mTOR pathway inhibition prevents neuroinflammation and neuronal death in a mouse model of cerebral palsy

• Published in: Neurobiology of disease Vol. 85; pp. 144 - 154
• Main Authors: Srivastava, Isha N, Shperdheja, Jona, Baybis, Marianna, Ferguson, Tanya, Crino, Peter B
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01-01-2016; Elsevier
• Subjects: Animals; Animals, Newborn; Anti-Inflammatory Agents - pharmacology; Autophagy; Brain - drug effects; Brain - pathology; Brain - physiopathology; Cell death; Cell Death - drug effects; Cell Death - physiology; Cerebral palsy; Cerebral Palsy - drug therapy; Cerebral Palsy - pathology; Cerebral Palsy - physiopathology; Disease Models, Animal; Hypoxia-Ischemia, Brain; Inflammation; Lipopolysaccharides; Mice, Inbred C57BL; Microglia; mTOR; Neuroimmunomodulation - drug effects; Neuroimmunomodulation - physiology; Neurology; Neurons - drug effects; Neurons - pathology; Neurons - physiology; Neuroprotective Agents - pharmacology; Rapamycin; Signal Transduction - drug effects; Sirolimus - pharmacology; TOR Serine-Threonine Kinases - metabolism; chloroquine; Cerebral palsy; rapa; Cell death; hypoxia–ischemia-lipopolysaccharide; mTOR; HIL; Inflammation; CHQ; Autophagy; rapamycin; Microglia; Rapamycin
• ISSN: 0969-9961; 1095-953X
• DOI: 10.1016/j.nbd.2015.10.001

Abstract Background and purpose Mammalian target of rapamycin (mTOR) pathway signaling governs cellular responses to hypoxia and inflammation including induction of autophagy and cell survival. Cerebral palsy (CP) is a neurodevelopmental disorder linked to hypoxic and inflammatory brain injury however, a role for mTOR modulation in CP has not been investigated. We hypothesized that mTOR pathway inhibition would diminish inflammation and prevent neuronal death in a mouse model of CP. Methods Mouse pups (P6) were subjected to hypoxia–ischemia and lipopolysaccharide-induced inflammation (HIL), a model of CP causing neuronal injury within the hippocampus, periventricular white matter, and neocortex. mTOR pathway inhibition was achieved with rapamycin (an mTOR inhibitor; 5 mg/kg) or PF-4708671 (an inhibitor of the downstream p70S6kinase, S6K, 75 mg/kg) immediately following HIL, and then for 3 subsequent days. Phospho-activation of the mTOR effectors p70S6kinase and ribosomal S6 protein and expression of hypoxia inducible factor 1 (HIF-1α) were assayed. Neuronal cell death was defined with Fluoro-Jade C (FJC) and autophagy was measured using Beclin-1 and LC3II expression. Iba-1 labeled, activated microglia were quantified. Results Neuronal death, enhanced HIF-1α expression, and numerous Iba-1 labeled, activated microglia were evident at 24 and 48 h following HIL. Basal mTOR signaling, as evidenced by phosphorylated-S6 and -S6K levels, was unchanged by HIL. Rapamycin or PF-4,708,671 treatment significantly reduced mTOR signaling, neuronal death, HIF-1α expression, and microglial activation, coincident with enhanced expression of Beclin-1 and LC3II, markers of autophagy induction. Conclusions mTOR pathway inhibition prevented neuronal death and diminished neuroinflammation in this model of CP. Persistent mTOR signaling following HIL suggests a failure of autophagy induction, which may contribute to neuronal death in CP. These results suggest that mTOR signaling may be a novel therapeutic target to reduce neuronal cell death in CP.