Protective Role of Nuclear Factor E2-Related Factor 2 against Acute Oxidative Stress-Induced Pancreatic β

Oxidative stress is implicated in the pathogenesis of pancreatic β-cell dysfunction that occurs in both type 1 and type 2 diabetes. Nuclear factor E2-related factor 2 (NRF2) is a master regulator in the cellular adaptive response to oxidative stress. The present study found that MIN6 β-cells with stable knockdown of Nrf2 (Nrf2-KD) and islets isolated from Nrf2-knockout mice expressed substantially reduced levels of antioxidant enzymes in response to a variety of stressors. In scramble MIN6 cells or wild-type islets, acute exposure to oxidative stressors, including hydrogen peroxide (H2O2) and S-nitroso-N-acetylpenicillamine, resulted in cell damage as determined by decrease in cell viability, reduced ATP content, morphology changes of islets, and/or alterations of apoptotic biomarkers in a concentration- and/or time-dependent manner. In contrast, silencing of Nrf2 sensitized MIN6 cells or islets to the damage. In addition, pretreatment of MIN6 β-cells with NRF2 activators, including CDDO-Im, dimethyl fumarate (DMF), and tert-butylhydroquinone (tBHQ), protected the cells from high levels of H2O2-induced cell damage. Given that reactive oxygen species (ROS) are involved in regulating glucose-stimulated insulin secretion (GSIS) and persistent activation of NRF2 blunts glucose-triggered ROS signaling and GSIS, the present study highlights the distinct roles that NRF2 may play in pancreatic β-cell dysfunction that occurs in different stages of diabetes

Understanding the tensile behaviors of ultra-thin ZnO nanowires via molecular dynamics simulations

By using molecular dynamics (MD) method, the tensile behavior of ultra-thin ZnO nanowires in <0001 > orientation with three different diameters have been investigated respectively. Through the numerical simulations, the tensile properties including Young’s modulus and yielding stress are obtained as functions of strain rates, temperatures and diameter sizes. The simulation results indicate that the nanowire Young’s modulus and yielding stress would decrease with the increasing of diameter size. In addition, a significant dependence of tensile properties on temperature was also observed with the Young’s modulus and yielding stress decreasing on average by 8% and 18% respectively, while the temperature rises from 0.1 K to 400 K. However, in our simulations the Young’s modulus and yielding stress have no obvious change with different strain rates. Lastly, the structure of ultra-thin ZnO nanowires could be transformed at the strain of ∼7%-11% while the nanowires eventually fracture at the strain of nearly 15%

Largescale Transcriptomics Analysis Suggests Over-Expression of BGH3, MMP9 and PDIA3 in Oral Squamous Cell Carcinoma.

Oral squamous cell carcinoma (OSCC) has been reported as the most prevalent cancer of the head and neck region, while early diagnosis remains challenging. Here we took a comprehensive bioinformatics study on microarray data of 326 OSCC clinical samples with control of 165 normal tissues. The cell interaction pathways of ECM-receptor interaction and focal adhesion were found to be significantly regulated in OSCC samples. Further analysis of the topological properties and expression consistency identified that three hub genes in the gene interaction network, MMP9, PDIA3 and BGH3, were consistently up-expressed in OSCC samples. When being validated on additional microarray datasets of 41 OSCC samples, the validation rate of over-expressed BGH3, MMP9, and PDIA3 reached 90%, 90% and 84% respectively. At last, immuno-histochemical assays were done to test the protein expression of the three genes on newly collected clinical samples of 35 OSCC, 20 samples of pre-OSCC stage, and 12 normal oral mucosa specimens. Their protein expression levels were also found to progressively increase from normal mucosa to pre-OSCC stage and further to OSCC (ANOVA p = 0.000), suggesting their key roles in OSCC pathogenesis. Based on above solid validation, we propose BGH3, MMP9 and PDIA3 might be further explored as potential biomarkers to aid OSCC diagnosis

(<em>S</em>)-α-Chlorohydrin Inhibits Protein Tyrosine Phosphorylation through Blocking Cyclic AMP - Protein Kinase A Pathway in Spermatozoa

<div><p>α-Chlorohydrin is a common contaminant in food. Its (<em>S</em>)-isomer, (<em>S</em>)-α-chlorohydrin (SACH), is known for causing infertility in animals by inhibiting glycolysis of spermatozoa. The aim of present work was to examine the relationship between SACH and protein tyrosine phosphorylation (PTP), which plays a critical role in regulating mammalian sperm capacitation. In vitro exposure of SACH 50 µM to isolated rat epididymal sperm inhibited PTP. Sperm-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDS) activities, the intracellular adenosine 5′-triphosphate (ATP) levels, 3′-5′-cyclic adenosine monophosphate (cAMP) levels and phosphorylation of protein kinase A (PKA) substrates in rat sperm were diminished dramatically, indicating that both glycolysis and the cAMP/PKA signaling pathway were impaired by SACH. The inhibition of both PTP and phosphorylation of PKA substrates by SACH could be restored by addition of cAMP analog dibutyryl-cAMP (dbcAMP) and phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Moreover, addition of glycerol protected glycolysis, ATP levels, phosphorylation of PKA substrates and PTP against the influence of SACH. These results suggested SACH inhibited PTP through blocking cAMP/PKA pathway in sperm, and PTP inhibition may play a role in infertility associated with SACH.</p> </div

The model by which SACH inhibits cAMP/PKA mediated protein phosphorylation through blocking glycolysis in spermatozoa during capacitation.

<p>The inhibition of GAPDS by SACH results in depletion of ATP and then depresses of P-PKAs and PTP. Glycerol overcomes these effects through restoring glycolysis, and IBMX and dbcAMP, the activators of PKA, reverse in part the inhibitions of P-PKAs and PTP.</p

Glycerol rescues glycolysis, PTP and PKA after inhibition by SACH.

<p>Rat spermatozoa were exposed to a series of concentrations of SACH in capacitating conditions for 6 hours and both GAPDS activity (A) and ATP level (B) were significantly reduced. n = 3, * <i>p</i><0.05 vs. control. (C and D) Rat sperm were exposed to a serial of concentrations of glycerol in the presence of 100 µM SACH for 6 hours and GAPDS activity and ATP were measured. n = 3, <i>a p</i><0.01, <i>b p</i><0.001 vs. the 100 µM SACH group. (E, F, G and H) With the same treatment as in (C and D), sperm were subjected to Western Blot analyses with anti-PTP (E and F) and anti-P-PKAs (G and H) antibodies. n = 2, * <i>p</i><0.05, ** <i>p</i><0.01 vs. control.</p

The role of depletion of cAMP in inhibition of PTP and P-PKAs by SACH.

<p>(A) cAMP levels in rat sperm decreased by SACH after incubation in capacitating conditions for 6 hours, * <i>p</i><0.05 vs. control. (B C, D and E) Rat sperm were incubated in complete BWW supplemented with 50 µM SACH, 100 µM SACH and 10 µM H89 or in BWW-HCO₃⁻ in the presence and absence of 0.25 mM dbcAMP and 0.1 mM IBMX as indicated at the bottoms of the figures. After 6 hours of incubation, PTP (B) and P-PKAs (D) were identified by Western Blot, and levels of phosphorylation were quantitated by densitometry analysis of representative bands (C, E). n = 3, * <i>p</i><0.05, ** <i>p</i><0.01, *** <i>p</i><0.001 vs. control.</p

Organic Extract Contaminants from Drinking Water Activate Nrf2-Mediated Antioxidant Response in a Human Cell Line

Traditional risk assessment methods face challenges in estimating risks from drinking waters that contain low-levels of large numbers of contaminants. Here, we evaluate the toxicity of organic contaminant (OC) extracts from drinking water by examining activation of nuclear factor E2-related factor 2 (Nrf2)-mediated antioxidant response. In HepG2 cells, the Nrf2-mediated antioxidant responsemeasured as Nrf2 protein accumulation, expression of antioxidant response element (ARE)-regulated genes and ARE-luciferase reporter gene assays were activated by OC extracts from drinking water sources that detected 25 compounds in 9 classification groups. Individual OCs induced oxidative stress at concentrations much higher than their environmental levels; however, mixtures of contaminants induced oxidative stress response at only 8 times the environmental levels. Additionally, a synthetic OC mixture prepared based on the contamination profiling of drinking water induced ARE activity to the same extent as the real-world mixture, reinforcing our conclusion that these mixture exposures produce responses relevant for human exposure situations. Our study tested the possibility of assessing toxicity of OCs of drinking water using a specific ARE-pathway measurement. This approach should be broadly useful in assisting risk assessment of mixed environmental exposure

Immunohistochemical labeling of normal oral mucosa (A,D,G), oral leukoplakia (B,E,H) and oral squamous cell carcinoma (G,H,I) for MMP9 (A,B,C), BGH3 (D,E,F) and PDIA3 (G,H,I).

<p>Brown staining represents positive expression of proteins. MMP9 expression in stroma cells is low (A). Positive MMP9 cytoplasmic staining of basal cells in OLK (B). Strong nuclear and cytoplasmic MMP9 staining of OSCC (C). Negative BGH3 expression in NOM (D). Weak or moderate BGH3 staining of the basement membrane in OLK (E). Strong positive BGH3 expression in tumor basement membrane and extracellular skeletal stroma of OSCC (F). Negative PDIA3 staining in NOM (G). Moderate to strong PDIA3 staining in the cytoplasm and nucleus of OLK epithelium cells (H). High PDIA3 expression in the cytoplasm and cell membrane of OSCC (I).</p