Aggravation of focal cerebral ischemia by tissue plasminogen activator is reversed by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitor but does not depend on endothelial NO synthase.
OBJECTIVE
It has repeatedly been reported that the thrombolytic tissue plasminogen activator (tPA) may aggravate ischemic injury after stroke. The underlying mechanisms, however, remain unknown. We hypothesized that tPA induces an inhibition of endothelial NO synthase (eNOS) after focal ischemia that is responsible for ischemic damage and may be restored by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors.


METHODS
We examined the effects of tPA, administered either alone or in combination with rosuvastatin, on ischemic injury, on eNOS expression, and cell signaling after 90 minutes of intraluminal middle cerebral artery occlusion.


RESULTS
In wild-type mice, tPA delivered immediately after ischemia significantly increased infarct volume 24 hours after reperfusion. Coadministration of rosuvastatin completely reversed the tPA-induced brain damage. Western blots of ischemic brain lysates showed that tPA markedly diminished eNOS levels, increased extracellular regulated kinase (ERK)-2, and decreased MAP kinase/p38 activity. Cotreatment with rosuvastatin prevented the decrease in eNOS, reduced ERK-1/-2 and normalized p38 levels. To elucidate the role of eNOS in tPA-induced ischemic injury, we also evaluated tPA effects in eNOS knockout mice. In eNOS knockout animals, tPA again significantly increased infarct size after transient focal ischemia.


CONCLUSIONS
In a mouse model of focal cerebral ischemia, tPA induces eNOS inhibition, ERK-2 activation, and p38 inhibition, possibly as part of a more complex signaling response exacerbating brain injury. 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibition reverses the effects of tPA by a mechanism independent of eNOS.
Kilic
Ertugrul
E
Department of Neurology, University Hospital Zurich, Switzerland. ertugrul.kilic@usz.ch
Kilic
Ulkan
U
Matter
Christian M
CM
Lüscher
Thomas F
TF
Bassetti
Claudio L
CL
Hermann
Dirk M
DM
D000818:Animals; D015153:Blotting, Western; D001921:Brain / Q000473:pathology; D002545:Brain Ischemia / Q000188:drug therapy*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005464:Fluorobenzenes / Q000494:pharmacology; D015971:Gene Expression Regulation, Enzymologic; D025782:Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent / Q000378:metabolism*; D007511:Ischemia / Q000473:pathology; D017078:Laser-Doppler Flowmetry; D020935:MAP Kinase Signaling System; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D019950:Mitogen-Activated Protein Kinase 1 / Q000378:metabolism; D052250:Nitric Oxide Synthase Type III / Q000737:chemistry* / Q000378:metabolism; D011743:Pyrimidines / Q000494:pharmacology; D000068718:Rosuvastatin Calcium; D015398:Signal Transduction; D020521:Stroke / Q000628:therapy*; D013449:Sulfonamides / Q000494:pharmacology; D015912:Thrombolytic Therapy / Q000379:methods*; D013997:Time Factors; D010959:Tissue Plasminogen Activator / Q000494:pharmacology*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism
D004791:Enzyme Inhibitors; D005464:Fluorobenzenes; D011743:Pyrimidines; D013449:Sulfonamides; D000068718:Rosuvastatin Calcium; D025782:Hydroxymethylglutaryl-CoA-Reductases, NADP-dependent; D052250:Nitric Oxide Synthase Type III; D019950:Mitogen-Activated Protein Kinase 1; D048051:p38 Mitogen-Activated Protein Kinases; D010959:Tissue Plasminogen Activator