Biomedical subjects

Dao-Yao He

Publications and source records attributed to Dao-Yao He.

8 recordsLinked to original sources

PubMed2006

Autoregulation of glial cell line-derived neurotrophic factor expression: implications for the long-lasting actions of the anti-addiction drug, Ibogaine.

We recently showed that the up-regulation of the glial cell line-derived neurotrophic factor (GDNF) pathway in the midbrain, is the molecular mechanism by which the putative anti-addiction drug Ibogaine mediates its desirable action of reducing alcohol consumption. Human reports and studies in rodents have shown that a single administration of Ibogaine results in a long-lasting reduction of drug craving (humans) and drug and alcohol intake (rodents). Here we determine whether, and how, Ibogaine exerts its long-lasting actions on GDNF expression and signaling. Using the dopaminergic-like SHSY5Y cell line as a culture model, we observed that short-term Ibogaine exposure results in a sustained increase in GDNF expression that is mediated via the induction of a long-lasting autoregulatory cycle by which GDNF positively regulates its own expression. We show that the initial exposure of cells to Ibogaine or GDNF results in an increase in GDNF mRNA, leading to protein expression and to the corresponding activation of the GDNF signaling pathway. This, in turn, leads to a further increase in the mRNA level of the growth factor. The identification of a GDNF-mediated, autoregulatory long-lasting feedback loop could have important implications for GDNF's potential value as a treatment for addiction and neurodegenerative diseases.

Cell Line, Tumor↗

PubMed2006

The dopamine D3 receptor is part of a homeostatic pathway regulating ethanol consumption.

We recently identified a homeostatic pathway that inhibits ethanol intake. This protective pathway consists of the scaffolding protein RACK1 and brain-derived neurotrophic factor (BDNF). RACK1 translocates to the nucleus after exposure of neurons to ethanol and increases expression of BDNF (McGough et al., 2004). We also found that increasing the levels of BDNF via systemic administration of RACK1 expressed as a Tat-fusion protein (Tat-RACK1) reduces ethanol consumption, whereas reduction of BDNF levels augments this behavior (McGough et al., 2004). Based on these results, we hypothesized that activation of the BDNF receptor TrkB is necessary for the effects of BDNF on ethanol intake and that gene products downstream of BDNF negatively regulate ethanol consumption. Here, we show that inhibition of the BDNF receptor TrkB increases voluntary ethanol consumption in wild-type mice but not in mice lacking one copy of the BDNF gene (BDNF(+/-)). We also find that increases in the levels of BDNF, mediated by ethanol or RACK1, lead to increased dorsal striatal levels of the dopamine D3 receptor (D3R), a gene downstream of BDNF, via activation of the TrkB receptor. Finally, we show that the Tat-RACK1-mediated reduction of ethanol consumption is attenuated by coinjection with either the Trk inhibitor K252a or the dopamine D3R-prefering antagonist U-99194A [5, 6-dimethoxy-2-(di-n-propylamino)indan], suggesting that activation of the BDNF pathway via RACK1 leads to increased expression of the dopamine D3R, which in turn mediates the attenuation of ethanol consumption.

Alcohol Drinking↗

PubMed2006

Homer isoforms differentially regulate cocaine-induced neuroplasticity.

Homer proteins modulate neuroplasticity in excitatory synapses and are dynamically regulated by cocaine. Whereas acute cocaine elevates immediate-early gene (short) isoforms of Homer1 in the nucleus accumbens, withdrawal from repeated cocaine administration downregulates the expression of constitutive Homer1 isoforms. The present study determined whether or not this downregulation in constitutive Homer expression in the accumbens is necessary for enduring alterations in cocaine-induced changes in the brain and behavior. The long vs short Homer isoforms were overexpressed in the rat nucleus accumbens during drug abstinence, and the adaptations elicited by repeated cocaine on glutamate transmission and motor behavior were measured. It was found that both chronic and acute overexpression of constitutive, but not short, Homer isoforms abolished cocaine-induced sensitization of locomotor hyperactivity and prevented the development of glutamate abnormalities in the accumbens, including the reduction in basal extracellular glutamate content and the sensitized glutamate response to a subsequent cocaine challenge injection. Together, these data indicate that the enduring reduction of long Homer isoforms in the nucleus accumbens of cocaine-withdrawn rats is necessary for the expression of cocaine-induced neuroplasticity.

Anesthetics, Local↗

PubMed2005

Glial cell line-derived neurotrophic factor mediates the desirable actions of the anti-addiction drug ibogaine against alcohol consumption.

Alcohol addiction manifests as uncontrolled drinking despite negative consequences. Few medications are available to treat the disorder. Anecdotal reports suggest that ibogaine, a natural alkaloid, reverses behaviors associated with addiction including alcoholism; however, because of side effects, ibogaine is not used clinically. In this study, we first characterized the actions of ibogaine on ethanol self-administration in rodents. Ibogaine decreased ethanol intake by rats in two-bottle choice and operant self-administration paradigms. Ibogaine also reduced operant self-administration of ethanol in a relapse model. Next, we identified a molecular mechanism that mediates the desirable activities of ibogaine on ethanol intake. Microinjection of ibogaine into the ventral tegmental area (VTA), but not the substantia nigra, reduced self-administration of ethanol, and systemic administration of ibogaine increased the expression of glial cell line-derived neurotrophic factor (GDNF) in a midbrain region that includes the VTA. In dopaminergic neuron-like SHSY5Y cells, ibogaine treatment upregulated the GDNF pathway as indicated by increases in phosphorylation of the GDNF receptor, Ret, and the downstream kinase, ERK1 (extracellular signal-regulated kinase 1). Finally, the ibogaine-mediated decrease in ethanol self-administration was mimicked by intra-VTA microinjection of GDNF and was reduced by intra-VTA delivery of anti-GDNF neutralizing antibodies. Together, these results suggest that GDNF in the VTA mediates the action of ibogaine on ethanol consumption. These findings highlight the importance of GDNF as a new target for drug development for alcoholism that may mimic the effect of ibogaine against alcohol consumption but avoid the negative side effects.

Alcoholism↗

PubMed2004

RACK1 and brain-derived neurotrophic factor: a homeostatic pathway that regulates alcohol addiction.

Alcoholism is a devastating disease that manifests as uncontrolled drinking. Consumption of alcohol is regulated by neurochemical systems within specific neural circuits, but endogenous systems that may counteract and thus suppress the behavioral effects of ethanol intake are unknown. Here we demonstrate that BDNF plays a role in reducing the behavioral effects of ethanol, including consumption, in rodents. We found that decreasing the levels of BDNF leads to increased behavioral responses to ethanol, whereas increases in the levels of BDNF, mediated by the scaffolding protein RACK1, attenuate these behaviors. Interestingly, we found that acute exposure of neurons to ethanol leads to increased levels of BDNF mRNA via RACK1. Importantly, acute systemic administration of ethanol and voluntary ethanol consumption lead to increased levels of BDNF expression in the dorsal striatum. Taken together, these findings suggest that RACK1 and BDNF are part of a regulatory pathway that opposes adaptations that lead to the development of alcohol addiction.

Alcohol Drinking↗

PubMed2003

Pituitary adenylate cyclase-activating polypeptide (PACAP(1-38)) enhances N-methyl-D-aspartate receptor function and brain-derived neurotrophic factor expression via RACK1.

We recently identified a novel mechanism for modulation of the phosphorylation state and function of the N-methyl-d-aspartate (NMDA) receptor via the scaffolding protein RACK1. We found that RACK1 binds both the NR2B subunit of the NMDA receptor and the nonreceptor protein-tyrosine kinase, Fyn. RACK1 inhibits Fyn phosphorylation of NR2B and decreases NMDA receptor-mediated currents in CA1 hippocampal slices (Yaka, R., Thornton, C., Vagts, A. J., Phamluong, K., Bonci, A., and Ron, D. (2002) Proc. Natl. Acad. Sci. U. S. A. 99, 5710-5715). Here, we identified the signaling cascade by which RACK1 is released from the NMDA receptor complex and identified the consequences of the dissociation. We found that activation of the cAMP/protein kinase A pathway in hippocampal slices induced the release of RACK1 from NR2B and Fyn. This resulted in the induction of NR2B phosphorylation and the enhancement of NMDA receptor-mediated activity via Fyn. We identified the neuropeptide, pituitary adenylate cyclase activating polypeptide (PACAP(1-38)), as a ligand that induced phosphorylation of NR2B and enhanced NMDA receptor potentials. Finally, we found that activation of the cAMP/protein kinase A pathway induced the movement of RACK1 to the nuclear compartment in dissociated hippocampal neurons. Nuclear RACK1 in turn was found to regulate the expression of brain-derived neurotrophic factor induced by PACAP(1-38). Taken together our results suggest that activation of adenylate cyclase by PACAP(1-38) results in the release of RACK1 from the NMDA receptor and Fyn. This in turn leads to NMDA receptor phosphorylation, enhanced activity mediated by Fyn, and to the induction of brain-derived neurotrophic factor expression by RACK1.

Adenylyl Cyclases↗

PubMed2003

Cellular adaptation to chronic ethanol results in altered compartmentalization and function of the scaffolding protein RACK1.

BACKGROUND: Previously, we found that acute ethanol induces the translocation of the scaffolding protein RACK1 to the nucleus. Recently, we found that nuclear RACK1 mediates acute ethanol induction of immediate early gene c-fos expression. Alterations in gene expression are thought to lead to long-term changes that ultimately contribute to the development of alcohol addiction and toxicity. Therefore, we sought to determine the effects of chronic exposure of cells to ethanol on the cellular compartmentalization of RACK1 and on c-fos messenger RNA (mRNA) and protein expression. METHODS: Rat C6 glioma cells were used as the cell culture model. Immunohistochemistry was implemented to visualize the localization of RACK1 and to monitor the protein level of c-fos. Reverse-transcription polymerase chain reaction was used to measure c-fos mRNA levels. The Tat-protein transduction method was used to transduce recombinant Tat-RACK1 into cells as previously described. RESULTS: Chronic exposure of cells to 200 mM ethanol for 24 and 48 hr resulted in the gradual re-distribution of RACK1 out of the nucleus. It is interesting to note that acute ethanol re-challenge immediately after chronic treatment did not result in RACK1 translocation to the nucleus, and nuclear compartmentalization of RACK1 in response to acute ethanol was detected only after 24 hr of withdrawal. Similar patterns were obtained for c-fos expression. Chronic exposure to ethanol did not result in an increase in mRNA or protein levels of c-fos. Furthermore, acute ethanol exposure did not increase c-fos protein levels in cells that were first treated chronically with ethanol. However, transduction of exogenous RACK1 expressed as a Tat-fusion protein was able to rescue c-fos mRNA expression after chronic ethanol exposure. CONCLUSIONS: Our data suggest that RACK1 nuclear compartmentalization and ethanol-induced c-fos expression are transient and are desensitized to ethanol during prolonged exposure to high concentrations. The desensitization is temporary, and RACK1 can respond to acute ethanol treatment after a 24-hr withdrawal period. Our data further suggest that the altered compartmentalization of RACK1 leads to differences in c-fos expression upon acute or chronic exposure to ethanol. In summary, RACK1 is an important molecular mediator of the acute and chronic actions of ethanol on the expression of c-fos. These findings could have implications for the molecular signaling pathways leading to pathologic states associated with alcoholism, including toxicity.

Adaptation, Physiological↗

PubMed2002

Ethanol induces gene expression via nuclear compartmentalization of receptor for activated C kinase 1.

Scaffolding proteins such as receptor for activated C kinase (RACK) 1 are involved in the targeting of signaling proteins and play an important role in the regulation of signal transduction cascades. Recently, we found that in cultured cells and in vivo, acute ethanol exposure induces the nuclear compartmentalization of RACK1. To elucidate a physiological role for nuclear RACK1, the Tat protein transduction system was used to transduce RACK1 and RACK1-derived fragments into C6 glioma cells. We found that nuclear RACK1 is mediating the induction of the immediate early gene c-fos expression induced by ethanol. First, transduction of full-length RACK1 (Tat-RACK1) resulted in the induction of c-fos expression and enhancement of ethanol activities. Second, we determined that the C terminus of RACK1 (Tat-RACK1DeltaN) is mediating transcription. Third, we identified a dominant negative fragment of RACK1 that inhibited the nuclear compartmentalization of endogenous RACK1 and inhibited ethanol-induction of c-fos mRNA and protein expression. Last, acute exposure to ethanol or transduction of full-length Tat-RACK1 resulted in an increase in mRNA levels of an activator protein 1 site-containing gene, PAC1 (pituitary adenylate cyclase-activating polypeptide receptor type I), suggesting that nuclear RACK1 is involved in the regulation of the expression of genes that are altered upon acute ethanol treatment. These results may therefore have important implications for the study of alcohol addiction.

Animals↗