The impact of urban pollution on metal contamination of selected forest pockets in Cape Town, South Africa.

Urban forests are exposed to metals, such as manganese, copper, and zinc in the atmosphere that originate from anthropogenic activities, that include vehicle-related traffic, industries, construction sites, fossil fuel burning for heating and cooking purposes, and resuspension processes related to urban surfaces. Not only is the rich biodiversity of plant and animal species in forests under threat, but so are the biodiversity of soil, sustaining ecosystem functions, as well as human health. The objective of this study was therefore to determine the concentrations of manganese, copper, and zinc arising from urban, industrial, and traffic-related pollution in the remote and/or untouched urban indigenous forests using soil, leaf litter, and key forest organisms (mosses, lichens, and millipedes) in three forests (Platbos, Orange Kloof, and Newlands) in the Western Cape, South Africa. Elevated concentrations of these metals were found in the forests closest to the city, as well as at sites in close proximity of vehicle traffic.

Trictide, a tricellulin-derived peptide to overcome cellular barriers.

The majority of tight junction (TJ) proteins restrict the paracellular permeation of solutes via their extracellular loops (ECLs). Tricellulin tightens tricellular TJs (tTJs) and regulates bicellular TJ (bTJ) proteins. We demonstrate that the addition of recombinantly produced extracellular loop 2 (ECL2) of tricellulin opens cellular barriers. The peptidomimetic trictide, a synthetic peptide derived from tricellulin ECL2, increases the passage of ions, as well as of small and larger molecules up to 10 kDa, between 16 and 30 h after application to human epithelial colorectal adenocarcinoma cell line 2. Tricellulin and lipolysis-stimulated lipoprotein receptor relocate from tTJs toward bTJs, while the TJ proteins claudin-1 and occludin redistribute from bTJs to the cytosol. Analyzing the opening of the tricellular sealing tube by the peptidomimetic using super-resolution stimulated-emission depletion microscopy revealed a tricellulin-free area at the tricellular region. Cis-interactions (as measured by fluorescence resonance energy transfer) of tricellulin-tricellulin (tTJs), tricellulin-claudin-1, tricellulin-marvelD3, and occludin-occludin (bTJs) were strongly affected by trictide treatment. Circular dichroism spectroscopy and molecular modeling suggest that trictide adopts a ß-sheet structure, resulting in a peculiar interaction surface for its binding to tricellulin. In conclusion, trictide is a novel and promising tool for overcoming cellular barriers at bTJs and tTJs with the potential to transiently improve drug delivery.