Elsevier

Medical Hypotheses

Volume 84, Issue 4, April 2015, Pages 379-380
Medical Hypotheses

Is blue light, cryptochrome in the eye, and magnetite in the brain involved in the development of frontotemporal dementia and other diseases?

https://doi.org/10.1016/j.mehy.2015.01.031Get rights and content

Abstract

When cryptochrome in the retina is exposed to blue light, it undergo series of complicated chemical reactions. One of these intermediates has magnetic properties. It could be a link between the magnetic stage of cryptochrome in the retina and magnetite in the brain. A disturbance in this system could be involved in the development of frontotemporal dementia and other mental disturbances like Alzheimer’s disease. There could also be a link between circadian rhythms and memory dysfunction connected to schizophrenia, type 2 diabetes, and blue light.

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.

References (18)

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