Acetaminophen-Induced Rat Hepatotoxicity Based on M1/M2-Macrophage Polarization, in Possible Relation to
Yuka Tsuji1, Mizuki Kuramochi1, Hossain M Golbar1,2
1Veterinary Pathology, Graduate School of Life and Environmental Sciences, Osaka Prefecture University, 1-58 Rinku-Ourai-Kita, Izumisano City, Osaka 598-8531, Japan.
Abstract:
Overdose of acetaminophen (APAP), an antipyretic drug, is an important cause of liver injury. However, the mechanism in the rat model remains undetermined. We analyzed APAP-induced hepatotoxicity using rats based on M1/M2-macrophage functions in relation to damage-associated molecular patterns (DAMPs) and autophagy. Liver samples from six-week-old rats injected with APAP (1000 mg/kg BW, ip, once) after 15 h fasting were collected at hour 10, and on days 1, 2, 3, and 5. Liver lesions consisting of coagulation necrosis and inflammation were seen in the affected centrilobular area on days 1 and 2, and then, recovered with reparative fibrosis by day 5. Liver exudative enzymes increased transiently on day 1. CD68+ M1-macrophages increased significantly on days 1 and 2 with increased mRNAs of M1-related cytokines such as IFN-g and TNF-α, whereas CD163+ M2-macrophages appeared later on days 2 and 3. Macrophages reacting to MHC class II and Iba1 showed M1-type polarization, and CD204+ macrophages tended to be polarized toward M2-type. At hour 10, interestingly, HMGB1 (representative DAMPs) and its related signals, TLR-9 and MyD88, as well as LC3B+ autophagosomes began to increase. Collectively, the pathogenesis of rat APAP hepatotoxicity, which is the first, detailed report for a rat model, might be influenced by macrophage functions of M1 type for tissue injury/inflammation and M2-type for anti-inflammatory/fibrosis; particularly, M1-type may function in relation to DAMPs and autophagy. Understanding the interplayed mechanisms would provide new insight into hepato-pathogenesis and contribute to the possible development of therapeutic strategies.
Insights
Acetaminophen overdose causes liver injury in rats, driven by M1 macrophages and damage-associated molecular patterns (DAMPs). M2 macrophages aid in recovery and fibrosis, offering insights into therapeutic strategies.
Area of Science:
- Hepatology and Immunology
- Toxicology
- Cellular Biology
Background:
- Acetaminophen (APAP) overdose is a significant cause of drug-induced liver injury.
- The precise mechanisms underlying APAP hepatotoxicity in rat models require further elucidation.
- Understanding the roles of immune cells and molecular pathways is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the pathogenesis of APAP-induced hepatotoxicity in rats.
- To analyze the involvement of M1/M2-macrophage polarization in relation to damage-associated molecular patterns (DAMPs) and autophagy.
- To provide a detailed mechanistic understanding of APAP hepatotoxicity in a rat model.
Main Methods:
- Rats were administered a single high dose of acetaminophen (1000 mg/kg).
- Liver tissues were collected at various time points (10 hours, days 1, 2, 3, and 5) post-administration.
- Analysis included histological examination, enzyme assays, and assessment of macrophage markers (CD68, CD163, CD204), cytokine expression (IFN-γ, TNF-α), DAMPs (HMGB1), and autophagy markers (LC3B).
Main Results:
- Acetaminophen induced liver lesions characterized by necrosis and inflammation, followed by recovery with fibrosis.
- M1 macrophages (CD68+) increased early, correlating with pro-inflammatory cytokines, while M2 macrophages (CD163+) appeared later, associated with anti-inflammatory and fibrotic processes.
- Increased levels of HMGB1, TLR-9, MyD88, and autophagosomes (LC3B+) were observed early, suggesting a role for DAMPs and autophagy in the initial injury phase.
Conclusions:
- Rat APAP hepatotoxicity involves a dynamic interplay between M1 macrophages (driving injury/inflammation) and M2 macrophages (promoting resolution/fibrosis).
- Early M1 macrophage activation appears linked to DAMPs and autophagy, contributing to the initial liver damage.
- This study offers novel insights into the complex mechanisms of APAP-induced liver injury in rats, potentially guiding therapeutic interventions.
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