Alpha-toxin facilitates the generation of CXC chemokine gradients and stimulates neutrophil homing in Staphylococcus aureus pneumonia

BACKGROUND: Staphylococcus aureus alpha-toxin is a major virulence factor, but its mechanism of action in vivo is incompletely understood. METHODS: We examined the role of alpha-toxin in S. aureus pneumonia using the mouse model of intranasal lung infection with S. aureus strain 8325-4 (hla(+) S. aureus) and an alpha-toxin-deficient mutant strain made on the 8325-4 background (hla(-) S. aureus). RESULTS: Intranasal infection of mice with hla(-) S. aureus resulted in substantially less lung injury and inflammation, pulmonary edema, and tissue bacterial burden than did infection with hla(+) S. aureus. Furthermore, fewer mice infected with hla(-) S. aureus died of the infection, compared with those infected with hla(+) S. aureus. Levels of the CXC chemokines keratinocyte-derived chemokine and macrophage inflammatory protein-2 were significantly lower in the airways of mice infected with hla(-) S. aureus, and this difference was the result of reduced secretion of newly synthesized chemokines into the airway. Consistent with these data, significantly fewer neutrophils were present in the airways and lungs of mice infected with hla(-) S. aureus, compared with those infected with hla(+) S. aureus. CONCLUSIONS: These data suggest that alpha-toxin enhances virulence by facilitating the generation of CXC chemokine gradients and stimulating chemokine-induced neutrophil influx in S. aureus pneumonia.     

Family history of diabetes and risk of atherosclerotic cardiovascular disease in Korean men and women

The importance of family history of type 2 diabetes (FHD) as a risk factor for atherosclerotic cardiovascular disease (ASCVD) remains controversial. A report of diabetes in parents and siblings was used to establish FHD in a cohort of 1,005,230 Koreans aged 30-95 years insured by the National Health Insurance Corporation who had a biennial medical evaluation during 1992-1995. ASCVD morbidity and mortality from 1993 to 2005 were examined in relation to FHD and other ASCVD risk factors. The risk of ischemic heart disease (IHD) increased significantly (19%) in men with FHD but not in women. A strong interaction was observed between FHD and personal history of diabetes for the occurrence of ASCVD; men with both diabetes and FHD were at significantly increased risk of developing IHD, cerebrovascular disease and ASCVD with hazard ratios (HR) of 2.28, 2.07, and 2.12, respectively, compared to those who had neither FHD nor type 2 diabetes. Corresponding risks were 2.64, 2.03, and 2.10 in women, respectively. This study demonstrates that risk of ASCVD is increased among those with diabetes and a family history of diabetes; suggesting that genetic factors associated with occurrence of familial diabetes may increase risk of ASCVD beyond the risk among people without FHD.     

Association of abdominal fat distribution and cardiometabolic risk factors among obese Korean adolescents

The association between abdominal fat distribution and cardiometabolic risk factors using direct measures of abdominal fat in adolescents has not been extensively researched. This study was designed to investigate the association between visceral and subcutaneous fat and cardiometabolic risk factors, in obese Korean adolescents. The study enrolled 175 adolescents (72 boys, 103 girls), from ages nine to 19 years, who were referred to the Obesity Clinic of Asan Medical Center. Body mass index (BMI) and waist circumference (WC) were measured for each study participant. Visceral adipose tissue (VAT) and subcutaneous adipose tissue (SAT) areas were calculated by computed tomography. Blood pressure, fasting plasma glucose, total cholesterol, triglycerides, HDL cholesterol, insulin and homeostasis model assessment (HOMA) score were measured. Systolic blood pressure, HDL cholesterol, fasting insulin and the HOMA score were significantly correlated with BMI, WC, VAT and SAT. In addition, VAT was significantly correlated with diastolic blood pressure and triglyceride levels. On multiple regression analysis, VAT was independently correlated with blood pressure, triglycerides, HDL cholesterol, fasting insulin and the HOMA score, while SAT was independently correlated with systolic blood pressure, fasting insulin and the HOMA score. This study determined that cardiovascular risk factors are closely associated with VAT, while insulin resistance is closely associated with both VAT and SAT among obese Korean adolescents.     

Ligands for peroxisome proliferator-activated receptorγ and retinoic acid receptor inhibit growth and induce apoptosis of human breast cancer cells in vitro and in BNX mice

Induction of differentiation and apoptosis in cancer cells through ligands of nuclear hormone receptors (NHRs) is a novel and promising approach to cancer therapy. All-trans-retinoic acid (ATRA), an RA receptor-specific NHR ligand, is now used for selective cancers. The NHR, peroxisome proliferator-activated receptor γ (PPARγ) is expressed in breast cancer cells. Activation of PPARγ through a synthetic ligand, troglitazone (TGZ), and other PPARγ-activators cause inhibition of proliferation and lipid accumulation in cultured breast cancer cells. TGZ (10⁻⁵ M, 4 days) reversibly inhibits clonal growth of MCF7 breast cancer cells and the combination of TGZ (10⁻⁵ M) and ATRA (10⁻⁶ M, 4 days) synergistically and irreversibly inhibits growth and induces apoptosis of MCF7 cells, associated with a dramatic decrease of their bcl-2 protein levels. Similar effects are noted with in vitro cultured breast cancer tissues from patients, but not with normal breast epithelial cells. The observed apoptosis mediated by TGZ and ATRA may be related to the striking down-regulation of bcl-2, because forced over-expression of bcl-2 in MCF7 cells cultured with TGZ and ATRA blocks their cell death. TGZ significantly inhibits MCF7 tumor growth in triple immunodeficient mice. Combined administration of TGZ and ATRA causes prominent apoptosis and fibrosis of these tumors without toxic effects on the mice. Taken together, this combination may provide a novel, nontoxic and selective therapy for human breast cancers.     

Valorization of papaya fruit waste through low-cost fractionation and microbial conversion of both juice and seed lipids

Papaya (Carica papaya) is widely cultivated in many tropical regions of the world. With an estimated 30–50% cull rate, there is a large amount of off-grade papaya produced. Here, we report very low-cost processing of culled papaya fruit waste, without needing any complex mechanized operations, to yield several products, including seed oil, sugar-rich puree, detoxified/defatted seed meal, and crude myrosinase and glucosinolates with antimicrobial and biofumigation applications. We then demonstrated that both puree and seed oil can serve as effective carbon substrates for cultivation of the oleaginous yeast Yarrowia lipolytica to produce single-cell proteins and high-value recombinant protein products. To use papaya seed oil for culturing Y. lipolytica, the concentration of the inhibitory substance benzyl isothiocyanate (BITC) in the oil needs to be minimized. If the culled fruits (and hence seeds) were stored frozen prior to drying, a very high level (>30 mM) of BITC was detected in the oil extracted from the dried seeds. However, if the seeds were not frozen prior to drying, oil from dried papaya seeds contained almost no BITC, and could support vigorous growth of Y. lipolytica, with efficient production of a functional nanobody fusion protein at a level similar to that achieved using olive oil. By using both juice and seed lipid, rather than juice alone, Y. lipolytica biomass produced per unit papaya more than doubled. As Y. lipolytica is amenable to genetic manipulation, and is known as a proficient cell factory with many industrial applications, the papaya waste valorization technology could potentially be extended to produce additional useful products such as biofuel and oleochemicals from Y. lipolytica.

Seed oil from papaya waste was validated as a novel carbon substrate for Yarrowia lipolytica to produce high-value products.     

Effect of Sulfonylureas Administered Centrally on the Blood Glucose Level in Immobilization Stress Model

Sulfonylureas are widely used as an antidiabetic drug. In the present study, the effects of sulfonylurea administered supraspinally on immobilization stress-induced blood glucose level were studied in ICR mice. Mice were once enforced into immobilization stress for 30 min and returned to the cage. The blood glucose level was measured 30, 60, and 120 min after immobilization stress initiation. We found that intracerebroventricular (i.c.v.) injection with 30 µg of glyburide, glipizide, glimepiride or tolazamide attenuated the increased blood glucose level induced by immobilization stress. Immobilization stress causes an elevation of the blood corticosterone and insulin levels. Sulfonylureas pretreated i.c.v. caused a further elevation of the blood corticosterone level when mice were forced into the stress. In addition, sulfonylureas pretreated i.c.v. alone caused an elevation of the plasma insulin level. Furthermore, immobilization stress-induced insulin level was reduced by i.c.v. pretreated sulfonylureas. Our results suggest that lowering effect of sulfonylureas administered supraspinally against immobilization stress-induced increase of the blood glucose level appears to be primarily mediated via elevation of the plasma insulin level.     

Murrayafoline A Induces a G0/G1-Phase Arrest in Platelet-Derived Growth Factor-Stimulated Vascular Smooth Muscle Cells

The increased potential for vascular smooth muscle cell (VSMC) growth is a key abnormality in the development of atherosclerosis and post-angioplasty restenosis. Abnormally high activity of platelet-derived growth factor (PDGF) is believed to play a central role in the etiology of these pathophysiological situations. Here, we investigated the anti-proliferative effects and possible mechanism(s) of murrayafoline A, a carbazole alkaloid isolated from Glycosmis stenocarpa Guillamin (Rutaceae), on PDGF-BB-stimulated VSMCs. Murrayafoline A inhibited the PDGF-BB-stimulated proliferation of VSMCs in a concentration-dependent manner, as measured using a non-radioactive colorimetric WST-1 assay and direct cell counting. Furthermore, murrayafoline A suppressed the PDGF-BB-stimulated progression through G₀/G₁ to S phase of the cell cycle, as measured by [³H]-thymidine incorporation assay and cell cycle progression analysis. This anti-proliferative action of murrayafoline A, arresting cell cycle progression at G₀/G₁ phase in PDGF-BB-stimulated VSMCs, was mediated via down-regulation of the expression of cyclin D1, cyclin E, cyclin-dependent kinase (CDK)2, CDK4, and proliferating cell nuclear antigen (PCNA), and the phosphorylation of retinoblastoma protein (pRb). These results indicate that murrayafoline A may be useful in preventing the progression of vascular complications such as restenosis after percutaneous transluminal coronary angioplasty and atherosclerosis.