Lysosomal rupture induced by structurally distinct chitosans either promotes a type 1 IFN response or activates the inflammasome in macrophages

Chitosan is a family of glucosamine and N-acetyl glucosamine polysaccharides with poorly understood immune modulating properties. Here, functional U937 macrophage responses were analyzed in response to a novel library of twenty chitosans with controlled degree of deacetylation (DDA, 60-98%), molecular weight (1 to >100 kDa), and acetylation pattern (block vs. random). Specific chitosan preparations (10 or 190 kDa 80% block DDA and 3, 5, or 10 kDa 98% DDA) either induced macrophages to release CXCL10 and IL-1ra at 5-50 mug/mL, or activated the inflammasome to release IL-1beta and PGE2 at 50-150 mug/mL. Chitosan induction of these factors required lysosomal acidification. CXCL10 production was preceded by lysosomal rupture as shown by time-dependent co-localization of galectin-3 and chitosan and slowed autophagy flux, and specifically depended on IFN-beta paracrine activity and STAT-2 activation that could be suppressed by PGE2. Chitosan induced a type I IFN paracrine response or inflammasome response depending on the extent of lysosomal rupture and cytosolic foreign body invasion. This study identifies the structural motifs that lead to chitosan-driven cytokine responses in macrophages and indicates that lysosomal rupture is a key mechanism that determines the endogenous release of either IL-1ra or IL-1beta.

Uncontrolled Keywords

Acetylation; Chemokine CXCL12/metabolism; Chitosan/chemistry/*pharmacology; Dinoprostone/metabolism; Humans; Inflammasomes/*metabolism; Interferon Type I/*metabolism; Interleukin 1 Receptor Antagonist Protein/metabolism; Interleukin-1beta/metabolism; Lysosomes/drug effects/*pathology; Macrophages/drug effects/*metabolism; Proton Magnetic Resonance Spectroscopy; U937 Cells; *Chitin/chitosan; *Immunomodulation; *Inflammasome; *Macrophage; *Type 1 interferon