Heteroreceptor complexes formed by dopamine D1, histamine H3 and N-methyl-D-aspartate glutamate receptors as targets to prevent neuronal death in Alzheimer's disease

Alzheimer’s disease (AD) is a neurodegenerative disorder causing progressive memory loss and cognitive dysfunction. Anti-AD strategies targeting cell receptors consider them as isolated units. However, many cell surface receptors cooperate and physically contact each other forming complexes having different biochemical properties than individual receptors. We here report the discovery of dopamine D , histamine H , and N-methylD-aspartate (NMDA) glutamate receptor heteromers in heterologous systems and in rodent brain cortex. Heteromers were detected by coimmunoprecipitation and in situ proximity ligation assays (PLA) in the rat cortex where H receptor agonists, via negative cross-talk, and H receptor antagonists, via cross-antagonism, decreased D receptor agonist signaling determined by ERK1/2 or Akt phosphorylation and counteracted D receptormediated excitotoxic cell death. Both D and H receptor antagonists also counteracted NMDA toxicity suggesting a complex interaction between NMDA receptors and D -H receptor heteromer function. Likely due to heteromerization, H receptors act as allosteric regulator for D and NMDA receptors. By bioluminescence resonance energy transfer (BRET), we demonstrated that D or H receptors form heteromers with NR1A/NR2B NMDA receptor subunits. D -H -NMDA receptor complexes were confirmed by BRET combined with fluorescence complementation. The endogenous expression of complexes in mouse cortex was determined by PLA and similar expression was observed in wild-type and APP/PS1 mice. Consistent with allosteric receptor-receptor interactions within the complex, H receptor antagonists reduced NMDA or D receptor-mediated excitotoxic cell death in cortical organotypic cultures. Moreover, H receptor antagonists reverted the toxicity induced by ß -amyloid peptide. Thus, histamine H receptors in D -H -NMDA heteroreceptor complexes arise as promising targets to prevent neurodegeneration

Human depression: a new approach in quantitative psychiatry

The biomolecular approach to major depression disorder is explained by the different steps that involve cell membrane viscosity, Gsα protein and tubulin. For the first time it is hypothesised that a biomolecular pathway exists, moving from cell membrane viscosity through Gsα protein and Tubulin, which can condition the conscious state and is measurable by electroencephalogram study of the brain's γ wave synchrony

Gene Expression Changes in the Prefrontal Cortex, Anterior Cingulate Cortex and Nucleus Accumbens of Mood Disorders Subjects That Committed Suicide

Suicidal behaviors are frequent in mood disorders patients but only a subset of them ever complete suicide. Understanding predisposing factors for suicidal behaviors in high risk populations is of major importance for the prevention and treatment of suicidal behaviors. The objective of this project was to investigate gene expression changes associated with suicide in brains of mood disorder patients by microarrays (Affymetrix HG-U133 Plus2.0) in the dorsolateral prefrontal cortex (DLPFC: 6 Non-suicides, 15 suicides), the anterior cingulate cortex (ACC: 6NS, 9S) and the nucleus accumbens (NAcc: 8NS, 13S). ANCOVA was used to control for age, gender, pH and RNA degradation, with P≤0.01 and fold change±1.25 as criteria for significance. Pathway analysis revealed serotonergic signaling alterations in the DLPFC and glucocorticoid signaling alterations in the ACC and NAcc. The gene with the lowest p-value in the DLPFC was the 5-HT2A gene, previously associated both with suicide and mood disorders. In the ACC 6 metallothionein genes were down-regulated in suicide (MT1E, MT1F, MT1G, MT1H, MT1X, MT2A) and three were down-regulated in the NAcc (MT1F, MT1G, MT1H). Differential expression of selected genes was confirmed by qPCR, we confirmed the 5-HT2A alterations and the global down-regulation of members of the metallothionein subfamilies MT 1 and 2 in suicide completers. MTs 1 and 2 are neuro-protective following stress and glucocorticoid stimulations, suggesting that in suicide victims neuroprotective response to stress and cortisol may be diminished. Our results thus suggest that suicide-specific expression changes in mood disorders involve both glucocorticoids regulated metallothioneins and serotonergic signaling in different regions of the brain

Characteristics of [3H]inositol(1,3,4,5)tetrakisphosphate recognition sites in human cerebellar membranes

The characteristics of specific [3H]Ins(1,3,4,5)P4 binding sites in human cerebellar membranes were determined in this study. Binding rapidly reached steady state, possessed a pH optimum of 4.5-5.1 and was greater in the absence of BSA than in its presence. Heparin inhibited both specific and pseudospecific binding of the ligand, whereas only the specific binding was inhibited by non-radioactive Ins(1,3,4,5)P4. Calcium at a concentration of 1 mM, reduced binding by 27%. Competition studies with other inositol phosphates showed specificity for Ins(1,3,4,5)P4 with a pI50 value of 6.87 and a Hill coefficient of 0.27, indicating two sites. Ins(1,2,5,6)P4, Ins(1,3,4,6)P5, Ins(3,4,5,6)P4 displaced binding with IC50 values ranging from 0.1-1 microM, Ins(1,2,5,6)P4 and Ins(1,3,4,5,6)P5 being the most potent. Ins(1,4)P2 and Ins(1,5,6)P3 had lesser effects on binding. Rosenthal analysis of [3H]Ins(1,3,4,5)P4 saturation binding data at low ligand concentrations gave a KD of 27 nM and a Bmax of 33 pmol/mg protein. It is concluded that [3H]Ins(1,3,4,5)P4 binding sites in human cerebellar membranes have similar characteristics to these sites reported in the literature in animal cerebellar tissue, but are in greater abundance

Neurotransmitters, signal transduction and second-messengers in Alzheimer's disease

It has long been assumed that widespread changes in postsynaptic neurotransmitter receptor function are not a feature of the disrupted neurotransmission seen in the brains with Alzheimer's disease (AD). However, recent evidence from postmortem brain and fibroblast studies suggests that both the neurotransmitter receptor/G-protein-modulated adenylyl cyclase and the phosphatidylinositol hydrolysis signal transduction cascades are disrupted in AD. Such disruptions may severely limit the functional integrity of key receptor types and undermine pharmacological attempts to ameliorate disease symptomatology through neurotransmitter replacement strategies. The involvement of some signalling mechanisms in the regulation of beta-amyloid precursor protein metabolism suggests also that disrupted signal transduction may exacerbate AD pathology

Characterization of [3H]inositol 1,4,5-trisphosphate binding sites in human temporal cortical and cerebellar membranes

The characteristics of [3H]Ins(1,4,5)P3 binding to human temporal cortical and cerebellar membranes have been determined and compared with the binding to calf cerebellar membranes. Association and dissociation of ligand was very rapid, k1 and k-1 values of the order of 7 x 10(7) M-1 min-1 and 0.2 min-1, respectively. KD values were 2.7 and 3.5 nM for temporal cortex and cerebellum, respectively. The corresponding Bmax values were 165 and 482 fmol/mg protein. Binding was influenced in a biphasic manner by calcium. The temporal cortical binding was inhibited by Ins(1,4,5)P3 and analogues with the following IC50 values (nM): Ins(1,4,5)P3 9.5 and 6.2 (two different salts from different sources), Ins(2,4,5)P3 42, Ins(1,3,4,5)P4 670, Ins(1,2,5,6)P4 2620, Ins(3,4,5,6)P4 4300, Ins(1,3,4,5,6)P5 5490, InsP(6)5280, Ins(4,5)P2 2600, Ins(1)P 3300, with the IC50 values for Ins(1,5,6)P3, Ins(1,4)P2 and Ins(4)P being > 25 microM. The IC50 value for heparin was 2.1 micrograms/ml. A similar pattern was seen in the cerebellum. In both tissues, the Hill slopes were near unity for all compounds except Ins(3,4,5,6)P4, where the slope was 0.4. The calf cerebellum had a similar ligand specificity (although the potency was generally lower) when values were expressed relative to that of Ins(1,4,5)P3, with the possible exception of Ins(1,3,4,5)P4, which had a greater relative potency. These data would suggest that in the human temporal cortex and cerebellum, [3H]Ins(1,4,5)P3 binding sites are expressed in different densities, but have similar properties. There may, however, be species differences in the [3H]Ins(1,4,5)P3 recognition site