Neuregulin’s role in regulating the anti-inflammatory pathway
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Inflammation can be up-regulated by microglia and macrophages through the release of pro-inflammatory cytokines such as tumour necrosis factor-alpha (TNF-α). Excess production of TNF-α can lead to a variety of diseases and even tissue necrosis. Recently, the expression of alpha seven acetylcholine receptors (α7AChR) by microglia have been shown to decrease the amount of TNF-α released. This anti-inflammatory pathway has been studied extensively where researchers are able to reduce TNF-α concentration through α7AChR expression and increases in the concentration of its ligand. I have shown that Neuregulin is able to increase the expression of α7AChR in microglia and macrophages. Using three immortalized cell lines, BV-2, EOC-20 and RAW 264.7, and primary microglial cells harvest from mice I investigated the role that neuregulin plays in the anti-inflammatory process. Neuregulin signals through the ErbB receptors, a family of tyrosine kinase receptors, to facilitate the effects on ACh expression. My results show that ErbB4 is expressed in BV-2, EOC-20 and RAW 264.7 cell lines while ErbB2-4 receptors are expressed in primary microglia. As well, I was able to show that ErbB4 became phosphorylated upon binding to NRG in immortalized cell lines. Using an Enzyme Linked Immunsorbent Assay to analyze TNF- α concentration in microglia and macrophages, I was able to demonstrate that increased levels of α7AChRs did not result in a reduction in TNF-α concentration. These results showed that NRG is able to increase α7AChRs in microglia and macrophages after the phosphorylation of the ErbB4 receptors. As well, this increase in α7AChR does not relate to a reduction in TNF-α, thus under these experimental conditions does not have an effect on the anti-inflammatory pathway.