-induced collagen damage. There were no changes in the levels of elastin or fibrillin mRNA.
Vitamin C as an anti-inflammatory agent
Vitamin C has anti-inflammatory action and inhibits NFκB to affect pro-inflammatory cytokines (TNF-α·IL-1·IL-6·IL-8). It has anti-inflammatory effects in acne or rosacea, promotes wound healing and prevents postinflammatory hyperpigmentation.
-To be continued
