Background: Although salivary gland epithelial cells (SGECs) are key players in the pathogenesis of autoimmune epithelitis that characterizes primary Sjӧgren’s Syndrome (pSS), the mechanisms sustaining SGECs activation in pSS remain largely undetermined. Therefore, therapeutic strategies to counteract SGECs activation in pSS are also lacking. In previous studies, we revealed that maladaptive autophagy sustains survival and pro-inflammatory activation of SGECs in pSS (1).

Objectives: To determine the therapeutic potential of JAK/STAT inhibition with baricitinib to restore homeostatic regulation of SGECs in pSS, by reducing autophagy, survival, and expression of adhesion molecules.

Methods: Primary SGECs were isolated from minor salivary glands (SG) of large cohort of patients with pSS or sicca syndrome and subjected to mechanistic and functional studies including flow-cytometry, immunoblotting, and immunofluorescence to assess autophagy (autophagic-flux, LC3IIB, p62, LC3B+/LAMP1+ staining), apoptosis (annexin V/PI, Caspase-3) and activation (ICAM, VCAM). Focus score and germinal centers were determined in homologous SG biopsies to assess correlations of findings with histological disease severity. Primary SGECs of patients with pSS were treated with Baricitinib (1 mM) for 24 prior to assessment of autophagy, apoptosis and activation.

Results: SGECs from pSS patients (n=29) exhibited increased autophagy (as determined by autophagic-flux p=0.001; LC3IIB p=0.02; p62 p=0.064; LC3IIB/LAMP1+ staining), increased expression of anti-apoptotic molecules (Bcl2 p=0.006), and reduced apoptosis (Annexin-V/PI p=0.002, Caspase-3 p=0.057) compared to sicca (n=16). Induction of autophagy in pSS SGECs correlated with histologic disease severity. Treatment of pSS SGECs with baricitinib ex vivo suppressed autophagy, increased apoptosis, and reduced expression of adhesion molecules.

Conclusion: SGECs in the inflammatory milieu of pSS are characterized by induction of autophagy and pro-survival mechanisms, and by expression of adhesion molecules. These changes correlate with SG infiltration with immune cells and with histologic disease severity. Among clinically available therapies, the JAK/STAT inhibitor baricitinib effectively reduced autophagy, countered the state of maladaptive activation of SGECs, and restored epithelial cell homeostasis. Transcriptomics and metabolomics studies are ongoing to dissect the specific mechanisms responsible for these beneficial effects.

REFERENCES:

[1]Colafrancesco S, et al. Maladaptive autophagy in the pathogenesis of autoimmune epithelitis in Sjӧgren’s Syndrome. Arthritis Rheumatol 2021.

Disclosure of Interests: Serena Colafrancesco Speakers bureau: Novartis

Sobi, Grant/research support from: Eli Lilly, cristiana barbati: None declared, Roberta Priori: None declared, Federico Giardina: None declared, angelica gattamelata: None declared, raffaella izzo: None declared, Bruna Cerbelli: None declared, Carla Giordano: None declared, Susanna Scarpa: None declared, Massimo Fusconi: None declared, Francesca Romana Spinelli Speakers bureau: Eli Lilly

Pfizer

Abbvie, Giulio Cavalli: None declared, cristiano alessandri: None declared, Fabrizio Conti: None declared