Scutellarin inhibits caspase-11 activation and pyroptosis in macrophages via regulating PKA signaling

@#Inflammatory caspase-11 senses and is activated by intracellular lipopolysaccharide (LPS) leading to pyroptosis that has critical role in defensing against bacterial infection, whereas its excess activation under pathogenic circumstances may cause various inflammatory diseases. However, there are few known drugs that can control caspase-11 activation. We report here that scutellarin, a flavonoid from Erigeron breviscapus, acted as an inhibitor for caspase-11 activation in macrophages. Scutellarin dose-dependently inhibited intracellular LPS-induced release of caspase-11p26 (indicative of caspase-11 activation) and generation of N-terminal fragment of gasdermin D (GSDMD-NT), leading to reduced pyroptosis. It also suppressed the activation of non-canonical nucleotide-binding oligomerization domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome as evidenced by reduced apoptosis-associated speck-like protein containing a CARD (ASC) speck formation and decreased interleukin-1 beta (IL-1β) and caspase-1p10 secretion, whereas the NLRP3-specific inhibitor MCC950 only inhibited IL-1β and caspase-1p10 release and ASC speck formation but not pyroptosis. Scutellarin also suppressed LPS-induced caspase-11 activation and pyroptosis in RAW 264.7 cells lacking ASC expression. Moreover, scutellarin treatment increased Ser/Thr phosphorylation of caspase-11 at protein kinase A (PKA)-specific sites, and its inhibitory action on caspase-11 activation was largely abrogated by PKA inhibitor H89 or by adenylyl cyclase inhibitor MDL12330A. Collectively, our data indicate that scutellarin inhibited caspase-11 activation and pyroptosis in macrophages at least partly via regulating the PKA signaling pathway.

Metformin enhances ATP-stimulated inflammasomeactivation in LPS-primed peritoneal macrophages / 中国药理学通报

Aim To explore the influence of metformin(a first-line drug for type 2 diabetes) on ATP-induced inflammasome activation and the release of interleukin-1β(IL-1β) by LPS-activated peritoneal macrophages, a commonly-used inflammatory cell model.Methods Peritoneal macrophages were elicited by intraperitoneal injection of 30 g·L-1 thioglycollate into C57BL/6 mice.Inflammasome was activated and cell pyroptosis was induced by LPS plus ATP treatment, and the pyroptotic cells were calculated after propidium iodide(PI) staining.The protein levels of IL-1β and caspase-1 expressed in the cells and released from them into the supernatant were evaluated by Western blot.Immunofluorescent microscopy was recruited to detect the subcellular distribution and fluorescent intensity of the purinergic P2X7 receptor(P2X7R).Results Metformin per se did not induce pyroptosis in LPS-activated peritoneal macrophages, but it significantly and dose-dependently increased cell pyroptosis induced by ATP treatment.At protein levels, maturated IL-1β(17 ku) could not be released from the cells upon single LPS or LPS plus metformin stimulation;but after ATP was added, maturated IL-1β was released into the supernatants of the cells.Moreover, metformin dose-dependently increased the protein levels of both maturated IL-1β and active caspase-1 released by the LPS-activated peritoneal macrophages upon ATP stimulation.Conclusion Metformin intensifies the activation of inflammasome and increases the release of active caspase-1 and maturated IL-1β upon ATP stimulation in the LPS-activated peritoneal macrophages, which should promote inflammatory responses.

Cucurbitacin E induces autophagy in HeLa cells by inhibiting mTORC1 activity / 中国药理学通报

Aim To study the mechanism of cucurb-itacin E ( CuE )-induced autophagy in HeLa cells. Methods Improved MTT assay was adopted to meas-ure the effect of CuE on cell proliferation. Western blot was used to determine the phosphorylation levels of downstream signaling proteins of mTORC1 and the ex-pression of autophagy associated proteins. ResultsCuE inhibited the proliferation of HeLa cells in a dose-dependent manner, and the 24-h IC50 of CuE was 4. 01μmol· L-1 . CuE significantly inhibited the phospho-rylation of p70 S6 K in a time-and dose-dependent man-ner as evidenced by decreased phosphorylation levels of the mTORC1 substrate. Meanwhile, the expression of LC3-II, a marker for autophagosome formation, was elevated by CuE treatment, and was further increased in the presence of chloroquine. Furthermore, CuE re-duced the levels of p62/SQSTM1 . These results indi-cated that CuE induced autophagy in HeLa cells. The decreased levels of phosphorylated ULK1 S757 were posi-tively correlated with autophagy induction in HeLa cells. Conclusion CuE is likely to induce autophagy through inhibiting mTORC1 activity.

Valproic acid exerts differential effects on cytokine synthesis in human peripheral lymphocytes / 中国病理生理杂志

AIM: Valproic acid (VPA) is a histone deacetylase inhibitor and is believed to have anti-tumor activity. The present study aims to investigate the effect of VPA on the, apoptosis and cytokine synthesis of human peripheral lymphocytes. METHODS: The activation and cytokine synthesis in lymphocytes in whole blood stimulated with phorbol dibutyrate (PDB) and ionomycin were evaluated with flow cytometry after fluorescent staining. The mitochondrial membrane potential was examined using 3, 3-dihexyloxacarbocyanine iodide [DiOC6(3)]staining. RESULTS: VPA at low doses (1 and 5 mmol/L) promoted CD69 expression in activated lymphocytes, whereas it turned to inhibit the expression of CD69 at a high dose (25 mmol/L). Meanwhile, VPA at low doses increased the mitochondrial membrane potential, while a high dose of VPA decreased it in activated lymphocytes. Furthermore, interleukin-2 (IL-2) synthesis was enhanced by low doses of VPA but inhibited by a high dose. However, interferon-γ (IFN-γ) and tumor necrosis factor-α (TNF-α) synthesis were dose-dependently enhanced by VPA as compared with those of PDB plus ionomycin-treated cells. CONCLUSION: VPA exerts biphasic effect on the further activation and apoptosis of human peripheral lymphocytes stimulated with mitogens and exhibits differential activity on the synthesis of several important cytokines in human lymphocytes.

Anti-HIV-1 activity of five anthraquinone derivatives / 中国病理生理杂志

AIM: To investigate the anti-HIV-1 activity of five anthraquinone derivatives (emodin,rhein,chrysophanol,physcion and aloe-emodin) in vitro.METHODS: Viral replication was estimated by observation of cytopathogenesis and measurement of HIV-1 p24 antigen production in HIV-1ⅢB acutely infected C8166 cells. The anti-HIV-1 activity was evaluated by the 50% effective concentrations (EC50) and selective indexes (SI) of these derivatives.RESULTS: These anthraquinone derivatives inhibited HIV-1ⅢB replication on syncytia formation induced by HIV-1ⅢB infection with EC50 mean values of (11.44±0.93)μmol/L (emodin),(51.28±2.86)μmol/L (rhein),(90.58±2.30)μmol/L (chrysophanol),(8.59±0.38)μmol/L (physcion) and (0.89±0.08)μmol/L (aloe-emodin),respectively. The p24 antigen production with EC50 mean values were (11.61±0.56)μmol/L (emodin),(12.35±4.73)μmol/L (rhein),(39.63±2.87)μmol/L (chrysophanol),>250 μmol/L (physcion) and (2.75±0.20)μmol/L (aloe-emodin) respectively. CONCLUSION: These structurally-related chemicals show different anti-HIV-1 activity in vitro. Among them,aloe-emodin is the most potent inhibitor to HIV-1 replication.