Neutrophil Elastase and Endogenous Inhibitors in Behçet's Disease Saliva.

Behcet's disease (BD) is a vasculitis of unknown aetiology typified by chronic recurrent oral ulcers and systemic inflammatory manifestations. Neutrophils, and specifically their protease neutrophil elastase (NE), have been implicated in its pathology. Although NE is an effective anti-microbial, excessive NE can damage host tissue. Recurrent oral ulceration is a primary BD symptom, therefore we hypothesized that excessive neutrophil infiltration evidenced by increased NE and a reduction in specific endogenous inhibitors, secretory leucocyte protease inhibitor (SLPI) and alpha1-anti-trypsin (alpha 1AT) contributes to BD mucosal instability. NE, SLPI and alpha 1AT were quantified in saliva from BD patients with active oral ulcers (BDa) and quiet without ulcers (BDq), recurrent aphthous stomatitis (RASa; RASq) and healthy controls (HC). Although BDq saliva had marginally higher median NE levels (1112 ng/ml) compared to both RASq (1043 ng/ml) and HC (999 ng/ml), SLPI was significantly reduced in BDq (P < 0 center dot 01). Despite decreased SLPI protein, mRNA expression was significantly increased in BDq buccal epithelial swabs compared to RASq and HC (P < 0 center dot 05,P < 0 center dot 001). NE remained enzymatically active, although alpha 1AT levels were at least eight times higher than SLPI in all groups, suggesting that alpha 1AT does not have a primary role in counteracting NE in saliva. Furthermore, NE levels in BDa patients medicated with both azathioprine (AZA) and colchicine (COLC) were significantly lower than those on COLC (P = 0 center dot 0008) or neither (P = 0 center dot 02), indicating that combining AZA + COLC may help to regulate excessive NE during ulceration. This study showed that enzymatically active NE coupled with reduced SLPI in BD saliva may contribute to recurrent oral ulcerations.