Inhibiting 5-hydroxytryptamine receptor 3 alleviates pathological changes of a mouse model of Alzheimer's disease

Extracellular amyloid beta(Aβ) plaques are main pathological feature of Alzheimer’s disease.However,the specific type of neuro ns that produce Aβ peptides in the initial stage of Alzheimer’s disease are unknown.In this study,we found that 5-hydroxytryptamin receptor 3A subunit(HTR3A) was highly expressed in the brain tissue of transgenic amyloid precursor protein and presenilin-1 mice(an Alzheimer’s disease model) and patients with Alzheimer’s disease.To investigate whether HTR3A-positive interneurons are associated with the production of Aβ plaques,we performed double immunostaining and found that HTR3A-positive interneurons were clustered around Aβ plaques in the mouse model.Some amyloid precursor protein-positive or β-site amyloid precursor protein cleaving enzyme-1-positive neurites near Aβ plaques were co-localized with HTR3A interneurons.These results suggest that HTR3A-positive interneurons may partially contribute to the generation of Aβ peptides.We treated 5.0-5.5-month-old model mice with tro pisetron,a HTR3 antagonist,for 8 consecutive weeks.We found that the cognitive deficit of mice was partially reversed,Aβ plaques and neuroinflammation we re remarkably reduced,the expression of HTR3 was remarkably decreased and the calcineurin/nuclear factor of activated T-cell 4 signaling pathway was inhibited in treated model mice.These findings suggest that HTR3A interneurons partly contribute to generation of Aβ peptide at the initial stage of Alzheimer’s disease and inhibiting HTR3 partly reve rses the pathological changes of Alzheimer’s disease.

Bioassay-guided isolation of saikosaponins with agonistic activity on 5-hydroxytryptamine 2C receptor from Bupleurum chinense and their potential use for the treatment of obesity

5-Hydroxytryptamine 2C(5-HT2C) receptor is one of the major targets of anti-obesity agents, due to its role in regulation of appetite. In the present study, the 70% EtO H extract of the roots of Bupleurum chinense was revealed to have agonistic activity on 5-HT2 C receptor, and the subsequent bioassay-guided isolation led to identification of several saikosaponins as the active constituents with 5-HT2 C receptor agonistic activity in vitro and anti-obesity activity in vivo. The new compound, 22-oxosaikosaponin d(1), was determined by extensive spectroscopic analyses(HR-ESI-MS, IR, and 1D and 2D NMR). The primary structure-activity relationship study suggested that the intramolecular ether bond between C-13 and C-28 and the number of sugars at C-3 position were closely related to the 5-HT2 C receptor agonistic activity. Saikosaponin a(3), the main saponin in B. chinense, showed obviously agonistic activity on 5-HT2 C receptor with an EC50 value of 21.08 ± 0.33 μmol×L^(–1) in vitro and could reduce food intake by 39.1% and 69.2%, and weight gain by 13.6% and 16.4%, respectively, at 3.0 and 6.0 mg×kg^(–1) in vivo. This investigation provided valuable information for the potential use of B. chinense as anti-obesity agent.

Domesticated HERV-W env contributes to the activation of the small conductance Ca^(2+)-activated K^(+)type 2 channels via decreased 5-HT4 receptor in recent-onset schizophrenia

The human endogenous retroviruses type W family envelope(HERV-W env)gene is located on chromosome 7q21-22.Our previous studies show that HERV-W env is elevated in schizophrenia and HERV-W env can increase cal-cium influx.Additionally,the 5-HTergie system and particularly 5-hydroxytryptamine(5-HT)receptors play a prominent role in the pathogenesis and treatment of schizophrenia.5-hydroxytryptamine receptor 4(5-HT4R)agonist can block calcium channels.However,the underlying relationship between HERV-W env and 5-HT4R in the etiology of schizophrenia has not been revealed.Here,we used enzyme-linked immunosorbent assay to detect the concentration of HERV-W env and 5-HT4R in the plasma of patients with schizophrenia and we found that there were decreased levels of 5-HT4R and a negative correlation between 5-HT4R and HERV-W env in schizophrenia.Overexpression of HERV-W env decreased the transcription and protein levels of 5-HT4R but increased small conductance Ca^(2+)-activated K^(+)type 2 channels(SK2)expression levels.Further studies revealed that HERV-w env could interact with 5-HT4R.Additionally,luciferase assay showed that an essential region(-364 to-176 from the transcription start site)in the SK2 promoter was required for HERV-W env-induced SK2 expression.Importantly,5-HT4R participated in the regulation of SK2 expression and promoter activity.Electrophysiological recordings suggested that HERV-Wenv could increase SK2 channel currents and the increase of SK2 currents was inhibited by 5-HT4R.In condusion,HERV-W env could activate SK2 channels via decreased 5-HT4R,which might exhibit a novel mechanism for HERV-Wenv to influence neuronal activity in schizophrenia.

3,4’,5-三羟基茂-3-β-单-D-葡萄糖甙抑制血小板组胺诱导的兔主动脉条收缩

将花生四烯酸激活的血小板加入兔主动脉条浴槽液中引起动脉条明显收缩。苯海拉明，ＴＸＡ２受体阻断剂或３，４’，５－三羟基芪－３－β－单－Ｄ－葡萄糖甙（Ｐｏｌ）均可减弱此种收缩作用，以苯海拉明效价最高，提示此血管条收缩主要归因于血小板释放的组胺，其次为ＴＸＡ２；Ｐｏｌｌ．４×１０－３ｍｏｌ／Ｌ及４．２×１０－３ｍｏｌ／Ｌ有显著抑制血小板诱导主动脉条的收缩作用。Ｐｏｌ使组胺收缩血管条量效曲线不平行右移，效能下降，具有非竞争性抑制组胺收缩血管作用。

Switching-on of serotonergic calcium signaling in activated hepatic stellate cells

AIM:To investigate serotonergic Ca 2+ signaling and the expression of 5-hydroxytryptamine(5-HT) receptors,as well as Ca 2+ transporting proteins,in hepatic stellate cells(HSCs) . METHODS:The intracellular Ca 2+ concentration([Ca 2+ ]i) of isolated rat HSCs was measured with a fluorescence microscopic imaging system.Quantitative PCR was per-formed to determine the transcriptional levels of 5-HT receptors and endoplasmic reticulum(ER) proteins involved in Ca 2+ storage and release in cultured rat HSCs. RESULTS:Distinct from quiescent cells,activated HSCs exhibited[Ca 2+ ]i transients following treatment with 5-HT,which was abolished by U-73122,a phospholipase C inhibitor.Upregulation of 5-HT2A and 5-HT2B receptors,but not 5-HT3,was prominent during trans-differentiation of HSCs.Pretreatment with ritanserin,a 5-HT2 antagonist,inhibited[Ca 2+ ]i changes upon application of 5-HT.Expression of type 1 inositol-5'-triphosphate receptor and type 2 sarcoplasmic/endoplasmic reticulum Ca 2+ ATPase were also increased during activation of HSCs and serve as the major isotypes for ER Ca 2+ storage and release in activated HSCs.Ca 2+ binding chaperone proteins of the ER,including calreticulin,calnexin and calsequestrin,were up-regulated following activation of HSCs. CONCLUSION:The appearance of 5-HT-induced[Ca 2+ ]i response accompanied by upregulation of metabotropic 5-HT2 receptors and Ca 2+ transporting/chaperone ER proteins may participate in the activating process of HSCs.

Neurotoxicity of prenatal alcohol exposure on medullary pre-B?tzinger complex neurons in neonatal rats

Prenatal alcohol exposure disrupts the development of normal fetal respiratory function, but whether it perturbs respiratory rhythmical discharge activity is unclear. Furthermore, it is unknown whether the 5-hydroxytryptamine 2A receptor（5-HT2AR） is involved in the effects of prenatal alcohol exposure. In the present study, pregnant female rats received drinking water containing alcohol at concentrations of 0%, 1%, 2%, 4%, 8% or 10%（v/v） throughout the gestation period. Slices of the medulla from 2-day-old neonatal rats were obtained to record respiratory rhythmical discharge activity. 5-HT2 AR protein and m RNA levels in the pre-B？tzinger complex of the respiratory center were measured by western blot analysis and quantitative RT-PCR, respectively. Compared with the 0% alcohol group, respiratory rhythmical discharge activity in medullary slices in the 4%, 8% and 10% alcohol groups was decreased, and the reduction was greatest in the 8% alcohol group. Respiratory rhythmical discharge activity in the 10% alcohol group was irregular. Thus, 8% was the most effective alcohol concentration at attenuating respiratory rhythmical discharge activity. These findings suggest that prenatal alcohol exposure attenuates respiratory rhythmical discharge activity in neonatal rats by downregulating 5-HT2 AR protein and m RNA levels.

Dissecting the novel abilities of aripiprazole: The generation of anti-colorectal cancer effects by targeting Gαq via HTR2B

Colorectal cancer(CRC)is a type of malignant tumor that seriously threatens human health and life,and its treatment has always been a difficulty and hotspot in research.Herein,this study for the first time reports that antipsychotic aripiprazole(Ari)against the proliferation of CRC cells both in vitro and in vivo,but with less damage in normal colon cells.Mechanistically,the results showed that5-hydroxytryptamine 2B receptor(HTR2B)and its coupling protein G protein subunit alpha q(Gaq)were highly distributed in CRC cells.Ari had a strong affinity with HTR2B and inhibited HTR2B downstream signaling.Blockade of HTR2B signaling suppressed the growth of CRC cells,but HTR2B was not found to have independent anticancer activity.Interestingly,the binding of Gaq to HTR2B was decreased after Ari treatment.Knockdown of Gaq not only restricted CRC cell growth,but also directly affected the antiCRC efficacy of Ari.Moreover,an interaction between Ari and Gaq was found in that the mutation at amino acid 190 of Gaq reduced the efficacy of Ari.Thus,these results confirm that Gaq coupled to HTR2B was a potential target of Ari in mediating CRC proliferation.Collectively,this study provides a novel effective strategy for CRC therapy and favorable evidence for promoting Ari as an anticancer agent.

Effects of Ginseng Fruit Saponins on Serotonin System in Sprague-Dawley Rats with Myocardial Infarction, Depression, and Myocardial Infarction Complicated with Depression

Background： Our previous studies have demonstrated that the levels of 5-hydroxytryptamine （5-HT） and 5-HT 2A receptor （5-HT2AR） in serum and platelet were associated with depression and myocardial infarction （MI）, and pretreatment with ginseng fruit saponins （GFS） before MI and depression had an effect on the 5-HT system. In this study, the effects of GFS on the 5-HT system in the Sprague-Dawley （SD） rats with MI, depression, and MI ＋ depression were evaluated. Methods： A total of eighty SD rats were allocated to four groups： MI, depression, MI ＋ depression, and control groups （n = 20 in each group）. Each group included two subgroups （n = 10 in each subgroup）： Saline treatment subgroup and GFS treatment subgroup. The levels of 5-HT, 5-HT2AR, and serotonin transporter （SERT） were quantified in serum, platelet lysate, and brain tissue through the enzyme-linked immunosorbent assay method, respectively. Results： Compared with those in the saline treatment subgroups, the levels of 5-HT in serum and platelet lysate statistically significantly increased in the GFS treatment subgroups of MI, depression, and MI ＋ depression groups （serum： all P = 0.000; platelet lysate： P = 0.002, 0.000, 0.000, respectively）. However, the 5-HT levels in brain homogenate significantly decreased in the GFS treatment subgroups compared with those in the saline treatment subgroups in MI and depression groups （P = 0.025 and 0.044 respectively）, and no significant difference was observed between saline and GFS treatment subgroups in MI ＋ depression group （P = 0.663）. Compared with that in GFS treatment subgroup of control group, the 5-HT2AR levels in the platelet lysate significantly decreased in GFS treatment subgroups of MI, depression, and MI ＋ depression groups （all P = 0.000）. Compared to those in the saline treatment subgroups, the serum SERT levels significantly decreased in the GFS treatment subgroups in MI, depression, and MI ＋ depression groups （P = 0.009, 0.038, and P = 0.001, respectively）, while the SERT levels of platelet lysate significantly decreased in GFS treatment subgroup of MI group （P = 0.000）, significantly increased in GFS treatment subgroup of depression group （P = 0.019）, and slightly changed in GFS treatment subgroup of MI ＋ depression group （P = 0.219）. No significant changes for SERT levels in brain homogenate could be found between the saline and GFS treatment subgroups in MI, depression, and MI ＋ depression groups （P = 0.421, 0.076 and P = 0.642）. Conclusions： This study indicated that GFS might inhibit the reuptake of 5-HT from serum to platelet according to decreased 5-HT2AR in platelet and SERT in serum and platelet. The change of 5-HT in serum after GFS treatment was inconsistent with that in the brain. It seemed that GFS could not pass through the blood-brain barrier to affect the central serotonergic system.