cytochrome-c-t and Hypothermia

Mild hypothermia is a robust neuroprotective treatment for stroke. Understanding the mechanisms underlying hypothermia's benefits will lead to more effective treatments to prevent stroke damage. Delta protein kinase C (deltaPKC) is a kinase that has been strongly implicated in executing ischemic damage. We investigated the effects of hypothermia on deltaPKC activation, as determined by its subcellular translocation, proteolytic cleavage, and phosphorylation in a focal cerebral ischemia model. The amount of constitutively activated C-terminal catalytic fragment of deltaPKC (CF-deltaPKC) increased after stroke. Both hypothermia (30 degrees C) and the caspase-3-specific inhibitor, Z-DQMD-FMK, blocked the accumulation of activated deltaPKC in the penumbra. Other hallmarks of deltaPKC activation, its translocation to the mitochondria, and nucleus were observed in the penumbra as early as 10 mins after reperfusion. These events were blocked by hypothermia. Hypothermia also blocked CF-deltaPKC increases in the mitochondria and nuclei. Conversely, a specific deltaPKC activator, psideltaRACK, decreased the neuroprotective effect of hypothermia. Finally, deltaPKC activity may lead to mitochondrial injury and cytochrome c release, as the timing of cytochrome c release corresponded to the time course of deltaPKC translocation. Both cytochrome c release and deltaPKC translocation were blocked by hypothermia. In conclusion, hypothermia protects against ischemic damage in part by suppressing deltaPKC activation after stroke.

Topics: Active Transport, Cell Nucleus; Animals; Brain Ischemia; Caspase Inhibitors; Cell Membrane; Cysteine Proteinase Inhibitors; Cytochromes c; Enzyme Activation; Hypothermia; Isoenzymes; Male; Mitochondria; Phosphorylation; Protein Kinase C-delta; Rats; Rats, Sprague-Dawley; Receptors for Activated C Kinase; Receptors, Cell Surface

Although hypothermia is an effective treatment for perinatal cerebral hypoxic-ischemic (HI) injury, it remains unclear how long and how deep we need to maintain hypothermia to obtain maximum neuroprotection. We examined effects of prolonged hypothermia on HI immature rat brain and its protective mechanisms using the Rice-Vannucci model. Immediately after the end of hypoxic exposure, the pups divided into a hypothermia group (30 degrees C) and a normothermia one (37 degrees C). Rectal temperature was maintained until they were sacrificed at each time point before 72h post HI. Prolonged hypothermia significantly reduced macroscopic brain injury compared with normothermia group. Quantitative analysis of cell death using H&E-stained sections revealed the number of both apoptotic and necrotic cells was significantly reduced by hypothermia after 24h post HI. Hypothermia seemed to decrease the number of TUNEL-positive cells. Immunohistochemistry and Western blot showed that prolonged hypothermia suppressed cytochrome c release from mitochondria to cytosol and activation of both caspase-3 and calpain in cortex, hippocampus, thalamus and striatum throughout the experiment. These results showed that prolonged hypothermia significantly reduced neonatal brain injury even when it was started after HI insult. Our results suggest that prolonged hypothermia protects neonatal brain after HI by reducing both apoptosis and necrosis.

Topics: Animals; Animals, Newborn; Apoptosis; Body Temperature; Brain; Carrier Proteins; Caspase 3; Caspases; Cytochromes c; Humans; Hypothermia; Hypoxia-Ischemia, Brain; In Situ Nick-End Labeling; Infant; Microfilament Proteins; Necrosis; Rats; Rats, Wistar; Time Factors

Topics: Cytochromes; Cytochromes c; Electrocardiography; Heart; Humans; Hypothermia

Topics: Adenosine Triphosphate; Animals; Body Temperature; Cardiac Surgical Procedures; Cytochromes; Cytochromes c; Haplorhini; Hypothermia; Resuscitation; Thoracic Surgery