Pro inflammatory cytokine production by polymorphonuclear neutrophils following a 12-day period of intensified training

Abstract

This thesis investigated whether resting and/or exercise-induced interleukin-8 (IL-8) and tumor necrosis factor-α (TNF-α) production by antigen-stimulated polymorphonuclear neutrophils (PMN) would alter over a 12-day intensified training period (ITP). Ten physically active males completed seventeen exercise sessions in total, including: two main trials (30-min self-paced treadmill run (RPETR), 10 km time trial), completed before (MTPRE) and after (MTPOST) a twelve day ITP, and two V̇O2max tests completed before (VO2PRE) and after (VO2POST) the ITP. Blood samples were collected via venepuncture before and after the RPETR at MTPRE and MTPOST. PMN were isolated from whole blood and incubated for 18 h with lipopolysaccharide (LPS) antigen. IL-8 and TNF-α production by LPS-stimulated PMN was determined using enzyme-linked immunosorbent assay (ELISA) tests. TNF-α production by LPS-stimulated PMN significantly elevated in response to the RPETR at MTPRE (P = 0.004) and MTPOST (P = 0.047). IL-8 production only significantly increased in response to the RPETR at MTPRE (P = 0.033) but not at MTPOST (P = 0.199). The absolute RPETR-induced increase in TNF-α and IL-8 concentrations by LPS-stimulated PMN were lower at MTPOST compared to MTPRE. Blood PMN concentration increased significantly following the completion of RPETR at MTPRE (P = 0.02) and MTPOST (P = 0.016). Resting and RPETR-induced blood PMN concentrations did not significantly differ between MTPRE and MTPOST (P = 0.521). Following the completion of the ITP, V̇O2max (P = 0.696) and 10 km time to completion scores (P = 0.457; d = 0.32) did not change. The severity of upper-respiratory tract symptoms (URTS) increased in six out of ten participants following the ITP. Self-reported general (P = 0.040) and sport-related (P = 0.005) stress scores were higher at MTPOST compared to MTPRE. The identification of increased stress states, more severe URTS, and decreased physical performance capacities in participants indicates that overreaching may have been achieved following the ITP. Reduced pro-inflammatory cytokine production in response to acute exercise following a period of intensified training may predispose athletes to impaired inflammatory responses during exercise which may contribute to the pathogenesis of reported URTS in athletes who are overtraining.