Impaired Mitophagy of Erythrocytes Leads to Anemia in Patients with Myelodysplastic Syndromes

Objective: To investigate the change of mitophagy level of bone marrow nucleated red blood cell in anemia patients with myelodysplastic syndromes (MDS), to explore its significance in the anemic pathogenesis of MDS.

Methods: Fifty anemia patients with MDS and twenty-six normal controls were enrolled in this study. The mitophagy were observed by transmission electron microscopy (TEM). The level of autophagy-associated protein LC3B, the number of mitochondria, mitochondrial membrane potential, the level of ROS in GlycoA + nucleated red blood cell were measured by Flow cytometry .The expression of AMPK, ULK1, mTOR mRNA of GlycoA + nucleated red blood cell were measured by real time PCR. The expression of the mitochondrial outer membrane protein TOM20 in GlycoA + nucleated red blood cell were detected by Western blotting.

Results: (1) Autophagosome or autolysosome including mitochondria were scarcely observed by TEM. (2) The expression of LC3B in GlycoA + nucleated red blood cell in high-risk MDS patients(0.22±0.12) was significantly lower than that in normal controls (0.43±0.22, P<0.01), and lower than that in low-risk MDS patients (0.40±0.16, P<0.01), there were no significant difference in expression of LC3B between normal controls and low-risk MDS patients (P>0.05); (3) The number of mitochondria in GlycoA + nucleated red blood cell in high-risk MDS patients (937.17±707.85) was significantly higher than that in normal controls (513.49±372.33, P<0.05), and higher than that in low-risk MDS patients (461.74±438.02, P<0.01), there were no significant difference in number of mitochondria between normal controls and low-risk MDS patients (P>0.05); (4) The level of mitochondrial membrane potential in GlycoA + nucleated red blood cell in high-risk MDS patients(4.24±3.00)was significantly higher than that in normal controls (2.04±1.11, P<0.01), and higher than that in low-risk MDS patients (2.11±1.10, P<0.01), there were no significant difference in the level of mitochondrial membrane potential between normal controls and low-risk MDS patients(P>0.05); (5) The level of ROS in GlycoA + nucleated red blood cell in high-risk MDS patients(438.65±322.83)was significantly higher than that in normal controls (242.77±136.87, P<0.01), and higher than that in low-risk MDS patients(197.40+95.07, P<0.01), there were no significant difference in the level of ROS between normal controls and low-risk MDS patients(P>0.05); (6) The expression of AMPK mRNA in GlycoA + nucleated red blood cell in high-risk MDS patients(1.06±1.51) was significantly lower than that in low-risk MDS patients (4.35±4.79, P>0.05), there were no significant difference with normal controls(P>0.05). (7) The exception of ULK1 mRNA in GlycoA + nucleated red blood cell in high-risk MDS patients (0.64±0.91) was significantly lower than that in normal controls (2.70±3.27, P<0.01), and lower than that in low-risk MDS patients(4.82±4.81, P<0.01);(8)The level of mTOR mRNA in GlycoA + nucleated red blood cell in high-risk MDS patients (2.81±2.80) was significantly higher than that in normal controls (1.28±0.81, P<0.05),and higher than that in low-risk MDS patients (0.85±0.74, P<0.05), there were no significant difference in expression of AMPK,ULK1and mTOR mRNA between low-risk MDS patients and normal controls (P>0.05). (9) The expression of mitochondrial outer membrane protein TOM20 in high-risk MDS patients was higher than that in normal controls.

Conclusion: The pathogenesis of anemia in MDS may be correlated with declining mitophagy level, increasing damaged mitochondria, increasing ROS, DNA damage, and shortening the life of nucleated red blood cells, it may be an effective method to induce mitophagy to correct anemia in MDS.