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Expression of the inducible nitric oxide synthase (iNOS) in human leukocytes: responses to running exercise
A M Niess1, M Sommer, E Schlotz
1Medical Clinic und Polyclinic, Department of Sports Medicine, University of Tuebingen, Germany. andreas.niess@uni-tuebingen.de
Introduction:
We examined the influence of two different bouts of vigorous running exercise on the expression of the inducible nitric oxide synthase (iNOS) in leukocytes (LE).
Methods:
In study 1, 10 trained runners competed in a half marathon (HM) lasting 90.5 +/- 11.0 min. In study 2, 8 untrained subjects performed a graded treadmill test followed by a continuous run (CR) until exhaustion (11.3 +/- 1.3 min). iNOS mRNA levels were assessed by RT/PCR at rest, 0, 3, and 24 h after HM and CR. In study 2, iNOS was additionally analyzed at the protein level in lympho- (L), mono- (M), and granulocytes (G) by flow cytometry at rest and up to 48 h after CR.
Results:
Analysis revealed a rise of the iNOS transcript directly after the HM in 8 of 10 subjects. In study 2, the expression of iNOS protein at rest differed between L (mean +/- SE: 30.9 +/- 4.5% iNOS positive cells), M (91.3 +/- 4.0%), and G (64.9 +/- 10.3%): 3 h after CR, expression of iNOS increased in L (67.3 +/- 7.4%) and G (90.3 +/- 2.9%) and was still elevated 48 h post-exercise. However, our measurements failed to detect significant changes of leukocyte iNOS mRNA in response to CR. After the HM, our findings were paralleled by elevated plasma levels of interleukin-8, myeloperoxidase (MPO), and partly of TNF-alpha, whereas CR only induced a low rise of MPO.
Conclusion:
Our investigations revealed an increased expression of iNOS at the transcriptional and translational level in response to vigorous exercise. This reflects an inflammatory response and may contribute to an exercise-induced rise of endogenous nitric oxide production. It remains unclear if these effects serve an in-vivo immunoregulatory or cell-damaging role.