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P T Schumacker

Publications and source records attributed to P T Schumacker.

At least 19 recordsLinked to original sources
PubMed2001

Reactive oxygen species are downstream products of TRAF-mediated signal transduction.

Members of the TNFR (tumor necrosis factor receptor) superfamily are involved in regulating activation and differentiation of cells as well as cell survival and programmed cell death/apoptosis. Multimerization of TNFRs can lead to recruitment of TRAFs (TNFR-associated factors) by the receptors resulting in activation of kinases and transcription factors, such as c-Jun N-terminal kinase and nuclear factor kappaB (NF-kappaB). Signal transduction triggered by TNF-alpha also induces an increase in intracellular reactive oxygen species (ROS). ROS have been suggested to play a role in NF-kappaB activation, which is thought to promote cell survival. However, oxidation of proteins and lipids by ROS can also result in apoptosis. The processes generating intracellular ROS and the mechanism(s) regulating the cellular redox status have not been fully elucidated. We investigated whether TRAFs play a role in controlling intracellular ROS levels. Our results indicate that recruitment of TRAFs to the plasma membrane of human embryonic kidney (HEK) 293 cells is crucial for activation of signaling pathways, which regulate ROS production in mitochondria. TRAF-mediated changes in ROS levels enhanced NF-kappaB activation but were not dependent on NF-kappaB-inducing kinase. Consistent with its anti-apoptotic function, Bcl-x(L) interfered with TRAF-mediated ROS generation but not NF-kappaB activation. Taken together, our results suggest a novel role of TRAFs in signal transduction pathways triggered by TNFR-related proteins, which balance cell survival and apoptosis by regulating the electron transport in mitochondria.

Apoptosis↗
PubMed2001

Model for hypoxic pulmonary vasoconstriction involving mitochondrial oxygen sensing.

We tested whether mitochondria function as the O(2) sensor underlying hypoxic pulmonary vasoconstriction (HPV). In buffer-perfused rat lungs, rotenone, myxothiazol, and diphenyleneiodonium, which inhibit mitochondria in the proximal region of the electron transport chain (ETC), abolished HPV without attenuating the response to U46619. Cyanide and antimycin A inhibit electron transfer in the distal region of the ETC, but they did not abolish HPV. Cultured pulmonary artery (PA) myocytes contract in response to hypoxia or to U46619. The hypoxic response was abolished while the response to U46619 was maintained in mutant (rho(0)) PA myocytes lacking a mitochondrial ETC. To test whether reactive oxygen species (ROS) derived from mitochondria act as signaling agents in HPV, the antioxidants pyrrolidinedithiocarbamate and ebselen and the Cu,Zn superoxide dismutase inhibitor diethyldithiocarbamate were used. These abolished HPV without affecting contraction to U46619, suggesting that ROS act as second messengers. In cultured PA myocytes, oxidation of intracellular 2',7'-dichlorofluorescin diacetate (DCFH) dye increased under 2% O(2), indicating that myocytes increase their generation of H(2)O(2) during hypoxia. This was attenuated by myxothiazol, implicating mitochondria as the source of increased ROS during HPV. These results indicate that mitochondrial ATP is not required for HPV, that mitochondria function as O(2) sensors during hypoxia, and that ROS generated in the proximal region of the ETC act as second messengers in the response.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed2001

Qian-Kun-Nin, a Chinese herbal medicine formulation, attenuates mitochondrial oxidant stress in cardiomyocytes.

Qian-Kun-Nin is a Chinese herbal medicine formulation used for several indications, including the treatment of cardiovascular diseases. This formulation contains herbs which possess antioxidant properties. In this study, Qian-Kun-Nin's ability to confer protection to cardiomyocytes against reactive oxygen species (ROS) generated during mitochondrial electron transport inhibition was tested. The intracellular fluorescent probe 2',7'-dichlorofluorescin diacetate (DCFH-DA, sensitive to H(2)O(2) and hydroxyl radicals) was used to assess intracellular ROS, and propidium iodide (PI) was used to assess viability in cultured chick embryonic cardiomyocytes. Qian-Kun-Nin significantly attenuated oxidation of DCFH in cells exposed to the mitochondrial site III inhibitor, antimycin A, consistent with a decrease in oxidative stress. These attenuated oxidant levels were associated with improved cell survival. After antimycin A exposure, Qian-Kun-Nin decreased cell death from 51. 6+/-3.3% in untreated cells to 27.3+/-3.8% in treated cells at 2 h. We conclude that Qian-Kun-Nin attenuates oxidant stress and protects cells from lethal oxidant damage during mitochondrial electron transport inhibition, and thus its therapeutic potential in treating cardiovascular diseases may relate to its antioxidant properties.

Analysis of Variance↗
PubMed2001

Signal transduction of flumazenil-induced preconditioning in myocytes.

The objective of this study was to examine the role of oxygen radicals, protein kinase C (PKC), and ATP-sensitive K(+) (K(ATP)) channels in mediating flumazenil-produced preconditioning. Chick cardiomyocyte death was quantified using propidium iodide, and oxygen radical generation was assessed using 2',7'-dichlorofluorescin oxidation. Preconditioning was initiated with 10 min of ischemia followed by 10 min of reoxygenation. Alternatively, flumazenil was infused for 10 min and removed 10 min before ischemia. Flumazenil (10 microM) and preconditioning increased oxygen radicals [1,693 +/- 101 (n = 3) and 1,567 +/- 98 (n = 3), respectively, vs. 345 +/- 53 (n = 3) in control] and reduced cell death similarly [22 +/- 3% (n = 5) and 18 +/- 2% (n = 6), respectively, vs. controls 49 +/- 5% (n = 8)]. Protection and increased oxygen radicals by flumazenil were abolished by pretreatment with the antioxidant thiol reductant 2-mercaptopropionyl glycine (800 microM; 52 +/- 10%, n = 6). Specific PKC inhibitors Go-6976 (0.1 microM) and chelerythrine (2 microM), given during ischemia and reoxygenation, blocked flumazenil-produced protection (47 +/- 5%, n = 6). The PKC activator phorbol 12-myristate 13-acetate (0.2 microM), given during ischemia and reoxygenation, reduced cell death similarly to that with flumazenil [17 +/- 4% (n = 6) and 22 +/- 3% (n = 5)]. Finally, 5-hydroxydecanoate (1 mM), a selective mitochondrial K(ATP) channel antagonist given during ischemia and reoxygenation, abolished the protection of flumazenil and phorbol 12-myristate 13-acetate. Thus flumazenil mimics preconditioning to reduce cell death in cardiomyocytes. Oxygen radicals activate mitochondrial K(ATP) channels via PKC during the process.

Animals↗
PubMed2000

Reactive oxygen species generated at mitochondrial complex III stabilize hypoxia-inducible factor-1alpha during hypoxia: a mechanism of O2 sensing.

During hypoxia, hypoxia-inducible factor-1alpha (HIF-1alpha) is required for induction of a variety of genes including erythropoietin and vascular endothelial growth factor. Hypoxia increases mitochondrial reactive oxygen species (ROS) generation at Complex III, which causes accumulation of HIF-1alpha protein responsible for initiating expression of a luciferase reporter construct under the control of a hypoxic response element. This response is lost in cells depleted of mitochondrial DNA (rho(0) cells). Overexpression of catalase abolishes hypoxic response element-luciferase expression during hypoxia. Exogenous H(2)O(2) stabilizes HIF-1alpha protein during normoxia and activates luciferase expression in wild-type and rho(0) cells. Isolated mitochondria increase ROS generation during hypoxia, as does the bacterium Paracoccus denitrificans. These findings reveal that mitochondria-derived ROS are both required and sufficient to initiate HIF-1alpha stabilization during hypoxia.

Androstadienes↗
PubMed2000

Redox regulation of p53 during hypoxia.

The transcription factor p53 can induce growth arrest or death in cells. Tumor cells that develop mutations in p53 demonstrate a diminished apoptotic potential, which may contribute to growth and tumor metastasis. Cellular levels of p53 are stabilized during hypoxia. The present study tested the hypothesis that reactive oxygen species (ROS) released from mitochondria regulate the cytosolic redox state and are required for the stabilization of p53 protein levels in response to hypoxia. Our results indicate that hypoxia (1.5% O2) increases mitochondrial ROS generation and increases p53 protein levels in human breast carcinoma MCF-7 cells and in normal human diploid fibroblast IMR-90 cells. MCF-7 cells depleted of their mitochondrial DNA (rho(o) cells) failed to stabilize p53 protein levels during hypoxia. The antioxidant N-acetylcysteine and the Cu/Zn superoxide dismutase inhibitor diethyldithiocarbamic acid abolished the hypoxia-induced increases in ROS and p53 levels. Rotenone, an inhibitor of mitochondrial complex I, and 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate, a mitochondrial anion channel inhibitor, also abolished the increase in ROS signal and p53 levels during hypoxia. The p53-dependent gene p21WAF1/CIP1 was also induced by hypoxia in both MCF-7 and IMR-90 cells without affecting the growth rate of either cell line. In contrast, both cell lines exhibited increases in p21WAF1/CIP1 expression and growth arrest after gamma irradiation. Primary chick cardiac myocytes and murine embryonic fibroblasts also showed an increase in p53 protein levels in response to hypoxia without cell death or growth arrest. These results indicate that mitochondria regulate p53 protein levels during hypoxia through a redox-dependent mechanism involving ROS. Despite p53-induction, hypoxia alone does not cause either growth arrest or cell death.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed2000

Role of oxidants in NF-kappa B activation and TNF-alpha gene transcription induced by hypoxia and endotoxin.

The transcription factor NF-kappa B stimulates the transcription of proinflammatory cytokines including TNF-alpha. LPS (endotoxin) and hypoxia both induce NF-kappa B activation and TNF-alpha gene transcription. Furthermore, hypoxia augments LPS induction of TNF-alpha mRNA. Previous reports have indicated that antioxidants abolish NF-kappa B activation in response to LPS or hypoxia, which suggests that reactive oxygen species (ROS) are involved in NF-kappa B activation. This study tested whether mitochondrial ROS are required for both NF-kappaB activation and the increase in TNF-alpha mRNA levels during hypoxia and LPS. Our results indicate that hypoxia (1.5% O2) stimulates NF-kappa B and TNF-alpha gene transcription and increases ROS generation as measured by the oxidant sensitive dye 2',7'-dichlorofluorescein diacetate in murine macrophage J774.1 cells. The antioxidants N-acetylcysteine and pyrrolidinedithiocarbamic acid abolished the hypoxic activation of NF-kappa B, TNF-alpha gene transcription, and increases in ROS levels. Rotenone, an inhibitor of mitochondrial complex I, abolished the increase in ROS signal, the activation of NF-kappa B, and TNF-alpha gene transcription during hypoxia. LPS stimulated NF-kappa B and TNF-alpha gene transcription but not ROS generation in J774.1 cells. Rotenone, pyrrolidinedithiocarbamic acid, and N-acetylcysteine had no effect on the LPS stimulation of NF-kappa B and TNF-alpha gene transcription, indicating that LPS activates NF-kappa B and TNF-alpha gene transcription through a ROS-independent mechanism. These results indicate that mitochondrial ROS are required for the hypoxic activation of NF-kappa B and TNF-alpha gene transcription, but not for the LPS activation of NF-kappa B.

Animals↗
PubMed2000

Outer mitochondrial membrane permeability can regulate coupled respiration and cell survival.

Coupled cellular respiration requires that ATP and ADP be efficiently exchanged between the cytosol and the mitochondrial matrix. When growth factors are withdrawn from dependent cells, metabolism is disrupted by a defect in ATP/ADP exchange across the mitochondrial membranes. Unexpectedly, we find that this defect results from loss of outer mitochondrial membrane permeability to metabolic anions. This decrease in anion permeability correlates with the changes in conductance properties that accompany closure of the voltage-dependent anion channel (also known as mitochondrial porin). Loss of outer membrane permeability (i) results in the accumulation of stored metabolic energy within the intermembrane space in the form of creatine phosphate, (ii) is prevented by the outer mitochondrial membrane proteins Bcl-x(L) and Bcl-2, and (iii) can be reversed by growth factor readdition. If outer membrane impermeability persists, the disruption of mitochondrial homeostasis culminates in loss of outer mitochondrial membrane integrity, cytochrome c redistribution, and apoptosis. The recognition that outer membrane permeability is regulated under physiological conditions has important implications for the understanding of bioenergetics and cell survival.

Adenosine Diphosphate↗
PubMed2000

Preconditioning in cardiomyocytes protects by attenuating oxidant stress at reperfusion.

Cardiomyocyte death after ischemia/reperfusion correlates with oxidant stress, and antioxidants confer protection in that model. Preconditioning (PC) with hypoxia or adenosine also confers protection, leading us to hypothesize that PC protects by attenuating oxidant generation during subsequent ischemia/reperfusion. Chick cardiomyocytes were preconditioned with 10 minutes of hypoxia or adenosine (100 micromol/L), followed by 1 hour of simulated ischemia and 3 hours of reperfusion. Adenosine PC decreased cell death from 50+/-3% to 18+/-4% and enhanced the return of contractions during reperfusion, as observed previously with hypoxic PC. A transient burst of dichlorofluorescein (sensitive to H2O2 oxidation that was significantly attenuated by PC initiated by hypoxia or adenosine was seen at reperfusion. The protein kinase C (PKC) inhibitor Go-6976 and the mitochondrial ATP-sensitive K(+) (K(ATP)) channel inhibitor 5-hydroxydecanoate each abolished protection and abrogated the PC-induced attenuation of reperfusion oxidant stress. By contrast, when given only at reperfusion, the K(+) channel opener pinacidil or the antioxidants 2-mercaptopropionylglycine and 1,10-phenanthroline decreased oxidant stress at reperfusion and improved survival and return of contractions. Thus, PC protection is associated with an attenuation of the oxidant burst at reperfusion, regardless of the method by which PC is triggered. Loss of PC protection associated with PKC inhibition or K(ATP) channel inhibitors is associated with a restoration of that oxidant stress. These results suggest a mechanism for PC protection and reveal a functional link between PKC activation and K(ATP) channel activation in that pathway.

Animals↗
PubMed2000

TRAF4 deficiency leads to tracheal malformation with resulting alterations in air flow to the lungs.

TRAF4 is one of six identified members of the family of TNFR-associated factors. While the other family members have been found to play important roles in the development and maintenance of a normal immune system, the importance of TRAF4 has remained unclear. To address this issue, we have generated TRAF4-deficient mice. Despite widespread expression of TRAF4 in the developing embryo, as well as in the adult, lack of TRAF4 expression results in a localized, developmental defect of the upper respiratory tract. TRAF4-deficient mice are born with a constricted upper trachea at the site of the tracheal junction with the larynx. This narrowing of the proximal end of the trachea results in respiratory air flow abnormalities and increases rates of pulmonary inflammation. These data demonstrate that TRAF4 is required to regulate the anastomosis of the upper and lower respiratory systems during development.

Animals↗
PubMed2000

Cellular oxygen sensing by mitochondria: old questions, new insight.

Hypoxia elicits a variety of adaptive responses at the tissue level, at the cellular level, and at the molecular level. A physiological response to hypoxia requires the existence of an O(2) sensor coupled to a signal transduction system, which in turn activates the functional response. Although much has been learned about the signaling systems activated by hypoxia, no consensus exists regarding the nature of the underlying O(2) sensor or whether multiple sensors exist. Among previously considered mechanisms, heme proteins have been suggested to undergo allosteric modification in response to O(2) binding or release at different PO(2) levels. Other studies suggest that ion channels may change conductance as a function of PO(2), allowing them to signal the onset of hypoxia. Still other studies suggest that NADPH oxidase may decrease its generation of reactive O(2) species (ROS) during hypoxia. Recent data suggest that mitochondria may function as O(2) sensors by increasing their generation of ROS during hypoxia. These oxidant signals appear to act as second messengers in the adaptive responses to hypoxia in a variety of cell types. Such observations contribute to a growing awareness that mitochondria do more than just generate ATP, in that they initiate signaling cascades involved in adaptive responses to hypoxia and that they participate in the control of cell death pathways.

Animals↗
PubMed1999

Cells depleted of mitochondrial DNA (rho0) yield insight into physiological mechanisms.

A resurgence of interest in mitochondrial physiology has recently developed as a result of new experimental data demonstrating that mitochondria function as important participants in a diverse collection of novel intracellular signaling pathways. Cells depleted of mitochondrial DNA, or rho0 cells, lack critical respiratory chain catalytic subunits that are encoded in the mitochondrial genome. Although rho0 cells contain petit mitochondria, they cannot support normal oxidative phosphorylation and must survive and replicate using ATP derived solely from glycolysis. Without a functional electron transport chain, rho0 cells cannot normally regulate redox potential and their mitochondria appear to be incapable of generating reactive oxygen species. Emerging evidence suggests that these signals are important components in a number of mitochondria-initiated signaling pathways. The present article focuses on how rho0 cells have contributed to an understanding of the role that mitochondria play in distinct physiological pathways involved with apoptosis, glucose-induced insulin secretion, and oxygen sensing.

Animals↗
PubMed1999

Nitric oxide acutely inhibits neuronal energy production. The Committees on Neurobiology and Cell Physiology.

Disruption of mitochondrial respiration has been proposed as an action of nitric oxide (NO) responsible for its toxicity, but the effects of NO on the energetics of intact central neurons have not been reported. We examined the effects of NO on mitochondrial function and energy metabolism in cultured hippocampal neurons. The application of NO from NO donors or from dissolved gas produced a rapid, reversible depolarization of mitochondrial membrane potential, as detected by rhodamine-123 fluorescence. NO also produced a progressive concentration-dependent depletion of cellular ATP over 20 min exposures. The energy depletion produced by higher levels of NO (2 microM or more) was profound and irreversible and proceeded to subsequent neuronal death. In contrast to the effects of NO, mitochondrial protonophores produced complete depolarizations of mitochondrial membrane potential but depleted the neuronal ATP stores only partially. Inhibitors of mitochondrial oxidative phosphorylation (rotenone or 3-nitropropionic acid) or of glycolysis (iodoacetate plus pyruvate) also produced only partial ATP depletion, suggesting that either process alone could partially maintain ATP stores. Only by combining the inhibition of glycolytic energy production with the inhibition of mitochondria could the effects of NO in depleting energy and inducing delayed toxicity be duplicated. These results show that NO has rapid inhibitory actions on mitochondrial metabolism in living neurons. However, the severe ATP-depleting effects of high concentrations of NO are not fully explained by the direct effects on mitochondrial activity alone but must involve the inhibition of glycolysis as well. These inhibitory effects on energy production may contribute to the delayed toxicity of NO in vitro and in ischemic stroke.

Adenosine Triphosphate↗
PubMed1999

Extract from Scutellaria baicalensis Georgi attenuates oxidant stress in cardiomyocytes.

Extract from Scutellaria baicalensis Georgi Attenuates Oxidant Stress in Cardiomyocytes. Journal of Molecular and Cellular Cardiology (1999) 31, 1885-1895. Scutellaria baicalensis Georgi is a Chinese herbal medicine used to treat allergic and inflammatory diseases. The medicinal effects of S. baicalensis root may result, in part, from its constituent flavones reported to have antioxidant properties. Since oxidants play multiple roles in cells, we tested whether S. baicalensis could confer protection in a cardiomyocyte model of ischemia and reperfusion. The intracellular fluorescent probes 2',7'-dichlorofluorescin diacetate (DCFH-DA, sensitive to H(2)O(2) and hydroxyl radicals) and dihydroethidium (DHE, sensitive to superoxide) were used to assess intracellular reactive oxygen species (ROS), and propidium iodide (PI) was used to assess viability in cultured embryonic cardiomyocytes. S. baicalensis extract (SbE) quickly attenuated levels of oxidants generated during transient hypoxia and during exposure to the mitochondrial site III inhibitor antimycin A, as measured by DCFH oxidation or by DHE oxidation. These attenuated oxidant levels were associated with improved survival and function. Cell death after ischemia/reperfusion decreased from 47+/-3 % in untreated to 26+/-2 % in S. baicalensis treated cells (P<0.001). After antimycin A exposure, S. baicalensis decreased cell death from 49+/-6 % in untreated to 23+/-4 % in treated cells. Return of contraction occurred in S. baicalensis-treated cells but was not observed in control cells. Other in vitro studies revealed that baicalein, a major flavone component of SbE can directly scavenge superoxide, hydrogen peroxide, and hydroxyl radicals. Collectively, these findings indicate that SbE and its constituent flavones such as baicalein can attenuate oxidant stress and protect cells from lethal oxidant damage in an ischemia-reperfusion model.

Animals↗
PubMed1999

Bcl-xL prevents cell death following growth factor withdrawal by facilitating mitochondrial ATP/ADP exchange.

Growth factor withdrawal is associated with a metabolic arrest that can result in apoptosis. Cell death is preceded by loss of outer mitochondrial membrane integrity and cytochrome c release. These mitochondrial events appear to follow a relative increase in mitochondrial membrane potential. This change in membrane potential results from the failure of the adenine nucleotide translocator (ANT)/voltage-dependent anion channel (VDAC) complex to maintain ATP/ADP exchange. Bcl-xL expression allows growth factor-deprived cells to maintain sufficient mitochondrial ATP/ADP exchange to sustain coupled respiration. These data demonstrate that mitochondrial adenylate transport is under active regulation. Efficient exchange of ADP for ATP is promoted by Bcl-xL expression permitting oxidative phosphorylation to be regulated by cellular ATP/ADP levels and allowing mitochondria to adapt to changes in metabolic demand.

Adenosine Diphosphate↗
PubMed1999

Generation of superoxide in cardiomyocytes during ischemia before reperfusion.

Although a burst of oxidants has been well described with reperfusion, less is known about the oxidants generated by the highly reduced redox state and low O(2) of ischemia. This study aimed to further identify the species and source of these oxidants. Cardiomyocytes were exposed to 1 h of simulated ischemia while oxidant generation was assessed by intracellular dihydroethidine (DHE) oxidation. Ischemia increased DHE oxidation significantly (0.7 +/- 0.1 to 2.3 +/- 0.3) after 1 h. Myxothiazol (mitochondrial site III inhibitor) attenuated oxidation to 1.3 +/- 0.1, as did the site I inhibitors rotenone (1.0 +/- 0.1), amytal (1.1 +/- 0.1), and the flavoprotein oxidase inhibitor diphenyleneiodonium (0.9 +/- 0.1). By contrast, the site IV inhibitor cyanide, as well as inhibitors of xanthine oxidase (allopurinol), nitric oxide synthase (nitro-L-arginine methyl ester), and NADPH oxidase (apocynin), had no effect. Finally, DHE oxidation increased with Cu- and Zn-containing superoxide dismutase (SOD) inhibition using diethyldithiocarbamate (2.7 +/- 0.1) and decreased with exogenous SOD (1.1 +/- 0.1). We conclude that significant superoxide generation occurs during ischemia before reperfusion from the ubisemiquinone site of the mitochondrial electron transport chain.

Acetophenones↗
PubMed1999

Role of reactive oxygen species in acetylcholine-induced preconditioning in cardiomyocytes.

We examined the ability of ACh to mimic ischemic preconditioning in cardiomyocytes and the role of ATP-sensitive potassium (KATP) channels and mitochondrial reactive oxygen species (ROS) in mediating this effect. Chick embryonic ventricular myocytes were studied in a flow-through chamber while flow rate, pH, PO2, and PCO2 were controlled. Cell viability was quantified with propidium iodide (5 microM), and production of ROS was measured using 2', 7'-dichlorofluorescin diacetate. Data were expressed as means +/- SE. Preconditioning with 10 min of ischemia followed by 10 min of reoxygenation or 10 min of ACh (1 mM) followed by a drug-free period before 1 h of ischemia and 3 h of reoxygenation reduced cell death to the same extent [preconditioning 19 +/- 2% (n = 6, P < 0.05) ACh 21 +/- 5% (n = 6, P < 0.05) vs controls 42 +/- 5% (n = 9)]. Like preconditioning, ACh increased ROS production threefold before ischemia [0.60 +/- 0.16 (n = 7, P < 0.05) vs. controls, 0.16 +/- 0. 03 (n = 6); arbitrary units]. Protection and increased ROS production during ACh preconditioning were abolished with 5-hydroxydecanoate (5-HD, 100 microM), a selective mitochondrial K(ATP) channel antagonist, and the thiol reductant 2-mercaptopropionyl glycine (2-MPG, 1 mM), an antioxidant [cell death: 5-HD+ACh 37 +/- 7% (n = 5), 2-MPG+ACh 47 +/- 6% (n = 6); ROS signals: 5-HD+ACh 0.09 +/- 0.03 (n = 5), 2-MPG+ACh 0.01 +/- 0.04 (n = 4)]. In addition, ACh-induced ROS signaling was blocked by the mitochondrial site III electron transport inhibitor myxothiazol (0.02 +/- 0.07, n = 5). These results demonstrate that activation of mitochondrial K(ATP) channels and increased ROS production from mitochondria are important intracellular signals that participate in ACh-induced preconditioning in cardiomyocytes.

Acetylcholine↗