Responses to ethanol in C57BL/6 versus C57BL/6 × 129 hybrid mice

Although genetic background alters responses to ethanol, there has not yet been a methodical quantification of differences in ethanol-related behaviors between inbred and hybrid mice commonly used in gene-targeting studies. Here, we compared C57BL/6NTac × 129S6/SvEvTac F1 hybrid mice (B6129S6) with C57BL/6NTac inbred mice (B6NT), and C57BL/6J × 129X1/SvJ (B6129X1) and C57BL/6J × 129S4/SvJae F1 hybrids (B6129S4) with C57BL/6J mice (B6J), in five commonly used tests: continuous access two-bottle choice drinking, intermittent limited-access binge drinking, ethanol clearance, ethanol-induced loss of the righting reflex, and conditioned place preference (CPP) for ethanol. We found that inbred B6J and B6NT mice showed greater ethanol preference and consumption than their respective hybrids when ethanol was continuously available. Within the intermittent limited-access drinking procedure, though all lines showed similar intake over eight drinking sessions, the average of all sessions showed that B6NT mice drank significantly more ethanol than B6129S6 mice. In addition, B6J mice consumed more ethanol than B6129X1 mice, although they drank less than B6129S4 mice. No differences in ethanol LORR duration were observed between inbred and hybrid mice. Although ethanol clearance was similar among B6J mice and their respective hybrids, B6NT mice cleared ethanol more rapidly than B6129S6 mice. All lines developed CPP for ethanol. Our findings indicate that it may not be necessary to backcross hybrids to an inbred B6 background to study many ethanol-related behaviors in gene-targeted mice.

Inhibition of PKCδ reduces cisplatin-induced nephrotoxicity without blocking chemotherapeutic efficacy in mouse models of cancer

Cisplatin is a widely used cancer therapy drug that unfortunately has major side effects in normal tissues, notably nephrotoxicity in kidneys. Despite intensive research, the mechanism of cisplatin-induced nephrotoxicity remains unclear, and renoprotective approaches during cisplatin-based chemotherapy are lacking. Here we have identified PKCδ as a critical regulator of cisplatin nephrotoxicity, which can be effectively targeted for renoprotection during chemotherapy. We showed that early during cisplatin nephrotoxicity, Src interacted with, phosphorylated, and activated PKCδ in mouse kidney lysates. After activation, PKCδ regulated MAPKs, but not p53, to induce renal cell apoptosis. Thus, inhibition of PKCδ pharmacologically or genetically attenuated kidney cell apoptosis and tissue damage, preserving renal function during cisplatin treatment. Conversely, inhibition of PKCδ enhanced cisplatin-induced cell death in multiple cancer cell lines and, remarkably, enhanced the chemotherapeutic effects of cisplatin in several xenograft and syngeneic mouse tumor models while protecting kidneys from nephrotoxicity. Together these results demonstrate a role of PKCδ in cisplatin nephrotoxicity and support targeting PKCδ as an effective strategy for renoprotection during cisplatin-based cancer therapy.

Should the reorganization of addiction-related research across all the National Institutes of Health be structural?--The devil is truly in the details

The recent proposal to dissolve the National Institute on Alcohol Abuse and Alcoholism and National Institute on Drug Abuse and create a new institute for substance use, abuse, and addiction will require significant effort by the staff of both institutes, the Advisory Councils, and outside experts to overcome complex challenges that could threaten its success. Although integration of the grants portfolios can be achieved, harmonization of goals and policies related to legal use of alcohol versus illegal consumption of drugs will present serious challenges. Consolidating the infrastructure of the 2 existing institutes would entail avoiding encroachment on grant funding. A new institute for substance use, abuse, and addiction would require an enormous amount of cooperation from other institutes as the portfolios of research on alcohol, tobacco, and other drug abuse should logically be transferred to the new institute. In the near term, a structural reorganization would be less efficient and more costly than the individual institutes are currently. Increasing efficiency and reducing costs over time will necessitate careful strategic planning. Success in this difficult task would be made easier and less costly by first implementing carefully placed building blocks of increasing functional reorganization. The newly created institute should increase opportunities for specialization within disorders of addiction, attract new leadership, and build a novel strategic plan that will energize scientists and staff and incorporate ideas of stakeholders to advance the public good in preventing and treating alcohol, tobacco, and all addictions. Attention must be paid to the devil in the details.

Mouse model of middle cerebral artery occlusion

Stroke is the most common fatal neurological disease in the United States. The majority of strokes (88%) result from blockage of blood vessels in the brain (ischemic stroke). Since most ischemic strokes (~80%) occur in the territory of middle cerebral artery (MCA), many animal stroke models that have been developed have focused on this artery. The intraluminal monofilament model of middle cerebral artery occlusion (MCAO) involves the insertion of a surgical filament into the external carotid artery and threading it forward into the internal carotid artery (ICA) until the tip occludes the origin of the MCA, resulting in a cessation of blood flow and subsequent brain infarction in the MCA territory. The technique can be used to model permanent or transient occlusion. If the suture is removed after a certain interval (30 min, 1 h, or 2 h), reperfusion is achieved (transient MCAO); if the filament is left in place (24 h) the procedure is suitable as a model of permanent MCAO. This technique does not require craniectomy, a neurosurgical procedure to remove a portion of skull, which may affect intracranial pressure and temperature. It has become the most frequently used method to mimic permanent and transient focal cerebral ischemia in rats and mice. To evaluate the extent of cerebral infarction, we stain brain slices with 2,3,5-triphenyltetrazolium chloride (TTC) to identify ischemic brain tissue. In this video, we demonstrate the MCAO method and the determination of infarct size by TTC staining.

PKC-delta promotes renal tubular cell apoptosis associated with proteinuria

Proteinuria may contribute to progressive renal damage by inducing tubulointerstitial inflammation, fibrosis, and tubular cell injury and death, but the mechanisms underlying these pathologic changes remain largely unknown. Here, in a rat kidney proximal tubular cell line (RPTC), albumin induced apoptosis in a time- and dose-dependent manner. Caspase activation accompanied albumin-induced apoptosis, and general caspase inhibitors could suppress this activation. In addition, Bcl-2 transfection inhibited apoptosis and attenuated albumin-induced Bax translocation to mitochondria and cytochrome c release from the organelles, further confirming a role for the intrinsic pathway of apoptosis in albuminuria-associated tubular apoptosis. We observed phosphorylation and activation of PKC-delta early during treatment of RPTC cells with albumin. Rottlerin, a pharmacologic inhibitor of PKC-delta, suppressed albumin-induced Bax translocation, cytochrome c release, and apoptosis. Moreover, a dominant-negative mutant of PKC-delta blocked albumin-induced apoptosis in RPTC cells. In vivo, we observed activated PKC-delta in proteinuric kidneys of streptozotocin-induced diabetic mice and in kidneys after direct albumin overload. Notably, albumin overload induced apoptosis in renal tubules, which was less severe in PKC-delta-knockout mice. Taken together, these results suggest that activation of PKC-delta promotes tubular cell injury and death during albuminuria, broadening our understanding of the pathogenesis of progressive proteinuric kidney diseases.

Neurobiological mechanisms contributing to alcohol-stress-anxiety interactions

This article summarizes the proceedings of a symposium that was presented at a conference entitled "Alcoholism and Stress: A Framework for Future Treatment Strategies." The conference was held in Volterra, Italy on May 6-9, 2008 and this symposium was chaired by Jeff L. Weiner. The overall goal of this session was to review recent findings that may shed new light on the neurobiological mechanisms that underlie the complex relationships between stress, anxiety, and alcoholism. Dr. Danny Winder described a novel interaction between D1 receptor activation and the corticotrophin-releasing factor (CRF) system that leads to an increase in glutamatergic synaptic transmission in the bed nucleus of the stria terminalis. Dr. Marisa Roberto presented recent data describing how protein kinase C epsilon, ethanol, and CRF interact to alter GABAergic inhibition in the central nucleus of the amygdala. Dr. Jeff Weiner presented recent advances in our understanding of inhibitory circuitry within the basolateral amygdala (BLA) and how acute ethanol exposure enhances GABAergic inhibition in these pathways. Finally, Dr. Brian McCool discussed recent findings on complementary glutamatergic and GABAergic adaptations to chronic ethanol exposure and withdrawal in the BLA. Collectively, these investigators have identified novel mechanisms through which neurotransmitter and neuropeptide systems interact to modulate synaptic activity in stress and anxiety circuits. Their studies have also begun to describe how acute and chronic ethanol exposure influence excitatory and inhibitory synaptic communication in these pathways. These findings point toward a number of novel neurobiological targets that may prove useful for the development of more effective treatment strategies for alcohol use disorders.

The N-type calcium channel is a novel target for treating alcohol use disorders

We recently validated the N-type calcium channel as a target for the treatment of alcoholism and anxiety. N-type calcium channels are neuronal presynaptic ion channels that regulate neurotransmitter release at many sites in the brain. Mice lacking N-type calcium channels exhibit reduced ethanol consumption and show resistance to the acute intoxicating effects of ethanol. In wild type rodents, pretreatment with a novel N- and T-type calcium channel blocker, NP078585, reduces the intoxicating and reinforcing effects of ethanol and abolishes stress-induced reinstatement of alcohol seeking. Here we discuss these findings and expand upon their implications for the N-type calcium channel as a target for drug development. An important consideration in the development of drugs to treat any addiction is that the medication itself not be addictive. We attempted, and failed, to generate a conditioned place preference for NP078585, suggesting that NP078585 is not rewarding.

Amygdala protein kinase C epsilon controls alcohol consumption

Alcoholism is a progressive disorder that involves the amygdala. Mice lacking protein kinase C epsilon (PKCepsilon) show reduced ethanol consumption, sensitivity and reward. We therefore investigated whether PKCepsilon signaling in the amygdala is involved in ethanol consumption. Local knockdown of PKCepsilon in the amygdala reduced ethanol consumption and preference in a limited-access paradigm. Further, mice that are heterozygous for the PKCepsilon allele consume less ethanol compared with wild-type mice in this paradigm. These mice have a >50% reduction in the abundance of PKCepsilon in the amygdala compared with wild-type mice. We conclude that amygdala PKCepsilon is important for ethanol consumption in mice.

The role of the equilibrative nucleoside transporter 1 (ENT1) in transport and metabolism of ribavirin by human and wild-type or Ent1-/- mouse erythrocytes

The polar nucleoside drug ribavirin is front-line treatment for chronic hepatitis C virus infection. The human equilibrative nucleoside transporter (ENT) 1 transports ribavirin into erythrocytes where it is phosphorylated. These phosphorylated metabolites accumulate in the erythrocytes and produce dose-limiting hemolytic anemia. Here, we examined the in vitro and ex vivo transport and metabolism of ribavirin by erythrocytes isolated from humans and Ent1-null mice. Ribavirin (2.4 microM) uptake was significantly higher (1044 +/- 255 amol/microg/10 s) into erythrocytes from Ent1(+/+) mice compared with that from Ent1(-/-) mice (76.48 +/- 11.20 amol/microg/10 s). Our results showed a saturable (K(m) of 382 +/- 75.1 microM) transport of [(3)H]ribavirin into erythrocytes from Ent1(+/+) mice. We found that ribavirin concentration rapidly (within 60 s) reached equilibrium in erythrocytes using a time course of [(3)H]ribavirin transport (2.5 microM) and metabolism in mouse and human erythrocytes for 8 h. However, total radioactivity of ribavirin was predominantly attributed to the phosphorylated metabolites ribavirin monophosphate and ribavirin triphosphate. Our findings allow us to estimate ribavirin transport, diffusion, and metabolic clearance and to predict in vivo accumulation of ribavirin phosphates in erythrocytes of both mice and humans. Our modeling of ribavirin in erythrocytes on long-term administration of ribavirin suggests that the accumulation of ribavirin inside the cells is dependent on ENT1/Ent1 transport and the rates of intracellular phosphorylation and the degradation of the phosphorylated metabolites. We predict that Ent1(+/+) and Ent1(-/-) mice will serve as excellent models to investigate the contribution of Ent1 to the pharmacokinetics and toxicity of ribavirin in vivo.

Protein kinases and addiction

Although drugs of abuse have different chemical structures and interact with different protein targets, all appear to usurp common neuronal systems that regulate reward and motivation. Addiction is a complex disease that is thought to involve drug-induced changes in synaptic plasticity due to alterations in cell signaling, gene transcription, and protein synthesis. Recent evidence suggests that drugs of abuse interact with and change a common network of signaling pathways that include a subset of specific protein kinases. The best studied of these kinases are reviewed here and include extracellular signal-regulated kinase, cAMP-dependent protein kinase, cyclin-dependent protein kinase 5, protein kinase C, calcium/calmodulin-dependent protein kinase II, and Fyn tyrosine kinase. These kinases have been implicated in various aspects of drug addiction including acute drug effects, drug self-administration, withdrawal, reinforcement, sensitization, and tolerance. Identifying protein kinase substrates and signaling pathways that contribute to the addicted state may provide novel approaches for new pharmacotherapies to treat drug addiction.

Neurotoxic catecholamine metabolite in nociceptors contributes to painful peripheral neuropathy

The neurotoxic effects of catecholamine metabolites have been implicated in neurodegenerative diseases. As some sensory neurons express tyrosine hydroxylase and monoamine oxidase (MAO), we investigated the potential contribution of catecholamine metabolites to neuropathic pain in a model of alcoholic neuropathy. The presence of catecholamines in sensory neurons is supported by capsaicin-stimulated epinephrine release, an effect enhanced in ethanol-fed rats. mRNA for enzymes in dorsal root ganglia involved in catecholamine uptake and metabolism, dopamine beta-hydroxylase and MAO-A, were decreased by neonatal administration of capsaicin. Ethanol-induced hyperalgesia was attenuated by systemic and local peripheral administration of inhibitors of MAO-A, reduction of norepinephrine transporter (NET) in sensory neurons and a NET inhibitor. Finally, intradermal injection of 3,4-dihydroxyphenylglycolaldehyde (DOPEGAL), a neurotoxic MAO-A catecholamine metabolite, produced robust mechanical hyperalgesia. These observations suggest that catecholamines in nociceptors are metabolized to neurotoxic products by MAO-A, which can cause neuronal dysfunction underlying neuropathic pain.

Hypertensive encephalopathy and the blood-brain barrier: is deltaPKC a gatekeeper?

Hypertensive encephalopathy is a life-threatening condition due to elevation of cerebral perfusion pressure beyond the limits of autoregulation. Breakdown of the blood-brain barrier (BBB) leads to cerebral edema and reduced blood flow. In this issue of the JCI, Mochly-Rosen and colleagues demonstrate a novel molecular strategy for preserving the BBB in a model of hypertension-induced encephalopathy (see the related article beginning on page 173). Using a rationally designed peptide inhibitor of deltaPKC, they stabilized the BBB and improved mortality in hypertensive rats. This study highlights the therapeutic potential of deltaPKC inhibitors in hypertensive encephalopathy and provides incentive to elucidate deltaPKC signaling pathways that mediate BBB dysfunction in other disease states.

Alcohol-induced stress in painful alcoholic neuropathy

Chronic alcohol consumption induces a painful small-fiber peripheral neuropathy, the severity of which increases during alcohol withdrawal. Chronic alcohol consumption also produces a sustained increase in stress hormones, epinephrine and corticosterone, that is exacerbated during alcohol withdrawal. We report that adrenal medullectomy and administration of a glucocorticoid receptor antagonist, mifepristone (RU 38486), both prevented and reversed a model of painful peripheral neuropathy in alcohol binge-drinking rats. Chronic administration of stress levels of epinephrine to rats that had undergone adrenal medullectomy and were being fed the alcohol diet reconstituted this phenotype. Intrathecal administration of oligodeoxynucleotides antisense to the beta(2)-adrenergic- or glucocorticoid-receptor also prevented and reversed the pro-nociceptive effects of ethanol. Our results suggest a convergence of the effects of mediators of the hypothalamic-pituitary- and sympathoadrenal-stress axes on sensory neurons in the induction and maintenance of alcohol-induced painful peripheral neuropathy.

Amygdala protein kinase C epsilon regulates corticotropin-releasing factor and anxiety-like behavior

Corticotropin-releasing factor (CRF), its receptors, and signaling pathways that regulate CRF expression and responses are areas of intense investigation for new drugs to treat affective disorders. Here, we report that protein kinase C epsilon (PKCepsilon) null mutant mice, which show reduced anxiety-like behavior, have reduced levels of CRF messenger RNA and peptide in the amygdala. In primary amygdala neurons, a selective PKCepsilon activator, psiepsilonRACK, increased levels of pro-CRF, whereas reducing PKCepsilon levels through RNA interference blocked phorbol ester-stimulated increases in CRF. Local knockdown of amygdala PKCepsilon by RNA interference reduced anxiety-like behavior in wild-type mice. Furthermore, local infusion of CRF into the amygdala of PKCepsilon(-/-) mice increased their anxiety-like behavior. These results are consistent with a novel mechanism of PKCepsilon control over anxiety-like behavior through regulation of CRF in the amygdala.

Protein kinase C epsilon regulates gamma-aminobutyrate type A receptor sensitivity to ethanol and benzodiazepines through phosphorylation of gamma2 subunits

Ethanol enhances gamma-aminobutyrate (GABA) signaling in the brain, but its actions are inconsistent at GABA(A) receptors, especially at low concentrations achieved during social drinking. We postulated that the epsilon isoform of protein kinase C (PKCepsilon) regulates the ethanol sensitivity of GABA(A) receptors, as mice lacking PKCepsilon show an increased behavioral response to ethanol. Here we developed an ATP analog-sensitive PKCepsilon mutant to selectively inhibit the catalytic activity of PKCepsilon. We used this mutant and PKCepsilon(-/-) mice to determine that PKCepsilon phosphorylates gamma2 subunits at serine 327 and that reduced phosphorylation of this site enhances the actions of ethanol and benzodiazepines at alpha1beta2gamma2 receptors, which is the most abundant GABA(A) receptor subtype in the brain. Our findings indicate that PKCepsilon phosphorylation of gamma2 regulates the response of GABA(A) receptors to specific allosteric modulators, and, in particular, PKCepsilon inhibition renders these receptors sensitive to low intoxicating concentrations of ethanol.

nPKCepsilon, a P2Y2-R downstream effector in regulated mucin secretion from airway goblet cells

Airway goblet cell mucin secretion is controlled by agonist activation of P2Y(2) purinoceptors, acting through Gq/PLC, inositol-1,4,5-trisphosphate (IP(3)), diacylglycerol, Ca(2+) and protein kinase C (PKC). Previously, we showed that SPOC1 cells express cPKCalpha, nPKCdelta, nPKCepsilon, and nPKCeta; of these, only nPKCdelta translocated to the membrane in correlation with mucin secretion (Abdullah LH, Bundy JT, Ehre C, Davis CW. Am J Physiol Lung Physiol 285: L149-L160, 2003). We have verified these results and pursued the identity of the PKC effector isoform by testing the effects of altered PKC expression on regulated mucin release using SPOC1 cell and mouse models. SPOC1 cells overexpressing cPKCalpha, nPKCdelta, and nPKCeta had the same levels of ATPgammaS- and phorbol-1,2-myristate-13-acetate (PMA)-stimulated mucin secretion as the levels in empty retroviral vector expressing cells. Secretagogue-induced mucin secretion was elevated only in cells overexpressing nPKCepsilon (14.6 and 23.5%, for ATPgammaS and PMA). Similarly, only SPOC1 cells infected with a kinase-deficient nPKCepsilon exhibited the expected diminution of stimulated mucin secretion, relative to wild-type (WT) isoform overexpression. ATPgammaS-stimulated mucin secretion from isolated, perfused mouse tracheas was diminished in P2Y(2)-R null mice by 82% relative to WT mice, demonstrating the utility of mouse models in studies of regulated mucin secretion. Littermate WT and nPKCdelta knockout (KO) mice had nearly identical levels of stimulated mucin secretion, whereas mucin release was nearly abolished in nPKCepsilon KO mice relative to its WT littermates. We conclude that nPKCepsilon is the effector isoform downstream of P2Y(2)-R activation in the goblet cell secretory response. The translocation of nPKCdelta observed in activated cells is likely not related to mucin secretion but to some other aspect of goblet cell biology.

A semisynthetic epitope for kinase substrates

The ubiquitous nature of protein phosphorylation makes it challenging to map kinase-substrate relationships, which is a necessary step toward defining signaling network architecture. To trace the activity of individual kinases, we developed a semisynthetic reaction scheme, which results in the affinity tagging of substrates of the kinase in question. First, a kinase, engineered to use a bio-orthogonal ATPgammaS analog, catalyzes thiophosphorylation of its direct substrates. Second, alkylation of thiophosphorylated serine, threonine or tyrosine residues creates an epitope for thiophosphate ester-specific antibodies. We demonstrated the generality of semisynthetic epitope construction with 13 diverse kinases: JNK1, p38alpha MAPK, Erk1, Erk2, Akt1, PKCdelta, PKCepsilon, Cdk1/cyclinB, CK1, Cdc5, GSK3beta, Src and Abl. Application of this approach, in cells isolated from a mouse that expressed endogenous levels of an analog-specific (AS) kinase (Erk2), allowed purification of a direct Erk2 substrate.

Early editorial manuscript screening versus obligate peer review: A randomized trial

Peer review is a cornerstone of scientific publication. However, it is time consuming for reviewers and contributors, and must be balanced with editorial oversight for balance and bias. To test a more efficient method of reviewing manuscripts, we performed a randomized trial comparing traditional peer review for all manuscripts received by the Annals of Neurology with an early screening approach in which six editors rejected a manuscript without external review when the chance of acceptance was deemed very low. Of the 351 manuscripts entered into the trial, 88 were randomized to traditional external review and 263 to early screening. Rates of final acceptance were similar in the two groups (p = 0.41). Final decisions were more delayed for traditional review (mean 48 days versus 18 days with early screening; p < 0.0001) and more reviewers were required for each manuscript (mean 2.3 versus 0.7 with early screening; p < 0.0001). Among accepted manuscripts, reviewer ratings of scientific and clinical impact were similar. We conclude that a method of early screening of manuscripts for appropriateness for publication results in substantial decreases in the time between manuscript submission and publication decisions, and reduces the burden on reviewers with minimal impact on the quality of accepted manuscripts. Editorial screening is now journal policy.

Severity of alcohol-induced painful peripheral neuropathy in female rats: role of estrogen and protein kinase (A and Cepsilon)

Small-fiber painful peripheral neuropathy, a complication of chronic ethanol ingestion, is more severe in women. In the present study, we have replicated this clinical finding in the rat and evaluated for a role of estrogen and second messenger signaling pathways. The alcohol diet (6.5% ethanol volume:volume in Lieber-DeCarli formula) induced hyperalgesia with more rapid onset and severity in females. Following ovariectomy, alcohol failed to induce hyperalgesia in female rats, well past its time to onset in gonad intact males and females. Estrogen replacement reinstated alcohol neuropathy in the female rat. The protein kinase A (PKA) inhibitor (Walsh inhibitor peptide, WIPTIDE) only attenuated alcohol-induced hyperalgesia in female rats. Inhibitors of protein kinase Cepsilon (PKCepsilon-I) and extracellular-signal related kinase (ERK) 1/2 (2'-amino-3'-methoxyflavone (PD98059) and 1,4-diamino-2, 3-dicyano-1, 4-bis (2-aminophenylthio) butadiene (U0126)) attenuated hyperalgesia in males and females, however the degree of attenuation produced by PKCepsilon-I was much greater in females. In conclusion, estrogen plays an important role in the expression of pain associated with alcohol neuropathy in the female rat. In contrast to inflammatory hyperalgesia, in which only the contribution of PKCepsilon signaling is sexually dimorphic, in alcohol neuropathy PKA as well as PKCepsilon signaling is highly sexually dimorphic.

Increased sensitivity to the aversive effects of ethanol in PKCε null mice revealed by place conditioning

Determining the intracellular signaling pathways that mediate the rewarding effects of ethanol may help identify drug targets to curb excessive alcohol consumption. Mice lacking the epsilon isoform of protein kinase C (PKCepsilon) voluntarily consumed less ethanol than wild-type mice in two-bottle choice and operant self-administration assays. Decreased consumption may reflect either increased or decreased sensitivity to the rewarding effects of ethanol. Alternatively, decreased voluntary consumption may reflect a change in sensitivity to the aversive effects of ethanol. The authors used place conditioning to determine that PKCepsilon null mice have an increased sensitivity to the aversive effects of ethanol but a decreased sensitivity to the rewarding effects of ethanol. Together these data suggest that PKCepsilon null mice voluntarily consume less ethanol because they derive less reward and are more sensitive to the aversive effects of ethanol.