Recombinant granulocyte colony-stimulating factor induces production of human neutrophil peptides in lung cancer patients with neutropenia

Antimicrobial peptides: a promising strategy for lung cancer drug discovery?

INTRODUCTION

Antimicrobial peptides (AMPs), also called host defense peptides (HDPs), are identified in almost any form of life, which play an important role in innate immune systems. They have a broad spectrum of antifungal, antiviral, antibacterial, and anticancer activities. Lung cancer remains the leading cause of global cancer-related death. Unfortunately, lung cancer chemotherapy is accompanied by serious side effects, nonspecific toxicity, and multidrug resistance. Hence, to overcome these drawbacks, anticancer peptides (ACPs) derived from AMPs may represent a potential promising synergistic treatment strategy for lung cancer.

AREAS COVERED

In this review, the authors provide the recent advancements in the use of AMPs for the treatment of lung cancer. Furthermore, the anti-lung cancer modes of action of these peptides have been fully reviewed. Importantly, various strategies for increasing the efficiency and safety of AMPs have been discussed.

EXPERT OPINION

The combination of AMPs and other cancer treatment approaches such as chemotherapy, nanoparticle-based delivery systems, and photodynamic therapy can be used as a promising revolutionary strategy for the treatment of lung cancer. The most significant limitations of this strategy that need to be focused on are low efficiency and off-target events.

Cellular response to Trypanosoma cruzi infection induces secretion of defensin α-1, which damages the flagellum, neutralizes trypanosome motility, and inhibits infection

Human defensins play a fundamental role in the initiation of innate immune responses to some microbial pathogens. Here we show that colonic epithelial model HCT116 cells respond to Trypanosoma cruzi infection by secreting defensin α-1, which reduces infection. We also report the early effects of defensin α-1 on invasive trypomastigotes that involve damage of the flagellar structure to inhibit parasite motility and reduce cellular infection. Short exposure of defensin α-1 to trypomastigotes shows that defensin α-1 binds to the flagellum, resulting in flagellar membrane and axoneme alterations, followed by breaking of the flagellar membrane connected to the trypanosome body, leading to detachment and release of the parasite flagellum. In addition, defensin α-1 induces a significant reduction in parasite motility in a peptide concentration-dependent manner, which is abrogated by anti-defensin α-1 IgG. Preincubation of trypomastigotes with a concentration of defensin α-1 that inhibits 50% trypanosome motility significantly reduced cellular infection by 80%. Thus, human defensin α-1 is an innate immune molecule that is secreted by HCT116 cells in response to T. cruzi infection, inhibits T. cruzi motility, and plays an important role in reducing cellular infection. This is the first report showing a novel cellular innate immune response to a human parasite by secretion of defensin α-1, which neutralizes the motility of a human parasite to reduce cellular infection. The mode of activity of human defensin α-1 against T. cruzi and its function may provide insights for the development of new antiparasitic strategies.

ProHNPs are the principal α-defensins of human plasma

BACKGROUND

Human neutrophil peptides (HNPs) were discovered as abundant antimicrobial peptides of azurophil granules. Later studies revealed that most HNPs were produced by myelocytes and metamyelocytes and secreted into the bone marrow plasma as the inert proforms, proHNPs. Despite the vast amounts of proHNPs released into bone marrow plasma, little has been done to characterize these. Numerous studies have investigated HNPs in plasma, linking them to a variety of diseases, but without distinguishing between HNPs and their proforms.

MATERIALS AND METHODS

We used an antibody with specificity against the propiece of proHNPs to investigate proHNPs in plasma and tissue.

RESULTS

In contrast to previous studies using HNP antibodies, we found proHNPs to be many-fold more abundant than HNPs in plasma with a mean concentration of 2 μg/mL. The concentration was substantially higher in bone marrow plasma in accordance with the bone marrow being the site of origin of plasma proHNPs. ProHNPs were not bound to high molecular weight plasma proteins. Accordingly, proHNPs were filtered in the kidneys and resorbed in the proximal tubules.

CONCLUSIONS

Most HNPs in plasma are in fact proHNPs, which is important given the differences in their origin and biological activities.

[Biological characteristics of defensin and its disease-resistance genetic engineering]

Defensin is a kind of cysteine-rich small peptide, which has a broad spectrum of resistance to bacteria with a special resistance mechanism. So far, a large number of studies on defensins have been reported, and the different types of defensins have been isolated from various organisms. A broad prospect of application on defensins has been displayed both in genetic engineering and medicine field. This article reviewed the classification and the biological characteristics of defensins, including mammalian α-, β-, θ-defensins, insect defensins, and plant defensins. The molecular structures, antibacterial activities, and antibacterial mechanisms of these definsins were summarized. The two mechanisms of de-fensin, including independent membrane mechanism and targeting of intracellular compounds by defensins, are ex-pounded. This paper also summarized the researches on isolation and expression of defensin genes and disease resistance genetic engineering of mammal and plant defensins. A prospect of the future applications of defensin both in biophar-maceutical sciences and plant disease resistance genetic engineering was discussed.

Human defensin alpha-1 causes Trypanosoma cruzi membrane pore formation and induces DNA fragmentation, which leads to trypanosome destruction

Human defensins play a fundamental role in the initiation of innate immune responses to some microbial pathogens. Here we show that human defensin alpha-1 displays a trypanocidal role against Trypanosoma cruzi, the causative agent of Chagas' disease. The toxicity of human defensin alpha-1 against T. cruzi is mediated by membrane pore formation and the induction of nuclear and mitochondrial DNA fragmentation, leading to trypanosome destruction. Exposure of trypomastigote and amastigote forms of T. cruzi to defensin alpha-1 significantly reduced parasite viability in a peptide concentration-dependent and saturable manner. The toxicity of defensin alpha-1 against T. cruzi is blocked by anti-defensin alpha-1 immunoglobulin G. Electron microscopic analysis of trypomastigotes exposed to defensin alpha-1 revealed pore formation in the cellular and flagellar membranes, membrane disorganization, and blebbing as well as cytoplasmic vacuolization. Furthermore, human defensin alpha-1 enters the trypanosome when membrane pores are present and is associated with later intracellular damage. Trypanosome membrane depolarization abolished the toxicity of defensin alpha-1 against the parasite. Preincubation of trypomastigotes with defensin alpha-1 followed by exposure to human epithelial cells significantly reduced T. cruzi infection in these cells. Thus, human defensin alpha-1 is an innate immune molecule that causes severe toxicity to T. cruzi and plays an important role in reducing cellular infection. This is the first report showing that human defensin alpha-1 causes membrane pore formation in a human parasite, leading to trypanosome destruction.

A Proteomic Analysis of Human Hemodialysis Fluid

The vascular compartment is an easily accessible compartment that provides an opportunity to measure analytes for diagnostic, prognostic, or therapeutic indications. Both serum and plasma have been analyzed extensively by proteomic approaches in an effort to catalog all proteins and polypeptides. Limitations of such approaches in obtaining a comprehensive catalog of proteins include the fact that a handful of proteins constitute over 90% of plasma protein content and that the renal glomeruli filter out proteins and polypeptides that are smaller than 66 kDa from blood. We chose to study hemodialysis fluid because it contains a higher concentration of small proteins and polypeptides and is also simultaneously depleted of the most abundant proteins present in blood. Using gel electrophoresis in combination with LC-MS/MS, we identified 292 proteins of which greater than 70% had not been previously identified from serum or plasma. More than half of the proteins identified from the hemodialysis fluid were smaller than 40 kDa. We also found 50 N-terminally acetylated peptides that allowed us to unambiguously map the N termini of mature forms of the corresponding proteins. Several identified proteins, including cytokines, were only present as predicted transcripts in data bases and thus represent novel proteins. The proteins identified in this study could serve as biomarkers in serum using more sensitive methods such as ELISA-specific antibodies.

High concentrations of alpha-defensins in plasma and bronchoalveolar lavage fluid of patients with acute respiratory distress syndrome

alpha-Defensins, antimicrobial peptides localized in neutrophils, participate in tissue damage through their cytotoxic effects in neutrophil-mediated pulmonary diseases. Neutrophils play an important role in the pathogenesis of acute respiratory distress syndrome (ARDS). We measured alpha-defensins levels in plasma and bronchoalveolar lavage fluid (BALF) of ARDS patients to assess the kinetics of alpha-defensins in ARDS. Plasma alpha-defensins levels were higher in ARDS patients than in control subjects, and BALF levels were also higher in ARDS patients than in control subjects. In ARDS, BALF alpha-defensins levels correlated with those of interleukin (IL)-8, and plasma alpha-defensins levels also correlated with Lung Injury Score. Peripheral neutrophil alpha-defensins contents were higher in ARDS than the control. IL-8 dose-dependently stimulated alpha-defensins release from cultured neutrophils and these levels were higher in ARDS than the control. Reverse-phase high performance liquid chromatography showed high plasma levels of pro-defensins, precursors of alpha-defensins from the bone marrow in ARDS, although alpha-defensins in peripheral and BALF neutrophils were mature type. In conclusion, high plasma alpha-defensins in ARDS patients result from the release of pro-defensins from bone marrow, rather than mature alpha-defensins from neutrophils that accumulate in the alveolar space. The alpha-defensins contents of peripheral neutrophils in ARDS are higher and easier to release than control.

Multiple roles of antimicrobial defensins, cathelicidins, and eosinophil-derived neurotoxin in host defense

Mammals generate a diverse array of antimicrobial proteins, largely represented by defensins or cathelicidins. The direct in vitro microbicidal activity of antimicrobial proteins has long been considered an important innate immune defense, although the in vivo relevance has only very recently been established for certain defensins and cathelicidins. Mammalian defensins and cathelicidins have also been shown to have multiple receptor-mediated effects on immune cells. Beta-defensins interact with CCR6; murine beta-defensin-2 in addition activates TLR4. Cathelicidins act on FPRL1-expressing cells. Furthermore, several defensins have considerable immunoenhancing activity. Thus, it appears that mammalian antimicrobial proteins contribute to both innate and adaptive antimicrobial immunity.

Raised plasma concentrations of alpha-defensins in patients with idiopathic pulmonary fibrosis

BACKGROUND

Neutrophils are thought to play an important role in the pathogenesis of idiopathic pulmonary fibrosis (IPF). Human neutrophils contain antimicrobial and cytotoxic peptides in the azurophil granules which belong to a family of mammalian neutrophil peptides named alpha-defensins. A study was undertaken to investigate the role of alpha-defensins in the pathogenesis of IPF.

METHODS

The concentrations of alpha-defensins (human neutrophil peptides (HNPs) 1, 2, and 3) in plasma and bronchoalveolar lavage (BAL) fluid of 30 patients with IPF and 15 healthy subjects were measured by radioimmunoassay.

RESULTS

The concentrations of alpha-defensins in plasma, but not in BAL fluid, were significantly higher in IPF patients than in controls. BAL fluid concentrations of interleukin (IL)-8 in patients with IPF, which were significantly higher than in controls, correlated with those of alpha-defensins. An inverse relationship was seen between plasma alpha-defensin levels and the arterial oxygen tension (PaO(2)) and pulmonary function (vital capacity (%VC), forced expiratory volume in 1 second (FEV(1)), and carbon monoxide transfer factor (%TLCO)) in patients with IPF. Plasma levels of alpha-defensins also correlated with the clinical course in IPF patients with an acute exacerbation. Immunohistochemically, positive staining was observed inside and outside neutrophils in the alveolar septa, especially in dense fibrotic areas.

CONCLUSION

These findings suggest that alpha-defensins play an important role in the pathogenesis of IPF, and that the plasma alpha-defensin level may be a useful marker of disease severity and activity.

Neutrophil defense in patients undergoing bone marrow transplantation: bactericidal/permeability-increasing protein (BPI) and defensins in graft-derived neutrophils

BACKGROUND

Even after neutrophil counts return to near normal levels, patients undergoing myeloablative chemotherapy and bone marrow transplantation (BMT) are at risk for invasive bacterial infections, raising the possibility that their neutrophil function might be impaired. To assess potential qualitative defects in neutrophil function in patients undergoing BMT, we measured neutrophil content of the antimicrobial (poly)peptides BPI and defensins.

METHODS

Neutrophil extracts were analyzed for content of BPI by Western blotting and ELISA and for defensin peptides by acid-urea polyacrylamide gel electrophoresis (PAGE). Antibacterial activity of neutrophil extracts was measured against Escherichia coli K1/r, a clinical isolate sensitive to synergistic killing by BPI and defensins.

RESULTS

Neutrophil extract BPI content on post-BMT days +20, +30, and +100 (169+/-35, 232+/-57, and 160+/-55 ng per 106 neutrophils, respectively) was similar to the neutrophil BPI content of normal controls (163+/-35 ng per 106 neutrophils). Neutrophil defensin content also did not vary during this time-span. Activity of neutrophil extracts against E. coli K1/r did not differ between BMT patients and controls.

CONCLUSION

At post-BMT days +20 to +100, neutrophils derived from engrafted marrow contain normal quantities of BPI and defensins. Any deficiencies of neutrophil function during this phase are not due to inadequate expression of these antimicrobial (poly)peptides but could reflect abnormalities in other aspects of neutrophil function.

Elevated levels of alpha-defensins in plasma and BAL fluid of patients with active pulmonary tuberculosis

STUDY OBJECTIVES

To investigate the role of neutrophil peptides named alpha-defensins in patients with pulmonary tuberculosis (TB).

PATIENTS

Thirty-seven patients with TB and 25 healthy subjects.

MEASUREMENTS AND RESULTS

Concentrations of alpha-defensins (human neutrophil peptide [HNP]-1, HNP-2, and HNP-3) were measured by radioimmunoassay in plasma and BAL fluid (BALF). Concentrations of alpha-defensins were significantly higher in plasma and BALF of patients with TB than in healthy subjects. In BALF of patients with TB, the concentration of alpha-defensins correlated positively with the levels of interleukin 8, and higher concentrations of alpha-defensins in BALF were also detected in patients with cavitary lesions. There was an inverse relationship between plasma alpha-defensins and FEV(1)/FVC ratio before treatment, and between plasma concentrations of alpha-defensins before treatment and the improvement in percentage of vital capacity after treatment. Plasma alpha-defensin concentrations returned to the normal range after treatment.

CONCLUSION

Our data suggest that alpha-defensins released from neutrophils may play an important role in the pathogenesis of TB, and that plasma alpha-defensin concentration may be a useful marker of disease severity and deterioration of pulmonary function.

Plasma and BAL fluid concentrations of antimicrobial peptides in patients with Mycobacterium avium-intracellulare infection

STUDY OBJECTIVES

To investigate the roles of human alpha-defensin (HAD), human beta-defensin (HBD)-1, and HBD-2, novel antimicrobial peptides, in patients with Mycobacterium avium-intracellulare infection (MAI).

PATIENTS

The study included 25 patients (10 men) with MAI who visited our hospital between June 1998 and August 1999.

MEASUREMENTS AND RESULTS

In patients with pulmonary MAI, we measured HAD and HBD-1, and HBD-2 levels in plasma and in BAL fluid (BALF) by radioimmunoassay. Plasma concentrations of HAD and HBD-2 in those patients were higher than those in control subjects, whereas HBD-1 levels were similar to those in the control subjects. High levels of HAD and HBD-2, but not HBD-1, also were observed in the BALF of MAI patients. There was a positive correlation between HAD and interleukin (IL)-8 concentrations in the BALF of patients with MAI. BALF HBD-2 concentrations also correlated positively with those of plasma HBD-2 and BALF IL-1 beta in MAI patients. Patients with cavity formation on the chest roentgenogram had higher HAD and HBD-2 levels in their BALF than those of patients without cavity formation. Treatment with clarithromycin combined with two or three other antibiotics, including ethambutol, rifampicin, ofloxacin, or ciprofloxacin, for at least 6 months resulted in a significant fall in plasma HBD-2 concentrations in responders, but not in nonresponders.

CONCLUSION

Our findings suggest that HAD and HBD-2 may participate in host defense and local remodeling of the respiratory tract in patients with MAI and that plasma HBD-2 levels may be a useful marker of disease activity in patients with pulmonary MAI.