Chitinase 3-like-1 contributes to acetaminophen-induced liver injury by promoting hepatic platelet recruitment.

Acetaminophen, also called paracetamol outside the United States, is a commonly used painkiller, with over 50 million people in the United States taking the drug weekly. While paracetamol is safe at standard doses, overdose can cause acute liver failure, which leads to 30,000 patients being admitted to emergency care in the United States each year. There is only one approved antidote to overdoses, which becomes significantly less effective if its application is delayed by more than a few hours. This has incentivized research into identify new drug targets that could lead to additional treatment options. Acetaminophen overdose triggers blood clotting and inflammation, contributing to liver injury. It also causes a decrease in cells called platelets circulating in the blood, which has been observed in both mice and humans. In mice, this occurs because platelets accumulate in the liver. Removing these excess cells appears to reduce the severity of the damage caused by acetaminophen, but it remains unclear how the drug triggers their accumulation in the liver. In 2018, researchers showed that a protein called Chi3l1 plays an important role in another form of liver damage. Shan et al. ­ including many of the researchers involved in the 2018 study ­ have examined whether the protein also contributes to acetaminophen damage in the liver. Shan et al. showed that mice lacking the gene that codes for Chi3l1 developed less severe liver injury and had fewer platelets in the liver following acetaminophen overdose. They also found that human patients with acute liver failure due to acetaminophen had high levels of Chi3l1 and significant accumulation of platelets in the liver. To test whether damage could be prevented, Shan et al. used antibodies to neutralize Chi3l1 in mice after giving them an acetaminophen overdose. This reduced platelet accumulation in the liver and the associated damage. These findings suggest that targeting Chi3l1 may be an effective strategy to prevent liver damage caused by acetaminophen overdose. Further research could help develop new treatments for acetaminophen-induced liver injury and perhaps other liver conditions.