Pregnancy Hypertension: An International Journal of Women's Cardiovascular Health
Peptides do not prevent cleavage of endoglin to produce soluble endoglin
Introduction
Soluble fms-like tyrosine kinase-1 (sFlt-1) and soluble endoglin (sEng) are anti-angiogenic factors that cause endothelial dysfunction seen in preeclampsia [1]. Adenoviral over-expression of sEng and sFlt1 in rats phenocopies the hallmarks of severe preeclampsia [1], [2]. Furthermore, serum sEng is markedly increased in women with preeclampsia [3]. Such studies highlight the critical role of sEng in severe preeclampsia.
Matrix metalloproteinase 14 (MMP-14; MT1-MMP) cleaves membrane bound endoglin at a specific peptide sequence close to the transmembrane domain, producing sEng [4]. We demonstrated that this mechanism plays a role in placental production of sEng [5]. Conceivably, blocking the cleavage of endoglin by MMP14 could represent a drug strategy to decrease sEng.
Recently, Valbuena-Diez et al. showed peptides with a sequence straddling the same amino acid sequence on transmembrane endoglin at the MMP14 cleavage site can reduce sEng release both in vitro and in vivo [6]. Conceivably, the peptides may work by blocking sEng release through competitive inhibition.
Given the therapeutic potential for such peptides to treat preeclampsia, we sought to independently validate this important finding in four separate in vitro systems including primary human tissues and a plasmid over-expression system.
Section snippets
Generation of endoglin peptides
Two sets of small peptides were ordered from Auspep (Pty Ltd, Victoria, Australia). One, therapeutic peptide, has an identical sequence to the MMP14 cleavage site on membrane bound endoglin (TSKGLVLP – cleavage site peptide). The second, a control peptide, is identical to a sequence in the extracellular portion of endoglin distant to the cleavage site. (GPRTVTVK – control peptide). The peptides were purified to >90% purity by Auspep, as previously published [6] (Fig. 1).
JAR cells
JAR cells
Results and discussion
We obtained two sets of peptides with the same amino acid sequence used in a report suggesting endoglin-like peptides could reduce sEng release [6]. The candidate therapeutic (named ‘cleavage site peptide’) is the same amino acid sequence that includes the specific glycine–leucine region on membrane endoglin where MMP-14 cleaves membrane bound endoglin to produce sEng (Fig. 1). The second peptide is identical in sequence as an extracellular region of endoglin distant from the MMP-14 cleavage
Ethics Statement
Human Ethics approval was obtained from the Mercy Health Human Research Ethics Committee.
Funding
The National Health and Medical Research Council of Australia provided salary (#1062418 to T.K, #628927 to N.H, #1050765 to S.T.) and project support (#1048707) and Australian Postgraduate Award to F.B.
Competing Interests
The authors have declared that no competing interests exist.
Acknowledgements
The authors acknowledge Clinical Research midwives Gabrielle Pell, Debra Jinks, Rachel Murdoch and Genevieve Christophers and the Obstetrics midwifery staff and patients at the Mercy Hospital for Women (Heidelberg) for their provision of placental tissue.
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