Abstract:
Neuroinflammation occurs in a number of different disease states and is hugely damaging within the ischemic brain. Tolerance; the phenomenon by which a low level inflammatory stimulus induces a hyporesponsive and thus anti-inflammatory state following a secondary stimulus, has been demonstrated to induce neuroprotection through a number of mechanisms. The toll-like receptor (TLR) family of innate pattern recognition receptors are essential regulators of the immune system and previous research has demonstrated that activation of TLR 2, 3, 4, 9 and recently 7, by their ligands can induce tolerance to a pro-inflammatory stimulus or model of ischemia. However whilst this has been demonstrated in vitro and in vivo with multiple murine and rodent models, tolerance has not been induced in human cerebrovascular endothelial cells. As human and murine toll like receptor regulation and expression varies considerably, further experimentation in the human model is required. This thesis is the first to determine the expression of toll-like receptors in a commercially available human cerebrovascular endothelial cell line, to determine the functional response following TLRs 3 and 7 activation of these cells and to determine the functional effect of TLRs 3 and 7 ligands co-treated with a pro-inflammatory stimulus in these cells. The results indicate that TLR3 and 4 were expressed and that ligands of both these and TLR7 were able to mediate a change in basolateral adhesion. Following co-treatment with a proinflammatory stimulus it was observed that the TLR7 ligand Imiquimod is able to attenuate the subsequent pro-inflammatory cascade. In contrast it was found that treatment with a TLR 3 ligand mediated synergistic effects when administered with a pro-inflammatory stimulus. This thesis therefore demonstrates contrasting functional effects of viral TLR ligands when administered with a pro- inflammatory insult and indicates that the FDA approved Imiquimod is able to attenuate inflammation at clinically relevant time points.
