Leukotriene B4 at low dosage negates the catabolic effect of prostaglandin E2 in human patellar tendon fibroblasts

Tendinopathy often involves inflammation and matrix degeneration. The inflammatory mediators such as prostaglandin E-2 (PGE(2)) and leukotriene B-4 (LTB4) are implicated in the development of tendinopathy. Therefore, the purpose of this study was to determine the effect of PGE2 and LTB4 on the proliferation of human patellar tendon fibroblasts (HPTFs), the gene expression of collagen type 1, MMP-1 and MMP-3, as well as the protein secretion of these gene products by the cells. The results showed that LTB4 at low doses (0. 1 and I nM) significantly increased cell proliferation compared to controls and LTB4 at 0. 1 nM negated the PGE(2)-induced decrease in cell proliferation. In addition, PGE(2) at 100 ng/ml significantly increased the expression of MMP-1 and MMP-3 at both mRNA and protein levels. These stimulatory effects were significantly diminished by co-treatment with LTB4 at 0. 1 nM. Finally, neither PGE(2) nor LTB4 treatment affected collagen type I gene expression. These results suggest that low levels of LTB4 counterbalance the negative effects mediated by PGE(2) on tendon fibroblast proliferation and MNIP production, which may lead to matrix degradation. Thus, our findings suggest that although LTB4 is generally thought to be pathogenic, low levels of LTB4 are actually beneficial in maintaining tendon tissue homeostasis. (c) 2006 Elsevier B.V. All rights reserved.