Monocyte- and cytokine-induced downregulation of angiotensin-converting enzyme in cultured human and porcine endothelial cells.
We investigated the effects of monocytes on endothelial cell (EC) ectoenzyme activity. Coculture of human aortic ECs with human monocytes (2 x 10(5) monocytes per 2-cm2 well) led to a decrease in EC angiotensin-converting enzyme (ACE) activity (64.5 +/- 3.5% of control) but not aminopeptidase N, aminopeptidase P, and 5'-nucleotidase activities. Similar results were obtained using human umbilical vein EC-human monocyte and porcine aortic EC-porcine monocyte cocultures. The decrease in ACE activity was monocyte concentration and coculture time dependent, reaching a maximum of 65% decrease in activity at 120 hours. Monocyte-mediated reduction in ACE activity did not require cell to cell contact, since exposure of ECs to conditioned medium from cocultures (CCCM) or from monocyte cultures (MCM) produced a decrease in ACE activity similar to that observed in EC-monocyte cocultures. Exogenously added tumor necrosis factor (TNF)-alpha and interleukin (IL)-1 alpha, two known secretory products of monocytes, simulated the effects of monocytes on ACE activity. Western blot analysis revealed a decrease in the amount of ACE protein in TNF-alpha-treated and CCCM-treated ECs compared with control ECs. Both TNF-alpha and IL-1 alpha were present in CCCM and MCM but not EC-conditioned medium. Incubation of the cocultures with a mixture of neutralizing antibodies against TNF-alpha and IL-1 totally abolished the monocyte-induced decrease in ACE activity. In conclusion, monocytes decrease ACE activity in cultured ECs through the release of cytokines such as TNF-alpha and IL-1.
Papapetropoulos
A
A
Vascular Biology Center, Medical College of Georgia, Augusta 30912-2500, USA.
Antonov
A
A
Virmani
R
R
Kolodgie
F D
FD
Munn
D H
DH
Marczin
N
N
Ryan
J W
JW
Gerrity
R G
RG
Catravas
J D
JD
D015720:5'-Nucleotidase / Q000378:metabolism*; D000626:Aminopeptidases / Q000378:metabolism*; D000818:Animals; D000906:Antibodies / Q000276:immunology; D018826:CD13 Antigens / Q000378:metabolism*; D018920:Coculture Techniques; D016207:Cytokines / Q000494:pharmacology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000187:drug effects / Q000201:enzymology*; D006801:Humans; D007375:Interleukin-1 / Q000276:immunology / Q000494:pharmacology; D008297:Male; D009000:Monocytes / Q000502:physiology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism*; D013552:Swine; D014409:Tumor Necrosis Factor-alpha / Q000276:immunology / Q000494:pharmacology
D000906:Antibodies; D016207:Cytokines; D007375:Interleukin-1; D014409:Tumor Necrosis Factor-alpha; D015720:5'-Nucleotidase; D000626:Aminopeptidases; D018826:CD13 Antigens; C022750:X-Pro aminopeptidase; D007703:Peptidyl-Dipeptidase A