Postnatal Azithromycin Is Neuroprotective and Anti-Inflammatory in a Piglet Model of Hypoxic-Ischemic Encephalopathy

There is an urgent need for cytoprotective therapies for hypoxic-ischemic encephalopathy in low- and middle-income countries, where therapeutic hypothermia is not beneficial. Infection and inflammation are important risk factors for hypoxic-ischemic encephalopathy in sub-Saharan Africa, and immunomodulatory therapies might improve outcomes. Azithromycin is neuroprotective in rodent hypoxic-ischemic encephalopathy models but validation in large animal models is needed. Our aim was to assess safety and efficacy of intravenous azithromycin after inflammation-amplified hypoxia-ischemia in newborn piglets.

Twenty-five piglets underwent inflammation-amplified hypoxia-ischemia by bilateral carotid artery occlusion and reduction in FiO₂ to 6% at 4 hours after the start of Escherichia coli liposaccharide infusion (2 mcg/kg bolus+1 mcg/kg per hour over 12 hours). At 1 hour after inflammation-amplified hypoxia-ischemia, piglets were randomized to receive vehicle (n=12) or azithromycin 20 mg/kg over 1 hour (n=13), repeated at 24 and 48 hours. Piglets underwent neurocritical care for 65 hours, including continuous amplitude-integrated encephalography, magnetic resonance imaging/magnetic resonance spectroscopy at 60 hours, and brain immunohistochemistry. Group differences were evaluated by Bayesian analysis with noninformative priors; the a priori threshold probability of superiority (Pr_[sup]) was set at 95%.

Insult severity did not differ between groups. Plasma azithromycin peak concentration (C_max) of ≈2 mg/mL and brain tissue concentrations of ≈1.5 mg/kg were achieved. Azithromycin was associated with improved amplitude-integrated encephalography background (Pr_[sup]=98.6%), an overall increase in neuronal nuclear antigen (NeuN+) cells (Pr_[sup]=97.8%), increase in Iba1 (ionized calcium-binding adapter molecule 1)+cells (Pr_[sup]=99.6%) and increase in Iba1 ramification index (resting microglial morphology; Pr_[sup]=99.6%). The treatment benefit on magnetic resonance spectroscopy lactate to N-acetyl aspartate peak area ratio was modest (Pr_[sup] of 82.7% and 68.5% in the thalamic and white matter voxels, respectively).

Azithromycin, administered after inflammation-amplified hypoxia-ischemia was safe and associated with increased neuronal survival, microglial immunomodulation, enhanced amplitude-integrated encephalography recovery, and a modest benefit on lactate to N-acetyl aspartate peak area ratio. These safety and efficacy data of azithromycin as a monotherapy hold promise to improve outcomes for hypoxic-ischemic encephalopathy in low- and middle-income countries.