CD31 induces inflammatory response by promoting hepatic inflammatory response and cell apoptosis

To investigate whether CD31 could regulate paracetamol-induced liver injury, thereby providing a new direction for the prevention and treatment of drug-induced hepatitis.

Wild-type (WT) mice were treated with acetaminophen (APAP) (250 mg/kg) or isodose of phosphate-buffered saline (PBS). 1, 3, 6 and 12 h after the treatment, the messenger RNA (mRNA) and protein expression level of CD31 in the liver of mice were determined by Real-time reverse transcription polymerase chain reaction (RT-PCR) and Western blotting, respectively. Once CD31 was confirmed to be involved in APAP-induced liver injury, the acute liver injury model in WT mice and CD31 gene deficient (CD31-/-) mice induced by APAP was established. Serum samples were collected at 8 and 24 h after APAP injection (250 mg/kg), and the activity of serum alanine aminotransferase (ALT) was measured. The liver tissues of mice were isolated and analyzed by hematoxylin and eosin (HE) staining. Meanwhile, mononuclear cells (MNCs) were isolated from the liver tissues of mice. The number of infiltrating macrophages and neutrophils was detected by flow cytometry, and the activation level of these cells was analyzed. The expression levels of proinflammatory cytokines in liver tissues, such as TNF-α, IL-1β, keratinocyte chemoattractant (KC), MCP-1 and IL-6, were determined by RT-PCR. The expression levels of cytokines in serum were detected by enzyme-linked immunosorbent assay (ELISA). Moreover, the protein expression levels of JNK, Caspase-3, and cytochrome P450 2E1 (CYP2E1) in liver tissues were detected by Western blotting.

After APAP treatment, we found that WT mice were more sensitive to APAP-induced liver injury. The level of ALT in WT mice was significantly higher than that of CD31-/- mice, meanwhile, more necrotic or apoptotic cells were found in WT mice. Results also indicated that the expression levels of inflammatory cytokines, including KC, IL-1β, MCP-1 and IL-6, were significantly higher in WT mice. Meanwhile, the number of infiltrating macrophages and neutrophils in the liver tissues of WT mice were much more than that of CD31-/- mice.

APAP-treated CD31-/- mice exhibited less liver injury when compared with WT mice. We also confirmed that CD31 was greatly involved in APAP-induced inflammatory response by promoting hepatic inflammatory and cell apoptosis, which might provide a new strategy for the prevention and treatment of drug-induced hepatitis.