Localization of expression of human beta defensin-1 in the pancreas and kidney

Reduced expression of central innate defense molecules in pancreatic biopsies from subjects with Type 1 diabetes

AIMS/HYPOTHESIS

Defensins play a crucial role in the innate immune system's first defense against microbial threats. However, little is known about the defensin system in the pancreas, especially in relation to Type 1 diabetes. We explore the expression of defensins in different disease stages of Type 1 diabetes and correlated obtained findings to the degree of inflammation, providing new insights into the disease and the innate immune system.

MATERIAL AND METHODS

Pancreases from non-diabetic human organ donors of different age groups and donors with Type 1 diabetes with different disease duration were examined. Sections from head, body and tail of the pancreas were stained for eight different defensins and for immune cells; CD3+, CD45+, CD68+ and NES+ (granulocytes).

RESULTS

In non-diabetic adult controls the level of expression for defensins Beta-1,Alpha-1, Cathelicidin and REG3A correlated with the level of inflammation. In contrast, individuals with Type  1 diabetes exhibit a reduction or absence of several central defensins regardless of the level of inflammation in their pancreas. The expression of Cathelicidin is present in neutrophils and macrophages but not in T-cells in subjects with Type 1 diabetes.

CONCLUSIONS

Obtained findings suggest a pancreatic dysfunction in the innate immune system and the bridging to the adaptive system in Type 1 diabetes. Further studies on the role of the local innate immune system in Type 1 diabetes is needed.

Antimicrobial peptides and other potential biomarkers of critical illness in SARS-CoV-2 patients with acute kidney injury. AMPAKI-CoV study

Antimicrobial peptides (AMPs) constitute a complex network of 10-100 amino acid sequence molecules widely distributed in nature. While over 300 AMPs have been described in mammals, cathelicidins and defensins remain the most extensively studied. Some publications have explored the role of AMPs in COVID-19, but these findings are preliminary, and in vivo studies are still lacking. In this study, we report the plasma levels of five AMPs (LL-37, α-defensin 1, α-defensin 3, β-defensin 1, and β-defensin 3), using the ELISA technique (MyBioSource, San Diego, CA, United States, kits MBS2601339 (beta-defensin 1), MBS2602513 (beta-defensin 3), MBS703879 (alpha-defensin 1), MBS706289 (alpha-defensin 3), MBS7234921 (LL37)), and the measurement of six cytokines (tumor necrosis factor-α, interleukin-1β, interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1), through the magnetic bead immunoassay Milliplex® and the MAGPIX® System (MilliporeSigma, Darmstadt, Germany, kit HCYTOMAG-60 K (cytokines)), in 15 healthy volunteers, 36 COVID-19 patients without Acute Kidney Injury (AKI) and 17 COVID-19 patients with AKI. We found increased levels of α-defensin 1, α-defensin 3 and β-defensin 3, in our COVID-19 population, when compared to healthy controls, along with higher levels of interleukin-6, interleukin-10, interferon-γ, and monocyte chemoattractant protein-1. These findings suggest that these AMPs and cytokines may play a crucial role in the systemic inflammatory response and tissue damage characterizing severe COVID-19. The levels of α-defensin 1 and α-defensin 3 were significantly higher in COVID-19 AKI group in comparison to the non-AKI group. Furthermore, IL-10 and the product IL-10 × IL-1B showed excellent performance in discriminating AKI, with AUCs of 0.86 and 0.88, respectively. Among patients with COVID-19, AMPs may play a key role in the inflammation process and disease progression. Additionally, α-defensin 1 and α-defensin 3 may mediate the AKI process in these patients, representing an opportunity for further research and potential therapeutic alternatives in the future.

Identification of Novel Disease-Relevant Genes and Pathways in the Pathogenesis of Type 1 Diabetes: A Potential Defect in Pancreatic Iron Homeostasis

Multiple pathways contribute to the pathophysiological development of type 1 diabetes (T1D); however, the exact mechanisms involved are unclear. We performed differential gene expression analysis in pancreatic islets of NOD mice versus age-matched congenic NOD.B10 controls to identify genes that may contribute to disease pathogenesis. Novel genes related to extracellular matrix development and glucagon and insulin signaling/secretion were changed in NOD mice during early inflammation. During "respective" insulitis, the expression of genes encoding multiple chemosensory olfactory receptors were upregulated, and during "destructive" insulitis, the expression of genes involved in antimicrobial defense and iron homeostasis were downregulated. Islet inflammation reduced the expression of Hamp that encodes hepcidin. Hepcidin is expressed in β-cells and serves as the key regulator of iron homeostasis. We showed that Hamp and hepcidin levels were lower, while iron levels were higher in the pancreas of 12-week-old NOD versus NOD.B10 mice, suggesting that a loss of iron homeostasis may occur in the islets during the onset of "destructive" insulitis. Interestingly, we showed that the severity of NOD disease correlates with dietary iron intake. NOD mice maintained on low-iron diets had a lower incidence of hyperglycemia, while those maintained on high-iron diets had an earlier onset and higher incidence of disease, suggesting that high iron exposure combined with a loss of pancreatic iron homeostasis may exacerbate NOD disease. This mechanism may explain the link seen between high iron exposure and the increased risk for T1D in humans.

Recombinant human β-defensin130 inhibited the growth of foodborne bacteria through membrane disruption and exerted anti-inflammatory activity

Foodborne pathogens causing food poisoning and infections are detrimental to human health, and the abuse of antibiotics induced severe antibiotic resistance in past decades. Thus, it is urgent to develop new antimicrobial agents. In the current study, human β-defensin 130 (hBD130), which is an antimicrobial peptide identified in human macrophages in 2017, was initially produced in Pichia pastoris. The purified hBD130 demonstrated broad bactericidal spectrum against foodborne pathogens through a membrane disruption, with concentrations ranging from 10 to 45 μg/mL. Moreover, hBD130 showed a low hemolytic effect and nearly no cytotoxicity to mammalian cells with a dosage of 400 μg/mL. In addition, the secretion amounts and mRNA levels of NO, IL-6, IL-1β, and TNF-α in LPS-induced mouse macrophage were significantly decreased with 1 mg/mL of hBD130. Taken together, these results showed that hBD130 is a promising antimicrobial agent to treat foodborne bacterial infections and inflammation.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10068-022-01087-y.

Impact of successful pediatric ureteropelvic junction obstruction surgery on urinary HIP/PAP and BD-1 levels

INTRODUCTION

In the pediatric patient whose ureteropelvic junction obstruction (UPJO) is not always symptomatic, imaging is the most common means of detecting surgical success. There is interest, however, in other means of post-operative monitoring. A panel of antimicrobial peptides (AMPs) has been previously found to be elevated in UPJO, but the impact of surgical correction on these AMPs is unknown.

OBJECTIVE

To determine if elevated levels of candidate urinary AMP biomarkers of urinary tract obstruction decrease following UPJO repair.

STUDY DESIGN

Pediatric patients undergoing surgical correction of an UPJO were recruited for participation. Bladder urine from uninfected consenting/assenting patients was collected immediately prior to surgery and then at least 6 months afterward. Based on prior studies demonstrating significant elevation of beta defensin 1 (BD-1), hepatocarcinoma-intestine-pancreas/pancreatitis-associated protein (HIP/PAP), cathelicidin (LL-37), and neutrophil gelatinase-associated lipocalin (NGAL) in patients with UPJO versus control patients, we performed enzyme-linked immunosorbent assays on these four AMPs to compare their expression before and after surgical intervention. If found to significantly decrease, AMP levels were compared to healthy controls. AMP levels were normalized to urine creatinine. Results were analyzed with paired t test or Wilcoxon test using Graphpad software. Correlation was calculated using Pearson or Spearman correlation. A p-value of <0.05 was considered significant.

RESULTS

13 UPJO patients were included in this study; 9 were male (69%). Age at surgery was a median of 4.3 years (average 6.1, range 0.4-18.4 years). Follow-up urine samples were collected a median of 27.4 months after surgery (average 27.4; range 7.8-45.3 months). All 13 patients had clinical improvement and/or signs of improved hydronephrosis on post-operative imaging. HIP/PAP and BD-1 significantly decreased in post-surgical samples compared to pre-surgical samples (p = 0.02 and 0.01, respectively); NGAL and LL-37 did not significantly change. Overall, HIP/PAP decreased in 12 patients (92%) and BD-1 decreased in 11 patients (85%). BD-1 levels after successful repair were not different from healthy controls (p = 0.06).

DISCUSSION

Urinary biomarkers of obstruction should detect significant obstructive pathology as well as reflect its resolution. This would enable their use in post-operative monitoring and augment current methods of determining successful surgical outcome through imaging.

CONCLUSIONS

The AMPs HIP/PAP and BD-1 are significantly elevated in UPJO but then significantly decrease after pyeloplasty, with BD-1 returning to healthy control levels. As a result, these AMPs could serve as markers of successful surgical intervention.

The -44 C/G (rs1800972) polymorphism of the β-defensin 1 is associated with increased risk of developing type 2 diabetes mellitus

Background

The aim of this study was to establish the association of two polymorphisms of the β‐defensin 1 gene (DEFB1, OMIM#602056) with the risk of developing type 2 diabetes mellitus (T2DM) in a group of Mexican patients.

Methods

The 5′UTR −20 G/A, and −44 C/G polymorphisms of DEFB1 gene were genotyped by 5′ exonuclease TaqMan assays in a group of 252 patients with T2DM and 522 healthy control.

Results

Under dominant and additive models adjusted for the risk factors, the C allele of the −44 C/G polymorphism was associated with increased risk of T2DM (OR = 1.63, 95% CI = 1.07–2.48, pC_dom = 0.021 and OR = 1.42, 95% CI = 1.05–1.91, pC_add = 0.023, respectively). In addition, the linkage disequilibrium analysis showed that AC haplotype was associated with an increased risk of developing T2DM (OR = 4.39, p = 0.04). The in‐silico analysis showed that the −44 C allele produces a binding site for the transcription factor Ikaros (IK).

Conclusion

This study demonstrates that the C allele of −44 C/G polymorphism, as well as haplotype AC are associated with the presence of T2DM in the Mexican population. The variation in this polymorphism of the DEFB1 gene could increase the migration of the macrophages to pancreatic islets accelerate the β‐cell dysfunction in T2DM.

Antimicrobial Peptide Human Neutrophil Peptide 1 as a Potential Link Between Chronic Inflammation and Ductal Adenocarcinoma of the Pancreas

OBJECTIVES

Defensins are antimicrobial peptides playing a role in innate immunity, in epithelial cell regeneration, and in carcinogenesis of inflammation-triggered malignancies. We analyzed this role in pancreatic ductal adenocarcinoma (PDAC) in the context of its association with chronic pancreatitis (CP).

METHODS

Human tissue of healthy pancreas, CP, and PDAC was screened for defensins by immunohistochemistry. Defensin α 1 (human neutrophil peptide 1 [HNP-1]) expression was validated using mass spectrometry and microarray analysis. Human neutrophil peptide 1 expression and influences of proinflammatory cytokines (tumor necrosis factor α, interleukin 1β, and interferon γ) were studied in human pancreatic cancer cells (Colo 357, T3M4, PANC-1) and normal human pancreatic duct epithelial cells (HPDE).

RESULTS

Accumulation of HNP-1 in malignant pancreatic ductal epithelia was seen. Spectrometry showed increased expression of HNP-1 in CP and even more in PDAC. At RNA level, no significant regulation was found. In cancer cells, HNP-1 expression was significantly higher than in HPDE. Proinflammatory cytokines significantly led to increased HNP-1 levels in culture supernatants and decreased levels in lysates of cancer cells. In HPDE cytokines significantly decreased HNP-1 levels.

CONCLUSIONS

Inflammatory regulation of HNP-1 in PDAC tissue and cells indicates that HNP-1 may be a link between chronic inflammation and malignant transformation in the pancreas.

mRNA expression and localization of LPS-induced β-defensin isoforms in rat salivary glands

β-defensins are small, cationic peptides with broad-spectrum antimicrobial activity that are produced by mucosal epithelia. However, little is known about the expression of β-defensins in the major salivary glands. The purpose of this study was to characterize expression of rat β-defensin-1 (RBD-1) and -2 (RBD-2) mRNA within the major salivary glands together with the effect of injection of intraductal lipopolysaccharide (LPS) on that expression. β-defensin mRNA expression was quantitated by RT-PCR in salivary gland tissues and salivary acinar and striated duct cells collected by laser captured microdissection. RBD-1 and -2 were expressed in the parotid gland, the submandibular gland, and the sublingual gland. β-defensins were expressed in both the acinar and striated duct cells of the major salivary glands. Intraductal injection of LPS increased expression of RBD-1 and -2 mRNA, which peaked at 12 hrs. These results suggest that salivary cells (acinar and striated duct cells) have the potential to produce β-defensins.

Human β-defensins and psoriasin/S100A7 expression in salivary glands: anti-oncogenic molecules for potential therapeutic approaches

BACKGROUND

Host defence peptides (HDPs), including human β-defensins (hBDs) and psoriasin/S100A7, exert antimicrobial and immunoregulatory functions of the innate defense system. In addition to these functions, the search for cancer biomarkers has identified HDPs as playing a potential role in both tumor suppression and oncogenesis. Although HDPs are highly expressed in salivary glands, their role as molecules for potential diagnostic and therapeutic approaches has not yet been analyzed.

OBJECTIVE

The aim of the present study was to investigate whether expression levels of putative pro- or anti-oncogenic hBDs, including hBD-1, -2, -3, and psoriasin/S100A7, are altered in salivary gland tumor tissue as potential targets for molecular-based therapeutic approaches.

METHODS

We analyzed the expression levels of hBD-1, -2, -3, and psoriasin/S100A7 by quantitative real-time polymerase chain reaction (qrt-PCR) and immunohistochemistry in a case control study by comparing salivary gland tumor samples relative to healthy control specimens from 58 patients. Expression level analysis of hBD-1, -2, -3, and psoriasin/S100A7 by qrt-PCR was normalized to the endogenous 18S rRNA expression levels.

RESULTS

The results demonstrate the significant downregulation of hBD-1 (p < 0.001), hBD-2 (p = 0.003), hBD-3 (p = 0.002), and psoriasin/S100A7 (p = 0.003) mRNA in human salivary gland tumors compared with healthy control specimens. Protein expression levels of hBD-1, -2, -3, and psoriasin/S100A7 in salivary gland tumor tissue were strongly reduced compared with healthy control specimens.

CONCLUSION

The data indicates a putative role of the innate defense system in salivary gland tumor formation. The identification of immunoregulatory molecules as diagnostic biomarkers or therapeutic targets could provide new approaches for molecular-based diagnostic and therapeutic support to treat salivary gland tumors as well as other malignancies. We suggest that HDPs should be taken into consideration for use in molecular-based therapeutic approaches.

Nuclear factor kappa B plays a pivotal role in polyinosinic-polycytidylic acid-induced expression of human β-defensin 2 in intestinal epithelial cells

Intestinal epithelial cells (IECs) play an important role in protecting the intestinal surface from invading pathogens by producing effector molecules. IECs are one of the major sources of human beta-defensin 2 (hBD-2), and can produce it in response to a variety of stimuli. Although IECs express Toll-like receptor 3 (TLR-3) and can respond to its ligand, double-stranded RNA (dsRNA), hBD-2 expression in response to dsRNA has not been elucidated. In the present study, using an artificial analogue of dsRNA, polyinosinic-polycytidylic acid (poly I:C), we investigated whether the human IEC line, HT-29, can produce hBD-2 in response to poly I:C. HT-29 cells can express hBD-2 mRNA only when stimulated with poly I:C. The induction of hBD-2 mRNA expression was observed at 3 h after stimulation and peaked at 12 h of post-stimulation. Pre-incubation of the cells with nuclear factor kappa B (NF-κB)-specific inhibitor, l-1-4'-tosylamino-phenylethyl-chloromethyl ketone (TPCK) and isohelenine abolished the expression of hBD-2. Detection of the poly I:C signal by TLR-3 on the surface of HT-29 cells was revealed by pre-incubating the cells with anti-TLR-3 antibody. The 5'-regulatory region of the hBD-2 gene contains two NF-κB binding sites. A luciferase assay revealed the importance of the proximal NF-κB binding site for poly I:C-induced expression of hBD-2. Among NF-κB subunits, p65 and p50 were activated by poly I:C stimulation and accumulated in the nucleus. Activation of the p65 subunit was investigated further by determining its phosphorylation status, which revealed that poly I:C stimulation resulted in prolonged phosphorylation of p65. These results indicate clearly that NF-κB plays an indispensable role in poly I:C induced hBD-2 expression in HT-29 cells.

Tolerance of bacteriuria after urinary diversion is linked to antimicrobial peptide activity

OBJECTIVES

To compare the cationic antimicrobial peptide gene expression profiles and urinary cationic antimicrobial activities of patients after urinary diversion according to their urinary tract infection (UTI) status. Ileal conduit urinary diversion joins the bacterial-tolerant ileal epithelium and intolerant urothelium. After this procedure, one quarter of patients develop repeated symptomatic UTIs. Such development might reflect the altered innate immune mechanisms centered on epithelial expression and urinary activity of cationic antimicrobial peptides, such as defensins.

METHODS

Ileal and ureteral biopsy specimens from ileal conduit subjects with (n = 18) and without (n = 18) recurrent symptomatic UTIs were assessed for cationic antimicrobial peptide gene expression using quantitative reverse transcriptase polymerase chain reaction. Overnight urine collections were analyzed for antimicrobial activity against a laboratory Escherichia coli strain, and infecting organisms were isolated from individual subjects.

RESULTS

Overall, the ureteral epithelium showed increased expression of human α-defensin 5 and decreased expression of the human β-defensin 1 after urinary diversion (P < .05). No significant changes were seen for the ileal epithelium. The expression levels of both defensins also did not differ significantly according to UTI status. Urinary cationic activity against infecting bacterial isolates from the individual subjects was significantly greater in those with symptomatic UTI (P < .001), and the activities against the laboratory E. coli strain were similar.

CONCLUSIONS

The changes in the human β-defensin 1 and human α-defensin 5 expression profiles and the link between symptomatic infection and high urinary antimicrobial activity suggest that innate mechanisms play significant roles in balancing bacterial tolerance and killing after ileal conduit urinary diversion. Future work needs to determine whether these changes can be therapeutically modulated to benefit the patients.

Polymorphisms of beta defensins are associated with the risk of severe acute pancreatitis

AIMS

Bacterial translocation from the intestinal tract plays an important role in severe acute pancreatitis (AP). Human β-defensins are a family of antimicrobial peptides present at the mucosal surface. The aim of this study was to investigate the relevance of single nucleotide polymorphisms (SNPs) in the DEFB1 gene and copy number polymorphisms of the DEFB4 genes in AP.

METHODS

124 AP patients (30 with mild and 94 with severe disease) and 100 healthy controls were enrolled in the study. Three SNPs of the DEFB1 gene [G-20A (c.-20G→A), C-44G (c.-44C→G) and G-52A (c.-52G→A)] were genotyped by Custom TaqMan assay. The DEFB4 gene copy number was determined by means of a TaqMan real-time PCR assay.

RESULTS

Significantly higher frequencies of the AA genotype of G-20A (c.-20G→A) and the AA genotype of G-52A (c.-52G→A) were observed among the patients with severe AP (SAP) compared with the healthy controls (38 vs. 20 and 41 vs. 18%, respectively). The GG protective genotype of C-44G (c.-44C→G) SNP was much less frequent (1%) among the patients than among the controls (9%). A higher frequency of a lower (<4) copy number of the DEFB4 gene was observed in the patients with SAP compared with the healthy controls (62 vs. 24%, respectively).

CONCLUSIONS

The variations in the genes encoding human β-defensin-1 and -2 may be associated with the risk of SAP. and IAP.

Functional polymorphisms of DEFB1 gene in type 1 diabetes Brazilian children

We analyzed three functional 5' un-translated region beta-defensin 1 (DEFB1) single nucleotide polymorphism (SNPs) in a group of 170 type 1 diabetes (T1D) patients. In order to evaluate the SNPs influence on the disease onset and the development of other autoimmune disorder, such as celiac disease (CD) and autoimmune thyroid disease (AITD), patients were stratified according to the presence of AITD, CD, and both AITD and CD. As control group, we studied 191 healthy children and adolescent not presenting a familiar historic of T1D, CD or AITD. DEFB1 SNPs were in Hardy-Weinberg equilibrium both in healthy controls and T1D patients, as well in the T1D patients stratified according to the presence of other autoimmune disorder(s). Allele, genotype, and haplotype frequencies of T1D patients globally considered were comparable to healthy controls ones. No evidence of any association of DEFB1 SNPs with the onset of AIDT, CD, and both AITD and CD on T1D patients was evidenced. Only a minor trend was found for an increased frequency of the - 20 G allele in T1D patients only presenting AITD vs. T1D patients not presenting AITD or CD, as well as an increase of those haplotypes comprising the - 20 G allele when compared with the GCA haplotype. We also evaluated the influence of functional DEFB1 SNPs on the age of T1D onset: no significant statistical conclusion was achieved. Further studies are envisaged, in order to elucidate the possible role of functional DEFB1 polymorphisms in the onset of TD1 and other autoimmune-related disorders.

Human beta-defensin-1, a potential chromosome 8p tumor suppressor: control of transcription and induction of apoptosis in renal cell carcinoma

Human beta-defensin-1 (hBD-1) is a candidate tumor suppressor gene located on chromosome 8p23. Previously, we showed that cancer-specific loss of hBD-1 was found in 90% of renal clear cell carcinomas and in 82% of prostate cancers. To investigate the possible mechanisms of decreased gene expression and determine the function of hBD-1 protein in urological cancers, we sequenced hBD-1 gene coding regions in prostatic and renal cancer samples. We then analyzed the frequency distribution of promoter polymorphisms and determined the effect of these base changes on transcriptional activity of the hBD-1 promoter. A polymorphism at -688 bases upstream of the ATG start codon affects hBD-1 promoter activity, leading to a rate of reporter gene transcription that is 40% to 50% lower than the wild-type sequence when tested in either DU145 or TSU-Pr1 cell lines. In addition, a polymorphism at -44 bases was shown to enhance transcription up to 2.3 times more than the wild-type sequence in the same cell lines. In addition, three novel hBD-1 promoter mutations were found in renal and prostate cancer clinical samples. An iso-5-aza-2'-deoxycytidine treatment was effective in transcription up-regulation in DU145, suggesting a possible upstream methylation-dependent effect. Synthetic hBD-1 peptide inhibited bladder cancer cell TSU-Pr1 proliferation. Overexpression of the hBD-1 gene in renal cancer cells SW156 resulted in caspase-3-mediated apoptosis. These data support the hypothesis that hBD-1 is a potential tumor suppressor gene for urological cancers. Promoter point mutations may be responsible for cancer-specific loss of hDB-1 expression.

The changing of the guard: Molecular diversity and rapid evolution of beta-defensins

Defensins are small cationic peptides involved in innate immunity and are components of the first line of defence against invading pathogens. beta-defensins are a subgroup of the defensin family that display a particular cysteine spacing and pattern of intramolecular bonding. These molecules are produced mostly by epithelia lining exposed surfaces and appear to have both antimicrobial and cell signalling functions. The unusually high degree of sequence variation in the mature peptide produced by the paralogous and in some cases orthologous genes implies extensive specialisation and species specific adaptation. Here we review recent functional data that are an important addition to our knowledge of the innate immune response and novel antibiotic design. We also consider the organisation and evolution of the genomic loci harbouring these genes where radical and rapid changes in beta-defensin sequences have been shown to result from the interplay of both positive and negative selection. Consequently these genes provide some unusually clear glimpses of the processes of duplication and specialisation that have shaped the mammalian genome.

Glucose regulation of beta-defensin-1 mRNA in human renal cells

We previously showed that beta-defensin-1 (BD-1), an anti-microbial peptide, is up-regulated during progressive hyperglycemia in the kidneys of the GK rat [R.A. Page, C.A. Morris, J.D. Williams, C.J. von Ruhland, A.N. Malik, Isolation of diabetes-associated kidney genes using differential display, Biochem. Biophys. Res. Commun. 232 (1997) 49-53, R.A. Page, A.N. Malik, Elevated levels of beta-defensin-1 mRNA in diabetic kidneys of GK rats, Biochem. Biophys. Res. Commun. 310 (2003) 513-521]. In this paper, we show that human beta-defensin-1 (hBD-1) mRNA is directly up-regulated by glucose in cultured human renal cells. hBD-1 mRNA levels increased by approximately 7-fold and approximately 4-fold in human embryonic kidney (HEK) cells and human mesangial cells (HMC) grown in 25mM glucose for four days, as determined by quantitative real-time PCR. Immunofluorescence showed that the hBD1 protein is located in the cytoplasm of HEK cells and transfected HMCs. The highest levels of hBD-1 mRNA were found in the kidney compared with 21 other human tissues. The increased expression of hBD-1 mRNA in cultured HMCs in high glucose suggests a role for hBD-1 in the molecular pathways induced during hyperglycemia.

Lipopolysaccharide induced-in vivo increases in β-defensins of the rat parotid gland

Antimicrobial beta-defensins are thought to protect epithelial surfaces. Their mobilization in response to inflammation was studied in the rat parotid gland using an ELISA assay. Bacterial lipopolysaccharide (LPS), injected into the parotid duct on one side, induced a marked local inflammatory response in the parotid gland as judged by several fold increases in myeloperoxidase activity and, in histological sections, infiltration of neutrophils. Three hours after the injection, beta-defensin 1 and 3 were increased (by 41% and 15%, respectively, P<0.01) as compared to the contralateral gland. Though still elevated 6h after the injection, the percentage figures for beta-defensin 1 were, at this time, somewhat lower (30%) compared to the situation at 3h, while those for defensin 3 were significantly higher 65% (P<0.01); neither at the early nor at the late time of observation were any changes in the level of beta-defensin 2 observed. The beta-defensins under study were not detected in submandibular and sublingual glands, neither were they detected in the inflamed submandibular gland, showing also here several fold increases in myeloperoxidase activity and, in addition, the presence of inflammatory cells, following ductal injection of LPS towards the gland.

The interaction of urinary tract infection and renal insufficiency

Urinary tract infections (UTIs) are among the most common infections caused by microorganisms, and pyelonephritis is the most severe infection of the urogenital tract. The risk of developing chronic renal insufficiency due to a UTI without other risk factors is low. The pathogenicity and virulence of the infective microorganisms as well as the efficiency of local or systemic defence mechanisms determine the course and severity of the disease. Virulence properties (adhesins, toxins, capsule, iron uptake) are encoded by genomic structures and the determination of virulence is influenced by the host situation. In renal insufficiency, a variety of quite different substances (uraemic toxins, betaine, amino acids, creatinine, urea, glucose) influence the microbial environment. Defence factors (Tamm-Horsfall protein, defensin, phagocytic activity of granulocytes) and underlying anatomical lesions as well as pre-existing renal disease determine the severity of UTI and the prognosis of renal insufficiency.

[Recurrent urinary tract infections in women. Virulence of pathogens and host reaction]

The interactions of host-specific and microbial factors are responsible for recurrent urinary tract infections (rUTI). The anatomical properties of the female urogenital tract favor colonization by uropathogens. Local factors such as glucose concentration of the urine, stability of the lactobacilli population, the influence of estrogens, the activity of Tamm-Horsfall protein or of defensins, and disturbance of the systemic defense mechanisms dictate the course of an infection. The most prominent uropathogen is E. coli. It expresses various virulence factors including adhesions, toxins, iron uptake systems, and a capsule. It is still unclear if there are virulence factors characteristic for E. coli strains causing rUTI. The formation of intracellular reservoirs by invasion of uroepithelial cells by E. coli could be another, as yet little noticed cause for rUTI. Therefore, in cases of rUTI the application of intracellularly active antibiotics should be considered.

Gene expression profiles in developing nephrons using Lim1 metanephric mesenchyme-specific conditional mutant mice

BACKGROUND

Lim1 is a homeobox gene that is essential for nephrogenesis. During metanephric kidney development, Lim1 is expressed in the nephric duct, ureteric buds, and the induced metanephric mesenchyme. Conditional ablation of Lim1 in the metanephric mesenchyme blocks the formation of nephrons at the nephric vesicle stage, leading to the production of small, non-functional kidneys that lack nephrons.

METHODS

In the present study, we used Affymetrix probe arrays to screen for nephron-specific genes by comparing the expression profiles of control and Lim1 conditional mutant kidneys. Kidneys from two developmental stages, embryonic day 14.5 (E14.5) and 18.5 (E18.5), were examined.

RESULTS

Comparison of E18.5 kidney expression profiles generated a list of 465 nephron-specific gene candidates that showed a more than 2-fold increase in their expression level in control kidney versus the Lim1 conditional mutant kidney. Computational analysis confirmed that this screen enriched for kidney-specific genes. Furthermore, at least twenty-eight of the top fifty (56%) candidates (or their vertebrate orthologs) were previously reported to have a nephron-specific expression pattern. Our analysis of E14.5 expression data yielded 41 candidate genes that are up-regulated in the control kidneys compared to the conditional mutants. Three of them are related to the Notch signaling pathway that is known to be important in cell fate determination and nephron patterning.

CONCLUSION

Therefore, we demonstrate that Lim1 conditional mutant kidneys serve as a novel tissue source for comprehensive expression studies and provide a means to identify nephron-specific genes.

Antimicrobial peptides as microbicidal contraceptives: prophecies for prophylactics--a mini review

The global increase in human immunodeficiency virus/acquired immune deficiency syndrome (HIV/AIDS) and sexually transmitted infections (STIs) has led to the introduction of barrier methods, such as condoms. However, drawbacks associated with condoms, such as men being reluctant to use them and women being unable to negotiate their use, have led to the search for better and acceptable alternatives, namely the microbicides. These are gel formulations that, when used prior to sexual intercourse, protect against the transmission of HIV and other STIs. However, after observing the side-effects of nonoxynol-9, a component of the microbicidal formulations available on the market, the focus has shifted to natural available compounds demonstrating the preferred protective effects. Antimicrobial peptides (AMPs) are one such group of compounds present in a wide range of organisms from bacteria to humans. The existing 750 or so, low-molecular-weight, cationic charged peptides are classified into five major groups based on their three-dimensional structure obtained by nuclear magnetic resonance studies. The hypothesized mode of action seems to be the interaction of the positively charged peptides with the negatively charged phospholipids present on the surface of the cell membrane. Various studies have demonstrated the effect of several AMPs, namely, defensins, protegrins, cathelicidins, cecropins, polyphemusins, magainins and melittins, against various STI-causing pathogens and HIV/herpes simplex virus, both in vitro and in vivo. The contraceptive efficacies of magainin and nisin in vitro and in vivo are worth mentioning. We believe these peptides are suitable candidates in the development of newer mechanism-based microbicides in future.

Antimicrobial peptides: premises and promises

Antimicrobial peptides (AMPs) are an important component of the natural defences of most living organisms against invading pathogens. These are relatively small (< 10kDa), cationic and amphipathic peptides of variable length, sequence and structure. During the past two decades several AMPs have been isolated from a wide variety of animals, both vertebrates and invertebrates, and plants as well as from bacteria and fungi. Most of these peptides are obtained from different sources like macrophages, neutrophils, epithelial cells, haemocytes, fat body, reproductive tract, etc. These peptides exhibit broad-spectrum activity against a wide range of microorganisms including Gram-positive and Gram-negative bacteria, protozoa, yeast, fungi and viruses. A few peptides have also been found to be cytotoxic to sperm and tumour cells. AMPs are classified based on the three dimensional structural studies carried out with the help of NMR. The peptides are broadly classified into five major groups namely (a) peptides that form alpha-helical structures, (b) peptides rich in cysteine residues, (c) peptides that form beta-sheet, (d) peptides rich in regular amino acids namely histatin, arginine and proline and (e) peptides composed of rare and modified amino acids. Most of these peptides are believed to act by disrupting the plasma membrane leading to the lysis of the cell. AMPs have been found to be excellent candidates for developing novel antimicrobial agents and a few of these peptides show antimicrobial activity against pathogens causing sexually transmitted infection (STI), including HIV/HSV. Peptides, namely magainin and nisin have been shown to demonstrate contraceptive properties in vitro and in vivo. A few peptides have already entered clinical trials for the treatment of impetigo, diabetic foot ulcers and gastric helicobacter infections. In this review, we discuss the source, structures and mode of action with special reference to therapeutic considerations of various AMPs.

Minireview: functions of the renal tract epithelium in coordinating the innate immune response to infection

Infection of the urinary tract remains one of the most common infections affecting mankind. Renal epithelial cells, being one of the first cells to come into contact with invading organisms, are in a key position to coordinate host defense. The epithelium not only provides a physical barrier to infection, but can also augment the immune response via the production of a number of inflammatory mediators and antimicrobial proteins. Recent work has demonstrated that cells of the innate immune system, including epithelial cells, express toll-like receptors (TLRs), with the capacity to recognize bacterial components. Although the exact mechanisms remain unclear, engagement of TLRs can lead to epithelial cell activation and the production of inflammatory mediators. These include complement proteins, other bactericidal peptides, and chemotactic cytokines. The resulting inflammatory infiltrate serves to aid bacterial clearance, but can also lead to renal damage. In this review, we describe how renal epithelial cells contribute to the innate immune response to ascending urinary tract infection. We specifically relate previous work to more recent developments in this field. An improved understanding of the mechanisms involved may highlight potential therapeutic avenues to aid bacterial clearance and prevent the renal scarring associated with infection.

Primate defensins

Defensins are endogenous, cysteine-rich antimicrobial peptides that contribute to host defence against bacterial, fungal and viral infections. There are three subfamilies of defensins in primates: alpha-defensins are most common in neutrophils and Paneth cells of the small intestine; beta-defensins protect the skin and the mucous membranes of the respiratory, genitourinary and gastrointestinal tracts; and theta-defensins, which are expressed only in Old World monkeys, lesser apes and orangutans, are lectins with broad-spectrum antiviral efficacy. Here, their discovery and recent advances in understanding their properties and functions are described.

Microarray analysis of focal segmental glomerulosclerosis

BACKGROUND

Focal segmental glomerulosclerosis (FSGS) is a leading cause of chronic renal failure in children. Recent studies have begun to define the molecular pathogenesis of this heterogeneous condition. Here we use oligonucleotide microarrays to obtain a global gene expression profile of kidney biopsy specimens from patients with FSGS in order to better understand the pathogenesis of this disease.

METHODS

We extracted RNA from renal biopsy samples of 10 patients with the diagnosis of FSGS and from 5 control kidney samples, and produced labeled cRNA for hybridization to Affymetrix human U133A microarrays.

RESULTS

We identified a gene expression fingerprint for FSGS that contained 429 of 22,283 possible genes, each with a p < 0.01, using RMA normalization, Welch t test, and at least a 1.8-fold change in 5 of the 10 patients examined. We also found gene expression differences in samples from subsets of patients who had either nephrotic syndrome or renal insufficiency. This screen identified many genes and genetic pathways that have already been implicated in the pathogenesis of FSGS. In addition, we found changes in gene expression in genetic pathways that have not been studied in FSGS.

CONCLUSIONS

Oligonucleotide DNA microarray analysis of renal biopsy specimens identified a gene expression fingerprint in samples from a heterogeneous population of patients with FSGS. The genes and genetic pathways identified in this study can be compared to results of similar studies of other diseases to examine specificity and used to study the pathogenesis of FSGS.

Antimicrobial activity of innate immune molecules against Streptococcus pneumoniae, Moraxella catarrhalis and nontypeable Haemophilus influenzae

Background

Despite its direct connection to the nasopharynx which harbors otitis media pathogens as part of its normal flora, the middle ear cavity is kept free of these bacteria by as yet unknown mechanisms. Respiratory mucosal epithelia, including those of the middle ear and eustachian tube, secrete antimicrobial effectors including lysozyme, lactoferrin and β defensins-1 and -2. To elucidate the role of these innate immune molecules in the normal defense and maintenance of sterility of respiratory mucosa such as that of the middle ear, we assessed their effect on the respiratory pathogens nontypeable Haemophilus influenzae (NTHi) 12, Moraxella catarrhalis 035E, and Streptococcus pneumoniae 3, and 6B.

Methods

Two assay methods, the radial assay and the liquid broth assay, were employed for testing the antimicrobial activity of the molecules. This was done in order to minimize the possibility that the observed effects were artifacts of any single assay system employed. Also, transmission electron microscopy (TEM) was employed to evaluate the effect of antimicrobial innate immune molecules on OM pathogens. For the statistical analysis of the data, Student's t-test was performed.

Results

Results of the radial diffusion assay showed that β defensin-2 was active against all four OM pathogens tested, while treatment with β defensin-1 appeared to only affect M. catarrhalis. The radial assay results also showed that lysozyme was quite effective against S. pneumoniae 3 and 6B and was partially bacteriostatic/bactericidal against M. catarrhalis. Lysozyme however, appeared not to affect the growth of NTHi. Thus, lysozyme seems to have a more pronounced impact on the growth of the Gram-positive S. pneumoniae as compared to that of Gram-negative pathogens. Lactoferrin on the other hand, enhanced the growth of the bacteria tested. The results of the radial assays were confirmed using liquid broth assays for antimicrobial activity, and showed that lysozyme and β defensin-2 could act synergistically against S. pneumoniae 6B. Moreover, in the liquid broth assay, β defensin-1 showed a modest inhibitory effect on the growth of S. pneumoniae 6B. As assessed by ultrastructural analysis, lysozyme and β defensin-2, and to a much lesser extent, β defensin-1, appeared to be able to cause damage to the bacterial membranes.

Conclusions

Here we report that lysozyme and the β defensins can inhibit the growth of clinical isolates of otitis media pathogens – namely NTHi strain 12, S. pneumoniae strains 3 and 6B and M. catarrhalis strain 035E – and cause ultrastructural damage to these pathogens. Moreover, we demonstrate that lysozyme and β defensin-2 can act synergistically against S. pneumoniae. These findings are consistent with the concept that secreted antimicrobial peptides and other components of innate immunity constitute the first line of defense protecting host mucosal surfaces, including the tubotympanal (eustachian tube and middle ear cavity) mucosa, against pathogens.

Nonparallel secretion of antibacterial activity and protein in porcine pancreatic juice

The antimicrobial activity of exocrine pancreatic juice is an important component of gastrointestinal tract innate defenses, yet little is known about whether secretion is regulated in parallel with digestive enzymes. In this study, we used 8 pigs with pancreatic catheters to quantify antibacterial activity and measure protein content (indicator of enzyme secretion) of pancreatic juice collected hourly from 0700 to 1900, with the animals adapted to being fed at 0800 and 1600. Antibacterial activity in the samples of pancreatic juice was quantified by comparing the growth inhibition of Staphylococcus aureus subsp. aureus strain ATCC 6538P relative to a known concentration of gentamicin. Antibacterial activity (U/mL and /min) was highest in samples collected 1 hour prior to feeding (equivalent to 0.6 microgram gentamicin/mL), declined as the meal was consumed, and was lower (P < 0.05) in samples collected while the meals were being digested (0.41 microgram gentamicin/mL). Protein content was negatively correlated with antibacterial activity, with protein secretion lower (mg/mL and /min) before feeding, with an increase as the pigs ate and digested the meals (P < 0.05). The results indicate that the antibacterial activity in pancreatic juice is not secreted in parallel with protein secretion, suggesting that regulation involves alternative signaling pathways or contrasting responses to shared signals.

Effect of the antibacterial activity of pig pancreatic juice on human multiresistant bacteria

INTRODUCTION

The role of the exocrine pancreas in regulating gut microflora colonization is unclear. The main objective in the current study was to assess the effect of pancreatic fluid on the growth of pathogenic bacteria and fungi.

METHODS

The antibacterial activity of pure pig pancreatic juice collected from catheterized, healthy, conscious, and anesthetized pigs was investigated with multiresistant microbial isolates and nonpathogenic strains. Studies were performed on pathogenic bacterial and fungi as well as lactic acid bacteria and reference strains.

RESULTS

Pancreatic juice was effective (P < 0.01) against multidrug resistant bacterial pathogens, whereas lactic acid bacteria were insensitive. The antibacterial action was independent of pancreatic juice proteolytic activity. The in vitro antibacterial properties of pancreatic juice last for several hours. Data suggest that broth composition may modulate the intensity of pancreatic juice antibacterial activity.

CONCLUSIONS

Pancreatic juice antibacterial activity may be an important factor in limiting the colonization of pathogenic bacteria in the gastrointestinal tract. We postulate that observed antibacterial activity of the pancreatic juice could play an important role as one of the factors of innate immunity.

The role of defensins in lung biology and therapy

Innate host defence, involving both cellular and humoral mediators, is a prominent function of the human airways. Cellular mediators of innate immunity include dendritic cells, natural killer cells, cytotoxic T cells, macrophages and neutrophils, while humoral mediators of innate immunity consist of components of the epithelial lining fluid (ELF) covering the airways. Microbicidal substances in the ELF can selectively disrupt bacterial cell walls and membranes, sequester microbial nutrients or act as decoys for microbial attachment. Antimicrobial components of airway secretions include lysozymes, lactoferrin, secretory leukoprotease inhibitor, defensins and cathelicidins. Defensins are the most widely studied family of antimicrobial peptides present in airway fluid. Humans produce at least 10 different defensin molecules, six alpha-defensins and four beta-defensins similar in structure and function. Direct evidence that defensins have central roles in host defense has only recently become available. Some defensins and defensin-like molecules could serve as templates for the development of pulmonary pharmaceuticals. As potential therapeutics, they possess several desirable properties, including the ability to kill a broad spectrum of micro-organisms while permitting little development of microbial resistance. Many peptides can also neutralize effects of lipopolysaccharide on macrophages and other host defense cells and decrease the release of proinflammatory cytokines thereby giving protection against septic shock. Protegrin-1 is a minidefensin isolated from pig leukocytes and has proved to be an attractive template for large-scale development of antibacterials. One such protegrin analog, iseganan is in phase III clinical trials for the treatment of oral mucositis secondary to systemic chemotherapy. Other prospective uses of iseganan include control of respiratory pathogens in patients with cystic fibrosis and reduction of oral bacteria to prevent ventilator-associated pneumonia. However, in order to advance the production and clinical testing of peptide-based therapeutics, technical hurdles of synthesizing large quantities of complexly folded peptides must be first overcome. Strategies to develop potent peptide-based microbicides are promising in the struggle against increasingly resistant pathogens.

Hepatocyte growth factor inhibits intrinsic antibacterial activity of Madin-Darby canine kidney cells

We investigated whether or not polarized renal epithelial cells produce antibacterial factors, which aid in host defense at the cell surface of renal epithelium. A model of polarized Madin-Darby canine kidney (MDCK) epithelial cells grown on filters was used to test for the presence of apically or basolaterally secreted factors on the growth of non-virulent (XL1-Blue) and uropathogenic (J96) strains of Escherichia coli (E. coli). Growth of both XL1-Blue and J96 strains of E. coli in medium on the apical and basolateral surface of MDCK cells was inhibited as compared to bacterial growth in medium not exposed to MDCK cells. The inhibition of bacterial growth was similar in both apical and basolateral surface medium. Pretreatment of MDCK cells with hepatocyte growth factor (HGF) blunted the inhibition of XL1-Blue and J96 growth in apical and basolateral surface medium as compared to growth in medium on the surfaces of untreated MDCK cells. Immunofluorescent analysis demonstrated the presence of beta-defensin isoforms 1-3 in MDCK cells, with isoform 1 being the most prevalent form observed. HGF treatment reduced the amount of immunoreactive beta-defensin-1 in MDCK cells. These data demonstrate that polarized renal epithelium produce antibacterial factors. The renotropic growth factor HGF inhibits these antibacterial factors. beta-defensins may contribute to this antibacterial activity and play an important role in renal epithelial resistance to bacterial infections.

Decreased excretion of antimicrobial proteins and peptides in saliva of patients with oral candidiasis

BACKGROUND

Antimicrobial peptides in saliva appear to play a crucial role in the regulation of oral Candida growth, and study on antimicrobial excretion in saliva and oral candidiasis appears useful for the analysis of pathophysiology of oral candidiasis.

METHODS

To clarify the role of saliva in the regulation of oral Candida growth, the levels of antimicrobial proteins and peptides and their excretion rates were examined in saliva obtained from 50 patients with oral candidiasis and 35 healthy individuals.

RESULTS

The inhibitory activities of patients' saliva against Candida adhesion with HeLa cells and against Candida growth (radiolabeled glucose incorporation) were lower than those of saliva from the healthy controls. The salivary levels of lactoferrin (Lf; 11 +/- 9 microg/ml), secretory immunoglobulin A (sIgA; 160 +/- 37 microg/ml), beta-defensin 1 (375 +/- 37 ng/ml), and beta-defensin 2 (412 +/- 51 ng/ml) in the patients were largely lower than those in the control group (33 +/- 14 microg/ml, 204 +/- 51 microg/ml, 452 +/- 89 ng/ml, and 530 +/- 142 ng/ml, respectively), although the transferrin (Tf) and secretory component (SC) levels were almost same in both groups, and alpha-defensin 1 was slightly increased in the patient group (660 +/- 115 ng/ml vs. 467 +/- 168 ng/ml). In addition, the excretion rates of the proteins and peptides were largely decreased in the patients (Tf: 14 +/- 2 microg/10 min vs. 34 +/- 7 microg/10 min; Lf: 18 +/- 11 microg/10 min vs. 139 +/- 43 microg/10 min; sIgA: 300 +/- 132 microg/10 min vs. 900 +/- 207 microg/10 min; SC: 112 +/- 46 microg/10 min vs. 292 +/- 64 microg/10 min; alpha-defensin 1: 1223 +/- 431 ng/10 min vs. 2044 +/- 612 ng/10 min; beta-defensin 1: 687 +/- 243 ng/10 min vs. 1985 +/- 295 ng/10 min; and beta-defensin 2: 784 +/- 299 ng/10 min vs. 2288 +/- 278 ng/10 min).

CONCLUSION

These results conclusively suggest that oral candidiasis is associated with salivary gland hypofunction and that decreases of salivary antibacterial proteins induce Candida overgrowth.

What are renal defensins defending?

Defense against the susceptibility and damaging effects of urinary tract infection is complex and vital, as injury can lead to progressive renal injury and chronic renal failure. Recently the defensins, a family of small cationic antimicrobial peptides found in neutrophils and renal epithelial cells, have been shown to have a number of key biological properties that equip them to undertake a pivotal role in combating infection. We describe the capability of these ubiquitous and abundant peptides in the process of innate immunity, and more recently discovered roles in the adaptive immune response to infection. Furthermore, we also discuss their potential to influence other key components of the inflammatory response to infection. Despite the current state of knowledge, we are only just beginning to understand the significance of defensins as pivotal peptides in host defence and their possibilities as therapeutic targets of the future.

Bactericidal activity of renal tubular cells: the putative role of human beta-defensins

Renal tubular epithelial cells (RTC) form a barrier between the host and ascending microbes in upper urinary tract infection. Previous studies have shown the ability of the kidney to produce defensins--antimicrobial peptides that play a pivotal role in unspecific host defense. To further clarify the role of renal epithelium for direct antibacterial activity we investigated the expression, regulation and production of antimicrobial peptides by cultured human RTC. Cell culture supernatants of RTC exert strong bactericidal activity against Escherichia coli and Klebsiella pneumoniae, two of the most important pathogens in urinary tract infections. The antimicrobial effect depends on salt concentration, a typical feature of human defensins. RT-PCR of RNA from cultured proximal and distal RTC showed constitutive expression of human beta-defensin 1 (hbd-1) and human beta-defensin 2 (hbd-2) whereas only hbd-1 expression could be detected in RNA preparation from renal biopsy material. Hbd-2 expression of RTC was induced by inflammatory processes as shown by semiquantitative competitive RT-PCR. Coincubation of the cultured cells with IL-1alpha or E. coli promote the strongest hbd-2 induction whereas TNF-alpha and LPS lead to a weaker or no (IL-6) hbd-2 induction. This is the first evidence that human RTC are able to produce antibacterial substances in a biologically relevant amount and that beta-defensins are candidate proteins responsible for this effect.

Biology and clinical relevance of naturally occurring antimicrobial peptides

Within the last decade, several peptides have been discovered on the basis of their ability to inhibit the growth of potential microbial pathogens. These so-called antimicrobial peptides participate in the innate immune response by providing a rapid first-line defense against infection. Recent advances in this field have shown that peptides belonging to the cathelicidin and defensin gene families are of particular importance to the mammalian immune defense system. This review discusses the biology of these molecules, with emphasis on their structure, processing, expression and function. Current evidence has shown that both cathelicidins and defensins are multifunctional and that they act both as natural antibiotics and as signaling molecules that activate host cell processes involved in immune defense and repair. The abnormal expression of these peptides has also been associated with human disease. Current and future studies are likely to implicate the presence of antimicrobial peptides in several unexplained human inflammatory disorders and to provide novel therapeutic approaches to the treatment of disease.

Expression of human beta-defensins 1 and 2 in kidneys with chronic bacterial infection

BACKGROUND

Constitutive expression and localization of antimicrobial human beta-defensin-1 (HBD-1) in human kidneys as a potential mechanism of antimicrobial defense has been previously reported. Inducible expression of human beta-defensin-2 (HBD-2) has been described in various epithelial organs but not for the urogenital tract.

METHODS

We investigated the gene- and protein expression of HBD-1 and HBD-2 by reverse transcriptase-polymerase chain reaction, and immunohistochemistry in 15 normal human kidney samples and 15 renal tissues with chronic bacterial infection. Additionally, cell culture experiments were performed to study HBD gene expression by real-time RT-PCR in response to inflammatory cytokines TNFalpha and IL-1beta as well as lipopolysaccharide from Gram-negative bacteria.

RESULTS

Constitutive HBD-1 gene- and protein expression was detected in normal renal tissue and kidneys with chronic infection. As a novel finding, inducible HBD-2 gene- and protein expression was demonstrated in tubulus epithelia with chronic infection but not in normal renal tissue. In pyelonephritic kidneys HBD-1 and HBD-2 expression showed a similar pattern of localization in distal tubules, loops of Henle and in collecting ducts of the kidney. Furthermore, real-time RT-PCR of kidney derived cell lines stimulated with inflammatory agents TNF-alpha, IL-1beta and LPS revealed a strong increase in relative HBD-2 transcription level and also a slight increase in relative HBD-1 transcription level.

CONCLUSIONS

Upregulated HBD-2 expression in renal tubulus epithelium indicates a role of a wider range of human defensins for antimicrobial host defense in the urogenital tract than previously recognized.

Human alpha-defensins HNPs-1, -2, and -3 in renal cell carcinoma: influences on tumor cell proliferation

The alpha-defensins human neutrophil peptides (HNPs)-1, -2, and -3 have been described as cytotoxic peptides with restricted expression in neutrophils and in some lymphocytes. In this study we report that HNPs-1, -2, and -3 are also expressed in renal cell carcinomas (RCCs). Several RCC lines were found to express mRNA as well as the specific peptides of HNP-1, -2, and -3 demonstrated by reverse transcriptase-polymerase chain reaction, mass spectrometric, and flow cytometric analyses. At physiological concentrations HNPs-1, -2, and -3 stimulated cell proliferation of selected RCC lines in vitro but at high concentrations were cytotoxic for all RCC lines tested. As in RCC lines, alpha-defensins were also detected in vivo in malignant epithelial cells of 31 RCC tissues in addition to their expected presence in neutrophils. In most RCC cases randomly, patchy immunostaining of alpha-defensins on epithelial cells surrounding neutrophils was seen, but in six tumors of higher grade malignancy all tumor cells were diffusely stained. Cellular necrosis observed in RCC tissues in association with extensive patches of HNP-1, -2, and -3, seemed to be related to high concentrations of alpha-defensins. The in vitro and in vivo findings suggest that alpha-defensins are frequent peptide constituents of malignant epithelial cells in RCC with a possible direct influence on tumor proliferation.

Induction of human β-defensin-2 expression in human astrocytes by lipopolysaccharide and cytokines

Defensins are cationic peptides with broad-spectrum antimicrobial activity. They are members of a supergene family consisting of alpha and beta subtypes and each subtype is comprised of a number of different isoforms. For example, human alpha-defensin (HAD) has six isoforms, which are expressed by polymorphonuclear leukocytes and Paneth cells. In contrast, human beta-defensin (HBD) has two isoforms that are expressed by epithelial cells of the skin, gut, respiratory and urogenital tracts. Recently, HBD-1 was detected in human brain biopsy tissue. However, little is known about the expression of HBD-1 or HBD-2 in the CNS and whether neural cells can secrete these peptides. For the present study, human astrocyte, microglial, meningeal fibroblast and neuronal cultures were probed for the expression of HBD-1 and HBD-2 mRNA and protein. Each cell type was either maintained in tissue culture medium alone or in medium containing lipopolysaccharide (LPS) at concentrations ranging from 0.1 to 1 microgram/mL, interleukin-1 beta (IL-1beta) at 1-50 ng/mL, or tumor necrosis factor alpha (TNF-alpha) at the same concentrations. The expression of HBD-1 and HBD-2 mRNAs was monitored by RT-PCR. The cDNA products were sequenced to characterize the gene product. HBD-2 protein was detected by immunoblot, immunoprecipitation and immunocytochemistry. Results of these studies showed that HBD-1 mRNA was detected in all cell cultures except in those enriched for neurons. In contrast, HBD-2 mRNA was detected only in astrocyte cultures that were treated with LPS, IL-1beta or TNF-alpha. The detection of the respective proteins correlated positively with the mRNA results. As such, these data represent the first demonstration of HBD-2 expression by astrocytes and suggest that this peptide may play a role in host defense against bacterial CNS pathogenesis.

Expression of the peptide antibiotics human beta defensin-1 and human beta defensin-2 in normal human skin

Normal human skin is remarkably resistant to infection from the large numbers of microorganisms that routinely colonize its surface. In addition to the role of skin as a mechanical barrier, it has long been recognized that skin and other epithelia can produce a range of anti-microbial chemicals that play an important part in eliminating potential cutaneous pathogens. Anti-microbial peptides are an important evolutionarily conserved innate host defense mechanism in many organisms. Human beta defensin-1 and -2 are cysteine-rich, cationic, low molecular weight anti-microbial peptides that have recently been shown to be expressed in epithelial tissues. In this study, we describe the characterization of human beta defensin-1 and -2 mRNA and peptide expression in normal human skin. Using reverse transcription-polymerase chain reaction we demonstrate that human beta defensin-1 is consistently expressed in skin samples from various body sites. Human beta defensin-2 demonstrates expression that is more variable and is more readily detectable in facial skin and foreskin compared with skin from abdomen and breast. In situ hybridization localizes the human beta defensin-1 and -2 transcripts to keratinocytes within interfollicular skin. Using specific antibodies, we have shown that human beta defensin-1 and -2 peptides are localized to the Malpighian layer of the epidermis and/or stratum corneum and that there are interindividual and site-specific differences in intensity of immunostaining and the pattern of peptide localization. The localization of human beta defensins to the outer layer of the skin is consistent with the hypothesis that human beta defensins play an essential part in cutaneous innate immunity.

Defensins -- innate immunity at the epithelial frontier

Physical barrier function was formerly believed to play the major role in mucosal protection against luminal bacteria. This view has now been challenged by the discovery of specialized molecules that possess antimicrobial activity. More than 100 peptides have been identified so far, and the number is still growing. These peptides are distributed widely and conserved throughout phylogeny. The epithelial expression of antimicrobial peptides is of particular interest as many pathogens adhere to epithelial surfaces and may eventually invade the host. This rapidly acting defence system of innate immunity is already engaged before adoptive immune interactions take place. These antimicrobial peptides consist of constitutive and inducible forms, potentiating this barrier function in terms of an inflammatory response. One important subgroup of antimicrobial peptides is the family of defensins, which are classified as alpha (alpha-) and beta (beta-) defensins. Eight different peptides with varying antimicrobial properties have been identified. They are distributed widely in humans, and organ-specific expression patterns have been observed. Homologous peptides have been found in other mammals, vertebrates, invertebrates, insects and plants. The identification of alpha-defensins and their murine counterparts, cryptdins, in the small intestine prompted intensive research into epithelial antimicrobial defence.

Structural analysis of human beta-defensin-1 and its significance in urinary tract infection

Human beta-defensin-1 (hBD-1) is a 36-amino-acid antimicrobial peptide that functions in the host innate defense. We developed a highly sensitive radioimmunoassay for hBD-1 and identified several hBD-1 peptides in human kidney, urine, and plasma by amino acid sequencing and mass spectrometry. Large quantities of hBD-1 peptides are produced in the kidney, are released into the tubular lumen as 47-amino-acid pro-hBD1, and then undergo proteolytic processing and generate multiple truncated forms. The respective urine and plasma concentrations of hBD-1 in patients with pyelonephritis are 48.1 +/- (SEM) 15.7 pmol/mg creatinine and 2.66 +/- 0.41 pmol/ml, 3.1-fold and 1.8-fold those of normal individuals. hBD-1 is thought to contribute to mucosal defense in the urinary tract. Our findings provide a better understanding of the biosynthesis of this peptide and its pathophysiological significance in infectious diseases.

Differential expression of caprine beta-defensins in digestive and respiratory tissues

We identified two novel beta-defensin precursors, preproGBD-1 and preproGBD-2, in the tissues of a goat. Although the precursors were identical in 96.8% of their bases and 88.2% (60 of 68) of their amino acids, preproGBD-1 was expressed principally in the tongue and respiratory tract, whereas preproGBD-2 expression predominated throughout the intestine. These findings exemplify the phenomenon of tissue-specific expression in a family of host defense peptides that arose before the avian and mammalian lineages diverged.