To Explore the Role of Sestrin2/mTORC1 on Autophagy and Protein Synthesis in Transient Global Ischemia-Induced Hippocampal Neuronal Injury

A brief yet complete disruption of blood flow to the brain, or “transient global ischemia (TGI)”, may cause delayed neuronal death in hippocampus. This neuronal death occurs 2-4 d after TGI within a specific neuronal population of hippocampus, namely the CA1 pyramidal neurons. Clinically, TGI occurs in such serious cardiovascular disorders as cardiogenic shock after myocardial infarction or reversible severe hypotension. The underlying mechanisms of delayed CA1 neuronal loss following TGI are not well understood. Cerebral ischemia can cause excessive reactive oxygen species (ROS) generation and result in neuronal damage. Recent studies suggest that sestrin2 is a crucial regulator for ROS scavenging enzymes such as peroxiredoxins. Also, it was revealed that sestrin2 may regulate autophagy and protein synthesis related-translation machinery through the effect of mammalian target of rapamycin complex1 (mTORC1) and may have a pivotal for longevitity. It is thus reasonable to assume that sestrin2 signaling may act as an endogenous protective response, regulate ROS formation, accommodate cell metabolism to survive and would be vital to lessen TGI-induced neuronal injury. However, the role of sestrin2 in cerebral ischemia is not well studied. In this project, we attempt to define a novel protective pathway involving sestrin2 signaling which may regulate the autophagy and protein synthesis through the effect of mTORC1 in TGI-induced neuronal damage in hippocampus. Three specific aims will be tested. We’ll first determine if TGI-induced neuronal damage in hippocampus may relate to excessive ROS formation and concomitantly induce the change of sestrin2, mTORC1 , autophagy and protein synthetic machinery. Secondly, we’ll determine the causal relationship in this endogenous protective pathway among sestrin2/mTORC1 and related molecules involving autophagy and protein synthesis. Thirdly, we’ll determine if sestirn2 signaling is involving the underlying mechanisms in some medications possessing neuroprotective effects such as thiazolidinedione drugs, stains and minocycline. These aims will be accomplished by using rat TGI model and investigating sestrin2 and mTORC1 activity with immunoblotting and imunohistochemistry study. The detrimental effect of excessive ROS generation will be measured with protein carbonyl, malondialdehyde, 8-OH-dG for protein, lipid and DNA damage respectively. The outcome measurement will include the extent of DNA fragmentation and neuronal count by cresyl violet staining in hippocampal CA1 subfield. We’ll use pharmacological and molecular approaches with inhibitors and siRNA for sestrin2 to validate this signaling pathway. Several commonly used medications including pioglitazine, rosuvastatin and minocycline with neuroprotective effects may have direct or indirect mechanisms involving induction of sestirn2 and worth to explore. The ultimate goal of this project is to develop protective strategies and prevent TGI-induced neuronal injury in hippocampus via modulation of the sestrin2/mTORC1 signaling pathways, regulating autophagy and protein synthesis and hence lessening ROS formation and adapting cell metabolism to survive. The ability to reduce TGI-induced neuronal injury in hippocampus may have therapeutic implication not only in TGI but also in other stroke syndromes.

Project ID:PC10308-1871
External Project ID:MOST103-2314-B182-026-MY2