Biochemical effects of d-tetrandrine and thalicarpine

8-, 9-, and 11-Aryloxy Dimeric Aporphines and Their Pharmacological Activities

Aporphines, a major group of aporphinoid alkaloids, exhibit interesting and diverse pharmacological activities. A set of dimeric aporphines with an aryloxy group at C8, C9, and C11 have been isolated from six genera and shown to elicit various biological activities such as antitumor, antimalarial, antimicrobial, antiplatelet aggregation, antifibrotic, immunosuppressive, and vasorelaxant properties. In this review, the nomenclature, chemical structures, botanical sources, pharmacological activities, and synthetic approaches of this set of dimeric alkaloids are presented.

Tetrandrine suppresses lipopolysaccharide-induced microglial activation by inhibiting NF-κB and ERK signaling pathways in BV2 cells

Background and Objective

Tetrandrine (TET) is a bisbenzylisoquinoline alkaloid extracted from Stephania tetrandra Moore. Recent studies have suggested that TET can reduce the inflammatory response in microglia, but the mechanisms remain unclear. The aim of this study is to investigate whether TET can inhibit lipopolysaccharide (LPS)-induced microglial activation and clarify its possible mechanisms.

Study Design/Materials and Methods

Cell viability assays and cell apoptosis assays were used to determine the working concentrations of TET. Then, BV2 cells were seeded and pretreated with TET for 2 h. LPS was then added and incubated for an additional 24 hours. qRT-PCR and ELISA were used to measure the mRNA or protein levels of IL1β and TNFα. Western blotting was utilized to quantify the expression of CD11b and cell signaling proteins.

Results

TET at optimal concentrations (0.1 µM, 0.5 µM or 1 µM) did not affect the cell viability. After TET pretreatment, the levels of IL1β and TNFα (both in transcription and translation) were significantly inhibited in a dose-dependent manner. Further studies indicated that phospho-p65, phospho-IKK, and phospho-ERK 1/2 expression were also suppressed by TET.

Conclusions

Our results indicate that TET can effectively suppress microglial activation and inhibit the production of IL1β and TNFα by regulating the NF-kB and ERK signaling pathways. Together with our previous studies, we suggest that TET would be a promising candidate to effectively suppress overactivated microglia and alleviate neurodegeneration in glaucoma.

Antitumor activity of thaliblastine (NSC-68075) in experimental ovarian tumor cell lines sensitive and resistant to cisplatin

Cytotoxicity of thaliblastine (thalicarpine, TBL; NSC-68075) and/or cisplatin (DDP) in DDP-sensitive (O-342) and-resistant (O-342/DDP) rat ovarian tumor cell lines was comparatively determined using the MTT assay. The 50% inhibitory dose (ID50) of DDP was found to be 6.2 microM in O-342 cells and 23.4 microM in O-342/DDP cells, while, vice versa, the ID50 of TBL was 39.3 micrograms/ml in the sensitive line and 27.3 micrograms/ml in the resistant line. Furthermore, simultaneous exposure of cells to DDP and TBL showed a significant superiority over DDP alone in O-342 cells, as evaluated with variance analysis (P less than 0.001). This enhancing effect of TBL on DDP cytotoxicity, however, was not observed in the resistant cells.

The potentiating action of tetrandrine in combination with chloroquine or qinghaosu against chloroquine-sensitive and resistant falciparum malaria

Using chloroquine-sensitive (CS) and chloroquine-resistant (CR) strains of Plasmodium falciparum in vitro, interactions between tetrandrine (TT) and either chloroquine (CQ) or qinghaosu (QHS, artemisinin) were assessed using isobolograms. Sums of the fractional inhibitory concentration for the combination of the two drugs are less than one and therefore, we can conclude that in vitro TT and CQ or QHS act synergistically against CS and CR falciparum malaria. Remarkably, using CR malaria, TT can lower the IC50 dose of CQ as much as 40 fold. These drug combinations may impair the advantage that the development of CQ resistance conveys on the parasite.

Effect of tetrandrine on micronucleus formation and sister-chromatid exchange in both in vitro and in vivo assays

The genotoxicity of tetrandrine, a drug potentially useful for the treatment of silicosis, was studied using the micronucleus and the sister-chromatid exchange (SCE) assay systems. Cultured Chinese hamster lung (V79) cells were used for the in vitro micronucleus and sister-chromatid exchange studies. Mouse bone marrow was used for the in vivo micronucleus assay and mouse spleen cells for the in vivo/in vitro sister-chromatid exchange analysis. The results show that SCE levels in V79 and in spleen cells were significantly elevated by treatment with tetrandrine at doses above 0.08 mg/ml and 100 mg/kg bw, respectively. Increased tetradrine-induced SCE in vitro was metabolic activation dependent. Tetrandrine failed to induce micronuclei at any of the doses tested. A decrease of replicative index with an increase in the concentration of tetrandrine was found both in vitro and in vivo. These results indicate that tetrandrine is a weak indirect-acting genotoxicant.

Studies of the chronic toxicity of tetrandrine in dogs: an inhibitor of silicosis

Dogs administered tetrandrine at low dose (3 mg/kg) and medium dose (10 mg/kg) levels showed no toxic changes. Administration of the drug at a high dose level (40 mg/kg) for 2 months may induce focal necrosis of liver cells, abnormal liver function, and acceleration of erythrocyte sedimentation rate. After the dogs had received tetrandrine for 6 months continuously, necrosis of liver tissue appeared. After continuous administration of tetrandrine, accumulation of the drug in liver, lung, kidney, and adrenal gland was observed. The amount of drug stored in the organs increased with the quantity of drug given to the animal.

Antitumor antibiotic bioactivation, biotransformation and derivatization by microbial systems

Microbial transformations refer to reactions catalyzed by microbial enzymes, especially when specific and useful metabolites accumulate in fermentation media. These transformations have tremendous potential for use in the development of new antitumor drugs and these can also be used as models of mammalial metabolism. Microbial transformation experiments with antibiotics such as bleomycin, anthracyclines and with a variety of plant products are described.