# Mechanisms of Neuroprotective Therapy in TBI

> **NIH VA I01** · RALPH H JOHNSON VA MEDICAL CENTER · 2020 · —

## Abstract

Traumatic brain injury (TBI) is a neurodegenerative disease in which nitric oxide (NO)-based anti-inflammatory
and anti-excitotoxicity mechanisms are derailed, resulting in a disturbed NO metabolome. NO metabolites S-
nitrosoglutathione (GSNO) and peroxynitrite (ONOO-) participate in opposing mechanisms (neuroprotection
and neurodegeneration, respectively) by regulation of neuronal nitric oxide synthase (nNOS)- and calpain-
mediated deleterious mechanisms. A prolonged and sustained increase in neuronal ONOO- (a reaction product
of NO and superoxide) production causes sustained activation of calpains and thus a deleterious
nNOS/peroxynitrite/calpain system, leading to axonal injury and neuronal cell death following TBI. Increased
synthesis of ONOO- results in reduced NO bioavailability for GSNO, a reaction product of NO and glutathione,
biosynthesis, resulting in loss of GSNO/S-nitrosylation-mediated regulations of nNOS and calpains.
Exogenously administered GSNO reduces the deleterious activities of ONOO- by reversibly down regulating
nNOS, thus reducing neuronal ONOO- and calpain activity.
 Based on documented deleterious role of nNOS in TBI as summarized in Introduction and Background
sections, the focus of this study is to investigate the role of nNOS-derived NO metabolome in TBI. However, to
evaluate the relative contributions of inducible NOS (iNOS) and endothelial NOS (eNOS), the studies are also
proposed using iNOS and eNOS knock out mice. Using a controlled cortical impact (CCI) mouse model of TBI,
we propose to investigate the mechanisms of the opposing roles of ONOO- versus GSNO for neuroprotection
and functional recovery. GSNO inhibits nNOS and calpain activities by cysteine S-nitrosylation of these
proteins. Therefore, studying reversible inhibition of nNOS and calpain by GSNO offers a novel approach to
down regulate the nNOS/peroxynitrite/calpain signaling cascade for improved functional recovery in TBI.
Based on these findings, we hypothesize that the nNOS/peroxynitrite/calpain activities participate in TBI
disease pathology. This system maintains sustained and prolonged ONOO- production and thus axonal and
neuronal cell injury and subsequent neurodegeneration whereas GSNO, via the mechanism of S-
nitrosylation, reversibly inhibits the deleterious activities of nNOS and calpain to reduce ONOO- and
associated neurodegeneration, and aids in functional recovery in a mouse model of TBI.
Specific Aim 1 will determine whether GSNO-mediated mechanisms confer neuroprotection and aid in
functional recovery by blocking the deleterious nNOS/peroxynitrite/calpain system in a young adult mouse
modelofTBI.Theproposedstudyisdesignedtoinvestigateperoxynitritevs.GSNO-basedmechanismsduring
the chronic phase of injury at 1 month and 3 months following TBI using wild type and genetically engineered
(nNOS, iNOS and eNOS knock out) young adult male and female mice.
Specific Aim 2 will determine the preclinical efficacy and clinical relevance of GSNO ther...

## Key facts

- **NIH application ID:** 9861194
- **Project number:** 5I01BX003401-04
- **Recipient organization:** RALPH H JOHNSON VA MEDICAL CENTER
- **Principal Investigator:** Avtar K Singh
- **Activity code:** I01 (R01, R21, SBIR, etc.)
- **Funding institute:** VA
- **Fiscal year:** 2020
- **Award amount:** —
- **Award type:** 5
- **Project period:** 2017-01-01 → 2020-12-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9861194

## Citation

> US National Institutes of Health, RePORTER application 9861194, Mechanisms of Neuroprotective Therapy in TBI (5I01BX003401-04). Retrieved via AI Analytics 2026-05-27 from https://api.ai-analytics.org/grant/nih/9861194. Licensed CC0.

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