Pathogenic fungus Microsporum canis activates the NLRP3 inflammasome.
Microsporum canis is a pathogenic fungus with worldwide distribution that causes tinea capitis in animals and humans. M. canis also causes invasive infection in immunocompromised patients. To defy pathogenic fungal infection, the host innate immune system is the first line of defense. As an important arm of innate immunity, the inflammasomes are intracellular multiprotein complexes that control the activation of caspase-1, which cleaves proinflammatory cytokine pro-interleukin-1β (IL-1β) into its mature form. To determine whether the inflammasome is involved in the host defense against M. canis infection, we challenged human monocytic THP-1 cells and mouse dendritic cells with a clinical strain of M. canis isolated from patients with tinea capitis. We found that M. canis infection triggered rapid secretion of IL-1β from both THP-1 cells and mouse dendritic cells. Moreover, by using gene-specific shRNA and competitive inhibitors, we determined that M. canis-induced IL-1β secretion was dependent on NLRP3. The pathways proposed for NLRP3 inflammasome activation, namely, cathepsin B activity, K(+) efflux, and reactive oxygen species production, were all required for the inflammasome activation triggered by M. canis. Meanwhile, Syk, Dectin-1, and Card9 were found to be involved in M. canis-induced IL-1β secretion via regulation of pro-IL-1β transcription. More importantly, our data revealed that M. canis-induced production of IL-1β was dependent on the NLRP3 inflammasome in vivo. Together, this study unveils that the NLRP3 inflammasome exerts a critical role in host innate immune responses against M. canis infection, and our data suggest that diseases that result from M. canis infection might be controlled by regulating the activation of inflammasomes.
Unit of Innate Immunity, Key Laboratory of Molecular Virology and Immunology, Institut Pasteur of Shanghai, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai, China.
Liming
L
Mao
Liping
L
Zhang
Hua
H
Li
Wei
W
Chen
Hongbin
H
Wang
Shuxian
S
Wu
Caiqin
C
Guo
Ailing
A
Lu
Guiwen
G
Yang
Liguo
L
An
Paride
P
Abliz
Guangxun
G
Meng
D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002478:Cells, Cultured; D003713:Dendritic Cells / Q000276:immunology / Q000382:microbiology; D055785:Gene Knockdown Techniques; D006801:Humans; D058847:Inflammasomes / Q000378:metabolism*; D053583:Interleukin-1beta / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D008864:Microsporum / Q000276:immunology* / Q000302:isolation & purification; D009000:Monocytes / Q000276:immunology / Q000382:microbiology; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; D014006:Tinea Capitis / Q000276:immunology / Q000382:microbiology
D002352:Carrier Proteins; D058847:Inflammasomes; D053583:Interleukin-1beta; D000071199:NLR Family, Pyrin Domain-Containing 3 Protein; C453881:NLRP3 protein, human; C492716:Nlrp3 protein, mouse