1
|
Hernandezine induces autophagic cell death in human pancreatic cancer cells via activation of the ROS/AMPK signaling pathway. Acta Pharmacol Sin 2022; 44:865-876. [PMID: 36284209 PMCID: PMC10042859 DOI: 10.1038/s41401-022-01006-1] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2021] [Accepted: 03/14/2022] [Indexed: 01/18/2023] Open
Abstract
AbstractHernandezine (Her) is a bisbenzylisoquinoline alkaloid extracted from the traditional Chinese herbal medicine Thalictrum glandulosissimum. Evidence shows that Her is a natural agonist of adenosine monophosphate (AMP)-activated protein kinase (AMPK) and induces apoptosis and autophagy in tumor cells. In this study, we investigated the role of autophagy in Her-induced cell death in human pancreatic cancer cell lines. We showed that Her dose-dependently suppressed cell proliferation, promoted autophagy and induced autophagic death in pancreatic ductal adenocarcinoma (PDAC) cell lines Capan-1 and SW1990. The IC50 values of Her in inhibition of Capan-1 and SW1990 cells were 47.7 μM and 40.1 μM, respectively. Immunoblotting showed that Her (1−40 μM) promoted the conversion of LC3-I to LC3-II, and Her exerted concentration-dependent and time-dependent effects on autophagy activation in PDAC cells. In transmission electron microscopy and fluorescence image analysis, we found that autophagic vacuoles were significantly increased in Her-treated cells. Knockdown of ATG5, a key gene in the autophagy pathway, alleviated the activation of autophagy by Her. These results demonstrated that Her induced autophagy in PDAC cells. Intensely activated autophagy could promote cell death. The autophagy inhibitors, BafA1 and HCQ significantly inhibited Her-induced cell death, implying that Her induced autophagic cell death in PDAC cells. Moreover, we showed that Her activated autophagy by increasing the phosphorylation of AMPK and decreasing the phosphorylation of mTOR/p70S6K. Knockdown of AMPKα relieves the autophagic cell death induced by Her. Furthermore, Her concentration-dependently enhanced reactive oxygen species (ROS) generation in PDAC cells. Antioxidants could reduce the phosphorylation of AMPK and suppress autophagic cell death induced by Her. Our study provides evidence for the development of Her as a therapeutic agent for the treatment of pancreatic cancer.
Collapse
|
2
|
Cañon-Jones H, Cortes H, Castillo-Ruiz M, Schlotterbeck T, San Martín R. Quillaja saponaria (Molina) Extracts Inhibits In Vitro Piscirickettsia salmonis Infections. Animals (Basel) 2020; 10:E2286. [PMID: 33287333 PMCID: PMC7761688 DOI: 10.3390/ani10122286] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 11/06/2020] [Accepted: 11/10/2020] [Indexed: 12/26/2022] Open
Abstract
P. salmonis infections are the cause of major bacterial disease in salmonids in Chile, and the reason for using more antibiotics compared to other salmon-producing countries. Vaccination and antibiotics have not been efficient and new approaches are needed. The safety of Quillaja saponaria extracts was measured by cytotoxicity using flow cytometry of cytopathic and death of fish cell cultures and efficacy was assessed using in vitro infection models with pathogenic P. salmonis. Cytotoxicity was low and control of in vitro infections was achieved with all products, with protection of over 90%. Minimum inhibitory concentrations were much higher than those in the infection using cell cultures. These results suggest a dual mechanism of action where less purified extracts with a combination of saponin and non-saponin components simultaneously decrease P. salmonis infection while protecting cell lines, rather than exerting a direct antimicrobial effect. Quillaja saponins controlled in vitro infections with P. salmonis and could be considered good candidates for a new, safe and sustainable method of controlling fish bacterial infectious diseases.
Collapse
Affiliation(s)
- Hernán Cañon-Jones
- Núcleo de Investigación Aplicada en Ciencias Veterinarias y Agronómicas, Facultad de Medicina Veterinaria y Agronomía, Universidad de Las Américas, Santiago 7500975, Chile
| | | | - Mario Castillo-Ruiz
- Escuela de Química y Farmacia, Facultad de Medicina, Universidad Andres Bello, Santiago 8370146, Chile;
- Departamento de Ciencias Químicas y Biológicas, Facultad de Ciencias de la Salud, Universidad Bernardo O Higgins, Santiago 8370993, Chile
| | | | | |
Collapse
|
3
|
Green Tea Seed Isolated Saponins Exerts Antibacterial Effects against Various Strains of Gram Positive and Gram Negative Bacteria, a Comprehensive Study In Vitro and In Vivo. EVIDENCE-BASED COMPLEMENTARY AND ALTERNATIVE MEDICINE 2018; 2018:3486106. [PMID: 30598684 PMCID: PMC6287149 DOI: 10.1155/2018/3486106] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/09/2018] [Revised: 11/04/2018] [Accepted: 11/08/2018] [Indexed: 01/22/2023]
Abstract
Bacteria are one of the major causes of severe infections and diseases of plants and animals. Salmonella are crucially important due to infection in poultry leading to huge economical loses. Due to high cost and microbial resistance to the currently available chemical antibiotics, demand of screening natural products with antibiotics effects is increased. Plants are rich sources of natural bioactive compounds with antibiotic effects. Saponins are natural compounds of plant sources having a diverse range of applications. In present study we investigated the in vitro and in vivo antibacterial activities of green tea seed extracted saponins. Green tea seeds crude extract was prepared in 70% ethanol by continuous reflux in heating mantel for 5 hours. Crude saponins were extracted from the crude ethanolic extract of green tea seed by column chromatography using macroporous resin (D101). Saponin mixture in fraction 1 (Fr1) was obtained from crude saponins extract via column chromatography. Fr2 and Fr3 were isolated from saponins mixture by preparative HPLC. Antibacterial activities of the isolated saponins fractions were investigated against Escherichia coli (ATCC 25922), Streptococcus aureus (ATCC 12600), and six serovars of Salmonella. In vitro antibacterial activities were determined by disc-diffusion method and growth inhibition in liquid culture using 96-well plate. Results showed that the green tea isolated saponins fractions possess antibacterial effects in the following order Fr1>Fr2>Fr3. Antibacterial mechanism of saponins was elucidated by cell wall and membrane damaging potential of saponins determined by measuring AKP and soluble proteins levels. Fr1 was further used for in vivo antibacterial activities. Five-week grown chickens were selected for in vivo work, divided into three groups as control, infected, and treatment groups. Infected and treatment groups chickens were infected with bacteria and only treatment group chickens were treated with saponins. The qRT- PCR analysis of the blood and feces samples of the different groups' animals shows the presence of bacteria only in infected group while reduced expression levels of the bacterial pathogens were found in the samples of treatment group. Our results demonstrated that the green tea seed saponins used in this study possess strong antibacterial activities.
Collapse
|
4
|
Kucukkurt I, Akkol EK, Karabag F, Ince S, Süntar I, Eryavuz A, Sözbilir NB. Determination of the regulatory properties of Yucca schidigera extracts on the biochemical parameters and plasma hormone levels associated with obesity. REVISTA BRASILEIRA DE FARMACOGNOSIA-BRAZILIAN JOURNAL OF PHARMACOGNOSY 2016. [DOI: 10.1016/j.bjp.2015.12.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
|
5
|
Lorent JH, Quetin-Leclercq J, Mingeot-Leclercq MP. The amphiphilic nature of saponins and their effects on artificial and biological membranes and potential consequences for red blood and cancer cells. Org Biomol Chem 2015; 12:8803-22. [PMID: 25295776 DOI: 10.1039/c4ob01652a] [Citation(s) in RCA: 141] [Impact Index Per Article: 15.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Saponins, amphiphiles of natural origin with numerous biological activities, are widely used in the cosmetic and pharmaceutical industry. Some saponins exhibit relatively selective cytotoxic effects on cancer cells but the tendency of saponins to induce hemolysis limits their anticancer potential. This review focused on the effects of saponin activity on membranes and consequent implications for red blood and cancer cells. This activity seems to be strongly related to the amphiphilic character of saponins that gives them the ability to self-aggregate and interact with membrane components such as cholesterol and phospholipids. Membrane interactions of saponins with artificial membrane models, red blood and cancer cells are reviewed with respect to their molecular structures. The review considered the mechanisms of these membrane interactions and their consequences including the modulation of membrane dynamics, interaction with membrane rafts, and membrane lysis. We summarized current knowledge concerning the mechanisms involved in the interactions of saponins with membrane lipids and examined the structure activity relationship of saponins regarding hemolysis and cancer cell death. A critical analysis of these findings speculates on their potential to further develop new anticancer compounds.
Collapse
Affiliation(s)
- Joseph H Lorent
- Université catholique de Louvain, Louvain Drug Research Institute, Cellular and Molecular Pharmacology (FACM), Avenue Mounier 73, B1.73.05, B-1200 Brussels, Belgium.
| | | | | |
Collapse
|
6
|
Effects of saponins against clinical E. coli strains and eukaryotic cell line. J Biomed Biotechnol 2012; 2012:286216. [PMID: 22500084 PMCID: PMC3303633 DOI: 10.1155/2012/286216] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2011] [Accepted: 11/22/2011] [Indexed: 11/17/2022] Open
Abstract
Saponins are detergent-like substances showing antibacterial as well as anticancer potential. In this study, the effects of saponins from Quillaja saponaria were analyzed against prokaryotic and eukaryotic cells. Multidrug-resistant clinical E. coli strains were isolated from human urine. As eukaryotic cells, the CHO-K1 cell lines were applied. Antibacterial effect of ampicillin, streptomycin, and ciprofloxacin in the presence of saponins was measured by cultivation methods. Properties of saponins against CHO-K1 cells were measured by the MTT test, hemolysis assay and flow cytometry. Saponin from Quillaja saponaria has a cytotoxic effect at concentrations higher than 25 μg/mL and in the range of 12-50 μg/mL significantly increases the level of early apoptotic cells. Saponin at dose of 12 μg/mL enhances the six E. coli strains growth. We postulate that saponins increase the influx of nutrients from the medium into E. coli cells. Saponins do not have synergetic effects on antibacterial action of tested antibiotics. In contrary, in the presence of saponins and antibiotics, more CFU/mL E. coli cells were observed. This effect was similar to saponins action alone towards E. coli cells. In conclusion, saponins was cytotoxic against CHO-K1 cells, whereas against E. coli cells this effect was not observed.
Collapse
|
7
|
De Geyter E, Swevers L, Soin T, Geelen D, Smagghe G. Saponins do not affect the ecdysteroid receptor complex but cause membrane permeation in insect culture cell lines. JOURNAL OF INSECT PHYSIOLOGY 2012; 58:18-23. [PMID: 22057058 DOI: 10.1016/j.jinsphys.2011.09.005] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/15/2011] [Revised: 09/02/2011] [Accepted: 09/07/2011] [Indexed: 05/25/2023]
Abstract
This project studied the effects of four saponins with a triterpenoid (Quillajasaponaria saponin and aescin) or steroid structure (digitonin and diosgenin which is the deglycosylated form of dioscin) on insect cells, namely Schneider S2 cells of Drosophila melanogaster (Diptera). A series of different experiments were performed to investigate potential mechanisms of action by saponins with regard to ecdysteroid receptor (EcR) responsiveness, cell viability, cell membrane permeation, and induction of apoptosis with DNA fragmentation and caspase-3 like activity. Major results were that (1) exposure of S2 cells containing an EcR-based reporter construct to a concentration series of each saponin scored no EcR activation, while (2) a loss of ecdysteroid signaling was observed with median inhibitory concentrations (IC(50)'s) of 3-50 μM, and in parallel (3) a concentration-dependent change in loss of cell numbers in an cell viability assay with median effective concentrations (EC(50)'s) of 8-699 μM. In continuation, it was of interest that (4) a trypan blue assay with Q. saponaria saponin confirmed the cell membrane permeation effect leading to cell toxicity with a median lethal concentration (LC(50)) value of 44 μM, and interestingly this effect was very rapid. Another three interesting observations were that (5) exposure to 20E at 500 nM as used in the EcR-based report assay induced caspase-3 like activities which may help to explain the discrepancies between loss of EcR-responsiveness and cell viability, (6) low concentrations of saponins induced DNA fragmentation and caspase-3 like activities, confirming their potential to induce apoptosis, and (7) the saponin effects were counteracted with addition of cholesterol to the culture medium. In general the data obtained provide evidence that the anti-ecdysteroid action by saponins is not based on a true antagonistic interaction with EcR signaling, but can be explained by a cytotoxic action due to permeation of the insect cell membrane.
Collapse
Affiliation(s)
- Ellen De Geyter
- Laboratory of Agrozoology, Department of Crop Protection, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | | | | | | | | |
Collapse
|
8
|
Abramov AY, Ionov M, Pavlov E, Duchen MR. Membrane cholesterol content plays a key role in the neurotoxicity of β-amyloid: implications for Alzheimer's disease. Aging Cell 2011; 10:595-603. [PMID: 21332922 DOI: 10.1111/j.1474-9726.2011.00685.x] [Citation(s) in RCA: 73] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023] Open
Abstract
Beta amyloid (βA) plays a central role in the pathogenesis of the most common and devastating neurodegenerative disorder, Alzheimer's disease (AD). The mechanisms of βA neurotoxicity remain controversial, but include dysregulation of calcium homeostasis and oxidative stress. A large body of data suggest that cholesterol plays a significant role in AD. In mixed cultures containing hippocampal neurons and astrocytes, we have shown that neurotoxic βA peptides (1-42 and 25-35) cause sporadic cytosolic calcium ([Ca(2+) ](c) ) signals in astrocytes but not in neurons, initiating a cascade that ends in neuronal death. We now show, using the cholesterol-sensitive fluorescent probe, Filipin, that membrane cholesterol is significantly higher in astrocytes than in neurons and mediates the selective response of astrocytes to βA. Thus, lowering [cholesterol] using mevastatin, methyl-β-cyclodextrin or filipin prevented the βA-induced [Ca(2+) ](c) signals, while increased membrane [cholesterol] increased βA-induced [Ca(2+) ](c) signals in both neurons and astrocytes. Addition of βA to lipid bilayers caused the appearance of a conductance that was significantly higher in membranes containing cholesterol. Increasing membrane [cholesterol] significantly increased βA-induced neuronal and astrocytic death. We conclude that a high membrane [cholesterol] promotes βA incorporation into membranes and increased [Ca(2+) ](c) leading to cell death.
Collapse
Affiliation(s)
- Andrey Y Abramov
- Department of Molecular Neuroscience, UCL Institute of Neurology, Queen Square, London, UK.
| | | | | | | |
Collapse
|
9
|
Kaczorek E, Olszanowski A. Uptake of Hydrocarbon by Pseudomonas fluorescens (P1) and Pseudomonas putida (K1) Strains in the Presence of Surfactants: A Cell Surface Modification. WATER, AIR, AND SOIL POLLUTION 2011; 214:451-459. [PMID: 21258434 PMCID: PMC3003147 DOI: 10.1007/s11270-010-0436-7] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/09/2009] [Accepted: 04/06/2010] [Indexed: 05/05/2023]
Abstract
The objective of this research was the evaluation of the effects of exogenous added surfactants on hydrocarbon biodegradation and on cell surface properties. Crude oil hydrocarbons are often difficult to remove from the environment because of their insolubility in water. The addition of surfactants enhances the removal of hydrocarbons by raising the solubility of these compounds. These surfactants cause them to become more vulnerable to degradation, thereby facilitating transportation across the cell membrane. The obtained results showed that the microorganism consortia of bacteria are useful biological agents within environmental bioremediation. The most effective amongst all, as regards biodegradation, were the consortia of Pseudomonas spp. and Bacillus spp. strains. The results indicated that the natural surfactants (rhamnolipides and saponins) are more effective surfactants in hydrocarbon biodegradation as compared to Triton X-100. The addition of natural surfactants enhanced the removal of hydrocarbon and diesel oil from the environment. Very promising was the use of saponins as a surfactant in hydrocarbon biodegradation. This surfactant significantly increases the organic compound biodegradation. In the case of those surfactants that could be easily adsorbed on cells of strains (e.g., rhamnolipides), a change of hydrophobicity to ca. 30-40% was noted. As the final result, an increase in hydrocarbon biodegradation was observed.
Collapse
Affiliation(s)
- Ewa Kaczorek
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Skłodowskiej-Curie 2, 60-965 Poznań, Poland
| | - Andrzej Olszanowski
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Skłodowskiej-Curie 2, 60-965 Poznań, Poland
| |
Collapse
|
10
|
Kaczorek E, Moszyńska S, Olszanowski A. Modification of cell surface properties of Pseudomonas alcaligenes S22 during hydrocarbon biodegradation. Biodegradation 2010; 22:359-66. [PMID: 20820883 PMCID: PMC3046353 DOI: 10.1007/s10532-010-9406-4] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2010] [Accepted: 08/10/2010] [Indexed: 12/03/2022]
Abstract
Biodegradation of water insoluble hydrocarbons can be significantly increased by the addition of natural surfactants one. Very promising option is the use of saponins. The obtained results indicated that in this system, after 21 days, 92% biodegradation of diesel oil could be achieved using Pseudomonas alcaligenes. No positive effect on the biodegradation process was observed using synthetic surfactant Triton X-100. The kind of carbon source influences the cell surface properties of microorganisms. Modification of the surface cell could be observed by control of the sedimentation profile. This analytical method is a new approach in microbiological analysis.
Collapse
Affiliation(s)
- Ewa Kaczorek
- Institute of Chemical Technology and Engineering, Poznan University of Technology, Pl. M. Skłodowskiej-Curie 2, 60-965, Poznań, Poland.
| | | | | |
Collapse
|
11
|
Cell hydrophobicity of Pseudomonas spp. and Bacillus spp. bacteria and hydrocarbon biodegradation in the presence of Quillaya saponin. World J Microbiol Biotechnol 2006. [DOI: 10.1007/s11274-006-9282-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
12
|
Pelah D, Abramovich Z, Markus A, Wiesman Z. The use of commercial saponin from Quillaja saponaria bark as a natural larvicidal agent against Aedes aegypti and Culex pipiens. JOURNAL OF ETHNOPHARMACOLOGY 2002; 81:407-409. [PMID: 12127245 DOI: 10.1016/s0378-8741(02)00138-1] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
The larvicidal activity of commercial bark saponin extract (Sigma) from Quillaja saponaria was studied on 3rd-4th instar larvae of Aedes aegypti and Culex pipiens (vectors for dengue fever and Western Nile virus, respectively). The larvae were exposed to serial concentrations (1000, 800, 500, 300, 100, 10, 1, 0.1 and 0.01 mg/l) of the extract for 1, 3, 5, 7 and 11 days. The results indicate that commercial bark saponin is toxic, causing 100% larval mortality in A. aegypti and C. pipiens after 1 and 5 days at a dosage of 800 and 1000 mg/l, respectively. Interestingly, while bark saponins had a toxic effect on larvae there was no effect on egg hatchability in either species. The results obtained suggest that, in addition to their known activities, saponins can also serve as natural larvicidal compounds.
Collapse
Affiliation(s)
- D Pelah
- The Institutes for Applied Research, Ben-Gurion University of the Negev, Beer-Sheva 84105, Israel
| | | | | | | |
Collapse
|
13
|
Hwang SJ, Cha JY, Park SG, Joe GJ, Kim HM, Moon HB, Jeong SJ, Lee JS, Shin DH, Ko SR, Park JK. Diol- and triol-type ginseng saponins potentiate the apoptosis of NIH3T3 cells exposed to methyl methanesulfonate. Toxicol Appl Pharmacol 2002; 181:192-202. [PMID: 12079428 DOI: 10.1006/taap.2002.9413] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
In this study we investigated the effect of ginseng saponins on the p53-dependent apoptosis in NIH3T3 cells exposed to methyl methanesulfonate (MMS), an alkylating agent. Trypan blue exclusion assay, cell morphology studies, and apoptotic index determined by acridine orange staining showed that the postincubation of MMS-exposed cells in medium containing diol- (PD) or triol-type (PT) ginseng saponins potentiate the apoptotic cell death. FACS analysis indicated that the increased apoptotic cell population in the saponin-postincubation group was accompanied by the accumulation of cells in G0/G1 phase. By Western blot analyses it was demonstrated that postincubation of saponins increases the expression of p53 and p21 in MMS-exposed cells but decreased that of CDK2, cyclin E and D1, and PCNA. The upregulation of p53 and p21 and downregulation of CDK2 was shown to be p53-dependent in experiments using the p53 antisense oligonucleotide. These results suggest that ginseng saponins contain components potentiating the apoptosis of MMS-exposed NIH3T3 cells via p53 and p21 activation, accompanied with by downregulation of cell cycle-related protein expression.
Collapse
Affiliation(s)
- Sung Jin Hwang
- Division of Biological Science, Wonkwang University, Iksan, Chonbuk 570-749, South Korea
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
14
|
Ho LJ, Chang DM, Lee TC, Chang ML, Lai JH. Plant alkaloid tetrandrine downregulates protein kinase C-dependent signaling pathway in T cells. Eur J Pharmacol 1999; 367:389-98. [PMID: 10079015 DOI: 10.1016/s0014-2999(98)00941-8] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Tetrandrine, a purified traditional Chinese medicinal herb that acts as an immunosuppressant and a Ca2+ channel blocker, has been clinically used to treat patients with arthritis, silicosis and hypertension. Since T cells play a critical role as autoreactive and pathogenic population in autoimmune diseases, in this study, we examined the immunosuppressive effect of tetrandrine on human peripheral blood T cells. We showed that tetrandrine inhibited phorbol 12-myristate 13-acetate (PMA) + ionomycin-induced T cell proliferation, interleukin-2 secretion and the expression of the T cell activation antigen, CD71. Further investigation of the molecular mechanism demonstrated that tetrandrine inhibited the expression of the protein kinase C-dependent interleukin-2 receptor alpha chain and CD69 but not the expression of the Ca2+-dependent CD40 ligand and CD69. Interestingly, when tetrandrine and cyclosporin A were added together, significant synergism in the suppression of T cell activation was observed. Moreover, of the several tetrandrine analogues studied, hernandezine was the most potent inhibitor of protein kinase C signaling events. These results also suggest that the protein kinase C-inhibitory capacity of tetrandrine and its analogues may not be associated with their function as Ca2+ channel blockers. Lastly, we showed that, within therapeutic concentrations, tetrandrine and its analogues could induce cellular apoptosis, which is defective in autoimmune diseases. In conclusion, our findings provide novel information about the molecular mechanism of the immunosuppressive effect of tetrandrine and its analogues in human peripheral blood T cells.
Collapse
Affiliation(s)
- L J Ho
- Graduate Institute of Life Sciences, National Defense Medical Center, Taipei, Taiwan, ROC
| | | | | | | | | |
Collapse
|
15
|
Liles MR, Edelstein PH, Cianciotto NP. The prepilin peptidase is required for protein secretion by and the virulence of the intracellular pathogen Legionella pneumophila. Mol Microbiol 1999; 31:959-70. [PMID: 10048038 DOI: 10.1046/j.1365-2958.1999.01239.x] [Citation(s) in RCA: 100] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Prepilin peptidases cleave, among other substrates, the leader sequences from prepilin-like proteins that are required for type II protein secretion in Gram-negative bacteria. To begin to assess the importance of type II secretion for the virulence of an intracellular pathogen, we examined the effect of inactivating the prepilin peptidase (pilD) gene of Legionella pneumophila. Although the pilD mutant and its parent grew similarly in bacteriological media, they did differ in colony attributes and recoverability from late stationary phase. Moreover, at least three proteins were absent from the mutant's supernatant, indicating that PilD is necessary for the secretion of Legionella proteins. The absence of both the major secreted protein and a haemolytic activity from the mutant signalled that the L. pneumophila zinc metalloprotease is excreted via type II secretion. Most interestingly, the pilD mutant was greatly impaired in its ability to grow within Hartmannella vermiformis amoebae and the human macrophage-like U937 cells. As reintroduction of pilD into the mutant restored inefectivity and as a mutant lacking type IV pilin replicated like wild type, these data suggested that the intracellular growth of L. pneumophila is promoted by proteins secreted via a type II pathway. Intratracheal inoculation of guinea pigs revealed that the LD50 for the pilD mutant is at least 100-fold greater than that for its parent, and the culturing of bacteria from infected animals showed a rapid clearance of the mutant from the lungs. This is the first study to indicate a role for PilD and type II secretion in intracellular parasitism.
Collapse
Affiliation(s)
- M R Liles
- Department of Microbiology-Immunology, Northwestern University, Chicago, IL 60611, USA
| | | | | |
Collapse
|