DNA Repair Agents
Since photoaging is in part due to DNA damage caused by
UV radiation, enhancing the skin’s ability to repair DNA
damage will reduce actinic damage. This is the basis for
the photoprotective use of DNA repair enzymes, which are
active irrespective of whether they are applied before or
after exposure to UV radiation. The following are some
examples.
Liposome-Encapsulated T4 Endonuclease V
After the bacterial phage enzyme T4 endonuclease V
identifies cyclobutane pyrimidine dimers, the main DNA
photolesions produced by UV-B radiation, this enzyme
initiates their repair and stimulates their removal.61 T4
endonuclease V also reduces the synthesis and expression
of immunosuppressive cytokines that contribute to the
risk of skin cancer, such as tumor necrosis factor-a and
interleukin-10.62 Thus, it protects the skin against sunburn
and sunlight-induced immunosuppression and enhances the
proper functioning of the endogenous DNA repair system.
Encapsulation of this enzyme in liposomes facilitates its
distribution throughout the skin. A number of clinical trials
have been done in patients with xeroderma pigmentosum
because this treatment has been shown to be particularly
useful in that setting.63