Regulatory effects of Ningdong granule on microglia-mediated neuroinflammation in a rat model of Tourette's syndrome

Mechanistic insights and therapeutic approaches in tic disorders: The distinctive role of ethnomedicine and modern medical interventions

Tic disorders (TDs) are a class of neurodevelopmental disorders that have received considerable scientific attention. The genesis of TDs is increasingly understood as a complex interplay of neurobiological, genetic, and immunological factors. Animal model studies have elucidated the pathophysiology of TDs, paving the way for innovative therapeutic approaches. This review provides a comprehensive analysis of the etiologic basis, experimental framework, and treatment strategies for TDs, highlighting the contributions of ethnomedicine and modern medicine. Our synthesis aims to deepen the understanding of the disease and spur the development of superior treatments. In addition, we present new insights and hypotheses for the future management of TDs, emphasizing the need for continued research into their etiology and progression, as well as the pursuit of more effective therapies. We advocate personalized, holistic care strategies that focus on symptom relief and improving patients' quality of life. Overall, this review provides a critical compendium for TD researchers and practitioners to help navigate the complexities of these disorders.

Neuroglia in Tourette syndrome and obsessive-compulsive disorder

In recent years, neuroglia have drawn the attention of researchers in the fields of neurology and psychiatry. Besides their well-known functions providing support to neurons, myelinating axons, and clearing up debris, a constantly growing of evidence indicates that glial cells are key contributors to the pathophysiology of neuropsychiatric disorders. Alterations in microglia, astrocytes, and oligodendrocytes have been described in Tourette syndrome (TS) and obsessive-compulsive disorder (OCD). The sudden onset of tics and OCD-like symptoms after infection in children (Pediatric Autoimmune Neuropsychiatric Disorder Associated with Streptococcal Infections) suggests a connection with the immune system; in fact, neuroinflammation has been reported. Many imaging studies revealed abnormal myelination in the brain of TS and OCD patients, highlighting the implication of oligodendroglia in the connectivity alterations. Moreover, animal models have unveiled a cell-autonomous role of microglia and astrocytes in the etiology of pathologic grooming, which links these glial cells to the related disorder trichotillomania. This chapter reviews the state of the art and current gaps in the literature, proposing possible pathomechanisms and future research directions.

Rhynchophylline Alleviates Hyperactivity and Cognitive Flexibility Impairment Associated With Inhibition of Inflammatory Responses in Mice That Partly Lack the Dopamine Transporter Protein

BACKGROUND AND AIMS

Rhynchophylline (RHY) can alleviate some cognitive flexibility impairment and stereotyped behavior for attention-deficit hyperactivity disorder (ADHD) and Tourette syndrome (TS) patients as one of a key extract and an active ingredient in Ningdong granule (NDG), which is a Traditional Chinese medicine (TCM) preparation widely used in the treatment of ADHD and TS children in China; however, the underlying mechanism is not well understood. Therefore, this study aimed to evaluate how RHY alleviates hyperactivity and cognitive flexibility impairment while inhibiting inflammatory responses in mice that partly lack dopamine transporter protein (DAT- mice).

METHODS

Male DAT- mice were randomly divided into the RHY group (n = 8) and administered RHY (30 mg/kg) in the DAT- group (n = 8) and administered saline (i.p., 10 mL/kg) in wild-type (WT) mice as the WT control group (n = 8). Hyperactivity and cognitive flexibility impairment were evaluated by the open field test (OFT) and the Morris water maze (MWM) test. The levels of the inflammatory factors of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) in cortical homogenates were tested by enzyme-linked immunosorbent assays (ELISA) after 8 weeks of treatment with RHY. In vitro, primary microglia and astrocytes extracted from the cortices of DAT- neonatal mice and WT neonatal mice were treated with lipopolysaccharide (LPS) (1 mg/mL) to induce neuroinflammatory responses and with RHY (20 mM) for 48 h. The levels of the inflammatory factors TNF-α, IL-1β, inducible nitric oxide synthase (iNOS), and cyclooxygenase-2 (COX2) in the culture medium were measured at 6 h, 24 h, and 48 h after treatment with LPS and RHY.

RESULTS

RHY ameliorated hyperactivity and cognitive flexibility impairment in DAT- mice and inhibited the expression of the inflammatory factors TNF-α, IL-1β, iNOS, and COX-2 in microglia and astrocytes in vitro, and also inhibited the expression of TNF-α and IL-1β in cortical homogenates after 8 weeks of treatment.

CONCLUSION

RHY improved hyperactivity and cognitive flexibility impairment through inhibiting inflammatory responses in DAT- mice.

The inflammatory injury in the striatal microglia-dopaminergic-neuron crosstalk involved in Tourette syndrome development

Background

Tourette syndrome (TS) is associated with immunological dysfunction. The DA system is closely related to TS development, or behavioral stereotypes. Previous evidence suggested that hyper-M1-polarized microglia may exist in the brains of TS individuals. However, the role of microglia in TS and their interaction with dopaminergic neurons is unclear. In this study, we applied iminodipropionitrile (IDPN) to establish a TS model and focused on the inflammatory injury in the striatal microglia-dopaminergic-neuron crosstalk.

Methods

Male Sprague-Dawley rats were intraperitoneally injected with IDPN for seven consecutive days. Stereotypic behavior was observed to verify the TS model. Striatal microglia activation was evaluated based on different markers and expressions of inflammatory factors. The striatal dopaminergic neurons were purified and co-cultured with different microglia groups, and dopamine-associated markers were assessed.

Results

First, there was pathological damage to striatal dopaminergic neurons in TS rats, as indicated by decreased expression of TH, DAT, and PITX3. Next, the TS group showed a trend of increased Iba-1 positive cells and elevated levels of inflammatory factors TNF-α and IL-6, as well as an enhanced M1-polarization marker (iNOS) and an attenuated M2-polarization marker (Arg-1). Finally, in the co-culture experiment, IL-4-treated microglia could upregulate the expression of TH, DAT, and PITX3 in striatal dopaminergic neurons vs LPS-treated microglia. Similarly, the TS group (microglia from TS rats) caused a decreased expression of TH, DAT, and PITX3 compared with the Sham group (microglia from control rats) in the dopaminergic neurons.

Conclusion

In the striatum of TS rats, microglia activation is M1 hyperpolarized, which transmits inflammatory injury to striatal dopaminergic neurons and disrupts normal dopamine signaling.

Qinglong Zhidong Decoction Alleviated Tourette Syndrome in Mice via Modulating the Level of Neurotransmitters and the Composition of Gut Microbiota

Qinglong Zhidong Decoction (QLZDD), a traditional Chinese medicine (TCM) prescription, has been effectively used to alleviate Tourette syndrome (TS) in children. However, the therapeutic mechanism of QLZDD on TS has not been evaluated. The present study aims to elucidate the therapeutic effect and the possible therapeutic mechanism of QLZDD on TS in mouse model. A 3,3-iminodipropionitrile (IDPN, 350 mg/kg)-induced-TS mouse model was established. The mice were randomly divided into the control group, the model group, the haloperidol group (14 mg/kg), the low-, middle-, or high-QLZDD-dose groups (6.83 g/kg, 13.65 g/kg, 27.3 g/kg). QLZDD was administrated orally once a day for 4 weeks. The tic-like behavior was recorded weekly. Then, neurotransmitters and neurotransmitter receptors were analyzed by ELISA, immunohistochemistry (IHC), and quantitative reverse transcription PCR in striatum. Further, the alteration to intestinal flora was monitored by 16s rRNA sequencing, and the role of gut microbiota in the alleviation of TS by QLZDD was investigated. QLZDD ameliorated the tic-like behavior, and decreased the level of excitatory neurotransmitters such as Glu and DA and increased the level of the inhibitory neurotransmitter GABA significantly. Moreover, QLZDD significantly blocked the mRNA expression and the protein expression of D1R and D2R in the striatum, while activated the levels of DAT and GABAR. Interestingly, QLZDD mediated the composition of gut microbiota by increasing the abundance of Lactobacillus and Bacteroides but decreasing the abundance of Alloprevotella and Akkermansia. Taken together, QLZDD ameliorated the tic-like behavior in TS mouse, its mechanism of action may be associated with restoring the balance of gut microbiota and neurotransmitters. The study indicated a promising role of QLZDD in alleviating TS and a therapeutic strategy for fighting TS in clinical settings.

Effects of Chemogenetic Inhibition of D1 or D2 Receptor-Containing Neurons of the Substantia Nigra and Striatum in Mice With Tourette Syndrome

As tourette syndrome (TS) is a common neurobehavioral disorder, the primary symptoms of which include behavioral stereotypies. Dysfunction of the substantia nigra-striatum network could be the main pathogenesis of TS, which is closely associated with dopamine (DA) and its receptors. TS is often resistant to conventional treatments. Therefore, it is necessary to investigate the neurobiological mechanisms underlying its pathogenesis. In this study, we investigated whether chemogenetic activation or inhibition of dopaminergic D1 receptor (D1R)- or D2 receptor (D2R)-containing neurons in the substantia nigra pars compacta (SNpc) or dorsal striatum (dSTR) affected the stereotyped behavior and motor functions of TS mice. Intraperitoneal injection of 3,3'-iminodipropionitrile (IDPN) was used to induce TS in mice. Stereotyped behavior test and open-field, rotarod, and grip strength tests were performed to evaluate stereotyped behavior and motor functions, respectively. Immunofluorescence labeling was used to detect the co-labeling of virus fluorescence and D1R or D2R. We found that chemogenetic inhibition of D1R- or D2R-containing neurons in the SNpc and dSTR alleviated behavioral stereotypies and motor functions in TS mice. Chemogenetic activation of D1R-containing neurons in the dSTR aggravated behavioral stereotypies and motor functions in vehicle-treated mice, but neither was aggravated in TS mice. In conclusion, chemogenetic inhibition of D1R- or D2R-containing neurons in the SNpc and dSTR alleviated behavioral stereotypies of TS, providing a new treatment target for TS. Moreover, the activation of D1R-containing neurons in the dSTR may contribute to the pathogenesis of TS, which can be chosen as a more precise target for treatment.