Differential regulation of interleukin-8 and human beta-defensin 2 in Pseudomonas aeruginosa-infected intestinal epithelial cells

Adjudicative efficacy of Bifidobacterium animalis subsp. lactis BLa80 in treating acute diarrhea in children: a randomized, double-blinded, placebo-controlled study

The goal of this study is to assess the efficacy and safety of Bifidobacterium animalis subsp. lactis BLa80, as an adjunct treatment for diarrhea in children with a randomized, double-blinded, placebo-controlled study design. Eligible diarrheal children, aged 0-3 years without the need for antibiotic treatment based on clinical diagnosis when recruited, were randomized into the intervention group (IG, n = 58, with probiotic) or the control group (CG, n = 53, placebo). The primary assessment was the duration of diarrhea. Fecal samples were collected for biochemical index measurement, analysis of gut microbiome composition, and prediction of gene family abundances. The total duration of diarrhea in the IG (122.6 ± 13.1 h) was significantly shorter than in the CG (148.4 ± 17.6 h, p < 0.001). More children in the IG showed improvements in diarrhea compared to the CG, both in intention-to-treat analysis (81.7% vs. 40.0%, p < 0.001) and per protocol analysis (84.4% vs 45.3%, p < 0.001). Cathelicidin level in the IG was significantly higher than that in the CG after the intervention (4415.00 ± 1036.93 pg/g vs. 3679.49 ± 871.18 pg/g, p = 0.0175). The intervention led to an increased abundance of Bifidobacterium breve and Collinsella aerofaciens species, higher alpha-diversity (p < 0.05), and enrichment of functional genes in the gut microbiota related to immunity regulation. Administration of BLa80 at a dose of 5 × 109 CFU/day resulted in a shorter duration of diarrhea and alterations in gut microbiome composition and gene functions.

Mechanisms and regulation of defensins in host defense

As a family of cationic host defense peptides, defensins are mainly synthesized by Paneth cells, neutrophils, and epithelial cells, contributing to host defense. Their biological functions in innate immunity, as well as their structure and activity relationships, along with their mechanisms of action and therapeutic potential, have been of great interest in recent years. To highlight the key research into the role of defensins in human and animal health, we first describe their research history, structural features, evolution, and antimicrobial mechanisms. Next, we cover the role of defensins in immune homeostasis, chemotaxis, mucosal barrier function, gut microbiota regulation, intestinal development and regulation of cell death. Further, we discuss their clinical relevance and therapeutic potential in various diseases, including infectious disease, inflammatory bowel disease, diabetes and obesity, chronic inflammatory lung disease, periodontitis and cancer. Finally, we summarize the current knowledge regarding the nutrient-dependent regulation of defensins, including fatty acids, amino acids, microelements, plant extracts, and probiotics, while considering the clinical application of such regulation. Together, the review summarizes the various biological functions, mechanism of actions and potential clinical significance of defensins, along with the challenges in developing defensins-based therapy, thus providing crucial insights into their biology and potential clinical utility.

Human β-Defensin 2 and Its Postulated Role in Modulation of the Immune Response

Studies described so far suggest that human β-defensin 2 is an important protein of innate immune response which provides protection for the human organism against invading pathogens of bacterial, viral, fungal, as well as parasitical origin. Its pivotal role in enhancing immunity was proved in infants. It may also be considered a marker of inflammation. Its therapeutic administration has been suggested for maintenance of the balance of systemic homeostasis based on the appropriate composition of the microbiota. It has been suggested that it may be an important therapeutic tool for modulating the response of the immune system in many inflammatory diseases, offering new treatment modalities. For this reason, its properties and role in the human body discussed in this review should be studied in more detail.

Beneficial effect of probiotics on Pseudomonas aeruginosa-infected intestinal epithelial cells through inflammatory IL-8 and antimicrobial peptide human beta-defensin-2 modulation

The human pathogen Pseudomonas aeruginosa can rapidly induce fatal sepsis, even in previously healthy infants or children treated with appropriate antibiotics. To reduce antibiotic overuse, exploring novel complementary therapies, such as probiotics that reportedly protect patients against P. aeruginosa infection, would be particularly beneficial. However, the major mechanism underlying the clinical effects is not completely understood. We thus aimed to investigate how probiotics affect IL-8 and human beta-defensin 2 (hBD-2) in P. aeruginosa-infected intestinal epithelial cells (IECs). We infected SW480 IECs with wild type PAO1 P. aeruginosa following probiotic treatment with Lactobacillus rhamnosus GG or Bifidobacterium longum spp. infantis S12, and analysed the mRNA expression and secreted protein of IL-8 and hBD-2, Akt signalling and NOD1 receptor protein expression. We observed that probiotics enhanced hBD-2 expression but suppressed IL-8 responses when administered before infection. They also enhanced P. aeruginosa-induced membranous NOD1 protein expression and Akt activation. The siRNA-mediated Akt or NOD1 knockdown counteracted P. aeruginosa-induced IL-8 or hBD-2 expression, indicating regulatory effects of these probiotics. In conclusion, these data suggest that probiotics exert reciprocal regulation of inflammation and antimicrobial peptides in P. aeruginosa-infected IECs and provide supporting evidence for applying probiotics to reduce antibiotic overuse.

Expression of XBP1s in peritoneal mesothelial cells is critical for inflammation-induced peritoneal fibrosis

Intraperitoneal inflammation is the most important determinant of peritoneal fibrosis in patients with long-term peritoneal dialysis (PD). Spliced x-box binding protein-1 (XBP1s), a major proximal effector of unfolded protein response (UPR) signaling, plays an indispensable role in inflammation. Our study demonstrated that the inflammatory factor interleukin-1β (IL-1β) dose- and time-dependently induced XBP1s upregulation and interleukin-6 (IL-6) secretion, as well as the expression of the fibrotic marker fibronectin. However, these effects were prevented by the IRE1 endonuclease inhibitor STF083010 since it time-dependently reduced IL-1β-induced Xbp1 mRNA splicing, XBP1s protein expression, inflammatory factor IL-6 secretion and the expression of the fibrotic marker fibronectin in human peritoneal mesothelial cells (HPMCs). The overexpression and knockdown of XBP1s in HPMCs had a similar effect on fibronectin expression. In a rat model of peritoneal inflammation, STF083010 significantly attenuated chlorhexidine digluconate-induced XBP1s and α-smooth muscle actin expression, as well as fibrotic tissue proliferation, in the peritoneum. Our results suggest that XBP1s is a strong pathogenic factor that mediates inflammation-induced peritoneal fibrosis in peritoneal dialysis.

The contribution of interleukin-8 genotypes and expression to nasopharyngeal cancer susceptibility in Taiwan

The incidence rate of nasopharyngeal cancer (nasopharyngeal carcinoma [NPC]) is much higher in Southeast Asia than in western countries. Interleukin-8 (IL-8), a chemokine produced by macrophages, epithelial cells, airway smooth muscle cells, and endothelial cells, is an important immuno-mediator in the development and progression of many types of cancer. Genetic variations in IL-8 have been associated with the risks of NPC and other cancers. In the current study, we evaluated the role of IL-8 in NPC at the levels of DNA, RNA, and protein in a Taiwanese population. First, in a case-control study, 176 NPC patients and 352 cancer-free controls were genotyped, and the associations of IL-8 T - 251A, C + 781T, C + 1633T, and A + 2767T polymorphisms with NPC risk were evaluated. Second, the NPC tissue samples were assessed for their IL-8 mRNA and protein expression by real-time quantitative reverse transcription polymerase chain reaction (PCR) and Western blotting, respectively. Regarding the IL-8 promoter T - 251A, the TA and AA genotypes were associated with significantly decreased risks of NPC compared with the wild-type TT genotype (adjusted odds ratio = 0.61 and 0.52, 95% confidence interval = 0.47-0.93 and 0.37-0.91, P = .0415 and .0289, respectively). The mRNA and protein expression levels for NPC tissues revealed no significant associations among the 20 NPC samples with different genotypes. These findings suggest that IL-8 may play an important role in the carcinogenesis of NPC in Taiwan.

Differential Effects of Statins on Inflammatory Interleukin-8 and Antimicrobial Peptide Human Β-Defensin 2 Responses in Salmonella-Infected Intestinal Epithelial Cells

Alternative therapies are needed to reduce the use of antibiotics and incidence of drug-resistant Salmonellosis. Previous studies have revealed important roles of statins in regulating innate immunity. Therefore, we investigated the effects of statins on innate immunity in Salmonella-infected intestinal epithelial cells (IECs), which are involved in mucosal innate immunity. SW480 cells and Akt siRNA- or vitamin D receptor (VDR) siRNA-transfected SW480 cells were infected by wild-type S. Typhimurium strain SL1344 in the presence or absence of statins. The mRNA or protein expression was analyzed by real-time quantitative PCR or western blot analysis, respectively. Simvastatin or fluvastatin caused IL-8 (interleukin-8) suppression, but increased hBD-2 mRNA expression in Salmonella-infected SW480 cells. Both statins enhanced phosphorylated Akt and VDR expressions. Akt or VDR knockdown by siRNA counteracted the suppressive effect of simvastatin on IL-8 expression, whereas VDR knockdown diminished the enhanced hBD-2 expression in Salmonella-infected SW480 cells. Therefore, we observed differential regulation of statins on inflammatory IL-8 and anti-microbial hBD-2 expressions in Salmonella-infected IECs via PI3K/Akt signaling and VDR protein expression, respectively. The enhanced activity of antimicrobial peptides by statins in Salmonella-infected IECs could protect the host against infection, and modulation of pro-inflammatory responses could prevent the detrimental effects of overwhelming inflammation in the host.

The Anti-inflammatory Effects of Glycerol-supplemented Probiotic Lactobacillus reuteri on Infected Epithelial cells In vitro

Background:

One of the most interesting effects of probiotics is their ability to modulate the immune system through the induction of cytokines and to enhance the host immune response.

Aims:

The purpose of this study was to evaluate the anti-inflammatory effect of glycerol-supplemented Lactobacillus reuteri on the transcription level of interleukin (IL)-8 and human-beta-defensin (hBD)-2 expressed by epithelial cells after exposure to bacteria.

Materials and Methods:

The confluent-cultured HaCat cell line (10⁵ cells/mL) was exposed to Streptococcus mutans ATCC-25175 and Porphyromonas gingivalis ATCC-33277 (10⁷ colony-forming units [CFU]/mL) for 24 h and challenged with probiotic L. reuteri ATCC-55730 (10⁷ CFU/mL) supplemented with glycerol. Subsequently, the transcription levels of IL-8 and hBD-2 in HaCat cells were analyzed using reverse-transcription polymerase chain reaction (RT-PCR). In addition, cell viability was analyzed using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. All the obtained data were statistically analyzed using the one-way analysis of variance test, with P < 0.05 set as the level of significance.

Results:

The MTT assays confirmed no cytotoxic effects of glycerol-supplemented L. reuteri on HaCat cells (viability >90%). mRNA expression of IL-8 and hBD-2 increased after exposure to both bacteria. The presence of glycerol-supplemented L. reuteri significantly reduced the expression of IL-8 and hBD-2 on HaCat cells (P < 0.05).

Conclusion:

Glycerol-supplemented L. reuteri reduced the expression of IL-8 and hBD-2, and the results may be proof of principle for a probiotic approach to combating inflammation. However, further studies are needed to validate this probiotic effect.

Identification of a new small bioactive peptide from Lactobacillus gasseri supernatant

Ten lactic acid bacteria (LAB) strains, previously isolated from human ileal biopsy of healthy volunteers, were screened for production and secretion of molecules having anti-bacterial and anti-biofilm activities. Because many recent reports indicate that LAB secreted molecules may exert immune-modulatory action, we also tested the effect on human intestinal HCT116 cells challenged with bacterial lipopolysaccharides. One of the Lactobacillus gasseri strains, SF1109, strongly inhibited: (1) Pseudomonas aeruginosa growth; (2) Escherichia coli biofilm production; (3) LPS induction of P-ERK1/2 in HCT116 cells, and was selected for further characterisation of the secreted active molecule. Cell-free supernatant of the L. gasseri SF1109 was analysed and one 1.3 kDa peptide has been characterised. Eight out twelve amino acids of this peptide were identified allowing the synthesis of an octa-peptide which still presented the mentioned activities.

Vitamin D differentially regulates Salmonella-induced intestine epithelial autophagy and interleukin-1β expression

AIM

To investigate the effects of active vitamin D3 on autophagy and interleukin (IL)-1β expression in Salmonella-infected intestinal epithelial cells (IECs).

METHODS

Caco-2 cells, NOD2 siRNA-, Atg16L1 siRNA- or vitamin D receptor (VDR) siRNA-transfected Caco-2 cells were pretreated with 1,25-dihydroxyvitamin D3 (1,25D3), and then infected by wild-type S. typhimurium strain SL1344. The conversion of LC3-I to LC3-II was detected by Western blot analysis and LC3⁺ autophagosome was analyzed by immunofluorescence. Caco-2 cells or VDR siRNA-transfected cells were pretreated with 1,25D3, and then infected by SL1344. Membrane protein and total RNA were analyzed by Western blot and RT-PCR for VDR and Atg16L1 protein and mRNA expression, respectively. Atg16L1 siRNA-transfected Caco-2 cells were pretreated by 1,25D3 and then infected with SL1344. Total RNA was analyzed by RT-PCR for IL-1β mRNA expression.

RESULTS

The active form of vitamin D, 1,25D3, showed enhanced VDR-mediated Atg16L1 mRNA expression, membranous Atg16L1 protein expression leading to enhanced autophagic LC3II protein expression and LC3 punctae in Salmonella-infected Caco-2 cells which was counteracted by Atg16L1 and VDR siRNA, but Atg16L1 mediated suppression of IL-1β expression. Thus, active vitamin D may enhance autophagy but suppress inflammatory IL-1β expression in Salmonella-infected IECs.

CONCLUSION

Active vitamin D might enhance autophagic clearance of Salmonella infection, while modulation of inflammatory responses prevents the host from detrimental effects of overwhelming inflammation.

Proline-arginine rich (PR-39) cathelicidin: Structure, expression and functional implication in intestinal health

Proline-Arginine-39 (PR-39) is a small cationic, proline and arginine rich, cathelicidin that plays an important role in the porcine innate immune system. Although PR-39 was first discovered in intestinal cell lysates of pigs, subsequent research has indicated that it is primarily expressed in bone marrow and other lymphoid tissues including the thymus and spleen, as well as in leukocytes. Mature PR-39 cathelicidin has anti-microbial activity against many gram-negative and some gram-positive bacteria. PR-39 is also a bridge between the innate and adaptive immune system with recognized immunomodulatory, wound healing, anti-apoptotic, and pro-angiogenic functions. The purpose of this review is to summarize our current knowledge about the structure, expression, and functions of PR-39 and its potential to promote intestinal homeostasis. This understanding is relevant in the search of alternative therapeutics against diarrheic enterocolitis, a major problem faced by pork producers both in terms of costs and risk of zoonosis.

The differential effects of 1,25-dihydroxyvitamin D3 on Salmonella-induced interleukin-8 and human beta-defensin-2 in intestinal epithelial cells

Salmonellosis or Salmonella, one of the most common food-borne diseases, remains a major public health problem worldwide. Intestinal epithelial cells (IECs) play an essential role in the mucosal innate immunity of the host to defend against the invasion of Salmonella by interleukin (IL)-8 and human β-defensin-2 (hBD-2). Accumulated research has unravelled important roles of vitamin D in the regulation of innate immunity. Therefore, we investigated the effects of 1,25-dihydroxyvitamin D3 (1,25D3) on Salmonella-induced innate immunity in IECs. We demonstrate that pretreatment of 1,25D3 results in suppression of Salmonella-induced IL-8 but enhancement of hBD-2, either protein secretion and mRNA expression, in IECs. Furthermore, 1,25D3 enhanced Salmonella-induced membranous recruitment of nucleotide oligomerization domain (NOD2) and its mRNA expression and activation of protein kinase B (Akt), a downstream effector of phosphoinositide 3-kinase (PI3K). Inhibition of the PI3K/Akt signal counteracted the suppressive effect of 1,25D3 on Salmonella-induced IL-8 expression, while knock-down of NOD2 by siRNA diminished the enhanced hBD-2 expression. These data suggest differential regulation of 1,25D3 on Salmonella-induced IL-8 and hBD-2 expression in IECs via PI3K/Akt signal and NOD2 protein expression, respectively. Active vitamin D-enhanced anti-microbial peptide in Salmonella-infected IECs protected the host against infection, while modulation of proinflammatory responses by active vitamin D prevented the host from the detrimental effects of overwhelming inflammation. Thus, active vitamin D-induced innate immunity in IECs enhances the host's protective mechanism, which may provide an alternative therapy for invasive Salmonella infection.

De Novo sphingolipid synthesis is essential for Salmonella-induced autophagy and human beta-defensin 2 expression in intestinal epithelial cells

BACKGROUND

Sphingolipids are important for innate immune response to eliminate infected pathogens and involved in autophagy. On the other hand, nucleotide-binding oligomerization domain-containing protein 2 (NOD2) served as an intracellular pattern recognition receptor to enhance host defense by inducing autophagy and the production of antimicrobial peptides, such as human beta-defensin-2 (hBD-2). However, the role of sphingolipids in Salmonella-induced autophagy and hBD-2 response in intestinal epithelial cells has not been previously elucidated.

METHODS

Salmonella typhimurium wild-type strain SL1344 was used to infect SW480, an intestinal epithelial cell. hBD-2 and interleukin-8 (IL-8) mRNA expressions were assessed in SW480 cells using RT-PCR, and intracellular signaling pathways and autophagy protein expression were analyzed by Western blot in SW480 cells in the presence or absence of inhibitors or transfected with siRNA.

RESULTS

We demonstrated that inhibition of de novo sphingolipid synthesis repressed the membrane recruitment of NOD2 and autophagy-related protein 16-like 1 (Atg16L1), suppressed Salmonella-induced autophagic protein LC3-II expression, and reduced NOD2-mediated hBD-2 response in Salmonella-infected SW480 cells. Contrasting to the utilization of membrane cholesterol on maintenance of Salmonella-containing vacuoles and anti-inflammation by Salmonella, sphingolipids act on epithelial defense against the invasive pathogen.

CONCLUSIONS

Our results offer mechanistic insights on the role of de novo sphingolipid synthesis in the innate immunity of intestinal epithelial cells to Salmonella infection. The pharmaceuticals enhancing or diet enriched with sphingolipids may induce the dual anti-bacterial mechanisms. The role of de novo sphingolipid synthesis on inflammatory bowel disease is deserved to be further investigated.

NEU1 Sialidase Regulates Membrane-tethered Mucin (MUC1) Ectodomain Adhesiveness for Pseudomonas aeruginosa and Decoy Receptor Release

Airway epithelia express sialylated receptors that recognize exogenous danger signals. Regulation of receptor responsiveness to these signals remains incompletely defined. Here, we explore the mechanisms through which the human sialidase, neuraminidase-1 (NEU1), promotes the interaction between the sialoprotein, mucin 1 (MUC1), and the opportunistic pathogen, Pseudomonas aeruginosa. P. aeruginosa flagellin engaged the MUC1 ectodomain (ED), increasing NEU1 association with MUC1. The flagellin stimulus increased the association of MUC1-ED with both NEU1 and its chaperone/transport protein, protective protein/cathepsin A. Scatchard analysis demonstrated NEU1-dependent increased binding affinity of flagellin to MUC1-expressing epithelia. NEU1-driven MUC1-ED desialylation rapidly increased P. aeruginosa adhesion to and invasion of the airway epithelium. MUC1-ED desialylation also increased its shedding, and the shed MUC1-ED competitively blocked P. aeruginosa adhesion to cell-associated MUC1-ED. Levels of desialylated MUC1-ED were elevated in the bronchoalveolar lavage fluid of mechanically ventilated patients with P. aeruginosa airway colonization. Preincubation of P. aeruginosa with these same ex vivo fluids competitively inhibited bacterial adhesion to airway epithelia, and MUC1-ED immunodepletion completely abrogated their inhibitory activity. These data indicate that a prokaryote, P. aeruginosa, in a ligand-specific manner, mobilizes eukaryotic NEU1 to enhance bacterial pathogenicity, but the host retaliates by releasing MUC1-ED into the airway lumen as a hyperadhesive decoy receptor.