| Abstract No.: | C-B3066 |
| Country: | Canada |
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| Title: | ATTENUATION OF LPS INDUCED SICKNESS BEHAVIOUR THROUGH INTERRUPTION OF TLR4 SIGNALLING IN MICROGLIA |
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| Authors/Affiliations: | 1 Dustin Hines*; 1 Hyun Beom Choi; 1 Rochelle Hines; 1 Anthony Phillips; 1 Brian MacVicar;
1 University of British Columbia, Vancouver, BC, Canada
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| Content: | Sickness behaviour is the term for the profound behavioural changes, such as loss of appetite, decreased motility and lack of interest in the environment that are triggered by infections and inflammation. The inflammation that underlies the changes seen in sickness behavior has also been implicated in chronic conditions such as depression and neurodegeneration. Peripheral administration of the bacterial endotoxin lipopolysaccharide (LPS) in rodents triggers sickness behavior in part through activation of the innate immunity receptor Toll Like Receptor 4 (TLR4). LPS delivered systemically signals to the CNS in circumventricular regions lacking blood brain barrier and in the perivascular compartment surrounding blood vessels via activation of the TLR4 receptor complex that is selectively expressed on microglia. Objective: The objective of the current experiments was to block the activation of TLR4 in microglia, and examine resulting effects on CNS immune signaling, microglia morphology and sickness behavior. Methods: We developed interfering peptides to specifically block two intracellular sites within the TLR4/IL-1 receptor (TIR) domain of TLR4, a key structural motif for signal transduction. Disruption of TIR signaling through adaptor proteins will result in altered production of cytokines, such as TNFalpha. This LPS-induced cytokine release from microglia is thought to be the initiating component of behavioural changes seen with sickness behaviour. Results: We use ELSIA and Western blotting to determine whether tat conjugated TLR4 interfering peptides could effectively prevent the second messenger activation and cytokine production induced by LPS in microglia using brain slices and in vivo. We show here that interfering peptides against intracellular TLR4 signaling effectively prevent LPS second messenger activation, cytokine formation and microglial activation in brain slices and in the whole animal. Using live two photon microscopy we also show that LPS induced microglia morphology changes can be blocked by tat peptide blockade of TLR4 receptor signaling. In addition TLR4 interfering peptide treatment in mice and rats reduces the behavioral changes caused by LPS injections, as assessed in the open field and using the intracranial self-stimulation paradigm. Conclusion: Therefore the use of tat conjugated interfering peptides targeting TLR4 signaling is a novel way to modify microglia induced actions of LPS, and ultimately inflammation and sickness behaviour.
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