Strategies to improve hemorheology and clinical outcome of sickle cell anemia patients by red blood cell derived nitric oxide
Final Report Abstract
Red blood cells (RBC) of patients with sickle cell disease including sickle cell anemia (SCA) and hemoglobin C disease (SC) show altered function and are more fragile and prone to hemolysis. The recent project aimed to investigate RBC function and underlying mechanisms a) at baseline, b) after RBC-NOS modulation as well as in response to pro- and antioxidants, c) after shear rate application and finally d) after physical activity. The results of a) confirm recent literature of reduced RBC deformability in SC and SCA compared to healthy controls (AA). ROS levels were higher in SCA patients compared to AA, but also higher phosphatidylserine levels were observed in RBC of SCA. This eryptosis marker was shown to relate to the high ROS levels. RBC-microparticle (MP) levels were also higher in SCA patients which were shown to affect arterial stiffness. One of the surprising key findings suggests that applied medication - involving hydroxycarbamide (HU) - has a major impact on RBC function. In particular, HU treated SCA showed higher RBC deformability compared to non-HU treated patients but still lower RBC deformability compared to healthy controls. Further, HU treated patients showed decreased RBC-NOS activation and reduced S-nitrosylation of α-spectrin, a cytoskeletal protein, compared to non-treated SCA. RBC NO levels were higher with this medication, highly possible because of NO donor properties of this medication. These higher NO levels also increased the marker for oxidative/nitrosative stress. It was speculated that HU treatment possibly affects RBC deformability by increasing the levels of fetal hemoglobin which inhibits the polymerization of sickle hemoglobin. Further studies are needed to elucidate the relation of HU medication in relation to fetal hemoglobin and if and how this relates to the changes observed in the RBC-NOS/NO/S-nitrosylation cascade. Data of b) suggest that indirect and direct RBC-NOS modulation affects RBC deformability which might, in part, be related to altered RBC-NOS dependent NO production. Surprisingly, addition of SNP, a NO donor, positively affects RBC deformability independent of Akt/RBC-NOS activation pathway. NO levels in RBC were higher after SNP treatment - like observed for HU, but in contrast to HU treatment, SNP application decreased total ROS/RNS and eryptosis. Oxidative stress worsened the eryptosis and formation of RBC-MP while anti-oxidants did the opposite. Arterial stiffness correlated with the extent of RBC-MP which in turn affected the expression of adhesion molecules. The data concluded that oxidative stress promotes eryptosis and RBC-MP release which are potentially involved in macrovascular dysfunction in SCA. Results of c) led to the conclusion that moderate shear rate applied in vitro did not affect RBC deformability of SCA but did reduce RBC-NOS activation and surprisingly increased S-nitrosylation of α-spectrin. The results indicated that low levels of shear rate are somewhat safe for the integrity of RBC but further studies are needed to understand the role of shear rate and shear stress for RBC function. Results of d) suggested that aerobic training helped to strengthen the self-confidence of SCA patients. Moreover, regular activity improved ventilatory efficiency, reduced nitrosative stress and plasma free hemoglobin levels known to be involved in the pathophysiology of this disease. The effects of exercise on RBC-NOS / NO pathways were rather low. Overall, the data concluded that shear and NO application affected RBC function of SCA which involved the RBC-NOS/NO pathway but also the oxidant system, RBC integrity and RBC-MP release which might also affect vascular function. But also RBC-NOS independent effects have been shown and thus, further studies are now needed to investigate the effects of shear and NO on RBC but also vascular function in SCA in more detail.
Publications
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Red blood cell nitric oxide synthase modulates red blood deformability in sickle cell anemia, Clin Hemorheol Microcirc, 61:47-53 (2016)
Mozar A, Connes P, Collins B, Hardy-Dessources M-D, Romana M, Lemonne N, Bloch W, Grau M
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Hydroxyurea therapy modulates sickle cell anemia red blood cell physiology: Impact on RBC deformability, oxidative stress, nitrite levels and nitric oxide synthase signalling pathway, Nitric Oxide, 81:28-35 (2018)
Nader E, Grau M, Fort R, Collins B, Cannas G, Gauthier A, Walpurgis K, Martin C, Bloch W, Poutrel S, Hot A, Renoux C, Thevis M, Joly P, Romana M, Guillot N, Connes P
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Effect of acute exercise on RBC deformability and RBC nitric oxide synthase signalling pathway in young sickle cell anaemia patients, Scientific Reports, 9(1):11813 (2019)
Grau M, Jerke M, Nader E, Schenk A, Renoux C, Collins B, Dietz T, Bizjak DA, Joly P, Bloch W, Connes P, Prokop A
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Impact of a six-week training program on ventilatory efficiency, red blood cell rheological parameters and red blood cell nitric oxide signaling in young sickle cell anemia patients: A pilot study, Journal of Clinical Medicine, 8(12). pii: E2155 (2019)
Grau M, Nader E, Jerke M, Schenk A, Renoux C, Dietz T, Collins B, Bizjak DA, Joly P, Bloch W, Prokop A, Connes P
