"Leaching or not leaching": an alternative approach to antimicrobial materials via copolymers containing crown ethers as active groups.

In this work, new copolymers containing either MMA and 18C6 crown-ether pendants, or PEG, MMA and 18C6 crown-ether pendants were synthesized to test the idea that sequestering structural alkali-earth ions from the bacterial outer membrane (OM) may lead to bacterial death. The copolymers were obtained either via uncontrolled radical polymerization or ATRP; the latter approached allowed us to produce not only linear copolymers but also branched Y-like structures. After checking for the capability of complexing magnesium and calcium ions, the antimicrobial activity of all copolymers was tested placing their casted plaques in contact with pure water E. coli suspensions. All plaques adsorbed alkali-earth ions and killed bacteria, albeit with different antimicrobial efficiencies. Differences in the latter characteristic were attributed to different plaque roughness. The role of the 18C6 crown-ether pendants was elucidated by pre-saturating plaques with Mg/Ca ions, the marked reduction in antimicrobial efficiency indicating that losing the latter from OM due to surface complexation does play an important role in killing bacteria at short (<5 h) contact times. At longer times, the mode of action is instead related to the poly-cationic nature acquired by the plaques due to ion sequestering.

Study of the antibacterial activity in the gas phase of a chemical formulation for household waste management.

UNLABELLED: The aim of this study was to formulate a product (microbicide mixture) that could slow down the bacterial proliferation during the storage of household waste. We used harmless and natural components, known for their antimicrobial properties, in the liquid phase at direct contact with the microbes. The antimicrobial activity of the microbicide mixture formulated was evaluated over a range of concentration in two types of tests, in the liquid and in the gas phase. Once the efficacy of antimicrobial agent in the liquid phase in direct contact with the microbe (Escherichia coli) was confirmed, we adopted a new approach to evaluate the effect of the vapour phase both on the microbes' growth and on its duration. Here, we show that the perfect combination that gives rise to an antimicrobial mixture useful to control microbial growth (Staphylococcus aureus, Escherichia coli, Debaryomyces hansenii or Penicillium citrinum) up to 4 weeks is the one between more volatile agents (2-propanol and limonene) and a less volatile agent (cinnamaldehyde). The pleasant smell as well as the synergic antibacterial and antifungal function of the natural components of this mixture makes it attractive in domestic waste management. SIGNIFICANCE AND IMPACT OF THE STUDY: The novelty of this work is two-fold: on the one hand, to test various antimicrobial components of different volatility in a single microbicide mixture, and on the other, to study antimicrobial activity in the gas phase, other than the liquid phase. While previous authors tested the components individually as antimicrobial agents in the liquid phase at direct contact with the microbes, we tested them altogether as a mixture both in the liquid and in gas phase. The aim of this study was to disinfect small environments, such as garbage containers, by favouring the diffusion of the vapour phase to avoid the growth of microbes. This study proposes a new approach in the management and storage of household waste by inhibiting bacterial proliferation in the garbage can.

Hyperoxia and nitric oxide reduce surfactant components (DSPC and surfactant proteins) and increase apoptosis in adult and fetal rat type II pneumocytes.

Nitric oxide (NO) alone or in conjunction with hyperoxia can have protective or detrimental effects on the lung. Our hypothesis was that hyperoxia in conjunction with NO would result in increased cellular dysfunction and apoptotic cell death in adult and fetal Type II pneumocytes (TIIP) in a dose-dependent manner. The TIIP were obtained from adult and 19-day fetal rat lungs. The TIIP were then exposed to 100, 200 and 500 micro M of the NO-donor, Glyco-SNAP-2, alone or in conjunction with 95% oxygen for 24 h. While low-dose NO exposure alone did not increase cytotoxicity, in conjunction with hyperoxia, there was a significant dose-dependent increase in apoptotic cell death of adult TIIP as well as fetal TIIP. Choline incorporation into disaturated phosphatidylcholine was markedly decreased in adult TIIP while the fetal TIIP had similar values as controls. However, the mRNAs of surfactant proteins A, B and C as well as iNOS were significantly reduced in fetal TIIP. Exogenous peroxynitrite also increased nitrotyrosine formation in fetal TIIP as did hyperoxia and NO. The effect of hyperoxia and NO could be abrogated with catalase and superoxide dismutase. These findings may have significant clinical implications in the use of NO in premature infants.

Activation and mitochondrial translocation of protein kinase Cdelta are necessary for insulin stimulation of pyruvate dehydrogenase complex activity in muscle and liver cells.

In L6 skeletal muscle cells and immortalized hepatocytes, insulin induced a 2-fold increase in the activity of the pyruvate dehydrogenase (PDH) complex. This effect was almost completely blocked by the protein kinase C (PKC) delta inhibitor Rottlerin and by PKCdelta antisense oligonucleotides. At variance, overexpression of wild-type PKCdelta or of an active PKCdelta mutant induced PDH complex activity in both L6 and liver cells. Insulin stimulation of the activity of the PDH complex was accompanied by a 2.5-fold increase in PDH phosphatases 1 and 2 (PDP1/2) activity with no change in the activity of PDH kinase. PKCdelta antisense blocked insulin activation of PDP1/2, the same as with PDH. In insulin-exposed cells, PDP1/2 activation was paralleled by activation and mitochondrial translocation of PKCdelta, as revealed by cell subfractionation and confocal microscopy studies. The mitochondrial translocation of PKCdelta, like its activation, was prevented by Rottlerin. In extracts from insulin-stimulated cells, PKCdelta co-precipitated with PDP1/2. PKCdelta also bound to PDP1/2 in overlay blots, suggesting that direct PKCdelta-PDP interaction may occur in vivo as well. In intact cells, insulin exposure determined PDP1/2 phosphorylation, which was specifically prevented by PKCdelta antisense. PKCdelta also phosphorylated PDP in vitro, followed by PDP1/2 activation. Thus, in muscle and liver cells, insulin causes activation and mitochondrial translocation of PKCdelta, accompanied by PDP phosphorylation and activation. These events are necessary for insulin activation of the PDH complex in these cells.

Insulin receptor substrate-2 phosphorylation is necessary for protein kinase C zeta activation by insulin in L6hIR cells.

We have investigated glycogen synthase (GS) activation in L6hIR cells expressing a peptide corresponding to the kinase regulatory loop binding domain of insulin receptor substrate-2 (IRS-2) (KRLB). In several clones of these cells (B2, F4), insulin-dependent binding of the KRLB to insulin receptors was accompanied by a block of IRS-2, but not IRS-1, phosphorylation, and insulin receptor binding. GS activation by insulin was also inhibited by >70% in these cells (p < 0.001). The impairment of GS activation was paralleled by a similarly sized inhibition of glycogen synthase kinase 3 alpha (GSK3 alpha) and GSK3 beta inactivation by insulin with no change in protein phosphatase 1 activity. PDK1 (a phosphatidylinositol trisphosphate-dependent kinase) and Akt/protein kinase B (PKB) activation by insulin showed no difference in B2, F4, and in control L6hIR cells. At variance, insulin did not activate PKC zeta in B2 and F4 cells. In L6hIR, inhibition of PKC zeta activity by either a PKC zeta antisense or a dominant negative mutant also reduced by 75% insulin inactivation of GSK3 alpha and -beta (p < 0.001) and insulin stimulation of GS (p < 0.002), similar to Akt/PKB inhibition. In L6hIR, insulin induced protein kinase C zeta (PKC zeta) co-precipitation with GSK3 alpha and beta. PKC zeta also phosphorylated GSK3 alpha and -beta. Alone, these events did not significantly affect GSK3 alpha and -beta activities. Inhibition of PKC zeta activity, however, reduced Akt/PKB phosphorylation of the key serine sites on GSK3 alpha and -beta by >80% (p < 0.001) and prevented full GSK3 inactivation by insulin. Thus, IRS-2, not IRS-1, signals insulin activation of GS in the L6hIR skeletal muscle cells. In these cells, insulin inhibition of GSK3 alpha and -beta requires dual phosphorylation by both Akt/PKB and PKC zeta.

Protein kinase C (PKC)-alpha activation inhibits PKC-zeta and mediates the action of PED/PEA-15 on glucose transport in the L6 skeletal muscle cells.

Overexpression of the PED/PEA-15 protein in muscle and adipose cells increases glucose transport and impairs further insulin induction. Like glucose transport, protein kinase C (PKC)-alpha and -beta are also constitutively activated and are not further stimulatable by insulin in L6 skeletal muscle cells overexpressing PED (L6(PED)). PKC-zeta features no basal change but completely loses insulin sensitivity in L6(PED). In these cells, blockage of PKC-alpha and -beta additively returns 2-deoxy-D-glucose (2-DG) uptake to the levels of cells expressing only endogenous PED (L6(WT)). Blockage of PKC-alpha and -beta also restores insulin activation of PKC-zeta in L6(PED) cells, with that of PKC-alpha sixfold more effective than PKC-beta. Similar effects on 2-DG uptake and PKC-zeta were also achieved by 50-fold overexpression of PKC-zeta in L6(PED). In L6(WT), fivefold overexpression of PKC-alpha or -beta increases basal 2-DG uptake and impairs further insulin induction with no effect on insulin receptor or insulin receptor substrate phosphorylation. In these cells, overexpression of PKC-alpha blocks insulin induction of PKC-zeta activity. PKC-beta is 10-fold less effective than PKC-alpha in inhibiting PKC-zeta stimulation. Expression of the dominant-negative K(281)-->W PKC-zeta mutant simultaneously inhibits insulin activation of PKC-zeta and 2-DG uptake in the L6(WT) cells. We conclude that activation of classic PKCs, mainly PKC-alpha, inhibits PKC-zeta and may mediate the action of PED on glucose uptake in L6 skeletal muscle cells.

Insulin-activated protein kinase Cbeta bypasses Ras and stimulates mitogen-activated protein kinase activity and cell proliferation in muscle cells.

In L6 muscle cells expressing wild-type human insulin receptors (L6hIR), insulin induced protein kinase Calpha (PKCalpha) and beta activities. The expression of kinase-deficient IR mutants abolished insulin stimulation of these PKC isoforms, indicating that receptor kinase is necessary for PKC activation by insulin. In L6hIR cells, inhibition of insulin receptor substrate 1 (IRS-1) expression caused a 90% decrease in insulin-induced PKCalpha and -beta activation and blocked insulin stimulation of mitogen-activated protein kinase (MAPK) and DNA synthesis. Blocking PKCbeta with either antisense oligonucleotide or the specific inhibitor LY379196 decreased the effects of insulin on MAPK activity and DNA synthesis by >80% but did not affect epidermal growth factor (EGF)- and serum-stimulated mitogenesis. In contrast, blocking c-Ras with lovastatin or the use of the L61,S186 dominant negative Ras mutant inhibited insulin-stimulated MAPK activity and DNA synthesis by only about 30% but completely blocked the effect of EGF. PKCbeta block did not affect Ras activity but almost completely inhibited insulin-induced Raf kinase activation and coprecipitation with PKCbeta. Finally, blocking PKCalpha expression by antisense oligonucleotide constitutively increased MAPK activity and DNA synthesis, with little effect on their insulin sensitivity. We make the following conclusions. (i) The tyrosine kinase activity of the IR is necessary for insulin activation of PKCalpha and -beta. (ii) IRS-1 phosphorylation is necessary for insulin activation of these PKCs in the L6 cells. (iii) In these cells, PKCbeta plays a unique Ras-independent role in mediating insulin but not EGF or other growth factor mitogenic signals.

Insulin-stimulated cardiac glucose uptake is impaired in spontaneously hypertensive rats: role of early steps of insulin signalling.

OBJECTIVE: Although the heart is one of the target organs of insulin, it is still unknown whether the effect of insulin on cardiac muscle is preserved in essential hypertension, where insulin resistance has been observed in skeletal muscle. METHODS: We evaluated cardiac glucose uptake and the early steps of insulin signalling in spontaneously hypertensive (SHR, 10-12 weeks old) and in age-matched normotensive Wistar-Kyoto (WKY) rats. Cardiac glucose uptake (micromol/100 g per min) was assessed by 2-[14C]deoxyglucose method. After an overnight fast, 16 WKY rats and 17 SHR underwent a hyperinsulinemic euglycemic clamp. In particular, 2-h intravenous (i.v.) infusion of insulin (10 mU/kg per min) or saline (NaCl 0.9%) was administered, followed by an i.v. bolus injection of 2-[14C]deoxyglucose (100 microCi/kg) to measure cardiac glucose uptake. RESULTS: During saline infusion, cardiac glucose uptake was significantly higher in SHR compared to WKY rats (85 +/- 18 versus 8 +/- 3 mg/kg per min, P < 0.01). Furthermore, insulin was able to markedly increase cardiac glucose uptake in WKY rats whereas this insulin action was entirely abolished in SHR; thus, the cardiac glucose uptake became similar in the two rat strains (76 +/- 16 versus 82 +/- 16 mg/kg per min, not significant). More importantly, during saline infusion SHR showed a significantly higher phosphorylation of insulin receptor substance-1 (IRS-1) coupled to enhanced association of the p85 subunit of phosphatidylinositol 3-kinase (PI 3-kinase) to IRS-1 and to an increased PI 3-kinase activity compared to WKY rats. As expected, insulin exposure evoked an activation of its signalling cascade in WKY rats. In contrast, in SHR, the hormone failed to activate post-receptor molecular events. CONCLUSIONS: Our data indicate that the heart of SHR shows an overactivity of the proximal steps of insulin signalling which cannot be further increased by the exposure to the hormone. This abnormality may account for the marked increase of basal cardiac glucose uptake and the loss of insulin-stimulated glucose uptake observed in SHR.

PED/PEA-15: an anti-apoptotic molecule that regulates FAS/TNFR1-induced apoptosis.

PED/PEA-15 is a recently cloned 15 kDa protein possessing a death effector domain (DED). In MCF-7 and HeLa cells, a fivefold overexpression of PED/PEA-15 blocked FasL and TNFalpha apoptotic effects. This effect of PED overexpression was blocked by inhibition of PKC activity. In MCF-7 and HeLa cell lysates, PED/PEA-15 co-precipitated with both FADD and FLICE. PED/PEA-15-FLICE association was inhibited by overexpression of the wild-type but not of a DED-deletion mutant of FADD. Simultaneous overexpression of PED/PEA-15 with FADD and FLICE inhibited FADD-FLICE co-precipitation by threefold. Based on cleavage of the FLICE substrate PARP, this inhibitory effect was paralleled by a threefold decline in FLICE activation in response to TNF-alpha. TNFalpha, in turn, reduces PED association with the endogenous FADD and FLICE of the cells. Thus, PED/PEA-15 is an endogenous protein inhibiting FAS and TNFR1-mediated apoptosis. At least in part, this function may involve displacement of FADD-FLICE binding through the death effector domain of PED/PEA-15.

PED/PEA-15 gene controls glucose transport and is overexpressed in type 2 diabetes mellitus.

We have used differential display to identify genes whose expression is altered in type 2 diabetes thus contributing to its pathogenesis. One mRNA is overexpressed in fibroblasts from type 2 diabetics compared with non-diabetic individuals, as well as in skeletal muscle and adipose tissues, two major sites of insulin resistance in type 2 diabetes. The levels of the protein encoded by this mRNA are also elevated in type 2 diabetic tissues; thus, we named it PED for phosphoprotein enriched in diabetes. PED cloning shows that it encodes a 15 kDa phosphoprotein identical to the protein kinase C (PKC) substrate PEA-15. The PED gene maps on human chromosome 1q21-22. Transfection of PED/PEA-15 in differentiating L6 skeletal muscle cells increases the content of Glut1 transporters on the plasma membrane and inhibits insulin-stimulated glucose transport and cell-surface recruitment of Glut4, the major insulin-sensitive glucose transporter. These effects of PED overexpression are reversed by blocking PKC activity. Overexpression of the PED/PEA-15 gene may contribute to insulin resistance in glucose uptake in type 2 diabetes.

In NIH-3T3 fibroblasts, insulin receptor interaction with specific protein kinase C isoforms controls receptor intracellular routing.

Insulin increased protein kinase C (PKC) activity by 2-fold in both membrane preparations and insulin receptor (IR) antibody precipitates from NIH-3T3 cells expressing human IRs (3T3hIR). PKC-alpha, -delta, and -zeta were barely detectable in IR antibody precipitates of unstimulated cells, while increasing by 7-, 3.5-, and 3-fold, respectively, after insulin addition. Preexposure of 3T3hIR cells to staurosporine reduced insulin-induced receptor coprecipitation with PKC-alpha, -delta, and -zeta by 3-, 4-, and 10-fold, respectively, accompanied by a 1.5-fold decrease in insulin degradation and a similar increase in insulin retroendocytosis. Selective depletion of cellular PKC-alpha and -delta, by 24 h of 12-O-tetradecanoylphorbol-13-acetate (TPA) exposure, reduced insulin degradation by 3-fold and similarly increased insulin retroendocytosis, with no change in PKC-zeta. In lysates of NIH-3T3 cells expressing the R1152Q/K1153A IRs (3T3Mut), insulin-induced coprecipitation of PKC-alpha, -delta, and -zeta with the IR was reduced by 10-, 7-, and 3-fold, respectively. Similar to the 3T3hIR cells chronically exposed to TPA, untreated 3T3Mut featured a 3-fold decrease in insulin degradation, with a 3-fold increase in intact insulin retroendocytosis. Thus, in NIH-3T3 cells, insulin elicits receptor interaction with multiple PKC isoforms. Interaction of PKC-alpha and/or -delta with the IR appears to control its intracellular routing.