G2/M cell-cycle arrest and apoptosis by n-3 fatty acids in a pancreatic cancer model.

BACKGROUND: n-3 fatty acids (n-3FA) have anti-inflammatory and anti-proliferative effects including modulation of pro-inflammatory cascade mediators and cytokine elaboration (i.e., TNF-alpha, IL-10 and PGE(2)) in many cell lines. However, mechanisms of anti-proliferative effects have not been clearly defined. MATERIALS AND METHODS: MIA PaCa-2 pancreatic cancer cells were treated either with n-3FA (treatment), media (control), or n-6FA (control) for all experiments. Cellular proliferation was evaluated with WST-1 reagent. Cells were stained with propidium iodide and analyzed by flow cytometry for cell-cycle arrest, which was further analyzed by cdc2 expression. Membrane and media lipid concentrations were analyzed by high-performance liquid chromatography. Apoptosis was evaluated by AnnexinV-FITC flow cytometry and reconfirmed by poly (ADP-ribose) polymerase (PARP) cleavage and B(cl)-2 expression. RESULTS: Propidium iodide flow cytometry of MIA PaCa-2 dosed with n-3FA showed a decrease in cells in G1 phase (11-17%) and an increase cells in G2 phase (7-13%) from controls. cdc2 expression was also decreased at 24 h compared to controls. Annexin-V staining of n-3FA-treated cells demonstrated time-dependent increased apoptosis and PARP cleavage was present only in the n-3FA treatment group. Phospho-B(cl)-2 was also decreased in the n-3FA-treated cells compared to controls. CONCLUSIONS: Co-incubation of MIA PaCa-2 cells with n-3FA results in both dose- and time-dependent cell-cycle arrest. Cells also progress to cell death via apoptosis. These data support the potential applicability for n-3FA as an antiproliferative and pro-apoptotic strategy.

A priori dietary omega-3 lipid supplementation results in local pancreatic macrophage and pulmonary inflammatory response attenuation in a model of experimental acute edematous pancreatitis (AEP).

BACKGROUND: Acute pancreatitis is often complicated by multiorgan dysfunction, which is postulated to occur in part by macrophage infiltration into the pancreas. Eicosapentaenoic acid (EPA), an omega-3 fatty acid, is the principal biologic component of fish oil and has clinically and experimentally been demonstrated to be anti-inflammatory. We hypothesized that dietary EPA supplementation before the induction of pancreatitis would attenuate both M-mediated local pancreatic and systemic pulmonary inflammatory response in an in vivo model of acute edematous pancreatitis (AEP). METHODS: Male Sprague-Dawley (SD) rats were pretreated 2 times per day with oral gavage with EPA (omega-3 fatty acid; 5 mg/kg/dose) or omega-6 fatty acid control (5 mg/kg/dose) or saline (equal volume) for 2 weeks. AEP was induced in omega-3, omega-6, and saline pretreated rats by 5 hourly subcutaneous (SC) injections of cerulein. Pancreas, lung, and serum were harvested 3 hours after the last cerulein injection. Severity of pancreatitis was confirmed by serum amylase and by histopathologic score. Pancreatic macrophage infiltration was assessed by confocal fluorescent microscopy, and pulmonary leukocyte respiratory burst (LRB) analysis was performed on mononuclear cells obtained from bronchioalveolar lavage (BAL). RESULTS: All animals demonstrated acute pancreatitis through hyperamylasemia and histopathologic examination. Confocal analysis demonstrated significantly lower macrophage infiltration, and BAL analysis by flow cytometry demonstrated significantly lower (p < .05) LRB in the omega-3-treated group compared with the omega-6 and the saline pancreatitis group. CONCLUSIONS: Attenuation of both pancreatic MPhi inflammatory response and pulmonary leukocyte respiratory burst in AEP by EPA supports further investigation into the potential role for EPA dietary supplementation in the progression of pancreatitis-associated sequelae.

Modulation of the ubiquitin-proteasome proteolytic pathway by eicosapentaenoic acid supplementation in a model of progressive malignancy.

BACKGROUND: A benefit for eicosapentaenoic acid (EPA) supplementation for protein maintenance in cancer patients exists, although specific mechanisms are unknown. As the ubiquitin-proteasome proteolytic (UPP) pathway has been implicated in protein use in malignancy, we determined mRNA levels for UPP components in the liver and muscles from EPA-treated rats bearing the methylcholanthrene (MCA) fibrosarcoma. METHODS: Rats implanted with MCA tumor were divided into 3 groups on day 13: EPA (5 g/kg per day plus 10 IU vitamin E/g fat), corn oil (5 g/kg per day plus 10 IU vitamin E/g fat), and saline (5 g/kg per day plus 10 IU E/g saline). On day 29, tumor volume (TV) was determined; liver and quadriceps muscles were also excised to determine gene expression of C2, C3, E2(14k), and E3alpha by reverse transcription-polymerase chain reaction (RT-PCR). RESULTS: EPA-treated rats demonstrated a reduced TV of 21% compared with the 28% and 30% TV of corn oil- and saline-treated rats, respectively. Muscle mRNA levels of E2(14k) and E3alpha in EPA-treated animals were decreased compared with corn oil- and saline-treated animals. EPA treatment also decreased hepatic C2, C3, and E2(14k) mRNA levels compared with saline treatment. CONCLUSION: EPA supplement decreased skeletal muscle E2(14k), E3alpha, and hepatic C2 mRNA levels compared with the isocaloric, isonitrogenous corn oil supplement, supporting a treatment-specific effect. The decrease in hepatic C3 and E2(14k) mRNA levels induced by EPA were partly because of caloric benefit and partly attributable to a treatment-specific effect. Additionally, differences in the hepatic and muscle gene expressions of UPP components suggested an organ-specific effect for omega-3 fatty acid activity.

Omega-3 fatty acids: implications for the treatment of tumor-associated inflammation.

Our in vivo and in vitro studies using omega-3 fatty acids (FA) have provided insight into the biological effects and mechanisms of their anti-inflammatory action(s). The implications for this research are profound because there are few nutritional therapies available that have the potential to be clinically effective in malignancies and other chronic inflammatory conditions as omega-3 FA. In this summary of experiments the biological effects of omega-3 FA are discussed and the potential mechanisms of action presented.

Eicosapentaenoic acid supplementation reduces tumor volume and attenuates cachexia in a rat model of progressive non-metastasizing malignancy.

BACKGROUND: Eicosapentaenoic acid (EPA) has been shown to have anti-inflammatory and tumor growth inhibitory effects clinically and experimentally; evidence also supports the role of EPA in attenuating cancer-associated weight loss, but the mechanisms of these effects remain to be defined. As the liver plays a central role in modulating nutritional status and the cachexia syndrome, we examined the liver and nutritional parameters indicative of cachexia along with the tumor volume in response to oral EPA supplementation in a rat model of progressive non-metastasizing malignancy. METHODS: Fischer 344 rats implanted with the methylcholanthrene-induced fibrosarcoma (MCA) were trained to meal-feed with access to food from 8:00 PM to 8:00 AM and water ad libitum. On day 13, rats were randomly divided into 3 study groups: (1) 5.0 g/kg per day EPA plus 10 IU vitamin E/g fat, (2) 5.0 g/kg per day corn oil plus 10 IU vitamin E/g fat, and (3) 5.0 g/kg per day saline plus 10 IU vitamin E/g saline. The treatment was delivered via oral gavage twice daily. The animals were killed on day 29, and serum plus tissues (ie, liver and lung) were collected and frozen for analysis. Parameters evaluated include the following: tumor volume, weight loss, liver weight, total liver protein, liver lipid content, serum albumin content, and macrophage inflammatory protein-2 (MIP-2) levels. RESULTS: EPA-treated rats showed a reduction in tumor volume compared with corn oil (25% reduction, p < .01) and saline (33% reduction, p < .01) animals. EPA rats also demonstrated increased liver weight (p < .01) and total liver protein levels (p < .03) over saline-treated animals. EPA- and corn oil-treated rats received more calories than the saline group because of the dietary fat treatments (p < .01) and had elevated lipid content in their livers (p = .05 and p = .04, respectively) compared with saline rats. Serum albumin (a marker of liver function) and MIP-2 levels (a marker of the hepatic acute phase response) were not different between treatment groups. CONCLUSIONS: EPA supplementation resulted in a dramatic reduction of tumor volume and mild improvements in weight maintenance. In addition, EPA-treated animals demonstrated increased total liver protein and serum protein levels. Regression analyses showed that the weight and protein differences between treatment groups were not correlated with individual tumor volumes. The increase in liver and serum protein was not explained by differences in albumin or MIP-2. We conclude that the tumor growth inhibitory effects and anticachexiogenic effects of EPA are independent phenomena, and the effects on cachexia may be related to increased levels of undefined protein(s) in the liver and serum. To our knowledge, this is the first study to demonstrate the effects of EPA in the MCA fibrosarcoma model and is also novel in its evaluation of EPA as an anticachexiogenic therapy in progressive non-metastasizing malignancy. Further studies may identify the protein(s) elevated in the liver and the mechanisms for the development of EPA nutritional therapies for the treatment of progressive malignancies.