RNA interference-mediated inhibition of brain-derived neurotrophic factor expression increases cocaine's cytotoxicity in cultured cells

7,8-Dihydroxyflavone blocks the development of behavioral sensitization to MDPV, but not to cocaine: Differential role of the BDNF-TrkB pathway

3,4-Methylenedioxypyrovalerone (MDPV) acts as a dopamine transporter blocker and exerts powerful psychostimulant effects. In this study we aimed to investigate the bidirectional cross-sensitization between MDPV and cocaine, as well as to evaluate the role of the BDNF-TrkB signaling pathway in the development of locomotor sensitization to both drugs. Mice were treated with MDPV (1.5 mg/kg) or cocaine (10 or 15 mg/kg) once daily for 5 days. After withdrawal (10 days), animals were challenged with cocaine (8 mg/kg) or MDPV (1 mg/kg). For biochemical determinations, MDPV (1.5 mg/kg) or cocaine (15 mg/kg) were administered acutely or repeatedly, and BDNF, D3R and G9a transcription levels as well as pro- and mature BDNF protein levels were determined. Our results demonstrate that repeated administration of MDPV or cocaine sensitizes to cocaine and MDPV locomotor effects. After an acute or a repeated exposure to MDPV, cortical mRNA BDNF levels were increased, while a decrease in mBDNF protein levels in the nucleus accumbens 2 h after repeated exposure was evidenced. Interestingly, such decline was involved in the development of locomotor sensitization, thus the pretreatment with 7,8-dihydroxyflavone (10 mg/kg), a TrkB agonist, blocked the development of sensitization to MDPV but not to cocaine, for which no changes in the BDNF-TrkB signaling pathway were observed at early withdrawal. In conclusion, a bidirectional cross-sensitization between MDPV and cocaine was evidenced. Our findings suggest that decreased BDNF-TrkB signaling has an important role in the behavioral sensitization to MDPV, pointing TrkB modulation as a target to prevent MDPV sensitization.

siRNA-mediated inhibition of endogenous brain‑derived neurotrophic factor gene modulates the biological behavior of HeLa cells

Brain-derived neurotrophic factor (BDNF) is expressed in a number of neural and non-neuronal tumors. The present study investigated the effect of endogenous BDNF on the biological behavior of cervix cancer cells using small interfering RNA (siRNA). HeLa, a cervix cancer cell line with high expression of BDNF, was used as a living model to screen out the effective sequences of short hairpin RNA of the BDNF gene, and the effects of RNA interference on proliferation, apoptosis, migration and invasion of these cells were evaluated. Among the 4 siRNAs examined, siRNA1 caused a 99% reduction in the relative BDNF mRNA level, while a 58% decrease in the relative BDNF protein level (p<0.01) was noted, and thus this siRNA was selected as the most efficient for use in the present study. In subsequent experiments, MTT assay revealed that BDNF silencing caused marked inhibition of HeLa cell proliferation while Hoechst 33258 staining assay demonstrated apoptosis-related changes in cell morphology. Downregulation of BDNF expression induced cell cycle arrest in the G1 phase as shown by flow cytometry. As indicated by Transwell migration and invasion assays, downregulation of BDNF expression suppressed the migratory and invasive capabilities of the HeLa cells. Together, our data revealed that BDNF modulates the proliferation, apoptosis, migratory and invasive capabilities of HeLa cells. BDNF siRNA may represent a novel therapy or drug target for preventing the tumorigenesis of cervical cancer.

Prefrontal cortical BDNF: A regulatory key in cocaine- and food-reinforced behaviors

Brain-derived neurotrophic factor (BDNF) affects synaptic plasticity and neural structure and plays key roles in learning and memory processes. Recent evidence also points to important, yet complex, roles for BDNF in rodent models of cocaine abuse and addiction. Here we examine the role of prefrontal cortical (PFC) BDNF in reward-related decision making and behavioral sensitivity to, and responding for, cocaine. We focus on BDNF within the medial and orbital PFC, its regulation by cocaine during early postnatal development and in adulthood, and how BDNF in turn influences responding for drug reinforcement, including in reinstatement models. When relevant, we draw comparisons and contrasts with experiments using natural (food) reinforcers. We also summarize findings supporting, or refuting, the possibility that BDNF in the medial and orbital PFC regulate the development and maintenance of stimulus-response habits. Further investigation could assist in the development of novel treatment approaches for cocaine use disorders.

Nonviral vectors for the delivery of small interfering RNAs to the CNS

While efficient methods for cell line transfection are well described, for primary neurons a high-yield method different from those relying on viral vectors is lacking. Viral vector-based primary neuronal infection has several drawbacks, including complexity of vector preparation, safety concerns and the generation of immune and inflammatory responses, when used in vivo. This article will cover the different approaches that are being used to efficiently deliver genetic material (both DNA and small interfering RNA) to neuronal tissue using nonviral vectors, including the use of cationic lipids, polyethylenimine derivatives, dendrimers, carbon nanotubes and the combination of carbon-made nanoparticles with dendrimers. The effectiveness, both in vivo and in vitro, of the different methods to deliver genetic material to neural tissue is discussed.

Repeated stress prevents cocaine-induced activation of BDNF signaling in rat prefrontal cortex

In this report we provide evidence that repeated stress prevents cocaine-induced activation of BDNF expression and signaling in rat prefrontal cortex. A single injection of cocaine up-regulates BDNF expression in sham (i.e. unstressed) rats but not in repeatedly stressed rats. Similarly, the expression as well as trafficking of the high affinity BDNF receptor trkB promoted by the psychostimulant is impaired in chronically-stressed rats challenged with cocaine. Moreover, among the different intracellular signaling pathways that can be activated by the neurotrophin, i.e. ERK1/2-, Akt- and PLCgamma-pathway, we found that cocaine is able to selectively activate the ERK1/2 pathway in sham animals, but not in rats exposed to repeated stress. Notably, such changes take place in chronically-stressed animals although they still retain the ability to increase neuronal activity as measured by the enhancement of Arc gene expression. In summary, we have demonstrated that stress globally interferes with BDNF-mediated signaling responses to cocaine challenge, providing key insights into the molecular basis of stress-cocaine interaction and indicating the critical role of the prefrontal cortex in mediating such interaction.

Effects of psychostimulants on neurotrophins implications for psychostimulant-induced neurotoxicity

It is well documented that psychostimulants may alter neuronal function and neurotransmission in the brain. Although the mechanism of psychostimulants is still unknown, it is known that these substances increase extracellular level of several neurotransmitters including dopamine (DA), serotonin, and norepinephrine by competing with monoamine transporters and can induce physical tolerance and dependence. In addition to this, recent findings also suggest that psychostimulants may damage brain neurons through mechanisms that are still under investigation. In the recent years, it has been demonstrated that almost all psychostimulants are able to affect a class of proteins, called neurotrophins, in the peripheral and central nervous system (CNS). Neurotrophins, such as nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF), have relevant action on neurons involved in psychostimulant action, such as DA and serotonergic neurons, and can play dual roles: first, in neuronal survival and death, and, second, in activity-dependent plasticity. In this review, we will focalize on the effects of psychostimulants on this class of proteins, which may be implicated, at least in part, in the mechanism of the psychostimulant-induced neurotoxicity. Moreover, since altered neurotrophins may participate in the pathogenesis of psychiatric disorders and psychiatric disorders are common in drug users, one plausible hypothesis is that psychostimulants can cause psychosis through interfering with neurotrophins synthesis and utilization by CNS neurons.