Primary mitochondrial activity of gossypol in yeast and mammalian cells

Gossypol Inhibits Electron Transport and Stimulates ROS Generation in Yarrowia lipolytica Mitochondria

This work studied the effect of gossypol on the mitochondrial respiratory chain of Yarrowia lipolytica. The compound was shown to inhibit mitochondrial electron transfer and stimulate generation of reactive oxygen species. The inhibition kinetics in oxidation of various substrates (NADH, succinate, α-glycerophosphate and pyruvate + malate) by isolated mitochondria was investigated. Analysis of the kinetic parameters showed gossypol to inhibit two fragments of the mitochondrial electron transfer chain: a) between coenzyme Q and cytochrome b with K(IIIi) of 118.3 μM (inhibition by the noncompetitive type), and b) at the level of exogenous NADH dehydrogenase with of K(Ii) 17.2 μM (inhibition by the mixed type).

Erwinia chrysanthemi tolC is involved in resistance to antimicrobial plant chemicals and is essential for phytopathogenesis

TolC is the outer-membrane component of several multidrug resistance (MDR) efflux pumps and plays an important role in the survival and virulence of many gram-negative bacterial animal pathogens. We have identified and characterized the outer-membrane protein-encoding gene tolC in the bacterial plant pathogen Erwinia chrysanthemi EC16. The gene was found to encode a 51-kDa protein with 70% identity to its Escherichia coli homologue. The E. chrysanthemi gene was able to functionally complement the E. coli tolC gene with respect to its role in MDR efflux pumps. A tolC mutant of E. chrysanthemi was found to be extremely sensitive to antimicrobial agents, including several plant-derived chemicals. This mutant was unable to grow in planta and its ability to cause plant tissue maceration was severely compromised. The tolC mutant was shown to be defective in the efflux of berberine, a model antimicrobial plant chemical. These results suggest that by conferring resistance to the antimicrobial compounds produced by plants, the E. chrysanthemi tolC plays an important role in the survival and colonization of the pathogen in plant tissue.

Gossypol inhibition of mitosis, cyclin D1 and Rb protein in human mammary cancer cells and cyclin-D1 transfected human fibrosarcoma cells

The antiproliferative effects of gossypol on human MCF-7 mammary cancer cells and cyclin D1-transfected HT-1060 human fibrosarcoma cells were investigated by cell cycle analysis and effects on the cell cycle regulatory proteins Rb and cyclin D1. Flow cytometry of MCF-7 cells at 24 h indicated that 10 microM gossypol inhibited DNA synthesis by producing a G1/S block. Western blot analysis using anti-human Rb antibodies and anti-human cyclin D1 antibodies in MCF-7 cells and high- and low-expression cyclin D1-transfected fibrosarcoma cells indicated that, after 6 h exposure, gossypol decreased the expression levels of these proteins in a dose-dependent manner. Gossypol also decreased the ratio of phosphorylated to unphosphorylated Rb protein in human mammary cancer and fibrosarcoma cell lines. Gossypol (10 microM) treated also decreased cyclin D1-associated kinase activity on histone H1 used as a substrate in MCF-7 cells. These results suggest that gossypol might suppress growth by modulating the expression of cell cycle regulatory proteins Rb and cyclin D1 and the phosphorylation of Rb protein.

Induction of neutrophil Mac-1 integrin expression and superoxide production by the medicinal plant extract gossypol

Gossypol is present in antiinflammatory poultices made from the medicinal tree Thespesia populnea. Isolated human neutrophils exposed to 3-20 microM gossypol for 15-90 min were assayed in vitro for superoxide production and surface expression of Mac-1 (CD11b/CD18). Gossypol increased superoxide production in a time- and concentration-dependent fashion consistent with a moderate, delayed respiratory burst. Surface Mac-1 expression was increased within 15 min by 3-5 microM gossypol, resulting in a 14-fold increase over controls and a threefold greater increase over that produced by PMA. Staurosporine failed to block gossypol induction of superoxide and Mac-1, while EDTA inhibited induction of Mac-1 only, implicating a calcium-dependent mechanism. Gossypol increased intracellular calcium to peak levels, but in a delayed fashion as compared to FMLP. These findings demonstrate that gossypol is a highly potent stimulant of Mac-1 expression and suggest at least two protein kinase C-independent pathways of neutrophil activation. The resultant exhaustion of neutrophils may account for the antiinflammatory properties of plants containing gossypol.

Selective alteration of mitochondrial function by Ditercalinium (NSC 335153), a DNA bisintercalating agent

The bifunctional intercalator Ditercalinium (NSC 335153) demonstrates an anti-tumoral cytotoxicity markedly different from other intercalating agents. A delayed toxicity is observed in eucaryotic cells, both in vitro and in vivo, at drug concentrations far below those required to observe immediate toxic effects. Fluorescence microscopy demonstrates that Ditercalinium and the mitochondrial-staining fluorophore DiOC2(5) are concentrated in the same cellular organelles of L1210 cells. Electron microscopy of Ditercalinium-treated cells reveals extensive and progressive swelling of mitochondria, with no other ultrastructural changes observed. Ditercalinium uptake and toxicity are in part related to mitochondrial membrane potential. However, drug accumulation itself does not immediately alter the mitochondrial membrane potential. Cellular ATP pool levels and the rate of respiration fall progressively after drug treatment. Nucleotide pools in DC3F cells, measured between drug treatment and death, show marked drops in pyrimidine levels while purine nucleotide levels decline more slowly. Addition of uridine or cytidine partially rescues Ditercalinium-treated cells, while toxicity is increased in the presence of 2-deoxyglucose. The combined evidence indicates that the toxicity of Ditercalinium to murine leukemia cells (L1210) and Chinese Hamster lung cells (DC3F) is due to disruption of mitochondrial function.