Fatty acid desaturase activity in mature red blood cells and implications for blood storage quality

Abstract

BackgroundIncreases in the red blood cell (RBC) degree of fatty acid desaturation are reported in response to exercise, aging, or diseases associated with systemic oxidant stress. However, no studies have focused on the presence and activity of fatty acid desaturases (FADS) in the mature RBC.Study design and methodsSteady state metabolomics and isotope‐labeled tracing experiments, immunofluorescence approaches, and pharmacological interventions were used to determine the degree of fatty acid unsaturation, FADS activity as a function of storage, oxidant stress, and G6PD deficiency in human and mouse RBCs.ResultsIn 250 blood units from the REDS III RBC Omics recalled donor population, we report a storage‐dependent accumulation of free mono‐, poly‐(PUFAs), and highly unsaturated fatty acids (HUFAs), which occur at a faster rate than saturated fatty acid accumulation. Through a combination of immunofluorescence, pharmacological inhibition, tracing experiments with stable isotope‐labeled fatty acids, and oxidant challenge with hydrogen peroxide, we demonstrate the presence and redox‐sensitive activity of FADS2, FADS1, and FADS5 in the mature RBC. Increases in PUFAs and HUFAs in human and mouse RBCs correlate negatively with storage hemolysis and positively with posttransfusion recovery. Inhibition of these enzymes decreases accumulation of free PUFAs and HUFAs in stored RBCs, concomitant to increases in pyruvate/lactate ratios. Alterations of this ratio in G6PD deficient patients or units supplemented with pyruvate‐rich rejuvenation solutions corresponded to decreased PUFA and HUFA accumulation.ConclusionFatty acid desaturases are present and active in mature RBCs. Their activity is sensitive to oxidant stress, storage duration, and alterations of the pyruvate/lactate ratio.

Red Blood Cell Metabolism in Patients with Propionic Acidemia

“…These results contrast with previous research that has shown an increase in odd-numbered LCFA, but with the exception of GLA, support studies which assert no change in long-chain poly unsaturated fatty acids (LCPUFA) in the PA erythrocytes [14,43,44]. On the other hand, our results are interesting in that they follow opposite trends to those reported recently in the context of storage and the oxidant stress-induced activation of fatty acid desaturases, suggesting that in the absence of additional stressors, RBCs from PA patients are capable of withstanding oxidant stress through the basal activation of other redox pathways (e.g., the PPP) [45]. Since the rate-limiting enzyme of the PPP is glucose 6-phosphate dehydrogenase, which is coded by a gene on chromosome X, it is interesting to speculate whether G6PD dosage might impact the severity of PA in a sex-dependent fashion, with RBCs from females predicted to be better protected from oxidant stress than males carrying the PCC deficiency [22,46].…”

Inductively-Coupled Plasma Mass Spectrometry–Novel Insights From an Old Technology Into Stressed Red Blood Cell Physiology

“…While dysregulation of iron metabolism has been previously associated with increased propensity for lipid stress in stored RBCs or under pathological conditions (e.g., sickle cell disease or thalassemia) (Howie et al, 2019;Buehler et al, 2021), to the best of our knowledge no study has been published correlating intraand extra-cellular levels of iron to the intra-and extracellular RBC metabolome. In our study, iron levels correlated positively with markers of increased oxidant stress in aging RBCs-such as hypoxanthine (Nemkov et al, 2018b) and increased levels of poly-unsaturated fatty acids (consistent with activation of fatty acid desaturases) (Thomas et al, 2021). The former observation is relevant in that RBC-specific AMPD3, the rate-limiting enzyme of AMP deamination upstream to hypoxanthine synthesis-is positively regulated by intracellular calcium levels and oxidant stress (Nemkov et al, 2018b).…”

Blood bank storage of red blood cells increases RBC cytoplasmic membrane order and bending rigidity

“…of oxidant stress and pyruvate/lactate ratios, perhaps as a result of residual fatty acid desaturase activity in the mature RBC or moonlighting function of other enzymes sensitive to NADH/ NAD + ratios [49].…”