Hydropersulfides Inhibit Lipid Peroxidation and Protect Cells from Ferroptosis

Abstract

Hydropersulfides (RSSH) are believed to serve important roles in vivo, including as scavengers of damaging oxidants and electrophiles. The α-effect makes RSSH not only much better nucleophiles than thiols (RSH), but also much more potent H-atom transfer agents. Since HAT is the mechanism of action of the most potent small-molecule inhibitors of phospholipid peroxidation and associated ferroptotic cell death, we have investigated their reactivity in this context. Using the fluorescence-enabled inhibited autoxidation (FENIX) approach, we have found RSSH to be highly reactive toward phospholipid-derived peroxyl radicals (k inh = 2 × 10 5 M −1 s −1 ), equaling the most potent ferroptosis inhibitors identified to date. Related (poly)sulfide products resulting from the rapid self-reaction of RSSH under physiological conditions (e.g., disulfide, trisulfide, H 2 S) are essentially unreactive, but combinations from which RSSH can be produced in situ (i.e., polysulfides with H 2 S or thiols with H 2 S 2 ) are effective. In situ generation of RSSH from designed precursors which release RSSH via intramolecular substitution or hydrolysis improve the radical-trapping efficiency of RSSH by minimizing deleterious self-reactions. A brief survey of structure−reactivity relationships enabled the design of new precursors that are more efficient. The reactivity of RSSH and their precursors translates from (phospho)lipid bilayers to cell culture (mouse embryonic fibroblasts), where they were found to inhibit ferroptosis induced by inactivation of glutathione peroxidase-4 (GPX4) or deletion of the gene encoding it. These results suggest that RSSH and the pathways responsible for their biosynthesis may act as a ferroptosis suppression system alongside the recently discovered FSP1/ubiquinone and GCH1/BH 4 /DHFR systems.

Identification of structurally diverse FSP1 inhibitors that sensitize cancer cells to ferroptosis

“…As observed in our primary and follow up screens, these 19 compounds directly inhibited purified FSP1 in vitro (Figure S2 and S3) and triggered cell death in the H460 C GPX4 KO cells, but not the H460 C Cas9 cells (Figure 1I). We named these validated FSP1 inhibitors -ferroptosis sensitizer [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19]. The structures of FSEN1-19, their IC50 for inhibition of purified FSP1 activity, and their EC50 for triggering cell death in H460 C GPX4 KO cells are shown in Figure 2.…”

“…Cellular ferroptosis sensitivity is determined by a variety of metabolic processes, including pathways that regulate labile iron pools and the generation of reactive oxygen species (ROS), the addition and removal of oxidation-sensitive polyunsaturated fatty acids (PUFAs) to and from phospholipids, and ferroptosis defense systems that suppress the accumulation of lipid peroxides 1,2 . These ferroptosis defense systems function through two mechanisms, the conversion of lipid peroxides into non-toxic lipid alcohols by the glutathione (GSH) peroxidase GPX4 3 and the generation of endogenous antioxidants that prevent lipid radical propagation, such as the generation of the reduced form of coenzyme Q10 (CoQ) (i.e., ubiquinol) by ferroptosis suppressor protein 1 (FSP1) 4,5 and dihydroorotate dehydrogenase (DHODH) 6 , tetrabiohydropterin by GTP cyclohydroxylase-1 (GCH1) 7,8 , and hydropersulfides by enzymatic and non-enzymatic pathways 9,10 .…”

Cysteine hydropersulfide reduces lipid peroxidation and protects against myocardial ischaemia-reperfusion injury - Are endogenous persulfides mediators of ischaemic preconditioning?

“…Previous studies in E.coli bacteria and cultured cells demonstrated that treatment with Cys-SSS-Cys generates CysSSH, conferring antioxidant protection against electrophile-induced cell death [ 10 , 21 ]. Recent studies revealed that enhancement of persulfides by synthetic persulfide donors promotes anti-inflammatory effects in macrophages [ 22 ] and inhibits lipid peroxidation in cultured fibroblasts [ 23 ]. Whilst these findings have unravelled some unique properties of persulfides in vitro , the physiological relevance of CysSSH in tissue/organs remains unclear.…”

Mechanism of ferroptosis in traditional chinese medicine for clinical treatment: A review

“…Glutathione usually exists in the reduced state GSH, but GSH is converted into the oxidized state, GSSG, under the action of oxidative stress, and the ratio of GSH/GSSG can be considered an important indicator for oxidative stress research ( Sun et al, 2022 ). There are three major inhibitory systems of ferroptosis: the cysteine/GSH/GPX4 axis, NADPH/FSP1/CoQ10 system, and GCH1/BH4/DHFR system ( Feng-Jiao et al, 2022 ; Liu et al, 2022 ; Wu et al, 2022 ). The cysteine/GSH/GPX4 axis is an important pathway for ferroptosis, and gene knockout or inhibition of GPX4 activity is an important method to induce ferroptosis.…”

“…Extramitochondrial ubiquinone can be obtained from the reduction of CoQ10 by FSP1, which can directly capture lipid free radicals or indirectly oxidize α-tocopherol. The guanosine triphosphate cyclohydrolase, GCH1, is a GPX4-independent ferroptosis suppressor gene that cooperates with GPX4 inhibitors to induce ferroptosis ( Wu et al, 2022 ). The purpose of this article is to review the current studies of the ferroptosis in traditional Chinese medicines used in the treatment of various diseases.…”