Thalidomide Analogues Suppress Lipopolysaccharide-Induced Synthesis of TNF-α and Nitrite, an Intermediate of Nitric Oxide, in a Cellular Model of Inflammation

Abstract

An unregulated neuroinflammation accompanies numerous chronic and acute neurodegenerative disorders and it is postulated that such a neuroinflammatory component likely exacerbates disease progression. A key player in brain inflammation is the microglial cell; a vital soluble factor synthesized by activated microglial cells is the key cytokine, tumor necrosis factor–alpha (TNF-α). Additionally, microglial cells release IL-1α/β, reactive oxygen species (ROS), such as superoxide (O₂^-) and reactive nitrogen species (RNS) like nitric oxide (NO). Nitric oxide reactive oxygen species can undergo various forms of interactions in cells whereby the synthesis of RNS / ROS intermediates are generated that can damage cell membranes. The presence of oxidative damaged cells is implicated with the abnormal cellular activity in brain or in the spinal cord, and is a classical feature of neurodegenerative disorders. To aid characterize this process, a quantitative analysis of nitrite generation was undertaken on agents developed to lower TNF-α levels in cell culture. Nitrite is a stable end product of nitric oxide metabolism and, thereby, acts as a surrogate measure of the highly unstable nitric oxide. Utilizing a RAW 264.7 cellular model of lipopolysaccharide-induced inflammation that induces high levels of TNF-α protein accompanied by a robust generation of nitrite, the properties of a series of thalidomide-based TNF-α synthesis inhibitors were evaluated to reduce the levels of both. Specific analogues of thalidomide effectively suppressed the generation of both TNF-α and nitrite at well-tolerated doses.