Acute stress elicited by bungee jumping suppresses human innate immunity

Abstract

Although a relation between diminished human immunity and stress is well recognized both within the general public and the scientific literature, the molecular mechanisms by which stress alters immunity remain poorly understood. We explored a novel model for acute human stress involving volunteers performing a first-time bungee jump from an altitude of 60 m and exploited this model to characterize the effects of acute stress in the peripheral blood compartment. Twenty volunteers were included in the study; half of this group was pretreated for 3 d with the β-receptor blocking agent propranolol. Blood was drawn 2 h before, right before, immediately after and 2 h after the jump. Plasma catecholamine and cortisol levels increased significantly during jumping, which was accompanied by significantly reduced ex vivo inducibility of proinflammatory cytokines as well as activation of coagulation and vascular endothelium. Kinome profiles obtained from the peripheral blood leukocyte fraction contained a strong noncanonical glucocorticoid receptor signal transduction signature after jumping. In apparent agreement, jumping down-regulated Lck/Fyn and cellular innate immune effector function (phagocytosis). Pretreatment of volunteers with propranolol abolished the effects of jumping on coagulation and endothelial activation but left the inhibitory effects on innate immune function intact. Taken together, these results indicate that bungee jumping leads to a catecholamine-independent immune suppressive phenotype and implicate noncanonical glucocorticoid receptor signal transduction as a major pathway linking human stress to impaired functioning of the human innate immune system.

Figure 1

Heart rate and blood pressure relative to jump. Heart rate and MAP relative to jump are shown. Both values changed significantly during the study, indicating that bungee jumping affected blood pressure and heart rate (P < 0.05). Heart rate response in time differed significantly between both groups (P < 0.05). Asterisks at the end of each curve indicate a significant (P < 0.05) change of the parameter during the experiment. P values indicate curve comparison. ^#Significant posttests between groups at the indicated time point.

Figure 2

Catecholamine and cortisol levels relative to jump. Levels of epinephrine and norepinephrine (A) and cortisol (B) in blood are shown. All values changed significantly during the study, indicating that bungee jumping affected catecholamine and cortisol levels (P < 0.05). No difference in catecholamines or cortisol levels was observed between both groups (P > 0.05). Asterisks at the end of each curve indicate a significant (P < 0.05) change of the parameter during the experiment. P values indicate curve comparison.

Figure 3

Blood leukocytes relative to jump. Numbers of leukocytes and differentiation relative to jump are shown. All values changed significantly during the study in both groups, indicating that bungee jumping affected leukocyte levels and differentiation (P < 0.05). Leukocyte numbers and differentiation did not differ between groups (P > 0.05). Asterisks at the end of each curve indicate a significant (P < 0.05) change of the parameter during the experiment. P values indicate curve comparison.

Figure 4

Cytokine levels after ex vivo LPS stimulation relative to jump. Levels of TNF-α, IL-8 and IL-10 after whole blood stimulation with endotoxin, as described in the Materials and Methods, are shown. TNF-α and IL-8, but not IL-10, values changed significantly (P < 0.05) during the study in both groups, indicating that bungee jumping affected the ex vivo release of proinflammatory cytokines to LPS (P < 0.05). No difference in cytokine levels were observed between both groups. Asterisks at the end of each curve indicate a significant (P < 0.05) change of the parameter during the experiment. P values indicate curve comparison.

Figure 5

Kinome profiling of human peripheral blood reveals acute stress-induced activation of noncanonical glucocorticoid receptor signal transduction. Peptides displaying differential significant phosphorylation by leukocyte lysates prepared from volunteer blood obtained 2 h before and directly after jumping were used to construct provisional signal transduction schemes, detailing the effects of acute stress on signaling biochemistry. Inconsistent peptides (for example, from the protein kinase C [PKC]α-responsive peptides, six peptides showed upregulation before jumping, whereas five other peptides were up-regulated after jumping) were discarded from the provisional signal transduction scheme. From the profiles obtained, a clear noncanonical glucocorticoid receptor signaling signature emerged. Arrows represent biochemical connection (bibliome). Green circles represent upregulation after the jump; red circles represent downregulation after the jump. Blue boxes depict kinases that are reported intermediates of noncanonical glucocorticoid signaling.

Figure 6

Phagocytosis and c-Fyn depression after bungee jumping. (A) Blood from four volunteers, taken 2 h before the jump and directly after jumping, was lysed, and the remaining leukocyte fraction was solubilized and subjected to immunoprecipitation using an anti-Fyn antibody and blotted with a pan phospho-Src family antibody. The results show that after jumping, Fyn activation in the leukocyte compartment is depressed. The upper band in the first lane is an artifact. (B) Phagocytosis index (number of phagocytosed fluorescein isothiocyanate–positive E. coli per cell) before and after a bungee jump was assessed. Phagocytosis index decreased after bungee jump in both groups (P < 0.05); no significant difference between control and propranolol group was observed. Asterisks indicate a significant (P < 0.05) change of the parameter respective to jump.

Figure 7

Coagulation parameters relative to jump. Levels of parameters of endothelial activation and coagulation relative to jump are shown. All values changed significantly during the study, indicating that bungee jumping affected endothelial activation and coagulation systems (P < 0.05). Factor 1 + 2, TAT complexes and tPA are shown as delta (%) from baseline. Asterisks at the end of each curve indicate a significant (P < 0.05) change of the parameter during the experiment. P values indicate curve comparison. ^#Significant posttests between groups at the indicated time point. FVIII, factor VIII.