ODP254 WFS1 Loss of Function Causes ER Stress-Mediated Inflammation in Pancreatic β-Cells
Authors: Morikawa Shuntaro , Blaher Lindsey , Urano Fumihiko 
Published: November 2022

Abstract
Wolfram syndrome is a rare genetic disorder characterized by juvenile-onset diabetes mellitus, optic nerve atrophy, hearing loss, diabetes insipidus, and progressive neurodegeneration. Pathogenic variants in the WFS1 gene are the main causes of Wolfram syndrome. WFS1 encodes a transmembrane protein localized to the endoplasmic reticulum (ER) and regulates the unfolded protein response (UPR). Loss of function of WFS1 leads to dysregulation of insulin production and secretion, ER calcium depletion, and cytosolic calpains activation, resulting in the activation of apoptotic cascades. Although the terminal UPR is well known to yield an inflammatory response called "sterilized inflammation" that accelerates β-cell dysfunction and death in diabetes, the contribution of β-cell inflammation to the development of diabetes in Wolfram syndrome has not been fully understood. Here we show that WFS1-deficiency enhances the gene expression of pro-inflammatory cytokines and chemokines, leading to cytokine-induced ER-stress and cell death in pancreatic β-cells. Under thechronic[BL1] high-glucose condition, CRISPR/Cas9-mediated Wfs1-knockout (KO) INS-1 832/13 cells, the pancreatic β-cell model of Wolfram syndrome, showed enhanced gene expression levels of ER stress markers (Chop, sXbp1, Bip, and Txnip). Moreover, the gene expression levels of pro-inflammatory cytokines (Il-1β, Il-6), chemokine (Ccl2), and vascular endothelial growth factor A (VegfA) were higher in Wfs1- KO INS-1 832/13 cells when compared to Wfs1-wild type INS-1 832/13 cells. [BL2] The high glucose-induced pro-inflammatory cytokine genes in Wfs1-KO INS-1 832/13 cells were mediated by the PKR-like ER-resident kinase (PERK) and inositol-requiring enzyme 1α (IRE1α)pathways. Furthermore, the IFN-γ and IL-1β treatment enhanced ER stress-mediated cell death and upregulated the pro-inflammatory cytokine gene expression in Wfs1-KO INS-1 832/13 cells. To confirm these findings, we investigated whether inflammation occurs in a mouse model of Wolfram syndrome. Compared to wild-type mice, 10-month-old whole body Wfs1-KO mouse islets showed a significantly higher density of Iba1, which is a marker for macrophage expression. The islet-infiltrated macrophages in these Wfs1-KO mice expressed the M1-macrophage marker (CD68). There was also strong fibrosis and a high density of endothelial cell marker (CD31) in the Wfs1-KO mouse islets. These results demonstrate that WFS1 loss-of-function enhances the inflammatory responses in pancreatic β-cells. The results in our study identified sterile inflammation as a new pathological mechanism in the development of diabetes in Wolfram syndrome. In Wolfram syndrome model mice, islets are highly infiltrated with macrophages, suggesting that the vicious cycle of ER stress and sterile inflammation accelerates the progression of diabetes in a cell-autonomous and cell-nonautonomous manner. A deeper understanding of the pathophysiology of Wolfram syndrome is essential for developing novel therapeutic targets for the disease.
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