TNF-alpha decreases expression of somatostatin, somatostatin receptors, and cortistatin in human coronary endothelial cells.
BACKGROUND
The objective of this study was to determine the expression of somatostatin (SST) and its receptors (SSTRs) and their regulation by TNF-alpha as well as cell proliferation in response to SST in human endothelial cells.


METHODS
Human coronary artery endothelial cells (HCAECs) were cultured without or with TNF-alpha (0.1, 1, or 10 ng/ml) for 24 h. The mRNA levels of SST, SSTR-1-5, as well as a housekeeping gene (beta-actin) were determined by real-time RT-PCR. Expression of SSTR-2 was also demonstrated by immunofluorescence staining. Cell proliferation in response to SST treatment (0.04, 0.2, or 1 ng/ml) was performed by [3H]thymidine incorporation.


RESULTS
Without TNF-alpha treatment, HCAECs showed mRNA expression of SST, SSTR-1, SSTR-2, and SSTR-5. The mRNA of SSTR-2 was expressed at a higher level than that of SSTR-1 and SSTR-5. However, SSTR-3 and SSTR-4 were not expressed or were minimally expressed. After treatment with TNF-alpha, the mRNA levels of SST, SSTR-1, SSTR-2, and SSTR-5 were significantly reduced in a dose-dependent fashion. TNF-alpha (1 ng/ml) reduced SST, SSTR-1, SSTR-2, and SSTR-5 by 93, 51, 85, and 99%, respectively, compared to controls (P < 0.001, t test). The immunoreactivity of SSTR-2 was also reduced after TNF-alpha treatment. SST-treated cells showed a significant reduction in [3H]thymidine incorporation in a dose-dependent manner. TNF-alpha treatment decreased SST inhibitory potential in cell proliferation.


CONCLUSIONS
HCAECs express SST, SSTR-1, SSTR-2, and SSTR-5, which are all decreased by TNF-alpha treatment. Furthermore, treatment with exogenous SST significantly reduces cell proliferation, and this inhibitory effect is also decreased by TNF-alpha.
Yan
Shaoyu
S
Molecular Surgeon Research Center, Division of Vascular Surgery and Endovascular Therapy, Michael E. DeBakey Department of Surgery, Baylor College of Medicine, Houston, Texas, USA.
Li
Min
M
Chai
Hong
H
Yang
Hui
H
Lin
Peter H
PH
Yao
Qizhi
Q
Chen
Changyi
C
D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000502:physiology; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D009479:Neuropeptides / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000032:analysis; D017481:Receptors, Somatostatin / Q000235:genetics* / Q000378:metabolism; D013004:Somatostatin / Q000235:genetics* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology*
D009479:Neuropeptides; D012333:RNA, Messenger; D017481:Receptors, Somatostatin; D014409:Tumor Necrosis Factor-alpha; C099323:cortistatin; C101130:somatostatin receptor type 1; D013004:Somatostatin; C094573:somatostatin receptor 5; C093733:somatostatin receptor 2