Hydrogen sulfide reduces ischemia and reperfusion injury in neuronal cells in a dose-and time-dependent manner

Abstract

Background: The ischemia-reperfusion injury (IRI) of neuronal tissue, such as the brain and retina, leads to possible cell death and loss of function. Current treatment options are limited, but preliminary observations suggest a protective effect of hydrogen sulfide (H2S). However, the dosage, timing, and mechanism of inhaled H2S treatment after IRI requires further exploration. Methods: We investigated possible neuroprotective effects of inhaled H2S by inducing retinal ische-mia–reperfusion injury in rats for the duration of 1 h (120 mmHg), followed by the administration of hydrogen sulfide (H2S) for 1 h at different time points (0, 1.5, and 3 h after the initiation of reper-fusion) and at different H2S concentrations (120, 80, and 40 ppm). We quantified the H2S effect by conducting retinal ganglion cell counts in fluorogold-labeled animals 7 days after IRI. The retinal tissue was harvested after 24 h for molecular analysis, including qPCR and Western blotting. Apop-totic and inflammatory mediators, transcription factors, and markers for oxidative stress were in-vestigated. Histological analyses of the retina and the detection of inflammatory cytokines in serum assays were also performed. Results: The effects of inhaled H2S were most evident at a concentration of 80 ppm administered 1.5 h after IRI. H2S treatment increased the expression of anti-apoptotic Bcl-2, decreased pro-apoptotic Bax expression, reduced the release of the inflammatory cytokines IL-1β and TNF-α, attenuated NF-κB p65, and enhanced Akt phosphorylation. H2S also downregulated NOX4 and cystathionine β-synthase. Histological analyses illustrated a reduction in TNF-α in retinal ganglion cells and lower serum levels of TNF-α in H2S-treated animals after IRI. Conclusion: After neuronal IRI, H2S mediates neuroprotection in a time-and dose-dependent manner. The H2S treatment modulated transcription factor NF-κB activation and reduced retinal inflammation.