Piperine sensitizes radiation-resistant cancer cells towards radiation and promotes intrinsic pathway of apoptosis

Comprehensive review of the phytochemistry, pharmacology, pharmacokinetics, and toxicology of alkamides (2016-2022)

Alkamides refer to a class of natural active small-molecule products composed of fatty acids and amine groups. These compounds are widely distributed in plants, and their unique structures and various pharmacological activities have caught the attention of scholars. This review provides a collection of literatures related to the phytochemistry, pharmacological effects, pharmacokinetics, and toxicity of alkamides published in 2016-2022 and their summary to provide references for further development of this class of ingredients. A total of 234 components (including chiral isomers) were summarized, pharmacological activities, such as anti-inflammatory, antitumor, antidiabetic, analgesic, neuroprotective, insecticidal, antioxidant, and antibacterial, and miscellaneous properties of alkamides were discussed. In addition, the pharmacokinetic characteristics and toxicity of alkamides were reviewed. However, information on the pharmacological mechanisms of the action, drug safety, and pharmacokinetics of alkamides is limited and thus requires further investigation and evaluation.

Breast cancer cells are sensitized by piperine to radiotherapy through estrogen receptor-α mediated modulation of a key NHEJ repair protein- DNA-PK

BACKGROUND

Non-homologous end joining, an important DNA-double-stranded break repair pathway, plays a prominent role in conferring resistance to radiotherapeutic agents, resulting in cancer progression and relapse.

PURPOSE

The molecular players involved in the radio-sensitizing effects of piperine and many other phytocompounds remain evasive to a great extent. The study is designed to assess if piperine, a plant alkaloid can alter the radioresistance by modulating the expression of non-homologous end-joining machinery.

METHODS AND MATERIALS

Estrogen receptor-positive/negative, breast cancer cells were cultured to understand the synergetic effects of piperine with radiotherapy. Cisplatin and Bazedoxifene were used as positive controls. Cells were exposed to γ- radiation using Low Dose gamma Irradiator-2000. The piperine effect on Estrogen receptor modulation, DNA-Damage, DNA-Damage-Response, and apoptosis was done by western blotting, immunofluorescence, yeast-based-estrogen-receptor-LacZ-reporter assay, and nuclear translocation analysis. Micronuclei assay was done for DNA damage and genotoxicity, and DSBs were quantified by γH2AX-foci-staining using confocal microscopy. Flow cytometry analysis was done to determine the cell cycle, mitochondrial membrane depolarization, and Reactive oxygen species generation. Pharmacophore analysis and protein-ligand interaction studies were done using Schrodinger software. Synergy was computed by compusyn-statistical analysis. Standard errors/deviation/significance were computed with GraphPad prism.

RESULTS

Using piperine, we propose a new strategy for overcoming acquired radioresistance through estrogen receptor-mediated modulation of the NHEJ pathway. This is the first comprehensive study elucidating the mechanism of radio sensitizing potential of piperine. Piperine enhanced the radiation-induced cell death and enhanced the expression and activation of Estrogen receptor β, while Estrogen receptor α expression and activation were reduced. In addition, piperine shares common pharmacophore features with most of the known estrogen agonists and antagonists. It altered the estrogen receptor α/β ratio and the expression of estrogen-responsive proteins of DDR and NHEJ pathway. Enhanced expression of DDR proteins, ATM, p53, and P-p53 with low DNA-PK repair complex (comprising of DNA-PKcs/Ku70/Ku80), resulted in the accumulation of radiation-induced DNA double-stranded breaks (as evidenced by MNi and γH2AX-foci) culminating in cell cycle arrest and mitochondrial-pathway of apoptosis.

CONCLUSION

In conclusion, our study for the first time reported that piperine sensitizes breast cancer cells to radiation by accumulating DNA breaks, through altering the expression of DNA-PK Complex, and DDR proteins, via selective estrogen receptor modulation, offering a novel strategy for combating radioresistance.

Piper nigrum Extract Inhibits the Growth of Human Colorectal Cancer HT-29 Cells by Inducing p53-Mediated Apoptosis

Colorectal cancer (CRC) is a prevalent malignancy of the digestive tract with the second highest mortality rate globally. Piper nigrum is a widely used traditional medicinal plant, exhibiting antitumor activity against various tumor cells. At present, research on the effect of Piper nigrum on CRC is limited to in vitro cytotoxicity, lacking comprehensive mechanism investigations. This study aimed to explore the inhibitory effect and mechanism of Piper nigrum extract (PNE) on HT-29 cells. Firstly, we identified the chemical components of PNE. Then, MTT assay, colony formation assay, JC-1 staining, and flow cytometry were used to analyze the effect of PNE on HT-29 cells in vitro. A xenograft model, histopathological examination, immunohistochemistry, and western blot were used to evaluate the tumor growth inhibitory activity and mechanism of PNE in vivo. The results indicated that PNE could inhibit cell proliferation and colony formation, reduce mitochondrial membrane potential, induce cell apoptosis in vitro, and inhibit tumor growth in vivo. Furthermore, PNE could regulate p53 and its downstream proteins, and subsequently activate the caspase-3 pathway. In summary, PNE probably induced apoptosis of HT-29 cells through the mitochondrial pathway mediated by p53. All these results suggested that PNE might be a potential natural-origin anti-CRC drug candidate.

Potential roles and molecular mechanisms of phytochemicals against cancer

Increasing evidence has been reported regarding phytochemicals, plant secondary metabolites, having therapeutic functions against numerous human diseases. Recently, phytochemicals (flavonoids, polyphenols, terpenoids, alkaloids, saponins, coumarins and so on) have shown promising anti-cancer efficacy with their distinct advantages of high efficiency and low toxicity. They regulate programmed cell death (apoptosis, pyroptosis, and autophagy), migration and senescence-related signaling pathways of cancer via the modulation of reactive oxygen species (ROS), mitogen activated protein kinase (MAPK) pathway, deleted in liver cancer 1 (DLC1), nuclear factor κ light-chain-enhancer of activated B cell (NF-κB) pathways and glycolytic enzymes. Here, we review the molecular mechanisms by which phytochemicals prevent the development of cancer. Furthermore, phytochemicals combined with chemotherapeutic agents could target the crosstalk among multiple signal cascades to block chemoresistance and attenuate carcinogenic properties, and can be considered as a novel and potential therapeutic strategy. Our review highlights that the mechanisms and promising applications are required to be understood to decisively establish the anti-cancer efficacy of natural phytochemicals.

Pepper Alkaloid Piperine Increases Radiation Sensitivity of Cancer Cells from Glioblastoma and Hypopharynx In Vitro

In our study, our aim was to examine the cytotoxic and radio-sensitizing effect of the alkaloid piperine, a major pungent of black pepper, on two different human epithelial tumor cell lines in vitro. The growth of the human cell lines T98G (glioblastoma) and FaDu (hypopharyngeal carcinoma) was examined under the influence of piperine in different concentrations. In addition, after combined treatment with ionizing radiation, long-term survival was investigated with a colony formation assay. The proliferation was analyzed using the BrdU-assay, while the DNA repair capacity was examined via the γH2AX assay. Piperine reduced the growth of both cell lines in a concentration-dependent manner as well as a time-dependent one. After combined treatment with piperine and ionizing radiation, an inhibition of clonogenic survival could be proven. A reduced proliferation capacity and an additive effect on DNA damage 24 h after irradiation are possible causal mechanisms, which were also demonstrated for both cell lines. Based on the results presented in this study, piperine was shown to have cytotoxic antitumor activity and a radio-sensitizing effect in micromolar concentrations in the human tumor cells that were tested. Based on these results piperine represents a potential therapeutic option in radio-oncological treatment.

Piperine-Loaded Glycyrrhizic Acid- and PLGA-Based Nanoparticles Modified with Transferrin for Antitumor : Piperine-Loaded Glycyrrhizic Acid- and PLGA-Based Nanoparticles

The purpose of this study was to enhance the antitumor effect of piperine by constructing the nanoparticles modified with transferrin (Tf-PIP-NPs) and evaluating their efficacy in vitro and in vivo. The Tf-PIP-NPs were prepared by the solvent evaporation method, and their properties were characterized. The effects of Tf-PIP-NPs on cytotoxicity, cell uptake, apoptosis, and mitochondrial membrane potential were evaluated in HepG2 cells, MDA-MB-231 cells, and 4T1 cells. In a 4T1 tumor-bearing mouse model, the antitumor efficacy of Tf-PIP-NPs was assessed in terms of tumor volumes, changes in body weight, HE staining, and immunohistochemical analysis. With a mean particle size of 112.2 ± 1.27 nm, the zeta potential of (- 28.0 ± 1.6 mV) Tf-PIP-NPs were rapidly internalized by tumor cells after 1 h through the transferrin receptor (TfR)-mediated endocytosis pathway, significantly inducing cellular apoptosis and mitochondrial membrane potential loss. Although Tf-PIP-NPs had no significant difference with PIP-NPs in tumor volume inhibition due to the presence of tumor microenvironment, it could significantly upregulate the expression of related pro-apoptotic proteins and induce tumor necrosis. We used the self-assembly properties of glycyrrhizic acid (GL) and polymer-PLGA to encapsulate piperine and modified with the transferrin, which provided a promising approach to improve the antitumor efficacy for anticarcinogen.

Traditional Chinese Medicine and Colorectal Cancer: Implications for Drug Discovery

As an important part of complementary and alternative medicine, traditional Chinese medicine (TCM) has been applied to treat a host of diseases for centuries. Over the years, with the incidence rate of human colorectal cancer (CRC) increasing continuously and the advantage of TCM gradually becoming more prominent, the importance of TCM in both domestic and international fields is also growing with each passing day. However, the unknowability of active ingredients, effective substances, and the underlying mechanisms of TCM against this malignant tumor greatly restricts the translation degree of clinical products and the pace of precision medicine. In this review, based on the characteristics of TCM and the oral administration of most ingredients, we herein provide beneficial information for the clinical utilization of TCM in the prevention and treatment of CRC and retrospect the current preclinical studies on the related active ingredients, as well as put forward the research mode for the discovery of active ingredients and effective substances in TCM, to provide novel insights into the research and development of innovative agents from this conventional medicine for CRC treatment and assist the realization of precision medicine.

Effect of Piperine in Combination with Gamma Radiation on A549 Cells

Background Lung cancer is a major constrain that increases mortality globally. Radiotherapy is one of the treatment modalities against lung cancer. A high dose of targeted radiation is required to achieve the treatment efficacy of cell killing. After radiotherapy, eventual tumor progression and therapy resistance are still a consequence of patient who undertakes nonsurgical radiation therapy. Piperine, a plant alkaloid, has been known to enhance the action of the anticancer drugs in various drug-resistant cancer cells. The aim of the current in vitro study was to study the effect of piperine on radiosensitizing property against A549 cells.

Methods In vitro radiosensitizing activity of piperine was elucidated on A549 cells using MTT (3-(4, 5-dimethylthiazol-2-yl)-25-diphenyltetrazolium bromide) assay. CompuSyn analysis was used to compute the combination index values to analyze the combinatory effect of piperine and radiation

Results and Conclusion We observed that piperine increased tumor cell killing in combination with the γ-radiation in vitro. However, further studies are warranted to understand the molecular mechanism of the radiosensitizing action of piperine.

Piperine Inhibits Cell Proliferation and Induces Apoptosis of Human Gastric Cancer Cells by Downregulating Phosphatidylinositol 3-Kinase (PI3K)/Akt Pathway

Background

Piperine has been reported to inhibit proliferation and induce apoptosis in various cancer cells. This study aimed to explore the efficacy and underlying mechanism of piperine in human gastric cancer.

Material/Methods

MTT assay was performed to examine the effect of piperine (concentrations of 0–300 μM) on the proliferation of human gastric cancer SNU-16 cells and normal human gastric epithelial GES-1 cells. Flow cytometry and Western blot were used to determine cell apoptosis and the expression level of protein (Cyto C, cleaved PARP, cleaved caspase-3, Bax, Bcl-2, Bad, Bcl-xl, PI3K, pPI3K, Akt, and pAkt), respectively. To further investigate the anti-tumor mechanism of piperine in SNU-16 cells, we used a small-molecule Akt activator SC79 in this study. The in vivo mechanism of piperine against gastric cancer was evaluated using a xenograft tumor model.

Results

The results showed that piperine inhibited proliferation and induced apoptosis of SNU-16 cells. Piperine upregulated the protein expression of Bax, Bad, Cyto C, cleaved PARP, and cleaved caspase-3, but downregulated the protein expression of Bcl-2, Bcl-xl, pPI3k, and pAkt. However, SC79 reversed the function of piperine on the apoptosis-related proteins. An in vivo study revealed that, compared with the control group, the tumor volume of mice treated with piperine was significantly reduced. Piperine enhanced cleaved caspase-3 expression but decreased Ki-67 expression in a dose-dependent manner. Moreover, the nontoxicity effect of piperine was confirmed by H&E staining analysis in kidney and heart tissues of mice.

Conclusions

Our findings suggest that piperine inhibits proliferation and induces apoptosis of human gastric cancer cells through inhibition of the PI3K/Akt signaling pathway.