The induction of apoptosis in human cervical carcinoma (HeLa) cells by gamma-linolenic acid

Differential effects of lipid fractions from silver carp brain on human cervical carcinoma cells in vitro

Previous research has revealed that n3 polyunsaturated fatty acids (PUFAs) exhibit anticancer activities. Lipids from a fish brain contain substantial n3 PUFAs. However, no research has been conducted on the action and mechanism of their potent anticancer activities. In this study, total lipids (TLs) from silver carp brain were isolated into polar lipids (PLs) and neutral lipids (NLs), and the anticancer potential of the lipid fractions (LFs) was investigated using the human cervical carcinoma HeLa cell line. LFs effectively inhibited the cell proliferation of HeLa cells in a time- and dose-dependent manner by cell cycle arrest at the S stage and by inducing apoptosis. Further analyses indicated that the loss of mitochondrial membrane potential could be one of mechanisms of apoptosis induced by LFs. Among the TLs, PLs have proven to be more effective in inducing cervical carcinoma cell death than NLs. This work will play a role in promoting lipids from silver carp brain as a potential preventive and therapeutic agent against human cervical carcinoma.

Multiple roles of dihomo-γ-linolenic acid against proliferation diseases

Considerable arguments remain regarding the diverse biological activities of polyunsaturated fatty acids (PUFA). One of the most interesting but controversial dietary approaches focused on the diverse function of dihomo-dietary γ-linolenic acid (DGLA) in anti-inflammation and anti-proliferation diseases, especially for cancers. This strategy is based on the ability of DGLA to interfere in cellular lipid metabolism and eicosanoid (cyclooxygenase and lipoxygenase) biosynthesis. Subsequently, DGLA can be further converted by inflammatory cells to 15-(S)-hydroxy-8,11,13-eicosatrienoic acid and prostaglandin E₁ (PGE₁). This is noteworthy because these compounds possess both anti-inflammatory and anti-proliferative properties. PGE1 could also induce growth inhibition and differentiation of cancer cells. Although the mechanism of DGLA has not yet been elucidated, it is significant to anticipate the antitumor potential benefits from DGLA.

Lipids, mitochondria and cell death: implications in neuro-oncology

Polyunsaturated fatty acids (PUFAs) are known to inhibit cell proliferation of many tumour types both in vitro and in vivo. Their capacity to interfere with cell proliferation has been linked to their induction of reactive oxygen species (ROS) production in tumour tissues leading to cell death through apoptosis. However, the exact mechanisms of action of PUFAs are far from clear, particularly in brain tumours. The loss of bound hexokinase from the mitochondrial voltage-dependent anion channel has been directly related to loss of protection from apoptosis, and PUFAs can induce this loss of bound hexokinase in tumour cells. Tumour cells overexpressing Akt activity, including gliomas, are sensitised to ROS damage by the Akt protein and may be good targets for chemotherapeutic agents, which produce ROS, such as PUFAs. Cardiolipin peroxidation may be an initial event in the release of cytochrome c from the mitochondria, and enriching cardiolipin with PUFA acyl chains may lead to increased peroxidation and therefore an increase in apoptosis. A better understanding of the metabolism of fatty acids and eicosanoids in primary brain tumours such as gliomas and their influence on energy balance will be fundamental to the possible targeting of mitochondria in tumour treatment.

Antioxidant enzyme activities and lipid peroxidation induced by eicosapentaenoic acid (EPA) in PC12 cells

Eicosapentaenoic acid (EPA) is one of the major dietary polyunsaturated fatty acids and induces apoptosis in several cancer cells. In this study, the EPA induced lipid peroxidation and response of antioxidative enzymes have been investigated in rat pheochromocytoma PC12 cells to elucidate the mechanisms of apoptosis induced by the polyunsaturated fatty acid EPA. We have analyzed superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX) activities and glutathione (GSH) contents in PC12 cells after exposure to different concentrations of EPA. Lipid peroxidation was shown to increase in the presence of EPA as an indication of the oxidative damage. Lipid peroxidation was enhanced by EPA in a dose-dependent manner, and the loss of cell viability was partially reversed by vitamin E. In the case of antioxidant enzyme activities, SOD and GPX activities and GSH contents increased significantly at 50 micromol/L EPA and were respectively 2.41-fold (p < 0.01), 3.49-fold (p < 0.05), and 1.43-fold (p < 0.05) higher than controls. The CAT activity at 10 micromol/L had the highest value and was increased by 25.83% (p < 0.05) compared to control. The results suggest that in PC12 cells the mechanism of apoptosis induced by EPA may be partly due to lipid peroxidation.

Induction of apoptosis in K562/ADM cells by gamma-linolenic acid involves lipid peroxidation and activation of caspase-3

Numerous studies have revealed that gamma-linolenic acid (GLA) possesses effective tumoricidal properties while not inducing damage to normal cells or creating harmful systemic side effects. It can exert anti-tumor efficacy against a variety of cancers including leukemia. However, little is known about the effects of GLA on leukemia resistant to chemotherapy, emerging as a serious clinical problem. The present study tested GLA-induced apoptosis in K562/ADM multidrug-resistant (MDR) leukemic cells and investigated its possible mechanisms. Using cell viability, fluorescent staining of nuclei, flow cytometric Annexin V/PI double staining and lactate dehydrogenase (LDH) release, we found that GLA could inhibit cell growth and induce apoptosis and secondary necrosis. The results showed that incubation with GLA concentrations of 10-60 microg/ml caused a dose- and time-dependent decrease of K562/ADM cell viability, and the IC50 value was 50.5 microg/ml at 24 h and 31.5 microg/ml at 48 h. Flow cytometry using Annexin V/PI double staining assessed apoptosis, necrosis and viability. Typical apoptotic nuclei were shown by staining of K562/ADM cells with DNA-binding fluorochrome Hoechst 33342, characterized by chromatin condensation and nuclear fragmentation. On the other hand, after treated K562/ADM cells with 20 microg/ml GLA for 48 h and with 40 microg/ml GLA for 12 h, the LDH release significantly increased, indicated losses of plasma membrane integrity and presence of necrosis. Further, the inhibition of GLA-induced apoptosis by a pan-caspase inhibitor (z-VAD-fmk) suggested the involvement of caspases. The increase of caspase-3 activity with GLA concentration confirmed its role in the process. The results also showed that the malondialdehyde (MDA) content was also significantly elevated, and antioxidant BHT could block GLA cytotoxity, indicating the cytotoxity induced by GLA may be due to lipid peroxidation.

Influence of prostaglandin A2 on Bax, Bcl-2 and PCNA expression in MCF-7 cells

The effects of 20 microg/mL exogenous prostaglandin A(2) (PGA(2)) were determined on Bax, Bcl-2 and proliferating cell nuclear antigen (PCNA) expression levels in MCF-7 cells. Flow cytometric analysis indicated a pronounced increase in the S phase and a decrease in the G(1) phase, whereas a significant increase in the DNA content preceding the G(0)/G(1) peak was also observed after 48 h of exposure to PGA(2). Confirmation of apoptosis was determined after 12 h, 36 h and 48 h of PGA(2) exposure employing the mitosensor reagent that detects potential changes in the mitochondrial membrane. Twenty-eight percent of PGA(2)-exposed cells were in apoptosis when compared to the 7.1% vehicle-treated cells after 48 h. PGA(2) exposure led to statistically significant increase (1.25-fold) over vehicle-treated controls in Bax expression levels. Decreases in Bcl-2 (0.79-fold), as well as PCNA (0.69-fold) expression levels over vehicle-treated controls were observed. The Bax/Bcl-2 ratio for PGA(2)-exposed cells was 2.7. The present study suggests that an accumulation in the S phase, a decrease in expression levels of PCNA, as well as an altered ratio in favor of Bax, could lead to the induction of apoptosis in these cells.

Application of a continuous bioreactor cascade to study the effect of linoleic acid on hybridoma cell physiology

The aim of the present study is to demonstrate the use of controlled bioreactors for toxicological studies. As a model system the effect of linoleic acid on hybridoma cells is studied in two well-controlled continuously operated bioreactors placed in series. In the first reactor the effect on rapid proliferating cells can be studied, while in the second reactor a special steady state is created, which allows studying the effect on apoptotic cells. Experiments are done at 0, 25, and 50 microM linoleic acid. At the end of the experiment with 50 microM linoleic acid, the concentration of linoleic acid is increased stepwise to determine the cytotoxic level. For rapid proliferating cells exposed to 25 and 50 microM stimulation of growth was observed. At 50 microM there was at the same time an increase in cell death through apoptosis. For stressed apoptotic cells linoleic acid caused partial growth inhibition at 25 and 50 microM and arrest of cell proliferation in the G(2)/M phase at 50 microM. For both, rapid proliferating cells and stressed apoptotic cells, complete growth inhibition occurred at 85 microM, with cells being arrested in the G(2)/M phase and dying mainly through necrosis. Cells in the bioreactor system appeared to be more sensitive towards linoleic acid than cells grown in multi-well plates. (IC(50) = 300 microM; IC(100) = 400 microM). Altogether the results of the present study reveal that the biostat experiments allow detailed analysis of the effect of a bioactive ingredient on cell physiology and behavior.

Toxicity of a mixture of fatty acids on human blood lymphocytes and leukaemia cell lines

The effect of a mixture of fatty acids upon lymphocyte and leukaemia cell death was examined. Peripheral lymphocytes from healthy subjects and two human leukaemia cell lines-Jurkat (T lymphocyte) and Raji (B lymphocyte) cells-were treated with increasing concentrations (0.1-0.4 mM) of a fatty acid mixture in a proportion mimicking that of the free fatty acids in plasma. Features of cell death were then evaluated. Phosphatidylserine externalization, and DNA fragmentation (apoptosis), and loss of cell membrane integrity (necrosis) and mitochondrial depolarization (common feature of cell death) were observed in leukaemia cells after the fatty acid treatment for up to 48 h. Human lymphocytes, however, when submitted to the same treatment presented apoptotic feature only. These findings indicate that a free fatty acid mixture (mimicking the proportion found in plasma) triggers apoptosis of leukaemia cell lines followed by loss of cell membrane integrity, whereas in human circulating lymphocytes the same treatment causes apoptosis only. Evidence is presented herein that mitochondria from leukaemic cells are more susceptible to the toxicity of the fatty acids than mitochondria from human circulating lymphocytes.

The effects of prostaglandin A2 on cell growth, cell cycle status and apoptosis induction in HeLa and MCF-7 cells

The effects of 20 microg/ml exogenous prostaglandin A(2) (PGA(2)) were evaluated on cell numbers in HeLa (human epithelial cervix carcinoma) and MCF-7 (human breast carcinoma) cells. In HeLa cells, PGA(2) reduced cell numbers significantly to 75% after 24 h (P < 0.05) and exposure of 48 h decreased cell numbers to 61% (P < 0.05) of the control. In MCF-7 cells, PGA(2) significantly reduced cell numbers to 48% after 24 h and to 20% after 48 h, compared to vehicle-treated control cells (P < 0.05). The anti-mitogenic effects were confirmed by morphological studies conducted after 48 h of exposure to PGA(2), when optimal effects were observed. HeLa and MCF-7 cells exposed to PGA(2), showed chromatin aggregation, cell membrane blebbing and uneven distribution of chromosomes. Cell cycle progression analysis of HeLa and MCF-7 cells, showed an increase in DNA content preceding the G(0)/G(1) peak after 48 h of exposure, which is indicative of apoptotic body formation.

Fatty acid oxidation and signaling in apoptosis

It is well established that fatty acid metabolites of cyclooxygenase, lipoxygenase (LOX), and cytochrome P450 are implicated in essential aspects of cellular signaling including the induction of programmed cell death. Here we review the roles of enzymatic and non-enzymatic products of polyunsaturated fatty acids in controlling cell growth and apoptosis. Also, the spontaneous oxidation of polyunsaturated fatty acids yields reactive aldehydes and other products of lipid peroxidation that are potentially toxic to cells and may also signal apoptosis. Significant conflicting data in terms of the role of LOX enzymes are highlighted, prompting a re-evaluation of the relationship between LOX and prostate cancer cell survival. We include new data showing that LNCaP, PC3, and Du145 cells express much lower levels of 5-LOX mRNA and protein compared with normal prostate epithelial cells (NHP2) and primary prostate carcinoma cells (TP1). Although the 5-LOX activating protein inhibitor MK886 killed these cells, another 5-LOX inhibitor AA861 hardly showed any effect. These observations suggest that 5-LOX is unlikely to be a prostate cancer cell survival factor, implying that the mechanisms by which LOX inhibitors induce apoptosis are more complex than expected. This review also suggests several mechanisms involving peroxisome proliferator activated receptor activation, BCL proteins, thiol regulation, and mitochondrial and kinase signaling by which cell death may be produced in response to changes in non-esterified and non-protein bound fatty acid levels. Overall, this review provides a context within which the effects of fatty acids and fatty acid oxidation products on signal transduction pathways, particularly those involved in apoptosis, can be considered in terms of their overall importance relative to the much better studied protein or peptide signaling factors.

Repression of cellular anaplerosis as the hypothesized mechanism of gamma-linolenic acid-induced toxicity to tumor cells

In in vitro cultures, the cell is virtually isolated and can no longer rely on mechanisms for physiological regulation of substrate availability found in tissues. More emphasis is laid on utilization of preponderant substrate in a proposed reciprocal relationship between glycolysis and free fatty acid (FFA) oxidation for energy. Supraphysiological concentrations of gamma-linolenic acid and some other polyunsaturated fatty acids (PUFAs) therefore suppress glycolysis but also inhibit FFA oxidation initiated through a cytochrome P450-mediated epoxidation of PUFA to inhibit fatty acid synthase (FAS) activity. FAS inhibition accumulates malonyl CoA which inhibits carnitine palmitoyl transferase I and prevents FFA oxidation. The cell is starved of energy and anabolic intermediates, leading to decreased proliferation or death for tumor cells. Tumor cells are more vulnerable to this induced toxicity due to possession of specific phenotypes of elevated expression for FAS and pyruvate kinase, type M2, both factors inducing tumor cell apoptosis on inhibition.

Gamma-linolenic acid induces apoptosis in B-chronic lymphocytic leukaemia cells in vitro

Gamma linolenic acid (GLA) is cytotoxic to many types of human cancer cells. Most chemotherapeutic agents are cytotoxic by inducing apoptosis. We examined the apoptotic activity of GLA on purified B-cells isolated from patients with B-cell chronic lymphocytic leukaemia (B-CLL) and from normal individuals. GLA significantly increased the degree of apoptosis in B-CLL B-cells after 24 hours of culture. The mean percentage of cells undergoing apoptosis when cultured in medium alone (spontaneous apoptosis) was 20% (range: 7 to 31%) (n=25) and in the presence of GLA (5 microg-60 microg) was: 42%-95%. In the presence of GLA 5 microg/ml and dexamethasone the degree of apoptosis was 86% (range: 72 to 100%). GLA induced apoptosis in B-CLL B-cells at a higher level than that observed with normal B-cells at all lower concentrations tested 5, 10 and 15 microg/ml: P=0.045; 0.027 and 0.022, respectively. At 30 microg/ml of GLA, no significant difference in the percentage of cells displaying apoptosis between B-CLL and normal B-cells was observed (P=0.075). GLA induced apoptosis in B-CLL T-cells at both 10 and 30 microg/ml. The degree of apoptosis in normal T-cells with GLA was also significant at the higher concentration of 30 microg/ml. Interleukin 4 (IL4), a viability factor in B-CLL, and vitamin E, an anti-oxidant, protected B-CLL B-cells against GLA (20 microg/ml)-induced apoptosis. These results demonstrate that GLA induces apoptosis in B-CLL B- and T-cells cells in vitro and that they are more susceptible to GLA-induced apoptosis than normal peripheral blood B- and T-cells.

Regulation of cellular differentiation and apoptosis by fatty acids and their metabolites

We have reviewed the literature regarding the effects of fatty acids and their metabolites on cellular differentiation and apoptosis. Results obtained in different studies have been variable, but some generalizations can be made. Differentiation was increased by incubation of cells with arachidonic acid (AA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA), prostaglandin E1 (PGE1), prostaglandin E2 (PGE2), or leukotriene D4 (LTD4). Effects of these agents on differentiation could be magnified with the simultaneous addition of other differentiation-inducing agents like dimethylsulfoxide or retinoic acid. AA and gamma-linolenic acid increased apoptosis while the effects of n-3 fatty acids (EPA and DHA) and of eicosanoids varied from stimulation to inhibition. These inconsistencies are attributed to the differences in methods used to evaluate differentiation and apoptosis, concentrations of fatty acids and serum, exposure time and the cell models used. Studies using the physiological concentrations of the fatty acids and standardized experimental conditions need to be conducted to establish effects of fatty acids and their metabolites on these cellular processes.

Docosahexaenoic acid is a potent inducer of apoptosis in HT-29 colon cancer cells

Some studies have shown that dietary intake of polyunsaturated fatty acids of the n-3 series may have inhibitory effect on the growth of tumor cells both in vivo and in vitro. However, the cellular and molecular mechanisms by which n-3 fatty acids reduce the growth of tumor cells remain poorly understood. In the present studies, we compared the potency of a variety of n-3 and n-6 fatty acids in modulating the apoptotic cell death in HT-29 colon cancer cells. Of all fatty acids examined, we found that docosahexaenoic acid (22:6n-3; DHA) is a potent inducer of apoptosis in a time- and dose-dependent manner. Indomethacin, a cyclooxygenase inhibitor, is ineffective in blocking the apoptosis induced by DHA, suggesting that DHA-induced apoptosis in HT-29 cells is not mediated through the cyclooxygenase pathway. In contrast, the DHA-induced apoptosis is partially reversed by a synthetic antioxidant, butylated hydroxytoluene, indicating that lipid peroxidation may be involved in apoptotic signaling pathway induced by DHA. DHA treatment decreased bcl-2 levels in association with apoptosis, whereas bax levels remained unchanged. These results suggest that decreased expression of bcl-2 by DHA might increase the sensitivity of cells to lipid peroxidation and to programmed cell death.

Gamma linolenic acid with tamoxifen as primary therapy in breast cancer

Gamma linolenic acid (GLA) has been proposed as a valuable new cancer therapy having selective anti-tumour properties with negligible systemic toxicity. Proposed mechanisms of action include modulation of steroid hormone receptors. We have investigated the effects of GLA with primary hormone therapy in an endocrine-sensitive cancer. Thirty-eight breast cancer patients (20 elderly Stage I-II, 14 locally advanced, 4 metastatic) took 8 capsules of oral GLA/day (total = 2.8 g) in addition to tamoxifen 20 mg od (T+GLA). Quality and duration of response were compared with matched controls receiving tamoxifen 20 mg od alone (n = 47). Serial tumour biopsies were taken to assess changes in oestrogen receptor (ER) and bcl-2 expression during treatment. GLA was well tolerated with no major side effects. T+GLA cases achieved a significantly faster clinical response (objective response vs. static disease) than tamoxifen controls, evident by 6 weeks on treatment (p = 0.010). There was significant reduction in ER expression in both treatment arms with T+GLA objective responders sustaining greater ER fall than tamoxifen counterparts (6-week biopsy p = 0.026; 6-month biopsy p = 0.019). We propose GLA as a useful adjunct to primary tamoxifen in endocrine-sensitive breast cancer. The effects of GLA on ER function and the apparent enhancement of tamoxifen-induced ER down-regulation by GLA require further investigation.

Peroxisome proliferator activated receptor-gamma (PPAR-gamma) mediates the action of gamma linolenic acid in breast cancer cells

Gamma linolenic acid (GLA) is a polyunsaturated fatty acid, which induces cytotoxicity and regulates cell adhesion in cancer cells. The molecular mechanism of these actions is not clear. We have shown that GLA acts via peroxisome proliferator activated receptors (PPARs), by stimulating their phosphorylation and translocation to the nucleus. Removing PPAR gamma with antisense oligos abolished the effect of GLA on the expression of adhesion molecules and tumour suppressor genes, whereas removal of PPAR alpha had no effect. Tissues from patients with breast cancer showed a reduction of expression of both PPARs in cancer tissues, as compared with normal. Thus, PPAR gamma serves as the receptor for GLA in the regulation of gene expression in breast cancer cells.

Regulation of fatty acid biosynthesis as a possible mechanism for the mitoinhibitory effect of fumonisin B1 in primary rat hepatocytes

The mitoinhibitory effect of fumonisin B1 (FB1) on the mitogenic response of epidermal growth factor (EGF) was investigated in primary hepatocyte cultures with respect to the alterations in the omega6 fatty acid metabolic pathway. Fatty acid analyses of hepatocytes showed that EGF treatment resulted in a significant decrease in the relative levels of 20:4omega6 (arachidonic acid) and an increase in 18:2omega6 (linoleic acid). Supplementation of the hepatocyte cultures with 20:4omega6 in the absence of EGF resulted in an increase in the total omega6 and omega6/omega3 fatty acid ratio. Addition of 20:5omega3 (eicosapentaenoic acid) resulted in an increase of the relative levels of the long chain omega3 fatty acids at the expense of the omega6 fatty acids. When 20:4omega6 and 20:5omega3 was added in the presence of EGF, the mitogenic response of EGF was increased and decreased respectively. When compared to the fatty acid profiles in the absence of EGF, the decreased mitogenic response coincided with a decrease of total omega6 fatty acids and total polyunsaturated fatty acids (PUFA). In addition, the saturated and mono-unsaturated fatty acids increased and the polyunsaturated/saturated (P/S) fatty acid ratio decreased which implied a more rigid membrane structure. Addition of prostaglandin E2 (PGE2) and prostaglandin E1 (PGE1) stimulated and inhibited the mitogenic response respectively. Ibuprofen, a known cyclooxygenase inhibitor, and FB1 inhibited the EGF-induced mitogenic response in a dose-dependent manner. The mitoinhibitory effect of FB1 on the EGF response was counteracted by the addition of PGE2. FB1 also disrupts the omega6 fatty acid metabolic pathway in primary hepatocytes, resulting in the accumulation of C18:2omega6 in phospatidylcholine and triacylglicerol. The disruption of the omega6 fatty acid metabolic pathway and/or prostaglandin synthesis is likely to be an important event in the mitoinhibitory effect of FB1 on growth factor responses.

Comparative study of the effects of polyunsaturated fatty acids and their metabolites on cell growth and tyrosine kinase activity in oesophageal carcinoma cells

The effects of exogenous gamma-linolenic acid (GLA), arachidonic acid (AA), prostaglandin E2 (PGE2) and prostaglandin A2 (PGA2) were evaluated on cell growth in two squamous oesophageal carcinoma cell lines, WHCO1 and WHCO3 and normal monkey kidney (NMK) cells. In both cancer cell lines all four compounds inhibited cell growth significantly. Indomethacin (I) alone, or in combination with either GLA or AA, caused marked inhibition of cell growth in WHCO3. Total tyrosine kinase (TK) activity was determined after exposure of all three cell types to the lipid compounds. Negligible differences were observed in TK activity between treated and untreated NMK cells. Small increases were noticed in WHCO1. Marked TK stimulation was observed in WHCO3. Addition of indomethacin to WHCO3 also increased TK activity above control value. Tyrosine phosphorylation status of exposed cells indicated that a band of approximately 55 kDa (approximately 55 kDa) was primarily influenced in both WHCO3 and WHCO1. PGA2 caused a decrease in tyrosine phosphorylation of the approximately 55 kDa protein in all three cell types. Negligible differences were observed in the tyrosine phosphorylation status of the approximately 55 kDa in NMK cells exposed to GLA, AA and PGE2 respectively. However, tyrosine phosphorylation of a number of other proteins (21.5-97.4 kDa) was observed in NMK cells. Flow cytometry studies showed an increase in S phase and decrease in G1 phase in WHCO3 exposed to PGE2 and PGA2. Indomethacin alone, or in combination with GLA and AA, respectively, lead to an increase in G1 and a decrease in S phase. Induction of p53 levels was observed in WHCO3 cells exposed to GLA, AA, PGA2, indomethacin and the combination of indomethacin and GLA or AA.

Inhibition of the expression of VE-cadherin/catenin complex by gamma linolenic acid in human vascular endothelial cells, and its impact on angiogenesis

Gamma linolenic acid (GLA) has been recently shown to inhibit tumour-induced angiogenesis. The present study investigated the effects of GLA on the HUVEC-specific adhesion. After treatment with GLA, HUVECs decreased the amounts of Triton soluble and insoluble VE-cadherin and beta-catenin and reduced tube formation in matrix in a concentration-dependent manner. An anti-VE-cadherin antibody dissociated HUVECs' colonies and exerted similar inhibitory effects on tube formation of HUVECs. These data indicate that the VE-cadherin/catenins complex is essential for formation and maintenance of new capillaries. It is concluded, therefore, that GLA inhibits tumour-induced angiogenesis partly via the decrease in the expression of VE-cadherin and beta-catenin.

Comparative anti-mitotic effects of lithium gamma-linolenate, gamma-linolenic acid and arachidonic acid, on transformed and embryonic cells

The effects of gamma-linolenic acid (GLA), the lithium salt of gamma-linolenic acid (LiGLA) and arachidonic acid (AA) were compared at doses of 50 microg/ml for periods of 6 and 24 h on cell cycle progression and apoptosis induction in transformed and in normal cells. In WHCO3 (oesophageal cancer) cells and on primary embryonic equine lung cells, we found LiGLA to be the most effective in apoptosis induction. After 24 h, 94% of the WHCO3 cancer cells and 44% of the primary embryonic equine lung cells exposed to LiGLA were apoptotic. The WHCO3 cancer cells were also very susceptible to the apoptosis-inducing effects of AA (56%) and GLA (44%), whereas the embryonic equine lung cells were much less affected by these two fatty acids. After 6 h exposure to all three compounds, most of the cycling WHCO3 cancer cells were blocked in S-phase. After 24 h treatment, some of the S-phase cells exposed to AA and GLA were apparently able to move into the G2/M phase, the LiGLA exposed cells were mostly apoptotic and no cycling cells were present. The primary embryonic equine lung cells were fairly resistant to the cytotoxic effects of GLA and AA. From our studies we conclude that, although LiGLA was the most toxic to the cancer cells, it is apparently less selective, compared to AA and GLA, in the killing of cancer and normal cells. It would also appear that the lithium might have added to the cytotoxic effects of LiGLA. The mechanism needs to be clarified.

The membrane phospholipid hypothesis as a biochemical basis for the neurodevelopmental concept of schizophrenia

The neurodevelopmental hypothesis of schizophrenia is becoming an important feature of research in the field. However, its major drawback is that it lacks any biochemical basis which might draw the diverse observations together. It is suggested that the membrane phospholipid hypothesis can provide such a biochemical basis and that the neurodevelopmental phospholipid concept offers a powerful paradigm to guide future research.