Effects of urokinase-type plasminogen activator in the acquisition, expression and reinstatement of cocaine-induced conditioned-place preference

Tranexamic acid for haemostasis and beyond: does dose matter?

Tranexamic acid (TXA) is a widely used antifibrinolytic agent that has been used since the 1960's to reduce blood loss in various conditions. TXA is a lysine analogue that competes for the lysine binding sites in plasminogen and tissue-type plasminogen activator impairing its interaction with the exposed lysine residues on the fibrin surface. The presence of TXA therefore, impairs the plasminogen and tPA engagement and subsequent plasmin generation on the fibrin surface, protecting fibrin clot from proteolytic degradation. However, critical lysine binding sites for plasmin(ogen) also exist on other proteins and on various cell-surface receptors allowing plasmin to exert potent effects on other targets that are unrelated to classical fibrinolysis, notably in relation to immunity and inflammation. Indeed, TXA was reported to significantly reduce post-surgical infection rates in patients after cardiac surgery unrelated to its haemostatic effects. This has provided an impetus to consider TXA in other indications beyond inhibition of fibrinolysis. While there is extensive literature on the optimal dosage of TXA to reduce bleeding rates and transfusion needs, it remains to be determined if these dosages also apply to blocking the non-canonical effects of plasmin.

Dynamic regulation of the extracellular matrix in reward memory processes: a question of time

Substance use disorders are a global health problem with increasing prevalence resulting in significant socioeconomic burden and increased mortality. Converging lines of evidence point to a critical role of brain extracellular matrix (ECM) molecules in the pathophysiology of substance use disorders. An increasing number of preclinical studies highlight the ECM as a promising target for development of novel cessation pharmacotherapies. The brain ECM is dynamically regulated during learning and memory processes, thus the time course of ECM alterations in substance use disorders is a critical factor that may impact interpretation of the current studies and development of pharmacological therapies. This review highlights the evidence for the involvement of ECM molecules in reward learning, including drug reward and natural reward such as food, as well as evidence regarding the pathophysiological state of the brain's ECM in substance use disorders and metabolic disorders. We focus on the information regarding time-course and substance specific changes in ECM molecules and how this information can be leveraged for the development of therapeutic strategies.

Sustained lentiviral-mediated overexpression of microRNA124a in the dentate gyrus exacerbates anxiety- and autism-like behaviors associated with neonatal isolation in rats

Autism spectrum disorders (ASD) are highly disabling psychiatric disorders. Despite a strong genetic etiology, there are no efficient therapeutic interventions that target the core symptoms of ASD. Emerging evidence suggests that dysfunction of microRNA (miR) machinery may contribute to the underlying molecular mechanisms involved in ASD. Here, we report a stress model demonstrating that neonatal isolation-induced long-lasting hippocampal elevation of miR124a was associated with reduced expression of its target BDNF mRNA. In addition, we investigated the impact of lentiviral-mediated overexpression of miR124a into the dentate gyrus (DG) on social interaction, repetitive- and anxiety-like behaviors in the neonatal isolation (Iso) model of autism. Rats isolated from the dams on PND 1 to PND 11 were assessed for their social interaction, marble burying test (MBT) and repetitive self-grooming behaviors as adults following miR124a overexpression. Also, anxiety-like behavior and locomotion were evaluated in the elevated plus maze (EPM) and open-field (OF) tests. Results show that, consistent with previously published reports, Iso rats displayed decreased social interaction contacts but increased repetitive- and anxiety-like behaviors. Interestingly, across both autism- and anxiety-like behavioral assays, miR124a overexpression in the DG significantly exacerbated repetitive behaviors, social impairments and anxiety with no effect on locomotor activity. Our novel findings attribute neonatal isolation-inducible cognitive impairments to induction of miR124a and consequently suppressed BDNF mRNA, opening venues for intercepting these miR124a-mediated damages. They also highlight the importance of studying microRNAs in the context of ASD and identify miR124a as a novel potential therapeutic target for improving mood disorders.

Zebrafish and conditioned place preference: a translational model of drug reward

Addiction and substance abuse are found ubiquitously throughout human society. In the United States, these disorders are responsible for amassing hundreds of billions of dollars in annual costs associated with healthcare, crime and lost productivity. Efficacious treatments remain few in number, the development of which will be facilitated by comprehension of environmental, genetic, pharmacological and neurobiological mechanisms implicated in the pathogenesis of addiction. Animal models such as the zebrafish (Danio rerio) have gained momentum within various domains of translational research, and as a model of complex brain disorders (e.g., drug abuse). Behavioral quantification within the conditioned place preference (CPP) paradigm serves as a measure of the rewarding qualities of a given substance. If the animal develops an increase in preference for the drug paired environment, it is inferred that the drug has positive-reinforcing properties. This paper discusses the utility of the zebrafish model in conjunction with the CPP paradigm and reports CPP behavior following acute exposure to 0.0%, 0.25%, 0.50%, and 1.00% alcohol, and 0 mg/L, 50 mg/L, 100 mg/L and 150 mg/L caffeine.

Inhibition of urokinase plasminogen activator "uPA" activity alters ethanol consumption and conditioned place preference in mice

Urokinase plasminogen activator, uPA, is a serine protease implicated in addiction to drugs of abuse. Using its specific inhibitor, B428, we and others have characterized the role of uPA in the rewarding properties of psychostimulants, including cocaine and amphetamine, but none have examined the role of uPA in ethanol use disorders. Therefore, in the current study, we extended our observations to the role of uPA in ethanol consumption and ethanol-induced conditioned place preference. The general aim of the present series of experiments was to investigate the effects of the administration of the B428 on voluntary alcohol intake and ethanol conditioned reward. A two-bottle choice, unlimited-access paradigm was used to compare ethanol intake between vehicle- and 3, 10, and 30 mg/kg B428-administered mice. For this purpose, the mice were presented with an ethanol solution (2.5%-20%) and water, at each concentration for 4 days, and their consumption was measured daily. Consumption of saccharin and quinine solutions was also measured. Systemic administration of B428 dose-dependently decreased ethanol intake and preference. Additionally, B428 mice did not differ from vehicle mice in their intake of graded solutions of tastants, suggesting that the uPA inhibition did not alter taste function. Also, ethanol metabolism was not affected following B428 injection. More importantly, 1.5 g/kg ethanol-induced conditioned place preference acquisition was blocked following B428 administration. Taken together, our results are the first to implicate uPA inhibition in the regulation of ethanol consumption and preference, and suggest that uPA may be considered as a possible therapeutic drug target for alcoholism and abstinence.

Selective lentiviral-mediated suppression of microRNA124a in the hippocampus evokes antidepressants-like effects in rats

Several lines of evidences suggest that the brain-derived neutrophic factor (BDNF) is implicated in the pathophysiology of depression. However, the molecular mechanisms are not fully understood. In the current study we aimed to investigate how genetic modulation of BDNF in the hippocampus using microRNa124a (miR124a)-expressing lentiviral vectors (LV) might affect depression-like behavior in adult rats. For this purpose, we assessed the expression level of miR124a and its direct target BDNF in the hippocampus and the cortex after 21-days exposure to social defeat stress. Results demonstrated that miR124a was up-regulated in the hippocampus but not in the cortex. In contrast, and as expected, BDNF transcripts were down-regulated. In a different set of experiments, male Wistar rats received bilateral intra-hippocampal or intra-cortical infusions of BDNF- and miR124a-expressing lentiviral vectors and depression-like behavior was assessed after 21-days social defeat stress using the novelty suppressed feeding, the sucrose preference and the forced swim tests. The results indicated that miR124a overexpression exacerbated depression-like behavior. However, an anti-depressant like effect was observed when BDNF or miR124a-silencers (siR124a) were injected into the hippocampus. Importantly, when expressed into the cortex, LV-miR124a, LV-siR124a and LV-BDNF had no effect on depression. Our findings indicate that hippocampal miR124a and its direct target BDNF play an important role in depression-like behavior. Taken together, the current results reveal, for the first time, a potential molecular regulation of miR124a on BDNF, and the pronounced behavioral consequences of this regulation shed light on the mechanisms underlying BDNF anti-depressant potential.

The utility of the zebrafish model in conditioned place preference to assess the rewarding effects of drugs

Substance abuse is a significant public health concern both domestically and worldwide. The persistent use of substances regardless of aversive consequences forces the user to give higher priority to the drug than to normal activities and obligations. The harmful and hazardous use of psychoactive substances can lead to a dependence syndrome. In this regard, the genetic and neurobiological underpinnings of reward-seeking behavior need to be fully understood in order to develop effective pharmacotherapies and other methods of treatment. Animal models are often implemented in preclinical screening for testing the efficacy of novel treatments. Several paradigms exist that model various facets of addiction including sensitization, tolerance, withdrawal, drug seeking, extinction, and relapse. Self-administration and, most notably, conditioned place preference (CPP) are relatively simple tests that serve as indicators of the aforementioned aspects of addiction by means of behavioral quantification. CPP is a commonly used technique to evaluate the motivational effects of compounds and experiences that have been associated with a positive or negative reward, which capitalizes on the basic principles of Pavlovian conditioning. During training, the unconditioned stimulus is consistently paired with a neutral set of environmental stimuli, which obtain, during conditioning, secondary motivational properties that elicit approach behavior in the absence of the unconditioned stimulus. For over 50 years, rodents have been the primary test subjects. However, the zebrafish (Danio rerio) is gaining favor as a valuable model organism in the fields of biology, genetics, and behavioral neuroscience. This paper presents a discussion on the merits, advantages, and limitations of the zebrafish model and its utility in relation to CPP.

Hippocampus-specific deletion of tissue plasminogen activator "tPA" in adult mice impairs depression- and anxiety-like behaviors

Anxiety and depression are multifactorial disorders that have become prominent health problems all over the world. Neurotrophic factors have emerged underlying pathogenesis of these diseases. Although a number of studies indicate that the hippocampus-brain-derived neurotrophic factor (BDNF) may be involved in these psychiatric illnesses, little is known about the molecular mediators of these disorders. In this study we further investigate the role of tissue plasminogen activator (tPA), a serine protease involved in pro-BDNF cleavage to BDNF, in depression and anxiety-like behaviors in adult mice. To address this issue, we investigated the effect of hippocampus tPA manipulation, using viral vectors, on anxiety- and depression-like behaviors, including the marble burying test (MBT), elevated plus maze (EPM), tail suspension test (TST), novelty suppressed feeding (NSF) and forced swim test (FST). Our results showed that tPA knock-down - using lentiviral vectors expressing specific short hairpin RNAs (LV-shRNA) - increased the number of buried marbles together with the digging time in the MBT and decreased the time spent in open the arms of an EPM. In addition, tPA-knock down in the hippocampus increased immobility in the FST and TST, and increased time to feed in the NSF test. These effects were reversed when tPA-over-expressing vectors (LV-tPA) were injected in the hippocampus. We also found that BDNF protein levels were elevated in the hippocampus of mice receiving tPA-expressing vectors. Together, our results imply that tPA manipulation may provide an effective therapeutic intervention for depression and anxiety disorders.

Involvement of nucleus accumbens dopamine D1 receptors in ethanol drinking, ethanol-induced conditioned place preference, and ethanol-induced psychomotor sensitization in mice

RATIONALE

Dopamine D1 receptor (D1R) signaling has been associated to ethanol consumption and reward in laboratory animals.

OBJECTIVES

Here, we hypothesize that this receptor, which is located within the nucleus accumbens (NAc) neurons, modulates alcohol reward mechanisms.

METHODS

To test this hypothesis, we measured alcohol consumption and ethanol-induced psychomotor sensitization and conditioned place preference (CPP) in mice that received bilateral microinjections of small interference RNA (siRNA)-expressing lentiviral vectors (LV-siD1R) producing D1R knock-down. The other group received control (LV-Mock) viral vectors into the NAc.

RESULTS

There were no differences in the total fluid consumed and also no differences in the amount of ethanol consumed between groups prior to surgery. However, after surgery, the LV-siD1R group consumed less ethanol than the control group. This difference was not associated to taste neophobia. In addition, results have shown that down-regulation of endogenous D1R using viral-mediated siRNA in the NAc significantly decreased ethanol-induced behavioral sensitization as well as acquisition, but not expression, of ethanol-induced place preference.

CONCLUSIONS

We conclude that decreased D1R expression into the NAc led to reduced ethanol rewarding properties, thereby leading to lower voluntary ethanol consumption. Together, these findings demonstrate that the D1 receptor pathway within the NAc controls ethanol reward and intake.

The selective metabotropic glutamate receptor 7 allosteric agonist AMN082 prevents reinstatement of extinguished ethanol-induced conditioned place preference in mice

Alcohol dependence is considered a major public health problem in modern societies. The role for glutamatergic neurotransmission in the reinforcing effects of ethanol is becoming increasingly evident. Our previous findings have shown that in rats, the mGluR7 positive allosteric agonist AMN082, but not its allosteric antagonist MMPIP, prevented ethanol consumption and preference in the two-bottle choice paradigm. This study was conducted to determine the effects of AMN082 and MMPIP on the extinction and reinstatement of ethanol-elicited place preference (CPP) in C57BL/6 mice. AMN082 and MMPIP were administered during extinction of ethanol CPP to determine whether mGluR7 signaling is required. Furthermore, the effects of AMN082 and MMPIP on reinstatement of CPP were also evaluated. Finally, spontaneous locomotor activity and ethanol pharmacokinetics were assessed following systemic administration of AMN082 and MMPIP. Our results indicate that mGluR7 pharmacological modulation had no effect on ethanol-elicited CPP extinction. In contrast, mGluR7 activation using AMN082 reduced ethanol-induced CPP reinstatement, an effect reversed by co-administration of MMPIP. Collectively, these results indicate, for the first time, that activation of the mGluR7 receptor is effective in reducing the reinstatement of conditioned rewarding effects of ethanol. Taken together, the efficacy of AMN082 on the various phases of alcohol-CPP could represent an interesting pharmacological approach and could open a new line of research for the development of therapies to reduce ethanol intake in patients.

Regulation of MiR-124, Let-7d, and MiR-181a in the accumbens affects the expression, extinction, and reinstatement of cocaine-induced conditioned place preference

Molecular adaptations underlying drug seeking and relapse remain largely unknown. Studies highlight post-transcriptional modifications mediated by microRNAs (miRNAs) in addiction and other neurological disorders. We have previously shown that chronic cocaine suppresses miR-124 and let-7d and induces the expression of miR-181a in mesolimbic pathway. To further address the role and target gene regulation network of these miRNAs in vivo in cocaine addiction, we developed lentiviral vector (LV)-expressing miRNAs and their corresponding silencers for stable and regulatable miRNA expression. We tested in vivo miRNA gain and loss of function on cocaine-induced conditioned place preference (CPP) by localized LV-miRNA regulation in the nucleus accumbens (NAc). LV-miR-124 and let-7d expression in the NAc attenuates cocaine CPP, whereas LV-miR-181a enhances it. Silencing miRNAs by corresponding LV-miRNA silencers expressing perfect miRNA target sequences inversed this effect on cocaine CPP. Doxycycline treatment for switching off silencer expression abolished the observed behavioral changes. Behavioral changes mediated by LV-miRNA regulation resulted in dynamic alterations in transcription factors, receptors, and other effector genes involved in cocaine-induced plasticity. Our results describe a complex regulatory pathway mediated by miRNAs in cocaine-mediated neuronal adaptations.

Lentiviral vector-mediated gene transfer and RNA silencing technology in neuronal dysfunctions

Lentiviral-mediated gene transfer in vivo or in cultured mammalian neurons can be used to address a wide variety of biological questions, to design animal models for specific neurodegenerative pathologies, or to test potential therapeutic approaches in a variety of brain disorders. Lentiviruses can infect nondividing cells, thereby allowing stable gene transfer in postmitotic cells such as mature neurons. An important contribution has been the use of inducible vectors: the same animal can thus be used repeatedly in the doxycycline-on or -off state, providing a powerful mean for assessing the function of a gene candidate in a disorder within a specific neuronal circuit. Furthermore, lentivirus vectors provide a unique tool to integrate siRNA expression constructs with the aim to locally knockdown expression of a specific gene, enabling to assess the function of a gene in a very specific neuronal pathway. Lentiviral vector-mediated delivery of short hairpin RNA results in persistent knockdown of gene expression in the brain. Therefore, the use of lentiviruses for stable expression of siRNA in brain is a powerful aid to probe gene functions in vivo and for gene therapy of diseases of the central nervous system. In this chapter, I review the applications of lentivirus-mediated gene transfer in the investigation of specific gene candidates involved in major brain disorders and neurodegenerative processes. Major applications have been in polyglutamine disorders, such as synucleinopathies and Parkinson's disease, or in investigating gene function in Huntington's disease, dystonia, or muscular dystrophy. Recently, lentivirus gene transfer has been an invaluable tool for evaluation of gene function in behavioral disorders such as drug addiction and attention-deficit hyperactivity disorder or in learning and cognition.