[Glomerular expression of tumor necrosis factor alpha (TNF-alpha) and of its receptors]

TNF alpha is generated in inflammatory lesions of the glomerulus. Both resident mesangial cells and infiltrating macrophages contribute to this generation, when exposed to bacterial lipopolysaccharide and immune complexes, respectively. TNF alpha has multiple actions on glomerular cells and on distant target cells that appear to promote in turn either amplification or limitation of TNF alpha release and TNF alpha binding. For instance, there is in vitro evidence that locally generated reactive oxygen metabolites: 1) cause increased release of TNF alpha into the extracellular space by accelerating the cleavage of its cell-associated precursor, and 2) reduce the expression of both cell-associated and soluble TNF alpha receptors. Thus it might be expected that reactive oxygen metabolites released at the site of glomerular inflammation limit autocrine, juxtacrine and paracrine effects of TNF alpha and simultaneously increase its widespread release into the circulation.