Retinoic acid and calcitriol inhibition of growth and NADH oxidase of normal and immortalized human keratinocytes

Adriamycin tolerance in human mesothelioma lines and cell surface NADH oxidase

Adriamycin tolerant human mesothelioma cell lines derived from a single tumor prior to either chemotherapy or radiation therapy and a susceptible cell line were investigated. Not only was growth resistant to low doses of adriamycin but an unusual pattern of resistance was encountered in which cells seemed to better tolerate high adriamycin doses than intermediate doses. The differential growth susceptibility of the tolerant lines compared to A549 lung carcinoma and the bimodal dose response correlated with differences in the specific activity of a plasma membrane-associated NADH oxidase (NOX). Plasma membrane fractions of high purity were isolated by aqueous two-phase partition and assayed directly. The NADH oxidase activity of the plasma membranes for the susceptible cell line was maximally inhibited by 1 microM adriamycin whereas the NADH oxidase activity of the tolerant lines was less and was maximally inhibited by 0.1 microM adriamycin with 1 and 10 microM adriamycin being less inhibitory than 0.1 microM adriamycin. The findings suggest a relationship between the growth response to adriamycin of the adriamycin tolerant mesothelioma lines and the activity of the plasma membrane-associated NADH oxidase activity of the cell surface in these cell lines.

Preferential inhibition by (-)-epigallocatechin-3-gallate of the cell surface NADH oxidase and growth of transformed cells in culture

A drug-responsive and cancer-specific NADH oxidase of the mammalian plasma membrane, constitutively activated in transformed cells, was inhibited preferentially in HeLa and human mammary adenocarcinoma by the naturally-occurring catechin of green tea, (-)-epigallocatechin-3-gallate (EGCg). With cells in culture, EGCg preferentially inhibited growth of HeLa and mammary adenocarcinoma cells compared with growth of mammary epithelial cells. Inhibited cells became smaller, and cell death was accompanied by a condensed and fragmented appearance of the nuclear DNA as revealed by fluorescence microscopy with 4',6-diamidino-2-phenylindole, suggestive of apoptosis. Mammary epithelial cells recovered from EGCg treatment even at 50 microM, whereas growth of HeLa and mammary adenocarcinoma cells was inhibited by EGCg at concentrations as low as 1 microM with repeated twice-daily additions and did not recover from treatment with 50 microM EGCg. The findings correlate inhibition of cell surface NADH oxidase activity and inhibition of growth with EGCg-induced apoptosis.

Cell membrane redox systems and transformation

Cell membrane redox systems carry electrons from intracellular donors and transport them to extracellular acceptors. This phenomenon appears to be universal. Numerous reviews have emphasized not only the bioenergetic mechanisms of redox systems but also the antioxidant defense mechanisms in which they participate. Moreover, significant progress has been made in the modulation of the membrane redox systems on cell proliferation. Because membrane redox systems play a key role in the regulation of cell growth, they need to be somehow linked into the signaling pathways resulting in either controlled or unregulated growth by both internal and external signals. Ultimately, these sequential events lead to either normal cell proliferation or cancer cell formation. However, much less is known about the involvement of membrane redox in transformation or tumorgenesis. In this review, the facts and ideas are summarized concerning the redox systems and tumorgenesis in several aspects, such as the regulation of cell growth and the effect on cell differentiation and on signaling pathways. In addition, information on a unique tumor-associated nicotinamide adenine dinucleotide (NADH) oxidase (tNOX) protein is reviewed.

NADH oxidase activity of soybean plasma membranes inhibited by submicromolar concentrations of ATP

The activity of an auxin-stimulated NADH oxidase activity from soybean hypocotyls was inhibited by submicromolar concentrations of ATP. Auxins are plant growth regulators that increase the rate of cell enlargement in plant stems. A synthetic auxin, 2,4-dichlorophenoxyacetic acid (2,4-D), was used. The inhibition was half maximal at 1 nM ATP and was not observed with other nucleotides and nucleosides. The inhibition was the result of an increase in the Km for NADH from about 60 microM to > 100 microM and was noncompetitive. The decrease in Km due to ATP was enhanced by the addition of 1 microM 2,4-D. The Vmax of the plasma membrane NADH oxidase was approximately doubled (1.5-2.8-fold) by ATP and by 1 microM 2,4-D. No further increase in the Vmax was observed by the combination of 1 nM to 0.1 mM ATP in the presence of 1 microM 2,4-D. The results demonstrate a response of the NADH oxidase activity of isolated vesicles of soybean plasma membranes to ATP distinct from that observed previously with other nucleotide di- and triphosphates. The results are suggestive either of control of the cell surface NADH oxidase by phosphorylation or a direct response to ATP binding at nanomolar concentrations of ATP.

Redox modulation of the response of NADH oxidase activity of rat liver plasma membranes to cyclic AMP plus ATP

NADH oxidase activity of rat liver plasma membranes was inhibited by low concentrations (1-100 nM) of ATP. The inhibition was amplified by addition of nanomolar concentrations (0.1-10) of cyclic AMP. The inhibition was complex and related to a marked increase in the Km for NADH at high NADH concentrations together with a concomitant decrease in the Vmax. In the absence of added or residual ATP, cyclic AMP was without effect. The response of cyclic AMP + ATP was inhibited by low concentrations of the selective inhibitor of cyclic AMP-dependent protein kinase, H-89 but not by staurosporin. The Vmax but not the Km was modified by treating the plasma membranes with a mild oxidizing agent, N-chlorosuccinamide, or with the reducing agent, dithiothreitol. In the presence of dithiothreitol, the Vmax was reduced by cyclic AMP + ATP. In contrast, in the presence of N-chlorosuccinamide, the Vmax was increased by cyclic AMP + ATP relative to cyclic AMP + ATP alone. Thus, the effect of cyclic AMP + ATP on the Vmax could be either an increase or a decrease depending on whether the membranes were oxidized or reduced. The results demonstrate regulation of NADH oxidase activity of rat liver plasma membranes through cyclic AMP-mediated phosphorylation by membrane-located protein kinase activities where the final response is dependent on the oxidation-reduction status of the plasma membranes.

Inhibition of plasma membrane NADH oxidase activity and growth of HeLa cells by natural and synthetic retinoids

Several retinoids, both natural and synthetic, were evaluated for their ability to modulate NADH oxidase activity of plasma membranes of cultured HeLa cells and the growth of HeLa cells in culture. Both NADH oxidase activity and the growth of cells were inhibited by the naturally-occurring retinoids all trans-retinoic acid (tretinoin) and retinol as well as by the synthetic retinoids, trans-acitretin, 13-cis-acitretin, etretinate and arotonoid ethylester (Ro 13-6298). For all retinoids tested, inhibition of NADH oxidase activity and inhibition of growth were correlated closely. With tretinoin, etretinate and arotonoid ethylester, NADH oxidase activity and cell growth were inhibited in parallel in proportion to the logarithm of retinoid concentration over the range of concentrations 10(-8) to 10(-5) M. Approximately 70% inhibition of both NADH oxidase activity and growth was reached at 10 microM. With retinol, trans-acitretin and 13-cis-acitretin, inhibition of NADH oxidase activity and growth also were correlated but maximum inhibition of both was about 40% at 10 microM. The possibility is suggested that inhibition of the plasma membrane NADH oxidase activity by retinoids may be related to their mechanism of inhibition of growth of HeLa cells in culture.

Capsaicin inhibits plasma membrane NADH oxidase and growth of human and mouse melanoma lines

Hormone- and growth factor-stimulated NADH oxidase of the mammalian plasma membrane is thought to be involved in the control of normal cell proliferation. The aim of this study was to determine the effect of the naturally occurring quinone analogue capsaicin (8-methyl-N-vanillyl-6-noneamide) on the NADH oxidase activity of plasma membranes and cell growth of human primary melanocytes, the A-375 and SK-MEL-28 human melanoma cell cultures. NADH oxidase activity was inhibited preferentially in the A-375 melanoma cells but not in the primary melanocytes, by capsaicin. Inhibition of growth and the NADH oxidase by capsaicin could be induced in resistant SK-MEL-28 melanoma cells by co-administration of capsaicin with t-butyl hydroperoxide, a mild oxidising agent. Death of the inhibited cells was accompanied by nuclear changes suggestive of apoptosis. With B16 mouse melanoma, capsaicin inhibited both the NADH oxidase activity and growth in culture. Growth of B16 melanoma, transplanted in C57BL/6 mice, was significantly inhibited by capsaicin injected directly into the tumour site when co-administered with t-butyl hydroperoxide. The findings correlate the inhibition of cell surface NADH oxidase activity with inhibition of growth and capsaicin-induced apoptosis, and also suggest that the extent of inhibition may relate to the oxidation state of the plasma membrane.

The plasma membrane NADH-diaphorase is active during selective phases of the cell cycle in mouse neuroblastoma cell line NB41A3. Its relation to cell growth and differentiation

Plasma membrane oxidoreductases have been described in all cells and use extracellular impermeant electron acceptors (DCIP, Ferricyanide) that are reduced by NADH. They appear to regulate the overall cell activity in response to oxidative stress from the cellular environment. An NADH-DCIP reductase has been described at the plasma membrane of NB41A3, a neuroblastoma cell line (Zurbriggen and Dryer (1993) Biochim. Biophys. Acta 1183, 513-520) whose activation with extracellular impermeant substrates promotes cell growth. Elutriation was performed to separate cells and the various fractions were analysed for enzyme activity on intact cells combined with flow cytometry. These studies showed that the enzyme is mostly induced and activated during the G1 and during the G2/M-phases. These observations were further corroborated with specific inhibitors of the cell cycle. A three-fold increase in enzyme activity was observed in the presence of alpha-amanitin, a specific cell cycle inhibitor of the G1-phase. Taxol, a specific inhibitor of the M-phase, also induces a significant increase in enzyme activity. FACS analysis of taxol -treated and alpha-amanitin-treated cells corroborated these data. The cells have been synchronized and the enzyme activity was measured at different time intervals. An activity increase was observed after ca. 2-3 h, that corresponds to a raise in the M-phase, according to FACS data. Furthermore, NTera-2 cells - a human neuroblastoma cell line that differentiates into fully mature neurones in the presence of retinoic acid - exhibit a 50% decrease in the enzyme activity during the G0-phase upon differentiation, compared to undifferentiated cells. Together the data presented in this paper show that this plasma membrane NADH-diaphorase affects cell growth and differentiation and is strongly modulated at various phases of the cell cycle.

Capsaicin inhibits preferentially the NADH oxidase and growth of transformed cells in culture

A hormone- and growth factor-stimulated NADH oxidase of the mammalian plasma membrane, constitutively activated in transformed cells, was inhibited preferentially in HeLa, ovarian carcinoma, mammary adenocarcinoma, and HL-60 cells, all of human origin, by the naturally occurring quinone analog capsaicin (8-methyl-N-vanillyl-6-noneamide), compared with plasma membranes from human mammary epithelial, rat liver, normal rat kidney cells, or HL-60 cells induced to differentiate with dimethyl sulfoxide. With cells in culture, capsaicin preferentially inhibited growth of HeLa, ovarian carcinoma, mammary adenocarcinoma, and HL-60 cells but was largely without effect on the mammary epithelial cells, rat kidney cells, or HL-60 cells induced to differentiate with dimethyl sulfoxide. Inhibited cells became smaller and cell death was accompanied by a condensed and fragmented appearance of the nuclear DNA, as revealed by fluorescence microscopy with 4',6-diamidino-2-phenylindole, suggestive of apoptosis. The findings correlate capsaicin inhibition of cell surface NADH oxidase activity and inhibition of growth that correlate with capsaicin-induced apoptosis.

Differential response of the NADH oxidase of plasma membranes of rat liver and hepatoma and HeLa cells to thiol reagents

NADH oxidase activity of plasma membranes from rat hepatoma and HeLa cells responded to thiol reagents in a manner different from that of plasma membranes of liver. Specifically, the NADH oxidase activity of plasma membranes of HeLa cells was inhibited by submicromolar concentrations of the thiol reagents p-chloromercuribenzoate (PCMB), N-ethylmaleimide (NEM), or 5,5'-dithiobis-(2-nitrophenylbenzoic acid) (DTNB), whereas that of the rat liver plasma membranes was unaffected or stimulated over a wide range of concentrations extending into the millimolar range. With some hepatoma preparations, the NADH oxidase activity of hepatoma plasma membranes was stimulated rather than inhibited by PCMB, whereas with all preparations of hepatoma plasma membranes, NEM and DTNB stimulated the activity. In contrast, NADH oxidase activity of rat liver plasma membrane was largely unaffected over the same range of PCMB concentrations that either stimulated or inhibited with rat hepatoma or HeLa cell plasma membranes. Dithiothreitol and glutathione stimulated NADH oxidase activity of plasma membranes of rat liver and hepatoma but inhibited that of HeLa plasma membranes. The findings demonstrate a difference between the NADH oxidase activity of normal rat liver plasma membranes of rat hepatoma and HeLa cell plasma membranes in addition to the differential response to growth factors and hormones reported previously (Bruno et al., 1992). Results are consistent with a structural modification of a NADH oxidase activity involving thiol groups present in plasma membranes of rat hepatoma and HeLa cells but absent or inaccessible with plasma membranes of rat liver.

Cyclic AMP-plus ATP-dependent modulation of the NADH oxidase activity of porcine liver plasma membranes

Plasma membranes of porcine liver, highly purified by aqueous two-phase partition, oxidized NADH in the absence of added external acceptors. The oxidation was resistant to cyanide and responded to nanomolar concentrations of ATP alone or ATP in the presence of cyclic AMP. Both the Km for NADH and the long-term activity of the oxidase were affected. Upon incubation at 37 degrees C with cyclic AMP (0.1-10 nM) and ATP (1-100 nM), the NADH oxidase activity was inhibited. The inhibition was complex and due to an approx. 5-fold increase in the Km for NADH compared to the NADH oxidase of membranes incubated in the absence of cyclic AMP + ATP. The response to cAMP + ATP was rapid and occurred within seconds of ATP addition. The response was inhibited by the selective inhibitor of cyclic AMP-dependent protein kinase, H-89. Neither cyclic AMP alone nor ATP alone at nanomolar concentrations elicited a rapid response. However, 10 nM ATP alone did result in similar alteration of Km and Vmax as did ATP + 0.1 nM cyclic AMP. The response to ATP alone or in preparations depleted of cyclic AMP required higher ATP concentrations than with cAMP present or occurred more slowly with a lag of 1-2 min. The NADH oxidase activity of porcine plasma membranes after cyclic AMP + ATP treatment retained high activity with storage at 4 degrees C, whereas that of unincubated or sham-incubated plasma membranes was reduced with time of storage at 4 degrees C. In some but not all instances, NADH oxidase activity inactivated by incubation with NADH at 37 degrees C or after storage at 4 degrees C could be reactivated by incubation with cyclic AMP plus ATP. As with the alteration in Km, cyclic AMP alone was without effect and ATP alone was much less effective than the combination. The results demonstrate ATP-dependent modulation of the NADH oxidase activity of isolated plasma membranes at physiological concentrations of ATP. This modulation may have functional significance in mediating the hormone and growth factor responsiveness of the plasma membrane NADH oxidase activity.

Mode of action of bullatacin, a potent antitumor acetogenin: inhibition of NADH oxidase activity of HeLa and HL-60, but not liver, plasma membranes

Bullatacin, a potential antitumor substance isolated from plants of the Annonaceae, and analogs of bullatacin, known collectively as acetogenins, have been reported previously to show potent activity in the inhibition of growth of murine tumors and human tumor xenografts grown in athymic mice as well as an ability to inhibit mitochondrial electron transport. In this report, we show activity of bullatacin in inhibition of NADH oxidase activity of plasma membrane vesicles isolated from HeLa cells and HL-60 cells but not with plasma membrane vesicles isolated from rat livers which, unlike the inhibition of mitochondrial activity, correlated with the ability of the acetogenins to kill tumor cells. Additionally, bullatacin is active against HL-60 cells that are resistant to adriamycin which may suggest utility for bullatacin in management of drug-resistant cells and cell lines.

Hormone- and growth factor-stimulated NADH oxidase

An NADH oxidase activity of animal and plant plasma membrane is described that is stimulated by hormones and growth factors. In plasma membranes of cancer cells and tissues, the activity appears to be constitutively activated and no longer hormone responsive. With drugs that inhibit the activity, cells are unable to grow although growth inhibition may be more related to a failure of the cells to enlarge than to a direct inhibition of mitosis. The hormone-stimulated activity in plasma membranes of plants and the constitutively activated NADH oxidase in tumor cell plasma membranes is inhibited by thiol reagents whereas the basal activity is not. These findings point to a thiol involvement in the action of the activated form of the oxidase. NADH oxidase oxidation by Golgi apparatus of rat liver is inhibited by brefeldin A plus GDP. Brefeldin A is a macrolide antibiotic inhibitor of membrane trafficking. A model is presented where the NADH oxidase functions as a thiol-disulfide oxidoreductase activity involved in the formation and breakage of disulfide bonds. The thiol-disulfide interchange is postulated as being associated with physical membrane displacement as encountered in cell enlargement or in vesicle budding. The model, although speculative, does provide a basis for further experimentation to probe a potential function for this enzyme system which, under certain conditions, exhibits a hormone- and growth factor-stimulated oxidation of NADH.

Angiotensin II stimulates NADH and NADPH oxidase activity in cultured vascular smooth muscle cells

The signaling pathways involved in the long-term metabolic effects of angiotensin II (Ang II) in vascular smooth muscle cells are incompletely understood but include the generation of molecules likely to affect oxidase activity. We examined the ability of Ang II to stimulate superoxide anion formation and investigated the identity of the oxidases responsible for its production. Treatment of vascular smooth muscle cells with Ang II for 4 to 6 hours caused a 2.7 +/- 0.4-fold increase in intracellular superoxide anion formation as detected by lucigenin assay. This superoxide appeared to result from activation of both the NADPH and NADH oxidases. NADPH oxidase activity increased from 3.23 +/- 0.61 to 11.80 +/- 1.72 nmol O2-/min per milligram protein after 4 hours of Ang II, whereas NADH oxidase activity increased from 16.76 +/- 2.13 to 45.00 +/- 4.57 nmol O2-/min per milligram protein. The NADPH oxidase activity was stimulated by exogenous phosphatidic and arachidonic acids and was partially inhibited by the specific inhibitor diphenylene iodinium. NADH oxidase activity was increased by arachidonic and linoleic acids, was insensitive to exogenous phosphatidic acid, and was inhibited by high concentrations of quinacrine. Both of these oxidases appear to reside in the plasma membrane, on the basis of migration of the activity after cellular fractionation and their apparent insensitivity to the mitochondrial poison KCN. These observations suggest that Ang II specifically activates enzyme systems that promote superoxide generation and raise the possibility that these pathways function as second messengers for long-term responses, such as hypertrophy or hyperplasia.