Protective Effect of Erythromycin Pre-adaptation on Focal Cerebral Ischemia in Rats and its Changes in TNF-α and nNOS.

Context: Ischemic stroke accounts for 85% of all types of stroke. Ischemic preconditioning can provide protection against cerebral ischemic injury. Erythromycin can induce ischemic preconditioning in brain tissue.

Objective: The study intended to investigate the protective effects of erythromycin preconditioning on infarct volume after focal cerebral ischemia in rats and on the expression of tumor necrosis factor-alpha (TNF-α) and neuronal nitric oxide synthases (nNOS) in rat-brain tissue.

Design: The research team performed an animal study.

Setting: The study took place in the Department of Neurosurgery at the First Hospital of China Medical University in Shenyang, China.

Animals: The animals were 60 healthy male Wistar rats, aged 6 to 8 weeks and weighing 270 to 300 g.

Intervention: The research team randomly divided the rats into a control group in simple randomization and intervention groups preconditioning them according to their body weights using different concentrations of erythromycin-5, 20, 35, 50, and 65 mg/kg, with 10 rats in each group. The team induced focal cerebral ischemia and reperfusion using a modified, longa-wire embolization method. The control group, also 10 rats, received an injection intramuscularly of normal saline.

Outcome Measures: The research team: (1) calculated the volume of cerebral infarction using triphenyltetrazolium chloride (TTC) staining with image analysis software and (2) investigated the effects of erythromycin preconditioning on the expression of TNF-α and nNOS mRNA and protein in the rat-brain tissue using real-time polymerase chain reaction (PCR) and Western blot.

Results: Erythromycin preconditioning reduced the volume of cerebral infarction after induction of cerebral ischemia, showing a U-shaped, dose-response relationship, and the cerebral infarction volume significantly decreased in the 20-, 35-, and 50-mg/kg erythromycin preconditioning groups (P < .05). Erythromycin preconditioning at 20-, 35-, and 50-mg/kg significantly down-regulated the mRNA and protein expression of TNF-α in the rat-brain tissue (P < .05), with the 35-mg/kg erythromycin preconditioning group having the most significant downregulation. Erythromycin preconditioning at 20-, 35-, and 50-mg/kg upregulated the mRNA and protein expression of nNOS in the rat-brain tissue (P < .05), with the 35-mg/kg erythromycin preconditioning group having the most significant upregulation of the mRNA and protein of nNOS.

Conclusions: Erythromycin preconditioning had a protective effect against focal cerebral ischemia in rats, and the best protective effect occurred for the 35-mg/kg preconditioning. The reason may be related to the fact that erythromycin preconditioning significantly upregulated nNOS and downregulated TNF-α in the brain tissue.