NLRP3 inflammasome activation by mycobacterial ESAT-6 and dsRNA in intraocular tuberculosis

Soumyava Basu; Benjamin J Fowler; Nagaraj Kerur; Kristine B Arnvig; Narsing A Rao

doi:10.1016/j.micpath.2017.11.044

NLRP3 inflammasome activation by mycobacterial ESAT-6 and dsRNA in intraocular tuberculosis

Microb Pathog. 2018 Jan:114:219-224. doi: 10.1016/j.micpath.2017.11.044. Epub 2017 Nov 24.

Authors

Soumyava Basu¹, Benjamin J Fowler², Nagaraj Kerur³, Kristine B Arnvig⁴, Narsing A Rao⁵

Affiliations

¹ L V Prasad Eye Institute, Mithu Tulsi Chanrai Campus, Bhubaneswar, India; Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY, USA. Electronic address: basu@lvpei.org.
² Department of Ophthalmology and Visual Sciences, University of Kentucky, Lexington, KY, USA.
³ University of Virginia, Charlottesville, VA, USA.
⁴ Institute of Structural and Molecular Biology, University College, London, UK.
⁵ USC Eye Institute, The Keck School of Medicine, University of Southern California, Los Angeles, CA, USA.

PMID: 29180292
DOI: 10.1016/j.micpath.2017.11.044

Abstract

The molecular basis of intraocular tuberculosis (TB) is not well understood. In this study, we investigated the role of two constituents of viable Mycobacterium tuberculosis - Early Secreted Antigenic Target-6 (ESAT-6), and mycobacterial RNA- in inflammasome activation in the retinal pigment epithelium (RPE), a key site of inflammation in intraocular TB. We found that ESAT-6 induced caspase-1 activation and inflammasome priming in mouse RPE cells, substantially more in wild-type than in Tlr2/3/4/7/9^-/-, Myd88^-/- or Nlrp3^-/- RPE cells. Sub-retinal ESAT-6 injection resulted in greater RPE degeneration in wild-type than in Nlrp3^-/- mice. In human ocular TB tissue sections, NLRP3 staining was noted in retina as well as RPE. Mycobacterial RNA, specifically its double stranded component, also induced caspase-1 activation, and the double stranded RNA was immunolocalized to human ocular TB sections. Our observations suggest that inflammasome activation in RPE by viable M. tuberculosis could potentially contribute to human intraocular TB.

Keywords: ESAT-6; Inflammasome; Intraocular tuberculosis; NLRP3; RNA.

MeSH terms

Animals
Antigens, Bacterial / genetics
Antigens, Bacterial / immunology*
Bacterial Proteins / genetics
Bacterial Proteins / immunology*
Caspase 1 / genetics
Caspase 1 / immunology
Host-Parasite Interactions
Humans
Inflammasomes / genetics
Inflammasomes / immunology*
Mice
Mice, Inbred C57BL
Mycobacterium tuberculosis / genetics
Mycobacterium tuberculosis / immunology*
NLR Family, Pyrin Domain-Containing 3 Protein / genetics
NLR Family, Pyrin Domain-Containing 3 Protein / immunology*
RNA, Bacterial / genetics
RNA, Bacterial / immunology*
RNA, Double-Stranded / genetics
RNA, Double-Stranded / immunology*
Retinal Pigment Epithelium / immunology
Retinal Pigment Epithelium / microbiology
Tuberculosis, Ocular / genetics
Tuberculosis, Ocular / immunology*
Tuberculosis, Ocular / microbiology

Substances

Antigens, Bacterial
Bacterial Proteins
ESAT-6 protein, Mycobacterium tuberculosis
Inflammasomes
NLR Family, Pyrin Domain-Containing 3 Protein
Nlrp3 protein, mouse
RNA, Bacterial
RNA, Double-Stranded
Caspase 1