T Cell-Induced Colitis Is Exacerbated by Prolonged Stress: A Comparison in Male and Female Mice.

Psychological stress exposure is well recognized to exacerbate inflammatory bowel disease (IBD) but the mechanisms involved remain poorly understood. In this study, chronic T cell-mediated colitis was induced by adoptively transferring CD4+CD45RBhigh splenic T cells from C57BL/6 WT donor mice into Rag1tm1Mom mice. Two weeks after T cell transfer, mice were exposed to a prolonged restraint stressor (RST) for 8 h per day for 6 consecutive days. The colitis phenotype was assessed via histopathology and semi-quantitative rt-PCR at humane endpoints or 10 weeks post-T-cell transfer. Mice that received the T cell transplant developed chronic colitis marked by increases in colonic histopathology and inflammatory cytokines. Colonic histopathology was greater in males than females regardless of RST exposure but RST exposure increased histopathology scores in females such that they reached scores observed in the males. This pattern was consistent with cytokine gene expression and protein levels in the colon (especially for IFN-γ, IL-17A, and TNF-α). Serum cytokine levels were not strongly affected by exposure to the stressor. Using a murine model of chronic T cell-mediated colitis, this study demonstrates that biological sex strongly influences colonic inflammation and exposure to chronic stress has a more pronounced effect in females than in males.

Stressor-Induced Increases in Circulating, but Not Colonic, Cytokines Are Related to Anxiety-like Behavior and Hippocampal Inflammation in a Murine Colitis Model.

Stressor exposure increases colonic inflammation. Because inflammation leads to anxiety-like behavior, we tested whether stressor exposure in mice recovering from dextran-sulfate-sodium (DSS)-induced colitis enhances anxiety-like behavior. Mice received 2% DSS for five consecutive days prior to being exposed to a social-disruption (SDR) stressor (or being left undisturbed). After stressor exposure, their behavior was tested and colitis was assessed via histopathology and via inflammatory-cytokine measurement in the serum and colon. Cytokine and chemokine mRNA levels in the colon, mesenteric lymph nodes (MLNs), hippocampus, and amygdala were measured with RT-PCR. SDR increased anxiety-like behaviors, which correlated with serum and hippocampal IL-17A. The stressor also reduced IL-1ß, CCL2, and iNOS in the colonic tissue, but increased iNOS, IFNγ, IL-17A, and TNFα in the MLNs. A network analysis indicated that reductions in colonic iNOS were related to elevated MLN iNOS and IFNγ. These inflammatory markers were related to serum and hippocampal IL-17A and associated with anxiety-like behavior. Our data suggest that iNOS may protect against extra-colonic inflammation, and when suppressed during stress it is associated with elevated MLN IFNγ, which may coordinate gut-to-brain inflammation. Our data point to hippocampal IL-17A as a key correlate of anxiety-like behavior.

Polyethylene Glycol 3350 Changes Stool Consistency and the Microbiome but not Behavior of CD1 Mice.

OBJECTIVES: Polyethylene Glycol 3350 (PEG3350) is a laxative commonly used to treat constipation in children. The Food and Drug Administration has received reports of increased anxiety, aggression, and obsessive--compulsive behaviors in children administered PEG3350. Thus, we assessed whether daily administration of PEG3350 leads to anxiety-like behavior in mice. METHODS: Outbred CD-1 IGS mice were administered either a high or a low dose of PEG3350 via daily oral gavage for 2 weeks. As a laxative comparison and control, additional mice were given a high or low dose of magnesium citrate or vehicle (water). Weight and stool consistency were assessed after each gavage to determine laxative effectiveness. Anxiety-like behaviors were assessed using light/dark, open field, and elevated plus maze (EPM) tests at baseline, after 2 weeks of daily gavage, and after a 2 week washout in experiment 1, and after 2 weeks of daily gavage in experiment 2. Stool samples were collected for microbiome analysis in experiment 2 at baseline, after 2 weeks of daily gavage, and after 2 weeks washout. RESULTS: PEG3350 and magnesium citrate significantly changed stool consistency, as well as microbiome alpha and beta diversity. Anxiety-like behaviors were not, however, different in mice administered low or high doses of PEG3350 or magnesium citrate. CONCLUSIONS: Although changes in stool consistency and the gut microbiome occurred, administration of PEG3350 did not alter anxiety-like behaviors.