Hypertonic saline resuscitation after mesenteric ischemia/reperfusion induces ileal apoptosis.
BACKGROUND
We have previously demonstrated that hypertonic saline (HS) resuscitation decreased inflammation and mucosal injury after mesenteric ischemia/reperfusion (I/R). In contrast to I/R cell necrosis, apoptosis provides controlled cell death that minimizes inflammation. We therefore hypothesized that HS resuscitation after mesenteric I/R would induce apoptosis and decrease mucosal injury.


METHODS
Rats underwent 60 minutes of superior mesenteric artery occlusion (SMAO) and then received no resuscitation or resuscitation with 4 mL/kg of HS, 4 mL/kg of lactated Ringer's (LR) solution (equal volume), or 32 mL/kg of LR solution (equal salt load). Rats were killed at 6 hours of reperfusion, and ileum was harvested for analysis. DNA fragmentation (apoptosis) was assessed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end-labeling (TUNEL) and mucosal injury by histology (Chiu score 0-5). Caspase-3 (proapoptotic mediator) and Bcl-xL (antiapoptotic mediator) protein expression were analyzed by Western immunoblot.


RESULTS
SMAO with no resuscitation, SMAO with 4 mL/kg of LR, and SMAO with 32 mL/kg of LR increased apoptosis (quantitated by TUNEL) and I/R-induced mucosal injury (quantitated by Chiu score). This was associated with an increase to similar levels in both proapoptotic caspase-3 and antiapoptotic Bcl-xL protein expression. Moreover, SMAO with 4 mL/kg of HS further increased apoptosis but decreased mucosal injury. This was associated with a differential expression of proapoptotic caspase-3 over antiapoptotic Bcl-xL.


CONCLUSIONS
HS resuscitation after mesenteric I/R significantly increased ileal mucosal apoptosis while decreasing mucosal injury and may represent a novel mechanism by which HS resuscitation after mesenteric I/R reduces inflammation and imparts protection to the gut.
Gonzalez
Ernest A
EA
Department of Surgery, The University of Texas Medical School at Houston, Houston, Texas 77030, USA. Ernest.A.Gonzalez@uth.tmc.edu
Kozar
Rosemary A
RA
Suliburk
James W
JW
Weisbrodt
Norman W
NW
Mercer
David W
DW
Moore
Frederick A
FA
D000818:Animals; D017209:Apoptosis; D053148:Caspase 3; D020169:Caspases / Q000378:metabolism; D007082:Ileum / Q000503:physiopathology; D020287:In Situ Nick-End Labeling; D007413:Intestinal Mucosa / Q000503:physiopathology*; D008297:Male; D051381:Rats; D017207:Rats, Sprague-Dawley; D015427:Reperfusion Injury / Q000503:physiopathology / Q000628:therapy*; D012462:Saline Solution, Hypertonic / Q000627:therapeutic use
D012462:Saline Solution, Hypertonic; C505410:Casp3 protein, rat; D053148:Caspase 3; D020169:Caspases