Ghrelin protects musculocutaneous tissue from ischemic necrosis by improving microvascular perfusion.

Persistent ischemia in musculocutaneous tissue may lead to wound breakdown and necrosis. The objective of this experimental study was to analyze, whether the gastric peptide ghrelin prevents musculocutaneous tissue from necrosis and to elucidate underlying mechanisms. Thirty-two C57BL/6 mice equipped with a dorsal skinfold chamber containing ischemic musculocutaneous tissue were allocated to four groups: 1) ghrelin; 2) N(ω)-nitro-l-arginine methyl ester (l-NAME); 3) ghrelin and l-NAME; and 4) control. Microcirculation, inflammation, angiogenesis, and tissue survival were assessed by fluorescence microscopy. Inducible and endothelial nitric oxide synthase (iNOS I and eNOS), vascular endothelial growth factor (VEGF), as well as nuclear factor κB (NF-κB) were assessed by Western blot analysis. Ghrelin-treated animals showed an increased expression of iNOS and eNOS in critically perfused tissue compared with controls. This was associated with arteriolar dilation, increased arteriolar perfusion, and a sustained functional capillary density. Ghrelin further upregulated NF-κB and VEGF and induced angiogenesis. Finally, ghrelin reduced microvascular leukocyte-endothelial cell interactions, apoptosis, and overall tissue necrosis (P < 0.05 vs. control). Inhibition of nitric oxide by l-NAME did not affect the anti-inflammatory and angiogenic action of ghrelin but completely blunted the ghrelin-induced tissue protection by abrogating the arteriolar dilation, the improved capillary perfusion, and the increased tissue survival. Ghrelin prevents critically perfused tissue from ischemic necrosis. Tissue protection is the result of a nitric oxide synthase-mediated improvement of the microcirculation but not due to induction of angiogenesis or attenuation of inflammation. This might represent a promising, noninvasive, and clinically applicable approach to protect musculocutaneous tissue from ischemia.

N-acetylcysteine attenuates leukocytic inflammation and microvascular perfusion failure in critically ischemic random pattern flaps.

INTRODUCTION: Microcirculatory dysfunction causes ischemia resulting in tissue necrosis. N-acetylcysteine (NAC) has been shown capable of protecting tissue from ischemic necrosis. However, the mechanism of action of NAC is yet not fully understood. OBJECTIVE: Herein, we studied whether NAC is capable of attenuating microvascular perfusion failure in critically ischemic musculo-cutaneous tissue. MATERIAL AND METHODS: A laterally based skin flap was elevated in the dorsum of C57BL/6 mice and fixed into a dorsal skinfold chamber. Arteriolar perfusion, functional capillary density, leukocytic inflammation, apoptotic cell death, and non-perfused tissue area were repetitively analyzed over 10 days by intravital fluorescence microscopy. Treatment with either 100mg/kg NAC or saline (control) was started 30 min before surgery and was continued until day 10 after flap elevation. RESULTS: Surgery induced leukocytic inflammation, microvascular perfusion failure, apoptosis, and tissue perfusion failure. NAC was capable of significantly attenuating the area of non-perfused tissue. This was associated by a marked arteriolar dilation and an increased capillary perfusion. NAC further reduced the ischemia-associated leukocytic response and significantly attenuated apoptotic cell death in all areas of the flap. CONCLUSION: NAC is effective to attenuate leukocytic inflammation and microvascular perfusion failure in critically ischemic tissue. Thus, NAC treatment may represent a promising approach to improve the outcome of ischemically endangered flap tissue.