Non-Essential Role for TLR2 and Its Signaling Adaptor Mal/TIRAP in Preserving Normal Lung Architecture in Mice

Myeloid differentiation factor 88 (MyD88) and MyD88-adaptor like (Mal)/Toll-interleukin 1 receptor domain containing adaptor protein (TIRAP) play a critical role in transducing signals downstream of the Toll-like receptor (TLR) family. While genetic ablation of the TLR4/MyD88 signaling axis in mice leads to pulmonary cell death and oxidative stress culminating in emphysema, the involvement of Mal, as well as TLR2 which like TLR4 also signals via MyD88 and Mal, in the pathogenesis of emphysema has not been studied. By employing an in vivo genetic approach, we reveal here that unlike the spontaneous pulmonary emphysema which developed in Tlr4^−/− mice by 6 months of age, the lungs of Tlr2^−/− mice showed no physiological or morphological signs of emphysema. A more detailed comparative analysis of the lungs from these mice confirmed that elevated oxidative protein carbonylation levels and increased numbers of alveolar cell apoptosis were only detected in Tlr4^−/− mice, along with up-regulation of NADPH oxidase 3 (Nox3) mRNA expression. With respect to Mal, the architecture of the lungs of Mal^−/− mice was normal. However, despite normal oxidative protein carbonylation levels in the lungs of emphysema-free Mal^−/− mice, these mice displayed increased levels of apoptosis comparable to those observed in emphysematous Tlr4^−/− mice. In conclusion, our data provide in vivo evidence for the non-essential role for TLR2, unlike the related TLR4, in maintaining the normal architecture of the lung. In addition, we reveal that Mal differentially facilitates the anti-apoptotic, but not oxidant suppressive, activities of TLR4 in the lung, both of which appear to be essential for TLR4 to prevent the onset of emphysema.     

Zinc inhibits magnesium-dependent migration of human breast cancer MDA-MB-231 cells on fibronectin

Metastasis is the major cause of breast cancer mortality. The strength of cell adhesion to extracellular matrix is critical to cancer cell migration. Integrins, the primary mediators of cell to extra-cellular matrix adhesion, contain distinct divalent cation-binding sites. Binding of manganese and magnesium is vital to integrin-mediated cancer cell adhesion and migration. We hypothesized that zinc, a divalent cation, can modulate breast cancer metastasis through interfering with these divalent cation-dependent integrin-mediated cancer cell adhesion and migration. MDA-MB-231 cells were cultured in a zinc-depleted medium supplemented with 0 (control), 2.5, 5, 10, 25 and 50 μM of zinc to mimic severe zinc-deficiency, moderate zinc-deficiency, adequate zinc and three levels of zinc-supplementation: low-, moderate- and high-levels of zinc-supplementation, respectively. Zinc treatments had no effect on cellular zinc concentration, cell number and cell viability. Zinc at 5–50 μM reduced migration distance of MDA-MB-231 cells on fibronectin by 43–86% and migration rate on fibronectin by 72–90%. Zinc induced a dose-dependent inhibition of cell adhesion to fibronectin (R²=?0.98). Zinc at 10–50 μM reduced magnesium-facilitated cell adhesion to fibronectin in a dose-dependent manner (R²=?0.90). However, zinc had no effect on manganese-facilitated cell adhesion to fibronectin. Zinc at 5–50 μM caused rounding of the normally elongated, irregular-shaped MDA-MB-231 cells and disappearance of F-actin. Anti-integrin α5- and β1-subunit blocking antibodies inhibited magnesium-facilitated cell adhesion to fibronectin by 95 and 99%, respectively. In summary, zinc inhibited MDA-MB-231 cell migration on fibronectin by interfering with magnesium-dependent integrin-, likely integrin α5/β1-, mediated adhesion.     

Prospects for seascape repair: Three case studies from eastern Australia

Three case studies spanning tropical, subtropical and temperate environments highlight the minimum potential benefits of investing in repair of coastal seascapes. Fisheries, a market benefit indicator readily understood by a range of stakeholders from policymakers to community advocates, were used as a surrogate for ecosystem services generated through seascape habitat restoration. For each case study, while recognising that biological information will always remain imperfect, the prospects for seascape repair are compelling.     

MVB-12, a fourth subunit of metazoan ESCRT-I, functions in receptor downregulation

After ligand binding and endocytosis, cell surface receptors can continue to signal from endosomal compartments until sequestered from the cytoplasm. An important mechanism for receptor downregulation in vivo is via the inward budding of receptors into intralumenal vesicles to form specialized endosomes called multivesicular bodies (MVBs) that subsequently fuse with lysosomes, degrading their cargo. This process requires four heterooligomeric protein complexes collectively termed the ESCRT machinery. In yeast, ESCRT-I is a heterotetrameric complex comprised of three conserved subunits and a fourth subunit for which identifiable metazoan homologs were lacking. Using C. elegans, we identify MVB-12, a fourth metazoan ESCRT-I subunit. Depletion of MVB-12 slows the kinetics of receptor downregulation in vivo, but to a lesser extent than inhibition of other ESCRT-I subunits. Consistent with these findings, targeting of MVB-12 to membranes requires the other ESCRT-I subunits, but MVB-12 is not required to target the remaining ESCRT-I components. Both endogenous and recombinant ESCRT-I are stable complexes with a 1:1:1:1 subunit stoichiometry. MVB-12 has two human homologs that co-localize and co-immunoprecipitate with the ESCRT-I component TSG101. Thus, MVB-12 is a conserved core component of metazoan ESCRT-I that regulates its activity during MVB biogenesis.     

Evidence for non-genomic transmission of ecological information via maternal behavior in female rats

Maternal behavior is flexible and programs offspring development. Using a novel manipulation, we demonstrate that rat maternal behavior is sensitive to ecologically relevant stimuli. Long-Evans hooded rat dams (F0) and pups were exposed to a predator condition (cat odor) or a control condition (no odor) for 1 h on the day of parturition. Predator-exposed F0 dams displayed significantly more maternal behavior (licking/grooming, arched-back nursing) relative to control-exposed dams across five subsequent observation days. Female offspring (F1) were raised to adulthood, bred and maternal behavior was observed. F1 dams reared by a predator-exposed F0 dam displayed significantly higher maternal behavior relative to F1 dams reared by a control-exposed F0 dam across 5 days of observation. Increased levels of maternal behavior in predator-reared (PR) F1 dams were evident even in F1 females that had been cross-fostered (CF) from a control-exposed F0 dam, suggesting a non-genomic transmission of increased levels of maternal behavior. Lactating PR F1 dams had significantly elevated estrogen receptor alpha and beta mRNA in the medial preoptic area relative to control-reared (CR) F1 dams. Furthermore, among CR F1 dams, there was no significant difference between those dams that had been CF from predator-exposed F0 dams and those that had been sham CF. These results support the hypothesis that flexible rat maternal behavior can shape offspring development according to current environmental conditions. The results also suggest that estrogen signaling may be part of an epigenetic mechanism by which changes in maternal behavior are passed from F0 to F1 dams.     

Why is sterility virulence most common in sexually transmitted infections? Examining the role of epidemiology

Sterility virulence, or the reduction in host fecundity due to infection, occurs in many host–pathogen systems. Notably, sterility virulence is more common for sexually transmitted infections (STIs) than for directly transmitted pathogens, while other forms of virulence tend to be limited in STIs. This has led to the suggestion that sterility virulence may have an adaptive explanation. By focusing upon finite population models, we show that the observed patterns of sterility virulence can be explained by consideration of the epidemiological differences between STIs and directly transmitted pathogens. In particular, when pathogen transmission is predominantly density invariant (as for STIs), and mortality is density dependent, sterility virulence can be favored by demographic stochasticity, whereas if pathogen transmission is predominantly density dependent, as is common for most directly transmitted pathogens, sterility virulence is disfavored. We show these conclusions can hold even if there is a weak selective advantage to sterilizing.