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Platelet-dependent accumulation of leukocytes in sinusoids mediates hepatocellular damage in bile duct ligation-induced cholestasis.

ABSTRACT: BACKGROUND: Although it is well known that extrahepatic cholestasis induces liver damage, the mechanisms are still not completely understood. The aim of the present study was to evaluate the role of platelets and P-selectin in cholestasis-induced liver injury. EXPERIMENTAL APPROACH: C57BL/6 mice underwent bile duct ligation (BDL) and pretreatment with an anti-GP1balpha antibody, which depletes platelets, an anti-P-selectin antibody or a control antibody. Hepatic platelet and leukocyte recruitment as well as microvascular perfusion were determined by intravital fluorescence microscopy. KEY RESULTS: BDL caused significant liver damage and sinusoidal perfusion failure. BDL further induced hepatic platelet accumulation with widespread intravascular platelet aggregates, increased platelet adhesion in postsinusoidal venules and massive platelet accumulation in liver sinusoids. Administration of the anti-GP1balpha antibody reduced systemic platelet count by 90%. Depletion of platelets in BDL mice not only abolished accumulation and adhesion of platelets in sinusoids and venules but also restored sinusoidal perfusion and reduced liver enzymes by more than 83%. Platelet depletion further reduced BDL-associated sinusoidal leukocyte accumulation by 48% although leukocyte-endothelium interactions in venules were not affected. Immunoneutralization of P-selectin also inhibited hepatic microvascular accumulation of platelets and leukocytes, and protected against cholestasis-provoked hepatocellular damage. CONCLUSIONS AND IMPLICATIONS: Platelets play an important role in BDL-induced liver injury by promoting leukocyte recruitment and deteriorating microvascular perfusion. Moreover, our findings demonstrate that cholestasis-induced accumulation of platelets is mediated by P-selectin. Thus, targeting platelet accumulation may be a useful strategy against liver damage associated with obstructive jaundice.

SUBMITTER: Laschke MW

PROVIDER: S-EPMC2199386 | biostudies-other | 2008 Jan

REPOSITORIES: biostudies-other

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Project description:Male Sprague-Dawley rats weighing 250-300 g were purchased from Japan SLC Co. (Shizuoka, Japan). The animals were housed under a daily controlled 12-h light and 12-h dark cycle at 23 °C with free access to rat chow (Japan SLC Co.) and water for 1 week prior to the experiments. Rats were laparotomized under ether anesthesia in each experiment, and the common bile duct of each rat was ligated between the liver hilus and small intestine. Control animals underwent a sham operation with exposure but without ligation of the common bile duct. After the CBDL or sham operation, animals were allowed access to food and water ad libitum. Groups of three rats were sacrificed under ether anesthesia at 1, 3 and 12 hr after the CBDL or sham operation. At the time of sacrifice, the right lateral liver lobe was removed and flash-frozen in liquid nitrogen and stored at -80 °C. Total RNA isolated from frozen livers using TRIzol reagent (Invitrogen Co., Carlsbad, CA) was mixed to minimize variation among animals. Poly(A) RNA was purified using Oligotex-dT30 (Takara Shuzo Co., Ltd., Kyoto, Japan) in accordance with manufacturer’s instructions. Fluorescence-labeled probes were prepared by reverse transcription using a superscript II reverse transcriptase (Invitrogen Co.) and cyanine-3- and cyanine-5-dUTP (Perkin-Elmer Inc., Wellesley, MA). Poly(A) RNAs derived from rats that has undergone CBDL and from those that has undergone a sham operation were labeled with cyanine-3 and cyanine-5, respectively, and vise varsa. Fluorescence-labeled probes were purified using a MinElute PCR Products Purification Kit (Quiagen GmbH, Hilden, Germany) in accordance with manufacturer’s instructions. Each purified probe was suspended in hybridization buffer containing 1.6 mg/mL poly(A) (Roche Diagnostics, Basel, Switzerland) and yeast tRNA (Roche Diagnostics), 0.67 mg/mL herring sperm, 16% 20 x SSC and 0.3% SDS and applied to a cDNA microarray containing 1,800 rat genes on a slide glass (Asahi Technoglass Co., Tokyo, Japan). Three house-keeping genes (GAPDH, HPRT and b-actin) and rat unrelated traits (Lambda DNA) were also spotted on the slide as internal positive and negative controls, respectively. Hybridization was carried out twice to eliminate any dye bias. In one experiment, duplicate slides were hybridized with probes derived from CBDL and control rats that had been labeld with cyanine-3 and cyanine-5, respectively. In a replicate experiment, other duplicate slides were hybridized with probes derived from CBDL rats and control rats that had been labeled with cyanine-5 and cyanine-3, respectively (color swap). Then, the slides were cover-slipped and incubated in a sealed chamber (Asahi Technoglass Co.) for 16 hrs under a humidified (65 °C) condition. After being washed in low-stringency buffer (2 x SSC and 0.1% SDS), high-stringency buffer (0.2 x SSC and 0.1% SDS) and 0.2 x SSC and then rinsing with 99.5% ethanol, the slide was dried by centrifugation at low speed and used for scanning. Fluorescence was scanned by using a ScanArray 4000 (Packard BioChip Technologies, Billerica, MA) and quantified by using QuantArray Software (Packard BioChip Technologies, Billerica, MA). Keywords: time-course

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Platelet-dependent accumulation of leukocytes in sinusoids mediates hepatocellular damage in bile duct ligation-induced cholestasis.

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