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Resident Department of Neurology and Ophthalmology Michigan State University East Lansing, Michigan
Postdoctoral Fellow Department of Neurology and Ophthalmology Michigan State University
Assistant Professor Department of Neurology and Ophthalmology A-217 Clinical Center Michigan State University East Lansing, Michigan 48824-1376 fax 517/432-9414 arshad.majid{at}ht.msu.edu
Published Online, January 11, 2005. www.theannals.com, DOI 10.1345/aph.1E423
Evidence suggests that minocycline is protective in rodent models of stroke even when administered 5 hours after the onset of ischemia.2-4 Minocycline has also been shown to be protective in models of other neurologic diseases.5 The neuroprotective effects of minocycline include reduction of inflammation by inhibiting microglial activation and prevention of apoptosis by inhibiting caspases.2,5 It is possible that minocycline may benefit patients presenting too late to receive alteplase. It is also possible that coadministration of alteplase and minocycline after ischemic stroke may confer greater benefit than alteplase alone. Before clinical trials to test the benefits of coadministration, it is important to determine whether minocycline has any effects on the activity of alteplase. The purpose of this study was to investigate the effect of minocycline on clot lysis by alteplase.
Methods. Recombinant alteplase was obtained in single-chain form from Cayman Chemical (Ann Arbor, MI). Methods were based upon a published protocol for the spectrophotometric measurement of clot lysis.6 Briefly, the dye Coomassie Brilliant Blue R-250 was bound to proteins in diluted plasma from human donors, and clots were formed by adding thrombin. The clots were washed, fresh diluted plasma was added, and the amount of lysis in the presence of various agents was measured by increasing absorbance at 540 nm due to the release of dye-bound proteins from the clot. Measurements were taken every 20 minutes for 3 hours, plus a final measurement after complete lysis occurred. Experiments were performed once in 7 individuals.
Results. As shown in Figure 1, a small amount of lysis occurred in the absence of added alteplase, likely from endogenous lytic factors within the plasma. Minocycline had no apparent clot lysis activity itself, with results similar to controls. Significant lysis was obtained with alteplase, achieving an average of 78% total clot lysis after 3 hours. Minocycline at 3 concentrations had no significant effect on the amount of clot lysis produced by alteplase. In agreement with previously published data, plasminogen activator inhibitor significantly inhibited clot lysis by alteplase, demonstrating the validity of the procedure used in this study.7
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Discussion. Minocycline is neuroprotective in transient and permanent focal ischemia models, reducing infarct size by 34–40% even when administered 5 hours after the onset of ischemia.3 Minocycline is therefore a candidate drug for clinical testing in humans. Patients presenting within 3 hours of symptom onset could potentially be treated with both alteplase and minocycline. The concentrations of minocycline tested in this study include both clinically achievable and higher values.8 Our data suggest that minocycline has no clot lysis activity itself and does not affect the clot lysis activity of alteplase at these concentrations.
References
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