Lipid of the Month

Each month we highlight a lipid of scientific interest. The LIPID MAPS® Lipid of the Month Archive lists lipids highlighted from 2015 - present.

October 2021

Lipid of the month N-Retinylidene-N-retinylethanolamine

October’s Lipid of the Month is N-Retinylidene-N-retinylethanolamine or A2E. It forms rarely, but accumulates in the eye and is associated with age-related eye diseases such as macular degeneration. It’s chemical identity was determined in 19961 .

Light falling on receptors in the retina isomerises a double bond in retinal, converting it from cis to trans. This triggers the process of signalling to the brain that you have seen something. There follows a series of reactions to recycle the retinal back to the cis conformation to detect another photon.

Sometimes, the retinal escapes this cycle and reacts with the ethanolamine headgroup of PE lipids. More rarely, but associated with exposure to bright light, this species can react with a second retinal to form A2E. While A2E formation is rare, there is no enzymatic mechanism to degrade it. Over time, this orange-coloured and fluorescent molecule accumulates in retinal pigment epithelial cells. 

Clearly, coloured molecules in the eye are going to affect vision, but A2E can also disrupt membrane integrity as it behaves like a detergent. In addition, any (or all) of the double bonds in the retinal can be modified by reactive oxygen species to form epoxides which have been shown to cause DNA damage2.


Lipid of the Month Archive