Mouse liver is more resistant than skeletal muscle to heat-induced apoptosis
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SHORT COMMUNICATION
Mouse liver is more resistant than skeletal muscle to heat-induced apoptosis Yifan Chen 1
&
Tianzheng Yu 2
Received: 11 June 2020 / Revised: 5 August 2020 / Accepted: 27 August 2020 # Cell Stress Society International 2020
Abstract During passive heat stress, shifting of blood flow from the hepato-splanchnic to peripheral regions produces less favorable physiological conditions in the liver than in the skeletal muscle. We were wondering if the two organs differ in susceptibility to heat injury and thus examined the effects of heat shock exposure on apoptotic and heat stress-related markers in the gastrocnemius muscle and liver of mice. During heat exposure, mice had a peak core body temperature of 41.1 ± 0.7 °C. Heat-exposed mice showed higher levels of reactive oxygen species (ROS), cleaved caspases, fragmented DNA, and Drp1 protein expression in the gastrocnemius muscles than control mice. These changes were not observed in the livers of heat-exposed mice. Furthermore, the levels of glucocorticoid receptor, HSP70, and HSF1 proteins were significantly elevated in the gastrocnemius muscles of heat-exposed mice compared with that of control mice. The livers of heat-exposed mice also revealed increased expression of HSP70 but no changes in the other proteins. These results demonstrate that heat exposure induces significantly lower levels of the stress response and apoptosis in the liver than in the skeletal muscle of mice. The liver tissue resistance against heat stress is associated with low levels of heat-induced ROS production and mitochondrial fission protein expression. Keywords Hyperthermia . Heat tolerance . Hepatic ischemia . Mitochondrial dynamics . DNM1L
Introduction Heat stress-induced changes vary widely between different organs, which may produce a less favorable physiological environment in some organs. Skeletal muscle and the liver account for two major portions of whole-body resting energy expenditure consisting of ~ 20% and 17% in human and ~ 30% and 20% in rat respectively (Rolfe and Brown 1997). During passive heat stress, blood flow distribution shifts from the hepato-splanchnic region (Crandall et al. 2008) to the skeletal muscle (Chiesa et al. 2016). This imposes challenges especially on liver function. Failure to have an adequate blood supply to meet tissue metabolic demand is one of the major
* Yifan Chen [email protected] 1
Department of Military and Emergency Medicine, Hébert School of Medicine, Uniformed Services University, 4301 Jones Bridge Road, Bethesda, MD 20814, USA
2
Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, MD, USA
causes of organ dysfunction/injury. Organ-related differences exist with respect to the coverage, severity, and reversibility of ischemia/reperfusion injury, indicating that ischemia of skeletal muscle is much better tolerated compared with that of other organs (Kalogeris et al. 2012). Whether the liver and the skeletal muscle differ in resistance against heat injury remains undetermined. Heat exposur
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