The In Vivo Fluorescence of Tryptophan Moieties in Human Skin Increases with UV Exposure and is a Marker for Epidermal Proliferation

Abstract

We have investigated the in vivo fluorescence of human skin with UV excitation and the effect of UV irradiation on the UV fluorescence. A particular chromophore was found to be very sensitive to suberythemogenic UV radiation. This chromophore has the spectral characteristics of tryptophan residues in proteins and is characterized by a fluorescence excitation maximum at 295 nm. The fluorescence of this chromophore in human epidermis has an excitation maximum that is coincident with the maximum of the action spectrum of most UV-induced photobiologic responses to human skin. The fluorescence of the chromophore was found to increase with UV exposure. The action spectrum was determined by following the increase of the emission at 345 nm with excitation at 295 nm as a function of skin exposure to a number of wavelengths in the UV region of the spectrum. The results show that irradiation in the UVB (290-320 nm) is more effective in producing the change in the fluorescence of tryptophan. Irradiation in the UVA (320-380 nm) was found to be capable of producing the increase but to a smaller extent. Whereas tryptophan fluorescence is found in both the epidermis and the dermis, it is only the epidermal component that increases with UV exposure. The change in 295 nm fluorescence with UV exposure was determined to be oxygen dependent. The fluorescence of tryptophan moieties measured in situ was found to increase when epidermal proliferation increases. This was verified by inducing epidermal repair after mechanical insult (tape stripping). The results suggest two possible scenarios for the UV-induced increase of the fluorescence: a prompt photooxidation of tryptophan moieties or a fast proliferation response to the insult created by UV irradiation.

In vivospectrofluorimetry reveals endogenous biomarkers that report healthspan and dietary restriction inCaenorhabditis elegans

“…In vivo fluorescence spectroscopy has been previously used on humans and other mammals to measure endogenous autofluorescent species of skin and other tissues (Leffell et al 1988;Kollias et al 1998;Brancaleon et al 1999;Gillies et al ., 2000;Doukas et al ., 2001;Na et al ., 2001;Sandby-Moller et al ., 2003). Fluorescent species that are common in many biological tissues include the aromatic amino acids (tryptophan, tyrosine and phenylalanine), cross-linked collagen and elastin, lipofuscin, NADH, and FAD.…”

Antiaging Action of Retinol: From Molecular to Clinical

“…The first scan was used to record the skin fluorescence with excitation in the range of 250-500 nm. This scan goes through the major fluorescence maxima naturally occurring in skin with excitations at: (a) 295 nm, attributed to tryptophan moieties and related to epidermal cell proliferation and epidermal thickening [11,12,16,17] ; (b) 335 nm, attributed to pepsin-digestible collagen crosslinks; (c) 370 nm, attributed to collagenase-digestible collagen crosslinks, and (d) 400-420 nm, attributed to elastin crosslinks. For a review of the skin fluorescence maxima see Kollias et al [18] .…”

“…Recently, in vivo noninvasive methods that can objectively measure parameters related to skin biology and that complement the more subjective clinical evaluation have been developed [10] . In the case of skin aging, in vivo fluorescence spectroscopy provides an important marker that has been shown to relate epidermal thickness and epidermal cell proliferation rate in mice [11] and in humans [12][13][14] . Up to now, fluorescence spectroscopy has not been used to measure epidermal proliferation induced by ROL.…”

Spectral characteristics of autofluorescence and second harmonic generation from ex vivo human skin induced by femtosecond laser and visible lasers

“…When the laser light of a certain wavelength induces the skin specimen, native fluorescent species can be analyzed spectroscopically (Brancaleon et al 1999, Chance and Thorell 1959, Laiho et al 2005, Na et al 2000, Pena et al 2005. The collagen with a microcrystalline triclinic structure can easily produce optical SHG signals when an fs laser source excites it (Campagnola and Loew 2003, Cox et al 2000, 2003aGeorgiou et al 2000, Laiho et al 2005Pena et al 2005).…”

“…The collagen with a microcrystalline triclinic structure can easily produce optical SHG signals when an fs laser source excites it (Campagnola and Loew 2003, Cox et al 2000, 2003aGeorgiou et al 2000, Laiho et al 2005Pena et al 2005). Tissue spectroscopy of skin has become a very promising method for many fields of the morphologic and biochemical information of skin (Laiho et al 2005, Pena et al 2005, Rebecca and Eva 1996, the identification of skin native fluorophore (Laiho et al 2005, Na et al 2000, Pena et al 2005, diagnosing diseases (Beauvoit and Chance 1998, Brancaleon et al 2001, Hewett et al 2000, Kollias and Stamatas 2002, Licha et al 2000, Sterenborg et al 1994, skin aging and photoaging (Brancaleon et al 1999, Kollias et al 1998. The tissue spectroscopy of human skin has long been studied (Alvarez-Roman et al 2004, Brancaleon et al 1999, Gillies et al 2000, König and Riemann 2003, Laiho et al 2005, Masters and So 1999, Masters et al 1997, Na et al 2000, Pena et al 2005, Rajadhyaksha et al 1995, Teuchner et al 2003.…”