POSSIBILITY OF REDUCING DRUG-INDUCED LIVER INJURY BY THERMAL PRECONDITIONING

Y. Iwashita¹, K. Yae¹, A. Maeda², K. Nagata³, H. Kameyama³, J. Iiyama¹

¹Kumamoto Health Science University, Rehabilitation, Kumamoto, Japan, ²Kumamoto University Graduate School of Medical Sciences, Nephrology, Kumamoto, Japan, ³Kumamoto Health Science University, Medical Technology, Kumamoto, Japan

Background: In Japan, there is a bathing custom of soaking in hot water. Warming the body is expected to improve vascular function, activate the innate immunity, promote relaxation, and alleviate pain. On the other hand, It has long been known that thermal stimulation during acute inflammation can exacerbate inflammation. In our previous basic studies in mice, we found that pre-conditioning with mild thermal stimulation (MSTP), a mild thermal stimulus that raises deep body temperature by 1-2°C 6 hours prior to injury induction, increases the molecular chaperone heat shock protein (Hsp) 27 and reduces increased renal ischemia-reperfusion injury and cisplatin-induced renal injury. The amplification of Hsp27 is not kidney-specific, and temporal phase control of thermal stimulation interventions may reduce cellular damage in various organs.

Purpose: In this study, we aimed to confirm the effects of MSTP on a mouse model of drug-induced acute liver injury induced by carbon tetrachloride (CCl4) and to elucidate some of its mechanisms of action.

Methods: ICR mice were divided into a control group (n=3), a CCl4-injected group (CCl4, n=7), and a CCl4-injected group after MSTP (MSTP, n=8). Heating was performed using a far-infrared sauna device at 39°C for 15 minutes (rectal temperature increased by 1.5-2.0°C), followed by 15 minutes at 35°C to keep the mice warm. Serum and liver tissue were collected 6 or 24 hours after CCl4 injection. ALT, a marker of liver injury, and HE-stained liver tissue were evaluated in a blinded fashion; Hsp27 and ATG5, an autophagy marker, were evaluated by Western blotting.
Values were expressed as means ± S.D. Statistical analysis was performed using Unpaired t test to determine differences between 2 groups and ANOVA with P values < 0.05 were considered statistically significant.

Results: ATG5 at 6 hours after CCl4 injection was increased in the MSTP group (1.4±0.1-fold, p<0.05) compared to the CCl4 group, indicating an autophagy-promoting effect of MSTP. The CCl4 group showed a significant increase in ALT (72.8±28.2 IU/L, p<0.01) compared to the control group (20.0±2.6 IU/L), which was considered to be an escape from the hepatocytes. On the other hand, MSTP significantly reduced the CCl4-induced ALT increase (33.0±4.1 IU/L, p<0.05). 24 hours later, Hsp27 expression was not different in the CCl4 group compared to the control group, whereas it tended to increase in the MSTP group (p=0.06), suggesting that it contributed to the reduction of ALT hepatocyte excretion. This was thought to contribute to the reduction of ALT hepatocyte deviation. In the evaluation of tissue damage grade, there were no statistical differences among all groups, but the MSTP group showed slightly higher values, suggesting an effect of intracellular morphological changes due to autophagy promotion (control: 0.0±0.0, CCl4: 0.3±0.6, MSTP: 1.0±0.8).

Conclusions: MSTP in mice promotes autophagy and intracellular morphological changes, while reducing CCl4-induced hepatocellular disruption defects at 24 hours by increasing Hsp27.

Implications: MSTP is expected to reduce cell and tissue damage and may be useful not only for treatment but also for daily health maintenance. It is important to further elucidate the mechanisms.

Funding acknowledgements: No grants were received for this research.

Keywords:
CCl4-induced liver injury
Mild systemic thermal preconditioning
Autophagy

Topics:
Professional issues

Did this work require ethics approval? Yes

Institution: Kumamoto Health Science University

Committee: Kumamoto Health Science University Experimental Animal Experiment Committee

Ethics number: no. 21-11