Release of diamine oxidase into plasma by glycosaminoglycans in rats

Recombinant human diamine oxidase prevents hemodynamic effects of continuous histamine infusion in guinea pigs

OBJECTIVE

To test whether recombinant human diamine oxidase (rhDAO) with a mutated heparin-binding motif (mHBM), which shows an increased alpha-distribution half-life, prevents histamine-induced hemodynamic effects.

MATERIAL

Thirty-eight female guinea pigs were either pretreated with rhDOA_mHBM or buffer.

TREATMENT AND METHODS

Guinea pigs received a continuous infusion of histamine. Heart rate (HR), body core temperature and mean arterial pressure (MAP) were measured and blood was collected.

RESULTS

Continuous intravenous infusion of 8 µg/kg/min histamine increased mean peak plasma histamine levels from 5 (± 0.3 SEM) to 28 ng/mL (± 4.9 SEM) after 30 min but had no effect on oxygen saturation. Guinea pigs pretreated with 4 mg/kg rhDAO_mHBM showed lower mean HR (p = 0.008), histamine plasma concentrations (p = 0.002), and higher body core temperatures at the end of the histamine challenge (p = 0.02) compared to controls. Cessation of histamine infusion led to a rebound increase in MAP, but this hemodynamic instability was prevented by rhDAO_mHBM. Pretreatment with 4 mg/kg rhDAO_mHBM reduced urinary histamine (p = 0.004) and 1-Methylhistamine (p < 0.0001) concentrations compared to controls.

CONCLUSIONS

Prophylactic infusion of rhDAO_mHBM prevents hemodynamic effects in a guinea pig model of continuous histamine infusion. These findings might help in the translation from animals to humans and in the selection of the optimal dosing of rhDAO_mHBM during human histamine challenge studies.

Heparin-binding motif mutations of human diamine oxidase allow the development of a first-in-class histamine-degrading biopharmaceutical

Background

Excessive plasma histamine concentrations cause symptoms in mast cell activation syndrome, mastocytosis, or anaphylaxis. Anti-histamines are often insufficiently efficacious. Human diamine oxidase (hDAO) can rapidly degrade histamine and therefore represents a promising new treatment strategy for conditions with pathological histamine concentrations.

Methods

Positively charged amino acids of the heparin-binding motif of hDAO were replaced with polar serine or threonine residues. Binding to heparin and heparan sulfate, cellular internalization and clearance in rodents were examined.

Results

Recombinant hDAO is rapidly cleared from the circulation in rats and mice. After mutation of the heparin-binding motif, binding to heparin and heparan sulfate was strongly reduced. The double mutant rhDAO-R568S/R571T showed minimal cellular uptake. The short α-distribution half-life of the wildtype protein was eliminated, and the clearance was significantly reduced in rodents.

Conclusions

The successful decrease in plasma clearance of rhDAO by mutations of the heparin-binding motif with unchanged histamine-degrading activity represents the first step towards the development of rhDAO as a first-in-class biopharmaceutical to effectively treat diseases characterized by excessive histamine concentrations in plasma and tissues.

Funding

Austrian Science Fund (FWF) Hertha Firnberg program grant T1135 (EG); Sigrid Juselius Foundation, Medicinska Understödsförening Liv och Hälsa rft (TAS and SeV).

Diamine oxidase in relation to diamine and polyamine metabolism

Diamine oxidase catalyzes the oxidative deamination of short chain aliphatic diamines, like putrescine, and histamine. The enzyme is rate-limiting in the terminal catabolism of polyamines, which are endogenous polycations important for cell growth and differentiation. This review examines the behavior of diamine oxidase in mammalian tissues in relation to diamine and polyamine metabolism under physiological and pathological conditions. The role of diamine oxidase in the control of putrescine levels in growing tissues and the known mechanisms responsible for the enzyme expression are also described.

Postheparin plasma diamine oxidase values in the follow up of patients with small bowel Crohn's disease

Measurement of postheparin plasma diamine oxidase (PHD) activity has been proposed to assess mucosal integrity in several diseases of the small intestine. In Crohn's disease, PHD values identify a group of patients with predominantly small bowel mucosal damage. To determine the role of mucosal involvement in the progression of small bowel Crohn's disease and whether different PHD values can predict different outcomes the changes in PHD values in 41 patients with small bowel Crohn's disease admitted consecutively to our department were investigated. The test was performed during periods of active disease and after either medical or surgical treatment had resulted in improvement. PHD values were significantly lower than in normal subjects (normal range 3.7-7.7 U/ml). In 35 patients with active disease (Crohn's disease activity index (CDAI) greater than 150) two groups were identified by choosing a cut off value of 2 U/ml: 93% of the 15 patients with PHD values lower than 2 U/ml (mean (SD) 1.36 (0.46) U/ml) relapsed at least once in the following year, while only the 20% of the 20 whose values were higher than 2 U/ml (mean (SD) 3.69 (1.50)) relapsed in the same period. The data were statistically significant (Yates's corrected chi 2 = 15.63; p less than 0.0001). The positive and negative predictive values of the test were 93% and 80%, respectively. During relapses, PHD values were consistently lower than previous values, and increased significantly after effective medical or surgical treatment. In the six patients in whom there were no changes in disease activity (CDAI persistently less than 150), there was no change in PHD values. This test may be useful for identifying Crohn's disease patients who are likely to relapse. Furthermore, the data indicate that mucosal damage is common in active small bowel Crohn's disease and improves at least in part after treatment.

Plasma postheparin diamine oxidase in patients with small intestinal lymphoma

Diamine oxidase (DAO) is an enzyme located almost exclusively in villus tip enterocytes. Its plasma activity is enhanced by intravenous heparin which releases the enzymes from small bowel enterocytes into the blood. Plasma postheparin DAO (PHD) values have been shown to be significantly lower in patients with malabsorption and villous atrophy, thus suggesting that PHD reflects the mature enterocytic mass. In this study we have assayed PHD in five patients with small bowel lymphoma (two with immunoproliferative small intestinal disease [IPSID] and three with non-IPSID lymphoma) associated with malabsorption syndrome and small bowel mucosa atrophy. The PHD test was performed at diagnosis, after partial or complete remission induced by chemotherapy, and during the follow-up. The PHD values, very low at diagnosis (0.66 +/- 0.12 U/ml), increased during chemotherapy and reached the normal range (greater than 3.7 U/ml) when complete remission occurred. The PHD values rapidly and consistently decreased whenever the disease relapsed. Our data indicate that in patients with small bowel lymphoma PHD test is a sensitive marker of small bowel mucosa damage and suggest that it could be useful in monitoring the recovery of mucosal lesions induced by chemotherapy.

Polarized secretion of diamine oxidase by intestinal epithelial cells and its stimulation by heparin

The Caco-2 cells have been used as a model system to study the pathways of diamine oxidase secretion by the intestinal epithelium. When grown in Transwell filter chamber devices, the polarized cell monolayers released the enzyme preferentially into the basal chamber. Heparin (1-10 USP U/mL) rapidly induced a marked stimulation of enzyme secretion only when in contact with the basolateral cell membrane, where high affinity binding sites for [3H]heparin were also exclusively located. Among the other glycosaminoglycans tested, only heparan sulfate (150 mg/mL) was able to induce enzyme release; chondroitin sulfate (150 mg/mL) and dermatan sulfate (150 mg/mL) were without effect. Four monoclonal antibodies specific for human diamine oxidase were produced and found to immunoprecipitate a single protein with a molecular weight of 95,000 (under reducing conditions) from the culture medium of Caco-2 cells. Immunofluorescence staining of cryostat sections of human small intestine with these four antibodies localized diamine oxidase at the lateral and basal sides of the villus cells. Staining was markedly reduced in specimens obtained from patients who received doses of heparin in vivo. This study concludes that release of diamine oxidase by intestinal cells occurs specifically at the basolateral aspect of the cells, most likely through the constitutive secretory pathway. Heparin may induce its marked stimulation of enzyme release by complexing with diamine oxidase bound to the cell surface or through interaction with specific binding sites also located in the basolateral membrane. In the intestinal mucosa in vivo, the basal aspect of the villus cells represents the main site of diamine oxidase storage in the presence of normal circulating levels of heparin.