Oxomollugin, an oxidized substance in mollugin, inhibited LPS-induced NF-κB activation via the suppressive effects on essential activation factors of TLR4 signaling

Oxomollugin is a degraded product of mollugin and was found to be an active compound that inhibits LPS-induced NF-κB activation. In this study, we investigated the inhibitory activity of oxomollugin, focusing on TLR4 signaling pathway, resulting in NF-κB activation. Oxomollugin inhibited the LPS-induced association of essential factors for initial activation of TLR4 signaling, MyD88, IRAK4 and TRAF6. Furthermore, oxomollugin showed suppressive effects on LPS-induced modification of IRAK1, IRAK2 and TRAF6, LPS-induced association of TRAF6-TAK1/TAB2, and followed by IKKα/β phosphorylation, which critical in signal transduction leading to LPS-induced NF-κB activation. The consistent results suggested that oxomollugin inhibits LPS-induced NF-κB activation via the suppression against signal transduction in TLR4 signaling pathway.The activities of oxomollugin reported in this study provides a deeper understanding on biological activity of mollugin derivatives as anti-inflammatory compounds.

Mollugin prevents CLP-induced sepsis in mice by inhibiting TAK1-NF-κB/MAPKs pathways and activating Keap1-Nrf2 pathway in macrophages

Sepsis is a life-threatening organ dysfunction associated with macrophage overactivation. Targeted therapy against macrophages is considered a promising strategy for sepsis treatment. Mollugin (MLG), a compound extracted from traditional Chinese medicine Rubia cordifolia L., possesses anti-tumor and anti-inflammatory activities. This study aimed to investigate the anti-inflammatory effects and mechanisms of MLG in macrophages and its therapeutic role in CLP-induced sepsis in mice. The results demonstrated that MLG downregulated the inflammatory response induced by LPS or tumor necrosis factor α (TNF-α) in macrophages. Mechanistically, MLG suppressed the phosphorylation of TAK1, the upstream modulator of IKKα/β and MAPKs, thereby inhibiting the pro-inflammatory signaling transduction of NF-κB and MAPKs. Additionally, MLG also activated the Nrf2 antioxidant pathway, reducing intracellular reactive oxygen species. CETSA and molecular docking analyses revealed that MLG could effectively bind to TAK1 and Keap1, which may be involved in the inhibition of TAK1- NF-κB/MAPKs and activation of Nrf2 mediated by MLG. Animal study demonstrated that MLG ameliorated inflammatory injury of lung and liver in CLP-induced sepsis mice probably by reducing the levels of pro-inflammatory cytokines. Therefore, our study suggests that bi-directional roles of MLG in improving sepsis via blocking the TAK1-NF-κB/MAPKs and activating Nrf2 pathways, indicating its potential as a promising candidate drug for sepsis treatment.

Mollugin activates GLP-1R to improve cognitive dysfunction in type 2 diabetic mice

AIMS

The incidence of diabetic cognitive dysfunction is increasing year by year, and it has gradually become a research hot spot. Studies have shown that glucagon-like peptide-1 receptor (GLP-1R) agonists can improve cognitive dysfunction in diabetic patients. This study focuses on whether small molecule GLP-1R agonists from traditional Chinese medicine (TCM) can improve the diabetic cognitive dysfunction.

MATERIALS AND METHODS

The small molecules from TCM were screened by cell membrane chromatography (CMC) with GLP-1R-HEK293 cell membrane column. MTT assay, flow cytometry, immunofluorescence cytochemistry and other methods were used to determine the effects of mollugin on the apoptosis rate and reactive oxygen species (ROS) level of high glucose (HG)/hydrogen peroxide (H2O2) induced PC12 cells. Real-Time PCR was used to detect mRNA expression in mouse cerebral cortex. Water maze test was further used to confirm the effect of mollugin on cognitive dysfunction in T2DM mice.

KEY FINDINGS

Mollugin bound to GLP-1R, promoted Ca2+ influx, increased insulin secretion and cAMP content in β-TC-6 cells. Mollugin enhanced the cell viability, ameliorated apoptosis, reduced intracellular ROS levels in HG/H2O2-injured PC12 cells. Mollugin reduced the T2DM mice's escape latency, improved neuronal cell damage, decreased the expression of Pik3ca, Akt1 and Mapk1 mRNA in the cerebral cortex tissue.

SIGNIFICANCE

The results suggest that mollugin could improve cognitive dysfunction in T2DM mice through activating GLP-1R/cAMP/PKA signal pathway.

Mollugin suppresses proliferation and drives ferroptosis of colorectal cancer cells through inhibition of insulin-like growth factor 2 mRNA binding protein 3/glutathione peroxidase 4 axis

Increasing researches have demonstrated that targeting ferroptosis might be a new conceptual avenue to treat colorectal cancer (CRC). Mollugin is a phytochemical isolated from Rubia cordifolia L. with antitumor activity. However, whether ferroptosis mediates the antitumor activity of mollugin in CRC has not been explored. Our study aims to investigate the antitumor and pro-ferroptosis effects, and mechanisms of mollugin in CRC. We found that mollugin led to ferroptosis in CRC cells, resulting in reduced GSH level and elevated levels of ROS, Fe2+, and MDA. Mollugin treatment caused obvious decrease in cell viability and proliferation in CRC cells, which were aggravated by ferroptosis inducer erastin and attenuated by ferroptosis inhibitor ferrostatin-1. Tumor xenografts experiments proved that mollugin suppressed the tumor growth, while treatment with ferrostatin-1 attenuated the antitumor activity of mollugin in vivo. Integrated bioinformatics analysis showed that insulin-like growth factor 2 mRNA binding protein 3 (IGF2BP3) was highly expressed in CRC tissues and indicated poor prognosis. Further investigation indicated that the IGF2BP3/glutathione peroxidase 4 (GPX4) axis was involved in mollugin-regulated ferroptosis in CRC. In conclusions, Mollugin suppresses proliferation and drives ferroptosis of CRC cells by inhibiting the IGF2BP3/GPX4 axis, suggesting that mollugin may be a potential therapeutic option for CRC.

Changes in marker secondary metabolites revealed the medicinal parts, harvest time, and possible synthetic sites of Rubia cordifolia L

Rubia cordifolia L. is a significant medicinal plant. To investigate the changes of marker metabolites of R. cordifolia, the purpurin, mollugin, carbon, nitrogen contents, and the expression of genes involved in anthraquinones synthesis were examined. The findings indicated that the two secondary metabolites were only detected in stems and roots. Root purpurin content was 5-26 times higher than in stems, and root mollugin content was 92 times higher than in stems in June. These findings suggest that the potential of the roots as a medicinal part. The roots were found to have highest purpurin content in October (2.406 mg g-1), whereas the mollugin content was highest in August (6.193 mg g-1). However, the purpurin content in August was only 0.029 mg g-1 lower than that in October, making August a suitable harvest period for R. cordifolia. The expression 1-deoxy-D-xylulose 5-phosphate synthase (dxs) and 1-deoxy-D-xylulose-5-phosphate reductorisomerase (dxr) genes in roots showed an upward trend. However, the expression level of dxr gene was significantly higher than dxs with the range of 60-518 times higher, indicating the important role of dxr gene. Through correlation and redundancy analyses, it was found that mollugin showed positive correlation with carbon contents and carbon-nitrogen ratio of aerial parts. Additionally, purpurin showed a positive correlation with the expression of both genes. As a result, mollugin is likely to be synthesized in the aerial parts and then stored in the roots, whereas purpurin might be synthesized in the stems and roots. These findings could provide cultivation guidelines for R. cordifolia.

Mollugin induced oxidative DNA damage via up-regulating ROS that caused cell cycle arrest in hepatoma cells

Mollugin has been proven to have anti-tumor activity. However, its potential anti-tumor mechanism remains to be fully elaborated. Herein, we investigated the growth inhibition of HepG2 cells, as well as the anti-tumor effect of mollugin and its molecular mechanism on H22-tumor bearing mice. In vitro, mollugin was shown to have a strong inhibitory effect on HepG2 cells in a concentration-dependent manner. Mollugin induced S-phase arrest of HepG2 cells, and increased intracellular reactive oxygen species (ROS) levels. Comet assay demonstrated that mollugin induced DNA damage in HepG2 cells, as well as an increase in the expression of p-H2AX. In addition, mollugin induced changes in cyclin A2 and CDK2. However, the addition of antioxidant glutathione (GSH) was able to reverse the effect of mollugin. In vivo, mollugin significantly inhibited tumor growth and reduced the tendency of tumor volume growth in mice. The tumor cell density was found to be decreased in the administration group, and the content of ROS in the tumor tissue significantly increased. The expression of p-H2AX, cyclin A2 and CDK2 were consistent with in vitro results. Mollugin demonstrated anti-hepatocellular carcinoma activity in vitro and in vivo, and its anti-hepatocellular carcinoma activity was found to be related to DNA damage and cell cycle arrest induced by excessive ROS production in cells.

Revealing the mechanisms and the material basis of Rubia cordifolia L. on abnormal uterine bleeding with uniting simultaneous determination of four components and systematic pharmacology approach-experimental validation

The roots of Rubia cordifolia L. (RCL) have become an important medicine for abnormal uterine bleeding (AUB) and hemorrhage syndrome in Traditional Asian medicine. However, the underlying mechanism and the material basis of RCL for treating AUB has not been fully elucidated. In this study, quantitative evaluation of quinones, systematic pharmacology and experimental verification were adopted. Firstly, the Disease-Ingredient-Target network was established by Cytoscape, which was consistent with 23 compounds and 47 target genes. The hub targets were discovered by Maximal Clique Centrality (MCC) method with Cytohubba plugins of Cytoscape, and top 20 nodes were ranked by MCC. It was assumed that mollugin is the main ingredient of RCL for treating AUB. Pathways on which RCL acted were obtained from observation of its biological functions, KEGG pathways and Reactome pathway enrichment analysis. The possible mechanism of RCL for treating AUB was revealed for improvment of the blood clotting system, blood circulation, arachidonic acid metabolism and inflammation. Then, a novel method for evaluating the quality of RCL was established, and the content of mollugin in RCL was the higher than others. Finally, pharmacologic experiments confirmed that RCL could improve the inflammation by inhibiting the activity of COX-2 and cPLA₂ enzyme, ameliorate blood hypercoagulability by affecting coagulation cascade and fibrinolytic system. It was found that RCL inhibited the expression COX-2 and PAI-1 by reducing HIF-1α expression. The trend of each index of mollugin was consistent with that of RCL, indicating that it played an important role in RCL for treating AUB. The above results could provide a novel method for the quality evaluation of RCL and was expected to give us more important information regarding the use of RCL as a promising drug candidate for AUB, offering a fertility preserving medical, non-hormonal treatment choose for women with AUB.

Regulation of NF-κB/MAPK signaling pathway attenuates the acute lung inflammation in Klebsiella pneumonia rats by mollugin treatment

Present study evaluates the protective effect of mollugin against Klebsiella pneumonia (KP) and also postulates the possible mechanism of its action. Klebsiella pneumoniae (2.4 × 10⁸ CFU/ml) was used for the induction of KP. PMNs and WBC count was determined in the blood and bronchoalveolar lavage fluid (BALF) of Klebsiella pneumonia rat. Level of inflammatory cytokines in the blood of Klebsiella pneumonia rat was determined by ELISA methods. Moreover effect of mollugin was estimated by Western blot assay and RT-PCR method. Result of the study suggests that water content in lung was reduced in the mollugin treated group compared to pneumonia control group of rats. Count of PMNs and WBC were found to be reduced in mollugin treated group compared to pneumonia control group of rats. Level of inflammatory cytokines was also found to be reduced in the blood of mollugin treated group than pneumonia control group. Moreover treatment with mollugin attenuates the altered expression of p-MAPK, p-JNK and p-ERK protein and mRNA expression of NF-κB in the lung tissues of Klebsiella pneumonia rat. In conclusion, data of the study reveals that treatment with mollugin ameliorates Klebsiella pneumonia rat by reducing the lung inflammation. Inflammation of lung tissue was reduced by regulating the NF-κB/MAPK signaling pathway in mollugin treated group.

Mollugin enhances the osteogenic action of BMP-2 via the p38-Smad signaling pathway

Bone morphogenetic protein 2 (BMP-2) has been used clinically to encourage bone regeneration; although, there can be major side effects with larger doses. Therefore, there is a need to identify new small molecules to potentiate the osteogenic action of BMP-2. In this study, we investigated the effect of mollugin on bone formation in murine bi-potential mesenchymal progenitor C2C12 cells by combination with BMP-2. We found mollugin could enhance the BMP-2-mediated osteoblast differentiation of C2C12 cells. This was accompanied by the induction of other osteogenic BMPs. We also found the enhancing potential of mollugin may involve activation of the p38-Smad1/5/8 signaling axis. Furthermore, mollugin promoted skeletal development in zebrafish. The combination of BMP-2 with small molecules, including mollugin, could minimize its clinical limitations, and these molecules might lead to the development of effective stem cell stimulants for bone regeneration and fracture healing.

Syntheses and anti-inflammatory activity of azamollugin derivatives

Oxomollugin (2) is a degradation product of mollugin (1) and a potent inhibitor of NO-production including nuclear factor kappa B signals. In our endeavor to develop a potent anti-inflammatory compound, we synthesized several aza-derivatives of oxomollugin (2) and evaluated their NO-production inhibitory activity. Azamollugin (3) showed a potent inhibitory activity, and its activity (IC50 0.34μM) was proved to be more potent than that of oxomollugin (2, IC50 1.3μM).

Mollugin from Rubea cordifolia suppresses receptor activator of nuclear factor-κB ligand-induced osteoclastogenesis and bone resorbing activity in vitro and prevents lipopolysaccharide-induced bone loss in vivo

Osteopenic diseases, such as osteoporosis, are characterized by progressive and excessive bone resorption mediated by enhanced receptor activator of nuclear factor-κB ligand (RANKL) signaling. Therefore, downregulation of RANKL downstream signals may be a valuable approach for the treatment of bone loss-associated disorders. In this study, we investigated the effects of the naphthohydroquinone mollugin on osteoclastogenesis and its function in vitro and in vivo. Mollugin efficiently suppressed RANKL-induced osteoclast differentiation of bone marrow macrophages (BMMs) and bone resorbing activity of mature osteoclasts by inhibiting RANKL-induced c-Fos and NFATc1 expression. Mollugin reduced the phosphorylation of signaling pathways activated in the early stages of osteoclast differentiation, including the MAP kinase, Akt, and GSK3β and inhibited the expression of different genes associated with osteoclastogenesis, such as OSCAR, TRAP, DC-STAMP, OC-STAMP, integrin αν, integrin β3, cathepsin K, and ICAM-1. Furthermore, mice treated with mollugin showed significant restoration of lipopolysaccharide (LPS)-induced bone loss as indicated by micro-CT and histological analysis of femurs. Consequently, these results suggested that mollugin could be a novel therapeutic candidate for bone loss-associated disorders including osteoporosis, rheumatoid arthritis, and periodontitis.

Mollugin induces tumor cell apoptosis and autophagy via the PI3K/AKT/mTOR/p70S6K and ERK signaling pathways

Mollugin, a bioactive phytochemical isolated from Rubia cordifolia L., has shown preclinical anticancer efficacy in various cancer models. However the effects of mollugin in regulating cancer cell survival and death remains undefined. In the present study we found that mollugin exhibited cytotoxicity on various cancer models. The suppression of cell viability was due to the induction of mitochondria apoptosis. In addition, the presence of autophagic hallmarks was observed in mollugin-treated cells. Notably, blockade of autophagy by a chemical inhibitor or RNA interference enhanced the cytotoxicity of mollugin. Further experiments demonstrated that phosphatidylinositide 3-kinases/protein kinase B/mammalian target of rapamycin/p70S6 kinase (PI3K/AKT/mTOR/p70S6K) and extracellular regulated protein kinases (ERK) signaling pathways participated in mollugin-induced autophagy and apoptosis. Together, these findings support further studies of mollugin as candidate for treatment of human cancer cells.

Synthesis of novel and diverse mollugin analogues and their antibacterial and antioxidant activities

Novel and diverse mollugin analogues (1-12) were synthesized using PhB(OH)2/AcOH-mediated electrocyclization reaction as a key step. The newly synthesized compounds were screened for antioxidant and antibacterial activities. Compounds 1, 2, 5, 6, 8, and 10-12 showed high antioxidant activities in DPPH inhibition (IC50=0.52-1.11 μM) compared with BHT (IC50=9.67 μM). Compounds 3 exhibited potent antibacterial activity against Staphylococcus aureus (KCTC-1916) bacterial strain at 100 μg/mL. Structures of newly synthesized compounds were confirmed by IR, (1)H NMR, (13)C NMR data and high-resolution mass spectrometry.

Effects of lovastatin, clomazone and methyl jasmonate treatment on the accumulation of purpurin and mollugin in cell suspension cultures of Rubia cordifolia

AIM

To determine the IPP origin of the naphthoquinones (NQs) in Rubia cordifolia, and to evaluate the effects of methyl jasmonate (MeJA) treatment, MEP, and MVA pathway inhibitor treatment on the accumulation of anthraquinones (AQs) and NQs in cell suspension cultures of R. cordifolia.

METHODS

Cell suspension cultures of R. cordifolia were established. Specific inhibitors (lovastatin and clomazone) and MeJA were supplied to the media, respectively. Treated cells were sampled every three days. Content determination of purpurin (AQs) and mollugin (NQs) were carried out using RP-HPLC. The yield of the two compounds was compared with the DMSO-supplied group and the possible mechanism was discussed.

RESULTS

Lovastatin treatment increased the yield of purpurin and mollugin significantly. Clomazone treatment resulted in a remarkable decrease of both compounds. In the MeJA-treated cells, the purpurin yield increased, meanwhile, the mollugin yield decreased compared with control.

CONCLUSION

The IPP origin of mollugin in R. cordifolia cell suspension cultures was likely from the MEP pathway. To explain the different effects of MeJA on AQs and NQs accumulation, studies on the regulation and expression of the genes, especially after prenylation of 1,4-dihydroxy-2-naphthoic acid should be conducted.