Amended safety assessment of sodium picramate and picramic acid.

Sodium picramate is the sodium salt of picramic acid, a substituted phenolic compound. Sodium picramate and picramic acid function as hair colorants; they are reportedly used in 31 and 3 hair-dye products, respectively. No concentration-of-use data were available for sodium picramate, but picramic acid was reported to be used at 0.6%. The Cosmetic Ingredient Review Expert Panel recognized that adding picramic acid to a hair-dye formulation likely results in formation of a salt such as sodium picramate, which suggested that safety test data for one ingredient would be applicable to the other. Hair dyes containing these ingredients bear a caution statement and patch test instructions for determining whether the product causes skin irritation. The panel finds that the available data support the safety of these colorants in hair dyes and expects that sodium picramate would be used at concentrations comparable to those reported for picramic acid.

Neuroprotective effects of 2,4-dinitrophenol in an acute model of Parkinson's disease.

Neurons depend on mitochondria for homeostasis and survival, and thus, mitochondrial dysfunction has been implicated in neurodegenerative diseases, including Parkinson's disease (PD). Increasing evidence indicates the mitochondrial uncoupler, 2,4-dinitrophenol (DNP), protects neurons against neurodegeneration and enhances neural plasticity. Here, the authors evaluated the protective effects of intraperitoneally (i.p.) administered low dose DNP in an acute mouse model of PD. Mice were administered DNP (1 or 5mg/kg) for 12 consecutive days, and then on day 13, MPTP (20mg/kg, i.p.) was administered four times (with 2h intervals between injections) to induce PD. It was found that MPTP-induced motor dysfunction was ameliorated in the DNP-treated mice versus vehicle-treated controls. Additionally, DNP effectively attenuated dopaminergic neuronal loss observed in MPTP treated mice. Moreover, in primary cultured neurons, DNP at 10µM, but not at 100µM, prevented MPP+-induced cell death and mitochondrial membrane potential (MMP) reduction. In addition, DNP was observed to cause the nuclear translocation of Nrf2 in primary neurons. Taken together, these findings of the present study suggest that DNP protects dopaminergic neurons against neurodegeneration and maintains MMP integrity in PD by activating adaptive stress responses.

Absorption mechanism of three curcumin constituents through in situ intestinal perfusion method.

This study aimed to investigate the absorption mechanism of three curcumin constituents in rat small intestines. Self-emulsification was used to solubilize the three curcumin constituents, and the rat in situ intestinal perfusion method was used to study factors on drug absorption, including drug mass concentration, absorption site, and the different types and concentrations of absorption inhibitors. Within the scope of experimental concentrations, three curcumin constituents were absorbed in rat small intestines through the active transport mechanism.

Persistent reduced oxygen requirement following blood transfusion during recovery from hemorrhagic shock.

Our study intended to determine the effects on oxygen uptake (VO2) of restoring a normal rate of O2 delivery following blood transfusion (BT) after a severe hemorrhage (H). Spontaneously breathing urethane anesthetized rats were bled by removing 20 ml/kg of blood over 30 min. Rats were then infused with their own shed blood 15 min after the end of H. At mid-perfusion, half of the rats received a unique infusion of the decoupling agent 2,4-dinitrophenol (DNP, 6 mg/kg). VO2 and arterial blood pressure (ABP) were continuously measured throughout the study, along with serial determination of blood lactate concentration [La]. Animals were euthanized 45 min after the end of reperfusion; liver and lungs were further analyzed for early expression of oxidative stress gene using RT-PCR. Our bleeding protocol induced a significant decrease in ABP and increase in [La], while VO2 dropped by half. The O2 deficit progressively accumulated during the period of bleeding reached -114 ± 53 ml/kg, just before blood transfusion. Despite the transfusion of blood, a significant O2 deficit persisted (-82 ± 59 ml/kg) 45 min after reperfusion. This slow recovery of VO2 was sped up by DNP injection, leading to a fast recovery of O2 deficit after reperfusion, becoming positive (+460 ± 132 ml/kg) by the end of the protocol, supporting the view that O2 supply is not the main controller of VO2 dynamics after BT. Of note is that DNP also enhanced oxidative stress gene expression (up-regulation of NADPH oxidase 4 in the lung for instance). The mechanism of slow recovery of O2 requirement/demand following BT and the resulting effects on tissues exposed to relatively high O2 partial pressure are discussed.

Biosorption of nitrophenols on anaerobic granular sludge.

The sorption and desorption of 2-nitrophenol (2-NP), 4-nitrophenol (4-NP) and 2,4-dinitrophenol (2,4-DNP) on live anaerobic granular sludge was studied at five different sorbate (nitrophenols) concentrations between 10 x 10(3) - 90 x 10(3) microg l(-1). Experiments were conducted at room temperature (29 +/- 2 degrees C) and at an initial pH of 7.5. The maximum uptake capacity of live anaerobic granular sludge was found to b e 1,427, 1,511 and 1,865 microg g(-1) VSS for 2-NP, 4-NP and 2,4-DNP, respectively. The equilibrium data of three nitrophenols obeyed both Freundlich and linear isotherm models. Sorption was observed to be partially reversible. About 20-89%, 36-90% and 29-80% desorption was observed for 10 x 10(3) - 90 x 10(3) microg l(-1) sorbate concentrations of 2-NP, 4-NP and 2,4-DNP, respectively.

Absorption mechanism of three curcumin constituents through in situ intestinal perfusion method

This study aimed to investigate the absorption mechanism of three curcumin constituents in rat small intestines. Self-emulsification was used to solubilize the three curcumin constituents, and the rat in situ intestinal perfusion method was used to study factors on drug absorption, including drug mass concentration, absorption site, and the different types and concentrations of absorption inhibitors. Within the scope of experimental concentrations, three curcumin constituents were absorbed in rat small intestines through the active transport mechanism.

Immobilized pH gradient gel cell to study the pH dependence of drug lipophilicity.

An experimental setup to study the pH dependence of standard ion-transfer potentials at the water/NPOE interface is presented. The system is composed of a microhole generated by laser photoablation in a 12-microm polyethylene terephthalate film, the aqueous phase consisting of a commercial immobilized pH gradient gel reswelled in electrolyte solution and a droplet of organic solution. Two electrodes are used, an Ag/AgCl aqueous electrode and an Ag/AgTPBCl organic electrode. This setup is applied to the study of two ionizable compounds (pyridine, 2,4-dinitrophenol). Thermodynamic parameters such as the standard transfer potential, the Gibbs energy of transfer, and the partition coefficients of the ionized forms as well as the neutral forms of these drug compounds are evaluated by differential pulse voltammetry. The data obtained are summarized in ionic partition diagrams, which are a useful tool for predicting and interpreting the transfer behavior of ionized drugs at the liquid/liquid interfaces mimicking the biological membranes.

Regulation and characterization of two nitroreductase genes, nprA and nprB, of Rhodobacter capsulatus.

Among photosynthetic bacteria, strains B10 and E1F1 of Rhodobacter capsulatus photoreduce 2,4-dinitrophenol (DNP), which is stoichiometrically converted into 2-amino-4-nitrophenol by a nitroreductase activity. The reduction of DNP is inhibited in vivo by ammonium, which probably acts at the level of the DNP transport system and/or physiological electron transport to the nitroreductase, since this enzyme is not inhibited by ammonium in vitro. Using the complete genome sequence data for strain SB1003 of R. capsulatus, two putative genes coding for possible nitroreductases were isolated from R. capsulatus B10 and disrupted. The phenotypes of these mutant strains revealed that both genes are involved in the reduction of DNP and code for two major nitroreductases, NprA and NprB. Both enzymes use NAD(P)H as the main physiological electron donor. The nitroreductase NprA is under ammonium control, whereas the nitroreductase NprB is not. In addition, the expression of the nprB gene seems to be constitutive, whereas nprA gene expression is inducible by a wide range of nitroaromatic and heterocyclic compounds, including several dinitroaromatics, nitrofuran derivatives, CB1954, 2-aminofluorene, benzo[a]pyrene, salicylic acid, and paraquat. The identification of two putative mar/sox boxes in the possible promoter region of the nprA gene and the induction of nprA gene expression by salicylic acid and 2,4-dinitrophenol suggest a role in the control of the nprA gene for the two-component MarRA regulatory system, which in Escherichia coli controls the response to some antibiotics and environmental contaminants. In addition, upregulation of the nprA gene by paraquat indicates that this gene is probably a member of the SoxRS regulon, which is involved in the response to stress conditions in other bacteria.

Detoxication mechanism of exogenous monatomic phenols in pea seedlings.

The conversion of exogenous monatomic phenols (O-[1-(14)C]nitrophenol, 2,4-[1-14C]dinitrophenol, and alpha-[1-14C]naphthol) in pea seedlings has been investigated. It has been found that in the pea seedlings glycosylation of these phenols does not occur, but the main pathway of their detoxication is conjugation with the low-molecular-weight peptides. Approximately 80% of phenols absorbed by seedlings form phenol-peptide conjugates. The part of exogenous monatomic phenols is irreversibly bound to proteins via quinone-protein interaction. The amino acid content of the peptides involved in the conjugation process has been established. Penetration into the plant of monatomic exogenous phenols with a high dissociation constant leads to the stimulation of peptide formation.

Energization of Comamonas testosteroni ATCC 17454 for indicating toxic effects of chlorophenoxy herbicides.

The toxicity of chlorophenoxy herbicides to a bacterium, strongly related to the well-known species Delftia (formerly Comamonas) acidovorans that are able to detoxify these xenobiotics, was investigated. The oxidation of n-hexanol via alcohol dehydrogenases, coupled with the generation of ATP by electron transport phosphorylation (ETP), was used as an indicator for energy-toxic effects on the growth of Comamonas testosteroni ATCC 17454. Uncoupling--reductions in ATP synthesis accompanied by increased respiration--was found to be induced by 1 mM of the classic uncoupler 2,4-dinitrophenol (2,4-DNP) at pH 7.0 and 8.0. At pH 5.4 and 6.0, the ATP synthesis and respiration were strongly inhibited by both 2,4-DNP and the chlorophenoxy herbicides tested. In contrast, 5 mM of 2,4-dichlorophenoxyacetic acid (2,4-D) and of 2-(2,4-dichlorophenoxy)-propanoic acid (2,4-DCPP) were required for detectable uncoupling effects--reduction of the P/O ratios by about 30%--at pH 7.0. These chemicals may have less uncoupling power because the concentration of their protonated (undissociated) forms (pKa values 2.7 and 3.0) is an order of magnitude lower than that of 2,4-DNP (pKa = 4.0) at this pH value. Strong uncoupling accompanied by increased respiration, like that induced by 1 mM 2,4-DNP, was also caused by 5 mM 4-(2,4-dichlorophenoxy)-butyric acid (2,4-DCPB), which correlates with its high pKa value of 4.6. The order of toxicity of the chlorophenoxy herbicides (2,4-D < 2,4-DCPP < 2,4-DCPB) to the ETP, which correlates well with the lipophilicity of their undissociated forms (log P 2.7 < 3.4 < 3.5, respectively), was confirmed by measuring their capacity to inhibit the growth of Comamonas testosteroni ATCC 17454. The results show that energization via alcohol dehydrogenases can be used as an indicator for investigating energy-toxic effects of organics on the ETP and growth of chlorophenoxy herbicide-detoxifying bacteria.

Characterization of phosphofructokinase II and regulation of fructose 2,6-bisphosphate levels in Trichoderma reesei.

Phosphofructokinase II (PEK II) from Trichoderma reesei was partially purified (247-fold). The calculated Km values for fructose 6-phosphate and ATP were 0.7 mM and 40 microM, respectively. Upon incubation in the presence of [gamma-32P]ATP, the enzyme formed a radioactive phosphoprotein with molecular mass of 67 kDa in autoradiography analysis after SDS-PAGE. Upon incubation in the presence of ATP-Mg and the catalytic subunit of cAMP-dependent protein kinase, its activity was not modified. The same result was obtained when a cell-free extract of T. reesei was incubated with ATP-Mg and cAMP. 2,4-Dinitrophenol caused a transient rise in cAMP levels in the fungal cell. The results provide evidence that the fructose 2,6-bisphosphate level in T. reesei is independent of cAMP concentrations and not related to a cAMP-dependent mechanism, but to the availability of substrate fructose 6-phosphate.