Luminescent threat: toxicity of light stick attractors used in pelagic fishery.

Light sticks (LS) are sources of chemiluminescence commonly used in pelagic fishery, where hundreds are discarded and reach the shores. Residents from fishing villages report an improper use of LS contents on the skin. Given the scarce information regarding LS toxicity, the effects of LS solutions in cell cultures were evaluated herein. Loss of viability, cell cycle changes and DNA fragmentation were observed in HepG2 cell line and skin fibroblasts. A non-cytotoxic LS concentration increased the occurrence of the mutagenic lesion 1,N(6)-εdAdo in HepG2 DNA by three-fold. Additionally, in vitro incubations of spent LS contents with DNA generated dGuo-LS adducts, whose structure elucidation revealed the presence of a reactive chlorinated product. In conclusion, the LS contents were found to be highly cyto- and genotoxic. Our data indicate an urgent need for LS waste management guidelines and for adequate information regarding toxic outcomes that may arise from human exposure.

KeaA, a Dictyostelium Kelch-domain protein that regulates the response to stress and development.

BACKGROUND: The protein kinase YakA is responsible for the growth arrest and induction of developmental processes that occur upon starvation of Dictyostelium cells. yakA- cells are aggregation deficient, have a faster cell cycle and are hypersensitive to oxidative and nitrosoative stress. With the aim of isolating members of the YakA pathway, suppressors of the death induced by nitrosoative stress in the yakA- cells were identified. One of the suppressor mutations occurred in keaA, a gene identical to DG1106 and similar to Keap1 from mice and the Kelch protein from Drosophila, among others that contain Kelch domains. RESULTS: A mutation in keaA suppresses the hypersensitivity to oxidative and nitrosoative stresses but not the faster growth phenotype of yakA- cells. The growth profile of keaA deficient cells indicates that this gene is necessary for growth. keaA deficient cells are more resistant to nitrosoative and oxidative stress and keaA is necessary for the production and detection of cAMP. A morphological analysis of keaA deficient cells during multicellular development indicated that, although the mutant is not absolutely deficient in aggregation, cells do not efficiently participate in the process. Gene expression analysis using cDNA microarrays of wild-type and keaA deficient cells indicated a role for KeaA in the regulation of the cell cycle and pre-starvation responses. CONCLUSIONS: KeaA is required for cAMP signaling following stress. Our studies indicate a role for kelch proteins in the signaling that regulates the cell cycle and development in response to changes in the environmental conditions.

Role for YakA, cAMP, and protein kinase A in regulation of stress responses of Dictyostelium discoideum cells.

The Dictyostelium protein kinase YakA is required for the growth-to-development transition. During growth YakA controls the cell cycle, regulating the intervals between cell divisions. When starved for nutrients Dictyostelium cells arrest growth and undergo changes in gene expression, decreasing vegetative mRNAs and inducing the expression of pkaC. YakA is an effector of these changes, being necessary for the decrease of vegetative mRNA expression and the increase of protein kinase A (PKA) activity that will ultimately regulate expression of adenylyl cyclase, cAMP synthesis, and the induction of development. We report a role for this kinase in the response to nitrosoative or oxidative stress of Dictyostelium cells. Hydrogen peroxide and sodium nitroprusside arrest the growth of cells and trigger cAMP synthesis and activation of PKA in a manner similar to the well-established response to nutrient starvation. We have found that yakA null cells are hypersensitive to nitrosoative/oxidative stress and that a second-site mutation in pkaC suppresses this sensitivity. The response to different stresses has been investigated and YakA, cAMP, and PKA have been identified as components of the pathway that regulate the growth arrest that follows treatment with compounds that generate reactive oxygen species. The effect of different types of stress was evaluated in Dictyostelium and the YakA/PKA pathway was also implicated in the response to heat stress.