【Objective】 To investigate whether hydrogen sulfide (H2S) protected PC12 cells against chemical hypoxia-induced injury by inhibiting iNOS-NO pathway.【Method】 PC12 cells were treated with cobalt chloride (CoCl2) to set up a chemical hypoxia-induced cellular injury model. Cell viability was tested by Cell Counter Kit (CCK-8); morphological changes of apoptotic cells were detected by Hoechst33258 staining; Apoptotic rate was evaluated by propidium iodide staining and flow cytometry (FCM); Nitrite accumulation

an indicator of nitrogen monoxidum (NO) production

was measured in cell culture supernatants using the Griess reagent; the expression of the inducible enzyme of NO (iNOS) was determined by Western blot assay. 【Results】Exposure of PC12 cells to 600 µmol/L CoCl2 for 24h significantly enhanced iNOS expression. Pretreatment with 400 µmol/LNaHS(a donor of H2S) for 30 min prior to exposure of PC12 cells to 600 µmol/L CoCl2 not only inhibited CoCl2-induced increase in expression of iNOS and NO production

but also protected PC12 cells against injuries induced by 600 µmol/L CoCl2

enhancing cell viability and decreasing amount of apoptotic cells. Similarly

pretreatment with L-Canavanine (10 µmol/L)

an inhibitor of iNOS for 60 min prior to exposure of PC12 cells to CoCl2 also conferred the same cytoprotective effect of H2S. In addition

pretreatment with SB203580

an inhibitor of p38MAPK

for 60 min prior exposure of PC12 cells to 600 µmol/L CoCl2 could also down-regulate the expression of iNOS induced by CoCl2. 【Conclussions】The iNOS-NO pathway mediates CoCl2-induced injury and H2S can protect PC12 cells against chemical hypoxia-induced injury by inhibiting iNOS-NO pathway.