Vegetable Oil-Peroxidation Product 'Hydroxynonenal' Causes Hepatocyte Injury and Steatosis via Hsp70.1 and BHMT Disorders in the Monkey Liver

• Published in: Nutrients Vol. 15; no. 8; p. 1904
• Main Authors: Yamashima, Tetsumori, Mori, Yurie, Seike, Takuya, Ahmed, Sharif, Boontem, Piyakarn, Li, Shihui, Oikawa, Shinji, Kobayashi, Hatasu, Yamashita, Tatsuya, Kikuchi, Mitsuru, Kaneko, Shuichi, Mizukoshi, Eishiro
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 01.04.2023; MDPI
• Subjects: Alzheimer's disease; Animals; Apoptosis; Betaine-homocysteine S-methyltransferase; Betaine-Homocysteine S-Methyltransferase - metabolism; Blood; Calpain; calpain-cathepsin hypothesis; carbonylation; Carbonyls; Cell Death; Chemical properties; Choline; Cleavage; Death; Degeneration; Diabetes; Diet; Electron microscopy; Fatty acids; Fatty Liver; Haplorhini - metabolism; Health aspects; Hepatocytes; Hepatocytes - metabolism; Hippocampus; Homocysteine; Homocysteine S-methyltransferase; Hsp70 protein; Immunoblotting; International organizations; Ischemia; Laboratory animals; Lecithin; Lipid peroxidation; Lipids; Liver; Liver - metabolism; lysosomal rupture; Membranes; Metabolism; Metabolites; Metalloenzymes; Methyltransferase; Mitochondria; Monkeys; Neurodegeneration; Oxidation; Peroxidation; Peroxisomes; Phosphatidylcholine; Physiological aspects; Physiology; Proteins; Proteomics; Risk factors; Steatosis; Vegetable oils; Vegetables; Western blotting; Japan; lysosomal rupture; calpain-cathepsin hypothesis; cell death; betaine-homocysteine S-methyltransferase; carbonylation; phosphatidylcholine
• ISSN: 2072-6643; 2072-6643
• DOI: 10.3390/nu15081904

Hsp70.1 has a dual function as a chaperone protein and lysosomal stabilizer. In 2009, we reported that calpain-mediated cleavage of carbonylated Hsp70.1 causes neuronal death by inducing lysosomal rupture in the hippocampal CA1 neurons of monkeys after transient brain ischemia. Recently, we also reported that consecutive injections of the vegetable oil-peroxidation product 'hydroxynonenal' induce hepatocyte death via a similar cascade in monkeys. As Hsp70.1 is also related to fatty acid β-oxidation in the liver, its deficiency causes fat accumulation. The genetic deletion of betaine-homocysteine -methyltransferase (BHMT) was reported to perturb choline metabolism, inducing a decrease in phosphatidylcholine and resulting in hepatic steatosis. Here, focusing on Hsp70.1 and BHMT disorders, we studied the mechanisms of hepatocyte degeneration and steatosis. Monkey liver tissues with and without hydroxynonenal injections were compared using proteomics, immunoblotting, immunohistochemical, and electron microscopy-based analyses. Western blotting showed that neither Hsp70.1 nor BHMT were upregulated, but an increased cleavage was observed in both. Proteomics showed a marked downregulation of Hsp70.1, albeit a two-fold increase in the carbonylated BHMT. Hsp70.1 carbonylation was negligible, in contrast to the ischemic hippocampus, which was associated with ~10-fold increments. Although histologically, the control liver showed very little lipid deposition, numerous tiny lipid droplets were seen within and around the degenerating/dying hepatocytes in monkeys after the hydroxynonenal injections. Electron microscopy showed permeabilization/rupture of lysosomal membranes, dissolution of the mitochondria and rough ER membranes, and proliferation of abnormal peroxisomes. It is probable that the disruption of the rough ER caused impaired synthesis of the Hsp70.1 and BHMT proteins, while impairment of the mitochondria and peroxisomes contributed to the sustained generation of reactive oxygen species. In addition, hydroxynonenal-induced disorders facilitated degeneration and steatosis in the hepatocytes.