Indomethacin preconditioning induces ischemic tolerance by modifying zinc availability in the brain

Intracellular zinc overload causes neuronal injury during the course of neurological disorders, whereas mild levels of zinc are beneficial to neurons. Previous reports indicated that non-steroidal anti-inflammatory drugs, including indomethacin and aspirin, can reduce the risk of ischemic stroke. This study found that chronic pretreatment of rats with indomethacin, a non-selective cyclooxygenase inhibitor, provided tolerance to ischemic injuries in an animal model of stroke by eliciting moderate zinc elevation in neurons. Consecutive intraperitoneal injection of indomethacin (3 mg/kg/day for 28 days) led to modest increases in intraneuronal zinc as well as synaptic zinc content, with no significant stimulation of neuronal death. Furthermore, indomethacin induced the expressions of intracellular zinc homeostatic and neuroprotective proteins, rendering the brain resistant against ischemic damages and improving neurological outcomes. However, administration of a zinc-chelator, N,N,N',N'-tetra(2-picolyl)ethylenediamine (TPEN; 15 mg/kg/day), immediately after indomethacin administration eliminated the beneficial actions of the drug. Therefore, indomethacin preconditioning can modulate intracellular zinc availability, contributing to ischemic tolerance in the brain after stroke.