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Published on: August 14, 2014
Apoptotic and inflammatory cytokine protein expression in intestinal lymphocytes after acute treadmill exercise in
1School of Public Health and Health Systems, University of Waterloo, Waterloo, Ontario, Canada.
Aim:
Gastrointestinal disturbances are common in athletes following intense exercise. Variations in apoptotic protein expression and cell death may contribute to acute exercise-induced intestinal inflammation. The effect of age on apoptotic protein response in the intestinal compartment in response to exercise is not known. Using a mouse model, we examined the effects of a single bout of treadmill running in young and old mice on intestinal lymphocyte (IL) expression of the apoptosis-inducing cytokine TNF-α, the pro-apoptotic proteins caspase-3 and 7, the anti-apoptotic protein Bcl-2, and IL apoptotic status (% AnnexinV+).
Methods:
Young (3-4 months, N.=44) and old (13-14 months, N.=45) female C57Bl/6 mice were randomized to treadmill exercise (10 min warm-up, 20 min at 22 m min-1, 30 min at 25 m min-1, 30 min at 28 m min-1, 2º slope) with sacrifice immediately (IMM) or 2hr after (2Hr), or to a non-exercised control (SED). IL were removed and prepared for analysis of % apoptosis (flow cytometry) and determination of apoptotic protein and cytokine expression (Western blotting). Plasma corticosterone and 8-iso-PGF2α were measured by EIA.
Results:
Exercise was associated with a higher IL expression of caspase-3 in IMM and 2Hr groups vs. SED (P<0.001), a higher expression of TNF-α in the IMM group vs. SED (P<0.001), and a lower Bcl-2 expression in the IMM and 2Hr groups vs. SED (P<0.01). There was a trend (P=0.07) for increased caspase-7 expression after exercise. IL caspase-3 and 7 and TNF-α expression did not differ by age whereas Bcl-2 expression was lower (P<0.001) and % Annexin V+ IL was higher (P<0.05) in old vs. young mice. Plasma corticosterone and 8-iso-PGF2α were higher (P<0.001 and P<0.05) in IMM vs. SED mice but did not differ by age.
Conclusion:
The expression of the pro-apoptotic proteins, caspase-3 and caspase-7, and the apoptosis-inducing cytokine, TNF-α, in IL did not differ by age in this animal model in response to a single intense exercise challenge. However, Old mice had lower expression of the 'protective' anti-apoptotic protein Bcl-2 and a higher percentage of early apoptotic IL. Whether repeated exercise results in less IL resiliency in elderly individuals remains to be determined.
