Leptospira interrogans infection leads to IL-1β and IL-18 secretion from a human macrophage cell line through reactive oxygen species and cathepsin B mediated-NLRP3 inflammasome activation
Authors: Dingming Wang
Jie Yan
Guangpeng Tang
Ming Wang
David M Ojcius
Qing Ma
Ying Liu
Bijun Zhou
Shijun Li
Weilin Hu
Journal: Microbes and infection (2018)
Discipline: IMMUNOLOGY
Keywords: IL-1β and IL-18; Leptospira interrogans; Macrophages; NLRP3 inflammasome.
Affiliations: Guizhou Provincial Centre for Disease Control and Prevention, Guiyang, 550004, Guizhou, China; Department of Biomedical Sciences, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, 94103, USA. Electronic address: ., Guizhou Provincial Centre for Disease Control and Prevention, Guiyang, 550004, Guizhou, China., Department of Biomedical Sciences, Arthur A. Dugoni School of Dentistry, University of the Pacific, San Francisco, CA, 94103, USA., College of Animal Science, Guizhou University, Guiyang, 550025, Guizhou, China., Department of Medical Microbiology and Parasitology, College of Medicine, Zhejiang University, Hangzhou, 310058, Zhejing, China., Department of Medical Microbiology and Parasitology, College of Medicine, Zhejiang University, Hangzhou, 310058, Zhejing, China. Electronic address: .

Abstract:  Leptospirosis is a worldwide zoonosis caused by spirochetes from the genus Leptospira. Although there is a large diversity of clinical signs and symptoms, a severe inflammatory response is common to all leptospirosis patients. The mechanism of IL-1β secretion during Leptospira infection has been previously studied in mouse macrophages. However, the outcome of Leptospira infection is very different in human and murine macrophages, and the mechanisms responsible for IL-1β secretion in human macrophages had not been investigated. This study therefore examines the effects of Leptospira interrogans infection on inflammasome activation and proinflammatory cytokine expression in human macrophages. Increased mRNA and protein expression of NLRP3 was observed by real time RT-PCR and flow cytometry at 1 h after co-cultivation. Enzyme-linked immunosorbent assay (ELISA) determination showed that IL-1β and IL-18 are released in the culture supernatants at 1 h after cultivation. The inhibition assay showed that glybenclamide (a K+ efflux inhibitor that blocks NLRP3 inflammasome activation) and N-benzyloxycarbony-Val-Ala-Asp (O-methyl)-fluoromethylketone (Z-VAD-FMK; a caspase-1 inhibitor) and NLRP3 depletion with siRNAs reduced the levels of IL-1β and IL-18 release. Moreover, the levels of IL-1β and IL-18 production decreased in CA-074 (a cathepsin B inhibitor) and NAC (an anti-oxidant) pretreated human macrophages, compared to untreated controls. This study suggests that L. interrogans infection leads to reactive oxygen species (ROS)- and cathepsin B-dependent NLRP3 inflammasome activation, which subsequently mediates caspase-1 activation and IL-1β and IL-18 release. 

Retracted: No

PubPeer comments:
 Concern about Figure 4A. * Red boxes: The Wild type 2h panel looks very similar to the Scramble siRNA 1h panel * Blue boxes: The Wild type 24h panel looks very similar to the Scramble siRNA 24h panel Could the authors please check? ![file] , 
 Dear Elisabeth M Bik, Thank you very much for your comments. We will check the Fig you marked and respond to you as sooner as possible. Best regards, Shijun Li , 
 Dear Dr. Li, thank you so much for your quick reply. Much appreciated. I look forward to hear what happened. , 
 #1 Dear Bik, Thank you for your analysis. We are checking the data and will repeat the experiment if need be. Jie Yan , 
 No update from the authors, but a Corrigendum has been issued in September 2020, and can be found here: https: www.sciencedirect.com science article pii S1286457920301556?via%3Dihub This corrigendum does not appear to be visible from the landing page of the original paper. It reads:  The authors state that there was a duplication of panels in Figure 4A, which mistakenly took place when they assembled the composite Figure 4A, which contained 18 small panels, during the resubmission process. In the original Figure 4A, the Wild type 2 h panel is identical to the Scramble siRNA 1 h panel and the Wild type 24 h panel is identical to the Scramble siRNA 24 h panel. In this corrected version of Figure 4, Scramble siRNA 1 h panel and the Scramble siRNA 24 h panel of the Figure 4A are replaced with the corresponding representative image, respectively. The Figure 4A in the study aimed to show that siRNA significantly decreased the NLRP3 expression but the scramble siRNA (control siRNA) did not significantly decrease the NLRP3 expression in THP-1 cells. Scramble siRNA control was used to verify the effectiveness of NLRP3 siRNA in the NLRP3 expression. The authors are convinced that the mistake in the placement of the panel does not affect the interpretation of this experiment nor the conclusion of the study. The authors would like to note that the only changes are to the panels of Fig 4A scramble siRNA 1 h and Fig 4A scramble siRNA 24 h, and the rest of the figures are identical to the original published version. The authors apologize to the Editors of journal Microbe and Infection and to the readership for any inconvenience caused. ,