The Effects of Lithium on Inflammation Profiles and Nf-κB Nuclear Translocation in Raw 264.7 Macrophages Exposed to Rift Valley Fever Virus

IntroductionRift Valley fever virus is a mosquito-transmitted zoonotic viral infection that results in Rift Valley fever disease. RVFV and other viruses have developed mechanism to circumvent the immune recognition in an attempt to advance their viral progeny. The RVFV S segment encodes a non-structural protein (NSs) known to be the main virulence factor that aid in immune suppression and viral replication. Thus, this study is aimed at investigating the inflammatory effects of lithium using macrophages as innate immune model.MethodsThe supernatant from RVFV-infected Raw 264.7 cells and treated with lithium, was examined with Elisa assay kit to measure production levels of the cytokines and chemokines. The H2DCF-DA and DAF-2 DA oxidant florigenic assays were used to determine the levels of ROS and RNS by measuring the fluorescence intensity shown by the cells post RVFV-infection and lithium treatment. While on the other hand Western blotting assay was used to measure expression levels of the inflammatory proteins and immunocytochemistry measured the cellular location of the NF-κB.ResultsLithium have shown to stimulate production of IFN-γ 3 hrs pi and reached its peak 12 hrs later. Moreover, the secondary pro-inflammatory cytokine and chemokine, IL-6, and RANTES were elevated at 12 hrs pi. Lithium was shown to stimulate expression of the primary pro-inflammatory molecule, TNF-α as early as 3 hrs pi. In addition to TNF-α expression, the regulatory cytokine, IL-10, was stimulated by lithium and reached its peak 12 hrs pi. The RVFV-infected cells treated with lithium have shown lowered ROS and RNS production as opposed to lithium-free RVFV-infected control cells. The regulatory properties of lithium were further supported by the protein expression assay that showed low expression of the iNOS while stimulating heme oxygenase (HO) and IκB. Lithium was shown to reverse NF-κB nuclear translocation in RVFV-infected Raw 264.7 cells as shown by the Immunocytochemistry assay. Moreover, lithium lowered the presence of nuclear NF-κB in RVFV-infected cells as opposed to untreated RVFV-infected cells and 5 mg/ml LPS controls as shown by the protein expression assay.ConclusionThis study demonstrates that lithium inhibits NF-kB nuclear translocation and modulate inflammation profiles in RVFV-infected Raw 264.7 cells.