N. Vartiainen et al., Piroxicam and NS-398 rescue neurones from hypoxia/reoxygenation damage by a mechanism independent of cyclo-oxygenase inhibition, J NEUROCHEM, 76(2), 2001, pp. 480-489
We studied whether NS-398, a selective cyclo-oxygenase-2 (COX-2) enzyme inh
ibitor, and piroxicam, an inhibitor of COX-2 and the constitutively express
ed COX-1, protect neurones against hypoxia/reoxygenation injury. Rat spinal
cord cultures were exposed to hypoxia for 20 h followed by reoxygenation.
Hypoxia/reoxygenation increased lactate dehydrogenase (LDH) release, which
was inhibited by piroxicam (180-270 muM) and NS-398 (30 muM). Cell counts c
onfirmed the neuroprotection. Western blotting revealed no COX-1 or COX-2 p
roteins even after hypoxia/reoxygenation. Production of prostaglandin E-2 (
PGE(2)), a marker of COX activity, was barely measurable and piroxicam and
NS-398 had no effect on the negligible PGE(2) production. Hypoxia/reoxygena
tion increased nuclear factor-kappa B (NF-kappaB) binding activity, which w
as inhibited by piroxicam but not by NS-398. AP-1 binding activity after hy
poxia/reoxygenation was inhibited by piroxicam but strongly enhanced by NS-
398. However, both COX inhibitors induced activation of extracellular signa
l-regulated kinase (ERK) in neurones and phosphorylation of heavy molecular
weight neurofilaments, cytoskeletal substrates of ERK. It is concluded tha
t piroxicam and NS-398 protect neurones against hypoxia/reperfusion. The pr
otection is independent of COX activity and not solely explained by modulat
ion of NF-KB and AP-1 binding activity. Instead, piroxicam and NS-398-induc
ed phosphorylation through ERK pathway may contribute to the increased neur
onal survival.