Wunsch a_skin eye and brain

HUMAN LIGHT RESPONSE VIA SKIN, EYE AND BRAIN
International Light Association, Belgium hypothalamic pituitary axis (HPA) (8). While ABSTRACT
the production of the pituitary hormones is Ultraviolet light from sunlight unfolds a increased, the production of melatonin in the pineal gland is suppressed and vice versa. The pituitary gland functions are mainly which are controlled and reacted upon by associated with day and summer tasks, the pineal gland rules over night and winter. antagonistic organs in the brain, namely the pituitary and pineal gland, under the control stress reactions in the skin tissue under the action spectrum for dermal light stress is well systems have been attuned by the course of known since the groundbreaking research of evolution under the frequent influence of Niels Ryberg Finsen, the father of modern phototherapy and winner of the Nobel prize react upon bright light with the spectral for medicine in 1903 (3). It is associated with composition of sunlight. Understanding this the photochemical potential of ultraviolet heliotropic logic behind the coordination photoendocrine regulation in the brain is destructive photo-oxidations which concern essential for creating a reliable concept of biomolecules with chromophoric groups, while only one reaction is a photosynthesis, Keywords: Photoendocrinology, pituitary and pineal gland antagonism, photochemical light 1. INTRODUCTION
action spectrum of the optical radiation which seems to be most effective in inducing Bright light is, amongst other environmental the endocrine reaction in the HPA which is stimuli, a major releasing factor for stress located in the short wave segment of the reactions (5, 6, 12). Darkness for humans is visible spectrum with a sensitivity peak of a stimulus for regeneration reactions and around 460 nm. But not only the wavelength or color temperature of the visible radiation, but also the light intensity seems to be show clear variations depending on light, important for photoendocrine efficiency. acting as an antagonistic system controlled by pituitary and pineal gland. Without light entering the eye an involution of the pituitary different wavelengths in the visible range of gland can be observed after a while (7). the spectrum show different reactions in humans, under the evolutionary viewpoint lighting conditions leads to systemic stress reactions (12) with increased production of photodermatic reaction showing a spectral opponency in a number of simple organisms (AdrenoCorticoTrophic Hormone) and other always follow the same logic. Regarding the reactions after photic stimulation, blue and violet light is associated with bright light and red light is associated with darkness (3). 2. SUNLIGHT REACTIONS
stream and induces water retention in the kidneys. For the control of the inflammatory skin reactions, the cortisol is liberated environmental factors, seasons and local climate conditions. The spectral components essential that the liberation of the stress in the UV range underlie the most significant hormones is not only provided by the HPA, but there are also accessory stress hormone releasing systems located in the hair follicles photochemical potential and activity in the in the skin as well, which have been recently body. This particular range of radiation can only enter the skin but not the eye. The ocular lens provides filtering properties which make sure that the delicate retinal structures stimulation of pituitary secretion activity are protected from this aggressive part of the circumstance that there is a hormonal drain or loss caused by the UV radiation which substances are photosensitive (2) because reason for this informational demand lies in the significance of the UV reactions in the absorption of photon energy in the UV range. skin: 20 minutes under sunlight can lead to a The photon energy destroys or deactivates production of 25 000 international units of Vitamin D, but also, depending on individual controlled by feedback loops, the destruction of certain amounts of these hormones in the substances are liberated in the capillary skin leads to an increased production in the layers of the skin which lead to a dermal have been essential for survival under the different climatic and lighting conditions on vascularised and outer layers of the skin. earth. Under the pressure of evolution it has Under extreme conditions, the skin can take finally turned out that survival has been somehow foresee the content of UV in the individual has about 5 liters of blood, this equates to an amount of more than 3 liters. This seems to be a very high amount, but hormonal balance. In natural sunlight a high can be better understood if one knows, that the skin is one of the largest organs “in” the high levels of brightness and, what’s even body with a mass of about 12 kg (without more significant, a high content of blue subcutaneous fat layers). Massive dermal radiation. While UV is invisible, blue can be pooling can lead to a lethal condition of detected by the eye and thus can be used as circulatory shock reaction if not sufficiently counteracted, even the loss of 1 liter of blood can be rather harmful. This dermal pooling This system seems to be ingenious, but it effect has been used therapeutically since only works under natural sunlight conditions. As soon as there is artificial fluorescent light involved, the system begins to malfunction: of counteracting excessive dermal pooling the bright artificial light with high color stress reactions against high environmental pressure and increase the heart activity. In addition, a hormone of the posterior lobe of induces a hormonal imbalance which can be detrimental for health, especially under long Hormone) is directly released into the blood 3. ARTIFICIAL LIGHT AND HEALTH
lipoprotein and cholesterol metabolism. Another 30% develop deadly forms of dependent/sensitive and also the result of a circadian effectiveness and melatonin can be noticed. It mostly appears as if this circadian or chronobiological effectiveness is steroids and hormones of the thyroid gland used as a quality label for healthy lighting. are the major influences in this field and they The equation circadian effective = healthy are all hormones under pituitary control (4). has to be thoroughly examined. This kind of artificial light can be used for therapeutical certainly the result of multiple factors, so it purposes in treating SAD and other circadian will be difficult to prove the role of artificial disorders. It can also be used in helping shift lighting for this outcome, but the findings in workers to cope with their unhealthy working conditions. But these examples give no proof promoting effect of circadian effective light that this light is healthy, it only shows a certain therapeutic potential. For the largest part of a population it might be healthier to 4. CIRCADIAN LIGHTING AND VISION
use chronobiologically and endocrinologically neutral light sources in order not to interfere with their individual endocrine regulation processing of light signals. The optical part is responsible for vision processes while the energetic pathway controls the HPA via the simplified reflections on the functions of the purposes it is better if the surrounding light circadian system it might be practical to look does not contain high amounts of blue and only at the suppression of the hormone of violet wavelengths. The higher refraction for darkness (melatonin) in terms of a marker short wavelengths which occurs in optical substance for endocrine reagibility, but this media appears also in the eye. This causes a chromatic aberration effect with negative consequences for sharp vision. The different endocrinology. From the medical viewpoint, wavelengths focus on different planes in and it seems to be more important to look at the around the focus plane of the retina. Due to increased secretion of pituitary hormones. photooxidative effects (9, 11), the blue and The Proopiomelanocortin (POMC) is a very interesting candidate for further investigation, reactions in the optical media of the eye and because it is a multi – purpose peptide which in the fovea centralis. We find a number of shows the link between light influence and mechanisms in the eye which provide better systemic stress, even on the molecular and vision on one hand and less photooxidative genetic level. It is the precursor molecule for stress and damage on the other, in order to reduce the negative effects of blue light on catecholamines and cortisol), α-MSH and β- vision. First the number of blue receptors is up to 20 times less compared to the number of red cones in the fovea centralis (10). Endorphin. In the central nervous system β- Secondly there is a concentration of lutein, a Endorphin reduces pain, in the periphery it yellow pigment which filters out excrecent acts as an immune modulator. Α-MSH is the portions of blue and shows also antioxidative stimulates pigmentation (sic!), but it also protection substance is reduced in the eyes increases the heart rate, the concentration of of elderly people. Ophthalmologists have lipoproteins in the blood and stimulates the discovered that there is some evidence that activity of the thyroid gland. All these functionally compensated by the increased development of civilization’s diseases. In blur in the lens, which is also promoted by industrialized societies about 50% of the blue and ultraviolet light. As a consequence population die from cardio-vascular diseases they replace the lens in cataract surgery by a portions in order to protect the macula from further degeneration. This shows that even chemischen Strahlen des Lichts für Medicin depending on age and the amount of light which has to be processed during a person’s 4 HARBUZ MS et al. Hypothalamo-pituitary- lifetime. The question is, is it only the adrenal axis and chronic immune activation. Ann. N. Y. Acad. Sci. 992, 99-106, 2003.
increasing incidence of age related macular degeneration, which is found in 30% of the Light Perception on Metabolism in Man and industrialized nations? These people stay 90% of their time inside buildings while under the influence of artificial light, which has to be taken into account as well. We indeed find that there is a large number of Wschr. 14, 1713, 1935b.
potent light, such as mercury vapor lamps Lichtmangel. Klin. Wschr. 24/25, 18-21,
8 MILLER DB et al. Neuroendocrine aspects
of the response to stress. Metabolism 51, 5-
5. CONCLUSION
Epidemiologic data show that the incidence 9 OMATA, Y et al. Intra- and extracellular for civilization related health problems like reactive oxygen species generated by blue cardio-vascular diseases, cancer, immune light. J. Biomed. Mater. Res. A, 77A, 3,
deficiency, osteoporosis and age related macular degeneration is rising. All these disorders endocrinologically related to the influence of phototransduction by the human circadian light (12). Artificial light has become the system. Brain Res Rev 50, 213-228, 2005.
societies. The tendency in artificial lighting is environment as one mediator of blue light – the ubiquitous use of mercury vapor light induced mitochondrial suppression. Dent. sources with high color temperature. This Mat. 22, 8, 759-764, 2005.
12 SILBERNAGL, S et al. Taschenatlas der active radiation in the spectrum, which is medical viewpoint the question arises as to whether the use of mercury vapor light has a 145(2), 941-950, 2004.
diseases of civilization. In terms of prevention improvement of vision in healthy individuals, it may be better to use artificial light sources with a low content of blue and low color temperature and go for alternatives to the REFERENCES
Fax: +49-6221-161596 e-mail: [email protected] [email protected] Ultraviolettabsorption der Steroide. Berlin: de Gruyter, 1940.

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