The androgen-regulated epididymal sperm-binding protein, human beta-defensin 118 (DEFB118) (formerly ESC42), is an antimicrobial beta-defensin

Characterisation of defensins across the marsupial family tree

Defensins are antimicrobial peptides involved in innate immunity, and gene number differs amongst eutherian mammals. Few studies have investigated defensins in marsupials, despite their potential involvement in immunological protection of altricial young. Here we use recently sequenced marsupial genomes and transcriptomes to annotate defensins in nine species across the marsupial family tree. We characterised 35 alpha and 286 beta defensins; gene number differed between species, although Dasyuromorphs had the largest repertoire. Defensins were encoded in three gene clusters within the genome, syntenic to eutherians, and were expressed in the pouch and mammary gland. Marsupial beta defensins were closely related to eutherians, however marsupial alpha defensins were more divergent. We identified marsupial orthologs of human DEFB3 and 6, and several marsupial-specific beta defensin lineages which may have novel functions. Marsupial predicted mature peptides were highly variable in length and sequence composition. We propose candidate peptides for future testing to elucidate the function of marsupial defensins.

Molecular characterization, expression and immune functional analysis of cystatin 10 in turbot

BACKGROUND

Cystatin is a protease inhibitor that also regulates genes expression linked to inflammation and plays a role in defense and regulation.

METHODS AND RESULTS

Cystatin 10 (Smcys10) was cloned from Scophthalmus maximus and encodes a 145 amino acid polypeptide. The results of qRT-PCR showed that Smcys10 exhibited tissue-specific expression patterns, and its expression was significantly higher in the skin than in other tissues. The expression level of Smcys10 was significantly different in the skin, gill, head kidney, spleen and macrophages after Vibrio anguillarum infection, indicating that Smcys10 may play an important role in resistance to V. anguillarum infection. The recombinant Smcys10 protein showed binding and agglutinating activity in a Ca2+-dependent manner against bacteria. rSmcys10 treatment upregulated the expression of IL-10, TNF-α and TGF-β in macrophages of turbot and hindered the release of lactate dehydrogenase (LDH) from macrophages after V. anguillarum infection, which confirmed that rSmcys10 reduced the damage to macrophages by V. anguillarum. The NF-κB pathway was suppressed by Smcys10, as demonstrated by dual-luciferase analysis.

CONCLUSIONS

These results indicated that Smcys10 is involved in the host antibacterial immune response.

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.

Evolutionary diversification of defensins and cathelicidins in birds and primates

Divergent evolution for more than 310 million years has resulted in an avian immune system that is complex and more compact than that of primates, sharing much of its structure and functions. Not surprisingly, well conserved ancient host defense molecules, such as defensins and cathelicidins, have diversified over time. In this review, we describe how evolution influenced the host defense peptides repertoire, its distribution, and the relationship between structure and biological functions. Marked features of primate and avian HDPs are linked to species-specific characteristics, biological requirements, and environmental challenge.

Defensins: defenders of human reproductive health

BACKGROUND

Reproductive tract infection is an important factor leading to male and female infertility. Among female infertility factors, microbial and viral infections are the main factors affecting female reproductive health and causing tubal infertility, ectopic tubal pregnancy and premature delivery. Among male infertility factors, 13-15% of male infertility is related to infection. Defensins are cationic antibacterial and antiviral peptides, classified into α-defensins, β-defensins and θ-defensins. Humans only have α-defensins and β-defensins. Apart from their direct antimicrobial functions, defensins have an immunomodulatory function and are involved in many physiological processes. Studies have shown that defensins are widely distributed in the female reproductive tract (FRT) and male reproductive tract (MRT), playing a dual role of host defence and fertility protection. However, to our knowledge, the distribution, regulation and function of defensins in the reproductive tract and their relation to reproduction have not been reviewed.

OBJECTIVE AND RATIONALE

This review summarizes the expression, distribution and regulation of defensins in the reproductive tracts to reveal the updated research on the dual role of defensins in host defence and the protection of fertility.

SEARCH METHODS

A systematic search was conducted in PubMed using the related keywords through April 2022. Related data from original researches and reviews were integrated to comprehensively review the current findings and understanding of defensins in the human reproductive system. Meanwhile, female and male transcriptome data in the GEO database were screened to analyze defensins in the human reproductive tracts.

OUTCOMES

Two transcriptome databases from the GEO database (GSE7307 and GSE150852) combined with existing researches reveal the expression levels and role of the defensins in the reproductive tracts. In the FRT, a high expression level of α-defensin is found, and the expression levels of defensins in the vulva and vagina are higher than those in other organs. The expression of defensins in the endometrium varies with menstrual cycle stages and with microbial invasion. Defensins also participate in the local immune response to regulate the risk of spontaneous preterm birth. In the MRT, a high expression level of β-defensins is also found. It is mainly highly expressed in the epididymal caput and corpus, indicating that defensins play an important role in sperm maturation. The expression of defensins in the MRT varies with androgen levels, age and the status of microbial invasion. They protect the male reproductive system from bacterial infections by neutralizing lipopolysaccharide and downregulating pro-inflammatory cytokines. In addition, animal and clinical studies have shown that defensins play an important role in sperm maturation, motility and fertilization.

WIDER IMPLICATIONS

As a broad-spectrum antimicrobial peptide without drug resistance, defensin has great potential for developing new natural antimicrobial treatments for reproductive tract infections. However, increasing evidence has shown that defensins can not only inhibit microbial invasion but can also promote the invasion and adhesion of some microorganisms in certain biological environments, such as human immunodeficiency virus. Therefore, the safety of defensins as reproductive tract anti-infective drugs needs more in-depth research. In addition, the modulatory role of defensins in fertility requires more in-depth research since the current conclusions are based on small-size samples. At present, scientists have made many attempts at the clinical transformation of defensins. However, defensins have problems such as poor stability, low bioavailability and difficulties in their synthesis. Therefore, the production of safe, effective and low-cost drugs remains a challenge.

The antibacterial effect of Plectranthus scutellarioides (L.) R.Br. leaves extract against bacteria associated with peri-implantitis

Background and aim

The present study investigates Plectranthus scutellarioides (L.) R.Br. as potential antibacterial oral rinse against bacteria associated with peri-implantitis to prevent the initial infection as well as disease progression.

Experimental procedure

Phytochemical screening was done on P. scutellarioides lyophilized extract to identify the presence of chemical constituent by using mass-based identification. The extract was screened for its antibacterial activity against 4 Gram-positive aerobes (early colonizer) and 5 Gram-negative facultative anaerobes as well as obligate anaerobes (late colonizer) using disc diffusion method. The extract was tested for minimum inhibitory concentration (MIC), minimum bactericidal concentration (MBC), its cytotoxicity effects on human gingival fibroblast cell (HnGF) as well as bacteria morphological changes by scanning electron microscopy (SEM).

Results and conclusion

Four flavonoid compounds were identified namely quercetin-3-glucoside, quercitrin, quercetin 3-(6″-acetylglucoside) and quercetin 3-O-acetyl-rhamnoside. The sensitivity test revealed that P. scutellarioides extract was effective against all the bacteria tested. MIC concentrations for the Gram-positive aerobes were in the range of 1.56–12.50 mg/mL, and the MBC concentrations were within 3.13–12.50 mg/mL. For Gram-negative obligate anaerobes, the MIC concentration were within 3.13–12.50 mg/mL and MBC within 6.25–200.00 mg/mL. The ethanolic extract did not have any cytotoxic effect on HnGF cells at the tested concentrations. SEM images showed bacterial cell wall disruption for all the bacteria tested. The results showed that P. scutellarioides extract exerts its antibacterial property by disrupting the cell wall of all the bacteria tested. Hence, P. scutellarioides may benefit from further investigations on its safety for oral use as an adjunctive treatment for peri-implantitis.

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The quercetin derivatives reported in this study were the first been identified for this plant species.

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The optimize method used for the mass-based identification can be reproducible and applied for the future isolation, identification and characterizations of the plant chemical compounds.

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The plant extract was effective against all the bacteria tested and note that, there were no studies have been carried out on the effects of this plant on oral bacteria especially the obligate anaerobes.

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The plant extract also was not toxic towards HnGF.

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The SEM image showed the plant extract have exert its antibacterial activity through cell wall destruction.

β-defensin 118 attenuates inflammation and injury of intestinal epithelial cells upon enterotoxigenic Escherichia coli challenge

Background

Antimicrobial peptides including various defensins have been attracting considerable research interest worldwide, as they have potential to substitute for antibiotics. Moreover, AMPs also have immunomodulatory activity. In this study, we explored the role and its potential mechanisms of β-defensin 118 (DEFB118) in alleviating inflammation and injury of IPEC-J2 cells (porcine jejunum epithelial cell line) upon the enterotoxigenic Escherichia coli (ETEC) challenge.

Results

The porcine jejunum epithelial cell line (IPEC-J2) pretreated with or without DEFB118 (25 μg/mL) were challenged by ETEC (1×10⁶ CFU) or culture medium. We showed that DEFB118 pretreatment significantly increased the cell viability (P<0.05) and decreased the expressions of inflammatory cytokines such as the interleukin-1β (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α) in IPEC-J2 cells exposure to ETEC (P<0.05). Interestingly, DEFB118 pretreatment significantly elevated the abundance of the major tight-junction protein zonula occludens-1 (ZO-1), but decreased the number of apoptotic cells upon ETEC challenge (P<0.05). The expression of caspase 3, caspase 8, and caspase 9 were downregulated by DEFB118 in the IPEC-J2 cells exposure to ETEC (P<0.05). Importantly, DEFB118 suppressed two critical inflammation-associated signaling proteins, nuclear factor-kappa-B inhibitor alpha (IκB-α) and nuclear factor-kappaB (NF-κB) in the ETEC-challenged IPEC-J2 cells.

Conclusions

DEFB118 can alleviate ETEC-induced inflammation in IPEC-J2 cells through inhibition of the NF-κB signaling pathway, resulting in reduced secretion of inflammatory cytokines and decreased cell apoptosis. Therefore, DEFB118 can act as a novel anti-inflammatory agent.

Expression of anti-fungal peptide, β-defensin 118 in oral fibroblasts induced by C. albicans β-glucan-containing particles

Objective:

Methodology:

Results:

Conclusion:

An improved lentiviral system for efficient expression and purification of β-defensins in mammalian cells

β-Defensins are a family of conserved small cationic antimicrobial peptides with different significant biological functions. The majority of mammalian β-defensins are expressed in epididymis, and many of them are predicted to have post-translational modifications. However, only a few of its members have been well studied due to the limitations of expressing and purifying bioactive proteins with correct post-translational modifications efficiently. Here we developed a novel Fc tagged lentiviral system and Fc tagged prokaryotic expression systems provided new options for β-defensins expression and purification. The novel lentiviral system contains a secretive signal peptide, an N-terminal IgG Fc tag, a green fluorescent protein (GFP), and a puromycin selection marker to facilitate efficient expression and fast purification of β-defensins by protein A magnetic or agarose beads. It also enables stable and large-scale expression of β-defensins with regular biological activities and post-translational modification. Purified β-defensins such as Bin1b and a novel human β-defensin hBD129 showed antimicrobial activity, immuno-regulatory activity, and expected post-translational phosphorylation, which were not found in Escherichia coli (E. coli) in expressed form. Furthermore, we successfully applied the novel system to identify mBin1b interacting proteins, explaining Bin1b in a better way. These results suggest that the novel lentiviral system is a powerful approach to produce correct post-translational processed β-defensins with bioactivities and is useful to identify their interacting proteins. This study has laid the foundation for future studies to characterize function and mechanism of novel β-defensins.

The truncated human beta-defensin 118 can modulate lipopolysaccharide mediated inflammatory response in RAW264.7 macrophages

The family of human β-defensins consists of small cysteine-rich peptides, which are receiving significant attention due to their antimicrobial activity. The N-terminal cysteine motif of β-defensin is considered to contribute to its biological activity. Human β-defensin 118 (DEFB 118) is a particular anion β-defensin expressed predominantly in the male reproductive tract, but its physiological activity has not yet been revealed. In order to verify the potential role of the N-terminal domain of DEFB118 peptide in the regulation of infection, the truncated β-defensin core region of DEFB118 peptide was expressed with IMPACT-pTWIN1 system in Escherichia coli. Herein, the purified homogeneous DEFB118 peptide was identified by mass spectrometry and circular dichroism spectroscopy. The in vitro experiments revealed that DEFB118 peptide exhibited prominent LPS-binding potency (K_D: 2.94 nM). Moreover, the DEFB118 core peptide significantly inhibited the mRNA level of LPS-induced inflammatory cytokines including IL-α, IL-1β, IL-6 and TNF-α in RAW264.7 cells, and correspondingly decreased secretion of IL-6 and TNF-α. We concluded that strong binding of DEFB118 to LPS might prevent LPS from binding to its receptor, and hence inhibited cytokines secretion. The results of this study may be a benefit to elucidate the immune protection of DEFB118 in the male reproductive tract.

Declined expressing mRNA of beta-defensin 108 from epididymis is associated with decreased sperm motility in blue fox (Vulpes lagopus)

BACKGROUND

Fecundity is important for farm blue fox (Vulpes lagopus), who with asthenospermia have be a problem in some of farms in China. A key symptom of asthenospermia is decreased sperm motility. The decreased secreting beta-defensin108 (vBD108) of blue fox is speculated be related to asthenospermia. To clarify this idea, the mRNA expression of vBD108 in testis and epididymis of blue foxes with asthenospermia were detected and compared to the healthy one. The antibody was prepared and analyzed by immunohistochemistry.

RESULTS

The vBD108 in testis and epididymis was found both in blue fox with asthenospermia and healthy group by the method of immunohistochemistry. The expression of vBD108 mRNA in testes (P < 0.05) and epididymal corpus (P < 0.0001) in asthenospermia group was lower than that in healthy group.

CONCLUSIONS

These results suggested that vBD108 deficiency may related to blue fox asthenospermia. Meanwhile, the study on the blue fox vBD108 provides a hopeful direction to explore the pathogenesis of blue fox asthenospermia in the future.

Pigs Overexpressing Porcine β-Defensin 2 Display Increased Resilience to Glaesserella parasuis Infection

As the causative agent of Glässer’s disease, Glaesserella (Haemophilus) parasuis has led to serious economic losses to the swine industry worldwide. Due to the low cross-protection of vaccines and increasing antimicrobial resistance of G. parasuis, it is important to develop alternative approaches to prevent G. parasuis infection. Defensins are host defense peptides that have been suggested to be promising substitutes for antibiotics in animal production, while porcine β-defensin 2 (PBD-2) is a potent antimicrobial peptide discovered in pigs. Our previous study generated transgenic (TG) pigs overexpressing PBD-2, which displayed enhanced resistance to Actinobacillus pleuropneumoniae. In this study, the antibacterial activities of PBD-2 against G. parasuis are determined in vitro and in the TG pig model. The concentration-dependent bactericidal activity of synthetic PBD-2 against G. parasuis was measured by bacterial counting. Moreover, after being infected with G. parasuis via a cohabitation challenge model, TG pigs overexpressing PBD-2 displayed significantly milder clinical signs and less severe gross pathological changes than their wild-type (WT) littermates. The TG pigs also exhibited alleviated lung and brain lesions, while bacterial loads in the lung and brain tissues of the TG pigs were significantly lower than those of the WT pigs. Additionally, lung and brain homogenates from TG pigs possessed enhanced antibacterial activity against G. parasuis when compared with those from the WT pigs. Altogether, these proved that overexpression of PBD-2 could also endow pigs with increased resilience to G. parasuis infection, which further confirmed the potential of using the PBD-2 coding gene to develop disease-resistant pigs and provided a novel strategy to combat G. parasuis as well.

Expression and Functional Characterization of a Novel Antimicrobial Peptide: Human Beta-Defensin 118

Purpose

β-Defensin 118 (DEFB118) is a novel host defense peptide (HDP) identified in humans. To evaluate its potentials for future utilization, the DEFB118 gene was expressed in Escherichia coli (E. coli) and the recombinant protein was fully characterized.

Methods

The DEFB118 protein was obtained by heterologous expression using E. coli Rosetta (DE3). Antibacterial activity of DEFB118 was determined by using various bacterial strains. IPEC-J cells challenged by E. coli K88 were used to determine its influences on inflammatory responses.

Results

The E. coli transformants yielded more than 250 μg/mL DEFB118 protein after 4 h induction by 1.0 mM IPTG. The DEFB118 was estimated by SDS-PAGE to be 30 kDa, and MALDI-TOF analysis verified that it is a human β-defensin 118. Importantly, the DEFB118 showed antimicrobial activities against both Gram-negative bacteria (E. coli K88 and E. coli DH5α) and Gram-positive bacteria (S. aureus and B. subtilis), with a minimum inhibitory concentration (MIC) of 4 μg/mL. Hemolytic assays showed that DEFB118 had no detrimental impact on cell viability. Additionally, DEFB118 was found to elevate the viability of IPEC-J2 cells upon E. coli K88 challenge. Moreover, DEFB118 significantly decreased cell apoptosis in the late apoptosis phase and downregulated the expression of inflammatory cytokines such as IL-1β and TNF-α in IPEC-J2 cell exposure to E. coli K88.

Conclusions

These results suggested a novel function of the mammalian defensins, and the antibacterial and anti-inflammatory properties of DEFB118 may allow it as a potential substitute for conventionally used antibiotics or drugs.

Human β-Defensin 118 Attenuates Escherichia coli K88-Induced Inflammation and Intestinal Injury in Mice

Antibiotics are widely used to treat various inflammatory bowel diseases caused by enterotoxigenic Escherichia coli (ETEC). However, continuous use of antibiotics may lead to drug resistance. In this study, we investigated the role of human β-defensin 118 (DEFB118) in regulating the ETEC-induced inflammation and intestinal injury. ETEC-challenged or non-challenged mice were treated by different concentrations of DEFB118. We show that ETEC infection significantly increased fecal score (P < 0.05) and serum concentrations of interlukin-6 (IL-6) and tumor necrosis factor-α (TNF-α). Moreover, the concentrations of D-lactic acid, C-reactive protein (CRP), creatinine (CREA), and urea (P < 0.05) were both increased in the ETEC-challenged mice. However, DEFB118 significantly decreased their concentrations in the serum (P < 0.05). DEFB118 not only alleviated tissue damage in spleen upon ETEC challenge, but also increased the villus height in duodenum and ileum (P < 0.05). Moreover, DEFB118 improved the localization and abundance of tight junction protein ZO-1 in jejunal epithelium. Interestingly, DEFB118 decreased the expression levels of critical genes involving in mucosal inflammatory responses (NF-κB, TLR4, IL-1β, and TNF-α) and the apoptosis (caspase3) upon ETEC challenge (P < 0.05), whereas DEFB118 significantly upregulated the expression of mucosa functional genes such as the mucin1 (MUC1) and sodium-glucose transporter-1 (SGLT-1) in the ETEC-challenged mice (P < 0.05). These results indicated a novel function of the DEFB118. The anti-inflammatory effect of DEFB118 should make it an attractive candidate to prevent various bacteria-induced inflammatory bowel diseases.

Immunolocalization of androgen and vitamin D receptors in the epididymis of mature ram (Ovis aries)

This study illustrated the immunohistochemical distribution of androgen and vitamin D receptors of epididymis in 20 sexually mature ram (Rahmani breed) with average age ranged from (2^_4) years and average weight ranged from (50^_65kg). Androgen receptor was localized in the cytoplasm of both ciliated and non ciliated cells of efferent ductules, besides the principal cells via the entire epididymal duct. The principal cells of both corpus and proximal cauda epididymis showed the highest immunoreactivity to androgen receptors. Furthermore, vitamin D receptor was localized in the cytoplasm of all epithelium of the efferent ductules besides principal cells of all epididymal regions, however the immunoreaction was significantly higher in the efferent ductules, distal caput and distal cauda epididymis. In conclusion, these results suggest that the function of ram epididymis is regulated by both androgen and Vitamin D.

A Noncytotoxic Temporin L Analogue with In Vivo Antibacterial and Antiendotoxin Activities and a Nonmembrane-Lytic Mode of Action

Cytotoxic frog antimicrobial peptide Temporin L (TempL) is an attractive molecule for the design of lead antimicrobial agents due to its short size and versatile biological activities. However, noncytotoxic TempL variants with desirable biological activities have rarely been reported. TempL analogue Q3K,TempL is water-soluble and possesses a significant antiendotoxin property along with comparable cytotoxicity to TempL. A phenylalanine residue, located at the hydrophobic face of Q3K,TempL and the "d" position of its phenylalanine zipper sequence, was replaced with a cationic lysine residue. This analogue, Q3K,F8K,TempL, showed reduced hydrophobic moment and was noncytotoxic with lower antimicrobial activity. Interestingly, swapping between tryptophan at the fourth and serine at the sixth positions turned Q3K,F8K,TempL totally amphipathic as reflected by its helical wheel projection with clusters of hydrophobic and hydrophilic residues and the highest hydrophobic moment among these peptides. Surprisingly, this analogue, SW,Q3K,F8K,TempL, was as noncytotoxic as Q3K,F8K,TempL but showed augmented antimicrobial and antiendotoxin properties, comparable to that of TempL and Q3K,TempL. SW,Q3K,F8K,TempL exhibited appreciable survival of mice against P. aeruginosa infection and a lipopolysaccharide (LPS) challenge. Unlike TempL and Q3K,TempL, SW,Q3K,F8K,TempL adopted an unordered secondary structure in bacterial membrane mimetic lipid vesicles and did not permeabilize them or depolarize the bacterial membrane. Overall, the results demonstrate the design of a nontoxic TempL analogue that possesses clusters of hydrophobic and hydrophilic residues with impaired secondary structure and shows a nonmembrane-lytic mechanism and in vivo antiendotoxin and antimicrobial activities. This paradigm of design of antimicrobial peptide with clusters of hydrophobic and hydrophilic residues and high hydrophobic moment but low secondary structure could be attempted further.

The epididymal immune balance: a key to preserving male fertility

Up to 15% of male infertility has an immunological origin, either due to repetitive infections or to autoimmune responses mainly affecting the epididymis, prostate, and testis. Clinical observations and epidemiological data clearly contradict the idea that the testis confers immune protection to the whole male genital tract. As a consequence, the epididymis, in which posttesticular spermatozoa mature and are stored, has raised some interest in recent years when it comes to its immune mechanisms. Indeed, sperm cells are produced at puberty, long after the establishment of self-tolerance, and they possess unique surface proteins that cannot be recognized as self. These are potential targets of the immune system, with the risk of inducing autoantibodies and consequently male infertility. Epididymal immunity is based on a finely tuned equilibrium between efficient immune responses to pathogens and strong tolerance to sperm cells. These processes rely on incompletely described molecules and cell types. This review compiles recent studies focusing on the immune cell types populating the epididymis, and proposes hypothetical models of the organization of epididymal immunity with a special emphasis on the immune response, while also discussing important aspects of the epididymal immune regulation such as tolerance and tumour control.

A β-defensin gene of Trachinotus ovatus might be involved in the antimicrobial and antiviral immune response

Defensins are a group of small cationic and cysteine-rich peptides that are important components of the innate immune system. However, studies on defensins in teleosts are very limited, particularly studies on defensin functions through in vivo assays. In this study, we cloned and identified one β-defensin (TroBD) the golden pompano, Trachinotus ovatus, and analyzed the functions of TroBD in both in vivo and in vitro assays. TroBD is composed of 63 amino acids and shares high sequence identities (27.27-98.41%) with known β-defensins of other teleosts. The protein has a signature motif of six conserved cysteine residues within the mature peptide. The expression of TroBD was most abundant in the head kidney and spleen and was significantly upregulated following infection by Vibrio harveyi and viral nervous necrosis virus (VNNV). Purified recombinant TroBD (rTroBD) inhibited the growth of V. harveyi, and its antimicrobial activity was influenced by salt concentration. TroBD was found to have a chemotactic effect on macrophages in vitro. The results of an in vivo study demonstrated that TroBD overexpression/knockdown in T. ovatus significantly reduced/increased bacterial colonization or viral copy numbers in tissues. Taken together, these results indicate that TroBD plays a significant role in both antibacterial and antiviral immunity and provide new avenues for protection against pathogen infection in the aquaculture industry.

Piscidin-1-analogs with double L- and D-lysine residues exhibited different conformations in lipopolysaccharide but comparable anti-endotoxin activities

To become clinically effective, antimicrobial peptides (AMPs) should be non-cytotoxic to host cells. Piscidins are a group of fish-derived AMPs with potent antimicrobial and antiendotoxin activities but limited by extreme cytotoxicity. We conjectured that introduction of cationic residue(s) at the interface of polar and non-polar faces of piscidins may control their insertion into hydrophobic mammalian cell membrane and thereby reducing cytotoxicity. We have designed several novel analogs of piscidin-1 by substituting threonine residue(s) with L and D-lysine residue(s). L/D-lysine-substituted analogs showed significantly reduced cytotoxicity but exhibited either higher or comparable antibacterial activity akin to piscidin-1. Piscidin-1-analogs demonstrated higher efficacy than piscidin-1 in inhibiting lipopolysaccharide (LPS)-induced pro-inflammatory responses in THP-1 cells. T15,21K-piscidin-1 (0.5 mg/Kg) and T15,21dK-piscidin-1 (1.0 mg/Kg) demonstrated 100% survival of LPS (12.0 mg/Kg)-administered mice. High resolution NMR studies revealed that both piscidin-1 and T15,21K-piscidin-1 adopted helical structures, with latter showing a shorter helix, higher amphipathicity and cationic residues placed at optimal distances to form ionic/hydrogen bond with lipid A of LPS. Remarkably, T15,21dK-piscidin-1 showed a helix-loop-helix structure in LPS and its interactions with LPS could be sustained by the distance of separation of side chains of R7 and D-Lys-15 which is close to the inter-phosphate distance of lipid A.

Characterization of the antimicrobial peptide family defensins in the Tasmanian devil (Sarcophilus harrisii), koala (Phascolarctos cinereus), and tammar wallaby (Macropus eugenii)

Defensins comprise a family of cysteine-rich antimicrobial peptides with important roles in innate and adaptive immune defense in vertebrates. We characterized alpha and beta defensin genes in three Australian marsupials: the Tasmanian devil (Sarcophilus harrisii), koala (Phascolarctos cinereus), and tammar wallaby (Macropus eugenii) and identified 48, 34, and 39 defensins, respectively. One hundred and twelve have the classical antimicrobial peptides characteristics required for pathogen membrane targeting, including cationic charge (between 1+ and 15+) and a high proportion of hydrophobic residues (>30%). Phylogenetic analysis shows that gene duplication has driven unique and species-specific expansions of devil, koala, and tammar wallaby beta defensins and devil alpha defensins. Defensin genes are arranged in three genomic clusters in marsupials, whereas further duplications and translocations have occurred in eutherians resulting in four and five gene clusters in mice and humans, respectively. Marsupial defensins are generally under purifying selection, particularly residues essential for defensin structural stability. Certain hydrophobic or positively charged sites, predominantly found in the defensin loop, are positively selected, which may have functional significance in defensin-target interaction and membrane insertion.

Systems Biology-Based Investigation of Cellular Antiviral Drug Targets Identified by Gene-Trap Insertional Mutagenesis

Viruses require host cellular factors for successful replication. A comprehensive systems-level investigation of the virus-host interactome is critical for understanding the roles of host factors with the end goal of discovering new druggable antiviral targets. Gene-trap insertional mutagenesis is a high-throughput forward genetics approach to randomly disrupt (trap) host genes and discover host genes that are essential for viral replication, but not for host cell survival. In this study, we used libraries of randomly mutagenized cells to discover cellular genes that are essential for the replication of 10 distinct cytotoxic mammalian viruses, 1 gram-negative bacterium, and 5 toxins. We herein reported 712 candidate cellular genes, characterizing distinct topological network and evolutionary signatures, and occupying central hubs in the human interactome. Cell cycle phase-specific network analysis showed that host cell cycle programs played critical roles during viral replication (e.g. MYC and TAF4 regulating G0/1 phase). Moreover, the viral perturbation of host cellular networks reflected disease etiology in that host genes (e.g. CTCF, RHOA, and CDKN1B) identified were frequently essential and significantly associated with Mendelian and orphan diseases, or somatic mutations in cancer. Computational drug repositioning framework via incorporating drug-gene signatures from the Connectivity Map into the virus-host interactome identified 110 putative druggable antiviral targets and prioritized several existing drugs (e.g. ajmaline) that may be potential for antiviral indication (e.g. anti-Ebola). In summary, this work provides a powerful methodology with a tight integration of gene-trap insertional mutagenesis testing and systems biology to identify new antiviral targets and drugs for the development of broadly acting and targeted clinical antiviral therapeutics.

Infectious diseases result in millions of deaths and cost billions of dollars annually. Hence, there is urgency for developing more innovative and effective antiviral therapeutics. In this study, we used libraries of randomly mutagenized cells to discover cellular genes that are essential for the replication of 10 distinct cytotoxic mammalian viruses. We herein reported over 700 candidate cellular genes, over 20% of which were independently selected by multiple viruses in one or more cell types. Using systems biology-based analysis, we found that host genes associated with viral replication tended to occupy central hubs in the human protein interactome and to be ancient genes with low evolutionary rates, compared to non-virus-associated genes. Cell cycle phase-specific sub-network analysis showed that host cell cycle program played important roles during viral replication by regulating specific cell cycle phases. Moreover, we presented novel evidences to suggest that host genes supporting viral replication were frequently implicated in Mendelian and orphan diseases, or played critical roles in cancer. Importantly, we found approximately 110 new putative druggable antiviral targets by merging genome-wide gene-trap insertional mutagenesis, drug-gene network, and bioinformatics data. Furthermore, we have demonstrated the use of a computable representation of genetic testing to effectively identify new potential antiviral indications for existing drugs. In summary, this study presents new and important methodologies for developing broadly active antiviral therapeutics.

Single Amino Acid Substitutions at Specific Positions of the Heptad Repeat Sequence of Piscidin-1 Yielded Novel Analogs That Show Low Cytotoxicity and In Vitro and In Vivo Antiendotoxin Activity

Piscidin-1 possesses significant antimicrobial and cytotoxic activities. To recognize the primary amino acid sequence(s) in piscidin-1 that could be important for its biological activity, a long heptad repeat sequence located in the region from amino acids 2 to 19 was identified. To comprehend the possible role of this motif, six analogs of piscidin-1 were designed by selectively replacing a single isoleucine residue at a d (5th) position or at an a (9th or 16th) position with either an alanine or a valine residue. Two more analogs, namely, I5F,F6A-piscidin-1 and V12I-piscidin-1, were designed for investigating the effect of interchanging an alanine residue at a d position with an adjacent phenylalanine residue and replacing a valine residue with an isoleucine residue at another d position of the heptad repeat of piscidin-1, respectively. Single alanine-substituted analogs exhibited significantly reduced cytotoxicity against mammalian cells compared with that of piscidin-1 but appreciably retained the antibacterial and antiendotoxin activities of piscidin-1. All the single valine-substituted piscidin-1 analogs and I5F,F6A-piscidin-1 showed cytotoxicity greater than that of the corresponding alanine-substituted analogs, antibacterial activity marginally greater than or similar to that of the corresponding alanine-substituted analogs, and also antiendotoxin activity superior to that of the corresponding alanine-substituted analogs. Interestingly, among these peptides, V12I-piscidin-1 showed the highest cytotoxicity and antibacterial and antiendotoxin activities. Lipopolysaccharide (12 mg/kg of body weight)-treated mice, further treated with I16A-piscidin-1, the piscidin-1 analog with the highest therapeutic index, at a single dose of 1 or 2 mg/kg of body weight, showed 80 and 100% survival, respectively. Structural and functional characterization of these peptides revealed the basis of their biological activity and demonstrated that nontoxic piscidin-1 analogs with significant antimicrobial and antiendotoxin activities can be designed by incorporating single alanine substitutions in the piscidin-1 heptad repeat.

Targeted inactivation of the mouse epididymal beta-defensin 41 alters sperm flagellar beat pattern and zona pellucida binding

During epididymal maturation, sperm acquire the ability to swim progressively by interacting with proteins secreted by the epididymal epithelium. Beta-defensin proteins, expressed in the epididymis, continue to regulate sperm motility during capacitation and hyperactivation in the female reproductive tract. We characterized the mouse beta-defensin 41 (DEFB41), by generating a mouse model with iCre recombinase inserted into the first exon of the gene. The homozygous Defb41(iCre/iCre) knock-in mice lacked Defb41 expression and displayed iCre recombinase activity in the principal cells of the proximal epididymis. Heterozygous Defb41(iCre/+) mice can be used to generate epididymis specific conditional knock-out mouse models. Homozygous Defb41(iCre/iCre) sperm displayed a defect in sperm motility with the flagella primarily bending in the pro-hook conformation while capacitated wild-type sperm more often displayed the anti-hook conformation. This led to a reduced straight line motility of Defb41(iCre/iCre) sperm and weaker binding to the oocyte. Thus, DEFB41 is required for proper sperm maturation.

Potential Use of Antimicrobial Peptides as Vaginal Spermicides/Microbicides

The concurrent increases in global population and sexually transmitted infection (STI) demand a search for agents with dual spermicidal and microbicidal properties for topical vaginal application. Previous attempts to develop the surfactant spermicide, nonoxynol-9 (N-9), into a vaginal microbicide were unsuccessful largely due to its inefficiency to kill microbes. Furthermore, N-9 causes damage to the vaginal epithelium, thus accelerating microbes to enter the women's body. For this reason, antimicrobial peptides (AMPs), naturally secreted by all forms of life as part of innate immunity, deserve evaluation for their potential spermicidal effects. To date, twelve spermicidal AMPs have been described including LL-37, magainin 2 and nisin A. Human cathelicidin LL-37 is the most promising spermicidal AMP to be further developed for vaginal use for the following reasons. First, it is a human AMP naturally produced in the vagina after intercourse. Second, LL-37 exerts microbicidal effects to numerous microbes including those that cause STI. Third, its cytotoxicity is selective to sperm and not to the female reproductive tract. Furthermore, the spermicidal effects of LL-37 have been demonstrated in vivo in mice. Therefore, the availability of LL-37 as a vaginal spermicide/microbicide will empower women for self-protection against unwanted pregnancies and STI.

Liquid storage of boar semen: Current and future perspectives on the use of cationic antimicrobial peptides to replace antibiotics in semen extenders

Antibiotics are of great importance in boar semen extenders to ensure long shelf life of spermatozoa and to reduce transmission of pathogens into the female tract. However, the use of antibiotics carries a risk of developing resistant bacterial strains in artificial insemination laboratories and their spread via artificial insemination. Development of multiresistant bacteria is a major concern if mixtures of antibiotics are used in semen extenders. Minimal contamination prevention techniques and surveillance of critical hygiene control points proved to be efficient in reducing bacterial load and preventing development of antibiotic resistance. Nevertheless, novel antimicrobial concepts are necessary for efficient bacterial control in extended boar semen with a minimum risk of evoking antibiotic resistance. Enhanced efforts have been made in recent years in the design and use of antimicrobial peptides (AMPs) as alternatives to conventional antibiotics. The male genital tract harbors a series of endogenic substances with antimicrobial activity and additional functions relevant to the fertilization process. However, exogenic AMPs often exert dose- and time-dependent toxic effects on mammalian spermatozoa. Therefore, it is important that potential newly designed AMPs have only minor impacts on eukaryotic cells. Recently, synthetic magainin derivatives and cyclic hexapeptides were tested for their application in boar semen preservation. Bacterial selectivity, proteolytic stability, thermodynamic resistance, and potential synergistic interaction with conventional antibiotics propel predominantly cyclic hexapeptides into highly promising, leading candidates for further development in semen preservation. The time scale for the development of resistant pathogens cannot be predicted at this moment.

Variants of self-assembling peptide, KLD-12 that show both rapid fracture healing and antimicrobial properties

KLD-12 (KLD) is a 12-residue self-assembling peptide that can adopt nano-structures and is known for its tissue-engineering properties. Our objective was to introduce antimicrobial attribute to KLD which would help in preventing secondary infection associated with external application of such tissue engineering materials. Considering the net charge of KLD-12, varying number of cationic arginine residues were added to its N-terminus. KLD variants showed appreciable bactericidal properties without any significant increase in cytotoxicity against tested mammalian cells. Further, these variants adopted β-sheet structures and self-assembled into nano-structures comparable to that of KLD. Interestingly, the KLD variants with two (KLD-2R) and three (KLD-3R) arginine residues added to its N-terminus showed significant osteogenic effect which was comparable or better than the original peptide as evident from the alkaline phosphatase activity assay, mineralized nodule formation and expression of different osteogenic genes. Particularly, application of KLD-2R in rats to the site of a drill-hole (0.8 mm diameter) that was created in the femur metaphysis displayed significantly higher bone regeneration compared to that of KLD. The results demonstrate a simple way to improve biological property of a self-assembling peptide with tissue engineering property.

An evolutionary history of defensins: a role for copy number variation in maximizing host innate and adaptive immune responses

Defensins represent an evolutionary ancient family of antimicrobial peptides that play diverse roles in human health and disease. Defensins are cationic cysteine-containing multifunctional peptides predominantly expressed by epithelial cells or neutrophils. Defensins play a key role in host innate immune responses to infection and, in addition to their classically described role as antimicrobial peptides, have also been implicated in immune modulation, fertility, development, and wound healing. Aberrant expression of defensins is important in a number of inflammatory diseases as well as modulating host immune responses to bacteria, unicellular pathogens, and viruses. In parallel with their role in immunity, in other species, defensins have evolved alternative functions, including the control of coat color in dogs. Defensin genes reside in complex genomic regions that are prone to structural variations and some defensin family members exhibit copy number variation (CNV). Structural variations have mediated, and continue to influence, the diversification and expression of defensin family members. This review highlights the work currently being done to better understand the genomic architecture of the β-defensin locus. It evaluates current evidence linking defensin CNV to autoimmune disease (i.e., Crohn’s disease and psoriasis) as well as the contribution CNV has in influencing immune responses to HIV infection.

An unprecedented alteration in mode of action of IsCT resulting its translocation into bacterial cytoplasm and inhibition of macromolecular syntheses

IsCT, a 13-residue, non-cell-selective antimicrobial peptide is comprised of mostly hydrophobic residues and lesser cationic residues. Assuming that placement of an additional positive charge in the non-polar face of IsCT could reduce its hydrophobic interaction, resulting in its reduction of cytotoxicity, an analog, I9K-IsCT was designed. Two more analogs, namely, E7K-IsCT and E7K,I9K-IsCT, were designed to investigate the impact of positive charges in the polar face as well as polar and non-polar faces at a time. These amino acid substitutions resulted in a significant enhancement of therapeutic potential of IsCT. IsCT and E7K-IsCT seem to target bacterial membrane for their anti-bacterial activity. However, I9K-IsCT and E7K,I9K-IsCT inhibited nucleic acid and protein syntheses in tested E. coli without perturbing its membrane. This was further supported by the observation that NBD-IsCT localized onto bacterial membrane while NBD-labeled I9K-IsCT and E7K,I9K-IsCT translocated into bacterial cytoplasm. Interestingly, IsCT and E7K-IsCT were significantly helical while I9K-IsCT and E7K,I9K-IsCT were mostly unstructured with no helix content in presence of mammalian and bacterial membrane-mimetic lipid vesicles. Altogether, the results identify two novel cell-selective analogs of IsCT with new prototype amino acid sequences that can translocate into bacterial cytoplasm without any helical structure and inhibit macromolecular syntheses.

Molecular modeling of the human sperm associated antigen 11 B (SPAG11B) proteins

Antimicrobial proteins and peptides are ubiquitous in nature with diverse structural and biological properties. Among them, the human beta-defensins are known to contribute to the innate immune response. Besides the defensins, a number of defensin-like proteins and peptides are expressed in many organ systems including the male reproductive system. Some of the protein isoforms encoded by the sperm associated antigen 11B (SPAG11) gene in humans are beta-defensin-like and exhibit structure dependent and salt tolerant antimicrobial activity, besides contributing to sperm maturation. Though some of the functional roles of these proteins are reported, the structural and molecular features that contribute to their antimicrobial activity is not yet reported. In this study, using in silico tools, we report the three dimensional structure of the human SPAG11B proteins and their C-terminal peptides. web-based hydropathy, amphipathicity, and topology (WHAT) analyses and grand average of hydropathy (GRAVY) indices show that these proteins and peptides are amphipathic and highly hydrophilic. Self-optimized prediction method with alignment (SOPMA) analyses and circular dichroism data suggest that the secondary structure of these proteins and peptides primarily contain beta-sheet and random coil structure and alpha-helix to a lesser extent. Ramachandran plots show that majority of the amino acids in these proteins and peptides fall in the permissible regions, thus indicating stable structures. The secondary structure of SPAG11B isoforms and their peptides were not perturbed with increasing NaCl concentration (0-300 mM) and at different pH (3, 7, and 10), thus reinforcing our previously reported observation that their antimicrobial activity is salt tolerant. To the best of our knowledge, for the first time, results of our study provide vital information on the structural features of SPAG11B protein isoforms and their contribution to antimicrobial activity.

The Role of the Immune Response in Chlamydia trachomatis Infection of the Male Genital Tract: A Double-Edged Sword

Chlamydia trachomatis (CT) is the most prevalent bacterial sexually transmitted infection in the world, with more than 100 million cases reported annually. While there have been extensive studies into the adverse effects that CT infection has on the female genital tract, and on the subsequent ability of these women to conceive, studies into the consequences on male fertility have been limited and controversial. This is in part due to the asymptomatic nature of the infection, where it is estimated that 50% of men with Chlamydia fail to show any symptoms. It is accepted, however, that acute and/or persistent CT infection is the causative agent for conditions such as urethritis, epididymitis, epididymo-orchitis, and potentially prostatitis. As with most infections, the immune system plays a fundamental role in the body’s attempts to eradicate the infection. The first and most important immune response to Chlamydia infection is a local one, whereby immune cells such as leukocytes are recruited to the site of infections, and subsequently secrete pro-inflammatory cytokines and chemokines such as interferon gamma. Immune cells also work to initiate and potentiate chronic inflammation through the production of reactive oxygen species (ROS), and the release of molecules with degradative properties including defensins, elastase, collagenase, cathespins, and lysozyme. This long-term inflammation can lead to cell proliferation (a possible precursor to cancer), tissue remodeling, and scarring, as well as being linked to the onset of autoimmune responses in genetically disposed individuals. This review will focus on the ability of the immune system to recognize and clear acute and persistent chlamydial infections in the male genital tract, and on the paradoxical damage that chronic inflammation resulting from the infection can cause on the reproductive health of the individual.

Androgenic regulation of beta-defensins in the mouse epididymis

BACKGROUND

The majority of beta-defensin family members are exclusively expressed in the epididymis, and some members have been shown to play essential roles in sperm maturation and fertility in rats, mice and humans. Therefore, beta-defensins are hypothesized to be potential targets for contraception and infertility diagnosis and treatment. Clarifying the regulatory mechanisms for the expression of these genes is necessary. Androgen/androgen receptor (AR) signaling plays an important regulatory role in epididymal structure and function. However, very little is known about the androgenic regulation on the production and secretion of the epididymal beta-defensins.

METHODS

The expression of beta-defensins was detected by quantitative RT-PCR. The androgen dependence of beta-defensins was determined by bilateral orchiectomy and androgen supplementation. The androgen response elements (AREs) in the promoters of beta-defensins were identified using the MatInspector software. The binding of AR to AREs was assayed by ChIP-PCR/qPCR.

RESULTS

We demonstrated that 23 mouse caput epididymal beta-defensins were differentially regulated by androgen/androgen receptor. Six genes, Defb18, 19, 20, 39, 41, and 42, showed full regulation by androgens. Ten genes, Defb15, 30, 34, 37, 40, 45, 51, 52, 22 and Spag11a, were partially regulated by androgens. Defb15, 18, 19, 20, 30, 34, 37, 39, 41, 42, 22 and Spag11a were associated with androgen receptor binding sites in their promoter or intronic regions, indicating direct regulation of AR. Six genes, Defb1, 12, 13, 29, 35, and spag11b/c, exhibited an androgen-independent expression pattern. One gene, Defb25, was highly dependent on testicular factors rather on androgens.

CONCLUSIONS

The present study provides novel insights into the mechanisms of androgen regulation on epididymal beta-defensins, enabling a better understanding of the function of beta-defensins in sperm maturation and fertility.

Alpha-melanocyte stimulating hormone: an emerging anti-inflammatory antimicrobial peptide

The alpha-melanocyte stimulating hormone (α-MSH) is a neuropeptide belonging to the melanocortin family. It is well known for its anti-inflammatory and antipyretic effects and shares several characteristics with antimicrobial peptides (AMPs). There have been some recent reports about the direct antimicrobial activity of α-MSH against various microbes belonging to both fungal and bacterial pathogens. Similar to α-MSH's anti-inflammatory properties, its C-terminal residues also exhibit antimicrobial activity parallel to that of the entire peptide. This review is focused on the current findings regarding the direct antimicrobial potential and immunomodulatory mechanism of α-MSH and its C-terminal fragments, with particular emphasis on the prospects of α-MSH based peptides as a strong anti-infective agent.

Combination of alpha-melanocyte stimulating hormone with conventional antibiotics against methicillin resistant Staphylococcus aureus

Our previous studies revealed that alpha-melanocyte stimulating hormone (α-MSH) is strongly active against Staphylococcus aureus (S. aureus) including methicillin resistant S. aureus (MRSA). Killing due to α-MSH occurred by perturbation of the bacterial membrane. In the present study, we investigated the in vitro synergistic potential of α-MSH with five selected conventional antibiotics viz., oxacillin (OX), ciprofloxacin (CF), tetracycline (TC), gentamicin (GM) and rifampicin (RF) against a clinical MRSA strain which carried a type III staphylococcal cassette chromosome mec (SCCmec) element and belonged to the sequence type (ST) 239. The strain was found to be highly resistant to OX (minimum inhibitory concentration (MIC) = 1024 µg/ml) as well as to other selected antimicrobial agents including α-MSH. The possibility of the existence of intracellular target sites of α-MSH was evaluated by examining the DNA, RNA and protein synthesis pathways. We observed a synergistic potential of α-MSH with GM, CF and TC. Remarkably, the supplementation of α-MSH with GM, CF and TC resulted in ≥64-, 8- and 4-fold reductions in their minimum bactericidal concentrations (MBCs), respectively. Apart from membrane perturbation, in this study we found that α-MSH inhibited ∼53% and ∼47% DNA and protein synthesis, respectively, but not RNA synthesis. Thus, the mechanistic analogy between α-MSH and CF or GM or TC appears to be the reason for the observed synergy between them. In contrast, α-MSH did not act synergistically with RF which may be due to its inability to inhibit RNA synthesis (<10%). Nevertheless, the combination of α-MSH with RF and OX showed an enhanced killing by ∼45% and ∼70%, respectively, perhaps due to the membrane disrupting properties of α-MSH. The synergistic activity of α-MSH with antibiotics is encouraging, and promises to restore the lost potency of discarded antibiotics.

Antimicrobial activity and molecular mechanism of the CRES protein

Cystatin-related epididymal spermatogenic (CRES) protein, a member of the cystatin superfamily of cysteine protease inhibitors (also known as CST8), exhibits highly specific, age-dependent expression in mouse testis and epididymis. The CRES protein possesses four highly conserved cysteine residues which govern the overall conformation of the cystatins through the formation of two disulfide bonds. Previous studies have revealed that other cystatin family members, such as cystatin 3 and cystatin 11, show antibacterial activity in vitro. This prompted us to investigate the potential antimicrobial activity of the CRES protein. Colony forming assays and spectrophotometry were used to investigate the effects of recombinant CRES protein on Escherichia coli (E. coli) and Ureaplasma urealyticum (Uu), respectively, in vitro. After incubation of E. coli with CRES recombinant protein fused with glutathione-S-transferase (GST), a substantial decrease in colony forming units was observed, and the effect was dose and time dependent. Furthermore, it took longer for Uu to grow to plateau stage when incubated with GST-CRES recombinant protein compared with the control GST. The antibacterial and Anti-Uu activities were not impaired when the cysteine residues of CRES protein were mutated, indicating that the antimicrobial effect was not dependent on its disulfide bonds. Functional analysis of three CRES polypeptides showed that the N-terminal 30 residues (N30) had no antimicrobial activity while N60 showed similar activity as full-length CRES protein. These results suggest that the active center of CRES protein resides between amino acid residues 31 and 60 of its N-terminus. Mechanistically, E. coli membrane permeabilization was increased in a dose-dependent manner, and macromolecular synthesis was inhibited on treatment with GST-CRES. Together, our data on the antimicrobial activities of CRES protein suggest that it is a novel and innate antimicrobial protein which protecting the male reproductive tract against invading pathogens.

Tissue expression and developmental regulation of chicken cathelicidin antimicrobial peptides

Cathelicidins are a major family of antimicrobial peptides present in vertebrate animals with potent microbicidal and immunomodulatory activities. Four cathelicidins, namely fowlicidins 1 to 3 and cathelicidin B1, have been identified in chickens. As a first step to understand their role in early innate host defense of chickens, we examined the tissue and developmental expression patterns of all four cathelicidins. Real-time PCR revealed an abundant expression of four cathelicidins throughout the gastrointestinal, respiratory, and urogenital tracts as well as in all primary and secondary immune organs of chickens. Fowlicidins 1 to 3 exhibited a similar tissue expression pattern with the highest expression in the bone marrow and lung, while cathelicidin B1 was synthesized most abundantly in the bursa of Fabricius. Additionally, a tissue-specific regulatory pattern was evident for all four cathelicidins during the first 28 days after hatching. The expression of fowlicidins 1 to 3 showed an age-dependent increase both in the cecal tonsil and lung, whereas all four cathelicidins were peaked in the bursa on day 4 after hatching, with a gradual decline by day 28. An abrupt augmentation in the expression of fowlicidins 1 to 3 was also observed in the cecum on day 28, while the highest expression of cathelicidin B1 was seen in both the lung and cecal tonsil on day 14. Collectively, the presence of cathelicidins in a broad range of tissues and their largely enhanced expression during development are suggestive of their potential important role in early host defense and disease resistance of chickens.

Molecular characterization of a tandem-repeat galectin-9 (RuGlec9) from Korean rose bitterling (Rhodeus uyekii)

Galectin-9 is a b-galactoside-binding lectin that regulates many cellular functions, ranging from cell adhesion to pathogen recognition. We isolated and characterized the cDNA of tandem-repeat galectin-9 (RuGlec9) from the Korean rose bitterling (Rhodeus uyekii), an endemic Korean fish belonging to the Acheilognathinae subfamily of the Cyprinidae family. RuGlec9 cDNA is 1486 bp long and encodes a polypeptide of 323 amino acids containing two carbohydrate-recognition domains connected by a linker peptide. The deduced amino acid sequence of RuGlec9 shows 45-84% amino acid sequence identity to other galectin-9 sequences, including those from mammals and fish. RuGlec9 appeared in a large cluster with other galectin-9 sequences from fish and is more closely related to galectin-9 from Danio rerio than to those of other fish and mammals. RuGlec9 mRNA was expressed highly in the testis, spleen, intestine, stomach, and liver, and moderately in the brain, kidney, ovary, and gills of normal Korean rose bitterling. RuGlec9 mRNA expression in the spleen was increased by lipopolysaccharide. These results suggest that RuGlec9 plays a role in innate immunity in Korean rose bitterling.

Genomic organization, tissue distribution and functional characterization of the rat Pate gene cluster

The cysteine rich prostate and testis expressed (Pate) proteins identified till date are thought to resemble the three fingered protein/urokinase-type plasminogen activator receptor proteins. In this study, for the first time, we report the identification, cloning and characterization of rat Pate gene cluster and also determine the expression pattern. The rat Pate genes are clustered on chromosome 8 and their predicted proteins retained the ten cysteine signature characteristic to TFP/Ly-6 protein family. PATE and PATE-F three dimensional protein structure was found to be similar to that of the toxin bucandin. Though Pate gene expression is thought to be prostate and testis specific, we observed that rat Pate genes are also expressed in seminal vesicle and epididymis and in tissues beyond the male reproductive tract. In the developing rats (20-60 day old), expression of Pate genes seem to be androgen dependent in the epididymis and testis. In the adult rat, androgen ablation resulted in down regulation of the majority of Pate genes in the epididymides. PATE and PATE-F proteins were found to be expressed abundantly in the male reproductive tract of rats and on the sperm. Recombinant PATE protein exhibited potent antibacterial activity, whereas PATE-F did not exhibit any antibacterial activity. Pate expression was induced in the epididymides when challenged with LPS. Based on our results, we conclude that rat PATE proteins may contribute to the reproductive and defense functions.

Evaluation of amoebicidal potential of Paneth cell cryptdin-2 against Entamoeba histolytica

BACKGROUND

Amoebiasis is a major public health problem in tropical and subtropical countries. Currently, metronidazole is the gold choice medication for the treatment of this disease. However, reports have indicated towards the possibility of development of metronidazole-resistance in Entamoeba strains in near future. In view of the emergence of this possibility, in addition to the associated side effects and mutagenic ability of the currently available anti-amoebic drugs, there is a need to explore newer therapeutics against this disease. In this context, the present study evaluated the amoebicidal potential of cryptdin-2 against E. histolytica.

METHODS/PRINCIPAL FINDINGS

In the present study, cryptdin-2 exhibited potent in-vitro amoebicidal activity against E. histolytica in a concentration dependent manner at a minimum amoebicidal concentration (MAC) of 4 mg/L. Scanning electron microscopy as well as phase contrast microscopic investigations of cryptdin-2 treated trophozoites revealed that the peptide was able to induce significant morphological alterations in terms of membrane wrinkling, leakage of the cytoplasmic contents and damaged plasma membrane suggesting a possible membrane dependent amoebicidal activity. N-phenyl napthylamine (NPN) uptake assay in presence of sulethal, lethal as well as twice the lethal concentrations further confirmed the membrane-dependent mode of action of cryptdin-2 and suggested that the peptide could permeabilize the plasma membrane of E. histolytica. It was also found that cryptdin-2 interfered with DNA, RNA as well as protein synthesis of E. histolytica exerting the highest effect against DNA synthesis. Thus, the macromolecular synthesis studies correlated well with the observations of membrane permeabilization studies.

SIGNIFICANCE/CONCLUSIONS

The amoebicidal efficacy of cryptdin-2 suggests that it may be exploited as a promising option to combat amoebiasis or, at least, may act as an adjunct to metronidazole and/or other available anti-amoebic drugs.

Characterization of a novel lysozyme-like 4 gene in the rat

Lysozyme-like proteins (LYZLs) belong to the class of c-type lysozymes and are not well characterized in many species including the rat. In this study, using in silico and molecular biology techniques, we report the identification, cloning and characterization of rat Lyzl4 gene and also determine the expression pattern of Lyzl1, Lyzl3 and Lyzl6. The rat Lyzl genes were found to be distributed on three chromosomes and all of them retained the characteristic eight cysteine signature of c-type lysozyme. Homology modeling of rat LYZL4 indicated that its structure is similar to that of the mouse SLLP1. In the male reproductive tract of rat, Lyzl gene expression was confined to the testis. Lyzl1 and Lyzl4 were found to be expressed in tissues beyond the male reproductive tract, whereas Lyzl3 and Lyzl6 were not. Lyzl expression in the developing (10-60 day old) rats was androgen dependent in the testis. Immunodetection using antibodies against rat LYZL4 revealed the presence of LYZL4 protein in the germinal layer of the testes and on the sperm tail. Recombinant LYZL4 did not exhibit antibacterial, muramidase and isopeptidase activities characteristic to c-type lysozyme. To the best of our knowledge, for the first time we report the characterization of Lyzl genes in the rat. Results of our study indicate that rat LYZL proteins may have an important role in male reproductive tract function.

Immunophysiology and pathology of inflammation in the testis and epididymis

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

Purification and structural characterization of a novel antibacterial peptide from Bellamya bengalensis: activity against ampicillin and chloramphenicol resistant Staphylococcus epidermidis

Increasing tendency of clinical bacterial strains resistant to conventional antibiotics has being a great challenge to the public's health. Antimicrobial peptides, a new class of antibiotics is known to have the activity against a wide range of bacteria resistant to conventional antibiotics. An antimicrobial peptide of 1676 Da was purified from Bellamya bengalensis, a fresh water snail, using ultrafiltration and reversed phase liquid chromatography. The effect of this peptide on Staphylococcus epidermidis resistant to ampicillin and chloramphenicol was investigated; the MIC and MBC values were 8 μg/ml and 16 μg/ml, respectively. Complete sequence of the peptide was determined by tandem mass spectrometry (MS/MS). Further, peptide net charge, hydrophobicity and molecular modeling were evaluated in silico for better understanding the probable mechanisms of action. The peptide showed the specificity to bacterial membranes. Hence, this reported peptide revealed a promising candidate to contribute in the development of therapeutic agent for Staphylococcal infections.