# Role of RBC Reactive Oxygen Species and Their Vicious Cycle in Sickle Vasculopathy

> **NIH NIH R01** · DUKE UNIVERSITY · 2020 · $397,500

## Abstract

Role of RBC Reactive Oxygen Species and Their Vicious Cycle in Sickle Vasculopathy
Abstract:
In sickle cell disease (SCD), red blood cells (RBCs) play an active role in vasoocclusion, largely
through adhesion to endothelium and activation of leukocytes. While it is established that excessive
production of reactive oxygen species (ROS) in sickle RBCs leads to oxidative damage and
accelerated hemolysis, the contribution of RBC ROS to RBC adhesion and leukocyte activation
remains unclear. Here, we provide evidence for a novel pathogenic mechanism of sickle RBC ROS that
promotes adhesion and vasoocclusion in SCD. We show that NADPH oxidase (Nox)-dependent ROS
production in sickle RBCs mediates adhesion to the vascular endothelium. This ROS production is
regulated by MEK/ERK and G-protein coupled-receptor kinase 2 (GRK2), a mechanism that can itself
be stimulated by inflammatory cytokines and external ROS. Consequently, sickle RBC ROS form a
positive feedback loop with MEK/ERK and GRK2. These findings suggest that ROS, MEK/ERK and
GRK2 create an intracellular cycle regulating sickle RBC-induced vasoocclusion. We also have
implicated small nucleolar RNAs (snoRNAs) as regulators of RBC ROS. Specifically, these unusual
regulators of cellular ROS are present in sickle RBCs at high levels that correspond to elevated ROS
levels and RBC adhesion. We hypothesize that this deleterious cycle in sickle RBCs acts to promote
vasoocclusion and drive SCD pathophysiology. We further hypothesize that disrupting components of
this cycle can prevent vasoocclusion. Accordingly, we have recently shown that blocking MEK/ERK
with MEK inhibitors reduces vasoocclusion in SCD mouse models. We also now demonstrate that
scavenging ROS in sickle RBCs ex vivo suppresses ERK activation and sickle RBC-induced
vasoocclusion in vivo. Additionally, we show that non-coding snoRNAs regulate pathologic RBC ROS
production, since silencing these snoRNAs in mice reduces ROS levels in normal and sickle RBCs. We
propose to further validate dynamic contributions of the RBC ROS cycle to vasoocclusive events and
SCD pathophysiology, with the following Specific Aims. In SA1, we will show that the RBC ROS cycle is
critical in controlling the cellular processes of vasoocclusion, and that disrupting this loop in vivo by
scavenging ROS prevents vasoocclusion; in SA2, we will test the hypothesis that sickle RBC GRK2 is a
druggable target to suppress this vicious cycle leading to cell activation; and in SA3, we will determine
the role of the non-coding snoRNAs in ROS-stimulated sickle RBC pathology. Our long-term goal is to
identify remediable sickle RBC abnormalities to reduce oxidative damage and vasoocclusion. We
strongly believe that our studies will not only provide novel insights into the exact mechanisms of
vasoocclusion and SCD pathophysiology, but will also lay the foundation for more rational approaches
to therapies that better prevent oxidative damage and vasoocclusion in SCD.

## Key facts

- **NIH application ID:** 9948739
- **Project number:** 5R01HL137930-04
- **Recipient organization:** DUKE UNIVERSITY
- **Principal Investigator:** Rahima Zennadi
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $397,500
- **Award type:** 5
- **Project period:** 2017-08-16 → 2021-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9948739

## Citation

> US National Institutes of Health, RePORTER application 9948739, Role of RBC Reactive Oxygen Species and Their Vicious Cycle in Sickle Vasculopathy (5R01HL137930-04). Retrieved via AI Analytics 2026-07-02 from https://api.ai-analytics.org/grant/nih/9948739. Licensed CC0.

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