Introduction of NOS II Gene into Primary Cultures of Bovine and Human Endothelial Cells

In recent years, endothelial cells, activated by cytokines (1 ) have been found to phagocytose Gram-positive and Gram-negative bacteria (2 –14 ), and exhibit microbicidal activity toward S. aureus (15 ). One of the enzymes induced by cytokine treatment is nitric oxide synthase (NOS), which is responsible for the generation of nitric oxide (NO�) from the oxidative metabolism of L-arginine (16 ,17 ). Despite the voluminous literature pertaining to cytokine-activation of NOS II in macrophages and the role NO� plays in control of intracellular pathogens, there are few studies investigating the microbicidal activity of endothelial-derived NO�. Typical of such reports is that of Oswald et al. (18 ) in which immortalized brain endothelial cells were treated with combinations of different cytokines, monitoring NO� production and subsequent Schistosomulum killing. Although there were cytokine mixtures that resulted in a high killing rate concomitant with a high NO� flux, there were other cytokine combinations where such a correlation was not present (18 ). These findings point to the fact that cytokines induce a broad spectrum of enzymes, one of which happens to be NOS II. In the absence of more compelling data, it becomes difficult to assign microbicidal activity to specific reactions of NO�. We have recently developed techniques to stably introduce a retroviral vector encoding NOS II into primary cultures of endothelial cells (19 ). These methods will allow inquiries into the importance of cellular-derived NO� in host immune response.