Modulation of antitumour activity of macrophages by regulation of eicosanoids and cytokine production

Leukotriene biosynthesis inhibition ameliorates acute lung injury following hemorrhagic shock in rats

Background

Hemorrhagic shock followed by resuscitation is conceived as an insult frequently induces a systemic inflammatory response syndrome and oxidative stress that results in multiple-organ dysfunction syndrome including acute lung injury. MK-886 is a leukotriene biosynthesis inhibitor exerts an anti inflammatory and antioxidant activity.

Objectives

The objective of present study was to assess the possible protective effect of MK-886 against hemorrhagic shock-induced acute lung injury via interfering with inflammatory and oxidative pathways.

Materials and methods

Eighteen adult Albino rats were assigned to three groups each containing six rats: group I, sham group, rats underwent all surgical instrumentation but neither hemorrhagic shock nor resuscitation was done; group II, Rats underwent hemorrhagic shock (HS) for 1 hr then resuscitated with Ringer's lactate (1 hr) (induced untreated group, HS); group III, HS + MK-886 (0.6 mg/kg i.p. injection 30 min before the induction of HS, and the same dose was repeated just before reperfusion period). At the end of experiment (2 hr after completion of resuscitation), blood samples were collected for measurement of serum tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6). The trachea was then isolated and bronchoalveolar lavage fluid (BALF) was carried out for measurement of leukotriene B₄ (LTB₄), leukotriene C₄ (LTC₄) and total protein. The lungs were harvested, excised and the left lung was homogenized for measurement of malondialdehyde (MDA) and reduced glutathione (GSH) and the right lung was fixed in 10% formalin for histological examination.

Results

MK-886 treatment significantly reduced the total lung injury score compared with the HS group (P < 0.05). MK-886 also significantly decreased serum TNF-α & IL-6; lung MDA; BALF LTB₄, LTC₄ & total protein compared with the HS group (P < 0.05). MK-886 treatment significantly prevented the decrease in the lung GSH levels compared with the HS group (P < 0.05).

Conclusions

The results of the present study reveal that MK-886 may ameliorate lung injury in shocked rats via interfering with inflammatory and oxidative pathways implicating the role of leukotrienes in the pathogenesis of hemorrhagic shock-induced lung inflammation.

Effect of ω-3 and ω-9 fatty acid rich oils on lipoxygenases and cyclooxygenases enzymes and on the growth of a mammary adenocarcinoma model

BACKGROUND

Nutritional factors play a major role in cancer initiation and development. Dietary polyunsaturated fatty acids (PUFAs) have the ability to induce modifications in the activity of lipoxygenase (LOX) and cyclooxygenase (COX) enzymes that affect tumour growth. We studied the effect of two diets enriched in 6% Walnut and Peanut oils that are rich in ω-3 and ω9 PUFAs respectively on a murine mammary gland adenocarcinoma as compared with the control (C) that received commercial diet.

RESULTS

Peanut oil enriched diet induced an increase in membrane arachidonic acid (AA) content and the cyclooxygenase enzyme derived 12-HHT (p < 0.05) and simultaneously showed decrease in 12-LOX, 15-LOX-2, 15-LOX-1 and PGE activities (p < 0.05) that corresponded to higher apoptosis and lower mitosis seen in this group (p < 0.05). Furthermore, Peanut oil group showed lower T-cell infiltration (p < 0.05), number of metastasis (p < 0.05) and tumour volume (p < 0.05) and longer survival rate compared to other groups.

CONCLUSIONS

The results of the present study showed that Peanut oil-enriched diet protects against mammary cancer development by modulating tumour membrane fatty acids composition and LOX and COX enzyme activities.

Synergistic effect of indomethacin with adriamycin and cisplatin on tumor growth

In this study, we have examined the antitumor effect of combined administrations of indomethacin (IND) with chemotherapeutic drugs on tumor growth. Colon 26 clone 20 (C20) cells and monocyte chemotactant protein-1 (MCP-1) transfected C20 cells (C20betaA-2-1) were used and these cells were inoculated into the footpad of BALB/c mice. At day 1 after tumor inoculation, treatment with 0.001% IND via the drinking water was commenced. At days 4, 6, and 8, adriamycin or cisplatin was administered intravenously at a dose of 5 mg/kg or intraperitoneally at a dose of 2 mg/kg, respectively. Although IND, adriamycin and cisplatin only partially reduced the growth of the C20 tumors after treatment with each drug on its own, a marked synergistic effect was observed when they were given in combination. A synergistic effect between IND and cisplatin on C20betaA-2-1 was also observed. However, IND itself showed no suppression of C20betaA-2-1 tumor growth. These results suggest that combination of indomethacin with chemotherapeutic drugs could be an effective form of cancer chemotherapy. The observed effects may be dependent on the expression of MCP-1.

Does dietary alpha-linolenic acid promote liver metastases in pancreatic carcinoma initiated by BOP in Syrian hamster?

BACKGROUND

alpha-Linolenic acid (ALA) has been shown to have a promoting effect on pancreatic carcinogenesis. The purpose of this study was to evaluate the influence of ALA on liver metastases in a model of BOP-induced pancreatic ductular carcinoma in the Syrian golden hamster.

METHODS

While the control group (group V) received a standard diet low in fat (soya oil, 3 w/v) without ALA, groups I-IV were fed a diet high in fat (soya oil 25 w/v) with increasing percentages of ALA (2.5, 5, 7.5 and 10%) for 16 weeks.

RESULTS

No significant differences in mean body weight and pancreas weight were found between the groups. But significant differences (p = 0.0001) were observed in the mean weight of the resected liver. Treatment with BOP alone resulted in the induction of well-differentiated ductal pancreatic adenocarcinoma in 91%, while all groups treated with different amounts of ALA had induction of 100%. The incidence of liver metastases differed significantly between the groups. The incidence of liver metastases in group I (2.5% ALA) was 18%, in group II (5% ALA) 27%, in group III (7.5% ALA) 50%, and in group IV (10% ALA) 91%. Moreover, the diameter of liver metastases increased significantly according to ALA supplementation (p = 0.001).

CONCLUSION

The results indicate that dietary ALA increases liver metastases in BOP-initiated pancreatic cancer.

Evidence supporting involvement of leukotrienes in LPS-induced hypothermia in mice

The aim of the present study was to examine a possible involvement of leukotrienes (LTs) in lipopolysaccharide (LPS)-induced body temperature (Tb) response. We examined the effect of MK-886, an inhibitor of LT synthesis, on changes in Tb, plasma tumor necrosis factor-alpha (TNF-alpha), hypothalamic LT, and PGE2 production. Intraperitoneal injection of LPS (50 microgramg/mouse) led to a decrease in Tb starting 1 h after the injection. The hypothermic effect of LPS was accompanied by a significant elevation in TNF-alpha level in plasma and in LT and PGE2 production by ex vivo-incubated hypothalamus. MK-886 (1 mg/kg ip) administered 4 h before LPS efficaciously prevented LPS-induced hypothermia in mice. Pretreatment of mice with MK-886 did not alter the LPS-stimulated increase in plasma TNF-alpha. MK-886 significantly inhibited LT and enhanced PGE2 production in hypothalamus compared with LPS alone. These results suggest that 1) LPS-induced hypothermia may be mediated by LTs and 2) the antihypothermic effect of MK-886 is not associated with TNF-alpha bioactivity.

Inhibition of the synthesis of eicosanoid-like substances in a human oral cancer cell line by interferon-gamma and eicosapentaenoic acid

The objectives were to examine the production of eicosanoids in a Chinese human oral cancer cell line (OEC-M1) and to test the effects of interferon-gamma (IFN-gamma), eicosapentaenoic acid (EPA) and enzyme inhibitors on this biosynthesis. The eicosanoids were identified by reverse phase-high performance liquid chromatography. Two predominant peaks appeared in the chromatograms. One compound (P-1) was identified by ultraviolet absorption at a lambda(max) of 278nm with shoulders at 272 and 284nm. The other compound (P-2) was identified by ultraviolet absorption at a lambda(max) of 284 nm with shoulders at 278 and 290 nm. The production of P- was significantly inhibited by the addition of IFN-gamma (200 and 400 U/ml), and EPA (10 to 40 microM). It was only partially inhibited (p < 0.05) by indomethacin (INDO) (0.5 and 1 microM), nordihydroguaiaretic acid (NDGA) (30 and 60 microM/ml), and eicosa-5,8,11,14-tetraynoic acid (ETYA) (20-60 microM). It was almost completely inhibited by indomethacin (2 and 3 microM), and dexamethasone (0.6 and 6 microM). The production of P-2 was almost completely inhibited by IFN-gamma (200 and 400 U/ml), and partially inhibited (p < 0.05) by EPA (10 and 20 microM), NDGA (30 and 60 microM), ETYA (20 and 40 microM), dexamethasone (0.6 and 6 microM). The production of both peaks was significantly reduced by excluding arachidonic acid (AA), and almost completely inhibited by heating at 100 degrees C for 10 min during incubation. These results demonstrate that two eicosanoid-like compounds are synthesized by the OEC-M cell line and that their production can be modulated by IFN-gamma, EPA, indomethacin, NDGA, ETYA, and dexamethasone.