A role for nitric oxide-mediated glandular hypofunction in a non-apoptotic model for Sjögren's syndrome

Abstract

Objective. To investigate a role for the inflammatory mediator, nitric oxide (NO) in SS, an autoimmune condition characterized by salivary and lacrimal gland hypofunction resulting from failure of acinar cells to secrete. Methods. FURA-2 microfluorimetry was used to measure agonist-evoked changes of [Ca2+]i in isolated mouse and human salivary acinar cells following exposure to NO donors. Results. NO had a biphasic effect on salivary acinar function. Acute exposure to NO (2 min) caused a cyclic guanosine monophosphate (GMP)-dependent, 1-H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-sensitive increase in the Ca2+ signal elicited in response to acetylcholine (ACh) stimulation, consistent with stimulation of ryanodine receptors by cyclic adenosine diphosphate ribose. Prolonged exposure to NO (>40 min) significantly reduced the ACh-evoked Ca2+ signal by a mechanism independent of cyclic GMP. We found no differences between the responses of human and mouse acinar cells. Conclusion. Our data show that chronic exposure to NO, which is known to be elevated in SS, could have a role in salivary gland hypofunction. We note a similarity in the response to stimulation of salivary acinar exposed to NO and that which we have previously reported in salivary acinar cells isolated from patients with SS. We speculate that NO-mediated nitrosylation of one or more elements of the signal transduction pathway could underlie down-regulation of salivary function in SS. © The Author 2009. Published by Oxford University Press on behalf of the British Society for Rheumatology. All rights reserved.