NLRC4 gene silencing-dependent blockade of NOD-like receptor pathway inhibits inflammation, reduces proliferation and increases apoptosis of dendritic cells in mice with septic shock

Septic shock is one of the most significant health concerns across the world, involving hypo-perfusion and defects in tissue energy. The current study investigates the role of NLR family CARD domain containing protein 4 (NLRC4) in septic shock-induced inflammatory reactions, lung tissue injuries, and dendritic cell (DC) apoptosis. Septic shock mice models were established by modified cecal ligation and puncture and injected with retroviral vector expressing siRNA-NLRC4. DCs were then isolated and transfected with siRNA-NLRC4. The degree of lung tissue injury, cell cycle distribution, cell apoptosis and cell viability of DCs were assessed. NLRC4 was found to be expressed at high levels in mice with septic shock. NLRC4 silencing inhibited the activation of the NOD-like receptor (NLR) pathway as evidenced by the decreased levels of NOD1, NOD2, RIP2, and NF-κB. In addition, NLRC4 silencing reduced the inflammatory reaction as attributed by reduced levels of IL-1β, TNF-α and IL-6. Suppressed NLRC4 levels inhibited cell viability and promoted cell apoptosis evidenced by inhibited induction of DC surface markers (CD80, CD86, and MHC II), along with alleviated lung tissue injury. In conclusion, NLRC4 silencing ameliorates lung injury and inflammation induced by septic shock by negatively regulating the NLR pathway.

Innate immunity in the simplest animals - placozoans

BACKGROUND

Innate immunity provides the core recognition system in animals for preventing infection, but also plays an important role in managing the relationship between an animal host and its symbiont. Most of our knowledge about innate immunity stems from a few animal model systems, but substantial variation between metazoan phyla has been revealed by comparative genomic studies. The exploration of more taxa is still needed to better understand the evolution of immunity related mechanisms. Placozoans are morphologically the simplest organized metazoans and the association between these enigmatic animals and their rickettsial endosymbionts has recently been elucidated. Our analyses of the novel placozoan nuclear genome of Trichoplax sp. H2 and its associated rickettsial endosymbiont genome clearly pointed to a mutualistic and co-evolutionary relationship. This discovery raises the question of how the placozoan holobiont manages symbiosis and, conversely, how it defends against harmful microorganisms. In this study, we examined the annotated genome of Trichoplax sp. H2 for the presence of genes involved in innate immune recognition and downstream signaling.

RESULTS

A rich repertoire of genes belonging to the Toll-like and NOD-like receptor pathways, to scavenger receptors and to secreted fibrinogen-related domain genes was identified in the genome of Trichoplax sp. H2. Nevertheless, the innate immunity related pathways in placozoans deviate in several instances from well investigated vertebrates and invertebrates. While true Toll- and NOD-like receptors are absent, the presence of many genes of the downstream signaling cascade suggests at least primordial Toll-like receptor signaling in Placozoa. An abundance of scavenger receptors, fibrinogen-related domain genes and Apaf-1 genes clearly constitutes an expansion of the immunity related gene repertoire specific to Placozoa.

CONCLUSIONS

The found wealth of immunity related genes present in Placozoa is surprising and quite striking in light of the extremely simple placozoan body plan and their sparse cell type makeup. Research is warranted to reveal how Placozoa utilize this immune repertoire to manage and maintain their associated microbiota as well as to fend-off pathogens.

Dual transcriptome of the immediate neutrophil and Candida albicans interplay

Background

Neutrophils are traditionally considered transcriptionally inactive. Compared to other immune cells, little is known about their transcriptional profile during interaction with pathogens.

Methods

We analyzed the meta-transcriptome of the neutrophil-Candida albicans interplay and the transcriptome of C. albicans challenged with neutrophil extracellular traps (NETs) by RNA-Seq, considering yeast and hypha individually in each approach.

Results

The neutrophil response to C. albicans yeast and hyphae was dominated by a morphotype-independent core response. However, 11 % of all differentially expressed genes were regulated in a specific manner when neutrophils encountered the hyphal form of C. albicans. While involving genes for transcriptional regulators, receptors, and cytokines, the neutrophil core response lacked typical antimicrobial effectors genes. Genes of the NOD-like receptor pathway, including NLRP3, were enriched.

Neutrophil- and NET-provoked responses in C. albicans differed. At the same time, the Candida transcriptome upon neutrophil encounter and upon NET challenge included genes from various metabolic processes and indicate a mutual role of the regulators Tup1p, Efg1p, Hap43p, and Cap1p. Upon challenge with neutrophils and NETs, the overall Candida response was partially morphotype-specific. Yet again, actual oppositional regulation in yeasts and hyphae was only detected for the arginine metabolism in neutrophil-infecting C. albicans.

Conclusions

 Taken together, our study provides a comprehensive and quantitative transcript profile of the neutrophil–C. albicans interaction. By considering the two major appearances of both, neutrophils and C. albicans, our study reveals yet undescribed insights into this medically relevant encounter. Hence, our findings will facilitate future research and potentially inspire novel therapy developments.

Electronic supplementary material

The online version of this article (10.1186/s12864-017-4097-4) contains supplementary material, which is available to authorized users.

Transcriptome analysis of human adipocytes implicates the NOD-like receptor pathway in obesity-induced adipose inflammation

Adipose tissue inflammation increases with obesity, but adipocyte vs. immune cell contributions are unclear. In the present study, transcriptome analyses were performed on highly-purified subcutaneous adipocytes from lean and obese women, and differentially expressed genes/pathways were determined in both adipocyte and stromal vascular fraction (SVF) samples. Adipocyte but not SVF expression of NOD-like receptor pathway genes, including NLRP3 and PYCARD, which regulate caspase-1-mediated IL-1β secretion, correlated with adiposity phenotypes and adipocyte class II major histocompatibility complex (MHCII) gene expression, but only MHCII remained after adjusting for age and body mass index. IFNγ stimulated adipocyte MHCII, NLRP3 and caspase-1 expression, while adipocyte MHCII-mediated CD4(+) T cell activation, an important factor in adipose inflammation, induced IFNγ-dependent adipocyte IL-1β secretion. These results uncover a dialogue regulated by interactions among T cell IFNγ and adipocyte MHCII and NLRP3 inflammasome activity that appears to initiate and escalate adipose tissue inflammation during obesity.