In the absence of adequate oxygen, cancer cells that are grown in hypoxic solid tumors resist treatment using antitumor drugs (such as doxorubicin, DOX), owing to their attenuated intracellular production of reactive oxygen species (ROS). Hyperbaric oxygen (HBO) therapy favorably improves oxygen transport to the hypoxic tumor tissues, thereby increasing the sensitivity of tumor cells to DOX. However, the use of HBO with DOX potentiates the ROS-mediated cytotoxicity of the drug toward normal tissues. In this work, we hypothesize that regional oxygen treatment by an implanted oxygen-generating depot may enhance the cytotoxicity of DOX against malignant tissues in a highly site-specific manner, without raising systemic oxygen levels. Upon implantation close to the tumor, the oxygen-generating depot reacts with the interstitial medium to produce oxygen in situ, effectively shrinking the hypoxic regions in the tumor tissues. Increasing the local availability of oxygen causes the cytotoxicity of DOX that is accumulated in the tumors to be significantly enhanced by the elevated production of ROS, ultimately allaying the hypoxia-induced DOX resistance in solid malignancies. Importantly, this enhancement of cytotoxicity is limited to the site of the tumors, and this feature of the system that is proposed herein is unique.

No abstract

Chlorinated water is commonly used in industrial operations to wash and sanitize fresh-cut, minimally processed produce. Here we compared 42 human outbreak strains that represented nine distinct Escherichia coli O157:H7 genetic lineages (or clades) for their relative resistance to chlorine treatment. A quantitative measurement of resistance was made by comparing the extension of the lag phase during growth of each strain under exposure to sublethal concentrations of sodium hypochlorite in Luria-Bertani or brain heart infusion broth. Strains in clade 8 showed significantly (P < 0.05) higher resistance to chlorine than strains from other clades of E. coli O157:H7. To further explore how E. coli O157:H7 responds to oxidative stress at transcriptional levels, we analyzed the global gene expression profiles of two strains, TW14359 (clade 8; associated with the 2006 spinach outbreak) and Sakai (clade 1; associated with the 1996 radish sprout outbreak), under sodium hypochlorite or hydrogen peroxide treatment. We found over 380 genes were differentially expressed (more than twofold; P < 0.05) after exposure to low levels of chlorine or hydrogen peroxide. Significantly upregulated genes included several regulatory genes responsive to oxidative stress, genes encoding putative oxidoreductases, and genes associated with cysteine biosynthesis, iron-sulfur cluster assembly, and antibiotic resistance. Identification of E. coli O157:H7 strains with enhanced resistance to chlorine decontamination and analysis of their transcriptomic response to oxidative stress may improve our basic understanding of the survival strategy of this human enteric pathogen on fresh produce during minimal processing.

(G2019S) mutation of leucine-rich repeat kinase 2 (LRRK2) is the most common genetic cause of both familial and sporadic Parkinson's disease (PD) cases. Twelve-to sixteen-month-old (G2019S) LRRK2 transgenic mice prepared by us displayed progressive degeneration of substantia nigra pars compacta (SNpc) dopaminergic neurons and parkinsonism phenotypes of motor dysfunction. LRRK2 is a member of mixed lineage kinase subfamily of mitogen-activated protein kinase kinase kinases (MAPKKKs). We hypothesized that (G2019S) mutation augmented LRRK2 kinase activity, leading to overphosphorylation of downstream MAPK kinase (MKK) and resulting in activation of neuronal death signal pathway. Consistent with our hypothesis, (G2019S) LRRK2 expressed in HEK 293 cells exhibited an augmented kinase activity of phosphorylating MAPK kinase 4 (MKK4) at Ser 257 , and protein expression of active phospho-MKK4 Ser257 was upregulated in the SN of (G2019S) LRRK2 transgenic mice. Protein level of active phospho-JNK Thr183/Tyr185 and phospho-c-Jun Ser63 , downstream targets of phospho-MKK4 Ser257 , was increased in the SN of (G2019S) LRRK2 mice. Upregulated mRNA expression of pro-apoptotic Bim and FasL, target genes of phospho-c-Jun Ser63 , and formation of active caspase-9, caspase-8 and caspase-3 were also observed in the SN of (G2019S) LRRK2 transgenic mice. Our results suggest that mutant (G2019S) LRRK2 activates MKK4-JNK-c-Jun pathway in the SN and causes the resulting degeneration of SNpc dopaminergic neurons in PD transgenic mice.

Multidrug resistance (MDR) resulting from the overexpression of drug transporters such as P-glycoprotein (Pgp) increases the efflux of drugs and thereby limits the effectiveness of chemotherapy. To address this issue, this work develops an injectable hollow microsphere (HM) system that carries the anticancer agent irinotecan (CPT-11) and a NO-releasing donor (NONOate). Upon injection of this system into acidic tumor tissue, environmental protons infiltrate the shell of the HMs and react with their encapsulated NONOate to form NO bubbles that trigger localized drug release and serve as a Pgp-mediated MDR reversal agent. The site-specific drug release and the NO-reduced Pgp-mediated transport can cause the intracellular accumulation of the drug at a concentration that exceeds the cell-killing threshold, eventually inducing its antitumor activity. These results reveal that this pH-responsive HM carrier system provides a potentially effective method for treating cancers that develop MDR.

Preliminary results showed that the distribution patterns of R(1) and pAV-45 images are highly correlated with normalized FDG images, and the initial 5-min early time frame of 1-6 min is potentially useful in providing complementary FDG-like information to the amyloid plaque density by late-phase AV-45 images.

This study investigates the effects of chitosan (CS) on the opening of epithelial tight junctions (TJs) and paracellular transport at microscopic, ultrastructural, and computed-tomographic levels in Caco-2 cell monolayers and animal models. Using immunofluorescence staining, CS treatment was observed to be associated with the translocation of JAM-1 (a trans-membrane TJ protein), resulting in the disruption of TJs; the removal of CS was accompanied by the recovery of JAM-1. Ultrastructural observations by TEM reveal that CS treatment slightly opened the apical intercellular space, allowing lanthanum (an electron-dense tracer) to stain the intercellular surface immediately beneath the TJs, suggesting the opening of TJs. Following the removal of CS, the TJs were completely recovered. Similar microscopic and ultrastructural findings were obtained in animal studies. CS nanoparticles were prepared as an insulin carrier. The in vivo fluorescence-microscopic results demonstrate that insulin could be absorbed into the systemic circulation, while most CS was retained in the microvilli scaffolds. These observations were verified in a biodistribution study following the oral administration of isotope-labeled nanoparticles by single-photon emission computed tomography. Above results reveal that CS is a safe permeation enhancer and is an effective carrier for oral protein delivery.

No abstract