T‐oligos augment UV‐induced protective responses in human skin

Abstract

We have shown that DNA oligonucleotides substantially homologous to the telomere 3-prime overhang sequence (T-oligos) increase DNA repair capacity (DRC) in cultured human cells and decrease UV-induced mutation rate and photocarcinogenesis in mouse skin. To investigate the protective effects of T-oligos in intact human skin, paired skin explants obtained from adult donors were treated with T-oligos or diluent alone for 24 h, then UVB- or sham-irradiated, and processed after 6, 24, 48, 72, and 96 h for histological analysis. After UV irradiation apoptotic epidermal cells were comparable in diluent- and T-oligo-treated skin. Proliferating (Ki67+) cells were sparse in sham-irradiated skin and for 24 h after UV in both diluent- and T-oligo-treated specimens. However, compared to diluent controls, at 48 and 72 h T-oligos significantly inhibited UV-induced rebound hyperproliferation. Maximum and comparable cyclobutane pyrimidine dimers (CPDs) were detected immediately after UV irradiation in diluent- and T-oligo-treated skin, but CPDs were strikingly reduced in T-oligo- vs. diluent-treated skin at 24, 48, and 72 h. Total and activated p53 protein was increased in T-oligo- vs. diluent-pretreated skin at the time of irradiation, and up to 3-fold increases persisted for 24 h post-UV. Over 5 days, UV irradiation and T-oligo comparably increased expression of melanogenic proteins and each increased epidermal melanin content 3- to 5-fold, with distinct nuclear capping in many keratinocytes. In combination, these findings predict that T-oligo treatment will increase melanogenesis, prolong epidermal arrest, and increase DNA repair rate after UV irradiation, thus decreasing the severity of acute and chronic photodamage in human skin. Moreover, the data document an inducible SOS-like response consisting of increased melanogenesis and increased DNA repair capacity in human skin following UV-induced damage that is also produced by T-oligos in the absence of initial damage.

Topical Thymidine Dinucleotide Treatment Reduces Development of Ultraviolet-Induced Basal Cell Carcinoma in Ptch-1+/− Mice

“…To determine the effect of pTT on DNA repair, skin samples were processed for CPD immunostaining ( Figure 2A (Figure 2C), confirming earlier results in acutely UV-irradiated murine 8 and human skin 28 and indicating that pTT treatment persistently reduces the number of cells with a detectable level of CPDs, even after 7 months of chronic UV exposure. In addition, 8-oxo-dG immunostaining was used to detect UV-induced oxidative DNA damage repair ( Figure 2B).…”

“…The number and size of BCCs were evaluated by a blinded investigator using computer-assisted image analysis (Image J NIH software; National Institutes of Health, Bethesda, MD). 28,31 Adjacent sections were processed for immunohistology. After dewaxing and dehydration, antigen unmasking was done by boiling the slides in citrate buffer, pH ϭ 6, for 20 minutes.…”

“…8 In human or rodent skin with epidermal melanocytes, pTT also stimulates protective melanogenesis. 28,29 Additionally, inhibition of cyclooxygenese-2 (Cox-2), the proinflammatory enzyme whose overexpression has been linked to photocarcinogenesis, reduces skin cancer development in UV-irradiated mice. 6 We have shown that pTT treatment of cells in vitro, of mouse skin in vivo, or of human skin ex vivo decreases the constitutive and UV-induced levels of Cox-2 through p53 activation, known to inhibit Cox-2 expression, 30 by reducing NF-B-dependent Cox-2 transcription.…”

Ultraviolet A within Sunlight Induces Mutations in the Epidermal Basal Layer of Engineered Human Skin

“…These data are consistent with previous findings. 27 The isotype and omitted antibody controls were negative for staining.…”

Modifying skin pigmentation – approaches through intrinsic biochemistry and exogenous agents

“…Oligonucleotides that imitate this telomere overhang (T-oligos) presumably induce protective DNA damage responses. Gilchrest and coworkers found that in human skin explants treated with T-oligos and irradiated with UVB, there was a strikingly reduced amount of DNA damage and a 3-5 fold increase in melanin content compared to untreated UV-irradiated samples [88]. Sunscreens containing Toligos could be efficient in enhancing skin pigmentation and in protecting against photodamage and skin cancer.…”