ABSTRACT
BACKGROUND: Enterocytes produce intestinal alkaline phosphatase (iAP), which detoxifies lipopolysaccharide (LPS), a mediator in necrotizing enterocolitis (NEC) pathogenesis. We hypothesize that aberrant expression or function of iAP contributes to the pathogenesis of NEC. MATERIALS AND METHODS: Newborn Sprague Dawley rat pups were divided into three main groups. Control pups were breast fed, while two groups were exposed to intermittent hypoxia, LPS, and formula feeding for 4 d to induce NEC. Bovine iAP, with and without the presence of LPS, was administered orally to one of the NEC groups. The intestine was harvested and used to detect alkaline phosphatase (AP) activity and protein expression. Terminal ileum sections were used to grade intestinal injury and stained for AP. Comparisons were made with adult rat duodenum. RESULTS: Compared with adult rats, control pups expressed significantly less AP protein but had 2-fold higher AP activity. NEC pup AP activity was significantly decreased compared to controls (P < or = 0.05), which paralleled both the AP protein expression and immunofluorescence assay results. Following iAP administration, immunofluorescence, protein expression, and activity of AP were significantly increased compared with NEC pups without iAP supplementation. All NEC pups had intestinal injury grades > or = 2 on a 4-point scale, while control and iAP-treated pups had grades < 0.25 (P < 0.001). CONCLUSIONS: Enteral administration of iAP to rat pups with experimental NEC increased AP activity levels to that of controls, and appears to protect the intestine. This opens up a new area of study in NEC pathophysiology as well as a potential novel treatment strategy to prevent the development of NEC.
Subject(s)
Alkaline Phosphatase/metabolism , Enterocolitis, Necrotizing/enzymology , Isoenzymes/metabolism , Alkaline Phosphatase/therapeutic use , Animals , Animals, Newborn , Cattle , Enterocolitis, Necrotizing/etiology , Enterocolitis, Necrotizing/pathology , Enterocolitis, Necrotizing/prevention & control , Ileum/pathology , Rats , Rats, Sprague-DawleyABSTRACT
Combination chemotherapy forms the backbone of cancer treatment. There is a need for new drug combinations for the treatment of mantle cell lymphoma (MCL). Herein, we show that gallium maltolate, a novel gallium compound, synergizes with bortezomib, a proteasome inhibitor, to induce cell death in MCL Granta cells. Cells exposed to either agent displayed caspase-3 activation, a loss of mitochondrial membrane potential, and a decrease in chymotrypsin-like activity. These effects were increased with both agents in combination. Our results show for the first time that the proteasome may be a target for gallium maltolate and suggest that the therapeutic potential of combination bortezomib and gallium maltolate warrants further investigation.
Subject(s)
Apoptosis/drug effects , Boronic Acids/pharmacology , Lymphoma, Mantle-Cell/pathology , Organometallic Compounds/pharmacology , Protease Inhibitors/pharmacology , Pyrazines/pharmacology , Pyrones/pharmacology , Bortezomib , Caspase 3/metabolism , Cell Division/drug effects , Cell Line, Tumor/drug effects , Chymotrypsin/antagonists & inhibitors , Drug Screening Assays, Antitumor , Drug Synergism , Enzyme Activation/drug effects , Humans , Membrane Potential, Mitochondrial/drug effects , Neoplasm Proteins/antagonists & inhibitors , Proteasome InhibitorsABSTRACT
Clinical studies have shown gallium nitrate to have significant antitumor activity against non-Hodgkin's lymphoma and bladder cancer, thus indicating that gallium-based drugs have potential for further development as antineoplastic agents. In this study, we compared the cytotoxicity of gallium maltolate, a novel gallium compound, with gallium nitrate in lymphoma cell lines, including p53 variant and unique gallium nitrate-resistant cells. We found that gallium maltolate inhibited cell proliferation and induced apoptosis through the mitochondrial pathway at lower concentrations and more rapidly than gallium nitrate. Gallium maltolate produced an increase in intracellular reactive oxygen species (ROS) within 2 h of incubation with cells; this effect could be blocked by mitoquinone, a mitochondria-targeted antioxidant. The role of the transferrin receptor (TfR) in gallium maltolate's action was examined using monoclonal antibody (MoAb) 42/6 to block TfR function. However, although MoAb 42/6 reduced gallium maltolate-induced caspase-3 activity, it had only a minor effect on cell growth inhibition. Importantly, gallium maltolate induced apoptosis in cells resistant to gallium nitrate, and, unlike gallium nitrate, its cytotoxicity was not affected by cellular p53 status. Cellular gallium uptake was greater with gallium maltolate than with gallium nitrate. We conclude that gallium maltolate inhibits cell proliferation and induces apoptosis more efficiently than gallium nitrate. Gallium maltolate is incorporated into lymphoma cells to a greater extent than gallium nitrate via both TfR-independent and -dependent pathways; it has significant activity against gallium nitrate-resistant cells and acts independently of p53. Further studies to evaluate its antineoplastic activity in vivo are warranted.
