[Hydrogen sulfide stimulates the development of rat glioblastoma]

To address the hypothesis that hydrogen sulfide (H(2)S) is a functionally significant stimulator in the development of glioblastoma (GBM) and explore the mechanism of stimulation.

Forty adult Sprague-Dawley (SD) rats were given intracerebral injection of rat C6 glioma cell suspension, and an intraperitoneal injection of sodium hydrosulfide (NaHS), an exogenous H(2)S donor. The 40 rats were randomly divided into 4 groups of 10 rats in each: the control group, NaHS group, C6 glioma group (intracerebral implantation of C6 glioma cells) and C6-NaHS group (intracerebral implantation of C6 glioma cells and intraperitoneal injection of NaHS). Food and water were freely available during all phases of the experiment. Physical symptoms were observed and the tumor size was measured. Histological changes were examined by pathology. Immunohistochemical staining was used to analyze the expression of HIF-1α and integrated optical density (IOD) was used to determine the tumor microvessel density (MVD). The H(2)S content in the brain was measured.

The physical symptoms of tumor-bearing rats became more serious after NaHS injection. The H(2)S level in the C6 glioma group was higher than that in the control group [(35.25 ± 1.03) nmol/g vs. (29.12 ± 0.94) nmol/g, P < 0.05], and the highest H(2)S level was found in the C6-NaHS group. The pathological examination showed that the implanted tumors were predominantly spheroid with a distinct border and no capsule could be detected. Neovascular proliferation was also observed. Foci of tumor necrosis, intratumoral hemorrhage, pseudopalisades and tumor cavity were clearly observed. The glioma cells had scant eosinophilic cytoplasm and enlarged hyperchromatic nuclei. All these phenomena were more markedly in the C6-NaHS group compared with that in other three groups. The mean tumor volume was significantly different between the C6 and C6-NaHS rats [(32.0 ± 6.9) mm(3) vs. (67.8 ± 11.9) mm(3), P < 0.001]. Immunohistochemical analysis exhibited that the hypoxia-inducible factor-1alpha (HIF-1α) and CD34 expression were significantly increased after the intraperitoneal injection of NaHS in the C6-NaHS rats (comparing the IOD between C6-NaHS group and C6 group, HIF-1α: 133 962.9 ± 451.4 vs. 38 569.8 ± 408.6, P < 0.001; CD34: 73 368.6 ± 404.8 vs. 14 570.6 ± 748.7, P < 0.001). Moreover, compared with the C6 group, there were higher MVD in the C6-NaHS group [(41.2 ± 7.9)/mm(2) vs. (97.0 ± 10.8)/mm(2), P < 0.001].

H(2)S serves as a stimulator in the development of rat glioblastoma and exogenous H(2)S strongly promotes the tumor growth. The stimulating mechanisms include the increase of HIF-1α expression and neovascular formation. H(2)S may be a significant regulator in the development of tumor.