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

Abstract

Acute exposure to high concentrations of hydrogen sulfide (H₂S), 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 H₂S using human bronchial BEAS-2B (BEAS) and GFP-tagged G3BP1-stably transfected CHO cells. We first examined the changes in intracellular H₂S concentration by NaHS exposure. Qualitative and quantitative analyses revealed that intracellular H₂S levels rapidly increased after NaHS exposure and accumulated in cells dose dependently. In terms of the response to H₂S 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 H₂S-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 H₂S, H₂S is rapidly taken up by pulmonary cells and induces SG formation and translational repression via eIF2α phosphorylation, thereby protecting against cell death.