Prevention of Infrared-A Radiation Mediated Detrimental Effects in Human Skin

P. Schroeder, PhD; C. Calles, Dipl.-Biol (MSc); J. Krutmann, MD


Skin Therapy Letter. 2009;14(5) 

In This Article

Detrimental Effects of IRA and Underlying Molecular Mechanisms

More than 20 years ago, Kligman reported that IR in guinea pigs causes actinic skin damage that resembled skin damage caused by UV.[2] This observation has since been confirmed in another animal model.[3] Moreover, IRA was reported to interfere with apoptotic pathways, thus preventing UV-damaged cells from executing programmed cell death, which indicates a co-carcinogenic potential for IRA.[4,5] Until now in vivo carcinogenesis studies for IRA alone and in combination with other noxae like UV have not been published. For IRC, the occurrence of a skin lesion described as erythema ab igne, which may progress to squamous cell carcinoma, has been reported.[6] However, interference with apoptotic pathways,[4] involvement in the repair of damaged DNA,[5] stimulation of proliferation and accelerated woundhealing[7] underline the necessity to further investigate the role of IRA in photocarcinogenesis.

The molecular basis of IRA induced photoaging of the skin was assessed by Schieke et al,[8] who were the first to show that physiological doses of IRA lead to a disturbance of the dermal extracellular matrix by upregulation of the expression of the collagen degrading enzyme matrixmetalloproteinase-1 (MMP1). This finding was confirmed in independent in vivo and in vitro studies by different laboratories.[9,10] In addition, IRA exposure was recently shown to lead to a downregulation of collagen de novo synthesis.[11] The IRA-induced upregulation of MMP1 was found to be different from that induced by UV at the mechanistic level, since it involves the formation of mitochondrial reactive oxygen species (ROS) and the subsequent initiation of a retrograde signaling response (i.e., from the mitochondria to the nucleus) in human skin.[12,13] The omnipresence of IRA, its biophysical properties, and the fact that it acts differently from UV points to the necessity of including specific IRA-directed strategies in modern sunscreens.