Comparative quantitative analysis of ultraviolet B-induced skin blood flow change using laser Doppler perfusion imaging technique

Topical application of superoxide dismutase mediated by HIV-TAT peptide attenuates UVB-induced damages in human skin

The purpose of this study was to evaluate whether topical application of superoxide dismutase with cell penetrating peptide (HIV-TAT) could protect against skin damage induced by UVB irradiation in humans. The permeability through stratum corneum of large proteins linked to TAT peptide was firstly confirmed by confocal microscopy and tape stripping. Ten healthy volunteers with either Fitzpatrick skin type II or III were recruited in this clinical study. TAT-SOD (300units/cm(2)) and vehicle cream were applied on two symmetric areas of both inner upper arms 1h prior to UVB irradiation. After one hour of pretreatment, subjects received 10 incremental doses of UVB on pretreated areas. 24h later, erythema, blood flow and apoptotic cells were measured. Pretreatment with TAT-SOD 1h prior to UVB radiation promoted a mean minimal erythema dose (MED) increase of 36.6±18.4% (p=0.013<0.05. n=10) compared to vehicle control. The median blood flow values of all subjects following 2 and 3-MED of UVB were 107.8±51.0units and 239.5±88.0units respectively, which account for 26% and 25% decrease with respect to vehicle groups. These data suggest that TAT-SOD significantly suppresses UVB induced erythema formation and blood flow rise. Furthermore, pretreatment with TAT-SOD 1h prior to 2-MED of UVB irradiation reduced the apoptotic sunburn cell formation by 47.6±8.6% (p<0.0001) in all subjects. Evaluating results generated from all measurements, we conclude that topical application of TAT-SOD significantly attenuates UVB-induced skin damage in man. These biological effects of TAT-SOD are probably mediated via its free radical scavenging properties, clearly differentiating it from other physical sunscreen agents.

Phototesting with a divergent UVB beam in the investigation of anti-inflammatory effects of topically applied substances

BACKGROUND

Phototesting based on a single exposure to a divergent ultraviolet B (UVB) beam with radially decreasing UVB doses can be used to determine an individual's minimal erythema dose (MED). Laser Doppler perfusion imaging (LDPI) data can be combined with dosimetry data to produce objective dose-response plots in addition to the MED. The aim of this study was to investigate whether the divergent beam protocol could be used to demonstrate and quantify the anti-inflammatory effects of clobetasol diproprionate (Dermovate), pharmaceutical-grade acetone and a gel vehicle, applied after skin provocation by UVB.

METHOD

Sixteen Caucasian subjects were illuminated with the divergent beam on three areas close together on the left side of their upper backs. Two of the provoked areas on each subject were treated with acetone, gel vehicle or Dermovate, and one area was left untreated as a control. Skin blood perfusion was assessed 6 and 24 h after UVB illumination using LDPI. The reaction diameter, the mean perfusion, and the average dose-response plots for each group and treatment were extracted from the LDPI data.

RESULTS

Application of the topical steroid clobetasol diproprionate after UVB provocation markedly decreased the inflammatory response. Acetone and the gel vehicle also showed mild anti-inflammmatory effects in two of the parameters but not for the mean perfusion response. The mean diameter differences between controls and treated reactions had predominantly positive 99% confidence intervals. Analysis of the dose-response data at doses higher than the MED showed a linear relationship (0.89<or=R2<or=0.98) for all reactions but with lower gradients in treated reactions, mostly marked for clobetasol diproprionate.

CONCLUSIONS

The divergent beam protocol can be used to demonstrate and quantify the effects of topical agents on the UVB reaction, in terms of reaction diameter, mean perfusion and changes in dose-response characteristics. The dose-response approach seems to be applicable even in diagnostic testing of an individual patient's response to UVB.

Laser Dopplers to determine cutaneous blood flow

BACKGROUND

Laser Dopplers can be useful in determining the relative amount of blood flowing through superficial skin. These instruments may be useful in assessing blood flow in healing wounds, flaps, and grafts.

OBJECTIVE

To review the theory and types of laser Dopplers available.

METHODS

This work includes a review of the literature.

RESULTS

Laser Dopplers potentially have a broad range of applications in dermatologic surgery and dermatology. Because laser Dopplers can quantify blood flow, the course of wound healing over time can be studied; however, for predicting viability of skin flaps and grafts, laser Dopplers have not been able to supplant clinical assessment.

CONCLUSION

Laser Dopplers provide an additional means of assessing superficial blood flow in the skin. This blood flow, which can be quantified, may be useful in studying wound and flap and graft healing.