m6A RNA methylation controls salivary gland epithelial cell function and has a protective role in Sjögren's disease

Objectives The RNA epitranscriptomic modification known as N6 -methyladenosine (m 6 A) represents a novel mechanism of gene regulation that is poorly understood in human autoimmune diseases. Our research explores the role of this RNA m 6 A modification in salivary gland epithelial cells (SGEC) and its impact on the pathogenesis of Sjögren’s disease (SjD). Methods SGECs from SjD patients and controls were analysed for m 6 A writers METTL3 and METTL14 expression using RNA-seq, quantitative PCR and immunohistochemistry. Functional assays assessed the impact of METTL3 knockdown or pharmacological inhibition on proinflammatory gene expression and immune cell interactions (using transwell and coculture systems). Mechanistic studies examined METTL3-mediated m 6 A modifications in double-stranded RNA (dsRNA) formation through immunofluorescence. Unsupervised clustering identified patterns of interferon activation in salivary glands and their correlation with m 6 A writers. Results METTL3 and METTL14 were elevated in SGEC from SjD patients in comparison to controls. Paradoxically, inhibiting METTL3 increased proinflammatory gene expression, enhancing SGEC’s ability to attract immune cells and activate B cells. Conversely, inhibiting the eraser FTO had the opposite effect. METTL3-mediated m 6 A modifications prevented dsRNA formation and IFN signalling activation. SGEC from SjD showed insufficient METTL3 upregulation compared with controls in response to inflammatory triggers, indicating a limited capacity to regulate the inflammatory response. SjD patients with elevated disease activity and higher interferon signature exhibit reduced METTL3 expression. Conclusions Impairment of m 6 A modifications in SGEC in response to inflammatory triggers favour the formation of dsRNA, potentially amplifying the interferon loop and contributing to SjD pathogenesis.