Ischaemic accumulation of succinate controls reperfusion injury through mitochondrial ROS.

Ischaemia-reperfusion injury occurs when the blood supply to an organ is disrupted and then restored, and underlies many disorders, notably heart attack and stroke. While reperfusion of ischaemic tissue is essential for survival, it also initiates oxidative damage, cell death and aberrant immune responses through the generation of mitochondrial reactive oxygen species (ROS). Although mitochondrial ROS production in ischaemia reperfusion is established, it has generally been considered a nonspecific response to reperfusion. Here we develop a comparative in vivo metabolomic analysis, and unexpectedly identify widely conserved metabolic pathways responsible for mitochondrial ROS production during ischaemia reperfusion. We show that selective accumulation of the citric acid cycle intermediate succinate is a universal metabolic signature of ischaemia in a range of tissues and is responsible for mitochondrial ROS production during reperfusion. Ischaemic succinate accumulation arises from reversal of succinate dehydrogenase, which in turn is driven by fumarate overflow from purine nucleotide breakdown and partial reversal of the malate/aspartate shuttle. After reperfusion, the accumulated succinate is rapidly re-oxidized by succinate dehydrogenase, driving extensive ROS generation by reverse electron transport at mitochondrial complex I. Decreasing ischaemic succinate accumulation by pharmacological inhibition is sufficient to ameliorate in vivo ischaemia-reperfusion injury in murine models of heart attack and stroke. Thus, we have identified a conserved metabolic response of tissues to ischaemia and reperfusion that unifies many hitherto unconnected aspects of ischaemia-reperfusion injury. Furthermore, these findings reveal a new pathway for metabolic control of ROS production in vivo, while demonstrating that inhibition of ischaemic succinate accumulation and its oxidation after subsequent reperfusion is a potential therapeutic target to decrease ischaemia-reperfusion injury in a range of pathologies

Determining Litter Mass Loss By the Plant Tagging Approach

The spatial and temporal context in which plant litter decomposes is a critical consideration when selecting methods to study litter decomposition. Some plants, such as emergent macrophytes, do not abscise leaves, and their shoots may remain standing for extended periods, such that plant biomass begins decomposition in an upright aerial position. This chapter describes a method for estimating decomposition rates by using a non-destructive plant tagging approach. Brightly coloured electrical cable ties are used to label individual shoots or leaves and follow them during the course of senescence and decomposition. Tagged shoots are periodically collected and the mass loss rates of leaf blades, sheaths or stems are determined based on declines in either area-specific mass or other morphometric measures used to estimate the initial dry mass of the tagged plant parts. Nutrient and microbial dynamics can also be determined by analyzing periodically collected plant material that had been tagged. Application of the method has provided accurate mass loss data in many situations where the standard litter-bag approach falls short of mimicking the natural sequence of the decomposition process in the field

Cover & Contents

Additional file 2. Install manual for Python environment, Anaconda Python distribution and OpenCV-Python binding