NF-κB Controls Resistance of Human Salivary Gland (HSG) Cells to Apoptosis in an &lt;i&gt;in Vitro&lt;/i&gt; Model of Sjogren’s Syndrome

Yan Wang,Carole Mcarthur,Alexander Shnyra,Agostino Molteni,Syed A Jamal,Luis F Torres-Romero

doi:10.4236/ojra.2014.43025

Abstract

Aim: To elucidate the anti-apoptotic properties of nuclear factor kappa light-chain-enhancer of activated B cells (NF-κB) and feedback regulation of NF-κB by nuclear factor of kappa light-chain-enhancer of activated B-cells inhibitor alpha (IκBα). Methods: We developed an in vitro model of Sjogren’s syndrome by transfecting human salivary gland (HSG) and acinar cells (NS-SV-AC) with a plasmid-encoding IκBαM (pCMV-IκBαM), a degradation-resistant IκBα (nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha)-mutant, and examined TNF-induced apoptosis and anti-apoptotic properties of NF-κB. Apoptosis and induction of pro-apoptotic and anti-apoptotic genes were investigated by cDNA arrays, RT-PCR, electrophoretic mobility shift assays, and western blot. Results: In the presence of NF-κB inhibitors, TNF-induced apoptosis was markedly increased in both salivary gland and acinar cells. Increased caspase-3 activity was present in both HSG and NS-SV-AC cells. IκBαM-transfected salivary gland cells were more sensitive to TNF-induced apoptosis than IκBαM-transfected acinar cells. Transcription of pro-apoptotic genes was confirmed in both HSG and NS-SV-AC cells that were transfected with IκBαM. Results from caspase-3 activity assay confirmed previous experiments showing an apoptotic role for NF-κB. Conclusion: Data from gene expression arrays suggest that different mechanisms may operate during TNF-induced apoptosis in salivary gland ductal and acinar cells.

Highlights

Sjogren’s Syndrome (SS) is an autoimmune disease that involves inflammation of salivary glands, lacrimal glands, and other tissues of the body [1]
NF-κB suppression differentially regulates apoptosis-related genes in ductal and acinar cells. In both IκBαM-Human Salivary Gland (HSG) and NS-SV-AC cells, Tumor Necrosis Factor (TNF) induced a transient decrease in IκB protein within 20 - 30 min of stimulation which was restored upon a 24-hr treatment due to NF-κB dependent transactivation of IκB gene and de novo synthesis of IκB protein (Figure 1(c), lane 2)
We speculate that HSG ductal cells represent type I cells which are able to activate high amounts of initiator caspase-8 at the death-inducing signaling complex (DISC), facilitating the downstream activation of an executioner caspase-3 [31]

Summary

Introduction

Sjogren’s Syndrome (SS) is an autoimmune disease that involves inflammation of salivary glands, lacrimal glands, and other tissues of the body [1]. Apoptosis of salivary gland tissue is a hallmark of the disease. The pathogenesis of SS is poorly understood, both genetic and infectious factors have been implicated [3]. Both cell-mediated and humoral responses accompanied by pro-inflammatory cytokines, such as TNF-alpha, IL-1, IL-6, IL-8, IL 17, IL-23, and the recently discovered IL-34, transcription factors such as NF-κB and STAT3, caspases and other proteins that mediate programmed cell death have been implicated in the pathogenesis of SS [4] [5]. Symptoms result from tissue destruction but the mechanism of destruction, generally agreed to be induced by cytokines, is poorly understood

Objectives

Methods

Results

Discussion

Conclusion