The Investigation of Anti-Microglia/Macrophage Mechanisms of Different Tak1/Tabs Regulators and Their Protective Effects in Intracerebral Hemorrhage and Brain Abscess

Despite the advent of modern treatments, intracerebral hemorrhage (ICH) and brain abscess both remain the potentially fatal central nervous system (CNS) diseases. A plethora of evidence has been indicated microglia/macrophage activation, astrocyte dysfunction, glutamate-induced excitotoxicity, overproduction of inflammatory mediators/cytokines and matrix metalloproteinase (MMPs) which participate in the disruption of blood-brain barrier and neural death. Microglia/macrophage activation is evident within hours following CNS stress by hemorrhage or infection, and the immune response elicited involves the rapid induction of several proinflammatory, cytokines and effectors, including cytokines, cyclooxygenase (COX), inducible nitric oxidase (iNOS) and matrix metalloproteinase (MMP). Key regulators of neuroinflammation are the signaling NF-κB and p38/JNK MAP kinase, which share a common upstream activator, the mitogen-activated protein kinase kinase kinase (MAPK3K) TGF-β-activated kinase 1 (TAK1). Also, TAK1-binding proteins (TABs) including TAB1, TAB2 and TAB3, could bind in collaboration with TAK1 by specific functionally ubiquitination and association, which results in autophosphorylation and activation of TAK1. TAK1/TAB complex phosphorylates the MAPK kinase and inhibitor kappa B kinase β (IKKβ) for activation of AP-1 and NF-κB pathways. Current findings suggested that TAK1/TAB regulators (as the small-molecule compounds or endogenous effectors) could down-regulate inflammatory responses and phagocytic activation. However, there were opposite findings in some conditional knockout mice. Therefore, knowledge remains limited on the contributions of TAK1/TABs regulators to the treatment of ICH or brain abscess. In our preliminary studies, it was found a TAK1/TAB regulator (LC53) with inhibition on monocytic MMP-9 gelationolysis and protein expression through TAK1/TAB2/3/IKK inhibition. Also, this regulator attenuated microglial COX-2/iNOS expression, and brain gelationolysis/edema in ICH animal model. The aims of this project will to investigate three major points, first, to evaluate and identify the effects of potential TAK1/TAB regulators including the expression of inflammatory mediators or phagocytic functions such as phagocytosis and migration in microglia/macrophage. Also, the regulatory functions were compared as cell-specific actions. Second, to identify the mechanisms of these regulators on the signallings of TAK1/TAB1/2/3 by their interference with phosphorylation or ubiquitination to affect protein stability or binding activity. Also the down-stream signal effectors such as MAPK or NF-κB will be clarified. Third, we will execute the experimental animal models including intracerebral hemorrhage (collagenase induction) and brain abscess (LPS/LTA induction) to investigate the neuroprotective functions and mechanisms of TAK1/TAB regulators in brain injury and microglia/macrophage activation. On the other hand, the conditional knockout mice (TAK1- and TAB2-KO) will be studied to understand and compare the long-term therapeutic issues. Our study will elucidate the importance of targeting TAK1/TABs as promising therapeutic approach to counteract the progression of ICH and brain abscess.