Issue inhibitor of metalloproteinases-3 inhibits shedding of L-selectin from leukocytes

Although the enzyme or enzymes mediating shedding of L-selectin have not ye t been identified, this activity can be blocked by synthetic hydroxamic aci d-based inhibitors of metalloproteinases such as Ro 31-9790, However, the e ndogenous matrix metalloproteinase inhibitor tissue inhibitor of metallopro teinases (TIMP)-1 does not block L-selectin shedding. Here, we report that TIMP-3, but not TIMP-2, inhibits L-selectin shedding from mouse and human l ymphocytes, Jurkat T cells, and human monocytes, TIMP-3 has an IC50 of 0.3- 0.4 mu M on these cell types compared with 0.7-4.8 mu M for Ro 31-9790, A m etalloproteinase (tumor necrosis factor-alpha (TNF-alpha)converting enzyme; ADAM17) has recently been identified which cleaves the pro-form of TNF-alp ha to produce soluble cytokine, We compared inhibition of L-selectin sheddi ng by TIMPs and Ro 31-9790 with inhibition of TNF-alpha shedding from human monocytes, TIMP-3 inhibited TNF-alpha shedding (IC50 of 0.1 mu M), as did Ro 31-9790 (IC50 of 0.4 mu M). TIMP-2 had a partial effect, and TIMP-1 did not inhibit. This study confirms that L-selectin sheddase is a metalloprote inase, but not a matrix metalloproteinase, and investigates the relationshi p between shedding of L-selectin and TNF-alpha.