Decreased innervation of eczematous skin in NC/Nga atopic mice during chronic mild stress

Chronic mild stress modulates 5-HT1A and 5-HT2A receptor expression in the cerebellar cortex of NC/Nga atopic-like mice

Atopic eczema symptoms may worsen due to stress. In the present study, the cerebellar cortex of the atopic-like mouse NC/Nga was studied regarding the effect of chronic mild stress on expression of two well-characterized serotonergic receptors (R), 5-HT1A and 5-HT2A. In total 24 mice were used. Sixteen of these mice were subjected to unpredictable stressors for 12 weeks, and 8 mice were used as controls. In order to evoke an eczema, a mite antigen was applied to 16 mice from week 9 of the experiment. Thus, three groups of mice, stressed eczematous (SE), non-stressed eczematous (NSE) and stressed control (SC), respectively, were obtained. The expression of the 5-HT1AR was analyzed using quantitative immunohistochemistry. For evaluation of 5-HT2AR a semi-quantitative technique was used, the cell density and signal intensity being measured. The highest average value for 5-HT1AR expression, in the Purkinje cells, was recorded in the NSE group, while the lowest average was in the SC group. 5-HT1AR expression differed significantly between the groups. The highest average value for density of 5-HT2AR positive Purkinje cells was evident in the SE group, while the lowest was in the SC group, this difference between groups also being statistically significant. In addition, the signal intensity was highest in the SE group, with a difference compared to the other groups. In conclusion, chronic mild stress modulates serotonergic receptor expressions in the cerebellar cortex of atopic-like mice.

Substance P alterations in skin and brain of chronically stressed atopic-like mice

BACKGROUND

Stress is known to worsen the symptoms of atopic eczema (AE). Substance P is likely to play an important role in the development and pathogenesis of AE.

OBJECTIVE

To examine a possible connection between chronic mild stress and changes in the expression of substance P and its receptor (R) neurokinin (NK) 1 in the skin and stress-related brain regions in NC/Nga atopic-like mice.

METHODS

The mice were divided into three groups (eight animals per group): SE (stressed eczematous), NSE (non-stressed eczematous) and SC (stressed control). Ears and brains of the mice were investigated using immunohistochemistry and RT-PCR.

RESULTS

In the skin, there was a decrease in the number of substance P immunoreactive nerve fibres in SE compared with SC group. RT-PCR showed a strong tendency to an increase in mRNA for NK1R in the skin of SE compared with NSE mice. There was an increase in the number of mast cells and the degree of their degranulation in the SE compared with both other groups. A decrease in substance P immunoreactivity in medial hippocampus was found in SE compared with NSE animals. In prefrontal cortex and central amygdala, there were no significant differences in substance P immunoreactivity between the three groups.

CONCLUSION

Exposure to chronic mild stress in NC/Nga atopic-like mice may result in altered expression patterns of substance P in the skin and hippocampus.

Effect of chronic mild stress on serotonergic markers in the skin and brain of the NC/Nga atopic-like mouse strain

Atopic eczema is often worsened by stress. While acute stress is associated with increased turnover of serotonin (5-hydroxytryptamine; 5-HT), chronic stress causes a decrease. In chronic stress, there is a decrease of the 5-HT1A receptor (R)- and an increase in the 5-HT2AR-responsiveness to 5-HT. In the present study, the impact of chronic mild stress on the expression of 5-HT1A and 5-HT2A receptors and serotonin transporter protein (SERT) was investigated in eczematous skin and brain of atopic-like NC/Nga mice. Twenty-four NC/Nga mice were subjected to chronic mild stress for 12 weeks, and eczema was induced by applying a mite antigen (Dermatophagoides pteronyssinus) on the ears for the last 4 weeks. The mice were divided into three groups, eight per group, stressed eczematous (SE), non-stressed eczematous (NSE) and stressed control (SC). The biopsies were analysed by immunohistochemistry, using a streptavidin-biotin technique. There was an increased number of 5-HT containing dermal mast cell-like mononuclear cells in the skin of mice with eczema (SE and NSE, respectively) compared with the SC, and a tendency to more 5-HT-positive cells in the SE compared with the NSE group. Increased 5-HT1AR immunoreactivity (IR) in the skin and hippocampus of the eczematous groups compared to the control group was seen, but no difference between the SE and NSE groups. The epidermal immunoreactivity for 5-HT2AR was highest in the SE and NSE compared to the SC group, and was also higher in the SE compared to NSE. 5-HT2AR expression was also seen on nerve bundles, the number and intensity of such bundles being decreased in the SE compared to the NSE group. In the CA1 area of the hippocampus, there was an increase in the quantity of cells immunoreactive for 5-HT2AR in the SE versus the NSE group and also in the SE versus the SC group. SERT-IR was found also on nerve bundles with a decreased number in the SE compared to the NSE and SC group. There is a modulation of the expression of serotonergic markers in the eczematous skin and brain of the atopic-like mouse during chronic mild stress.