Effects of Acute Stress or Centrally Injected Interleukin-1beta on Neuropeptide Expression in the Immune System

Acute stress stimulates the expression and release of corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) from the hypothalamus, and the pro-opiomelanocortin products beta-endorphin and ACTH from the anterior pituitary. These neuropeptides are also expressed in immune tissues, and it has been proposed that they may modulate immune responses to stress through paracrine mechanisms. We subjected rats to restraint stress or central injection of interleukin (IL)-1beta to determine whether these acute stimuli can alter the expression of neuropeptides in the spleen and thymus. Restraint stress significantly increased the contents of all these neuropeptides in thymic, but not splenic, extracts. A single icv injection of IL-1beta increased contents of CRH, AVP, ACTH and beta-endorphin in the spleens of both sham-operated and adrenalectomised (ADX) rats. IL-1beta increased thymic contents of CRH and ACTH in sham-operated rats but these increases were not observed in ADX rats. These results suggest that the effects of IL-1beta on neuropeptide expression in the spleen are independent of glucocorticoids, whereas IL-1beta stimulation of neuropeptide expression in the thymus is dependent on circulating glucocorticoids. There were significant correlations between increases in CRH, ACTH and beta-endorphin in the spleen, and between CRH and ACTH in the thymus, consistent with the suggestion that IL-1beta-induced increases in ACTH and beta-endorphin may be mediated through CRH. These results provide evidence that stressors can directly influence neuropeptide expression in immune tissues. Thus stress may influence immune functions through paracrine mechanisms involving locally synthesised neuropeptides as well as through activation of the hypothalamo-pituitary-adrenal axis.     

Anxiety in recovery from severe burn injury: an experimental comparison

Adjustment to burn injury is a slow process that often results in high distress and anxiety. This study aimed to investigate the impact on anxiety of viewing various types of photographic stimuli (including burn injuries), comparing a burn-injured and control sample. An experimental design was used comparing those recovering from a burn injury with age- and gender-matched controls. Thirty participants from a burns support group and their matched controls were asked to complete a trait anxiety measure (STAI Y-2). Participants then completed the state anxiety measure (STAI Y-1) after viewing different types of photographic stimuli (burn injuries, uninjured body parts, neutral) under controlled experimental conditions. Results demonstrated significant differences in anxiety levels between groups with respect to trait anxiety and state anxiety after each experimental condition. Age of injury was also found to be a significant influence over trait anxiety. A significant effect of experimental condition was found, as was a significant interaction between group and condition. Those with burn injuries were more anxious than controls - a difference that was further exaggerated when participants viewed photographs of burned or uninjured body parts in an experimental setting.