Renal temperature reduction progressively favors mitochondrial ROS production over respiration in hypothermic kidney preservation

Abstract

Background Hypothermia, leading to mitochondrial inhibition, is widely used to reduce ischemic injury during kidney preservation. However, the exact effect of hypothermic kidney preservation on mitochondrial function remains unclear. Methods We evaluated mitochondrial function [i.e. oxygen consumption and production of reactive oxygen species (ROS)] in different models (porcine kidney perfusion, isolated kidney mitochondria, and HEK293 cells) at temperatures ranging 7–37 °C. Results Lowering temperature in perfused kidneys and isolated mitochondria resulted in a rapid decrease in oxygen consumption (65% at 27 °C versus 20% at 7 °C compared to normothermic). Decreased oxygen consumption at lower temperatures was accompanied by a reduction in mitochondrial ROS production, albeit markedly less pronounced and amounting only 50% of normothermic values at 7 °C. Consequently, malondialdehyde (a marker of ROS-induced lipid peroxidation) accumulated in cold stored kidneys. Similarly, low temperature incubation of kidney cells increased lipid peroxidation, which is due to a loss of ROS scavenging in the cold. Conclusions Lowering of temperature highly affects mitochondrial function, resulting in a progressive discrepancy between the lowering of mitochondrial respiration and their production of ROS, explaining the deleterious effects of hypothermia in transplantation procedures. These results highlight the necessity to develop novel strategies to decrease the formation of ROS during hypothermic organ preservation. Electronic supplementary material The online version of this article (10.1186/s12967-019-2013-1) contains supplementary material, which is available to authorized users.

Hibernator-Derived Cells Show Superior Protection and Survival in Hypothermia Compared to Non-Hibernator Cells

“…Although a mild hypothermia can be protective in stress conditions such as hypoxia [26], deep hypothermia is a strong stress model [17,23,27]. Interestingly, all cell types survived a relatively shorter cooling time of 6h.…”

“…Although a mild hypothermia can be protective in stress conditions such as hypoxia [26], deep hypothermia is a strong stress model [17,23,27]. Interestingly, all cell types survived a relatively shorter cooling time of 6 h. However, after 24 h both non-hibernating derived cell lines showed complete cell death, which was preceded by a strong decrease in mitochondrial respiration and a collapse of mitochondrial membrane potential (MMP).…”

“…With similar observations being made in hypothermia, it can be viewed as a special form of IRI. At lower temperature, mitochondria have been shown to strongly decrease their activity but still produce ROS [23]. This discrepancy in oxygen consumption and ROS formation may result from a mismatch in the activity of the five mitochondrial respiratory complexes; while complex I and II are accepting electrons, complex IV is not able to release them properly, resulting in a loss of mitochondrial ATP production and the production of free radicals.…”

Protection of the transplant kidney during cold perfusion with doxycycline: proteomic analysis in a rat model

“…The preservation of mitochondrial structure and their ability to balance ATP production and consumption in hypothermic conditions is one of the factors that allows hibernating animals to survive the hibernation season. The described phenomenon can be the explanation for their resistance to IRI resembled by repetitive cycles of torpor and arousal during hibernation state [38,39].…”

“…Hendriks et al showed that lowering renal temperature progressively favors mitochondrial ROS production over mitochondrial respiration in human kidney cells [39]. Interestingly, renal cells of hibernating animal (hamster) undergoing hypothermia and rewarming showed not only the maintenance of ATP production and a proper mitochondrial network structure, but also no increase in ROS [37].…”