Modes of activation of mitogen-activated protein kinases and their roles in cepharanthine-induced apoptosis in human leukemia cells

Pharmacological Activity of Cepharanthine

Cepharanthine, a natural bisbenzylisoquinoline (BBIQ) alkaloid isolated from the plant Stephania Cephalantha Hayata, is the only bisbenzylisoquinoline alkaloid approved for human use and has been used in the clinic for more than 70 years. Cepharanthine has a variety of medicinal properties, including signaling pathway inhibitory activities, immunomodulatory activities, and antiviral activities. Recently, cepharanthine has been confirmed to greatly inhibit SARS-CoV-2 infection. Therefore, we aimed to describe the pharmacological properties and mechanisms of cepharanthine, mainly including antitumor, anti-inflammatory, anti-pathogen activities, inhibition of bone resorption, treatment of alopecia, treatment of snake bite, and other activities. At the same time, we analyzed and summarized the potential antiviral mechanism of cepharanthine and concluded that one of the most important anti-viral mechanisms of cepharanthine may be the stability of plasma membrane fluidity. Additionally, we explained its safety and bioavailability, which provides evidence for cepharanthine as a potential drug for the treatment of a variety of diseases. Finally, we further discuss the potential new clinical applications of cepharanthine and provide direction for its future development.

Characterization of Cepharanthin Nanosuspensions and Evaluation of Their In Vitro Activity for the HepG2 Hepatocellular Carcinoma Cell Line

BACKGROUND

Conventional cancer therapeutics has enormous toxicity and severe side effects that generate multi-drug resistance. Therefore, an urgent need exists for new alternative therapeutic agents for cancer treatment. Cepharanthin (CEP) has anti-cancer potential but has poor aqueous solubility, which limits its clinical use. Nanosuspensions (NS) are attractive as insoluble drug delivery systems.

OBJECTIVES

In this study, we used D-alpha Tocopherol acid Polyethylene Glycol Succinate (TPGS), Polyvinylpyrrolidone (PVP) VA64, and Croscamellose Sodium (CCS) as stabilizers to produce TPGS-CEP-NS, PVP VA64-CEP-NS, and CCS-CEP-NS by wet-milling technology, and then characterized the NS and evaluated their functional activities in vitro.

METHODS

CEP Nanosuspensions (CEP-NS) were prepared by the wet-milling method. The prepared NS were characterized by particle size distribution, zeta potential, morphology, surface properties, and molecular interactions. The NS were evaluated for their effects on HepG2 cells in vitro. The evaluations included assessment of cellular cytotoxicity, cellular apoptosis, NS uptake by cells, and mitochondrial membrane potential changes.

RESULTS

CEP-NS showed an appropriate particle size and were physically stable. All CEP-NS exhibited HepG2 enhanced anti-proliferative effects by reducing cell viability, enhanced cellular uptake, induced cellular apoptosis, and mitochondrial membrane potential loss.

CONCLUSIONS

CEP-NS may be effective therapeutic agents for the treatment of hepatocellular carcinoma.

Molecular mechanisms and therapeutic implications of tetrandrine and cepharanthine in T cell acute lymphoblastic leukemia and autoimmune diseases

Inappropriately activated T cells mediate autoimmune diseases and T cell acute lymphoblastic leukemia (T-ALL). Glucocorticoid and chemotherapeutic agents have largely extended lives of these patients. However, serious side effects and drug resistance often limit the prognosis of considerable number of the patients. The efficient treatment of autoimmune diseases or T-ALL with drug resistance remains an important unmet demand clinically. Bisbenzylisoquinoline alkaloids tetrandrine and cepharanthine have been applied for the treatment of certain types of autoimmune diseases and cancers, while studies on their action mechanisms and their further applications combined with glucocorticoids or chemotherapeutic agents remains to be expanded. This review introduced molecular mechanisms of tetrandrine and cepharanthine in T cells, including their therapeutic implications. Both tetrandrine and cepharnthine influence the growth of activated T cells via several kinds of signaling pathways, such as NF-κB, caspase cascades, cell cycle, MAPK, and PI3K/Akt/mTOR. According to recent preclinical and clinical studies, P-glycoprotein inhibitory effect of tetrandrine and cepharnthine could play a significant role on T cell-involved refractory diseases. Therefore, tetrandrine or cepharanthine combined with glucocorticoid or other anti-leukemia drugs would bring a new hope for patients with glucocorticoid-resistant autoimmune disease or refractory T-ALL accompanied with functional P-glycoprotein. In conclusion, bisbenzylisoquinoline alkaloids tetrandrine and cepharanthine can regulate several signaling pathways in abnormally activated T cells with low toxicity. Bisbenzylisoquinoline alkaloids deserve to be paid more attention as a lead compound to develop new drugs for the treatment of T cell-involved diseases in the future.

RNA modifications in brain tumorigenesis

RNA modifications are emerging as critical regulators in cancer biology, thanks to their ability to influence gene expression and the predominant protein isoforms expressed during cell proliferation, migration, and other pro-oncogenic properties. The reversibility and dynamic nature of post-transcriptional RNA modifications allow cells to quickly adapt to microenvironmental changes. Recent literature has revealed that the deregulation of RNA modifications can promote a plethora of developmental diseases, including tumorigenesis. In this review, we will focus on four key post-transcriptional RNA modifications which have been identified as contributors to the pathogenesis of brain tumors: m6A, alternative polyadenylation, alternative splicing and adenosine to inosine modifications. In addition to the role of RNA modifications in brain tumor progression, we will also discuss potential opportunities to target these processes to improve the dismal prognosis for brain tumors.

Cepharanthine combined with 5-fluorouracil inhibits the growth of p53-mutant human colorectal cancer cells

Mutant p53 is primarily responsible for ineffectiveness of many anticancer drugs. The present study showed that cepharanthine alone or combined with 5-fluorouracil effectively controlled the growth of HT-29 human colorectal cancer cells harboring mutant p53 both in vitro and in vivo. The combination of cepharanthine and 5-fluorouracil additively induced apoptotic and necrotic cell death. Their combination significantly upregulated the expression of BAK and cleaved PARP in tumor tissues. Moreover, cepharanthine could prevent 5-fluorouracil-induced BCRP and MRP1 expression. These findings suggest that cepharanthine is a promising agent for treating patients with colorectal cancer containing p53 mutation.

Cepharanthine: An update of its mode of action, pharmacological properties and medical applications

BACKGROUND

Cepharanthine (CEP) is a drug used in Japan since the 1950s to treat a number of acute and chronic diseases, including treatment of leukopenia, snake bites, xerostomia and alopecia. It is the only approved drug for Human use in the large class of bisbenzylisoquinoline alkaloids. This natural product, mainly isolated from the plant Stephania cephalantha Hayata, exhibits multiple pharmacological properties including anti-oxidative, anti-inflammatory, immuno-regulatory, anti-cancer, anti-viral and anti-parasitic properties.

PURPOSE

The mechanism of action of CEP is multifactorial. The drug exerts membrane effects (modulation of efflux pumps, membrane rigidification) as well as different intracellular and nuclear effects. CEP interferes with several metabolic axes, primarily with the AMP-activated protein kinase (AMPK) and NFκB signaling pathways. In particular, the anti-inflammatory effects of CEP rely on AMPK activation and NFκB inhibition.

CONCLUSION

In this review, the historical discovery and development of CEP are retraced, and the key mediators involved in its mode of action are presented. The past, present, and future of CEP are recapitulated. This review also suggests new opportunities to extend the clinical applications of this well-tolerated old Japanese drug.

Tetrandrine and cepharanthine induce apoptosis through caspase cascade regulation, cell cycle arrest, MAPK activation and PI3K/Akt/mTOR signal modification in glucocorticoid resistant human leukemia Jurkat T cells

Tetrandrine (TET) and cepharanthine (CEP) are two bisbenzylisoquinoline alkaloids isolated from the traditional herbs. Recent molecular investigations firmly supported that TET or CEP would be a potential candidate for cancer chemotherapy. Prognosis of patients with glucocorticoid resistant T cell acute lymphoblastic leukemia (T-ALL) remains poor; here we examined the anti-T-ALL effects of TET and CEP and the underlying mechanism by using the glucocorticoid resistant human leukemia Jurkat T cell line in vitro. TET and CEP significantly inhibited cell viabilities and induced apoptosis in dose- and time-dependent manner. Further investigations showed that TET or CEP not only upregulated the expression of initiator caspases such as caspase-8 and 9, but also increased the expression of effector caspases such as caspase-3 and 6. As the important markers of apoptosis, p53 and Bax were both upregulated by the treatment of TET and CEP. However, TET and CEP paradoxically increased the expression of anti-apoptotic proteins such as Bcl-2 and Mcl-1, and activated the survival protein NF-κB, leading to high expression of p-NF-κB. Cell cycle arrest at S phase accompanied by increase in the amounts of cyclin A2 and cyclin B1, and decrease in cylcin D1 amount in cells treated with TET or CEP will be another possible mechanism. During the process of apoptosis in Jurkat T cells, treatment with TET or CEP also increased the phosphorylation of JNK and p38. The PI3K/Akt/mTOR signaling pathway modification appears to play significant role in the Jurkat T cell apoptosis induced by TET or CEP. Moreover, TET and CEP seemed to downregulate the expressions of p-PI3K and mTOR in an independent way from Akt, since these two drugs strongly stimulated the p-Akt expression. These results provide fundamental insights into the clinical application of TET or CEP for the treatment of patients with relapsed T-ALL.

Analysis of six active components in Radix tinosporae by nonaqueous capillary electrophoresis with mass spectrometry

Nonaqueous capillary electrophoresis with mass spectrometry has advantages for the analysis of active components in herbs. Here, a rapid nonaqueous capillary electrophoresis with mass spectrometry method was developed to separate, identify, and quantify palmatin, columbin, cepharanthine, menisperine, magnoflorine, and 20-hydroxyecdysone in Radix tinosporae. Electrospray ionization MS^1-3 spectra of the six components were collected and possible cleavage pathways of main fragment ions were elucidated. The conditions that could affect separation, such as the composition of running buffer and applied voltage, were studied, and the conditions that could affect the mass spectrometry detection, such as the composition and flow rate of sheath liquid, the pressure of nitrogen gas, and the temperature and flow rate of the dry gas, were also optimized. Under the optimized conditions, the correlation coefficient was >0.99. The relative standard deviations of migration time and peak areas were <10%. The recoveries were calculated to be 99.31-107.80% in real samples. It has been demonstrated that the proposed method has good potential to be applied to determine the six bioactive components in Radix tinosporae.

Cepharanthine hydrochloride reverses P‑glycoprotein-mediated multidrug resistance in human ovarian carcinoma A2780/Taxol cells by inhibiting the PI3K/Akt signaling pathway

Ovarian cancer has the highest mortality rate among gynecologic malignant tumors. The major obstacle to treatment success is multidrug resistance (MDR) to chemotherapy drugs. Cepharanthine hydrochloride (CH), a natural alkaloid-derived compound, has shown MDR reversal potency in several tumor cell lines; however, the molecular mechanism is not entirely known. In the present study, we assessed whether CH sensitized malignant cells to chemotherapy drugs in ovarian cancer and explored the relevant mechanism. We found that CH reduced the IC50 value of paclitaxel and increased intracellular rhodamine-123 accumulation in human ovarian cancer A2780/Taxol cells in a concentration-dependent manner. Reverse transcription polymerase chain reaction and western blot assay demonstrated that CH inhibited MDR1 expression as indicated by reduced mRNA and protein levels in A2780/Taxol cells. In addition, the inhibitory effect was strengthened after CH was combined with the specific PI3K/Akt signaling pathway inhibitor LY294002. Furthermore, p‑Akt expression decreased gradually with the concentration of CH (2, 4 and 8 µM). Taken together, these findings indicated that CH reversed P‑glycoprotein-mediated MDR in A2780/Taxol cells by inhibiting the PI3K/Akt signaling pathway.

Docosahexaenoic acid attenuates LPS-stimulated inflammatory response by regulating the PPARγ/NF-κB pathways in primary bovine mammary epithelial cells

BACKGROUND

Docosahexaenoic acid (DHA) is a major dietary n-3 polyunsaturated fatty acid (n-3 PUFA) in fish oil, and has been reported to possess a number of biological properties, such as anti-inflammatory, antitumor and immune-regulatory properties. However, whether DHA exert anti-inflammatory effect on lipopolysaccharide (LPS)-induced mastitis remains unclear. In this study, we investigate the effect and underlying mechanisms of the effects of DHA on LPS-stimulated primary bovine mammary epithelial cells (bMEC).

METHODS

The experiment was divided into six groups as followed: control group, GW9662+LPS+DHA (100μM) group, LPS and LPS+DHA (25, 50 and 100μM) groups. bMEC were treated with DHA for 3h before LPS (200μg/ml) stimulation, and incubated with the PPARγ inhibitor GW9662 for 12h before DHA treatment. The mRNA levels of TNF-α, IL-6 and IL-1β were measured by quantitative real-time PCR (qRT-PCR). Western blot was employed for measuring the transcriptional activity of NF-κB and PPARγ.

RESULTS

Our results showed that DHA pretreatment significantly decreased the mRNA expression of tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and interleukin-1β (IL-1β) in bMEC stimulated with LPS. Besides, DHA suppressed the phosphorylation of nuclear transcription factor-kappaB (NF-κB) p65 and degradation inhibitor of NF-κBα (IκBα) in NF-κB signal pathway, and activated proliferator activated receptor gamma (PPARγ). But, all those effects were obviously abolished by addition of GW9662, a specific inhibitor of PPARγ.

CONCLUSION

In conclusion, these results indicated that DHA may attenuate LPS-stimulated inflammatory response in bMEC by suppressing NF-κB activation through a mechanism partly dependent on PPARγ activation.

Suppression of phospho-p85α-GTP-Rac1 lipid raft interaction by bichalcone analog attenuates cancer cell invasion

The p85α subunit of phosphatidylinositol 3-kinase (PI3K) acts as a key regulator of cell proliferation and motility, which mediates signals that confer chemoresistance to many human cancer cells. Using small interfering RNAs against matrix metalloproteinase-2 (MMP-2) and the MMP-2 promoter-driven luciferase assay, we showed that the new synthetic bichalcone analog TSWU-CD4 inhibits the invasion of human cancer cells by down-regulating MMP-2 expression. Treatment with TSWU-CD4 inhibited MMP-2 expression and cell invasion, which were restored by ectopic wild type (wt) p85α or a constitutively active form of MAPK kinase 3 (CA MKK3), CA MKK6, or CA p38α mitogen-activated protein kinase (MAPK). The attenuated formation of lipid raft-associated phospho (p)-p85α-GTP-Rac1 complexes, protein kinase B (Akt) Ser 473 phosphorylation, and cell invasion by TSWU-CD4 was reversed by overexpression of wt p85α or the p85α Brc-homology (BH) domain. The ectopic expression of CA Rac1^L61 (but not wt Rac1) could overcome the suppression of Ser 473 phosphorylation, lipid raft association of Akt, the interaction between GTP-bound Rac1 and p85α in lipid rafts, and cell invasion by TSWU-CD4. The involvement of Akt activity in the functions of NF-κB-mediated MMP-2 was further confirmed through the attenuation of Akt phosphorylation signaling using the Akt-specific inhibitor MK-2206 and ectopic expression of NF-κB p65. Collectively, the inhibitory effect of TSWU-CD4 on cancer cell invasion was likely to suppress the p-p85α-GTP-Rac1 interaction in lipid rafts by targeting the p85α BH domain, which resulted in the suppression of MMP-2 expression via the PI3K-Akt-mediated ERK-MKK3/MKK6-p38 MAPK-NF-κB signaling pathway. © 2016 Wiley Periodicals, Inc.

Baicalein attenuates inflammatory responses by suppressing TLR4 mediated NF-κB and MAPK signaling pathways in LPS-induced mastitis in mice

Baicalein is a phenolic flavonoid presented in the dry roots of Scutellaria baicalensis Georgi. It has been reported that baicalein possesses a number of biological properties, such as antiviral, antioxidative, anti-inflammatory, antithrombotic, and anticancer properties. However, the effect of baicalein on mastitis has not yet been reported. This research aims to detect the effect of baicalein on lipopolysaccharide (LPS)-induced mastitis in mice and to investigate the molecular mechanisms. Baicalein was administered intraperitoneally 1h before and 12h after LPS treatment. The results indicated that baicalein treatment markedly attenuated the damage of the mammary gland induced by LPS, suppressed the activity of myeloperoxidase (MPO) and the levels of tumor necrosis factor (TNF-α) and interleukin (IL-1β) in mice with LPS-induced mastitis. Besides, baicalein blocked the expression of Toll-like receptor 4 (TLR4) and then suppressed the phosphorylation of nuclear transcription factor-kappaB (NF-κB) p65 and degradation inhibitor of NF-κBα (IκBα) and, and inhibited the phosphorylation of p38, extracellular signal-regulated kinase (ERK) and c-jun NH2-terminal kinase (JNK) in mitogen-activated protein kinase (MAPK) signal pathway. These findings suggested that baicalein may have a potential prospect against mastitis.

Role of p38 MAP Kinase Signal Transduction in Solid Tumors

Mitogen-activated protein kinases (MAPKs) mediate a wide variety of cellular behaviors in response to extracellular stimuli. One of the main subgroups, the p38 MAP kinases, has been implicated in a wide range of complex biologic processes, such as cell proliferation, cell differentiation, cell death, cell migration, and invasion. Dysregulation of p38 MAPK levels in patients are associated with advanced stages and short survival in cancer patients (e.g., prostate, breast, bladder, liver, and lung cancer). p38 MAPK plays a dual role as a regulator of cell death, and it can either mediate cell survival or cell death depending not only on the type of stimulus but also in a cell type specific manner. In addition to modulating cell survival, an essential role of p38 MAPK in modulation of cell migration and invasion offers a distinct opportunity to target this pathway with respect to tumor metastasis. The specific function of p38 MAPK appears to depend not only on the cell type but also on the stimuli and/or the isoform that is activated. p38 MAPK signaling pathway is activated in response to diverse stimuli and mediates its function by components downstream of p38. Extrapolation of the knowledge gained from laboratory findings is essential to address the clinical significance of p38 MAPK signaling pathways. The goal of this review is to provide an overview on recent progress made in defining the functions of p38 MAPK pathways with respect to solid tumor biology and generate testable hypothesis with respect to the role of p38 MAPK as an attractive target for intervention of solid tumors.

Expression of activating transcription factor 2 in inflammatory macrophages in obese adipose tissue

OBJECTIVE

White adipose tissue (WAT) of obesity is in the state of inflammation with progressive infiltration by macrophages and overproduction of reactive oxygen species (ROS), which can induce WAT dysfunction, including insulin resistance and adipocytokine dysregulation. Activating transcription factor 2 (ATF2) is a member of the ATF/cAMP response element binding family of transcription factors and known to be activated by cellular stressors, such as inflammatory cytokines, lipopolysaccharide (LPS), and ROS. DESIGN AND METHODS, RESULTS: Here, we show that ATF2 protein was significantly more induced in WAT of ob/ob mice compared with C57BL/6J mice. Total and phosphorylated ATF2 were highly expressed in infiltrated macrophages. Furthermore, flow cytometry analysis demonstrated that ATF2 expression was high in CD11c-positive/CD301-negative M1 macrophages. Phosphorylation of ATF2 was induced by treatment with either H2 O2 or LPS in RAW264.7 macrophage cells, and suppression of ATF2 expression by small-interfering RNA induced mRNA levels of ATF3, an anti-inflammatory molecule in macrophages in WAT.

CONCLUSIONS

These results suggest that ATF2 is an important transcriptional factor relating to inflammation through the suppression of ATF3 in M1 macrophages of WAT.

Cyclooxygenase-2 is induced by p38 MAPK and promotes cell survival

The Na+ ionophore monensin affects cellular pH and, depending on its concentration, causes the survival or death of tumor cells. In the present study, we elucidated the survival pathway activated in U937 cells, a human lymphoma-derived cell line. These cells treated with monensin at a concentration of 5 µM were growth-arrested in G1, activated p38 mitogen-activated protein kinase (MAPK) and showed an increased expression of cyclooxygenase-2 (COX-2). The latter two molecular events were linked, as pharmacological inhibition of the MAPK did not allow COX-2 increased expression. Furthermore, we showed that p38 and COX-2 keep monensin-stressed U937 cells alive, as pharmacological inhibition of each enzyme caused cell death.

DC-81-enediyne induces apoptosis of human melanoma A375 cells: involvement of the ROS, p38 MAPK, and AP-1 signaling pathways

Melanoma is one of the most chemoresistant cancers in patient care. The remission rate of current therapy remains low. DC-81, an antitumor antibiotic produced by Streptomyces species, belongs to pyrrolo[2,1-c][1,4]benzodiazepine (PBD), which is a potent inhibitor of nucleic acid synthesis. An enediyne contains either DNA intercalating groups or DNA minor groove binding functions and these are potent DNA-damaging agents due to their ability to generate benzenoid diradicals. We have previously reported an efficient synthesis and antitumor activity of a series of novel PBD hybrids linked with enediyne. The purpose of this study was to examine the mechanism of the antiproliferative effect of DC-81-enediyne agent on human melanoma A375 cells. DC-81-enediyne induced an increase in Ca(2+) level and reactive oxygen species (ROS) generation as detected by flow cytometric assay. Western blot analysis showed that DC-81-enediyne induced the phosphorylation of p38 and activating transcription factor 2 (ATF-2). By using the luciferase reporter assay, activating protein-1 (AP-1) activity was further enhanced after A375 cells were treated with graded concentrations of DC-81-enediyne. DC-81-enediyne treatment-induced A375 cell apoptosis was significantly abrogated by the addition of Ca(2+), ROS, and p38 inhibitors. Collectively, our studies indicate that DC-81-enediyne induces A375 cell apoptosis through an increased Ca(2+) and ROS generation, which involves p38 phosphorylation and enhanced ATF-2/AP-1 expressions, leading to caspase-3 activity, poly(ADP-ribose)polymerase cleavage, M30 CytoDeath staining, and subsequent apoptotic cell death.

Cepharanthine exerts antitumor activity on cholangiocarcinoma by inhibiting NF-kappaB

Cholangiocarcinoma (CCA) is a major cause of cancer deaths in northeast Thailand. It is aggressive, highly metastatic, and responds poorly to traditional chemotherapy. We demonstrated the potential for Cepharanthine (CEP), a biscoclaurine alkaloid extracted from Stephania cepharantha, to treat CCA. CEP significantly inhibited growth of human CCA cell lines in a dose- and time-dependent manner, regardless of the histologic type of tumor origin. Increasing cell apoptosis via caspase-3 and capase-9 activation was demonstrated in CEP-treated cells. We found that CEP controlled the growth of CCA cells through nuclear factor-kappa B (NF-kappaB) inactivation by inhibiting nuclear translocation. CEP treatment effectively reduced tumor size in CCA-inoculated mice without serious side effects. CEP also increased cell apoptosis in primary histocultures of CCA patients' tissues; this was demonstrated by immunohistochemistry using TUNEL staining. Our results suggest that CEP possesses therapeutic potential against human CCA.

The role of ATF-2 in oncogenesis

Activating Transcription Factor-2 is a sequence-specific DNA-binding protein that belongs to the bZIP family of proteins and plays diverse roles in the mammalian cells. In response to stress stimuli, it activates a variety of gene targets including cyclin A, cyclin D and c-jun, which are involved in oncogenesis in various tissue types. ATF-2 expression has been correlated with maintenance of a cancer cell phenotype. However, other studies demonstrate an antiproliferative or apoptotic role for ATF-2. In this review, we summarize the signaling pathways that activate ATF-2, as well as its downstream targets. We examine the role of ATF-2 in carcinogenesis with respect to other bZIP proteins, using data from studies in human cancer cell lines, human tumours and mouse models, and we propose a potential model for its function in carcinogenesis, as well as a theoretical basis for its utility in anticancer drug design.

The effects of biscoclaurine alkaloid cepharanthine on mammalian cells: implications for cancer, shock, and inflammatory diseases

The extract of Stephania cepharantha Hayata contains biscoclaurine alkaloids such as cepharanthine, which have been used widely in Japan for the treatment of patients with radiation-induced leukopenia, alopecia areata, exudative otitis media, and venomous snakebites. Many investigations have proven that the alkaloid cepharanthine exerts diverse pharmacological effects that include membrane-stabilizing, multidrug resistance-reversing, antitumor, apoptosis-inducing, anti-inflammatory, free radical scavenging, anti-HIV-1, antiallergic and immunomodulatory effects. The purpose of our review is to describe various therapeutic approaches using cepharanthine and their potential efficacy.

Cepharanthine triggers apoptosis in a human hepatocellular carcinoma cell line (HuH-7) through the activation of JNK1/2 and the downregulation of Akt

Cepharanthine (CEP), a biscoclaurine alkaloid, has been reported to induce cell death, however, the molecular mechanism of this phenomenon remains unclear. We herein report that CEP induced apoptosis in HuH-7 cells through nuclear fragmentation, DNA ladder formation, cytochrome c release, caspase-3 activation and poly-(ADP-ribose)-polymerase cleavage. CEP triggered the generation of reactive oxygen intermediates, the activation of mitogen activated protein kinase (MAPK) p38, JNK1/2 and p44/42, and the downregulation of protein kinase B/Akt. Antioxidants and SP600125, an inhibitor of JNK1/2, but not inhibitors of p38 MAPK and MEK1/2, significantly prevented cell death, thus implying that reactive oxygen species and JNK1/2 play crucial roles in the CEP-induced apoptosis of HuH-7 cells.

Cepharanthine potently enhances the sensitivity of anticancer agents in K562 cells

A major impediment to cancer treatment is the development of resistance by the tumor. P-glycoprotein (P-gp) and multidrug resistance protein 1 (MRP1) are involved in multidrug resistance. In addition to the extrusion of chemotherapeutic agents through these transporters, it has been reported that there are differences in the intracellular distribution of chemotherapeutic agents between drug resistant cells and sensitive cells. Cepharanthine is a plant alkaloid that effectively reverses resistance to anticancer agents. It has been previously shown that cepharanthine is an effective agent for the reversal of resistance in P-gp-overexpressing cells. Cepharanthine has also been reported to have numerous pharmacological effects besides the inhibition of P-gp. It has also been found that cepharanthine enhanced sensitivity to doxorubicin (ADM) and vincristine (VCR), and enhanced apoptosis induced by ADM and VCR of P-gp negative K562 cells. Cepharanthine changed the distribution of ADM from cytoplasmic vesicles to nucleoplasm in K562 cells by inhibiting the acidification of cytoplasmic organelles. Cepharanthine in combination with ADM should be useful for treating patients with tumors.

The role of MAPK signal pathways during Francisella tularensis LVS infection-induced apoptosis in murine macrophages

Francisella tularensis is a highly virulent intracellular pathogen responsible for tularemia. This bacterium is capable of infecting many mammalian species and various cell types, but little is known about the mechanisms of survival and interactions with host cells. We examined the number of infected host cells, cytotoxicity and the role of apoptosis or necrosis in infection-induced cell death. Our results demonstrate that F. tularensis LVS induces apoptosis of infected macrophages within 10 h. At later time points we were also able to detect a dramatic increase in the proportion of necrotic macrophages. We investigated the signalling pathways involved in infection-induced cell death by analysing three mitogen-activated protein kinase (MAPK) pathways that are known to be activated by LPS stimulation; p42/p44 MAPK (Erk1/2), transcription factor c-Jun and p38 MAPK. We identified post-translational activation of both p42 MAPK and p44 MAPK by phosphorylation at threonine and tyrosine residues after infection. Furthermore, treatment of infected cells with MEK1/2 inhibitors abrogated phosphorylation of p42/p44 MAPK and inhibited macrophage apoptosis and necrosis after infection. In contrast, phosphorylation and kinase activity of p38 MAPK was significantly lower in F. tularensis-infected cells, and inhibition of p38 MAPK activity induced apoptosis in uninfected cells. When we monitored JNK-dependent phosphorylation of the transcription factor c-Jun, we did not observe any reactivity with either SAPK/JNK or phospho-SAPK/JNK antibodies at any time point. In conclusion, we demonstrate that F. tularensis LVS infection induces macrophage apoptosis. This process requires activation of the p42/p44 MAPK pathway and is associated with reduced p38 MAPK activity, indicating that infection-induced cell death can be caused by perturbation of these two signalling pathways.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.

Involvement of the p38 mitogen-activated protein kinase cascade in hepatocellular carcinoma

BACKGROUND

The mitogen-activated protein kinase (MAPK) cascade is activated in response to various extracellular stimuli. The authors investigated the involvement of the p38 MAPK, a member of the MAPK superfamily, cascade in hepatoma cell lines and in human hepatocellular carcinoma (HCC) tissue specimens.

METHODS

Constitutively active mutant of MAPK kinase 6 (MKK6), which is upstream of p38 MAPK, was transfected into the HepG2 and HuH7 human hepatoma cell lines. The constitutive active mutant was constructed by replacing Ser-189 and Thr-193 with Glu. The growth and death of mutant MKK6-transfected hepatoma cells were analyzed by the WST-1 and sub-G1 assays. The surgically resected livers of 20 HCC patients were divided histologically into tumorous (T) and nontumorous (NT) lesions. p38 MAPK activity was analyzed using in vitro kinase assay and MKK6 activity was measured using Western blot analysis.

RESULTS

Mutant MKK6 transfection increased p38 MAPK activity, cytochrome c release from the mitochondria to the cytosol, and caspase-3 activity, accompanied by apoptosis. In contrast, SB203580, a p38 MAPK-specific inhibitor, prevented MKK6-induced apoptosis in hepatoma cell lines. In the T lesions of 20 HCC parients, p38 MAPK and MKK6 activities were significantly lower compared with NT lesions (P < 0.05). There was a significant positive correlation between p38 MAPK and MKK6 activity (r = 0.507, P < 0.05). Larger tumors (> 20 mm) exhibited lower levels of p38 MAPK and MKK6 activity than did smaller tumors (P < 0.05).

CONCLUSIONS

These findings suggested that reduction of the p38 MAPK cascade may account, in part, for the resistance to apoptosis, leading to the unrestricted cell growth of human HCC.