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Background: Solamargine (SM), a steroidal glycoalkaloid isolated from the Chinese herb Solanum incanum, has been shown to inhibit the growth of some cancer cell lines and induce significant apoptosis. However, the effects of SM on multidrug-resistant (MDR) cells and the molecular mechanisms involved are poorly understood. The purpose of this study was to evaluate the anti-MDR effects of SM and the associated mechanisms in MDR K562/A02 cells., Methods: The cytotoxicity of SM was measured by 3-(4,5-dimethylthiazol)-2,5-diphenyltetrazolium bromide (MTT) assay. The 14',6-diamidino-2-phenylindole (DAPI) nuclear staining and flow cytometry were used to detect SM-induced apoptosis. The mRNA expression of P-glycoprotein (P-gp) was investigated by real-time PCR (RT-PCR). Western blotting was used to determine the expression of Bcl-2, Bax, and actin. The changes in the morphology of actin were examined with immunofluorescence staining., Results: MTT results showed that SM effectively killed the MDR sublines K562/A02, KB/VCR, and H460/paclitaxel (Taxol), and their parental cell lines K562, KB, and H460 to an equivalent or more sensitive degree. Based on the results by flow cytometry and immunostaining, the pro-apoptotic effects of SM were observed in MDR K562/A02 cells. Furthermore, the RT-PCR results showed that SM induced the downregulation of MDR1 mRNA. In addition, the expression of P-gp and actin was decreased in the SM-treated cells, as measured by western blotting and immunostaining., Conclusions: These results demonstrate that SM effectively triggers apoptosis in MDR tumor cells, which is associated with actin disruption and downregulation of MDR1 expression. This compound may merit further investigation as a potential therapeutic agent that bypasses the MDR mechanism for the treatment of MDR tumors.

Objective: To study the effect of anisodamine on neuronal death and hydroxyl radical (OH.) production during forebrain ischemia-reperfusion in gerbils., Methods: The tested gerbils were divided into 3 groups, including sham-operated, control and anisodamine groups. In each group, there were 8 animals for biochemical examination and 6 animals for histologic study. Forebrain ischemia was induced by occlusion the bilateral common carotid arteries for 10 min in gerbils. 2, 3- and 2, 5-DHBA outputs were determined by high performance liquid chromatography coupled with electrochemical detection. Behavioral change was tested by open field test and neuronal death was assessed by histological examination., Results: The exploratory activities of gerbils in the control group were significantly higher than those in the anisodamine group on all test days. The amount of viable-looking neurons in the medial, middle and lateral CA1 sectors in anisodamine group were 41% +/- 12%, 50% +/- 21% and 67% +/- 15% of the sham-operated gerbils, respectively, being significantly higher than those in the control group (3% +/- 2%, 4% +/- 3% and 7% +/- 4% of sham, P < 0.01). The 2, 3-DHBA outputs in the control group increased by 5 fold of the sham-operated gerbils after reperfusion for 60 min, but the 2, 3-DHBA outputs in the anisodamine group were only 2.4 fold of sham-operated gerbils, being significantly lower than that in the control group (P < 0.01). The 2, 5-DHBA outputs in the control group were significantly higher than those in the sham-operated group (P < 0.05)., Conclusion: Anisodamine has inhibitory effects on neuronal death and OH.production during cerebral ischemia-reperfusion in gerbils.

The present study was designed to examine the effect of higher concentration of anisodamine on alpha-adrenergic responses in isolated canine blood vessels. Up to 10(-3) mol/L, anisodamine did not significantly affect the responses of saphenous vein to alpha 2-adrenergic agonist UK-14, 304. In contrast, anisodamine (10(-5), 10(-4), 10(-3) mol/L) caused the concentration-response curves of femoral artery to norepinephrine (pA2 = 4.81 +/- 0.11) to phenylephrine (pA2 = 4.86 +/- 0.20) shift markedly. However, the antagonism on the alpha 1-adrenergic responses of canine femoral artery to norepinephrine and phenylephrine by higher concentrations of anisodamine produces dose ratios which yield a linear Schild regression with a slope less than unity, indicating an inequilibrium between agonist, antagonist, and receptors. The probable mechanisms involved are discussed.

Anisodamine was used as an antishock (chiefly septic) drug beginning in the early 1960s in China. Its underlining mechanism was believed to be due to its vasodilative action. But in normal animals it only produces slight vasodilation. Our work during the recent 15 years proved that anisodamine is not only beneficial in the treatment for septic shock, but also for hemorrhagic, traumatic, and SMAO shock, and its mechanism of action are based on its following biological actions: (1) it has membrane stabilization and cell protection action, which was probably related to its calcium antagonist action; (2) it protects ischemia intestine from releasing shock factors; and (3) its inhibition of endotoxin binding to cells and tissue at the membrane level probably makes it an special antishock drug for septic shock.

The effects of anisodamine on acetylcholine-induced endothelium-dependent relaxation were studied in organ chambers and under bioassay conditions. In organ chamber experiments, both acetylcholine and bradykinin induced an endothelium-dependent relaxation of norepinephrine-contracted canine femoral arteries in a concentration-dependent manner; the relaxation induced by acetylcholine, but not that by bradykinin, was inhibited by anisodamine or atropine in a concentration-dependent manner. In bioassay experiments, a denuded ring of left circumflex coronary artery was superfused with perfusate passed through segment of femoral artery with endothelium or a direct superfusion line. Acetylcholine induced the release of relaxing factor(s) from the segment with endothelium causing a relaxation of bioassay ring and the relaxation was eliminated by anisodamine infused into the perfusion line above, but not below, the perfused segment. The results suggest that anisodamine, like atropine, is able to inhibit acetylcholine-induced endothelium-dependent relaxation by blocking endothelial muscarinic receptors which activate the release of endothelium-derived relaxing factor(s).

Organ chamber experiments were designed to determine the effects of anisodamine, an alkaloid structurally related to atropine, on prejunctional M2- and postjunctional M2-muscarinic receptors in isolated canine saphenous veins. The results showed that both acetylcholine-induced contraction and dilatation were inhibited in a competitive manner by anisodamine or atropine. The affinity of anisodamine for pre- and postjunctional muscarinic receptors was comparable (pKB = 7.78 and 7.86, respectively). However, compared with atropine, the affinity of anisodamine for prejunctional M2-receptors was about 1/8; while that for postjunctional M1-receptors was only 1/25 of that of atropine (pKB = 8.69 and 9.25, respectively for atropine). The data demonstrate that anisodamine is a non-selective muscarinic antagonist, a modulator rather than a vasodilator. The probable mechanisms involved are discussed.

In this study, we observed the endotoxin induced platelet aggregation, 5-HT and beta-g releases, cellular cAMP decrease, and also the changes of morphology and membrane fluidity of platelet. These changes play an important role in septic shock, especially in disseminated intravascular coagulation (DIC) and respiratory distress syndrome (RDS). After anisodamine (654) intervention all the parameters mentioned above were improved to a certain extent. This preliminary study of the inhibiting mechanism of 654 on rabbit platelets activated by ET supports the clinical possibility of using 654 for relieving DIC and RDS.