Impaired autophagy increases susceptibility to endotoxin-induced chronic pancreatitis

L Xia,Z Xu,N Grabe,G Kroemer,F Bergmann,F Fortunato,J P Neoptolemos,T Hackert,M W Büchler,X Zhou

doi:10.1038/s41419-020-03050-3

Abstract

Chronic pancreatitis (CP) is associated with elevated plasma levels of bacterial lipopolysaccharide (LPS) and we have demonstrated reduced acinar cell autophagy in human CP tissue. Therefore, we investigated the role of autophagy in experimental endotoxin-induced pancreatic injury and aimed to identify LPS in human CP tissue. Pancreatic Atg7-deficient mice were injected with a single sub-lethal dose of LPS. Expression of autophagy, apoptosis, necroptosis, and inflammatory markers was determined 3 and 24 h later utilizing immunoblotting and immunofluorescence. The presence of LPS in pancreatic tissue from mice and from patients and healthy controls was determined using immunohistochemistry, immunoblots, and chromogenic assay. Mice lacking pancreatic autophagy exhibited local signs of inflammation and were particularly sensitive to the toxic effect of LPS injection as compared to control mice. In response to LPS, Atg7Δpan mice exhibited enhanced vacuolization of pancreatic acinar cells, increase in TLR4 expression coupled to enhanced expression of NF-κΒ, JNK, and pro-inflammatory cytokines by acinar cells and enhanced infiltration by myeloid cells (but not Atg7F/F controls). Cell death was enhanced in Atg7Δpan pancreata, but only necroptosis and trypsin activation was further amplified following LPS injection along with elevated pancreatic LPS. The presence of LPS was identified in the pancreata from all 14 CP patients examined but was absent in the pancreata from all 10 normal controls. Altogether, these results support a potential role for metabolic endotoxemia in the pathogenesis of CP. Moreover, the evidence also supports the notion that autophagy plays a major cytoprotective and anti-inflammatory role in the pancreas, and blunting metabolic endotoxemia-induced CP.

Highlights

Chronic pancreatitis (CP) is a progressive fibroinflammatory disease of the pancreas in which both exocrine and endocrine components are irreversibly damaged, eventually compromising the function of the organ[1,2]
We have shown that human pancreatitis is associated with disabled autophagic ATG7 and ATG5, as well as a reduction of LAMP2 protein expression, impairing acinar cell autophagy signaling[4,5,6]
Activation of autophagy in the pancreas of Atg7 flox/flox (Atg7F/F) mice after LPS To investigate whether endotoxemia affected pancreatic autophagy, we injected LPS systemically via the intraperitoneal (i.p.) route into mice and determined the levels of LC3-II and p62 in the pancreas

Summary

Introduction

Chronic pancreatitis (CP) is a progressive fibroinflammatory disease of the pancreas in which both exocrine and endocrine components are irreversibly damaged, eventually compromising the function of the organ[1,2]. We have shown that human pancreatitis is associated with disabled autophagic ATG7 and ATG5, as well as a reduction of LAMP2 protein expression, impairing acinar cell autophagy signaling[4,5,6]. We and others have shown that genetic intervention leading to the local removal of essential autophagy genes such as autophagyrelated 5 and 7, Atg[5], Atg[7], or lysosomal-associated membrane protein-2 (Lamp2) promotes the development of pancreatitis in rodents[3,5,6,7,8,9]. Basal autophagy levels are high in acinar cells of the exocrine pancreas, which synthesize digestive enzymes[12]

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Results

Conclusion