In vitro immunosuppressive properties of the plant alkaloid tetrandrine

Rho GTPase signaling in rheumatic diseases

Rho guanosine triphosphatase (GTPases), as molecular switches, have been identified to be dysregulated and involved in the pathogenesis of various rheumatic diseases, mainly including rheumatoid arthritis, osteoarthritis, systemic sclerosis, and systemic lupus erythematosus. Downstream pathways involving multiple types of cells, such as fibroblasts, chondrocytes, synoviocytes, and immunocytes are mediated by activated Rho GTPases to promote pathogenesis. Targeted therapy via inhibitors of Rho GTPases has been implicated in the treatment of rheumatic diseases, demonstrating promising effects. In this review, the effects of Rho GTPases in the pathogenesis of rheumatic diseases are summarized, and the Rho GTPase-mediated pathways are elucidated. Therapeutic strategies using Rho GTPase inhibitors in rheumatic diseases are also discussed to provide insights for further exploration of targeted therapy in preclinical studies and clinical practice. Future directions on studies of Rho GTPases in rheumatic diseases based on current understandings are provided.

A critical review: traditional uses, phytochemistry, pharmacology and toxicology of Stephania tetrandra S. Moore (Fen Fang Ji)

ABSTRACT

Stephania tetrandra S. Moore (S. tetrandra) is distributed widely in tropical and subtropical regions of Asia and Africa. The root of this plant is known in Chinese as "Fen Fang Ji". It is commonly used in traditional Chinese medicine to treat arthralgia caused by rheumatism, wet beriberi, dysuria, eczema and inflamed sores. Although promising reports have been published on the various chemical constituents and activities of S. tetrandra, no review comprehensively summarizes its traditional uses, phytochemistry, pharmacology and toxicology. Therefore, the review aims to provide a critical and comprehensive evaluation of the traditional use, phytochemistry, pharmacological properties, pharmacokinetics and toxicology of S. tetrandra in China, and meaningful guidelines for future investigations.

Traditional Chinese Medicine for Refractory Nephrotic Syndrome: Strategies and Promising Treatments

Refractory nephrotic syndrome (RNS) is an immune-related kidney disease with poor clinical outcomes. Standard treatments include corticosteroids as the initial therapy and other immunosuppressants as second-line options. A substantial proportion of patients with RNS are resistant to or dependent on immunosuppressive drugs and often experience unremitting edema and proteinuria, cycles of remission and relapse, and/or serious adverse events due to long-term immunosuppression. Traditional Chinese medicine has a long history of treating complicated kidney diseases and holds great potential for providing effective treatments for RNS. This review describes the Chinese medical theories relating to the pathogenesis of RNS and discusses the strategies and treatment options using Chinese herbal medicine. Available preclinical and clinical evidence strongly supports the integration of traditional Chinese medicine and Western medicine for improving the outcome of RNS. Herbal medicine such as Astragalus membranaceus, Stephania tetrandra S. Moore, and Tripterygium wilfordii Hook F can serve as the alternative therapy when patients fail to respond to immunosuppression or as the complementary therapy to improve therapeutic efficacy and reduce side effects of immunosuppressive agents. Wuzhi capsules (Schisandra sphenanthera extract) with tacrolimus and tetrandrine with corticosteroids are two herb-drug combinations that have shown great promise and warrant further studies.

Anti-inflammatory effects of Stephania tetrandra S. Moore on interleukin-6 production and experimental inflammatory disease models

Deregulation of interleukin-6 (IL-6) expression caused the synthesis and release of many inflammatory mediators. It is involved in chronic inflammation, autoimmune diseases, and malignancy. Stephania tetrandra S. Moore is a Chinese medicinal herb which has been used traditionary as a remedy for neuralgia and arthritis in China. To investigate the anti-inflammatory effects of S. tetrandra S. Moore in vitro and in vivo, its effects on the production of IL-6 and inflammatory mediators were analysed. When human monocytes/macrophages stimulated with silica were treated with 0.1–10 μg/ml S. tetranda S. Moore, the production of IL-6 was inhibited up to 50%. At these concentrations, it had no cytotoxicity effect on these cells. It also suppressed the production of IL-6 by alveolar macrophages stimulated with silica. In addition, it inhibited the release of superoxide anion and hydrogen peroxide from human monocytes/macrophages. To assess the anti-fibrosis effects of S. tetrandra S. Moore, its effects on in vivo experimental inflammatory models were evaluated. In the experimental silicosis model, IL-6 activities in the sera and in the culture supernatants of pulmonary fibroblasts were also inhibited by it. In vitro and in vivo treatment of S. tetrandra S. Moore reduced collagen production by rat lung fibroblasts and lung tissue. Also, S. tetrandra S. Moore reduced the levels of serum GOT and GPT in the rat cirrhosis model induced by CCL₄, and it was effective in reducing hepatic fibrosis and nodular formation. Taken together, these data indicate that it has a potent anti-inflammatory and antifibrosis effect by reducing IL-6 production.

Lancifoliaine, a new bisbenzylisoquinoline from the bark of Litsea lancifolia

A new bisbenzylisoquinoline, lancifoliaine (1), together with seven known alkaloids--N-allyllaurolitsine (2), reticuline (3), actinodaphnine, norboldine, pallidine, cassythicine and boldine--were isolated from the stem bark of Litsea lancifolia (Lauraceae). In addition to that of lancifoliaine, complete ¹³C-NMR data of N-allyl-laurolitsine (2) was also reported. The alkaloidal structures were elucidated by means of high field 1D- and 2D-NMR IR, UV, and LCMS-IT-TOF spectral data. N-Allyllaurolitsine (2) showed a moderate vasorelaxant activity on isolated rat aorta.

Inhibition of Respiratory Burst Activity in Alveolar Macrophages by Bisbenzylisoquinoline Alkaloids: Characterization of Drug-Cell Interaction

The objective of this study was to investigate the effects of various bisbenzylisoquinoline (BBIQ) alkaloids on respiratory burst activity of alveolar macrophages and to characterize the interaction of these drugs with alveolar phagocytes. BBIQ alkaloids were chosen for study because they exhibit a wide range of antifibrotic potencies in a rat model, with tetrandrine being very effective and tubocurarine being ineffective. These drugs inhibited zymosan-stimulated oxygen consumption with a potency sequence of tetrandrine (TT) approximately fangchinoline (FA) > berbamine (BE) approximately cepharanthine (CE) approximately cycleanine (CY) >> tubocurarine (TU). This inhibition of respiratory burst activity could not be attributed to a drug-induced decline in the ATP content of these pneumocytes. Drug binding to alveolar macrophages was directly dependent on temperature and drug concentration. The sequence for binding capacity was FA > TT approximately BE approximately CY > CE >> TU. Therefore, there was no simple relationship between binding capacity and inhibitory potency. Binding capacity was not related to lipophilicity of these alkaloids. In addition, tetrandrine failed to bind to metabolically dead cells or sonicated macrophage preparations. These data suggest that the interaction of BBIQ alkaloids with phagocytes is not simply nonspecific binding to membrane lipids. Alteration of the cytoskeletal system with vinblastine, taxol, or cytochalasin B decreased tetrandrine binding by approximately 33% when added separately and by 93% when added jointly. Pre-exposure of alveolar macrophages to stimulants increased the ability of BBIQ alkaloids to inhibit both oxygen consumption and superoxide release. These data suggest that the mechanism by which BBIQ alkaloids inhibit activation of phagocytes involves microtubules and bules and microfilaments. Pre-exposure of macrophages to stimulants would change the conformation of cytoskeletal components and may make these structures more susceptible to drug interaction.

Tetrandrine inhibits activation of rat hepatic stellate cells stimulated by transforming growth factor-beta in vitro via up-regulation of Smad 7

Tetrandrine is a bisbenzylisoquinoline alkaloid derived from the root of a Chinese herbal medicine Stephania tetrandra S. Moore, which has been used traditionally for the treatment of hepatofibrogenic disease in China for several decades. In the present study, the inhibitory effects of tetrandrine lower concentrations (0.25, 0.5, 1, 2 mg/L) on culture-activation and transforming growth factor-beta(1) (TGF-beta(1))-stimulated activation of quiescent rat hepatic stellate cells (HSCs) in vitro were assessed, and the possible relations between the underlying mechanism of these effects and TGF-beta signaling via its receptors were investigated. As shown by the examination of alpha-SMA using immunocytochemical staining or Western blot, tetrandrine inhibited both culture-activation and TGF-beta(1)-stimulated activation of HSCs. Further investigations revealed that, in this process, TGF-beta(1) mRNA expression was suppressed significantly in contrast to an up-regulation of Smad 7, while the expressions of type I and type II TGF-beta(1) receptors and Smad 3 mRNA were insignificantly changed by tetrandrine. These results suggest that tetrandrine at lower concentrations has a significant inhibiting effect on culture-activation and TGF-beta(1)-stimulated activation of rat HSCs, and that it may be due to an up-regulation of Smad 7 which in turn blocks TGF-beta(1) expression and its downstream signaling.

Induction of apoptosis in human hepatoblastoma cells by tetrandrine via caspase-dependent Bid cleavage and cytochrome c release

Tetrandrine, a bis-benzylisoquinoline alkaloid from the root of Stephania tetrandra, induces apoptosis in human T-cell lines, lung carcinoma and hepatoblastoma cells. However, the mechanisms by which tetrandrine inhibits tumor cell growth are poorly understood. The purpose of the present study was to investigate the intracellular signaling mechanism of tetrandrine-induced apoptosis in HepG2 cells. The induction of apoptosis was determined by morphological analysis and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. Treatment of cells with tetrandrine caused the upregulation of p53, downregulation of Bcl-X(L), cleavage of Bid and Bax, and release of cytochrome c, which were accompanied by activation of caspases 9, 3 and 8. The activation of caspases 9 and 3 preceded that of caspase 8. A broad-spectrum caspase inhibitor and a caspase 8-specific inhibitor completely blocked tetrandrine-induced Bid processing, cytochrome c release, activation of caspase 3, and cell death. These findings and data showing the early release of cytochrome c, cleavage of Bid and downregulation of Bcl-X(L) suggest that the mitochondrial pathway is primarily involved in tetrandrine-induced apoptosis. The activation of caspase 8 after early caspases 9 and 3 activation might act as an amplification loop for activation of upstream signals such as Bid cleavage or cytochrome c release. These data suggest that tetrandrine may constitute a plausible therapeutic for hepatocellular carcinoma.

Inhibition of proliferation and induction of apoptosis by tetrandrine in HepG2 cells

Tetrandrine is a bisbenzylisoquinoline alkaloid derived from the root of Stephania tetrandra S. Moore, which has been reported to elicit in vitro cytotoxic effects on HeLa cells, and in vivo suppressive effects on mouse ascites tumors. In the present study, we examined the antiproliferative and apoptosis-inducing activity of tetrandrine in HepG2 cells, a human hepatoma cell line. Tetrandrine showed potent cytotoxic activity in HepG2 cells (IC(50)=9.0+/-1.0 micro M) following incubation for 48 h. Dose-dependent induction of apoptosis was observed by agarose gel electrophoresis and flow cytometric analysis. Treatment of HepG2 cells with tetrandrine resulted in the activation of caspase-3 protease, and subsequent proteolytic cleavage of poly(ADP-ribose) polymerase. These results suggest that tetrandrine is potentially useful as a chemotherapeutic/chemopreventive agent in hepatocellular carcinoma.

Plant alkaloid tetrandrine and its analog block CD28-costimulated activities of human peripheral blood T cells: potential immunosuppressants in transplantation immunology

BACKGROUND

T lymphocyte activation mediated by CD28 costimulation plays a critical role in graft rejection. Plant alkaloid tetrandrine, purified from a Chinese antirheumatic herb, is a potent immunosuppressant. Here, we examined its effects on several CD28-costimulated T-cell activities. In addition, such effects were readily compared with the effects of three tetrandrine analogs.

METHODS

T lymphocytes were purified from whole blood by negative selection. The stimuli that mimic CD28 costimulation included both anti-CD3 + anti-CD28 monoclonal antibody and PMA+anti-CD28 monoclonal antibody. The determination of CD28-costimulated cell proliferation was performed by tritium uptake, cytokine production by ELISA, cell surface interleukin 2Ra and CD69 expression by flow cytometry, and mixed leukocyte reaction by tritium uptake. Drug cytotoxicity was determined by trypan blue exclusion, propidium iodide staining, and MTT colorimetric assays.

RESULTS

Tetrandrine inhibited CD28-costimulated T-cell proliferation and cytokine production through a mechanism different from that of cyclosporine. In addition, tetrandrine down-regulated both T helper 1 and T helper 2 cytokine production in CD4+ and CD8+ T-cell subpopulations. By examining cytokine production and T-cell activation marker expression, we further demonstrated that, among tetrandrine and its analogs tested, dauricine was the most potent suppressor of CD28-costimulated T-cell activities. Furthermore, the different immunosuppressive activities of these compounds were not associated with their cytotoxic capacities. Finally, the unparalleled inhibitory potency of dauricine on both mixed leukocyte reaction and CD28-costimulated T-cell proliferation suggests that dauricine preferentially targeted CD28-costimulated T-cell activities.

CONCLUSIONS

This is the first report to show that tetrandrine and its analogs potently inhibited both PMA+CD28-costimulated and CD3 + CD28-costimulated activation of human peripheral blood T cells. Based upon their structural similarity and different immunosuppressive potency, these in vitro data also provide very useful information for further identification and development of more potent and less toxic immunosuppressants to achieve transplantation success.

Complement modulatory activity of bisbenzylisoquinoline alkaloids isolated from Isopyrum thalictroides--I. Influence on classical pathway in human serum

Eleven bisbenzylisoquinoline alkaloids (BBI) were isolated from the plant Isopyrum thalictroides (L.). Treatment of normal human serum (NHS) with BBI resulted in a diminution of the haemolytic activity of the classical pathway (CP). The mode of action of the main alkaloids isopyruthaline (It1), fangchinoline (It2) and isotalictrine (It3) on CP activation was investigated in vitro. The inhibition was time- and temperature-related and for Itl and It3 depended on the concentration of Ca2+ and Mg2+ ions. It was established that the substances reduced C1 haemolytic activity. It2 and It3 enhanced the complement consumption caused by heat aggregated human IgG (HAGG). The BBI prevented the formation of C3 convertase of the classical pathway. The loss of haemolytic activity was partially restored by the addition of C142 reagent (zymosan-treated guinea pig serum) to alkaloids-treated NHS. The addition of the late components C3-9 (EDTA-treated rat sera) recovered to some extent the haemolytic activity of It1-treated NHS, but not of It2- and It3-treated NHS.

Plant alkaloid tetrandrine downregulates protein kinase C-dependent signaling pathway in T cells

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.

Potent inhibitory effect of tetrandrine on experimental allergic conjunctivitis in mice

This study investigated the effectiveness of tetrandrine (TDR) on experimental allergic conjunctivitis secondary to ragweed pollen. SWR/J mice were divided as follows: group 1, normal controls; group 2, sensitized but untreated; group 3, sensitized, buffered saline (BS)-treated; and group 4, sensitized, TDR-treated. The last three groups were exposed to ragweed through topical contact on the nasal and conjunctival mucosae followed by challenge with the allergen on the conjunctiva. Groups 3 and 4 received doses of BS and TDR, respectively. The allergic conjunctivitis was evaluated by scoring of the clinical signs and histopathology. mRNA gene expression of interleukin 1 beta (IL-1 beta) and IL-5 in the conjunctiva was analyzed by polymerase chain reaction techniques. All mice exposed to ragweed developed allergic conjunctivitis clinically and histologically. The conjunctivitis was significantly modulated by intraperitoneal injection of a new anti-inflammatory agent, TDR. Histopathologic analysis demonstrated that TDR strikingly reduced the conjunctival eosinophil infiltration and the number of intact and degranulating mast cells. IL-1 beta and Il-5 mRNA gene expression in the conjunctiva of TDR-treated mice was dramatically down-regulated compared with untreated and BS-treated controls. The results indicate that TDR may have potential clinical use in the treatment of conjunctivitis.

Tetrandrine: a new ligand to block voltage-dependent Ca2+ and Ca(+)-activated K+ channels

Extensive pharmacological investigations on tetrandrine, one of the traditional medicinal alkaloids, are reviewed. Tetrandrine has been used clinically in China for centuries in the treatment of many diseases. A recent series of studies has revealed major mechanisms underlying its multiple pharmacological and therapeutic actions. One of the most interesting discoveries is that tetrandrine is a new kind blocker of the voltage-activated, L-type Ca2+ channel in a variety of excitable cells, such as cardiac, GH3 anterior pituitary and neuroblastoma cells, as well as in rat neurohypophysial nerve terminals. Although tetrandrine does not belong to any of the three classical Ca2+ channel blocker groups, electrophysiological and radioligand binding studies show that tetrandrine is an L-type Ca2+ channel blocker with its binding site located at the benzothiazepine receptor on the alpha 1-subunit of the channel. In addition, tetrandrine is a blocker of the voltage-dependent T-type Ca2+ channel. It is clear that tetrandrine's actions in the treatment of cardiovascular diseases, including hypertension and supraventricular arrhythmia, are due primarily to its blocking of voltage-activated L-type and T-type Ca2+ channels. Furthermore, this alkaloid is a potent blocker of the Ca(2+)-activated K+ (K(Ca)) channels of neurohypophysial nerve terminals. The blocking kinetics of tetrandrine on the K(Ca) channel is quite different from that of typical K(Ca) channel blockers such as tetraethylammonium and Ba2+. Although the clinical role of tetrandrine as a blocker of the K(Ca) channels is unclear, it is a promising ligand for the study of K(Ca) channel function.

Dual effects of tetrandrine on cytosolic calcium in human leukaemic HL-60 cells: intracellular calcium release and calcium entry blockade

1. Tetrandrine (TET, a Ca2+ antagonist of Chinese herbal origin) and thapsigargin (TSG, an endoplasmic reticulum Ca2+ pump inhibitor) concentration-dependently mobilized Ca2+ from intracellular stores of HL-60 cells, with EC50 values of 20 microM and 0.8 nM, respectively. After intracellular Ca2+ release by 30 nM TSG, there was no more discharge of Ca2+ by TET (100 microM), and vice versa. 2. Pretreatments with 100 nM rauwolscine (alpha 2-adrenoceptor antagonist), 100 nM prazosin (alpha 1-adrenoceptor antagonist), 10 nM phorbol myristate acetate (PMA, a protein kinase C activator) or 100 nM staurosporine (a protein kinase C inhibitor) had no effect on 100 microM TET-induced intracellular Ca2+ release. 3. After intracellular Ca2+ release by 30 nM TSG in Ca(2+)-free medium, readmission of Ca2+ caused a substantial and sustained extracellular Ca2+ entry. The latter was almost completely inhibited by 100 microM TET (IC50 of 20 microM) added just before Ca2+ readmission. In Ca(2+)-containing medium, 30 nM TSG caused a sustained phase of cytosolic Ca2+ elevation, which could be abolished by 100 microM TET. TET was also demonstrated to retard basal entry of extracellular Mn2+ and completely inhibit TSG-stimulated extracellular Mn2+ entry. 4. TSG-induced extracellular Ca2+ entry was insensitive to the L-type Ca2+ channel blocker, nifedipine (1 microM), but was completely inhibited by the non-selective Ca2+ channel blocker La3+ (300 microM). Depolarization with 100 mM KCl did not raise the cytosolic Ca2+ level. 5. These data suggest that (a) TET and TSG mobilized the same Ca2+ pool and TET-induced intracellular Ca2+ release was independent of protein kinase C activity and ox-adrenoceptor activation,and (b) TET blocked the voltage-insensitive Ca2+ entry pathway activated by TSG. These dual effects on HL-60 cells were also observed with hernandezine (HER), a TET-like compound and in another cell type, murine B lymphoma M12.4 cells.

Anti-inflammatory activity of the isoquinoline alkaloid, tetrandrine, against established adjuvant arthritis in rats

Two isoquinoline plant alkaloids, tetrandrine (1) and berbamine (2), have been evaluated for anti-inflammatory activity in an acute paw oedema assay and in adjuvant-induced arthritis in rats. 1 but not 2 suppressed the chronic inflammation in the arthritis model but neither compound was active in the acute inflammation assay. In the adjuvant-induced polyarthritis, 1 was not effective when given at the time of inoculation (Day 0), nor just before (Day 7-10) signs of arthritis were evident. However, when given on a therapeutic dose schedule (Days 10-13) or continually (Day -1 to +14) on a prophylactic schedule, signs of arthritis including weight loss due to cachexia were significantly reduced. Given orally, 1 was considerably more potent than aspirin but not gastro-irritant and may be a promising lead for the development of a safe and effective treatment of chronic inflammatory diseases.

Comparative effects of tetrandrine and berbamine on guineapig airway microvascular leakage induced by platelet-activating factor and other allergic mediators

The bisbenzylisoquinoline analogues, tetrandrine and berbamine, were investigated for their effects on guineapig airway microvascular leakage, an animal model of asthma and allergic inflammation. Significant inhibition of microvascular leakage by tetrandrine was observed with all four allergic mediators used in these experiments. By contrast, berbamine was able to suppress microvascular leakage induced by platelet-activating factor and bradykinin, but not by leukotriene D4 or histamine. These results indicate that tetrandrine has broad-spectrum inhibitory activity on allergic mediators, and may have value for the therapy of diseases in which these mediators have a role in pathogenesis.

Synergy between tetrandrine and FK506 in prevention of diabetes in BB rats

Delayed administration of tetrandrine, a novel broad-spectrum anti-inflammatory agent, to BB rats at a dosage schedule of 20 mg kg-1 day-1 from 79 days of age reduced the cumulative incidence of diabetes from 73.1 to 41.7% (p < 0.01). Brief treatment with the potent immunosuppressive agent FK506 at a dosage schedule of 0.5 mg kg-1 day-1 from 79 days of age for 5 days had no significant effect on the cumulative incidence of diabetes (66.7%, p > 0.1). However, the combination of tetrandrine and FK506 in the afore-mentioned dosage schedules reduced the incidence of diabetes to only 3.6% (p < 0.001). These results suggest that the strong synergy between tetrandrine and FK506 may offer a safe and effective therapeutic strategy for the treatment of patients with recent onset or imminent IDDM.

Selective inhibition of T-cell-dependent immune responses by bisbenzylisoquinoline alkaloids in vivo

The bisbenzylisoquinoline (BBI) alkaloids, chondocurine, tetrandrine, isotetrandrine and cepharanthine, were tested for immunosuppressive activity in mice. A plaque-forming cell (PFC) response to a T-cell-dependent antigen, sheep red blood cell, was significantly suppressed by a 7 day treatment of chondocurine or tetrandrine at 1 mg/kg/day and of isotetrandrine at 50 mg/kg/day, but not suppressed by cepharanthine treatment. The suppressive effect of chondocurine was greater when it was given after immunization rather than before or concurrently. However, it did not affect the PFC response to a T-cell-independent antigen, lipopolysaccharide. A delayed-type hypersensitivity was also suppressed by chondocurine treatment. There was no significant change in lymphocyte number and proportion of T-cell subsets in the BBI alkaloid-treated mice. These data suggest that there is selective inhibition by chondocurine and tetrandrine of the T-cell-dependent immune reactions.

Comparative effects of tetrandrine and berbamine on subcutaneous air pouch inflammation induced by interleukin-1, tumour necrosis factor and platelet-activating factor

The effects of the bisbenzylisoquinoline alkaloids tetrandrine and berbamine on the action of IL-1, TNF and PAF were investigated in the rat subcutaneous air pouch model of inflammation. Both compounds were equipotent in the suppression of leukocyte infiltration into air pouches induced by IL-1 and TNF, with ED50 values in the range 20-30 mg/kg/3 days. Both were also equipotent in suppression of PMN infiltration induced by PAF with ED50 values in the same range as that for IL-1 and TNF. However, tetrandrine was more potent than berbamine as a suppressant of PAF-induced MNC infiltration, but much less potent than berbamine in carageenen-induced PMN infiltration. These results suggest that these bisbenzylisoquinolines may have value in the therapy of chronic inflammatory diseases where IL-1, TNF and PAF have a role in pathogenesis.

Comparative effects of tetrandrine and berbamine on production of the inflammatory cytokines interleukin-1 and tumor necrosis factor

Tetrandrine and berbamine are bisbenzylisoquinoline compounds which differ from each other in a minor way in terms of chemical structure, yet tetrandrine is 6-18 times more potent than berbamine in terms of inhibitory effects on production of interleukin-1 and tumor necrosis factor (TNF alpha) by monocytes and macrophages, and TNF beta production by lymphocytes. Moreover, tetrandrine significantly suppressed phosphoinositide turnover while berbamine did not. These findings may provide important insights into structure-activity relationships and the design of novel analogues and congeners useful in the therapy of chronic inflammatory and auto-immune diseases.

Binding of bisbenzylisoquinoline alkaloids to phosphatidylcholine vesicles and alveolar macrophages: relationship between binding affinity and antifibrogenic potential of these drugs

A group of bisbenzylisoquinoline alkaloids has been shown to exhibit various degrees of effectiveness in preventing silica-induced fibrosis in animal models. The objective of the present study was to characterize the binding of several of these alkaloids to phosphatidylcholine vesicles and rat alveolar macrophages using fluorometric and equilibrium dialysis methods, respectively. The lipid binding affinity of these alkaloids was found to depend upon several structural factors including hydrophobic substitutions, chiral configurations, and double oxygen bridge-restricted confirmation of the benzylisoquinoline moieties. Tetrandrine, which is a highly effective agent in preventing fibrosis, showed strong binding to both lipid vesicles and alveolar macrophages. In contrast, certain analogues of tetrandrine such as curine and tubocurine, which have little or no effect on silicosis, exhibited only weak binding to lipid vesicles and almost no binding to cells. The moderate binding affinity of fangchinoline to vesicles and cells corresponded to a moderate effectiveness of the compound as an antifibrogenic agent. Methoxyadiantifoline, an alkaloid of unknown antifibrogenic potential, also exhibited high binding affinities for lipid and cells. In conclusion, the results of these studies indicate that alveolar macrophages exhibit large binding capacities for certain members of this class of bisbenzylisoquinoline alkaloids. A positive correlation was observed between binding affinity to alveolar macrophages and the reported antifibrotic potency of these compounds. These data also suggest that the ability of these drugs to interact with alveolar macrophages may be a key step in inhibition of the progression of silica-induced pulmonary disease.

Plasmodium falciparum: effects of phaeanthine, a naturally-occurring bisbenzylisoquinoline alkaloid, on chloroquine-resistant and -sensitive parasites in vitro, and its influence on chloroquine activity

Phaeanthine, a bisbenzylisoquinoline alkaloid which occurs naturally in Triclisia species, was extracted from Triclisia patens (Menispermaceae) obtained from Sierra Leone (West Africa). In vitro, phaeanthine was found to be twice as potent against a chloroquine-resistant Plasmodium falciparum strain (K1), as against a chloroquine-sensitive clone (T9-96), with 50% inhibitory concentrations of 365.85 (+/- 11.41) nM and 704.87 (+/- 81.48) nM respectively. At a sub-inhibitory concentration of 80.35 nM, chloroquine resistance was not reversed by phaeanthine. Isobolograms constructed from experiments with chloroquine/phaeanthine combinations showed antagonism in T9-96 and an additive effect in K1. In a 48-hour microtest, phaeanthine at antimalarial concentrations showed no cytotoxicity to mammalian (KB) cells in vitro.

Comparative immunopharmacology and toxicology of the bisbenzylisoquinoline alkaloids tetrandrine and berbamine

Comparison of the bisbenzylisoquinolines tetrandrine and berbamine shows that both drugs are equipotent in terms of enhancement of antibody responses and suppression of delayed-type hypersensitivity (DTH) responses to sheep red blood cell antigens. Both compounds are also equally active when given to mice during the induction and expression phases of DTH. Using a model of experimental brucellosis in mice, it was found that both compounds did not affect antibody responses, while they caused equipotent suppression of DTH. By contrast, berbamine but not tetrandrine caused significant suppression of spleen weight. Also, berbamine caused a significantly greater enhancement of spleen colony counts of Brucella abortus than tetrandrine. Short-term toxicology studies showed no toxic effects at bioactive doses.

Demonstration of the induction of apoptosis (programmed cell death) by tetrandrine, a novel anti-inflammatory agent

Tetrandrine, a bisbenzylisoquinoline alkaloid, was found to cause death of malignant lymphoid and myeloid cells but not of Epstein-Barr virus-transformed lymphoblastoid cells. The death took the form of apoptosis (programmed cell death), the nature of the process being confirmed by DNA gel electrophoresis and electron microscopy. The induction of apoptosis by tetrandrine was much more rapid in CEM-C7 cells (4 h) than in the same cells treated with glucocorticoids (40 h), and did not require de novo protein synthesis. These results suggest that the anti-inflammatory and immunosuppressive properties of tetrandrine are mediated by novel mechanisms worthy of further investigation. They also indicate that tetrandrine may have value as an anti-neoplastic agent.

Tetrandrine, a plant alkaloid, inhibits the production of tumour necrosis factor-alpha (cachectin) hy human monocytes

Human mononuclear leucocytes (MNL) or the adherent fraction (monocytes) produced tumour necrosis factor-alpha (TNF-alpha) (by ELISA) in culture when stimulated with killed Staphylococcus aureus. The bisbenzylisoquinoline alkaloid, tetrandrine inhibited the capacity of MNL and monocytes to produce TNF-alpha at a concentration range of 0.1 to 5 micrograms/ml. Tetrandrine may be potentially useful in the treatment of inflammatory diseases in which TNF-alpha plays a major role.

Inhibition of prostaglandin and leukotriene generation by the plant alkaloids tetrandrine and berbamine

We compared the effects of two bisbenzylisoquinoline compounds on leukotriene and prostaglandin generation by human monocytes and neutrophils. The results show that tetrandrine had a much greater effect than berbamine on leukotriene generation. However, both compounds were equally potent in suppression of prostaglandin generation. This inhibitory effect on prostaglandin generation can be overcome by exogenous arachidonic acid (AA), suggesting that the site of inhibition is not on the cyclooxygenase enzyme complex, but more proximally on the phospholipase-mediated release of AA from the cell membrane, similar to the action of corticosteroids. These results, together with previous findings of inhibitory effects on other inflammatory mediators such as histamine, platelet-activating-factor (PAF) and interleukin 1 (IL-1) indicate that these plant alkaloids may be useful lead compounds for the development of a new class of anti-inflammatory drugs.

Anti-inflammatory and immunosuppressive properties of the bis-benzylisoquinolines: in vitro comparisons of tetrandrine and berbamine

Tetrandrine and berbamine are two naturally occurring analogues with a bis-benzylisoquinoline structure. Comparative in vitro studies show that tetrandrine has significantly greater suppressive effects on adherence, locomotion and 3H-deoxyglucose uptake of neutrophils, as well as the mitogen-induced lymphocyte responses and mixed lymphocyte reactions. Also, tetrandrine displayed anti-oxidant activity while berbamine did not. By contrast, berbamine demonstrated a significantly greater capacity for inhibition of NK cell cytotoxicity. These results show that tetrandrine is superior to berbamine in most aspects of anti-inflammatory and immunosuppressive activity. Since these two alkaloids differ by only one substitution in the side chain of one of the benzene rings, these findings may provide further insight into structure-activity relationships and clues to the synthesis and development of active analogues of this promising class of drugs for the treatment of chronic inflammatory diseases.

Effects of the newer antifungal agents (bifonazole, ICI 195, 739 and amorolfin) on in vitro phagocytic, lymphocytic and natural-killer cell responses

Amphotericin B and some of the imidazole drugs have been shown to suppress certain neutrophil and lymphocyte functions both in vitro and in vivo. We present here the in vitro effects of: amorolfin, a morpholine derivative; the imidazoles clotrimazole and ketoconazole; the N-substituted imidazole bifonazole and a triazole (ICE 195, 739), on neutrophil and lymphocyte function. All of these drugs inhibited neutrophil random migration, chemotaxis and hexose monophosphate shunt activity. The effects of the drugs on neutrophil adherence, deoxyglucose transport and beta-glucuronidase release were variable while lysozyme release was unaffected. Natural Killer cell cytoxicity was depressed by all drugs tested except for amorolfin. Mitogen-induced lymphocyte blastogenesis was suppressed by all the antifungal drugs tested. Similar results were obtained using the mitogens phytohaemagglutinin, concanavalin A and pokeweed mitogen. The mechanism of action of these drugs on these cell functions remains unknown, there may be a correlation between their effects on fungi and their effects on leukocytes. Clearance of systemic fungal infection is heavily dependent on integrity of the cellular immune system and it is clearly undesirable that antifungal drugs have immunosuppressive properties. Further studies are required to determine the in vivo and clinical relevance of our observations.

Inhibition of neutrophil locomotion, natural killer cell cytotoxicity and lymphocyte transformation by 1-methyl-3-phenyl-1,2,4-triazinium-5-olate, a novel triazinium zwitterion

We studied a novel triazinium zwitterion compound for its effects on neutrophil locomotion and deoxyglucose uptake, Natural Killer (NK) cell cytotoxicity and mitogen-induced lymphocyte transformation. The results show significant inhibition of neutrophil locomotion at concentrations of 10 micrograms/ml or greater; by contrast, there was no significant effect on neutrophil deoxyglucose uptake. Significant suppression of NK cell cytotoxicity occurred at similar concentrations in a dose-dependent fashion. Marked suppression of mitogen-induced lymphocyte transformation was also observed for all three mitogens used in the assays. This effect was dose-dependent, reversible by washing and still evident even when it was added 37 h after the initiation of cultures. These results suggest that 1-methyl-3-phenyl-1,2,4-triazinium-5-olate may have application as an anti-inflammatory and immunosuppressive agent.