الفهرس 
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Abstract
Drug induced liver injury (DILI) is a worldwide problem and is the cause of about 50% of cases of acute liver failure mostly due to acetaminophen toxicity. Also DILI causes withdrawal of many drugs from the market.
Acetaminophen (APAP) is a safe analgesic antipyretic drug when used in therapeutic dose but toxic dose of acetaminophen either intentionally or accidentally can lead to serious liver injury.
Acetaminophen is metabolized in liver by conjugation with glucuronic acid and sulfate giving APAP-glucuronide and APAP-sulfate by glucuronyltransferase and sulfotransferase. When glucuronyltransferase and sulfotransferase become saturated, acetaminophen is metabolized by CYP2E1 to a metabolically active compound called NAPQI (N-acetyl-p-benzoquinone imine). Normally, NAPQI is detoxified by glutathione that can be easily depleted in acetaminophen overdose leading to covalent binding of NAPQI with hepatocyte macromolecules leading to toxic hepatocellular injury.
Silymarin (SLM) is herbal medicine that has a hepatoprotective action through several mechanisms as decreasing free radicals, increasing the glutathione content, inhibiting lipid peroxidation and restoring the function of enzymes, and so generating membrane stabilization and preventing toxic metabolic liver injury.
Early diagnosis of acetaminophen induced liver injury is very important to prevent development of acute liver failure and the need for liver transplantation. The current biomarkers used for diagnosis as ALT, AST and ALP are not specific for liver diseases, cannot be detected early before development of hepatocytes necrosis and cannot give an idea about mechanism or prognosis of liver injury therefore, we need to use new biomarkers for early diagnosis of DILI.
MicroRNAs are short non-coding RNAs involved in post-transcriptional regulation of gene expression. In our study, we assessed the expression of microRNA 122 and microRNA 192 (the liver enriched microRNAs).
Other promissing biomarkers assessed in our study include L-glutamate dehydrogenase and total cytokeratin 18. L-glutamate dehydrogenase is a mitochondrial enzyme present mainly in hepatocytes. In acetaminophen induced liver injury, it is released into circulation after mitochondrial damage and hepatocyte necrosis. Advantages of L-glutamate dehydrogenase include its early detection and it can reflect severity of liver injury.
Total cytokeratin 18, another biomarker, is present in a high concentration in liver cells and is released in circulation after hepatocyte damage. It can be early detected and can give an idea about prognosis of liver injury.
The goal of this study is to show the expression of microRNA 122 and microRNA 192 and their role in diagnosis of acetaminophen induced liver injury. Also to show the role of L-glutamate dehydrogenase and total cytokeratin 18 in early detection of acetaminophen induced liver injury.
In the current study, rats were divided into ten groups control group was given normal saline of 0.9% NaCl orally once daily for four days, Silymarin prevention group was given silymarin 100 mg/kg orally once daily for four days, Acetaminophen group was given acetaminophen intraperitoneally 300 mg/kg once then rats were sacrificed after 6 hours, Silymarin and acetaminophen group was given silymarin 100 mg/kg orally once daily for four days, then on the fourth day of the experiment, acetaminophen 300 mg/kg was given intraperitoneally and rats were sacrificed after 6 hours, Acetaminophen group was given acetaminophen 300 mg/kg intraperitoneally once then rats were sacrificed after 8 hours, Silymarin and acetaminophen group was given silymarin 100 mg/kg orally once daily for four days, then on the fourth day of the experiment, acetaminophen 300 mg/kg was given intraperitoneally and rats were sacrificed after 8 hours, Acetaminophen group was given acetaminophen 300 mg/kg intraperitoneally once then rats were sacrificed after 12 hours, Silymarin and acetaminophen group was given silymarin 100 mg/kg orally once daily for four days, then on the fourth day of the experiment, acetaminophen 300 mg/kg was given intraperitoneally and rats were sacrificed after 12 hours, Acetaminophen group was given acetaminophen 300 mg/kg intraperitoneally once then rats were sacrificed after 24 hours, Silymarin and acetaminophen group was given silymarin 100 mg/kg orally once daily for four days, then on the fourth day of the experiment, acetaminophen 300 mg/kg was given intraperitoneally and rats were sacrificed after 24 hours.
In all groups, serum level of ALT, AST and ALP were measured. Liver tissue sections were stained by H&E to examine histopathological changes. Serum levels of L-glutamate dehydrogenase and total cytokeratin18 using ELISA were measured. The liver tissue was analyzed for microRNA 122 and microRNA 192 genes expression using quantitative real-time PCR.
Our results showed that acetaminophen induced liver injury caused an elevation in the serum level of ALT, AST and ALP. Silymarin could reduce them in a significant manner in addition it improved the histological alterations.
Also our results showed that acetaminophen induced liver injury caused an increase in serum levels of L-glutamate dehydrogenase and total cytokeratin 18. Silymarin could decrease their serum levels.
Also acetaminophen induced liver injury was associated with up-regulation in the expression of microRNA 122 and microRNA 192 genes while silymarin down-regulated their expression in liver tissue.
We concluded that microRNA 122, microRNA 192, L-glutamate dehydrogenase and total cytokeratin 18 may be a promising platform in early diagnosis of acetaminophen induced liver injury so we will be able to treat the case before the development of liver failure or the need for liver transplantation.