4-Octyl Itaconate Activates Nrf2 Signaling to Inhibit Pro-Inflammatory Cytokine Production in Peripheral Blood Mononuclear Cells of Systemic Lupus Erythematosus Patients

Abstract

Background/Aims: Increased production of multiple pro-inflammatory cytokines, including tumor necrosis factor (TNF)-α, interleukin (IL)-1β, and IL-6, plays an essential pathogenic role in the progression of systemic lupus erythematosus (SLE). Recent studies have characterized itaconate as a novel and potent nuclear-factor-E2-related factor 2 (Nrf2) activator that activates Nrf2 signaling by alkylating cysteine residues on Keap1 (Kelch-like ECH-associated protein 1). Methods: THP-1 human macrophages and peripheral blood mononuclear cells (PBMCs) of SLE patients were treated with 4-octyl itaconate (OI). Nrf2 signaling activation was tested by qPCR assay and western blotting. mRNA expression and the production of multiple pro-inflammatory cytokines were tested by qPCR and enzyme-linked immunosorbent assays, respectively. Nuclear factor (NF)-κB activation was tested by the p65 DNA-binding assay. Results: We demonstrated that OI, the cell-permeable derivative of itaconate, induced Keap1-Nrf2 dissociation, Nrf2 protein accumulation, and nuclear translocation, which enabled the transcription and expression of multiple Nrf2-dependentantioxidant enzymes (heme oxygenase-1, NAD(P)H:quinone oxidoreductase 1, and glutamate-cysteine ligase modifier subunit) in THP-1 human macrophages. OI also induced significant Nrf2 activation in SLE patient-derived PBMCs. OI pretreatment inhibited mRNA expression and the production of multiple pro-inflammatory cytokines (TNF-α, IL-1β, and IL-6) in SLE patient-derived PBMCs and lipopolysaccharide (LPS)-activated THP-1 cells. OI potently inhibited NF-κB activation in SLE patient-derived PBMCs and LPS-activated THP-1 cells. Importantly, Nrf2 silencing (by targeted short hairpin RNA) or knockout (by CRISPR/Cas9 gene-editing method) almost abolished OI-induced anti-oxidant and anti-inflammatory actions in SLE patient-derived PBMCs and LPS-activated THP-1 cells. Conclusion: OI activates Nrf2 signaling to inhibit the production of pro-inflammatory cytokines in human macrophages and SLE patient-derived PBMCs. OI and itaconate could have important therapeutic value for the treatment of SLE.

Dimethyl itaconate protects against fungal keratitis by activating the Nrf2/HO‐1 signaling pathway

“…Our results are in accordance with those of other work indicating that DI limits the production of cytokines in LPS‐treated macrophages . In addition, OI, another itaconate derivative, downregulates the levels of cytokines in mononuclear cells …”

“…Immunostaining showed that DI treatment increased the accumulation of Nrf2 in the nuclei of infected HCECs. Our results are consistent with those of studies showing that a derivative of itaconate induces the nuclear accumulation of Nrf2 in human macrophages …”

“…We show here that in infected HCECs, BT or ZnPP treatment separately blocked the DI‐induced inhibition of IL‐1β, IL‐8 and IL‐6. These results are consistent with those of other work showing that the downregulation of cytokines induced by OI is almost completely reversed in Nrf2‐deficient macrophages . Furthermore, the effect of blocking the DI‐induced inhibition of cytokines was much greater in HCECs pretreated with a combination of BT and ZnPP than in HCECs treated with either BT or ZnPP separately.…”

“…We found that the DI‐induced upregulation of HO‐1 expression was inhibited by BT pretreatment in HCECs. These data are consistent with those of studies showing that OI‐induced HO‐1 expression is blocked in Nrf2‐deficient macrophages or when Nrf2 is silenced . We show here that in infected HCECs, BT or ZnPP treatment separately blocked the DI‐induced inhibition of IL‐1β, IL‐8 and IL‐6.…”

“…In addition, itaconate reduces ICL activity and dampens the growth of microorganisms in ICL‐dependent environments . Studies of DI and itaconate derivatives in immunity have indicated their therapeutic effects in multiple diseases, including psoriasis and systemic lupus erythematosus . In our study, DI exhibited anti‐inflammatory effects during A. fumigatus infection and inhibited the growth of A. fumigatus , indicating the protective potential of DI in fungal keratitis.…”