N-acetyltransferase polymorphism in patients with Behçet's disease

Pathophysiology of the Behçet's Disease

Behçet's disease (BD) is a multisystemic disease of unknown etiology characterized by chronic relapsing oral-genital ulcers and uveitis. Multiple systemic associations including articular, gastrointestinal, cardiopulmonary, neurologic, and vascular involvement are also observed in BD. Although the etiopathogenesis of the disease remains unknown, increased neutrophil functions such as chemotaxis, phagocytosis, and excessive production of reactive oxygen species (ROS), including superoxide anion, which may be responsible for oxidative tissue damage seen in BD, and also immunological alterations, T lymphocyte abnormalities in both subpopulation and function have been considered to be correlated with the etiopathogenesis of BD. There is some clinical evidence suggesting that emotional stress and hormonal alterations can influence the course and disease activity of BD.

Cytochrome P450 polymorphisms in patients with Behcet's disease

OBJECTIVES

Although the etiopathogenesis of Behcet's disease (BD) remains unknown, increased neutrophil functions such as chemotaxis, phagocytosis and excessive production of reactive oxygen species, including superoxide anion, may be responsible for the oxidative tissue damage observed in BD. Cytochrome P-450 are a multigene family of enzymes involved in the detoxification and occasional activation of a wide variety of chemicals. Our aim was to investigate CYP2C9 and CYP2C19 polymorphisms in patients with BD.

METHODS

Sixty-two subjects with BD and 107 healthy control subjects were enrolled in the study. Polymorphisms of CYP2C9 and CYP2C19 were performed by real-time PCR with a LightCycler instrument. We researched associations between CYP polymorphisms and BD.

RESULTS

The frequencies of wild-type and heterozygous CYP2C19*2 genotypes were 66.1% and 33.9% in the patients and 83.2% and 16.8% in the controls, respectively. There was a 2.53-fold increased risk of Behcet's disease in individuals with the CYP2C19*2 heterozygous genotype (OR = 2.53; 95% CI, 1.22-5.25) when compared with the control group. But the CYP2C9*2, CYP2C9*3 and CYP2C19*3 gene polymorphisms were not related to an increased risk of developing BD.

CONCLUSIONS

We observed that patients with BD presented with a higher prevalence of the heterozygous CYP2C19*2 genotype. Hereditary deficiencies of this enzyme activity may lead to an imbalance between pro- and antioxidant systems, resulting in the formation of excessive reactive oxygen species.

N-acetyltransferase 2 polymorphisms in patients with Behcet's disease

It is possible that dietary, environmental factors and/or genetic polymorphisms in xenobiotic-metabolizing enzymes may contribute to the development of Behcet's disease. As N-acetyltransferase (NAT) 2 is an important xenobiotic-metabolizing enzyme and theoretically the nonacetylated xenobiotics may induce an autoimmune mechanism, the aim of the present study was to investigate whether the genetic polymorphism of NAT2 plays a role in susceptibility to Behcet's disease. Forty Behcet's disease patients and 82 control subjects were enrolled in the study. NAT2*5A, NAT2*6A, NAT27*A/B and NAT2*14A polymorphisms were detected by using real time PCR with LightCycler (Roche Diagnostics GmbH, Mannheim, Germany). The NAT2*5A and NAT2*6A mutant genotypes carried an increased risk of developing Behcet's disease [odds ratio (OR) = 66.29, 95% confidence interval (CI) = 8.21-535.33; and OR = 24; 95% CI = 2.04-304.98, respectively]. The NAT2*7A/B and NAT2*14A gene polymorphisms were not an increased risk for developing Behcet's disease. As a result of this study we conclude the NAT2 slow acetylator status may be a determinant in susceptibility to Behcet's disease. This finding may have implications for the theories of the pathogenesis of the disease as well as for therapeutic aspects.

Acetylator phenotype in Behçet's disease

The purpose of this study was to determine the acetylator status in Behçet's disease (BD) patients and compare it to a matched group of normal individuals. Thirty-seven healthy volunteers and forty-one BD patients were included. Detailed history was taken from the patients. HLA-B51 was determined in the BD patients. In addition, the Clinical Manifestation Index (C.M.I.) was determined for each patient. Pathergy test was also done. After an overnight fast, each control subject and patient received a single oral dose of 100 mg of DDS. A blood sample was collected after 3 hours and the plasma was separated for determination of dapsone/monoacetyldapsone by HPLC. The frequency of slow acetylators in healthy individuals was 70.2%, while the frequency of rapid acetylators was 29.8%. The frequency of slow acetylators in BD patients was 53.7%, while the frequency of non-acetylators (undetected monoacetyldapsone MADDS in plasma) was 46.3%. There were no rapid acetylators among the BD patients. There was a strong negative association between the acetylator status and the severity of BD. In addition, acetylator status correlated with HLA-B51, in that BD patients with positive HLA-B51 were characterized by a very slow or non-acetylator status. Slow or non-acetylators had more severe BD. We conclude that BD patients have a unique acetylator status. This finding may have implications for the theories for the pathogenesis of the disease as well as for therapeutic aspects.