Ghrelin improves tissue perfusion in severe sepsis via downregulation of endothelin-1.
OBJECTIVE
Severe sepsis is associated with increased total peripheral resistance (TPR) and decreased organ blood flow, in which endothelin-1 (ET-1) plays an important role. Plasma levels of ghrelin, a newly-identified endogenous ligand for growth hormone secretagogue receptor and a potent vasodilatory peptide, are significantly reduced in sepsis. Ghrelin downregulation heralds the hypodynamic response in severe sepsis. Therefore, we hypothesized that the administration of exogenous ghrelin improves organ blood flow by downregulation of ET-1 under such conditions.


METHODS
Male adult Sprague-Dawley rats were subjected to sepsis by cecal ligation and puncture (CLP). At 5 h post-CLP, a bolus intravenous injection of 2 nmol ghrelin was followed by a continuous infusion of 12 nmol ghrelin via a primed mini-pump over 15 h. At 20 h post-CLP (i.e., severe sepsis), cardiac output (CO), stroke volume (SV), TPR, and organ blood flow were measured using (141)Ce-microspheres. Plasma ET-1 levels and preproET-1 gene expression in the liver, small intestine, and kidneys were measured by ELISA and RT-PCR, respectively. The direct effect of ghrelin on ET-1 production was studied using cultured human umbilical vein endothelial cells (HUVECs) treated with tumor necrosis factor-alpha (TNF-alpha).


RESULTS
Ghrelin administration reduced TPR, increased CO, SV, and organ blood flow, downregulated preproET-1 gene expression, and decreased plasma levels of ET-1 in sepsis. Ghrelin inhibited TNF-alpha-induced ET-1 release from HUVECs in a dose-dependent manner. Moreover, ghrelin inhibited TNF-alpha-induced activation of nuclear factor-kappaB (NF-kappaB) in HUVECs.


CONCLUSIONS
The improvement of tissue perfusion by ghrelin in severe sepsis appears to be mediated by downregulation of ET-1 involving a NF-kappaB-dependent pathway.
Wu
Rongqian
R
Center for Immunology and Inflammation, Institute for Medical Research, North Shore-Long Island Jewish (LIJ) Health System, USA.
Dong
Weifeng
W
Zhou
Mian
M
Cui
Xiaoxuan
X
Hank Simms
H
H
Wang
Ping
P
D000208:Acute Disease; D000818:Animals; D002478:Cells, Cultured; D003108:Colonic Diseases / Q000097:blood / Q000188:drug therapy*; D015536:Down-Regulation; D042783:Endothelial Cells / Q000187:drug effects / Q000378:metabolism; D019332:Endothelin-1 / Q000097:blood / Q000378:metabolism*; D004797:Enzyme-Linked Immunosorbent Assay; D054439:Ghrelin; D007262:Infusions, Intravenous; D007421:Intestine, Small / Q000098:blood supply; D007668:Kidney / Q000098:blood supply; D008099:Liver / Q000098:blood supply; D008297:Male; D008863:Microspheres; D016328:NF-kappa B / Q000378:metabolism; D036361:Peptide Hormones / Q000494:pharmacology / Q000627:therapeutic use*; D010477:Perfusion; D051381:Rats; D017207:Rats, Sprague-Dawley; D012039:Regional Blood Flow; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018805:Sepsis / Q000097:blood / Q000188:drug therapy*; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology
D019332:Endothelin-1; D054439:Ghrelin; D016328:NF-kappa B; D036361:Peptide Hormones; D014409:Tumor Necrosis Factor-alpha