Effects of hyaluronate on CD44 expression of infiltrating cells in exudate of rat air pouch, induced by sensitization with lipopolysaccharide.

Abstract

To investigate the effects of hyaluronate (HA) on CD44 expression of infiltrating cells in vivo. Intra-air pouch injection of 10 microg lipopolysaccharide (LPS) with 0.4, 4.0, or 40 mg HA, 40 mg carboxymethylcellulose (CMC), or saline was performed on rats immunized with LPS. The percentage of CD44+ cells in the exudate of the air pouch was measured by flow cytometry, and the concentrations of interleukin 1beta (IL-1beta) and tumor necrosis factor-alpha (TNF-alpha) in the air pouch exudate were measured by ELISA. IL-1beta and TNF-alpha in the air pouch lining layer were stained by immunohistochemistry. The percentage of CD44+ cells in air pouch exudate was greater in the presence of HA, with a dose dependent increase (0.4 mg, 9.4+/-2.6%, n = 4; 4.0 mg, 13.8+/-2.9%, n = 4; 40 mg, 24.9+/-6.3%, n = 3; p < 0.05), while it was 4.9+/-1.2% (n = 4) in the presence of 40 mg CMC. The concentration of IL-1beta was lower in the presence of 40 mg HA (251.0+/-61.4 pg/ml, n = 4) or 40 mg CMC (168.2+/-43.5 pg/ml, n = 4; p < 0.05) than in saline (403.0+/-60.5 pg/ml, n = 4). The concentration of TNF-alpha was lower in the presence of 40 mg HA (14.0+/-6.7 pg/ml, n = 4) or 40 mg CMC (7.04+/-7.0 pg/ml, n = 4) than in saline (38.2+/-12.2 pg/ml, n = 4). Extensively stained lining cells in superficial layer of the air pouch with IL-1beta and TNF-alpha were observed in rats inoculated with 0.4 mg HA. These findings suggest that HA might affect the inflammatory process through modifying CD44 expression on infiltrating cells in air pouch exudate.