The anti-inflammatory effect of omega-3 polyunsaturated fatty acids dramatically decreases by iron in the hippocampus of diabetic rats.

AIMS: Receptor for advanced glycation end products (RAGE) production is induced by diabetes. Microglial cells are activated by RAGE and produce inflammatory cytokines such as tumor necrosis factor-α (TNF-α) and oxidative stress markers. Persistent production of TNF-α can provide a link between diabetes and Alzheimer's disease (AD). The purpose of this study was to investigate the effect of concomitant use of omega-3 polyunsaturated fatty acids (ω-3 PUFAs) with iron supplements on microglial cell activation and inflammatory conditions in the hippocampus of type 2 diabetic rats. MAIN METHODS: Diabetic and normal Wistar rats were divided into six groups. Oxidative stress markers (total oxidant status (TOS), total antioxidant capacity (TAC), and malondialdehyde (MDA)), mRNA expression and protein levels of RAGE and TNF-α were evaluated in the hippocampus of the controls and supplemented with ferrous sulfate and ω-3 PUFAs alone and together rats. Also, the entry of microglia cells into the hippocampus was evaluated by immunohistochemistry technique. KEY FINDINGS: Levels of the microglial activation (2.4 fold, p < 0.0001), MDA (84%, p < 0.0001) and oxidative stress index (OSI) (11%, p = 0.0094), mRNA expression and protein contents of RAGE (1.83 fold and 82% respectively) and TNF-α (2.25 fold and 86% respectively) were strongly influenced by negative effect of iron compared to the group receiving only ω-3 PUFAs which was dramatically improved by vitamin E. SIGNIFICANCE: These observations indicated that the co-supplementation of ferrous sulfate with ω-3 PUFAs decreases the anti-inflammatory ability of ω-3 PUFAs in the hippocampus of diabetic rats via RAGE/TNF-α-induced oxidative stress pathway up-regulation.

Inhibition of CEA release from epithelial cells by lipid A of Gram-negative bacteria.

A number of bacterial species, both pathogenic and non-pathogenic, use the human CEACAM family members as receptors for internalization into epithelial cells. The GPI-linked CEA and CEACAM6 might play a role in the innate immune defense, protecting the colon from microbial invasion. Previous studies showed that CEA is released from epithelial cells by an endogenous GPI-PLD enzyme. GPI-PLD activity was reported to be inhibited by several synthetic and natural forms of lipid A. We hypothesized that CEA engagement by Gram-negative bacteria might attenuate CEA release from epithelial cells and that this might facilitate bacterial colonization. We tested the hypothesis by examining the effect of Escherichia coli on CEA release from colorectal cancer cells in a co-culture experiment. A subconfluent monolayer culture of colorectal cancer cells (LS-180, Caco-2 and HT29/219) was incubated with E. coli. While there was a significant reduction in CEA secretion from LS-180 and HT29/219 cells, we found only a small reduction of CEA shedding from Caco-2 cells compared to the level from the untreated control cells. Furthermore, lipid A treatment of LS-180 cells inhibited CEA release from the cells in a dosedependent manner. Western blot analysis of total lysates showed that CEA expression levels in cells co-cultured with bacteria did not differ from those in untreated control cells. These results suggest that lipid A of Gram-negative bacteria might play a role in preventing the release of CEA from mucosal surfaces and promote mucosal colonization by bacteria.