AUTHOR=Verma Vivek , Gupta Surbhi , Kumar Parveen , Yadav Sonal , Dhanda Rakesh Singh , Gaind Rajni , Arora Renu , Frimodt-Møller Niels , Yadav Manisha 

TITLE=Involvement of NLRP3 and NLRC4 Inflammasome in Uropathogenic E. coli Mediated Urinary Tract Infections

JOURNAL=Frontiers in Microbiology

VOLUME=10

YEAR=2019

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2019.02020

DOI=10.3389/fmicb.2019.02020

ISSN=1664-302X

ABSTRACT=<sec><title>Background</title><p>Inflammatory response during urinary tract infection (UTI) is mediated by innate immune defense. Nod like receptors (NLRs) have been proposed to work simultaneously beside TLR pathways to mediate pro-inflammatory response and maintain tissue homeostasis. Some <italic>in vitro</italic> reports have showed the involvement of <italic>NLRP3</italic> inflammasome during uropathogenic <italic>Escherichia coli</italic> (UPEC) mediated UTI. So we have sought to determine the status of various inflammasomes and their components in UPEC mediated UTI.</p></sec><sec><title>Methods</title><p>A total of 186 females experiencing the first episode of UTI were recruited for the study and forty were found to be positive for UPEC (≥10<sup>5</sup> CFU/ml) in their urine (<italic>N</italic> = 40). Further, we analyzed the expression of <italic>NLRP3</italic>, <italic>NLRC4</italic>, <italic>NAIP</italic>, <italic>AIM2</italic>, <italic>ASC</italic>, <italic>CASPASE-4</italic>, and <italic>CASPASE-1</italic> gene at mRNA and protein level in the blood of UPEC confirmed study subjects through real time qPCR and immunoblotting. Healthy females (<italic>N</italic> = 40) visiting the OPD for health checkups, family planning advice and subjects undergoing routine medical examinations, were recruited as healthy control subjects. Pro-inflammatory cytokines (IL-6, IL-8, IFN-γ, TNF-α and MCP-1) were measured in the plasma of patients and controls through ELISA. For investigation of the involvement of <italic>NLRC4</italic> and <italic>NLRP3</italic> inflammasome, <italic>in vitro</italic> studies were performed using co-immunoprecipitation and confocal microscopy.</p></sec><sec><title>Results</title><p>Most of the inflammatory regulators studied (i.e., <italic>NLRP3, NAIP, NLRC4, ASC</italic>, and <italic>CASPASE-1</italic>) were found to be up-regulated at both mRNA and protein levels in the UPEC infected UTI patients. Also, pro-inflammatory cytokines (IL-6, IL-8, IFN-γ, TNF-α, and MCP-1) were found to be up-regulated in the patients group. However, no significant difference was observed in the expression of <italic>AIM2</italic> and <italic>CASPASE-4</italic> genes at both mRNA and protein levels. Further, <italic>in vitro</italic> studies have shown the involvement of NLRC4 inflammasome in UPEC infected THP1 derived macrophages.</p></sec><sec><title>Conclusion</title><p>Involvement of <italic>NLRP3</italic> and <italic>NLRC4</italic> inflammasomes in UPEC infected UTI is evident from our findings. This is the first report showing levels of inflammasome and its components in UTI patients suggesting a possible role during UPEC mediated UTI. We have also reported the involvement of <italic>NLRC4</italic> inflammasome for the first time during UTI infection.</p></sec>