Crude Heparin Preparations Unveil the Presence of Structurally Diverse Oversulfated Contaminants

Nowadays, pharmaceutical heparin is purified from porcine and bovine intestinal mucosa. In the past decade there has been an ongoing concern about the safety of heparin, since in 2008, adverse effects associated with the presence of an oversulfated chondroitin sulfate (OSCS) were observed in preparations of pharmaceutical porcine heparin, which led to the death of patients, causing a global public health crisis. However, it has not been clarified whether OSCS has been added to the purified heparin preparation, or whether it has already been introduced during the production of the raw heparin. Using a combination of different analytical methods, we investigate both crude and final heparin products and we are able to demonstrate that the sulfated contaminants are intentionally introduced in the initial steps of heparin preparation. Furthermore, the results show that the oversulfated compounds are not structurally homogeneous. In addition, we show that these contaminants are able to bind to cells in using well known heparin binding sites. Together, the data highlights the importance of heparin quality control even at the initial stages of its production.

Detection and Extraction of Heparin from Camel Lungs

Background: Heparin is an essential drug used as an anticoagulant. Access to raw material suitable for heparin extraction is critical for creating a viable business opportunity. In Saudi Arabia, large amounts of raw material with potential for heparin extraction are wasted. Objective: To extract heparin and low-molecular-weight heparin (LMWH) from the camel lung, and measure its potency and activity. Methods: Heparin preparation included three steps: extraction, electrophoretic identification, and activity measurement. Fresh lung tissue (100 g) was minced and homogenized in a blender. Crude heparin extracts were prepared using Charles’s or Volpi’s method with slight modifications. Heparin was purified by electrophoresis using high-purity agarose gels in barium acetate buffer. The heparin activity of purified samples was assayed spectrophotometrically using commercial heparin kits. Results: Charles’s and Volpi’s extraction methods were simple and easy to establish. The yield was 90 mg crude heparin per 100 g of camel lung tissue following Volpi’s extraction protocol, whereas Charles’s method did not yield any heparin. The separation of heparin and LMWH by gel electrophoresis resulted in sharp and clear product bands using material prepared according to Volpi’s method. The heparin preparation had an anti-factor Xa activity of 37 IU/mg, indicating weak potency. Conclusion: Preparation of active heparin from camel lung tissue is a technology applicable in manufacturing. Further method development is needed to increase heparin purity and potency.

Differential effect of three commercial heparins on Na+/H+ exchange and growth of PASMC

Heparin preparations vary in chemical content and in antiproliferative activity for pulmonary artery smooth muscle cells (PASMC). Intracellular alkalinization via stimulation of the Na+/H+ antiporter appears to be a permissive event for proliferation of PASMC. We wondered whether the variable effect of heparin preparations on PASMC growth might be due to different degrees of inhibition of the Na+/H+ antiporter and whether variations in chemical formulation might correlate with the inhibition. Fluorescent microscopy of bovine PASMC was done using a dye with which fluorescence varies directly with intracellular pH (pHi). Bovine PASMC were preincubated with three heparin preparations previously shown to vary in antiproliferative activity, at 1.0 microgram/ml for 24 h. Platelet-derived growth factor (PDGF; 60 ng/ml) on PASMC without heparin resulted in a rise in pHi of 0.27 +/- 0.02 pH units. The rise in pH units in heparin-treated PASMC was 0.34 +/- 0.03 with Choay, 0.21 +/- 0.02 with Elkins-Sinn, and 0.07 +/- 0.02 with Upjohn (+/-SE; all P < 0.05; n = 5). Upjohn heparin incubation for as little as 15 min still impeded the rise in pH induced by PDGF. Heparin did not block the Na+/H+ exchanger directly, as it still restored pHi in response to an acid load. Compared with PASMC proliferation induced by 60 ng/ml PDGF, 1 microgram/ml of Choay, Elkins-Sinn, and Upjohn heparin produced -4 +/- 7.4, 1.4 +/- 4.8, and 48 +/- 2.2% inhibition of PDGF control, respectively (P < 0.05 for Upjohn compared with PDGF and Choay). The heparins varied in protein content and amino acid composition. However, amino acid and glucosamine composition, total sulfation, and extent of 3-O-sulfation did not predict their activity. Thus inhibition of PDGF activation of the Na+/H+ antiporter by a given heparin preparation correlated well with its ability to inhibit PASMC proliferation.

Low-Mr heparin is as potent as conventional heparin in releasing lipoprotein lipase, but is less effective in preventing hepatic clearance of the enzyme

This study compares a low-Mr heparin preparation with conventional heparin with respect to its interaction with lipoprotein lipase (LPL) in vitro and its effects on the enzyme in vivo. Both heparin preparations were polydisperse in binding to LPL, but on average the low-Mr preparation showed lower affinity. Thus both conventional and low-Mr heparin bound quantitatively to immobilized LPL, and were eluted as broad peaks when a salt gradient was applied, but the peak for low-Mr heparin was shifted towards lower salt concentrations. To displace LPL from immobilized heparin a higher concentration of low-Mr than of conventional heparin was needed. Injection of the low-Mr heparin into intact rats resulted in lower plasma LPL activity than did injection of an equal mass of conventional heparin, but when the liver was excluded from the circulation both heparin preparations resulted in similar plasma LPL activities. In perfused rat hearts, low-Mr heparin had at least the same effect on the release of LPL activity as did conventional heparin. In perfused livers, on the other hand, low-Mr heparin was less effective than conventional heparin in preventing the rapid uptake of exogenous labelled LPL. Hence the apparently lower average affinity of low-Mr heparin for LPL does not result in a demonstrably lower potency to release the enzyme from endothelial binding sites in peripheral tissues, but does result in a substantially decreased effect on the hepatic clearance of the enzyme.

Factors influencing the acceleration of human factor XIa inactivation by antithrombin III

Controversy exists in the literature concerning the potentiating effect of heparin on the inactivation rate of factor XIa by antithrombin III (AT III) in both purified systems and in plasma. We have analyzed the factors that could influence this reaction and found that ionic strength of the medium, as well as the type and concentration of the heparin preparations accounted for the major discrepancies in the literature. At I = 0.43 N, a preparation of bovine lung heparin at 1 U/mL did not augment the inactivation rate of factor XIa by inhibitors in plasma or by purified AT III. However, when ionic strength was decreased, a progressive increase in the potentiating effect was observed, reaching 6.5-fold at I = 0.15 N. At saturating concentrations of heparin, which results in the formation of 100% AT III-heparin complex, (greater than ten-fold molar excess over AT III) in purified systems, all heparin preparations (porcine, bovine, low molecular weight [LMW], and high affinity) yielded an approximately 30-fold augmentation of the factor XIa inactivation rate. However, when heparin was less than saturating, we observed that various heparin preparations affected the AT III-induced inactivation of factor XIa to different degrees even though they exhibited the same inhibitory activity (1 U/mL) against thrombin. This variation resulted from differences in the number of AT III binding sites in each heparin preparation, despite a similar Kd for each. Addition of high molecular weight kininogen (HK) to AT III-heparin complexes did not enhance their ability to inhibit factor XIa, and high concentrations of HK decreased the inactivation rate. A high therapeutic dose of heparin only permits the formation of 2.5% to 16.5% of the AT III-heparin complexes that can be achieved at saturation. We observed that 1 U/mL heparin (bovine lung heparin) (high therapeutic concentration) in virtually undiluted plasma only accelerated the inactivation rate of factor XIa (in the absence of other active enzymes) less than two-fold. These new observations further support our previous conclusion that therapeutic levels of heparin have little to no influence on the inactivation rate of factor XIa in plasma.

Factors influencing the acceleration of human factor XIa inactivation by antithrombin III

Controversy exists in the literature concerning the potentiating effect of heparin on the inactivation rate of factor XIa by antithrombin III (AT III) in both purified systems and in plasma. We have analyzed the factors that could influence this reaction and found that ionic strength of the medium, as well as the type and concentration of the heparin preparations accounted for the major discrepancies in the literature. At I = 0.43 N, a preparation of bovine lung heparin at 1 U/mL did not augment the inactivation rate of factor XIa by inhibitors in plasma or by purified AT III. However, when ionic strength was decreased, a progressive increase in the potentiating effect was observed, reaching 6.5-fold at I = 0.15 N. At saturating concentrations of heparin, which results in the formation of 100% AT III-heparin complex, (greater than ten-fold molar excess over AT III) in purified systems, all heparin preparations (porcine, bovine, low molecular weight [LMW], and high affinity) yielded an approximately 30-fold augmentation of the factor XIa inactivation rate. However, when heparin was less than saturating, we observed that various heparin preparations affected the AT III-induced inactivation of factor XIa to different degrees even though they exhibited the same inhibitory activity (1 U/mL) against thrombin. This variation resulted from differences in the number of AT III binding sites in each heparin preparation, despite a similar Kd for each. Addition of high molecular weight kininogen (HK) to AT III-heparin complexes did not enhance their ability to inhibit factor XIa, and high concentrations of HK decreased the inactivation rate. A high therapeutic dose of heparin only permits the formation of 2.5% to 16.5% of the AT III-heparin complexes that can be achieved at saturation. We observed that 1 U/mL heparin (bovine lung heparin) (high therapeutic concentration) in virtually undiluted plasma only accelerated the inactivation rate of factor XIa (in the absence of other active enzymes) less than two-fold. These new observations further support our previous conclusion that therapeutic levels of heparin have little to no influence on the inactivation rate of factor XIa in plasma.