Clinical findings suggest that inflammatory disease symptoms are aggravated by ongoing, repeated stress, but not by acute stress. We hypothesized that, compared with single acute stressors, chronic repeated stress may engage different physiological mechanisms that exert qualitatively different effects on the inflammatory response. Because inhibition of plasma extravasation, a critical component of the inflammatory response, has been associated with increased disease severity in experimental arthritis, we tested for a potential repeated stress-induced inhibition of plasma extravasation. Repeated, but not single, exposures to restraint stress produced a profound inhibition of bradykinin-induced synovial plasma extravasation in the rat. Experiments examining the mechanism of inhibition showed that the effect of repeated stress was blocked by adrenalectomy, but not by adrenal medullae denervation, suggesting that the adrenal cortex mediates this effect. Consistent with known effects of stress and with mediation by the adrenal cortex, restraint stress evoked repeated transient elevations of plasma corticosterone levels. This elevated corticosterone was necessary and sufficient to produce inhibition of plasma extravasation because the stress-induced inhibition was blocked by preventing corticosterone synthesis and, conversely, induction of repeated transient elevations in plasma corticosterone levels mimicked the effects of repeated stress. These data suggest that repetition of a mild stressor can induce changes in the physiological state of the animal that enable a previously innocuous stressor to inhibit the inflammatory response. These findings provide a potential explanation for the clinical association between repeated stress and aggravation of inflammatory disease symptoms and provide a model for study of the biological mechanisms underlying the stress-induced aggravation of chronic inflammatory diseases.
There is considerable evidence that stress can exacerbate a number of chronic inflammatory diseases. For example, repeated mild daily stressors have been associated with exacerbation of rheumatoid arthritis (1, 2), ulcerative colitis (3), inflammatory bowel disease (4), and asthma (5). Patients with rheumatoid arthritis (6) cite stress as the most frequent antecedent of symptom flares, and stress management interventions can reduce symptoms (7). Similarly, studies in animal models of arthritis (8, 9) demonstrate that stress can exacerbate disease activity. Very little is known, however, about the biological mechanisms by which stress may exert these effects.Acute stress (10, 11), as well as acute activation of neuroendocrine circuits known to be activated by stressful stimuli (12, 13), transiently suppresses the inflammatory response. However, exacerbation of inflammatory diseases has been correlated with chronic repeated exposure to stressful stimuli rather than with exposure to a single acute stressor (2-4). We hypothesized that, compared with single acute stressors, chronic repeated stress may engage differe...