Decrease in alpha-1 antiproteinase antitrypsin is observed in primary Sjogren's syndrome condition

Targeting alarmin release reverses Sjogren's syndrome phenotype by revitalizing Ca2+ signalling

BACKGROUND

Primary Sjogren's syndrome (pSS) is a systemic autoimmune disease that is embodied by the loss of salivary gland function and immune cell infiltration, but the mechanism(s) are still unknown. The aim of this study was to understand the mechanisms and identify key factors that leads to the development and progression of pSS.

METHODS

Immunohistochemistry staining, FACS analysis and cytokine levels were used to detect immune cells infiltration and activation in salivary glands. RNA sequencing was performed to identify the molecular mechanisms involved in the development of pSS. The function assays include in vivo saliva collection along with calcium imaging and electrophysiology on isolated salivary gland cells in mice models of pSS. Western blotting, real-time PCR, alarmin release, and immunohistochemistry was performed to identify the channels involved in salivary function in pSS.

RESULTS

We provide evidence that loss of Ca2+ signaling precedes a decrease in saliva secretion and/or immune cell infiltration in IL14α, a mouse model for pSS. We also showed that Ca2+ homeostasis was mediated by transient receptor potential canonical-1 (TRPC1) channels and inhibition of TRPC1, resulting in the loss of salivary acinar cells, which promoted alarmin release essential for immune cell infiltration/release of pro-inflammatory cytokines. In addition, both IL14α and samples from human pSS patients showed a decrease in TRPC1 expression and increased acinar cell death. Finally, paquinimod treatment in IL14α restored Ca2+ homeostasis that inhibited alarmin release thereby reverting the pSS phenotype.

CONCLUSIONS

These results indicate that loss of Ca2+ signaling is one of the initial factors, which induces loss of salivary gland function along with immune infiltration that exaggerates pSS. Importantly, restoration of Ca2+ signaling upon paquinimod treatment reversed the pSS phenotype thereby inhibiting the progressive development of pSS.

A Review of Alpha-1 Antitrypsin Binding Partners for Immune Regulation and Potential Therapeutic Application

Alpha-1 antitrypsin (AAT) is the canonical serine protease inhibitor of neutrophil-derived proteases and can modulate innate immune mechanisms through its anti-inflammatory activities mediated by a broad spectrum of protein, cytokine, and cell surface interactions. AAT contains a reactive methionine residue that is critical for its protease-specific binding capacity, whereby AAT entraps the protease on cleavage of its reactive centre loop, neutralises its activity by key changes in its tertiary structure, and permits removal of the AAT-protease complex from the circulation. Recently, however, the immunomodulatory role of AAT has come increasingly to the fore with several prominent studies focused on lipid or protein-protein interactions that are predominantly mediated through electrostatic, glycan, or hydrophobic potential binding sites. The aim of this review was to investigate the spectrum of AAT molecular interactions, with newer studies supporting a potential therapeutic paradigm for AAT augmentation therapy in disorders in which a chronic immune response is strongly linked.