Shear Stress Ameliorates Superoxide Impairment to Erythrocyte Deformability With Concurrent Nitric Oxide Synthase Activation.

ABSTRACT: The cellular deformability of red blood cells (RBC) is exceptional among mammalian cells and facilitates nutrient delivery throughout the microcirculation; however, this physical property is negatively impacted by oxidative stress. It remains unresolved whether the molecular determinants of cellular deformability - which in the contemporary model of RBC are increasingly recognized - are sensitive to free radicals. Moreover, given cellular deformability has recently been demonstrated to increase following exposure to specific doses of mechanical stimulation, the potential for using shear "conditioning" as a novel method to reverse free-radical induced impairment of cell mechanics is of interest. We thus designed a series of experiments that explored the effects of intracellular superoxide (O₂ ^-) generation on the deformability of RBC and also activation of pivotal molecular pathways known to regulate cell mechanics - i.e., PI3K/Akt kinase and RBC nitric oxide synthase (NOS). In addition, RBC exposed to O₂ ^- were conditioned with specific shear stresses, prior to evaluation of cellular deformability and activation of PI3K/Akt kinase and RBC-NOS. Intracellular generation of O₂ ^- decreased phosphorylation of RBC-NOS at its primary activation site (Ser¹¹⁷⁷) (p < 0.001), while phosphorylation of Akt kinase at its active residue (Ser⁴⁷³) was also diminished (p < 0.001). Inactivation of these enzymes following O₂ ^- exposure occurred in tandem with decreased RBC deformability. Shear conditioning significantly improved cellular deformability, even in RBC previously exposed to O₂ ^-. The improvement in cellular deformability may have been the result of enhanced molecular signaling, given RBC-NOS phosphorylation in RBC exposed to O₂ ^- was restored following shear conditioning. Impaired RBC deformability induced by intracellular O₂ ^- may be due, in part, to impaired activation of PI3K/Akt, and downstream signaling with RBC-NOS. These findings may shed light on improved circulatory health with targeted promotion of blood flow (e.g., exercise training), and may prove fruitful in future development of blood-contacting devices.

SUBMITTER: Kuck L 

PROVIDER: S-EPMC6370721 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature