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

作者：Srivastava Isha N; Shperdheja Jona; Baybis Marianna; Ferguson Tanya; Crino Peter B^*

来源：Neurobiology of Disease, 2016, 85: 144-154.

DOI：10.1016/j.nbd.2015.10.001

• Cerebral palsy
• mTOR
• Rapamycin
• Cell death
• Autophagy
• Inflammation
• Microglia

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-1 alpha) 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-1 alpha 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-1 alpha 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.

• 出版日期2016-1