Erythronecroptosis: an overview of necroptosis or programmed necrosis in red blood cells

Necroptosis is considered a programmed necrosis that requires receptor-interacting protein kinase 1 (RIPK1), receptor-interacting protein kinase 3 (RIPK3), and pore-forming mixed lineage kinase domain-like protein (MLKL) to trigger a regulated cell membrane lysis. Membrane rupture in necroptosis has been shown to fuel innate immune response due to release of damage-associated molecular patterns (DAMPs). Recently published studies indicate that mature erythrocytes can undergo necroptosis as well. In this review, we provide an outline of multiple cell death modes occurring in erythrocytes, discuss possible immunological aspects of diverse erythrocyte cell deaths, summarize available evidence related to the ability of erythrocytes to undergo necroptosis, outline key involved molecular mechanisms, and discuss the potential implication of erythrocyte necroptosis in the physiology and pathophysiology. Furthermore, we aim to highlight the interplay between necroptosis and eryptosis signaling in erythrocytes, emphasizing specific characteristics of these pathways distinct from their counterparts in nucleated cells. Thus, our review provides a comprehensive summary of the current knowledge of necroptosis in erythrocytes. To reflect critical differences between necroptosis of nucleated cells and necroptosis of erythrocytes, we suggest a term erythronecroptosis for necroptosis of enucleated cells.

Prediction and characterization of a novel hemoglobin-derived mutant peptide (mTgHbP7) from Tegillarca granosa

The hemoglobin (Hb) is identified in Tegillarca granosa and its derived peptides have been proved to possess antibacterial activity against gram-positive and gram-negative bacteria. In this study, we identified a series of novel antimicrobial peptides (AMPs) and artificially mutated AMPs derived from subunits of T. granosa Hbs, among which, a mutant T. granosa hemoglobin peptide (mTgHbP) mTgHbP7, was proved to possess predominant antibacterial activity against three bacteria strains (Vibrio alginolyticus, V. parahaemolyticus and Escherichia coli). Besides, mTgHbP7 was predicted to form α-helical structure, which was known to be an important feature of bactericidal AMPs. Furthermore, upon contact with HEK293 cell line, we confirmed that mTgHbP7 had no cytotoxicity to mammalian cell even at a high concentration of 160 μM. Therefore, the findings reported here provide a rationalization for antimicrobial peptide prediction and optimization from mollusk hemoglobin, which will be useful for future development of antimicrobial agents.

Bioinformatic Analysis of the Wound Peptidome Reveals Potential Biomarkers and Antimicrobial Peptides

Wound infection is a common and serious medical condition with an unmet need for improved diagnostic tools. A peptidomic approach, aided by mass spectrometry and bioinformatics, could provide novel means of identifying new peptide biomarkers for wound healing and infection assessment. Wound fluid is suitable for peptidomic analysis since it is both intimately tied to the wound environment and is readily available. In this study we investigate the peptidomes of wound fluids derived from surgical drainages following mastectomy and from wound dressings following facial skin grafting. By applying sorting algorithms and open source third party software to peptidomic label free tandem mass spectrometry data we provide an unbiased general methodology for analyzing and differentiating between peptidomes. We show that the wound fluid peptidomes of patients are highly individualized. However, differences emerge when grouping the patients depending on wound type. Furthermore, the abundance of peptides originating from documented antimicrobial regions of hemoglobin in infected wounds may contribute to an antimicrobial wound environment, as determined by in silico analysis. We validate our findings by compiling literature on peptide biomarkers and peptides of physiological significance and cross checking the results against our dataset, demonstrating that well-documented peptides of immunological significance are abundant in infected wounds, and originate from certain distinct regions in proteins such as hemoglobin and fibrinogen. Ultimately, we have demonstrated the power using sorting algorithms and open source software to help yield insights and visualize peptidomic data.

Cryptic Host Defense Peptides: Multifaceted Activity and Prospects for Medicinal Chemistry

Host defense peptides (HDPs) comprise a heterogeneous group of evolutionarily conserved and biologically active small molecules that are produced by different organisms. HDPs are widely researched because they often have multiple biological activities, for example antimicrobial, immunomodulatory and anticancer activity. In this context, in this review we focus on cryptic HDPs, molecules derived specifically from proteolytic processing of endogenous precursor proteins. Here, we explore the biological activity of such molecules and we further discuss the development of optimized sequences based on these natural cryptic HDPs. In addition, we present clinical-phase studies of cryptic HDPs (natural or optimized), and point out the possible applicability of these molecules in medicinal chemistry.

The extremely halophilic archaeon Halobacterium salinarum ETD5 from the solar saltern of Sfax (Tunisia) produces multiple halocins

The extremely halophilic archaeon Halobacterium salinarum strain ETD5 was previously isolated from the solar saltern of Sfax (Tunisia) and shown to encode and express halocin S8. The Hbt. salinarum ETD5 culture supernatant was shown here to exhibit high antimicrobial activity against several halophilic archaea and bacteria of different genera, showing a cross-domain inhibition. The antimicrobial activity was destroyed by proteases, thus pointing to halocins. A bioguided purification procedure was applied using two chromatography steps and antimicrobial assays directed against Halorubrum chaoviator ETR14. In-gel screening assay showed the presence of two antimicrobial bands of approximately 8 and 14 kDa, for which characterization was investigated by N-terminal sequencing and mass spectrometry. The full-length form of halocin S8 that contains 81 amino acids and differs from the 36 amino acid short-length halocin S8 previously described from an uncharacterized haloarchaeon S8a, was identified in the 8 kDa halocin band. A novel halocin that we termed halocin S14 was found in the 14 kDa band. It exhibits amino acid sequence identities with the N-terminally truncated region of the archaeal Mn-superoxide dismutase. These results show that Hbt. salinarum ETD5 produces multiple halocins, a feature that had not been described until now in the domain Archaea.

Cryptides: latent peptides everywhere

Proteomic surveys with top-down platforms are today revealing thousands of naturally occurring fragments of bigger proteins. Some of them have not functional meaning because they derive from pathways responsible for protein degradation, but many have specific functions, often completely different from that one of the parent proteins. These peptides encrypted in the protein sequence are nowadays called cryptides. They are frequent in the animal and plant kingdoms and represent a new interesting -omic field of investigation. To point out how much widespread is their presence, we describe here the most studied cryptides from very common sources such as serum albumin, immunoglobulins, hemoglobin, and from saliva and milk proteins. Given its vastness, it is unfeasible to cover the topic exhaustively, therefore only several selected examples of cryptides from other sources are thereafter reported. Demanding is the development of new -omic platforms for the functional screening of new cryptides, which could provide suggestion for peptides and peptido-mimetics with variegate fields of application.

High-Throughput Identification of Antimicrobial Peptides from Amphibious Mudskippers

Widespread existence of antimicrobial peptides (AMPs) has been reported in various animals with comprehensive biological activities, which is consistent with the important roles of AMPs as the first line of host defense system. However, no big-data-based analysis on AMPs from any fish species is available. In this study, we identified 507 AMP transcripts on the basis of our previously reported genomes and transcriptomes of two representative amphibious mudskippers, Boleophthalmus pectinirostris (BP) and Periophthalmus magnuspinnatus (PM). The former is predominantly aquatic with less time out of water, while the latter is primarily terrestrial with extended periods of time on land. Within these identified AMPs, 449 sequences are novel; 15 were reported in BP previously; 48 are identically overlapped between BP and PM; 94 were validated by mass spectrometry. Moreover, most AMPs presented differential tissue transcription patterns in the two mudskippers. Interestingly, we discovered two AMPs, hemoglobin β1 and amylin, with high inhibitions on Micrococcus luteus. In conclusion, our high-throughput screening strategy based on genomic and transcriptomic data opens an efficient pathway to discover new antimicrobial peptides for ongoing development of marine drugs.

Fungicidal activity of peptides encoded by immunoglobulin genes

Evidence from previous works disclosed the antimicrobial, antiviral, anti-tumour and/or immunomodulatory activity exerted, through different mechanisms of action, by peptides expressed in the complementarity-determining regions or even in the constant region of antibodies, independently from their specificity and isotype. Presently, we report the selection, from available databases, of peptide sequences encoded by immunoglobulin genes for the evaluation of their potential biological activities. Synthetic peptides representing the translated products of J lambda and J heavy genes proved to act in vitro against pathogenic fungi, entering yeast cells and causing their death, and exerted a therapeutic effect in a Galleria mellonella model of infection by Candida albicans. No haemolytic, cytotoxic and genotoxic effects were observed on mammalian cells. These findings raise the hypothesis that antibodies could be the evolutionary result of the adaptive combination of gene products ancestrally devoted to innate antimicrobial immunity.

Expression of hemoglobin-α and β subunits in human vaginal epithelial cells and their functional significance

Hemoglobin (Hb) is a major protein involved in transport of oxygen (O2). It consists of Hb-α and Hb-β subunits, which are normally expressed by cells of erythroid lineage. However, till recently, it was not known whether non-erythroid cells like vaginal cells synthesize Hb and whether it has any functional significance. Therefore, we designed the following objectives: (1) to establish in-vitro culture system of human primary vaginal epithelial cells (hPVECs), (2) to determine whether Hb-α and Hb-β proteins are truly synthesized by hPVECs, (3) to evaluate the effect of LPS (lipopolysaccharide) on the expression of Hb-α and Hb-β proteins (4) to decipher the significance of the Hb-α and Hb-β expression in hPVECs and (5) to determine the molecular mechanism regulating the expression of Hb-α in hPVECs. To accomplish these studies, we applied a battery of assays such as RT-PCR, qRT-PCR, Flow cytometry, western blot, and immunofluorescence, Electrophoretic mobility shift assay (EMSA) and chromatin immunoprecipitation (ChIP). The results revealed the expression of Hb-α and Hb-β at both mRNA and protein level in hPVECs. The expression was significantly upregulated following LPS treatment (10μg/ml for 6 hrs) and these results are comparable with the expression induced by LPS in human vaginal epithelial cell line (VK2/E6E7). These cells constitutively produced low levels of pro-inflammatory (IL-6) and anti-inflammatory (IL-10) cytokines. Also, the response of phosphorylated (p65)-NF-κB to LPS was upregulated with increased expression of IL-6, Toll-like receptor-4 (TLR4) and human beta defensin-1 (hBD-1) in hPVECs and VK2/E6E7 cells. However, Bay 11-7082 treatment (5μM for 24 hrs) could neutralize the effect of LPS-induced p65-NF-κB activity and represses the production`of Hb-α and Hb-β. The results of EMSA revealed the presence of putative binding sites of NF-κB in the human Hb-α promoter region (nt-115 to -106). ChIP analysis confirmed the binding of NF-κB to Hb-α promoter. In conclusion, the present findings revealed for the first time that hPVECs synthesized Hb-α and Hb-β and the expression is comparable with the expression of VK2/E6E7 cells. The identification of NF-κB regulatory sequences in Hb-α promoter, whose activation is associated with immune response of hPVECs, indicating Hb-α and Hb-β may act as an endogenous antimicrobial defense protein against vaginal inflammation/infections.

Immunological properties of oxygen-transport proteins: hemoglobin, hemocyanin and hemerythrin

It is now well documented that peptides with enhanced or alternative functionality (termed cryptides) can be liberated from larger, and sometimes inactive, proteins. A primary example of this phenomenon is the oxygen-transport protein hemoglobin. Aside from respiration, hemoglobin and hemoglobin-derived peptides have been associated with immune modulation, hematopoiesis, signal transduction and microbicidal activities in metazoans. Likewise, the functional equivalents to hemoglobin in invertebrates, namely hemocyanin and hemerythrin, act as potent immune effectors under certain physiological conditions. The purpose of this review is to evaluate the true extent of oxygen-transport protein dynamics in innate immunity, and to impress upon the reader the multi-functionality of these ancient proteins on the basis of their structures. In this context, erythrocyte-pathogen antibiosis and the immune competences of various erythroid cells are compared across diverse taxa.

Hb40-61a: Novel analogues help expanding the knowledge on chemistry, properties and candidacidal action of this bovine α-hemoglobin-derived peptide

This study expands the knowledge on chemical synthesis and properties of Hb40-61a as well as provides results of the first steps given towards knowing how it kills Candida cells. For the first time, this peptide, its all-D analogue (D-Hb40-61a) and its fluorescently labeled analogue (FAM-Hb40-61a) were successfully assembled on resin at 60°C using conventional heating in all steps. Purified and characterized, these peptides exhibited very low toxicity on human erythrocytes. Hb40-61a and D-Hb40-61a were equally active against Candida strains, ruling out sterically specific interactions on their working mechanism. Cell permeabilization assays confirmed progressive damage of the yeast plasma membrane with increasing concentrations of Hb40-61a. While experiment using the fluorescent probe DiBAC4(5) revealed that this synthetic hemocidin alters the yeast plasma membrane potential, test employing DPH indicated that Hb40-61a might affect its dynamics. Exposure of the yeast cells to FAM-Hb40-61a showed that the peptide accumulates in the cell membrane at the ½ MIC, but stains about 97% of the cells at the MIC. Such effect is salt-dependent and partially energy-dependent. These new findings indicate that the central target of Hb40-61a in Candida cells is the plasma membrane and that this synthetic hemocidin should be considered as a potential candidacidal for topic uses.

HbAHP-25, an In-Silico Designed Peptide, Inhibits HIV-1 Entry by Blocking gp120 Binding to CD4 Receptor

Human Immunodeficiency Virus (HIV-1) poses a serious threat to the developing world and sexual transmission continues to be the major source of new infections. Therefore, the development of molecules, which prevent new HIV-1 infections, is highly warranted. In the present study, a panel of human hemoglobin (Hb)-α subunit derived peptides and their analogues, with an ability to bind gp120, were designed in-silico and their anti-HIV-1 activity was evaluated. Of these peptides, HbAHP-25, an analogue of Hb-α derived peptide, demonstrated significant anti-HIV-1 activity. HbAHP-25 was found to be active against CCR5-tropic HIV-1 strains (ADA5 and BaL) and CXCR4-tropic HIV-1 strains (IIIB and NL4-3). Surface plasmon resonance (SPR) and ELISA revealed direct interaction between HbAHP-25 and HIV-1 envelope protein, gp120. The peptide prevented binding of CD4 to gp120 and blocked subsequent steps leading to entry and/or fusion or both. Anti-HIV activity of HbAHP-25 appeared to be specific as it failed to inhibit the entry of HIV-1 pseudotyped virus (HIV-1 VSV). Further, HbAHP-25 was found to be non-cytotoxic to TZM-bl cells, VK2/E6E7 cells, CEM-GFP cells and PBMCs, even at higher concentrations. Moreover, HbAHP-25 retained its anti-HIV activity in presence of seminal plasma and vaginal fluid. In brief, the study identified HbAHP-25, a novel anti-HIV peptide, which directly interacts with gp120 and thus has a potential to inhibit early stages of HIV-1 infection.

BF-30 effectively inhibits ciprofloxacin-resistant bacteria in vitro and in a rat model of vaginosis

Bacterial infections are becoming increasingly difficult to treat due to the increasing number of multidrug-resistant strains. Cathelicidin-BF (BF-30) is a cathelicidin-like antimicrobial peptide and exhibits broad antimicrobial activity against bacteria. In the present study, the antibacterial activity of BF-30 against ciprofloxacin-resistant Escherichia coli and Staphylococcus aureus was examined, and the protective effects of this peptide against these bacteria in rats with bacterial vaginosis were identified for the first time. The data showed that BF-30 had effective antimicrobial activities against ciprofloxacin-resistant E. coli and S. aureus. The minimal inhibitory concentrations for both bacterial strains were 16 μg/ml, and the minimal bactericidal concentrations were 64 and 128 μg/ml, respectively. A time course experiment showed that the CFU counts rapidly decreased after BF-30 treatment, and the bacteria were nearly eliminated within 4 h. BF-30 could reduce the fold change (CFU/ml) in local colonization by drug-resistant E. coli and S. aureus to 0.01 at a dose of 0.8 mg/kg/day in the rats' vaginal secretions. In addition, BF-30 induced membrane permeabilization and bound to the genomic DNA, interrupting protein synthesis. Taken together, our data demonstrate that BF-30 has potential therapeutic value for the prevention and treatment of bacterial vaginosis.

Molecular cloning and expression of α-globin and β-globin genes from crocodile (Crocodylus siamensis)

The first report of complete nucleotide sequences for α- and β-globin chains from the Siamese hemoglobin (Crocodylus siamensis) is given in this study. The cDNAs encoding α- and β-globins were cloned by RT-PCR using the degenerate primers and by the rapid amplification of cDNA ends method. The full-length α-globin cDNA contains an open reading frame of 423 nucleotides encoding 141 amino acid residues, whereas the β-globin cDNA contains an open reading frame of 438 nucleotides encoding 146 amino acid residues. The authenticity of both α- and β-globin cDNA clones were also confirmed by the heterologous expression in Escherichia coli (E. coli). This is the first time that the recombinant C. siamensis globins were produced in prokaryotic system. Additionally, the heme group was inserted into the recombinant proteins and purified heme-bound proteins were performed by affinity chromatography using Co(2+)-charged Talon resins. The heme-bound proteins appeared to have a maximum absorbance at 415 nm, indicated that the recombinant proteins bound to oxygen and formed active oxyhemoglobin (HbO2). The results indicated that recombinant C. siamensis globins were successfully expressed in prokaryotic system and possessed an activity as ligand binding protein.

Molecular identification of vaginal fluid by microbial signature

The discrimination of body fluids in forensic examinations can play an important role in crime scene reconstruction. Conventional methods rely on the detection of antigens or enzymatic activity, limiting detection sensitivity and specificity, particularly on old forensic samples. Methods based on human RNA analysis are not easily applicable to samples exposed to harsh and degrading environments. An alternative approach based on the identification of prokaryotic genomes was developed. Specific bacterial communities are characteristic typical of different human non-sterile body fluids: the molecular characterization of a microbial signature, and not the typing of single bacterial species, can effectively lead to univocal identification of these fluids. A multiplex real time PCR assay was developed using oligonucleotide mixtures targeting genomes specific for a selected group of bacteria. Microflora DNA (mfDNA) was extracted from vaginal, oral and fecal clinical swabs. In addition forensic samples were processed. Vaginal samples showed a strong specific signal for bacteria of the female genital tract. Oral samples clearly showed signal for bacteria present in saliva, and in fecal samples the main signal was from Enterococcaceae. Vaginal casework samples showed results comparable to freshly collected ones; moreover the DNA extracted was successfully used for STR typing. Also mixtures of body fluids were analyzed, providing a microbiological signature compatible with the presence of microbes of oral, fecal and vaginal origin. The presented method can be useful in identifying biological fluids, and it is based on DNA technologies already available in forensic laboratories and feasible for further high throughput automation.

Analyzing the cryptome: uncovering secret sequences

The mammalian cryptome consists of bioactive peptides generated by the proteolysis of precursor proteins. It is speculated that the cryptide repertoire increases the complexity of the proteome by an order of magnitude. Cryptides have been found to function in a wide range of processes including neuronal signaling, antigen presentation, and the inflammatory response. Due to their potential as therapeutic agents, there has been an increasing interest in studying cryptides. In this review, we discuss different approaches for discovering these hidden peptides and how proteomic tools can be utilized to aid in their identification and characterization.

Identification and characterization of anti-microbial peptides from rabbit vaginal fluid

Antimicrobial peptides (AMPs) serve as a first line of host defense and represent an important, though poorly understood components of the innate immune system. The present study was an attempt to identify and characterize the major molecules having anti-bacterial activities from the vaginal fluid of rabbit, Oryctologus cuniculus. AMPs from the rabbit vaginal fluid (RVF) were identified in the acid extracts of pooled RVF samples after RP-HPLC purification. The protein, RVFAMP was effective against gram negative (Escherichia coli and Pseudomonas aeruginosa) and gram positive (Staphylococcus aureus and Streptococcus pyogenes) bacteria. The results of acid urea-PAGE-gel overlay assay (AU-PAGE-GOA) demonstrated clear zone of growth inhibition of E. coli corresponding to 6 and 15 kDa protein bands. LC-MS data of these proteins indicated that 15 kDa protein consists of lysozyme, lipopolysaccharide binding protein (LBP), hemoglobin-α and β subunits (Hb-α/β), whereas 9 kDa protein band consists of transthyretin and calcyclin while uteroglobulin and neutrophil antibacterial peptide-5 (NAMP-5) are present in the 6 kDa protein band. Of the eight proteins, Hb-α derived protein was further characterized, as it showed the highest Probability Based Mowse Score (PBMS) of 288. A 25mer peptide, RVFHbαp was active against several clinical pathogens as demonstrated by minimum inhibitory concentration (MIC) and radial diffusion assays (RDA). The interaction of RVFHbαP with bacterial liposome membrane was assessed by calcein dye leakage assay. RVFHbαP did not show cytotoxicity against human endocervical cells (End1/E6E7) or erythrocytes. RT-PCR and immunofluorescence results revealed the expression of RVFHbαP mRNA and protein in rabbit vaginal tissue. To the best our knowledge, this is the first report describing the detection of AMPs in RVFs. In conclusion, these studies indicated that vaginal epithelial cells (VEC) derived RVFHbαP may have therapeutic potential in the management of reproductive well being of rabbits. The major reason for undertaking this study in rabbits is that, it forms an excellent in vivo model system for human's studies.