Effect of N-Acetyl-Seryl-Aspartyl-Lysyl-Proline on DNA and Collagen Synthesis in Rat Cardiac Fibroblasts

Abstract

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 mol/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 469Ϯ594 to 24 598Ϯ1051 cpm (PϽ0.001). Cotreatment with 1 nmol/L Ac-SDKP reduced stimulation to control levels (10 373Ϯ200 cpm, PϽ0.001). We measured hydroxyproline content and incorporation of 3 H-proline into collagenous fibroblast proteins and found that Ac-SDKP blocked endothelin-1 (10 Ϫ8 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 mol/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.

Effects of Monotherapy of Temocapril or Candesartan with Dose Increments or Combination Therapy with Both Drugs on the Suppression of Diabetic Nephropathy

“…In addition, the order of combination did not make any difference in either the BPlowering or the anti-albuminuric effect. The mechanisms responsible for the excellent effects of the combinations may involve more complete blockade of RAS, activation of angiotensin type 2 receptors, and/or increased levels of bradykinins and N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) (24)(25)(26)(27)(28). We have recently shown that in patients with diabetic nephropathy, addition of an ARB to an ACEI reduced both BP and ACR, and the reduction of ACR was closely associated with the reduction of urinary markers of oxidative stress (29).…”

Reinventing the ACE inhibitors: some old and new implications of ACE inhibition

“…This protects high-affinity receptors, blocks receptor desensitization and decreases internalization, thereby potentiating BK beyond blocking its hydrolysis. 156,157 ACEis also directly activate the bradykinin B 1 receptor by acting at the zinc-binding pentameric consensus sequence HEXXH (195)(196)(197)(198)(199) of the B 1 receptor, a motif that is present in the active center of ACE but absent from the B 2 receptor. ACEis, when activating the B1 receptor, elevate intracellular calcium ([Ca 2+ ]i) and release NO from cultured cells.…”

“…196 AcSDKP has antiproliferative and antifibrotic activities, and it protects hematopoietic stem cells against chemotherapy-induced injury 196 and limits cardiac fibrosis. 197 The current-generation ACEis in clinical use are essentially mixed N-and C-domain inhibitors. 198 Captopril has been noted to be modestly N-selective depending on Cl À concentration, whereas lisinopril and enalaprilat are more C-selective 194,199 (Figure 3).…”

N-Acetyl-Seryl-Aspartyl-Lysyl-Proline Inhibits TGF-β–Mediated Plasminogen Activator Inhibitor-1 Expression via Inhibition of Smad Pathway in Human Mesangial Cells

“…The plasma levels of Ac-SDKP were shown to be increased by fivefold after the administration of ACE-I in humans (13). Ac-SDKP was shown to suppress the proliferation of renal fibroblasts (14) and to inhibit DNA synthesis as well as collagen deposition in cardiac fibroblasts (15). In a hypertensive rat model, long-term administration of Ac-SDKP can ameliorate renal fibrosis and ventricular hypertrophy (16,17).…”