ProBDNF collapses neurite outgrowth of primary neurons by activating RhoA

Background

Neurons extend their dendrites and axons to build functional neural circuits, which are regulated by both positive and negative signals during development. Brain-derived neurotrophic factor (BDNF) is a positive regulator for neurite outgrowth and neuronal survival but the functions of its precursor (proBDNF) are less characterized.

Methodology/Principal Findings

Here we show that proBDNF collapses neurite outgrowth in murine dorsal root ganglion (DRG) neurons and cortical neurons by activating RhoA via the p75 neurotrophin receptor (p75NTR). We demonstrated that the receptor proteins for proBDNF, p75NTR and sortilin, were highly expressed in cultured DRG or cortical neurons. ProBDNF caused a dramatic neurite collapse in a dose-dependent manner and this effect was about 500 fold more potent than myelin-associated glycoprotein. Neutralization of endogenous proBDNF by using antibodies enhanced neurite outgrowth in vitro and in vivo, but this effect was lost in p75NTR^−/− mice. The neurite outgrowth of cortical neurons from p75NTR deficient (p75NTR^−/−) mice was insensitive to proBDNF. There was a time-dependent reduction of length and number of filopodia in response to proBDNF which was accompanied with a polarized RhoA activation in growth cones. Moreover, proBDNF treatment of cortical neurons resulted in a time-dependent activation of RhoA but not Cdc42 and the effect was absent in p75NTR^−/− neurons. Rho kinase (ROCK) and the collapsin response mediator protein-2 (CRMP-2) were also involved in the proBDNF action.

Conclusions

proBDNF has an opposing role in neurite outgrowth to that of mature BDNF. Our observations suggest that proBDNF collapses neurites outgrowth and filopodial growth cones by activating RhoA through the p75NTR signaling pathway.     

4-O-carboxymethylascochlorin protected against microglial-mediated neurotoxicity in SH-SY5Y and BV2 cocultured cells from LPS–induced neuroinflammation and death by inhibiting MAPK,NF-κB,and Akt pathways

In our previous studies, structurally similar compounds of ascochlorin and ascofuranone exhibited anti-inflammatory activity. Neural inflammation plays a significant role in the commence and advancement of neurodegenerative diseases. It is not known whether 4-O-carboxymethylascochlorin (AS-6) regulates the initial stage of inflammatory responses at the cellular level in BV2 microglia cells. We here investigated the anti-inflammatory effects of AS-6 treatment in microglia cells with the microglial protection in neurons. We found that the lipopolysaccharide (LPS)-stimulated production of nitric oxide, a main regulator of inflammation, is suppressed by AS-6 in BV2 microglial cells. In addition, AS-6 dose-dependently suppressed the increase in COX-2 protein and messenger RNA levels in LPS-stimulated BV2 cells. Moreover, AS-6 inhibited the expression and secretion of proinflammatory cytokines in BV2 microglial cells. At the intracellular level, AS-6 inhibited LPS-activated nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) in BV2 microglial cells. AS-6 negatively affected mitogen-activated protein kinases (MAPK) and Akt phosphorylation: Phosphorylated forms of ERK, JNK, p38, and Akt decreased. To check whether AS-6 protects against inflammatory inducer-mediated neurotoxicity, neuronal SH-SY5Y cells were coincubated with BV2 cells in conditioned medium. AS-6 exerted a neuroprotective effect by suppressing microglial activation by LPS or amyloid-β peptide. AS-6 is a promising suppressor of inflammatory responses in LPS-induced BV2 cells by attenuating NF-κB and MAPKs signaling. AS-6 protected against microglial-mediated neurotoxicity in SH-SY5Y and BV2 cocultured cells from LPS–induced neuroinflammation and death via inhibiting MAPK, NF-κB, and Akt pathways.     

Piezoelectric effect stimulates the rearrangement of chondrogenic cells and alters ciliary orientation via atypical PKCζ

Therapeutic ultrasound was administered to patients suffering from bone fracture with FDA approval. Bone and cartilage are piezoelectric materials. To investigate the effects of piezoelectricity on the cells of chondrogenic lineage, we applied ultrasound stimulation on an AT-cut quartz coverslip to generate electric field fluctuations. The bone-marrow-derived mesenchymal stem cells (BMMSC) and primary chondrocytes were cultured on either glass or quartz coverslips for ultrasound stimulation. The cells were immunofluorescent-labeled for the assessment of cell arrangement and ciliary orientation. Ultrasound and piezoelectricity both stimulate cell migration and disrupt ciliary orientation induced by directional migration. In particular, piezoelectric effects on cell rearrangement can be abolished by the inhibitor specifically targeting atypical Protein kinase C zeta (PKCζ). Our findings shed light on the possibility of cellular modulation by using piezoelectric manipulation.     

Change of arthropod abundance in burned forests: Different patterns according to functional guilds

Forest fires are one of the most frequent and important causes of forest disturbances, the occurrence of which is globally increasing due to the effects of climate change. This study aimed to determine the impacts of fire and human activity on arthropod communities in affected forests. Twelve study sites in three burned areas were selected for this study. Intensities of disturbance in the study sites were characterized as follows: Disturbance Degree (DD) 0 (no fire), DD 1 (surface fire), DD 2 (crown fire), and DD 3 (crown fire followed by reforestation). Arthropods were collected using pitfall traps. Fourteen arthropod taxa (families, orders or classes), which are relatively homogeneous in their feeding habits and abundant, were analyzed. Depth of litter layer was selected as an environmental indicator for disturbance intensity, as it decreases linearly as the degree of disturbance increased. Changes of arthropod abundance in response to disturbance differed among functional guilds. As disturbance intensity increased, the abundance of detritivores decreased, but the abundance of herbivores increased. However, the abundance of predators varied between taxa. Formicidae and Araneae increased in disturbed sites, whereas Carabidae and Staphylinidae did not change. The abundance of Thysanura and Diptera was highly correlated with disturbance intensity, and may be suitable as a bioindicator for forest disturbance. Arthropod communities were more heterogeneous in forests of intermediate disturbance.     

Cost-Effectiveness Comparison of Genechip and Conventional Drug Susceptibility Test for Detecting Multidrug-Resistant Tuberculosis in China

Background

Genechip (CapitalBio, Beijing, China) is a system for diagnosing resistance to rifampin and isoniazid, which shows high efficiency in detecting drug-resistant tuberculosis. Here, we firstly evaluated the costs of Genechip for detecting the drug susceptibility of Mycobacterium tuberculosis, compared to conventional drug susceptibility test (DST) in laboratories in China.

Methodology/Principal Findings

Data on the costs of the two tests were collected at four hospitals. Costs were calculated using the essential factor cost calculation method. The costs of diagnosing a single case of multidrug-resistant tuberculosis (MDR-TB) using Genechip and DST were US$22.38 and $53.03, respectively. Taking into account the effect on costs from failure of a certain number of tests to accurately diagnose MDR-TB, the costs of Genechip and DST increased by 17.65% and 5.22%, respectively. The cost of both tests decreased with the increasing prevalence of MDR-TB disease, and the cost of Genechip at a sensitivity of more than 50% was lower than that of DST. When price of Genechip was varied to 50%, 80%, 150%, and 200% of the original price, the cost of Genechip at sensitivities of more than 30%, 40%, 60%, and 70%, respectively, was also lower than that of DST.

Conclusions/Significance

This study showed that Genechip was a more cost-effective method of diagnosing MDR-TB compared to conventional DST.