C1 inhibitor and
prolylcarboxypeptidase modulate prekallikrein activation on endothelial cells.
J Allergy Clin Immunol 2023;
152:961-971.e7. [PMID:
37399947 PMCID:
PMC10592223 DOI:
10.1016/j.jaci.2023.06.017]
[Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 05/19/2023] [Accepted: 06/05/2023] [Indexed: 07/05/2023]
Abstract
BACKGROUND
We examined how prekallikrein (PK) activation on human microvascular endothelial cells (HMVECs) is regulated by the ambient concentration of C1 inhibitor (C1INH) and prolylcarboxypeptidase (PRCP).
OBJECTIVE
We sought to examine the specificity of PK activation on HMVECs by PRCP and the role of C1INH to regulate it, high-molecular-weight kininogen (HK) cleavage, and bradykinin (BK) liberation.
METHODS
Investigations were performed on cultured HMVECs. Immunofluorescence, enzymatic activity assays, immunoblots, small interfering RNA knockdowns, and cell transfections were used to perform these studies.
RESULTS
Cultured HMVECs constitutively coexpressed PK, HK, C1INH, and PRCP. PK activation on HMVECs was modulated by the ambient C1INH concentration. In the absence of C1INH, forming PKa on HMVECs cleaved 120-kDa HK completely to a 65-kDa H-chain and a 46-kDa L-chain in 60 minutes. In the presence of 2 μM C1INH, only 50% of the HK became cleaved. C1INH concentrations (0.0-2.5 μM) decreased but did not abolish BK liberated from HK by activated PK. Factor XII did not activate when incubated with HMVECs alone for 1 hour. However, if incubated in the presence of HK and PK, factor XII became activated. The specificity of PK activation on HMVECs by PRCP was shown by several inhibitors to each enzyme. Furthermore, PRCP small interfering RNA knockdowns magnified C1INH inhibitory activity on PK activation, and PRCP transfections reduced C1INH inhibition at any given concentration.
CONCLUSIONS
These combined studies indicated that on HMVECs, PK activation and HK cleavage to liberate BK were modulated by the local concentrations of C1INH and PRCP.
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