No abstract

Anxiety disorders are the most commonly reported mental disorders [1]. If not treated, patients with chronic anxiety disorders progress toward depression [2]. In mice, anxiety/depression can be induced by stressors such as immobilization, forced swimming, and antibiotics [3]. Exposure to immobilization stress (IS) stimulates the secretion of adrenal hormones such as glucocorticoids and proinflammatory cytokines such as interleukin (IL)-6 and gut dysbiosis via the activation of the hypothalamopituitary-adrenal (HPA) axis, while brain-derived neurotrophic factor (BDNF) expression is suppressed [4, 5]. However, gut dysbiosis causes gastrointestinal inflammation and increases anxiety/depression via the activation of the microbiota-gut-brain (MGB) axis [6]. Gut microbiota in humans and animals consist of > 1,000 bacterial species [7]. Gut bacterial composition fluctuates by endogenous and exogenous factors such as diet, drugs, stressors, and hormones [7, 8]. Exposure to IS causes gut dysbiosis, including increased Proteobacteria population, and psychiatric disorders in mice [7, 8]. However, some bifidobacteria and lactobacilli alleviated psychiatric disorders. Lactobacillus reuteri, Lactobacillus plantarum, and Bifidobacterium adolescentis IM38, and Bifidobacterium adolescentis NK98 alleviate anxiety in animals [9-12]. Nevertheless, the effects of gut bacteria on anxiety/ depression still remain unclear. Therefore, in the present study, we selected BDNF expression-inducing NK41 and NK46 in the gut bacteria collection isolated from human feces using corticosteronestimulated SH-SY5Y cells and examined their effects on ISinduced anxiety/depression in mice. NK41 and NK46 were cultured in general media for probiotics such as MRS broth (BD, USA), collected by centrifugation (5,000 g, 20 min), and suspended in phosphatebuffered saline (for in vitro study) or 1% dextrose (for in vivo study) according to the method of Jang et al. [10]. SH-SY5Y cells were cultured according to the method of Lee, et al. [13]. All animal experiments were approved by the Institutional Animal Care and Use Committee of the

Gut dysbiosis is closely connected with the outbreak of psychiatric disorders with colitis. Bifidobacteria-fermented red ginseng (fRG) increases the absorption of ginsenoside Rd and protopanxatriol into the blood in volunteers and mice. fRG and Rd alleviates 2,4,6-trinitrobenzenesulfonic acid-induced colitis in mice. Therefore, to understand the gut microbiota-mediated mechanism of fRG against anxiety/depression, we examined the effects of red ginseng (RG), fRG, ginsenoside Rd, and protopanaxatriol on the occurrence of anxiety/depression, colitis, and gut dysbiosis in mice. Mice with anxiety/depression were prepared by being exposed to two stressors, immobilization stress (IS) or Escherichia coli (EC). Treatment with RG and fRG significantly mitigated the stress-induced anxiety/depression-like behaviors in elevated plus maze, light-dark transition, forced swimming (FST), and tail suspension tasks (TST) and reduced corticosterone levels in the blood. Their treatments also suppressed the stress-induced NF-κB activation and NF-κB+/Iba1+ cell population in the hippocampus, while the brain-derived neurotrophic factor (BDNF) expression and BDNF+/NeuN+ cell population were increased. Furthermore, treatment with RG or fRG suppressed the stress-induced colitis: they suppressed myeloperoxidase activity, NF-κB activation, and NF-κB+/CD11c+ cell population in the colon. In particular, fRG suppressed the EC-induced depression-like behaviors in FST and TST and colitis more strongly than RG. fRG treatment also significantly alleviated the EC-induced NF-κB+/Iba1+ cell population and EC-suppressed BDNF+/NeuN+ cell population in the hippocampus more strongly than RG. RG and fRG alleviated EC-induced gut dysbiosis: they increased Bacteroidetes population and decreased Proteobacteria population. Rd and protopanaxatriol also alleviated EC-induced anxiety/depression and colitis. In conclusion, fRG and its constituents Rd and protopanaxatriol mitigated anxiety/depression and colitis by regulating NF-κB-mediated BDNF expression and gut dysbiosis.

Background Gut microbiota closely communicate in the immune system to maintain a balanced immune homeostasis in the gastrointestinal tract of the host. Oral administration of probiotics modulates gut microbiota composition. In the present study, we isolated Lactobacillus rhamnosus HDB1258, which induced tumor necrosis factor (TNF)-α and interleukin (IL)-10 expression in macrophages, from the feces of breastfeeding infants and examined how HDB1258 could regulate the homeostatic immune response in mice with or without lipopolysaccharide (LPS)-induced systemic inflammation. Results Oral administration of HDB1258 significantly increased splenic NK cell cytotoxicity, peritoneal macrophage phagocytosis, splenic and colonic TNF-α expression, TNF-α to IL-10 expression ratio, and fecal IgA level in control mice, while Th1 and Treg cell differentiation was not affected in the spleen. However, HDB1258 treatment significantly suppressed peritoneal macrophage phagocytosis and blood prostaglandin E2 level in mice with LPS-induced systemic inflammation. Its treatment increased LPS-suppressed ratios of Treg to Th1 cell population, Foxp3 to T-bet expression, and IL-10 to TNF-α expression. Oral administration of HDB1258 significantly decreased LPS-induced colon shortening, myeloperoxidase activity and NF-κB+/CD11c+ cell population in the colon, while the ratio of IL-10 to TNF-α expression increased. Moreover, HDB1258 treatment shifted gut microbiota composition in mice with and without LPS-induced systemic inflammation: it increased the Cyanobacteria and PAC000664_g (belonging to Bacteroidetes) populations and reduced Deferribacteres and EU622763_s group (belonging to Bacteroidetes) populations. In particular, PAC001066_g and PAC001072_s populations were negatively correlated with the ratio of IL-10 to TNF-α expression in the colon, while the PAC001070_s group population was positively correlated. Conclusions Oral administered HDB1258 may enhance the immune response by activating innate immunity including to macrophage phagocytosis and NK cell cytotoxicity in the healthy host and suppress systemic inflammation in the host with inflammation by the modulation of gut microbiota and IL-10 to TNF-α expression ratio in immune cells.

Excessive exposure to stressors such as social defeat, immobilization, antibacterials, and pathogen infection stimulate the release of adrenal hormones noradrenaline, adrenaline, and glucocorticoids through the activation of the hypothalamic-pituitary-adrenal (HPA) axis and the secretion of proinflammatory cytokines IL-6 and TNFα. This results in the occurrence of psychiatric disorders, colitis, and gut dysbiosis [1, 2]. Treatment with 2,4,6trinitrobenzenesulfonic acid (TNBS), a colitis inducer, causes colitis, gut dysbiosis, and cognitive impairment in mice [3]. Oral gavage of ampicillin causes gut dysbiosis, colitis, and anxiety/depression in mice [4]. Infection with pathogens such as TNBS-induced Escherichia coli and ampicillin-induced Klebsiella oxytoca in the intestine of mice causes colitis with psychiatric disorders, including anxiety/depression and memory impairment, through the activation of the microbiota-gut-brain (MGB) axis [3-5]. However, Lactobacillus mucosae NK41 alleviates E. coli K1 (K1)-induced cognitive impairment, depression, and colitis in mice by the amelioration of gut dysbiosis [5]. Gut microbiota consist of > 1,000 bacterial species in humans and animals [6] and display a variety of physiological functions such as modulation of the host's immune and nervous systems and defense against pathogen attacks [6, 7]. However, the induction of gut opportunistic E. coli K1 by immobilization stress (IS) causes colitis and psychiatric disorders [5, 8]. Bifidobacterium adolescentis IM38 mitigates anxiety in IS-treated mice [9]. Lactobacillus reuteri NK33 (NK33), B. adolescentis NK98 (NK98), and their (1:1) mixture were also reported to alleviate IS-induced anxiety/depression in mice [10]. However, at present, the gut microbiota-mediated inhibitory mechanism of probiotics NK33 and NK98 against anxiety/depression remains unclear. Therefore, in the present study, we examined the effects of NK33, NK98, and their mixtures (1:1, 4:1, and 9:1) on K1-induced gut dysbiosis, colitis, and depression in mice. Male C57BL/6 mice (5 weeks of age; 19-21 g in weight) were supplied by Koatech Inc. (Republic of Korea). The animals were maintained under controlled condition (temperature, 20 ± 2°C; humidity, 50 ± 10%; light-dark cycle, 12 h). The mice received standard laboratory chow with tap water ad libitum. All animal experiments were approved by the Institutional Animal Care and Use Committee of the University (IACC No. KUASP(SE)-19-152) and were performed according to the University Guide for Laboratory Animal Care and Usage. NK33 and NK98 were cultured in MRS broth (BD, USA) for probiotics and K1 was cultured in the tryptic soy broth (BD). Cultured bacteria were centrifuged (5,000 g, 20 min, 4 o C) and suspended in 1% maltose. The mice with K1-induced depression were prepared following a previous report [8]. To evaluate the effects of NK33 and NK98 on the occurrence of depression, the mice were randomly divided into seven groups (CON, EC, Lactobacillus reuteri NK33 (NK33) and Bifidobacterium adolescentis NK98 (NK98...