Transcriptional analysis of THP-1 cells infected with Leishmania infantum indicates no activation of the inflammasome platform

Abstract

Leishmaniasis is caused by intracellular parasites transmitted to vertebrates by sandfly bites. Clinical manifestations include cutaneous, mucosal or visceral involvement depending upon the host immune response and the parasite species. To assure their survival inside macrophages, these parasites developed a plethora of highly successful strategies to manipulate various immune system pathways. Considering that inflammasome activation is critical for the establishment of a protective immune response in many parasite infections, in this study we determined the transcriptome of THP-1 cells after infection with L. infantum, with a particular focus on the inflammasome components. To this end, the human cell line THP-1, previously differentiated into macrophages by PMA treatment, was infected with L. infantum promastigotes. Differentiated THP-1 cells were also stimulated with LPS to be used as a comparative parameter. The gene expression signature was determined 8 hours after by RNA-seq technique. Infected or uninfected THP-1 cells were stimulated with nigericin (NIG) to measure active caspase-1 and TNF-α, IL-6 and IL-1β levels in culture supernatants after 8, 24 and 48 hours. L. infantum triggered a gene expression pattern more similar to non-infected THP-1 cells and very distinct from LPS-stimulated cells. Some of the most up-regulated genes in L. infantum-infected cells were CDC20, CSF1, RPS6KA1, CD36, DUSP2, DUSP5, DUSP7 and TNFAIP3. Some up-regulated GO terms in infected cells included cell coagulation, regulation of MAPK cascade, response to peptide hormone stimulus, negative regulation of transcription from RNA polymerase II promoter and nerve growth factor receptor signaling pathway. Infection was not able to induce the expression of genes associated with the inflammasome signaling pathway. This finding was confirmed by the absence of caspase-1 activation and IL-1β production after 8, 24 and 48 hours of infection. Our results indicate that L. infantum was unable to activate the inflammasomes during the initial interaction with THP-1 cells.

Leishmania Parasites Differently Regulate Antioxidant Genes in Macrophages Derived From Resistant and Susceptible Mice

“…CD36 is also important for host resistance to infection, and its deficiency significantly reduces mycobacteria burden (Hawkes et al, 2010), whereas its induction helps control severe malaria through parasite clearance (Olagnier et al, 2011). Increased transcription of CD36 has been reported for Leishmania infantum (Gatto et al, 2020) and Leishmania amazonensis (Okuda et al, 2016). However, while CD36 −/− macrophages are infected but do not support L. amazonensis proliferation, L. major amastigotes do not recruit CD36 and proliferate normally in CD36 −/− macrophages (Okuda et al, 2016).…”

Advances in Understanding Leishmania Pathobiology: What Does RNA-Seq Tell Us?

“…L. infantum did not activate the inflammasomes in the THP-1 human macrophage infected cells (Gatto et al, 2020). In fact, L. infantum triggered a gene expression pattern more similar to non-infected THP-1 cells yet very different from LPS-stimulated cells.…”

“…Some of the most up-regulated genes in L. infantum-infected cells were related to: cell cycle (CDC20, CDKN2C, CNNL2), glycolysis/gluconeogenesis (ENO1), metabolism of carbohydrates (AGRN), signal transduction (RIT1, RPS6KA1, ILR6, SFPQ), MAPK signaling (RPS6KA1), gene expression (NOTCH2), ubiquitin mediated proteolysis (CDC20) and interleukin signaling (TNFRSF14, TNFRSF1B, ILR6, CSF1). Genes associated with the inflammasome signaling pathway were not differentially expressed and caspase-1 activation and IL-1β production were absent following infection (Gatto et al, 2020). Genes significantly upregulated or downregulated in macrophages following infection with various Leishmania species are summarized in Tables 3, 4, respectively.…”

“…L . infantum did not activate the inflammasomes in the THP-1 human macrophage infected cells ( Gatto et al, 2020 ). In fact, L .…”

Functional study ofLeishmania braziliensisprotein arginine methyltransferases (PRMTs) reveals that PRMT1 and PRMT5 are required for macrophage infection

“…For cell differentiation, THP-1 monocytes were incubated with 30 ng·mL -1 4α-phorbol 12-myristate 13-acetate – PMA (Sigma Aldrich) for 24 hours (39). After the differentiation period, the medium with nondifferentiated cells was removed, and the cells were incubated in fresh RPMI-1640 medium for 48 hours for complete maturation and improvement of phagocytic properties (40); then, the cells were infected with Leishmania .…”