TUBULIN AS A REGULATOR OF PHOSPHATIDYLSERINE EXPOSURE IN RED BLOOD CELLS AND ITS IMPACT ON HAEMORRHEOLOGY

MELISA BALACH; ETCHEVERRY, MICAELA; MONESTEROLO NE; SANTANDER V; RIVELLI JF; URETA MIRALLA, LUCIA BELEN; CASALE C; ALEXIS CAMPETELLI

Mendoza

Congreso; SAIB 2022; 2023

SAIB

Previously, our group showed that in erythrocytes from diabetic and hypertensive patients, plasma membrane tubulin is increased when compared with erythrocytes from normal subjects. At the plasma membrane, tubulin inhibits several P-ATPases, including lipid flippases which results in increased phosphatidylserine (PS) exposure. Since in normal erythrocytes, the progressive PSexposure becomes a senescence signal that leads to macrophage-mediated phagocytosis during eryptosis, we set out to determine whether the increase in membrane tubulin influences erythrocytes lifespan and whether this effect contributes to the development of anemia. For this, we performed an experiment with rats where the content of erythrocytes membrane tubulin was naturally altered ((Wistar Kyoto strain (WK, normotensive), diabeticized WK (streptozotocin treatment) and SHR (spontaneously hypertensive rats)), or modified pharmacologically by Taxol or Tyrosine treatment. During a period of 7 weeks, we monitored the erythrocyte half-life time, erythrocyte PS exposure and the reticulocyte count in peripheral blood, among other parameters. We found that in erythrocytes from SHR, diabetic, as well as in Taxol-treated WK animals, the PS exposure was higher than in WK and Tyrosine-treated SHR rats. Accordingly, the erythrocyte half-life was shorter in SHR, diabetics and Taxol-treated WK than erythrocytes from WK rats, showing an inverse correlation between PS exposure and erythrocyte half-life time. Furthermore, thoseanimal groups with increased PS exposure and shortened erythrocyte half-life time displayed increased reticulocyte count. Theblood c ount displayed a slight decrease in RBC count, hematocrit and haemoglobin values, for Taxol-treated WK, suggesting a mild anemia only in this animal group. The case of Tyrosine-treated SHR rats deserve a separate analysis. For this animal groupwe found a massive PS exposure peak at week 11 post birth, and this peak was time correlated with an increased death rate and anincre ase in reticulocyte count, suggesting that Tyrosine accelerates the clearance of a population of red blood cells. Our hypothesis is that this population could be related to erythrocyte age and experiments are underway to probe it. As a consequence of the accelerated red blood cells clearance, the spleen can increase its size. We looked at the spleen/body weight ratio and found a marked increase in the size of the spleen in Taxol-treated animals and a slight increase in SHR rats; while in Tyrosine-treated SHR rats, the spleen size was much similar to that of WK rats, which confirm the spleen involvement in the erythrocyte clearance. These results suggest that, in red blood cells, plasma membrane tubulin can regulate the lifespan of these cells through a mechanism that involves the regulation of lipid flippases.