Timing-dependent effects of restraint stress on eosinophilic airway inflammation in mice.

Background: Chronic stress has been proposed to aggravate allergic inflammation, whereas acute stress may have functional beneficial effects. The aim of this study was to investigate the influence of timing of single short restraint stress (RST) in a model of eosinophilic airway inflammation.

Methods: The airways of ovalbumin (OVA)-sensitized mice were exposed to an intranasal OVA challenge. RST was applied in two different ways; either 2 h before (pre-stress) or after (post-stress) the OVA challenge, respectively, or as a combination of stress before and after (double-stress) the OVA challenge. One group of mice was also treated with metyrapone (ME) prior to a pre-stress challenge. The inflammatory cell response was evaluated in bronchoalveolar lavage fluid (BALF), lung and nasal tissue, as well as bone marrow.

Result: RST applied prior to the OVA challenge (pre-stress) inhibited OVA-induced airway inflammation in BALF and lung tissue, and reduced nasal histopathology compared to unstressed mice. Given as post-stress or double-stress, RST did not affect the inflammation in BALF, lungs or nasal tissue. Pre-treatment with ME prevented the pre-challenge stress evoked decrease in inflammation in BALF and lungs.

Conclusion: Effects of RST on eosinophilic airway inflammation appear to be strongly dependent on timing and, as could be judged from the ME inhibition pattern, also corticosterone dependent. Hypothalamic-pituitary-adrenal axis activation probably influences eosinophilic inflammation through specific sequences of compartmental activation and thereby timing effects are evident on cellular recruitment pattern during the allergic reaction.