In vitro effect of acetyl-N-Ser-Asp-Lys-Pro (AcSDKP) analogs resistant to angiotensin I-converting enzyme on hematopoietic stem cell and progenitor cell proliferation

The tetrapeptide Acetyl-N-Ser-Asp-Lys-Pro (AcSDKP), an inhibitor of hematop oietic stem cell proliferation, is known to reduce in vivo the damage resul ting from treatment with chemotherapeutic agents or ionizing radiation on t he stem cell compartment, Recently, AcSDKP has been shown to be a physiolog ical substrate of the N-active site of angiotensin I-converting enzyme (ACE ), Four analogs of the tetrapeptide expressing a high stability towards ACE degradation in vitro have been synthesized in order to provide new molecul es likely to improve the myeloprotection displayed by AcSDKP, These analogs are three pseudopeptides with a modified peptidic bond, Ac-Ser Psi(CH2-NH) Asp-Lys-Pro, Ac-Ser-Asp-Psi(CH2-NH)Lys-Pro, Ac-Ser-Asp-Lys Psi(CH2-N)Pro, a nd one C-terminus modified peptide (AcSDKP-NH2), We report here that these analogs reduce in vitro the proportion of murine colony-forming units-granu locyte/macrophage in S-phase and inhibit the entry into cycle of high proli ferative potential colony-forming cells, The efficacy of AcSDKP analogs in preventing in vitro primitive hematopoietic stem cells from entering into c ycle suggests that these molecules could be new candidates for the powerful inhibition of hematopoietic stem and progenitor cell proliferation in vivo .