Lipopolysaccharide aggravated DOI-induced Tourette syndrome: elaboration for recurrence of Tourette syndrome

Effects of low-doses of methamphetamine on d-fenfluramine-induced head-twitch response (HTR) in mice during ageing and c-fos expression in the prefrontal cortex

BACKGROUND

The head-twitch response (HTR) in mice is considered a behavioral model for hallucinogens and serotonin 5-HT_2A receptor function, as well as Tourette syndrome in humans. It is mediated by 5-HT_2A receptor agonists such as ( ±)- 2,5-dimethoxy-4-iodoamphetamine (DOI) in the prefrontal cortex (PFC). The 5-HT_2A antagonist EMD 281014, can prevent both DOI-induced HTR during ageing and c-fos expression in different regions of PFC. Moreover, the nonselective monoamine releaser methamphetamine (MA) suppressed DOI-induced HTR through ageing via concomitant activation of inhibitory 5-HT_1A receptors, but enhanced DOI-evoked c-fos expression. d-Fenfluramine is a selective 5-HT releaser and induces HTR in mice, whereas MA does not. Currently, we investigated whether EMD 281014 or MA would alter: (1) d-fenfluramine-induced HTR frequency in 20-, 30- and 60-day old mice, (2) d-fenfluramine-evoked c-fos expression in PFC, and (3) whether blockade of inhibitory serotonergic 5-HT_1A- or adrenergic ɑ₂-receptors would prevent suppressive effect of MA on d-fenfluramine-induced HTR.

RESULTS

EMD 281014 (0.001-0.05 mg/kg) or MA (0.1-5 mg/kg) blocked d-fenfluramine-induced HTR dose-dependently during ageing. The 5-HT_1A antagonist WAY 100635 countered the inhibitory effect of MA on d-fenfluramine-induced HTR in 30-day old mice, whereas the adrenergic ɑ₂ antagonist RS 79948 reversed MA's inhibitory effect in both 20- and 30- day old mice. d-Fenfluramine significantly increased c-fos expressions in PFC regions. MA (1 mg/kg) pretreatment significantly increased d-fenfluramine-evoked c-fos expression in different regions of PFC. EMD 281014 (0.05 mg/kg) failed to prevent d-fenfluramine-induced c-fos expression, but significantly increased it in one PFC region (PrL at - 2.68 mm).

CONCLUSION

EMD 281014 suppressed d-fenfluramine-induced HTR but failed to prevent d-fenfluramine-evoked c-fos expression which suggest involvement of additional serotonergic receptors in the mediation of evoked c-fos. The suppressive effect of MA on d-fenfluramine-evoked HTR is due to well-recognized functional interactions between stimulatory 5-HT_2A- and the inhibitory 5-HT_1A- and ɑ₂-receptors. MA-evoked increases in c-fos expression in PFC regions are due to the activation of diverse monoaminergic receptors through increased synaptic concentrations of 5-HT, NE and/or DA, which may also account for the additive effect of MA on d-fenfluramine-evoked changes in c-fos expression. Our findings suggest potential drug receptor functional interaction during development when used in combination.

Lopez S, Amodeo DA. Impact of specific serotonin receptor modulation on restricted repetitive behaviors

Restricted, repetitive behaviors (RRBs) are commonly divided into two behavioral categories, lower-order and higher-order RRBs. Individuals displaying lower-order motoric RRBs may express repetitive hand flapping behaviors, body rocking back and forth movements, and continuous body spinning. Higher-order RRBs most commonly cover the behavior inflexibility and cognitive rigidity commonly found in disorders such as autism spectrum disorder and obsessive-compulsive disorder. Various neuropsychiatric disorders are plagued by RRBs yet no FDA-approved treatments have been identified. In rodents, lower-order RRBs are commonly measured through various tasks, such as repetitive self-grooming, marble burying, and stereotypic motor behaviors. This review focuses on the effects that modulation of specific serotonin receptors have on lower-order RRBs. Although there is research examining how changes in 5-HT1A, 5-HT1B, 5-HT2A, 5-HT2B, 5-HT2C, 5-HT3, 5-HT6, and 5-HT7 receptor modulation, more research has focused on the 5-HT1A, 5-HT2A, and 5-HT2C receptors. The accumulating data suggest that increasing 5-HT1A activation decreases RRBs while blocking 5-HT1A activation has no effect on RRBs. While there are mixed findings regarding the impact of 5-HT2A modulation on RRBs, the general trend shows mixed effects of 5-HT2A receptor activation RRB expression, whereas blockade generally decreases RRBs. 5-HT2C receptor activation can modulate RRBs in either direction depending on the 5-HT2C drug used, blocking 5-HT2C activation only seems to show therapeutic properties when 5-HT2C activation is already elevated. The other 5-HT receptors have been explored far less but show promise as potential targets for regulating RRBs. Although it is less clear due to the involvement of 5-HT1D, 5-HT1A activation increases RRBs, and blocking 5-HT1A tends to decrease RRBs. 5-HT2B activation could reduce RRBs, while inhibiting 5-HT2B does not impact RRBs. Increasing 5-HT3 has not been shown to affect RRBs. Yet, increases in RRBs have been observed in Htr3a KO mice. 5-HT6 receptor activation can increase RRBs, while blocking 5-HT6 activity tends to decrease RRBs. Lastly, neither increasing or blocking 5-HT7 activity can reduce RRBs. In sum, there is no uniform pattern in whether all specific 5-HT receptors affect RRBs in either direction, instead, there is evidence suggesting that different 5-HT receptors can modulate RRBs in different directions. Further researching the less explored receptors and aiming to understand why these receptors can differently modulate RRBs, may play a key role in developing therapeutics that treat RRBs.

Role of the NRG1/ErbB4 and PI3K/AKT/mTOR signaling pathways in the anti-psychotic effects of aripiprazole and sertindole in ketamine-induced schizophrenia-like behaviors in rats

Schizophrenia is a common mental disorder affecting patients' thoughts, behavior, and cognition. Recently, the NRG1/ErbB4 signaling pathway emerged as a candidate therapeutic target for schizophrenia. This study investigates the effects of aripiprazole and sertindole on the NRG1/ErbB4 and PI3K/AKT/mTOR signaling pathways in ketamine-induced schizophrenia in rats. Young male Wistar rats received ketamine (30 mg/kg, intraperitoneally) for 5 consecutive days and aripiprazole (3 mg/kg, orally) or sertindole (2.5 mg/kg, orally) for 14 days. The proposed pathway was investigated by injecting LY294002 (a selective PI3K inhibitor) (25 μg/kg, intrahippocampal injection) 30 min before the drugs. Twenty-four hours after the last injection, animals were subjected to behavioral tests: the open field test, sucrose preference test, novel object recognition task, and social interaction test. Both aripiprazole and sertindole significantly ameliorated ketamine-induced schizophrenic-like behavior, as expected, because of their previously demonstrated antipsychotic activity. Besides, both drugs alleviated ketamine-induced oxidative stress and neurotransmitter level changes in the hippocampus. They also increased the gamma-aminobutyric acid and glutamate levels and glutamate decarboxylase 67 and parvalbumin mRNA expression in the hippocampus. Moreover, aripiprazole and sertindole increased the NRG1 and ErbB4 mRNA expression levels and PI3K, p-Akt, and mTOR protein expression levels. Interestingly, pre-injecting LY294002 abolished all the effects of the drugs. This study reveals that the antipsychotic effects of aripiprazole and sertindole are partly due to oxidative stress reduction as well as NRG1/ErbB4 and PI3K/AKT/mTOR signaling pathways activation. The NRG1/ErbB4 and PI3K signaling pathways may offer a new therapeutic approach for treating schizophrenia in humans.

The Efficacy of Fecal Microbiota Transplantation for Children With Tourette Syndrome: A Preliminary Study

Therapies for Tourette syndrome (TS) are insufficient, and novel therapies are needed. Fecal microbiota transplantation (FMT) has been a potential therapy for several neurological diseases. Here, we report a preliminary study to investigate the effects of FMT on patients with TS. Five patients with TS received a single administration of FMT via endoscopy. Tic symptoms were assessed by Yale Global Tic Severity Scale-Total Tic Score (YGTSS-TTS) and adverse effects were recorded at week 8 following FMT. Lipopolysaccharide (LPS) levels and 14 cytokines levels were measured. The microbiota profile in feces were analyzed by shotgun metagenomics. Four patients (4/5) responded positively to FMT (YGTSS-TTS reduction rate >25%) at week 8 with high safety. The levels of LPS and cytokines varied after FMT. FMT shifted the composition of the gut microbiota in patients close to that of the donor and continuously changed the abundance of Bacteroides coprocola, Dialister succinatiphilus and Bacteroides vulgatus. The restoration of B.coprocola was correlated with the improvement in tic symptoms (Spearman R = -0.900, P = 0.037). In conclusion, FMT was indicated a potential effective and safe alternative for patients with TS. However, larger clinical trials are needed to confirm the influence of microbiota in TS. Trial Registration: chictr.org.cn Identifier: ChiCTR-IIR-17011871, URL: http://www.chictr.org.cn/showproj.aspx?proj=19941.

Lactobacillus plantarum PS128 ameliorates 2,5-Dimethoxy-4-iodoamphetamine-induced tic-like behaviors via its influences on the microbiota-gut-brain-axis

We previously reported a novel psychobiotic strain of Lactobacillus plantarum PS128 (PS128) which could ameliorate anxiety-like& depression-like behaviors and modulate cerebral dopamine (DA) and serotonin (5-HT) in mice. Here, we examine the possibility of using PS128 administration to improve tic-like behaviors by using a 5-HT_2A and 5-HT_2C receptor agonist 2,5-Dimethoxy-4-iodoamphetamine (DOI). PS128 was orally administered to male Wistar rat for 2 weeks before two daily DOI injections. We recorded the behaviors immediately after the second DOI injection and compared the results with control and haloperidol treatment groups. PS128 significantly reduced tic-like behaviors and pre-pulse inhibition deficit in a threshold-dose of 10⁹ CFU per day. Brain tissue analysis showed that DOI induced abnormal DA efflux in the striatum and prefrontal cortex, while PS128 ingestion improved DA metabolism and increased norepinephrine (NE) levels in these two regions. In addition, PS128 ingestion increased DA transporter and β-arrestin expressions and decreased DOI-induced phosphorylation of DA and cAMP regulated phosphoprotein of molecular weight 32 kDa (DARPP-32) at Thr34 and extracellular regulated protein kinases (ERK). PS128 ingestion also modulated peripheral 5-HT levels and shaped the cecal microbiota composition, which helps to alleviate DOI-induced dysbiosis. These results suggested that PS128 ameliorated DOI-induced tic-like hyper-active behaviors via stabilizing cerebral dopaminergic pathways through its modulation of host's microbiota-gut-brain axis. Thus, we believe there are potentials for utilizing psychobiotics to improve syndromes caused by DA dysregulation in DA-related neurological disorders and movement disorders such as Tourette syndrome.

Rhynchophylline Attenuates Tourette Syndrome via BDNF/NF-κB Pathway In Vivo and In Vitro

Tourette syndrome (TS) is characterized by one of the chronic neuropsychiatric disorders in multiple children, and the pathogenesis of Tourette syndrome (TS) has not been previously elucidated.The aim of this study was designed to investigate the effects of rhynchophylline (RH) on Tourette syndrome (TS) in rats.TS model was established in rats and BV2 cells by the selective 5-HT2A/2C agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI). Behavior evaluations including stereotypy recording and autonomic activity test were performed. Inflammatory cytokine levels such as interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in serum, striatum, and cell supernatant were detected. The expression levels of BDNF/NF-κB pathway in striatum and BV2 cells were measured by Western blot. Dopamine (DA) and dopamine receptor D 2 (D2) in striatum were also measured.Data indicated that RH significantly decreased IL-6, IL-1β, and TNF-α in serum, striatum, and cell supernatant of TS model, with altered expression of P-NF-κBp65, P-IκBα, and BDNF in TS rats, and DOI-induced BV2 cells, as evidenced by Western blot analysis and immunohistochemistry analysis. RH also significantly reduced the levels of DA and D2 in striatum.Our results shown that the regulation of BDNF/NF-κB pathway might be involved in the effects of RH on TS model.