J. Photochem. Photobiol. B: Biol., 18 (1993) 281-285 281 Artificial sunlight irradiation induces ultraweak photon emission in human skin fibroblasts Hugo J. Niggli Cosmital SA (Research Company of Wella AG, Darmstadt (Germany)), Rte de Cht%alles 21, CH-1723 Marly (Switzerland) (Received December 10, 1992; accepted December 30, 1992) zyxwvutsrqponmlkjihgfedcbaZYXWVUTSRQPONMLKJIHGFEDCB Abstract Photons participate in many atomic and molecular interactions and changes in the physical universe. In recent years sophisticated detection procedures for the measurement of ultraweak photons in a variety of different cells have been performed leading to the conclusion that plant, animal and human cells emit ultraweak photons. Using an extremely low-noise, high-sensitive photon-counting system, which allows maximal exploitation of the potential capabilities of a photomultiplier tube, ultraweak photons were quantitated in human skin fibroblasts. It was found that light from an artificial sunlight source induces ultraweak photon emission in these cells. However, the results demonstrate that this induction is significantly lower in normal fibroblasts compared with those obtained from a donor suffering from xeroderma pigmentosum disease group A, a disease characterized by deficient repair of DNA. The largest increase in ultraweak photon emission after UV exposure was measured in mitomycin-C-induced post-mitotic xeroderma pigmentosum cells which showed 10-20 times higher ultraweak photon intensities than mitotic UV-irradiated normal cells. These data suggest that xeroderma pigmentosum cells tend to lose the capacity of efficient storage of ultraweak photons, indicating the existence of an efficient intracellular photon trapping system within human cells Keywords: Ultraweak, Photon, Fibroblast, Skin, Human, Ultraviolet, UVB 1. Introduction At the beginning of this century, Carl Huter ingeniously suggested that radiation processes are involved in cell metabolism and cell communication [l]. It was Alexander G. Gurwitsch in the early 1920s who started biological experiments in order to show that ultraweak photons transmit infor- mation in living systems as I have summarized [2]. Some workers have demonstrated the existence of this very weak radiation emanating from biological tissues, whereas others have been unable to find such an effect, although working with measuring equipment of a similar sensitivity [2]. Recently, several workers have agreed that plant, animal and human cells emit ultraweak photons, also called ultraweak luminescence (UL) [2-71. According to one model, this radiation results from radical reactions such as lipid peroxidation [5]. In studies of microsomal lipid peroxidation, it has been shown that the amount of malonal- dehyde production and the intensity of emitted light are related [8]. However, a highly interesting alternative model published in 1983 by Nag1 and Popp [9] suggests that there is a negative feedback loop in living cells which couples states of a coherent ultraweak photon field with the confor- mational state of cellular DNA. These workers postulate photon transfer or radiationless chemical pumping from the cytoplasmic metabolism which results in changes in the DNA conformation via exciplex and/or excimer formation. Their hypoth- esis is based on experimental data reviewed by Birks [lo] who also suggested that these excimers are precursors of the pyrimidine photodimers which play a key role in the radiation damage of DNA. Since the conformation of the DNA molecule is believed to be of importance for the regulation of nuclear information transfer, such processes in turn influence the metabolic activity of a cell, thus closing the feedback loop. Several studies [3,11] indicate that this ultraweak radiation in mammalian cells is very low. Never- theless, Musumeci and coworkers [12] discrimi- nated very recently between normal and tumour human tissues on the basis of ultraweak photon loll-1344/93/$6.00 0 1993 - Elsevier Se-quoia. All rights reserved