Severe acute pancreatitis (SAP) remains one of the most formidable challenges in gastrointestinal emergency medicine. Affecting approximately 20–30% of acute pancreatitis patients, SAP carries a mortality rate as high as 20–30%, primarily driven by systemic inflammatory response syndrome (SIRS) and multiple organ dysfunction syndrome (MODS). Among the myriad complications, pancreatitis-associated intestinal injury (PAII) has emerged as a critical "second hit" that perpetuates and amplifies systemic inflammation through gut barrier failure and subsequent bacterial/endotoxin translocation. Despite decades of research, effective therapeutic strategies targeting PAII remain scarce.
Now, a research team from the Affiliated Hospital of Jiangnan University, led by Dr. Jun Yang, has unveiled a groundbreaking mechanism by which Rhein—a natural anthraquinone compound derived from traditional Chinese medicinal herbs including rhubarb (Rheum palmatum) and aloe—confers potent protection against SAP-associated intestinal injury. Their findings, published in the Chinese Medical Journal on March 20, 2026, identify the peroxisome proliferator-activated receptor γ (PPARγ)/NOD-like receptor thermal protein domain associated protein 3 (NLRP3)/macrophage polarization axis as a critical regulatory pathway with significant therapeutic potential.
The intestinal barrier: ground zero in SAP progression
The intestinal epithelium serves as the body's first line of defense against luminal pathogens and endotoxins. Under physiological conditions, tight junction proteins—including ZO-1, ZO-2, Claudin-1, and Occludin—form a formidable barrier that maintains gut homeostasis. However, in SAP, pancreatic necrosis and inflammation release a torrent of pro-inflammatory cytokines that compromise intestinal microcirculation, disrupt tight junctions, and induce enterocyte apoptosis. The resultant barrier failure allows bacteria and lipopolysaccharide (LPS) to translocate into the bloodstream, igniting a vicious cycle of systemic inflammation that accelerates MODS progression.
Rhein restores intestinal barrier integrity
Using a well-established cerulein/LPS-induced SAP mouse model, the investigators demonstrated that Rhein administration (50 mg/kg) significantly ameliorated both pancreatic and intestinal damage. Rhein-treated mice exhibited markedly reduced serum amylase and lipase levels—key biomarkers of pancreatic injury—along with attenuated pancreatic edema, necrosis, and inflammatory infiltration.
Critically, Rhein exerted profound protective effects on the intestinal compartment. Histological examination revealed preserved colonic architecture with reduced inflammatory cell infiltration and restored villus length. At the molecular level, Rhein significantly upregulated the expression of tight junction proteins (ZO-1, ZO-2, Claudin-1, Occludin) in colonic tissues, which translated into functional barrier recovery as evidenced by substantially reduced serum LPS levels, indicating effective containment of bacterial translocation and systemic endotoxemia.
Reprogramming the intestinal immune microenvironment
Macrophages serve as master regulators of intestinal immune homeostasis, exhibiting remarkable functional plasticity. These cells can polarize into classically activated pro-inflammatory (M1) macrophages that secrete copious interleukin (IL)-1β, IL-6, and tumor necrosis factor-alpha, or alternatively activated anti-inflammatory/repair (M2) macrophages that promote tissue regeneration. In SAP, intestinal macrophages predominantly adopt the M1 phenotype, creating a pro-inflammatory milieu that exacerbates tissue injury.
Immunofluorescence analysis revealed that Rhein treatment dramatically reshaped this landscape. The abundance of M1 macrophages (NOS2⁺) was significantly reduced, while M2 macrophages (CD206⁺) increased correspondingly—a phenotypic switch that shifted the intestinal microenvironment from "inflammatory storm" toward immune homeostasis and tissue repair.
The molecular master switch: PPARγ
PPARγ, a nuclear receptor essential for M2 macrophage maturation and anti-inflammatory responses, emerged as the central mediator of Rhein's effects. While PPARγ expression was markedly suppressed in colonic tissues of SAP mice, Rhein treatment significantly restored both its expression and phosphorylation. To validate mechanistic dependency, the PPARγ antagonist GW9662 was co-administered—and it completely abolished Rhein's protective benefits. GW9662 reversed the M1/M2 imbalance, downregulated tight junction proteins, elevated serum LPS, and exacerbated histopathological injury, confirming PPARγ as the indispensable mediator.
Downstream suppression of NLRP3 inflammasome
Mechanistic dissection revealed that Rhein inhibits the NLRP3 inflammasome—a multiprotein complex that serves as a critical driver of sterile inflammation in SAP. In LPS/IFN-γ-stimulated bone marrow-derived macrophages, Rhein treatment suppressed NLRP3 expression, caspase-1 cleavage, GSDMD activation, and subsequent IL-1β/IL-18 secretion. All these effects were reversed by GW9662, positioning NLRP3 as a key downstream effector of PPARγ-mediated macrophage reprogramming.
Translational implications
This study provides the first comprehensive evidence that Rhein alleviates PAII by activating the PPARγ/NLRP3/macrophage polarization axis, offering several key insights: it establishes a direct link between PPARγ activation, inflammasome suppression, and macrophage phenotypic switching; positions Rhein—already known for its favorable safety profile in traditional medicine—as a promising candidate for repurposing in SAP management; and validates the PPARγ/NLRP3 axis as a novel druggable pathway for interventions aimed at restoring intestinal immune homeostasis.
While acknowledging limitations, including the use of a single SAP etiology and potential dose-dependent toxicity concerns, the findings lay a robust foundation for future translational research. The study opens new avenues for investigating Rhein's efficacy in clinically relevant SAP models and advancing toward potential clinical applications for this life-threatening condition.
