. Pentoxifylline protects against endotoxin-induced acute renal failure in mice. Am J Physiol Renal Physiol 291: F1090 -F1095, 2006; doi:10.1152/ajprenal.00517.2005.-Acute renal failure (ARF) in septic patients drastically increases the mortality to 50 -80%. Sepsis induces several proinflammatory cytokines including tumor necrosis factor-␣ (TNF-␣), a major pathogenetic factor in septic ARF. Pentoxifylline has several functions including downregulation of TNF-␣ and endothelia-dependent vascular relaxation. We hypothesized that pentoxifylline may afford renal protection during endotoxemia either by downregulating TNF-␣ and/or by improving endothelial function. In wild-type mice, pentoxifylline protected against the fall in glomerular filtration rate (GFR; 105.2 Ϯ 6.6 vs. 50.2 Ϯ 6.6 l/min, P Ͻ 0.01) at 16 h of LPS administration (2.5 mg/kg ip). This renal protective effect of pentoxifylline was associated with an inhibition of the rise in serum TNF-␣ (1.00 Ϯ 0.55 vs. 7.02 Ϯ 2.40 pg/ml, P Ͻ 0.05) and serum IL-1 (31.3 Ϯ 3.6 vs. 53.3 Ϯ 5.9 pg/ml, P Ͻ 0.01) induced by LPS. Pentoxifylline also reversed the LPS-related increase in renal iNOS and ICAM-1 and rise in serum nitric oxide (NO). Enhanced red blood cell deformability by pentoxifylline may have increased shear rate and upregulated eNOS. Studies were therefore performed in eNOS knockout mice. The renal protection against endotoxemia with pentoxifylline was again observed as assessed by GFR (119.8 Ϯ 18.0 vs. 44.5 Ϯ 16.2 l/min, P Ͻ 0.05) and renal blood flow (0.86 Ϯ 0.08 vs. 0.59 Ϯ 0.05 ml/min, P Ͻ 0.05). Renal vascular resistance significantly decreased with the pentoxifylline (91.0 Ϯ 5.8 vs. 178.0 Ϯ 7.6 mmHg ⅐ ml Ϫ1 ⅐ min Ϫ1 , P Ͻ 0.01). Thus pentoxifylline, an FDA-approved drug, protects against endotoxemia-related ARF and involves a decrease in serum TNF-␣, IL-1, and NO as well as a decrease in renal iNOS and ICAM-1. sepsis; tumor necrosis factor SEPSIS IS KNOWN TO OCCUR annually in 751,000 Americans and accounts for 215,000 deaths, a number equivalent to the overall deaths due to myocardial infarction (1). Moreover, sepsis is a major cause of acute renal failure (ARF) in intensive care units; sepsis-related ARF is associated with a 70 -80% mortality (33,34).Both inflammatory and vasoactive mediators are involved in the pathophysiology of sepsis-related ARF. TNF-␣ plays a central role in this process. Serum levels of TNF-␣ are induced early in endotoxemia in humans (25). Moreover, elevated serum levels of the type I and type II receptors for TNF-␣ are shown to be predictive factors for ARF in patients with septic shock (12). The role of TNF-␣ as a pathogenetic factor in experimental ARF was supported by the observation that pretreatment with a TNF-soluble receptor (TNF s R p55 ) significantly attenuated endotoxemia-related ARF (19). It has also been shown that endotoxemic ARF is caused by TNF acting directly on TNF receptor-1 in the kidney (6). TNF-␣ participates in the magnification of the response mediated by the release of other cytokines and active substan...