Molecular characterization, expression analysis, and bactericidal activity of the derivative peptides of TFPI-1 and TFPI-2 in half-smooth tongue sole, Cynoglossus semilaevis

A review of soluble factors and receptors involved in fish skin immunity: The tip of the iceberg

The immune system of fish possesses soluble factors, receptors, pathways and cells very similar to those of the other vertebrates' immune system. Throughout evolutionary history, the exocrine secretions of organisms have accumulated a large reservoir of soluble factors that serve to protect organisms from microbial pathogens that could disrupt mucosal barrier homeostasis. In parallel, a diverse set of recognition molecules have been discovered that alert the organism to the presence of pathogens. The known functions of both the soluble factors and receptors mentioned above encompass critical aspects of host defense, such as pathogen binding and neutralization, opsonization, or modulation of inflammation if present. The molecules and receptors cooperate and are able to initiate the most appropriate immune response in an attempt to eliminate pathogens before host infection can begin. Furthermore, these recognition molecules, working in coordination with soluble defence factors, collaboratively erect a robust and perfectly coordinated defence system with complementary specificity, activity and tissue distribution. This intricate network constitutes an immensely effective defence mechanism for fish. In this context, the present review focuses on some of the main soluble factors and recognition molecules studied in the last decade in the skin mucosa of teleost fish. However, knowledge of these molecules is still very limited in all teleosts. Therefore, further studies are suggested throughout the review that would help to better understand the functions in which the proteins studied are involved.

Antimicrobial and Immunoregulatory Activities of TS40, a Derived Peptide of a TFPI-2 Homologue from Black Rockfish (Sebastes schlegelii)

Tissue factor pathway inhibitor-2 (TFPI-2) is a Kunitz-type serine protease inhibitor. Previous reports have shown that TFPI-2 plays an important role in innate immunity, and the C-terminal region of TFPI-2 proved to be active against a broad-spectrum of microorganisms. In this study, the TFPI-2 homologue (SsTFPI-2) of black rockfish (Sebastods schegelii) was analyzed and characterized, and the biological functions of its C-terminal derived peptide TS40 (FVSRQSCMDVCAKGAKQHTSRGNVRRARRNRKNRITYLQA, corresponding to the amino acid sequence of 187-226) was investigated. The qRT-PCR (quantitative real-time reverse transcription-PCR) analysis showed that the expression of SsTFPI-2 was higher in the spleen and liver. The expression of SsTFPI-2 increased significantly under the stimulation of Listonella anguillarum. TS40 had a strong bactericidal effect on L. anguillarum and Staphylococcus aureus. Further studies found that TS40 can destroy the cell structure and enter the cytoplasm to interact with nucleic acids to exert its antibacterial activity. The in vivo study showed that TS40 treatment could significantly reduce the transmission of L. anguillarum and the viral evasion in fish. Finally, TS40 enhanced the respiratory burst ability, reactive oxygen species production and the expression of immune-related genes in macrophages, as well as promoted the proliferation of peripheral blood leukocytes. These results provide new insights into the role of teleost TFPI-2.

A teleost bactericidal permeability-increasing protein-derived peptide that possesses a broad antibacterial spectrum and inhibits bacterial infection as well as human colon cancer cells growth

The bactericidal permeability-increasing protein (BPI) is a multifunctional cationic protein produced by neutrophils with antibacterial, antitumor, and LPS-neutralizing properties. In teleost, a number of BPIs have been reported, but their functions are very limited. In this study, an N-terminal peptide, BO18 (with 18 amino acids), derived from rock bream (Oplegnathus fasciatus) BPI, was synthesized and investigated for its antibacterial spectrum, action mechanism, immunoregulatory property as well as the inhibition effects on bacterial invasion and human colon cancer cells growth. The results showed that BO18 was active against Gram-positive bacteria Bscillus subiilis, Micrococcus luteus, and Staphylococcus aureus, as well as Gram-negative bacteria Vibrio alginolyticus, Vibrio litoralis, Vibrio parahaemolyticus and Vibrio vulnificus. BO18 treatment facilitated the bactericidal process of erythromycin and rifampicin by enhancing the permeability of the outer membrane. During its interaction with V. alginolyticus, BO18 exerted its antibacterial activity by destroying cell membrane integrity, penetrating into the cytoplasm and binding to genomic DNA and total RNA. In vitro analysis indicated BO18 could enhance the respiratory burst ability and regulate the expression of immune related genes of macrophages. In vivo detection showed the administration of fish with BO18 before bacterial infection significantly reduced pathogen dissemination and replication in tissues. In addition, BO18 exerted a cytotoxic effect on the growth of human colon cancer cells HT-29. Together, these results add new insights into the function of teleost BPIs, and support that BO18 is a novel and broad-spectrum antibacterial peptide with potential to apply in fighting pathogenic infection in aquaculture.

Expression analysis of tissue factor pathway inhibitors TFPI-1 and TFPI-2 in Paralichthys olivaceus and antibacterial and anticancer activity of derived peptides

Tissue factor pathway inhibitors (TFPI), including TFPI-1 and TFPI-2, are Kunitz-type serine protease inhibitors that mainly inhibit the blood coagulation induced by tissue factors. Previous reports on teleost proved TFPI play important roles in innate immunity. In this study, two TFPI (PoTFPI-1 and PoTFPI-2) molecules from Japanese flounder (Paralichthys olivaceus) were analyzed and characterized for their expression patterns, antibacterial and anticancer activities of the C-terminal derived peptides. Quantitative real time RT-PCR analysis shows that constitutive PoTFPI-1 expression occurred, in increasing order, in the brain, muscle, spleen, gills, head kidney, blood, intestine, heart, and liver; PoTFPI-2 was expressed, in increasing order, in the brain, gills, head kidney, muscle, intestine, spleen, liver, heart, and blood. Under the stimulation of fish pathogens, both PoTFPI-1 and PoTFPI-2 expressions increased significantly in a manner that depended on the pathogens, tissue type, and infection stage. Furthermore, C-terminal peptides TP25 and TP26, derived from PoTFPI-1 and PoTFPI-2, respectively, were synthesized and proved to be active against Micrococcus luteus (for TP25 and TP26) and Staphylococcus aureus (for TP25) via retardation effects on bacterial nucleic acids. In addition, TP25 and TP26 also displayed significant inhibitory effects on human colon cancer cell line HT-29. These results reveal that both PoTFPI-1 and PoTFPI-2 play important roles in host innate immunity. The antibacterial activity and anticancer cells function of TP25 and TP26 will add new insights into the roles of teleost TFPI.

TC26, a teleost TFPI-1 derived antibacterial peptide that induces degradation of bacterial nucleic acids and inhibits bacterial infection in vivo

At present, several reports have indicated that the C-terminal peptides of tissue factor pathway inhibitor 1 (TFPI-1) were active antibacterial peptides. However, the functions of TFPI-1 C-terminal peptides in teleost are still very limited. In this study, a C-terminal peptide, TC26 (with 26 amino acids), derived from common carp (Cyprinus carpio) TFPI-1, was synthesized and investigated for its antibacterial spectrum, action mechanism, as well as the in vivo effects on bacterial invasion. Our results showed that TC26 was active against Gram-positive bacteria Micrococcus luteus and Staphylococcus aureus, as well as Gram-negative bacterium Vibrio vulnificus. TC26 treatment facilitated the bactericidal process of erythromycin by enhancing the out-membrane permeability of V. vulnificus. During the bactericidal process, TC26 killed the target bacterial cells Vibrio vulnificus, by destroying cell membrane integrity, penetrating into the cytoplasm and inducing degradation of genomic DNA and total RNA. In vivo study showed that administration of turbot with TC26 before bacterial infection significantly reduced pathogen dissemination and replication in tissues. These results indicated that TC26 is a novel and active antibacterial peptide and may play a vital role in fighting pathogenic infection in aquaculture.

Association of TFPI polymorphisms rs8176592, rs10931292, and rs10153820 with venous thrombosis: A meta-analysis

BACKGROUND

Tissue factor pathway inhibitor (TFPI) polymorphisms are known to be involved in venous thrombosis; however, any correlation between the TFPI polymorphisms rs8176592, rs10931292, and rs10153820 and venous thrombosis remains controversial. This meta-analysis aimed to elucidate the relationship between these TFPI polymorphisms and the susceptibility to venous thrombosis.

METHODS

A literature search for relevant studies was conducted in PubMed, Embase, Cochrane Library, China National Knowledge Infrastructure (CNKI), and Wanfang Med Online databases. Odds ratios (ORs) and their corresponding 95% confidence intervals (95% CIs) were calculated using fixed-effect/random-effect models by the STATA 12.0 software. Sources of heterogeneity were analyzed by subgroup analysis.

RESULTS

Eleven case-control studies involving 3740 subjects (1362 venous thrombosis patients and 2378 healthy controls) were included. The TFPI rs8176592 polymorphism was associated with increased risk of venous thrombosis in the whole population, while no significant association was found between rs10931292/rs10153820 and venous thrombosis. In subgroup analysis based on ethnicity, an increased risk was observed with rs8176592 polymorphism in Asians (Recessive model, OR = 1.48, 95% CI = 1.06-2.07, P = .023). An increased risk associated with rs10931292 was identified in non-Asians (Recessive model, OR = 1.42, 95% CI = 1.03-1.97, P = .033). No significant association was found in either Asians or non-Asians with the rs10153820 polymorphism. In subgroup analysis based on source of controls, increased risks were identified in the hospital-based group with rs8176592 polymorphism and in the population-based group with rs10931292 polymorphism, whereas decreased risk was identified in the hospital-based group with the rs10931292 and rs10153820 polymorphisms.

CONCLUSION

Meta-analysis suggested that different TFPI polymorphisms may have different associations with venous thrombosis. TFPI rs8176592 polymorphism may increase the risk of venous thrombosis, especially in Asians and hospital-based patients. The TFPI rs10931292 polymorphism may increase the venous thrombosis risk for both non-Asians and population-based patients. Moreover, rs10931292 and rs10153820 polymorphisms of TFPI may decrease the risk of venous thrombosis for hospital-based patients.

Post-transcriptional, post-translational and pharmacological regulation of tissue factor pathway inhibitor

: Tissue factor (TF) pathway inhibitor (TFPI) is an endogenous natural anticoagulant that readily inhibits the extrinsic coagulation initiation complex (TF-FVIIa-Xa) and prothrombinase (FXa, FVa and calcium ions). Alternatively, spliced TFPI isoforms (α, β and δ) are expressed by vascular and extravascular cells and regulate thrombosis and haemostasis, as well as cell signalling functions of TF complexes via protease-activated receptors (PARs). Proteolysis of TFPI plays an important role in regulating physiological roles of the TF pathway in host defense and possibly haemostasis. Elimination of TFPI inhibition has therefore been proposed as an approach to improve haemostasis in haemophilia patients. In this review, we focus on posttranscription and translational modification of TFPI and its function in thrombosis and how pharmacological inhibitors and endogenous proteases interfere with TFPI and alter haemostasis.

Under control: The innate immunity of fish from the inhibitors' perspective

The innate immune response involves a concerted network of induced gene products, preformed immune effectors, biochemical signalling cascades and specialised cells. However, the multifaceted activation of these defensive measures can derail or overshoot and, if left unchecked, overwhelm the host. A plenty of regulatory devices therefore mediate the fragile equilibrium between pathogen defence and pathophysiological manifestations. Over the past decade in particular, an almost complete set of teleostean sequences orthologous to mammalian immunoregulatory factors has been identified in various fish species, which prove the remarkable conservation of innate immune-control concepts among vertebrates. This review will present the current knowledge on more than 50 teleostean regulatory factors (plus additional fish-specific paralogs) that are of paramount importance for controlling the clotting cascade, the complement system, pattern-recognition pathways and cytokine-signalling networks. A special focus lies on those immunoregulatory features that have emerged as potential biomarker genes in transcriptome-wide research studies. Moreover, we report on the latest progress in elucidating control elements that act directly with immune-gene-encoding nucleic acids, such as transcription factors, hormone receptors and micro- and long noncoding RNAs. Investigations into the function of teleostean inhibitory factors are still mainly based on gene-expression profiling or overexpression studies. However, in support of structural and in-vitro analyses, evidence from in-vivo trials is also available and revealed many biochemical details on piscine immune regulation. The presence of multiple gene copies in fish adds a degree of complexity, as it is so far hardly understood if they might play distinct roles during inflammation. The present review addresses this and other open questions that should be tackled by fish immunologists in future.

TC38, a teleost TFPI-2 peptide that kills bacteria via penetration of the cell membrane and interaction with nucleic acids

Tissue factor pathway inhibitor 2 (TFPI-2) is an analog of TFPI-1 and a potent endogenous inhibitor of tissue factor (TF)-mediated blood coagulation. Recent reports have proven that the C-terminal of TFPI-2 peptides in humans and several other vertebrates possesses antibacterial activity against Gram-positive and Gram-negative bacteria. In our previous study, we reported that the TFPI-2 peptide, TC38 in tongue sole (Cynoglossus semilaevis) was active against Micrococcus luteus. In this study, we further examine the antimicrobial spectrum, mechanism of action, and function of TC38 in tongue sole. Our results indicate that TC38 is active against the Gram-negative bacteria Vibrio ichthyoenteri, Vibrio litoralis, Vibrio parahaemolyticus, and Vibrio vulnificus, as well as the fish Megalocytivirus, infectious spleen and kidney necrosis virus (ISKNV). The mechanism of action of TC38 against V. vulnificus was explored. The results showed that TC38 killed V. vulnificus cells without lysis of the cell membrane. FITC-labeled TC38 was able to penetrate the cell membrane and bind to DNA and RNA, then disrupt cellular function, eventually leading to cell death. Administration of TC38 to tongue sole significantly improved its defense against V. vulnificus infection. Overall, these results indicate that TC38 is a novel peptide with a broad antimicrobial spectrum. Furthermore, the unique action of TC38 against V. vulnificus adds new insights to the mechanism of action of vertebrate TFPI peptides. Moreover, TC38 is an interesting antimicrobial agent that could be useful in the fight against pathogenic invasion in aquaculture.

A TFPI-1 peptide that induces degradation of bacterial nucleic acids, and inhibits bacterial and viral infection in half-smooth tongue sole, Cynoglossus semilaevis

Tissue factor pathway inhibitor 1 (TFPI-1) is a serine protease inhibitor that inhibits tissue factor (TF)-mediated coagulation. The C-terminal region of TFPI-1 could be cleaved off and proved to be antimicrobial against a broad-spectrum of microorganism. In a previous study, a C-terminal peptide, TC24 (with 24 amino acids), derived from tongue sole (Cynoglossus semilaevis) TFPI-1, was synthesized and found antibacterial against Micrococcus luteus. In the present study, the antibacterial spectrum and the action mode of TC24 was further examined, and its in vivo function was analyzed. Our results showed that TC24 also possesses bactericidal activity against Staphylococcus aureus and Vibrio vulnificus. During its interaction with the target bacterial cells, TC24 destroyed cell membrane integrity, penetrated into the cytoplasm, and induced degradation of genomic DNA and total RNA. In vivo study showed that administration of tongue sole with TC24 before bacterial and viral infection significantly reduced pathogen dissemination and replication in tissues. These results indicated that TC24 is a novel antimicrobial peptide against bacterial and viral pathogens, and that the observed effect of TC24 on bacterial RNA adds new insights to the action mechanism of fish antimicrobial peptides. Moreover, TC24 may play an important role in fighting pathogenic infection in aquaculture.