IIBYT   23944
INSTITUTO DE INVESTIGACIONES BIOLOGICAS Y TECNOLOGICAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Evidence for chaos in mitochondrial dynamics.
Autor/es:
JACKELYN M. KEMBRO; SONIA CORTASSA; MIGUEL A. AON
Lugar:
San Diego
Reunión:
Encuentro; Biophysical Society 56th Annual Meeting; 2012
Institución organizadora:
Biophysical Society
Resumen:
The triggering of post-ischemic arrhythmias and heart contractile dysfunction at acute levels of oxidative stress and energetic failure represents a new paradigm in pathophysiology. Mitochondrial network oscillations are able to drive the excitability of the heart cell setting the stage of cardiac fibrillation. Not known is whether chaotic mitochondrial dynamics can give rise to fibrillation, considered as a form of spatio-temporal chaos in electrical activity. Thus, herein we seek for evidence of the existence of mitochondrial chaos. An upgraded computational model of mitochondrial redox-energetics including reactive oxygen species (ROS) production and ROS scavenging in both mitochondrial and cytoplasmic compartments was utilized to search for chaotic dynamics under oxidative stress. Stability analysis of the model showed that mitochondrial oscillations can be observed when the superoxide, O2.−, scavenging capacity is compromised in energized mitochondria. The transition between stable steady states and oscillatory dynamics is characterized by a series of Hopf bifurcations (HB), from which subcritical ones are observed with large positive maximum Lyapunov exponents. This behavior is a signature of sensitivity to initial conditions, a hallmark of chaos. Return plots show that the oscillatory regime comprises large amplitude cycles of membrane potential, NADH, O2.−, and H2O2 with complex wave forms. A three dimensional phase plane plot of mitochondrial ADP, NADH, and O2.− at the subcritical HB shows a strange attractor. The power spectrum of the corresponding time series exhibits a power law distribution, characterized by a broad spectrum of frequencies (spectral exponent = -2.3), while other mitochondrial state variables such as O2.− showed exponential decay. Detrended fluctuation analysis of the time series indicated that the signals do not correspond to colored noise. Taken together our results suggest that mitochondria can exhibit chaotic dynamics under conditions of reduced O2.− scavenging capacity.