Acute stress modulates the histamine content of mast cells in the gastrointestinal tract through interleukin-1 and corticotropin-releasing factor release in rats

Abstract

Stress results in activation of the hypothalamic pituitary adrenal axis and affects illnesses such as neuroinflammatory syndrome. In vivo acute stress (restraint stress) induces gastrointestinal function disturbances through colonic mast cell activation. This study investigated the effect of acute stress in histamine content of colonic mast cells, and the central role of interleukin-1 (IL-1) and corticotropin-releasing factor (CRF) in this effect. After a restraint stress session colonic segments were isolated and submitted to three protocols: (i) determination of histamine levels by radioimmunoassay (RIA) after incubation with 48/80 compound, (ii) evaluation by histology of mucosal mast cell (MMC) number and (iii) determination of histamine immunoreactivity of MMC. These procedures were conducted (1) in sham or stressed rats, (2) in stressed rats previously treated with intracerebroventricular (I.C.V.) IL-1ra or alpha-helical CRF9-41, (3) in naive rats pretreated with I.C.V. rhIL-1beta or CRF and (4) in rats treated with central IL-1beta and CRF plus alpha-helical CRF and IL-1ra, respectively (cross-antagonism reaction). Acute stress increases histamine content in colonic mast cells, without degranulation. I.C.V. pretreatment with IL-1ra or alpha-helical CRF9-41 blocked stress-induced mast cell histamine content increase. Both I.C.V. rhIL-1beta and CRF injections reproduced the stress-linked changes. I.C.V. treatment with CRF antagonist blocked I.C.V. rhIL-1beta-induced mast cell histamine content increase, whereas central IL-1ra did not affect stress events induced by I.C.V. CRF administration. These results suggest that in rats acute stress increases colonic mast cell histamine content. This effect is mediated by the release in cascade in the brain first of IL-1 and secondly of CRF.

Figure 1

A, influence of stress on histamine mast cell release after 48/80 compound stimulation. Note that stress increases histamine mast cell content. B, MMC histamine immunohistochemical labelling in stressed (▪) vs.control (□) rats. The number of MMC with a high DAB colouration: intensity +, was expressed as a percentage of total MMC coloured with DAB (low intensity). A significant increase of MMC histamine level label in stressed rats was observed compared with the label control. Results are expressed as means ± S.E.M., *P < 0.05 from control values.

Figure 5. Histamine immunoreactivity labelling in a distal colonic segment in both naive and stressed rats

Note a higher intensity of DAB colouration in stressed animals (right-hand panel) compared with controls (left-hand panel).

Figure 2. Effect of α-helical CRF and IL-1ra on stress-induced histamine content modulation in mast cells

Note the antagonistic effect of both α-helical CRF and IL-1ra in stress-induced enhancement of histamine synthesis in proximal and distal colonic mast cells. Results are expressed as means ± S.E.M., *P < 0.05 from control values. ▪, control; , stressed + saline i.c.v.; , stressed +α-helical CRF (20 μg kg⁻¹i.c.v.); □, stressed + IL-1ra (40 μg kg⁻¹i.c.v.).

Figure 3. Influence of central rhIL-1β and CRF administration on histamine content enhancement in mast cells

Note that CRF administered i.c.v. enhanced histamine levels in mast cells. A similar effect was observed in animals treated by an i.c.v. rhIL-1β administration. Results are expressed as means ± S.E.M., *P < 0.05 from control values. ▪, control; , rhIL-1β (80 ng kg⁻¹i.c.v.); □, CRF (20 μg kg⁻¹i.c.v.).

Figure 4. Relationship between activation of central rhIL-1 b and CRF receptors

Note that a -helical CRF suppresses rhIL-1 b -induced enhancement of histamine synthesis,whereas IL-1ra failed to reverse the i.c.v. CRF-induced histamine synthesis enhancement in mast cells. Results are expressed as means ±s.e.m., *: P < 0.05 from control values. ▪, control; ,rhIL-1β (80 ng kg¹i.c.v.); , CRF (20 μg kg⁻¹i.c.v.); , α -helical CRF (20 μg kg⁻¹i.c.v.) + rhIL-1β (80 ng kg⁻¹i.c.v.); □, IL-1ra (40 μg kg⁻¹i.c.v.) + CRF (20 μg kg⁻¹i.c.v.).