Intracellular hydrogen sulfide induces stress granule formation and translational repression through eIF2α phosphorylation.

Acute exposure to high concentrations of hydrogen sulfide (HS), a toxic gaseous substance, can cause potentially lethal respiratory damages. Stress granules (SGs) are cytoprotective membrane-less intracellular organelles formed transiently in response to various stressors. We examined SG formation and the underlying molecular mechanism following exposure to high concentrations of HS using human bronchial BEAS-2B (BEAS) and GFP-tagged G3BP1-stably transfected CHO cells. We first examined the changes in intracellular HS concentration by NaHS exposure. Qualitative and quantitative analyses revealed that intracellular HS levels rapidly increased after NaHS exposure and accumulated in cells dose dependently. In terms of the response to HS taken up after exposure to 2.5-10 mM NaHS, both cell lines formed discrete SG assemblies within 1 h. SG formation induced by NaHS exposure was enhanced by treatment with glutathione (GSH) or thioredoxin (Trx) inhibitor but suppressed by treatment with a PERK inhibitor or integrated stress response inhibitor. Levels of phosphorylation of eIF2 α, which is essential for canonical SG formation, were significantly and dose-dependently increased in NaHS-exposed BEAS cells. Phosphorylation of eIF2α was further increased by GSH or Trx inhibitor treatment. These results suggest that GSH and Trx play protective roles in HS-induced SG formation. PERK, a kinase of eIF2α, might activate the pathway partially. Levels of newly synthesized proteins were markedly reduced in NaHS-exposed cells. In summary, when humans inhale high concentrations of HS, HS is rapidly taken up by pulmonary cells and induces SG formation and translational repression via eIF2α phosphorylation, thereby protecting against cell death.