title: The anti-inflammatory peptide Ac-SDKP is released from thymosin-β4 by renal meprin-α and prolyl oligopeptidase.
abstract: N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural tetrapeptide with anti-inflammatory and antifibrotic properties. Previously, we have shown that prolyl oligopeptidase (POP) is involved in the Ac-SDKP release from thymosin-β4 (Tβ4). However, POP can only hydrolyze peptides shorter than 30 amino acids, and Tβ4 is 43 amino acids long. This indicates that before POP hydrolysis takes place, Tβ4 is hydrolyzed by another peptidase that releases NH2-terminal intermediate peptide(s) with fewer than 30 amino acids. Our peptidase database search pointed out meprin-α metalloprotease as a potential candidate. Therefore, we hypothesized that, prior to POP hydrolysis, Tβ4 is hydrolyzed by meprin-α. In vitro, we found that the incubation of Tβ4 with both meprin-α and POP released Ac-SDKP, whereas no Ac-SDKP was released when Tβ4 was incubated with either meprin-α or POP alone. Incubation of Tβ4 with rat kidney homogenates significantly released Ac-SDKP, which was blocked by the meprin-α inhibitor actinonin. In addition, kidneys from meprin-α knockout (KO) mice showed significantly lower basal Ac-SDKP amount, compared with wild-type mice. Kidney homogenates from meprin-α KO mice failed to release Ac-SDKP from Tβ4. In vivo, we observed that rats treated with the ACE inhibitor captopril increased plasma concentrations of Ac-SDKP, which was inhibited by the coadministration of actinonin (vehicle, 3.1 ± 0.2 nmol/l; captopril, 15.1 ± 0.7 nmol/l; captopril + actinonin, 6.1 ± 0.3 nmol/l; P < 0.005). Similar results were obtained with urinary Ac-SDKP after actinonin treatment. We conclude that release of Ac-SDKP from Tβ4 is mediated by successive hydrolysis involving meprin-α and POP.
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Nitin
authors.initials: N
authors.lastname: Kumar
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Pablo
authors.initials: P
authors.lastname: Nakagawa
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Branislava
authors.initials: B
authors.lastname: Janic
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Cesar A
authors.initials: CA
authors.lastname: Romero
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Morel E
authors.initials: ME
authors.lastname: Worou
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Sumit R
authors.initials: SR
authors.lastname: Monu
authors.affiliation: Department of Public Health Sciences, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Edward L
authors.initials: EL
authors.lastname: Peterson
authors.affiliation: 21st Century Therapeutics, Inc., Detroit, Michigan;
authors.forename: Jiajiu
authors.initials: J
authors.lastname: Shaw
authors.affiliation: Department of Internal Medicine, Henry Ford Health System, Detroit, Michigan; and.
authors.forename: Frederick
authors.initials: F
authors.lastname: Valeriote
authors.affiliation: Department of Biology, North Carolina A & T State University, Greensboro, North Carolina.
authors.forename: Elimelda M
authors.initials: EM
authors.lastname: Ongeri
authors.affiliation: Department of Biology, North Carolina A & T State University, Greensboro, North Carolina.
authors.forename: Jean-Marie V
authors.initials: JM
authors.lastname: Niyitegeka
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan;
authors.forename: Nour-Eddine
authors.initials: NE
authors.lastname: Rhaleb
authors.affiliation: Hypertension and Vascular Research Division, Department of Internal Medicine, Henry Ford Hospital, Detroit, Michigan; ocarret1@hfhs.org.
authors.forename: Oscar A
authors.initials: OA
authors.lastname: Carretero
mesh_terms: D000818:Animals; D001794:Blood Pressure; D002216:Captopril; D006877:Hydroxamic Acids; D007668:Kidney / Q000378:metabolism*; D008297:Male; D008666:Metalloendopeptidases / Q000378:metabolism*; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009842:Oligopeptides / Q000378:metabolism*; D000085822:Prolyl Oligopeptidases; D011897:Random Allocation; D017207:Rats, Sprague-Dawley; D012697:Serine Endopeptidases / Q000378:metabolism*; D013947:Thymosin / Q000378:metabolism*; D000099201:Thymosin beta(4)
chemical_list: D002216:Captopril; D006877:Hydroxamic Acids; D008666:Metalloendopeptidases; D009842:Oligopeptides; D000085822:Prolyl Oligopeptidases; D012697:Serine Endopeptidases; D013947:Thymosin; D000099201:Thymosin beta(4); C053833:meprin A; C058504:goralatide; C010531:actinonin
keywords: N-acetyl-seryl-aspartyl-lysyl-proline; angiotensin-converting enzyme; meprin-α; prolyl oligopeptidase; thymosin-β4