Simvastatin improves sepsis-induced mortality and acute kidney injury via renal vascular effects

Abstract

Acute kidney injury (AKI) occurs in about half of patients in septic shock and the mortality of AKI with sepsis is extremely high. An effective therapeutic intervention is urgently required. Statins are 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors that also have pleiotropic actions. They have been reported to increase the survival of septic or infectious patients. But the effect of simvastatin, a widely used statin, on sepsis-induced AKI is unknown. The effects of simvastatin and tumor necrosis factor (TNF)-alpha neutralizing antibody were studied in a clinically relevant model of sepsis-induced AKI using cecal ligation and puncture (CLP) in elderly mice. Simvastatin significantly improved CLP-induced mortality and AKI. Simvastatin attenuated CLP-induced tubular damage and reversed CLP-induced reduction of intrarenal microvascular perfusion and renal tubular hypoxia at 24 h. Simvastatin also restored towards normal CLP-induced renal vascular protein leak and serum TNF-alpha. Neither delayed simvastatin therapy nor TNF-alpha neutralizing antibody improved CLP-induced AKI. Simvastatin improved sepsis-induced AKI by direct effects on the renal vasculature, reversal of tubular hypoxia, and had a systemic anti-inflammatory effect.

Figure 1. Effect of simvastatin on survival after CLP

Aged mice were subjected to CLP. Simvastatin (40mg/kg) or vehicle was administered for 3 days before CLP. Open circles indicate CLP group (N=19). Closed circles indicate Statin+CLP group (N=19). (P < 0.05)

Figure 2. Effect of simvastatin on renal function following surgery

Mice were treated as in Figure 1. Mice were sacrified at indicated times for measurement of serum BUN (A) and creatinine by HPLC method (B). Closed circles indicate CLP group. Open circles indicate Statin+CLP group. Closed squares indicate Sham group. Values are mean ± SE (N= 6∼16 per group). #, P < 0.05 vs. CLP. ##, P < 0.05 vs. Sham.

Figure 3. Effect of simvastatin on renal histology

Mice were treated as in Figure 1. Mice were sacrified at 24 hrs after surgery. Histology of cortex in Sham group (A, D), CLP group (B, E), Statin+CLP group (C, F), Original magnification: X200 (A, B, C), X400 (D, E, F). (G) The tubular damage score (see Methods section) was measured in the cortex (left panel) and the outer stripe of the outer medulla (OSOM) (right panel). Values are mean ± SE (N=6∼16 per group). #, P < 0.05 vs. CLP. ##, P < 0.05 vs. Sham.

Figure 4. Effect of simvastatin on renal vascular permeability

Mice were treated as in Figure 1. Mice were sacrified at 24 hrs after surgery. Evans blue dye (EBD) leakage in kidney tissue (see Methods) was measured at 6 hrs and 24 hrs following surgery. Values are mean ± SE (N = 4∼6 per group). #, P < 0.05 vs. CLP. ##, P < 0.05 vs. Sham.

Figure 5. Effect of simvastatin on pimonidazole incorporation following surgery

Mice were treated as in Figure 1. Mice were sacrified at 24 hrs after surgery. Histology of the cortex and the OSOM in Sham group (A), CLP group (B), and Statin+CLP group (C). Original magnification, X200. (D) The hypoxic score (see Methods) was measured in the cortex and the OSOM. Values are mean ± SE (N=3∼7 per group). #, P < 0.05 vs. CLP. ##, P < 0.05 vs. Sham.

Figure 6. Effect of simvastatin on renal microvascular perfusion following surgery

Mice were treated as in Figure 1. Mice were sacrified at 24 hrs after surgery. Histology of cortex (A, B, C) and OSOM (D, E, F) in Sham group (A, D), CLP group (B, E), Statin+CLP group (C, F). Original magnification, X400.

Figure 7. Effect of simvastatin on serum TNF-alpha

Mice were treated as in Figure 1. Mice were sacrified at 24 hrs after surgery. Values are mean ± SE (N= 9 per group). #P < 0.05 vs. CLP.

Figure 8. Effect of TNF-alpha neutralizing antibody on renal function following CLP surgery

TNF-alpha neutralizing antibody or normal mouse IgG was administered at a dose of 800 ug/kg BW immediately after CLP. Mice were sacrified at 24 hrs after CLP for measurement of serum BUN (A) and creatinine by HPLC method (B). Values are mean ± SE (N=5∼16 per group). #, P < 0.05 vs. sham.