mitochondrial katp channel opener prevents ischemia-reperfusion injury in rat liver

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    orally administered 60 minutes before hepatic ischemia. Nicorandil significantly decreasedplasma levels of alanine aminotransferase and lactate dehydrogenase by about 50% and

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    428inhibited the remarkably increased TUNEL-positive hepatocytes after reperfusion. Somemediators associated with apoptosis were analyzed by Western blotting. Cytochrome-c andcaspase-3 levels in the cytosol increased after reperfusion; nicorandil inhibited the releaseof cytochrome-c and activation of caspase-3. The expression of Bax and Bcl-2 wassignificantly increased after reperfusion, being slightly inhibited by the administration ofnicorandil. These results suggest that the protective effects of nicorandil against hepaticischemia-reperfusion injury correlate with the inhibition of mitochondrial cytochrome-crelease and caspase-3 activation. These findings demonstrate that nicorandil may becomea therapeutic drug for ischemia reperfusion-related liver injury.

    HE morbidity associated with hepatic resections undertotal vascular exclusion and liver transplantation is

    rtly attributable to ischemia-reperfusion (IR) injury. Aspathophysiology of hepatic IR injury has become

    adily apparent, many mediators, including tumor necro-factor-, interleukin-1, platelet activating factor, cellularhesion molecules, and reactive oxygen species, have beenwn to play critical roles in this type of injury.13 Anderstanding of the complex mechanisms involved in thisury is required to improve morbidity.n various organs, initial exposures to brief ischemicriods produce cellular tolerance for a subsequent pro-ged ischemic insult.4 This phenomenon, termed ischemicconditioning, has been studied mainly in the heart andr.2,3,5 In the heart, a number of substances and signalingthways have been proposed to exert the cardioprotectiveects of ischemic preconditioning,5 for example, mito-ndrial KATP (mito KATP) channels rather than sar-emmal KATP channels.

    6,7 Therefore, it has been re-

    ported that KATP channel openers have a pharmacologicalpreconditioning effect on myocardial protection.8

    The KATP channels were discovered by Noma9 in 1983

    in ventricular myocytes isolated from guinea pigs. Inoueet al10 first demonstrated KATP channels in the mitochon-drial inner membrane of isolated rat livers. These chan-nels, which are composed of two proteins, an inwardlyrectifying potassium channel (Kir6.x) and a sulfonylureareceptor (SUR), are expressed in numerous tissues,including heart, brain, skeletal muscle, and pancreas.11

    Recently, Malhi et al12 reported that Kir6.1 and SUR1

    From the Department of Hepato-Biliary-Pancreatic Surgery,Graduate School of Medicine, Osaka City University, Osaka,Japan.

    Address reprint requests to Seikan Hai, MD, Department ofHepato-Biliary-Pancreatic Surgery, Graduate School of Medi-cine, Osaka City University, 1-4-3 Asahimachi, Abeno-ku, Osaka545-8585, Japan. E-mail: m4011498@msic.med.osaka-cu.ac.jpitochondrial KATP Channel Openerchemia-Reperfusion Injury in Rat

    Hai, S. Takemura, Y. Minamiyama, K. Yamasaki, Sd S. Suehiro

    ABSTRACT

    Ischemia-reperfusion injury is responsible founder total vascular exclusion or after liver trathat mitochondrial KATP channel openers hapharmacological preconditioning action. Howchannel openers can reduce ischemia-reperfuwas to determine the effects of the mitochoischemia-reperfusion injury in the rat liver.ischemia for 45 minutes followed by 120 minu1-1345/05/$see front matter:10.1016/j.transproceed.2004.12.112eventser

    mamoto, S. Kodai, S. Tanaka, K. Hirohashi,

    morbidity associated with liver surgerylantation. Recently, it has been reportedn effect on myocardial protection via ar, it remains unclear as to whether KATPinjury in the liver. The aim of this studyal KATP channel opener, nicorandil, onle Wistar rats were subjected to 73%of reperfusion. Nicorandil (3 mg/kg) was 2005 by Elsevier Inc. All rights reserved.360 Park Avenue South, New York, NY 10010-1710

    Transplantation Proceedings, 37, 428431 (2005)

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    MITOCHONDRIAL CHANNEL OPENER 429NAs were expressed in the intact rat liver as well as inlated primary rat hepatocytes. Although the liver alsotains KATP channels, it remains unclear as to whetherTP channel openers can reduce IR injury in the liver.his study used nicorandil, a mito KATP channel opener,ich has been used clinically for the treatment of anginatoris. Nicorandil has been shown in rat myocardial mito-ndria13 to produce nitric oxide (NO), which plays anportant role in ischemic preconditioning of rat livers.14

    TERIALS AND METHODSgs

    orandil (SG-75) was purchased from Chugai Pharmaceutical. Ltd.

    imals and Hepatic Ischemia

    le 8-week-old Wistar rats (190 to 220 g body weight) purchasedm SLC (Shizuoka, Japan) had free access to food and water. Allmals were anesthetized with urethane (5 mg/kg intraperitone-) and placed in a supine position. To induce the hepaticemia, a laparotomy was performed. The blood supply to the leftmedian lobes of the liver was interrupted by placement of an

    aumatic vascular clamp to produce 73% hepatic ischemia for 45utes. The body temperature was maintained at 3637C by ating lamp. Reperfusion was initiated by removal of the vascularmp. The animals were sacrificed at 120 minutes after reperfu-n; SG-75 (3 mg/kg) was orally administered 60 minutes beforehepatic ischemia.

    perimental Protocol

    the initial series of experiments, the protective effects of SG-75re tested in the following groups: Group 1: sham: animalsjected to anesthesia and laparotomy. Group 2: SG-75sham:mals subjected to anesthesia and laparotomy but treated with-75 at 60 minutes before hepatic ischemia. Group 3: ischemia-erfusion (IR): animals subjected to 45 minutes of hepaticemia, followed by 120 minutes of reperfusion. Group 4: SG-75R: animals subjected to 45 minutes of hepatic ischemia treatedh SG-75 60 minutes before hepatic ischemia.

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    parinized blood samples collected from the aorta were sepa-ed to plasma by centrifugation at 12,000g for 5 minutes andred at 20C until assayed for alanine aminotransferase (ALT)lactate dehydrogenase (LDH). After exsanguination, the livers

    re perfused with 50 mL of ice-cold saline via the abdominalta. The postischemic hepatic lobes were collected, includingtion immediately frozen under liquid nitrogen and stored at0C.

    paration of Hepatic Mitochondria

    osolic and mitochondrial-enriched fractions obtained from por-s of the liver were rinsed in 0.15 mol/L KCl, scissor-minced, andogenized in 3 volumes of 0.25 mol/L sucrose. Low-speedtrifugation was performed to remove cellular debris and obtainwhole cell lysates. For preparation of the mitochondrial-

    iched fractions, whole cell lysates were centrifuged at 500g for

    minutes. The supernate was spun at 2600g for 10 minutes. The Sulting pellet was resuspended in a buffer consisting ofmmol/L Tris-HCl (pH 7.4), 0.25 mol/L sucrose, and 5.4 mmol/Lylenediaminetetraacetic acid.

    rameter of Hepatic Injury

    e degree of hepatic injury was assessed by ALT and LDH plasmaels, as measured by SRL Co., Osaka, Japan. The hematologiclyses were performed using an autoanalyzer system (Hitachi0).

    tology

    er samples fixed in 10% formaldehyde were embedded inaffin. Replicate sections (4-m) were stained with hematoxylin-in for the evaluation of apoptosis on the basis of morphologicaleria, such as cell shrinkage, chromatin condensation, and mar-ation.

    NEL Assay

    optosis was determined by staining with the terminal deoxynu-otidyl transferase-mediated dUTP nick end labeling (TUNEL)ay (ApopTag Peroxidase In Situ Apoptosis Detection Kit,ergen, Purchase, NY). The number of apoptotic hepatocytes wasnted in 20 high-power (400) fields using a microscope.

    stern Blot Analysis for Cytochrome-c, Bax, Bcl-2, andspase-3

    ual amounts of total protein loaded onto 15% polyacrylamides were transferred to PVDF membranes. Thereafter, the mem-nes were treated with anti-cytochrome-c (BD Biosciencesrmingen, Franklin Lakes, NJ, USA), anti-Bax (BD Biosciencesrmingen), anti-Bcl-2 (BD Biosciences Pharmingen), or anti-pase-3 (Cell Signaling Technology, Beverly, Mass, USA) ac-ding to the manufacturers instructions. Mean density of thed area was measured using the Scion Image Beta 4.02 (Scion,derick, Md, USA) after obtaining black and white images asF files by an image scanner.

    tistical Analysis

    ta were analyzed with the Tukey-Kramer test; the results aresented as mean values SE. Significance was declared whenP value was less than .05.

    SULTSects of SG-75 on Hepatic Ischemia-Reperfusion Injury

    e effects of SG-75 on ALT plasma levels are shown inble 1. Plasma levels of ALT and LDH in the IR groupre markedly increased to 6128 370 IU/L and 24,486 6 IU/L, respectively. Administration of SG-75 signifi-tly decreased the levels to 2633 309 and 12,288 1572/L, respectively.

    Table 1. Plasma Levels of Alanine Aminotransferase

    Sham IR

    -75 () 133 33 6128 370P .05

    -75 () 119 11 2633 309

    esults are expressed as mean SE (IU/L).

    G-75, nicorandil; IR, ischemia reperfusion.

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