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-α (TNF-α), 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 μM) 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-α (201±10 u ml(−1); sham shocked rats=undetectable), neutropenia, enhanced MPO activity in the ileum (0.11±0.06 u × 10(−3) g(−1) tissue; sham shocked rats=0.02±0.001 u × 10(−3) g(−1) tissue) and in the lung (1.5±0.2 u × 10(−3) g(−1) tissue; sham shocked rats=0.19±0.05 u × 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 μg 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 × 10(−3) g kg(−1)), reduced serum TNF-α (13±5 u ml(−1)) and MPO activity in the ileum (0.065±0.002 u × 10(−3) g(−1) tissue) and in the lung (0.7±0.03 μ g  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

Adrenocorticotropin reverses vascular dysfunction and protects against splanchnic artery occlusion shock

1. Tumour necrosis factor (TNF-α) is involved in the pathogenesis of splanchnic artery occlusion (SAO) shock. On the other hand, inhibition of TNF-α is an important component of the mechanism of action of melanocortins in reversing haemorrhagic shock. We therefore investigated the effects of the melanocortin peptide ACTH-(1–24) (adrenocorticotropin fragment 1–24) on the vascular failure induced by SAO shock. 2. SAO-shocked rats had a decreased survival rate (0% at 4 h of reperfusion, while sham-shocked rats survived for more than 4 h), enhanced serum TNF-α concentrations (755±81 U ml(−1)), decreased mean arterial blood pressure, leukopenia, and increased ileal leukocyte accumulation, as revealed by means of myeloperoxidase activity (MPO=9.4±1 U g(−1) tissue). Moreover, aortic rings from shocked rats showed a marked hyporeactivity to phenylephrine (PE, 1 nM–10 μM) (E(max) and ED(50) in shocked rats=7.16 mN mg(−1) tissue and 120 nM, respectively; E(max) and ED(50) in sham-shocked rats=16.31 mN mg(−1) tissue and 100 nM, respectively), reduced responsiveness to acetylcholine (ACh, 10 nM-10 μM) (E(max) and ED(50) in shocked rats=30% relaxation and 520 nM, respectively; E(max) and ED(50) in sham-shocked rats=82% relaxation and 510 nM, respectively) and increased staining for intercellular adhesion molecule-1 (ICAM-1). 3. ACTH-(1–24) [160 μg kg(−1) intravenously (i.v.), 5 min after SAO] increased survival rate [SAO+ACTH-(1–24)=80% at 4 h of reperfusion], reversed hypotension, reduced serum TNF-α (55±13 U ml(−1)), ameliorated leukopenia, reduced ileal MPO (1.2±0.2 U g(−1) tissue), restored the reactivity to PE, improved the responsiveness to ACh and blunted the enhanced immunostaining for ICAM-1 in the aorta. 4. Adrenalectomy only in part–but not significantly–reduced the ACTH-induced shock reversal, the survival rate of SAO+ACTH-(1–24) adrenalectomized rats being 60% at 4 h of reperfusion; and methylprednisolone (80 mg(−1) i.v., 5 min after SAO) had a non-significant effect (10% survival) at 4 h of reperfusion. 5. The present data show that melanocortins are effective also in SAO shock, their effect being, at least in part, mediated by reduced production of TNF-α. Furthermore, they demonstrate, for the first time, that this inhibition is responsible for the adrenocorticotropin-induced reversal of vascular failure and leukocyte accumulation