The Systemic Administration of the Histamine H1 Receptor Antagonist/Inverse Agonist Chlorpheniramine to Pregnant Rats Impairs the Development of Nigro-Striatal Dopaminergic Neurons

Intranasal delivery of herbal medicine for disease treatment: A systematic review

BACKGROUND

Intranasal administration has been adopted in traditional medicine to facilitate access to the bloodstream and central nervous system (CNS). In modern medicine, nasal drug delivery systems are valuable for disease treatment because of their noninvasiveness, good absorption, and fast-acting effects.

OBJECTIVE

This study aimed to systematically organize preclinical and clinical studies on intranasal herbal medicines to highlight their potential in drug development.

METHODS

A comprehensive search for literature until February 2023 was conducted on PubMed and the Web of Science. From the selected publications, we extracted key information, including the types of herbal materials, target diseases, intranasal conditions, methods of toxicity evaluation, main outcomes, and mechanisms of action, and performed quality assessments for each study.

RESULTS

Of the 45 studies, 13 were clinical and 32 were preclinical; 28 studies used herbal extracts, 9 used prescriptions, and 8 used natural compounds. The target diseases were rhinosinusitis, influenza, fever, stroke, migraine, insomnia, depression, memory disorders, and lung cancer. The common intranasal volumes were 8-50 µl in mice, 20-100 µl in rats, and 100-500 µl in rabbits. Peppermint oil, Ribes nigrum folium, Melia azedarach L., Elaeocarpus sylvestris, Radix Bupleuri, Da Chuan Xiong Fang, Xingnaojing microemulsion, and Ginsenoside Rb1 emerged as potential candidates for rapid intranasal therapy. The in vivo toxicity assessments were based on mortality, body weight, behavioral changes, mucociliary activity, histopathology, and blood tests. Most intranasal treatments were safe, except for Cyclamen europaeum, Jasminum sambac, Punica granatum L., and violet oil, which caused mild adverse effects. At lower doses, intranasal herbal treatments often show greater effects than oral administration. The actions of intranasal herbal medicine mainly involve regulating inflammation and neurotransmission, with the olfactory bulb and anterior cingulate cortex to be relevant brain regions.

CONCLUSION

Intranasal delivery of herbal materials holds promise for enhancing drug delivery efficacy and reducing treatment duration, offering a potential future perspective for developing intranasal therapies for various diseases.

Calcium and Neural Stem Cell Proliferation

Intracellular calcium plays a pivotal role in central nervous system (CNS) development by regulating various processes such as cell proliferation, migration, differentiation, and maturation. However, understanding the involvement of calcium (Ca2+) in these processes during CNS development is challenging due to the dynamic nature of this cation and the evolving cell populations during development. While Ca2+ transient patterns have been observed in specific cell processes and molecules responsible for Ca2+ homeostasis have been identified in excitable and non-excitable cells, further research into Ca2+ dynamics and the underlying mechanisms in neural stem cells (NSCs) is required. This review focuses on molecules involved in Ca2+ entrance expressed in NSCs in vivo and in vitro, which are crucial for Ca2+ dynamics and signaling. It also discusses how these molecules might play a key role in balancing cell proliferation for self-renewal or promoting differentiation. These processes are finely regulated in a time-dependent manner throughout brain development, influenced by extrinsic and intrinsic factors that directly or indirectly modulate Ca2+ dynamics. Furthermore, this review addresses the potential implications of understanding Ca2+ dynamics in NSCs for treating neurological disorders. Despite significant progress in this field, unraveling the elements contributing to Ca2+ intracellular dynamics in cell proliferation remains a challenging puzzle that requires further investigation.

The Roles of Histamine Receptor 1 (hrh1) in Neurotransmitter System Regulation, Behavior, and Neurogenesis in Zebrafish

Histamine receptors mediate important physiological processes and take part in the pathophysiology of different brain disorders. Histamine receptor 1 (HRH1) is involved in the development of neurotransmitter systems, and its role in neurogenesis has been proposed. Altered HRH1 binding and expression have been detected in the brains of patients with schizophrenia, depression, and autism. Our goal was to assess the role of hrh1 in zebrafish development and neurotransmitter system regulation through the characterization of hrh1-/- fish generated by the CRISPR/Cas9 system. Quantitative PCR, in situ hybridization, and immunocytochemistry were used to study neurotransmitter systems and genes essential for brain development. Additionally, we wanted to reveal the role of this histamine receptor in larval and adult fish behavior using several quantitative behavioral methods including locomotion, thigmotaxis, dark flash and startle response, novel tank diving, and shoaling behavior. Hrh1-/- larvae displayed normal behavior in comparison with hrh1+/+ siblings. Interestingly, a transient abnormal expression of important neurodevelopmental markers was evident in these larvae, as well as a reduction in the number of tyrosine hydroxylase 1 (Th1)-positive cells, th1 mRNA, and hypocretin (hcrt)-positive cells. These abnormalities were not detected in adulthood. In summary, we verified that zebrafish lacking hrh1 present deficits in the dopaminergic and hypocretin systems during early development, but those are compensated by the time fish reach adulthood. However, impaired sociability and anxious-like behavior, along with downregulation of choline O-acetyltransferase a and LIM homeodomain transcription factor Islet1, were displayed by adult fish.

Increased Nuclear FOXP2 Is Related to Reduced Neural Stem Cell Number and Increased Neurogenesis in the Dorsal Telencephalon of Embryos of Diabetic Rats through Histamine H1 Receptors

Diabetic rat embryos have increased cortical neurogenesis and neuron maturation, and their offspring presented altered neuron polarity, lamination, and diminished neuron excitability. The FOXP2 overexpression results in higher cortical neurogenesis by increasing the transition of radial glia to the intermediate progenitor. Similarly, histamine through H₁-receptor activation increases cortical neuron differentiation. Indeed, blocking the H₁-receptor by the systemic administration of chlorpheniramine to diabetic pregnant rats prevents increased neurogenesis. Here, we explore the relationship between the H₁-receptor and FOXP2 on embryo neurogenesis from diabetic dams. Through qRT-PCR, Western blot, immunohistofluorescence, and flow cytometry, we showed an increased FOXP2 expression and nuclear localization, a reduced Nestin expression and -positive cells number, and a higher PKCα expression in the cortical neuroepithelium of fourteen-day-old embryos from diabetic rats. Interestingly, this scenario was prevented by the chlorpheniramine systemic administration to diabetic pregnant rats at embryo day twelve. These data, together with the bioinformatic analysis, suggest that higher H₁-receptor activity in embryos under high glucose increases FOXP2 nuclear translocation, presumably through PKCα phosphorylation, impairing the transition of radial glia to intermediate progenitor and increasing neuron differentiation in embryos of diabetic rats.

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.

Histamine Is Responsible for the Neuropathic Itch Induced by the Pseudorabies Virus Variant in a Mouse Model

Pseudorabies virus (PRV) is the causative agent of pseudorabies (PR). It can infect a wide range of mammals. PRV infection can cause severe acute neuropathy (the so-called “mad itch”) in nonnatural hosts. PRV can infect the peripheral nervous system (PNS), where it can establish a quiescent, latent infection. The dorsal root ganglion (DRG) contains the cell bodies of the spinal sensory neurons, which can transmit peripheral sensory signals, including itch and somatic pain. Little attention has been paid to the underlying mechanism of the itch caused by PRV in nonnatural hosts. In this study, a mouse model of the itch caused by PRV was elaborated. BALB/c mice were infected intramuscularly with 10⁵ TCID₅₀ of PRV TJ. The frequency of the bite bouts and the durations of itch were recorded and quantified. The results showed that the PRV-infected mice developed spontaneous itch at 32 h postinfection (hpi). The frequency of the bite bouts and the durations of itch were increased over time. The mRNA expression levels of the receptors and the potential cation channels that are relevant to the itch-signal transmission in the DRG neurons were quantified. The mRNA expression levels of tachykinin 1 (TAC1), interleukin 2 (IL-2), IL-31, tryptases, tryptophan hydroxylase 1 (TPH1), and histidine decarboxylase (HDC) were also measured by high-throughput RNA sequencing and real-time reverse transcription PCR. The results showed that the mean mRNA level of the HDC in the DRG neurons isolated from the PRV-infected mice was approximately 25-fold higher than that of the controls at 56 hpi. An immunohistochemistry (IHC) was strongly positive for HDC in the DRG neurons of the PRV-infected mice, which led to the high expression of histamine at the injected sites. The itch of the infected mice was inhibited by chlorphenamine hydrogen maleate (an antagonist for the histamine H1 receptor) in a dose-dependent manner. The mRNA and protein levels of the HDC in the DRG neurons were proportional to the severity of the itch induced by different PRV strains. Taken together, the histamine synthesized by the HDC in the DRG neurons was responsible for the PRV-induced itch in the mice.

Long-Term Functional and Cytoarchitectonic Effects of the Systemic Administration of the Histamine H1 Receptor Antagonist/Inverse Agonist Chlorpheniramine During Gestation in the Rat Offspring Primary Motor Cortex

The transient histaminergic system is among the first neurotransmitter systems to appear during brain development in the rat mesencephalon/rhombencephalon. Histamine increases FOXP2-positive deep-layer neuron differentiation of cortical neural stem cells through H₁ receptor activation in vitro. The in utero or systemic administration of chlorpheniramine (H₁ receptor antagonist/inverse agonist) during deep-layer cortical neurogenesis decreases FOXP2 neurons in the developing cortex, and H₁R- or histidine decarboxylase-knockout mice show impairment in learning and memory, wakefulness and nociception, functions modulated by the cerebral cortex. Due to the role of H₁R in cortical neural stem cell neurogenesis, the purpose of this study was to evaluate the postnatal impact of the systemic administration of chlorpheniramine during deep-layer cortical neuron differentiation (E12–14) in the primary motor cortex (M1) of neonates (P0) and 21-day-old pups (P21). Chlorpheniramine or vehicle were systemically administered (5 mg/kg, i.p.) to pregnant Wistar rats at gestational days 12–14, and the expression and distribution of deep- (FOXP2 and TBR1) and superficial-layer (SATB2) neuronal cortical markers were analyzed in neonates from both groups. The qRT-PCR analysis revealed a reduction in the expression of Satb2 and FoxP2. However, Western blot and immunofluorescence showed increased protein levels in the chlorpheniramine-treated group. In P21 pups, the three markers showed impaired distribution and increased immunofluorescence in the experimental group. The Sholl analysis evidenced altered dendritic arborization of deep-layer neurons, with lower excitability in response to histamine, as evaluated by whole-cell patch-clamp recording, as well as diminished depolarization-evoked [³H]-glutamate release from striatal slices. Overall, these results suggest long-lasting effects of blocking H₁Rs during early neurogenesis that may impact the pathways involved in voluntary motor activity and cognition.

Histamine in the Crosstalk Between Innate Immune Cells and Neurons: Relevance for Brain Homeostasis and Disease

Histamine is a biogenic amine playing a central role in allergy and peripheral inflammatory reactions and acts as a neurotransmitter and neuromodulator in the brain. In the adult, histamine is produced mainly by mast cells and hypothalamic neurons, which project their axons throughout the brain. Thus, histamine exerts a range of functions, including wakefulness control, learning and memory, neurogenesis, and regulation of glial activity. Histamine is also known to modulate innate immune responses induced by brain-resident microglia cells and peripheral circulating monocytes, and monocyte-derived cells (macrophages and dendritic cells). In physiological conditions, histamine per se causes mainly a pro-inflammatory phenotype while counteracting lipopolysaccharide-induced inflammation both in microglia, monocytes, and monocyte-derived cells. In turn, the activation of the innate immune system can profoundly affect neuronal survival and function, which plays a critical role in the onset and development of brain disorders. Therefore, the dual role of histamine/antihistamines in microglia and monocytes/macrophages is relevant for identifying novel putative therapeutic strategies for brain diseases. This review focuses on the effects of histamine in innate immune responses and the impact on neuronal survival, function, and differentiation/maturation, both in physiological and acute (ischemic stroke) and chronic neurodegenerative conditions (Parkinson's disease).

Rapid immunohistological measurement of tyrosine hydroxylase in rat midbrain by near-infrared instrument-based detection

We present a robust, fresh-frozen approach to immunohistochemistry (IHC), without committing the tissue to IHC via fixation and cryopreservation while maintaining long-term storage, using LiCor-based infrared (IR) quantification for sensitive assessment of TH in immunoreacted midbrain sections for quantitative comparison across studies. In fresh-frozen tissue stored up to 1 year prior to IHC reaction, we found our method to be highly sensitive to rotenone treatment in 3-month-old Sprague-Dawley rats, and correlated with a significant decline in rotarod latency-to-fall measurement by approximately 2.5 fold. The measured midbrain region revealed a 31 % lower TH signal when compared to control (p < 0.01 by t test, n = 5). Bivariate analysis of integrated TH counts versus rotarod latency-to-fall indicates a positive slope and modest but significant correlation of R² = 0.68 (p < 0.05, n = 10). These results indicate this rapid, instrument-based quantification method by IR detection successfully quantifies TH levels in rat brain tissue, while taking only 5 days from euthanasia to data output. This approach also allows for the identification of multiple targets by IHC with the simultaneous performance of downstream molecular analysis within the same animal tissue, allowing for the use of fewer animals per study.