The medicinal leech as a valuable model for better understanding the role of a TLR4-like receptor in the inflammatory process
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Despite extensive investigation focused on both the molecular characteristics and the expression level of Toll-like receptors (TLRs) during the inflammatory response in vertebrates, few data are available in the literature on the role of these proteins in invertebrate’s immune response. Here, we propose the medicinal leech as a valuable model to better elucidate the role of TLR4 and its related products, such as tumor necrosis factor (TNF-α), after activation of the leech peripheral immune system with the endogenous medicinal leech recombinant allograft inflammatory factor-1 (rHmAIF-1) or with an exogenous stimulus, such as lipopolysaccharide (LPS). Our results indicate that activated macrophages (HmAIF-1+) and granulocytes (CD11b+) express both TLR4 and its coreceptor CD14. Moreover, functional studies performed by injecting a cyanobacterium selective TLR4 antagonist CyP demonstrated that only the TLR4 pathway was blocked, while the immune response caused by lipoteichoic acid (LTA) treatment is not affected. These results are consistent with literature on vertebrates, indicating that TLR4 functions as a LPS receptor while the recognition of LTA may involve other pathways.
KeywordsTLR4 LPS Cyanobacterial product Macrophage Granulocyte
N.B. (PhD students of the “Biotechnology, Biosciences and Surgical Technology” course) is supported by a PhD fellowship of the DBSV, University of Insubria. The authors wish to thank Prof. Jacopo Vizioli (University of Lille, France), for providing us the anti HmAIF1 antibody.
AG, MM and CR conceived and designed the experiments. RG and NB performed the experiments. AG and RG analyzed the data and wrote the manuscript. GT and MdeE provided expertise for TEM and imaging and contributed reagents/materials/analysis tools. All authors critically reviewed the manuscript.
This study was technically supported by the Centro Grandi Attrezzature (CGA) core facilities of the University of Insubria. The authors’ research was funded by CARIPLO (Fondazione Cassa di Risparmio delle Province Lombarde) -2016-0835 Ricerca malattie invecchiamento 2016: FRAMYEVO and Fondi per l’Ateneo (FAR 2017) to Grimaldi, de Eguileor and Tettamanti.
Compliance with ethical standards
All applicable international, national and/or institutional guidelines for the care and use of animals were followed.
Conflict of interest
The authors declare that they have no conflict of interest.
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