Science and Mathematics Faculty Publications

A secretagogue-siRNA conjugate confers resistance to cytotoxicity in a cell model of Sjögren's syndrome

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Arthritis & Rheumatism





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Objective—Sjögren's syndrome (SjS) is characterized by xerophthalmia and xerostomia resulting from loss of secretory function due to immune cell infiltration in lacrimal and salivary glands. Current SjS therapeutic strategies employ secretagogues to induce secretion via muscarinic receptor stimulation. Based on our expertise on muscarinic type-3-receptor (M3R), we are utilizing ligands specific for muscarinic receptor to deliver siRNA into cells via receptor-mediated endocytosis, thereby altering epithelial cell responses to external cues such as pro-inflammatory or death signals while simultaneously stimulating secretion.

Methods—Carbachol was synthesized with an active choline group and conjugated with siRNA targeting caspase-3, and a human salivary gland cell line (HSG) was used to test the efficacy of this conjugate.

Results—Lipofectamine transfection of conjugate into cells resulted in 78%-reduction in caspase-3 gene expression, while external conjugate treatment of HSG cells resulted in similar intracellular calcium release and induction of endocytosis as carbachol stimulation indicating that the siRNA and carbachol portions of conjugate retained function after conjugation. HSG cells treated with conjugate (without Lipofectamine transfection) exhibited a 50% reduction in caspase-3 gene and protein expression indicating our conjugate is effective in delivering functional siRNA into cells via receptor-mediated endocytosis. Furthermore, TNF-α induced apoptosis was significantly reduced in conjugate treated cells.

Conclusions—In conclusion, a secretagogue-siRNA conjugate prevented cytokine-induced apoptosis in salivary epithelial cells, which is critical to maintain fluid secretion and potentially reverse the clinical hallmark of SjS.