Piperlongumine induces apoptosis and G2/M phase arrest in human osteosarcoma cells by regulating ROS/PI3K/Akt pathway

Piperlongumine: the amazing amide alkaloid from Piper in the treatment of breast cancer

Piperlongumine (PL), an alkaloid found primarily in the fruits and roots of the plant Piper longum L. (Piperaceae), is a natural compound that exhibits potent activity against various cancer cell proliferation. The most frequently caused malignancy in women globally, breast cancer (BC), has been demonstrated to be significantly inhibited by PL. Apoptosis, cell cycle arrest, increased ROS generation, and changes in the signalling protein's expression are all caused by the numerous signalling pathways that PL impacts. Since BC cells resist conventional chemotherapeutic drugs (doxorubicin, docetaxel etc.), researchers have shown that the drugs in combination with PL can exhibit a synergistic effect, greater than the effects of the drug or PL alone. Recently, techniques for drug packaging based on nanotechnology have been employed to improve PL release. The review has presented an outline of the chemistry of PL, its molecular basis in BC, its bioavailability, toxicity, and nanotechnological applications. An attempt to understand the future prospects and direction of research about the compound has also been discussed.

Combination of ethyl acetate fraction from Calotropis gigantea stem bark and sorafenib induces apoptosis in HepG2 cells

The cytotoxicity of the ethyl acetate fraction of the Calotropis gigantea (L.) Dryand. (C. gigantea) stem bark extract (CGEtOAc) has been demonstrated in many types of cancers. This study examined the improved cancer therapeutic activity of sorafenib when combined with CGEtOAc in HepG2 cells. The cell viability and cell migration assays were applied in HepG2 cells treated with varying concentrations of CGEtOAc, sorafenib, and their combination. Flow cytometry was used to determine apoptosis, which corresponded with a decline in mitochondrial membrane potential and activation of DNA fragmentation. Reactive oxygen species (ROS) levels were assessed in combination with the expression of the phosphatidylinositol-3-kinase (PI3K)/ protein kinase B (Akt)/ mammalian target of rapamycin (mTOR) pathway, which was suggested for association with ROS-induced apoptosis. Combining CGEtOAc at 400 μg/mL with sorafenib at 4 μM, which were their respective half-IC50 concentrations, significantly inhibited HepG2 viability upon 24 h of exposure in comparison with the vehicle and each single treatment. Consequently, CGEtOAc when combined with sorafenib significantly diminished HepG2 migration and induced apoptosis through a mitochondrial-correlation mechanism. ROS production was speculated to be the primary mechanism of stimulating apoptosis in HepG2 cells after exposure to a combination of CGEtOAc and sorafenib, in association with PI3K/Akt/mTOR pathway suppression. Our results present valuable knowledge to support the development of anticancer regimens derived from the CGEtOAc with the chemotherapeutic agent sorafenib, both of which were administered at half-IC50, which may minimize the toxic implications of cancer treatments while improving the therapeutic effectiveness toward future medical applications.

Targeting signaling pathways in osteosarcoma: Mechanisms and clinical studies

Osteosarcoma (OS) is a highly prevalent bone malignancy among adolescents, accounting for 40% of all primary malignant bone tumors. Neoadjuvant chemotherapy combined with limb-preserving surgery has effectively reduced patient disability and mortality, but pulmonary metastases and OS cells' resistance to chemotherapeutic agents are pressing challenges in the clinical management of OS. There has been an urgent need to identify new biomarkers for OS to develop specific targeted therapies. Recently, the continued advancements in genomic analysis have contributed to the identification of clinically significant molecular biomarkers for diagnosing OS, acting as therapeutic targets, and predicting prognosis. Additionally, the contemporary molecular classifications have revealed that the signaling pathways, including Wnt/β-catenin, PI3K/AKT/mTOR, JAK/STAT3, Hippo, Notch, PD-1/PD-L1, MAPK, and NF-κB, have an integral role in OS onset, progression, metastasis, and treatment response. These molecular classifications and biological markers have created new avenues for more accurate OS diagnosis and relevant treatment. We herein present a review of the recent findings for the modulatory role of signaling pathways as possible biological markers and treatment targets for OS. This review also discusses current OS therapeutic approaches, including signaling pathway-based therapies developed over the past decade. Additionally, the review covers the signaling targets involved in the curative effects of traditional Chinese medicines in the context of expression regulation of relevant genes and proteins through the signaling pathways to inhibit OS cell growth. These findings are expected to provide directions for integrating genomic, molecular, and clinical profiles to enhance OS diagnosis and treatment.

Natural borneol serves as an adjuvant agent to promote the cellular uptake of piperlongumine for improving its antiglioma efficacy

Piperlongumine (PL) can selectively inhibit the proliferation of various cancer cells by increasing reactive oxygen species (ROS) level to cause a redox imbalance in cancer cells rather than in normal cells. However, the clinical application of PL is limited by its poor cellular uptake. Natural borneol (NB) is extracted from the fresh branches and leaves of Cinnamomum camphora (L.) Presl. with the purity of (+)-borneol no less than 96.0%. NB has been often used as an adjuvant agent to promote the cellular uptake of other drugs. This study aims to investigate the effect of NB on the cellular uptake of PL for improving its antiglioma efficacy and underlying mechanism. NB obviously promoted the cellular uptake of PL with a 1.3-fold increase in the maximum peak concentration and an earlier peak time of 30 min in C6 glioma cells. The cellular uptake of PL was enhanced by NB through down-regulating the expression levels of P-glycoprotein (ABCB1) and breast cancer resistance protein (ABCG2). The combination of NB and PL significantly induced higher levels of ROS, which increased apoptosis and enhanced G2/M cycle arrest of C6 glioma cells, compared to PL alone administration. NB-enhanced antiglioma efficacy of PL without side effects was confirmed in tumor-bearing mice, which was attributed to the improved cellular uptake of PL. The distribution of PL in the tumor tissue of combined group increased 2.39 times than that of PL-treated group. We firstly report NB as an adjuvant agent to improve the antiglioma efficacy of PL in a ROS-dependent manner, which is due to the enhanced cellular uptake of PL by NB though down-regulating the expression levels of ABCB1 and ABCG2. This work provides a new strategy to promote the cellular uptake of PL with great potential for the treatment of glioma.

Piperlongumine combined with vitamin C as a new adjuvant therapy against gastric cancer regulates the ROS-STAT3 pathway

OBJECTIVE

To investigate the effects of piperlongumine (PL) and vitamin C (VC) on signal transducer and activator of transcription 3 (STAT3) signalling in gastric cancer cell lines.

METHODS

In vivo tumour xenograft anticancer assays were undertaken to confirm the anticancer activity of PL. Cell viability, flow cytometry and Western blot assays were undertaken to evaluate the anticancer effects of PL, VC and combinations of PL and VC in AGS and KATO III cells.

RESULTS

Both PL and VC induced apoptosis and inhibited cell proliferation in AGS and KATO III cells. These effects were dependent on reactive oxygen species (ROS). PL effectively suppressed STAT3 activation while VC caused abnormal activation of STAT3. The combination of PL and VC exhibited a stronger apoptotic effect compared with either agent alone. PL reversed the abnormal activation of STAT3 by VC, which could be a key to their synergistic effect.

CONCLUSIONS

PL combined with VC exhibited a stronger anticancer effect by regulating the ROS-STAT3 pathway, suggesting that this combination might be a potential adjuvant therapy for gastric cancer.

Design, synthesis and anti-tumor evaluation of 1,2,4-triazol-3-one derivatives and pyridazinone derivatives as novel CXCR2 antagonists

Chemokine receptor 2 (CXCR2) is the receptor of glutamic acid-leucine-arginine sequence-contained chemokines CXCs (ELR⁺ CXCs). In recent years, CXCR2-target treatment strategy has come a long way in cancer therapy. CXCR2 antagonists could block CXCLs/CXCR2 axis, and are widely used in regulating immune cell migration, tumor metastasis, apoptosis and angiogenesis. Herein, two series of new CXCR2 small-molecule inhibitors, including 1,2,4-triazol-3-one derivatives 1-11 and pyridazinone derivatives 12-22 were designed and synthesized based on the proof-to-concept. The pyridazinone derivative 18 exhibited good CXCR2 antagonistic activity (69.4 ± 10.5 %Inh at 10 μM) and demonstrated its significant anticancer metastasis activity in MDA-MB-231 cells and remarkable anti-angiogenesis activity in HUVECs. Furthermore, noteworthy was that 18 exhibited an obvious synergistic effect with Sorafenib in anti-proliferation assay in MDA-MB-231 cells. Moreover, 18 showed a distinct reduction of the phosphorylation levels of both PI3K and AKT proteins in MDA-MB-231 cells, and also affected the expression levels of other PI3K/AKT signaling pathway-associated proteins. The molecular docking studies of 18 with CXCR2 also verified the rationality of our design strategy. All of these results revealed pyridazinone derivative 18 as a promising CXCR2 antagonist for future cancer therapy.

Overview of piperlongumine analogues and their therapeutic potential

Natural products have long been an important source for discovery of new drugs to treat human diseases. Piperlongumine (PL) is an amide alkaloid isolated from Piper longum L. (long piper) and other piper plants and has received widespread attention because of its diverse biological activities. A large number of PL derivatives have been designed, synthesized and assessed in many pharmacological functions, including antiplatelet aggregation, neuroprotective activities, anti-diabetic activities, anti-inflammatory activities, anti-senolytic activities, immune activities, and antitumor activities. Among them, the anti-tumor effects and application of PL and its derivatives are most extensively studied. We herein summarize the development of PL derivatives, the structure and activity relationships (SARs), and their therapeutic potential on the treatments of various diseases, especially against cancer. We also discussed the challenges and future directions associated with PL and its derivatives in these indications.

Piperlongumine Analogs Promote A549 Cell Apoptosis through Enhancing ROS Generation

Chemotherapeutic agents, which contain the Michael acceptor, are potent anticancer molecules by promoting intracellular reactive oxygen species (ROS) generation. In this study, we synthesized a panel of PL (piperlongumine) analogs with chlorine attaching at C2 and an electron-withdrawing/electron-donating group attaching to the aromatic ring. The results displayed that the strong electrophilicity group at the C2-C3 double bond of PL analogs plays an important role in the cytotoxicity whereas the electric effect of substituents, which attached to the aromatic ring, partly contributed to the anticancer activity. Moreover, the protein containing sulfydryl or seleno, such as TrxR, could be irreversibly inhibited by the C2-C3 double bond of PL analogs, and boost intracellular ROS generation. Then, the ROS accumulation could disrupt the redox balance, induce lipid peroxidation, lead to the loss of MMP (Mitochondrial Membrane Potential), and ultimately result in cell cycle arrest and A549 cell line death. In conclusion, PL analogs could induce in vitro cancer apoptosis through the inhibition of TrxR and ROS accumulation.

Cigarette Smoke Exposure Inhibits Osteoclast Apoptosis via the mtROS Pathway

It is widely known that smoking is a risk factor for bone loss and plays a key role in osteopenia. Despite this well-known association, the mechanisms by which smoking affects bone have not been definitively established. Since smoking increases bone loss and potentially affects bone resorption in response to mechanical force, we investigated the impact of cigarette smoke on osteoclast numbers and underlying mechanisms in a mouse model of orthodontic tooth movement (OTM). The experimental group was exposed to once-daily cigarette smoke while the control group was not, and tooth movement distance and osteoclast numbers were assessed. In addition, the effect of cigarette smoke extract (CSE) on osteoclast precursor proliferation and osteoclast apoptosis was assessed in vitro. We found that cigarette smoke exposure enhanced bone remodeling stimulated by mechanical force and increased osteoclast numbers in vivo. Also, CSE increased the number of osteoclasts by inhibiting osteoclast apoptosis via the mitochondrial reactive oxygen species/cytochrome C/caspase 3 pathway in vitro. Moreover, exposure of mice to cigarette smoke affected bone marrow cells, leading to increased formation of osteoclasts in vitro. This study identifies a previously unknown mechanism of how smoking has a detrimental impact on bone.

Piperlongumine Attenuates High Calcium/Phosphate-Induced Arterial Calcification by Preserving P53/PTEN Signaling

Vascular calcification frequently occurs in the process of chronic kidney disease, atherosclerosis and aging, resulting in an increased prevalence of cardiovascular events. Piperlongumine (PLG) is a natural product isolated from Piper longum L. Here, we aimed to explore the effect of PLG in high calcium- and phosphate-induced vascular calcification and the associated mechanism. Flow cytometry assays showed that PLG at concentrations <10 μM did not promote vascular smooth muscle cells (VSMCs) apoptosis, and PLG at concentrations >2.5 μM inhibited VSMCs proliferation. Thus, 2.5 μM PLG was selected for subsequent experiments. Alizarin red staining and ALP activity assays showed that PLG inhibited calcium deposition of VSMCs treated with high calcium/phosphate medium. PLG also decreased the expression of osteogenic genes and proteins, including Runx2, Bmp2, and OPN, as determined by qRT-PCR and western blotting. In a vitamin D-induced aortic calcification mouse model, a 5 mg/kg dose of PLG decreased calcium deposition in the aortic wall as well as Runx2 expression. With regard to the mechanism, we found that the levels of P53 mRNA and protein in both VSMCs and mouse aortic tissues were decreased in the calcification models, and we observed that PLG preserved the levels of P53 and its downstream gene PTEN. Concurrent treatment of VSMCs with P53 ShRNA and PLG blunted the anti-calcific effect of PLG. In conclusion, PLG attenuates high calcium/phosphate-induced vascular calcification by upregulating P53/PTEN signaling in VSMCs. PLG may act as a promising herbal extract for the clinical management of vascular calcification.

Low molecular weight-PAHs induced inflammation in A549 cells by activating PI3K/AKT and NF-κB signaling pathways

Our previous study has demonstrated that two low molecular weight-polycyclic aromatic hydrocarbons (LMW-PAHs), phenanthrene (Phe) and fluorene (Flu), alone and as a mixture could induce oxidative damage and inflammation in A549 cells. However, the associated mechanisms have not been well discussed. The aim of this study was to further investigate the roles of PI3K/AKT and NF-κB signaling pathways in the inflammatory effects in A549 cells induced by Phe, Flu and their mixture. The results indicated that Phe, Flu and their mixture significantly activated PI3K/AKT and NF-κB signaling pathways by increasing the phosphorylation levels of PI3K, AKT, IκBα and NF-κB p65. In addition, pro-inflammatory cytokine expressions of TNF-α and IL-6 induced by the binary mixture of Phe and Flu were all alleviated by co-treatment with PI3K/AKT and NF-κB specific inhibitors (LY294002 and BAY11-7082). The results suggested that PI3K/AKT and NF-κB signaling pathways played an important role in LMW-PAHs induced inflammation in A549 cells.

Piperlongumine inhibits head and neck squamous cell carcinoma proliferation by docking to Akt

Piperlongumine (PL) is a biologically active alkaloid isolated from the long pepper roots and widely used as a traditional medicine in Ayurvedic medicine. However, the mechanism of PL's effect on head and neck squamous cell carcinoma (HNSCC) is not well understood. We performed cell experiments to confirm PL's inhibitory effect on HNSCC and employing cisplatin as positive control. Next, we conducted bioinformatics to predict PL's potential targets and verified by western blotting. Molecular docking, Biacore experiment and kinase activity assays were applied to elucidate the mechanism by which PL inhibited target activity. In vivo efficacy was verified by xenotransplantation and immunohistochemistry. PL inhibited proliferation, promoted late apoptosis, arrested cell cycle and inhibited DNA replication of the HEp-2 and FaDu cell lines. Employing bioinformatics, we found that PL's target was Akt and PL attenuated Akt phosphorylation. We found from molecular docking, Biacore experiment and kinase activity assay that PL inhibited Akt activation by docking to Akt to restrain its activity. In addition, PL significantly inhibited the growth of xenograft tumors by down regulating the expression of p-Akt in vivo. This study provides new insights into the molecular functions of PL and indicate its potential as a therapeutic agent for HNSCC.

The potential role of the 5,6-dihydropyridin-2(1H)-one unit of piperlongumine on the anticancer activity

Piperlongumine (PL), a potent anticancer agent from the plant long pepper (Piper longum), contains the 5,6-dihydropyridin-2(1H)-one heterocyclic scaffold and cinnamoyl unit. In this paper, we synthesized a series of PL analogs and evaluated their cytotoxicity against cancer cells for the sake of exploring which pharmacophore plays a more potent role in enhancing the anticancer activities of PL. These results illustrated that the position effect, not the electronic effect, of substituents plays a certain role in the cytotoxicity of PL and its analogs. More important, the 5,6-dihydropyridin-2(1H)-one unit, a potent pharmacophore in enhancing the antiproliferative activities of PL, could react with cysteamine and lead to ROS generation, and then bring about the occurrence of ROS-induced downstream events, followed by cell cycle arrest and apoptosis. This work suggests that introducing a lactam unit containing Michael acceptors may be a potent strategy to enhancing the anticancer activity of drugs.

Gamabufotalin suppressed osteosarcoma stem cells through the TGF-β/periostin/PI3K/AKT pathway

AIMS

To investigate the effect of gamabufotalin (GBT) on metastasis and modulation of stemness features in osteosarcoma, and the molecular mechanisms underlying such effects.

METHODS

Human osteosarcoma U2OS/MG-63 cell lines were used in this study. Cell proliferation, migration, and invasion were determined by MTT assay, wound healing assay, and cell invasion assay, respectively. The inhibitive effect of GBT on stemness was assessed by flow cytometry and mammosphere formation. The protein levels of related proteins were detected by western blotting analysis. The effect of GBT on tumorigenicity and metastasis was determined by immunofluorescence staining and immunohistochemistry in vivo experiments.

RESULTS

We found that GBT suppressed the viability of U2OS/MG-63 cells in a time- and dose-dependent manner. Notably, GBT had no effect on the viability of human fetal osteoblastic (hFOB) 1.19 cells. Moreover, GBT increased the width of wounds, reduced the number of invasive osteosarcoma cells and reversed the epithelial-mesenchymal transition phenotype. Notably, we found that, compared with hFOB1.19 cells, the levels of transforming growth factor-β (TGF-β), periostin, phosphorylated-AKT (p-AKT), and phosphorylated-PI3K (p-PI3K) were higher in spheroids group than in parent cells. In addition, GBT reduced the ratio of CD133+ cells, the size of spheroids and Nanog, as well as the protein levels of SRY-box transcription factor 2 (SOX2), and octamer-binding protein 3/4 (OCT3/4). Our in vivo experiments showed that GBT consistently reduced lung metastasis lesions, the expression levels of matrix metalloproteinase 2 (MMP2), TGF-β, periostin, p-AKT, and p-PI3K (immunohistochemistry staining), as well as that of CD133 in tumor tissues (immunofluorescence analysis). From a mechanistic point of view, exogenous TGF-β/periostin/PI3K/AKT overexpression neutralized the reduction of GBT-decreased invasion/migration and the suppression of stemness properties.

CONCLUSION

Collectively, our data demonstrated that GBT inhibited the viability and tumorigenesis capability of osteosarcoma cells by blocking the TGF-β/periostin/PI3K/AKT signaling pathway. Therefore, GBT may represent a promising therapeutic agent for the management of osteosarcoma.

Piperlongumine, a potent anticancer phytotherapeutic: Perspectives on contemporary status and future possibilities as an anticancer agent

Piperlongumine, a white to beige biologically active alkaloid/amide phytochemical, has high pharmacological relevance as an anticancer agent. Piperlongumine has several biological activities, including selective cytotoxicity against multiple cancer cells of different origins at a preclinical level. Several preclinical studies have documented the anticancer potential of piperlongumine through its targeting of multiple molecular mechanisms, such as cell cycle arrest, anti-angiogenesis, anti- invasive and anti-metastasis pathways, autophagy pathways, and intrinsic apoptotic pathways in vitro and in vivo. Mechanistically, piperlongumine inhibits cancer growth by resulting in the accumulation of intracellular reactive oxygen species, decreasing glutathione and chromosomal damage, or modulating key regulatory proteins, including PI3K, AKT, mTOR, NF-kβ, STATs, and cyclin D1. Furthermore, combined treatment with piperlongumine potentiates the anticancer activity of conventional chemotherapeutics and overcomes resistance to chemo- and radio- therapy. Nanoformulation of piperlongumine has been associated with increased aqueous solubility and bioavailability and lower toxicity, thus enhancing therapeutic efficacy in both preclinical and clinical settings. The current review highlights anticancer studies on the occurrence, chemical properties, chemopreventive mechanisms, toxicity, bioavailability, and pharmaceutical relevance of piperlongumine in vitro and in vivo.

Low-dose Sevoflurane Attenuates Cardiopulmonary Bypass (CPB)- induced Postoperative Cognitive Dysfunction (POCD) by Regulating Hippocampus Apoptosis via PI3K/AKT Pathway

BACKGROUND

Cardiopulmonary bypass (CPB) caused postoperative cognitive dysfunction (POCD) was characterized by hippocampus apoptosis, which seriously limited the therapeutic efficacy and utilization of CPB in clinic. Recent data indicated that sevoflurane anesthesia might alleviate CPB-induced POCD, however, the underlying mechanisms are still unclear.

METHODS

In the present study, the in vivo CPB-POCD models were established by using aged Sprague-Dawley (SD) male rats and the in vitro hypoxia/reoxygenation (H/R) models were inducted by using the primary hippocampus neuron (PHN) cells.

RESULTS

The results showed that CPB impaired cognitive functions and induced hippocampus apoptosis in rat models, which were alleviated by pre-treating rats with low-dose sevoflurane. In addition, the phosphatidylinositol 3 kinase (PI3K)/protein kinase B (AKT) signal pathway was inactivated in the hippocampus tissues of CPB-POCD rats, which were rescued by low-dose sevoflurane treatment. Of note, the PI3K/AKT inhibitor (LY294002) abrogated the protective effects of low-dose sevoflurane on CPB-POCD rats. Consistently, the in vitro results showed that H/R treatment induced cell apoptosis and inhibited cell viability in PHN cells, which were attenuated by low-dose sevoflurane. Similarly, LY294002 abrogated the inhibiting effects of low-dose sevoflurane on H/R-induced PHN cell death.

CONCLUSION

Taken together, low-dose sevoflurane attenuated CPB-induced POCD by inhibiting hippocampus apoptosis through activating PI3K/AKT signal pathway.