Four-Octyl Itaconate Attenuates UVB-Induced Melanocytes and Keratinocytes Apoptosis by Nrf2 Activation-Dependent ROS Inhibition

Abstract

Vitiligo is an acquired skin depigmentation disease in which excessive reactive oxygen species (ROS) play a critical pathogenic role in melanocyte destruction. The complex crosstalk between melanocytes and keratinocytes in vitiligo suggests that treatments aimed at protecting both the cells might be meaningful. In this study, we investigated the effect of 4-octyl itaconate (4-OI), an itaconate derivative, on ultraviolet B- (UVB-) induced apoptosis in HaCaT and PIG1 cells and the underlying mechanisms. HaCaT and PIG1 cells were pretreated with 4-OI (50 or 100 μM) for 24 h and then exposed to 300 mJ/cm2 UVB (emission range 290–320 nm, emission peak 310 nm). ROS levels and cell apoptosis were investigated using fluorescence microscopy and flow cytometry 24 h after irradiation. In addition, nuclear translocation and the expression of pathway-related proteins and mRNAs were detected using confocal microscopy, western blotting, and qRT-PCR, respectively. Our results demonstrated that UVB induced apoptosis in HaCaT and PIG1 cells, whereas inhibition of ROS production could reverse this effect. Furthermore, 4-OI attenuated UVB-induced apoptosis in HaCaT and PIG1 cells in a concentration-dependent manner by reducing the ROS levels. Moreover, 4-OI induced nuclear translocation and activation of nuclear factor erythroid 2-related factor 2 (Nrf2), and Nrf2 silencing reversed the inhibitory effect of 4-OI on the UVB-induced increase in ROS production and apoptosis in HaCaT and PIG1 cells. In addition, in vivo experiments using the Institute of Cancer Research mouse model showed that 4-OI via tail vein injection (10 mg/kg/day for six consecutive days) could reduce skin damage induced by UVB (400 mJ/cm2/day for five consecutive days). In conclusion, 4-OI can protect melanocytes and keratinocytes from UVB-induced apoptosis by Nrf2 activation-dependent ROS inhibition and can potentially treat skin disorders associated with oxidative stress, such as vitiligo.

4-OI Protects MIN6 Cells from Oxidative Stress Injury by Reducing LDHA-Mediated ROS Generation

“…By reducing oxidative stress and inflammation, 4-OI inhibited LPS-induced acute lung injury in mice, which was confirmed by the reduced lung tissue damage and inflammatory response [ 53 ]. Furthermore, 4-OI administered through tail-vein injection attenuated UVB-induced skin damage in mice by inhibiting ROS production [ 54 ]. Since ROS are one of the main factors driving islet cell death during hypoxia, we hypothesized that 4-OI could protect MIN6 cells against hypoxic injury through the inhibition of ROS production.…”

Itaconate: A Potent Macrophage Immunomodulator

“…Another study also showed that 4-OI significantly inhibited ROS production by activating Nrf2, which in turn caused downregulation of AMPK phosphorylation levels, and improved free fatty acid-induced oxidative stress and lipid metabolism disorders in hepatocytes [ 43 ]. Itaconate has also attenuated inflammatory damage through activation of Nrf2 in other diseases such as osteoarthritis [ 44 – 47 ], nerve injury [ 48 , 49 ], cardiovascular disease [ 50 , 51 ], systemic lupus erythematosus [ 52 ], vitiligo [ 53 ], periodontitis [ 54 ], fungal keratitis [ 55 ], and diabetic wound repair [ 56 ]. Consequently, itaconate, as an Nrf2 agonist, may present new therapeutic opportunities for many inflammatory diseases.…”

The signaling pathways and therapeutic potential of itaconate to alleviate inflammation and oxidative stress in inflammatory diseases

“…As described in ‘5.2.1 Regulating KEAP1 activity’, itaconate increases the alkylation of cysteine residues 151, 257, 273, 288, and 297 on KEAP1, enhances the degradation of KEAP1 and leads to the dissociation and activation of Nrf2. Bambouskova et al demonstrated that itaconate and DI reacted with glutathione and activated Nrf2 [ 21 ], then in the process of periodontal destruction [ 179 ], liver fibrosis [ 72 ], vitiligo [ 180 ], pulmonary fibrosis [ 181 ], renal injury [ 175 ], osteoporosis [ 182 ], and neurodegenerative diseases [ 183 ], itaconate and its derivatives functioned as activators of the Nrf2 pathway and attenuated oxidative stress. Moreover, Yi et al reported that itaconate activated Nrf2 to mitigate oxidative stress in liver IRI, which demonstrated the antioxidant effect in nonimmune cells [ 163 ].…”