ABSTRACT
Pancreatitis is an inflammatory disease of the pancreas that can arise due to various factors, including environmental risks such as diet, alcohol, and smoking, as well as genetic predispositions. In some cases, pancreatitis may progress and become chronic, leading to irreversible damage and impaired pancreatic function. Genome-wide association studies (GWAS) have identified polymorphisms at the X-linked CLDN2 locus as risk factors for both sporadic and alcohol-related chronic pancreatitis. CLDN2 encodes claudin-2 (CLDN2), a paracellular cation-selective channel localized at tight junctions and expressed in the pancreas and other secretory organs. However, whether and how CLDN2 may modify pancreatitis susceptibility remains poorly understood. We aimed to clarify the potential role of CLDN2 in the onset and progression of pancreatitis.
We employed multiple methodologies to examine the role of CLDN2 in human pancreatic tissue, caerulein-induced experimental pancreatitis mouse model, and pancreatic ductal epithelial organoids. In both human chronic pancreatitis tissues and caerulein-induced experimental pancreatitis, CLDN2 protein was significantly upregulated in pancreatic ductal epithelial cells. Our studies using pancreatic ductal epithelial organoids and mice demonstrated the inflammatory cytokine IFNγ upregulates claudin-2 expression at both RNA and protein levels. Following caerulein treatment, Ifng KO mice had diminished upregulation of CLDN2 relative to WT mice, indicating that caerulein-induced claudin-2 expression is partially driven by IFNγ. Functionally, Cldn2 knockout mice developed more severe caerulein-induced experimental pancreatitis, indicating CLDN2 plays a protective role in pancreatitis development. Pancreatic ductal epithelial organoid-based studies demonstrated that CLDN2 is critical for sodium-dependent water transport and necessary for cAMP-driven, CFTR-dependent fluid secretion. These findings suggest that functional crosstalk between CLDN2 and CFTR is essential for fluid transport in pancreatic ductal epithelium, which may protect against pancreatitis by adjusting pancreatic ductal secretion to prevent worsening autodigestion and inflammation.
In conclusion, our studies suggest CLDN2 upregulation during pancreatitis may play a protective role in limiting disease development, and decreased CLDN2 function may increase pancreatitis severity. These results point to the possibility of modulating pancreatic ductal CLDN2 function as an approach for therapeutic intervention of pancreatitis.
Competing Interest Statement
C.R.W, L.Sh. and F.K-H. are cofounders and equity holders of Claudyn Biotech.
Footnotes
We have increased the mechanistic understanding behind claudin-2 enhancement in pancreatitis through the following new key findings. 1. Role of inflammation in claudin-2 regulation: We have shown that interferon-gamma drives the upregulation of claudin-2 both in vitro and in vivo, suggesting that pancreatic inflammation can induce claudin-2 expression to limit the development of pancreatitis. This finding provides a novel link between inflammatory signaling and epithelial barrier regulation in the pancreas. 2. Mechanistic Insights into CFTR function in pancreatic ducts: We have demonstrated mechanistically in organoid studies how CFTR is functionally tied to sodium-dependent water transport in pancreatic ductal epithelium. Similar to CFTR inhibition, claudin-2 knockout can block forskolin-mediated secretion in pancreatic ductal organoids. This highlights the integral role of claudin-2 in regulating fluid transport and maintaining pancreatic ductal function under pathological conditions.
