Paeoniflorin alleviated experimental Sjögren's syndrome by inhibiting NLRP3 inflammasome activation of submandibular gland cells via activating Nrf2/HO-1 pathway.

BACKGROUND

Total glucosides of white paeony (TGP) has been used for treatment of Sjögren's syndrome (SS) patients. Paeoniflorin (PF) is the main active ingredient of TGP and has antioxidant and anti-inflammatory effects, but its underlying mechanism on SS remains to be explored. Aberrant activation of NLRP3 inflammasome can cause injury of submandibular gland (SG) in SS. However, whether PF regulates NLRP3 inflammasome activation in SS is unknown.

OBJECTIVE

This study aims to investigate whether PF alleviated SS through suppressing NLRP3 inflammation activation and to explore the mechanism of PF in improving Sjögren-like symptoms in non-obese diabetic (NOD) mice.

METHODS

The gene expression profiles of the labial gland (LG) between SS patients and non-SS patients were analyzed by bioinformatics. Non-obese diabetic (NOD) mice were selected as SS model. Mice were divided into normal saline group and two different doses of PF-treatment groups (50 and 100 mg/kg). The SS-like symptoms and pathological changes of submandibular gland (SG) were analyzed after 4 weeks of administration. SG cells were treated with or without PF and with or without ML385 (a specific inhibitor of Nrf2) in vitro, and then lipopolysaccharide(LPS) and adenosine triphosphate (ATP) were used to induce NLRP3 inflammasome activation in SG cells. Results NLRP3 was up-regulated in LG of SS patients and SG of SS mice. PF alleviated SS-like symptoms in SS mice. Compared with control group, NLRP3 and caspase-1 in the SG, and serum IL-1β and IL-18 of NOD mice were decreased in PF group. Furthermore, we found that PF inhibited NLRP3 activation via activating the Nrf2/HO-1 pathway in SG cells. In addition, we observed the activation of Nrf2/HO-1 in the SG of mice after PF administration.

CONCLUSIONS

Our findings suggested that PF inhibited NLRP3 inflammasome activation through regulating the Nrf2/HO-1 axis in SG of SS mice, which might be the underlying mechanism for the therapeutic effects of PF on SS.