Angelicin attenuates sepsis-associated acute liver injury via p38 MAPK inhibition and NF-κB-mediated Nrf2/Keap1 activation to suppress inflammation and oxidative stress

Abstract

Sepsis-associated acute liver injury (SALI) is a frequent and clinically severe complication of sepsis, in which inflammatory responses and oxidative stress are involved. Angelicin (ANG), one of the main active components in the traditional Chinese medicine Psoralea corylifolia Linn., has anti-inflammatory and antioxidant bioactivities. In this study, the protective effect of ANG on SALI and its specific mechanism are investigated by establishing a mouse model of caecal ligation and puncture (CLP)-induced SALI and an in vitro sepsis model in LPS-stimulated AML12 cells. These results show that ANG can alleviate liver injury and improve liver function in SALI mice. ANG decreases the mRNA expression levels of the pro-inflammatory factors Il-1β, Il-6, and Tnf-α and increases the mRNA expression level of the anti-inflammatory factor Il-10, which suggests its anti-inflammatory effects. The results of the biochemical kit assay and DHE staining show that ANG can decrease the levels of MDA and ROS and increase the level of GSH and the activities of CAT and SOD, which suggests that ANG has antioxidant effects. Mechanistically, ANG exerts anti-inflammatory effects by inhibiting the NF-κB and p38 MAPK pathways and exerting antioxidant effects by activating the Nrf2/Keap1 pathway. Additionally, cell transfection experiments indicate that activation of the Nrf2/Keap1 pathway by ANG may depend on the inhibition of the NF-κB pathway. In conclusion, ANG attenuates SALI by inhibiting the NF-κB and p38 MAPK pathways, thereby activating the Nrf2/Keap1 pathway and making it a promising therapeutic intervention for SALI.

1. Introduction

Sepsis is a systemic inflammatory response caused by infection, and when this inflammatory response is out of control, it may lead to damage to multiple organ systems [1]. The liver is a key effector in sepsis pathogenesis, orchestrating host defense via microbial antigen clearance, immune cell recruitment, and inflammation-associated metabolic shifts, thereby frequently becoming a major affected organ [2]. Sepsis not only causes acute liver injury, leading to liver failure but also may lead to serious complications, such as biliary obstruction, hepatic encephalopathy, and multiple organ dysfunction syndrome (MODS) [2]. However, few studies have investigated sepsis-associated acute liver injury (SALI).

Recent investigations revealed that physiological responses, including oxidative stress, inflammatory signaling, and programmed cell death (apoptosis), play essential protective roles against SALI [3]. However, excessive activation of these pathways paradoxically aggravates tissue damage in vivo [4]. As heterologous phagocytes in innate immunity, macrophages detect pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) by expressing pattern-recognition receptors [5]. During sepsis pathogenesis, hepatic non-parenchymal cells, including Kupffer cells, hepatic sinusoidal endothelial cells, and stellate cells, serve as the primary defense mechanism by capturing and eliminating invading pathogenic microorganisms and their byproducts, thereby providing systemic protection while maintaining hepatic homeostasis [6]. Moreover, liver-resident and recruited immune cells produce multiple proinflammatory cytokines and chemokines that lead to liver injury and dysfunction during sepsis [7]. Liver dysfunction has been demonstrated to be a distinct and independent predictor of adverse outcomes in critically ill patients [8], whereas pre-existing hepatic impairment predisposes individuals to sepsis, subsequent multi-organ failure, and increased mortality. Therefore, anti-inflammatory interventions that mitigate liver injury and restore hepatic function could improve outcomes in sepsis patients [9].

Extensive evidence indicates that various signaling pathways, particularly the mitogen-activated protein kinase (MAPK) and nuclear factor-κB (NF-κB) pathways, critically regulate inflammatory responses during sepsis pathogenesis [10]. The MAPK family, which comprises extracellular signal-regulated kinases 1/2 (ERK1/2), p38 mitogen-activated protein kinase (p38 MAPK), and c-Jun N-terminal kinase (JNK), modulates the transcriptional regulation of proinflammatory mediators, including inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2). Moreover, NF-κB, a heterodimer of p50/p65 subunits that complex with inhibitory κB (IκB) proteins, plays a bidirectional role in both host defense and inflammation.