Decreased production of inflammatory mediators in human osteoarthritic chondrocytes by conjugated linoleic acids

Osteoarthritic chondrocytes (OC) produce excessive prostaglandin E₂ (PGE₂) and nitric oxide (NO), which function as inflammation mediators in the pathogenesis of osteoarthritis (OA). This study examined the effect of CLA alone and in combination with other PUFA on the FA composition and the production of PGE₂ and NO in OC cultures isolated from OA patients. Human OC were grown in monolayer and treated with one of the following PUFA treatments: CLA, CLA+arachidonic acid (CLA/AA), CLA_EPA (CLA/EPA), linoleic acid (LA), LA+AA (LA/AA), LA+EPA (LA/EPA), and ethanol (as a vehicle control) at 10 and 20 μM for 6 d. Supplementation of PUFA at 10 μM for 6 d did not introduce any cytotoxic effects or morphological changes in OC, whereas 20 μM resulted in apoptosis. Cultures of OC treated with CLA, CLA/AA, and CLA/EPA had higher concentrations of CLA isomers, and these isomers were not detected in other treatments. Supplementation of CLA or LA alone to the OC led to a lower PGE₂ production compared to the control. Combination of CLA/EPA resulted in the lowest PGE₂ production in cultured OC. OC cultures treated with CLA were lower in NO production than the control, whereas the LA/AA treatment demonstrated the lowest NO production. The fact that CLA alone or in combination with other PUFA modulated PGE₂ and NO production in human OC cultures suggests that these 18∶2 isomers may have the potential to influence OA pathogenesis.     

Effects of high corn oil diet on preneoplastic murine colons: Prostanoid production and lipid composition

In the present study, the effect of normal (5% by wt) and high (23.5% by wt) corn oil diets on prostanoid production and on the lipid composition of preneoplastic colonic epithelium was investigated. CF₁ mice (female, 3–4-weeks-old) were fed a normal corn oil dietad libitum and were treated with the colon carcinogen 1,2-dimethylhydrazine (DMH, 20 mg/kg/wk) or saline (control) for 24 wk. At this stage, all animals received the AIN-76 diet (normal corn oil)ad libitum. Following the last injection, half of the animals from each treatment group were randomly allocated to a high corn oil diet for 5 to 10 wk, whereas the remaining animals continued on the normal corn oil diet. After 5 wk of feeding, the colonic mucosa of carcinogentreated animals had a higher level of bicyclic prostaglandin E₂ (PGE₂) than had the animals in the control groups; prostanoid synthesis in the colonic mucosa of control animals was unaffected by the high corn oil diet. Preneoplastic colonic mucosa of animals fed the high corn oil diet had a significantly higher level of PGE₂ than corresponding control colonic mucosa. The 6-keto-prostaglandin F_1α/thromboxane B₂ ratio was significantly lower in the DMH-treated groups than in the control groups, and was unaffected by dietary treatments. After 10 wk of feeding a particular diet, the differences in the fatty acid composition between the control and DMH-treated groups were minor. Our findings demonstrate that the preneoplastic colonic epithelium differs from that of normal epithelium with respect to prostanoid synthesis.     

Effects of dietary corn oil and salmon oil on lipids and prostaglandin E2 in rat gastric mucosa

Three groups of male rats were fed either a corn oilenriched diet (17%, w/w), a salmon oil-enriched diet (12.5%) supplemented with corn oil (4.5%) or a low-fat diet (4.4%) for eight wk to investigate the possible relationships between dietary fatty acids and lipid composition, and prostaglandin E₂ level and phospholipase A₂ activity in the rat gastric mucosa. High-fat diets induced no important variation in total protein, phospholipid and cholesterol contents of gastric mucosa. Compared with a low-fat diet, corn oil produced a higher n−6/n−3 ratio in mucosal lipids, whereas this ratio was markedly lowered by a fish oil diet. In comparison with the low-fat diet, the production of prostaglandin E₂(PGE₂) in gastric mucosa of rats fed salmon oil was significantly, decreased by a factor of 2.8. In the corn oil group, PGE₂ production tended to decrease, but not significantly. In comparison with the low-fat diet, both specific and total gastric mucosal phospholipase A₂ activities were increased (+18 and 23%, respectively) in the salmon oil group; they were unchanged in the corn oil group. It is suggested that the decrease of gastric PGE₂ in rats fed fish oil is not provoked by a decrease in phospholipase A₂ activity but may be the result of the substitution of arachidonic acid by n−3 PUFA or activation of PGE₂ catabolism.     

Modulation of respiratory syncytial virus-induced prostaglandin E<Subscript>2</Subscript> production by n−3 long-chain polyunsaturated fatty acids in human respiratory epithelium

Infection with respiratory syncytial virus (RSV) results in substantial infant morbidity and has been associated with the subsequent development of childhood asthma. Inflammatory mediators produced by both the epithelium and tissue leukocytes during RSV infection stimulate the release of chemotactic factors by the respiratory epithelium and the subsequent influx of inflammatory cells, predominantly neutrophils. We investigated the production of inflammatory mediators [prostaglandin E₂ (PGE₂), interleukin (IL)-1β, tumor necrosis factor α] and chemokines [IL-8, RANTES (regulation on activation, normal T cell expressed and secreted)] by alveolar epithelial cells in response to RSV infection. Infection of a human alveolar epithelial transformed cell line (A549 cells) with live RSV substantially increased production of PGE₂, IL-8, and RANTES. By altering cell membrane FA through incorporation of the long-chain PUFA (LCPUFA) arachidonic acid, EPA, and DHA, we were subsequently able to significantly modulate PGE₂ production by the infected epithelium. Because of the dynamic nature of the effects of PGE₂ on lung function, regulation of this prostaglandin during RSV infection by n−3 LCPUFA has the potential to significantly alter the disease process.     

Differential effects of dietary fatty acids on the accumulation of arachidonic acid and its metabolic conversion through the cyclooxygenase and lipoxygenase in platelets and vascular tissue

Semisynthetic diets containing either corn oil (CO) or butter (B) (11 and 2.2 en % as linoleic acid, respectively) were fed to male rabbits for periods of 3 weeks and 3 months. The CO diet, in respect to the B diet, induced higher levels of linoleic acid (LA) and lower levels of arachidonic acid (AA) in platelet phospholipids, lower levels of AA in aortic phosphatidylinositol (PI) and accumulation of both LA and AA in liver lipids. The thresholds for aggregation with AA, but not with collagen, were higher in the CO group and the formation of thromboxane B₂ (TXB₂) from [¹⁴C] AA, but not from endogenous substrate after collagen stimulation, was lower in the same group. Formation of PGE₂-like material by incubated aortas was higher in the B group. In the CO group, platelet cyclooxygenase appeared to be selectively depressed. The correlations among diet-induced fatty acid changes in platelet and aortic lipids, platelet aggregation and thromboxane and prostacyclin formation are discussed.     

Influence of omega-3 and omega-6 fatty acid sources on prostaglandin levels in mice

Studies from this laboratory, employing a hairless mouse model, have indicated that a polyunsaturated fatty acid source rich in omega-3 (n−3) fatty acid (FA) inhibits ultraviolet (UV)-carcinogenic expression, when compared to that of diets containing predominantly n−6 fatty acids. Omega-3 FA is a poor substrate for cyclo-oxygenase, the rate-limiting step in prostaglandin (PG) synthesis—the latter, particularly PGE₂, are known to influence tumor biology. Based upon this rationale, plasma and cutaneous PGE₂ levels were determined from hairless mice fed diets containing either 4% or 12% corn or menhaden oil. After two weeks on the respective diets, plasma PGE₂ levels of corn oil-fed animals were approximately 6-fold greater than those of the menhaden oil-fed groups. A similar response was found in the dermis. Although the relationship to carcinogenic expression is unknown, dietary n−3 FA content can have a pronounced effect upon PGE₂ levels and possesses the potential for influencing other immunomodulators.     

Arachidonic acid,prostaglandin E2 and leukotriene C4 levels in gingiva and submandibular salivary glands of rats fed diets containing n−3 fatty acids

The effect of dietary n−3 fatty acids on prostaglandin E₂ (PGE₂) and leukotriene C₄ (LTC₄) levels in rat salivary glands and gingiva was examined in two separate nutritional studies. In the first set of experiments, two groups of male weanling Sprague-Dawley rats were fed semipurified diets containing 10% corn oil (control group) or 10% menhaden oil (experimental group). Rats were killed after 8 wk on the diets; the fatty acid composition of total phospholipids and the concentrations of PGE₂ and its precursor, arachidonic acid, were measured in gingiva and submandibular salivary glands (SMSG). Dietary n−3 fatty acids were incorporated into the tissue phospholipids. Arachidonic acid levels were reduced by 56% in gingiva and SMSG of rats fed menhaden oil compared with the control rats fed the diet containing corn oil. The concentrations of PGE₂ in SMSG and gingiva of rats fed the diet containing menhaden oil were reduced by 74% and 83%, respectively. In a subsequent nutritional study, we tested whether the diet-induced reduction in tissue arachidonic acid levels would also result in a corresponding decrease in LTC₄ production. Three groups of rats were fed diets containing 5% corn oil (group 1), 4% ethyl ester concentrate of n−3 fatty acids plus 1% corn oil (group 2), or 5% ethyl ester concentrate of n−3 fatty acids (group 3). After 6 wk of feeding, gingiva and SMSG were analyzed for arachidonic acid content andin vitro production of LTC₄. Arachidonic acid content of total phospholipids was about 60% lower in gingiva and 69% lower in SMSG of rats fed the ethyl ester concentrate of n−3 fatty acids (groups 2 and 3) than those of the control group fed the corn oil diet (group 1). Upon incubation with calcium ionophore, gingiva and SMSG from rats fed the n−3 fatty acids rich diet produced significantly less TLC₄ than those from rats of the control group. Because PGE₂ and LTC₄ are believed to be important biochemical mediators of periodontal disease, one may speculate that a diet-induced reduction in their levels may have a beneficial effect upon the course of the disease. The function of salivary glands may also be altered because of the role of these eicosanoids in salivary secretions. Presented in part for the Hatton Award Competition at the American Association for Dental Research Meeting, San Francisco, California, March 15–19, 1989, and at the International Association for Dental Research Meeting, Acapulco, Mexico, April 17–21, 1991.     

γ-linolenic acid-containing diet attenuates bleomycin-induced lung fibrosis in hamsters

Although bleomycin (BLM), an antineoplastic drug, is used in the treatment of a variety of tumors, the mechanism(s) that contribute to its induced lung injury and fibrosis are not fully elucidated. Since alterations in the levels of certain fatty acid metabolites have been associated with BLM-induced lung injury, we tested the effects of dietary γ-linolenic acid (GLA)-containing evening primrose oil on BLM-induced morphological alterations in the hamster lung, the marked elevation of tissue hydroxyproline (a marker for collagen synthesis), and elevated generation of arachidonic acid metabolites (marker of inflammatory mediators). Our data revealed that after 14 d of dietary GLA-containing oil (i) BLM-induced elevation of lung hydroxyproline was suppressed (P<0.05), (ii) the marked BLM-induced elevation of lung leukotriene B₄ (LTB₄) (a marker of polymorphonuclear generation of proinflammatory LTB₄) was significantly suppressed (P<0.05). The decrease in LTB₄ was accompanied by marked elevations (P<0.05) of lung prostaglandin E₁ (PGE₁) and 15-hydroxyeicosatrienoic acid (15-HETrE), both with known antiinflammatory properties. Taken together, data from these studies suggest that dietary GLA-containing oil contributes to tissue elevation of PGE₁ and 15-HETrE, which in vivo may attenuate lung inflammation and fibrosis.     

Dedifferentiation of Human Cardiac Myofibroblasts Is Independent of Activation of COX-2/PGE2 Pathway

The differentiation of cardiac fibroblasts to myofibroblasts is considered to be a critical step in activation and progression of cardiac fibrosis in heart disease. TGF-β is one of the key cytokines that promotes transition of fibroblasts to myofibroblasts. Dedifferentiation of formed myofibroblasts or reversal of formed myofibroblasts to fibroblasts remains incompletely understood. Prostaglandin E₂ (PGE₂) has been shown to dedifferentiate human lung myofibroblasts. The role of activation of the COX-2/PGE₂ pathway in dedifferentiation of cardiac myofibroblasts remains unknown. Here, we show that phorbol 12-myristate 13-acetate (PMA) but not PGE₂ induces dedifferentiation of de novo adult human cardiac myofibroblasts stimulated by TGF-β1 from human cardiac fibroblasts as evidenced by reduced expression of α-smooth muscle actin (α-SMA). PMA remarkably increased endogenous levels of PGE₂ in human cardiac myofibroblasts. Pretreatment of myofibroblasts with NS-398, a selective COX-2 inhibitor, and PF-04418948, a selective PGE₂ receptor type 2 (EP2) antagonist, had no effect on expression of α-SMA nor abolished the dedifferentiation induced by PMA. Our results indicated that endogenous and exogenous PGE₂ has no effects on dedifferentiation of cardiac myofibroblasts. PMA-induced dedifferentiation of cardiac myofibroblast is independent of activation of COX-2 and PGE₂ pathway. The mechanism in PMA-induced reversal of cardiac myofibroblasts needs to be explored further.     

Modulation of phorbol ester-associated events in epidermal cells by linoleate and arachidonate

To elucidate the events elicited by the skin tumor promotor 12-O-tetradecanoylphorbol-13-acetate (TPA), which are modulated by linoleic acid (LA) and arachidonic acid (AA), the activity of these fatty acids in cultured mouse epidermal cells was compared. Approximately 94% of either exogenous radiolabelled fatty acid was incorporated into the total phospholipid pool over 15 h. The relative distribution among the phospholipid classes differed, however, such that approximately 70% of phospholipid-associated [¹⁴C]-LA was found in phosphatidylcholine, compared to approximately 30% for [¹⁴C]AA. Phosphatidylethanolamine and phosphatidylinositol/phosphatidylserine contained 17 and 13% of the phospholipid [¹⁴C]LA, and 34 and 30% of [¹⁴C]AA, respectively. Prostaglandin (PG) E₂ production was low but similar in unstimulated cultures prelabelled with either [¹⁴C]LA or [¹⁴C]AA. However, in cultures treated with TPA (1.6 μM), [¹⁴C]AA-prelabelling resulted in approximately three times the amount of [¹⁴C]PGE₂ compared with cultures prelabelled with [¹⁴C]LA. Cultured cells were found to contain significant δ6 desaturase activity, which may enable conversion of LA to AA, and thus may account for the observed PGE₂ production from [¹⁴C]LA treated cells. AA-Supplemented (1.6 μM) cultures supported approximately twice the induction of ornithine decarboxylase activity by TPA compared with cultures treated with 1.8 μM LA. Activation of partially purified protein kinase C was similar for either fatty acid tested over a 10–300 μM dose range. Overall, the results suggest that LA does not have the same biological activity as AA with regard to several TPA-associated events known to be important in skin tumor promotion. This reduced biological activity of LA may be partly responsible for the known inhibition of mouse skin tumor promotion by high dietary levels of LA [Leyton, J., Lee, M.L., Locniskar, M.F., Belury, M.A., Slaga, T.J., Bechtel, D., and Fischer, S.M. (1991)Cancer Res. 51, 907–915].     

Influence of C18 long chain fatty acids on butyrate degradation by a mixed culture

Butyrate degradation in the presence of C₁₈ long chain fatty acids (LCFAs) was examined under anaerobic conditions at 21 °C. Butyrate degradation rates were a function of linoleic acid (LA) and oleic acid (OA) concentration but independent of the amount of stearic acid (SA) added. Within 2–4 h, butyrate reached undetectable levels in the control cultures. However, in cultures fed with LA, butyrate was removed within between 12 and 25 h and within 2–12 h for cultures inoculated with OA or SA. Propionate was detected in cultures fed with 50 mg dm^?3 LA and in cultures inoculated with OA and SA. LA exerted a greater inhibitory effect on butyrate‐degrading organisms than OA and SA with longer removal times observed in cultures fed with LA. The propionate and acetate removal times and quantity produced were not related to the type and concentration of LCFA. Copyright © 2004 Society of Chemical Industry     

Lactose fermentation in the presence of C18 fatty acids

Lactose degradation in the presence of C₁₈ long chain fatty acids was examined under anaerobic conditions at 37 °C. The lactose degradation rate was a function of linoleic acid (LA) and oleic acid (OA) concentrations but independent of the amount of stearic acid (SA) added. In cultures fed with LA, lactose was removed within approximately 12 h and within 6 h for cultures inoculated with OA or SA. Glucose, a product of lactose degradation, was only observed in cultures fed with 500–700 mg dm^?3 LA and 1000 mg dm^?3 OA. No galactose was detected under any of the conditions examined. The cause of glucose accumulation is likely due to inhibition of acidogens by LA and OA. Lactate was detected under all conditions examined. LA was more inhibitory on lactate‐consuming organisms than OA and SA and larger amounts of lactate were observed in cultures fed with LA. In addition to lactate, butyrate, propionate and acetate were also observed. Accumulation of volatile fatty acids was a function of the type and concentration of long chain fatty acids. In cultures fed with SA, lower levels of butyrate and acetate were observed when compared with those inoculated with LA and OA and no propionate was detected. Copyright © 2004 Society of Chemical Industry     

Effect of palm oil carotene on breast cancer tumorigenicity in nude mice

Biological therapies are new additions to breast cancer treatment. Among biological compounds, β-carotene has been reported to have immune modulatory effects, in particular, enhancement of natural killer cell activity and tumor necrosis factor-alpha production by macrophages. The objective of this study was to investigate the effect of palm carotene supplementation on the tumorigenicity of MCF-7 human breast cancer cells injected into athymic nude mice and to explore the mechanism by which palm carotenes suppress tumorigenesis. Forty-eight 4-wk-old mice were injected with 1×10⁶ MCF-7 cells into their mammary fat pad. The experimental group was supplemented with palm carotene whereas the control group was not. Significant differences were observed in tumor incidence (P<0.001) and tumor surface area and metastasis to lung (P<0.005) between the two groups. Natural killer (NK) cells and B-lymphocytes in the peripheral blood of carotene-supplemented mice were significantly increased (P<0.05 and P<0.001, respectively) compared with controls. These results suggest that palm oil carotene is able to modulate the immune system by increasing peripheral blood NK cells and B-lymphocytes and suppress the growth of MCF-7 human breast cancer cells.     

The effect of long-chain monoenes on prostaglandin E2 synthesis by rat skin

In order to ascertain whether the dermal lesions observed in male rats fed rapeseed oils are due to impaired prostaglandin biosynthesis, endogenous levels of prostaglandin E₂ (PGE₂) in skin and the capacity of this tissue to synthesize PGE₂ from arachidonic acid was investigated. Male Sprague-Dawley rats were fed from weaning for 8 weeks either a standard rat diet (chow) or semisynthetic diets containing 20% by weight of the following fat sources: corn oil; commercial lard; commercial lard to which was added 5.4% free erucic acid; rendered pig fat; or the following rapeseed oils:Brassica napus var. Zephyr;B. campestris var. Span;B. campestris var. Arlo (15%) and var. Echo (85%) designated HEAR (high erucic acid rapeseed). The long-chain monoene content (18∶1, 20∶1, and 22∶1) of the diets fed ranged from 30 to 71 mole % and that of skin from 27 to 74 mole %. A significant (P<0.01) correlation was found between the level of 18∶2n−6 in the diet and the endogenous PGE₂ levels in skin and the capacity of this tissue to synthesize PGE₂. No relationship was found between these two PGE₂ parameters and the level of erucic acid in the diet. The rate of turnover of PGE₂ appeared to be lower in rats fed rapeseed oil as evidenced by the relatively high endogenous PGE₂ levels when these oils were fed (96 to 105 μg/g). On the other hand, the lowest capacity for PGE₂ synthesis was found with skin from rats fed Zephyr rapeseed oil, rats which also had the most severe incidence of hair loss and dermal lesions. Significant (P<0.01) negative correlations were observed between the level of monoenes and specifically the level of oleic (18∶1n−9) acid in the diets and PGE₂ synthesis capacity of skin, possibly confirming the known inhibitory effect of 18∶1n−9 on the prostaglandin synthesizing enzyme system. Contribution No. 687, Animal Research Institute.     

Effects of a Novel GPR55 Antagonist on the Arachidonic Acid Cascade in LPS-Activated Primary Microglial Cells

Neuroinflammation is a crucial process to maintain homeostasis in the central nervous system (CNS). However, chronic neuroinflammation is detrimental, and it is described in the pathogenesis of CNS disorders, including Alzheimer’s disease (AD) and depression. This process is characterized by the activation of immune cells, mainly microglia. The role of the orphan G-protein-coupled receptor 55 (GPR55) in inflammation has been reported in different models. However, its role in neuroinflammation in respect to the arachidonic acid (AA) cascade in activated microglia is still lacking of comprehension. Therefore, we synthesized a novel GPR55 antagonist (KIT 10, 0.1–25 µM) and tested its effects on the AA cascade in lipopolysaccharide (LPS, 10 ng / mL)-treated primary rat microglia using Western blot and EIAs. We show here that KIT 10 potently prevented the release of prostaglandin E₂ (PGE₂), reduced microsomal PGE₂ synthase (mPGES-1) and cyclooxygenase-2 (COX-2) synthesis, and inhibited the phosphorylation of Ikappa B-alpha (IκB-α), a crucial upstream step of the inflammation-related nuclear factor-kappaB (NF-κB) signaling pathway. However, no effects were observed on COX-1 and -2 activities and mitogen-activated kinases (MAPK). In summary, the novel GPR55 receptor antagonist KIT 10 reduces neuroinflammatory parameters in microglia by inhibiting the COX-2/PGE₂ pathway. Further experiments are necessary to better elucidate its effects and mechanisms. Nevertheless, the modulation of inflammation by GPR55 might be a new therapeutic option to treat CNS disorders with a neuroinflammatory background such as AD or depression.     

Eicosanoid synthesis in 7,12-dimethylbenz(a)anthracene-induced mammary carcinomas in Sprague-Dawley rats fed primrose oil,menhaden oil or corn oil diet

The comparative effects of high-fat diets (20%, w/w) on eicosanoid synthesis during mammary tumor promotion in 7,12-dimethylbenz(a)anthracene (DMBA)-induced rats were studied using diets containing 20% primrose oil (PO), 20% menhaden oil (MO) or 20% corn oil (CO). Sprague-Dawley rats fed the PO or MO diet had 21% or 24% fewer adenocarcinomas, respectively, than rats fed the CO diet. Histologically (i.e., mitotic figures, inflammatory cell infiltration and necrosis), the CO-fed rats exhibited the highest frequency of changes within tumors. Plasma fatty acid composition was significantly altered by diet, reflecting the composition of the oils which were being fed. Only the plasma of PO-fed rats contained detectable levels of gamma-linolenic acid (GLA). Arachidonic acid (AA) levels were significantly higher (p<0.05) in PO-fed than in CO- or MO-fed rats. MO-fed rats had significantly higher levels of plasma palmitic acid, while palmitoleic, eicosapentaenoic (EPA) and docosahexaenoic (DHA) acids were detected only in MO-fed rats. As expected, linoleic acid (LA) and AA levels were lower (p<0.05) in the MO-fed rats than in PO- or CO-fed groups. The plasma of the CO-fed rats contained significantly higher levels of oleic acid. Eicosanoid synthesis in mammary carcinomas of rats fed the 20%-fat diets was 2–10 times higher than in mammary fat pads of control rats. The synthesis of PGE₁ and LTB₄ was significantly (p<0.05) higher in PO-fed rats than in CO-fed or MO-fed rats, although PGE values were significantly (p<0.05) higher in CO-fed rats than in Mo or PO groups. The synthesis of eicosanoids in both mammary fat pads and mammary carcinomas of MO-fed rats was lower (p<0.05) than in tissues of rats fed either CO or PO diets due to less AA precursor being fed and/or to competition between n−6 and n−3 fatty acids for cyclooxygenase and lipoxygenase. The ratios of monoenoic to dienoic eicosanoids in both mammary fat pads and mammary carcinomas were higher in the PO group than in the MO or CO groups. These results suggest that inclusion of GLA (PO feeding) or EPA and DHA (MO feeding) in the diet may decrease malignancy by altering eicosanoid profiles.     

Docosahexaenoic acid and other dietary polyunsaturated fatty acids suppress leukotriene synthesis by mouse peritoneal macrophages

The efficacy of individual ω-t-3 polyunsaturated fatty acids (PUFA) in altering eicosanoid synthesis in peritoneal macrophages was studied by feeding mice for 10 days a diet containing 2 wt% fat, which included 0.5 wt% ethyl esters of eicosapentaenoic acid (EPA), docosahexaenoic acid (DHA) or linolenic acid (LNA). Upon stimulation with calcium ionophore A23187, macrophages from these animals produced significantly lower amounts of leukotriene C₄, leukotriene B₄ and 12-hydroxyeicosatetraenoic acid, prostaglandin E₂ and 6-keto prostaglandin F_1α compared with those obtained from animals on the diets containing olive oil or safflower oil. The decrease in leukotriene synthesis was similar in the animals fed DHA, EPA or LNA diets. This depression of eicosanoids by DHA and EPA was associated with decreased levels of arachidonic acid (AA); however, LA that altered eicosanoids did not have the same effect on AA levels.     

Effects of different polunsaturated fatty acids on growth-related early gene expression and cell growth

Effects of polyunsaturated fatty acids on expression of early-response genesc-fos and Egr-1 and induction of cell growth were assessed in Swiss 3T3 fibroblasts. Stimulation with arachidonic acid increased mRNA levels ofc-fos and Egr-1. This effect was inhibited by preincubation with cyclooxygenase inhibitors and restored by addition of prostaglandin E₂ (PGE₂), the predominant eicosanoid produced in Swiss 3T3 fibroblasts. Further signaling of PGE₂ was mediated by a protein kinase C-dependent pathway, since downregulation, or inhibition, of protein kinase C reduced increases in mRNA levels. Parallel to the stimulatory effects on mRNA levels, AA and PGE₂ also increased cell growth, as determined by uptake of [³H]-thymidine. In contrast to arachidonic acid, n-3 fatty acids eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) did not increasec-fos and Egr-1 mRNA levels or cell growth. Furthermore, preliminary data indicate that EPA and DHA even reduce the stimulatory effect of AA, which is associated with reduced formation of PGE₂. In conclusion, our data indicate that AA increases expression of growth-related early genesc-fos and Egr-1 in Swiss 3T3 fibroblasts by its conversion to PGE₂ and subsequent activation of protein kinase C, whereas n-3 fatty acids do not activate this signaling cascade.     

Chemerin Affects P4 and E2 Synthesis in the Porcine Endometrium during Early Pregnancy

Chemerin, belonging to the adipokine family, exhibits pleiotropic activity. We hypothesised that the adipokine could be involved in the regulation of steroidogenesis in the porcine endometrium. Thus, the aim of this study was to determine the effect of chemerin on the key steroidogenic enzyme proteins’ abundance (Western blot), as well as on P₄ and E₂ secretion (radioimmunoassay) by the porcine endometrium during early pregnancy and the mid-luteal phase of the oestrous cycle. Moreover, we investigated the hormone impact on Erk and Akt signalling pathway activation (Western blot). Chemerin stimulated E₂ production on days 10 to 11 of pregnancy. On days 10 to 11 and 15 to 16 of gestation, and on days 10 to 11 of the cycle, chemerin enhanced the expression of StAR and all steroidogenic enzyme proteins. On days 12 to 13 of pregnancy, chemerin decreased StAR and most of the steroidogenic enzyme proteins’ abundance, whereas the P450_C17 abundance was increased. On days 27 to 28 of pregnancy, chemerin increased StAR and P450_C17 protein contents and decreased 3βHSD protein amounts. It was noted that the adipokine inhibited Erk1/2 and stimulated Akt phosphorylation. The obtained results indicate that chemerin affected P₄ and E₂ synthesis through the Erk1/2 and Akt signalling pathways.     

Lipid composition and prostaglandin synthesis in mouse lung microsomes: Alterations following the ingestion of menhaden oil

Three groups of male mice were fed a normal diet or a semisynthetic diet containing either 10% hydrogenated coconut oil (CO group) or 10% menhaden oil (MO group) for two wk. The synthetic diet altered the fatty acid composition of lung microsomal lipids. Mice ingesting menhaden oil contained greater amounts of eicosapentaenoic acid (20∶5 n−3), docosapentaenoic acid (22∶5 n−3) and docosahexaenoic acids (22∶6 n−3) and decreased amounts of n−6 fatty acids such as arachidonic and adrenic. Synthesis of prostaglandin E₂ and prostaglandin F_2α from exogenous arachidonic acid was significantly depressed in n−3 fatty acid-enriched lung microsomes. These studies indicated that dietary fish oil not only alters the fatty acid composition of lung microsomes but also lowers the capacity of lungs to synthesize prostaglandins from arachidonic acid.