Oral treatment with Lactobacillus reuteri attenuates depressive-like behaviors and serotonin metabolism alterations induced by chronic social defeat stress
Graphical abstract
Introduction
Depression is a devastating disorder, afflicting up to 300 million global people of all ages and representing one of the leading causes of disability worldwide (Global Burden of Disease Study, 2013 Collaborators; The United Nations World Health Organization stated in a February 2017 Fact Sheet on Depression). Although effective treatments are available, approximately one third of all patients with depression fail to respond to conventional antidepressant therapies (Rush et al., 2006), further contributing to the global burden of the disease. The last decade has witnessed a growing interest in the potential contribution of microbiota–gut–brain axis signaling to psychiatric disorders (Burokas et al., 2017; Cryan et al., 2019; Fung et al., 2017; Kelly et al., 2016; Scriven et al., 2018), although precise biological mechanisms remain unclear. Mice lacking a normal gut flora display reduced basal and stress-induced behavioral impairments associated with anxiety and depression. These phenotypes are restored following intestinal colonization (Diaz Heijtz et al., 2011). Furthermore, patients with major depressive disorder (MDD) harbor a microbiota distinct from that of healthy controls. Fecal transfer of the MDD microbiota to gut flora mice resulted in depression-like behaviors, including increased immobility time during the forced swim and reduced center distance traveled in the open-field test (Zheng et al., 2016). Similarly, the rats display increased immobility during the forced swim test and elevated pro-inflammatory cytokines in the maternal separation model of depression. The cytokine levels are restored to normal following treatment with the probiotic Bifidobacterium infantis (Desbonnet et al., 2010).
The pathways that mediate microbiota–gut–brain interactions in stress-associated depression involve the modulation of neuroimmunity (Bharwani et al., 2017), host metabolism (Zheng et al., 2016), neurotransmitter systems (Zhu et al., 2010), and vagal nerve (Bravo et al., 2011). Given the pivotal importance of neurotransmission to mood regulation, the impact of gut microbiota on the monoamine serotonin and on the excitatory amino acid glutamate was considered (Zhu et al., 2010). Serotonin (5-hydroxytryptamine, 5-HT) synthesis is reduced in patients with MDD. The increased 5-HT content in synaptic cleft is one of the most common targets in depression treatment (Marije aan het Rot et al., 2009). Liang et al. (2015) indicated that an antidepressant effect of L. helveticus NS8 in rats subjected to chronic restraint stress was due to restored hippocampal 5-HT and norepinephrine levels. More than 90% of 5-HT content in the body is synthesized in the gut by enterochromaffin cells (ECs), mucosal mast cells, and myenteric neurons (Gershon and Tack, 2007) and then distributed to various body sites. However, molecular mechanisms underlying the control for gut 5-HT metabolism remain unclear. Recent study demonstrated that the indigenous spore-forming bacteria (Sp) plays a critical role in regulating host 5-HT by direct metabolic (a-tocopherol, tyramine, butyrate and para aminobenzoic acid) signaling to promote 5-HT biosynthesis from colonic ECs (Yano et al., 2015). In addition, the human gut microbiota-induced 5-HT production in the colon of Germ-free (GF) mice is induced by microbiota-derived short-chain fatty acids (SCFAs), which stimulate EC cells to increase the transcription of TPH1 (tryptophan hydroxylase 1) mRNA (Reigstad et al., 2014).
This study aimed to investigate the role of microbe-induced gut–to–brain signal on depressive-like behaviors and serotonin metabolism alterations induced by chronic exposure to a psychosocial stressor. An animal model of susceptible mice to chronic social defeat stress (Aubry et al., 2019; Golden et al., 2011) was used to test whether the oral administration of a bacterium with immunomodulatory properties could modulate psychosocial stress-induced depressive-like behaviors, gut microbiota alteration, and serotonin metabolism. Lactobacillus reuteri 3 (L. reuteri 3) was isolated from the Peyer's patches, a well-characterized gut-associated lymphoid tissue and the entry site for luminal antigens (Kiyono et al., 2008). L. reuteri 3 was selected as a test organism because it showed anti-inflammatory in vitro when isolated from normal chow-diet mice and lacking-in-obesity mice (Sun et al., 2016). Furthermore, treatment with this strain decreases the pro-inflammatory cytokine levels and increases the ambulatory activity compared with the obese mice induced by high-fat diet (Qiao et al., 2015). The psychosocial stress-induced disruptions in the microbiota were examined, and whether the administration of a single bacterial strain can facilitate recovery of the dysbiosis community was investigated.
Section snippets
Animals
Male C57BL/6 mice (Beijing Vital River Laboratory Animal Technology Co., Ltd. Beijing, China) were purchased at 8 weeks of age and group housed (4/cage) upon arrival. Retired male CD-1 breeders were also purchased from Beijing Vital River Laboratory Animal Technology Co., Ltd. and individually housed upon arrival. Mice acclimated to the colony room (22 ± 1 °C, 60 ± 5% humidity) for a minimum of one week and were maintained on a 12h (07:00–19:00) light-dark schedule with free access to food and
Microbial treatment modulates stress-induced depression-like behaviors
Mice were subjected to the social interaction test, SPT, and TST on day 45 to assess the effect of L. reuteri 3 on depression-like behaviors (Fig. 1). The depressed mice displayed a significant reduction in the interaction ratio compared with control mice (Fig. 2B; Depression + VEH versus Control + VEH, 0.56 ± 0.21 versus 1.33 ± 0.32, respectively; p = 0.001, unpaired t-test). The Depression + L. reuteri 3 mice displayed a significantly higher interaction ratio than the Depression + VEH mice
Discussion
Recent studies reveal that the microbiota–gut–brain axis affects a variety of complex behaviors and contributes to the development and function of the nervous system (de J R De-Paula et al., 2018; Fung et al., 2017; Long-Smith et al., 2019). However, the molecular mechanism of bidirectional interaction between the microbiome and brain remains unknown. The influence of a single orally administered bacteria strain, L. reuteri 3, was demonstrated for the first time on depressive-like behaviors and
Conclusions
In summary, strong evidences were provided that despite the complexity of the gut microbiota, exposure to a single microbial strain Lactobacillus reuteri 3 can protect against depressive-like behaviors induced by chronic social defeat stress. While the current study did not delineate a mechanism of action of Lactobacillus reuteri 3 in attenuating stress-induced behavioral changes, results suggest that a more detailed investigation of gut microbiota, SCFAs, and serotonin metabolism will likely
Ethics statement
All procedures in this study were conducted in accordance with the National Institutes of Health guide for the care and use of laboratory animals (NIH Publications No. 8023, revised 1978) and according to the protocol approved by the Animal Care and Use Committee of Jining Medical University. All efforts were made to minimize animal suffering.
CRediT authorship contribution statement
Ruining Xie: Writing - original draft, Methodology. Pei Jiang: Funding acquisition, Supervision. Li Lin: Data curation. Jian Jiang: Investigation, Methodology. Bin Yu: Funding acquisition. Jingjing Rao: Formal analysis. Hui Liu: Project administration. Wei Wei: Resources, Software. Yi Qiao: Funding acquisition, Writing - review & editing, Project administration.
Declaration of competing interest
The authors report no conflict of interest.
Acknowledgements
This work was supported by grants from the National Natural Science Foundation of China (No.31600947, No.81603509 and No.81602846), Supporting Fund for Teachers' research of Jining Medical University (JY2017KJ005), and Shandong Medical and Health Science and Technology Development Program Project (Grant No. 2015WS0418).
References (58)
- et al.
Possible association of Bifidobacterium and Lactobacillus in the gut microbiota of patients with major depressive disorder
J. Affect. Disord.
(2016) - et al.
Bifidobacterium longum 1714 as a translational psychobiotic: modulation of stress, electrophysiology and neurocognition in healthy volunteers
Transl. Psychiatry
(2016) - et al.
Life without peripheral serotonin: insights from tryptophan hydroxylase 1 knockout mice reveal the existence of paracrine/autocrine serotonergic networks
ACS Chem. Neurosci.
(2012) - et al.
A diet enriched with curcumin promotes resilience to chronic social defeat stress
Neuropsychopharmacology
(2019) - et al.
Ketamine and imipramine reverse transcriptional signatures of susceptibility and induce resilience-specific gene expression profiles
Biol. Psychiatry
(2017) - et al.
The intestinal microbiota affect central levels of brain-derived neurotropic factor and behavior in mice
Gastroenterology
(2011) - et al.
The anxiolytic effect of Bifidobacterium longum NCC3001 involves vagal pathways for gut–brain communication
Neuro Gastroenterol. Motil.
(2011) - et al.
Oral treatment with Lactobacillus rhamnosus attenuates behavioural deficits and immune changes in chronic social stress
BMC Med.
(2017) - et al.
Ingestion of Lactobacillus strain regulates emotional behavior and central GABA receptor expression in a mouse via the vagus nerve
Proc. Natl. Acad. Sci.
(2011) - et al.
Targeting the microbiota-gut-brain axis: prebiotics have anxiolytic and antidepressant-like effects and reverse the impact of chronic stress in mice
Biol. Psychiatry
(2017)
Depression but not anxiety is associated with metabolic syndrome in primary care based community sample
Psychoneuroendocrinology
Social stress models in depression research: what do they tell us?
Cell Tissue Res.
A β3-adrenergic-leptin-melanocortin circuit regulates behavioral and metabolic changes induced by chronic stress
Biol. Psychiatry
Exploration of microbiota targets for major depressive disorder and mood related traits
J. Psychiatr. Res.
The microbiota-gut-brain axis
Physiol. Rev.
Relevance of gut microbiota in cognition, behaviour and Alzheimer's disease
Pharmacol. Res.
Effects of the probiotic Bifidobacterium infantis in the maternal separation model of depression
Neuroscience
Enteropathogenic Escherichia coli infection inhibits intestinal serotonin transporter function and expression
Gastroenterology
The gut microbiome: the role of a virtual organ in the endocrinology of the host
J. Endocrinol.
The effects of freezing on faecal microbiota as determined using MiSeq sequencing and culture-based investigations
PLoS One
Interactions between the microbiota, immune and nervous systems in health and disease
Nat. Neurosci.
The serotonin signaling system: from basic understanding to drug development for functional GI disorders
Gastroenterology
The treatment-naive microbiome in new-onset Crohn's disease
Cell Host Microbe
Global, regional, and national incidence, prevalence, and years lived with disability for 301 acute and chronic diseases and injuries in 188 countries, 1990-2013: a systematic analysis for the Global Burden of Disease Study 2013
Lancet
A standardized protocol for repeated social defeat stress in mice
Nat. Protoc.
Effect of isomalt consumption on faecal microflora and colonic metabolism in healthy volunteers
Br. J. Nutr.
Normal gut microbiota modulates brain development and behavior
Proc. Natl. Acad. Sci.
Transferring the blues: depression-associated gut microbiota induces neurobehavioural changes in the rat
J. Psychiatr. Res.
The mucosal immune system
Fundam. Immunol.
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These authors contributed equally to this work.