Oxygen Reperfusion Damage in an Insect

John R B Lighton,Pablo E Schilman,Marcelo Hermes-Lima

doi:10.1371/journal.pone.0001267

John R B Lighton, Pablo E Schilman + Show 1 more

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https://doi.org/10.1371/journal.pone.0001267

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Abstract

The deleterious effects of anoxia followed by reperfusion with oxygen in higher animals including mammals are well known. A convenient and genetically well characterized small-animal model that exhibits reproducible, quantifiable oxygen reperfusion damage is currently lacking. Here we describe the dynamics of whole-organism metabolic recovery from anoxia in an insect, Drosophila melanogaster, and report that damage caused by oxygen reperfusion can be quantified in a novel but straightforward way. We monitored CO2 emission (an index of mitochondrial activity) and water vapor output (an index of neuromuscular control of the spiracles, which are valves between the outside air and the insect's tracheal system) during entry into, and recovery from, rapid-onset anoxia exposure with durations ranging from 7.5 to 120 minutes. Anoxia caused a brief peak of CO2 output followed by knock-out. Mitochondrial respiration ceased and the spiracle constrictor muscles relaxed, but then re-contracted, presumably powered by anaerobic processes. Reperfusion to sustained normoxia caused a bimodal re-activation of mitochondrial respiration, and in the case of the spiracle constrictor muscles, slow inactivation followed by re-activation. After long anoxia durations, both the bimodality of mitochondrial reactivation and the recovery of spiracular control were impaired. Repeated reperfusion followed by episodes of anoxia depressed mitochondrial respiratory flux rates and damaged the integrity of the spiracular control system in a dose-dependent fashion. This is the first time that physiological evidence of oxygen reperfusion damage has been described in an insect or any invertebrate. We suggest that some of the traditional approaches of insect respiratory biology, such as quantifying respiratory water loss, may facilitate using D. melanogaster as a convenient, well-characterized experimental model for studying the underlying biology and mechanisms of ischemia and reperfusion damage and its possible mitigation.

Highlights

Oxygen is essential for most multicellular life-forms
As Joanisse and Storey state, ‘‘Damage resulting from oxidative stress, defined as any condition where the rate of reactive oxygen species (ROS) production surpasses the ability of antioxidant systems to buffer them, has been demonstrated under numerous conditions
We describe for the first time in any invertebrate animal the effects of anoxia-administered with both single and repeated reperfusions of O2-on metabolic kinetics, and on organismal integrity

Summary

INTRODUCTION

Oxygen is essential for most multicellular life-forms. it can be toxic due to its biotransformation into reactive oxygen species (ROS). To our knowledge, strong physiological evidence for reperfusion damage has yet to be reported in any invertebrate This is surprising because insects in particular are ideal models for studying the whole-organism physiological effects of hypoxia, anoxia and reperfusion. This is because their cells do not depend on a functioning heart and bloodstream for respiratory gas exchange. We describe for the first time in any invertebrate animal the effects of anoxia-administered with both single and repeated reperfusions of O2-on metabolic kinetics (assayed by mitochondrial CO2 output), and on organismal integrity (assayed in this case by water loss rate, which is an index of spiracular control, and of the functional integrity of the neuromuscular and respiratory systems)

RESULTS AND DISCUSSION

METHODS

Procedure