Chicken avian β-defensin 8 modulates immune response via the mitogen-activated protein kinase signaling pathways in a chicken macrophage cell line

Dietary ethylenediamine dihydroiodide mitigated Escherichia coli O78-induced immune and intestinal damage of ducks via suppression of NF-κB signal

This study investigated the effect of Ethylenediamine dihydroiodide (EDDI) on growth performance, immune function and intestinal health of meat ducks challenged with Avian pathogenic Escherichia coli (APEC). A total of 360 one-day-old Cherry Valley ducks with similar body weight were randomly allocated to 6 treatments (6 floor cages, 10 birds/cage). A 3 × 2 factor design was used with 3 dietary iodine levels (0, 8, 16 mg/kg in the form EDDI and whether APEC was challenged or not at 7-day-old ducks. The feeding period lasted for 20 d. The results showed that the addition of EDDI reduced APEC-induced decrease of the 20-d weight loss of meat ducks (P < 0.05), and alleviated the inflammatory response of liver tissue induced by APEC challenge in meat ducks. In terms of immune function, EDDI supplementation reduced the immune organ index and increased the immune cell count of meat ducks, reduced the level of endotoxins in the serum of meat ducks (P < 0.05), as well as inhibited the expression levels of liver and spleen inflammatory factors and TLR signaling pathway related genes induced by APEC (P < 0.05). In terms of intestinal health, EDDI inhibited APEC-induced decreases in ZO-3 genes expression and increases in IL-1β and TNF-α expression, increased relative abundance of beneficial bacteria in the cecum and content of metabolites. Pearson correlation analysis showed that there was a significant correlation between liver inflammatory factors and TLR4 signaling pathway genes, and there might be a significant correlation between intestinal microbial flora and other physiological indexes of meat ducks, which indicated that EDDI could reduce the damage to immune function and intestinal health caused by APEC challenge through regulating the structure of intestinal flora. Collectively, our findings suggest that the EDDI can promote growth performance, improve immune function and the intestinal barrier in APEC-challenged meat ducks, which may be related to the suppression of NF-κB signal.

New insight into the biological activity of Salmo salar NK-lysin antimicrobial peptides

NK-lysin is a potent antimicrobial peptide (AMP) with antimicrobial activity against bacteria, fungi, viruses, and parasites. NK-lysin is a type of granulysin, a member of the saposin-like proteins family first isolated from a pig's small intestine. In previous work, for the first time, we identified four variants of nk-lysin from Atlantic salmon (Salmo salar) using EST sequences. In the present study, we reported and characterized two additional transcripts of NK-lysin from S. salar. Besides, we evaluated the tissue distribution of three NK-lysins from S. salar and assessed the antimicrobial, hemolytic, and immunomodulatory activities and signaling pathways of three NK-lysin-derived peptides. The synthetic peptides displayed antimicrobial activity against Piscirickettsia salmonis (LF-89) and Flavobacterium psychrophilum. These peptides induced the expression of immune genes related to innate and adaptive immune responses in vitro and in vivo. The immunomodulatory activity of the peptides involves the mitogen-activated protein kinases-mediated signaling pathway, including p38, extracellular signal-regulated kinase 1/2, and/or c-Jun N-terminal kinases. Besides, the peptides modulated the immune response induced by pathogen-associated molecular patterns (PAMPs). Our findings show that NK-lysin could be a highly effective immunostimulant or vaccine adjuvant for use in fish aquaculture.

The Contribution of Antimicrobial Peptides to Immune Cell Function: A Review of Recent Advances

The development of novel antimicrobial agents to replace antibiotics has become urgent due to the emergence of multidrug-resistant microorganisms. Antimicrobial peptides (AMPs), widely distributed in all kingdoms of life, present strong antimicrobial activity against a variety of bacteria, fungi, parasites, and viruses. The potential of AMPs as new alternatives to antibiotics has gradually attracted considerable interest. In addition, AMPs exhibit strong anticancer potential as well as anti-inflammatory and immunomodulatory activity. Many studies have provided evidence that AMPs can recruit and activate immune cells, controlling inflammation. This review highlights the scientific literature focusing on evidence for the anti-inflammatory mechanisms of different AMPs in immune cells, including macrophages, monocytes, lymphocytes, mast cells, dendritic cells, neutrophils, and eosinophils. A variety of immunomodulatory characteristics, including the abilities to activate and differentiate immune cells, change the content and expression of inflammatory mediators, and regulate specific cellular functions and inflammation-related signaling pathways, are summarized and discussed in detail. This comprehensive review contributes to a better understanding of the role of AMPs in the regulation of the immune system and provides a reference for the use of AMPs as novel anti-inflammatory drugs for the treatment of various inflammatory diseases.

Chronic heat stress induces renal fibrosis and mitochondrial dysfunction in laying hens

BACKGROUND

Heat stress in laying hens negatively affects egg production and shell quality by disrupting the homeostasis of plasma calcium and phosphorus levels. Although the kidney plays an important role in calcium and phosphorus homeostasis, evidence regarding the effect of heat stress on renal injury in laying hens is yet to be elucidated. Therefore, the aim of this study was to evaluate the effects of chronic heat stress on renal damage in hens during laying periods.

METHODS

A total of 16 white-leghorn laying hens (32 weeks old) were randomly assigned to two groups (n = 8). One group was exposed to chronic heat stress (33 °C for 4 weeks), whereas the other group was maintained at 24 °C.

RESULTS

Chronic heat exposure significantly increased plasma creatinine and decreased plasma albumin levels (P < 0.05). Heat exposure also increased renal fibrosis and the transcription levels of fibrosis-related genes (COLA1A1, αSMA, and TGF-β) in the kidney. These results suggest that renal failure and fibrosis were induced by chronic heat exposure in laying hens. In addition, chronic heat exposure decreased ATP levels and mitochondrial DNA copy number (mtDNA-CN) in renal tissue, suggesting that renal mitochondrial dysfunction occurs under conditions of heat stress. Damaged mitochondria leak mtDNAs into the cytosol and mtDNA leakage may activate the cyclic GMP-AMP synthase (cGAS) stimulator of interferon genes (STING) signaling pathway. Our results showed that chronic heat exposure activated the cGAS-STING pathway as indicated by increased expression of MDA5, STING, IRF7, MAVS, and NF-κB levels. Furthermore, the expression of pro-inflammatory cytokines (IL-12) and chemokines (CCL4 and CCL20) was upregulated in heat-stressed hens.

CONCLUSIONS

These results suggest that chronic heat exposure induces renal fibrosis and mitochondrial damage in laying hens. Mitochondrial damage by heat stress may activate the mtDNA-cGAS-STING signaling and cause subsequent inflammation, which contributes to the progression of renal fibrosis and dysfunction.

Host Defense Peptides in Nutrition and Diseases: A Contributor of Immunology Modulation

Host defense peptides (HDPs) are primary components of the innate immune system with diverse biological functions, such as antibacterial ability and immunomodulatory function. HDPs are produced and released by immune and epithelial cells against microbial invasion, which are widely distributed in humans, animals, plants, and microbes. Notably, there are great differences in endogenous HDP distribution and expression in humans and animals. Moreover, HDP expression could be regulated by exogenous substances, such as nutrients, and different physiological statuses in health and disease. In this review, we systematically assessed the regulation of expression and mechanism of endogenous HDPs from nutrition and disease perspectives, providing a basis to identify the specificity and regularity of HDP expression. Furthermore, the regulation mechanism of HDP expression was summarized systematically, and the differences in the regulation between nutrients and diseases were explored. From this review, we provide novel ideas targeted the immune regulation of HDPs for protecting host health in nutrition and practical and effective new ideas using the immune regulation theory for further research on protecting host health from pathogenic infection and excessive immunity diseases under the global challenge of the antibiotic-abuse-induced series of problems, including food security and microbial resistance.

Campylobacter jejuni infection induces dynamic expression of avian host defense peptides in vitro and in vivo

Campylobacter jejuni is considered as the leading cause of worldwide foodborne bacterial gastroenteritis. Chicken is the main reservoir of C. jejuni. Avian innate immune responses to C. jejuni remain poorly defined. Chicken host defense peptides (HDPs) are the major components of avian innate immune system. This study aimed to characterize the chicken HDPs responses to C. jejuni in vitro and in vivo. In the HD11 macrophage cell line, the HDPs, including AvBD1-2, CATH1-3, AvBD7, AvBD4, and AvBD6, were relatively higher expressed in untreated cells, whereas the expressions were suppressed after C. jejuni infection. In contrast, C. jejuni infection significantly increased the expression of the lower expressed HDPs, such as AvBD3, AvBD5, AvBD8-14, and CATHB1, in untreated cells. In the chicken challenge experiment, the immune tissues of spleens and cecal tonsils were collected from C. jejuni-infected and uninfected chickens at 1, 3 and 15 day post inoculation (DPI). In spleens of C. jejuni-infected chickens, only AvBD14 expression was elevated at 1 DPI. The majority of avian HDPs were significantly up-regulated at 3 DPI and dramatically decreased to the levels of uninfected controls at 15 DPI. In chicken cecal tonsils, only AvBD9 and AvBD14 were significantly up-regulated at 1 DPI with C. jejuni infection. Collectively, C. jejuni infection induced dynamic expression of chicken HDPs in both macrophage HD11 and immune tissues of chickens. Suppression of chicken HDPs expression may be an evasion strategy of C. jejuni for persistent colonization in chicken intestine by circumventing the chicken immune system.

Beta-glucan enhanced immune response to Newcastle disease vaccine and changed mRNA expression of spleen in chickens

The present study was performed to investigate the effect of oral administration of β-glucan (G70), a product obtained from the cell wall of yeast, on Newcastle disease virus (NDV)-specific hemagglutination inhibition (HI) titers, lymphocyte proliferation, and the role of T lymphocyte subpopulations in chickens treated with live NDV vaccine. In addition, the influence of β-glucan on splenic gene expression was investigated by transcriptome sequencing. The results revealed that the supplementation of β-glucan boosted the titer of serum NDV HI increased the NDV stimulation index of lymphocytes in peripheral blood and intestinal tract, and promoted the differentiation of T lymphocytes into CD4⁺ T cells. The RNA sequencing (RNA-seq) analysis demonstrated that G70 upregulated the mRNA expressions related to G-protein coupled receptor and MHC class I polypeptide, and downregulated the mRNA expressions related to cathelicidin and beta-defensin. The immunomodulatory effect of G70 might function through mitogen-activated protein kinase signaling pathway. To sum up, G70 could boost the immunological efficacy of live NDV vaccine in chickens and could be applied as a potential adjuvant candidate in the poultry industry.

Effects of the Antimicrobial Peptide Mastoparan X on the Performance, Permeability and Microbiota Populations of Broiler Chickens

Restrictions on antibiotics are driving the search for alternative feed additives to promote gastrointestinal health and development in broiler chicken production. Proteins including antimicrobial peptides can potentially be applied as alternatives to antibiotics and are one of the most promising alternatives. We investigated whether the addition of MPX to the diet affects the production performance, immune function and the intestinal flora of the caecal contents of broiler chickens. One hundred one-day-old chickens were randomly divided into two groups: control (basal diet) and MPX (20 mg/kg) added to the basal diet. The results indicated that dietary supplementation with MPX improved the performance and immune organ index, decreased the feed conversion ratio, increased the villus length, maintained the normal intestinal morphology and reduced the IL-6 and LITNF mRNA expression levels of inflammation-related genes. In addition, MPX increased the mRNA expression of the digestive enzymes FABP2 and SLC2A5/GLUT5 and the tight junction proteins ZO-1, Claudin-1, Occludin, JAM-2 and MUC2, maintained the intestinal permeability and regulated the intestinal morphology. Moreover, MPX increased the CAT, HMOX1 and SOD1 mRNA expression levels of the antioxidant genes. Furthermore, a 16S rRNA microflora analysis indicated that the abundance of Lactobacillus and Lactococcus in the cecum was increased after addition of MPX at 14 d and 28 d. This study explored the feasibility of using antimicrobial peptides as novel feed additives for broiler chickens and provides a theoretical basis for their application in livestock.

Sodium butyrate alleviates LPS-induced kidney injury via inhibiting TLR2/4 to regulate rBD2 expression

Defensins represent an integral part of the innate immune system to ward off potential pathogens. The study used a rat model to investigate mechanisms by which sodium butyrate (NaB) regulates β-defensin to inhibit lipopolysaccharide (LPS)-induced nephrotoxicity. We found that NaB alleviated LPS-induced renal structural damage, as judged by reduced renal lesions and improved glomerular vascular structure. In addition, elevated levels of indicators of kidney damage creatinine and blood urine nitrogen, inflammatory mediators TNF-α, and IL-6 dropped after NaB administration. Rat β-defensin 2 (rBD2), as estimated by mRNA level, was significantly higher in LPS-treated kidneys, whereas the changes of rBD2 reduced in NaB-treated kidneys. In addition, NaB alleviated LPS-induced increase in TLRs mRNA expression. Mechanistically, the present study indicates that NaB has nephroprotective activity resulting from modulation of TLR2/4 to regulate rBD2 expression hence curbing inflammation. PRACTICAL APPLICATIONS: In practice, adding NaB to diet can improve animal performance. Our results suggest that dietary supplementation of NaB increases animal feed intake and improves the body's defense ability to relieve inflammation caused by bacteria. Especially in the age of resistance prohibition, sodium butyrate can partially replace antibiotics to induce the expression of body defensin. It may become a health care product to enhance the body's immunity.

The ARM repeat domain of hemocyanin interacts with MKK4 to modulate antimicrobial peptides expression

The mitogen-activated protein kinase (MAPK) intracellular signaling pathway mediates numerous biological processes, including antimicrobial immune response by inducing antimicrobial peptides (AMPs) production. Although MAPK signaling cascade proteins have been identified in penaeid shrimp, their modulation via the MKK4-p38-c-Jun cascade and effect on AMPs production is unknown. Here, we show that hemocyanin (PvHMC), antimicrobial peptides (anti-lipopolysaccharide factor, crustin, and penaeidins), and MKK4-p38-c-Jun cascade proteins are simultaneously induced by pathogens (Vibrio parahaemolyticus, Staphylococcus aureus, and white spot syndrome virus) in Penaeus vannamei. Intriguingly, knockdown of PvHMC with or without pathogen challenge attenuated the expression of MKK4-p38-c-Jun cascade proteins and their phosphorylation level, which consequently decreased AMPs expression. Further analysis revealed that PvHMC interacts via its armadillo (ARM) repeat domain with PvMKK4 to modulate the p38 MAPK signaling pathway. Thus, the ARM repeat domain enables penaeid shrimp hemocyanin to modulate AMPs expression during antimicrobial response by activating the p38 MAPK signaling pathway.

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Pathogens induce hemocyanin, MKK4-p38-c-Jun proteins, and antimicrobial peptide genes

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Hemocyanin modulates MKK4-p38-c-Jun cascade proteins to regulate AMPs gene expression

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Hemocyanin interacts with MKK4 to modulate p38 MAPK signaling in penaeid shrimp

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Deletion of the ARM repeat domain attenuates the interaction of hemocyanin with MKK4

The Effect of the Antimicrobial Peptide Plectasin on the Growth Performance, Intestinal Health, and Immune Function of Yellow-Feathered Chickens

The goal of the study was to test the effects of an antibiotic substitute, plectasin, on the growth performance, immune function, intestinal morphology and structure, intestinal microflora, ileal mucosal layer construction and tight junctions, ileal immune-related cytokines, and blood biochemical indices of yellow-feathered chickens. A total of 1,500 one-day-old yellow-feathered chicks were randomly divided into four dietary treatment groups with five replicates in each group and 75 yellow-feathered chicks in each replication, as follows: basal diet (group A); basal diet supplemented with 10 mg enramycin/kg of diet (group B), basal diet supplemented with 100 mg plectasin/kg of diet (group C), and basal diet supplemented with 200 mg plectasin/kg of diet (group D). It was found that the dietary antimicrobial peptide plectasin could improve the ADG and had better F/G for the overall period of 1–63 days. Dietary plectasin can enhance H9N2 avian influenza virus (AIV) and Newcastle disease virus (NDV) antibody levels of yellow-feathered chickens at 21, and 35 days of age. Dietary plectasin can enhance the intestine structure, inhibit Escherichia coli and proinflammatory cytokines in the ileum, and ameliorate the blood biochemical indices of yellow-feathered chickens at 21 days of age. This study indicates that the antimicrobial peptide plectasin has beneficial effects on the growth performance, intestinal health and immune function of yellow-feathered chickens.

Multi-epitope-Based Vaccine Designed by Targeting Cytoadherence Proteins of Mycoplasma gallisepticum

Mycoplasma gallisepticum causes chronic respiratory disease in chickens leading to large economic losses in the poultry industry, and the impacts remain to be a great challenge for a longer period. Among the other approaches, a vaccine targeting the adhesion proteins of M. gallisepticum would be a promising candidate in controlling the infection. Thus, the present study is aimed to design a multi-epitope vaccine candidate using cytoadhesion proteins of M. gallisepticum through an advanced immunoinformatics approach. As a result, the multi-epitope vaccine was constructed, which comprised potential T-cell and B-cell binding epitopes with appropriate adjuvants. The designed multi-epitope vaccine represented high antigenicity with viable physiochemical properties. The prospective three-dimensional structure of the epitope was predicted, refined, and validated. The molecular docking analysis of multi-epitope vaccine candidates with the chicken Toll-like receptor-5 predicted effective binding. Furthermore, codon optimization and in silico cloning ensured high expression. Thus, the present finding indicates that the engineered multi-epitope vaccine is structurally stable and can induce a strong immune response. Furthermore, the multi-epitope vaccine is suggested to be a suitable vaccine candidate for the M. gallisepticum infection due to its effective binding capacity and precise specificity.

Immunosecurity: immunomodulants enhance immune responses in chickens

The global population has increased with swift urbanization in developing countries, and it is likely to result in a high demand for animal-derived protein-rich foods. Animal farming has been constantly affected by various stressful conditions, which can be categorized into physical, environmental, nutritional, and biological factors. Such conditions could be exacerbated by banning on the use of antibiotics as a growth promoter together with a pandemic situation including, but not limited to, African swine fever, avian influenza, and foot-and-mouth disease. To alleviate these pervasive tension, various immunomodulants have been suggested as alternatives for antibiotics. Various studies have investigated how stressors (i.e., imbalanced nutrition, dysbiosis, and disease) could negatively affect nutritional physiology in chickens. Importantly, the immune system is critical for host protective activity against pathogens, but at the same time excessive immune responses negatively affect its productivity. Yet, comprehensive review articles addressing the impact of such stress factors on the immune system of chickens are scarce. In this review, we categorize these stressors and their effects on the immune system of chickens and attempt to provide immunomodulants which can be a solution to the aforementioned problems facing the chicken industry.