Effect of soya bean saponins on azoxymethane-induced preneoplastic lesions in the colon of mice.

The effect of saponins isolated from soya bean flour on the incidence of aberrant crypt foci (ACF) induced by azoxymethane (AOM) in the colonic wall of CF1 mice was investigated. Four weekly injections of AOM, a known colon carcinogen, were administered to mice. One week after the last injection, mice were placed on an AIN-76 diet supplemented with 3% soya bean saponins or continued on the basal AIN-76 diet. Another group of mice was placed on the saponin diet without AOM initiation to observe the effect of saponins on the growth characteristics of mice. Dietary intake of soya saponins significantly reduced the incidence of ACF at the end of 14 weeks (postinitiation). Noninitiated mice maintained on a similar soya bean saponin-supplemented diet did not show any adverse effects on the growth and overall health of the animals. These findings suggest that soya bean saponins can play an important role in inhibiting the incidence of ACF in the colon of mice.

Suppression of human T-cell growth in vitro by cis-unsaturated fatty acids: relationship to free radicals and lipid peroxidation.

Cis-unsaturated fatty acids such as dihomogamma-linolenic acid (DGLA), arachidonic acid (AA) and eicosapentaenoic acid (EPA), which form precursors to 1, 2 and 3 series prostaglandins (PGs), have been shown to suppress human T-cell growth in vitro by a prostaglandin E (PGE)-independent mechanism. In an earlier study, we showed that these fatty acids can induce free radical generation in human neutrophils and tumor cells. Here we show that cis-unsaturated fatty acids augment free radical generation and lipid peroxidation in human T-cells. The growth suppressive action of cis-unsaturated fatty acids on human T-cells could be blocked by anti-oxidant, vitamin E and the superoxide anion quencher superoxide dismutase. These results suggest that c-UFAs-induced cell growth suppression is a free radical dependent process.

Prostacyclin is a potent anti-mutagen.

Prostacyclin (PGI2) prevented genetic damage to the bone marrow cells of mice induced by gamma-radiation, benzo(a)pyrene(BP) and cis-platinum(cis-DDP). Carba-PGI2, an analogue of PGI2, was also effective against cis-DDP-induced mutagenicity. In a time-course study it was observed that the geno-protective action of PGI2, can last as long as 24 hr. 6-keto-PGF1 alpha, a major metabolite of PGI2 and c-AMP, a second messenger, were ineffective in bringing about this beneficial action. PGI2 did not influence free radical generation induced by phorbol myristate acetate in human peripheral leukocytes. This suggests that the genoprotective action of PGI2 is not mediated by its metabolite 6-keto-PGF1 alpha and the second messenger cyclic-AMP and is not due to any action on free radical generation. This geno-protective action of PGI2 would be futile if it interfered with the tumoricidal action of cis-DDP. It was observed that the cytotoxic action of cis-DDP against Meth-A tumor cells was not interfered with by PGI2 and carba-PGI2 both in vitro and in vivo. This description of the geno-protective action of PGI2 is important in the development of new strategies in cancer chemotherapy since, it is likely that anticancer drugs, at least cis-DDP can be given along with PGI2 to prevent genetic damage to normal cells without interfering with their tumoricidal action.

Effect of essential fatty acids on tumor cells.

An earlier study showed that essential fatty acids and their metabolites can kill tumor cells in vitro. This tumoricidal action can be correlated to an increase in generation of free radicals in the tumor cells. Evening primrose oil (EPO) is a rich source of linoleic acid and gamma-linolenic acid. We report that EPO can kill tumor cells both in vitro and in vivo. This tumoricidal action of EPO was associated with a threefold increase in superoxide generation. One of the factors that is capable of interfering with the cytotoxic action of fatty acids appears to be the protein content of the medium. Fatty acids can bind to protein and thus prevent their cytotoxic action.

Psoriasis: current concepts and new approaches to therapy.

Psoriasis is a common disorder characterized by marked increases in keratinocyte proliferation, abnormal patterns of keratinocyte differentiation, prominent alterations in dermal capillary vasculature and the presence of dermal and epidermal T cells, monocytes/macrophages and neutrophils. It is now known that psoriasis can occur due to abnormalities in essential fatty acid metabolism, lymphokine secretion, free radical generation, lipid peroxidation and eicosanoid metabolism. It is possible to suppress almost completely psoriatic lesions by judicious use of methotrexate, cyclosporine A, and eicosapentaenoic acid. Our studies have shown that in patients with psoriasis there is an increase in the generation of free radicals with an alteration in essential fatty acid metabolism and that side-effects of anti-cancer drugs can be blocked by essential fatty acids in vivo. Thus, essential fatty acid metabolism seems to play a crucial role both in the pathogenesis and treatment of psoriasis.

Cytotoxic action of cis-unsaturated fatty acids on human cervical carcinoma (HeLa) cells: relationship to free radicals and lipid peroxidation and its modulation by calmodulin antagonists.

Specific fatty acids such as linoleic acid (LA), gamma-linolenic acid (GLA), dihomo gamma linolenic acid (DGLA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) showed cytotoxicity towards human cervical (HeLa) cells in vitro. Cyclo-oxygenase inhibitor, indomethacin; lipoxygenase inhibitor, nordihydroguiaretic acid (NDGA); anti-oxidant, vitamin E; and calmodulin antagonists, trifluoperazine (TFP) and chlorpromazine (CPZ) blocked the cytotoxic action of these fatty acids. GLA-induced free radical generation and lipid peroxidation were also inhibited by indomethacin, NDGA, vitamin E, TFP and CPZ. Both indomethacin and NDGA also showed significant anti-oxidant property. These results suggest that fatty acid-induced cytotoxic action against HeLa cells is a free radical dependent process and that it can be modulated by calmodulin antagonists. These results are in contrast to those observed by us earlier with human breast cancer cells where in it was found that the tumoricidal action of fatty acids can be blocked by anti-oxidants but not by cyclo-oxygenase (CO) and lipoxygenase (LO) inhibitors. From these results it can be suggested that though free radicals are the mediators of the tumoricidal action of fatty acids, the mechanism of their production may be different in different types of tumor cells.

Free radical generation, lipid peroxidation and essential fatty acids in uncontrolled essential hypertension.

Vascular endothelium produces prostacyclin (PG12) and endothelium-derived vascular relaxing factor (EDRF), which are potent vasodilators and hence, may have a role in the regulation of blood pressure. Both PG12 and EDRF are readily degraded by free radicals, especially superoxide anion. Hence, we studied free radical generation and lipid peroxidation in patients with uncontrolled essential hypertension. It was observed that superoxide anion and hydrogen peroxide production by polymorphonuclear leukocytes (PMN) and the levels of lipid peroxides (measured by thiobarbituric acid assay) were higher in uncontrolled hypertensives compared to controls. Both free radical generation and the levels of lipid peroxides reverted to normal values when assayed after the control of hypertension. The calcium antagonist, verapamil, and beta-1 blocker, metoprolol, at the doses used inhibited free radical generation by phorbolmyristate acetate-stimulated PMNs. On the other hand, angiotensin II augmented free radical generation in normal PMN. In addition, it was also observed that both linoleic acid and arachidonic acid levels are low in the plasma of patients with hypertension compared to controls. These results suggest that increase in free radical generation by PMN and alterations in the plasma concentrations of essential fatty acids are closely associated with uncontrolled hypertension.

Stimulation of free radical generation in human leukocytes by various agents including tumor necrosis factor is a calmodulin dependent process.

The mechanism(s) involved in the generation of free radicals in human leukocytes by phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (FMP), lipopolysaccharide (LPS), arachidonic acid (AA), and recombinant-tumor necrosis factor-1-alpha (r-TNF-1 alpha) was investigated. Calmodulin antagonists, chlorpromazine and trifluoperazine, inhibited free radical generation in human leukocytes by these stimulants. Dexamethosone, an inhibitor of phospholipase A2, could also block free radical generation in human leukocytes induced by r-TNF 1 alpha. PMA, FMP, LPS and TNF can activate phospholipase A2 and induce the release of AA from the cell membrane lipid pool. AA induced free radical generation in human leukocytes can be inhibited by calmodulin antagonists. Hence, it is likely that calmodulin dependent events play a crucial role in the generation of free radicals by human leukocytes in response to various stimulants including TNF.

Free radical generation in human leukocytes by CIS-unsaturated fatty acids is a calmodulin dependent process.

The mechanism(s) involved in the generation of free radicals in human leukocytes by cis-unsaturated fatty acids, gamma-linolenic acid (GLA), and arachidonic acid (AA), was investigated. Calmodulin antagonists, chlorpromazine and trifluoperazine, inhibited free radical generation by human leukocytes in vitro induced by GLA, AA PMA (Phorbol myristate acetate), formyl-methionyl-leucyl-phenylalanine (FMLP) and lipopolysaccharide (LPS). On the other hand, chloroquine, a phospholipase A2 inhibitor, and colchicine, a microtubule disrupting agent, were without any effect. When sub-optimal concentrations of GLA and AA were added together, leukocytes showed an additive effect on free radical generation. These results indicate that Calmodulin dependent event(s) play a significant role in the generation of free radicals by human leukocytes.

Increase in free radical generation and lipid peroxidation following chemotherapy in patients with cancer.

Several anti-cancer drugs are known to bring about their tumoricidal actions by a free radical dependent mechanism. Majority of the studies reported that adriamycin, mitomycin C, bleomycin, etc., augment free radical generation and lipid peroxidation process in vitro. Our results reported here suggest that following chemotherapy both stimulated and unstimulated human polymorphonuclear leukocytes generate increased amounts of superoxide anion and hydrogen peroxide. This was accompanied by increased formation of lipid peroxidation products as measured by thiobarbituric acid assay. These results confirm that many anti-cancer drugs augment free radical generation and lipid peroxidation even in an vivo situation.