Huoxue Jiedu Recipe represses mitochondrial fission to alleviate submandibular gland inflammation in Sjögren's syndrome

Sjögren's syndrome (SS) is the second most common autoimmune rheumatism. Huoxue Jiedu Recipe (HXJDR) is a kind of traditional Chinese medicine with a variety of pharmacological functions; however, its biological function in SS has not been studied yet. Peripheral blood mononuclear cells (PBMCs) and serum samples were isolated from healthy controls and patients with SS. NOD/Ltj mice were used for developing the SS mouse model. The levels of inflammatory cytokines and NOD-like receptor family pyrin domain containing 3 (NLRP3) inflammasome-related markers as well as dynamin-related protein 1 (Drp1) were determined by ELISA, quantitative real-time PCR, and western blot analysis, respectively. Hematoxylin and eosin and TUNEL staining detected the pathological damage. A transmission electron microscope was used to observe the mitochondrial microstructure. Inflammatory cytokines IL-18, IL-1β, B-cell activating factor (BAFF), BAFF-receptor (BAFF-R), IL-6, and TNF-α in serum samples and NLRP3 inflammasome-related makers (NLRP3, cysteinyl aspartate-specific proteinase 1 [caspase-1], apoptosis-associated speck-like protein containing a caspase-1 recruitment domain [ASC], IL-1β) in PBMCs were greatly upregulated in patients with SS. Furthermore, cytoplasmic phosphorylation of Drp1 and mitochondrial Drp1 level were significantly increased in PBMCs, while mitochondrial swelling and fuzzy inner ridge were observed in PBMCs of patients with SS, suggesting increased mitochondrial fission. Compared with control mice, SS mice showed decreased salivary flow rate, increased submandibular gland index, and more severe inflammatory infiltration and damage as well as mitochondrial fission in submandibular gland tissues. After HXJDR administration, these effects were significantly reversed. HXJDR treatment could alleviate the inflammatory infiltration and pathological damage in submandibular glands of SS mice by inhibiting Drp-1-dependent mitochondrial fission.