Basic Study
Copyright ©The Author(s) 2015. Published by Baishideng Publishing Group Inc. All rights reserved.
World J Crit Care Med. Nov 4, 2015; 4(4): 287-295
Published online Nov 4, 2015. doi: 10.5492/wjccm.v4.i4.287
In vivo analysis of intestinal permeability following hemorrhagic shock
Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Erik B Kistler
Tom Alsaigh, Marisol Chang, Michael Richter, Rafi Mazor, Department of Bioengineering, the Institute of Engineering in Medicine, University of California San Diego, La Jolla, CA 92093-0412, United States
Erik B Kistler, Department of Anesthesiology and Critical Care, VA San Diego Healthcare System, San Diego, CA 92161-5085, United States
Author contributions: Alsaigh T, Chang M, Richter M, Mazor R and Kistler EB were involved in the conception and execution of experiments, data analysis and writing the manuscript; all authors drafted the article and made critical revisions related to the intellectual content of the manuscript and approved the final manuscript.
Supported by Career Development Award (CDA2) 1IK2BX001277-01A1 from the Department of Veterans Affairs, Veterans Health Administration, Office of Research and Development, the Foundation for Anesthesia Education and Research and the American Society of Critical Care Anesthesiologists and NIH GM085072-06.
Institutional review board statement: The animal protocol was reviewed and approved by the Animal Subjects Committee of the University of California, San Diego (A3033-01).
Institutional animal care and use committee statement: The animal protocol was reviewed and approved by the Animal Subjects Committee of the University of California, San Diego (A3033-01) and conforms to the Guide for the Care and Use of Laboratory Animals by the United States National Institutes of Health (NIH Publication No. 85-23, 1996).
Conflict-of-interest statement: To the best of our knowledge, no conflicts of interest exist.
Data sharing statement: No additional data are available.
Open-Access: This article is an open-access article which was selected by an in-house editor and fully peer-reviewed by external reviewers. It is distributed in accordance with the Creative Commons Attribution Non Commercial (CC BY-NC 4.0) license, which permits others to distribute, remix, adapt, build upon this work non-commercially, and license their derivative works on different terms, provided the original work is properly cited and the use is non-commercial. See: http://creativecommons.org/licenses/by-nc/4.0/
Correspondence to: Erik B Kistler, MD, PhD, Assistant Professor of Anesthesiology and Critical Care, VA San Diego Healthcare System, 3350 La Jolla Village Drive, San Diego, CA 92161-5085, United States. ekistler@ucsd.edu
Telephone: +1-858-5528585-6927 Fax: +1-858-5340104
Received: May 12, 2015
Peer-review started: May 20, 2015
First decision: June 24, 2015
Revised: July 20, 2015
Accepted: August 20, 2015
Article in press: August 21, 2015
Published online: November 4, 2015
Abstract

AIM: To determine the time course of intestinal permeability changes to proteolytically-derived bowel peptides in experimental hemorrhagic shock.

METHODS: We injected fluorescently-conjugated casein protein into the small bowel of anesthetized Wistar rats prior to induction of experimental hemorrhagic shock. These molecules, which fluoresce when proteolytically cleaved, were used as markers for the ability of proteolytically cleaved intestinal products to access the central circulation. Blood was serially sampled to quantify the relative change in concentration of proteolytically-cleaved particles in the systemic circulation. To provide spatial resolution of their location, particles in the mesenteric microvasculature were imaged using in vivo intravital fluorescent microscopy. The experiments were then repeated using an alternate measurement technique, fluorescein isothiocyanate (FITC)-labeled dextrans 20, to semi-quantitatively verify the ability of bowel-derived low-molecular weight molecules (< 20 kD) to access the central circulation.

RESULTS: Results demonstrate a significant increase in systemic permeability to gut-derived peptides within 20 min after induction of hemorrhage (1.11 ± 0.19 vs 0.86 ± 0.07, P < 0.05) compared to control animals. Reperfusion resulted in a second, sustained increase in systemic permeability to gut-derived peptides in hemorrhaged animals compared to controls (1.2 ± 0.18 vs 0.97 ± 0.1, P < 0.05). Intravital microscopy of the mesentery also showed marked accumulation of fluorescent particles in the microcirculation of hemorrhaged animals compared to controls. These results were replicated using FITC dextrans 20 [10.85 ± 6.52 vs 3.38 ± 1.11 fluorescent intensity units (× 105, P < 0.05, hemorrhagic shock vs controls)], confirming that small bowel ischemia in response to experimental hemorrhagic shock results in marked and early increases in gut membrane permeability.

CONCLUSION: Increased small bowel permeability in hemorrhagic shock may allow for systemic absorption of otherwise retained proteolytically-generated peptides, with consequent hemodynamic instability and remote organ failure.

Keywords: Small bowel ischemia, Hemorrhagic shock, Peptides, Microcirculation, Proteolysis

Core tip: Although the concept of systemically circulating molecules from the bowel in response to shock is not new (e.g., bacterial “translocation”), the premise that small, proteolytically-derived molecules transit the bowel early in shock has not previously been examined. We offer evidence that proteolytically-derived peptides formed in the gut reach the systemic circulation in experimental hemorrhagic shock. The time-course and spatial disposition of low-molecular weight peptides in vivo was examined using real-time fluorescent intravital microscopy of the microcirculation and systemically as a first step towards demonstrating a pivotal role that these factors may play in affecting hemodynamic instability in early shock.