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.