Expression of mitochondrial membrane–linked SAB determines severity of sex-dependent acute liver injury
Sanda Win, … , Tin A. Than, Neil Kaplowitz
Sanda Win, … , Tin A. Than, Neil Kaplowitz
Published December 2, 2019; First published September 5, 2019
Citation Information: J Clin Invest. 2019;129(12):5278-5293. https://doi.org/10.1172/JCI128289.
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Research Article Hepatology

Expression of mitochondrial membrane–linked SAB determines severity of sex-dependent acute liver injury

Abstract

SH3 domain–binding protein that preferentially associates with Btk (SAB) is an outer-membrane docking protein for JNK-mediated impairment of mitochondrial function. Deletion of Sab in hepatocytes inhibits sustained JNK activation and cell death. The current study demonstrates that an increase in SAB expression enhanced the severity of acetaminophen-induced (APAP-induced) liver injury. Female mice were resistant to liver injury and exhibited markedly decreased hepatic SAB protein expression compared with male mice. The mechanism of SAB repression involved a pathway from ERα to p53 expression that induced miR34a-5p. miR34a-5p targeted the Sab mRNA coding region, thereby repressing SAB expression. Fulvestrant or p53 knockdown decreased miR34a-5p and increased SAB expression in female mice, leading to increased injury from APAP and TNF/galactosamine. In contrast, an ERα agonist increased p53 and miR34a-5p, which decreased SAB expression and hepatotoxicity in male mice. Hepatocyte-specific deletion of miR34a also increased the severity of liver injury in female mice, which was prevented by GalNAc-ASO knockdown of Sab. Similar to mice, premenopausal women expressed elevated levels of hepatic p53 and low levels of SAB, whereas age-matched men expressed low levels of p53 and high levels of SAB, but there was no difference in SAB expression between the sexes in the postmenopausal stage. In conclusion, SAB expression levels determined the severity of JNK-dependent liver injury. Female mice expressed low levels of hepatic SAB protein because of the ERα/p53/miR34a pathway, which repressed SAB expression and accounted for the resistance to liver injury seen in these females.

Authors

Sanda Win, Robert W.M. Min, Christopher Q. Chen, Jun Zhang, Yibu Chen, Meng Li, Ayako Suzuki, Manal F. Abdelmalek, Ying Wang, Mariam Aghajan, Filbert W.M. Aung, Anna Mae Diehl, Roger J. Davis, Tin A. Than, Neil Kaplowitz

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Figure 2

Sex difference in p-JNK inhibition of mitochondrial respiration and SAB expression.

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Sex difference in p-JNK inhibition of mitochondrial respiration and SAB ...
(A) Isolated mitochondria from male or female littermates were incubated with ATP plus recombinant JNK (isoforms 1 + 2) or p-JNK (isoforms 1 + 2) and then ADP, oligomycin (Oligo), CCCP, or antimycin A (AA) were injected sequentially, and the OCR was measured with a Seahorse XF analyzer to determine state 3 and maximal respiration. Traces are representative of 5 separate experiments. *P < 0.05 versus JNK, by 1-way ANOVA with Bonferroni’s correction. Data are presented as the mean ± SD of multiple wells for each treatment. (B) Mitochondria were isolated as for the mitochondrial respiration assay. Mitochondria were preincubated with MitoSOX and then treated with JNK or p-JNK with ATP, and fluorescence intensity was measured to determine superoxide production. n = 3 mice/group. *P < 0.05 versus males, by paired, 2-tailed Student’s t test. (C) Mitochondria from WT male and female littermates were immunoblotted with anti-SAB, anti-OTC, or anti-PHB1. Representative immunoblot from 3 separate experiments. n = 10 mice/group. *P < 0.05 versus male mice, by paired, 2-tailed Student’s t test. (D) Immunoblot analysis of SAB expression in representative human liver homogenates from premenopausal women and matched men. (E) Age- and BMI-matched men and women were divided into the premenopausal group or the postmenopausal group according to serum estradiol (E2) and FSH levels and menstrual and gynecological history (see Supplemental Table 1). In each group, the male and female pairs are indicated by the same color symbol in the figure. All liver biopsy samples were histologically classified as mild, nonspecific abnormalities. SAB and GAPDH levels were determined by Western blotting and densitometry. n = 5 pairs in the premenopausal group and n = 3 pairs in the postmenopausal group. *P < 0.05 versus men, by paired, 2-tailed Student’s t test. Data are presented as the mean ± SEM.