Buck 2013 Abstract MiP2013

Buck LT(2013) The role of mitochondria in low oxygen signaling in turtle brain. Mitochondr Physiol Network 18.08.

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MiP2013, Book of Abstracts Open Access

Buck LT (2013)

Event: MiPNet18.08_MiP2013

Peter Hochachka lecture

Earth’s changing environment has been a major evolutionary force shaping the diversity of species both in the past and present. In particular, seasonal ice cover in northern latitudes has selected for hypoxia and anoxia tolerance in some species, such as freshwater turtles. At the northern reaches of their range North American western painted turtles spend 4 months or more buried in the mud bottom of ice covered lakes and ponds [1]. This offers a unique opportunity to understand how a vertebrate brain, an organ extremely sensitive to reduced oxygen availability in mammals, can function without oxygen [2]. Through oxidative phosphorylation mitochondria fuel the inherently high energetic demands of brain and in mammals mitochondria also play a key role in injury from hypoxic stress – including loss of calcium homeostasis and production of reactive oxygen species (ROS) leading to apoptosis and necrosis. Hypoxic or anoxic stress does not signal stress in turtle brain but rather protective mechanisms with the onset of anoxia. Indeed our data show that mitochondria play a key role in low oxygen signaling in turtle brain by a reduction in mitochondrial membrane potential and release of a relatively small but significant amount of calcium. The increase in cytosolic calcium signals a phosphatase based mechanism to decrease whole-cell glutamatergic (NMDA and AMPA) excitatory currents in pyramidal neurons. While in stellate neurons anoxia results in a large reduction in mitochondrial ROS production that increases the magnitude of GABAergic inhibitory neurotransmission. The increased GABA activity produces a chloride based shunting current that “arrests” action potentials in pyramidal cells resulting in metabolic depression and neuroprotection.

Labels: MiParea: Comparative MiP;environmental MiP 

Stress:Ischemia-reperfusion, Oxidative stress;RONS  Organism: Reptiles  Tissue;cell: Nervous system  Preparation: Intact cells 

Regulation: Calcium 

MiP2013, S03 

Affiliations, acknowledgements and author contributions

Department of Cell & Systems Biology, University of Toronto, Canada. - Email: [email protected]

References

1. Buck LT, Hochachka PW, Schön A, Gnaiger E (1993) Microcalorimetric measurement of reversible metabolic suppression induced by anoxia in isolated hepatocytes. Am J Physiol Regul Integr Comp Physiol 265: R1014-R1019.
2. Buck LT, Hogg DW, Rodgers-Garlick C, Pamenter ME (2012) Oxygen sensitive synaptic neurotransmission in anoxia-tolerant turtle cerebrocortex. Adv Exp Med Biol 758: 71-79.