Benzo[a]pyrene exposure promotes RIP1-mediated necroptotic death of osteocytes and the JNK/IL-18 pathway activation via generation of reactive oxygen species. (30th June 2022)

• Record Type: Journal Article
• Authors: Zhang, Tao; Shen, Yuchen; Zhu, Ruirong; Shan, Weiyan; Li, Yurong; Yan, Ming; Zhang, Yun
• Is Part Of: Toxicology. Volume 476(2022)
• Publication Date: 2022-06-30
• Subjects: ALP alkaline phosphatase -- α-MEM alpha-Minimum Essential Medium -- BaP benzo[a]pyrene -- BMD bone mineral density -- DCF-DA dichlorodihydrofluorescein diacetate -- FBS fetal bovine serum -- HO-1 heme oxygenase-1 -- IL-1β interleukin-1β -- JNK c-Jun N-terminal kinase -- LDH lactate dehydrogenase -- MDA malondialdehyde -- Micro-CT micro-computed tomography -- MLKL mixed lineage kinase domain-like protein -- NAC N-acetylcysteine -- Nec-1 necrostatin-1 -- Nrf2 nuclear factor E2-related factor 2 -- PAH polycyclic aromatic hydrocarbon -- RANKL receptor activator of nuclear factor (NF)-kB-ligand -- RIP1 receptor-interacting protein kinase 1 -- ROS reactive oxygen species -- SOD superoxide dismutase -- TRAP tartrate-resistant acid phosphatase; Benzo(a)pyrene -- Osteocytes -- Necroptosis -- JNK/IL-18 pathway -- Reactive oxygen species; Toxicology -- Periodicals; Chemicals -- Physiological effect -- Periodicals; 615.9005
• DOI: 10.1016/j.tox.2022.153244
• Languages: English
• ISSNs: 0300-483X

Abstract

Abstract: Benzo[a]pyrene (BaP) is a polycyclic aromatic hydrocarbon (PAH) of environmental pollutants, readily produced during the processing of petroleum and fatty foods. BaP exposure can cause skeletal deformities. However, whether BaP affects osteocytes, making up over 95% of all the bone cells, remains unknown. This study aimed to investigate the effect of BaP on osteocytes in vivo and in vitro, as well as explore the underlying mechanisms. The in vivo data showed that BaP (50 mg/kg) exposure for 12 weeks could cause bone destruction, and increase osteocytes death in mouse cortical femur. O ur in vitro results revealed that BaP (25–100 μmol/L) exposure inhibited cell viability of MLO-Y4 cells, and resulted in cell death in a dose-dependent manner. Furthermore, BaP exposure significantly triggered necroptosis of MLO-Y4 cells, as indicated by increased propidium iodide (PI)-positive cells and up-regulation of necroptosis-related protein expressions of receptor-interacting protein kinase 1 (RIP1), RIP3, and mixed lineage kinase domain-like protein (MLKL). This necrotic effect was reversed by the RIP1 inhibitor necrostatin-1 (Nec-1). Simultaneously, BaP activated the downstream c-Jun N-terminal kinase (JNK)/ interleukin (IL)-18 signaling pathway, which was suppressed after the JNK inhibitor SP600125 or Nec-1 treatment. In addition, BaP exposure promoted the production of intracellular reactive oxygen species (ROS), mitochondrial ROS (mtROS), and elevated malondialdehyde (MDA) levels; while BaP decreased superoxide dismutase (SOD) activity and antioxidant enzymes including nuclear factor E2 -related factor 2 (Nrf2) and heme oxygenase-1 (HO-1) levels, leading to oxidative damage. The ROS scavenger N-acetylcysteine (NAC) inhibited this necroptotic death and the JNK/IL-18 pathway activation. Collectively, BaP exposure may cause RIP1-mediated necroptotic death of osteocytes and activate the JNK/IL-18 pathway via ROS generation. Graphical Abstract: ga1 Highlights: BaP caused bone destruction and osteocytes death in vivo. BaP triggered necroptosis and activated the JNK/IL-18 pathway in MLO-Y4 cells. BaP promoted the production of ROS and mitochondria ROS, leading to oxidative stress. ROS contributed to BaP-induced necroptosis and the JNK/IL-18 pathway activation.