Investigation of the Molecular Mechanisms of Candesartan after Brain Injury

Investigation of the Molecular Mechanisms of Candesartan after Brain Injury

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Name: Peter Attilio

Rank: MAJ

Organization: Henry M. Jackson Foundation

Performance Site: Uniformed Services University of the Health Sciences

Year Published: 2017

Abstract Status:

Abstract

Nursing professionals are confronted with the devastating effects of TBI throughout the nursing care spectrum. Agitation and aggressiveness of patients after a TBI is a frequent occurrence early after TBI making bedside care extremely difficult. Additionally, many Nurse Practitioners are confronted with more mild complaints of memory and attention deficits that may also include headaches, fatigue and depression. While many of those who suffer from TBI express the desire for treatment of these problems, only about one in five of those patients actually receive the help that they need. This inability to obtain care is multifactorial and includes a lack of treatment options for these patients. Many of the therapies, such as the use of benzodiazepines for anxiety, have significant side effects and are aimed only at symptomatic treatment. Given this immense impact and lack of effective treatments, there is a critical need to understand in detail the mechanisms underlying TBI pathology and to develop new therapies.
Despite the failure of TBI clinical trials, several drugs have shown promise in improving outcomes in animal models of TBI. A major thrust of TBI research is to understand the discrepancy between animal and human drug trials for TBI. One important aspect of this is to develop a deeper understanding of the mechanisms through which drugs have efficacy in animals to be able to develop markers of target engagement during clinical trials. Our laboratory has shown that the angiotensin II receptor 1 (AT1R) blocking agent candesartan has efficacy in improving recovery from TBI in mice in part through reducing neuroinflammation. The mechanisms underlying these effects are poorly understood but probably result from candesartan action on multiple cell types including astrocytes and endothelial cells. Angiotensin signaling through the AT1 can stimulate cytokine release from astrocytes and enhance the integrity of the blood brain barrier through effects on vascular endothelial cells. Identifying the molecular mechanisms through which candesartan improves outcome after TBI should assist in efforts to determine whether candesartan is a suitable candidate for clinical trials for TBI. Thus, evaluation of these mechanisms directly addresses the TSNRP research priority of force health protection through the evaluation of potential therapies for the long-term treatment of TBI.
We propose that by delineating the changes in mRNA expression of astrocytes and endothelial cells after TBI and their response to candesartan treatment, we will obtain a more complete understanding of the actions of candesartan in regulating inflammation after TBI. We propose that by understanding the changes in mRNA expression of astrocytes and endothelial cells after TBI, and their response to candesartan treatment, a more complete understanding of the physiology of TBI will be obtained. Additionally, this will improve our understanding of the molecular changes that candesartan enacts providing additional therapeutic targets for the treatment of TBI. The aims of this study are to 1) determine the effects candesartan on the molecular response of astrocytes and brain vascular endothelial cells to TBI in mice and 2) determine which effects of candesartan require angiotensin 1 receptor (AT1R) signaling to produce its anti-inflammatory action after TBI in astrocytes and brain vascular endothelial cells.
The study design for this project will be to perform a controlled cortical impact (CCI) in a mouse model with a 30-day subcutaneous administration of candesartan initiated within 6-hours of injury. At the conclusion of the 30-day treatment period the animals will be euthanized, brain extracted, and cells populations isolated through fluorescent activated cell sorting. The individual cell populations of astrocytes and brain endothelial cells will then undergo RNA isolation and sequencing. Fold-change differences in inflammatory and reninangiotensin component gene expression will be identified as markers of treatment efficacy. This design will utilize wild-type mice for understanding the overall effects of candesartan. It will then be repeated in an AT1R knockout transgenic mouse line to identify which effects are AT1R mediated.
The conclusions of this study will provide a better understanding of the molecular mechanisms of TBI and those mechanisms underlying the anti-inflammatory effects of candesartan after TBI. This knowledge will help to identify possible treatment options for our soldiers suffering from the long-term sequela of TBI. Additionally, this information will enhance the foundation of military nursing science through the use of molecular science techniques to better understand a clinically relevant process. Ultimately aiding in building a foundation for the translation of research to improved care for our warfighters.