Dose-dependent inhibition of cell proliferation induced by lipid peroxidation products in rat hepatoma cells after enrichment with arachidonic acid

On the role of 4-hydroxynonenal in health and disease

Polyunsaturated fatty acids are susceptible to peroxidation and they yield various degradation products, including the main α,β-unsaturated hydroxyalkenal, 4-hydroxy-2,3-trans-nonenal (HNE) in oxidative stress. Due to its high reactivity, HNE interacts with various macromolecules of the cell, and this general toxicity clearly contributes to a wide variety of pathological conditions. In addition, growing evidence suggests a more specific function of HNE in electrophilic signaling as a second messenger of oxidative/electrophilic stress. It can induce antioxidant defense mechanisms to restrain its own production and to enhance the cellular protection against oxidative stress. Moreover, HNE-mediated signaling can largely influence the fate of the cell through modulating major cellular processes, such as autophagy, proliferation and apoptosis. This review focuses on the molecular mechanisms underlying the signaling and regulatory functions of HNE. The role of HNE in the pathophysiology of cancer, cardiovascular and neurodegenerative diseases is also discussed.

Novel Anticancer Platinum(IV) Complexes with Adamantylamine: Their Efficiency and Innovative Chemotherapy Strategies Modifying Lipid Metabolism

The impressive impact of cisplatin on cancer on one side and severe side effects, as well as the development of drug resistance during treatment on the other side, were the factors motivating scientists to design and synthesize new more potent analogues lacking disadvantages of cisplatin. Platinum(IV) complexes represent one of the perspective groups of platinum-based drugs. In this review, we summarize recent findings on both in vitro and in vivo effects of platinum(IV) complexes with adamantylamine. Based on a literary overview of the mechanisms of activity of platinum-based cytostatics, we discuss opportunities for modulating the effects of novel platinum complexes through interactions with apoptotic signaling pathways and with cellular lipids, including modulations of the mitochondrial cell death pathway, oxidative stress, signaling of death ligands, lipid metabolism/signaling, or intercellular communication. These approaches might significantly enhance the efficacy of both novel and established platinum-based cytostatics.

Clarithromycin: Immunomodulatory therapy of experimental sepsis and acute pyelonephritis by Escherichia coli

The potency of clarithromycin as immunomodulator was assessed in an experimental model of sepsis based on acute pyelonephritis by susceptible Escherichia coli. 55 rabbits were utilized; 5 for preliminary pharmacokinetic study and 50 for treatment. The latter were divided into 5 groups of treatment, A: controls; B: clarithromycin pretreatment; C: amikacin pretreatment; D: clarithromycin treatment on presentation of pulmonary oedema; and E; amikacin treatment on presentation of pulmonary oedema. Survival was recorded; tumour necrosis factor-alpha (TNFalpha), and malondialdehyde (MDA) were estimated in serum; activities of caspase-3 in monocyte cytosolic extracts were studied; and bacterial counts made in various organs. Median survival of animals of groups A, B, C, D and E was 1.0, 21.0, 12.5, 2.0 and 5.0 d, respectively. TNFalpha and MDA and monocyte caspase-3 activity of group A increased over time; no increases were detected in groups B and C. Concentrations of MDA and activities of monocytic caspase-3 were decreased after administration of clarithromycin in group D, an effect not occurring in group E. Bacterial load was decreased in renal tissue of group D compared to group A. It is concluded that intravenous clarithromycin might constitute a promising immunomodulator in sepsis even in the advent of pulmonary oedema.

Arachidonic and docosahexaenoic acids reduce the growth of A549 human lung-tumor cells increasing lipid peroxidation and PPARs

Polyunsaturated fatty acids (PUFAs) play an important role in both induction and prevention of carcinogenic process. It is well known that several types of neoplastic cells show decreased total PUFA content, contributing to their resistance to chemotherapy and lipid peroxidation. In the light of this, human lung cancer A549 cells, with low PUFA content, were exposed to arachidonic or docosahexaenoic acid to investigate the effect of n-6 and n-3 PUFAs on growth and elucidate underlying mechanisms. The bulk of the results showed that both n-6 PUFAs and n-3 PUFAs decrease human lung-tumor cell growth in a concentration-dependent manner, inducing cell death mainly evident at 100microM concentration. The mechanism underlying the antiproliferative effect of n-6 and n-3 PUFAs appeared to be the same, involving changes in fatty acid composition of biomembranes, production of cytostatic aldehydes derived from lipid peroxidation and able to affect DNA-binding activity of AP-1, and induction of PPAR. From these results it may be hypothesized that n-6 PUFAs, like n-3 PUFAs, are able to inhibit tumor growth.

Arachidonic acid suppresses growth of human lung tumor A549 cells through down-regulation of ALDH3A1 expression

Expression of aldehyde dehydrogenase 3A1 (ALDH3A1) in certain normal and tumor cells is associated with protection against the growth inhibitory effect of reactive aldehydes generated during membrane lipid peroxidation. We found that human lung tumor (A549) cells, which express high levels of ALDH3A1 protein, were significantly less susceptible to the antiproliferative effects of 4-hydroxynonenal compared to human hepatoma HepG2 or SK-HEP-1 cells that lack ALDH3A1 expression. However, A549 cells became susceptible to lipid peroxidation products when they were treated with arachidonic acid. The growth suppression of A549 cells induced by arachidonic acid was associated with increased levels of lipid peroxidation and with reduced ALDH3A1 enzymatic activity, protein, and mRNA levels. Furthermore, arachidonic acid treatment of the A549 cells resulted in an increased expression of peroxisome proliferator-activated receptor gamma (PPARgamma), whereas NF-kappaB binding activity was inhibited. Blocking PPARgamma using a selective antagonist, GW9662, prevented the arachidonic acid-mediated reduction of ALDH3A1 expression as well as the growth inhibition of A549 cells, suggesting the central role of PPARgamma in these phenomena. The increase in PPARgamma and the reduction in ALDH3A1 were also prevented by exposing cells to vitamin E concomitant with arachidonic acid treatment. In conclusion, our data show that the arachidonic acid-induced suppression of A549 cell growth is associated with increased lipid peroxidation and decreased ALDH3A1 expression, which may be due to activation of PPARgamma.

Effects of di(2-ethylhexyl) phthalate, a widely used peroxisome proliferator and plasticizer, on cell growth in the human keratinocyte cell line NCTC 2544

Phthalate esters are a widely used class of water-insoluble organic chemicals. The adverse effects of di(2-ethylhexyl) phthalate (DEHP) were chiefly studied in animals, while their potential toxicity to humans has not been properly evaluated. It was hypothesized that the effect of DEHP on human cells depends on the concentration, and this study examined the effects of different concentrations of DEHP on cell growth in cultured human keratinocytes NCTC 2544, together with the possible involvement of peroxisome proliferator-activated receptors (PPARs) in mediating the effects. After exposure to DEHP, the number of NCTC 2544 cells in the monolayer decreased in a concentration-dependent and time-dependent manner, whereas the cells that were detached from the monolayer increased, and died via necrosis. The decrease of cell growth was confirmed by the inhibition of pErk1, pErk2, and changes in the c-myc protein content. With regard to PPARs, the PPARbeta protein content increased, whereas PPARalpha decreased. To demonstrate the involvement of PPARbeta in inhibiting cell growth, the use of an antisense oligonucleotide against this receptor revealed the prevention of DEHP-induced cell growth inhibition. In addition, the treatment of keratinocytes with a specific ligand of PPARbeta (L165041) showed a concentration-dependent inhibition of cell growth, as with DEHP. In conclusion, the effect of DEHP on human keratinocytes is concentration dependent, and this effect is mediated via PPARs.

HSF1 down-regulates XAF1 through transcriptional regulation

Studies have indicated the role of HSF1 (heat-shock transcription factor 1) in repressing the transcription of some nonheat shock genes. XAF1 (XIAP-associated factor 1) was an inhibitor of apoptosis-interacting protein with the effect of antagonizing the cytoprotective role of XIAP. XAF1 expression was lower in gastrointestinal cancers than in normal tissues with the mechanism unclear. Here we showed that gastrointestinal cancer tissues expressed higher levels of HSF1 than matched normal tissues. The expression of XAF1 and HSF1 was negatively correlated in gastrointestinal cancer cell lines. Stress stimuli, including heat, hypo-osmolarity, and H2O2, significantly suppressed the expression of XAF1, whereas the alteration of HSF1 expression negatively correlated with XAF1 expression. We cloned varying lengths of the 5'-flanking region of the XAF1 gene into luciferase reporter vectors, and we evaluated their promoter activities. A transcription silencer was found between the -592- and -1414-nucleotide region that was rich in nGAAn/nT-TCn elements (where n indicates G, A, T, or C). A high affinity and functional HSF1-binding element within the -862/-821-nucleotide region was determined by electrophoretic mobility shift assay and chromatin immunoprecipitation assay. Inactivation of this "heat-shock element" by either site-directed mutation or an HSF1 inhibitor, pifithrin-alpha, restored the promoter activity of the silencer structure. Moreover, pretreatment with antioxidants suppressed HSF1 binding activity and increased the transcriptional activity and expression of XAF1. These findings suggested that endogenous stress pressure in cancer cells sustained the high level expression of HSF1 and subsequently suppressed XAF1 expression, implicating the synergized effect of two anti-apoptotic protein families, HSP and inhibitors of apoptosis, in cytoprotection under stress circumstances.

Immunomodulatory intervention in sepsis by multidrug-resistant Pseudomonas aeruginosa with thalidomide: an experimental study

Background

Thalidomide is an inhibitor of tumour necrosis factor-alpha (TNFα) that has been proven effective for the treatment of experimental sepsis by Escherichia coli. It was tested whether it might behave as an effective immunomodulator in experimental sepsis by multidrug-resistant (MDR) Pseudomonas aeruginosa.

Methods

Sepsis was induced by the intraperitoneal injection of 1 × 10⁸ cfu/kg inoculum of the test isolate in a total of 109 Wistar rats divided in three groups as follows: group A controls; group B administered seed oil 30 minutes before bacterial challenge; and group C administered 50 mg/kg of thalidomide diluted in seed oil 30 minutes before bacterial challenge. Blood was sampled for estimation of endotoxins (LPS), TNFα, interferon-gamma (IFNγ), nitric oxide (NO) and malondialdehyde (MDA). LPS was measured by the QCL-1000 LAL assay, TNFα and IFNγ by ELISA, NO by a colorimetric assay and MDA by the thiobarbiturate assay.

Results

Mean (± SE) survival of groups A, B and C were 18.60 ± 1.84, 12.60 ± 0.60 and 30.50 ± 6.62 hours (p of comparisons A to C equal to 0.043 and B to C equal to 0.002). Decreased TNFα and NO levels were found in sera of animals of group C compared to group A. Plasma levels of LPS, MDA and IFNγ did not differ between groups.

Conclusion

Intake of thalidomide considerably prolonged survival in experimental sepsis by MDR P.aeruginosa an effect probably attributed to decrease of serum TNFα.

N-6 polyunsaturated fatty acids confer hemodynamic stability in an experimental model of multiple trauma

Immunonutrition with diets enriched in polyunsaturated fatty acids (PUFAs) are becoming mandatory for multiple trauma patients. Solutions containing single n-6 PUFAs were administered intravenously in an experimental model of trauma. Thirty-five rabbits were studied; 13 controls; 10 administered gamma-linolenic acid (GLA) 30 min after fracture of the right femor; and 12 arachidonic acid (AA). Systolic, diastolic and mean arterial pressures and heart rate were recorded; serum levels of tumor necrosis factor-alpha (TNFalpha), malondialdehyde (MDA) and nitrate were estimated before and after therapy. Mean survival of controls, of animals treated with GLA and of animals treated with AA was 0.80, 1.41 and 3.60 days, respectively. Administration of PUFAs induced higher levels of blood pressure; that of AA decreased serum TNFalpha and tissue bacterial load compared to controls. Intravenous administration of n-6 PUFAs conferred hemodynamic stability and increased survival in a model of trauma rendering further research mandatory.

Clarithromycin co-administered with amikacin attenuates systemic inflammation in experimental sepsis with Escherichia coli

To assess the efficacy of clarithromycin as an immunomodulator in experimental sepsis with Escherichia coli, acute pyelonephritis was induced after ligation of the right ureter and injection of the test isolate into the renal pelvis in 40 rabbits. Four groups of treatment were applied with administration of therapy on advent of sepsis-associated pulmonary oedema, as follows: A: controls; B: clarithromycin; C: amikacin, D: both agents. Survival was recorded along with estimation of serum levels of endotoxins (LPS), of tumour necrosis factor-alpha (TNFalpha), malondialdehyde (MDA) and of bacterial counts. Mean survival of groups A, B, C and D was 2.51, 7.60, 10.25 and 11.40 days, respectively. Serum levels of TNFalpha and of MDA of group A increased over-time. Pulmonary oedema at 6 h after bacterial challenge was accompanied by increase of TNFalpha and MDA; administration of clarithromycin decreased their values. It is concluded that intravenous clarithromycin might constitute a promising immunomodulatory agent for the management of sepsis since its efficacy was proved after administration on presentation of sepsis-associated pulmonary oedema. The presented findings emphasise the need for further clinical research of the use of clarithromycin for the therapy of Gram-negative sepsis.

Decrease of human hepatoma cell growth by arachidonic acid is associated with an accumulation of derived products from lipid peroxidation

We showed that the metabolism of arachidonic acid (AA) in HepG2 cells generates reactive oxygen species (ROS), which activate the p38 mitogen-activated protein kinase (MAPK) pathway and the redox-sensitive transcription factors AP-1 and NF-kappaB, leading to the induction of the antioxidant manganese superoxide dismutase gene. The present study reports that AA decreases the HepG2 cell growth by 40% and 55% after a treatment for 24 and 48 h, respectively. This effect was blocked by an inhibitor of lipoxygenase/cytochrome P450 monooxygenase pathways and by the antioxidants. In addition, AA induced an oxidative stress, as an accumulation of malondialdehyde (MDA)-modified proteins, resulting to a generation of MDA and H(2)O(2) was observed after 24 h. This AA-induced oxidative stress was associated with the lack of an increase in the H(2)O(2)-degrading enzyme level. In contrast, 5,8,11,14-eicosatetraynoic acid, a nonmetabolizable analog of AA, had not effect. The peroxisome proliferator-activated receptor gamma (PPARgamma) with AA metabolites as ligands was upregulated by the fatty acid but was not involved in the AA effect because its transcriptional activity estimated by reporter gene assays was negatively controlled by p38 MAPK pathway. These findings suggest that the effect of AA on human hepatoma cell growth by inducing an oxidative stress may present a clinical interest in the treatment of the liver cancer.

4-hydroxynonenal and cell cycle

Lipid peroxidation is very low in proliferating cells and tumours and it might have a role in the regulation of cell proliferation and differentiation by acting through its products. 4-hydroxynonenal (HNE) has been proposed as a mediator of lipoperoxidation effects. It has been demonstrated that HNE can inhibit cell growth and induce differentiation in different leukemic cell lines. The onset of differentiation, induced by HNE, was accompanied by a reduction of c-myc expression. In HL-60 cells, HNE induced the accumulation of cells in the G0/G1 phase of the cell cycle. Cell cycle progression is regulated by three protein classes, the cyclins, the cyclin-dependent kinases (CDKs), and the CDK inhibitors (CKIs). In HL-60 cells, HNE decreased the expression of cyclin D1, D2 and A and caused an increase of p21 (the most important CKI) expression, whereas it did not affect CDK expressions. Since cyclins D/CDK2 and cyclin A/CDK2 phosphorylate pRB, HNE caused an increase of hypophosphorylated pRb. Hypophosphorylated pRb binds and inactivates the E2F transcription factors. Band-shift experiments demonstrated that HNE caused a decrease of "free" E2F, as well as an increase of pRb (and pRB family members) bound to E2F with consequent repression of the transcription.

Butterfat fatty acids differentially regulate growth and differentiation in Jurkat T-cells

Synthetic Conjugated Linoleic Acid mixture (CLA; c9,t11; t10,c12-18:2) has been previously shown to inhibit growth, and enhance apoptosis and IL-2 mRNA synthesis in human lymphoblastic Jurkat T-cells. In this study, two different butterfat types were evaluated and compared for their effects on Jurkat cell viability, oxidative stress, pro-apoptotic activity, and cytokine synthesis: the conventionally produced butterfat (CBF), and organic butterfat (OBF) containing significantly higher amounts of c9,t11 (Rumenic Acid, RA), trans-vaccenic acid (VA; t11-18:1), alpha-linolenic acid (ALA), and lower levels of linoleic acid (LA). Results from cell treatment with both butterfat mixtures showed comparable oxidative stress (superoxide production, intracellular GSH depletion,and lipid peroxides yield), NADPH oxidase activation, cytotoxicity (LDH release), and IL-2 transcript level, whereas the effects of enhanced growth-inhibitory and pro-apoptotic activities were associated with OBF treatment. To then investigate each butterfat-induced effect caused by RA, VA, LA, and ALA, cells were exposed to synthetic FA concentrations similar to those from the different butterfats. Higher oxidative stress (superoxide production, intracellular GSH depletion) was induced by alpha-linolenic (ALA) and linoleic (LA) incubation (P<0.01) and superoxide production was suppressed by specific PKCalpha inhibitor (Gö 6976) and linked to increased toxicity and IL-2 synthesis inhibition. By contrast, cell treatment with RA increased apoptosis and IL-2 synthesis. These results suggest that a supply of ALA and LA is responsible for BF-induced oxidative stress via PKCalpha-NADPH oxidase pathway, and that enhanced antiproliferative effects in OBF treated cells is essentially determined by RA-induced pro-apoptotic activity.

4-hydroxynonenal and TGF-beta1 concur in inducing antiproliferative effects on the CaCo-2 human colon adenocarcinoma cell line

4-Hydroxynonenal (HNE) has been demonstrated to exert its antiproliferative effect by up-regulating the c-Jun-N-terminal kinase (JNK), a member of the mitogen-activated protein kinase family (MAPKs). Transforming growth factor-beta1 (TGF-beta1) is the major negative regulatory factor in controlling cell proliferation, and Smads are its intracellular transducers. Recent data on human colon adenocarcinoma has shown a low HNE content paralleled by a marked alteration of TGF-beta1 levels within the tumor mass. The two events appear related because of the demonstrated marked ability of HNE to up-regulate expression and synthesis of TGF-beta1; the combined decreases of HNE and TGF-beta1 found in cancer cells provide a favorable condition for neoplastic progression. Furthermore, HNE is likely able to interact with the cytokine to enhance apoptosis and increase intracellular reactive oxygen species (ROS) formation in the CaCo-2 colon carcinoma cell line. The probable mechanism whereby HNE and TGF-beta1 interact to induce apoptosis is through cross-talk between the main signaling pathways of the two molecules (JNK and Smads), and the observed ROS production might only contribute to amplifying the apoptotic pathways. The network between the two signaling pathways here involved is now under investigation.

The significance of oxidant/antioxidant balance for the pathogenesis of experimental sepsis by multidrug-resistant Pseudomonas aeruginosa

OBJECTIVE

The significance of lipid peroxidation as an independent factor leading to sepsis by multidrug-resistant Pseudomonas aeruginosa. Design experimental study.

METHODS

Twenty-six rabbits were applied. They were divided into two groups; A (n=6) comprising controls, and B (n=20) comprising animals infected by the injection of 1x10(8) cfu/kg inoculum of the test pathogen into the left inner jugular vein. Six rabbits of group B were followed-up to estimate survival; all of the remaining were sacrificed. Blood was sampled for the determination of serum malondialdehyde (MDA) by the thiobarbiturate assay, total antioxidant status (TAS) by a chromogenic assay, tumor necrosis factor alpha by a bioassay on fibrosarcoma L929 cell line, and endotoxins (LPS) by the QCL-1000 LAL assay.

RESULTS

Mean survival of group B was 60.0+/-15.8 h. MDA was significantly higher in group B compared to group A at 30, 60, 120 and 150 min. TAS was statistically decreased in group B compared to group A at 30 and 60 min. Increases of MDA in group B were followed by reciprocal decreases of TAS (P of correlation <0.001). Hemodynamic instability was recorded in group B compared to group A 160 min after bacterial challenge.

CONCLUSIONS

Early alterations of oxidant/antioxidant balance occur in experimental sepsis by multidrug-resistant P. aeruginosa followed by hemodynamic instability. Results highlight the perspective of the administration of antioxidants as immunomodulatory treatment of sepsis in animal studies.

Lipid peroxidation and inguinal hernia repair. Tension-free vs. Andrews technique

AIM OF THE STUDY

To evaluate the early effect of inguinal hernia repair by the tension-free method compared to the conventional Andrew's technique on lipid peroxidation.

PATIENTS-METHODS

Thirty-four patients subjected to elective hernia repair were enrolled in the study divided in two groups. Group A (n=18) underwent hernia repair by the tension-free method using a polypropylene mesh. Group B (n=16) underwent hernia repair by the Andrew's technique (i.e. a modification of the Bassini's technique). Venous blood samples were drawn preoperatively and at 12, 24 and 48 h postoperatively. Malondialdehyde (MDA) was estimated by the thiobarbiturate assay.

RESULTS

Neutrophil counts were significantly higher in patients of group B compared to group A at 12 and 48 h postoperatively. Concentrations of fibrinogen were similar between the two groups. MDA was significantly higher in patients of group B hours compared to group A at 12, 24 and 48 h postoperatively. Positive correlation was found between neutrophil counts and MDA at 12 h (r: +0.43, P: 0.015) and 48 h (r: +0.496, P: 0.005) but not at 24 h. No correlation was found between serum fibrinogen and MDA.

CONCLUSION

Hernia repair by the Andrews's technique elicits a sustained triggering of lipid peroxidation, compared to the tension-free method.

Rapid alterations of serum fatty acids with the intravenous administration of an arachidonate solution

Polyunsaturated fatty acids (PUFAs) have been shown to possess a considerable anti-tumor and anti-bacterial effect in vitro. In an attempt to achieve serum concentrations of these acids similar to those applied in vitro, a solution of ethyl ester of arachidonic acid (AA) was administered intravenously at 25 mg/kg within 10 min in six male rabbits. Blood samples were collected before and 60 min after infusion from catheters inserted in the hepatic veins and in the carotid artery. Analysis of serum fatty acids was performed by gas chromatography mass spectrometry. Elevated concentrations of elongated fatty acids were detected in the hepatic veins after infusion. Mean concentrations of arachidonate in the hepatic veins and the carotid arteries after infusion of AA were 2.77 and 3.73 microM, respectively. It is concluded that the intravenous administration of a solution of AA might result in increased hepatic biosynthesis of serum saturated and unsaturated fatty acids of elongated carbon chains. The increasing interest for the application of PUFAs in therapeutics renders further study mandatory to clarify the significance of these findings.

Immunomodulatory clarithromycin treatment of experimental sepsis and acute pyelonephritis caused by multidrug-resistant Pseudomonas aeruginosa

Clarithromycin was administered intravenously to 55 rabbits to evaluate its effect on experimental sepsis caused by multidrug-resistant Pseudomonas aeruginosa. Acute pyelonephritis was induced after ligation of the right ureter and injection of 10(8) CFU of the test isolate per kg of body weight into the renal pelvis. The animals were divided into six groups: group A, controls; group B, rabbits that received one intravenous dose of 80 mg of clarithromycin per kg concomitantly with bacterial challenge; group C, rabbits that received two doses of clarithromycin, the second one of which was given 2 h after the first one; group D, rabbits that received 15 mg of amikacin per kg; group E, rabbits that received one dose of clarithromycin and amikacin; and group F, rabbits that received two doses of clarithromycin and amikacin. Serum endotoxin levels were estimated by the QCL-1000 Limulus amoebocyte lysate assay, tumor necrosis factor alpha (TNF-alpha) levels were measured by a bioassay, and malondialdehyde (MDA) levels were measured by the thiobarbiturate assay. Viable bacterial counts in various tissue samples were also assessed. The mean survival times of the animals in groups A, B, C, D, E, and F were 4.50, 7.69, 4.07, 4.55, 11.55, and 11.60 days, respectively (P = 0.033 for group D versus group F, P = 0.006 for group D versus group E, P = not significant for group B versus group E, P = 0.042 for group C versus group F). Serum endotoxin levels were similar between groups at all sampling times; TNF-alpha and MDA levels in groups B, C, E, and F decreased significantly over follow-up. The numbers of viable bacterial cells in the infected kidney were similar among the groups; those in the liver, spleen, lungs, and mesenteral lymph nodes were significantly decreased in groups B, E, and F compared to those in groups A and D. It is concluded that a prolongation of survival in animals with experimental sepsis caused by multidrug-resistant P. aeruginosa was achieved after coadministration of clarithromycin and amikacin and that the increased survival was probably attributable to the immunomodulatory properties of clarithromycin.

An overview of the effect of linoleic and conjugated-linoleic acids on the growth of several human tumor cell lines

Both n-6 and n-3 polyunsaturated fatty acids are dietary fats important for cell function, being involved in several physiologic and pathologic processes, such as tumorigenesis. Linoleic acid and conjugated linoleic acid, its geometrical and positional stereoisomer, were tested on several human tumor cell lines originating from different tissues and with different degrees of malignancy. This was to provide the widest possible view of the impact of dietary lipids on tumor development. While linoleic acid exerted different effects, ranging from inhibitory to neutral, even promoting growth, conjugated linoleic acid inhibited growth in all lines tested and was particularly effective against the more malignant cells, with the exception of mammary tumor cells, in which behavior was the opposite, the more malignant cell line being less affected. The inhibitory effect of conjugated linoleic acid on growth may be accompanied by different contributions from apoptosis and necrosis. The effects of conjugated linoleic acid on growth or death involved positive or negative variations in PPARs. The important observation is that a big increase of PPARalpha protein occurred in cells undergoing strong induction of apoptosis, whereas PPARbeta/delta protein decreased. Although PPARalpha and PPARbeta/delta seem to be correlated to execution of the apoptotic program, the modulation of PPARgamma appears to depend on the type of tumor cell, increasing as protein content, when inhibition of cell proliferation occurred. In conclusion, CLA may be regarded as a component of the diet that exerts antineoplastic activity and its effect may be antiproliferative or pro-apoptotic.

Generation of reactive oxygen species and radiation response in lymphocytes and tumor cells

Several types of lymphoid and myeloid tumor cells are known to be relatively resistant to radiation-induced apoptosis compared to normal lymphocytes. The intracellular generation of reactive oxygen species was measured in irradiated spleen cells from C57BL/6 and BALB/c mice and murine tumor cells (EL-4 and P388) by flow cytometry using dichlorodihydrofluoresceindiacetate and dihydrorhodamine 123 as fluorescent probes. The amount of reactive oxygen species generated per cell was low in the tumor cells compared to spleen cells exposed to 1 to 10 Gy of gamma radiation. This could be due to the higher total antioxidant levels in tumor cells compared to normal cells. Further, the changes in mitochondrial membrane potential and cytoplasmic Ca2+ content were appreciable in lymphocytes even at a dose of 1 Gy. In EL-4 cells, no such changes were observed at any of the doses used. About 65% of spleen cells underwent apoptosis 24 h after 1 Gy irradiation. However, under the same conditions, EL-4 and P388 cells failed to undergo apoptosis, but they accumulated in G2/M phase. Thus the intrinsic radioresistance of tumor cells may be due to a decreased generation of reactive oxygen species after irradiation and down-regulation of the subsequent events leading to apoptosis.

Effects of fatty acids on the growth of Caco-2 cells

Epidemiological studies suggest that polyunsaturated fatty acids may protect against colorectal neoplasia. In order to explore this observation, cell proliferation and viability, lipid composition, membrane fluidity, and lipid peroxidation were measured in Caco-2 cells after 48h incubation with various fatty acids. Saturated and monounsaturated fatty acids incorporated less well in the membranes than polyunsaturated fatty acids (PUFAs). All of the PUFAs tested had an inhibitory effect on cell proliferation/viability whereas the saturated and monounsaturated fatty acids did not. Addition of palmitic acid had no significant effect on membrane fluidity whereas unsaturated fatty acids increased membrane fluidity in a dose-dependent manner. PUFAs strongly increased tumor cell lipid peroxidation in a dose-dependent manner. Saturated and monounsaturated fatty acids increased lipid peroxidation in this cell line only at high concentration. Preincubation of Caco-2 cells with vitamin E prevented the inhibition of proliferation/viability, the elevation of the MDA concentration and the increased membrane fluidity induced by PUFAs. Our data indicate that PUFAs are potent inhibitors of the growth of colon cancer cells in vitro.

Systemic endotoxaemia following obstructive jaundice: the role of lactulose

BACKGROUND

Obstructive jaundice is often accompanied by bacterial translocation and subsequent sepsis. The effect of lactulose in preventing that process was evaluated in an experimental model. Obstructive jaundice was induced in 23 rabbits after common bile duct ligation.

METHODS

Animals were divided into two groups. Group A of 11 animals-controls and group B of 12 rabbits, which received 2 ml/kg of lactulose p.o. by a nasogastric tube. Blood was sampled daily, before and after operation. Samples were applied for culture and for estimation of endotoxins (LPS), tumor necrosis factor (TNFa), and malondialdehyde (MDA).

RESULTS

Mean (+/-SD) survival of animals of group A was 3.08+/-0.19 days compared to 5.36+/-0.41 days of animals of group B. Serum concentrations of LPS and TNFa of each day of treatment remain constant in animals of group A; they were steadily decreased in animals of group B reaching statistical significance on the fourth day. Similar changes were not found for MDA.

CONCLUSION

The administration of lactulose may prevent systemic endotoxaemia and the subsequent inflammatory response in an experimental model of obstructive jaundice, so as to extend survival. These results merit further clinical evaluation.

Lipid peroxidation in chronic gastritis; any influence of Helicobacter pylori?

In an attempt to investigate the significance of lipid peroxidation in the pathogenesis of gastritis associated with or without Helicobacter pylori infection, malonodialdehyde (MDA) levels were measured by the thiobarbiturate assay in the gastric juice of 101 patients undergoing upper GI endoscopy and correlated with histopathological findings. Elevated MDA levels were found in all patients with gastritis compared with controls. MDA levels were significantly correlated with the extent of the mucosal inflammation and with disease activity in patients with reactive gastritis. In patients with H. pylori associated gastritis MDA levels were not correlated with disease activity but rather with the degree of atrophy. In this case, MDA levels were equal or even less than in patients with reactive gastritis. MDA levels were not affected by the history of consumption of PPIs, of H(2)-blockers or of NSAIDs over the last month before the endoscopy. It is concluded that lipid peroxidation is a mechanism involved in the pathogenesis of gastritis associated or not to H. pylori infection.

Age-associated alteration of lipid peroxidation and superoxide dismutase activity in CBA and AKR mice

Oxidative modification of lipids, proteins and DNA by reactive oxygen species in the organism and imbalance between the concentrations of free radicals and the antioxidant defenses may be related to processes such as aging and diseases (cardiovascular, neurodegenerative, cancer, etc.). Although the relationship between oxidant status and antioxidant defence in aging of different species, organs or sexes has been investigated extensively, the studies have produced conflicting results. In order to determine the extent of age-associated alteration, oxidant production and antioxidant status were measured in tissues of CBA and AKR mice of both sexes. At the same time we will focus on lipid peroxidation (LPO) process and superoxide dismutase activity (SOD) of AKR mice related to ontogeny of thymic lymphoma in mice of different age and sex. Male and female CBA and AKR mice aged 3, 6, 12 or 18 months were used. Lipid-bound sialic acid (LSA) content was determined as a malignancy marker. LPO processes of CBA and AKR mice were monitored according to the presence of thiobarbituric acid reactive substances (TBARS) in liver and thymus, and antioxidant status as SOD activity in whole blood. TBARS concentration increased significantly with age in the liver of CBA and AKR mice of both sexes, but only in male thymuses of both strains. TBARS concentration in female thymuses of both strains was unchanged during aging. Thus, age-associated LPO processes of tumor-free mice of both strains were tissue-dependent. In the liver of tumor-bearing CBA and AKR mice as well as in thymuses of AKR mice, TBARS concentration significantly decreased and was neither sex nor tissue related. SOD activity was strain-dependent but independent of sex. However, SOD activity in mice with developed thymomas was drastically reduced in comparison to tumor-free mice. Our data indicate that age associated LPO processes in both strains are only tissue-dependent and SOD activity mainly strain-dependent in tumor-free mice. In tumor-bearing mice LPO processes and SOD activity were not tissue, sex or strain dependent.

Rapid alterations of serum oxidant and antioxidant status with the intravenous administration of n-6 polyunsaturated fatty acids

In an attempt to achieve the safe intravenous administration of two n-6 polyunsaturated fatty acids (PUFAs), gamma-linolenic acid (GLA) and arachidonic acid (AA), and to study the subsequent changes on the total oxidant and antioxidant status, various steadily increasing doses of each acid were injected intravenously at different infusion times in 28 male rabbits. Blood samples were collected at 15-min time intervals by the hepatic veins and from the carotid artery; oxidant status was determined by the thiobarbiturate assay and total antioxidant status (TAS) was assessed by a colorimetric assay. Both n-6 PUFAs were administered with safety at a dose of 25 mg/kg within 10 min accompanied by an increase of malonodialdehyde concentrations in the hepatic veins and in the carotid artery 30-45 min, respectively, after the end of the infusion of GLA and/or AA. Similar changes did not occur in red cell membranes after the infusion of AA. TAS presented reciprocal changes to malonodialdehyde production; the main consumption of TAS was observed in all samples 30-60 min after the end of the infusion of n-6 PUFAs. The above-mentioned rapid alterations occurring in both serum oxidant and antioxidant status after GLA might have a future clinical therapeutic significance in conditions like cancer and disseminated infectious diseases.

Biodegradation of viticulture wastes by Pleurotus: a source of microbial and human food and its potential use in animal feeding

The bioconversion of vineyard pruning and grape pomace by Pleurotus spp. using a solid state fermentation (SSF) was evaluated. Fruiting body production and chemical changes in the substrates after harvesting were measured. Biological efficiency and bioconversion ranged from 37.2 to 78.7% and from 16.7 to 38.8%, respectively. The best substrates for mycelial growth and mushroom yield were the mixtures with higher vineyard pruning content. Inclusion of pruning content had higher phenolic components and total sugars, better C/N ratio, and lower crude fat and total nitrogen than pomace. On the contrary, mycelium grew more slowly and scarcely in all treatments with 100% grape pomace. Moisture, protein, fat, and lignin contents were generally higher in mixtures with higher pomace proportion, whereas neutral detergent fiber, hemicellulose, and cellulose contents were higher with pruning content. Pleurotus strains may act depending on the availability of fiber fractions of substrate, and dynamic changes in digestion might occur as these fractions change during fungal growth. The recycling of viticulture residues through SSF by Pleurotus has great potential to produce human food and yields an available high-fiber feed for limited use in ruminants.