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.

The role of immune responses in tumor development is a central issue for tumor biology and immunology. IL-17 is an important cytokine for inflammatory and autoimmune diseases. Although IL-17 producing cells are detected in cancer patients and tumor bearing mice, the role of IL-17 in tumor development is controversial and mechanisms remain to be fully elucidated. In the current study, we found that the development of tumors was inhibited in IL-17 receptor A (IL-17R) deficient mice. A defect in IFN-γ receptor increased tumor growth whereas tumor growth was inhibited in mice that were deficient in both IL-17R and IFN-γR compared to wild type animals. Further experiments showed that neutralization of IL-17 by antibodies inhibited tumor growth in wild type mice whereas systemic administration of IL-17 promoted tumor growth. The IL-17R deficiency increased CD8 T cell infiltration whereas it reduced the infiltration of myeloid derived suppressor cells (MDSC) in tumors. In contrast, administration of IL-17 inhibited CD8 T cell infiltration and increased MDSC in tumors. Further analysis indicated that IL-17 was required for the development and tumor promoting activity of MDSC in tumor bearing mice. These data demonstrate that IL-17 mediated responses promote tumor development through the induction of tumor promoting microenvironments at tumor sites. IL-17 mediated regulation of MDSC is a primary mechanism for its tumor promoting effects. The study provides novel insights into the role of IL-17 in tumor development and has major implications for targeting IL-17 in treatment of tumors.

Allergen-induced contact hypersensitivity (CHS) is a T cell-mediated delayed-type immune response which has been considered to be primarily mediated by CD8+ T cytotoxic type I (Tc1) cells. IFN-γ, the prototype Tc1 (Th1) cytokine, has been implicated as the primary inflammatory cytokine for CHS. In this study, we demonstrate that neutralization of IL-17 rather than IFN-γ suppresses the elicitation of CHS. The suppression does not result from inhibition of the proliferation of allergen-activated T cells. Allergen sensitization induces the development of distinct CD8+ T cell subpopulations that produce IFN-γ or IL-17. Although CD8+ IL-17-producing cells are stimulated by IL-23, they are inhibited by IL-12, a prototypical stimulator of IFN-γ-producing Tc1 cells. This indicates that CD8+ IL-17-producing cells are distinct from Tc1 cells and are important in effector functions at the elicitation of CHS. These studies provide insights into a novel mechanism for CHS.

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. The ionotropic glutamate receptor subtype, N-methyl-D-as-1 plays an essential role in neuronal development, excitotoxicity, synaptic plasticity, and learning and memory (2). The ligand-gated NMDA receptor channel is a heteromer comprised of NR1 and at least one of four NR2 subunits (A-D) (3). The cytoplasmic tail of the NR2B subunit is phosphorylated on tyrosine residues (4) and is the most abundant tyrosine-phosphorylated protein in the postsynaptic density (5). Phosphorylation of NMDA receptor subunits regulates the activity of the channel (6). Specifically, application of a tyrosine kinase inhibitor causes a progressive decrease in NMDA receptor-mediated currents, and conversely, inhibition of protein-tyrosine phosphatases results in an increase in NMDA receptor-mediated currents (7). Subsequent studies have identified the Src family of protein-tyrosine kinases (PTKs) as enzymes that phosphorylate the NR2 subunits, regulating NMDA receptor activities (6 -8). Hence, modulation of NMDA receptor phosphorylation by Src family protein-tyrosine kinases is likely to play an important role in modulating glutamate-mediated pathways. In the recent years it has become increasingly apparent that the formation of localized signaling complexes, which include receptors, kinases, phosphatases and their substrates, are highly important for the regulation of signal transduction cascades (9, 10). Scaffolding proteins play a major role in the assembly of such signaling complexes (11). Recently, we identified the scaffolding protein RACK1 as a novel regulator of the phosphorylation state and function of the NMDA receptor. We found that RACK1 interacts with both the cytoplasmic tail of the NR2B subunit and Fyn and inhibits the ability of Fyn to phosphorylate the NR2B subunit and consequently inhibits NMDA receptor-mediated excitatory postsyna...

We previously found that brain-derived neurotrophic factor (BDNF)-haplodeficient mice exhibit greater ethanol-induced place preference and psychomotor sensitization, and greater ethanol consumption after deprivation, than control mice. We further observed that, in mice, voluntary ethanol intake increases BDNF expression in the dorsal striatum (DS). Here, we determined whether BDNF within the DS regulates ethanol self-administration in Long-Evans rats trained to self-administer a 10% ethanol solution. We observed a greater increase in BDNF expression after ethanol self-administration in the dorsolateral striatum (DLS) than in the dorsomedial striatum (DMS). We further found that downregulation of endogenous BDNF using viral-mediated siRNA in the DLS, but not in the DMS, significantly increased ethanol self-administration. Infusion of exogenous BDNF (0.25 g/l/side into the DMS; 0.25 and 0.75 g/l/side into the DLS) attenuated responding for ethanol when infused 3 h before the beginning of the self-administration session. Although the decrease in ethanol intake was similar in the DLS and DMS, BDNF infused in the DLS, but not in the DMS, induced an early termination of the drinking episode. Furthermore, the action of BDNF in the DLS was specific for ethanol, as infusion of the neurotrophic factor in the DMS, but not DLS, resulted in a reduction of sucrose intake. Together, these findings demonstrate that the BDNF pathway within the DLS controls the level of ethanol self-administration. Importantly, our results suggest that an endogenous signaling pathway within the same brain region that mediates drug-taking behavior also plays a critical role in gating the level of ethanol intake.

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 selfadministration 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 selfadministration 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.

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).

Hapten induced contact hypersensitivity (CHS) in the skin is a delayed type cellular immune response which can be mediated by CD8+ T cells that produce IFN-γ or IL-17. However, mechanisms for these cytokines in the elicitation of CHS remain to be fully elucidated. Here we show that adoptive transfer of CHS with hapten primed wild type CD8+ T cells is reduced in IFN-γR−/− or IL-17R−/− mice compared to wild type controls. The infiltration of granulocytes and macrophages in the hapten challenged skin of IL-17R−/− recipients is significantly reduced whereas it is less affected in IFN-γR−/− recipients although CD8+ T cell infiltration is inhibited in both recipients. In contrast, the activity of reactive oxidative species is significantly inhibited in IFN-γR−/− but is less affected in IL-17R−/− recipients. Further analysis reveals that the expression of chemokines and cytokines is differentially regulated in the hapten challenged skin of IFN-γR−/− or IL-17R−/− recipients compared to wild type controls. Interestingly, injection of recombinant IL-17 in the skin induces inflammation with a high level of leukocyte infiltration whereas injection of IFN-γ induces inflammation with a high level of reactive oxidative species. Moreover, neutralization of IL-17 in IFN-γR−/− or IFN-γ in IL-17R−/− mice further suppresses the adoptive transfer of CHS by hapten primed wild type CD8+ T cells. The study demonstrates that IFN-γ and IL-17 mediate the elicitation of CHS by different mechanisms and that both cytokines are required for optimal responses. This outcome improves understanding of pathogenesis and provides new insights into therapeutic strategies for CHS.