Phospholipid Peroxidation: Lack of Effect of Fatty Acid Pairing

Abstract

Phospholipids where both fatty acids are polyunsaturated are very rare. Most organisms prefer to couple their polyunsaturated fatty acids (PUFA) with either a saturated (SAT) or a monounsaturated (MUFA) fatty acid. This study examined if these natural couplings are there to protect PUFA from themselves. Specifically, does the coupling of PUFA to SAT or MUFA reduce the potential for increased rates of peroxidation by shrouding these highly peroxidisable fatty acids with less peroxidisable fatty acids? The influence of head group was examined by using the two most common phospholipids found in vertebrate membranes i.e. phosphatidylcholine and phosphatidylethanolamine species. Fatty acid pairings included 16:0/18:2 versus 18:2/18:2 and 16:0/22:6 versus 22:6/22:6. All phospholipids were incorporated into liposomes that were matched for their total PUFA content i.e. 25% PUFA/PUFA or 50% SAT/PUFA with phosphatidylcholine 16:0/16:0 used as the background phospholipid. An iron initiator (Fe²⁺/H₂O₂) was used to induce peroxidation and lipid hydroperoxide production was used to measure peroxidation. The results show that coupling of PUFA together on the same molecule does not increase peroxidation rates and therefore does not support the proposed hypothesis. The lower than expected levels of peroxidation measured for some phospholipid species (e.g. PtdEtn 22:6/22:6) is possibly due to the partitioning of these molecular species into the inner leaflet of the bilayer.

Anticancer effects of anandamide on head and neck squamous cell carcinoma cells via the production of receptor‐independent reactive oxygen species

“…It has previously been suggested that polyunsaturated fatty acids might increase intracellular oxidative stress, including lipid peroxidation . Because AEA is very similar to AA (arachidonic acid) in its chemical structure, we postulated that it might affect cell viability by increasing intracellular ROS.…”

“…It has previously been suggested that polyunsaturated fatty acids might increase intracellular oxidative stress, including lipid peroxidation. 18,19 Because AEA is very similar to AA (arachidonic acid) in its chemical structure, we postulated that it might affect cell viability by increasing intracellular ROS. We observed significantly higher production of ROS ( Figure 5A) and 8-isoprostanes (prostaglandin-like compounds formed from the free radicalcatalyzed peroxidation of fatty acids; Figure 5B) in the case of AEA than 2-AG and AA.…”

Perspectives on the membrane fatty acid unsaturation/pacemaker hypotheses of metabolism and aging

“…Moreover, the relative peroxidizabilities of free fatty acids may not always be relevant to how they act as acyl groups when attached to larger molecules (Cosgrove et al, 1987;Kubo et al, 2005;Norris et al, 2012;Wijesundera et al, 2008;Zerouga et al, 1995). For instance, phospholipids containing two DHA groups were peroxidized at the similar rates or sometimes a lower rate than phospholipids containing a DHA and a palmitic acyl group when put into liposomes composed of phospholipids with saturated fatty acyl groups, contrary to what would be predicted based on the peroxidizability indexes (Norris et al, 2012). Additionally, phosphatidylethanolamine with DHA appears to have protective effects against peroxidative damage when it is positioned in the outer leaflet of liposomes (Kubo et al, 2005).…”

Electrospray mass spectrometry as a tool to characterize phospholipid composition of plant cakes

“…Beside the precise PL composition, the PUFA distribution on the glycerol backbone of PL was worth knowing because the sn ‐2 position is likely to be implied in the increasing resistance of PL towards oxidation. This issue need further investigation due to controversial results in the literature . Moreover, further studies will be undertaken to quantify the amount of PL classes for the different cakes in order to fully characterize the PL fraction.…”