5-Lipoxygenase products: their biosynthesis in human gastric mucosa and possible involvement in inflammatory response and oxygen saturation index reduction in gastric ulcer patients

Ferulic acid nanoemulsion as a promising anti-ulcer tool: in vitro and in vivo assessment

OBJECTIVE

Ferulic acid (FA) is a promising nutraceutical molecule which exhibits antioxidant and anti-inflammatory properties, but it suffers from poor solubility and bioavailability. In the presented study, FA nanoemulsions were prepared to potentiate the therapeutic efficacy of FA in prevention of gastric ulcer.

METHODS

FA nanoemulsions were prepared, pharmaceutically characterized, and the selected nanoemusion was tested for its ulcer-ameliorative properties in rats after induction of gastric ulcer using ethanol, by examination of stomach tissues, assessment of serum IL-1β and TNF-α, assessment of nitric oxide, prostaglandin E2, glutathione, catalase and thiobarbituric acid reactive substance in stomach homogenates, as well as histological and immunohistochemical evaluation.

RESULTS

Results revealed that the selected FA nanoemulsion showed a particle size of 90.43 nm, sustained release of FA for 8 h, and better in vitro anti-inflammatory properties than FA. Moreover, FA nanoemulsion exhibited significantly better anti-inflammatory and antioxidant properties in vivo, and the gastric tissue treated with FA nanoemulsion was comparable to the normal control upon histological and immunohistochemical evaluation.

CONCLUSION

Findings suggest that the prepared ferulic acid nanoemulsion is an ideal anti-ulcer system, which is worthy of further investigations.

Expression of 5-oxoETE receptor in prostate cancer cells: critical role in survival

Previously, we reported that metabolism of arachidonic acid through the 5-lipoxygenase (5-LOX) pathway plays an important role in the survival and growth of human prostate cancer cells. Inhibition of 5-LOX by pharmacological inhibitors triggers apoptosis in prostate cancer cells within hours of treatment, which is prevented by the metabolites of arachidonate 5-lipoxygenase, 5(S)-hydroxyeicosatetraenoic acid (5(S)-HETE), and its dehydrogenated derivative, 5-oxoeicosatetraenoic acid (5-oxoETE). These findings suggested that 5-lipoxygenase metabolites are critical survival factors of prostate cancer cells. However, molecular mechanisms by which 5(S)-HETE and its derivative 5-oxoETE exert their effects on prostate cancer cell survival are yet to be understood. Here, we report that human prostate cancer cells differentially express a G-protein-coupled 5-oxoETE receptor (5-oxoER) in them. Blocking expression of 5-oxoER by short-interfering RNA (siRNA) significantly reduced the viability of prostate cancer cells, suggesting that 5-oxoER is critical for prostate cancer cell survival, and that the 5-LOX metabolite, 5-oxoETE, controls survival of prostate cancer cells through its own G-protein-coupled receptor, 5-oxoER.

Regional biosynthesis of prostaglandins and hydroxyeicosatetraenoic acids from arachidonic acid in the rat stomach tissue

The present study was conducted to determine regional differences in the biosynthesis of prostaglandins (PGs) and hydroxyeicosatetraenoic acids (HETEs) in the rat stomach tissue (fundus, corpus and pyloric antrum) from radioactive arachidonic acid (AA). The radioactive metabolites were validated by RP-HPLC using non-radioactive AA as substrate. PGE(2) was the major prostanoid in the tissue(.) The relative ratio of PGE(2):PGF(2)alpha:PGD(2) in the whole stomach was 1:0.5:0.1. Regionally, the fundus biosynthesized the largest amount of all three cyclo-oxygenase products. Among the lipoxygenase metabolites, 15S-HETE was the predominant product, while 12S-HETE was found to be the lowest. The relative ratio of 15S-HETE:5S-HETE:12S-HETE in the whole stomach was 1:0.6:0.4. Interestingly, the generation of lipoxygenase products was the highest in the pyloric antrum when compared to fundus or corpus. Thus, the regional differences in the biosyntheses of gastric PGs and monohydroxy fatty acids may be relevant to our understanding of corresponding differences in mucosal resistance or susceptibility to gastric disease.

Stimulated human gastric tumor cells (HGT) fail to synthesize eicosanoids

HGT cells are a human gastric tumor cell line. Preliminary data have shown that HGT cells incorporate exogenous arachidonic acid (AA) in their membrane lipids. However, we found that HGT cells are unable to produce significant amounts of AA metabolites after stimulation with calcium ionophore A23187. Furthermore, no lipoxygenase activity was detected in crude HGT cell extracts by employing an assay monitoring the in vitro utilization of linoleic acid. The meaning of these results is discussed in respect of the role of eicosanoids during cell proliferation.

Effects of eicosanoid metabolism inhibitors on growth of a human gastric tumour cell line (HGT)

HGT cells are a human gastric cell line derived from a tumour of the stomach. We have investigated the effects of lipoxygenase and cyclooxygenase metabolism inhibitors on HGT cell proliferation, on fatty acid composition of HGT cells and on the incorporation and distribution of arachidonic acid (AA) in HGT lipids. The cyclooxygenase inhibitor aspirin and both cyclooxygenase and the lipoxygenase inhibitor BW 755C suppressed cell proliferation in a concentration-dependent manner. The inhibition of HGT proliferation did not result from a modulation of the fatty acid composition of membrane lipid, which was not affected by treatment with the various inhibitors. Inhibitors of AA metabolism did not alter acylation of exogenous AA into HGT cells nor its subsequent distribution in the lipid and phospholipid species. The role of cyclooxygenase eicosanoids in HGT proliferation is discussed.

Incorporation of arachidonic acid in a human cancer gastric tumor cell line (HGT) at various stages of cell proliferation

Human cancer gastric cells (HGT) in culture were labeled with [14C]arachidonic acid. The kinetic of acylation of arachidonic acid was similar using cells after 3, 5 and 7 days of culture. However, the duration of the proliferation enhanced the acyltransfer to triglycerides and inhibited the transfer to phospholipids. After 8 h of incubation with [14C]arachidonic acid the radioactivity was predominantly recovered in the phosphatidylcholine and phosphatidylethanolamine species. Prelabeling-chase experiments indicated a preferential incorporation of arachidonic acid into phosphatidylcholine followed by a transfer of arachidonate to phosphatidylethanolamine.