ABSTRACT
CCL8 (MCP-2) is a chemoattractive cytokine associated with various immune-related pathologies. Recent studies show that CCL8 is significantly stimulated during acute respiratory distress syndrome in severely ill patients with COVID-19, making the inhibition of CCL8 activity a promising treatment. Lipopolysaccharide (LPS)-induced lung injury was evaluated in mice using a neutralizing antibody (1G3E5) against human CCL8. Pharmacokinetic studies indicated that following IP administration, 1G3E5 was sustained at higher levels and for a longer period compared to IV administration. CCL8 expression in the lungs was not enhanced by LPS, but CCR2 and CCR5 receptors were significantly stimulated. 1G3E5-mediated inhibition of CCL8 was associated with the reduction of pulmonary inflammation and suppression of various pro-inflammatory cytokines. These results point to a previously unrecognized, permissive role for CCL8 in mediating cytokine induction and ultimately sustaining inflammation. Disruption of CCL8 activity may provide a strategy for mitigating pulmonary inflammation during lung injury when related to abnormal cytokine induction.
ABSTRACT
Coronavirus disease 2019 (COVID-19) patients show lipid metabolic alterations, but the mechanism remains unknown. In this study, we aimed to investigate whether the Spike protein of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) impairs lipid metabolism in host cells. We generated a Spike cell line in HEK293 using the pcDNA vector carrying the Spike gene expression cassette. A control cell line was generated using the empty pcDNA vector. Gene expression profiles related to lipid metabolic, autophagic, and ferroptotic pathways were investigated. Palmitic acid (PA)-overload was used to assess lipotoxicity-induced necrosis. As compared with controls, the Spike cells showed a significant increase in lipid depositions in cell membranes as well as dysregulation of expression of a panel of molecules involving lipid metabolism, autophagy, and ferroptosis. The Spike cells showed an upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2), a multifunctional transcriptional factor, in response to PA. Furthermore, the Spike cells exhibited increased necrosis in response to PA-induced lipotoxicity compared to control cells in a time- and dose-dependent manner via ferroptosis, which could be attenuated by the Nrf2 inhibitor trigonelline. We conclude that the Spike protein impairs lipid metabolic and autophagic pathways in host cells, leading to increased susceptibility to lipotoxicity via ferroptosis which can be suppressed by a Nrf2 inhibitor. This data also suggests a central role of Nrf2 in Spike-induced lipid metabolic impairments.