Interleukin-22-Induced Antimicrobial Phospholipase A2 Group IIA Mediates Protective Innate Immunity of Nonhematopoietic Cells against Listeria monocytogenes

ILC3s restrict the dissemination of intestinal bacteria to safeguard liver regeneration after surgery

It is generally believed that environmental or cutaneous bacteria are the main origin of surgical infections. Therefore, measures to prevent postoperative infections focus on optimizing hygiene and improving asepsis and antisepsis. In a large cohort of patients with infections following major surgery, we identified that the causative bacteria are mainly of intestinal origin. Postoperative infections of intestinal origin were also found in mice undergoing partial hepatectomy. CCR6⁺ group 3 innate lymphoid cells (ILC3s) limited systemic bacterial spread. Such bulwark function against host invasion required the production of interleukin-22 (IL-22), which controlled the expression of antimicrobial peptides in hepatocytes, thereby limiting bacterial spread. Using genetic loss-of-function experiments and punctual depletion of ILCs, we demonstrate that the failure to restrict intestinal commensals by ILC3s results in impaired liver regeneration. Our data emphasize the importance of endogenous intestinal bacteria as a source for postoperative infection and indicate ILC3s as potential new targets.

Experimental bacterial dysbiosis with consequent immune alterations increase intrarectal SIV acquisition susceptibility

Variations in the composition of the intestinal bacterial microbiome correlate with acquisition of some sexually transmitted pathogens. To experimentally assess the contribution of intestinal dysbiosis to rectal lentiviral acquisition, we induce dysbiosis in rhesus macaques (RMs) with the antibiotic vancomycin prior to repeated low-dose intrarectal challenge with simian immunodeficiency virus (SIV) SIVmac239X. Vancomycin administration reduces T helper 17 (TH17) and TH22 frequencies, increases expression of host bacterial sensors and antibacterial peptides, and increases numbers of transmitted-founder (T/F) variants detected upon SIV acquisition. We observe that SIV acquisition does not correlate with measures of dysbiosis but rather associates with perturbations in the host antimicrobial program. These findings establish a functional association between the intestinal microbiome and susceptibility to lentiviral acquisition across the rectal epithelial barrier.

Response of gut microbiota and ileal transcriptome to inulin intervention in HFD induced obese mice

Inulin, as a dietary fiber, exerted prominent anti-obesity effects by modulating gut microbiota. However, the possible relationship and interplay of gut microbiome and function of distal intestine is still unclear now. This study aimed to investigate the possible targets of microbes and the related intestinal genes mediated by inulin. C57 BL/6 male mice were randomly allocated to chow diet (Chow) group, high-fat diet (HFD) group, and HFD supplemented with 3 % inulin (Inulin) group. Compared with HFD treatment, inulin supplementation significantly decreased the body weight, fat deposition, and fasting blood glucose level. In addition, mice treated with inulin had a remarkable alteration in the structure of cecal microbiota and transcriptomic profiling of ileum. In particular, inulin supplementation significantly reversed the HFD induced expression of Bacteroides, Allobaculum and nonrank_f_Bacteroidates_S24-7_group, and reversed the expression of genes belonging to phospholipase A2 (PLA2) family and cytochrome P450 (CYP450) family. In summary, inulin might alleviate HFD-induced fat deposition and metabolic disorders via regulating lipid metabolism of ileum, while the interaction between the sPLA2s and gut microbes might play important roles in the process.

A nonredundant role for T cell-derived interleukin 22 in antibacterial defense of colonic crypts

Interleukin (IL)-22 is central to immune defense at barrier sites. We examined the contributions of innate lymphoid cell (ILC) and T cell-derived IL-22 during Citrobacter rodentium (C.r) infection using mice that both report Il22 expression and allow lineage-specific deletion. ILC-derived IL-22 activated STAT3 in C.r-colonized surface intestinal epithelial cells (IECs) but only temporally restrained bacterial growth. T cell-derived IL-22 induced a more robust and extensive activation of STAT3 in IECs, including IECs lining colonic crypts, and T cell-specific deficiency of IL-22 led to pathogen invasion of the crypts and increased mortality. This reflected a requirement for T cell-derived IL-22 for the expression of a host-protective transcriptomic program that included AMPs, neutrophil-recruiting chemokines, and mucin-related molecules, and it restricted IFNγ-induced proinflammatory genes. Our findings demonstrate spatiotemporal differences in the production and action of IL-22 by ILCs and T cells during infection and reveal an indispensable role for IL-22-producing T cells in the protection of the intestinal crypts.

The good and the bad about separation anxiety: roles of IL-22 and IL-22BP in liver pathologies

The human liver fulfills several vital tasks daily and possesses an impressive ability to self-regenerate. However, the capacity of this self-healing process can be exhausted by a variety of different liver diseases, such as alcoholic liver damage, viral hepatitis, or hepatocellular carcinoma. Over time, all these diseases generally lead to progressive liver failure that can become fatal if left untreated. Thus, a great effort has been directed towards the development of innovative therapies. The most recently discovered therapies often involve modifying the patient's immune system to enhance a beneficial immune response. Current data suggest that, among others, the cytokine IL-22 might be a promising therapeutical candidate. IL-22 and its endogenous antagonist, IL-22BP, have been under thorough scientific investigation for nearly 20 years. While IL-22 is mainly produced by TH22 cells, ILC3s, NKT cells, or γδ T cells, sources of IL-22BP include dendritic cells, eosinophils, and CD4+ cells. In many settings, IL-22 was shown to promote regenerative potential and, thus, could protect tissues from pathogens and damage. However, the effects of IL-22 during carcinogenesis are more ambiguous and depend on the tumor entity and microenvironment. In line with its capabilities of neutralizing IL-22 in vivo, IL-22BP possesses often, but not always, an inverse expression pattern compared to its ligand. In this comprehensive review, we will summarize past and current findings regarding the roles of IL-22 and IL-22BP in liver diseases with a particular focus on the leading causes of advanced liver failure, namely, liver infections, liver damage, and liver malignancies.

Identification of a novel immune microenvironment signature predicting survival and therapeutic options for bladder cancer

Few studies have investigated the potential of tumor immune microenvironment genes as indicators of urinary bladder cancer. Here, we sought to establish an immune-related gene signature for determining prognosis and treatment options. We developed a ten-gene tumor immune microenvironment signature and evaluated its prognostic capacity on internal and external cohorts. Multivariate Cox regression and nomogram analyses revealed the prognostic risk model as an independent and effective indicator of prognosis. We observed lower proportions of CD8+ T cells, dendritic cells, regulatory T cells, higher proportions of macrophages and neutrophils in high UBC risk group. UBC tissues with high-risk score tend to exhibit high TP53 and RB1 mutation rates, high PD1/PD-L1 expression and poor-survival basal squamous subtypes, while those with low-risk score tend to have high FGFR3 mutation rates and luminal papillary subtypes. Unexpectedly, we found a highly significant positive correlation between glycolytic genes and risk score, highlighting metabolic competition in tumor ecosystem and potential therapeutic avenues. Our study thus revealed a tumor immune microenvironment signature for predicting prognostic and response to immune checkpoint inhibitors against bladder cancer. Prospective studies are required to further test the predictive capacity of this model.

Type IIA Secreted Phospholipase A2 in Host Defense against Bacterial Infections

The enzyme type IIA secreted phospholipase A2 (sPLA2-IIA) is crucial for mammalian innate host defense against bacterial pathogens. Most studies have investigated the role of sPLA2-IIA in systemic bacterial infections, identifying molecular pathways of bacterial resistance against sPLA2-IIA-mediated killing, and providing insight into sPLA2-IIA mechanisms of action. Sensitization of (antibiotic-resistant) bacteria to sPLA2-IIA action by blocking bacterial resistance or by applying sPLA2-IIA to treat bacterial infections might represent a therapeutic option in the future. Because sPLA2-IIA is highly expressed at mucosal barriers, we also discuss how sPLA2-IIA is likely to be an important driver of microbiome composition; we anticipate that future research in this area may bring new insights into the role of sPLA2-IIA in health and disease.

The microbiota programs DNA methylation to control intestinal homeostasis and inflammation

Although much research has been done on the diversity of the gut microbiome, little is known about how it influences intestinal homeostasis under normal and pathogenic conditions. Epigenetic mechanisms have recently been suggested to operate at the interface between the microbiota and the intestinal epithelium. We performed whole-genome bisulfite sequencing on conventionally raised and germ-free mice, and discovered that exposure to commensal microbiota induced localized DNA methylation changes at regulatory elements, which are TET2/3-dependent. This culminated in the activation of a set of 'early sentinel' response genes to maintain intestinal homeostasis. Furthermore, we demonstrated that exposure to the microbiota in dextran sodium sulfate-induced acute inflammation results in profound DNA methylation and chromatin accessibility changes at regulatory elements, leading to alterations in gene expression programs enriched in colitis- and colon-cancer-associated functions. Finally, by employing genetic interventions, we show that microbiota-induced epigenetic programming is necessary for proper intestinal homeostasis in vivo.

A Potential Role of Phospholipase 2 Group IIA (PLA2-IIA) in P. gingivalis-Induced Oral Dysbiosis

Porphyromonas gingivalis is an oral pathogen with the ability to induce oral dysbiosis and periodontal disease. Nevertheless, the mechanisms by which P. gingivalis could abrogate the host-microbe symbiotic relationship leading to oral dysbiosis remain unclear. We have recently demonstrated that P. gingivalis specifically increased the antimicrobial properties of oral epithelial cells, through a strong induction of the expression of PLA₂-IIA in a mechanism that involves activation of the Notch-1 receptor. Moreover, gingival expression of PLA₂-IIA was significantly increased during initiation and progression of periodontal disease in non-human primates and interestingly, those PLA₂-IIA expression changes were concurrent with oral dysbiosis. In this chapter, we present an innovative hypothesis of a potential mechanism involved in P. gingivalis-induced oral dysbiosis and inflammation based on our previous observations and a robust body of literature that supports the antimicrobial and proinflammatory properties of PLA₂-IIA as well as its role in other chronic inflammatory diseases.

Beneficial roles of probiotics on the modulation of gut microbiota and immune response in pigs

The importance of probiotics in swine production is widely acknowledged as crucial. However, gaps still remain in the exact roles played by probiotics in modulation of gut microbiota and immune response. This study determined the roles of probiotic Lactobacillus plantarum strain JDFM LP11in gut microbiota modulation and immune response in weaned piglets. L. plantarum JDFM LP11 increased the population of lactic acid bacteria in feces and enhanced the development of villi in the small intestine. Metagenome analysis showed that microbial diversity and richness (Simpson, Shannon, ACE, Chao1) and the relative abundance of the Firmicutes were higher in weaned piglets fed probiotics. Five bacterial families were different in the relative abundance, especially; Prevotellaceae occupied the largest part of microbial community showed the most difference between two groups. Transcriptome analysis identified 25 differentially expressed genes using RNA-sequencing data of the ileum. Further gene ontology and immune DB analysis determined 8 genes associated with innate defense response and cytokine production. BPI, RSAD2, SLPI, LUM, OLFM4, DMBT1 and C6 genes were down-regulated by probiotic supplementation except PLA2G2A. PICRUSt analysis predicting functional profiling of microbial communities indicated branched amino acid biosynthesis and butyrate metabolism promoting gut development and health were increased by probiotics. Altogether, our data suggest that L. plantarum JDFM LP11 increases the diversity and richness in the microbial community, and attenuates the ileal immune gene expression towards gut inflammation, promoting intestinal development in weaned piglets.

Roles of secreted phospholipase A2 group IIA in inflammation and host defense

Among all members of the secreted phospholipase A₂ (sPLA₂) family, group IIA sPLA₂ (sPLA₂-IIA) is possibly the most studied enzyme. Since its discovery, many names have been associated with sPLA₂-IIA, such as "non-pancreatic", "synovial", "platelet-type", "inflammatory", and "bactericidal" sPLA_2. Whereas the different designations indicate comprehensive functions or sources proposed for this enzyme, the identification of the precise roles of sPLA₂-IIA has remained a challenge. This can be attributed to: the expression of the enzyme by various cells of different lineages, its limited activity towards the membranes of immune cells despite its expression following common inflammatory stimuli, its ability to interact with certain proteins independently of its catalytic activity, and its absence from multiple commonly used mouse models. Nevertheless, elevated levels of the enzyme during inflammatory processes and associated consistent release of arachidonic acid from the membrane of extracellular vesicles suggest that sPLA₂-IIA may contribute to inflammation by using endogenous substrates in the extracellular milieu. Moreover, the remarkable potency of sPLA₂-IIA towards bacterial membranes and its induced expression during the course of infections point to a role for this enzyme in the defense of the host against invading pathogens. In this review, we present current knowledge related to mammalian sPLA₂-IIA and its roles in sterile inflammation and host defense.

Interleukin-17 family cytokines in protective immunity against infections: role of hematopoietic cell-derived and non-hematopoietic cell-derived interleukin-17s

Interleukin-17 family cytokines, consisting of six members, participate in immune response in infections and autoimmune and inflammatory diseases. The prototype cytokine of the family, IL-17A, was originally identified from CD4+ T cells which are now termed Th17 cells. Later, IL-17A-producing cells were expanded to include various hematopoietic cells, namely CD8+ T cells (Tc17), invariant NKT cells, γδ T cells, non-T non-B lymphocytes (termed type 3 innate lymphoid cells) and neutrophils. Some IL-17 family cytokines other than IL-17A are also expressed by CD4+ T cells: IL-17E by Th2 cells and IL-17F by Th17 cells. IL-17A and IL-17F induce expression of pro-inflammatory cytokines to induce inflammation and anti-microbial peptides to kill pathogens, whereas IL-17E induces allergic inflammation. However, the functions of other IL-17 family cytokines have been unclear. Recent studies have shown that IL-17B and IL-17C are expressed by epithelial rather than hematopoietic cells. Interestingly, expression of IL-17E and IL-17F by epithelial cells has also been reported and epithelial cell-derived IL-17 family cytokines shown to play important roles in immune responses to infections at epithelial sites. In this review, we summarize current information on hematopoietic cell-derived IL-17A and non-hematopoietic cell-derived IL-17B, IL-17C, IL-17D, IL-17E and IL-17F in infections and propose functional differences between these two categories of IL-17 family cytokines.