Modulation of glyceraldehyde 3 phosphate dehydrogenase activity and tyr-phosphorylation of Band 3 in human erythrocytes treated with ferriprotoporphyrin IX

Tyrosine phosphorylation of band 3 impairs the storage quality of suspended red blood cells in the Tibetan high-altitude polycythemia population

Due to environmental hypoxia on the Tibetan Plateau, local residents often exhibit a compensative increase in hemoglobin concentration to maintain the body's oxygen supply. However, increases in hemoglobin and hematocrit (Hct) pose a serious challenge to the quality of stored suspended red blood cells (SRBCs) prepared from the blood of high-hemoglobin populations, especially populations at high altitude with polycythemia in Tibet. To explore the difference in storage quality of SRBCs prepared from plateau residents with a high hemoglobin concentration, blood donors were recruited from Tibet (> 3600 m) and Chengdu (≈ 500 m) and divided into a high-altitude control (HAC) group, high-altitude polycythemia (HAPC) group and lowland control (LLC) group according to their hemoglobin concentration and altitude of residence. The extracellular acidification rate (ECAR), pyruvate kinase (PK) activity and band 3 tyrosine phosphorylation were analyzed on the day of blood collection. Then, whole-blood samples were processed into SRBCs, and storage quality parameters were analyzed aseptically on days 1, 14, 21 and 35 of storage. Overall, we found that tyrosine 21 phosphorylation activated glycolysis by releasing glycolytic enzymes from the cytosolic domain of band 3, thus increasing glucose consumption and lactate accumulation during storage, in the HAPC group. In addition, band 3 tyrosine phosphorylation impaired erythrocyte deformability, accompanied by the highest hemolysis rate in the HAPC group, during storage. We believe that these results will stimulate new ideas to further optimize current additive solutions for the high-hemoglobin population in Tibet and reveal new therapeutic targets for the treatment of HAPC populations.

The effects of low-intensity He-Ne laser irradiation on erythrocyte metabolism

Low-intensity laser irradiation (LILI) can improve the deformability of red blood cells (RBCs). It might be due to the LILI effects on adenosine triphosphate (ATP) level. However, ATP content may not be a valid surrogate marker for RBC deformability. The LILI effects on RBC glycolysis were studied in this paper. Hypertonic RBCs were used in this study. After 5 min irradiation with low-intensity He-Ne laser irradiation (LHNL) at 632.8 nm and 4.4 mW/cm(2), the concentration of intracellular glucose and the activities of phosphofructokinase (PFK) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were measured, respectively. There was no significant change in intracellular glucose concentration. The activity of PFK decreased significantly, but the activity of GAPDH increased significantly. In hypertonic RBCs, LHNL irradiation may decrease the activity of energy-consuming enzymes, but increases the activity of energy-generating enzymes in glycolysis, to improve the RBC deformability.

Dysregulation of L-arginine metabolism and bioavailability associated to free plasma heme

Severe Plasmodium falciparum malaria is associated with hypoargininemia, which contributes to impaired systemic and pulmonary nitric oxide (NO) production and endothelial dysfunction. Since intravascular hemolysis is an intrinsic feature of severe malaria, we investigated whether and by which mechanisms free heme [Fe(III)-protoporphyrin IX (FP)] might contribute to the dysregulation of l-arginine (l-Arg) metabolism and bioavailability. Carrier systems “y+” [or cationic amino acid transporter (CAT)] and “y+L” transport l-Arg into red blood cells (RBC), where it is hydrolyzed to ornithine and urea by arginase (isoform I) or converted to NO^· and citrulline by endothelial nitric oxide synthase (eNOS). Our results show a significant and dose-dependent impairment of l-Arg transport into RBC pretreated with FP, with a strong inhibition of the system carrier y+L. Despite the impaired l-Arg influx, higher amounts of l-Arg-derived urea are produced by RBC preexposed to FP caused by activation of RBC arginase I. This activation appeared not to be mediated by oxidative modifications of the enzyme. We conclude that l-Arg transport across RBC membrane is impaired and arginase-mediated l-Arg consumption enhanced by free heme. This could contribute to reduced NO production in severe malaria.

A novel D-glyceraldehyde-3-phosphate binding protein, a truncated albumin, with D-glyceraldehyde-3-phosphate dehydrogenase inhibitory property

We have purified a novel protein from mice muscle, which through N-terminal amino acid sequencing was identified as a truncated form of mouse albumin. The protein was found to be a monomer of approximately 64 kDa and located in the cytosol. The purified protein strongly crossreacted with commercial albumin antibody. Presence of this protein was observed in different mouse organs. Further biochemical studies as well as CD spectroscopy indicated that the protein binds D-glyceraldehyde-3-phosphate limiting the availability of the substrate to the enzyme D-glyceraldehyde-3-phosphate dehydrogenase, thereby inhibiting its catalytic activity. The implication of this protein in the control of glycolysis has been discussed.