Dietary iron restriction increases plaque stability in apolipoprotein-E-deficient mice

Accumulative evidence has supported the role of iron in the development of atherosclerosis. To test whether iron-mediated oxidative stress influences plaque stability, apoliporotein-E (ApoE)-deficient mice (3 months old) were placed on a chow diet or a low-iron diet for 3 months, and the abundance of interstitial collagen and the expression of the matrix degradation-associated enzyme, matrix metalloproteinase-9 (MMP-9), in vascular lesions were assessed. A low-iron diet appeared to reduce iron deposition while substantially increasing collagen content of lesions in mice. Immunostaining demonstrated lower expression of MMP-9 in lesions of iron-restricted animals. Likewise, SDS-PAGE zymography revealed lower gelatinolytic activities in aortic tissues and sera of the same group of animals. When older ApoE-deficient mice (5 months old) received a low-iron diet for 2 months, development of the lesion area was not significantly affected. However, the lesional collagen content was much higher in the iron-restricted group of animals, and MMP-9 expression in aortic tissues from the same group of mice was significantly lower. Treatment of murine J774 macrophages with increasing concentrations of ferric ammonium citrate significantly enhanced the amount of MMP-9 secreted. Together, these data indicate that decreased vascular iron content following dietary iron restriction in ApoE-deficient mice leads to lower matrix degradation capacity and increased plaque stability.     

OxLDL induces mitogen-activated protein kinase activation mediated via PI3-kinase/Akt in vascular smooth muscle cells

Oxidized low-density lipoprotein (OxLDL) is a risk factor in atherosclerosis and stimulates multiple signaling pathways, including activation of phosphatidylinositol 3-kinase (PI3-K)/Akt and p42/p44 mitogen-activated protein kinase (MAPK), which are involved in mitogenesis of vascular smooth muscle cells (VSMCs). We therefore investigated the relationship between PI3-K/Akt and p42/p44 MAPK activation and cell proliferation induced by OxLDL. OxLDL stimulated Akt phosphorylation in a time- and concentration-dependent manner, as determined by Western blot analysis. Phosphorylation of Akt stimulated by OxLDL and epidermal growth factor (EGF) was attenuated by inhibitors of PI3-K (wortmannin and LY294002) and intracellular Ca2+ chelator (BAPTA/AM) plus EDTA. Pretreatment of VSMCs with pertussis toxin, cholera toxin, and forskolin for 24 h also attenuated the OxLDL-stimulated Akt phosphorylation. In addition, pretreatment of VSMCs with wortmannin or LY294002 inhibited OxLDL-stimulated p42/p44 MAPK phosphorylation and [3H]thymidine incorporation. Furthermore, treatment with U0126, an inhibitor of MAPK kinase (MEK)1/2, attenuated the p42/p44 MAPK phosphorylation, but had no effect on Akt activation in response to OxLDL and EGF. Overexpression of p85-DN or Akt-DN mutants attenuated MEK1/2 and p42/p44 MAPK phosphorylation stimulated by OxLDL and EGF. These results suggest that the mitogenic effect of OxLDL is, at least in part, mediated through activation of PI3-K/Akt/MEK/MAPK pathway in VSMCs.     

Tumour necrosis factor-alpha enhances bradykinin-induced signal transduction via activation of Ras/Raf/MEK/MAPK in canine tracheal smooth muscle cells

Inhalation of tumour necrosis factor-alpha (TNF-alpha) induced a bronchial hyperreactivity to contractile agonists. However, the mechanisms of TNF-alpha involved in the pathogenesis of bronchial hyperreactivity were not completely understood. Therefore, we investigated the effect of TNF-alpha on bradykinin (BK)-induced inositol phosphate (IP) accumulation and Ca(2+) mobilization, and up-regulation of BK receptor density in canine cultured tracheal smooth muscle cells (TSMCs). Pretreatment of TSMCs with TNF-alpha potentiated BK-induced IP accumulation and Ca(2+) mobilization. However, there was no effect on the IP response induced by endothelin-1 (ET-1), 5-hydroxytryptamine (5-HT), and carbachol. Pretreatment with PDGF B-chain homodimer (PDGF-BB) also enhanced BK-induced IP response. These enhancements induced by TNF-alpha and PDGF-BB might be due to an increase in BK B(2) receptor density (B(max)), since [3H]BK binding to TSMCs was inhibited by the B(2) selective agonist and antagonist, BK and Hoe 140, but not by the B(1) selective reagents. The enhancing effects of TNF-alpha and PDGF-BB were attenuated by PD98059 (an inhibitor of activation of MAPK kinase, MEK) and cycloheximide (an inhibitor of protein synthesis), suggesting that TNF-alpha may share a common signalling pathway with PDGF-BB via protein(s) synthesis in TSMCs. Furthermore, overexpression of dominant negative mutants, H-Ras-15A and Raf-N4, significantly suppressed p42/p44 mitogen-activated protein kinase (MAPK) activation induced by TNF-alpha and PDGF-BB and attenuated the effect of TNF-alpha on BK-induced IP response, indicating that Ras and Raf may be required for activation of these kinases. These results suggest that the augmentation of BK-induced responses produced by TNF-alpha might be, at least in part, mediated through activation of Ras/Raf/MEK/MAPK pathway in TSMCs.     

Germanium oxide inhibits the transition from G2 to M phase of CHO cells

We report here for the first time that germanium oxide (GeO(2)) blocks cell progression. GeO(2) is not genotoxic to Chinese hamster ovary (CHO) cells and has limited cytotoxicity. However, GeO(2) arrests cells at G2/M phase. The proportion of cells stopped at G2/M phase increased dose-dependently up to 5 mM GeO(2) when treated for 12 h, but decreased at GeO(2) concentration was greater than 5 mM. Analysis of 5-bromodeoxyuridine-labeled cells indicated that GeO(2) delayed S phase progression in a dose-dependent manner, and blocked cells at G2/M phase. Microscopic examination confirmed that GeO(2) treatment arrested cells at G2 phase. Similar to several other events that cause G2 block, the GeO(2)-induced G2 block can also be ameliorated by caffeine in a dose- and time-dependent manner. To explore the mechanism of G2 arrest by GeO(2), cyclin content and cyclin-dependent kinase activity were examined. Cyclin B1 level was not affected after GeO(2) treatment in CHO cells. However, GeO(2) decreased p34(cdc2) kinase (Cdk1) activity. The kinase activity recovered within 9 h after GeO(2) removal and correlated with the transition of G2/M-G1 phase of the cells. This result suggests that GeO(2) treatment reduces Cdk1 activity and causing the G2 arrest in CHO cells.     

Three-dimensional cytomorphology in fine needle aspiration biopsy of parathyroid lesions

OBJECTIVE: To elucidate three-dimensional (3-D) cytomorphology in fine needle aspiration biopsy (FNAB) of parathyroid lesions. STUDY DESIGN: Ultrasound-guided FNAB was performed on parathyroid lesions from 10 patients with hyperparathyroidism. The aspirates were stained and observed under a light microscope (LM). The aspirates were also fixed, dehydrated, critical point dried, spattered with gold ions and observed with a scanning electron microscope (SEM). Findings under SEM were correlated with the appearances under LM as well as with serum parathyroid hormone (PTH) concentrations. RESULTS: Under LM, nine cases displayed isokaryosis and one case, anisokaryosis. These appearances corresponded to isocytosis or anisocytosis under SEM. Under SEM, 3-D cytomorphology of parathyroid lesions displayed isocytotic, scattered cells in five cases, uniform cellular arrangements in four cases and anisocytotic, scattered cells in one case. The cell surface was rather smooth in five cases. The other five cases had significant granules on the cell surfaces; these all had serum PTH concentrations > or = 268 pg/mL. CONCLUSION: 3-D cytomorphology in FNAB of parathyroid lesions was a rather smooth cell surface in cases with low serum PTH and a granular cell surface in cases with significantly increased serum PTH. These characteristics and the absence of microvilli might be helpful in the differential diagnosis between parathyroid and follicular thyroid lesions.     

Synchrony: a neuronal mechanism for attentional selection?

Attentional selection involves brain processes that select and control the flow of information into the mechanisms that underlie perception and consciousness. One theory proposes that the neural activity that represents the stimuli or events to be attended to is selected through modification of its synchrony. Recent experimental evidence supports this theory, by showing that changes in attentional focus increase the synchrony of neural firing in some neuron pairs and decrease it in others.     

Strain improvement to enhance the production of recombinant penicillin acylase in high-cell-density Escherichia coli cultures

Using fed-batch operation for high-cell-density cultivation, efforts are frequently made for optimization of culture parameters, particularly feeding strategy. The current study also emphasized the importance of selecting strains for the production of recombinant proteins in high-cell-density cultures. With Escherichia coli penicillin acylase (PAC) as a target protein, the host/vector system of MDdeltaP7 harboring pTrcKnPAC2902 and pKS12 was designed for optimization of fed-batch cultivation for recombinant protein production. The host, MDdeltaP7, potentially had a high translational and periplasmic processing efficiency for pac expression. On the other hand, the vector, pTrcKnPAC2902, was genetically constructed for pac overexpression. Coexistence of the other vector, pKS12, significantly enhanced PAC production by improving cell physiology and reducing the amount of inclusion body formation upon pac overexpression. An extremely high volumetric PAC activity at 37,500 U/L was obtained with the use of the developed host/vector system under optimum fed-batch culture conditions.     

Efficient synthesis of 'redox-switched' naphthoquinone thiol-crown ethers and their biological activity evaluation

Series of naphthoquinone thiol-crown ethers had been prepared. The antibacterial, antifungal, and cytotoxic activities of these synthetic naphthoquinone thiol-crown ethers were investigated. All of the compounds tested displayed antibacterial, cytotoxic and antifungal activities. The bis-naphthoquinone thiol-crown ether 7a was the most potent inhibitor among tested analogues against Staphylococcus aureus methicillin resistance with MIC value of 2.68 microM.     

Characterization of bradykinin receptors in canine cultured corneal epithelial cells: Pharmacological and functional studies

The pharmacological properties of bradykinin (BK) receptors were characterized in canine cultured corneal epithelial cells (CECs) using [(3)H]-BK as a radioligand. Analysis of binding isotherms gave an apparent equilibrium dissociation constant of 0.34 +/- 0.07 nM and a maximum receptor density of 179 +/- 23 fmol/mg protein. Neither a B(1) receptor-selective agonist (des-Arg(9)-BK) nor antagonist ([Leu(8), des-Arg(9)]-BK) significantly inhibited [(3)H]-BK binding to CECs, thus excluding the presence of B(1) receptors in canine CECs. The specific binding of [(3)H]-BK to CECs was inhibited by B(2) receptor-selective agonists (BK and kallidin) and antagonists (Hoe 140 and [D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK), with a best fit using a one-binding-site model. The order of potency for the inhibition of [(3)H]-BK binding was BK = Hoe 140 > kallidin > [D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK. Stimulation of CECs by BK produced a concentration-dependent accumulation of inositol phosphates (IP) and an initial transient peak of intracellular Ca(2+). B(2) receptor-selective antagonist ([D-Arg(0), Hyp(3), Thi(5,8), D-Phe(7)]-BK) significantly antagonized the BK-induced responses with dissociation constants of 6.0-6.1. Pretreatment of CECs with pertussis toxin (PTX) or cholera toxin did not alter the BK-induced IP accumulation. Incubation of CECs in the absence of external Ca(2+) led to a significant attenuation of the IP accumulation induced by BK. These results demonstrate that BK directly stimulates phospholipase C-mediated signal transduction through BK B(2) receptors via a PTX-insensitive G protein in canine CECs. This effect may function as the transducing mechanism for BK-mediated cellular responses.