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A component of fish oil not only protects cells critical to vision from potentially lethal initial insults, but also from those that occur in the future. The omega-3 fatty acid, DHA, and its derivatives “precondition” photoreceptor and retinal pigment epithelial (RPE) cells to survive.
DHA and docosanoids (molecules made in the brain at the onset of injury or disease) are responsible for activating sustained cellular mechanisms that elicit long-term preconditioning protection. A preconditioning PC stimulus is a sub-lethal or pharmacologic stressor that activates a counter-regulatory protective response to a future lethal stimulus. Preconditioning takes place when the blood supply to an organ is interrupted for a short time and then reestablished.
The protective response from that first injury would carry over to a subsequent blood supply shortage, much like the immunity a vaccine confers against future exposures to disease. This happens in the heart, brain and retina, as well as other organs. To harness the therapeutic potential of preconditioning, it is very important to identify the molecules directly involved.
Fish oil contains two types of polyunsaturated fatty acids (PUFAs) — omega-3 (docosahexaenoic acid or DHA) and omega-6 (arachidonic acid or AA). They have distinctly different actions. Omega-3 PUFAs and their enzymatic metabolic derivatives, docosanoids, display potent anti-inflammatory and pro-resolving properties in contrast to the pro-inflammatory actions of omega-6 PUFA derivatives. The researchers found that although they are released concomitantly, DHA can alter the action of AA. When they supplemented DHA prior to the oxidative stress insult, the synthesis of protective DHA derivatives increased while AA synthesis decreased over time.
DHA and the induction of docosanoid synthesis is necessary for preconditioning protection, and thus daily survival, of photoreceptor and RPE cells. Omega-3 impairments are associated with neuroinflammation, which contributes to photoreceptor cell dysfunction and death, enhancing the synthesis of docosanoids may provide an opportunity for halting or ameliorating debilitating retinal degenerative diseases, such as the dry form of age-related macular degeneration.
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