Patients
Eligibility criteria were based on our previous work(4). This trial had approval from the Shanghai ethics committee (Register Number: ACTRN12611000980932). All subjects participating in the current trial provided signed informed consent. The trial was registered prior to patient enrollment in ANZCTR (Australia New Zealand Clinical Trials Registry; Research Register Number, U1111-1124-2612; Principal investigator, Feixiang Wu; Registered Data, 09/2011). Ten patients with obstructive jaundice due to bile duct or pancreatic head neoplasms were enrolled, along ten chronic cholecystitis or liver hemangioma cases forming the control group. The patients assessed had American Society of Anesthesiologists physical statuses I and II, respectively, and were 40-70 years old. All participating patients were scheduled for elective surgery for the underlying diseases from June 2011 to December 2011 in Eastern Hepatobiliary surgical hospital, Shanghai, China.
Exclusion criteria comprised: (1) age>70 years or <20 years; (2) pronounced obesity (body mass index >30 kg/m2); (3) previous cardiovascular, pulmonary, or kidney disease; (4) hepatic encephalopathy, psychiatric disease, or neuropathology; (5) acid-base balance alteration, blood electrolyte imbalance, diabetes, sepsis, or overt weight loss resulting from cancer.
Vascular reactivity Measurement
Vascular reactivity was measured prior to anesthesia the day of surgery. Upon arrival to the operating room following fasting (8 to 10h), electrocardiography monitoring (lead II), finger pulse oximetry and non-invasive blood pressure assessment were carried out. Under local anesthesia, the left radial artery was punctured and catheterized, and connected via a sensor to a waveform analyzer (Vigileo system, Edwards life sciences, USA). Parameters were set with no adjustment, for continuous monitoring of cardiac output (CO), cardiac output index (CI), each-volume (SV), stroke volume index (SVI) and stroke volume variation (SVV). After puncturing the right internal jugular vein and indwelling a three-cavity central venous catheter under local anesthesia, central venous pressure (CVP) was simultaneously recorded. Body circulation resistance (SVR) and body circulation resistance index (SVRI) were calculated by inputting the obtained CVP values. Recorded values were averaged from three separate measurements. Ringer lactate solution was continuously instilled at 2 ml/kg/h. The patients were placed in the supine position for 20 minutes or more after entering the surgical room, and vascular reactivity was observed upon tension relief. After recording baseline values for mean arterial pressure (MAP), HR, CO, CI, SVR and SVRI, continuous infusion of increasing concentrations of noradrenaline for 5 min (30 and 60 ng.kg-1min-1) was performed, with a 20-minute interval between the two concentrations to allow recovery. Systolic blood pressure did not exceed 160 mmHg at the maximum dose. Stable for 3 minutes during each administration, systolic blood pressure and the heart rate returned to pre-test levels, fluctuating up and down within 5%.
Preparation of Total Protein Extracts
Artery samples near or surrounding the removed tissues were collected. About 100 mg of these samples were washed with cold PBS buffer three times. After PBS removal, 1 ml of lysis buffer (9.5 M Urea, 65 mM DTT, 4% CHAPS and 0.2% IPG buffer, mixed with enzyme inhibitors at 50:1 v/v) was added. The samples were then homogenized with a Dounce homogenizer after vertexing. Next, ultrasonication of the specimens was performed 5 times at 15-second intervals on ice (80W, 10 seconds). Supernatants were collected and stored at -80℃ after centrifugation (12,000 g, 4℃) for 45 minutes. Quantitative analysis of total protein in artery samples was performed with Bio-Rad protein assay reagents.
Two-Dimensional Electrophoresis (2-DE)
Proteins (100μg) were firstly resolved by isoelectrofocusing (IEF) with gel strips measuring pH values between 3 and 10 based on a non-linear gradient (IPG strip, 18 cm; GE Healthcare, Waukesha, WI, USA). Strip rehydration was carried out in a Protein IEF Cell (GE Healthcare) in the passive (4h) and active (12h) modes at room temperature. Simultaneous IEF was carried out on an Ettan IPGphor Isoelectric Focusing system as follows: (a) 30 V for 12h; (b) voltage gradient to 500 V in 1h; (c) gradient to 1000 V in 1h; (d) gradient to 8000 V in 8h; (e) 500 V for 4h. Next, IPG strips were placed onto vertical 12.5% polyacrylamide gels in an Ettan-DALT Six system (GE Healthcare). Second-dimension SDS-PAGE was performed on a Hofer SE 600 system (GE Healthcare) at 5 W/gel for 30 min followed by 180 W for 4h. Protein spots were detected after silver staining on an UMax Powerlook 2110XL scanner (GE Healthcare).
Trypsin Digestion and Gel Extraction
Spots of interest were excised from Coomassie Brilliant Blue treated gels after 2 Milli-Q water (15 min) and 4 NH4HCO3 (25 mM in 50% acetonitrile; 30 minutes) washes. After washing, the gel pieces were submitted to acetonitrile (50 mL) dehydration until opacity and further placed at 60ºC to total dryness; rehydration was carried out in 50 mM NH4HCO3. Next, the samples were digested with trypsin (12.5 ng/mL; Promega, Madison, USA) in 10-mL reactions. The samples were chilled on ice for 45 min followed by addition of 25 mM NH4HCO3 and overnight incubation (37ºC). After centrifugation, supernatants were submitted to 3 extractions with 50% acetonitrile containing 0.1% trifluoroacetic acid. The resulting mixtures were vacuum-dried. In MALDI-TOF/TOF, peptide elution was performed with 0.7 mL α-cyano-4-hydroxy-cinnamic acid (Sigma, St. Louis, MO, USA) in 0.1% trifluoroacetic acid/50% acetonitrile.
Mass Spectrometry
A 5800 MALDI TOF/TOF analyzer (Applied Biosystem, Framingham, MA, USA) was employed for assessments. Mass spectrum (m/z 800–4000) acquisition was in the positive ion reflector mode. The top 20 ions in terms of intensity were submitted to MS/MS sequencing in the 2 kV mode. The NCBI protein database was queried for matched MS/MS spectra by Matrix Science (http://www.matrixscience.com) for the identification of proteins: taxonomy, Green Plants; peptide tolerance, 1.2 Da; MS/MS tolerance, 0.6 Da; 1 incomplete cleavage allowed; modification, methionine oxidation. Based on MASCOT probability assessment (P<0.05), significant hits were used for protein identification. The identified proteins were examined for sub-cellular localization and function with TargetP (http://www.cbs.dtu.dk/services/TargetP/) or PSORT (http://psort.hgc.jp/). Further, potentially related pathways and biochemical reactions were queried in Uniprot (http://www.uniprot.org/) and Genome-Net (http://www.genome.ad.jp/kegg/).
Western Blot
Aorta segment lysis was performed with chilled lysis buffer in presence of protease inhibitors. Lysate centrifugation was carried out at 12,000 rpm for 15 min at 4°C. Total protein in the supernatant was quantitated with a BSA assay kit (P0006, Beyotime, Jiangsu, China). Protein separation was performed by 10% sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and protein bands were electro-transferred onto polyvinylidene difluoride (PVDF) membranes. The samples were incubated overnight at 4°C with anti-tropomyosin β, anti-transgelin, anti-annexin, anti-gelsolin, anti-HSP-27, anti-cofilin-1 and anti-GAPDH (1:1000; Abcam, Cambridge, UK) primary antibodies. Further incubation was performed with goat anti-mouse or anti-rabbit secondary antibodies (1:10,000; Santa Cruz Biotechnology, USA) for 1h in ambient conditions. Development was carried out with the BeyoECL kit (Beyotime, China) and a Tanon 5200 system.
Statistical Analysis
Spot intensities for differentially expressed proteins in D gels were obtained from three independent experiments. One-way analysis of variance and Duncan’s multiple range test were employed for comparisons. P<0.05 was deemed statistically significant.