Salivary Hsp72 does not track exercise stress and caffeine-stimulated plasma Hsp72 responses in humans

Abstract

Heat shock protein 72 (Hsp72) has been detected within saliva, and its presence may contribute to oral defence. It is currently unknown how physiological stress affects salivary Hsp72 or if salivary Hsp72 concentrations reflect plasma Hsp72 concentrations. We studied the effect of exercise upon salivary Hsp72 expression, and using caffeine administration, investigated the role of sympathetic stimulation upon salivary Hsp72 expression. Six healthy males performed two treadmill running exercise bouts in hot conditions (30°C) separated by 1 week in a randomized cross-over design, one with caffeine supplementation (CAF) the other with placebo (PLA). Plasma and saliva samples were collected prior to, during and post-exercise and assayed for Hsp72 concentration by ELISA. Exercise significantly increased plasma Hsp72, but not salivary Hsp72 concentration. Mean salivary Hsp72 concentration (5.1 ± 0.8 ng/ml) was significantly greater than plasma Hsp72 concentration (1.8 ± 0.1 ng/ml), and concentrations of salivary and plasma Hsp72 were unrelated. Caffeine supplementation and exercise increased the concentration of catecholamines, salivary α-amylase and total protein, whilst the salivary Hsp72:α-amylase ratio was lower in CAF. Salivary Hsp72 was not altered by exercise stress nor caffeine supplementation, and concentrations did not track plasma Hsp72 concentration.

Salivary extracellular heat shock protein 70 (eHSP70) levels increase after 59 min of intense exercise and correlate with resting salivary secretory immunoglobulin A (SIgA) levels at rest

“…Second, sedentary healthy males participated in the present study. Given the effect of the subject's exercise history and physical fitness, it is impossible to compare the results of our study with those of a previous study involving endurance-trained males (Fortes and Whitham 2011). Further studies are required to investigate the effects of exercise stress on salivary eHSP70, with respect to the subject's exercise habits, intensity and duration of exercise intervention, ambient temperature during exercise, and times of sample collection.…”

“…In the present study, an increase in the NLR continued until 4 h after exercise, suggesting that sympathetic nerve activity may be promoted by exercise. However, Fortes and Whitham (2011) presumptively suggested another mechanism involving acinar cells release of salivary eHSP70 via exosomes, not via sympathetic nerve stimuli but rather via parasympathetic nerve stimuli. Acceleration of parasympathetic nerve activity induces a decrease in the NLR (Nozaki et al 2000) and an increase in the saliva flow rate.…”

“…To the best of our knowledge, there is only one study examining the effect of exercise on salivary eHSP70 (Fortes and Whitham 2011). Fortes and Whitham (2011) reported a lack of change in salivary eHSP70 in response to multiple stresses, such as exercise stress, caffeine intake, and hyperthermia exposure, in athletes.…”

“…Fortes and Whitham (2011) reported a lack of change in salivary eHSP70 in response to multiple stresses, such as exercise stress, caffeine intake, and hyperthermia exposure, in athletes. In that study, healthy endurance-trained males performed intense exercise, consisting of 30 min of treadmill running at 50 % VO 2max (first bout) and 30 min at 70 % (second bout) in hot conditions (30°C).…”

“…Actually, a single bout of exercise increases circulating eHSP70 level (Walsh et al 2001;Febbraio et al 2002;Fehrenbach et al 2005) and heat stress further boosts this increase (Gibson et al 2014). However, Fortes and Whitham (2011) reported that eHSP70 in the saliva unchanged during and until 20 min after the exercise (60 min of treadmill running at 50−70 % VO 2max ) with hot environment (30°C). The change in salivary eHSP70 levels after exercise has not been adequately examined.…”