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SC COBRE in Oxidants, Redox Balance and Stress Signaling

Mariana Pehar, Ph.D

Mariana Pehar, PhD
Assistant Professor
Cell and Molecular Pharmacology & Experimental Therapeutics
2006    PhD, Universidad de la Rep├║blica-Uruguay

Oxidant-induced toxicity of neurotrophins in aging and disease

Neurotrophins constitute a family of closely related proteins that regulate the differentiation and survival of neuronal populations during development and modulate neuronal plasticity in the mature nervous system. The family includes four members: nerve growth factor (NGF), brain derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3) and neurotrophin-4 (NT-4). Approximately forty years after their original discovery, it was shown that members of this family could also induce apoptosis of neurons during development and pathological conditions. Neurotrophins remain the prototype of the paradoxical activity elicited by trophic factors. NGF accumulates in many pathological conditions involving tissue inflammation, including neurodegenerative diseases, acute brain or spinal cord injury, chronic pain syndromes, and autoimmune diseases such as rheumatoid arthritis, psoriasis and systemic lupus erythematosus. The increase in NGF levels in these pathological conditions coexists with the oxidative environment linked to the inflammatory response. Therefore, NGF constitutes a likely target for oxidative modifications. While signaling by trophic factors is essential for the survival, growth and differentiation of cells and tissues, I discovered that posttranslational oxidative-modifications turned NGF into a powerful death stimulus for motor neurons. Indeed, oxidative-modified NGF has the exceptional ability to induce motor neuron apoptosis at physiologically relevant concentrations (10,000-fold less compared to that required by native NGF). My long-term research goal is to understand how oxidative stress modulates cell signaling in aging and neuroinflammation. The primary objective of this proposal in particular, is to examine how oxidative stress governs the switch between pro-survival and pro-death signaling of neurotrophins. To approach this objective, I will focus on the following Specific Aims: Aim 1. Characterize the effect of oxidative modifications in the biological activity of NGF and related neurotrophins using unnatural amino acid mutagenesis; Aim 2. Identify the sites of oxidative modification of NGF in vivo using mass spectrometry analysis; Aim 3. Evaluate the effects of blocking nitrated NGF as a potential therapeutic approach in
pathological conditions.