NLRPs, microbiota, and gut homeostasis: unravelling the connection.

Within the NOD-like receptor (NLR) family, there are several NLRP (NLR family, pyrin domain-containing) proteins that are involved in the formation of inflammasomes. These multi-protein complexes are a key part of the network of cellular events required for secretion of the pro-inflammatory cytokines IL-1ß and IL-18. The NLRP3 inflammasome is the best-characterized member of the family and has recently been implicated in gut homeostasis and determining the severity of inflammation in inflammatory bowel disease (IBD) and inflammation-associated colorectal cancer. This led to the discovery that NLRP6 and NLRP12 also contribute to the maintenance of intestinal homeostasis and modulation of the gut microbiota, which in turn influences the intestine and distant organs. In this review, we bring together the latest data on the potential roles of NLRP family members in gut health and disease and identify the most pressing questions that remain to be answered to further our understanding of human diseases including IBD, inflammation-associated cancers, and metabolic syndromes linked with obesity.

NLRP10 Enhances CD4+ T-Cell-Mediated IFNγ Response via Regulation of Dendritic Cell-Derived IL-12 Release.

NLRP10 is a nucleotide-binding oligomerization domain-like receptor that functions as an intracellular pattern recognition receptor for microbial products. Here, we generated a Nlrp10-/- mouse to delineate the role of NLRP10 in the host immune response and found that Nlrp10-/- dendritic cells (DCs) elicited sub-optimal IFNγ production by antigen-specific CD4+ T cells compared to wild-type (WT) DCs. In response to T-cell encounter, CD40 ligation or Toll-like receptor 9 stimulation, Nlrp10-/- DCs produced low levels of IL-12, due to a substantial decrease in NF-κB activation. Defective IL-12 production was also evident in vivo and affected IFNγ production by CD4+ T cells. Upon Mycobacterium tuberculosis (Mtb) infection, Nlrp10-/- mice displayed diminished T helper 1-cell responses and increased bacterial growth compared to WT mice. These data indicate that NLRP10-mediated IL-12 production by DCs is critical for IFNγ induction in T cells and contributes to promote the host defense against Mtb.

Remarkable stability of an instability-prone lentiviral vector plasmid in Escherichia coli Stbl3.

Large-scale production of plasmid DNA to prepare therapeutic gene vectors or DNA-based vaccines requires a suitable bacterial host, which can stably maintain the plasmid DNA during industrial cultivation. Plasmid loss during bacterial cell divisions and structural changes in the plasmid DNA can dramatically reduce the yield of the desired recombinant plasmid DNA. While generating an HIV-based gene vector containing a bicistronic expression cassette 5'-Olig2cDNA-IRES-dsRed2-3', we encountered plasmid DNA instability, which occurred in homologous recombination deficient recA1 Escherichia coli strain Stbl2 specifically during large-scale bacterial cultivation. Unexpectedly, the new recombinant plasmid was structurally changed or completely lost in 0.5 L liquid cultures but not in the preceding 5 mL cultures. Neither the employment of an array of alternative recA1 E. coli plasmid hosts, nor the lowering of the culture incubation temperature prevented the instability. However, after the introduction of this instability-prone plasmid into the recA13E. coli strain Stbl3, the transformed bacteria grew without being overrun by plasmid-free cells, reduction in the plasmid DNA yield or structural changes in plasmid DNA. Thus, E. coli strain Stbl3 conferred structural and maintenance stability to the otherwise instability-prone lentivirus-based recombinant plasmid, suggesting that this strain can be used for the faithful maintenance of similar stability-compromised plasmids in large-scale bacterial cultivations. In contrast to Stbl2, which is derived wholly from the wild type isolate E. coli K12, E. coli Stbl3 is a hybrid strain of mixed E. coli K12 and E. coli B parentage. Therefore, we speculate that genetic determinants for the benevolent properties of E. coli Stbl3 for safe plasmid propagation originate from its E. coli B ancestor.

The rhapsody of NLRPs: master players of inflammation...and a lot more.

The Nucleotide-binding oligomerization domain, Leucine-rich Repeat and Pyrin domain containing (NLRP) family and corresponding inflammasomes are important intracellular sensors of microbial pathogens and stress signals that promote caspase-1-mediated release of IL-1ß and IL-18. Studies using targeted disruption of NLRP1 and NLRP3 have revealed key roles for these inflammasomes in innate immunity and inflammation, as well as in autoimmune diseases, metabolic disorders, and cancers. The newly identified family members NLRP6, NLRP10, and NLRP12 are emerging as important molecules regulating gut homeostasis in mouse models, as well as being correlated to human diseases. Here, we review our current knowledge of NLRP1 and NLRP3 biology, from molecular structure, function, and proposed models of activation to associations with several human disorders. New insights into novel NLRPs that act as regulators of intestinal immunity are also discussed.