USE OF THE ANIMAL MODEL HIRUDO VERBANA (LEECH) TO EVALUATE THE POSSIBLE CORRELATION BETWEEN IMMUNE RESPONSE, AMYOLOIDOGENESIS AND CHRONIC INFLAMMATION

Toll-like receptors, essential pattern-recognition receptors (PRRs) of the innate immune system, recognize a range of conserved molecules of invading pathogens. Among them, TLR4 is expressed on the cell surface on both hematopoietic and non-hematopoietic cells, including cells of the central nervous system, playing a crucial role in both innate and neuroimmune responses. It is the receptor of LPS (Lipopolysaccharide) endotoxins, the major outer membrane components of Gram- bacteria and a potent activator of innate immunity and inflammatory response, inducing the expression of the proinflammatory molecules IL-18 and TNF-α. Recently, amyloidogenesis has been identified as new player in innate immune responses and has been proposed as a detoxifying event to fight ROS (reactive oxygen species) increase, given that an excessive oxidative stress becomes harmful to cells when their antioxidant capacities result insufficient to retain the appropriate redox state. Thus, an uncontrolled activation of the innate immune system can lead to amyloid fibrils accumulation and chronic inflammation. In addition, it has been shown that LPS and TLR4 are associated with Alzheimer disease (AD), characterized by the accumulation of amyloid fibrils and neuroinflammation. Within this context, microglia in the brain and monocytes/neutrophils in the periphery have a prominent role in initiating and regulating inflammation processes. Here we propose the use of the medicinal leech, Hirudo verbana, as a powerful model system to understand the role of TLR4 in innate immune response and neuroimmune activation. The advantages of using this model is found in its innate immune system that is very similar to Vertebrate’s one, but lacking the complex cross-talk typical of adaptive immunity. Our in vivo and in vitro approaches, by means of histological, ultrastructural, immunohistochemical and Western Blot techniques aim to correlate amyloid fibrils and ROS production with LPS treatment, clarifying the relationship between peripheral and central nervous system immune responses. Furthermore, by blocking TLR4 intracellular cascade we demonstrate that both macrophages and microglia cells undergo to a rescue process that implicate amyloid fibrils degradation and restoration of physiological conditions. In conclusion, our study is promising to gain novel insight about the correlation between peripheral/neuro inflammation and amyloid accumulation.