P1536: erythrocytes’ oxidative stress and antioxidant response in patients with hereditary spherocytosis and β-thalassemia minor – a small number case study

Background: Hereditary spherocytosis (HS) and β-thalassemia (β-tal) are both associated with oxidative stress, despite their different etiologies. The pathologic red blood cells (RBC) are metabolically stressed to maintain cell integrity, accumulating oxidative stress-induced damage within the cells. To counteract the oxidative modifications, the RBC are equipped with an efficient antioxidant system, which includes several enzymes, such as catalase (CAT) and some non-enzymatic antioxidants, namely ascorbic acid (AA). In a previous work (DOI: 10.1016/j.freeradbiomed.2020.10.084) we hypothesized that AA could be an important player in the RBC antioxidant defense in patients with non-immune hemolytic anemias (NIHAs) and that its mobilization from plasma to the RBC’s cytosol could be an adaptive mechanism to face erythrocyte’s oxidative stress, in these patients. Aims: Our aim was to test that hypothesis, by studying the redox status and antioxidant system of RBC from non-splenectomized patients with HS and β-tal minor separately. Methods: In 13 healthy individuals (control group), 14 non-splenectomized patients with HS and 11 patients with β-tal minor, we evaluated the total antioxidant status (TAS), AA levels and CAT activity in both plasma and RBC’s cytosol by spectroscopy methods. Results: When compared with the control group, both HS and β-tal patients presented statistically significant increased AA levels and lower TAS values in RBC. CAT activity showed similar values in RBC from HS, β-tal and control group. No differences were found for TAS and AA levels in plasma among all groups. We observed significant negative correlations between RBC AA with plasma AA in both HS (r= -0.741, p=0.002) and β-tal (r= -0.742, p= 0.009), not observed in the control group. Additionally, RBC TAS was positively correlated with RBC AA in HS (r=0.534, p=0.049) and RBC TAS was positively correlated with RBC CAT activity in β-tal (r= 0.743, p=0.009). Summary/Conclusion: The finding of a significant increase in RBC AA levels and the significant lower RBC TAS values alongside with a significant negative correlation between RBC AA and plasma AA levels in both HS and β-tal, support the hypothesis that AA may play an important role in the erythrocyte’s adaptive response to oxidative stress and, thereby, in its antioxidant defense system. We speculate that the mobilization of AA from plasma to the RBC is an adaptive mechanism to oxidative stress that occurs in both HS and β-tal. Moreover, the RBC TAS appears to result from different antioxidant responses, as shown by the significant positive correlations found between RBC TAS and RBC AA levels or RBC TAS and RBC Cat activity for HS and β-tal, respectively. These findings might be related to the distinct etiology of the studied anemias. Further studies are needed to better explore about the role of other players in the antioxidant response, not only in HS and β-tal, but also in other oxidative stress associated congenital anemias. Acknowledgments: Financial support from FCT/MCTES through national funds to Applied Molecular Biosciences Unit (UCIBIO), UIDP/04378/2020 and UIDB/04378/2020 and the project LA/P/0140/2020 of Associate Laboratory Institute for Health and Bioeconomy (i4HB). and Daniela Melo’s PhD Grant (SFRH/BD/139622/2018).