Leishmania donovani inhibits inflammasome‐dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2

• Published in: The FASEB journal 2017-11, Vol.31 (11), p.5087-5101
• Main Authors: Gupta, Anand Kumar, Ghosh, Kuntal, Palit, Shreyasi, Barua, Jayita, Das, Pijush K., Ukil, Anindita
• Format: Article
• Language: English
• Subjects: A20 protein; Animals; Caspase; Caspase-1; Cell activation; Down-regulation; foam cell; IL-1β; Inflammasomes; Inflammasomes - genetics; Inflammasomes - metabolism; Interleukin-1beta - biosynthesis; Interleukin-1beta - genetics; Leishmania; Leishmania donovani; Leishmania donovani - metabolism; Leishmaniasis, Visceral - genetics; Leishmaniasis, Visceral - metabolism; Leishmaniasis, Visceral - pathology; Liver; Macrophage Activation; Macrophages; Macrophages - metabolism; Macrophages - parasitology; Macrophages - pathology; Maturation; Mice; Mitochondria; Mitochondrial uncoupling protein 2; NF-kappa B - genetics; NF-kappa B - metabolism; NF-κB protein; NF‐κB; NLR Family, Pyrin Domain-Containing 3 Protein - genetics; NLR Family, Pyrin Domain-Containing 3 Protein - metabolism; Parasitic diseases; Proteins; Reactive oxygen species; Reactive Oxygen Species - economics; Reactive Oxygen Species - metabolism; Regulatory proteins; Ribonucleic acid; RNA; Rodents; ROS; Signaling; Spleen; Tumor Necrosis Factor alpha-Induced Protein 3 - biosynthesis; Tumor Necrosis Factor alpha-Induced Protein 3 - genetics; Uncoupling Protein 2 - biosynthesis; Uncoupling Protein 2 - genetics; Vector-borne diseases; Visceral leishmaniasis
• ISSN: 0892-6638; 1530-6860
• DOI: 10.1096/fj.201700407R

In visceral leishmaniasis, we found that the antileishmanial drug Amp B produces a higher level of IL‐1β over the infected control. Moreover, administering anti‐IL‐1β antibody to infected Amp B–treated mice showed significantly less parasite clearance. Investigation revealed that Leishmania inhibits stimuli‐induced expression of a multiprotein signaling platform, NLRP3 inflammasome, which in turn inhibits caspase‐1 activation mediated maturation of IL‐1β from its pro form. Attenuation of NLRP3 and pro‐IL‐1β in infection was found to result from decreased NF‐κB activity. Transfecting infected cells with constitutively active NF‐κB plasmid increased NLRP3 and pro‐IL‐1β expression but did not increase mature IL‐1β, suggesting that IL‐1β maturation requires a second signal, which was found to be reactive oxygen species (ROS). Decreased NF‐κB was attributed to increased expression of A20, a negative regulator of NF‐κB signaling. Silencing A20 in infected cells restored NLRP3 and pro‐IL‐1β expression, but also increased matured IL‐1β, implying an NF‐κB‐independent A20‐modulated IL‐1β maturation. Macrophage ROS is primarily regulated by mitochondrial uncoupling protein 2 (UCP2), and UCP2‐silenced infected cells showed an increased IL‐1β level. Short hairpin RNA‐mediated knockdown of A20 and UCP2 in infected mice independently documented decreased liver and spleen parasite burden and increased IL‐1β production. These results suggest that Leishmania exploits A20 and UCP2 to impair inflammasome activation for disease propagation.—Gupta, A. K., Ghosh, K., Palit, S., Barua, J., Das, P. K., Ukil, A. Leishmania donovani inhibits inflammasome‐dependent macrophage activation by exploiting the negative regulatory proteins A20 and UCP2. FASEB J. 31, 5087–5101 (2017). www.fasebj.org