Selective PDE4B and PDE4D inhibitors produce distinct behavioral responses to ethanol and GABAergic drugs in mice

Apremilast is a phosphodiesterase (PDE) type 4 inhibitor that is nonselective at subtypes PDE4A-D. It modulates ethanol and GABAergic responses via protein kinase A (PKA) phosphorylation of specific GABA_A receptor subunits and has opposite effects on ethanol-induced ataxia in wild-type and GABA_A β3-S408/409A knock-in mice. We hypothesized that these different effects are due to preferential actions at different PDE4 subtypes. To test this hypothesis, we compared effects of selective PDE4 inhibitors on responses to ethanol and GABAergic drugs in male and female C57BL/6J mice. The PDE4B inhibitor A33 accelerated recovery from ataxia induced by ethanol and diazepam but did not alter ataxia induced by propofol. The PDE4D inhibitor D159687 accelerated recovery from diazepam-induced ataxia but prolonged recovery from ethanol- and propofol-induced ataxia. A33 shortened, while D159687 prolonged, the sedative-hypnotic effects of ethanol. Both drugs shortened diazepam's sedative-hypnotic effects. The modulatory effects of A33 and D159687 were completely prevented by the PKA inhibitor H89. Only D159687 prevented development of acute functional tolerance to ethanol-induced ataxia. D159687 transiently reduced two-bottle choice drinking in male and female mice that had consumed ethanol for 3 weeks and transiently reduced two-bottle choice, every-other-day drinking in male mice. A33 did not alter drinking in either procedure. Neither drug altered binge-like ethanol consumption or blood ethanol clearance. Thus, D159687 produced behavioral effects similar to apremilast, although it produced a more transient and smaller reduction in drinking. These results indicate that PDE4D inhibition contributes to apremilast's ability to reduce drinking, whereas PDE4B inhibition is not involved.

Apremilast-induced increases in acute ethanol intoxication and decreases in ethanol drinking in mice involve PKA phosphorylation of GABAA β3 subunits

We previously showed that apremilast, an FDA-approved PDE4 inhibitor, selectively alters behavioral responses to ethanol and certain GABAergic drugs in a PKA-dependent manner in C57BL6/J mice. Here, we investigated if PKA phosphorylation of β3 GABAA receptor subunits is involved in apremilast regulation of ethanol, propofol, or diazepam responses. Apremilast prolonged rotarod ataxia and loss of the righting reflex by ethanol and propofol in wild-type mice, but not in β3-S408A/S409A knock-in mice. In contrast, apremilast hastened recovery from the ataxic and sedative effects of diazepam in both genotypes. These findings suggest that apremilast modulation of ethanol and propofol behaviors in wild-type mice is mediated by β3 subunit phosphorylation, whereas its actions on diazepam responses involve a different mechanism. The PKA inhibitor H-89 prevented apremilast modulation of ethanol-induced ataxia. Apremilast sensitized wild-type males to ethanol-induced ataxia and decreased acute functional tolerance (AFT) in females but had no effect in β3-S408A/S409A mice of either sex. These results could not be attributed to genotype differences in blood ethanol clearance. There were also no baseline genotype differences in ethanol consumption and preference in two different voluntary drinking procedures. However, the ability of apremilast to reduce ethanol consumption was diminished in β3-S408A/S409A mice. Our results provide strong evidence that PKA-dependent phosphorylation of β3 GABAA receptor subunits is an important mechanism by which apremilast increases acute sensitivity to alcohol, decreases AFT, and decreases ethanol drinking.

Deletion of Tlr3 reduces acute tolerance to alcohol and alcohol consumption in the intermittent access procedure in male mice

Pharmacological studies implicate toll-like receptor 3 (TLR3) signaling in alcohol drinking. We examined the role of TLR3 in behavioral responses to alcohol and GABAergic drugs by studying Tlr3 ^-/- mice. Because of opposing signaling between TLR3 and MyD88 pathways, we also evaluated Myd88 ^-/- mice. Ethanol consumption and preference decreased in male but not in female Tlr3 ^-/- mice during two-bottle choice every-other-day (2BC-EOD) drinking. There were no genotype differences in either sex during continuous or limited-access drinking. Null mutations in Tlr3 or Myd88 did not alter conditioned taste aversion to alcohol and had small or no effects on conditioned place preference. The Tlr3 null mutation did not alter acute alcohol withdrawal. Male, but not female, Tlr3 ^-/- mice took longer than wild-type littermates to recover from ataxia by ethanol or diazepam and longer to recover from sedative-hypnotic effects of ethanol or gaboxadol, indicating regulation of GABAergic signaling by TLR3. Acute functional tolerance (AFT) to alcohol-induced ataxia was decreased in Tlr3 ^-/- mice but was increased in Myd88 ^-/- mice. Thus, MyD88 and TLR3 pathways coordinately regulate alcohol consumption and tolerance to intoxicating doses of alcohol and GABAergic drugs. Despite similar alcohol metabolism and similar amounts of total alcohol consumed during 2BC and 2BC-EOD procedures in C57BL/6J mice, only 2BC-EOD drinking induced tolerance to alcohol-induced ataxia. Ataxia recovery was inversely correlated with level of drinking in wild-type and Tlr3 ^-/- littermates. Thus, deleting Tlr3 reduces alcohol consumption by reducing AFT to alcohol and not by altering tolerance induced by 2BC-EOD drinking.

Mutation of the inhibitory ethanol site in GABAA ρ1 receptors promotes tolerance to ethanol-induced motor incoordination

Genes encoding the ρ1/2 subunits of GABA_A receptors have been associated with alcohol (ethanol) dependence in humans, and ρ1 was also shown to regulate some of the behavioral effects of ethanol in animal models. Ethanol inhibits GABA-mediated responses in wild-type (WT) ρ1, but not ρ1(T6'Y) mutant receptors expressed in Xenopus laevis oocytes, indicating the presence of an inhibitory site for ethanol in the second transmembrane helix. In this study, we found that ρ1(T6'Y) receptors expressed in oocytes display overall normal responses to GABA, the endogenous GABA modulator (zinc), and partial agonists (β-alanine and taurine). We generated ρ1 (T6'Y) knockin (KI) mice using CRISPR/Cas9 to test the behavioral importance of the inhibitory actions of ethanol on this receptor. Both ρ1 KI and knockout (KO) mice showed faster recovery from acute ethanol-induced motor incoordination compared to WT mice. Both KI and KO mutant strains also showed increased tolerance to motor impairment produced by ethanol. The KI mice did not differ from WT mice in other behavioral actions, including ethanol intake and preference, conditioned taste aversion to ethanol, and duration of ethanol-induced loss of righting reflex. WT and KI mice did not differ in levels of ρ1 or ρ2 mRNA in cerebellum or in ethanol clearance. Our findings indicate that the inhibitory site for ethanol in GABA_A ρ1 receptors regulates acute functional tolerance to moderate ethanol intoxication. We note that low sensitivity to alcohol intoxication has been linked to risk for development of alcohol dependence in humans.

Sedative and Motor Incoordination Effects of Ethanol in Mice Lacking CD14, TLR2, TLR4, or MyD88

BACKGROUND

In our companion article, we examined the role of MyD88-dependent signaling in ethanol (EtOH) consumption in mice lacking key components of this inflammatory pathway and observed differential effects on drinking. Here, we studied the role of these same signaling components in the acute sedative, intoxicating, and physiological effects of EtOH. Toll-like receptor 4 (TLR4) has been reported to strongly reduce the duration of EtOH-induced sedation, although most studies do not support its direct involvement in EtOH consumption. We examined TLR4 and other MyD88 pathway molecules to determine signaling specificity in acute EtOH-related behaviors. We also studied other GABAergic sedatives to gauge the EtOH specificity and potential role for GABA in EtOH's sedative and intoxicating effects in the mutant mice.

METHODS

Loss of righting reflex (LORR) and recovery from motor incoordination were studied following acute injection of EtOH or other sedative drugs in male and female control C57BL/6J mice versus mice lacking CD14, TLR2, TLR4 (C57BL/10ScN), or MyD88. We also examined EtOH-induced hypothermia and blood EtOH clearance in these mice.

RESULTS

Male and female mice lacking TLR4 or MyD88 showed reduced duration of EtOH-induced LORR and faster recovery from EtOH-induced motor incoordination in the rotarod test. MyD88 knockout mice had slightly faster recovery from EtOH-induced hypothermia compared to control mice. None of the mutants differed from control mice in the rate of blood EtOH clearance. All of the mutants showed similar decreases in the duration of gaboxadol-induced LORR, but only mice lacking TLR4 were less sensitive to the sedative effects of pentobarbital. Faster recovery from diazepam-induced motor impairment was observed in CD14, TLR4, and MyD88 null mice of both sexes.

CONCLUSIONS

TLR4 and MyD88 were key mediators of the sedative and intoxicating effects of EtOH and GABAergic sedatives, indicating a strong influence of TLR4-MyD88 signaling on GABAergic function. Despite the involvement of TLR4 in EtOH's acute behaviors, it did not regulate EtOH consumption in any drinking model as shown in our companion article. Collectively, our studies demonstrate differential effects of TLR-MyD88 components in the acute versus chronic actions of EtOH.

Ethanol Consumption in Mice Lacking CD14, TLR2, TLR4, or MyD88

BACKGROUND

Molecular and behavioral studies support a role for innate immune proinflammatory pathways in mediating the effects of alcohol. Increased levels of Toll-like receptors (TLRs) have been observed in animal models of alcohol consumption and in human alcoholics, and many of these TLRs signal via the MyD88-dependent pathway. We hypothesized that this pathway is involved in alcohol drinking and examined some of its key signaling components.

METHODS

Different ethanol (EtOH)-drinking paradigms were studied in male and female control C57BL/6J mice versus mice lacking CD14, TLR2, TLR4 (C57BL/10ScN), or MyD88. We studied continuous and intermittent access 2-bottle choice (2BC) and 1-bottle and 2BC drinking-in-the-dark (DID) tests as well as preference for saccharin, quinine, and NaCl.

RESULTS

In the 2BC continuous access test, EtOH intake decreased in male TLR2 knockout (KO) mice, and we previously reported reduced 2BC drinking in male and female CD14 KO mice. In the intermittent access 2BC test, EtOH intake decreased in CD14 KO male and female mice, whereas drinking increased in MyD88 KO male mice. In the 2BC-DID test, EtOH drinking decreased in male and female mice lacking TLR2, whereas drinking increased in MyD88 KO male mice. In the 1-bottle DID test, EtOH intake decreased in female TLR2 KO mice. TLR2 KO and CD14 KO mice did not differ in saccharin preference but showed reduced preference for NaCl. MyD88 KO mice showed a slight reduction in preference for saccharin.

CONCLUSIONS

Deletion of key components of the MyD88-dependent pathway produced differential effects on EtOH intake by decreasing (TLR2 KO and CD14 KO) or increasing (MyD88 KO) drinking, while deletion of TLR4 had no effect. Some of the drinking effects depended on the sex of the mice and/or the EtOH-drinking model.

Functional reconstitution of Arabidopsis thaliana plant uncoupling mitochondrial protein (AtPUMP1) expressed in Escherichia coli

The Arabidopsis thaliana uncoupling protein (UCP) gene was expressed in Escherichia coli and isolated protein reconstituted into liposomes. Linoleic acid-induced H+ fluxes were sensitive to purine nucleotide inhibition with an apparent K(i) (in mM) of 0.8 (GDP), 0.85 (ATP), 0.98 (GTP), and 1.41 (ADP); the inhibition was pH-dependent. Kinetics of AtPUMP1-mediated H+ fluxes were determined for lauric, myristic, palmitic, oleic, linoleic, and linolenic acids. Properties of recombinant AtPUMP1 indicate that it represents a plant counterpart of animal UCP2 or UCP3. This work brings the functional and genetic approaches together for the first time, providing strong support that AtPUMP1 is truly an UCP.

Possible basic and specific functions of plant uncoupling proteins (pUCP)

Evidence has been provided that the plant uncoupling proteins (pUCP) play basic physiological roles similar to the other uncoupling protein subfamily members (mammalian UCP1,2,3,4 and BMCP) and are effective in the situations of slight uncoupling that leads to: (1) accelerated respiration and metabolic rates that are beneficial to plant growth and development; (2) decreased formation of reactive oxygen species in mitochondria; and, (3) mild thermogenesis, inevitably accompanying the previous two phenomena. Hypothetically, specific physiological roles of pUCP such as cut off of ATP synthesis could be manifested in connection with climacteric respiratory rise during fruit ripening, seed dormancy, and plant senescence. pUCP might also facilitate growth under low temperatures, e.g., during seed germination or in roots. The existence of these specific roles is suggested by the immunochemical and functional localization of pUCP in mitochondria of fruits, seeds and roots of various plant species.

Important amino acid residues of potato plant uncoupling protein (StUCP)

Chemical modifications were used to identify some of the functionally important amino acid residues of the potato plant uncoupling protein (StUCP). The proton-dependent swelling of potato mitochondria in K(+)-acetate in the presence of linoleic acid and valinomycin was inhibited by mersalyl (K(i) = 5 microM) and other hydrophilic SH reagents such as Thiolyte MB, iodoacetate and 5, 5'-dithio-bis-(2-nitrobenzoate), but not by hydrophobic N-ethylmaleimide. This pattern of inhibition by SH reagents was similar to that of brown adipose tissue uncoupling protein (UCP1). As with UCP1, the arginine reagent 2,3-butadione, but not N-ethylmaleimide or other hydrophobic SH reagents, prevented the inhibition of StUCP-mediated transport by ATP in isolated potato mitochondria or with reconstituted StUCP. The results indicate that the most reactive amino acid residues in UCP1 and StUCP are similar, with the exception of N-ethylmaleimide-reactive cysteines in the purine nucleotide-binding site.

Plant uncoupling mitochondrial protein activity in mitochondria isolated from tomatoes at different stages of ripening

In the present study we have observed a higher state of coupling in respiring mitochondria isolated from green as compared to red tomatoes (Lycopersicon esculentum, Mill.). Green tomato mitochondria produced a membrane potential (deltapsi) high enough to phosphorylate ADP, whereas in red tomato mitochondria, BSA and ATP were required to restore deltapsi to the level of that obtained with green tomato mitochondria. This supports the notion that such uncoupling in red tomato mitochondria is mediated by a plant uncoupling mitochondrial protein (PUMP; cf. Vercesi et al., 1995). Nevertheless, mitochondria from both green and red tomatoes exhibited an ATP-sensitive linoleic acid (LA)-induced deltapsi decrease providing evidence that PUMP is also present in green tomatoes. Indeed, proteoliposomes containing reconstituted green or red tomato PUMP showed LA uniport and LA-induced H+ transport. It is suggested that the higher concentration of free fatty acids (PUMP substrates) in red tomatoes could explain the lower coupling state in mitochondria isolated from these fruits.

Fatty acid cycling mechanism and mitochondrial uncoupling proteins

We hypothesize that fatty acid-induced uncoupling serves in bioenergetic systems to set the optimum efficiency and tune the degree of coupling of oxidative phosphorylation. Uncoupling results from fatty acid cycling, enabled by several phylogenetically specialized proteins and, to a lesser extent, by other mitochondrial carriers. It is suggested that the regulated uncoupling in mammalian mitochondria is provided by uncoupling proteins UCP-1, UCP-2 and UCP-3, whereas in plant mitochondria by PUMP and StUCP, all belonging to the gene family of mitochondrial carriers. UCP-1, and hypothetically UCP-3, serve mostly to provide nonshivering thermogenesis in brown adipose tissue and skeletal muscle, respectively. Fatty acid cycling was documented for UCP-1, PUMP and ADP/ATP carrier, and is predicted also for UCP-2 and UCP-3. UCP-1 mediates a purine nucleotide-sensitive uniport of monovalent unipolar anions, including anionic fatty acids. The return of protonated fatty acid leads to H+ uniport and uncoupling. UCP-2 is probably involved in the regulation of body weight and energy balance, in fever, and defense against generation of reactive oxygen species. PUMP has been discovered in potato tubers and immunologically detected in fruits and corn, whereas StUCP has been cloned and sequenced froma a potato gene library. PUMP is supposed to act in the termination of synthetic processes in mature fruits and during the climacteric respiratory rise.

Activation of the potato plant uncoupling mitochondrial protein inhibits reactive oxygen species generation by the respiratory chain

A variety of plant tissues contain an uncoupling mitochondrial protein (PUMP), recently described and characterized by our group. In this study we show that the inhibition of PUMP activity in potato tuber mitochondria significantly increases mitochondrial H2O2 generation, while PUMP substrates, such as linoleic acid, reduce mitochondrial H2O2 generation. This H2O2 generation occurred mainly by the dismutation of superoxide radicals formed through monoelectronic reduction of O2 by semiquinone forms of coenzyme Q. The results presented suggest that protection against mitochondrial oxidative stress may be a physiological role of PUMP.

Reconstituted plant uncoupling mitochondrial protein allows for proton translocation via fatty acid cycling mechanism

Potato and tomato plant uncoupling mitochondrial protein (PUMP) was reconstituted into liposomes, and K+ or H+ fluxes associated with fatty acid (FA)-induced ion movement were measured using fluorescent ion indicators potassium binding benzofuraneisophthalate and 6-methoxy-N-(3-sulfopropyl)-quinolinium. We suggest that PUMP, like its mammalian counterpart, the uncoupling protein of brown adipose tissue mitochondria (Garlid, K. D., Orosz, D. E., Modrianský, M., Vassanelli, S., and Jeek, P. (1996), J. Biol. Chem. 271, 2615-2702), allows for H+ translocation via a FA cycling mechanism. Reconstituted PUMP translocated anionic linoleic and heptylbenzoic acids, undecanesulfonate, and hexanesulfonate, but not phenylvaleric and abscisic acids or Cl-. Transport was inhibited by ATP and GDP. Internal acidification of protein-free liposomes by linoleic or heptylbenzoic acid indicated that H+ translocation occurs by FA flip-flopping across the lipid bilayer. However, addition of valinomycin after FA-initiated GDP-sensitive H+ efflux solely in proteoliposomes, indicating that influx of anionic FA via PUMP precedes a return of protonated FA carrying H+. Phenylvaleric acid, unable to flip-flop, was without effect. Kinetics of FA and undecanesulfonate uniport suggested the existence of an internal anion binding site. Exponential flux-voltage characteristics were also studied. We suggest that regulated uncoupling in plant mitochondria may be important during fruit ripening, senescence, and seed dormancy.

Ca2+-independent permeabilization of the inner mitochondrial membrane by peroxynitrite is mediated by membrane protein thiol cross-linking and lipid peroxidation

Peroxynitrite anion, the reaction product of superoxide and nitric oxide, is a potent biological oxidant, which inactivates mammalian heart mitochondrial NADH-coenzyme Q reductase (complex I), succinate dehydrogenase (complex II), and ATPase, without affecting cytochrome c oxidase (complex IV). In this paper, we evaluated the effect of peroxynitrite on mitochondrial membrane integrity and permeability under low calcium concentration. Phosphate buffer was used in most of our experiments since Hepes, Tris, mannitol, and sucrose were found to inhibit the oxidative chemistry of peroxynitrite. Peroxynitrite (0.1-1.0 mM) caused a dose-dependent decrease in the ability of mitochondria to build up a membrane potential when N,N,N',N'-tetramethyl-p-phenylenediamine/ascorbate were used as substrate. Elimination of the membrane potential was accompanied by penetration of the osmotic support (KCl/NaCl) into the matrix as judged by the parallel occurrence of mitochondrial swelling. This swelling was partially inhibited by dithiothreitol (DTT) or butylated hydroxytoluene (BHT) and was insensitive to ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, ADP, and cyclosporin A. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis of solubilized membrane proteins indicated that alterations in membrane permeability were associated with the production of protein aggregates due to membrane protein thiol cross-linking. The protective effect of DTT on both mitochondrial swelling and protein polymerization suggests the involvement of disulfide bonds in the membrane permeabilization process. In addition, the increase in thiobarbituric acid-reactive substances and the partial inhibitory effect of BHT indicate the occurrence of lipid peroxidation. These results support the idea that under our experimental conditions peroxynitrite causes mitochondrial structural and functional alterations by Ca2+-independent mechanisms through lipid peroxidation and protein sulfhydryl oxidation.

Evidence for anion-translocating plant uncoupling mitochondrial protein in potato mitochondria

Transport properties of plant mitochondria from potato tubers were investigated using the swelling technique and membrane potential measurements. Proton-dependent swelling of fatty acid-depleted mitochondria in potassium acetate with valinomycin was possible only in the presence of fatty acids (linoleic acid and 12-(4-azido-2-nitrophenylamino)dodecanoic acid) and was inhibited by various purine nucleotides including ATP, GDP, and GTP. Swelling representing uptake of hexanesulfonate was also inhibited by purine nucleotides. Also, the membrane potential of fatty acid-depleted potato mitochondria energized by succinate declined upon the addition of linoleic acid or 12-(4-azido-2-nitrophenylamino)dodecanoic acid, and this decrease was prevented by ATP and other purine nucleotides. These transport activities are identical to those reported for brown adipose tissue mitochondria and related to the uncoupling protein; therefore, we ascribed them to the plant mitochondrial uncoupling protein (PUMP). A major difference between plant and mammalian uncoupling protein is that PUMP transports small hydrophilic anions such as Cl- very slowly, if at all. We suggest that PUMP may play an important role in plant physiology, where a regulated uncoupling and thermogenesis can proceed during fruit and seed development.

Are age and ethics related?

Ethical values of 171 college students at California State University, Chico, were measured, using a subset of the Rokeach (1968, 1971) Value Survey. Nonparametric statistical analysis, four value measures, and four different consistent tests of significance and probability showed, surprisingly, that the younger students were more ethical than the older students. College students under 21 scored significantly higher ethically on three out of the four measures. Younger college students valued equality, freedom, and honesty more than their older classmates did. Surprisingly also, the younger students were significantly more concerned with being helpful and intellectual and were less involved in pursuing an exciting life and in social recognition than were the older students.

[Characteristics of the demand for cranial computerized tomography: reasons and costs of the exam]

It was reviewed a series of 2860 cerebral computed tomography (CCT) in order to compare the main reasons at referral to investigation with the CCT results and the costs with normal and abnormal CCT. It was also studied the age and sex of the patients. Data were collected from one out of three diagnostic centers in Salvador, Brasil, for a three years period. The 2860 CCT exclude all investigation carried out for the follow-up of a previously diagnosed abnormality. CCT abnormalities were detected in 1152 (40.3%). The following reasons showed the highest proportion of abnormal CCT, for males and females respectively: demential syndrome (91.7 and 83.3%); cerebrovascular accidents (85.1 and 73.6%); infectious and parasitary diseases (76.5 and 78.6%); tumors (65.8 and 55.4%); and head injuries, 63.6% for males. In the female group, 65.0% of the CCT were normal, in a range of 65.0 to 80.0% for the age groups under 54 years old. In the male group, the highest proportion of normal CCT was found in the age groups: 25-34 (68.4%), < 15 (62.9%) and 35-44 (62.7%). The most common reasons for normal CCT for males and females were: headache (81.3 and 87.5%); dizziness/vertigo (79.3 and 78.6%); seizures (67.3 and 70.0%); psychomotor deficiency (72.0 and 67.7%) and "endocrine disorders", 75.0% for each sex. The highest proportion of normal CCT (65.3%) was requested by medical "convenios". The cost with normal CCT reached US$565,225 and with the abnormal ones, US$381,247. Costs with normal CCT were 2.2 higher for medical "convenios" as compared to those of the National Institute of Security requests and 2.8 more than those of private medicine.