Expression of cyclooxygenase-1 (COX-1) in labial salivary glands of Sjögren's syndrome

Abstract

COX plays an important role in inflammatory diseases such as rheumatoid arthritis. To determine the role of COX in Sjögren's syndrome (SS), we examined COX expression in the salivary glands of SS patients. We examined 15 patients with SS and two normal subjects. Labial salivary gland tissue samples were analysed immunohistochemically using anti-COX-1 and COX-2 antibodies. All biopsy samples from 15 patients with SS were stained for COX-1. In contrast, COX-1 immunostaining was not detected in normal salivary gland tissues. Co-expression of COX-1 and CD68 was confirmed by mirror section technique and double antibody immunostaining. This finding indicated that COX-1-expressing cells in SS salivary glands were infiltrating macrophages. In contrast to COX-1 staining, only a little COX-2 immunostaining was observed in salivary gland tissues from SS patients. These data suggest that COX-1 expression on infiltrating macrophages may contribute to the inflammatory process of salivary glands in SS.

Fig. 1

Immunohistochemical staining for COX-1 and COX-2 in representative salivary gland tissue sections from normal subjects and Sjögren's syndrome (SS) patients. Immunostaining was performed by the avidin-biotin-peroxidase complex method as described in PATIENTS and METHODS. Positive immunoreactivity appears as brown colour. Results of staining for COX-1 in salivary gland tissue section from a normal subject (b) and SS patients (a,c,e) are shown. Staining for COX-2 (f) using the same salivary gland section (e) is also shown. (d) The same salivary gland section (c) was stained with COX-1 antibody preincubated with antigen epitope polypeptides.

Fig. 2

Co-expression of COX-1 and CD68 by mirror section technique. (a) Representative section stained with COX-1. (b) Representative section stained with CD68. These ‘mirror’ sections demonstrated the co-expression of COX-1 and CD68.

Fig. 3

Double staining of consecutive sections of salivary gland from Sjögren's syndrome (SS) patients with anti-COX-1 and anti-CD68 antibodies. Sections were stained with the first antibody (anti-COX-1) using the peroxidase method and with second antibody (anti-CD68) using the alkaline phosphatase method as described in PATIENTS and METHODS. (A) SS salivary gland stained with goat IgG/mouse IgG. (B) SS salivary gland stained with goat IgG/anti-CD68. (C) SS salivary gland stained with anti-COX-1/mouse IgG. (D) SS salivary gland stained with anti-COX-1/anti-CD68.

Fig. 4

Effects of lipopolysaccharide (LPS) on COX expression of peripheral blood monocytes. (a) Peripheral blood monocytes isolated from a healthy volunteer were stimulated with LPS for 16 h. The cells were lysed and lysates were analysed by anti-COX-2 immunoblot. A representative example of three independent experiments. (b) Peripheral blood monocytes isolated from a healthy volunteer were stimulated with LPS for 16 h. The cells were lysed and lysates were analysed by anti-COX-1 immunoblot. (c) Peripheral blood monocytes isolated from a patients with Sjögren's syndrome (SS) were stimulated with LPS for 16 h. The cells were lysed and lysates were analysed by anti-COX-1 immunoblot. A representative example of three independent experiments.