Dysregulation of Mitochondrial Dynamics and the Muscle Transcriptome in ICU Patients Suffering from Sepsis Induced Multiple Organ Failure

BACKGROUND: Septic patients treated in the intensive care unit (ICU) often develop multiple organ failure including persistent skeletal muscle dysfunction which results in the patient's protracted recovery process. We have demonstrated that muscle mitochondrial enzyme activities are impaired in septic ICU patients impairing cellular energy balance, which will interfere with muscle function and metabolism. Here we use detailed phenotyping and genomics to elucidate mechanisms leading to these impairments and the molecular consequences. METHODOLOGY/PRINCIPAL FINDINGS: Utilising biopsy material from seventeen patients and ten age-matched controls we demonstrate that neither mitochondrial in vivo protein synthesis nor expression of mitochondrial genes are compromised. Indeed, there was partial activation of the mitochondrial biogenesis pathway involving NRF2alpha/GABP and its target genes TFAM, TFB1M and TFB2M yet clearly this failed to maintain mitochondrial function. We therefore utilised transcript profiling and pathway analysis of ICU patient skeletal muscle to generate insight into the molecular defects driving loss of muscle function and metabolic homeostasis. Gene ontology analysis of Affymetrix analysis demonstrated substantial loss of muscle specific genes, a global oxidative stress response related to most probably cytokine signalling, altered insulin related signalling and a substantial overlap between patients and muscle wasting/inflammatory animal models. MicroRNA 21 processing appeared defective suggesting that post-transcriptional protein synthesis regulation is altered by disruption of tissue microRNA expression. Finally, we were able to demonstrate that the phenotype of skeletal muscle in ICU patients is not merely one of inactivity, it appears to be an actively remodelling tissue, influenced by several mediators, all of which may be open to manipulation with the aim to improve clinical outcome. CONCLUSIONS/SIGNIFICANCE: This first combined protein and transcriptome based analysis of human skeletal muscle obtained from septic patients demonstrated that losses of mitochondria and muscle mass are accompanied by sustained protein synthesis (anabolic process) while dysregulation of transcription programmes appears to fail to compensate for increased damage and proteolysis. Our analysis identified both validated and novel clinically tractable targets to manipulate these failing processes and pursuit of these could lead to new potential treatments

Mitochondrial genoma involvement in ischemia/reperfusion-induced adaptive changes in human myocardial cell

Aim. Following previous studies on the ischemia-induced adaptive changes in human cardiac mitochondria, we examined in the present paper die interaction between nitric oxide-induced (NO) partial inhibition of Cyt. c oxidase (CyLOX) and mitochondrial encoded subunit 2 expression. Aim of the study was to investigate specific stages of the biochemical and molecular cascade which takes place in cytoprotective mechanisms of ischemic and reperfused cardiac cell. Methods. We examined human left ventricle samples obtained from 20 patients undergoing elective valve surgery before aortic cross-clamping, 20 +/- 2 min (prolonged ischemia), 58 +/- 5 min after cross-clamping (intermittent ischemia) and 21 +/- 4 min after reconstitution of coronary blood flow (reperfusion). Cyt.OX activity was determined by spectrophotometric method and adenosine triphosphate (ATP) content using bioluminescent assay. Malondialdehyde (MDA) assumed as reactive oxygen species (ROS) generation marker was determined by high-performance liquid chromatography method. on the same cardiac samples mitochondrial encoded Cyt.OX subunit 2 expression was examined by immunoblot analysis and blu native gel clectrophoresis method. Statistical study of obtained data was performed using repeated measures analysis of variance (ANOVA). Results. Prolonged as well intermittent ischemia caused reduction of Cyt.OX activity and ATP, a moderate accumulation of ROS and down-regulation of Cyt.OX subunit 2. When reperfused the cardiomyocytes showed a progressive increase of Cyt.OX activity, ATP pools and Cyt.OX subunit 2 expression. ROS generation was significantly increased by the rapid oxygen re-immission in the cardiac cell. Conclusion. These data confirm the suggestion that prolonged as well as intermittent ischemia induces activation of cytoprotective mechanisms crucial for cardiac cell survival. indeed, co-ordinated down-regulation of Cyt.OX activities, ATP pools and mitochondrial encoded Cyt.OX subunit 2 are in favour of an ischemia-activated,adaptive mechanism leading to transient and reversible oxidative injury. This observation is confirmed by reduction of apoptosis molecular markers and by complete recovery of mitochondrial oxidative activities in reperfused cardiac tissue