TNF-alpha is a roleplaying cytokine which acts as a trigger in many diseases. one of the mechanism is when TNF-alpha binds to the receptor and initiates the signalling pathway it results in the synthesis and release of Cytokines Chemokines Adhesion molecules and NOS. NOS when combined with free radicals for a potent peroxy nitryl free radical which aggravates the disease condition by nitrosylation of proteins. TNF-alpha in a nutshell increases oxidative stress.
I agree with Dr. Raju answer. In addition, TNF-alpha itself has been shown to induce reactive oxygen radicals and promote albumin permeabilty in solated rat glomeruli (McCarthy ET et al 1998). Thus, TNF-alpha-induced oxidative stress may contribute to a variety of tissue inflammation in type-2 diabetes.