Novel Approach for Assessment and Mitigation of Heat-Stress Effects

Abstract

We have characterized the efficacy of a Bacillus subtilis probiotic strain for the prevention of heat stress-related complications in rats. It has been shown that pre-treatment of rats with probiotic bacteria prevented microbial translocation from the gut into mesenteric lymph nodes and liver. Heat stressed animals without probiotic treatment had a high level of lipopolysaccharides (LPS) in the blood. In contrast, animals in the probiotic group, exposed to the same level of heat did not show elevation of LPS levels. Additionally, cytokine IL-10 concentration significantly increased in stressed animals without probiotic pretreatment, whereas administration of probiotic treatment before heat stress normalized the level of IL-10. We also found that the elevation of the temperature of the blood during heat stress causes an increase in the shedding of erythrocyte membrane vesicles. The elevation of temperature from 36.70.3 to 40.30.4 o C resulted in a significant increase of the concentration of vesicles in blood. At a temperature of 37 o C, mean vesicle concentrations found in rat blood was (1.40.2)×106 vesicles/μL, while after exposure to heat the concentration increased to (3.80.3)×106 vesicles/μL in the group of animals without probiotic treatment. Treatment with the probiotic before heat stress prevented vesiculation of erythrocytes in animals. The results have shown a high efficacy of the probiotic B. subtilis in the prevention of heat stress- related complications in rats. Additionally, the images of human erythrocytes and associated vesicles have been analyzed by a light microscopy system with spatial resolution of better than 90 nm. The samples were observed in an aqueous environment and required no freezing, dehydration, staining, shadowing, marking or any other form of manipulation. Temperature elevation has resulted in a significant increase in the concentration of structurally transformed erythrocytes (echinocytes) and vesicles in the blood. The process of vesicle separation from spiculated erythrocytes has been video recorded in real time. Accurate accounting of vesicle numbers and dimensions suggest that 86% of the lost erythrocyte material is lost not by vesiculation but by another, as yet - unknown mechanism. The increase in the number of vesicles associated with elevated temperatures may be indicative of the individual’s heat stress level and thereby serve as diagnostic test of erythrocyte stability and heat resistance and level of heat adaptation.