Effect of N-acetyl-seryl-aspartyl-lysyl-proline on DNA and collagen synthesis in rat cardiac fibroblasts.
N:-Acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural inhibitor of pluripotent hematopoietic stem cell entry into the S phase of the cell cycle and is normally present in human plasma. Ac-SDKP is exclusively hydrolyzed by ACE, and its plasma concentration is increased 5-fold after ACE inhibition in humans. We examined the effect of 0.05 to 100 nmol/L Ac-SDKP on 24-hour (3)H-thymidine incorporation (DNA synthesis) by cardiac fibroblasts both in the absence and presence of 5% FCS. Captopril (1 micromol/L) was added in all cases to prevent the degradation of Ac-SDKP. Treatment of cardiac fibroblasts with 5% FCS increased thymidine incorporation from a control value of 12 469+/-594 to 24 598+/-1051 cpm (P:<0.001). Cotreatment with 1 nmol/L Ac-SDKP reduced stimulation to control levels (10 373+/-200 cpm, P:<0.001). We measured hydroxyproline content and incorporation of (3)H-proline into collagenous fibroblast proteins and found that Ac-SDKP blocked endothelin-1 (10(-8) mol/L)-induced collagen synthesis in a biphasic and dose-dependent manner, causing inhibition at low doses, whereas high doses had little or no effect. It also blunted the activity of p44/p42 mitogen-activated protein kinase in a biphasic and dose-dependent manner in serum-stimulated fibroblasts, suggesting that the inhibitory effect of DNA and collagen synthesis may depend in part on blocking mitogen-activated protein kinase activity. Participation of p44/p42 in collagen synthesis was confirmed, because a specific inhibitor for p44/p42 activation (PD 98059, 25 micromol/L) was able to block endothelin-1-induced collagen synthesis, similar to the effect of Ac-SDKP. The fact that Ac-SDKP inhibits DNA and collagen synthesis in cardiac fibroblasts suggests that it may be an important endogenous regulator of fibroblast proliferation and collagen synthesis in the heart. Ac-SDKP may participate in the cardioprotective effect of ACE inhibitors by limiting fibroblast proliferation (and hence collagen production), and therefore it would reduce fibrosis in patients with hypertension.
Hypertension and Vascular Research Division, Henry Ford Hospital, Detroit, MI 48202-2689, USA. nrhaleb1@hfhs.org
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Rhaleb
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Peng
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Harding
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Tayeh
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LaPointe
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Carretero
D000804:Angiotensin II / Q000502:physiology*; D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000378:metabolism / Q000627:therapeutic use; D000818:Animals; D002455:Cell Division / Q000187:drug effects; D002478:Cells, Cultured; D003094:Collagen / Q000096:biosynthesis*; D004247:DNA / Q000096:biosynthesis; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000037:antagonists & inhibitors; D004789:Enzyme Activation / Q000187:drug effects; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005355:Fibrosis / Q000188:drug therapy; D005786:Gene Expression Regulation / Q000187:drug effects; D006801:Humans; D006973:Hypertension / Q000188:drug therapy; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases / Q000037:antagonists & inhibitors / Q000378:metabolism; D009206:Myocardium / Q000378:metabolism*; D009842:Oligopeptides / Q000097:blood / Q000378:metabolism / Q000494:pharmacology*; D007703:Peptidyl-Dipeptidase A / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin / Q000378:metabolism; D012084:Renin-Angiotensin System
D057911:Angiotensin Receptor Antagonists; D000806:Angiotensin-Converting Enzyme Inhibitors; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D009842:Oligopeptides; D044140:Receptor, Angiotensin, Type 1; D044139:Receptor, Angiotensin, Type 2; D011945:Receptors, Angiotensin; D000804:Angiotensin II; D003094:Collagen; D004247:DNA; D048052:Mitogen-Activated Protein Kinase 3; D020928:Mitogen-Activated Protein Kinases; D007703:Peptidyl-Dipeptidase A; C058504:goralatide