Recent advances in the research and development of human defensins

Human Defensins: Structure, Function, and Potential as Therapeutic Antimicrobial Agents with Highlights Against SARS CoV-2

The human defensins are a group of cationic antimicrobial peptides that range in size from 2 to 5 kDa and share a common structural motif of six disulphide-linked cysteines. Several naturally occurring human α- and β-defensins have been identified over the past two decades. They have a wide variety of antimicrobial effects, and their potential to avoid the development of resistance to antimicrobial treatment makes them attractive as therapeutic agents. Human defensins have recently been the focus of medical and molecular biology studies due to their promising application in medicine and the pharmaceutical industry. This work aims to provide a comprehensive summary of the current developments of human defensins, including their identification, categorization, molecular features, expression, modes of action, and potential application in medical settings. Current obstacles and future opportunities for using human defensins are also covered. Furthermore, we shed light on the potential of this class as an antiviral agent, particularly against SARS CoV-2, by providing an in silico-based investigation of their plausible mechanisms of action.

Functional characterization of novel anti-DEFA5 monoclonal antibody clones 1A8 and 4F5 in inflammatory bowel disease colitis tissues

BACKGROUND

The aberrant expression of α defensin 5 (DEFA5) protein in colonic inflammatory bowel diseases (IBDs) underlies the distinct pathogenesis of Crohn's colitis (CC). It can serve as a biomarker for differentiating CC from Ulcerative colitis (UC), particularly in Indeterminate colitis (IC) cases into UC and CC. We evaluated the specificity of commercially available anti-DEFA5 antibodies, emphasizing the need to further validate their appropriateness for a given application and highlighting the necessity for novel antibodies.

METHODS

We established two mice monoclonal DEFA5 antibody clones, 1A8 and 4F5, by immunizing mice with purified recombinant protein. We validated the specificity, sensitivity, and cross-reactivity of these antibodies in recognizing both endogenous and recombinant DEFA5 protein, especially for use in Immunohistochemistry (IHC), Western blot (WB), Immunoprecipitation (IP), and enzyme-linked immunosorbent assay (ELISA).

RESULTS

Clones 1A8 and 4F5 effectively recognized the endogenous DEFA5 in active human colon tissue from patients with diverticulitis (DV), UC, CC, and IC disease samples, as well as in transiently transfected HEK293T cells expressing DEFA5 with minimal non-confounding cross reactivity.

CONCLUSIONS

The 1A8 and 4F5 clones are useful for a wide variety of immunoassays, including WB, IHC, IP/WB, and ELISA. Their specificity enhances their potential as valuable tools for research applications in IBD colitis.

Preliminary evidence of immune infiltration and neutrophil degranulation in peripheral blood of non-obese OSA patients related to cognitive decline

Obstructive sleep apnea (OSA) patients have varying degrees of cognitive impairment, but the specific pathogenic mechanism is still unclear. Meanwhile, poor compliance with continuous positive airway pressure (CPAP) in OSA prompts better solutions. This study aimed to identify differentially expressed genes between the non-obese OSA patients and healthy controls, and to explore potential biomarkers associated with cognitive impairment. Cohorts of healthy control (n = 20) and non-obese, treatment-naïve OSA patients (n = 20) were recruited. We collected their peripheral blood mononuclear cells and neutrophils, and their cognitive performances were evaluated by the Montreal Cognitive Assessment (MoCA). The differentially expressed genes were identified by bioinformatic analysis and confirmed by PCR. Imbalanced immune cell proportions were assessed by Cibersort. Biomarkers related to enriched cellular pathways were measured by ELISA. OSA patients showed a significant decline in overall cognitive function and were associated with higher daytime sleepiness scores. Multiple signaling pathways were enriched in the non-obese OSA cohort, including upregulation of neutrophil-degranulation. Increased monocyte proportion and decreased NK cell proportion were figured out. The relevant genes, including upregulated defensin alpha 4 (DEFA4), haptoglobin (HP), survivin (BIRC5), and suppressed interferon gamma (IFNG) expression were detected. The relative expression of DEFA4 was significantly correlated with the MoCA score and sleep parameters. Biomarkers such as myeloperoxidase (MPO), H2O2, and lipocalin-2, as representatives of neutrophils' activation, elevated significantly in the OSA group. The data demonstrated a positive correlation between MPO and oxygen desaturation index (ODI) and a negative correlation between MPO and lowest oxygen saturation (LSaO2). The level of Lipocalin-2 was positively correlated with apnea-hypopnea index (AHI) and ODI and negatively correlated with LSaO2 and MoCA score. We also observed a negative correlation between H2O2 and mean oxygen saturation (MSaO2). Degranulation of neutrophils was activated in non-obese OSA patients without other complications. The process is related to OSA severity and cognitive impairment, implying its role in pathogenesis.

Synthesis of secretory leukocyte protease inhibitor using cell-free protein synthesis system

Secretory leukocyte protease inhibitor (SLPI) functions as a protease inhibitor that modulates excessive proteolysis in the body, exhibits broad-spectrum antimicrobial activity, regulates inflammatory responses, and plays an important role in the innate immunity. The purpose of the study was to artificially synthesize a SLPI, an antimicrobial peptide, and investigate its effect on antimicrobial activity against Porphyromonas gingivalis and interleukin-6 (IL-6) production. SLPI protein with a molecular weight of approximately 13 kDa was artificially synthesized using a cell-free protein synthesis (CFPS) system and investigated by western blotting and enzyme-linked immunosorbent assay (ELISA). Disulfide bond isomerase in the protein synthesis mixture increased the amount of SLPI synthesized. The synthesized SLPI (sSLPI) protein was purified and its antimicrobial activity was investigated based on the growth of Porphyromonas gingivalis and bacterial adhesion to oral epithelial cells. The effect of sSLPI on IL-6 production in human periodontal ligament fibroblasts (HPLFs) was examined by ELISA. Our results showed that sSLPI significantly inhibited the growth of Porphyromonas gingivalis and bacterial adhesion to oral epithelial cells and further inhibited IL-6 production by HPLFs. These results suggested that SLPI artificially synthesized using the CFPS system may play a role in the prevention of periodontal diseases through its antimicrobial and anti-inflammatory effects.

Anti-DEFA5 Monoclonal Antibody Clones 1A8 and 4F5 Immunoreactive Bioassay for Diagnosing Inflammatory Bowel Disease

Background

Robust evidence suggests that the aberrant expression of α defensin 5 protein (DEFA5) in colon inflammatory bowel diseases (IBDs) underlies the distinct pathogenesis of Crohn's colitis, can be exploited as a reliable diagnostic biomarker to differential diagnosis of Crohn's colitis (CC) from Ulcerative colitis (UC) in otherwise indeterminate colitis (IC). We evaluated the specificity of the commercially available anti-DEFA5 antibodies and showed further validation of their appropriateness for a given application is required.

Methods

We established two mouse monoclonal DEFA5 antibody clones 1A8 and 4F5 by immunizing the mice with purified recombinant protein and validated the specificity, selectivity and cross reactivity in recognizing the endogenous and recombinant DEFA5 protein, especially for Immunohistochemistry, Western blot, Immunoprecipitation, or enzyme-linked immunosorbent assay.

Results

Clones 1A8 and 4F5 recognized effectively the endogenous DEFA5 in active human diverticulitis (DV), UC, CC or IC disease samples, including transiently transfected HEK293T cells expressing DEFA5 with high degree of specificity and minimal non-confounding cross reactivity.

Conclusions

1A8 and 4F5 clones are worth studying in larger IBD cohorts to fully address whether DEFA5 expression may be used as a diagnostic biomarker to discrimination of the diagnosis of UC from CC or IC into authentic CC or UC or a colitis with different pathological characteristics.

Molecular dynamics simulations of human α-defensin 5 (HD5) crossing gram-negative bacterial membrane

Human α-defensin 5 (HD5) is a cationic antimicrobial peptide exhibiting a wide range of antimicrobial activities. It plays an important role in mucosal immunity of the small intestine. HD5 exerts its bactericidal activities through multiple mechanisms, one of which involves HD5 inducing the formation of pores in the bacterial membrane, subsequently allowing the peptide to enter the bacterial cytoplasm. Nevertheless, the precise molecular intricacies underlying its bactericidal mechanisms remain inadequately understood. In this work, the Potential of Mean Force (PMF) was computed to delve into the energetic properties governing the movement of HD5 across the lipopolysaccharide (LPS) membrane, which is a representative model of the gram-negative bacterial membrane. Our findings indicate that the most favorable free energy is attained when HD5 binds to the surface of the LPS membrane. This favorable interaction is primarily driven by the strong interactions between arginine residues in HD5 and the charged head groups of LPS, serving as the predominant forces facilitating the adhesion of HD5 to the membrane. Our analysis reveals that a dimeric form of HD5 alone is sufficient to create a water-filled channel in the membrane; however, achieving the complete lysis of the gram-negative bacterial membrane requires higher-order oligomerization of HD5. Our results suggest that HD5 employs the toroidal pore formation mechanism to disrupt the integrity of the LPS membrane. Furthermore, we identified that the primary energy barrier obstructing HD5 from traversing the membrane is localized within the hydrophobic core of the membrane, which is also observed for other defensins. Additionally, our study demonstrates that a mixture of HD5-LPS leads to a thinning of the membrane. Taken together, this work provides a deeper insight into the molecular intricacies governing the behavior of HD5 as it translocates through the gram-negative bacterial membrane.

β-defensin 2 synthesized by a cell-free protein synthesis system and encapsulated in liposomes inhibits adhesion of Porphyromonas gingivalis to oral epithelial cells

β-defensin 2 (BD-2), an antimicrobial peptide (AMP), is expressed by oral epithelial cells and plays an important role in innate immunity of the oral cavity. Cell-free protein synthesis (CFPS) systems have been studied for the synthesis of various proteins, however, the synthesis of BD-2 by a CFPS system has not been extensively explored. Liposomes have been developed as tools for drug delivery. A delivery of liposome-encapsulated AMP to oral epithelium may be useful to prevent oral infectious diseases. In the present study, we investigated the antimicrobial activity of the BD-2 protein, artificially synthesized using a CFPS system and encapsulated in liposomes. BD-2 protein was artificially synthesized using template DNA and a reconstituted CFPS system and was identified by western blotting. Bilayer liposomes were prepared using 1,2-dioleoyl-sn-glycero-3-phospho-choline and 3-sn-phosphatidylcholine from egg yolk. The artificially synthesized BD-2 was encapsulated in liposomes, collected by ultrafiltration, and detected by western blotting. Human oral epithelial cells were cultured with the liposome-encapsulated BD-2 and the concentration of BD-2 in the cell lysate of the culture with the synthesized BD-2 was higher than that of the control cultures. The antimicrobial activity of the synthesized BD-2 was investigated by an adhesion assay of Porphyromonas gingivalis to oral epithelial cells. The artificially synthesized BD-2 and its liposome significantly inhibited adhesion of P. gingivalis to oral epithelial cells. These results suggest that artificially synthesized BD-2 and liposome-encapsulated BD-2 show antimicrobial activity and can potentially play a role in oral healthcare for periodontal diseases.

Chemical Barrier Proteins in Human Body Fluids

Chemical barriers are composed of those sites of the human body where potential pathogens can contact the host cells. A chemical barrier is made up by different proteins that are part of the antimicrobial and immunomodulatory protein/peptide (AMP) family. Proteins of the AMP family exert antibacterial, antiviral, and/or antifungal activity and can modulate the immune system. Besides these proteins, a wide range of proteases and protease inhibitors can also be found in the chemical barriers maintaining a proteolytic balance in the host and/or the pathogens. In this review, we aimed to identify the chemical barrier components in nine human body fluids. The interaction networks of the chemical barrier proteins in each examined body fluid were generated as well.

β-Defensin: An adroit saviour in teleosts

β-Defensin (BD) is an important first line innate defense molecule with potent antimicrobial and immunomodulatory activities in fish. The signatures of β-defensins are the presence of a net cationic charge and three intramolecular disulfide bonds mediated by six conserved cysteines. It consists of three exons and two introns. The signal peptide is usually conserved and sequence divergence is mostly seen in mature peptide region. The diverse amino acid sequences of matured peptide contribute to a strong positive selection and broad-spectrum antimicrobial activity. It is constitutively expressed in both mucosal as well as systemic sites. Increased expression of β-defensin was mostly reported in bacterial and viral infections in fish. Its role during parasitic and fungal infections is yet to be investigated. β-Defensin isoforms such as BD-1, BD-2, BD-3, BD-4 and BD-5 can be witnessed even in early developmental days to different pathogenic exposure in fish. β-Defensins possess adjuvant properties to enhance antigen-specific immunity promoting both cellular and humoral immune response. It significantly reduces/increases bacterial colonization or viral copy numbers when overexpressed/knockdown. Based on its chemotactic and activating potentials, it can contribute to both innate and adaptive immune responses. With mediated expression, it can also control inflammation. It is potent governing resistance in early developmental days as well. Its expression in pituitary and testis suggests its participation in reproduction and endocrine regulation in fish. Overall, β-defensins is an important member of antimicrobial peptides (AMPs) with multifunctional role in general homeostasis and to pathogen exposure possessing tremendous therapeutic approaches.

Heterologous Expression and Functional Characterization of CAP18 from Oryctolagus cuniculus

BACKGROUND

Antimicrobial peptides belong to the innate defence system of creatures. These peptides attach to the bacterial membrane in order to die microorganisms by penetrating them. Hence, biotechnology researchers pay more attention to produce antimicrobial peptides for use in various fields. The studies showed that rabbit tissue with inflammation and skin ulcers would be producing CAP18 peptide, which belongs to the cathelicidin group.

METHODS

In this study, the optimized sequence of the cap18 gene was placed into the pPICZAα plasmid after the alpha-factor signal and transformed into Pichia pastoris (X-33 strain). Purification of the recombinant peptide was done based on its histidine tail at C-terminal, and western blotting method was used to demonstrate the purification of rCAP18. The antibacterial activity of the purified and desalted rCAP18 was investigated at different concentrations against pathogenic bacteria.

RESULTS

The maximum expression level of rCAP18 (17.5 kDa) was seen 90 h after induction of alcohol oxidase I (AOX1) promoter with methanol. The concentration of rCAP18 was 33 mg/L after purification with Ni-NTA Sepharose column. The function of rCAP18 (4.3, 5.7, 7 µg/ml) was investigated against Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Results showed that %CFU/cm² reached 28% after P. aeruginosa cells treatment with 7 μg/ml of rCAP18.

CONCLUSION

This study presented the findings related to heterologous expression of cap18 gene, and evaluation of rCAP18 antibacterial effects. Our results showed that rCAP18 plays a significant role in inhibiting bacterial growth, especially Gram-negative bacteria.

Relationship Between Human β-Defensin 2 and the Vaginal Environment

As one of the main antimicrobial peptides, human β-defensin 2 (HBD2) plays multiple roles in the lower genital tract. Based on the Nugent score as a diagnostic criterion for bacterial vaginosis, we sought to clarify the correlations among the Nugent score and interleukin-6 (IL-6) and HBD2 levels in vaginal secretions in association with various types of infection. Ninety-eight women were recruited for this study. Levels of HBD2 and IL-6 in vaginal wash were measured by enzyme-linked immunosorbent assays. According to the Nugent method, the number of Lactobacillus morphotypes per field of view was well correlated with the HBD2 level. The amount of HBD2 was also well correlated with the presence of Candida spp. (P < 0.01). In vitro experiments revealed that the expression of HBD2 from the human vaginal epithelial cell line, VK2/E6E7, was induced by the addition of heat-killed C. albicans (HKCA). The addition of HKCA induced expression of Dectin-1 mRNA. A luciferase assay for nuclear factor kappa-light-chain-enhancer of activated B cells (NFκB) responsive elements showed that HKCA activated NF-κB signaling. These results suggested that C. albicans induced the activation of Dectin-1 and (NF-κB) signaling, resulting in HBD2 expression. In conclusion, the expression of HBD2 positively correlated with the presence of Lactobacillus and Candida spp.

Identification and characterization of three novel antimicrobial peptides from Acipenser dabryanus

Antimicrobial peptides (AMPs) play essential roles in the innate immune system to protect against a wide variety of pathogens in aquatic environments. In this study, three very important AMPs, cathelicidin, hepcidin and defensin, were identified in the critically endangered Acipenser dabryanus. The full-length cDNA sequences of these three AMPs were identified from transcriptome sequencing and the rapid amplification of cDNA ends (RACE) technique. Phylogenetic analysis showed that cathelicidin formed a clade with the other members of the cathelicidin family, and similar results were obtained for hepcidin. The A. dabryanus β-defensin belonged to the fish class 2 β-defensins. A tissue distribution study showed that the three AMP transcripts could be detected constitutively in various tissues. The highest expression levels of cathelicidin and hepcidin were found in the liver, while defensin was primarily expressed in the skin. Bacterial challenge in vivo revealed significant changes in the gene expression of the three AMPs at both mucosal sites and systemic sites. Striking upregulation of cathelicidin and hepcidin was observed in the skin at 12 h post-challenge, with increases of more than 7000-fold and 1000-fold, respectively, compared to the control, and the expression of defensin mRNA was remarkably elevated in the hindgut (by 230-fold at 6 h post-challenge). Moreover, according to the expression profiles of the AMPs post-challenge, we found that the mucosal immune response occurred earlier than the systemic immune response following bacterial infection. Our results suggest that these three novel AMPs may play important roles in the innate immune system of A. dabryanus to protect against invading pathogens, especially during the mucosal immune response.

MC1R: Front and Center in the Bright Side of Dark Eumelanin and DNA Repair

Melanin, the pigment produced by specialized cells, melanocytes, is responsible for skin and hair color. Skin pigmentation is an important protective mechanism against the DNA damaging and mutagenic effects of solar ultraviolet radiation (UV). It is acknowledged that exposure to UV is the main etiological environmental factor for all forms of skin cancer, including melanoma. DNA repair capacity is another major factor that determines the risk for skin cancer. Human melanocytes synthesize eumelanin, the dark brown form of melanin, as well as pheomelanin, which is reddish-yellow in color. The relative rates of eumelanin and pheomelanin synthesis by melanocytes determine skin color and the sensitivity of skin to the drastic effects of solar UV. Understanding the complex regulation of melanocyte function and how it responds to solar UV has a huge impact on developing novel photoprotective strategies to prevent skin cancer, particularly melanoma, the most fatal form, which originates from melanocytes. This review provides an overview of the known differences in the photoprotective effects of eumelanin versus pheomelanin, how these two forms of melanin are regulated genetically and biochemically, and their impact on the DNA damaging effects of UV exposure. Additionally, this review briefly discusses the role of paracrine factors, focusing on α-melanocortin (α-melanocyte stimulating hormone; α-MSH), in regulating melanogenesis and the response of melanocytes to UV, and describes a chemoprevention strategy based on targeting the melanocortin 1 receptor (MC1R) by analogs of its physiological agonist α-MSH.

Hemolymph defensin from the hard tick Haemaphysalis longicornis attacks Gram-positive bacteria

Ticks are key vectors of some important diseases of humans and animals. Although they are carriers of disease agents, the viability and development of ticks are not harmed by the infectious agents due to their innate immunity. Antimicrobial peptides directly protect hosts against pathogenic agents such as viruses, bacteria, and parasites. Among the identified and characterized antimicrobial peptides, defensins have been considerably well studied. Defensins are commonly found among fungi, plants, invertebrates, and vertebrates. The sequence of the tick hemolymph defensin (HEdefensin) gene from the hard tick Haemaphysalis longicornis was analyzed after identification and cloning from a cDNA library. HEdefensin has a predicted molecular mass of 8.15 kDa including signal peptides and a theoretical isoelectric point of 9.48. Six cysteine residues were also identified in the amino acids. The synthetic HEdefensin peptide only showed antibacterial activity against Gram-positive bacteria such as Micrococcus luteus. A fluorescence propidium iodide exclusion assay also showed that HEdefensin increased the membrane permeability of M. luteus. Additionally, an indirect fluorescent antibody test showed that HEdefensin binds to M. luteus. These results suggested that HEdefensin strongly affects the innate immunity of ticks against Gram-positive bacteria.

A subchronic feeding safety evaluation of transgenic milk containing human β-defensin 3 on reproductive system of C57BL/6J mouse

Bovine mastitis is an infectious disease of the mammary gland which has been generally treated by antibiotic delivery. While the increasing drug-resistant bacteria and the high consumption of the antibiotic had become a noticeable concern. In a previous study, a mammary special vector expressing human β-defensin 3 (hBD3) was transfected into bovine fetal fibroblasts to produce mastitis-resistant bovine. This investigation focused on potential unintended effects of transgenic milk containing hBD3 produced by these mastitis-resistant bovine on the reproductive system of C57BL/6J mice. Mice were fed with diets containing transgenic milk or conventional milk, nutritionally balanced to an AIN93G diet for 90 days, and non-milk diet was selected as the negative group. The reproductive system was given special attention including reproductive organ/body ratios, necropsy and histopathology, serum sex hormone, sperm parameters, estrus cycle and the expression level of some specific genes which could indicate the development and function of reproductive system. No diet-related significant differences were observed among three groups in this 90-day feeding study. The results indicated that hBD3 milk does not appear to exert any effect on the reproductive system in C57BL/6J rats compared with conventional milk or the control diet.

Efficient production of a recombinant Venerupis philippinarum defensin (VpDef) in Pichia pastoris and characterization of its antibacterial activity and stability

VpDef is a novel defensin isolated from the clam Venerupis philippinarum. Previously it was expressed in Escherichia coli; however, the E. coli-derived recombinant VpDef did not show effective antimicrobial activity against Staphyloccocus aureus or the Gram-negative bacteria tested. As such, the goal of this study was to design, express, and purify a recombinant VpDef (rVpDef) in Pichia pastoris and to determine its antibacterial potency and stability. A 6.9 KDa rVpDef was successfully expressed as a secreted peptide in P. pastoris, and the amount of rVpDef accumulation was shown to reach as high as approximate 60 μg per 1 ml of culture medium only after an initial optimization was performed. The purified rVpDef demonstrated a broad antibacterial spectrum and was active against six typical common bacteria, both Gram-positive and Gram-negative. A minimal inhibition concentration of as low as 50 μg/ml was observed for rVpDef against the growth of E. coli O157 (ATCC 35150). Moreover, rVpDef was tolerant to temperature shock and proteinase digestion and maintained a high stability over a relatively broad pH range. In addition, rVpDef had a low hemolytic activity against rabbit erythrocytes. Taken together, this study demonstrated that rVpDef could be produced in a large-scale manner in P. pastoris and has a good antibacterial activity and suitable stability. This is the first report on heterologous expression of a biologically active VpDef in P. pastoris, supporting its use for both research and application purposes.

Human Beta Defensin 2 Selectively Inhibits HIV-1 in Highly Permissive CCR6⁺CD4⁺ T Cells

Chemokine receptor type 6 (CCR6)⁺CD4⁺ T cells are preferentially infected and depleted during HIV disease progression, but are preserved in non-progressors. CCR6 is expressed on a heterogeneous population of memory CD4⁺ T cells that are critical to mucosal immunity. Preferential infection of these cells is associated, in part, with high surface expression of CCR5, CXCR4, and α4β7. In addition, CCR6⁺CD4⁺ T cells harbor elevated levels of integrated viral DNA and high levels of proliferation markers. We have previously shown that the CCR6 ligands MIP-3α and human beta defensins inhibit HIV replication. The inhibition required CCR6 and the induction of APOBEC3G. Here, we further characterize the induction of apolipoprotein B mRNA editing enzyme (APOBEC3G) by human beta defensin 2. Human beta defensin 2 rapidly induces transcriptional induction of APOBEC3G that involves extracellular signal-regulated kinases 1/2 (ERK1/2) activation and the transcription factors NFATc2, NFATc1, and IRF4. We demonstrate that human beta defensin 2 selectively protects primary CCR6⁺CD4⁺ T cells infected with HIV-1. The selective protection of CCR6⁺CD4⁺ T cell subsets may be critical in maintaining mucosal immune function and preventing disease progression.

Characterization and antiviral activity of a newly identified defensin-like peptide, HEdefensin, in the hard tick Haemaphysalis longicornis

Tick defensins are antimicrobial peptides that play a major role in the innate immunity of ticks by providing a direct antimicrobial defense. In this study, we identified and characterized a defensin-like encoding gene, HEdefensin, from the expressed sequence tags (EST) database of hemolymph from the hard tick Haemaphysalis longicornis. Expression of the gene in whole adult ticks and in different organs was upregulated during blood feeding, though not after Langat virus (LGTV) challenge. A synthetic HEdefensin peptide demonstrated significant virucidal activity against LGTV but not against an adenovirus in co-incubation virucidal assays. Moreover, the RNAi-mediated gene silencing of HEdefensin did not significantly affect the virus titer as compared to the control group. The data reported here have established the in vitro virucidal activity of the peptide against LGTV. However, its role in the innate antiviral immunity of H. longicornis remains to be explored, and further studies are needed to fully evaluate the potential biological activities of the peptide against bacteria, fungi or parasites.

Studies on the Interaction of Tumor-Derived HD5 Alpha Defensins with Adenoviruses and Implications for Oncolytic Adenovirus Therapy

Defensins are small antimicrobial peptides capable of neutralizing human adenovirus (HAdV) in vitro by binding capsid proteins and blocking endosomal escape of virus. In humans, the alpha defensin HD5 is produced by specialized epithelial cells of the gastrointestinal and genito-urinary tracts. Here, we demonstrate, using patient biopsy specimens, that HD5 is also expressed as an active, secreted peptide by epithelial ovarian and lung cancer cells in situ This finding prompted us to study the role of HD5 in infection and spread of replication-competent, oncolytic HAdV type 3 (HAdV3). HAdV3 produces large amounts of penton-dodecahedra (PtDd), virus-like particles, during replication. We have previously shown that PtDd are involved in opening epithelial junctions, thus facilitating lateral spread of de novo-produced virions. Here, we describe a second function of PtDd, namely, the blocking of HD5. A central tool to prove that viral PtDd neutralize HD5 and support spread of progeny virus was an HAdV3 mutant virus in which formation of PtDd was disabled (mut-Ad3GFP, where GFP is green fluorescent protein). We demonstrated that viral spread of mut-Ad3GFP was blocked by synthetic HD5 whereas that of the wild-type (wt) form (wt-Ad3GFP) was only minimally impacted. In human colon cancer Caco-2 cells, induction of cellular HD5 expression by fibroblast growth factor 9 (FGF9) significantly inhibited viral spread and progeny virus production of mut-Ad3GFP but not of wt-Ad3GFP. Finally, the ectopic expression of HD5 in tumor cells diminished the in vivo oncolytic activity of mut-Ad3GFP but not of wt-Ad3GFP. These data suggest a new mechanism of HAdV3 to overcome innate antiviral host responses. Our study has implications for oncolytic adenovirus therapy.IMPORTANCE Previously, it has been reported that human defensin HD5 inactivates specific human adenoviruses by binding to capsid proteins and blocking endosomal escape of virus. The central new findings described in our manuscript are the following: (i) the discovery of a new mechanism used by human adenovirus serotype 3 to overcome innate antiviral host responses that is based on the capacity of HAdV3 to produce subviral penton-dodecahedral particles that act as decoys for HD5, thus preventing the inactivation of virus progeny produced upon replication; (ii) the demonstration that ectopic HD5 expression in cancer cells decreases the oncolytic efficacy of a serotype 5-based adenovirus vector; and (iii) the demonstration that epithelial ovarian and lung cancers express HD5. The study improves our understanding of how adenoviruses establish infection in epithelial tissues and has implications for cancer therapy with oncolytic adenoviruses.

Involvement of β-defensin 130 (DEFB130) in the macrophage microbicidal mechanisms for killing Plasmodium falciparum

Understanding the molecular defense mechanism of macrophages and identifying their effector molecules against malarial parasites may provide important clues for the discovery of new therapies. To analyze the immunological responses of malarial parasite-induced macrophages, we used DNA microarray technology to examine the gene profile of differentiated macrophages phagocytizing Plasmodium falciparum-parasitized erythrocytes (iRBC). The transcriptional gene profile of macrophages in response to iRBCs represented 168 down-regulated genes, which were mainly involved in the cellular immune response, and 216 upregulated genes, which were involved in cellular proteolysis, growth, and adhesion. Importantly, the specific upregulation of β-defensin 130 (DEFB130) in these macrophages suggested a possible role for DEFB130 in malarial parasite elimination. Differentiated macrophages phagocytizing iRBCs exhibited an increase in intracellular DEFB130 levels and DEFB130 appeared to accumulate at the site of iRBC engulfment. Transfection of esiRNA-mediated knockdown of DEFB130 into macrophages resulted in a remarkable reduction in their antiplasmodial activity in vitro. Furthermore, DEFB130 synthetic peptide exhibited a modest toxic effect on P. falciparum in vitro and P. yoelii in vivo, unlike scrambled DEFB130 peptide, which showed no antiplasmodial activity. Together, these results suggest that DEFB130 might be one of the macrophage effector molecules for eliminating malarial parasites. Our data broaden our knowledge of the immunological response of macrophages to iRBCs and shed light on a new target for therapeutic intervention.

Gomesin acts in the immune system and promotes myeloid differentiation and monocyte/macrophage activation in mouse

Due to the cytotoxic effect of antimicrobial peptides (AMP) against several microorganism and tumor cells has been proposed their association with the immune system. However, just a few reports have shown this relationship. In this study, mice were treated with gomesin, a β-hairpin AMP that exhibit high cytotoxicity against bacterial and tumor cells. Different effects in the immune system were observed, such as, decrease of CD3⁺ in T lymphocytes (Control: 17.7±1.4%; Gomesin: 7.67±1.2%) and in hematopoietic progenitors and increase of hematopoietic stem cell (Control: 0.046±0.004%; Gomesin: 0.067±0.003%), B220⁺ B lymphocytes (Control: 38.63±1.5%; Gomesin: 47.83±0.48%), and Mac-1⁺F4/80⁺ macrophages (Control: 11.76±3.4%; Gomesin: 27.13±4.0%). Additionally, macrophage increase was accompanied by an increase of macrophage phagocytosis (Control 20.85±1.53; Gomesin 31.32±1 Geometric mean), interleukin 6 (Control: 47.24±1.9ng/mL; Gomesin: 138.68±33.68ng/mL) and monocyte chemoattractant protein-1 (Control: 0.872±0.093ng/mL; Gomesin: 1.83±0.067ng/mL). Thus, this report showed immunomodulatory activity of gomesin in the immune system of mice.

Defensins: The Case for Their Use against Mycobacterial Infections

Human tuberculosis remains a huge global public health problem with an estimated 1/3rd of the population being infected. Defensins are antibacterial cationic peptides produced by a number of cell types, most notably neutrophil granulocytes and epithelial cells. All three defensin types (α-, β-, and θ-defensins) have antibacterial activities, mainly through bacterial membrane permeabilization. Defensins are effective against Gram-negative and Gram-positive bacteria including mycobacteria and are active both intra- and extracellularly. Mycobacterial resistance has never been demonstrated although the mprF gene encoding resistance in Staphylococcus aureus is present in the Mycobacterium tuberculosis genome. In addition to their antibacterial effect, defensins are chemoattractants for macrophages and neutrophils. There are many cases for their use for therapy or prophylaxis in tuberculosis as well. In conclusion, we propose that there is considerable scope and potential for exploring their use as therapeutic/prophylactic agents and more comprehensive survey of defensins from different species and their bioactivity is timely.

An overview of antifungal peptides derived from insect

Fungi are not classified as plants or animals. They resemble plants in many ways but do not produce chlorophyll or make their own food photosynthetically like plants. Fungi are useful for the production of beer, bread, medicine, etc. More complex than viruses or bacteria; fungi can be destructive human pathogens responsible for various diseases in humans. Most people have a strong natural immunity against fungal infection. However, fungi can cause diseases when this immunity breaks down. In the last few years, fungal infection has increased strikingly and has been accompanied by a rise in the number of deaths of cancer patients, transplant recipients, and acquired immunodeficiency syndrome (AIDS) patients owing to fungal infections. The growth rate of fungi is very slow and quite difficult to identify. A series of molecules with antifungal activity against different strains of fungi have been found in insects, which can be of great importance to tackle human diseases. Insects secrete such compounds, which can be peptides, as a part of their immune defense reactions. Active antifungal peptides developed by insects to rapidly eliminate infectious pathogens are considered a component of the defense munitions. This review focuses on naturally occurring antifungal peptides from insects and their challenges to be used as armaments against human diseases.

Defensin gene variation and HIV/AIDS: a comprehensive perspective needed

Both α- and β-defensins have anti-human immunodeficiency virus activity. These defensins achieve human immunodeficiency virus inhibition through a variety of mechanisms, including direct binding with virions, binding to and modulation of host cell-surface receptors with disruption of intracellular signaling, and functioning as chemokines or cytokines to augment and alter adaptive immune responses. Polymorphisms in the defensin genes have been associated with susceptibility to human immunodeficiency virus infection and disease progression. However, the roles that these defensins and their genetic polymorphisms have in influencing human immunodeficiency virus/acquired immunodeficiency syndrome outcomes are not straightforward and, at times, appear contradictory. Differences in populations, study designs, and techniques for genotyping defensin gene polymorphisms may have contributed to this lack of clarity. In addition, a comprehensive approach, where both subfamilies of defensins and their all-inclusive genetic polymorphism profiles are analyzed, is lacking. Such an approach may reveal whether the human immunodeficiency virus inhibitory activities of α- and β-defensins are based on parallel or divergent mechanisms and may provide further insights into how the genetic predisposition for susceptibility or resistance to human immunodeficiency virus/acquired immunodeficiency syndrome is orchestrated between these molecules.

Virucidal activity of Haemaphysalis longicornis longicin P4 peptide against tick-borne encephalitis virus surrogate Langat virus

BACKGROUND

Longicin is a defensin-like peptide, identified from the midgut epithelium of hard tick Haemaphysalis longicornis. Several studies have already shown the antimicrobial and parasiticidal activities of longicin peptide and one of its synthetic partial analogs, longicin P4. In this study, longicin peptides were tested for potential antiviral activity against Langat virus (LGTV), a tick-borne flavivirus.

METHODS

Longicin P1 and P4 peptides were chemically synthesized. Antiviral activity of the longicin peptides against LGTV was evaluated through in vitro virucidal assays, wherein the antiviral efficacy was determined by reduction in number of viral foci and virus yield. Additionally, longicin P4 was also tested for its activity against human adenovirus, a non-enveloped virus. Lastly, to assess the importance of longicin on the innate antiviral immunity of H. longicornis ticks, gene silencing through RNAi was performed.

RESULTS

Longicin P4 produced significant viral foci reduction and lower virus yield against LGTV, while longicin P1 failed to demonstrate the same results. Conversely, both longicin partial analogs (P1 and P4) did not show significant antiviral activity when tested on adenovirus. In addition, longicin-silenced ticks showed significantly higher virus titer after 7 days post-infection but a significantly lower titer was detected after an additional 14 days of observation as compared to the Luc dsRNA-injected ticks. Mortality in both groups did not show any significant difference.

CONCLUSION

Our results suggest that longicin P4 has in vitro antiviral activity against LGTV but not against a non-enveloped virus such as adenovirus. Likewise, though most cationic antimicrobial peptides like longicin act directly on target membranes, the exact mechanism of membrane targeting of longicin P4 in enveloped viruses, such as LGTV, requires further investigation. Lastly, while the in vitro virucidal capacity of longicin P4 was confirmed in this study, the role of the endogenous tick longicin in the antiviral defense of H. longicornis against LGTV still remains to be demonstrated.

The association of defensin HNP-2 with negatively charged membranes: A combined fluorescence and linear dichroism study

The association of defensin HNP-2 with negatively charged membranes has been studied using a new approach that combines fluorescence and linear dichroism (LD) spectroscopies with simulated LD spectra in order to characterise the binding kinetics and bound configurations of the peptide. Binding to membranes composed of mixtures of diacylglycerophosphocholines (PC) with either diacylglycerophosphoglycerol (PG) or diacylglycerophosphoserine (PS) was conducted at lipid:peptide ratios that yielded binding, but not membrane fusion. HNP-2 association with membranes under these conditions was a 2 stage-process, with both stages exhibiting first order kinetics. The fast initial step, with a half-life of < 1 min, was followed by a slower step with a half-life of > 3 min. Conversion between the states was estimated to have an enthalpy of activation of approximately 10 kJ mol(-1) and an entropy of activation of -0.2 kJ K mol(-1). LD spectra corresponding to each of the membrane bound states were generated by non-linear regression using a standard kinetic model. These spectra are interpreted in comparison with spectra calculated using the program Dichrocalc and reveal that the peptide associates with membranes in a small number of stable configurations. All of these configurations have a significant proportion of β-sheet structure residing in the plane of the membrane. Two configurations support structures previously proposed for defensins in membranes.

Escherichia coli Pyruvate Dehydrogenase Complex Is an Important Component of CXCL10-Mediated Antimicrobial Activity

Chemokines are best recognized for their role within the innate immune system as chemotactic cytokines, signaling and recruiting host immune cells to sites of infection. Certain chemokines, such as CXCL10, have been found to play an additional role in innate immunity, mediating CXCR3-independent killing of a diverse array of pathogenic microorganisms. While this is still not clearly understood, elucidating the mechanisms underlying chemokine-mediated antimicrobial activity may facilitate the development of novel therapeutic strategies effective against antibiotic-resistant Gram-negative pathogens. Here, we show that CXCL10 exerts antibacterial effects on clinical and laboratory strains of Escherichia coli and report that disruption of pyruvate dehydrogenase complex (PDHc), which converts pyruvate to acetyl coenzyme A, enables E. coli to resist these antimicrobial effects. Through generation and screening of a transposon mutant library, we identified two mutants with increased resistance to CXCL10, both with unique disruptions of the gene encoding the E1 subunit of PDHc, aceE. Resistance to CXCL10 also occurred following deletion of either aceF or lpdA, genes that encode the remaining two subunits of PDHc. Although PDHc resides within the bacterial cytosol, electron microscopy revealed localization of immunogold-labeled CXCL10 to the bacterial cell surface in both the E. coli parent and aceE deletion mutant strains. Taken together, our findings suggest that while CXCL10 interacts with an as-yet-unidentified component on the cell surface, PDHc is an important mediator of killing by CXCL10. To our knowledge, this is the first description of PDHc as a key bacterial component involved in the antibacterial effect of a chemokine.

Relative quantification of human β-defensins by a proteomics approach based on selected reaction monitoring

RATIONALE

A targeted proteomics method based on selected reaction monitoring (SRM) is a relevant approach for the analysis of multiple analytes in biological samples. Defensins are phylogenetically conserved small antimicrobial peptides contributing to innate host defense and exhibiting low immunogenicity, resistance to proteolysis and a broad range of antimicrobial activities. The goal of the present study was to develop and optimize SRM-based targeted proteomics methods for the detection of human β-defensins 1-4 in various biological fluids.

METHODS

An SRM-based targeted proteomics method was developed and validated for the detection of human β-defensins 1-4. The supernatants of resting and IL-1β-stimulated Caco2, HT-29 and SW-1116 colonic epithelial cells (CEC), cell lysates of CECs and tear samples of human healthy individuals were analyzed and the feasibility of the developed method was validated by ELISA and dot-blot analysis complemented by RT-qPCR.

RESULTS

Our results demonstrate that the developed SRM method offers an alternative approach for the cost-effective and rapid analysis of human β-defensins in samples with biological relevance.

CONCLUSIONS

A semi-quantitative targeted mass spectrometry method was developed and validated for the relative quantification of β-defensins 1-4 in cell culture supernatants and body fluid analyses.

Antimicrobial proteins and peptides in human lung diseases: A friend and foe partnership with host proteases

Lung antimicrobial proteins and peptides (AMPs) are major sentinels of innate immunity by preventing microbial colonization and infection. Nevertheless bactericidal activity of AMPs against Gram-positive and Gram-negative bacteria is compromised in patients with chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF) and asthma. Evidence is accumulating that expression of harmful human serine proteases, matrix metalloproteases and cysteine cathepsins is markedely increased in these chronic lung diseases. The local imbalance between proteases and protease inhibitors compromises lung tissue integrity and function, by not only degrading extracellular matrix components, but also non-matrix proteins. Despite the fact that AMPs are somewhat resistant to proteolytic degradation, some human proteases cleave them efficiently and impair their antimicrobial potency. By contrast, certain AMPs may be effective as antiproteases. Host proteases participate in concert with bacterial proteases in the degradation of key innate immunity peptides/proteins and thus may play immunomodulatory activities during chronic lung diseases. In this context, the present review highlights the current knowledge and recent discoveries on the ability of host enzymes to interact with AMPs, providing a better understanding of the role of human proteases in innate host defense.

Diagnostic model of saliva peptide finger print analysis of oral squamous cell carcinoma patients using weak cation exchange magnetic beads

Whole saliva (WS) was used for diagnosis of oral squamous cell carcinoma (OSCC); two polypeptides may be used for OSCC diagnosis.

Saliva diagnostics utilizing nanotechnology and molecular technologies to detect oral squamous cell carcinoma (OSCC) has become an attractive field of study. However, no specific methods have been established. To refine the diagnostic power of saliva peptide fingerprints for the early detection of OSCC, we screened the expression spectrum of salivary peptides in 40 T1 stage OSCC patients (and healthy controls) using MALDI-TOF-MS combined with magnetic beads. Fifty proteins showed significantly different expression levels in the OSCC samples (P<0.05). Potential biomarkers were also predicted. The novel diagnostic proteomic model with m/z peaks of 1285.6 Da and 1432.2 Da are of certain value for early diagnosis of OSCC.

Utilization of plant-derived recombinant human β-defensins (hBD-1 and hBD-2) for averting salmonellosis

We describe the use of plant-made β-defensins as effective antimicrobial substances for controlling salmonellosis, a deadly infection caused by Salmonella typhimurium (referred to further as S. typhi). Human β-defensin-1 (hBD-1) and -2 (hBD-2) were expressed under the control of strong constitutive promoters in tobacco plants, and bio-active β-defensins were successfully extracted. In the in vitro studies, enriched recombinant plant-derived human β-defensin-1 (phBD-1) and -2 (phBD-2) obtained from both T1 and T2 transgenic plants showed significant antimicrobial activity against Escherichia coli and S. typhi when used individually and in various combinations. The 2:1 peptide combination of phBD-1:phBD-2 with peptides isolated from T1-and T2-generation plants reduced the growth of S. typhi by 96 and 85 %, respectively. In vivo studies employing the mouse model (Balb/c) of Salmonella infection clearly demonstrated that the administration of plant-derived defensins individually and in different combinations enhanced the mean survival time of Salmonella-infected animals. When treatment consisted of the 2:1 phBD-1:phBD-2 combination, approximately 50 % of the infected mice were still alive at 206 h post-inoculation; the lowest number of viable S. typhi was observed in the liver and spleen of infected animals. We conclude that plant-made recombinant β-defensins (phBD-1 and phBD-2) are promising antimicrobial substances and have the potential to become additional tools against salmonellosis, particularly when used in combination.

Expression of porcine protegrin-1 in Pichia pastoris and its anticancer activity in vitro

Protegrin-1 (PG-1), a β-hairpin antimicrobial peptide (AMP), is amongst the shortest AMPs in sequence length while remaining active against a variety of microorganisms. The aim of this study was produce recombinant PG-1 and investigate its anticancer activity. A DNA sequence encoding the mature PG-1, fused with a 6His-tag, was cloned into the pPICZα-A vector and transformed into Pichia pastoris. Expression was induced following culture for ~96 h with 1% methanol at 28°C, and ~15.6 mg PG-1 was expressed in 100 ml culture medium. Following purification using a Ni-chelating Sepharose column, ~20 mg pure active PG-1 was obtained from 500 ml culture broth supernatant. The expressed PG-1/6His exhibited strong dose- and time-dependent anticancer activity against HepG2 cells in vitro.

ΔNp63 isoform-mediated β-defensin family up-regulation is associated with (lymph)angiogenesis and poor prognosis in patients with squamous cell carcinoma

Beside a role in normal development/differentiation, high p63 immunoreactivity is also frequently observed in squamous cell carcinoma (SCC). Due to the complexity of the gene, the role of each p63 isotype in tumorigenesis is still confusing. Constitutively produced or induced in inflammatory conditions, human beta-defensins (HβDs) are cationic peptides involved in host defenses against bacteria, viruses and fungi. Here, we investigated both the role of p63 proteins in the regulation of HβDs and the implication of these antimicrobial peptides in tumor (lymph)angiogenesis. Thus, in contrast to TAp63 isotypes, we observed that ΔNp63 proteins (α, β, γ) induce HβD1, 2 and 4 expression. Similar results were observed in cancer tissues and cell lines. We next demonstrated that ΔNp63-overexpressing SCC are associated with both a poor prognosis and a high tumor vascularisation and lymphangiogenesis. Moreover, we showed that HβDs exert a chemotactic activity for (lymphatic) endothelial cells in a CCR6-dependent manner. The ability of HβDs to enhance (lymph)angiogenesis in vivo was also evaluated. We observed that HβDs increase the vessel number and induce a significant increase in relative vascular area compared to negative control. Taken together, the results of this study suggest that ΔNp63-regulated HβD could promote tumor (lymph)angiogenesis in SCC microenvironment.

The first report of a Pelecaniformes defensin cluster: characterization of β-defensin genes in the crested ibis based on BAC libraries

Defensins play a key role in the innate immunity of various organisms. Detailed genomic studies of the defensin cluster have only been reported in a limited number of birds. Herein, we present the first characterization of defensins in a Pelecaniformes species, the crested ibis (Nipponia nippon), which is one of the most endangered birds in the world. We constructed bacterial artificial chromosome libraries, including a 4D-PCR library and a reverse-4D library, which provide at least 40 equivalents of this rare bird's genome. A cluster including 14 β-defensin loci within 129 kb was assigned to chromosome 3 by FISH, and one gene duplication of AvBD1 was found. The ibis defensin genes are characterized by multiform gene organization ranging from two to four exons through extensive exon fusion. Splicing signal variations and alternative splice variants were also found. Comparative analysis of four bird species identified one common and multiple species-specific duplications, which might be associated with high GC content. Evolutionary analysis revealed birth-and-death mode and purifying selection for avian defensin evolution, resulting in different defensin gene numbers among bird species and functional conservation within orthologous genes, respectively. Additionally, we propose various directions for further research on genetic conservation in the crested ibis.

Potential roles of placental human beta-defensin-3 and apolipoprotein B mRNA-editing enzyme catalytic polypeptide 3G in prevention of intrauterine transmission of hepatitis B virus

Approximately 5% of newborns were infected by hepatitis B virus (HBV) via intrauterine transmission and this is the main reason for high prevalence of HBV in endemic regions. However, the mechanisms by which intrauterine transmission is avoided in most cases remain elusive and placental natural anti-microbial factors may play a role in the prevention of HBV intrauterine transmission. The expression levels of human β-defensin-3 (HBD-3), apolipoprotein B mRNA-editing enzyme catalytic polypeptide 3G (A3G) and mannose binding lectin (MBL) were determined in the placenta of 30 HBV-seronegative pregnant women (controls), 7 HBV-seropositive pregnant women with infants infected via intrauterine transmission (infected group) and 30 HBV-seropositive pregnant women with non-infected infants (non-infected group). The expression of HBD-3, A3G, and MBL of placental trophoblast cell line Swan71 was determined after exposed to HBV. There were significant differences in placental HBD-3 and A3G levels among three groups, but the expression of MBL did not significantly differ. The expressions of HBD-3 and A3G were higher in non-infected group than controls and infected group, but not significantly different between infected group and controls. The exposure to HBV increased significantly the expression of HBD-3, A3G, and MBL by Swan 71. It may be concluded HBV up-regulates HBD-3 and A3G expression in vivo and in vitro in placental trophoblast and lack of this up-regulation is possibly associated with intrauterine transmission of HBV.

Relevance of α-defensins (HNP1-3) and defensin β-1 in diabetes

AIM: To investigate the genetic background of human defensin expression in type 1 and 2 diabetes.

METHODS: Associations between DEFA1/DEFA3 gene copy number polymorphism and diabetes as well as between the promoter polymorphisms of DEFB1 and diabetes were studied. The copy number variation of the DEFA1/DEFA3 genes was determined in 257 diabetic patients (117 patients with type 1 and 140 with type 2 diabetes). The control group consisted of 221 age- and gender-matched healthy blood donors. The cumulative copy numbers of the DEFA1/DEFA3 genes were detected by using quantitative PCR analysis. To evaluate the HNP 1-3 (human neutrophil peptide 1-3 or α-defensin) levels in the circulation, plasma HNP 1-3 concentrations were measured by ELISA. The expression of DEFA1/A3 in peripheral leukocytes of the diabetic patients was measured by quantitative RT PCR analysis. Three SNPs of the human DEFB1 (human defensin β-1) gene: DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946) were genotyped by Custom TaqMan^® Real Time PCR assay.

RESULTS: Significant differences were observed in HNP1-3 levels between the healthy subjects and both groups of diabetic patients. The mean ± SE was 28.78 ± 4.2 ng/mL in type 1 diabetes, and 29.82 ± 5.36 ng/mL in type 2 diabetes, vs 11.94 ± 2.96 ng/mL in controls; P < 0.01 respectively. There was no significant difference between patients with type 1 and type 2 diabetes in the high plasma concentrations of HNP1-3. The highest concentrations of α-defensin were found in diabetic patients with nephropathy (49.4 ± 4.8 ng/mL), neuropathy (38.7 ± 4.8 ng/mL) or cardiovascular complications (45.6 ± 1.45 ng/L). There was no significant difference in the cumulative copy numbers of DEFA1/DEFA3 genes between controls and patients, or between patients with the two types of diabetes. Comparisons of HNP 1-3 plasma level and DEFA1/A3 copy number of the same patient did not reveal significant relationship between defensin-α levels and the gene copy numbers (r² = 0.01). Similarly, no positive correlation was observed between the copy numbers and the mRNA expression levels of DEFA1/A3. Regarding the C-44G polymorphism of DEFB1, the GG “protective” genotype was much less frequent (1%-2%) among both groups of patients than among controls (9%).

CONCLUSION: Elevated HNP1-3 levels in diabetes are independent of DEFA1/DEFA3 copy numbers, but GG genotype of C-44G SNP in DEFB1 gene may result in decreased defensin β-1 production.

Melanocortins and the melanocortin 1 receptor, moving translationally towards melanoma prevention

Beginning in the last decade of the twentieth century, the fields of pigment cell research and melanoma have witnessed major breakthroughs in the understanding of the role of melanocortins in human pigmentation and the DNA damage response of human melanocytes to solar ultraviolet radiation (UV). This began with the cloning of the melanocortin 1 receptor (MC1R) gene from human melanocytes and the demonstration that the encoded receptor is functional. Subsequently, population studies found that the MC1R gene is highly polymorphic, and that some of its variants are associated with red hair phenotype, fair skin and poor tanning ability. Using human melanocytes cultured from donors with different MC1R genotypes revealed that the alleles associated with red hair color encode for a non-functional receptor. Epidemiological studies linked the MC1R red hair color variants to increased melanoma risk. Investigating the impact of different MC1R variants on the response of human melanocytes to UV led to the important discovery that the MC1R signaling activates antioxidant, DNA repair and survival pathways, in addition to stimulation of eumelanin synthesis. These effects of MC1R were absent in melanocytes expressing 2 MC1R red hair color variants that result in loss of function of the receptor. The importance of the MC1R in reducing UV-induced genotoxicity in melanocytes led us to design small peptide analogs of the physiological MC1R agonist α-melanocortin (α-melanocyte stimulating hormone; α-MSH) for the goal of utilizing them for melanoma chemoprevention.

Trefoil factor 3 isolated from human breast milk downregulates cytokines (IL8 and IL6) and promotes human beta defensin (hBD2 and hBD4) expression in intestinal epithelial cells HT-29

Trefoil factors (TFF) are secretory products of mucin producing cells. They play a key role in the maintenance of the surface integrity of oral mucosa and enhance healing of the gastrointestinal mucosa by a process called restitution. TFF comprises the gastric peptides (TFF1), spasmolytic peptide (TFF2), and the intestinal trefoil factor (TFF3). They have an important and necessary role in epithelial restitution within the gastrointestinal tract. Significant amounts of TFF are present in human milk. This study aimed to determine a possible correlation between TFF3 isolated from human breast milk and levels of cytokines (IL8 and IL6) and defensins (hBD2 and hBD4) in intestinal epithelial cells HT-29 treated with trefoil. Samples of human milk were collected within 2-4 weeks postpartum from healthy human mothers (18-30-years-old) by manual breast massage, and TFF3 was purified by ammonium sulfate precipitation, isoelectric precipitation, DEAE-chromatography, and gel filtration. In this work we measured the concentrations and mRNA levels of cytokines and defensins by immunoassay (ELISA) and semiquantitative RT-PCR technique, respectively. Also we measured the peroxidase activity. We present the first evidence of human milk TFF3 purification. Here we show that the presence of TFF3 isolated from milk strongly correlates with downregulation of IL8 and IL6 in human intestinal epithelial cells. On the other hand, TFF3 activated the epithelial cells in culture to produce beta defensins 2 (hBD2) and beta defensins 4 (hBD4). These findings suggest that TFF can activate intestinal epithelial cells and could actively participate in the immune system of breastfed babies by inducing the production of peptides related to innate defence, such as defensins.

Identification, expression and bioactivity of Paramisgurnus dabryanus β-defensin that might be involved in immune defense against bacterial infection

β-defensins are a large family of multi-disulfide-bonded peptides with broad-spectrum antimicrobial activities that contribute to innate host defense in many organisms, but little information is available about β-defensins produced by freshwater fish lacking scales. We therefore cloned and identified a β-defensin gene from Chinese loach (Paramisgurnus dabryanus) by designing degenerate primers and using thermal asymmetric interlaced PCR. This gene is the first defensin gene ever identified in a non-scaled freshwater fish. Annotation of the protein domain architecture showed that the putative Chinese loach β-defensin contains the signature motif of six conserved cysteines within the mature peptide, an aspect similar to β-defensins of other marine fish. We also used quantitative real-time PCR to investigate the expression pattern of the Chinese loach β-defensin gene, mRNA of which could be observed in various tissues. After challenge with the pathogenic bacterium Aeromonas hydrophila, β-defensin expression was induced in the eye, gill, skin, and spleen of the adult loach. The bioactivity of the recombinant P. dabryanus β-defensin was examined against pathogenic bacteria, and the results suggest that this class 2 β-defensin has potential applications for treatment of bacterial infections.

Diagnostic model of saliva peptide finger print analysis of primary Sjögren's syndrome patients by using weak cation exchange magnetic beads

Saliva diagnostics has become an attractive field utilizing nanotechnology and molecular technologies for pSS (primary Sjögren's syndrome). However, no specific methods have been established. To refine the diagnostic power of the saliva peptide finger print for the early detection of pSS, we screened the expression spectrum of salivary peptides in pSS patients by using mass spectrometry MALDI-TOF-MS (matrix-assisted laser-desorption ionization-time-of-flight MS) combined with magnetic bead. The present study was comprised 12 pSS patients and 13 healthy controls and broken down to two different phases. In the initial ‘exploratory phase’, we enrolled seven pSS patients with eight age- and sex-matched healthy volunteers. Proteomics analysis of the unstimulated salivary samples was conducted to generate proportional peptide mass fingerprints. A diagnostic model was established. The testing cohort of the second ‘validation phase’ was represented by five pSS patients and five age- and sex-matched healthy controls. The diagnostic power of this diagnostic panel was then validated. The results showed seven m/z (mass-to-charge) ratio peaks with significant differences. Five peptides were up-regulated and two down-regulated in the pSS patients compared with matched healthy subjects. In the validation phase, four out of five pSS patients were diagnosed as pSS, and four of the five healthy controls were diagnosed as healthy controls, respectively. Potential biomarkers were also primarily predicted. The novel diagnostic proteomic model with m/z peaks 1068.1 Da, 1196.2 Da, 1738.4 Da, 3375.3 Da, 3429.3 Da, 3449.7 Da and 3490.6 Da is of certain value for early diagnosis of pSS.

Defensins: natural component of human innate immunity

The widespread use of antibiotics has contributed to a huge increase in the number of resistant bacteria. New classes of drugs are therefore being developed of which defensins are a potential source. Defensins are a group of antimicrobial peptides found in different living organisms, involved in the first line of defense in their innate immune response against pathogens. This review summarizes the results of studies of this family of human antimicrobial peptides (AMPs). There is a special emphasis on describing the entire group and individual peptides, history of their discovery, their functions and expression sites. The results of the recent studies on the use of the biologically active peptides in human medicine are also presented. The pharmaceutical potential of human defensins cannot be ignored, especially considering their strong antimicrobial activity and properties such as low molecular weight, reduced immunogenicity, broad activity spectrum and resistance to proteolysis, but there are still many challenges and questions regarding the possibilities of their practical application.

Membrane orientation of Gα(i)β(1)γ(2) and Gβ(1)γ(2) determined via combined vibrational spectroscopic studies

The manner in which the heterotrimeric G protein complexes Gβ1γ2 and Gαiβ1γ2 interact with membranes is likely related to their biological function. We combined complementary measurements from sum frequency generation (SFG) vibrational and attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy to determine the possible membrane orientations of Gβ1γ2 and the Gαiβ1γ2 heterotrimer more precisely than could be achieved using SFG alone. The most likely orientations of Gβ1γ2 and the Gαiβ1γ2 heterotrimer were both determined to fall within a similar narrow range of twist and tilt angles, suggesting that Gβ1γ2 may bind to Gαi without a significant change in orientation. This "basal" orientation seems to depend primarily on the geranylgeranylated C-terminus of Gγ2 along with basic residues at the N-terminus of Gαi, and suggests that activated G protein-coupled receptors (GPCRs) must reorient G protein heterotrimers at lipid bilayers to catalyze nucleotide exchange. The innovative methodologies developed in this paper can be widely applied to study the membrane orientation of other proteins in situ.