Six critical questions for DNA repair enzymes in skincare products: a review in dialog

Concerns over existing sunscreen filters have reinforced the need to examine supplemental sun protection or repair of sun damage. Technology to enhance DNA repair has been available in skincare and sunscreen products for several decades, but skepticism and lack of familiarity with the supporting data remain prevalent. Here, we address six of the main questions raised by medical professionals regarding the efficacy of DNA repair enzymes in sun protection. These include the mode of delivery and mechanism of action, the effect on cellular responses and the amelioration of pre-cancers, cancers and photoaging. The conclusions are that topical DNA repair enzymes do enhance removal of DNA damage and reduce the appearance of new actinic keratoses as well as increase regression of existing lesions. Support for prevention of photoaging and skin cancer is significant but could be strengthened or disproven with additional research.

Sunscreen applied at ≥ 2 mg cm-2 during a sunny holiday prevents erythema, a biomarker of ultraviolet radiation-induced DNA damage and suppression of acquired immunity

BACKGROUND

Sun protection factor (SPF) is assessed with sunscreen applied at 2 mg cm^-2 . People typically apply around 0·8 mg cm^-2 and use sunscreen daily for holidays. Such use results in erythema, which is a risk factor for skin cancer.

OBJECTIVES

To determine (i) whether typical sunscreen use resulted in erythema, epidermal DNA damage and photoimmunosuppression during a sunny holiday, (ii) whether optimal sunscreen use inhibited erythema and (iii) whether erythema is a biomarker for photoimmunosuppression in a laboratory study.

METHODS

Holidaymakers (n = 22) spent a week in Tenerife (very high ultraviolet index) using their own sunscreens without instruction (typical sunscreen use). Others (n = 40) were given SPF 15 sunscreens with instructions on how to achieve the labelled SPF (sunscreen intervention). Personal ultraviolet radiation (UVR) exposure was monitored electronically as the standard erythemal dose (SED) and erythema was quantified. Epidermal cyclobutane pyrimidine dimers (CPDs) were determined by immunostaining, and immunosuppression was assessed by contact hypersensitivity (CHS) response.

RESULTS

There was no difference between personal UVR exposure in the typical sunscreen use and sunscreen intervention groups (P = 0·08). The former had daily erythema on five UVR-exposed body sites, increased CPDs (P < 0·001) and complete CHS suppression (20 of 22). In comparison, erythema was virtually absent (P < 0·001) when sunscreens were used at ≥ 2 mg cm^-2 . A laboratory study showed that 3 SED from three very different spectra suppressed CHS by around ~50%.

CONCLUSIONS

Optimal sunscreen use prevents erythema during a sunny holiday. Erythema predicts suppression of CHS (implying a shared action spectrum). Given that erythema and CPDs share action spectra, the data strongly suggest that optimal sunscreen use will also reduce CPD formation and UVR-induced immunosuppression.

Transparent Poly(methyl methacrylate)/TiO2 Nanocomposites for UV-Shielding Applications

Transparent poly(methyl methacrylate) (PMMA)/TiO2 nanocomposites have been prepared by solution mixing PMMA with organically soluble titania xerogel. The organically soluble titania xerogel in the form of amorphous phase has been synthesized via a simple sol-gel method, involving hydrolysis of tetrabutyl titanate (TBT) in trifluoroacetic acid (TFA) and gelation. The obtained PMMA/TiO2 nanocomposites were characterized by Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), thermogravimetry (TG) and ultraviolet-visible (UV-vis) absorption spectroscopy. The results showed that the interaction between titania nanoparticles and PMMA macromolecular chains led to a homogeneous dispersion of TiO2 in PMMA matrix. The resulting PMMA/TiO2 nanocomposites showed improved thermal stability, high transparency and high UV-shielding efficiency with a small amount of titania xerogel (£3.0 wt%). The present work is of interest for developing a series of transparent UV-shielding nanocomposites.