Hypoxia-mediated impaired erythrocyte Lands’ Cycle is pathogenic for sickle cell disease

Abstract

Although Lands’ cycle was discovered in 1958, its function and cellular regulation in membrane homeostasis under physiological and pathological conditions remain largely unknown. Nonbiased high throughput metabolomic profiling revealed that Lands’ cycle was impaired leading to significantly elevated erythrocyte membrane lysophosphatidylcholine (LysoPC) content and circulating and erythrocyte arachidonic acid (AA) in mice with sickle cell disease (SCD), a prevalent hemolytic genetic disorder. Correcting imbalanced Lands’ cycle by knockdown of phospholipase 2 (cPLA2) or overexpression of lysophosphatidycholine acyltransferase 1 (LPCAT1), two key enzymes of Lands’ cycle in hematopoietic stem cells, reduced elevated erythrocyte membrane LysoPC content and circulating AA levels and attenuated sickling, inflammation and tissue damage in SCD chimeras. Human translational studies validated SCD mouse findings and further demonstrated that imbalanced Lands’ cycle induced LysoPC production directly promotes sickling in cultured mouse and human SCD erythrocytes. Mechanistically, we revealed that hypoxia-mediated ERK activation underlies imbalanced Lands’ cycle by preferentially inducing the activity of PLA2 but not LPCAT in human and mouse SCD erythrocytes. Overall, our studies have identified a pathological role of imbalanced Lands’ cycle in SCD erythrocytes, novel molecular basis regulating Lands’ cycle and therapeutic opportunities for the disease.

Metabolic effect of alkaline additives and guanosine/gluconate in storage solutions for red blood cells

“…54 Based on the consideration that, in order to transport and deliver oxygen, transfused RBCs must remain intact and circulate in the bloodstream of the recipient, correlative studies have been published in mice and humans suggesting a role for lipid and purine oxidation (e.g., 5-hydroxyeisosatetraenoic acid and other hydroxyeisosatetraenoic acids, ATP, and hypoxanthine) in mediating RBC hemolysis and posttransfusion recovery. 24,35,55,56 These observations are relevant in that In the present study, we generated metabolomics data on five storage additives, including SAGM, the canonical European storage solution, and more recently introduced PAGGSM, as well as three alkaline additives (SOLX, E-SOL 5, and PAG3M). Of note, results on SAGM and PAGGSM we report here are consistent with findings reported by Rolfsson and colleagues, 39 who also explored the metabolic impact of other nonalkaline additives such as AS-1 and AS-3, but did not focus on the impact of intracellular alkalinization on stored erythrocyte metabolism.…”

Metabolomic and molecular insights into sickle cell disease and innovative therapies

“…23 Several metabolites identified in the screen include nucleosides (eg, adenosine), lipids (eg, sphingosine-1-phosphate [S1P], lysophospholipids, and free acyl fatty acids), and glycolytic intermediates (eg, 2,3bisphosphoglycerate [2,3-BPG]), which are significantly elevated in SCD blood. [23][24][25] In contrast, glutathione levels are significantly reduced. 26 Thus, metabolomics profiling reveals overall specific metabolic changes in SCD mice.…”

“…Metabolomics revealed that erythrocyte membrane lysophosphatidylcholine and circulating erythrocyte-derived arachidonic acid levels are elevated in SCD erythrocytes, which suggests that the Lands' cycle is impaired. 24 In vivo mouse studies showed that elevated PLA2 contributes to sickling, inflammation, and multiple tissue damage in SCD mice. 24 Cultured human sickle erythrocytes were treated with PLA2 small interfering RNAs, which reduced PLA2 activity and decreased sickling.…”

Circadian period 2: a missing beneficial factor in sickle cell disease by lowering pulmonary inflammation, iron overload, and mortality

“…Sickle-cell mice and control mice were generated by BMT as previously described (16)(17)(18). Prior to irradiation, recipient mice were treated with 0.2% neomycin for at least 48 h and were continuously treated for 2 wk postirradiation.…”

“…As previously described (17,18), BMT was performed to generate SCD → Per2 Luc mice and control mice. Sickle transplant mice expressing chimerism above 85% were used for experiments.…”