Is blue light, cryptochrome in the eye, and magnetite in the brain involved in the development of frontotemporal dementia and other diseases?
Introduction
Frontotemporal dementia is a common cause of dementia in people under 60 years and it is associated with retinal thinnening and neurodegeneration [1]. It reflects damage to the prefrontal regions of the frontal lobe. In addition the biological rhythms are disturbed resulting in sleep disturbances. Could a depletion in the cryptochrome system be involved in the development of this disease? Photopigments governing circadian photoreception have been localized to the inner retina [2] and cryptochrome transducer signals are important for growth, development, magnetosensitivity and circadian clocks. Human cryptochrome 2, which is highly represented in retina, has the molecular capability to function as a light sensitive magnetoreceptor [3]. The visible spectrum is in the range of 380–750 nm and blue light has its absorption spectra in the range of 420–490 nm.
Light can influence hormone release and other important biological functions. It strongly is influencing circadian rhythms, affecting genes that control an organisms internal clock. The circadian rhythms are controlled by a single brain area, the suprachiasmatic nucleus. It is located in the hypothalamus situated directly above the optic chiasm and receives input from specialized photosensitive ganglion cells in the retina.
Section snippets
The cryptochrome and the magnetite connection
Our retina consists of more than 60 different neurons, each playing a specific role in processing visual images [4]. The light-response mechanism is proposed to result from photoreduction of a protein bound flavin chromophore. Cryptochromes are mediating a response of blue light falling on the retina, triggering a cascade of reactions like the formation of free radicals. They are also involved in circadian clock rhythms. One of these intermediates has magnetic properties. Cryptochrome contains
Magnetite as a memory molecule
Iron is the most abundant transition metal in the brain. The human brain contains 5 million nanocrystals of magnetite (Fe3O4) per gram tissue, mostly in the range of 10–70 nm [9]. Nanocrystalline magnetite, a specific iron oxide of biogen origin, has been found in all organisms investigated and is present in various organs, including the brain. These crystals are different from anything else in the human body. It has the right properties for being a memory molecule like the highest electrical
Diseases linked to circadian rhythms and memory dysfunction
It has been suggested a connection between circadian rhythms and memory dysfunction in schizophrenia patients. In addition elderly patients often also suffer from Alzheimer’s disease or other forms from dementia. Possibly there are links between circadian rhythms, cryptochrome and magnetite and this could be disturbed in schizophrenia patients [10].
Type 2 diabetes arises as consequence of interactions between genetic predisposition and environmental triggers like disturbances of circadian
Conclusion
When blue light hits retina, a cascade of chemical reactions occur that results in a magnetic intermediate. This could possibly be in connected to the brain via the optic nerve to the suprachiasmatic nucleus which is controlling the circadian rhythms. Disturbances in this system can possibly be involved in mental diseases like frontotemporal dementia and Alzheimer’s disease. In addition the blue light can influence on the development of diseases like schizophrenia and type 2 diabetes. Common
Conflicts of interest
There are no conflicts of interest.
Acknowledgement
I wish to thank epidemiologist Leiv S. Bakketeig, Norwegian Institute of Public Health, Oslo for valuable comments on the manuscript.
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A thermal-stable Mn<sup>4+</sup>-doped far-red-emitting phosphor-converted LED for indoor plant cultivation
2022, Materials Today ChemistryCitation Excerpt :Plants use different families of light receptors to sense the wavelength, direction, and intensity of light. For example, cryptochrome senses blue light, but chlorophyll a, the main pigment for photosynthesis senses red light; however, phytochromes are primarily sensitive to red and far-red light [9–13]. Among the photochemical reaction of plant photomorphogenesis, the reversible reaction induced by red light is the most well studied.