Key Regulators of Adhesiogenesis, Including Vascular Endothelial Growth Factor (VEGF) and Transforming Growth Factor-β1 (TGF-β1), Are Reduced by the Antioxidant N-acetyl-L-cysteine (NAC) in a Rat Model of Intraabdominal Adhesions
Melanie L. Gainsbury, MD, Daniel I. Chu, MD, Laura D’Addese, MD, Karen L. Reed, PhD, Arthur F. Stucchi, PhD, James M. Beck, MD, FACS
Boston University Medical Center, Boston, MA
PURPOSE OF STUDY
Intraabdominal adhesions are a major source of morbidity and our understanding of their formation remains incomplete. Our laboratory previously demonstrated that NAC decreases adhesions. NAC has a plethora of documented in vitro effects including down-regulation of inflammation and angiogenesis, both pathways implicated in adhesiogenesis. In this study we characterized the effects of NAC on the expression of three key regulators of adhesiogenesis (VEGF, TGF-β1 and cyclooxygenase-2, COX2) in the post-operative peritoneum.
Wistar rats (n=32) were randomized to non-operative controls (NON-OP), operative controls (OP+Saline) or operative administration of NAC (OP+NAC). Adhesions were induced using our ischemic button model. Operated rats were administered either 1-ml normal saline or 1-ml NAC (150mg/kg) via intraperitoneal injection BID on pre-operative day 1, operative day and post-operative day 1. Animals were sacrificed on post-operative day 1 to evaluate peritoneal tissue for VEGF, TGF-β1 and COX2 mRNA expression by real time-PCR and protein levels by Western blot analysis.
SUMMARY OF RESULTS
NAC significantly reduced VEGF protein in peritoneal tissue by 75% vs. OP+Saline (p=0.014). While an operation reduced VEGF mRNA by 60% vs. NON-OP (p<0.001), NAC did not significantly change VEGF mRNA expression vs. OP+Saline. NAC significantly reduced TGF-β1 mRNA in tissue by 24% vs. OP+Saline (p<0.001). COX-2 protein and mRNA increased in tissue by over 910% and 522% (p<0.02), respectively, with an operation, but there was no further change with NAC.
NAC reduces VEGF protein and TGF-β1 mRNA expression in the post-operative peritoneum. These findings suggest at least two cellular pathways through which NAC may reduce adhesions.