DNA photodamage induced by UV phototherapy lamps and sunlamps in human skin in situ and its potential importance for skin cancer

Optical Behavior of Human Skin Substitutes: Absorbance in the 200-400 nm UV Range

The most recent generation of bioengineered human skin allows for the efficient treatment of patients with severe skin defects. Despite UV sunlight can seriously affect human skin, the optical behavior in the UV range of skin models is still unexplored. In the present study, absorbance and transmittance of the UGRSKIN bioartificial skin substitute generated with human skin cells combined with fibrin-agarose biomaterials were evaluated for: UV-C (200−280 nm), -B (280−315 nm), and -A (315−400 nm) spectral range after 7, 14, 21 and 28 days of ex vivo development. The epidermis of the bioartificial skin substitute was able to mature and differentiate in a time-dependent manner, expressing relevant molecules able to absorb most of the incoming UV radiation. Absorbance spectral behavior of the skin substitutes showed similar patterns to control native skin (VAF > 99.4%), with values 0.85−0.90 times lower than control values at 7 and 14- days and 1.05−1.10 times the control values at 21- and 28-days. UV absorbance increased, and UV transmission decreased with culture time, and comparable results to the control were found at 21 and 28 days. These findings support the use of samples corresponding to 21 or 28 days of development for clinical purposes due to their higher histological similarities with native skin, but also because of their absorbance of UV radiation.

Inhibition of nuclear factor-kappaB activation attenuates tubulointerstitial nephritis induced by gentamicin

BACKGROUND

Animals treated with gentamicin can show residual areas of interstitial fibrosis in the renal cortex. This study investigated the expression of nuclear factor-kappaB (NF-kappaB), mitogen-activated protein (MAP) kinases and macrophages in the renal cortex and structural and functional renal changes of rats treated with gentamicin or gentamicin + pyrrolidine dithiocarbamate (PDTC), an NF-kappaB inhibitor.

METHODS

38 female Wistar rats were injected with gentamicin, 40 mg/kg, twice a day for 9 days, 38 with gentamicin + PDTC, and 28 with 0.15 M NaCl solution. The animals were killed 5 and 30 days after these injections and the kidneys were removed for histological and immunohistochemical studies. The results of the immunohistochemical studies were scored according to the extent of staining. The fractional interstitial area was determined by morphometry.

RESULTS

Gentamicin-treated rats presented a transitory increase in plasma creatinine levels. Increased ED-1, MAP kinases and NF-kappaB staining were also observed in the renal cortex from all gentamicin-treated rats compared to control (p < 0.05). The animals killed on day 30 also presented fibrosis in the renal cortex despite the recovery of renal function. Treatment with PDTC reduced the functional and structural changes induced by gentamicin.

CONCLUSIONS

These data show that inhibition of NF-kappaB activation attenuates tubulointerstitial nephritis induced by gentamicin.

Narrow-band UV-B micro-phototherapy: a new treatment for vitiligo

BACKGROUND

Vitiligo is a common, acquired, often familial, melanocytopenic disorder with focal depigmentation of the skin. There are several new treatments, that appear to have higher success rates than previous therapies for the treatment of vitiligo. Among these, the most promising one appears to be narrow-band UV-B therapy.

OBJECTIVE

The aim of this open study is to evaluate the efficacy of the BIOSKIN micro-phototherapy in the treatment of vitiligo in 734 patients.

SUBJECTS AND METHODS

Seven hundred and thirty-four individuals affected by vitiligo (segmental and non-segmental) were treated for 12 months with a new device called BIOSKIN that can produce a focused beam of narrow UV-B (microphoto-therapy) on vitiligo patches only. Photographs of the subjects were taken at the beginning of the therapy and every month thereafter for 12 months. The response to treatment was estimated in two comparable photographs using planimetry. The duration of the clinical study was of 2 years and 8 months. At the end of this period 734 patients had received each a mean of 24 sessions of treatment during a period of 12 months.

RESULTS

Five hundred and ten subjects (69.48%) of the 734 achieved normal pigmentation on more than 75% of the treated areas. In particular, 112 of these were totally repigmented. One hundred and fifty-five (21.12%) individuals achieved 50-75% pigmentation of the treated areas, and 69 (9.40%) showed less than 50% repigmentation. No patients showed acute or chronic relevant adverse effects.

CONCLUSION

BIOSKIN UV-B microphototherapy seems highly effective in restoring pigmentation in patients affected by vitiligo. As no side-effects have been observed, this could represent the treatment of choice for vitiligo limited to less than 30% of the skin surface.

Measurement of UVB-Induced DNA damage and its consequences in models of immunosuppression

Exposure to UVB results in formation of cyclobutane pyrimidine dimers (CPDs) and 6-4 photoproducts in DNA. These can be quantified by a variety of techniques including alkaline gel electrophoresis, ELISAs, Southwestern blotting, and immunohistochemistry. Damage to DNA results in activation of damage response pathways, as indicated by Western blotting using antibodies specific for p53 and breast cancer-associated gene 1 (BRCA1) phosphorylation. The signal from DNA damage to activation of these response pathways appears to be mediated by FKBP12-rapamycin-associated protein (FRAP), since these phosphorylation events are blocked by rapamycin. UVB-induced DNA damage also leads to induction of immunosuppressive cytokines including tumor necrosis factor alpha (TNF-alpha) and interleukin (IL)-10 in skin. Induction of TNF-alpha by UVB is readily detectable in cultured normal human epidermal keratinocytes (NHEKs) using ELISA, while induction of IL-10 is readily detectable in cultured mouse keratinocytes but not in NHEKs. Induction of DNA damage by liposome-encapsulated HindIII results in induction of immunosuppressive responses similar to UVB. Clinical testing shows that liposome-encapsulated T4 endonuclease V or photolyase stimulates repair of CPDs in the skin of human subjects, and prevents UVB-induced immunosuppression. Stimulation of repair and prevention of immunosuppression have been linked to prevention of skin cancer by liposome-encapsulated T4 endonuclease V in repair-deficient xeroderma pigmentosum patients.

How fast are UV-dimers repaired in human skin DNA in situ?

Sheehan et al (2002) published a paper on UV-dimers in human skin and their repair with contradictions in their own data. In one experiment they applied two doses, 0.65 and 2 MED, but the apparent dimer levels, measured by a immunohistochemical technique, only increased in skin of type II (Fig 2a). The authors offered as explanation that the level of DNA damage would saturate. The dimer levels reached are at around 1 dimer per 1 million nucleotides, and there has been no evidence for saturation when a quantitative postlabeling technique has been used (Bykov et al, 1998). There is no reason for saturation until most of the thydmidyl-thymidine positions would be occupied in DNA, which, based on literature with other intrastrand cross-linkers, would require dimer levels 1 : 100 (Försti et al, 1989), or 10,000 times higher levels of dimer than that obtained by an irradiation at a MED dose.

Impact of UVA exposure on psychological parameters and circulating serotonin and melatonin

BACKGROUND

People tend to feel better after exposure to ultraviolet (UV) radiation. This study was performed to investigate the impact of UVA exposure on psychological and neuroendocrine parameters.

METHODS

Fifty-three volunteers were separated into 42 individuals who had UVA exposure and 11 individuals who had no UVA exposure. The UVA-exposed volunteers had irradiation sessions six times in a three-week period. All volunteers completed two questionnaires at baseline (T1) and at the end of the study (T3). For the determination of serotonin and melatonin serum levels of all volunteers blood samples were collected at baseline (T1), after the first UVA exposure (T2), and at the end of the study after the sixth exposure (T3).

RESULTS

UVA-exposed volunteers felt significantly more balanced, less nervous, more strengthened, and more satisfied with their appearance at T3. By contrast, the controls did not show significant changes of psychological parameters. In comparison to T1 and T3, serum serotonin was significantly higher and the serum melatonin was significantly lower for the volunteers exposed to UVA at T2. Both, for exposed and non-exposed volunteers serotonin and melatonin levels did not significantly differ at T1 and T3.

CONCLUSIONS

It remains obscure, whether the exposure to UVA or other components of the treatment were responsible for the psychological benefits observed. The changes of circulating neuroendocrine mediators found after UVA exposure at T2 may be due to an UVA-induced effect via a cutaneous pathway. Nevertheless, the positive psychological effects observed in our study cannot be attributed to circulating serotonin or melatonin.