TLR4 dependent heparan sulphate-induced pancreatic inflammatory response is IRF3-mediated

Abstract

BackgroundDegraded extracellular matrix can stimulate the innate immune system via the Toll-Like Receptor-4 (TLR4). In the pancreas, syndecan-anchored heparan sulphate (HS) on the ductal epithelium can be cleaved off its protein cores by the proteases (trypsin and elastase) and potentially activate TLR4 signalling.MethodsTo investigate this signalling event, a low sulphated HS (500 μg/ml) was infused into the biliary-pancreatic duct of C57BL/6J wild-type mice. Phosphate buffered saline (PBS) and lipopolysaccharide (LPS) were used as negative and positive controls, respectively. Mice were sacrificed after 1, 3, 6, 9, and 48 hours and tissues were analysed for neutrophil and cytokine contents. In order to study the TLR4 signalling pathway of HS in the pancreas, genetically engineered mice lacking TLR4, Myeloid Differentiation primary response gene (88) (MyD88) or Interferon Regulatory Factor 3 (IRF3) were subjected to pancreatic infusion of HS.ResultsNeutrophil sequestration and corresponding myeloperoxidase (MPO) activity in the pancreas were increased 9 hours following HS challenge. In wild-type mice, the monocyte chemoattractant protein-1(MCP-1) increased at 3 hours after infusion, while RANTES increased after 9 hours.TLR4, MyD88, and IRF3 knockout mice showed an abrogated neutrophil recruitment and myeloperoxidase activity in the HS group, while the LPS response was only abolished in TLR4 and MyD88 knockouts.ConclusionsThe results of this study show that HS is capable of initiating a TLR4-dependent innate immune response in the pancreas which is distinctly different from that induced by LPS. This inflammatory response was mediated predominantly through IRF3- dependent pathway. Release of HS into the pancreatic duct may be one important mediator in the pancreatic ductal defence.

Heparanase is preferentially expressed in human psoriatic lesions and induces development of psoriasiform skin inflammation in mice

“…In particular, ability of heparanase to stimulate macrophage activation and direct macrophage responses toward chronic inflammatory pattern was highlighted in our studies focusing on inflammatory bowel disease [21,62], mechanistically related to psoriasis. The exact mechanism underlying heparanase-dependent sensitization of macrophages is not fully understood, however generation of soluble HS degradation fragments (shown to stimulate TLR signaling both in vitro and in vivo [63,64]) may play a role. This feature of heparanase (further supported by reports describing augmented macrophage activation in the presence of increased heparanase levels in a model of neointimal lesions following vascular injury [20] and in atherosclerotic plaque progression toward vulnerability [65]), could be highly relevant to the enzyme’s role in the pathogenesis of psoriasis, as well.…”

Heparanase: From basic research to therapeutic applications in cancer and inflammation

“…HS is known to control inflammatory responses at multiple levels, including sequestration of cytokines/chemokines in the extracellular space, modulation of leukocyte interactions with endothelium and ECM, and initiation of innate immune responses through interactions with toll-like receptors 4 (TLR4) (Akbarshahi et al, 2011; Axelsson et al, 2012; Bode et al, 2012; Brunn et al, 2005; Gotte, 2003; Johnson et al, 2002; Parish, 2006; Wang et al, 2005). Thus, HS remodeling by heparanase may affect several aspects of inflammatory reactions, such as leukocyte recruitment, extravasation and migration towards inflammation sites; release of cytokines and chemokines anchored within the ECM or cell surfaces, as well as activation of innate immune cells (Goldberg et al, 2013; Li and Vlodavsky, 2009; Zhang et al, 2014).…”

Versatile role of heparanase in inflammation

“…HS is known to control inflammatory responses at multiple levels, including sequestration of cytokines/chemokines in extracellular space, modulation of leukocyte interactions with endothelium and ECM, and initiation of innate immune responses through interactions with toll-like receptor 4 (TLR4) (Akbarshahi et al, 2011; Axelsson et al, 2012; Bode et al, 2008; Brunn et al, 2005; Gotte, 2003; Johnson et al, 2002; Parish, 2006; Taylor and Gallo, 2006; Wang et al, 2005). Thus, HS enzymatic remodeling by heparanase may affect several aspects of inflammatory reactions, such as leukocyte recruitment, extravasation and migration towards inflammation sites; release of cytokines and chemokines anchored within the ECM or cell surfaces, as well as activation of innate immune cells.…”