TNF and retinal ischemia: Concordantly, in analyses conducted by Biermann et al. and Scheid et al., pre-conditioning as well as post-conditioning with H2S (80 ppm for 1 h before or at 0 and 1.5 h after ischemia/reperfusion, respectively) decreased the levels of pro-inflammatory cytokines TNF-α and Interleukin-1β, reduced the expression of the pro-apoptotic Bax protein and increased the expression of the anti-apoptotic protein BCL-2 in a rat model of retinal ischemia/reperfusion injury (Figure 2) [71].