The pH-induced swelling and collapse of a polybase brush synthesized by atom transfer radical polymerization

We have used neutron reflectometry to characterize the swelling behaviour of brushes of poly[2-(diethyl amino)ethyl methacrylate], a polybase, as a function of pH. The brushes, synthesized by the "grafting from" method of atom transfer radical polymerization, were observed to approximately double their thickness in low pH solutions, although the pK is shifted to a lower pH than in dilute solution. The composition-depth profile obtained from the reflectometry experiments for the swollen brushes reveals a region depleted in polymer between the substrate and the extended part of the brush.

The antioxidant enzyme peroxiredoxin-2 is depleted in lymphocytes seven days after ultra-endurance exercise

Purpose: Peroxiredoxin-2 (PRDX-2) is an antioxidant and chaperone-like protein critical for cell function. This study examined whether the levels of lymphocyte PRDX-2 are altered over one month following ultra-endurance exercise. Methods: Nine middle-aged men undertook a single-stage, multi-day 233 km (145 mile) ultra-endurance running race. Blood was collected immediately before (PRE), upon completion/retirement (POST), and following the race at DAY 1, DAY 7 and DAY 28. Lymphocyte lysates were examined for PRDX-2 by reducing SDS-PAGE and western blotting. In a sub-group of men who completed the race (n = 4) PRDX-2 oligomeric state (indicative of redox status) was investigated. Results: Ultra-endurance exercise caused significant changes in lymphocyte PRDX-2 (F (4,32) 3.409, p=0.020, ?(2) =0.299): seven-days after the race, PRDX-2 levels in lymphocytes had fallen to 30% of pre-race values (p=0.013) and returned to near-normal levels at DAY 28. Non-reducing gels demonstrated that dimeric PRDX-2 (intracellular reduced PRDX-2 monomers) was increased in 3 of 4 race completers immediately post-race, indicative of an "antioxidant response". Moreover, monomeric PRDX-2 was also increased immediately post-race in 2 of 4 race-completing subjects, indicative of oxidative damage, which was not detectable by DAY 7. Conclusions: Lymphocyte PRDX-2 was decreased below normal levels 7 days after ultra-endurance exercise. Excessive accumulation of reactive oxygen species induced by ultra-endurance exercise may underlie depletion of lymphocyte PRDX-2 by triggering its turnover after oxidation. Low levels of lymphocyte PRDX-2 could influence cell function and might, in part, explain reports of dysregulated immunity following ultra-endurance exercise.

Monitoring changes in thioredoxin and over-oxidised peroxiredoxin in response to exercise in humans

Introduction. Peroxiredoxin (PRDX) and thioredoxin (TRX) are antioxidant proteins that control cellular signalling and redox balance, although their response to exercise is unknown. This study aimed to assess key aspects of the PRDX-TRX redox cycle in response to three different modes of exercise. Methods. Healthy males (n = 10, mean ± SD: 22 ± 3 yrs) undertook three exercise trials on separate days: two steady-state cycling trials at moderate (60% VO2MAX; 27 min, MOD) and high (80% VO2MAX; 20 min, HIGH) intensities, and a low-volume high-intensity interval training trial (10 × 1 min 90% VO2MAX, LV-HIIT). Peripheral blood mononuclear cells were assessed for TRX-1 and over-oxidised PRDX (isoforms I-IV) protein expression before, during, and 30 min following exercise (post + 30). The activities of TRX reductase (TRX-R) and the nuclear factor kappa B (NF-κB) p65 subunit were also assessed. Results. TRX-1 increased during exercise in all trials (MOD, + 84.5%; HIGH, + 64.1%; LV-HIIT, + 205.7%; p < 05), whereas over-oxidised PRDX increased during HIGH only (MOD, - 28.7%; HIGH, + 202.9%; LV-HIIT, - 22.7%; p < .05). TRX-R and NF-κB p65 activity increased during exercise in all trials, with the greatest response in TRX-R activity seen in HIGH (p < 0.05). Discussion. All trials stimulated a transient increase in TRX-1 protein expression during exercise. Only HIGH induced a transient over-oxidation of PRDX, alongside the greatest change in TRX-R activity. Future studies are needed to clarify the significance of heightened peroxide exposure during continuous high-intensity exercise and the mechanisms of PRDX-regulatory control.

Lymphocyte peroxiredoxin-2 levels are depleted one week after ultra-endurance exercise

Peroxiredoxin-2 (PRDX-2) belongs to a family of thiol containing proteins and is important for antioxidant defense, redox signaling and cell function. This study examined whether lymphocyte PRDX-2 levels are altered over one month following ultra-endurance exercise. Nine middle-aged men participated in a 145 mile ultra-endurance running race event. Blood drawing was undertaken immediately before, upon completion/retirement, and at one, seven and twenty eight-days following the race. PRDX-2 levels were examined at each time-point, for all participants (n=9) by reducing SDS-PAGE and western blotting. Further analysis using non-reducing SDS-PAGE and western blotting was undertaken in a sub-group of men who completed the race (n = 4) to investigate PRDX-2 oligomeric state (indicative of oxidation state). Ultra-endurance exercise caused a significant alteration in lymphocyte PRDX-2 levels (F(4,32) 3.409, p=0.020, η2 =0.299): seven-days after the race PRDX-2 levels fell by 70% (p=0.013) and at twenty eight-days after the race returned to near-normal levels. PRDX-2 dimers (intracellular reduced PRDX-2 monomers) in three of the four participants, who finished the race, were increased upon race completion. Furthermore, PRDX-2 monomers (intracellular over-oxidized PRDX-2 monomers) in two of these four participants were present upon race completion, but absent seven-days after the race. This study found that PRDX-2 levels in lymphocytes were reduced below normal levels seven-days after an ultra-endurance running race. We suggest that excessive reactive oxygen species production, induced by ultra-endurance exercise may, in part, explain the depletion of lymphocyte PRDX-2 by triggering its turnover after oxidation.