Comparative immunopharmacology and toxicology of the bisbenzylisoquinoline alkaloids tetrandrine and berbamine

A novel autophagy inhibitor berbamine blocks SNARE-mediated autophagosome-lysosome fusion through upregulation of BNIP3

Increasing evidences reveal that autophagy inhibitor could enhance the effect of chemotherapy to cancer. However, few autophagy inhibitors are currently approved for clinical application in humans. Berbamine (BBM) is a natural compound extracted from traditional Chinese medicine that is widely used for treatment of a variety of diseases without any obvious side effects. Here we found that BBM is a novel auophagy inhibitor, which potently induced the accumulation of autophagosomes by inhibiting autophagosome-lysosome fusion in human breast cancer cells. Mechanistically, we found that BBM blocked autophagosome-lysosome fusion by inhibiting the interaction of SNAP29 and VAMP8. Furthermore, BBM induced upregulation of BNIP3 and the interaction between SNAP29 and BNIP3. BNIP3 depletion or SNAP29 overexpression abrogated BBM-mediated blockade of autophagosome-lysosome fusion through the interaction between SNAP29 and VAMP8, whereas BNIP3 overexpression blocked autophagosome-lysosome fusion through inhibition of the interaction between SNAP29 and VAMP8. These findings suggest that upregulation of BNIP3 and interaction between BNIP3 and SNAP29 could be involved in BBM-mediated blockade of autophagosome-lysosome fusion through inhibition of the interaction between SNAP29 and VAMP8. Our findings identify the critical role of BNIP3 in blockade of autophagosome-lysosome fusion mediated by BBM, and suggest that BBM could potentially be further developed as a novel autophagy inhibitor, which could enhance the effect of chemotherapy to cancer.

Inhibitory effects of bisbenzylisoquinolines on synthesis of the inflammatory cytokines interleukin-1 and tumour necrosis factor-alpha

Synthesis of IL-1beta and TNFalpha by human monocytesmacrophages was significantly inhibited by eleven bisbenzylisoquinolines and one half-molecule (benzylisoquinoline), with IC(50) values in the muM range. The results indicate that these compounds may have value in the therapy of human diseases where these inflammatory cytokines have a central role in pathogenesis.

Effect of Mahonia aquifolium stem bark crude extract and one of its polysaccharide components on production of IL-8

The crude hydroalcoholic extract of Mahonia aquifolium stem bark and a polysaccharide isolated from the extract were tested for their activity on interleukin-8 (IL-8) production by human monocytic cell line THP-1. The crude extract partly inhibited the IL-8 spontaneous production after 48-h treatment of the cells, while the polysaccharide was found to be a potent inducer of IL-8 production.

Cytokine mRNA in BALB/c mouse corneas infected with herpes simplex virus

PURPOSE

To investigate cytokine mRNA expression and the influence of acyclovir and tetrandrine on that expression in the corneas of mice infected with herpes simplex virus type 1 (HSV-1).

METHODS

Male BALB/c mice were infected in the right cornea with HSV-1. The corneas were harvested from control normal mice and from untreated, acyclovir-treated and tetrandrine-treated mice 14 days after infection. The infected corneas of each group were divided into inflamed and uninflamed depending on clinical observation. After total mRNA extraction from the corneas, gene expression of interleukin 1 beta (IL-1 beta), IL-6, tumour necrosis factor alpha (TNF-alpha) and transforming growth factor (beta (TGF-beta) was analysed by reverse transcription polymerase chain reaction.

RESULTS

No mRNA expression of the cytokines was found in normal corneas. IL-1 beta and TNF-alpha mRNA was seen in inflamed corneas, while mRNA expression of IL-6 and relatively weaker TGF-beta mRNA expression were found both in inflamed corneas and in infected but uninflamed corneas treated with acyclovir. TNF-alpha mRNA was present in the uninflamed corneas of tetrandrine-treated mice. No influence of either agent was found on TGF-beta gene expression.

CONCLUSIONS

The results suggest that local IL-1 beta and TNF-alpha gene expression is required for corneal inflammation, whereas IL-6 and TGF-beta may exert antiviral and inflammation regulatory activities in HSV corneal infection.

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.

Trypanocidal bisbenzylisoquinoline alkaloids are inhibitors of trypanothione reductase

Eleven bisbenzylisoquinoline (BBIQ) alkaloids were studied for in vitro trypanocidal activity against trypomastigote forms of the Y strain of Trypanosoma cruzi. The inhibitory activity of these compounds against trypanothione reductase (TR), a target enzyme for chemotherapy against Chagas disease, was also studied. Six BBIQ alkaloids (antioquine, cepharanthine, daphnoline, limacine, cycleanine and (-) curine) displayed a 50% lethal concentration (LC50) against T. cruzi of less than 100 microM. Daphnoline and curine, with LC50 values of 10 microM, are attractive for further investigation as potential anti-Chagasic drugs. Kinetic analyses suggested the BBIQ alkaloids are mixed inhibitors of TR. These compounds are reasonably potent inhibitors of TR; the best TR inhibitor, cepharanthine, had an IC50 of 15 microM, which is in the same order of magnitude as its LC50 against T. cruzi. The similar magnitudes of the IC50 and LC50 values suggest that inhibition of TR could contribute to the trypanocidal activity exhibited by the BBIQ alkaloids.

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 potently inhibits herpes simplex virus type-1-induced keratitis in BALB/c mice

This study investigated the effect of tetrandrine (TDR) on experimental herpes simplex keratitis (HSK) in mice. BALB/c mice were divided as follows: Group 1, untreated; Group 2, acyclovir (ACV)-treated from day 0 postinfection; Group 3, ACV-treated from day 7; Group 4, TDR-treated from day 0; and Group 5, TDR-treated from day 7. All mice were infected in the right cornea with herpes simplex virus (HSV) type I. TDR 30 mg/kg and ACV 120 mg/kg were administered intraperitoneally daily. The mice were observed for 14 days postinfection. Clinical inflammatory reactions and ocular histopathology were analyzed. The herpes specific antibody response and the delayed type hypersensitivity (DTH) response were studied. Of the 22 untreated mice, 16 developed HSK (incidence, 72.7%). TDR given from day 7 reduced the HSK incidence to 8.5% (p < 0.01); the incidence of HSK was 45.4% in mice treated with TDR from day 0 (p > 0.05). Systemic ACV given from day 0 inhibited HSK development (p < 0.01); ACV given from day 7 resulted in an HSK incidence of 50% (p > 0.05). The specific anti-HSV antibody response in the serum of mice treated with TDR or ACV either from day 0 or day 7 was significantly less than that of untreated mice (p < 0.01 and p < 0.05, respectively), and TDR treatment suppressed DTH responses to HSV (p < 0.05). Systemic TDR administered after HSV inoculation of the cornea significantly modulates murine HSK development at least partly by modifying the host immune/inflammatory response to the virus.

Effects of Chinese herbal products on mammalian retinal functions

Ocular ischemia and inflammation are two major factors which induce retinal degeneration. Treatment of these diseases has been difficult, though numerous agents have been tried. Natural products could be a good field to venture into because various medicinal plants have been used for centuries to treat circulation stasis, inflammation, visual disturbances, and eyesight failure. Tetramethyl-pyrazine, coumarin, methyl tyramine, rescinnamine, apocynin, and hesperetin are some natural products isolated from Chinese herbs for improving ocular blood flow, particularly in the choroid and retina. For ocular inflammation, at least a dozen natural products are reviewed in this article. Among those, matrine, tetrandrine and osthole draw particular attention, because they are effective mainly as interleukin-1 blockers, but not as arachidonate blockers. As a result, these agents are potent anti-inflammatory agents and are even more potent than the prototype corticosteroid, prednisolone. It is hoped that all aforementioned agents can be used to treat retinopathies resulting from ocular ischemia and/or ocular inflammation. Scoparone, corylifolinin, epigallocatechin-3-0-gallate, esculetin, and lespedezaflavanone A are some natural products which can improve retinal functions measured with electroretinogram's b-wave recovery. Further research should be carried out to relate natural products which can improve ocular blood flow and inflammation to retinal function and vice versa.

Tetrandrine inhibits breakdown of blood-aqueous barrier induced by endotoxin and interleukin-1 alpha in rats

Tetrandrine was shown to significantly inhibit uveitis induced by endotoxin and interleukin-1 alpha (IL-1 alpha) in rats. The dose-response curve of IL-1 alpha-induced uveitis was inhibited in a non-competitive manner. The maximum inflammation induced by IL-1 alpha was suppressed to 58.4%, 38.3% and 18.3% of the control peak by 5 mg/kg, 10 mg/kg and 20 mg/kg t.i.d. of tetrandrine, respectively. The maximum inflammation induced by endotoxin was suppressed to 56.5% and 38.0% by 5 mg/kg and 10 mg/kg t.i.d. of tetrandrine, respectively. The mechanism of tetrandrine's anti-inflammation could involve numerous pathways of inflammation processes and multiple inflammatory mediators. The results of this study indicate that tetrandrine appears to be a broad spectrum, non-steroidal, novel ocular anti-inflammatory agent.

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.

Effect of berbamine on blood and bone-marrow stem cells of cyclophosphamide-treated mice

The bisbenzylisoquinoline alkaloid berbamine has been used in China and Japan for the therapy of leukopaenic complications of cancer. Mice treated with non-toxic doses showed significant enhancement of neutrophil and lymphocyte counts in the circulation, but a decrease in the numbers of bone marrow stem cells in a dose-dependent manner after two weeks. Similar findings were observed in cyclophosphamide-treated mice. These results indicate that berbamine acts by stimulating the maturation and release of leukocyte progenitors, and may have value in leukopaenic patients.

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.

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.