Melanie L. Gainsbury

N-acetyl-l-cysteine decreases intra-abdominal adhesion formation through the upregulation of peritoneal fibrinolytic activity and antioxidant defenses.

BACKGROUND Intraperitoneal adhesions occur in more than 94% of patients after abdominal surgery. Mechanisms that decrease oxidative stress and upregulate peritoneal fibrinolysis reduce adhesions. N-acetyl-l-cysteine (NAC) is a clinically relevant antioxidant whose effect on peritoneal fibrinolysis and ability to decrease adhesions has not been established. The aims of this study were to determine if NAC reduces adhesions and to characterize its potential mechanism(s) of action. METHODS Male Wistar rats (n = 92) received 0.9% saline (OP Control), intraperitoneal NAC (150 mg/kg, OP + NAC), or oral NAC (1200 mg/kg) twice daily on preoperative day 1, day of operation, and postoperative day 1. Adhesions were induced on the day of operation using our previously described ischemic button model. Animals were killed on postoperative day 7 for adhesion scoring. Peritoneal tissue and fluid from the intraperitoneal NAC group were measured at 24 hours for fibrinolytic activity, tissue plasminogen activator (tPA), plasminogen activator inhibitor-1 (PAI-1), total glutathione, and 8-isoprostane (8-IP). The effect of NAC on tPA and PAI-1 production was tested in vitro in human mesothelial cells. The effect of NAC on intestinal wound healing was measured using colonic anastomotic burst pressures. RESULTS Intraperitoneal NAC reduced adhesions by 53% (P < .001) compared to OP Controls without affecting anastomotic wound healing. NAC increased the tPA/PAI-1 protein ratio and peritoneal fibrinolytic activity by 69% and 127%, respectively, compared to OP Controls (P < .05). NAC did not restore total glutathione levels in peritoneal adhesion tissue but decreased 8-IP by 46% and 65% (P < .05) in peritoneal tissue and fluid, respectively, compared to OP Controls. Human mesothelial cells incubated with NAC exhibited a concentration-dependent increase in the tPA/PAI-1 ratio, which supported in vivo observations (P < .05). Oral NAC did not decrease adhesions. CONCLUSION NAC administered intraperitoneally decreased adhesion formation while upregulating peritoneal fibrinolytic activity and antioxidant defenses without affecting normal anastomotic wound healing. These data suggest a potential new therapeutic use for NAC in adhesion prevention.

Histone deacetylase inhibitors decrease intra-abdominal adhesions with one intraoperative dose by reducing peritoneal fibrin deposition pathways

BACKGROUND We previously demonstrated that postoperative peritoneal injury and inflammation contribute to adhesiogenesis. Recent evidence suggests that in addition to their role of interfering with the acetylation status of nuclear histone proteins, histone deacetylase inhibitors (HDACIs) including valproic acid (VPA) can target nonhistone proteins to resolve inflammation and modulate immune cells. We hypothesized that HDACIs could reduce adhesions. METHODS Seventy-two rats underwent laparotomy with creation of 6 peritoneal ischemic buttons to induce adhesions. A single intraperitoneal (IP) dose of 50 mg/kg VPA was administered intraoperatively, whereas controls received vehicle. To evaluate the timing, 25 rats underwent ischemic button creation with either an intraoperative or a delayed IP dose of VPA at 1, 3, or 6 hours postoperatively. On postoperative day 7, adhesions were quantified. To investigate mechanisms, ischemic buttons were created in 24 rats and either VPA or saline was administered in 1 intraoperative dose. At 3 or 24 hours later, peritoneal fluid was collected and fibrinolytic activity measured. Alternatively, button tissue was collected 30 minutes postoperatively to measure tissue factor, fibrinogen, and vascular endothelial growth factor (VEGF) by real-time polymerase chain reaction or Western blot. RESULTS A single intraoperative dose of VPA reduced adhesions by 50% relative to controls (P < .001). Delayed dosing did not reduce adhesions. In operated animals, peritoneal fibrinolytic activity was not different between groups. Tissue factor mRNA was downregulated by 50% (P = .02) and protein by 34% (P < .01) in animals administered VPA versus saline. VPA decreased fibrinogen protein by 56% and VEGF protein by 25% compared with saline (P = .03). CONCLUSION These findings suggest that VPA rapidly reduces the extravasation of key adhesiogenic substrates into the peritoneum. A single, intraoperative intervention provides an ideal dosing strategy and indicates an exciting new role for HDACIs in adhesion prevention.

Hypoxia Upregulates Neurokinin-1 Receptor (NK-1R) Signaling in Rat Peritoneal Mesothelial Cells (RPMCs): A Key Early Event in Intraabdominal Adhesion Formation

Background/aim: We have reported that eating behavior differed in rats that underwent gastric bypass, sleeve gastrectomy, and/or duodenal switch procedures. Ileum transposition has been recently suggested as a metabolic surgery. The aim of the present study was to examine the eating behavior in rats that underwent ileum transposition (IT) and sleeve gastrectomy (SG). Methods: Male rats were subjected to laparotomy or IT, and 6 weeks later both groups underwent SG. Body weight was recorded weekly. Calorie intake, body composition, eating behavior, energy expenditure and fecal energy density were measured by comprehensive laboratory animal monitoring system, dual x-ray absorptiometry, and bomb calorimeter before and after surgery. Results: Body weight was lower in rats undergoing IT than those subjected to laparotomy (at 1 week, p 0.05) postoperatively. Fat compartment was reduced at 2 weeks after IT compared to laparotomy (p=0.02). After SG, body weight was reduced in both groups but more so in IT-rats (pre-operation 466±14 g vs. post-operation 378±21 g, p<0.01), which was due to reduced fat compartment. Satiety ratio was higher during daytime than nighttime regardless of surgery procedures. At both 2nd and 6th week after IT, satiety ratio was reduced during daytime but not nighttime. Calorie intake per 24 h per rat as well as per 100 g body weight was increased, which was on account of increases in number of meals, meal size, and meal duration, particularly during daytime. Rate of eating was unchanged neither during daytime nor nighttime. Energy expenditure (kcal/h/100 g body weight) was unchanged. The fecal energy density was unchanged. In laparotomy rats following SG, calorie intake relative to body weight was increased due to an increased appetite during daytime 2 weeks after SG. In IT-rats following SG, however, satiety ratio, calorie intake and energy expenditure were unchanged neither during daytime nor nighttime, but eating behavior was altered as characterized by reduced rate of eating during both daytime and nighttime, reduced meal size during nighttime, and increased meal duration during both daytime and nighttime. Conclusion: After IT procedure, satiety ratio was reduced and calorie intake increased, but these changes disappeared after additional SG. Instead, the altered eating behavior took place as manifested by eating slowly with small meal size, which may have the metabolic benefits.