Shenhuang Granules regulate the NLRP3/Caspase-1/GSDMD pathway to alleviate pyroptosis of pulmonary microvascular endothelial cells

Shenhuang Granules (SHG) attenuate sepsis-induced lung injury via the NLRP3/Caspase-1/GSDMD pathway. • (−)-Epicatechin gallate and gallic acid are the core bioactive monomers of SHG against PMVEC pyroptosis. • SHG inhibits pyroptosis by suppressing inflammasome assembly and pore formation. Ethnopharmacological relevance Shenhuang Granules (SHG) is a traditional Chinese medicine (TCM) formula composed of six medicinal materials: Panax ginseng C.A. Mey. (Ginseng Radix et Rhizoma), Rheum palmatum L. (Rhei Radix et Rhizoma), Sargentodoxa cuneata (Oliv.) Rehder & E.H. Wilson (Sargentodoxae Caulis), Taraxacum mongolicum Hand. -Mazz. (Taraxaci Herba), Aconitum carmichaelii Debeaux (Aconiti Lateralis Radix Praeparata), and Whitmania pigra Whitman (Hirudo). According to TCM theory, this formula is designed to replenish Qi and strengthen the body's resistance, clear heat and remove toxins, and promote blood circulation to eliminate blood stasis. In clinical practice, SHG has been used as an adjunctive therapy for sepsis, showing beneficial effects in ameliorating systemic inflammatory responses and microcirculatory disturbances. However, the underlying pharmacological mechanisms remain largely unclear. Aim of the study To validate that SHG and its active monomers alleviate sepsis-induced lung injury through targeted suppression of the NLRP3-driven PMVEC pyroptosis pathway. Materials and methods The chemical composition of SHG was analyzed by UHPLC-MS/MS. In vivo, SA-ARDS was induced in C57BL/6J mice by cecal ligation and puncture (CLP), with SHG (61.85 mg/mouse/d), its monomers, (−)-epicatechin gallate (ECG) and gallic acid (GA) (20 mg/kg/d), or the NLRP3 inhibitor MCC950 (10 mg/kg/d), were administered via intraperitoneal injection for 3 days prior to modeling. Lung injury severity and activation of the pyroptosis pathway were evaluated using histopathology, transmission electron microscopy, RT-qPCR, Western blotting, immunohistochemistry, immunofluorescence, and ELISA. In vitro, LPS-stimulated (1 μg/mL) PMVECs were used to screen 43 monomers, and the underlying mechanisms were subsequently verified. Results Compared with the Model group, SHG treatment significantly attenuated body weight loss in mice ( P  < 0.001), reduced the lung wet-to-dry (W/D) weight ratio ( P  < 0.05), and decreased Evans blue extravasation in lung tissues ( P  < 0.01). SHG also significantly downregulated the mRNA expression levels of pyroptosis-related genes, including Twik2 , Nlrp3 , Asc , Caspase-1 , and Gsdmd , in lung tissues (all P  < 0.01), and markedly reduced the protein expression of NLRP3, ASC, pro-Caspase-1, and Caspase-1 (all P  < 0.05). ELISA results further demonstrated that SHG significantly decreased serum levels of the inflammatory cytokines TNF-α, IL-1β, IFN-γ, IL-18, pro-IL-1β, and pro-IL-18 in mice (all P  < 0.05). In vitro, compared with the Model group, SHG significantly suppressed the transcriptional levels of Twik2 , Nlrp3 , Asc , Caspase-1 , and Gsdmd in PMVECs (all P  < 0.05), and reduced the protein expression of NLRP3, ASC, GSDMD, GSDMD-NT, and IL-1β (all P  < 0.05). Additionally, SHG markedly decreased lactate dehydrogenase (LDH) release ( P  < 0.0001) and attenuated extracellular potassium ion (K + ) efflux ( P  < 0.0001). Notably, ECG and GA individually exhibited potent inhibitory effects on PMVEC pyroptosis. Compared with the Model group, both ECG and GA significantly suppressed mRNA expression of Twik2, Nlrp3, Asc, Caspase-1, and Gsdmd (all P  < 0.05) and reduced protein levels of NLRP3 , ASC , Caspase-1 , and GSDMD (all P  < 0.05). Moreover, ECG significantly inhibited GSDMD-NT and IL-1β protein expression (all P  < 0.05). Both ECG and GA markedly reduced TNF-α, IL-1β, and pro-IL-18 levels (all P  < 0.05), and GA additionally suppressed IL-18 and pro-IL-1β expression (all P  < 0.01). Furthermore, both ECG and GA significantly decreased LDH release ( P  < 0.0001) and inhibited extracellular K + efflux ( P  < 0.0001). However, this study has several limitations, including a small sample size, the absence of dose-gradient and time-course analyses, insufficient functional validation of the TWIK2 channel, and the lack of quantitative pharmacokinetic and synergy analyses, which should be addressed in future studies. Conclusion Shenhuang Granules attenuated PMVEC pyroptosis and ameliorated sepsis-induced lung injury by suppressing TWIK2 and the downstream NLRP3/Caspase-1/GSDMD pathway, with GA and ECG as the key active components. Download: Download high-res image (484KB) Download: Download full-size image