Gracillin relieves pulmonary fibrosis by suppressing the STAT3 axis

ETHNOPHARMACOLOGICAL RELEVANCE

Pulmonary fibrosis (PF) is a persistent and refractory illness accompanied by inflammation and fibrosis. Gracillin, a natural steroidal saponin, is one of the components of Dioscorea quinqueloba which has been used in herbal medicines for treating some inflammatory diseases. Therefore, it may be a potential drug candidate for PF management.

AIM OF THE STUDY

This study aims to elucidate and verify the anti-pulmonary fibrosis effect of gracillin.

METHODS

We established an in vivo model of PF by treatment of mice with bleomycin (BLM) and an in vitro model by treatment of NIH-3T3 cells with TGF-β1. Pathological changes to the structure of lung tissue, pulmonary function, inflammatory exudation of bronchoalveolar lavage fluid (BALF) and deposition of collagen were detected in vivo, and extracellular matrix (ECM) deposition and migration were evaluated in vitro. The significance of gracillin on STAT3 phosphorylation and nuclear translocation were evaluated by western blotting, immunohistochemistry and immunofluorescence assays. The STAT3 transcriptional activity was quantified with a dual-luciferase reporter assay. Recovery experiments were performed by plasmid-directed overexpression of STAT3.

RESULTS

We found that gracillin could improve pulmonary function, reduce lung inflammation and mitigate collagen deposition to ameliorate BLM-induced PF in mice. Gracillin also suppressed TGF-β1-induced increases in ECM deposition biomarkers, including COL1A1, fibronectin, α-SMA, N-cad and vimentin, and repressed migration in NIH-3T3 cells. Additionally, gracillin suppressed the phosphorylation, nuclear translocation and transcriptional action of STAT3. Furthermore, the decreased ECM deposition and migration upon gracillin treatment were abrogated upon overexpression of STAT3 in NIH-3T3 cells.

CONCLUSIONS

Gracillin protects against PF by inhibiting the STAT3 axis, providing a safe and efficacious approach to treating PF.

Screening and identification of lipase inhibitors extracted from Dioscorea nipponica Makino by UV-vis and HPLC coupled to UPLC-Q-TOF-MS/MS

Dioscoreae nipponica Makino (D. nipponica) as the rhizome of dioscoreaceae rich in steroidal saponins, has been reported to have the hypolipidemic effects etc. However, it is still unclear which exact active components are primary responsible for the beneficial effects. This study was conducted to fish out the lipase inhibitors from D. nipponica, and evaluate the inhibitory activity on porcine pancreatic lipase (PPL) through in vitro kinetic assay using p-nitrophenyl palmitate as substrate. Accordingly, the ethanolic extract was subjected to D101 macroporous resin purification for spectrophotometric screening, high performance liquid chromatography (HPLC) separation and structural characterization by ultra-performance liquid chromatography-quadrupole time-of-flight mass spectrometry. Through orlistat validation, the PPL inhibitory activity and IC₅₀ value of the extract were respectively 68.34 ± 1.47 % and 107.05 μg/mL under the optimized inhibition conditions. From 6 steroidal saponins identified, the inhibitory components named the protodioscin, protogracillin, dioscin and gracillin were fished out by grouping separation and HPLC analysis. Furthermore, dioscin and gracillin with the parent structure of diogenin were confirmed as the major inhibitors by virtue of stability tests based on transformation of protodioscin and protogracillin. Finally, the inhibitory mechanism of the major inhibitors toward PPL was further clarified by kinetic analysis and molecular docking analysis. The proposed method not only revealed the PPL inhibitory components in D. nipponica, but also provided an effective approach to hierarchical screening of PPL inhibitors from natural plants.

Gracillin exerts anti-melanoma effects in vitro and in vivo: role of DNA damage, apoptosis and autophagy

BACKGROUND

Melanoma is an aggressive cancer. Gracillin has been reported to treat various types of cancer, such as colorectal and lung cancer. However, there is a paucity of research on the anti-melanoma effects of gracillin.

PURPOSE

The aim of this study was to assess the anti-melanoma effects and mechanisms of action of gracillin in vitro and in vivo.

METHODS

Cell viability was detected using MTT and crystal violet staining assays. Cell proliferation was examined by EdU staining assays. Cell cycle arrest and apoptosis were analyzed by flow cytometry. Autophagic flux was monitored under a confocal microscope. Protein levels were determined by immunoblotting. LY294002 and rapamycin (Rapa) were used to determine the involvement of PI3K/AKT/mTOR signaling in gracillin-mediated autophagy. Signal transducer and activator of transcription 3 (STAT3) was overactivated to explore the contribution of the STAT3 signaling pathway in the anti-melanoma effects of gracillin. A B16F10 allograft mouse model was developed to evaluate the anti-melanoma effects of gracillin in vivo.

RESULTS

We demonstrated that in melanoma cells, gracillin inhibited proliferation, induced G0/G1 phase cell cycle arrest, evoked apoptosis, and triggered autophagic cell death. Gracillin induced DNA damage in melanoma cells. Moreover, it suppressed the phosphorylation/activation of PI3K, AKT, mTOR, and 4E-BP1 in melanoma cells. Inhibiting PI3K/AKT and mTOR activity using LY294002 and Rapa, respectively, increased the protein level of LC3B-II in gracillin-treated melanoma cells. Furthermore, gracillin downregulated the protein levels of p-JAK2 (Tyr1007/1008), p-Src (Tyr416), and p-STAT3 (Tyr705) in melanoma cells. Over-expression of STAT3 in A375 cells significantly mitigated the cytotoxic and apoptotic effects of gracillin. In vivo studies showed that gracillin (1 mg/kg or 8 mg/kg, administered intraperitoneally for 16 consecutive days) suppressed B16F10 tumor growth and Src/STAT3 and AKT/mTOR signaling in tumors. No overt toxicity was observed in mice.

CONCLUSION

Induction of DNA damage, inhibition of PI3K/AKT/mTOR signaling and suppression of STAT3 signaling are involved in gracillin-mediated cell cycle arrest, autophagic cell death and apoptosis, respectively, in melanoma cells. These findings provide novel insights into the anti-melanoma molecular mechanisms of gracillin, and suggest a potential role of gracillin in melanoma management.

Quantitative determination of gracillin by HPLC-MS/MS after oral administration and its application to a pharmacokinetic study

A sensitive and credible high performance liquid chromatography hyphenated to mass spectrometry (HPLC-MS/MS) was established to quantify the concentration of gracillin in rat plasma. The plasma samples were subjected to a direct protein precipitation process with acetonitrile as a precipitant in a single-step. Ginsenoside Rb1 was selected as an internal standard (IS). The chromatographic separation of analyte and IS were carried out on an Inersil ODS-3 C18 column (250×4.6mm, 5μm) with a binary solvent system containing acetonitrile and 0.1% formic acid in water at a flow rate of 1mLmin(-1) under a gradient elution mode. Mass spectrometric detection was performed on a triple quadrupole tandem mass spectrometer by the multiple reaction monitoring (MRM) mode to examine the precursor-to-daughter ion transitions of 1110.3→948.2 for IS and 886.1→739.9 for gracillin, respectively, in a positive electrospray ionization mode. The calibration curve showed a promising linearity over a concentration range of 0.065-800ngmL(-1) with a better regression coefficient of r(2)=0.9960. The intra- and inter-day precisions (as relative standard deviation) of the assay at three quality control levels were all less than 3.48%, while the intra- and inter-day accuracies (as relative error) ranged from -8.43% to 9.74%, whose data were within the acceptable limits. The mean extraction recoveries of analyte from rat plasma were all more than 74.11%, and no notable matrix effect was observed. Stability experiments revealed that gracillin remained stable throughout the analytical procedure under various stored conditions. The above validated method was successfully used to investigate the pharmacokinetic behaviors of gracillin orally administrated to rats at three proportion doses. The pharmacokinetic analysis would pave the way for understanding the pharmacological actions and provide a meaningful foundation for further development and application in preclinical and clinical use of gracillin in the near future.