Under ambient light and in normal cells, protection against apoptosis, namely cytoprotection, is mediated by nitric oxide induced (NO-induced) elevations in cGMP, which activate cGMP-dependent protein kinase I (PKGI) isozymes. PKGI phosphorylates BAD, preventing it from binding BCL-XL, thus leading to decreased apoptosis. Thus, if NO stimulates anti-apoptotic effects in response to red light exposure, red light exposure should result in elevations in cGMP. To examine this hypothesis, neuroblastoma cells will be exposed to red light (2.88 J/cm2, 632 nm) and the cGMP Measurement Kit from Cayman Chemical Company will be used to measure and compare cGMP levels in exposed and unexposed cells. Results from this analysis will enable us to characterize the mechanism by which red light mediates cytoprotection.
