L-selectin shedding is inhibited by Ro 31-9790, but not by Ro 32-1541 or TIMP1.

(A) The chemical structures of the hydroxamic acid–based synthetic MMP inhibitors Ro 31-9790 and Ro 32-1541. The effects of synthetic inhibitors and the endogenous MMP inhibitor, TIMP1, on phorbol ester–induced L-selectin shedding from mouse lymphocytes are given below. Results are mean IC₅₀ (nM). Effects of inhibitors on ADAM17 and MMPs are given for comparison. Results (*IC₅₀ or ^†apparent Ki) are means pooled from published data using peptide or protein substrates in cell-free assays22,36 37; ni indicates no inhibition; nd, not determined. (B) In L-selectin shedding assays 30 μM Ro 31-9790 was required to inhibit L-selectin shedding by 90%. Ro 32-1541 (30 μM) and TIMP1 (10 μM) had no effect. Results are means of duplicate observations of L-selectin–positive lymphocytes following incubation with (■) or without (□) PMA. (C) Plasma from mice pretreated with Ro 31-9790 inhibits L-selectin shedding. Maximal inhibition was seen 60 minutes after a single injection of more than 3 mg/mouse but inhibitor levels had fallen by 120 minutes. Plasma from mice treated with Ro 32-1541 or TIMP1 did not inhibit L-selectin shedding. Results are mean number of L-selectin–positive lymphocytes of duplicate observations following incubation with PMA and plasma from mice pretreated with inhibitor for 60 minutes (■) or 120 minutes (). *1, 2, 3 and 6 mg/mouse equivalent to 33, 66, 100, and 200 mg/kg, respectively.