General anesthetics are widely used in clinical practice. On the molecular level, these compounds have been shown to modulate the activity of various neuronal ion channels. However, the functional relevance of identified sites in mediating essential components of the general anesthetic state, such as immobility and hypnosis, is still unknown. Using gene-targeting technology, we generated mice harboring a subtle point mutation (N265M) in the second transmembrane region of the beta3 subunit of the GABA(A) receptor. In these mice, the suppression of noxious-evoked movements in response to the intravenous anesthetics etomidate and propofol is completely abolished, while only slightly decreased with the volatile anesthetics enflurane and halothane. beta3(N265M) mice also display a profound reduction in the loss of righting reflex duration in response to intravenous but not volatile anesthetics. In addition, electrophysiological recordings revealed that anesthetic agents were significantly less effective in enhancing GABA(A) receptor-mediated currents, and in decreasing spontaneous action potential firing in cortical brain slices derived from mutant mice. Taken together, our results demonstrate that a single molecular target, and indeed a specific residue (N265) located within the GABA(A) receptor beta3 subunit, is a major determinant of behavioral responses evoked by the intravenous anesthetics etomidate and propofol, whereas volatile anesthetics appear to act via a broader spectrum of molecular targets.

Sevoflurane preconditioning preserves myocardial and renal function as assessed by biochemical markers in patients undergoing coronary artery bypass graft surgery under cardioplegic arrest. This study demonstrated for the first time translocation of protein kinase C isoforms delta and epsilon in human myocardium in response to sevoflurane.

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The high energy demands of the heart are primarily met by the mitochondrial oxidation of fatty acids and carbohydrates (glucose and lactate). 1 The amount of ATP produced depends on overall mitochondrial oxidative capacity, oxygen supply to the myocardium, and the supply of substrates for oxidative metabolism.1 In hypertrophy and HF, a decrease in high-energy phosphates in the heart has been observed. 5,6 However, it is not clear whether this is attributable entirely to a decrease in mitochondrial oxidative capacity, a switch in energy substrate preference, or a less efficient use of energy. The question also arises as to whether these metabolic changes are a consequence of HF, per se, or whether they are an early event that may contribute to the development and progression of HF.Glucose use in the heart is highly dependent on insulin, and any decrease in responsiveness of the heart to insulin can create a state of cardiac insulin-resistance.7 Insulin facilitates glucose entry by inducing the translocation of glucose transporter 4 (GLUT4) from intracellular storage vesicles to the sarcolemmal membrane.8 Decreasing GLUT4 availability exacerbates Background-Cardiac hypertrophy is accompanied by significant alterations in energy metabolism. Whether these changes in energy metabolism precede and contribute to the development of heart failure in the hypertrophied heart is not clear. Methods and Results-Mice were subjected to cardiac hypertrophy secondary to pressure-overload as a result of an abdominal aortic constriction (AAC). The rates of energy substrate metabolism were assessed in isolated working hearts obtained 1, 2, and 3 weeks after AAC. Mice subjected to AAC demonstrated a progressive development of cardiac hypertrophy. In vivo assessment of cardiac function (via echocardiography) demonstrated diastolic dysfunction by 2 weeks (20% increase in E/E′), and systolic dysfunction by 3 weeks (16% decrease in % ejection fraction). Marked cardiac insulin-resistance by 2 weeks post-AAC was evidenced by a significant decrease in insulin-stimulated rates of glycolysis and glucose oxidation, and plasma membrane translocation of glucose transporter 4. Overall ATP production rates were decreased at 2 and 3 weeks post-AAC (by 37% and 47%, respectively) because of a reduction in mitochondrial oxidation of glucose, lactate, and fatty acids that was not accompanied by an increase in myocardial glycolysis rates. Reduced mitochondrial complex V activity was evident at 3 weeks post-AAC, concomitant with a reduction in the ratio of phosphocreatine to ATP. Conclusions-The development of cardiac insulin-resistance and decreased mitochondrial oxidative metabolism are early metabolic changes in the development of cardiac hypertrophy, which create an energy deficit that may contribute to the progression from hypertrophy to heart failure.

Cardiac preconditioning represents the most potent and consistently reproducible method of rescuing heart tissue from undergoing irreversible ischaemic damage. Major milestones regarding the elucidation of this phenomenon have been passed in the last two decades. The signalling and amplification cascades from the preconditioning stimulus, be it ischaemic or pharmacological, to the putative end-effectors, including the mechanisms involved in cellular protection, are discussed in this review. Volatile anaesthetics and opioids effectively elicit pharmacological preconditioning. Anaesthetic-induced preconditioning and ischaemic preconditioning share many fundamental steps, including activation of G-protein-coupled receptors, multiple protein kinases and ATP-sensitive potassium channels (K(ATP) channels). Volatile anaesthetics prime the activation of the sarcolemmal and mitochondrial K(ATP) channels, the putative end-effectors of preconditioning, by stimulation of adenosine receptors and subsequent activation of protein kinase C (PKC) and by increased formation of nitric oxide and free oxygen radicals. In the case of desflurane, stimulation of alpha- and beta-adrenergic receptors may also be of importance. Similarly, opioids activate delta- and kappa-opioid receptors, and this also leads to PKC activation. Activated PKC acts as an amplifier of the preconditioning stimulus and stabilizes, by phosphorylation, the open state of the mitochondrial K(ATP) channel (the main end-effector in anaesthetic preconditioning) and the sarcolemmal K(ATP) channel. The opening of K(ATP) channels ultimately elicits cytoprotection by decreasing cytosolic and mitochondrial Ca(2+) overload.

Anesthetic postconditioning by isoflurane effectively protects against reperfusion damage by preventing opening of the mPTP through inhibition of glycogen synthase kinase 3beta.

Using autofluorescence in live cell imaging microscopy and a simulated model of ischemia, the authors present evidence that volatile anesthetics mediate their protection in cardiomyocytes by selectively priming mitoK(ATP) channels through multiple triggering protein kinase C-coupled signaling pathways. These observations provide important new insight into the mechanisms of anesthetic-induced preconditioning.

. Acute toxicity of doxorubicin on isolated perfused heart: response of kinases regulating energy supply. Am J Physiol Heart Circ Physiol 289: H37-H47, 2005. First published March 11, 2005; doi:10.1152/ajpheart.01057.2004 is a widely used and efficient anticancer drug. However, its application is limited by the risk of severe cardiotoxicity. Impairment of cardiac high-energy phosphate homeostasis is an important manifestation of both acute and chronic DXR cardiotoxic action. Using the Langendorff model of the perfused rat heart, we characterized the acute effects of 1-h perfusion with 2 or 20 M DXR on two key kinases in cardiac energy metabolism, creatine kinase (CK) and AMP-activated protein kinase (AMPK), and related them to functional responses of the perfused heart and structural integrity of the contractile apparatus as well as drug accumulation in cardiomyocytes. DXR-induced changes in CK were dependent on the isoenzyme, with a shift in protein levels of cytosolic isoenzymes from muscle-type CK to brain-type CK, and a destabilization of octamers of the mitochondrial isoenzyme (sarcometric mitochondiral CK) accompanied by drug accumulation in mitochondria. Interestingly, DXR rapidly reduced the protein level and phosphorylation of AMPK as well as phosphorylation of its target, acetyl-CoA-carboxylase. AMPK was strongly affected already at 2 M DXR, even before substantial cardiac dysfunction occurred. Impairment of CK isoenzymes was mostly moderate but became significant at 20 M DXR. Only at 2 M DXR did upregulation of brain-type CK compensate for inactivation of other isoenzymes. These results suggest that an impairment of kinase systems regulating cellular energy homeostasis is involved in the development of DXR cardiotoxicity. creatine kinase; adenosine 5Ј-monophosphate-activated protein kinase; anthracyclines; cardiac energetics; cardiotoxicity DOXORUBICIN (DXR) is a widely used and very efficient anticancer drug. However, its administration is limited by the risk of severe cardiotoxicity (31, 41). An important manifestation of DXR cardiotoxicity is an impaired cardiac high-energy phosphate metabolism. Acute and chronic consequences of DXR administration include compromised mitochondrial functions, such as respiration and generation of high-energy phosphates (30) and lowered phosphocreatine-to-creatine (PCr/Cr), PCr-to-ATP (PCr/ATP), and ATP-to-ADP (ATP/ADP) ratios as well as compromised calcium homeostasis (8,29,31). However, the involved molecular mechanisms are not yet entirely understood.The maintenance of stable concentrations of myocardial high-energy phosphates, ATP, and PCr is a fundamental principle in the vertebrate heart. The PCr/ATP ratio is constant across species, as well as within a species, over a wide range of physiological cardiac workloads (12). Different regulatory systems have evolved to control cellular energy production and utilization. A key player of this regulatory network is the concerted action of several kinase systems, in particular, the energy transfer and buffer system of c...