Last updated: 7th April 2008

Clinical Studies

Plasma {alpha}-defensin is associated with cardiovascular morbidity and mortality in type 1 diabetic patients. J Clin Endocrinol Metab. 2008 Jan 22 [Epub ahead of print] CONTEXT: alpha-Defensins are antimicrobial peptides of the innate immune system. In addition, experimental evidence suggests that alpha-defensins are pro-atherogenic. OBJECTIVE: To examine the predictive value of plasma alpha-defensin as a clinical marker of cardiovascular disease (CVD) in patients with type 1 diabetes. METHODS: In an observational, prospective design, 389 patients with long-lasting type 1 diabetes were examined for CVD at study start (1993; baseline), and followed through the Danish National Register for a median of 10.1 years (range 0.2 - 10.4 years). Plasma was collected in 1993 and stored at -80 degrees C till analysis of plasma alpha-defensin using an in-house radioimmunoassay. RESULTS: At baseline, plasma alpha-defensin was significantly higher in patients with than without nephropathy (median and interquartile ranges: 305 (205-321) vs. 223 (182-263) microg/L; P < 0.0001). During follow-up, 98 patients reached the primary end-point (fatal and non-fatal events of CVD). Prospectively, a baseline alpha-defensin within the upper versus the lower tertile significantly increased the co-variate adjusted risk for CVD-related morbidity and mortality to a hazard ratio of 2.8 (1.3-5.9) [median and 95% confidence intervals], P = 0.006. CONCLUSION: This study suggests that plasma alpha-defensin may serve as a clinical risk marker for CVD-related morbidity and mortality in type 1 diabetes. However, future studies are needed to clarify whether plasma alpha-defensin is causally linked to the development of CVD or an innocent bystander.

Isolation of human beta-defensin-4 in lung tissue and its increase in lower respiratory tract infection Respir Res. 2005 Nov 4;6:130 BACKGROUND: Human beta-defensin-4 (hBD-4), a new member of the beta-defensin family, was discovered by an analysis of the genomic sequence. The objective of this study was to clarify hBD-4 expression in human lung tissue, along with the inducible expression in response to infectious stimuli, localization, and antimicrobial activities of hBD-4 peptides. We also investigated the participation of hBD-4 in chronic lower respiratory tract infections (LRTI) by measuring the concentrations of hBD-4 peptides in human bronchial epithelial lining fluid (ELF). METHODS: The antimicrobial activity of synthetic hBD-4 peptides against E. coli and P. aeruginosa was measured by radial diffusion and colony count assays. We identified hBD-4 in homogenated human lung tissue by reverse-phase high-performance liquid chromatography coupled with a radioimmunoassay (RIA). Localization of hBD-4 was studied through immunohistochemical analysis (IHC). We investigated the effects of lipopolysaccharide (LPS) on hBD-4 expression and its release from small airway epithelial cells (SAEC). We collected ELF from patients with chronic LRTI using bronchoscopic microsampling to measure hBD-4 concentrations by RIA. RESULTS: hBD-4 exhibited salt-sensitive antimicrobial activity against P. aeruginosa. We detected the presence of hBD-4 peptides in human lung tissue. IHC demonstrated the localization of hBD-4-producing cells in bronchial and bronchiolar epithelium. The levels of hBD-4 peptides released from LPS-treated SAECs were higher than those of untreated control cells. ELF hBD-4 was detectable in 4 of 6 patients with chronic LRTI, while the amounts in controls were all below the detectable level. CONCLUSION: This study suggested that hBD-4 plays a significant role in the innate immunity of the lower respiratory tract.

Human defensin 5 expression in intestinal metaplasia of the upper gastrointestinal tract J Clin Pathol. 2005 Jul;58(7):687-94 BACKGROUND: Upper gastrointestinal tract intestinal metaplasia (IM) is termed Barrett's oesophagus (BO) or gastric intestinal metaplasia (GIM), depending on its location. BO and GIM are associated with chemical exposure resulting from gastro-oesophageal reflux and chronic Helicobacter pylori infection, respectively. Paneth cells (PCs), characterised by cytoplasmic eosinophilic granules, are found in a subset of IM at these sites, but histology may not accurately detect them. AIM: To determine human defensin 5 (HD5; an antimicrobial peptide produced by PCs) expression in BO and GIM, and to investigate its association with H pylori infection. METHODS: Endoscopic biopsies from 33 patients with BO and 51 with GIM, and control tissues, were examined by routine histology and for H pylori infection and HD5 mRNA and protein expression. RESULTS: In normal tissues, HD5 expression was specific for PCs in the small intestine. Five patients with BE and 42 with GIM expressed HD5, but few HD5 expressing cells in IM had the characteristic histological features of PCs. Most HD5 positive specimens were H pylori infected and most HD5 negative specimens were not infected. CONCLUSIONS: HD5 immunohistochemistry was often positive in IM when PCs were absent by conventional histology. Thus, HD5 immunohistochemistry may be superior to histology for identifying metaplastic PCs and distinguishing GIM from BO. The higher frequency of HD5 expression in GIM than in BO is associated with a higher frequency of H pylori infection, suggesting that in IM PCs may form part of the mucosal antibacterial response.

Bacterial vaginosis and vaginal fluid defensins during pregnancy Am J Obstet Gynecol. 2002 Nov;187(5):1267-71 OBJECTIVE: The purpose of this study was to examine the association between Gram stain findings of vaginal fluid and the concentration of vaginal fluid neutrophil defensins. STUDY DESIGN: Vaginal fluid specimens obtained from 749 women at 24 to 29 weeks of gestation were tested for bacterial vaginosis and assayed for neutrophil defensins. Bacterial vaginosis was studied as a categoric variable (negative, intermediate, and positive), whereas defensins were examined as a continuous measure and dichotomized on the basis of presence versus absence and at the 90th percentile. Multiple linear and logistic regression models were used to assess the relationship between bacterial vaginosis and defensins. RESULTS: Women with intermediate bacterial vaginosis were more likely to have elevated vaginal fluid neutrophil defensins (>90th percentile) than women with normal vaginal flora (adjusted odds ratio, 2.3; 95% CI, 1.3, 4.2), whereas women with frank bacterial vaginosis were not (adjusted odds ratio, 1.3; 95% CI, 0.7, 2.6). Among women with any detectable defensin (69.5% of the study population), intermediate bacterial vaginosis was associated positively with defensin concentrations in multiple linear regression models (P =.007). Women with intermediate and frank bacterial vaginosis had 5.9 microg/mL and 2.2 microg/mL higher defensin concentrations, respectively, than women who did not have bacterial vaginosis. The presence of leukocytes in vaginal fluids was associated positively with defensin concentrations (P <.0001). CONCLUSION: Changes in vaginal microflora during mid pregnancy are associated with an increased concentration of vaginal fluid neutrophil defensins.

Expression of human beta defensin (HBD-1 and HBD-2) mRNA in nasal epithelia of adult cystic fibrosis patients, healthy individuals, and individuals with acute cold Respiration. 2002;69(1):46-51 BACKGROUND: Lack or inactivation of defensins may facilitate chronic bacterial colonization in the cystic fibrosis (CF) lung. CF nasal epithelium exhibits typical biochemical abnormalities and can be used to study defensin expression in CF. OBJECTIVES: To evaluate the expression of beta defensin (HBD-1 and HBD-2) mRNA and the presence of inflammatory markers (percentage of neutrophils and IL-8 mRNA expression) in CF and non-CF nasal mucosa. METHODS: Case-control study. Nasal brushing samples were obtained from 22 stable adult CF patients and 32 non-CF controls (25 healthy individuals and 7 individuals with acute cold). Samples were subjected to analysis involving mRNA expression (semiquantitative RT-PCR) and differential cell counting. RESULTS: Defensins and inflammatory markers were expressed at low levels in healthy individuals and at high levels in subjects with acute cold. In non-CF controls, defensin expression correlated significantly with inflammatory parameters (p < 0.001). In CF, defensin mRNA expression was comparable to healthy individuals (p = 0.2). In contrast to non-CF controls, in CF patients high levels of inflammatory markers did not correlate with defensin mRNA levels. CONCLUSIONS: Defensin expression is not upregulated in CF epithelium in response to inflammatory stimuli. Further studies are necessary to elucidate whether this is a consequence of the CF gene mutation.

Genetic variants of human beta-defensin-1 and chronic obstructive pulmonary disease Biochem Biophys Res Commun. 2002 Feb 15;291(1):17-22 Chronic obstructive pulmonary disease (COPD) is due to interactions between cigarette smoke exposure and other risk factors. Genetic variations of human beta-defensin-1 (hBD-1), an endogenous antimicrobial peptide in the airway, were investigated in 60 patients and 213 healthy volunteers by single-strand conformation and restriction fragment length polymorphism analysis and DNA sequencing. Four nucleotide variations in the 5' and 3' untranslated regions and two nonsynonymous substitutions in the coding region were identified. Of these, a newly found Ile38 variant was observed in 15.0% of patients but only in 2.8% of healthy individuals and was significantly associated with the disease (OR = 6.1, 95% confidence intervals 2.0-8.3, P = 0.0012). More than 80% of those with Ile38 experienced sputum production for more than 3 months during the follow-up period. Genetic variations in hBD-1 may define a high-risk subgroup of COPD where the component of chronic bronchitis is predominant.

Purification and characterization of defensins from cystic fibrosis sputum Inflamm Res. 1997 Mar;46(3):98-102 OBJECTIVE AND DESIGN: Cystic fibrosis (CF) sputum contains large numbers of neutrophils whose most abundant granule proteins are defensins. Within phagolysosomes, defensins kill microbes; however, extracellular defensins can be toxic to human cells. To begin to explore the possibility that defensins damage CF airways, this study examines the concentration and properties of defensins in CF sputum. MATERIALS: As a source of biological material in which to assay levels of defensins, purulent sputum was collected from persons with CF hospitalized with exacerbations of bronchitis. Purulent CF sputum was also a source of material for purification of defensins. METHODS: Defensin concentration in the cell-free component of CF sputum was measured by immunoassay. Defensins acid-extracted from sputum were purified by Sephacryl S-200 gel filtration chromatography and reverse phase-high pressure liquid chromatography (HPLC). Toxicity of CF defensins was tested by incubating the purified defensins with a line of CF tracheal cells cultured in serum five medium. RESULTS: In 5 patients with CF, sputum defensin levels ranged from 300 to > 1600 micrograms/ml, higher than levels previously reported in any human secretion or fluid and greatly exceeding concentrations toxic to mammalian cells in vitro. HPCL-purified CF sputum defensins were pure as judged by acid urea-PAGE and N-terminal sequencing, which revealed a mixture of defensins-1, -2 and -3 at ratios of approximately 4:2:1. At > 10 micrograms/ml the purified mixture was toxic for a line of CF tracheal cells cultured in serum-free medium, as judged by reductions in cell numbers and increased permeability to trypan blue. CONCLUSIONS: This study suggests that defensins in CF sputum are intact and sufficiently abundant that they may damage airway epithelium.