LPS-squalene interaction on D-galactose intestinal absorption.

The dynamic and complex interactions between enteric pathogens and the intestinal epithelium often lead to disturbances in the intestinal barrier, altered fluid, electrolyte, and nutrient transport and can produce an inflammatory response. Lipopolysaccharide (LPS) is a complex polymer forming part of the outer membrane of Gram-negative bacteria. On the other hand, squalene is a triterpene present in high levels in the extra-virgin olive oil that has beneficial effects against several diseases and it has also anti-oxidant and anti-inflammatory properties. The aim of this work was to study whether the squalene could eliminate the LPS effect on D-galactose intestinal absorption in rabbits and Caco-2 cells. The results have shown that squalene reduced the effects of LPS on sugar absorption. High LPS doses increased D-galactose uptake through via paracellular but also decreased the active sugar transport because the SGLT1 levels were diminished. However, the endotoxin effect on the paracellular way seemed to be more important than on the transcellular route. At the same time, an increased in RELM-ß expression was observed. This event could be related to inflammation and cause a decrease in SGLT1 levels. In addition, MLCK protein is also increased by LPS which could lead to an increase in sugar transport through tight junctions. At low doses, the LPS could inhibit SGLT1 intrinsic activity. Bioinformatic studies by docking confirm the interaction between LPS-squalene as well as occur through MLCK and SGLT-1 proteins.

Proteasome versus Thioredoxin Reductase Competition as Possible Biological Targets in Antitumor Mixed Thiolate-Dithiocarbamate Gold(III) Complexes.

New mixed gold(III) derivatives with dithiocarbamate and thiolate ligands have been synthesized and characterized. They display high anticancer activity against colon cancer cell lines without affecting to differentiated enterocytes, high stability in phosphate-buffered saline solution, and resistance to gold reduction in the presence of reducing agents in the majority of the derivatives. Some of them show interaction with thioredoxin reductase as derived from in vitro analysis and computational studies. However, a competition between this enzyme and proteasome is detected in cells, which is corroborated by the determination of proteasomal chymotrypsin-like activity inhibition. In addition, some of these dithiocarbamate gold(III) derivatives reduce cell viability and proliferation by intrinsic apoptotic pathway, with changes in mitochondrial membrane potential, cytochrome c release and caspase-3 activation. Consequently, our results show new complexes with proteasome as possible target in colorectal cancer.

Interleukin-1beta reduces galactose transport in intestinal epithelial cells in a NF-kB and protein kinase C-dependent manner.

Interleukins (IL), aside from their role in the regulation of the immune cascade, they have also been shown to modulate intestinal transport function. IL-1ß is a potent inflammatory cytokine involved in many important cellular functions. The aim of this work was to study the in vitro effect of IL-1ß on d-galactose transport across intestinal epithelia in rabbit jejunum and Caco-2 cells. The results showed that d-galactose intestinal absorption was diminished in IL-1ß treated jejunum rabbits without affecting the Na(+), K(+)-ATPase activity. The presence of IL-1 cell-surface receptors was confirmed by addition to tissue of a specific IL-1 receptor antagonist (IL-1ra). The cytokine did not inhibit either the uptake of d-galactose nor modified the sodium-glucose transport (SGLT1) protein levels in the brush border membrane vesicles, suggesting an indirect IL effect. The IL-inhibition was significantly reversed in the presence of inhibitors of protein kinase C (PKC) and mitogen-activated protein kinases (MAPKs). The proteasome selective inhibitor completely abolished the IL-effect. Furthermore, the cytokine inhibition on galactose transport related to NF-kB activation was also confirmed in Caco-2 cells. In summary, the direct addition of IL-1ß to intestinal epithelia inhibits d-galactose transport by a possible reduction in the SGLT1 activity. This event may be mediated by several transduction pathways activated during the inflammatory processes related to several protein kinases and nuclear factor, NF-kB. The IL-effect is independent of hormonal milieu and nervous stimuli.

Inhibitory effect of IL-1ß on galactose intestinal absorption in rabbits.

BACKGROUND/AIMS: Recent studies from our laboratory have shown that nitric oxide is involved in the IL-1ß-induced inhibition of D-fructose intestinal transport in rabbits. The aim of this work was to further the studies of IL-1ß effect on D-galactose absorption in a septic state induced by intravenous administration of this cytokine. METHODS: Galactose intestinal absorption was assessed employing three techniques: sugar uptake in jejunum everted rings, transepithelial flux in Ussing-type chambers and uptake assays in brush border membrane vesicles. The level of the Na(+)/D-glucose cotransporter (SGLT1) expression was analyzed by Western blot. RESULTS: In sepsis condition the body temperature was increased and studies on cellular intestinal integrity have not shown modifications in the brush border membrane. However, D-galactose absorption across mucosa of jejunum was diminished in IL-1ß treated rabbits. The levels of SGLT-1 were no significantly different in both animal groups (control and IL-1ß treated), indicating that the cytokine could induce a reduction in the SGLT-1 functionality. The inhibition was significantly reversed by the activation of several PKC, PKA, MAPKs and nuclear factor (NF)-ĸB inhibitors administered 15 min before the IL-1ß. CONCLUSION: The inhibitory effect of IL-1ß on D-galactose absorption across mucosal side of enterocyte could be mediated by the activation of several kinases and nuclear factor (NF)-ĸB.

Nitric oxide involved in the IL-1ß-induced inhibition of fructose intestinal transport.

Interleukin-1ß (IL-1ß) is a pleiotropic cytokine produced by cells of the immune system and a large variety of other cell types including endothelial cells. It is released during inflammatory and infectious diseases, and possesses a wide spectrum of autocrine, paracrine and endocrine activities. The aim of this work was to examine the IL-1ß effect on D-fructose transport across rabbit jejunum and try to identify the mediators implicated in this process. A sepsis condition was induced for 90 min after intravenous (iv) administration of IL-1ß and body temperature was recorded. Studies on cellular intestinal integrity have not shown modifications of the epithelium and the basement membrane. D-fructose intestinal transport was studied in rabbit jejunum from control and treated animals and it was reduced in the latter ones. This cytokine decreased both the mucosal to serosal transepithelial flux and the transport across brush-border membrane vesicles of D-fructose. The inhibition was reversed by L-NAME (nitric oxide [NO] synthase inhibitor), but not by indomethacin (cyclooxygenase 1 and 2 inhibitor). Both inhibitors were administered iv 15 min before the IL-1ß. The protein levels of GLUT5 were not changed in all animal groups and those of mRNA were even increased. In summary, these findings indicate that IL-1ß, at the time assayed, induced a significant reduction in the relative intrinsic activity of GLUT5 and in this decrease are involved NO signalling pathways. In this way, blockage of D-fructose intestinal uptake by IL-1ß may be playing an essential role in the pathophysiology of septic shock.