Risks of mining to salmonid-bearing watersheds.

Mining provides resources for people but can pose risks to ecosystems that support cultural keystone species. Our synthesis reviews relevant aspects of mining operations, describes the ecology of salmonid-bearing watersheds in northwestern North America, and compiles the impacts of metal and coal extraction on salmonids and their habitat. We conservatively estimate that this region encompasses nearly 4000 past producing mines, with present-day operations ranging from small placer sites to massive open-pit projects that annually mine more than 118 million metric tons of earth. Despite impact assessments that are intended to evaluate risk and inform mitigation, mines continue to harm salmonid-bearing watersheds via pathways such as toxic contaminants, stream channel burial, and flow regime alteration. To better maintain watershed processes that benefit salmonids, we highlight key windows during the mining governance life cycle for science to guide policy by more accurately accounting for stressor complexity, cumulative effects, and future environmental change.

Decreased epithelial barrier function evoked by exposure to metabolic stress and nonpathogenic E. coli is enhanced by TNF-alpha.

A defect in mitochondrial activity contributes to many diseases. We have shown that monolayers of the human colonic T84 epithelial cell line exposed to dinitrophenol (DNP, uncouples oxidative phosphorylation) and nonpathogenic Escherichia coli (E. coli) (strain HB101) display decreased barrier function. Here the impact of DNP on macrophage activity and the effect of TNF-alpha, DNP, and E. coli on epithelial permeability were assessed. DNP treatment of the human THP-1 macrophage cell line resulted in reduced ATP synthesis, and, although hyporesponsive to LPS, the metabolically stressed macrophages produced IL-1beta, IL-6, and TNF-alpha. Given the role of TNF-alpha in inflammatory bowel disease (IBD) and the association between increased permeability and IBD, recombinant TNF-alpha (10 ng/ml) was added to the DNP (0.1 mM) + E. coli (10(6) colony-forming units), and this resulted in a significantly greater loss of T84 epithelial barrier function than that elicited by DNP + E. coli. This increased epithelial permeability was not due to epithelial death, and the enhanced E. coli translocation was reduced by pharmacological inhibitors of NF-kappabeta signaling (pyrrolidine dithiocarbamate, NF-kappabeta essential modifier-binding peptide, BAY 11-7082, and the proteosome inhibitor, MG132). In contrast, the drop in transepithelial electrical resistance was unaffected by the inhibitors of NF-kappabeta. Thus, as an integrative model system, our findings support the induction of a positive feedback loop that can severely impair epithelial barrier function and, as such, could contribute to existing inflammation or trigger relapses in IBD. Thus metabolically stressed epithelia display increased permeability in the presence of viable nonpathogenic E. coli that is exaggerated by TNF-alpha released by activated immune cells, such as macrophages, that retain this ability even if they themselves are experiencing a degree of metabolic stress.

Phosphatidylinositol 3'-kinase is a critical mediator of interferon-gamma-induced increases in enteric epithelial permeability.

The epithelial lining of mucosal surfaces acts as a barrier to regulate the entry of antigen and pathogens. Nowhere is this function of the contiguous epithelium more important than in the gut, which is continually exposed to a huge antigenic load and, in the colon, an immense commensal microbiota. We assessed the intracellular signaling events that underlie interferon (IFN) gamma-induced increases in epithelial permeability using monolayers of the human colonic T84 epithelial cell line. Confluent epithelial monolayers on semipermeable supports were treated with IFNgamma (20 ng/ml), and barrier function was assessed 48 h later by measuring transepithelial electrical resistance (TER: reflects passive ion flux), fluxes of (51)Cr-EDTA and horseradish peroxidase (HRP), and transcytosis of noninvasive, nonpathogenic Escherichia coli (strain HB101). Exposure to IFNgamma decreased barrier function as assessed by all four markers. The phosphatidylinositol 3'-kinase (PI-3K) inhibitors, LY294002 [2-(4-morpholinyl)-8-phenyl-1(4H)-benzopyran-4-one hydrochloride] and wortmannin, did not affect baseline permeability characteristics but completely blocked the drop in TER, increased fluxes of (51)Cr-EDTA and HRP, and significantly reduced E. coli transcytosis evoked by IFNgamma. In addition, use of the pan-protein kinase C (PKC) inhibitor, bisindolylmaleimide I (5 muM), but not rottlerin (blocks PKCdelta), partially ameliorated the drop in TER and inhibited increased E. coli transcytosis. Addition of the PI-3K and PKC inhibitors to epithelia 6 h after IFNgamma exposure still prevented the increase in paracellular permeability but not E. coli transcytosis. Thus, IFNgamma-induced increases in epithelial paracellular and transcellular permeability are critically dependent on PI-3K activity, which may represent an epithelial-specific target to treat immune-mediated loss of barrier function.