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

Abstract

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.

Combined intraoperative administration of a histone deacetylase inhibitor and a neurokinin-1 receptor antagonist synergistically reduces intra-abdominal adhesion formation in a rat model

“…Average colonic burst pressure was 267 ± 16.0 mmHg ( n = 6) for animals administered VPA plus NK-1RA and 225 ± 7.7 mmHg ( n = 9) for animals administered saline, values similar those previously reported by our laboratory, including VPA alone 20 and NK-1RA alone. 23 Additionally, there was no negative impact on fascial or cutaneous wound healing.…”

“…We previously showed that VPA administered alone significantly reduced fibrinogen protein in adhesive tissue. 20 In the present study, we show that within 30 minutes, a single intraperitoneal dose of VPA plus NK-1RA ( n = 5) significantly reduces adhesive tissue levels of fibrinogen protein compared with saline controls and nonoperated animals (Fig 4, A ). Fibrinogen levels continue to drop at 3 hours in the VPA plus NK-1RA treated animals compared with controls ( n = 5).…”

“…The intraperitoneal administration of VPA alone ( n = 34) reduces adhesions by 50.3% compared with saline controls ( P < .001), 20 and intraperitoneal NK-1RA alone ( n = 32) reduced adhesions by 57% ( P < .001). 14,23 The combination VPA plus NK-1RA ( n = 22), given intraperitoneally as a single dose at the time of operation, reduces adhesions by nearly 73% compared with saline controls ( P < .001; Fig 1).…”

“…In contrast, VPA alone reduced adhesions, but did not alter peritoneal fibrinolytic activity. 20 We therefore tested whether VPA plus NK-1RA administered in combination would modulate the peritoneal fibrinolytic system. In a bioassay measuring peritoneal fibrinolysis, a single dose of VPA plus NK-1RA ( n = 6) administered intraperitoneally at the time of operation significantly increases tPA activity at 3 ( n = 6) and 6 hours ( n = 6) postoperatively compared with 30 minutes ( n = 6) postoperatively and nonoperated controls ( n = 6; Fig 3).…”

“…A single perioperative dose of valproic acid (VPA), a prototypical class 1 histone deacetylation inhibitor, was shown to reduce postoperative adhesions by approximately 50% in a rat model. 20 VPA does not modulate the peritoneal fibrinolytic system, but instead reduces adhesions by decreasing signaling molecules that can mediate fibrin accumulation in the peritoneum. Specifically, VPA significantly reduced adhesion tissue levels of vascular endothelial growth factor (VEGF), a key modulator of vascular permeability as well as tissue factor and fibrinogen, key participants in the formation of the peritoneal fibrin matrix.…”