Is increased arachidonic acid release a cause or a consequence of replicative senescence?

Arachidonic acid (AA) has been related to both stimulation and inhibition of cellular proliferation. During replicative senescence of human fibroblasts, increased levels of AA have been thought to play a causal role in the limited proliferative capacity of the cells. To clarify the role of AA in the proliferation of normal fibroblasts and in cellular senescence, we examined uptake from and release of AA into the culture media and its effects on DNA synthesis. Our results indicate that some aspects of AA metabolism in normal human fibroblasts aged in culture are significantly different in comparison to early passage cells. Particularly, AA release following different mitogenic stimulation is higher in senescent than in young cells. Notwithstanding this significant difference, AA, at the concentration used, has no inhibitory effect on fibroblast DNA synthesis. Moreover AA and prostaglandins are responsible for the proliferative block in neither senescent cells nor mediate ceramide inhibition of DNA synthesis. So our results suggest that the increasing AA release is not causal, but rather the result of in vitro aging.

The protective role of different green tea extracts after oxidative damage is related to their catechin composition

The antioxidant activities of three different green tea extracts were investigated and compared by two different methods. By the first method, which evaluated the direct protective effect of the green tea extracts on lipid peroxidation, the extracts were added, at different concentrations, to a lipid model system, made by refined peanut oil, freshly submitted to a further bleaching and subjected to forced oxidation at 98 degrees C, by an oxidative stability instrument. By the second method, the effectiveness of the same extracts was checked in cultures of neonatal rat cardiomyocytes exposed to a free radical-generating system by evaluating conjugated diene production and lactate dehydrogenase release. All of the extracts revealed a strong antioxidant activity by both the methods, and a particular effectiveness was demonstrated by the extracts having higher amounts of (-)-epigallocathechin-3-gallate and (-)-epigallocathechin, as analyzed by reverse-phase HPLC analysis.

Five-year survival results of subcutaneous low-dose immunotherapy with interleukin-2 alone in metastatic renal cell cancer patients

After the discovery of its essential role in anticancer immunity, IL-2 cancer immunotherapy has shown that comparable results may be obtained with different schedules, including intravenous high-dose IL-2 as a bolus or as a 24-hour intravenous infusion or prolonged subcutaneous injection of low-dose IL-2 with or without IFN-alpha. This study shows the long-term results obtained in 92 metastatic renal cell cancer (RCC) patients with low-dose subcutaneous IL-2, which was given at 3 million IU twice/day for 5 days/week for 6 consecutive weeks. In nonprogressing patients, a second cycle was planned after a 21-day rest period, followed by maintenance therapy consisting of 5 days of treatment every month until disease progression. Complete response (CR) was achieved in only 2/92 (2%) patients, and partial response (PR) was observed in 19 patients (21%). Therefore, the response rate (CR + PR) was 21/92 (23%), with a median duration of response of 25 months. Stable disease (SD) occurred in 37 patients (40%), whereas the other 34 (37%) had a progressive disease (PD). The response rate was significantly higher in patients with a disease-free interval of >1 year than in those with a lower interval, in patients with a high performance status (PS) than in those with a low PS, and in patients with sites of disease other than the liver. A 5-year survival was obtained in 9/92 (9%) patients, and the percent of survival was significantly higher in patients with a response or SD than in those with PD. The treatment was well tolerated in all patients. This study confirms that low-dose subcutaneous IL-2 alone in an effective and well tolerated therapy of metastatic RCC, with results comparable to those described with more aggressive and toxic IL-2 schedules.

Dietary manipulation of delta-6-desaturase modifies phospholipid arachidonic acid levels and the urinary excretion of calcium and oxalate in the rat: insight in calcium lithogenesis

An anomalous n-6 polyunsaturated fatty acid composition in plasma and erythrocyte membrane phospholipids, namely increased levels of arachidonic acid (AA), has been reported in calcium nephrolithiasis and has been proposed to play an important role in its pathogenesis. To confirm this, in rats we modified phospholipid AA levels by dietary manipulation of the delta-6-desaturase, the rate-limiting enzyme of the fatty acid biosynthetic pathway, and evaluated the effect on cellular and renal functions predisposing to lithogenesis. Increased AA levels led to conditions at risk for nephrolithiasis: higher oxalate flux and lower sodium cotransport in erythrocytes and a rise in urinary prostaglandin E2, calcium, sodium, and oxalate levels; reduced AA levels reversed these changes. In vitro, in human erythrocytes the incorporation of exogenous AA into membranes increased band 3 protein phosphorylation directly activating the Ser/Thr protein kinase CK1 and induced a parallel raise in band 3-mediated oxalate transport. These findings demonstrate the pivotal role of phospholipid AA in modulating erythrocyte and renal transport of calcium and oxalate.

The impairment of essential fatty acid metabolism as a key factor in doxorubicin-induced damage in cultured rat cardiomyocytes

The clinical use of the antitumoral doxorubicin (DOX) is limited by its cardiotoxicity, which is mediated through different mechanisms. The membrane lipid peroxidation induced by DOX may cause disruption of the unsaturated fatty acyl chains; in the endoplasmic reticulum, containing the system catalyzing the desaturation/elongation of fatty acids, DOX could interfere with the metabolism of linoleic and alpha-linolenic acids. Using primary cultures of neonatal rat cardiomyocytes we demonstrated that the exposure to different concentrations of DOX (10(-5) and 10(-7) M) for 24 h caused an increase in the production of conjugated dienes, an impairment in the desaturation/elongation of essential fatty acids, and a reduction in the cellular content of highly unsaturated fatty acids. Conversely, 1 h exposure to 10(-5) M DOX was sufficient to induce alterations in the desaturation/elongation of linoleic and alpha-linolenic acids, but did not cause either formation of conjugated dienes or modification of the fatty acyl pattern. Therefore, DOX has a dual negative effect, depending on its concentration and on the time of exposure, one directed against the membrane highly unsaturated fatty acids, the other against the system which is required for the synthesis of these fatty acids themselves. These two effects synergically act in causing heart cell damage.

Concentration- and time-dependent effects of gamma-linolenic acid supplementation to tumor cells in culture

Gamma-linolenic acid (GLA) supplemented to neuroblastoma SK-N-BE, tubal carcinoma TG and colon carcinoma SW-620 cells was incorporated into phospholipids in all the cell lines (although to different extents), in a concentration- and time-dependent manner. All the cell lines were able to metabolize GLA to arachidonic acid, SK-N-BE being the most active. Supplementation with low GLA concentrations for short periods was not sufficient to impair cell proliferation; only higher amounts of GLA had an anti-proliferative effect also in short times. In these conditions, the antiproliferative effect of GLA is probably due to cellular dysfunction caused by fatty acid modifications.

Essential fatty acid metabolism in long term primary cultures of rat cardiomyocytes: a beneficial effect of n-6:n-3 fatty acids supplementation

In long term (21 days) primary cultures of neonatal rat cardiomyocytes, utilized as a model of in vitro senescence, we investigated the dual effect of the time length in culture and of the supplementation with n-6:n-3 fatty acid mixtures on linoleic (LA) and alpha-linolenic acid (ALA) metabolism. Cardiomyocytes were divided into groups receiving: (1) control medium; (2) control medium plus n-3 fatty acids; (3) and (4) control medium plus n-6 and n-3 fatty acids in the ratio 1:2 or 2:1, respectively. In control cells. senescence caused a reduction in the conversion of LA and ALA, and the decrease in their metabolites was bypassed by the different supplementations. The fatty acid composition of cardiomyocyte lipids was therefore affected by both senescence and supplementation, as evidenced by the n-6:n-3 fatty acid ratio and the unsaturation index (U.I.) in cellular lipids. The final result of ageing in culture and of fatty acid supplementations was in all the groups of cells but one (n-6:n-3, 2:1) an unbalance in the n-6:n-3 fatty acid ratio. All the supplementations were able to counteract the decrease in the U.I. observed with senescence, but only the n-6:n-3 (2:1) was able to do so by increasing the cellular content of the fatty acids which are precursors of anti-aggregation eicosanoids without altering the n-6:n-3 fatty acid ratio.

Partial depletion and multiple deletions of muscle mtDNA in familial MNGIE syndrome

OBJECTIVE

To describe the unique combination of partial depletion and multiple deletions of mitochondrial DNA (mtDNA) on muscle DNA analysis of three siblings with mitochondrial neurogastrointestinal encephalomyopathy (MNGIE).

BACKGROUND

MNGIE is a relatively homogeneous autosomal recessive disorder characterized by gastrointestinal dysmobility, ophthalmoparesis, peripheral neuropathy, mitochondrial myopathy, and altered white matter signal at brain imaging. Muscle multiple mtDNA deletions have been found in about half of the described cases.

METHODS

We studied three affected siblings (two were monozygotic twins) born to nonconsanguineous parents. Muscle mtDNA was investigated by quantitative Southern and Slot blot techniques and by PCR analysis. Morphologic confirmation in the muscle tissue was achieved by using in situ hybridization with a mtDNA probe complementary to an undeleted region and by DNA immunohistochemistry.

RESULTS

All three patients showed ragged red (RRF) and cytochrome c oxidase-negative fibers, as well as partial deficiency of complexes I and IV. Southern and Slot blot analyses showed mtDNA depletion in all patients. Multiple mtDNA deletions were also detected by PCR analysis. In situ hybridization demonstrated an overall signal weaker than controls, with a relatively higher signal in RRF. Antibodies against DNA showed a decreased cytoplasmic network.

CONCLUSIONS

The muscle histopathology and respiratory chain enzyme defects may be accounted for by the decreased mtDNA amount and by the presence of mtDNA deleted molecules; however, relative levels of mtDNA seem to correlate with life span in these patients. The combination of partial depletion and multiple deletions of mtDNA might indicate the derangement of a common genetic mechanism controlling mtDNA copy number and integrity.

Dual influence of aging and vitamin B6 deficiency on delta-6-desaturation of essential fatty acids in rat liver microsomes

Delta-6-desaturase (D6D) activity is influenced by many nutritional and non-nutritional factors, among which one of the most important is aging. D6D activity could be susceptible to the dual influence of aging itself and of nutritional deficiencies, due to the reduced intake and/or absorption of essential nutrients. Particularly, vitamin B6 deficiency might be a crucial factor for D6D activity in aged people. Using 20 month old Sprague-Dawley rats fed a diet with a subnormal level of vitamin B6, we evaluated D6D activity for linoleic acid (LA) and alpha-linolenic acid (ALA) in liver microsomes, and the fatty acid composition of microsomal total lipids. We observed a diminished D6D activity for LA and also for ALA in vitamin B6-deficient animals, being approximately 63% and 81% respectively of the corresponding activity in control rats. As a consequence, significant modifications in the relative molar content of microsomal fatty acids were observed. The content of arachidonic and docosahexaenoic acid, the main products of the conversion of LA and ALA respectively, decreased, LA content increased and a decrease in the unsaturation index was observed in liver microsomes of B6-deficient rats. The foregoing results suggest that the impairment of D6D activity by vitamin B6 deficiency might be an important factor in decreasing the synthesis of n-6 and n-3 PUFAs. This may be particularly important in aging, where D6D activity is already impaired.

Cytochrome c oxidase subunit I microdeletion in a patient with motor neuron disease

An out-of-frame mutation of the mitochondrial DNA-encoded subunit I of cytochrome c oxidase (COX) was discovered during investigation of a severe isolated muscle COX deficiency in a patient with motor neuron-like degeneration. The mutation is a heteroplasmic 5-bp microdeletion located in the 5' end of the COI gene, leading to premature termination of the corresponding translation product. Western blot analysis, immunohistochemistry, and single-fiber polymerase chain reaction demonstrated a tight correlation between COX defect, COX I expression, and percentage of mutation. COX subunits II, III, and IV were decreased as well, suggesting a defective assembly of COX holoenzyme. The mutation was associated with a clinical phenotype unusual for a mitochondrial disorder, that is, an isolated motor neuron disease (MND) with some atypical findings, including early onset, preferential involvement of the upper motor neuron, and increased cerebrospinal fluid protein content. MND may arise from impaired scavenging and overproduction of free oxygen radicals, a by-product of oxidative phosphorylation (OXPHOS). Our observation suggests that OXPHOS impairment could play a role in the pathogenesis of some MND cases.

Manipulation of lipid composition of rat heart myocytes aged in culture and its effect on alpha1-adrenoceptor stimulation

The fatty acid composition of the phosphoinositides was evaluated in cultured neonatal rat cardiomyocytes during the aging-like process in vitro, comparing data obtained from control and gamma-linolenic acid supplemented cardiomyocytes. The response to alpha1 stimulation was evaluated in both control and supplemented cells to verify the relationship between the alterations of the phosphoinositide fatty acid composition concomitant to culture aging and the cell response to exogenous stimuli. Arachidonate level decreased as a function of age in all the phosphoinositides, which appeared to be more saturated as cells aged in culture. Inositol phosphate production in response to alpha1 stimulation decreased as cells aged in culture. Supplementation of culture medium with gamma-linolenic acid caused significant modifications in the fatty acid pattern of the phosphoinositides, which appeared less saturated than the corresponding fractions isolated from unsupplemented cells during the aging-like process. The modifications induced by the supplementation in the phosphoinositide fatty acid composition prevented the age-related reduction of inositol phosphate production upon stimulation. These results clearly indicate a major role for the lipid composition in determining the response to alpha1 stimulation, suggesting a nutritional approach to overcome some of the impairments of molecular events related to the process of aging.

Linoleic acid metabolism in primary cultures of adult rat cardiomyocytes is impaired by aging

Many of the changes that occur in the rat cardiac muscle with advancing age are related to modifications in membrane fatty acid composition, polyunsaturated fatty acids decreasing and saturated increasing as the animal develops. In the present study, using cultured adult cardiomyocytes isolated from the hearts of rats of a broad (1-24 months) age range, we demonstrated that the modifications in the fatty acid pattern of cardiomyocytes have to be related to alterations in the mechanism of desaturation/elongation of essential fatty acids. In fact, independent of the age of the animal, heart cells in culture were capable of rapidly metabolizing radiolabeled linoleic acid taken up from the surrounding medium, but to a different extent. The ability of heart cells to metabolize linoleic acid to higher and more unsaturated metabolites decreased with the animal's age. As the age of the animal increased, the pattern of fatty acids of the cultured cardiomyocytes showed a gradual but significant shift, similar to those reported in the whole heart. Data here reported confirm that the basic aging-related process in the cellular model system may also be relevant to aging in the whole animal.

Age-related changes in essential fatty acid metabolism in cultured rat heart myocytes

We previously demonstrated that cultured neonatal rat myocytes have the capacity to desaturate/elongate essential fatty acids, alpha-linolenic acid conversion being higher than linoleic acid conversion. The whole process of highly unsaturated fatty acid formation from linoleic and alpha-linolenic acids slows with aging. In this study we grew heart myocytes in culture for different periods of time, and we observed a decrease in the desaturating/elongating activities for both substrates as the cells aged in culture. Alpha-linolenic acid conversion into highly unsaturated fatty acids was less impaired by aging than linoleic acid conversion. These modifications are correlated to the age-dependent alterations observed in the total lipid fatty acid composition, which caused a decrease in the unsaturation index. Changes in the lipid composition that occur in aging cultures parallel those reported for several tissues upon aging in the whole animal. The data herein reported may suggest the possibility of counteracting the effects of aging on lipid metabolism by supplementing cultures with appropriate amounts of highly unsaturated fatty acids.

Essential fatty acid metabolism in cardiomyocytes grown in media enriched with different N-6/N-3 fatty acid combinations

We have evaluated the effects of three different 18:3n-6, 20:5n-3 and 22:6n-3 fatty acid combinations on essential fatty acid (EFA) metabolism in rat cultured cardiomyocytes. The desaturating/elongating activities for linoleic (LA) and alpha-linolenic acid (ALA) were evaluated by radiolabeling the cells with 1-[14C]LA or 1-[14C]ALA and the fatty acid pattern of cardiomyocytes was assessed by gas chromatography. LA and ALA conversion to more unsaturated metabolites was reduced by increasing respectively n-3 and n-6 fatty acid concentration in the media. The all three combinations used reduced the saturated and increased the polyunsaturated fatty acid content of cardiomyocytes. The n-6/n-3 fatty acid ratio did not change compared to control cells in cardiomyocytes receiving the highest amount of 18:3n-6 and the lowest amounts of n-3 fatty acids. This combination may be suitable for modifying EFA desaturating/elongating activities without altering the physicochemical parameters which are related to the correct balance between n-6 and n-3 fatty acid content.

gamma-Linolenic acid supplementation can affect cancer cell proliferation via modification of fatty acid composition

We examined the effect of gamma-linolenic acid (GLA) supplementation on the growth and fatty acid composition of three human tumor cell lines (the neuroblastoma CHP-212, the tubal carcinoma TG, and the colon carcinoma SW-620), in order to evaluate the relationship between GLA-induced tumor cell death and the distribution of fatty acids in tumor cells. At the highest GLA concentrations (10 and 20 micrograms/ml), the DNA synthesis was completely abolished; at 5 micrograms/ml GLA only SW-620 cells did not proliferate, while CHP-212 and TG cells showed a residual [3H]-thymidine incorporation. GLA levels were very low in cells grown in control medium; GLA supplementation caused a significant incorporation of GLA itself in all the cell lines at each concentration. In TG and CHP-212 cells, GLA was metabolized, although to a different extent, to dihomo-gamma linolenic acid and arachidonic acid. SW-620 cells neither elongated nor desaturated the incorporated GLA. The highest cytostatic effect was reached when GLA was not transformed into its metabolites, suggesting that the GLA toxicity to tumor cells is not dependent on metabolites but is due to GLA itself.

Normalization of immune response and phosphoinositide fatty acid composition of peripheral blood lymphocytes in an alcoholic patient after alcohol abstinence

After 10 months of alcohol abstinence a malnourished alcoholic patient improved his nutritional status. The analysis of peripheral blood lymphocyte response to mitogenic stimulation with the antibody anti-CD3 and of the fatty acid composition of the (poly)-phosphoinositide fraction derived from lymphocytes revealed: 1) a similar [3H]-thymidine uptake as in control (non-drinker) subjects; 2) a similar relative molar content of the main fatty acids in the (poly)-phosphoinositides as in control subjects. Alcohol abstinence can normalize both the parameters, which are greatly altered during alcohol abuse. This suggests a link between nutritional status and lymphocyte responsiveness via phosphoinositide fatty acid composition.

Defective calcium increase and inositol phosphate production in anti-CD3-stimulated lymphocytes of alcoholics without progressive liver disease

Intracellular free calcium concentration, phosphoinositide turnover, and inositol phosphate production were analyzed in peripheral blood lymphocytes from seven well-nourished alcoholic patients without severe acute or chronic liver disease, before and after stimulation with anti-CD3 antibody. Seven comparable nondrinkers were studied as controls. A lower increase in intracellular free calcium concentration was detected in alcoholics, after anti-CD3 stimulation of lymphocytes, than in control subjects. Lymphocyte activation generated inositol phosphates in both controls and alcoholics, but inositol phosphate production was significantly lower in alcoholics. The agreement between these findings indicates that the reduction in inositol phosphates is one of the most important events in the early phases of lymphocyte activation in alcoholics.

Metabolism of linoleic and alpha-linolenic acids in cultured cardiomyocytes: effect of different N-6 and N-3 fatty acid supplementation

The metabolites of linoleic (LA) and alpha-linolenic (ALA) acids are involved in coronary heart disease. Both n-6 and n-3 essential fatty acids (EFAs) are likely to be important in prevention of atherosclerosis since the common risk factors are associated with their reduced 6-desaturation. We previously demonstrated the ability of heart tissue to desaturate LA. In this study we examined the ability of cultured cardiomyocytes to metabolize both LA and ALA in vivo, in the absence and in the presence of gamma linolenic acid (GLA), eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) alone or combined together. In control conditions, about 25% or LA and about 90% of ALA were converted in PUFAs. GLA supplementation had no influence on LA conversion to more unsaturated fatty acids, while the addition of n-3 fatty acids, alone or combined together, significantly decreased the formation of interconversion products from LA. Using the combination of n-6 and n-3 PUFAs, GLA seemed to counterbalance partially the inhibitory effect of EPA and DHA on LA desaturation/elongation. The conversion of ALA to more unsaturated metabolites was greatly affected by GLA supplementation. Each supplemented fatty acid was incorporated to a significant extent into cardiomyocyte lipids, as revealed by gas chromatographic analysis. The n-6/n-3 fatty acid ratio was greatly influenced by the different supplementations; the ratio in GLA+EPA+DHA supplemented cardiomyocytes was the most similar to that recorded in control cardiomyocytes. Since important risk factors for coronary disease may be associated with reduced 6-desaturation of the parent EFAs, administration of n-6 or n-3 EFA metabolites alone could cause undesirable effects. Since they appear to have different and synergistic roles, only combined treatment with both n-6 and n-3 metabolites is likely to achieve optimum results.

Essential fatty acid metabolism in cultured rat cardiomyocytes in response to either N-6 or N-3 fatty acid supplementation

In this study we demonstrate that cultured rat cardiomyocytes possess the capacity to desaturate/elongate essential fatty acids (EFAs). Alpha-linolenic acid (ALA) conversion to higher metabolites was greater than linoleic acid (LA) conversion, according to the higher affinity of the delta-6-desaturase enzyme for the n-3 than for the n-6 EFAs. Gamma-linolenic acid (GLA) supplementation to the culture medium had no influence on LA conversion; but the addition of eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids significantly decreased the formation of interconversion products from LA. The conversion of ALA to higher metabolites was greatly affected by GLA; EPA had no effect on ALA conversion, while DHA significantly inhibited it. Both GLA (converted mostly to dihomo-gamma-linolenic acid) and EPA can be removed from phospholipids and addressed to prostanoid biosynthesis, so avoiding their potential accumulation and the inhibition of their own production. Our data clearly indicate that supplementation of the culture medium with either n-6 or n-3 fatty acids can cause reduced levels of the other series of fatty acids. This effect may be undesirable, since both n-6 and n-3 fatty acids are important in the prevention of coronary diseases.

Incorporation of cholesterol oxidation products into cell lipids and their influence on the proliferation of cultured cardiomyocytes

We have investigated the incorporation of cholesterol oxidation products into cardiomyocyte lipids and related this to changes in cell proliferation, evaluated by measuring cellular protein content. Primary cultures of neonatal rat ventricular cells were supplemented with scalar concentrations of several cholesterol oxidation products (cholestan-5 alpha, 6 alpha-epoxy-3 beta-ol, 5 alpha-cholestane-3 beta, 5, 6 beta-triol, 5-cholesten-3 beta, 4 beta-diol, 5-cholesten-3 beta-ol-7-one, and 5-cholesten-3-one). Although all the cholesterol oxidation products were incorporated into the cardiomyocyte lipids when added to the medium at a concentration higher than 0.5 microM, the extent of the incorporation of the different cholesterol oxidation products differed, depending on the concentration in the culture medium and on the chemical structure of the compound. The effects of the cholesterol oxidation products on the cellular protein content were also different: 5 alpha-cholestane-3 beta, 5, 6 beta-triol was shown to be the most potent inhibitor of cell proliferation, followed by cholestan-5 alpha, 6 alpha-epoxy-3 beta-ol, 5-cholesten-3 beta, 4 beta-diol and 5-cholesten-3 beta-ol-7-one. 5-Cholesten-3-one did not affect the cellular protein content. The ability of cholesterol oxidation products to inhibit cell proliferation, and their capacity to increase the permeability of the plasma membrane to calcium, could be deleterious for cardiac cells.