Flavonoid: Quercetin, a Multifunctional Therapeutic Agent to Reverse Acute Crisis in a Transgenic Sickle Mouse Model
Authors: Thangaswamy Sangeetha , Billett Henny H , Branch Craig A , Suzuka Sandra M , Acharya Seetharama A 
Published: November 2023

Hypoxia acts as an initial trigger to amplify crisis episodes in SCD patients. The post capillary venular response to ischemia reperfusion injury includes abundant leukocyte adhesion, emigration, impairment of blood flow and enhanced oxidant production in transgenic sickle mice. Antioxidant mediated therapy to attenuate oxidative stress may reduce red cell sickling and inflammation and therefore may be beneficial for SCD. Based on this concept, we examined the efficacy of flavonoid quercetin to mitigate inflammation and vaso‐occlusion generated during hypoxia re‐oxygenation in acute sickle crisis model.MethodsAcute crisis in a transgenic sickle NY1DD mouse was experimentally induced by 18h hypoxia (8% oxygen, 0.5% CO2, and balance nitrogen) followed by 3h re‐oxygenation (H/R). NY1DD mice subjected to hypoxia were treated with a single dose of quercetin (200 mg/kg body weight) administered intraperitoneally at the onset of re‐oxygenation. In vivo intravital microscopic observation of cremaster post capillary venules was performed. Hemodynamic parameters were measured as described by Kaul et al 2004.ResultsNY1DD exhibits an intrinsic level of vaso‐occlusion and impairment of blood flow, which are increased during hypoxia re‐oxygenation. NY1DD mice exposed to H/R as indicated by an increased level of leukocyte adhesion (4.8± 0.58) and emigration (1.7± 0.28) vs normoxic NY1DD mice (1.6±0.26; 0.53±0.13). After treated with quercetin showed significant decreases in the level of leukocyte adhesion (0.47± 0.12; p<0.0001) and emigration (0.22±0.09) vs untreated NY1DD and wild type (0.50 ±0.01; 0.16±0.05). Vaso‐occlusion, both intrinsic and induced by hypoxia in NY1DD mice was normalized completely to wild type after quercetin treatment. We also observed a significant increase in red cell velocity (2.8±0.24; p<0.0001), wall shear rate (545±51.0; p<0.0001) and flow rate (1.03±0.13; p<0.001) after quercetin treatment when compared to untreated NY1DD (1.05±0.08; 211±17.8; 0.35±0.03) and wild type (3.5±0.3; 852.5±102.4; 1.25±0.17). All hemodynamic parameters were significantly increased after treatment with quercetin vs normoxia NY1DD, but didn't completely revert near to wild type. The level of lipid peroxidation product such as TBARS increased in H/R and reduced after quercetin treatment vs untreated NY1DD mice subjected to hypoxia. Expression of soluble cell adhesion molecules sP‐selectin, sE‐selectin and sVCAM‐1 were also significantly (p<0.04; p<0.02; p<0.04) reduced in plasma after treated with quercetin vs untreated NY1DD mice. We also observed slight changes in red cell density pattern and reduction in high‐density red cells after quercetin treatment.ConclusionOur studies reveal that quercetin improves all hemodynamic parameters significantly and does not reverse back to wild type. Although, quercetin was completely attenuates vaso‐occlusion after hypoxia. These results suggesting need for further analysis of multiple doses of quercetin for longer period to verify whether hemodynamic parameters are being back to normal. We suggest that these effects may stems from the multifunctional properties of quercetin, which decreases sRBC interaction with vascular bed in the acute transgenic mice model. Our present data provide a strong basis for the therapeutic application of flavonoids in SCD. More studies are needed to better understand the mechanism of action of quercetin in vivo and to further establish its therapeutic effect in SCD.