Systematical analysis of impacts of heat stress on the proliferation, apoptosis and metabolism of mouse hepatocyte

Abstract

Heat stress will stimulate cells of living organisms to generate heat shock proteins (Hsps). In the mouse liver, impacts of heat stress on hepatocyte proliferation, apoptosis and metabolism have not been studied systematically at different temperatures. In this research, the test mice were heated to 40, 42, 44 and 46°C, respectively, for 20 min and recovered at room temperature for 8 h in normal feeding conditions; the control animals were kept at room temperature without heat stress. The expression levels of Hsp70, Pcna, Bax, Bcl2, cytochrome P450 1A2 (CYP1A2), CYP2E1 and analog of CYP3A4 (not reported in mouse before), the parameters reflecting stress strength, cell proliferation, apoptosis and metabolism, were detected by western blotting, immunohistochemistry and semi-quantitative RT-PCR in test and control mice. Haematoxylin-eosin (H&E) staining and TUNEL analysis were further used to study the impacts of heat stress at different temperatures on hepatocellular necrosis and apoptosis. Serum AST and ALT levels, the markers of liver injury, were measured after heat stress at different temperatures. The data show that Hsp70 expression was significantly increased when temperature increased (P < 0.05). At lower temperatures (40 or 42°C), expression of Pcna, CYP1A2 and analog of CYP3A4 were considerably increased (P < 0.05) while hepatocyte necrosis and apoptosis were not induced (P > 0.05). At higher temperatures (44 or 46°C), expression of Pcna was decreased while hepatocyte necrosis and apoptosis were induced (P < 0.05). Expressions of CYP1A2 and analog of CYP3A4 were decreased especially at 46°C (P < 0.05). Expression of CYP2E1 could not be detected to increase at 40°C but was at high levels at 42, 44 and 46°C (P < 0.05). Expressions of AST and ALT were not different between the test mice and control mice at 40°C while they were significantly higher in the test mice than those in the control mice at 42 (P < 0.05), 44 and 46°C (P < 0.01). In conclusion, heat stress at lower temperatures promotes hepatocyte proliferation and improves the metabolic efficiency in mouse liver while heat stress at higher temperatures inhibits hepatocyte proliferation, promotes hepatocyte apoptosis and induces hepatocyte necrosis. This may give a hint to understanding human liver injury in high temperatures. Moreover, it is the first time that the analog of CYP3A4 was detected in mouse hepatocellular cytoplasm. It is worthwhile to dissect its function in future work.

Assessing the Short-Term Effects of Heatwaves on Mortality and Morbidity in Brisbane, Australia: Comparison of Case-Crossover and Time Series Analyses

“…Secondly, water loss and reduced plasma volume during hot days may facilitate the release of platelets into circulation and increase red and white cell counts, blood viscosity, and plasma cholesterol levels, which may be connected to the increased mortality from arterial thrombosis in hot weather [31]. Finally, results from a mice study indicate that heat stress will stimulate cells of living organisms to generate heat shock proteins which may cause systematic damages in the body [32].…”

Proper Heat Shock Pretreatment Reduces Acute Liver Injury Induced by Carbon Tetrachloride and Accelerates Liver Repair in Mice

“…But whether heat shock pretreatment can reduce acute liver injury induced by CCl 4 in mice has not been studied. Based on the results of analysis in a previous study 15 (Li et al , 2012), we think that heat shock at 40°C for 20 min is an optimal thermal pretreatment to induce HSP70 expression and improve liver function compared with heat shock at 42°C, 44°C and 46°C for 20 min. So mice received heat shock preconditioning at 40°C for 20 min (HS20 group) and subsequent CCl 4 administration.…”

“…Our previous work suggested that heat shock at 40°C for 20 min is a proper condition for heat shock preconditioning because it could effectively promote hepatocyte proliferation and improves the metabolic efficiency in the mouse liver 15 . So mice were anesthetized with urethane (1.4 g/kg, i.p.)…”

“…Our previous study showed that heat shock at a lower temperature (heat shock at 40°C for 20 min) significantly promotes hepatocyte proliferation and improves metabolic efficiency in the mouse liver, while heat shock at a higher temperature (heat shock at 46°C for 20 min) remarkably inhibits hepatocyte proliferation, promotes hepatocyte apoptosis and induces liver injury 15 . So we selected a proper temperature and time to study whether proper heat shock preconditioning could reduce liver injury and accelerate liver repair after acute liver failure induced by CCl 4 .…”

Fluorescence based cell counting in collagen monolayer cultures of primary hepatocytes

“…This demonstrates the high robustness of the combination of cell number determination and protein quantification under conditions when cells do not increase protein production or degrade the intracellular proteins. On the other hand, the method may be especially useful under conditions where the protein content per cell is expected to increase (Li et al 2012;Wu et al 1993) or decrease, e.g. in autophagy under stress conditions (Hopgood et al 1980;Liu et al 2009).…”