Regulation and functional impact of lipopolysaccharide induced Nod2 gene expression in the murine epididymal epithelial cell line PC1

A Potential Role for Gut Microbes in Mediating Effects of Omega-3 Fatty Acids in Inflammatory Bowel Diseases: A Comprehensive Review

Omega-3 polyunsaturated fatty acids (ω-3 PUFAs) have been associated with several inflammatory conditions, including inflammatory bowel diseases (IBDs), and found to have an impact on gut microbiota. In fact, some randomized controlled studies suggest benefits to IBD patients, but others do not. Our aim was to review recent evidence on the effects of omega-3 on IBD and establish the contribution of the gut microbiome. Omega-3 mediate anti-inflammatory effects in IBD through various mechanisms, including suppression of NLR family pyrin domain-containing 3 (NLRP3) inflammasome, Toll-like receptor-4 (TLR4), and nucleotide-binding oligomerization domain 2 (NOD2) signaling; this results in the repression of the nuclear factor-kappa B (Nf-kB) pathway and the secretion of pro-inflammatory cytokines. Omega-3 can also affect gut microbiota and revert the bacterial community to patterns associated with healthy status by increasing short-chain fatty acid (SCFA)-producing bacteria and enhancing the mucosal gut barrier, thus promoting homeostasis. The combination of these immunoregulatory effects and anti-inflammation properties with the promotion of a balanced gut microbiome environment could suggest that omega-3 might benefit IBD patients. Considering the microbiota of IBD patients while using omega-3 might predict and improve omega-3 effectiveness. Combining omega-3 with bacteria-altering therapy, such as probiotics and fecal microbiota transplantation, may further enhance its efficacy; however, further studies are required to elucidate mechanisms and potential preventive or treatment roles of omega-3 in IBD.

Leptin is upregulated in epididymitis and promotes apoptosis and IL-1β production in epididymal epithelial cells by activating the NLRP3 inflammasome

Epididymitis, one of the most common urological disease, is a significant cause of male infertility. Leptin is capable of modulating both reproduction and immune response. We analyzed the serum and seminal plasma levels of leptin in infertile patients with or without chronic epididymitis. Experimental epididymitis models were generated by administrating 200 μg Lipopolysaccharide (LPS) to Sprague-Dawley rats. The expression of leptin in epididymis were detected using qPCR, Western blots 6-72 h after injection, and using immunohistochemistry 72 h after injection. Besides, rat epididymal epithelial cells were isolated as an in vitro model and were treated with leptin (5-40 ng/ml, 6-48 h), LPS (1ug/ml, 6 h), and NLRP3 inflammasome inhibitor MCC950 (10 μM, 2 h). Cell Counting Kits-8 assay and Annexin V/PE assay were used to evaluate cell viability and apoptosis. Quantitive PCR and ELISA assay were used to detected inflammatory cytokines interleukin-1beta (IL-1β) production. Western Blots were used to detect molecular related to cell apoptosis, IL-1β maturation, and NLRP3 inflammasome. We found that patients with chronic epididymitis presented a significantly higher level of seminal plasma leptin and correlated declined sperm progressive motility. Leptin and leptin receptor expression in epididymis was significantly upregulated 24 h after LPS administration both in mRNA and protein level, and highly expressed in the epididymis epithelium 72 h after LPS administration. In epididymal epithelial cells, leptin reduced cell viability and promoted apoptosis in a concentration-dependent manner via cleavage of caspase-9, caspase-3, and PARP. Leptin enhanced the LPS-induced production of IL-1β, which was associated with increased IL-1β maturation and caspase-1 activation. Furthermore, NLRP3 inhibitor MCC950 attenuated the effects of leptin or co-treatment with LPS on NLRP3, ASC expression, IL-1β maturation, and caspase-1 activation, which indicated that leptin promotes IL-1β production via activating the NLRP3 inflammasome. These data suggested that leptin may act as a potential evaluation and treatment target for epididymitis and male subfertility.

An ex vivo ruminal ovine model to study the immediate immune response in the context of bacterial lipopolysaccharide

We have set up an ex vivo ovine ruminal model, which can mimic the multicellular process to explore the early steps in Salmonella typhimurium lipopolysaccharide (LPS) stimulation using RNA-seq technology. Ovine ruminal explants were collected for histological and transcriptional analysis and supernatants collected to quantitate lactate dehydrogenase (LDH) enzymes. A total of 8 and 523 genes were significantly over-expressed between LPS-treated and control tissues at 6 and 12 h, respectively. However, six and seven hundred and thirteen genes were substantially repressed between the aforementioned tissues, correspondingly. Key genes up-regulated in response to the addition of LPS were tumor necrosis factor (TNF), interlukin (IL)-1 beta(b), IL-6, IL-8, IL-17B, IL-19, MMP-1, MMP-3, and integrin alpha 2 (ITGA8, 9). This study shows for the first time that galectin-1 is up-regulated in an ex vivo ruminal segment model exposed to bacterial lipopolysaccharide following 6 h of incubation. The ruminal segment model has been shown to be a suitable tool to study the bacterial lipopolysaccharide effects on the ovine ruminal tissues prior to in vivo assessment.

Identification of genetic variation in NOD-like receptor 2 gene and influence of polymorphism on gene structure and function in buffalo (Bubalus bubalis)

Nucleotide-binding oligomerization domain (NOD)-like receptor 2 is one of the important mediators of innate as well as adaptive immune response to microbial infections. In this study, NOD-like receptor-2 was characterized by determining the full gene sequence and analyzing genetic diversity in Indian buffaloes. Sequence analysis of buffalo NOD2 revealed 3042 nucleotides long ORF, encoding 1013 amino acids from 12 exons. Domain structure analysis indicated existence of 8 leucine-rich repeat (LRR) domains in buffalo, cattle, sheep and mouse, along with central NACHT/NOD domain and two N-terminal CARD domains. Comparative sequence analysis among different buffalo breeds identified 46 polymorphic sites in NOD2 gene. Among coding region SNPs, 10 were non-synonymous, 7 synonymous and 3 were present in 5'UTR. Genotyping of two nsSNPs, revealed significant differences in the allele frequencies, distinguishing swamp and riverine buffaloes, having different utilities. Association analysis with mastitis in dairy buffaloes indicated significant variation in allelic frequencies at G1135A locus, between mastitis affected and non-affected animals. Further, NOD2 gene expression was quantified in different riverine buffalo tissues, using real-time PCR and lymph node displayed highest expression, compared to others organs included in the study. Overall, the study revealed buffalo NOD2 gene attributes, important to understand species specific immune response in ruminants.

Nod2: A Critical Regulator of Ileal Microbiota and Crohn's Disease

The human intestinal tract harbors large bacterial community consisting of commensal, symbiotic, and pathogenic strains, which are constantly interacting with the intestinal immune system. This interaction elicits a non-pathological basal level of immune responses and contributes to shaping both the intestinal immune system and bacterial community. Recent studies on human microbiota are revealing the critical role of intestinal bacterial community in the pathogenesis of both systemic and intestinal diseases, including Crohn’s disease (CD). NOD2 plays a key role in the regulation of microbiota in the small intestine. NOD2 is highly expressed in ileal Paneth cells that provide critical mechanism for the regulation of ileal microbiota through the secretion of anti-bacterial compounds. Genome mapping of CD patients revealed that loss of function mutations in NOD2 are associated with ileal CD. Genome-wide association studies further demonstrated that NOD2 is one of the most critical genetic factor linked to ileal CD. The bacterial community in the ileum is indeed dysregulated in Nod2-deficient mice. Nod2-deficient ileal epithelia exhibit impaired ability of killing bacteria. Thus, altered interactions between ileal microbiota and mucosal immunity through NOD2 mutations play significant roles in the disease susceptibility and pathogenesis in CD patients, thereby depicting NOD2 as a critical regulator of ileal microbiota and CD.

Role of the NOD1/NF-κB pathway on bovine neutrophil responses to crude lipopolysaccharide

Cytosolic nucleotide oligomerisation domain (NOD)-like receptors play an important role in host defence against infection. Reduced NOD1 expression has been observed in dysfunctional neutrophils derived from periparturient cattle known to be most susceptible to coliform mastitis. However, whether impairment of NOD1 suppresses the immune responses of bovine neutrophils during bacterial infections remains unknown. Crude (phenol extracted) lipopolysaccharide (cLPS), which often contains other immunostimulatory molecules, including NOD1 agonist, is known to induce almost the whole bacterial response. This study was conducted to explore the role of NOD1/nuclear factor (NF)-κB pathway in the cytokine and functional responses of bovine neutrophils challenged with Escherichia coli-derived cLPS. Freshly isolated blood neutrophils from healthy heifers were pre-incubated for 2 h with ML130, a selective inhibitor of NOD1/NF-κB pathway. Cells were then exposed to cLPS for additional 4 h. Inhibition of the NOD1/NF-κB pathway resulted in a decrease in cLPS-induced phosphorylation of the inhibitor of NF-κBα (IκBα) in neutrophils. Impairment of the NOD1/NF-κB pathway tended to down-regulate mRNA levels of pro-inflammatory cytokines interleukin (IL)-1β and tumour necrosis factor (TNF)-α, chemokines IL-8 and C-X-C motif ligand 2 (CXCL2), and adhesion molecules CD11b and CD62L, in cLPS-challenged cells. Functional analyses showed that blocking the NOD1/NF-κB pathway inhibited neutrophil migration and phagocytic killing capacity, and promoted neutrophil death upon cLPS stimulation. The data presented here demonstrate that activation of NOD1/NF-κB pathway contributes to the functional responses of neutrophils to cLPS.

The blood-epididymis barrier and inflammation

The blood-epididymis barrier (BEB) is a critical structure for male fertility. It enables the development of a specific luminal environment that allows spermatozoa to acquire both the ability to swim and fertilize an ovum. The presence of tight junctions and specific cellular transporters can regulate the composition of the epididymal lumen to favor proper sperm maturation. The BEB is also at the interface between the immune system and sperm. Not only does the BEB protect maturing spermatozoa from the immune system, it is also influenced by cytokines released during inflammation, which can result in the loss of barrier function. Such a loss is associated with an immune response, decreased sperm functions, and appears to be a contributing factor to post-testicular male infertility. Alterations in the BEB may be responsible for the formation of inflammatory conditions such as sperm granulomas. The present review summarizes current knowledge on the morphological, physiological and pathological components associated with the BEB, the role of immune function on the regulation of the BEB, and how disturbance of these factors can result in inflammatory lesions of the epididymis.

The microbiota protects against ischemia/reperfusion-induced intestinal injury through nucleotide-binding oligomerization domain-containing protein 2 (NOD2) signaling

Nucleotide-binding oligomerization domain-containing protein 2 (NOD2), an intracellular pattern recognition receptor, induces autophagy on detection of muramyl dipeptide (MDP), a component of microbial cell walls. The role of bacteria and NOD2 signaling toward ischemia/reperfusion (I/R)-induced intestinal injury response is unknown. Herein, we report that I/R-induced intestinal injury in germ-free (GF) C57BL/6 wild-type (WT) mice is worse than in conventionally derived mice. More important, microbiota-mediated protection against I/R-induced intestinal injury is abrogated in conventionally derived Nod2(-/-) mice and GF Nod2(-/-) mice. Also, WT mice raised in specific pathogen-free (SPF) conditions fared better against I/R-induced injury than SPF Nod2(-/-) mice. Moreover, SPF WT mice i.p. administered 10 mg/kg MDP were protected against injury compared with mice administered the inactive enantiomer, l-MDP, an effect lost in Nod2(-/-) mice. However, MDP administration failed to protect GF mice from I/R-induced intestinal injury compared with control, a phenomenon correlating with undetectable Nod2 mRNA level in the epithelium of GF mice. More important, the autophagy-inducer rapamycin protected Nod2(-/-) mice against I/R-induced injury and increased the levels of LC3(+) puncta in injured tissue of Nod2(-/-) mice. These findings demonstrate that NOD2 protects against I/R and promotes wound healing, likely through the induction of the autophagy response.

Molecular cloning and characterization of nucleotide binding and oligomerization domain-1 (NOD1) receptor in the Indian Major Carp, rohu (Labeo rohita), and analysis of its inductive expression and down-stream signalling molecules following ligands exposure and Gram-negative bacterial infections

Nucleotide binding and oligomerization domain-1 (NOD1) is a cytoplasmic pattern recognition receptor (PRR), and is a member of the NOD-like receptor (NLR) family. It senses a wide range of bacteria and viruses or their products, and plays a key role in inducing innate immunity. In this report, NOD1 gene was cloned and characterized in rohu (Labeo rohita), a fish species of highest commercial importance in the Indian subcontinent. The full-length rohu NOD1 (rNOD1) cDNA comprised of 3168 bp with a single open reading frame (ORF) of 2814 bp, encoding a polypeptide of 937 amino acids (aa) with an estimated molecular mass of 106.13 kDa. Structurally, it comprised of one caspase recruitment domain (CARD) at N-terminal, seven leucine rich repeat (LRR) regions at C-terminal and one NACHT domain in between N and C-terminals. Phylogenetically, rNOD1 was closely related to grass carp NOD1 (gcNOD1), and exhibited significant similarity (95.8%) and identity (91.0%) in their amino acids. Ontogenic expression analysis of rNOD1 and its associated down-stream signaling molecule RICK (receptor interacting serine–threonine kinase) by quantitative real-time PCR (qRT-PCR) revealed their constitutive expression in all embryonic developmental stages. Basal expression analysis of rNOD1 showed its wide range of expression in all examined tissues, highest was in spleen and the lowest was in blood. Inductive expression of rNOD1 was observed following LPS and poly I:C exposure, and Aeromonas hydrophila, Edwardsiella tarda and Shigella flexneri infections. Expression of RICK in various organs was significantly enhanced by ligands exposure and bacterial infections, and was correlated with the inductive expression of rNOD1. Together, these findings highlighted the important role of NOD1 in fish in response to pathogenic invasion.

Why are epididymal tumours so rare?

Epididymal tumour incidence is at most 0.03% of all male cancers. It is an enigma why the human epididymis does not often succumb to cancer, when it expresses markers of stem and cancer cells, and constitutively expresses oncogenes, pro-proliferative and pro-angiogenic factors that allow tumour cells to escape immunosurveillance in cancer-prone tissues. The privileged position of the human epididymis in evading tumourigenicity is reflected in transgenic mouse models in which induction of tumours in other organs is not accompanied by epididymal neoplasia. The epididymis appears to: (i) prevent tumour initiation (it probably lacks stem cells and has strong anti-oxidative mechanisms, active tumour suppressors and inactive oncogene products); (ii) foster tumour monitoring and destruction (by strong immuno-surveillance and -eradication, and cellular senescence); (iii) avert proliferation and angiogenesis (with persistent tight junctions, the presence of anti-angiogenic factors and misplaced pro-angiogenic factors), which together (iv) promote dormancy and restrict dividing cells to hyperplasia. Epididymal cells may be rendered non-responsive to oncogenic stimuli by the constitutive expression of factors generally inducible in tumours, and resistant to the normal epididymal environment, which mimics that of a tumour niche promoting tumour growth. The threshold for tumour initiation may thus be higher in the epididymis than in other organs. Several anti-tumour mechanisms are those that maintain spermatozoa quiescent and immunologically silent, so the low incidence of cancer in the epididymis may be a consequence of its role in sperm maturation and storage. Understanding these mechanisms may throw light on cancer prevention and therapy in general.

Schistosoma japonicum ova maintains epithelial barrier function during experimental colitis

AIM: To evaluate the impacts of Schistosoma japonicum (S. japonicum) ova on the tight junction barriers in a trinitrobenzenesulfonic acid (TNBS)-induced colitis model.

METHODS: Balb/c mice were randomly divided into three groups: control group; TNBS⁺ova^- group and TNBS⁺ova⁺ group. TNBS was used intracolonic to induce colitis and mice of the TNBS⁺ova⁺ group were pre-exposed to S. japonicum ova as a prophylactic intervention. Colon inflammation was quantified using following variables: mouse mortality, weight loss, colon extent and microscopic inflammation score. Serum expression of tumor necrosis factor-α and interferon-γ were assessed to evaluate the systemic inflammatory response. NOD2 and its mRNA were also tested. Bacterial translocations were tested by culturing blood and several tissues. ZO-1 and occludin were chosen as the representations of tight junction proteins. Both the proteins and mRNA were assessed.

RESULTS: Ova pre-treatment contributed to the relief of colitis and decreased the mortality of the models. NOD2 expression was significantly downregulated when pretreated with the ova. The TNBS injection caused a significant downregulation of ZO-1 and occludin mRNA together with their proteins in the colon; ova pre-exposure reversed these alterations. Treatment with S. japonicum ova in the colitis model caused lower intestinal bacterial translocation frequency.

CONCLUSION: S. japonicum ova can maintain epithelial barrier function through increasing tight junction proteins, thus causing less exposure of NOD2 to the luminal antigens which may activate a series of inflammatory factors and induce colitis.

Immunophysiology and pathology of inflammation in the testis and epididymis

The ability of spermatogenic cells to evade the host immune system and the ability of systemic inflammation to inhibit male reproductive function represent two of the most intriguing conundrums of male reproduction. Clearly, an understanding of the underlying immunology of the male reproductive tract is crucial to resolving these superficially incompatible observations. One important consideration must be the very different immunological environments of the testis, where sperm develop, and the epididymis, where sperm mature and are stored. Compared with the elaborate blood-testis barrier, the tight junctions of the epididymis are much less effective. Unlike the seminiferous epithelium, immune cells are commonly observed within the epithelium, and can even be found within the lumen, of the epididymis. Crucially, there is little evidence for extended allograft survival (immune privilege) in the epididymis, as it exists in the testis, and the epididymis is much more susceptible to loss of immune tolerance. Moreover, the incidence of epididymitis is considerably greater than that of orchitis in humans, and susceptibility to sperm antibody formation after damage to the epididymis or vas deferens increases with increasing distance of the damage from the testis. Although we still know relatively little about testicular immunity, we know less about the interactions between the epididymis and the immune system. Given that the epididymis appears to be more susceptible to inflammation and immune reactions than the testis, and thereby represents the weaker link in protecting developing sperm from the immune system, it is probably time this imbalance in knowledge was addressed.

Lipopolysaccharide-induced epididymitis disrupts epididymal beta-defensin expression and inhibits sperm motility in rats

Although more than 40 beta-defensins have been identified in rat epididymis, little is known about their regulation or their relation to male infertility caused by inflammation. Using a rat model of epididymitis induced by lipopolysaccharide (LPS), we examined expression of SPAG11E (also known as Bin1b), a caput epididymis-specific beta-defensin in rat. Unlike the expression of other beta-defensins in various epithelial cells with upregulated expression after LPS stimulation, expression of SPAG11E was significantly decreased by LPS at the mRNA and protein levels. LPS treatment also significantly decreased both sperm binding to SPAG11E and sperm motility, and supplementation of the spermatozoa with recombinant SPAG11E in vitro remarkably increased both SPAG11E binding and motility of sperm. To clarify whether decreased expression is a common pattern of epididymal beta-defensins after LPS stimulation, we examined the expression of another 12 epididymal beta-defensins expressed in the caput epididymis. For nine of these beta-defensins, expression was decreased, but for the other three, expression remained unaffected. These findings demonstrate that LPS-induced epididymitis can decrease the expression of epididymal beta-defensins and that disruption of SPAG11E expression is involved in the impairment of sperm motility.

Gnotobiotic IL-10; NF-kappaB mice develop rapid and severe colitis following Campylobacter jejuni infection

Limited information is available on the molecular mechanisms associated with Campylobacter jejuni (C. jejuni) induced food-borne diarrheal illnesses. In this study, we investigated the function of TLR/NF-kappaB signaling in C. jejuni induced pathogenesis using gnotobiotic IL-10(-/-); NF-kappaB(EGFP) mice. In vitro analysis showed that C. jejuni induced IkappaB phosphorylation, followed by enhanced NF-kappaB transcriptional activity and increased IL-6, MIP-2alpha and NOD2 mRNA accumulation in infected-mouse colonic epithelial cells CMT93. Importantly, these events were blocked by molecular delivery of an IkappaB inhibitor (Ad5IkappaBAA). NF-kappaB signalling was also important for C.jejuni-induced cytokine gene expression in bone marrow-derived dendritic cells. Importantly, C. jejuni associated IL-10(-/-); NF-kappaB(EGFP) mice developed mild (day 5) and severe (day 14) ulcerating colonic inflammation and bloody diarrhea as assessed by colonoscopy and histological analysis. Macroscopic analysis showed elevated EGFP expression indicating NF-kappaB activation throughout the colon of C. jejuni associated IL-10(-/-); NF-kappaB(EGFP) mice, while fluorescence microscopy revealed EGFP positive cells to be exclusively located in lamina propria mononuclear cells. Pharmacological NF-kappaB inhibition using Bay 11-7085 did not ameliorate C. jejuni induced colonic inflammation. Our findings indicate that C. jejuni induces rapid and severe intestinal inflammation in a susceptible host that correlates with enhanced NF-kappaB activity from lamina propria immune cells.