The Mitochondria-Targeted Antioxidant Mitoquinone Protects against Cold Storage Injury of Renal Tubular Cells and Rat Kidneys

Abstract

The majority of kidneys used for transplantation are obtained from deceased donors. These kidneys must undergo cold preservation/storage before transplantation to preserve tissue quality and allow time for recipient selection and transport. However, cold storage (CS) can result in tissue injury, kidney discardment, or long-term renal dysfunction after transplantation. We have previously determined mitochondrial superoxide and other downstream oxidants to be important signaling molecules that contribute to CS plus rewarming (RW) injury of rat renal proximal tubular cells. Thus, this study's purpose was to determine whether adding mitoquinone (MitoQ), a mitochondria-targeted antioxidant, to University of Wisconsin (UW) preservation solution could offer protection against CS injury. CS was initiated by placing renal cells or isolated rat kidneys in UW solution alone (4 h at 4°C) or UW solution containing MitoQ or its control compound, decyltriphenylphosphonium bromide (DecylTPP) (1 M in vitro; 100 M ex vivo). Oxidant production, mitochondrial function, cell viability, and alterations in renal morphology were assessed after CS exposure. CS induced a 2-to 3-fold increase in mitochondrial superoxide generation and tyrosine nitration, partial inactivation of mitochondrial complexes, and a significant increase in cell death and/or renal damage. MitoQ treatment decreased oxidant production ϳ2-fold, completely prevented mitochondrial dysfunction, and significantly improved cell viability and/or renal morphology, whereas DecylTPP treatment did not offer any protection. These findings implicate that MitoQ could potentially be of therapeutic use for reducing organ preservation damage and kidney discardment and/or possibly improving renal function after transplantation.

Cold Storage Exacerbates Renal and Mitochondrial Dysfunction Following Transplantation

“…Our laboratory previously showed that CS (4 hr) alone induces altered renal mitochondrial function (reduced respiratory complex I-IV activity, using a spectrophotometric assay and isolated renal mitochondria), leading to renal tubular injury [10]. However, it was not clear if mitochondrial damage extended to post-transplant.…”

“…We previously reported in isolated rat and pig kidneys that CS alone induced significant renal and mitochondrial injury [10,11]. In this study, we evaluated renal function after 4 hr CS combined with transplantation using a syngeneic transplantation model to minimize confounding effects of the host immune system.…”

“…Despite this, the mechanism of how CS negatively impacts overall graft function and survival is not well understood. Many laboratories, including our own, have published that renal CS (in vitro and ex vivo) induces mitochondrial injury, reactive oxygen species (ROS) generation, and cell death [7][8][9][10][11][12]. However, characterization of mitochondrial function after renal CS plus transplantation remains unknown.…”

Mitochondria-Targeted Antioxidants

“…Furthermore, several in vivo studies in rodents have shown that MitoQ 10 administered orally can protect mitochondria from oxidative damage in a number of models of pathology. These include cardiac ischemia/reperfusion (I/R) injury (Adlam et al 2005;Neuzil et al 2007), damage to endothelial cells in vivo by nitroglycerin (Esplugues et al 2006), hypertension (Graham et al 2009), sepsis (Lowes et al 2008;Supinski, Murphy, and Callahan 2009), adriamycin toxicity (Chandran et al 2009), kidney damage in type I diabetes (Chacko et al 2010), MPTP toxicity in the brain (Ghosh et al 2010), cold preservation of kidney for organ transplantation (Mitchell et al 2011), and cocaine toxicity (Vergeade et al 2010). Other antioxidant moieties such as plastoquinone (Skulachev et al 2009) and the nitroxide TEMPOL (Trnka et al 2008) have also proven to be effective protective agents in vivo (Dikalova et al 2010).…”

Maintaining Mitochondrial Morphology in AKI

“…11 Nonspecific antioxidants have proven disappointing as a therapy in AKI, perhaps partly because of the realization that nonmitochondrial ROS have important physiologic signaling roles in the kidney. 12 There has therefore been great interest in the development of antioxidants specifically targeted to the mitochondria; two such agents, mito Q and SkQ1, selectively accumulate in the mitochondrial matrix on account of their positive charge and have shown renoprotective effects in models of cold storage injury 13 and IRI, 14 respectively.…”