title: Strenuous resistive breathing induces proinflammatory cytokines and stimulates the HPA axis in humans.
abstract: Interleukin-1beta (IL-1beta) and interleukin-6 (IL-6), powerful stimulants of the hypothalamic-pituitary-adrenal (HPA) axis, increase in response to whole body exercise. Strenuous inspiratory resistive breathing (IRB), a form of clinically relevant "exercise" for the respiratory muscles, produces beta-endorphin through a largely unknown mechanism. We investigated (in 11 healthy humans) whether strenuous IRB produces proinflammatory cytokines and beta-endorphin in parallel with stimulation of the HPA axis, assessed by concurrent measurement of ACTH. Subjects underwent either severe [at 75% of maximal inspiratory pressure (P(m) (max))] or moderate (at 35% of P(m) (max)) IRB. Plasma cytokines, beta-endorphin, and ACTH were measured at rest (point R), at the point at which the resistive load could not be sustained (point F), and at exhaustion [15 min later (point E)]. During severe IRB, IL-1beta increased from 0.83 +/- 0.12 pg/ml at point R to 1.88 +/- 0. 53 and 4.06 +/- 1.27 pg/ml at points F and E, respectively (P < 0. 01). IL-6 increased from 5.30 +/- 1.02 to 10.33 +/- 2.14 and 11.66 +/- 2.29 pg/ml at points F and E, respectively (P = 0.02). ACTH and beta-endorphin fluctuated from 20.87 +/- 5.49 and 25.03 +/- 3.97 pg/ml at point R to 22.97 +/- 4.41 and 26.32 +/- 3.93 pg/ml, respectively, at point F and increased to 46.96 +/- 8.55 and 40.32 +/- 5.94 pg/ml, respectively, at point E (P < 0.01, point E vs. point F). There was a positive correlation between the IL-6 at point F and the ACTH and beta-endorphin at point E (r = 0.88 and 0.94, respectively; P < 0.01) as well as between the increase in IL-6 (between points R and F) and the increases in ACTH and beta-endorphin (between points F and E, r = 0.91 and 0.92, respectively; P < 0.01). Moderate IRB did not produce any change. We conclude that severe IRB produces proinflammatory cytokines and stimulates the HPA axis in humans secondary to the production of cytokines (especially IL-6).
authors.affiliation: Department of Critical Care, University of Athens Medical School, Evangelismos Hospital, GR-10675 Athens, Greece.
authors.forename: T
authors.initials: T
authors.lastname: Vassilakopoulos
authors.forename: S
authors.initials: S
authors.lastname: Zakynthinos
authors.forename: C
authors.initials: C
authors.lastname: Roussos
mesh_terms: D000324:Adrenocorticotropic Hormone / Q000097:blood; D000328:Adult; D000403:Airway Resistance / Q000502:physiology*; D016207:Cytokines / Q000097:blood / Q000378:metabolism*; D005260:Female; D006801:Humans; D007030:Hypothalamo-Hypophyseal System / Q000502:physiology*; D018836:Inflammation Mediators / Q000378:metabolism*; D008297:Male; D010913:Pituitary-Adrenal System / Q000502:physiology*; D011446:Prospective Studies; D012143:Respiratory Physiological Phenomena; D001615:beta-Endorphin / Q000097:blood
chemical_list: D016207:Cytokines; D018836:Inflammation Mediators; D001615:beta-Endorphin; D000324:Adrenocorticotropic Hormone