Retinal amino acid neurochemistry in health and disease

Abstract

Advances in basic retinal anatomy, genetics, biochemical pathways and neurochemistry have not only provided a better understanding of retinal function but have also allowed us to link basic science to retinal disease. The link with disease allowed measures to be developed that now provide an opportunity to intervene and slow down or even restore sight in previously ‘untreatable’ retinal diseases. One of the critical advances has been the understanding of the retinal amino acid neurotransmitters, related amino acids, their metabolites and functional receptors. This review provides an overview of amino acid localisation in the retina and examples of how retinal anatomy and amino acid neurochemistry directly links to understanding retinal disease. Also, the implications of retinal remodelling involving amino acid (glutamate) receptors are outlined in this review and insights are presented on how understanding of detrimental and beneficial retinal remodelling will provide better outcomes for patients using strategies for the preservation or restoration of vision. An internet‐based database of retinal images of amino acid labelling patterns and other amino acid‐related images in health and disease is located at http://www.aminoacidimmunoreactivity.com.

Studies on chemical composition of yellowfin tuna (Thunnus albacares, Bonnaterre, 1788) eye

“…The collagen content in YFTE would vary with the age of species. However it is well established that glycine is a major amino acid in collagen protein ) According to Kalloniatis et al (2013) glutamate is a major excitatory neurotransmitter in the retina and found to be most abundant amino acid in the eye of vertebrates. Other major amino acids are aspartic acid, alanine and leucine.…”

Vinpocetine modulates metabolic activity and function during retinal ischemia

“…Vinpocetine also modulated Müller cell amino acid homeostasis. Altered amino acid metabolism is a hallmark of retinal ischemia and other retinal pathologies (19,20,26,33,42,43,60). In this study, Müller cell glutamate-to-glutamine ratios were elevated following ischemia-reperfusion.…”

“…This pathway is closely linked to energy metabolism (reviewed in Ref. 33), and, thus, vinpocetine's actions on glucose availability could alter glutamate metabolism in Müller cells. Additionally, changes in Müller cell glutamate may affect neurons, as retinal neurotransmitters are sourced from Müller cells.…”

Expression of ionotropic glutamate receptors, AMPA, kainite and NMDA, in the pigeon retina

“…Glutamate is a major excitatory amino acid neurotransmitter in the central nervous system of vertebrates and appears to be involved in neuronal transmission in the retina (Massey and Redburn, 1987;Brandst€ atter and Hack, 2001;Yang, 2004;Kalloniatis et al, 2013). In the mammalian retina, glutamate acts in the vertical pathway of visual information, i.e., photoreceptorsebipolar cellseganglion cells.…”