Presentation Type

Poster

Faculty Mentor’s Full Name

Darrell Jackson

Faculty Mentor’s Department

BMED

Abstract

Stroke is the fifth leading cause of death annually in the United States, resulting in nearly 130,000 deaths per year. Ischemic stroke is the most common form of stroke and occurs when a blood vessel leading to the brain is blocked. This blockage leads to deprivation of oxygen and nutrients to brain tissue, resulting in a phenomenon known as delayed neuronal death (DND). In the hippocampus, a region susceptible to DND, there is high expression of glutamatergic AMPA receptors (AMPARs). The majority of AMPARs expressed in the hippocampus contain an edited form of the GluA2 (Q607R) subunit, and therefore are Ca2+-impermeable. Following oxygen-glucose deprivation/reperfusion (OGD/R), the GluA2 AMPAR subunit is internalized and subsequently degraded, leading to an increase in GluA2-lacking AMPARs that are Ca2+-permeable. The subsequent increase in intracellular calcium, mediated by Ca2+-permeable AMPARs following OGD/R, plays a key role in DND. Following OGD/R, there is an increase in the production of superoxide radicals. We hypothesize that OGD/R-induced internalization of GluA1 and GluA2 AMPAR subunits is mediated through a superoxide mechanism. SNB-19, a human astroglioma cell line, and SH-SY5Y, a human neuroblastoma cell line, were transiently transfected with GluA1/2 and different Rab proteins (Rab5, Rab7, or Rab11) to investigate the role of superoxide radicals in mediating OGD/R-induced GluA1 and GluA2 AMPAR subunit internalization and degradation. Following OGD/R-5 mins, there is a significant increase in the colocalization of the GluA1 and GluA2 subunits with Rab5, indicating the AMPAR subunits are undergoing internalization. GluA2 is also observed colocalizing with Rab7 following OGD/R-15 minutes, indicating that this subunit is being targeted for degradation. Treatment with MnTMPyP, a superoxide scavenger, ameliorated the internalization of GluA1 and GluA2, and the degradation of the GluA2 subunit following OGD/R. Our findings have shown that superoxide radicals play a vital role in the internalization of the GluA1 and GluA2 AMPAR subunits, and the degradation of the GluA2 AMPAR subunit.

Category

Health and Medical Science

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Apr 17th, 3:00 PM Apr 17th, 4:00 PM

Investigating the Role of Oxidative Stress in Mediating Excitotoxicity Following in vitro Ischemic/Reperfusion Insult

UC South Ballroom

Stroke is the fifth leading cause of death annually in the United States, resulting in nearly 130,000 deaths per year. Ischemic stroke is the most common form of stroke and occurs when a blood vessel leading to the brain is blocked. This blockage leads to deprivation of oxygen and nutrients to brain tissue, resulting in a phenomenon known as delayed neuronal death (DND). In the hippocampus, a region susceptible to DND, there is high expression of glutamatergic AMPA receptors (AMPARs). The majority of AMPARs expressed in the hippocampus contain an edited form of the GluA2 (Q607R) subunit, and therefore are Ca2+-impermeable. Following oxygen-glucose deprivation/reperfusion (OGD/R), the GluA2 AMPAR subunit is internalized and subsequently degraded, leading to an increase in GluA2-lacking AMPARs that are Ca2+-permeable. The subsequent increase in intracellular calcium, mediated by Ca2+-permeable AMPARs following OGD/R, plays a key role in DND. Following OGD/R, there is an increase in the production of superoxide radicals. We hypothesize that OGD/R-induced internalization of GluA1 and GluA2 AMPAR subunits is mediated through a superoxide mechanism. SNB-19, a human astroglioma cell line, and SH-SY5Y, a human neuroblastoma cell line, were transiently transfected with GluA1/2 and different Rab proteins (Rab5, Rab7, or Rab11) to investigate the role of superoxide radicals in mediating OGD/R-induced GluA1 and GluA2 AMPAR subunit internalization and degradation. Following OGD/R-5 mins, there is a significant increase in the colocalization of the GluA1 and GluA2 subunits with Rab5, indicating the AMPAR subunits are undergoing internalization. GluA2 is also observed colocalizing with Rab7 following OGD/R-15 minutes, indicating that this subunit is being targeted for degradation. Treatment with MnTMPyP, a superoxide scavenger, ameliorated the internalization of GluA1 and GluA2, and the degradation of the GluA2 subunit following OGD/R. Our findings have shown that superoxide radicals play a vital role in the internalization of the GluA1 and GluA2 AMPAR subunits, and the degradation of the GluA2 AMPAR subunit.