In vivo fluorescence excitation spectroscopy and in vivo Fourier‐transform Raman spectroscopy in human skin: evidence of H₂O₂ oxidation of epidermal albumin in patients with vitiligo

Abstract

Both fluorescence excitation spectroscopy and Fourier-transform Raman spectroscopy have been utilised to study in vivoH 2 O 2 -mediated oxidative stress in the depigmented epidermis of untreated patients with vitiligo by following the oxidation of disulfide bridges in human epidermal albumin and the fluorescence maxima of the tryptophan residue in position 214 of this protein. In normal healthy skin, the single tryptophan in albumin fluoresces with a l max at 295 nm which is in agreement with high concentrations (10 −3 M) of this protein. Fluorescence analysis of the depigmented epidermis of untreated patients with vitiligo revealed three distinct patient groups: (a) one with a peak at a l max of 280 nm (b) one with l max in the range 300-305 nm and (c) one with three peaks with excitation maxima in the region of a l max of 280, 290 and 300 nm. The peak at a l max of 280 nm was in agreement with low albumin concentrations. Epidermal H 2 O 2 concentrations in the mM range, as previously documented in untreated vitiligo, were followed with in vivo FT-Raman spectroscopy using the O -O stretch at 875 cm −1 . Here, we were able to assign the SO 2 stretch at 1040 cm −1 to cysteic acid, which was the expected peroxidation product of the disulfide bridges in albumin. Using human albumin we confirmed the oxidation of disulfide bridges as well as the concentration dependent fluorescence excitation maxima for Trp 214 in this protein. The removal of epidermal H 2 O 2 from the patients skin with a pseudocatalase (PC-KUS) yielded the loss of the O -O stretch at 875 cm −1 together with the loss of the SO 2 stretch at 1040 cm −1 in the Raman spectrum and a shift of the l max from 300-305 nm to 290/280 nm was observed in the fluorescence analysis. These new in vivo results add more evidence to the central role for H 2 O 2 -mediated oxidative stress in the pathomechanism of vitiligo.

Biomarkers of Epidermal Innate Immunity in Premature and Full-Term Infants

“…Albumin binds unsaturated fatty acids and calcium and may be involved in their transport (23). Its protective effects against H 2 O 2 oxidation may occur in the epidermis (25). The presence of albumin and keratin 1,10,11 in vernix is consistent with a proteomics identification of innate immune components (14).…”

Photosensitization of peptides and proteins by pterin derivatives

“…In addition, albumin is present in human skin [36], where there is an autocrine synthesis and regulation [37]. It has been reported that in patients affected by vitiligo, epidermal albumin oxidation takes place, but the mechanism of this process has not been elucidated [38]. We have studied the capability of Ptr to photoinduce chemical and structural changes in bovine serum albumin (BSA) and human serum albumin (HSA).…”

Identification of epidermal L‐tryptophan and its oxidation products by in vivo FT‐Raman Spectroscopy further supports oxidative stress in patients with vitiligo

“…12 Along these lines, we have shown earlier that epidermal albumin levels are affected by H 2 O 2 -mediated oxidation. 13 By using fluorescence spectroscopy we showed that low albumin levels in patients with vitiligo correspond to the presence of a 280 nm peak, while in healthy controls it is found at 295 nm. 13 However, in those in vivo studies we were left with one remaining unidentified peak at 300-305 nm in patients with acute condition of the disease.…”