The anti-inflammatory peptide Ac-SDKP is released from thymosin-β4 by renal meprin-α and prolyl oligopeptidase

Abstract

The anti-inflammatory peptide Ac-SDKP is released from thymosin-␤4 by renal meprin-␣ and prolyl oligopeptidase. Am J Physiol Renal Physiol 310: F1026 -F1034, 2016. First published March 9, 2016 doi:10.1152/ajprenal.00562.2015.-N-acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP) is a natural tetrapeptide with antiinflammatory and antifibrotic properties. Previously, we have shown that prolyl oligopeptidase (POP) is involved in the Ac-SDKP release from thymosin-␤4 (T␤4). However, POP can only hydrolyze peptides shorter than 30 amino acids, and T␤4 is 43 amino acids long. This indicates that before POP hydrolysis takes place, T␤4 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-␣ metalloprotease as a potential candidate. Therefore, we hypothesized that, prior to POP hydrolysis, T␤4 is hydrolyzed by meprin-␣. In vitro, we found that the incubation of T␤4 with both meprin-␣ and POP released Ac-SDKP, whereas no Ac-SDKP was released when T␤4 was incubated with either meprin-␣ or POP alone. Incubation of T␤4 with rat kidney homogenates significantly released Ac-SDKP, which was blocked by the meprin-␣ inhibitor actinonin. In addition, kidneys from meprin-␣ knockout (KO) mice showed significantly lower basal Ac-SDKP amount, compared with wild-type mice. Kidney homogenates from meprin-␣ KO mice failed to release Ac-SDKP from T␤4. 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 Ϯ 0.2 nmol/l; captopril, 15.1 Ϯ 0.7 nmol/l; captopril ϩ actinonin, 6.1 Ϯ 0.3 nmol/l; P Ͻ 0.005). Similar results were obtained with urinary Ac-SDKP after actinonin treatment. We conclude that release of Ac-SDKP from T␤4 is mediated by successive hydrolysis involving meprin-␣ and POP.N-acetyl-seryl-aspartyl-lysyl-proline; thymosin-␤4; meprin-␣; prolyl oligopeptidase; angiotensin-converting enzyme THE ANTI-INFLAMMATORY PEPTIDE N-acetyl-seryl-aspartyl-lysylproline (Ac-SDKP) was identified originally in the bone marrow (24). It has also been widely distributed in mammalian organs, plasma, urine, and circulating mononuclear cells (23,39,46). In animal diseases with hypertension, as well as cardiovascular and kidney disease, Ac-SDKP reduces inflammatory cell infiltration and collagen deposition in the heart, kidney, lung, and liver (14,15,33,34,37,44). Ac-SDKP is hydrolyzed by angiotensin-converting enzyme (ACE) and has a short half-life of 4.5 min in the circulation (16). Treatment with ACE inhibitors significantly increased plasma concentration of Ac-SDKP (2), and some of the ACE inhibitors protective effects were reported to be mediated by the increases in Ac-SDKP concentrations (34, 35).Thymosin-␤4 (T␤4) is a major G-actin-sequestering peptide that consists of 43 amino acids. Since it contains the Ac-SDKP sequence in its NH 2 -terminal, T␤4 is considered to be the precursor of 39). Our group has shown p...

Interaction of N‐acetyl‐seryl‐aspartyl‐lysyl‐proline with the angiotensin‐converting enzyme 2–angiotensin‐(1–7)–Mas axis attenuates pulmonary fibrosis in silicotic rats

“…Clinical studies involving ACE inhibitor therapy have shown increased plasma and tissue Ac‐SDKP concentrations, and some of the beneficial effects of ACE inhibitors in fibrotic diseases are attributable, in part, to increased Ac‐SDKP content (Kumar & Yin, ). It has been reported that Tβ4 is hydrolysed by meprin α and prolyl oligopeptidase, and meprin α knockout mice exhibited a significantly lower basal amount of Ac‐SDKP than wild‐type mice (Kumar et al., ). In the present study, we found that exogenous Ac‐SDKP attenuated silicosis in rats or in fibroblasts induced by Ang II, owing to activation of the ACE2–Ang‐(1–7)–AT 1 pathway.…”

“…Furthermore, acetyl-seryl-aspartyl-lysyl-proline (Ac-SDKP), an antifibrotic peptide, can be cleaved by the N-terminal of ACE (Masuyer, Douglas, Sturrock, & Acharya, 2015) and released from thymosin 4 (T 4), hydrolysed by meprin and prolyl oligopeptidase (Kumar et al, 2016). Ac-SDKP has been proved to attenuate lung fibrosis in silicotic rats (Xu et al, 2012) or in mice treated with bleomycin (Conte et al, 2016).…”

N‐acetyl‐seryl‐aspartyl‐lysyl‐proline is a valuable endogenous antifibrotic peptide for kidney fibrosis in diabetes: An update and translational aspects

“…Kumar et al. focused on the biology of POP. POP can cleave the peptide that is shorter than the sequence of 30 amino acids.…”

“…However, Tβ4 is indeed 43 amino acids; therefore, theoretically, an additional enzymatic cleavage process should be required. Kumar et al . clearly showed that meprin‐α is a potential responsible enzyme to cleave Tβ4 and subsequently enable POP to cleave Tβ4 fragments to synthesize AcSDKP.…”

Emerging roles of bioactive peptides on brain health promotion

“…Prosaposin-derived 18-mer peptide (PS18: LSELIIN-NATEELLIKGL) protected against Ab 1-42 -induced neurotoxicity via activation of the caspase pathway (Gao et al, 2016;Table 2). N-acetyl-serylaspartyl-lysylproline (Ac-SDKP) is a natural tetrapeptide with antiinflammatory and antifibrotic properties and it is released from thymosin-b4 by renal meprin-a and prolyl oligopeptidase (Kumar et al, 2016). Ac-SDKP facilitated hippocampal neurogenesis mediated by VEGF via the PI3K/GSK-3b/b-catenin signalling pathways (Kim et al, 2015; Table 2).…”