Given the failure of all clinical trials with cytoprotective therapy in intracerebral hemorrhage (ICH), new candidate therapy should have a pleiotropic effect which corresponds to the complex profile of ICH pathogenesis. Here, we propose that nuclear factor-erythroid E2-related factor 2 (Nrf2), a pleiotropic protein that regulates transcription of a battery of key cytoprotective, detoxifying, and phagocytosis-regulating genes represents a promising target for ICH therapy. Preliminary data suggest: (1) Cytoprotection: Activators of Nrf2 after ICH in rodents reduce oxidative stress, inflammation, and protect brain cells from damage, while Nrf2 gene deletion has the opposite effect;(2) Hematoma resolution: Activators of Nrf2 promote phagocytosis by brain microglia/macrophages and accelerate hematoma resolution in mice after ICH. This process is linked to Nrf2-mediated CD36 scavenger receptor expression, since blocking Nrf2 and CD36 inhibits phagocytosis by microglia. In addition, Nrf2-mediated clearance of neurotoxic hemoglobin could be through Nrf2- driven haptoglobin (Hp) expression, as Nrf2-activation improves, and severe hypohaptoglobinemia retards hemoglobin clearance after ICH. Thus, the overall hypothesis is that Nrf2 is a viable target in protecting the brain from damage during the both early and late stages of ICH pathology.
Three Specific Aims (SA) are included: (SA1) investigates Nrf2 as a regulator of cytoprotection and inflammation after intracerebral hemorrhage in an ICH-like in vitro model. We will subject primary neurons or microglia to """"""""ICH-like"""""""" environment and establish its consequences: cell death, oxidative stress, inflammatory response (microglia). Next, we will establish the cytoprotective role of Nrf2 (including preservation of phagocytotic functions) by using cells from Nrf2 deficient mice, DNA decoy to inhibit Nrf2, gene transfer to overexpress Nrf2, and pharmacologic agents to activate Nrf2. (SA2) Investigate Nrf2 as a mechanism to promote hematoma resolution after ICH. We will use Nrf2-, CD36-, and Hp-deficient mice (or microglia isolated from these mice) to explore the role of Nrf2 and its downstream targets, as well as CD36 and Hp, in hematoma resolution and their impact on secondary brain damage. (SA3) Investigate the clinical utility of sulforaphane (Nrf2 activator) as a treatment for ICH. We will use blood injection model of ICH in mouse to optimize conditions for the treatment of ICH with SF. We will first establish an optimal therapeutic dose with respect to the highest efficiency, safety, duration of treatment, and longest time window for effective treatment for ICH in mice. Our long term goal is to explore pharmacological and molecular therapies that will reduce ICH pathogenesis and improve functional recovery.
Intracerebral hemorrhage (ICH) accounts for 10 to 15% of all strokes and has a one-year mortality rate greater than 50-60%. There is no FDA approved effective treatment for ICH. In our study, we will determine if activation of transcription factor Nrf2, which regulates expression of many genes that increase resistance of brain cells to ICH- induced damage, may represent a viable target for ICH treatment. Our goal is to explore the underlying molecular mechanism of Nrf2's beneficial effect, and to establish the initial pharmacologic criteria for therapies using Nrf2-based approach.
