Differential cellular immunolocalization of renal tumour necrosis factor-alpha production during ischaemia versus endotoxaemia

Both renal ischaemia and endotoxaemia provoke renal dysfunction and cellula r injury. Although the clinical manifestation of each insult is similar (gl obal renal dysfunction), ischaemia and endotoxaemia induce different patter ns of cellular injury. Tumour necrosis factor-alpha (TNF-alpha) has been im plicated in both types of renal injury: however, it remains unknown whether differential cellular TNF-alpha expression accounts for these changes. We hypothesized that renal glomerular cells and tubular cells differentially e xpress TNF-alpha in response to ischaemia compared with endotoxaemia. To in vestigate this hypothesis, male Sprague Dawley rats were anaesthetized and exposed to various time-periods of renal ischaemia. with or without reperfu sion (sham operation = negative control), or lipopolysaccharide (LPS) 0.5 m g/kg intraperitoneally (i.p.), The kidneys were harvested following renal i njury, and rat TNF-alpha protein expression was determined (by enzyme-linke d immunosorbent assay), as were TNF-alpha bioactivity (by WEHI-164 cell clo ne cytotoxicity assay) and TNF-alpha cellular localization (by immunohistoc hemistry). TNF-alpha protein expression and TNF-alpha bioactivity peaked fo llowing 1 hr of ischaemia and 2 hr of reperfusion (48 +/- 11 pg/mg of prote in, P < 0.05, and 12 <plus/minus> 0.5 x 10(-3) units/mg of protein. P < 0.0 5, respectively). The concentration of TNF-<alpha> increased to a similar e xtent following exposure to LPS: however, while TNF-alpha production follow ing ischaemia-reperfusion injury localized predominantly to renal tubular e pithelial cells, animals exposed to LPS demonstrated a primarily glomerular distribution of TNF-alpha production. Hence, the cellular localization of renal TNF-alpha production appears to be injury specific, i.e. renal tubula r cells are the primary source of TNF-alpha following an ischaemic insult, whereas LPS induces glomerular TNF-alpha production. The cellular source of TNF-alpha following different insults may have therapeutic implications fo r targeted inhibition of TNF-alpha production.