Free total rhubarb anthraquinones protect intestinal mucosal barrier of SAP rats via inhibiting the NLRP3/caspase-1/GSDMD pyroptotic pathway.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhubarb is the peeled and dried roots of Rheum palmatum L. and Rheum tanguticum Maxim. ex Balf. or Rheum officinale Baill. Free total rhubarb anthraquinones (FTRAs) were isolated and extracted from rhubarb. Previous studies have revealed that the early administration of FTRAs protects the intestinal mucosal barrier in rats with severe acute pancreatitis (SAP), the mechanism of which is not yet clear. However, we observed an enhanced expression of intestinal pyroptotic factors in rats treated with SAP, which may be related to the mechanism of intestinal barrier protection by FTRAs. AIM OF THE STUDY: The main objective of this study was to investigate the mechanism by which FTRAs protect the intestinal mucosal barrier in SAP rats, focusing on the classical pyroptosis pathway. MATERIALS AND METHODS: SAP was induced in rats through retrograde injection of sodium taurocholate via the pancreaticobiliary duct. Subsequently, FTRAs (22.5, 45, and 90 mg/kg), rhubarb (900 mg/kg, positive control), and saline (control) were administered at 0 h (immediately), 12 h, and 24 h post-surgery. Pancreatic and intestinal tissue injury, positive PI staining rate, and expression levels of various factors in intestinal tissues were compared across different groups. These factors include diamine oxidase (DAO), lactate dehydrogenase (LDH), high mobility group box chromosomal protein 1(HMGB1) and pro-inflammatory factors in intestinal and serum, pyroptosis-associated factors, toll-like receptor 4 (TLR-4), nuclear factor kappa-B (NF-kB), apoptosis-associated speck-like protein (ASC), NOD-like receptor protein 3 (NLRP3), cysteine protease-1 (caspase-1) and Gasdermin (GSDMD). RESULTS: The findings indicated that FTRAs protected the damaged intestine and pancreas and restored the expression of intestinal epithelial junction proteins in SAP rats. Additionally, it reduced intestinal and serum levels of DAO, interleukin 1, interleukin 18, HMGB1, and LDH, attenuated intestinal Positive PI staining rate, and significantly decreased the expressions of TLR-4, NF-kB, ASC, NLRP3, caspase-1 and GSDMD in SAP rats. CONCLUSIONS: The results suggest that FTRAs inhibited pyroptosis through down-regulation of the NLRP3-Caspase-1-GSDMD and TLR-4- NF-kB signaling pathways of intestinal tissues., thereby protecting the intestinal barrier of SAP rats.

Optimal timing of free total rhubarb anthraquinones on immune regulation in rats with severe acute pancreatitis.

ETHNOPHARMACOLOGICAL RELEVANCE: Rhubarb is the peeled and dried root of Rheum palmatum L., Rheum tanguticum Maxim. ex Balf. or Rheum officinale Baill. Free total rhubarb anthraquinones (FTRAs) isolated and extracted from rhubarb display the beneficial effects of anti-inflammation and immunological modulation. The timing of immune regulation is a major problem in the immunotherapy for severe acute pancreatitis (SAP). several studies reported that FTRAs could reduce systemic inflammatory responses by inhibiting early immune overactivity in the gut in rats with SAP. But, the optimal timing of rhubarb and FTRAs administration is not clear in clinical practice. Therefore, the time window for the best efficacy of rhubarb and FTRAs in the treatment of SAP patients should be further elucidated. AIM OF THE STUDY: The main purpose of the present study was to evaluate the efficacy and optimal timing of immune modulation with FTRAs in the treatment of SAP in rats. MATERIALS AND METHODS: FTRAs (22.5, 45 and 90 mg/kg), Rhubarb (RHU) (900 mg/kg, positive control) or normal saline (vehicle control) were initiated at 0 (immediately), 48 and 72 h every 12 h for three times in total. The therapeutic effects of FTRAs and RHU on pancreas and intestinal tissues injury, secondary infection with pseudomonas aeruginosa (PA), amylase, lipase, D-lactic acid (DLA), endotoxin (ET), proinflammatory and anti-inflammatory cytokines, macrophages, dendritic cells and regulatory T cells (Tregs) in the blood, small intestine and/or mesenteric lymph node (MLN) were determined in rats with SAP after treatment. RESULTS: The results showed that administration of FTRAs at 0 h was superior to 48 h and 72 h, which significantly protected the injury of pancreas and intestinal tissues, reduced the mortality induced by secondary infection with PA, decreased the levels of amylase, lipase, DLA, ET, tumor necrosis factor α (TNF-α), interleukin 1ß (IL-1ß), IL-6, IL-8, IL-18 and Tregs, and increased the levels of IL-4, sTNF-αR, macrophages and dendritic cells, secretary immunoglobulin A (SIgA) in the blood and/or small intestinal tissues in rats with SAP. CONCLUSIONS: In conclusion, our studies indicate that the treatment window of FTRAs for SAP is within 48 h of development, administration of FTRAs at the early stage (0 h, immune overreaction period) was the optimal time and superior to that of 48 h and 72 h for its therapeutic efficacy. The earlier the administration of FTRAs, the better the therapeutic efficacy. Therefore, our data may provide a scientific rationale for the clinical application and optimal timing of FTRAs in the treatment of SAP.