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R C Kukreja

Publications and source records attributed to R C Kukreja.

At least 19 recordsLinked to original sources
PubMed2001

p38 Triggers late preconditioning elicited by anisomycin in heart: involvement of NF-kappaB and iNOS.

We investigated the role of stress-activated p38 MAP kinase (p38/SAPK-2) signaling in delayed preconditioning of the heart. Adult male out-bred ICR mice were treated with p38 activator, anisomycin (0.1 mg/kg IP), or vehicle (5% DMSO). Twenty-four hours later, hearts were perfused in Langendorff mode and subjected to 30 minutes of ischemia and 30 minutes of reperfusion. Improvement in postischemic recovery of end-diastolic pressure and reduction in infarct size was observed, which was abolished by SB203580, a specific p38 inhibitor, and pyrrolidinediethyldithiocarbamate (PDTC), the NF-kappaB inhibitor, but not by PD 98059, a specific inhibitor for MEK1 or 2. Transient increase in p38 phosphorylation was observed 15 minutes after anisomycin treatment which subsided by 30 minutes. Electrophoretic mobility shift assay demonstrated rapid activation of NF-kappaB DNA binding with anisomycin, peaking at 30 minutes. Western blot confirmed the accumulation of p50 and p65 in nuclear extracts after anisomycin treatment. Anisomycin-induced NF-kappaB DNA binding activity was inhibited by SB203580 and PDTC. Expression of inducible nitric oxide synthase (iNOS) mRNA, protein, and nitric oxide (NO) synthesis were enhanced in anisomycin-treated mice. SB203580 and PDTC blocked the increased expression of iNOS and increase in synthesis of NO. Selective iNOS inhibitor S-methylisothiourea abolished the protective effect of anisomycin. Furthermore, postischemic cardioprotective effect of anisomycin was absent in mice with targeted ablation of iNOS gene but not in the wild-type B6.129 mice. For the first time, these results suggest that direct pharmacological activation of p38 triggers delayed preconditioning by signaling mechanism involving NF-kappaB activation and synthesis of NO from iNOS.

Animals↗
PubMed2001

Gene transfer of heat-shock protein 70 reduces infarct size in vivo after ischemia/reperfusion in the rabbit heart.

BACKGROUND: Heat-shock protein 70 (HSP 70) plays a role in myocardial protection. No studies are available, however, to show that direct gene transfer of HSP 70 reduces myocardial infarction in vivo. METHODS AND RESULTS: Rabbit hearts were injected with vehicle or Ad.HSP70 at 3 sites (1.5x10(9) pfu, 50 microL/site) in the left ventricle (LV). Four days later, hearts were removed, and expression of inducible (HSP 70) and constitutive (HSC 70) proteins was measured in the LV and right ventricle (RV). Subsets of 5 to 7 animals in the vehicle-, Ad.lacZ-, and Ad.HSP70-treated groups were subjected to 30 minutes of ischemia and 3 hours of reperfusion. Infarct size was measured by tetrazolium staining. Increased expression of HSP 70 was observed in LV injected with Ad.HSP70 compared with vehicle-treated hearts. HSP 70 was undetectable in RV, the noninjected region of the heart. The expression of HSC 70 remained unchanged in hearts treated with vehicle or Ad.HSP70. Infarct size (% risk area) decreased to 24.5+/-2.8 in Ad.HSP70-injected hearts compared with 41.9+/-2.8 and 42.7+/-2.5 in the vehicle- and Ad.LacZ-treated hearts (P<0.01). The infarct size was not different between the vehicle- and Ad.LacZ-treated hearts (P>0.05). The risk areas (% of LV) were not different among the 3 groups, ie, 50.1+/-5.2, 47.7+/-3.5, and 53.3+/-2.9 in vehicle-, Ad.lacZ-, and Ad.HSP70-treated groups (P>0.05). CONCLUSIONS: Direct gene delivery of HSP 70 in vivo reduces the severity of ischemic injury in the heart.

Adenoviridae↗
PubMed2001

Bradykinin B2 receptor is involved in the late phase of preconditioning in rabbit heart.

Activation of bradykinin B2 receptor has been shown to confer short-term cardioprotection against a prolonged ischemic insult. The present study was designed to delineate the role of B2 receptor in the late phase of ischemic preconditioning. Anesthetized, open chest, male rabbits were assigned to 1 of 6 groups (n=8/group). Ischemic preconditioning was elicited by four 5-min occlusion periods interspersed with 10 min of reperfusion. To test the role of B2 receptors, rabbits were pretreated with specific receptor antagonist, HOE-140 (1 microgm/kg IV bolus), 15 min prior to ischemic preconditioning. Additionally, two separate groups of animals were treated by intra-atrial infusion with either bradykinin (0.05 microg/kg/min for 15 min) or saline. Twenty-four hours later, the animals were subjected to 30 min of ischemia and 3 h of reperfusion. Infarct size was determined by tetrazolium staining. Ischemic preconditioning reduced infarct size from 43.09+/-4.66 to 20.65+/-1.87 (% risk area, P<0.05), which was blocked by HOE-140 as indicated by increase in infarct size (36.72+/-4.04%, P<0.05). HOE-140 treatment had no significant effect on infarct size in the sham group. Similarly, intra-atrial infusion of bradykinin caused decrease in the infarct size from 52.36+/-2.17% in the saline control group to 22.83+/-1.71% (P<0.05). The degree of infarct limitation with bradykinin was comparable to ischemic preconditioning (20.65+/-1.87%v 22.83+/-1.71%, P>0.05). For the first time, these results provide evidence for the involvement of B2 receptor in the genesis of late phase of ischemic preconditioning.

Animals↗
PubMed2001

Adenosine-induced late preconditioning in mouse hearts: role of p38 MAP kinase and mitochondrial K(ATP) channels.

We investigated the role of p38 mitogen-activated protein kinase (MAPK) phosphorylation and opening of the mitochondrial ATP-sensitive K(+) [(K(ATP))(mito)] channel in the adenosine A(1) receptor (A(1)AR)-induced delayed cardioprotective effect in the mouse heart. Adult male mice were treated with vehicle (5% DMSO) or the A(1)AR agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA; 0.1 mg/kg ip). Twenty-four hours later, hearts were subjected to 30 min of global ischemia and 30 min of reperfusion in the Langendorff mode. Genistein or SB-203580 (1 mg/kg i.p.) given 30 min before CCPA treatment was used to block receptor tyrosine kinase or p38 MAPK phosphorylation, respectively. 5-Hydroxydecanoate (5-HD; 200 microM) was used to block (K(ATP))(mito) channels. CCPA produced marked improvement in left ventricular function, which was partially blocked by SB-203580 and 5-HD and completely abolished with genistein. CCPA caused a reduction in infarct size (12.0 +/- 2.0 vs. 30.3 +/- 3.0% in vehicle), which was blocked by genistein (29.4 +/- 2.3%), SB-203580 (28.3 +/- 2.6%), and 5-HD (33.9 +/- 2.4%). CCPA treatment also caused increased phosphorylation of p38 MAPK during ischemia, which was blocked by genistein, SB-203580, and 5-HD. The results suggest that A(1)AR-triggered delayed cardioprotection is mediated by p38 MAPK phosphorylation. Blockade of cardioprotection with 5-HD concomitant with decrease in p38 MAPK phosphorylation suggests a potential role of (K(ATP))(mito) channel opening in phosphorylation and ensuing the late preconditioning effect of A(1)AR.

Adenosine↗
PubMed2001

Chemical preconditioning with 3-nitropropionic acid in hearts: role of mitochondrial K(ATP) channel.

We investigated the cardioprotective effect of 3-nitropropionic acid (3-NPA), an inhibitior of mitochondrial succinate dehydrogenase, and we wanted to show whether this protection is mediated by of opening mitochondrial ATP-sensitive potassium (K(ATP)) channels. Adult rabbits were treated with either 3-NPA (3 mg/kg iv) or saline (n = 6 rabbits/group). After 30 min (for early phase) or 24 h (for late phase) of the treatment, the animals were subjected to 30 min of ischemia and 3 h of reperfusion (ischemia-reperfusion). 5-Hydroxydecanoate (5-HD, 5 mg/kg iv),the mitochondrial K(ATP) channel blocker, was administered 10 min before ischemia-reperfusion in the saline- and 3-NPA-treated rabbits. 3-NPA caused a decrease in the infarct size from 27.8 +/- 4.2% in the saline group to 16.5 +/- 1.0% in the 3-NPA-treated rabbits during early phase and from 30.4 +/- 4.2% in the saline group to 17.6 +/- 1.05 in the 3-NPA group during delayed phase (P < 0.05, % of risk area). The anti-infarct effect of 3-NPA was blocked by 5-HD as shown by an increase in infarct size to 33 +/- 2.7% (early phase) and 31 +/- 2.4% (delayed phase) (P < 0.05 vs. 3-NPA groups). 5-HD had no proischemic effect in control animals. Also, 3-NPA had no effect on systemic hemodynamics. We conclude that 3-NPA induces long-lasting anti-ischemic effects via opening of mitochondrial K(ATP) channels.

Adenosine Triphosphate↗
PubMed2001

Mitogen-activated protein kinases mediate heat shock-induced delayed protection in mouse heart.

We determined the role of p38 mitogen-activated protein kinase (MAPK), 72-kDa heat shock protein (HSP72), and antioxidant enzymes in whole body heat stress (HS)-induced cardioprotection in mouse hearts. Adult male mice were treated with either HS or anesthesia only. At 0.5, 48, 72, or 120 h later, the hearts were subjected to 20 min of global ischemia and 30 min of reperfusion in Langendorff mode. A significant protection against ischemia-reperfusion injury was observed 48 h after HS as demonstrated by: 1) reduction in infarct size; 2) decrease in leakage of lactate dehydrogenase; and 3) enhanced postischemic ventricular contractile function. No such protection was observed at other post-HS time points. HS caused an ~25% increase in phosphorylated c-Jun NH2-terminal kinase (JNK) but not p38 MAPK in the heart during the first 2-h post-HS time period. Cardioprotection was abolished by the MAPK inhibitor SB-203580, which also partially suppressed the HS-induced JNK phosphorylation. The protective effect was associated with a two- to threefold increase in HSP72 protein accumulation, but not antioxidant enzyme activities (catalase and Cu/Zn and Mn SOD) in the myocardium. Although HSP72 levels remained high 72 h after HS, the cardioprotection had already disappeared. We conclude that HS induces a transient delayed cardioprotection at 48 h after thermal stress in mice which appears to be mediated via a MAPK-signaling pathway.

Animals↗
PubMed2000

Pivotal role of nitric oxide in delayed pharmacological preconditioning against myocardial infarction.

The phenomenon of 'ischemic preconditioning' (IP) has been vigorously investigated during the past 15 years. As our knowledge on the possible protective mechanisms of IP has been increasingly expanded, novel approaches based on preconditioning with pharmacological agents have recently emerged. Two drugs have been used to induce delayed preconditioning against myocardial infarction caused by ischemia/reperfusion. One of the drugs was monophosphoryl lipid A (MLA)--a detoxified derivative of lipopolysaccharide from gram-negative strains; and another drug was RC552--a novel synthetic glycolipid that mimics the chemical structure of MLA. We have shown that pretreatment of adult mice with MLA or RC552 (350 microg/kg) 24 h prior to the global ischemia and reperfusion in the isolated perfused heart attenuated myocardial injury. Infarct size was significantly reduced in MLA or RC552-treated groups as compared with the vehicle-treated group. The delayed cardioprotection was associated with a moderate but significant increase of nitric oxide level in the ischemic myocardium. Treatment with S-methylisothiourea (3 mg/kg), a selective inhibitor of inducible nitric oxide synthase (iNOS) abolished MLA or RC552-induced delayed protection. In addition, neither MLA nor RC552 reduced infarct size in iNOS knockout mice. Our findings suggest that both MLA and RC552 are able to induce delayed myocardial preconditioning via iNOS-dependent pathway.

Adjuvants, Immunologic↗
PubMed2000

Inducible nitric oxide synthase mediates delayed myocardial protection induced by activation of adenosine A(1) receptors: evidence from gene-knockout mice.

BACKGROUND: The mechanism of delayed preconditioning induced by activation of adenosine A(1) receptors (A(1)ARs) is not fully understood. We determined the role of inducible nitric oxide synthase (iNOS) in mediating adenosine-induced late cardioprotection using pharmacological inhibitors and iNOS gene-knockout mice. METHODS AND RESULTS: Adult male mice were treated with saline or an A(1)AR agonist, 2-chloro-N(6)-cyclopentyladenosine (CCPA). Twenty-four hours later, the hearts were perfused in Langendorff mode and subjected to 30 minutes of global ischemia followed by 30 minutes of reperfusion. 8-Cyclopentyl-1,3-dipropylxanthine (DPCPX; 0.1 mg/kg IP) and S-methylisothiourea (SMT; 3 mg/kg IP) were used to block A(1)ARs and iNOS, respectively. Infarct size (IS) was measured by triphenyltetrazolium chloride staining, and iNOS expression was measured by Western blots. Myocardial IS was reduced from 24.0+/-3. 2% in the saline group to 12.2+/-2.5% in CCPA-treated mice (P<0.05). The infarct-reducing effect of CCPA was abrogated by DPCPX (29.3+/-3. 4%) and SMT (32.3+/-2.6%) and was absent in mice with targeted ablation of iNOS (23.9+/-1.6%). CCPA produced improvement in postischemic end-diastolic pressure, developed pressure, and rate-pressure product, which was also blocked by DPCPX and SMT. Increased iNOS protein expression observed in CCPA-treated hearts was diminished by DPCPX. CONCLUSIONS: Selective activation of A(1)ARs produces delayed cardioprotection against ischemia/reperfusion injury in the mouse. Increased iNOS expression concomitant with the lack of protective effect of A(1)AR activation in iNOS gene-knockout mice suggests a direct cause-and-effect relationship of iNOS in adenosine-induced late cardioprotection.

Adenosine↗
PubMed2000

Tyrosine kinase signaling in action potential shortening and expression of HSP72 in late preconditioning.

We investigated the role of tyrosine kinase (TK) signaling in the opening of the ATP-sensitive K(+) (K(ATP)) channel and 72-kDa heat shock protein (HSP72) expression during late preconditioning. Rabbits were subjected to surgical operation (sham) or were preconditioned (PC) with four cycles of 5 min of ischemia and 10 min of reperfusion. Twenty-four hours later, animals were subjected to 30 min of ischemia and 180 min of reperfusion. Genistein (1 mg/kg ip) was used to block the receptor TK. Six groups were studied: control, sham, genistein-sham, PC, genistein-PC, and vehicle-PC group (1% dimethyl sulfoxide). Genistein or vehicle was given 30 min before the surgical procedure. Genistein pretreatment decreased the expression of HSP72 in PC hearts and suppressed action potential duration shortening during ischemia in sham and PC groups. Infarct size (%risk area) was reduced in the PC (11.6 +/- 1.0%) and vehicle-PC (19.3 +/- 2.0%) compared with the control (40.0 +/- 3.8%) or sham (46.0 +/- 2.0%) groups (P < 0.05). Genistein pretreatment increased infarct size to 46.4 +/- 4.1% in the PC hearts. We conclude that TK signaling is involved in K(ATP) channel opening and HSP72 expression during late PC.

Action Potentials↗
PubMed1999

Role of KATP channel in heat shock and pharmacological preconditioning.

Heat shock (HS) and 4-monophosphoryl lipid A (MLA, a non-toxic analogue of endotoxin) protects the myocardium against ischemia-reperfusion injury. We studied the involvement of ATP-sensitive potassium channel (KATP channel) in ischemic protection induced by these stimuli. Anesthetized rabbits were preconditioned with either HS (by raising temperature to 42 degrees C for 15 min) or intravenous pretreatment with MLA (35 micrograms/kg). After 24 h, animals were re-anesthetized and subjected to 30-min regional ischemia followed by 180-min reperfusion (I/R). KATP channel blockers glibenclamide and/or 5-hydroxydecanoate (5-HD) were used to inhibit channel function. The 72 kD heat shock protein (HSP-72) was measured by Western blots. HS produced a marked reduction in infarct size (39.4 +/- 8.1% to 14.3 +/- 2.5%, p < 0.05) that was abolished by glibenclamide (42.3 +/- 3.2%) and 5-HD (33.7 +/- 4.8%) when given before I/R. These drugs failed to block HS protection when given before HS. Expression of HSP-72 was increased in all HS groups as compared to non-HS groups in both glibenclamide and 5-HD-treated rabbits. Similarly, pretreatment with MLA reduced infarct size from 40 +/- 8.6% to 15.1 +/- 1.5% (p < 0.05). The infarct size increased to 51.9 +/- 5.8 with 5-HD in MLA-treated rabbits. 5-HD did not alter infarct size significantly when given in vehicle-treated control rabbits. These data suggest that HS and MLA exert their anti-ischemic effect through activation of KATP channel.

ATP-Binding Cassette Transporters↗
PubMed1999

Essential role of inducible nitric oxide synthase in monophosphoryl lipid A-induced late cardioprotection: evidence from pharmacological inhibition and gene knockout mice.

BACKGROUND: Monophosphoryl lipid A (MLA), a nontoxic analogue of endotoxin, is a pharmacological agent that is known to have anti-ischemic effects. Mechanisms involved with the cardioprotection are still unclear. A role for inducible nitric oxide synthase (iNOS) was recently proposed. We tested this hypothesis using S-methylisothiourea (SMT), one of the specific pharmacological inhibitors of iNOS, as well as iNOS gene knockout mice. METHODS AND RESULTS: Adult male ICR or B6,129 mice were pretreated with either MLA 35 or 350 microg/kg IP (MLA35 or MLA350) or vehicle 24 hours before global ischemia/reperfusion, which was carried out in a Langendorff isolated perfused heart model (n=8 to 9 per group). Another group of MLA350 mice received SMT 3 mg/kg IP 30 minutes before heart perfusion. Ventricular contractile function and heart rate were not different between the groups during the preischemia and reperfusion periods (P>0.05). Preischemic basal coronary flow was significantly increased in all MLA350 but not MLA35 mice. Myocardial infarct size was reduced significantly, from 26.9+/-2.9% of risk area in vehicle-treated mice to 13.5+/-2.4% in the MLA350 group (mean+/-SEM, P<0.05). This reduction in infarct size was accompanied by augmented nitrite/nitrate accumulation, from 0.23+/-0. 05 nmol/mg protein in the vehicle group to 0.97+/-0.27 nmol/mg protein in MLA350 mice (P<0.01). Infarct size increased significantly, to 22.2+/-2.8% after treatment with SMT in the MLA350 group. Furthermore, MLA350 failed to reduce infarct size in iNOS knockout mice (25.5+/-3.6%). CONCLUSIONS: These results demonstrate a direct association of infarct size reduction with increased NO production with MLA350. An obligatory role for iNOS in mediating the cardioprotective effect induced by MLA was confirmed with the pharmacological inhibition and gene knockout mice.

Animals↗
PubMed1999

Myocardial ischemia/reperfusion injury in the inducible nitric oxide synthase knockout mice.

Inducible nitric oxide synthase (iNOS) plays an important role in the inflammatory process of certain major cardiac disorders including myocardial infarction and allograft rejection. However, the role of iNOS in acute myocardial ischemia has not been well defined. We determined the effects of genetically disruption of the intact iNOS system on cardiac tolerance to ischemia/reperfusion injury. Adult male wild-type (WT) and iNOS knockout (KO) B6,129 mice were subjected to 20 min global ischemia and 30 min reperfusion in a Langendorff isolated perfused heart model (37 degrees C, n = 10/each group). Ventricular contractile function, heart rate, coronary flow, and leakage of intracellular enzymes (CK and LDH) were not significantly different between the groups during pre-ischemia as well as reperfusion period (P > 0.05). Myocardial infarct size was also not significantly different between WT (20.2+/-2.0% of risk area) and KO mice (23.5+/-3.8%; Mean+/-SEM, P > 0.05). However, the post-ischemic heart rate was significantly preserved in KO as compared to WT (P < 0.05). We conclude that disruption of iNOS gene does not exacerbate ischemia/ reperfusion injury in the heart.

Animals↗
PubMed1999

Role of protein kinase C and 72 kDa heat shock protein in ischemic tolerance following heat stress in the rat heart.

Heat stress (HS) and the subsequent expression of 72 kDa heat shock protein (HSP 72) has been shown to enhance post-ischemic functional recovery and reduce infarct size. Because the synthesis of heat shock proteins involves activation of heat shock transcription factors through phosphorylation, we hypothesized that inhibition of protein kinase C (PKC) would block HS mediated protection and expression of HSP 72 in the heart. Five groups of rats were studied (1) Sham anesthetized, (2) HS group--animals were heat shocked by raising the whole body core temperature to 42 degrees C for 15 min, (3) Vehicle group--HS rats treated with 50% DMSO in saline, (4) PKC inhibitor-treated group--specific PKC antagonist, chelerythrine chloride (5 mg/kg, i.p) given 30 min prior to HS and (5) Vehicle treated control--non-HS rats treated with vehicle prior to ischemia/reperfusion. Hearts were subjected to 30 min of regional ischemia and 90 min of reperfusion 24 h after HS. Risk area was delineated by injection of 10% Evan's blue and infarct size determined using computer morphometry of tetrazolium stained sections. Infarct size (% area at risk) reduced significantly from 49.4 +/- 2.3% (n = 7) in sham to 10.0 +/- 2.5% (p < 0.01) and 9.1 +/- 3.0% in HS and vehicle treated HS groups respectively (p < 0.05) Treatment with chelerythrine prior to HS increased infarct size to 49.4 +/- 2.3% (p < 0.05). Infarct size in chelerythrine-treated non-HS ischemic/reperfused heart was 40.7 +/- 5.4%, which did not differ significantly from vehicle-treated sham group. Western blot analysis demonstrated marked increase in HSP 72 in HS groups (with or without vehicle treatment) and pretreatment with chelerythrine chloride failed to inhibit the expression of HSP 72. The results suggest that HS-induced ischemic tolerance is mediated via PKC pathway and this protection does not appear to be directly related to the expression of HSP 72 in rat heart.

Animals↗
PubMed1999

Induction of 72-kDa heat shock protein does not produce second window of ischemic preconditioning in rat heart.

Ischemic preconditioning (PC) induces delayed phase of protection, known as the second window of protection (SWOP). We investigated this phenomenon in rat and correlated it with the expression of 72-kDa heat shock protein (HSP 72). Rats were preconditioned with 1, 2, and 3 cycles of 5-min left anterior descending artery occlusions, each separated by a 10-min reperfusion (PC x 1, PC x 2 and PC x 3, respectively). Another group of rats was preconditioned with heat shock (HS) by raising temperature to 42 degreesC for 15 min. Twenty-four hours later, rats were given sustained ischemia for 30 min and 90 min of reperfusion. Infarct sizes (%risk area) were 40.0 +/- 7.5, 37.6 +/- 5.6, and 47.6 +/- 2.4 (mean +/- SE) for PC x 1, PC x 2, and PC x 3 hearts, respectively, which were not different from the sham (49.9 +/- 3.9, P > 0.05). In contrast, infarct size was reduced from 47.5 +/- 3.8% in sham to 4.7 +/- 2.3% (P < 0.01) 24 h after HS. Additionally, early PC significantly reduced infarct size from 47.5 +/- 3.8% in controls to 6.0 +/- 1.2 and 5.0 +/- 1.1% with PC x 1 and PC x 3. Repeated PC cycles induced over a threefold increase in HSP 70 mRNA after 2 h compared with sham (P < 0.05). HSP 72, which increased 24 h after PC or HS, was not significantly different between the two PC stimuli. We conclude that PC does not induce SWOP in rat heart despite enhanced expression of HSP 72. In contrast, HS-induced delayed protection was associated with enhanced accumulation of HSP 72. It is possible that SWOP and HS have distinct mechanisms of protection that may not be exclusively related to HSP 72 expression.

Animals↗
PubMed1999

Delayed ischemic preconditioning is mediated by opening of ATP-sensitive potassium channels in the rabbit heart.

Cardioprotection from preconditioning reappears 24 h after the initial stimulus. This phenomenon is called the second window of protection (SWOP). We hypothesized that opening of the ATP-sensitive potassium (KATP) channel mediates the protective effect of SWOP. Rabbits were preconditioned (PC) with four cycles of 5-min regional ischemia each followed by 10 min of reperfusion. Twenty-four hours later, the animals were subjected to sustained ischemia for 30 min followed by 180 min of reperfusion (I/R). Glibenclamide (Glib, 0.3 mg/kg ip) or 5-hydroxydecanoate (5-HD, 5 mg/kg iv) was used to block the KATP channel function. Infarct size was reduced from 41.2 +/- 2. 6% in sham-operated rabbits to 11.6 +/- 1.0% in PC rabbits, a 71% reduction (n = 11, P < 0.01). Treatment with Glib or 5-HD before I/R increased the infarct size to 43.4 +/- 2.6 and 37.8 +/- 1.9%, respectively (P < 0.01 vs. PC group, n = 12/group). Sham animals treated with either Glib or 5-HD had an infarct size of 39.0 +/- 3.4 and 37.8 +/- 1.5%, respectively, which was not different from control (40.0 +/- 3.8%) or sham (41.2 +/- 2.6%) I/R hearts. Monophasic action potential duration (APD) at 50% repolarization significantly shortened by 28.7, 26.6, and 23.3% in sham animals during 10, 20, and 30 min of ischemia. However, no further augmentation in the shortening of APD was observed in PC hearts. Glib and 5-HD significantly suppressed ischemia-induced epicardial APD shortening, suggesting that 5-HD may not be a selective blocker of the mitochondrial KATP channel in vivo. We conclude that SWOP is mediated by a KATP channel-sensitive mechanism that may have occurred because of the opening of the sarcolemmal KATP channel in vivo.

Action Potentials↗
PubMed1999

Delayed preconditioning with adenosine is mediated by opening of ATP-sensitive K(+) channels in rabbit heart.

The adenosine agonist 2-chloro-N(6)-cyclopentyladenosine (CCPA) induces delayed ischemic protection in vivo. We hypothesized that this protection is mediated by opening of ATP-sensitive K(+) (K(ATP)) channels and increased synthesis of 72-kDa heat shock protein (HSP 72). Six groups (n = 9-13 animals/group) of animals were studied: group I, control rabbits that received no treatment; group II, animals given glibenclamide (0.3 mg/kg iv) 30 min before ischemia; group III, animals given 5-hydroxydecanoate (5-HD; 5 mg/kg iv) 15 min before ischemia; group IV, rabbits treated with CCPA (0.1 mg/kg iv) 24 h before ischemia; and groups V and VI, CCPA-treated animals that received the K(ATP)-channel blockers glibenclamide or 5-HD, respectively, 30 or 15 min before ischemia. All animals were subjected to ischemia by 30 min of coronary artery occlusion followed by 3 h of reperfusion. Risk area was delineated by injection of 10% Evans blue dye, and infarct size was determined by triphenyltetrazolium staining. Action potential duration (APD) was measured with an epicardial electrode. HSP 72 was measured by Western blotting. CCPA caused a significant reduction in infarct size [12.02 +/- 1.0 vs. 40.0 +/- 3.8% (%area at risk) in controls, P < 0.01] that was blocked by glibenclamide (36.2 +/- 3.1%, P < 0.01) and 5-HD (35.0 +/- 2.9%, P < 0.01). Glibenclamide and 5-HD did not change infarct size in control rabbits. These blockers significantly suppressed ischemia-induced APD shortening in control and CCPA-treated animals. CCPA treatment did not induce HSP 72 in hearts. These data suggest that adenosine-initiated delayed protection is mediated via opening of K(ATP) channels but does not involve the synthesis of HSP 72.

Action Potentials↗
PubMed1999

Glycolipid RC-552 induces delayed preconditioning-like effect via iNOS-dependent pathway in mice.

We recently demonstrated that monophosphoryl lipid A (MLA)-induced delayed cardioprotection is mediated by inducible nitric oxide synthase (iNOS) in mice. In the present study, we determined whether RC-552, a novel synthetic glycolipid related in chemical structure to MLA, could afford similar protection. Adult mice were pretreated with vehicle or RC-552 (350 microg/kg ip, n = 7 mice/group) 24 h before global ischemia and reperfusion in a Langendorff isolated, perfused heart model. A group of RC-552-treated mice received S-methylisothiourea (SMT), a selective inhibitor of iNOS (3 mg/kg ip), 30 min before heart perfusion. Myocardial infarct size was significantly reduced from 19.2 +/- 2.0% in vehicle to 8.2 +/- 2.9% in RC-552 group (P < 0.05). Treatment with SMT abolished RC-552-induced reduction in infarct size (20.0 +/- 3.9%). In addition, RC-552 failed to reduce infarct size in isolated hearts from iNOS knockout mice (27.1 +/- 2.8%) compared with that in hearts from control knockout mice without drug treatment (22.9 +/- 5.4%). Acute buffer perfusion with RC-552 (0.1, 1.0, or 2.5 microg/ml) for 8 min immediately before ischemia-reperfusion did not reduce infarct size significantly. We concluded that RC-552 induces delayed cardioprotection via an iNOS-dependent pathway.

Animals↗