Bradykinin forming capacity of oversulfated chondroitin sulfate contaminated heparin in vitro

Abstract

Oversulfated chondroitin sulfate (OSCS) contaminated heparin has been associated with severe anaphylactoid reaction (AR), mainly in dialysed patients. Although attributed to bradykinin (BK) released during contact system activation by OSCS, no definitive evidence exists until now for a BK release during incubation of contaminated heparin with human plasma. In this study, we investigated the kinin forming capacity of OSCS and OSCS contaminated heparin when incubated in vitro with a pool of human plasma. At 100μg/mL, OSCS liberates BK in a profile similar but not identical to dextran sulfate, a well known activator of the plasma contact system. The results have highlighted that the quantity of BK accumulated during contact system activation depends not only on the concentration of OSCS but also on the plasma dilution and the presence of an angiotensin converting enzyme inhibitor. We demonstrate a highly significant correlation between the concentration of OSCS present in the contaminated heparin and BK released concentration. In conclusion, for the first time, we show that OSCS contaminated heparin incubated with human plasma has the capacity to liberate BK at a concentration that could explain the role of this inflammatory peptide in the pathophysiology of AR associated with OSCS contaminated heparin.

Characterization of currently marketed heparin products: Adverse event relevant bioassays

“…Because of the symptoms and the known ability of dextran sulfate to activate the contact system [3], research quickly focused on OSCS mediated activation of the contact system as a prime biochemical mechanism to link contaminated heparin with the adverse events. In subsequent research, OSCS was found to activate the kallikrein-kinin (KK) pathway in human plasma and this pathway was proposed to cause the production of vasoactive mediators such as bradykinin (BK) and the anaphylatoxins C3a and C5a in a factor XIIa (FXIIa) dependent manner [4][5][6][7][8]. Consistent with this hypothesis, OSCS alone and OSCS contaminated heparin induced hypotension in swine or rat blood pressure models [4,5,7].…”

“…Given the possibility that other OS-GAGs have similar FXIIa binding affinities and the concomitant potential to activate BK and C5a, we assessed the production of these specific vasoactive and inflammatory mediators using our well characterized set of OS-GAGs. In an earlier report, Adam et al, showed that OSCS alone caused a dose dependent increase of BK in plasma and that the levels of OSCS found in contaminated heparin samples were correlated with BK production [6].…”

“…5b shows a representative concentration-dependent OSCS BK production response (adapted from Fig. 1b of Adam et al [6]). A similar BK response was also observed for OSDS and OSHS (unpublished observations).…”

“…siliconized tubes) which detracts from the throughput of these tests. In addition, the method of plasma collection and storage also impacts KK auto activation, C5a and/or BK production [6,7]. In this work, we optimize bioassays for KK activity, BK and C5a which are readouts for activation of the contact system by polyanions.…”

“…Another class of assay involves the activation of the contact system [5,6,8,19]. With these tests, care must be taken as exposure of plasma to typical 96-well plate surfaces can auto-activate KK activity within minutes.…”