AUTHOR=Vagnerová Karla , Vodička Martin , Hermanová Petra , Ergang Peter , Šrůtková Dagmar , Klusoňová Petra , Balounová Kateřina , Hudcovic Tomáš , Pácha Jiří 

TITLE=Interactions Between Gut Microbiota and Acute Restraint Stress in Peripheral Structures of the Hypothalamic–Pituitary–Adrenal Axis and the Intestine of Male Mice

JOURNAL=Frontiers in Immunology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/immunology/articles/10.3389/fimmu.2019.02655

DOI=10.3389/fimmu.2019.02655

ISSN=1664-3224

ABSTRACT=<p>The gut microbiota play an important role in shaping brain functions and behavior, including the activity of the hypothalamus-pituitary-adrenocortical (HPA) axis. However, little is known about the effect of the microbiota on the distinct structures (hypothalamus, pituitary, and adrenals) of the HPA axis. In the present study, we analyzed the influence of the microbiota on acute restraint stress (ARS) response in the pituitary, adrenal gland, and intestine, an organ of extra-adrenal glucocorticoid synthesis. Using specific pathogen-free (SPF) and germ-free (GF) male BALB/c mice, we showed that the plasma corticosterone response to ARS was higher in GF than in SPF mice. In the pituitary, stress downregulated the expression of the gene encoding CRH receptor type 1 (<italic>Crhr1</italic>), upregulated the expression of the <italic>Fkbp5</italic> gene regulating glucocorticoid receptor sensitivity and did not affect the expression of the proopiomelanocortin (<italic>Pomc</italic>) and glucocorticoid receptor (<italic>Gr</italic>) genes. In contrast, the microbiota downregulated the expression of pituitary <italic>Pomc</italic> and <italic>Crhr1</italic> but had no effect on <italic>Fkbp5</italic> and <italic>Gr</italic>. In the adrenals, the steroidogenic pathway was strongly stimulated by ARS at the level of the steroidogenic transcriptional regulator <italic>Sf-1</italic>, cholesterol transporter <italic>Star</italic> and <italic>Cyp11a1</italic>, the first enzyme of steroidogenic pathway. In contrast, the effect of the microbiota was significantly detected at the level of genes encoding steroidogenic enzymes but not at the level of <italic>Sf-1</italic> and <italic>Star</italic>. Unlike adrenal <italic>Sf-1</italic>, the expression of the gene <italic>Lrh-1</italic>, which encodes the crucial transcriptional regulator of intestinal steroidogenesis, was modulated by the microbiota and ARS and this effect differed between the ileum and colon. The findings demonstrate that gut microbiota have an impact on the response of the pituitary, adrenals and intestine to ARS and that the interaction between stress and the microbiota during activation of glucocorticoid steroidogenesis differs between organs. The results suggest that downregulated expression of pituitary <italic>Pomc</italic> and <italic>Crhr1</italic> in SPF animals might be an important factor in the exaggerated HPA response of GF mice to stress.</p>