Mild Endotoxemia, Nuclear Factor (NF)-{kappa}B Translocation and Cytokine Increase during Exertional Heat Stress in Trained and Untrained Individuals. American journal of physiology. Regulatory, integrative and comparative physiology [Am J Physiol Regul Integr Comp Physiol] Journal article | | Title | Mild Endotoxemia, Nuclear Factor (NF)-{kappa}B Translocation and Cytokine Increase during Exertional Heat Stress in Trained and Untrained Individuals. | | Author(s) | Selkirk GA, McLellan TM, Wright HE, Rhind SG | | Institution | Kinesiology and Health Science Graduate Programme, York University, Toronto, Canada. | | Source | Am J Physiol Regul Integr Comp Physiol 2008 Jun 18. | | Abstract | This study examined endotoxin-mediated cytokinemia during exertional heat stress (EHS). Subjects were divided into trained (TR, n=12, VO2peak = 70 +/-2 mL.kgLBM(-1).min(-1)) and untrained (UT, n=11,VO2peak = 50 +/- 1 mL.kgLBM(-1).min(-1)) groups prior to walking at 4.5 km.h(-1) with 2% elevation in a climatic chamber (40 degrees C; 30% R.H.), wearing protective clothing until exhaustion (Exh). Venous blood samples at baseline and 0.5 degrees C rectal temperature increments (38.0 degrees C, 38.5 degrees C, 39.0 degrees C, 39.5 degrees C and 40.0 degrees C/Exh) were analyzed for endotoxin, lipopolysaccharide binding protein (LBP), circulating cytokines and intranuclear NF-kappaB translocation. Baseline and Exh samples were also stimulated with LPS (100 ng.mL(-1)) and cultured in vitro in a 37 degrees C water-bath for 30 min. Phenotypic determination of natural killer (NK) cell frequency was also determined. Enhanced blood (104 +/- 6 vs. 84 +/- 3 mL.kg(-1)) and plasma (64 +/- 4 versus 51 +/- 2 mL.kg(-1)) volumes were observed in TR compared to UT. EHS produced an increased concentration of circulating endotoxin in both TR (8 +/- 2 pg.mL(-1)) and UT (15 +/- 3 pg.mL(-1)) (range ND to 32 pg.mL(-1)) corresponding with NF-kappaB translocation and cytokine increases in both groups. In addition, circulating levels of TNF-alpha and IL-6 were also elevated combined with concomitant increases in IL-1ra in both groups and IL-10 in TR only. Findings suggest that the threshold for endotoxin leakage and inflammatory activation during EHS occurs at a lower temperature in UT compared to TR, and supports the endotoxin translocation hypothesis of exertional heat stroke, linking endotoxin tolerance and heat tolerance. Key words: splanchnic permeability, immune function, blood volume, cardiovascular/thermoregulatory strain, flow cytometry. | | Language | ENG | | Pub Type(s) | JOURNAL ARTICLE
| | PubMed ID | 18565834 |
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