Tempol (4 hydroxy-tempo) inhibits anoxia-induced progression of mitochondrial dysfunction and associated neurobehavioral impairment in neonatal rats.

Anoxia leads to a robust generation of reactive oxygen species/nitrogen species which can result in mitochondrial dysfunction and associated cell death in the cerebral cortex of neonates. The present study investigated the pharmacological role of tempol in the treatment of rat neonatal cortical mitochondrial dysfunction induced insult progression (day-1 to day-7) and associated neurobehavioral alterations post-anoxia. Rat pups of 30h age or postnatal day 2 (PND2) were randomly divided into 5 groups (n=5 per group): (1) Control; (2) Anoxia; (3) Anoxia+Tempol 75mg/kg; (4) Anoxia+Tempol 150mg/kg; and (5) Anoxia+Tempol 300mg/kg, and subjected to two episode of anoxia (10min each) at 24h of time interval in an enclosed chamber supplied with 100% N Tempol significantly decreased nitric oxide (NO) formation and simultaneously improved superoxide dismutase (SOD) and catalase (CAT) activities. Further, we observed a significantly (P<0.05) improvement in mitochondrial respiration, complex enzyme activities, mitochondrial membrane potential (MMP) along with attenuation of transition pore opening (MPT) after treatment with tempol. Furthermore, tempol decreased expression of mitochondrial Bax, cytochrome-C, caspase-9 and caspase-3 while the increase in expression of cytoplasmic Bax, mitochondrial Bcl-2 on day-7 in cortical region indicating regulation of intrinsic pathway of apoptosis. Further, it improved anoxia-induced neurobehavioral outcome (hanging and reflex latencies). Biochemical, molecular and behavioral studies suggest the role of tempol in preserving mitochondrial function and associated neurobehavioral outcomes after neonatal anoxia.