Aflatoxin B1 enhances pyroptosis of hepatocytes and activation of Kupffer cells to promote liver inflammatory injury via dephosphorylation of cyclooxygenase-2: an in vitro, ex vivo and in vivo study

Abstract

Aflatoxin B1 (AFB1), a food contaminant derived from Aspergillus fungi, has been reported to cause hepatic immunotoxicity via inflammatory infiltration and cytokines release. As a pro-inflammatory factor, cyclooxygenase-2 (COX-2) is widely involved in liver inflammation induced by xenobiotics. However, the mechanism by which AFB1-induced COX-2 regulates liver inflammatory injury via hepatocytes-Kupffer cells (KCs) crosstalk remains unclear and requires further elucidation. Here, we established a COX-2 upregulated model with AFB1 treatment in vivo (C57BL/6 mice, 1 mg/kg body weight, i.g, 4 weeks) and in vitro (human liver HepaRG cells, 1 μM for 24 h). In vivo, AFB1-treated mice exhibited NLRP3 inflammasome activation, inflammatory infiltration, and increased recruitment of KCs. In vitro, dephosphorylated COX-2 by protein phosphatase 2A (PP2A)-B55δ promoted NLRP3 inflammasome activation, including mitochondrial translocation of NLRP3, caspase 1 cleavage, and IL-1β release. Moreover, phosphorylated COX-2 at serine 601 (p-COX-2 Ser601 ) underwent endoplasmic reticulum (ER) retention for proteasome degradation. Furthermore, pyroptosis and inflammatory response induced by AFB1 were relieved with COX-2 genetic (siPTGS2) intervention or pharmaceutic (celecoxib, 30 mg/kg body weight, i.g, 4 weeks) inhibition of COX-2 via NLRP3 inflammasome suppression in vivo and in vitro. Ex vivo, in a co-culture system with murine primary hepatocytes and KCs, activated KCs induced by damaged signals from pyroptotic hepatocytes, formed a feedback loop to amplify NLRP3-dependent pyroptosis of hepatocytes via pro-inflammatory signaling, leading to liver inflammatory injury. Taken together, our data suggest a novel mechanism that protein quality control of COX-2 determines the intracellular distribution and activation of NLRP3 inflammasome, which promotes liver inflammatory injury via hepatocytes-KCs crosstalk.

Melatonin attenuates AFB1-induced cardiotoxicity via the NLRP3 signalling pathway

“… 28 Zhang et al. 9 reported that the severity of AFB1-induced liver inflammatory injury in mice was significantly alleviated by downregulating NLRP3 expression through inhibition of cyclooxygenase-2. These results imply that persistent activation of the NLRP3 inflammasome is a critical factor for instigating tissue damage.…”

“…Recently, AFB1 was found to activate the NLRP3 inflammasome in primary hepatocytes and Kupffer cells, leading to liver inflammatory injury. 9 It seems reasonable that a similar activation method may be induced by AFB1 in the heart.…”

Carcinogenesis: Failure of resolution of inflammation?

“…AFB 1 upregulates COX-2 which activates the inflammasome leading to tumor-promoting inflammation. In contrast, celecoxib reduced this inflammation demonstrating the regulation of inflammation by eicosanoids and inflammatory mediators ( Zhang et al, 2019 ). Additionally, etodolac, a COX-2 inhibitor, suppresses N -nitrosobis(2-oxopropyl)amine (BoP)-induced experimental biliary carcinogenesis ( Tsuneoka et al, 2005 ).…”

Icariside Ⅱ, a main compound in Epimedii Folium, induces idiosyncratic hepatotoxicity by enhancing NLRP3 inflammasome activation

“…In addition, IL-1 β can induce the production of TNF- α 49 , 50 , another key cytokine involved in amplifying and perpetuating the liver damage by triggering liver inflammation, neutrophils, and proinflammatory macrophage recruitment 51 , 52 , 53 , 54 . Moreover, NLRP3 inflammasome activation also leads to caspase-1-dependent pyroptosis 8 , this distinct form of programmed cell death could mediate liver injury 47 , 55 , 56 . In addition, one of important upstream signaling of NLRP3 inflammasome activation is ROS production 57 , 58 , which can lead to mitochondrial dysfunction through an intracellular oxidant stress in hepatocytes leading mainly to oncotic necrosis and less apoptosis 52 , 59 .…”