Figure 7.

Lithium attenuates pyroptotic injury by activating the Nrf2/HO-1 signaling pathway in PC12 cells subjected to OGD.

Con group: untreated PC12 cells; OGD group: PC12 cells subjected to OGD; OGD + LiCl group: PC12 cells subjected to OGD and treated with LiCl; OGD + LiCl + ATRA group: PC12 cells subjected to OGD and treated with LiCl treatment and the Nrf2 inhibitor ATRA. (A, B) NLRP3, ASC, pro-Caspase-1, Caspase-1, GSDMD, and IL-18 expression. (C, D) Nrf2 and HO-1 expression. (E) The expression levels of pyroptosis-related proteins were significantly higher in the OGD group than in the Con group, and this effect was largely reversed by treatment with LiCl. The expression levels of these proteins were significantly higher in the ATRA group than in the LiCl group, with the exception of pro-Caspase-1. Nrf2 and HO-1 expression levels were significantly increased by LiCl treatment, and this effect was largely reversed by treatment with the Nrf2 inhibitor ATRA. Data are shown as mean ± SD (n = 6). *P < 0.05, vs. control group; #P < 0.05, vs. OGD group; &P < 0.05, vs. OGD + LiCl group (one-way analysis of variance followed by least significant difference test). (F) Representative images of Nrf2 and HO-1 immunofluorescence. White arrows indicate neurons that were positive for Nrf2 staining (red, Alexa Fluor 647), HO-1 staining (green, Alexa Fluor 488), and cell nucleus staining (blue, DAPI). Scale bar: 50 μm. ASC: Apoptosis-associated speck-like protein; ATRA: all-trans retinoic acid; Con: control; DAPI: 4’,6-diamidino-2-phenylindole; GSDMD: gasdermin-d; HO-1: heme oxygenase-1; IL-18: interleukin-18; LiCl: lithium chloride; NLRP3: NOD-like receptors 3; Nrf2: nuclear factor E2-related factor 2; OGD: oxygen glucose deprivation.