Anxiolytic-like effects of hochuekkito in lipopolysaccharide-treated mice involve interleukin-6 inhibition

Behavioural and neurochemical alterations following acute inflammation induced by intraperitoneal and intratracheal injection with lipopolysaccharide in mice

The persistent symptoms of anxiety, depression, and fatigue that follow severe acute respiratory syndrome coronavirus 2 infection and accompany pulmonary inflammation pose significant clinical challenges. However, the correlation between pulmonary inflammation and mental health remains unclear. This study sought to examine the effects of intratracheal injection of lipopolysaccharide (LPS), a bacterial endotoxin, on anxiety-like behaviour in a mouse model suffering with pulmonary inflammation. The reactions of these animal models to new environments were evaluated using light-dark box and hole-board tests as anxiety-inducing stimuli. Microglial responses were evaluated via immunohistochemistry, and serum concentrations of tumour necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) were measured. Both intraperitoneal and intratracheal injections of LPS induced anxiety-like behaviours, as indicated by the outcomes of the light-dark box and hole-board tests. Serum levels of TNF-α and IL-6 considerably increased following both injection routes. The protein levels of the 5-HT2A and 5-HT1A receptors, which are crucial for neuropsychological function, in the frontal cortex and hippocampus of mice remained unchanged following LPS injections. Notably, hippocampal levels of brain-derived neurotrophic factor (BDNF) remarkably decreased following LPS injections. In the lungs, the administration of LPS via the intratracheal route led to a significant rise in the number of white blood cells present in the bronchoalveolar lavage fluid compared to the intraperitoneal injection method. These findings suggest that inflammation induced by intratracheal LPS injection may lead to anxiety-like behaviours in mice, potentially involving mechanisms related to hippocampal BDNF expression, which contributes to anxiety after pulmonary inflammation.

Ameliorating effect of chotosan and its active component, Uncaria hook, on lipopolysaccharide-induced anxiety-like behavior in mice

Introduction

In this study, we aimed to examine the effects of chotosan, a traditional Japanese botanical drug, and its active component, Uncaria hook, on anxiety-like behaviors induced by systemic inflammation in mice.

Methods

To induce systemic inflammation, the mice were treated with lipopolysaccharide (LPS), a bacterial endotoxin. Prior to LPS treatment, the mice were administered chotosan or Uncaria hook orally each day for 14 days. Anxiety-like behavior of the mice was evaluated using the light-dark test 24 h after LPS treatment.

Results

Repeated administration of chotosan prevented anxiety-like behavior in both normal and LPS-treated mice. Similarly, administration of Uncaria hook suppressed LPS-induced anxiety-like behavior in mice. Furthermore, treatment with tandospirone, a 5-HT1A receptor agonist, alleviated anxiety-like behavior in mice, whereas treatment with DOI, a 5-HT2A receptor agonist, enhanced anxiety-like behavior in mice. LPS treatment significantly increased serotonin (5-HT)2A receptor mRNA expression in the frontal cortex, whereas 5-HT1A receptor mRNA expression remained unchanged in the hippocampus. Notably, chotosan significantly suppressed the mRNA expression of 5-HT2A receptor.

Discussion

These findings indicate that chotosan exerts anxiolytic-like effects in the context of inflammation-induced anxiety, potentially mediated by the inhibition of 5-HT2A receptor hyperfunction in LPS-treated mice. Consequently, we postulate that chotosan may be effective in managing inflammation-induced anxiety-like behaviors.

Alleviating effect of vagus nerve cutting in Salmonella-induced gut infections and anxiety-like behavior via enhancing microbiota-derived GABA

The vagus nerve, a pivotal link within the gut-brain axis, plays a critical role in maintaining homeostasis and mediating communication between the gastrointestinal tract and the brain. It has been reported that gastrointestinal infection by Salmonella typhimurium (S. typhimurium) triggers gut inflammation and manifests as anxiety-like behaviors, yet the mechanistic involvement of the vagus nerve remains to be elucidated. In this study, we demonstrated that unilateral cervical vagotomy markedly attenuated anxiety-like behaviors induced by S. typhimurium SL1344 infection in C57BL/6 mice, as evidenced by the open field test and marble burying experiment. Furthermore, vagotomy significantly diminished neuronal activation within the nucleus of the solitary tract and amygdala, alongside mitigating aberrant glial cell activation in the hippocampus and amygdala. Additionally, vagotomy notably decreases serum endotoxin levels, counters the increase in splenic Salmonella concentration, and modulates the expression of inflammatory cytokines-including IL-6, IL-1β, and TNF-α-in both the gastrointestinal tract and brain, with a concurrent reduction in IL-22 and CXCL1 expression. This intervention also fostered the enrichment of beneficial gut microbiota, including Alistipes and Lactobacillus species, and augmented the production of gamma-aminobutyric acid (GABA) in the gut. Administration of GABA replicated the vagotomy's beneficial effects on reducing gut inflammation and anxiety-like behavior in infected mice. However, blockade of GABA receptors with picrotoxin abrogated the vagotomy's protective effects against gut inflammation, without influencing its impact on anxiety-like behaviors. Collectively, these findings suggest that vagotomy exerts a protective effect against infection by promoting GABA synthesis in the colon and alleviating anxiety-like behavior. This study underscores the critical role of the vagus nerve in relaying signals of gut infection to the brain and posits that targeting the gut-brain axis may offer a novel and efficacious approach to preventing gastrointestinal infections and associated behavioral abnormalities.

Comparative study of the effects of the three kinds of Kampo-hozai: Ninjinyoeito, Hochuekkito, and Juzentaihoto on anxious and low sociability behavior using NPY-knockout zebrafish

Ninjinyoeito, Hochuekkito, and Juzentaihoto are the three types of Kampo-hozai used to support the treatment of various diseases by energizing patients through improved mental health. While Kampo-hozais are clinically used to improve mental energy decline, a comparison between their effects on neuropsychiatric symptoms like anxiety and sociability and the strength of their effects has not been conducted. Therefore, this study compared the effects of Ninjinyoeito, Hochuekkito, and Juzentaihoto on psychiatric symptoms using neuropeptide Y knockout (NPY-KO) zebrafish, a suitable animal model for anxiety and low sociability. Neuropeptide Y knockout zebrafish were fed a Ninjinyoeito, Hochuekkito, or Juzentaihoto-supplemented diet for 4 days. Then, sociability was analyzed using a three-Chambers test and anxiety-like behavior was evaluated using the cold stress and novel tank tests. The results showed that Ninjinyoeito treatment improved the low sociability of neuropeptide Y knockout, while Hochuekkito and Juzentaihoto did not. Neuropeptide Y knockout exhibited anxiety-like behaviors, such as freezing and swimming in the wall area under cold stress, but Ninjinyoeito treatment improved these behaviors. However, these anxiety-like behaviors were not improved by Hochuekkito and Juzentaihoto. Ninjinyoeito treatment also improved anxiety-like behaviors of neuropeptide Y knockout in the novel tank test. However, no improvement was shown in the Hochuekkito and Juzentaihoto groups. This trend was also confirmed in the low water stress test using wild-type zebrafish. This study exhibits that among the three types of Kampo-hozai, Ninjinyoeito is the most effective in psychiatric disorders associated with anxiety and low sociability.