Gli2 Mediated Activation of Hedgehog Signaling Attenuates Acute Pancreatitis via Balancing Inflammatory Cytokines in Mice

Abstract

Background/aims: Inflammatory response is a determinant in the pathological progression of acute pancreatitis (AP). Previous studies have shown that the activation of hedgehog (Hh) signaling is a remarkable change in caerulein-induced AP. However, the relationship between Hh signaling and inflammation is largely ambiguous.

Methods: The AP mouse model was induced by injection of cerulein, and histological staining and serum enzymology assays were used to evaluate the establishment of AP. Western blot assay was used to determine the protein levels, cleavage of apoptotic proteins, and activation of the NF-κB signaling pathway. Cytokine array was used to screen inflammatory cytokines, and target cytokines' transcriptional expression and serum levels were examined by real-time PCR and enzyme-linked immunosorbent assay, respectively.

Results: The key transcriptional factor in Hh signaling, Gli2, was upregulated in the pancreas and other tissues during the process of AP, and it seems to be a characteristic feature of local inflammation in pancreatic tissue and systemic inflammatory response in multiple organs. The inflammatory NF-κB pathway is required for the activation of Hh signaling, as blockade of the NF-κB pathway by pyrrolidine dithiocarbamate impaired the Gli2 upregulation. Manipulation of Gli2 expression altered the activation of the NF-κB pathway correspondingly, as well as the cell apoptosis in cerulein-induced AP. Moreover, Gli2 upregulation changed the cytokine expression profile in mouse pancreatic acinar cells, mainly decreasing the pro-inflammatory cytokines interleukin (IL)-6, interferon-γ, and FasL. The anti-inflammatory cytokine IL-10 was upregulated by Gli2 overexpression. Interdiction of Gli2 by the Gli-specific inhibitor GANT61 exacerbated AP in mice and altered the balance of inflammatory cytokines.

Conclusions: This study indicates that Hh activation during AP development is a negative feedback of the inflammatory response, restricting inflammatory injury to the pancreas and other tissues. Thus, manipulation of Hh signaling should shed light on limiting inflammation and alleviating AP damage.

Keywords: Acute pancreatitis; Gli2; Hedgehog signaling; Inflammation; NF-κB.