Formoterol restores mitochondrial and renal function after ischemia-reperfusion injury

Abstract

Mitochondrial biogenesis may be an adaptive response necessary for meeting the increased metabolic and energy demands during organ recovery after acute injury, and renal mitochondrial dysfunction has been implicated in the pathogenesis of AKI. We proposed that stimulation of mitochondrial biogenesis 24 hours after ischemia/reperfusion (I/R)-induced AKI, when renal dysfunction is maximal, would accelerate recovery of mitochondrial and renal function in mice. We recently showed that formoterol, a potent, highly specific, and long-acting β2-adrenergic agonist, induces renal mitochondrial biogenesis in naive mice. Animals were subjected to sham or I/R-induced AKI, followed by once-daily intraperitoneal injection with vehicle or formoterol beginning 24 hours after surgery and continuing through 144 hours after surgery. Treatment with formoterol restored renal function, rescued renal tubules from injury, and diminished necrosis after I/R-induced AKI. Concomitantly, formoterol stimulated mitochondrial biogenesis and restored the expression and function of mitochondrial proteins. Taken together, these results provide proof of principle that a novel drug therapy to treat AKI, and potentially other acute organ failures, works by restoring mitochondrial function and accelerating the recovery of renal function after injury has occurred.

Keywords: acute renal failure; ischemia-reperfusion; mitochondria; proximal tubule; renal function; renal tubular epithelial cells.

Figure 1.

Treatment with formoterol restored kidney function and mitigated proximal tubule injury. Mice were subjected to sham or I/R surgery and subsequent treatment with vehicle (Veh) or formoterol (Form). Kidney function was assessed via serum creatinine (A) and tubular injury via KIM-1 immunoblot analysis (B). KIM-1 protein was measured in kidneys from mice 144 hours after injury and quantified by densitometry. Samples were analyzed via one-way ANOVA followed by a Student–Newman–Keuls post hoc test to evaluate differences between groups. Data points are mean±SEM; with bars with different superscripts are significantly different from one another (n=5, P<0.01). GAPDH, glyceraldehyde 3-phosphate dehydrogenase.

Figure 2.

Treatment with formoterol (Form) improved tubule histology. Mice were subjected to sham or I/R surgery, treated with vehicle (Veh) or formoterol 24 hours later, and were euthanized 144 hours after surgery. (A) PAS stain of representative slides of renal cortical tissue (magnification, ×10). (B) Scoring of tubular necrosis. (C) Scoring of interstitial widening. Samples were analyzed via one-way ANOVA followed by a Student–Newman–Keuls post hoc test to evaluate differences between groups. Data points are mean±SEM; bars with different superscripts are significantly different from one another (n=5, P<0.05).

Figure 3.

Formoterol (Form) restored mitochondrial protein expression after I/R-induced AKI. Mice were subjected to sham or I/R surgery and subsequent treatment with vehicle (Veh) or formoterol. Markers for MB were evaluated via immunoblot 144 hours after surgery. Shown are renal cortical lysate PGC-1α (A) and mitochondrial ETC proteins (B) NDUFB8 (middle graph) and COX I (bottom graph). Densitometric semiquantification is shown below the representative blots. Samples were analyzed via one-way ANOVA followed by a Student–Newman–Keuls post hoc test to evaluate differences between groups. Bars with different superscripts are significantly different from one another. Data points are mean±SEM and are relative values compared with control (n=6, P<0.05).

Figure 4.

Formoterol (Form) restored mitochondrial function in the kidney after I/R-induced AKI. Kidneys were excised followed by isolation of mitochondria. Shown are relative state 2 respiration (non-ADP–stimulated respiration) (A) and relative state 3 respiration (ADP-stimulated respiration) (B). These results of respiration are expressed as the mean±SEM and are relative values compared with control. Bars with different superscripts are significantly different from one another (n=7, P< 0.05). Veh, vehicle.