Background:The role of endothelial nitric oxide synthase (eNOS) in isoflurane postconditioning (IsoPC)-elicited cardioprotection is poorly understood. The authors addressed this issue using eNOS−/− mice. Methods:In vivo or Langendorff-perfused mouse hearts underwent 30 min of ischemia followed by 2 h of reperfusion in the presence and absence of postconditioning produced with isoflurane 5 min before and 3 min after reperfusion. Ca2+-induced mitochondrial permeability transition (MPT) pore opening was assessed in isolated mitochondria. Echocardiography was used to evaluate ventricular function. Results:Postconditioning with 0.5, 1.0, and 1.5 minimum alveolar concentrations of isoflurane decreased infarct size from 56 ± 10% (n = 10) in control to 48 ± 10%, 41 ± 8% (n = 8, P < 0.05), and 38 ± 10% (n = 8, P < 0.05), respectively, and improved cardiac function in wild-type mice. Improvement in cardiac function by IsoPC was blocked by NG-nitro-l-arginine methyl ester (a nonselective nitric oxide synthase inhibitor) administered either before ischemia or at the onset of reperfusion. Mitochondria isolated from postconditioned hearts required significantly higher in vitro Ca2+ loading than did controls (78 ± 29 &mgr;m vs. 40 ± 25 &mgr;m CaCl2 per milligram of protein, n = 10, P < 0.05) to open the MPT pore. Hearts from eNOS−/− mice displayed no marked differences in infarct size, cardiac function, and sensitivity of MPT pore to Ca2+, compared with wild-type hearts. However, IsoPC failed to alter infarct size, cardiac function, or the amount of Ca2+ necessary to open the MPT pore in mitochondria isolated from the eNOS−/− hearts compared with control hearts. Conclusions:IsoPC protects mouse hearts from reperfusion injury by preventing MPT pore opening in an eNOS-dependent manner. Nitric oxide functions as both a trigger and a mediator of cardioprotection produced by IsoPC.

PURPOSE We recently developed a new method for efficient generation of neural-like cells from mice bone marrow (BM)-derived mesenchymal stem cells (MSC) by exposing MSCs to epigenetic modifiers and a neural stem cell environment. These neurally induced MSCs (NI-MSCs) differentiate into neuronal- and glial-like cells in vitro, release neurotrophic factors NGF and BDNF, survive and integrate after transplantation in intact spinal cord. The aim of this study was to determine whether transplanted NI-MSCs survive, differentiate, and integrate in injured spinal cord (ISC) rats and promote functional recovery. METHODS Twenty rats, half grafted with MSCs and half with NI-MSCs, were used for survival and differentiation studies. Results were analyzed using triple-labeled immunohistochemistry. For motor function studies the 3 group of adult female Sprague Dawley rats received PBS (vehicle), MSCs, or NI-MSCs, respectively. Functional outcome was measured using the BBB scale. RESULTS Results demonstrated gradual improvement of locomotor function in NI-MSC-transplanted rats in comparison to vehicle and non-modified MSC-transplanted animals, with statistically significant differences at 7, 14, and 21 days post transplantation. Immunocytochemical studies revealed poor survival of NI-MSCs within the ISC as early as 3 weeks after transplantation. CONCLUSIONS Thus, there is a correlation between the degree of surviving NI-MSCs and extent of functional recovery.

Background:Cardioprotection by volatile anesthetic-induced preconditioning (APC) involves activation of protein kinase C (PKC). This study investigated the importance of APC-activated PKC in delaying mitochondrial permeability transition pore (mPTP) opening. Methods:Rat ventricular myocytes were exposed to isoflurane in the presence or absence of nonselective PKC inhibitor chelerythrine or isoform-specific inhibitors of PKC-&dgr; (rottlerin) and PKC-ϵ (myristoylated PKC-ϵ V1–2 peptide), and the mPTP opening time was measured by using confocal microscopy. Ca2+-induced mPTP opening was measured in mitochondria isolated from rats exposed to isoflurane in the presence and absence of chelerythrine or in mitochondria directly treated with isoflurane after isolation. Translocation of PKC-ϵ was assessed in APC and control cardiomyocytes by Western blotting. Results:In cardiomyocytes, APC prolonged time necessary to induce mPTP opening (261 ± 26 s APC vs. 216 ± 27 s control; P < 0.05), and chelerythrine abolished this delay to 213 ± 22 s. The effect of isoflurane was also abolished when PKC-ϵ inhibitor was applied (210 ± 22 s) but not in the presence of PKC-&dgr; inhibitor (269 ± 31 s). Western blotting revealed translocation of PKC-ϵ toward mitochondria in APC cells. The Ca2+ concentration required for mPTP opening was significantly higher in mitochondria from APC rats (45 ± 8 &mgr;m · mg−1 control vs. 64 ± 8 &mgr;m · mg−1 APC), and APC effect was reversed with chelerythrine. In contrast, isoflurane did not protect directly treated mitochondria. Conclusion:APC induces delay of mPTP opening through PKC-ϵ–mediated inhibition of mPTP opening, but not through PKC-&dgr;. These results point to the connection between cytosolic and mitochondrial components of cardioprotection by isoflurane.

BACKGROUND: Signal transduction cascade of anesthetic-induced preconditioning has been extensively studied, yet many aspects of it remain unsolved. Here, we investigated the roles of reactive oxygen species (ROS) and mitochondrial uncoupling in cardiomyocyte preconditioning by two modern volatile anesthetics: desflurane and sevoflurane. METHODS: Adult rat ventricular cardiomyocytes were isolated enzymatically. The preconditioning potency of desflurane and sevoflurane was assessed in cell survival experiments by evaluating myocyte protection from the oxidative stress-induced cell death. ROS production and flavoprotein fluorescence, an indicator of flavoprotein oxidation and mitochondrial uncoupling, were monitored in real time by confocal microscopy. The functional aspect of enhanced ROS generation by the anesthetics was assessed in cell survival and confocal experiments using the ROS scavenger Trolox. RESULTS: Preconditioning of cardiomyocytes with desflurane or sevoflurane significantly decreased oxidative stress-induced cell death. That effect coincided with increased ROS production and increased flavoprotein oxidation detected during acute myocyte exposure to the anesthetics. Desflurane induced significantly greater ROS production and flavoprotein oxidation than sevoflurane. ROS scavenging with Trolox abrogated preconditioning potency of anesthetics and attenuated flavoprotein oxidation. CONCLUSION: Preconditioning with desflurane or sevoflurane protects isolated rat cardiomyocytes from oxidative stress-induced cell death. Scavenging of ROS abolishes the preconditioning effect of both anesthetics and attenuates anesthetic-induced mitochondrial uncoupling, suggesting a crucial role for ROS in anesthetic-induced preconditioning and implying that ROS act upstream of mitochondrial uncoupling. Desflurane exhibits greater effect on stimulation of ROS production and mitochondrial uncoupling than sevoflurane.

Painful axotomy decreases KATP channel current (IKATP) in primary afferent neurons. Because cytosolic Ca2+ signaling is depressed in injured dorsal root ganglia (DRG) neurons, we investigated whether Ca2+–calmodulin (CaM)–Ca2+/CaM-dependent kinase II (CaMKII) regulates IKATP in large DRG neurons. Immunohistochemistry identified the presence of KATP channel subunits SUR1, SUR2, and Kir6.2 but not Kir6.1, and pCaMKII in neurofilament 200–positive DRG somata. Single-channel recordings from cell-attached patches revealed that basal and evoked IKATP by ionomycin, a Ca2+ ionophore, is activated by CaMKII. In axotomized neurons from rats made hyperalgesic by spinal nerve ligation (SNL), basal KATP channel activity was decreased, and sensitivity to ionomycin was abolished. Basal and Ca2+-evoked KATP channel activity correlated inversely with the degree of hyperalgesia induced by SNL in the rats from which the neurons were isolated. Inhibition of IKATP by glybenclamide, a selective KATP channel inhibitor, depolarized resting membrane potential (RMP) recorded in perforated whole-cell patches and enhanced neurotransmitter release measured by amperometry. The selective KATP channel opener diazoxide hyperpolarized the RMP and attenuated neurotransmitter release. Axotomized neurons from rats made hyperalgesic by SNL lost sensitivity to the myristoylated form of autocamtide-2-related inhibitory peptide (AIPm), a pseudosubstrate blocker of CaMKII, whereas axotomized neurons from SNL animals that failed to develop hyperalgesia showed normal IKATP inhibition by AIPm. AIPm also depolarized RMP in control neurons via KATP channel inhibition. Unitary current conductance and sensitivity of KATP channels to cytosolic ATP and ligands were preserved even after painful nerve injury, thus providing opportunities for selective therapeutic targeting against neuropathic pain.

Anesthetic preconditioning (APC) protects the heart from ischemia/reperfusion injury. We hypothesized that APC by isoflurane protects the heart by attenuating generation of reactive oxygen species (ROS) that delays opening of mitochondrial permeability transition pore (mPTP) via mild decrease in mitochondrial membrane potential (Δψm). ROS and Δψm were measured in rat cardiomyocytes by real‐time confocal microscopy using TMRE and CM‐H2DCFDA fluorescent dyes, respectively. Opening of mPTP, which initiates cell death, was detected as rapid and complete loss of TMRE fluorescence from mitochondria. APC by isoflurane (0.5 mM) decreased TMRE fluorescence (88±5% of control) and increased flavoprotein fluorescence (109±3% of control), indicating decrease in Δψm and mitochondrial uncoupling, respectively. Low dose of protonophore DNP (100 nM) produced similar effect. Pyruvate (25 μM) increased respiration and reversed mitochondrial depolarization and uncoupling. When exposed to oxidative stress, myocytes with partly decreased Δψm produced less ROS (62±5% of control) and exhibited a delay in mPTP opening (162±7% of control). Increase in Δψm by pyruvate increased production of ROS and shortened the time of mPTP opening. In conclusion, APC protects cardiomyocytes in part via mild decrease in Δψm that attenuates ROS production under stress and leads to the delay in mPTP opening.

We investigated the effects of different ischemia-mimetic factors on intracellular Ca2+ concentration ([Ca2+]i). Ventricular myocytes were isolated from adult Wistar rats, and [Ca2+]i was measured using fluorescent indicator fluo-4 AM by confocal microscopy. Intracellular pH was measured using c5-(and-6)-carboxy SNARF-1 AM, a dual emission pH-sensitive ionophore. Myocytes were exposed to hypoxia, extracellular acidosis (pH(o) 6.8), Na-lactate (10 mM), or to combination of those factors for 25 min. Monitoring of [Ca2+]i using fluo-4 AM fluorescent indicator revealed that [Ca2+]i accumulation increased immediately after exposing the cells to Na-lactate and extracellular acidosis, but not during cell exposure to moderate ischemia. Increase in [Ca2+]i during Na-lactate exposure decreased to control levels at the end of exposure period at extracellular pH 7.4, but not at pH 6.8. When combined, Na-lactate and acidosis had an additive effect on [Ca2+]i increase. After removal of solutions, [Ca2+]i continued to rise only when acidosis, hypoxia, and Na-lactate were applied together. Analysis of intracellular pH revealed that treatment of cells by Na-lactate and acidosis caused intracellular acidification, while short ischemia did not significantly change intracellular pH. Our experiments suggest that increase in [Ca2+]i during short hypoxia does not occur if pH(i) does not fall, while extracellular acidosis is required for sustained rise in [Ca2+]i induced by Na-lactate. Comparing to the effect of Na-lactate, extracellular acidosis induced slower [Ca2+]i elevation, accompanied with slower decrease in intracellular pH. These multiple effects of hypoxia, extracellular acidosis, and Na-lactate are likely to cause [Ca2+]i accumulation after the hypoxic stress.

Isoflurane protects the myocardium from ischemia and reperfusion (I/R) injury via protein kinase C (PKC) signaling pathway. It has been suggested that the mitochondrial permeability transition pore (mPTP) is the end effector of I/R injury, whereas PKC has a protective effect by blocking mPTP opening. Here we investigated whether anesthetic preconditioning (APC) with isoflurane delays mPTP opening and whether the PKC plays a role in isoflurane‐induced delay in mPTP opening. Isoflurane preconditioned rat cardiomyocytes were loaded with fluorescent probe tetramethylrhodamine ethyl ester (TMRE) and subjected to a simulated I/R injury by laser‐induced ROS production. Using the laser‐scanning confocal microscopy, we measured the time to 50% decrease in TMRE fluorescence, which coincides with depolarization of the mitochondria and represents an opening of mPTP. To confirm the role of mPTP, we used cyclosporine A (CsA). The role of PKC was tested using the non‐specific PKC inhibitor chelerythrine (CHEL). APC with isoflurane prolonged the mean depolarization time of the control fluorescence of 216±8 s, to 261±16 s. A similar time delay of 279±22 s was found in cells pretreated with CsA. Isoflurane‐induced delay in an mPTP opening was abrogated to 219±7 s in cells treated with CHEL. In conclusion, our results indicate that APC with isoflurane delays the opening of mPTP in a PKC‐dependent manner.