Crosstalk between autophagy and iron in melanoma progression

Introduction.Autophagy, a catabolic process of protein and organelle recycling by transferring defective cytoplasm and organelles into double-membraned vesicles to degrade and regenerate materials, plays a critical role in maintaining energy homeostasis. Inefficiency chemo-and radiotherapy is largely associated with the activation of autophagy. Among the metals needed by the living organism, iron occupies a special place. The rapid growth of malignant tumors requires much more iron than the metabolism of normal cells.Objective.To elucidate the relationship between autophagy and iron in melanoma progression.Materials and methods.In this study we used 2D- and 3D-culturing of melanoma cells with high expression of CD71 (mel P and mel Z) and low expression of CD71 (mel Gus and mel Ibr), flow cytometry and fluorescence microscopy.Results.The uptake of iron in cancer cells occurs through translocation of the complex of transferrin/receptor (CD71) in the cytoplasm with subsequent dissociation of iron from the complex. Chelation of iron by deferroxamine in melanoma cells mel P and mel Z reduced the level of autophagy about 2-fold. In the presence of an iron donor ferrum ammonium citrate the level of autophagy increased 2.5- fold. The same correlation was observed in melanoma cells with low expression of CD71. Chelation of iron in melanoma cells with high CD71 expression blocked the formation of capillary-like structures. In the presence of an iron donor the formation of capillary-like structures was also not observed. The same correlation was observed in melanoma cells with low expression of CD71. There was an increase in CD105 expression about 50 ± 5 % and 800 ± 50 % under the condition of iron chelation in melanoma cells with high and low expression of CD71, respectively. Quite unexpectably, iron donor also increased expression of CD105 about 35 ± 4 % and 300 ± 3 % in melanoma cells with high and low expression of CD71, respectivelyConclusions.The activation of autophagy promotes the survival of tumor cells by triggering a number of metabolic functions with the participation of iron.

Genetic variation in Fe toxicity tolerance is associated with the regulation of translocation and chelation of iron along with antioxidant defence in shoots of rice

Excess iron (Fe) is phytotoxic and causes reduced growth and productivity in rice. In this study we elucidated the mechanisms conferring differential tolerance to Fe-toxicity in rice seedlings. Excess Fe caused retardation in roots of both Pokkali and BRRI 51, but it caused no significant changes on growth parameters, Fe accumulation and OsIRT1 expression in shoots of Pokkali only compared with control plants. These results suggest that the Pokkali genotype does have mechanisms in shoots to withstand Fe toxicity. Pokkali maintained membrane stability and total soluble protein in shoots due to Fe toxicity, further confirming its ability to tolerate excess Fe. Furthermore, a significant decrease of Fe-chelate reductase activity and OsFRO1 expression in shoots of Pokkali suggests that limiting Fe accumulation is possibly regulated by Fe-reductase activity. Our extensive expression analysis on the expression pattern of three chelators (OsDMAS1, OsYSL15, OsYSL2 and OsFRDL1) showed no significant changes in expression in shoots of Pokkali due to Fe toxicity, whereas these genes were significantly upregulated under Fe-toxicity in sensitive BRRI 51. These results imply that regulation of Fe chelation in shoots of Pokkali contributes to its tolerance to Fe toxicity. Finally, increased catalase (CAT), peroxidase (POD), glutathione reductase (GR) and superoxide dismutase (SOD), along with elevated ascorbic acid, glutathione, cysteine, methionine and proline in shoots of Pokkali caused by Fe toxicity suggests that strong antioxidant defence protects rice plants from oxidative injury under Fe toxicity. Taking these results together, we propose that genetic variation in Fe-toxicity tolerance in rice is shoot based, and is mainly associated with the regulation of translocation and chelation of Fe together with elevated antioxidant metabolites in shoots.

The Urinary Antibiotic 5-Nitro-8-Hydroxyquinoline (Nitroxoline) Reduces the Formation and Induces the Dispersal of Pseudomonas aeruginosa Biofilms by Chelation of Iron and Zinc

ABSTRACTSince cations have been reported as essential regulators of biofilm, we investigated the potential of the broad-spectrum antimicrobial and cation-chelator nitroxoline as an antibiofilm agent. Biofilm mass synthesis was reduced by up to 80% at sub-MIC nitroxoline concentrations inPseudomonas aeruginosa, and structures formed were reticulate rather than compact. In preformed biofilms, viable cell counts were reduced by 4 logs at therapeutic concentrations. Complexation of iron and zinc was demonstrated to underlie nitroxoline's potent antibiofilm activity.

Detection of intracellular iron by its regulatory effect

Intracellular iron regulates gene expression by inhibiting the interaction of iron regulatory proteins (IRPs) with RNA motifs called iron-responsive elements (IREs). To assay this interaction in living cells we have developed two fluorescent IRE-based reporters that rapidly, reversibly, and specifically respond to changes in cellular iron status as well as signaling that modifies IRP activity. The reporters were also sufficiently sensitive to distinguish apo- from holotransferrin in the medium, to detect the effect of modifiers of the transferrin pathway such as HFE, and to detect the donation or chelation of iron by siderophores bound to the lipocalin neutrophil gelatinase-associated lipocalin (Ngal). In addition, alternative configurations of the IRE motif either enhanced or repressed fluorescence, permitting a ratio analysis of the iron-dependent response. These characteristics make it possible to visualize iron-IRP-IRE interactions in vivo.