The Role of HIF-2 in Neutrophilic Inflammation
Lead Research Organisation:
University of Sheffield
Department Name: Respiratory Medicine
Abstract
Neutrophils are white blood cells that are the first to travel from the blood to areas of infection or damage. They are very important in defending us against infections. However, because they contain many dangerous substances required to kill infectious agents, neutrophils can damage the body‘s own tissues if they are over-active or are not removed safely from tissues when their job is done. Over-active neutrophils are important in conditions such as arthritis and lung disease and ways to control their activity could lead to new treatments.
Neutrophils‘ activity is regulated by their ability to undergo a suicide process called apoptosis, which switches them off and leads to their safe destruction. One important signal regulating neutrophil suicide is the level of oxygen in their surroundings. Low levels of oxygen increase neutrophil survival and are commonly found in diseased tissues. I aim to study the pathways within neutrophils that prolong their survival when oxygen levels are low and may also regulate their ability to kill bacteria. We know cells sense oxygen levels via a family of proteins called HIF. Using neutrophils lacking different members of this family we hope to understand better how oxygen regulates the functions of these important cells.
Neutrophils‘ activity is regulated by their ability to undergo a suicide process called apoptosis, which switches them off and leads to their safe destruction. One important signal regulating neutrophil suicide is the level of oxygen in their surroundings. Low levels of oxygen increase neutrophil survival and are commonly found in diseased tissues. I aim to study the pathways within neutrophils that prolong their survival when oxygen levels are low and may also regulate their ability to kill bacteria. We know cells sense oxygen levels via a family of proteins called HIF. Using neutrophils lacking different members of this family we hope to understand better how oxygen regulates the functions of these important cells.
Technical Summary
Neutrophils perform their key roles in innate immune responses at inflamed sites that are typically oxygen deplete. The hypoxia inducible factor (HIF) pathway is known to be central to neutrophil oxygen sensing and responses to hypoxia. Recently, the HIF pathway was also found to regulate inflammation independent of hypoxia.
A crucial component of the HIF transcription factor, the HIF-alpha subunit (HIF-alpha, has three known isoforms (HIF1-3alpha). HIF-1alpha is required for neutrophil survival in hypoxia. Our preliminary data show unsuspected expression of HIF-2alpha (but not HIF-3alpha) in neutrophils and that its expression is altered in inflammatory disease.
I hypothesise HIF-1alpha and HIF-2alpha have distinct roles in regulating neutrophil function and apoptosis in response to inflammation and hypoxia.
I aim to:
(i) Characterise HIF-2alpha mRNA and protein expression in human neutrophils, compared with HIF-1alpha, and their regulation in hypoxia and following inflammatory mediator stimulation.
(ii) Examine the consequences of HIF-2alpha deficiency, compared with HIF-1alpha deficiency, in neutrophils from wild-type mice and mice with myeloid-targeted deficiency of HIF-1alpha or HIF-2alpha
(iii) Study in vivo models of inflammation in wild-type, HIF-1alpha and HIF-2alpha deficient mice
(iv) Study neutrophil function and apoptosis in patients with gain of function mutations in HIF-2alpha and VHL disease
This application builds on evidence HIF-2alpha may regulate neutrophil function and survival and uses a range of approaches (in vitro human and murine neutrophil studies, in vivo models of inflammation and study of informative patient groups) to understand the distinct roles of HIF-1alpha and HIF-2alpha in regulating neutrophilic inflammation. This will enhance understanding of the mechanisms of initiation and resolution of acute inflammation and potentially identify therapeutic targets to limit the exaggerated neutrophil responses associated with inflammatory disease.
A crucial component of the HIF transcription factor, the HIF-alpha subunit (HIF-alpha, has three known isoforms (HIF1-3alpha). HIF-1alpha is required for neutrophil survival in hypoxia. Our preliminary data show unsuspected expression of HIF-2alpha (but not HIF-3alpha) in neutrophils and that its expression is altered in inflammatory disease.
I hypothesise HIF-1alpha and HIF-2alpha have distinct roles in regulating neutrophil function and apoptosis in response to inflammation and hypoxia.
I aim to:
(i) Characterise HIF-2alpha mRNA and protein expression in human neutrophils, compared with HIF-1alpha, and their regulation in hypoxia and following inflammatory mediator stimulation.
(ii) Examine the consequences of HIF-2alpha deficiency, compared with HIF-1alpha deficiency, in neutrophils from wild-type mice and mice with myeloid-targeted deficiency of HIF-1alpha or HIF-2alpha
(iii) Study in vivo models of inflammation in wild-type, HIF-1alpha and HIF-2alpha deficient mice
(iv) Study neutrophil function and apoptosis in patients with gain of function mutations in HIF-2alpha and VHL disease
This application builds on evidence HIF-2alpha may regulate neutrophil function and survival and uses a range of approaches (in vitro human and murine neutrophil studies, in vivo models of inflammation and study of informative patient groups) to understand the distinct roles of HIF-1alpha and HIF-2alpha in regulating neutrophilic inflammation. This will enhance understanding of the mechanisms of initiation and resolution of acute inflammation and potentially identify therapeutic targets to limit the exaggerated neutrophil responses associated with inflammatory disease.
