The effects of recombinant human granulocyte-colony stimulating factor on vascular dysfunction and splanchnic ischaemia-reperfusion injury

1. The aim of our study was to investigate the effects of recombinant human granulocyte-colony stimulating factor in a rat model of splanchnic ischaemia-reperfusion injury. 2. Male anaesthetized rats were subjected to clamping of the splanchnic arteries for 45 min. This surgical procedure resulted in an irreversible state of shock (splanchnic artery occlusion shock. SAO shock). Sham operated animals were used as controls. Survival rate, serum tumour necrosis factor-alpha (TNF-alpha), neutrophil count, bone marrow myeloid precursor cells, myeloperoxidase activity (MPO; studied as a quantitative means to assess leukocyte accumulation), mean arterial blood pressure and the responsiveness of aortic rings to phenylephrine (PE, 1 nM-10 microM) were studied. 3. SAO shocked rats had a decreased survival rate (0% at 4 h of reperfusion, while sham shocked rats survived more than 4 h), increased serum levels of TNF-alpha (201 +/- 10 u ml-1; sham shocked rats = undetectable), neutropenia, enhanced MPO activity in the ileum (0.11 +/- 0.06 u x 10(-3) g-1 tissue; sham shocked rats = 0.02 +/- 0.001 u x 10(-3) g-1 tissue) and in the lung (1.5 +/- 0.2 u x 10(-3) g-1 tissue; sham shocked rats = 0.19 +/- 0.05 u x 10(-3) g-1 tissue) and unchanged bone marrow myeloid precursor cells. Furthermore aortic rings from shocked rats showed a marked hyporeactivity to PE. 4. Administration of recombinant human granulocyte colony stimulating factor (rh G-CSF; 5, 10 and 20 micrograms kg-1 5 min following the release of occlusion) increased in a dose-dependent manner survival rate (90% at 4 h of reperfusion with the dose of 20 u x 10(-3) g kg-1), reduced serum TNF-alpha (13 +/- 5 u ml-1) and MPO activity in the ileum (0.065 +/- 0.002 u x 10(-3) g-1 tissue) and in the lung (0.7 +/- 0.03 microgram kg-1 tissue), improved neutropenia and mean arterial blood pressure but did not modify bone marrow myeloid progenitor cells. Furthermore rh G-CSF, either in vivo or in vitro (200 nM for 1 h in the organ bath), restored to control values the hyporeactivity to PE. Finally rh G-CSF potently inhibited the activity of inducible nitric oxide synthase in peritoneal macrophages activated with endotoxin. 5. Our results suggest that rh G-CSF protects against splanchnic ischaemia reperfusion injury by a mechanism(s) that does not depend upon its haematopoietic effects.

Participation of tumour necrosis factor and nitric oxide in the mediation of vascular dysfunction in splanchnic artery occlusion shock

1. Splanchnic artery occlusion (SAO) shock is characterized by irreversible circulatory failure. Tumour necrosis factor (TNF-alpha) may affect the L-arginine/nitric oxide (NO) pathway, thus contributing to the cardiovascular derangements of circulatory shock. 2. We investigated the contribution of both TNF-alpha and the L-arginine/nitric oxide pathway to the vascular dysfunction of SAO shock. Anaesthetized rats, subjected to total occlusion of the superior mesenteric artery and the coeliac trunk for 45 min developed a severe shock state (SAO shock) resulting in a fatal outcome within 75-90 min after the release of occlusion. Sham operated animals were used as controls. SAO shocked rats had also a marked hypotension and enhanced macrophage and serum levels of TNF-alpha. Furthermore, aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE 1 nM-10 microM) and reduced responsiveness to acetylcholine (ACh 10 nM-10 microM). Endothelium-denuded aortic rings had also a marked hyporeactivity to phenylephrine, which was restored to control values by in vitro administration of NG nitro-L-arginine-methyl ester (L-NAME 10 microM). 3. In vivo administration of cloricromene (2 mg kg-1, i.v.), an inhibitor of TNF-alpha biosynthesis, increased survival, enhanced mean arterial blood pressure and reduced macrophage and serum levels of TNF-alpha. Furthermore, aortic rings from shocked rats treated with cloricromene exhibited a greater contractile response to phenylephrine and improved responsiveness to ACh when compared to aortic rings from vehicle-treated SAO shocked rats. 4. Our results suggest that TNF-alpha alters both endothelial and muscular L-arginine/nitric oxide pathways which in turn produce vascular dysfunction in SAO shock.