TNF and Hyperglycemia: In vitro data showed that β1-AR stimulation reduced inducible nitric oxide synthase (iNOS) expression and modulated other hyperglycemia-induced inflammatory molecules, such as interleukin (IL)-1β, tumor necrosis factor-α (TNF-α), and prostaglandin E2 (PGE2) in human retinal endothelial cells and rat Müller cells through the involvement of PKA, p38 MAPK, and p42/p44 MAPK [9,10].