title: Human neutrophil peptides inhibit cleavage of von Willebrand factor by ADAMTS13: a potential link of inflammation to TTP.
abstract: Infection or inflammation may precede and trigger formation of microvascular thrombosis in patients with acquired thrombotic thrombocytopenic purpura (TTP). However, the mechanism underlying this clinical observation is not fully understood. Here, we show that human neutrophil peptides (HNPs) released from activated and degranulated neutrophils inhibit proteolytic cleavage of von Willebrand factor (VWF) by ADAMTS13 in a concentration-dependent manner. Half-maximal inhibitory concentrations of native HNPs toward ADAMTS13-mediated proteolysis of peptidyl VWF73 and multimeric VWF are 3.5 μM and 45 μM, respectively. Inhibitory activity of HNPs depends on the RRY motif that is shared by the spacer domain of ADAMTS13. Native HNPs bind to VWF73 (KD = 0.72 μM), soluble VWF (KD = 0.58 μM), and ultra-large VWF on endothelial cells. Enzyme-linked immunosorbent assay (ELISA) demonstrates markedly increased plasma HNPs1-3 in most patients with acquired autoimmune TTP at presentation (median, ∼170 ng/mL; range, 58-3570; n = 19) compared with healthy controls (median, ∼23 ng/mL; range, 6-44; n = 18) (P < .0001). Liquid chromatography plus tandem mass spectrometry (LC-MS/MS) reveals statistically significant increases of HNP1, HNP2, and HNP3 in patient samples (all P values <.001). There is a good correlation between measurement of HNPs1-3 by ELISA and by LC-MS/MS (Spearman ρ = 0.7932, P < .0001). Together, these results demonstrate that HNPs1-3 may be potent inhibitors of ADAMTS13 activity, likely by binding to the central A2 domain of VWF and physically blocking ADAMTS13 binding. Our findings may provide a novel link between inflammation/infection and the onset of microvascular thrombosis in acquired TTP and potentially other immune thrombotic disorders.
authors.affiliation: Division of Laboratory Medicine, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL;
authors.forename: Vikram G
authors.initials: VG
authors.lastname: Pillai
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Jialing
authors.initials: J
authors.lastname: Bao
authors.affiliation: Division of Laboratory Medicine, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL;
authors.forename: Catherine B
authors.initials: CB
authors.lastname: Zander
authors.affiliation: Division of Pediatric Hematology/Oncology, Children's Hospital of Alabama, Birmingham, AL; and.
authors.forename: Jenny K
authors.initials: JK
authors.lastname: McDaniel
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Palaniappan S
authors.initials: PS
authors.lastname: Chetty
authors.affiliation: Department of Pathology and Laboratory Medicine, Children's Hospital of Philadelphia, Philadelphia, PA;
authors.forename: Steven H
authors.initials: SH
authors.lastname: Seeholzer
authors.affiliation: Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Khalil
authors.initials: K
authors.lastname: Bdeir
authors.affiliation: Department of Pathology and Laboratory Medicine, Perelman School of Medicine, University of Pennsylvania, Philadelphia, PA.
authors.forename: Douglas B
authors.identifier: 0000-0001-5986-504X
authors.initials: DB
authors.lastname: Cines
authors.affiliation: Division of Laboratory Medicine, Department of Pathology, University of Alabama at Birmingham, Birmingham, AL;
authors.forename: X Long
authors.identifier: 0000-0003-1680-5295
authors.initials: XL
authors.lastname: Zheng
mesh_terms: D000071120:ADAMTS13 Protein / Q000378:metabolism*; D020816:Amino Acid Motifs; D023082:Defensins / Q000378:metabolism*; D005260:Female; D006801:Humans; D007249:Inflammation / Q000378:metabolism / Q000473:pathology; D008297:Male; D009504:Neutrophils / Q000378:metabolism* / Q000473:pathology; D059748:Proteolysis; D011697:Purpura, Thrombotic Thrombocytopenic / Q000378:metabolism* / Q000473:pathology; D014841:von Willebrand Factor / Q000378:metabolism*
chemical_list: D023082:Defensins; D014841:von Willebrand Factor; D000071120:ADAMTS13 Protein; C099604:ADAMTS13 protein, human