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A critical role for hemolysin in Vibrio fluvialis-induced IL-1β secretion mediated by the NLRP3 inflammasome in macrophages.

Song L, Huang Y, Zhao M, Wang Z, Wang S, Sun H, Kan B, Meng G, Liang W, Ren Z - Front Microbiol (2015)

Bottom Line: The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection.VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β.Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention - Chinese Center for Disease Control and Prevention Beijing, China.

ABSTRACT
Vibrio fluvialis causes human diarrhea, but the pathogenesis is not well-studied. We hypothesized that V. fluvialis-secreted hemolysin (VFH) may induce IL-1β secretion through the activation of the NLRP3 inflammasome and contribute to the pathogenicity of V. fluvialis. To examine this possibility, we constructed VFH mutant and complement strains and demonstrated that V. fluvialis-induced IL-1β production and cytotoxicity in human monocytic THP-1 cells and mouse macrophages is attributed to VFH. To evaluate the role of VFH in vivo, we infected adult C57BL/6 mice intraperitoneally and suckling C57/B6 mice orally with various strains. The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection. VFH contributed to pathological changes and IL-1β release independent of colonization of V. fluvialis in the colon. VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β. Furthermore, using deficient mouse strains, we verified that V. fluvialis-induced IL-1β is mediated through activation of Caspase-1 and the NLRP3 inflammasome ex vivo. Confocal microscopy suggests that VFH contributes to cathepsin B release. Furthermore, V. fluvialis-induced IL-1β secretion requires potassium (K(+)) efflux and reactive oxygen species production. Our results provide new evidence for the role of VFH in the activation of the NLRP3 inflammasome and pathogenesis in response to V. fluvialis infection. Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

No MeSH data available.


Related in: MedlinePlus

Histopathological analysis of colon lesions. Five days C57 BL/6 sucking mice were inoculated orally with various strains or supernatant from cell-free overnight culture of various strain of V. fluvialis. Colons were collected 24 h p.i., and the specimens were fixed, embedded, cut, and stained with H.E. (A) Negative control mouse treated with PBS. (B) Infection with WT V. fluvialis. (C) Infection with the mutant strain Δvfh. (D) Infection with complemented mutant strain pUC-vfh. (E) Treatment with supernatant from Δvfh. (F) Treatment with supernatant from WT. (G) The pathology scoring in mice treated with WT or Δvfh or pUC-vfh strain. (H) The pathology scoring in mice treated with supernatant from Δvfh and WT. The result represent mean ± SD of six independent mice. ∗P < 0.05; ∗∗P < 0.01 and are shown as 200 magnification times, (A–H) 200×.
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Figure 4: Histopathological analysis of colon lesions. Five days C57 BL/6 sucking mice were inoculated orally with various strains or supernatant from cell-free overnight culture of various strain of V. fluvialis. Colons were collected 24 h p.i., and the specimens were fixed, embedded, cut, and stained with H.E. (A) Negative control mouse treated with PBS. (B) Infection with WT V. fluvialis. (C) Infection with the mutant strain Δvfh. (D) Infection with complemented mutant strain pUC-vfh. (E) Treatment with supernatant from Δvfh. (F) Treatment with supernatant from WT. (G) The pathology scoring in mice treated with WT or Δvfh or pUC-vfh strain. (H) The pathology scoring in mice treated with supernatant from Δvfh and WT. The result represent mean ± SD of six independent mice. ∗P < 0.05; ∗∗P < 0.01 and are shown as 200 magnification times, (A–H) 200×.

Mentions: To characterize the inflammatory histopathology in colon caused by V. fluvialis infection, we inoculated five-days-old sucking mice with various strains or cell-free supernatant from overnight culture with various strains by gavage. At 24 h p.i., there were no lesions or obvious abnormalities in the negative control mice treated with PBS (Figure 4A); however, WT V. fluvialis caused submucosal edema, vascular dilation, hyperemia, and inflammatory cell infiltration as indicated by red arrow (Figure 4B). Mice infected with Δvfh showed similar pathology to the control mice (Figure 4C), whereas the pUC-vfh strain induced severe lesions including obvious epithelial shedding, glandular structure damage and inflammatory cell infiltration as pointed by arrow (Figure 4D). The effects of the Δvfh and WT supernatants were similar to the effects of the Δvfh and WT strains. (Figures 4E,F). The summary data showed that the mice treated with WT V. fluvialis or supernatants of WT culture had significantly higher colon pathology scores than did those mice treated with Δvfh or supernatants of Δvfh (Figures 4G,H). All these data verify that VFH contributes to the pathogenicity of V. fluvialis in the colon.


A critical role for hemolysin in Vibrio fluvialis-induced IL-1β secretion mediated by the NLRP3 inflammasome in macrophages.

Song L, Huang Y, Zhao M, Wang Z, Wang S, Sun H, Kan B, Meng G, Liang W, Ren Z - Front Microbiol (2015)

Histopathological analysis of colon lesions. Five days C57 BL/6 sucking mice were inoculated orally with various strains or supernatant from cell-free overnight culture of various strain of V. fluvialis. Colons were collected 24 h p.i., and the specimens were fixed, embedded, cut, and stained with H.E. (A) Negative control mouse treated with PBS. (B) Infection with WT V. fluvialis. (C) Infection with the mutant strain Δvfh. (D) Infection with complemented mutant strain pUC-vfh. (E) Treatment with supernatant from Δvfh. (F) Treatment with supernatant from WT. (G) The pathology scoring in mice treated with WT or Δvfh or pUC-vfh strain. (H) The pathology scoring in mice treated with supernatant from Δvfh and WT. The result represent mean ± SD of six independent mice. ∗P < 0.05; ∗∗P < 0.01 and are shown as 200 magnification times, (A–H) 200×.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4440915&req=5

Figure 4: Histopathological analysis of colon lesions. Five days C57 BL/6 sucking mice were inoculated orally with various strains or supernatant from cell-free overnight culture of various strain of V. fluvialis. Colons were collected 24 h p.i., and the specimens were fixed, embedded, cut, and stained with H.E. (A) Negative control mouse treated with PBS. (B) Infection with WT V. fluvialis. (C) Infection with the mutant strain Δvfh. (D) Infection with complemented mutant strain pUC-vfh. (E) Treatment with supernatant from Δvfh. (F) Treatment with supernatant from WT. (G) The pathology scoring in mice treated with WT or Δvfh or pUC-vfh strain. (H) The pathology scoring in mice treated with supernatant from Δvfh and WT. The result represent mean ± SD of six independent mice. ∗P < 0.05; ∗∗P < 0.01 and are shown as 200 magnification times, (A–H) 200×.
Mentions: To characterize the inflammatory histopathology in colon caused by V. fluvialis infection, we inoculated five-days-old sucking mice with various strains or cell-free supernatant from overnight culture with various strains by gavage. At 24 h p.i., there were no lesions or obvious abnormalities in the negative control mice treated with PBS (Figure 4A); however, WT V. fluvialis caused submucosal edema, vascular dilation, hyperemia, and inflammatory cell infiltration as indicated by red arrow (Figure 4B). Mice infected with Δvfh showed similar pathology to the control mice (Figure 4C), whereas the pUC-vfh strain induced severe lesions including obvious epithelial shedding, glandular structure damage and inflammatory cell infiltration as pointed by arrow (Figure 4D). The effects of the Δvfh and WT supernatants were similar to the effects of the Δvfh and WT strains. (Figures 4E,F). The summary data showed that the mice treated with WT V. fluvialis or supernatants of WT culture had significantly higher colon pathology scores than did those mice treated with Δvfh or supernatants of Δvfh (Figures 4G,H). All these data verify that VFH contributes to the pathogenicity of V. fluvialis in the colon.

Bottom Line: The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection.VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β.Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

View Article: PubMed Central - PubMed

Affiliation: State Key Laboratory for Infectious Disease Prevention and Control, Collaborative Innovation Center for Diagnosis and Treatment of Infectious Diseases, National Institute for Communicable Disease Control and Prevention - Chinese Center for Disease Control and Prevention Beijing, China.

ABSTRACT
Vibrio fluvialis causes human diarrhea, but the pathogenesis is not well-studied. We hypothesized that V. fluvialis-secreted hemolysin (VFH) may induce IL-1β secretion through the activation of the NLRP3 inflammasome and contribute to the pathogenicity of V. fluvialis. To examine this possibility, we constructed VFH mutant and complement strains and demonstrated that V. fluvialis-induced IL-1β production and cytotoxicity in human monocytic THP-1 cells and mouse macrophages is attributed to VFH. To evaluate the role of VFH in vivo, we infected adult C57BL/6 mice intraperitoneally and suckling C57/B6 mice orally with various strains. The mice treated with 10(8) CFU wild-type V. fluvialis or cell-free supernatant containing VFH induced significantly higher IL-1β production in peritoneal lavage fluid or in colon compared with those infected with the mutant strain, while no effect on TNF and IL-6 production was observed at day 5 or 24 h post-infection. VFH contributed to pathological changes and IL-1β release independent of colonization of V. fluvialis in the colon. VFH has no effect on the synthesis of pro-IL-1β, but rather it triggers the processing of pro-IL-1β into IL-1β. Furthermore, using deficient mouse strains, we verified that V. fluvialis-induced IL-1β is mediated through activation of Caspase-1 and the NLRP3 inflammasome ex vivo. Confocal microscopy suggests that VFH contributes to cathepsin B release. Furthermore, V. fluvialis-induced IL-1β secretion requires potassium (K(+)) efflux and reactive oxygen species production. Our results provide new evidence for the role of VFH in the activation of the NLRP3 inflammasome and pathogenesis in response to V. fluvialis infection. Summary Sentence: Vibrio fluvialis-secreted hemolysin induces IL-1β secretion through the activation of the NLRP3 inflammasome and contributes to the pathogenicity of V. fluvialis.

No MeSH data available.


Related in: MedlinePlus