Carbon tetrachloride-induced hepatic injury through formation of oxidized diacylglycerol and activation of the PKC/NF-κB pathway

Abstract

Protein kinase C (PKC) participates in signal transduction, and its overactivation is involved in various types of cell injury. PKC depends on diacylglycerol (DAG) for its activation in vivo We have previously reported that DAG peroxides (DAG-O(O)H) activate PKC in vitro more strongly than unoxidized DAG, suggesting that DAG-O(O)H, if generated in vivo under oxidative stress, would act as an aberrant signal transducer. The present study examined whether DAG-O(O)H are formed in carbon tetrachloride (CCl 4 )-induced acute rat liver injury in association with activation of the PKC/nuclear factor (NF)-kB pathway. A single subcutaneous injection of CCl 4 resulted in a marked increase in hepatic DAG-O(O)H content. At the molecular level, immunohistochemistry and subcellular fractionation combined with immunoblotting localized PKCa, bI, bII and d isoforms to cell membranes, while immunoblotting showed phosphorylation of the p65 subunit of NF-kB, and immunoprecipitation using isoform-specific anti-PKC antibodies revealed specific association of PKCa and p65. In addition, expression of tumor necrosis factor a (TNFa) and neutrophil invasion increased in the CCl 4 -treated rats. Furthermore, we demonstrated that Vitamin E, one of the most important natural antioxidants that suppresses peroxidation of membrane lipids, significantly inhibited the CCl 4 -induced increase in hepatic DAG-O(O)H content and TNFa expression as well as phosphorylation of PKCa and p65. These data demonstrate for the first time that DAG-O(O)H are generated in the process of CCl 4 -induced liver injury, resulting in activation of the PKC/NF-kB pathway and TNFa-mediated aggravation of liver injury.

Aberrant Activation of Atypical Protein Kinase C in Carbon Tetrachloride–Induced Oxidative Stress Provokes a Disturbance of Cell Polarity and Sealing of Bile Canalicular Lumen

“…28 In CCl 4 -treated rat liver, Par-3 and aPKC were delocalized to the cytoplasm from ZO-1epositive cell-cell junctions ( Figure 4A and Figure 6 ½F6 ½F6…”

Antioxidant and proapoptotic effects of anthocyanins from bilberry extract in rats exposed to hepatotoxic effects of carbon tetrachloride

“…Oxidative stress caused by the accumulation of ROS plays the key role in the pathogenesis of liver damage [12,13]. Hepatotoxicity of CCl 4 occurs as a consequence of reductive dehalogenation which produces two extremely reactive radicals -trichloromethyl radical (CCl 3 • ) and trichloromethyl peroxide radical (CCl 3 O 2 • ).…”

“…Liver damage occurs due to improper balance between intracellular antioxidative markers (reduced glutathione, glutathione peroxidase, glutathione S-transferase, catalase, and superoxide dismutase) and reactive oxygen species (superoxide and hydroxyl radicals) which are formed in CCl 4 metabolism [18,17,19]. CCl 4 poisoning leads to different pathological changes, including oxidative damage to cell integrity, inflammation, fat degeneration, liver fibrosis, and necrosis [13,20].…”

Pathophysiological Characteristics of Non-Alcoholic Steatohepatitis-Like Changes in Cholesterol-Loaded Type 2 Diabetic Rats

“…The assay for DAG-O(O)H was performed as described (Toriumi et al 2013). Lipids were extracted from liver tissues using 2-propanol containing 1-palmitoyl-3-arachidoylglycerol hydroxide as an internal standard, 20 mmol/l butylated hydroxytoluene and 200 mmol/l triphenylphosphine.…”

“…Second, hepatic DAG and DAG-O(O)H levels were elevated by feeding cholesterol-enriched chow. Through this change, protein kinase C is activated, thus resulting in severe inflammation (Takekoshi et al 1995, Toriumi et al 2013. In actuality, the inflammatory genes, TNF-α and MCP-1, significantly increased in SDT fatty-Cho at 24 weeks of age.…”