Widespread expression of beta-defensin hBD-1 in human secretory glands and epithelial cells

Expression of the antimicrobial peptide, human beta-defensin 1, in duct cells of minor salivary glands and detection in saliva

The oral cavity is exposed to a variety of environmental insults. Salivary secretions play a critical role in maintaining oral health via innate host defense mechanisms and secretion of secretory IgA. Human beta-defensins (hBD) are antimicrobial peptides that are a component of the innate immune response; they are expressed in epithelia and are proposed to have a role in mucosal defense. hBD-1 mRNA is constitutively expressed in numerous mucosal tissues, including human gingiva and submandibular and parotid glands. Our objective was to detect the expression and localization of hBD-1 peptide in human salivary glands and in saliva. Minor salivary gland tissue was obtained from biopsies of patients with mucoceles (n = 20). hBD-1 peptide was detected by immunohistochemistry; expression was localized to the ductal cells and not the acinar cells of these glands. The peptide was located apically, toward the lumen in the duct cells. Further evaluation showed stronger hBD-1 expression in ducts with periductal inflammation, as indicated by the immunostaining of serial sections with anti-CD45 specific for B- and T-lymphocytes. Statistical analysis showed a strong correlation of hBD-1 staining and inflammation. Results of immunolocalization suggest that hBD-1 functions to protect salivary glands from retrograde infection, that expression of the peptide is enhanced in inflamed sites, and that post-transcriptional regulatory mechanisms may be involved in hBD-1 peptide expression. Western immunoblot analysis also detected hBD-1 peptide in unstimulated, whole, acidified saliva from normal volunteers. However, hBD-1 peptide associated with salivary mucin resulted in loss of the detection in a dot-immunoblot assay. Association of hBD-1 with salivary mucin may facilitate peptide distribution and adherence to oral surfaces and aid its function within the oral cavity.

Differential expression of human alpha- and beta-defensins mRNA in gastrointestinal epithelia

BACKGROUND

While defensins have received great attention for their role in bronchial innate immune defence, little is known about the expression levels of the four human epithelial defensins (HD5, HD6, hBD1 and hBD2) in the digestive tract. In this study we quantified the alpha- and beta-defensins mRNA in biopsies obtained from the gastrointestinal mucosa and identified the cells expressing the beta-defensin hBD1 mRNA in ileal mucosa.

MATERIAL AND METHODS

Biopsies from human stomach (corpus and antrum), duodenum, jejunum, ileum and colon were analysed for their expression of alpha- and beta-defensins. The mRNA of defensins was quantified by semiquantitative reverse transcription-polymerase chain reaction. Cells expressing beta-defensin hBD1 mRNA were identified by in situ hybridization with 35S-labelled RNA probes in tissue sections of human ileum.

RESULTS

The hBD1 mRNA was expressed at low levels with little variability throughout the gastrointestinal tract and was detected in all epithelial cells of ileal mucosa. HD5 and HD6 mRNA expression was restricted to the intestine and displayed high interindividual variability. The highest expression levels were observed in jejunum and ileum. Biopsies obtained from duodenum displayed low levels or no expression of HD5 and HD6. The expression level increased considerably in a biopsy obtained from a patient with acute coeliac sprue. In contrast, low levels were observed in a biopsy from a patient with coeliac sprue in remission.

CONCLUSIONS

The expression levels of hBD1, HD5 and HD6 throughout the gastrointestinal tract are tissue and peptide specific and these defensins are expressed with high interindividual variability.

Sensitivity of Actinobacillus actinomycetemcomitans and Capnocytophaga spp. to the bactericidal action of LL-37: a cathelicidin found in human leukocytes and epithelium

The bactericidal activity of synthetic LL-37, a cathelicidin, was assessed against Actinobacillus actinomycetemcomitans (three strains) and Capnocytophaga spp. (three strains). All strains were sensitive to LL-37, and exhibited 99% effective dose of 7.5-to-11.6 micrograms/ml. An amidated form of LL-37, pentamide-37, killed with about the same efficacy as LL-37. Partial inhibition of killing was noted at physiologic concentrations of NaCl, and complete inhibition was observed at 400 mM NaCl. At approximately the 99% effective dose--i.e., 10 micrograms/ml--LL-37 also lost activity against A. actinomycetemcomitans in the presence of native or heat-inactivated 10-15% normal human AB serum. Pentamide-37 was less sensitive to serum inhibition than LL-37. In conclusion, certain oral, gram-negative bacteria are sensitive to the bactericidal activity of LL-37 at low concentrations of serum and salt, a condition likely to be found within the membrane-delimited phagolysosome. Modified forms of LL-37, such as pentamide-37, may be more suitable for future therapeutic application in the presence of serum.

Beta-defensin expression in human mammary gland epithelia

Milk of mammalian species contains a wide spectrum of anti-infectious factors, some of which are heat stable. Focusing on recently discovered heat-stable antibacterial peptides called defensins, which are expressed in epithelial tissues such as airway, skin, and kidney, we hypothesized that mammary gland epithelia produce and secrete defensins onto the epithelial surface and into milk. Using a reverse-transcription PCR assay, we identified the human beta-defensin-1 (hBD-1) gene transcript in a human mammary gland epithelial cell line, MCF-12A, and in mammary glandular tissue of nine nonlactating women. Epithelial cells harvested from milk of lactating women also expressed hBD-1 mRNA. Presence of hBD-1 peptide in mammary epithelia was confirmed by immunostaining with an hBD-1 antibody. In contrast, expression of human beta-defensin-2 was not apparent both at mRNA and protein levels. Our findings suggest a biologic role of hBD-1 in the human mammary gland.

The human cationic antimicrobial protein (hCAP-18) is expressed in the epithelium of human epididymis, is present in seminal plasma at high concentrations, and is attached to spermatozoa

Innate immunity is important for the integrity of the host against potentially invasive pathogenic microorganisms in the environment. Antibiotic peptides with broad antimicrobial activity are part of the innate immune system. We investigated the presence of the cathelicidin, human cationic antimicrobial protein (hCAP-18), in the male reproductive system. We found strong expression of the hCAP-18 gene by in situ hybridization and hCAP-18 protein, as detected by immunohistochemistry, in the epithelium of the epididymis, but not in the testis. The highest expression in the epididymis was in the caudal part. Western blotting showed a doublet band, the upper part corresponding to the size of hCAP-18 in plasma and neutrophils. Using a specific enzyme-linked immunosorbent assay (ELISA), levels of 86.5 +/- 37.8 microg/ml (mean +/- standard deviation; range, 41.8 to 142.8 microg/ml; n = 10) were detected in seminal plasma from healthy donors, which is 70-fold higher than the level in blood plasma. Flow cytometry and immunocytochemistry revealed the presence of hCAP-18 on spermatozoa. ELISA measurement showed levels of 196 ng/10(6) spermatozoa, corresponding to 6.6 x 10(6) molecules of hCAP-18 per spermatozoon. Our results suggest a key role for hCAP-18 in the antibacterial integrity of the male reproductive system. The attachment of hCAP-18 to spermatozoa may implicate a role for hCAP-18 in conception.

Inducible expression of human beta-defensin 2 by Fusobacterium nucleatum in oral epithelial cells: multiple signaling pathways and role of commensal bacteria in innate immunity and the epithelial barrier

Human gingival epithelial cells (HGE) express two antimicrobial peptides of the beta-defensin family, human beta-defensin 1 (hBD-1) and hBD-2, as well as cytokines and chemokines that contribute to innate immunity. In the present study, the expression and transcriptional regulation of hBD-2 was examined. HBD-2 mRNA was induced by cell wall extract of Fusobacterium nucleatum, an oral commensal microorganism, but not by that of Porphyromonas gingivalis, a periodontal pathogen. HBD-2 mRNA was also induced by the proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) and phorbol myristate acetate (PMA), an epithelial cell activator. HBD-2 mRNA was also expressed in 14 of 15 noninflamed gingival tissue samples. HBD-2 peptide was detected by immunofluorescence in HGE stimulated with F. nucleatum cell wall, consistent with induction of the mRNA by this stimulant. Kinetic analysis indicates involvement of multiple distinct signaling pathways in the regulation of hBD-2 mRNA; TNF-alpha and F. nucleatum cell wall induced hBD-2 mRNA rapidly (2 to 4 h), while PMA stimulation was slower ( approximately 10 h). In contrast, each stimulant induced interleukin 8 (IL-8) within 1 h. The role of TNF-alpha as an intermediary in F. nucleatum signaling was ruled out by addition of anti-TNF-alpha that did not inhibit hBD-2 induction. However, inhibitor studies show that F. nucleatum stimulation of hBD-2 mRNA requires both new gene transcription and new protein synthesis. Bacterial lipopolysaccharides isolated from Escherichia coli and F. nucleatum were poor stimulants of hBD-2, although they up-regulated IL-8 mRNA. Collectively, our findings show inducible expression of hBD-2 mRNA via multiple pathways in HGE in a pattern that is distinct from that of IL-8 expression. We suggest that different aspects of innate immune responses are differentially regulated and that commensal organisms have a role in stimulating mucosal epithelial cells in maintaining the barrier that contributes to homeostasis and host defense.

Role of CCAAT/enhancer-binding protein site in transcription of human neutrophil peptide-1 and -3 defensin genes

The human neutrophil defensins (human neutrophil peptides (HNPs)), major components of azurophilic granules, contribute to innate and acquired host immunities through their potent antimicrobial activities and ability to activate T cells. Despite being encoded by nearly identical genes, HNP-1 is more abundant in the granules than HNP-3. We investigated the regulation of HNP-1 and HNP-3 expression at the transcriptional level using a promyelocytic HL-60 cell line. Luciferase analysis showed that transcriptional levels of HNP-1 and HNP-3 promoters were equivalent and that an approximately 200-bp region identical between promoters was sufficient for transcriptional activity. Furthermore, overlapping CCAAT/enhancer-binding protein (C/EBP) and c-Myb sites in the region were found to be required for efficient transcription. Gel mobility shift assay demonstrated that C/EBPalpha predominantly bound to the C/EBP/c-Myb sites using HL-60 nuclear extracts. No specific binding to C/EBP/c-Myb sites was observed in nuclear extracts from mature neutrophils, which expressed neither C/EBPalpha protein nor HNP mRNAs. Taken together, these findings suggest that the difference in the amounts of HNP-1 and HNP-3 peptides in neutrophils is caused by posttranscriptional regulation and that C/EBPalpha plays an important role in the transcription of HNP genes in immature myeloid cells.

Bombesin recovers gut-associated lymphoid tissue and preserves immunity to bacterial pneumonia in mice receiving total parenteral nutrition

OBJECTIVE

To study the ability of bombesin (BBS) to recover gut-associated lymphoid tissue (GALT) and preserve immunity in a lethal model of Pseudomonas aeruginosa (Ps) pneumonia in mice receiving total parenteral nutrition (TPN).

SUMMARY BACKGROUND DATA

TPN causes depression of mucosal immunity compared with enterally fed animals, which may explain the increased incidence of pneumonia in parenterally fed trauma patients. BBS prevents this TPN-induced GALT atrophy, depressed gastrointestinal and respiratory tract IgA levels, and impaired antiviral IgA-mediated mucosal immunity. The authors examined whether some supplement could be added to TPN to avoid this GALT atrophy and lower the incidence of infectious complications in the parenterally fed animal.

METHODS

Male mice were randomized to chow or intravenous (IV) TPN. After 5 days of IV TPN, mice received 0, 1, 2, or 3 days of BBS IV three times a day and then were killed to harvest Peyer's patch, intraepithelium, and lamina propria for cell yields. Gastrointestinal and respiratory tract IgA levels were analyzed by enzyme-linked immunosorbent assay. Next, mice underwent intranasal inoculation with liposomes alone (nonimmune) or liposome-containing Ps polysaccharide. Ps immune mice were catheterized and randomized to chow, IV TPN, or IV TPN + BBS. The liposome group received chow but no IV catheter. These mice were given an LD90 dose of intratracheal Ps, and death rates were recorded.

RESULTS

GALT and gastrointestinal and respiratory tract IgA levels improved to those in chow-fed mice after 3 days of BBS. Immunization reduced the death rate from 92% in chow-fed liposome-only animals to 20% in immunized animals. TPN-fed animals lost their mucosal immunity, with a death rate of 86% compared with 21% in the TPN + BBS group.

CONCLUSION

The results demonstrate that BBS reverses TPN-induced changes in GALT and preserves mucosal immunity. Ps immunization reduces the death rate in a gram-negative pneumonia model and maintains gastrointestinal and respiratory immunity in Ps immune mice receiving IV TPN.

Expression and Regulation of the Human β-Defensins hBD-1 and hBD-2 in Intestinal Epithelium

The intestinal epithelium forms a physical barrier to limit access of enteric microbes to the host and contributes to innate host defense by producing effector molecules against luminal microbes. To further define the role of the intestinal epithelium in antimicrobial host defense, we analyzed the expression, regulation, and production of two antimicrobial peptides, human defensins hBD-1 and hBD-2, by human intestinal epithelial cells in vitro and in vivo. The human colon epithelial cell lines HT-29 and Caco-2 constitutively express hBD-1 mRNA and protein but not hBD-2. However, hBD-2 expression is rapidly induced by IL-1α stimulation or infection of those cells with enteroinvasive bacteria. Moreover, hBD-2 functions as a NF-κB target gene in the intestinal epithelium as blocking NF-κB activation inhibits the up-regulated expression of hBD-2 in response to IL-1α stimulation or bacterial infection. Caco-2 cells produce two hBD-1 isoforms and a hBD-2 peptide larger in size than previously described hBD-2 isoforms. Paralleling the in vitro findings, human fetal intestinal xenografts constitutively express hBD-1, but not hBD-2, and hBD-2 expression, but not hBD-1, is up-regulated in xenografts infected intraluminally with Salmonella. hBD-1 is expressed by the epithelium of normal human colon and small intestine, with a similar pattern of expression in inflamed colon. In contrast, there is little hBD-2 expression by the epithelium of normal colon, but abundant hBD-2 expression by the epithelium of inflamed colon. hBD-1 and hBD-2 may be integral components of epithelial innate immunity in the intestine, with each occupying a distinct functional niche in intestinal mucosal defense.

Expression of beta-defensin genes by human salivary glands

This study investigated expression of genes encoding human beta-defensins 1 and 2 by human salivary glands. Tissues from surgical biopsies were collected fresh onto ice and stored in liquid nitrogen. Total RNA was extracted using Trizol reagent and human beta-defensin messenger RNA detected by reverse transcriptase polymerase chain reaction amplification. DNA sequencing of amplified fragments, after ligation into pGEM-T Easy vector and transformation of competent Escherichia coli, confirmed identities of cloned fragments. Human beta-defensin 1 messenger RNA was detected in all 25 samples that generated amplifiable cDNA, as assessed using abl-specific primers. Three of 13 submandibular gland samples (two normal, one chronically inflamed), and 2 of 2 minor salivary gland samples (one normal, one chronically inflamed) expressed human beta-defensin 2 messenger RNA. All six parotid gland samples studied were negative for human beta-defensin 2 messenger RNA. Thus, human beta-defensin 1 gene expression occurred in all human major and minor salivary glands studied, whereas human beta-defensin 2 expression occurred only in a small number of gland samples.

Ocular surface epithelia express mRNA for human beta defensin-2

Human skin, lung and trachea produce human beta defensin-2 (hBD-2), an inducible, transcriptionally regulated antibiotic peptide with activity against gram negative bacteria, which may explain the unusual resistance of these tissues to infection. Since an intact corneal epithelium is also highly resistant to infection, we examined whether human ocular surface epithelia might produce hBD-2. Conjunctival epithelial cells were obtained from a human cadaver eye, while corneal epithelial cells were obtained from both a cadaver eye and the eye of a living human patient. Using reverse transcription-polymerase chain reaction and custom primers for hBD-2, a 257 bp sequence was amplified from both human corneal and conjunctival epithelial cell cDNA, and the amino acid sequence of this DNA band was computer-matched with the known gene sequence of hBD-2 available through GenBank (Z71389). To determine whether bacterial by-products upregulate hBD-2 mRNA expression, we stimulated confluent SV 40-immortalized human corneal epithelial cells with bacterial culture supernatant prepared from either wild-type P. aeruginosa strain PAO1 or two different lipopolysaccharide (LPS) mutants of PAO1. Both of these mutants, strains AK1012 and PAO1 algC::tet, are deficient in phosphomannomutase activity which is required for the synthesis of both a complete polysaccharide core and the O side chain structures of the LPS molecule. Neither of these mutations affects the lipid A portion of LPS. Cells treated with P. aeruginosa wild-type PAO1 bacterial culture supernatant demonstrated strong upregulation of hBD-2 mRNA expression, whereas cells stimulated with culture supernatant produced by either of the LPS mutants showed little or no change in hBD-2 gene expression. LPS extracted from the bacterial culture supernatant was used to demonstrate that upregulation of hBD-2 is caused by LPS. Genistein blocked this upregulation suggesting that protein tyrosine kinase activity is involved. Thus, both human corneal and conjunctival epithelium express mRNA for hBD-2, and this expression is upregulated by bacterial LPS. Data obtained from LPS mutants suggest that lipid A, which is responsible for initiating a number of the pathophysiological manifestations induced by endotoxin in mammals, is not required. Stimulation of endogenous hBD-2 production via the active portion of LPS might have therapeutic potential.

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.

Induction of human beta-defensin-2 mRNA expression by Helicobacter pylori in human gastric cell line MKN45 cells on cag pathogenicity island

Helicobacter pylori is an etiological agent of gastritis, peptic ulcer, and gastric cancer. Human beta-defensin-2 (hBD-2) is an antimicrobial peptide which belongs to one of the most important host defense systems against bacterial infection in several epithelial tissues. We studied the effect of H. pylori on the expression of hBD-2 mRNA in MKN45 gastric mucosal cells. H. pylori, but not culture filtrate, increased the hBD-2 mRNA level in MKN45 cells; the inductive effect of H. pylori was not detected with Intestine 407 cells. Among H. pylori strains, strain OHPC0002, which lacks a cag Pathogenicity Island (PAI), did not induce hBD-2 mRNA in MKN45 cells. These results suggested that H. pylori cag PAI is critical for the induction of hBD-2 mRNA in MKN45 cells. Exposure of MKN45 cells to Salmonella typhimurium, S. enteritidis, S. typhi, and S. dublin, but not Escherichia coli ML35, also resulted in induction of hBD-2 mRNA.

Cloning and expression of bovine neutrophil beta-defensins. Biosynthetic profile during neutrophilic maturation and localization of mature peptide to novel cytoplasmic dense granules

beta-Defensins are microbicidal peptides implicated in host defense functions of phagocytic leukocytes and certain surface epithelial cells. Here we investigated the genetic structures and cellular expression of BNBD-4, -12, and -13, three prototypic bovine neutrophil beta-defensins. Characterization of the corresponding cDNAs indicated that BNBD-4 (41 residues) derives from a 63-amino acid prepropeptide and that BNBD-12 (38 residues) and BNBD-13 (42 residues) derive from a common 60-amino acid precursor (BNBD-12/13). The peptides were found to be encoded by two-exon genes that are closely related to bovine epithelial beta-defensin genes. BNBD-4 and BNBD-12/13 mRNAs were most abundant in bone marrow, but were expressed differentially in certain non-myeloid tissues. In situ hybridization and immunohistochemical studies demonstrated that BNBD-4 synthesis is completed early in myelopoiesis. BNBD-12 was localized exclusively to the novel dense granules, organelles that also contain precursors of cathelicidins, antimicrobial peptides that undergo proteolytic processing during phagocytosis. In contrast to cathelicidins, Western blot analyses revealed that mature beta-defensins are the predominant organellar form in myeloid cells. Stimulation of neutrophils with phorbol myristate acetate induced secretion of BNBD-12, indicating that it is co-secreted with pro-cathelicidins. The exocytosis of BNBD-12 by activated neutrophils reveals different mobilization pathways for myeloid alpha- and beta-defensins.

Human beta-defensin-1 mRNA is transcribed in tympanic membrane and adjacent auditory canal epithelium

The external auditory canal is less susceptible to infections than the sensitive middle-ear cavity. Since recent research has provided insight to the production of potent antimicrobial peptides from various surface epithelia, we wanted to investigate whether protection of the external auditory canal in part could be explained by the production of human beta-defensin-1 (HBD-1). This particular peptide is known to be constitutively expressed in various surface epithelia, such as airway, skin, and urogenital tissues. By reverse transcriptase PCR we demonstrate HBD-1 mRNA in the pars tensa and pars flaccida of the tympanic membrane and in the meatal skin. In situ hybridization studies localized the HBD-1 mRNA to the epidermal layer of these tissues. The HBD-1 transcripts were also evident in the sebaceous glands and in hair follicles of the meatal skin. In contrast, HBD-1 mRNA was not detected in the tympanal epithelium of the eardrum. The widespread presence of mRNA encoding for this broad-spectrum antimicrobial peptide in the meatal skin and tympanic membrane suggests that HBD-1 participates in the innate antimicrobial defense of the external auditory canal and middle-ear cavity.

Innate mechanisms of epithelial host defense: spotlight on intestine

The single layer of epithelial cells lining the intestinal tract is charged with a most difficult task: protecting the underlying biological compartments from both the normal commensal flora that reside within the intestinal lumen as well as the uninvited pathogens. To such an end, the intestinal epithelial cells are equipped with a panoply of defense mechanisms, both constitutive and inducible. This review focuses only on those defense mechanisms that are initiated and executed by the intestinal epithelial cell. Fitting these strict criteria are three major categories of epithelial host defense: enhanced salt and water secretion, expression of antimicrobial proteins and peptides, and production of intestinal mucins. Each of these areas is discussed in this review.

Pattern of expression of beta-defensins in oral squamous cell carcinoma

Human beta-defensin (hBD)-1 and hBD-2 are antimicrobial peptides that have been detected in certain types of epithelia, including the skin and oral epithelia. It has been suggested that bacterial infection is an important factor in the process of carcinogenesis. The expression of hBDs in oral squamous cell carcinoma (SCC) may be down-regulated. We studied the pattern of expression of hBD-1 and hBD-2 mRNA in oral (SCC) cell lines and in tumor samples obtained from four patients with oral SCC who underwent surgical resection, by reverse transcription-polymerase chain reaction (RT-PCR). Human gingival epithelial (HGE) cells were used as the control. The effect of various inflammatory cytokines on hBD-1 and hBD-2 expression in the HGE cells and SCC cell lines, was also studied. hBD-1 mRNA was detected in the Ca-9, SCC-9 and HSC-4 cell lines, but not in the SAS and KB cell lines. hBD-2 mRNA was detected in all five cell lines. All four tumor samples expressed both hBD-1 and hBD-2 mRNA, although the mRNA level of each protein varied. These results indicate that SCCs in which hBD expression is downregulated, may be susceptible to bacterial infection.

Cloning and characterization of the gene for a new epithelial beta-defensin. Genomic structure, chromosomal localization, and evidence for its constitutive expression

Mammalian beta-defensins are endogenous cysteine-rich peptide antibiotics that are produced either by epithelial cells lining the respiratory, digestive, and urogenital tracts or by granulocytes and macrophages. A growing body of evidence has implicated these peptides in host defense, particularly mucosal innate immunity. We previously reported the cloning of the full-length cDNA for a porcine beta-defensin (pBD-1), which was found to be expressed throughout the airway and oral mucosa. Here, we provide the structural organization of the pBD-1 gene, showing that the entire gene spans approximately 1.9 kilobases with two short exons separated by a 1.5-kilobase intron. Fluorescence in situ hybridization mapped the pBD-1 gene to porcine chromosome 15q14-q15. 1 within a region of conserved synteny to the chromosomal locations of human and mouse alpha- and beta-defensins. We also provide several independent lines of evidence showing that the pBD-1 gene is expressed constitutively during inflammation and infection, despite its resemblance to many inducible epithelial beta-defensins in amino acid sequence, genomic structure, and sites of expression. First, stimulation of primary porcine tongue epithelial cells with lipopolysaccharide, tumor necrosis factor-alpha, and interleukin (IL)-1beta failed to up-regulate the expression of pBD-1 mRNA. Second, pBD-1 gene expression was not enhanced in either digestive or respiratory mucosa of pigs following a 2-day infection with Salmonella typhimurium or Actinobacillus pleuropneumoniae. Last, direct transfection of the pBD-1 gene promoter into NIH/3T3 cells showed no difference in reporter gene activity in response to stimulation by lipopolysaccharide and IL-1beta. The constitutive expression of pBD-1 in airway and oral mucosa, which is consistent with a lack of consensus binding sites for nuclear factor-kappaB or NF-IL-6 in its promoter region, suggests that it may play a surveillance role in maintaining the steady state of microflora on mucosal surfaces.

Reduced antimicrobial peptide expression in human burn wounds

Severely burned skin ceases to perform its natural protective role and surrenders itself as a nidus and portal for bacterial invasion. Antimicrobial peptides are part of a non-specific chemical defence system, separate from cellular and humoral immunity. Two of these peptides, human beta-defensins 1 and 2 have been recently found in skin and are produced by keratinocytes. Beta defensins have potent bactericidal activity against a wide spectrum of bacterial and fungal organisms commonly responsible for burn wound infections. To date, expression of beta defensins has not been examined in the human burn wound. Our findings demonstrate that expression of hBD-2 is greatly decreased in the burn wound whereas hBD-1 appears to be preserved. These results may have important implications in the pathogenesis and treatment of invasive burn sepsis.

Efficient killing of inhaled bacteria in DeltaF508 mice: role of airway surface liquid composition

Cystic fibrosis mice have been generated by gene targeting but show little lung disease without repeated exposure to bacteria. We asked if murine mucosal defenses and airway surface liquid (ASL) Cl(-) were altered by the DeltaF508 cystic fibrosis transmembrane conductance regulator mutation. Naive DeltaF508 -/- and +/- mice showed no pulmonary inflammation and after inhaled Pseudomonas aeruginosa had similar inflammatory responses and bacterial clearance rates. We therefore investigated components of the innate immune system. Bronchoalveolar lavage fluid from mice killed Escherichia coli, and the microbicidal activity was inhibited by NaCl. Because beta-defensins are salt-sensitive epithelial products, we looked for pulmonary beta-defensin expression. A mouse homolog of human beta-defensin-1 (termed "MBD-1") was identified; the mRNA was expressed in the lung. Using a radiotracer technique, ASL volume and Cl(-) concentration ([Cl(-)]) were measured in cultured tracheal epithelia from normal and DeltaF508 -/- mice. The estimated ASL volume was similar for both groups. There were no differences in ASL [Cl(-)] in DeltaF508 -/- and normal mice (13.8 +/- 2.6 vs. 17.8 +/- 5.6 meq/l). Because ASL [Cl(-)] is low in normal and mutant mice, salt-sensitive antimicrobial factors, including MBD-1, may be normally active.

Innate antimicrobial activity of nasal secretions

Minimally manipulated nasal secretions, an accessible form of airway surface fluid, were tested against indigenous and added bacteria by using CFU assays. Antimicrobial activity was found to vary between donors and with different target bacteria and was markedly diminished by dilution of the airway secretions. Donor-to-donor differences in electrophoresis patterns of nasal secretions in sodium dodecyl sulfate-polyacrylamide gel electrophoresis (PAGE) and acid urea-PAGE analyses were readily observed, suggesting that polymorphic genes encode the secreted proteins. Three donors (of twenty-four total), whose nasal fluid yielded similar protein band patterns and did not kill indigenous bacteria, were determined to be heavy nasal carriers of Staphylococcus aureus. Their fluid was deficient in microbicidal activity toward a colonizing strain of S. aureus but the defect was corrected in vitro by a 1:1 addition of nasal fluid from noncarriers. The microbicidal activity of normal fluid was inactivated by heating it for 10 min to 100 degrees C and could not be restored solely by the addition of two major nasal antimicrobial proteins, lysozyme and lactoferrin. Several other known antimicrobial proteins and peptides, including statherin, secretory phospholipase A2, and defensins, were identified in nasal secretions and likely contribute to their total antimicrobial properties. Nasal fluid may serve as a useful model for the analysis of lower-airway secretions and their role in host defense against airway colonization and pulmonary infections.

A 450-kb contig of defensin genes on human chromosome 8p23

Defensins are a large family of host defense peptides expressed in leukocytes and epithelia. Using P1 and BAC clones, we have determined the organization of the human alpha-defensin genes and the beta-defensin gene HDEFB1 on chromosome 8p23. From the telomere, the order of the genes (with encoded peptides in parentheses) is HDEFA5 (HD-5), HDEFA1/1A (HNP-1/3), HDEFA4 (HNP-4), HDEFA6 (HD-6), and HDEFB1 (HBD-1). These genes span a region of approximately 450kb. Genes encoding intestinal Paneth cell defensins (HDEFA5 and HDEFA6) flank the myeloid defensin gene cluster (HDEFA1, HDEFA1A, HDEFA4). Based on our previous studies, the remaining known defensin gene, HDEFB2 (HBD-2), is about 400kb centromeric to HDEFB1. This map supports the hypothesis, originally proposed because of sequence similarities, that myeloid alpha-defensin genes evolved by reduplication and divergence from Paneth cell defensin genes, and identifies regions and clones, which should be useful in the search for new defensin genes.

Production of beta-defensin antimicrobial peptides by the oral mucosa and salivary glands

beta-Defensins are cationic peptides with broad-spectrum antimicrobial activity that are produced by epithelia at mucosal surfaces. Two human beta-defensins, HBD-1 and HBD-2, were discovered in 1995 and 1997, respectively. However, little is known about the expression of HBD-1 or HBD-2 in tissues of the oral cavity and whether these proteins are secreted. In this study, we characterized the expression of HBD-1 and HBD-2 mRNAs within the major salivary glands, tongue, gingiva, and buccal mucosa and detected beta-defensin peptides in salivary secretions. Defensin mRNA expression was quantitated by RNase protection assays. HBD-1 mRNA expression was detected in the gingiva, parotid gland, buccal mucosa, and tongue. Expression of HBD-2 mRNA was detected only in the gingival mucosa and was most abundant in tissues with associated inflammation. To test whether beta-defensin expression was inducible, gingival keratinocyte cell cultures were treated with interleukin-1beta (IL-1beta) or bacterial lipopolysaccharide (LPS) for 24 h. HBD-2 expression increased approximately 16-fold with IL-1beta treatment and approximately 5-fold in the presence of LPS. Western immunoblotting, liquid chromatography, and mass spectrometry were used to identify the HBD-1 and HBD-2 peptides in human saliva. Human beta-defensins are expressed in oral tissues, and the proteins are secreted in saliva; HBD-1 expression was constitutive, while HBD-2 expression was induced by IL-1beta and LPS. Human beta-defensins may play an important role in the innate defenses against oral microorganisms.

Antimicrobial defensin peptides of the human ocular surface

BACKGROUND/AIMS

The antimicrobial activity of the tear film exceeds the activity of its known constituents. The authors postulate that this excess activity is the result of antimicrobial peptides called defensins, and they aimed to look for defensins in the human eye.

METHODS

Evidence of defensin production was sought by reverse transcriptase polymerase chain reaction (RT-PCR). Intron spanning primers were designed for beta defensins 1 and 2, and alpha defensins 5 and 6. RT-PCR was performed on cornea, conjunctiva, and lacrimal gland samples, and reaction products were size fractionated and sequenced to confirm their identity. A monoclonal antibody was utilised for the detection of alpha defensins 1, 2, and 3 in tissue sections and in immunoblots of tears.

RESULTS

RT-PCR revealed beta defensin 1 message in samples of conjunctiva, cornea, and lacrimal gland. beta Defensin 2 message was detected in the conjunctiva and cornea but was absent from the lacrimal gland. alpha Defensin 5 and 6 message was absent in these tissues but alpha defensins 1, 2, and 3 were detected in normal tears, lacrimal gland, and inflamed conjunctiva by immunochemistry.

CONCLUSION

The data suggest the human eye innately produces a spectrum of antimicrobial defensin peptides. Defensins hold therapeutic potential in ocular infections as they have a broad spectrum of antimicrobial activity (bacteria fungi and viruses ) and accelerate epithelial healing.

The gut's role in metabolism, mucosal barrier function, and gut immunology

The gastrointestinal tract functions not only to absorb nutrients, it also plays an important immunologic role during health and critical illness. Under experimental and certain clinical conditions, stimulating the gut attentuates the stress response and avoids mucosal atrophy and increases permeability. Gut stimulation prevents atrophy of the gut-associated lymphoid tissue, the body's major defender of moist mucosal surfaces. A better understanding of gut function and improved nutrient delivery has clinical implications in the treatment of critically ill patients.

Antimicrobial peptides as mediators of epithelial host defense

Mammalian epithelial surfaces are remarkable for their ability to provide critical physiologic functions in the face of frequent microbial challenges. The fact that these mucosal surfaces remain infection-free in the normal host suggests that highly effective mechanisms of host defense have evolved to protect these environmentally exposed tissues. Throughout the animal and plant kingdoms, endogenous genetically encoded antimicrobial peptides have been shown to be key elements in the response to epithelial compromise and microbial invasion. In mammals, a variety of such peptides have been identified, including the well-characterized defensins and cathelicidins. A major source of these host defense molecules is circulating phagocytic leukocytes. However, more recently, it has been shown that resident epithelial cells of the skin and respiratory, alimentary, and genitourinary tracts also synthesize and release antimicrobial peptides. Both in vitro and in vivo data support the hypothesis that these molecules are important contributors to intrinsic mucosal immunity. Alterations in their level of expression or biologic activity can predispose the organism to microbial infection. The regulatory and developmental aspects of antimicrobial peptide synthesis are discussed from a perspective that emphasizes the possible relevance to pediatric medicine.

Activity of abundant antimicrobials of the human airway

Human airways produce several antimicrobial factors; the most abundant are lysozyme and lactoferrin. Despite their likely importance in preventing infection, and their possible key role in the pathogenesis of cystic fibrosis (CF), we know little about their antibacterial activity in the context of the CF airway. We found that abundant airway antimicrobial factors kill common CF pathogens, although Burkholderia was relatively resistant. To study the antibacterial activity, we developed a rapid, sensitive, and quantitative in vitro luminescence assay. Because NaCl concentrations may be elevated in CF airway surface liquid, we tested the effect of salt on antibacterial activity. Activity of individual factors and of airway lavage fluid was inhibited by high ionic strength, and it was particularly sensitive to divalent cations. However, it was not inhibited by nonionic osmolytes and thus did not require hypotonic liquid. The inhibition by ionic strength could be partially compensated by increased concentrations of antibacterial factors, thus there was no one unique salt concentration for inhibition. CF airway secretions also contain abundant mucin and elastase; however, these had no effect on antibacterial activity of lysozyme, lactoferrin, or airway lavage fluids. When studied at low NaCl concentrations, CF and non-CF airway lavage fluids contained similar levels of antibacterial activity. These results suggest approaches toward developing treatments aimed at preventing or reducing airway infections in individuals with CF.

The human cationic antimicrobial protein (hCAP18), a peptide antibiotic, is widely expressed in human squamous epithelia and colocalizes with interleukin-6

Peptide antibiotics are widespread in nature and, by providing a rapid first line of defense, may be key players in the innate immune system. Although epithelia are the main barriers shielding the internal environment from microorganisms, the role for peptide antibiotics in epithelial protection is unclear. We recently reported that the human cationic antimicrobial protein hCAP18, the precursor of the antimicrobial peptide called LL-37, is not expressed by normal human keratinocytes but is induced in various inflammatory skin disorders. In the present study we demonstrate that hCAP18 is consistently expressed at both mRNA and protein levels in squamous epithelia of the mouth, tongue, esophagus, cervix, and vagina in humans. The gene for hCAP18 contains promoter elements that are potentially regulated by interleukin-6, and our data further show a colocalization between interleukin-6 and hCAP18 expression in these tissues. Our finding that hCAP18 is widely produced in squamous epithelia suggests a role for this peptide in epithelial antimicrobial defense. Furthermore, colocalization with interleukin-6 indicates a potential local mechanism for the upregulation of hCAP18 at the epithelial surfaces.

Epithelial defensins impair adenoviral infection: implication for adenovirus-mediated gene therapy

Epithelial cells have been to participate actively in host defense by producing small cationic peptides called defensins. To investigate the biological activity of epithelial defensins in more detail, we expressed two defensins, hBD-1 and HD-5, in eukaryotic cell lines. Defensins were localized in the cytoplasm and in cell culture medium and exhibited strong microbicidal activity toward Escherichia coli, Pseudomonas aeruginosa, and Staphylococcus aureus. Moreover, our data indicate that the presence of defensins protected the cells from adenoviral infection. The presence of HD-5 or hBD-1 reduced the infectivity of Av1CF2 three- to fivefold. These results imply that defensins must be considered a serious obstacle whenever adenovirus is used to deliver genes to epithelial cells.

Synthetic peptides corresponding to the beta-hairpin loop of rabbit defensin NP-2 show antimicrobial activity

Mammalian defensins, a class of antibacterial peptides, are composed of 29-35 amino acids with six cysteines which form three disulfide bonds. Structural studies indicate a triple stranded beta-sheet structure with a well defined beta-hairpin loop at the C-terminal region. It is demonstrated in this report that 18 and 26 residue synthetic peptides corresponding to the beta-hairpin region, constrained by a single disulfide bond, have potent antimicrobial activity without hemolytic activity. Circular dichroism spectroscopy indicates that the single S-S bridge appears to constrain the peptides to a beta-structure. Peptides corresponding to the beta-hairpin region of defensins could thus be attractive candidates as therapeutic agents as well as good model compounds for investigation of the various physiological actions of defensins.

Epithelial peptide antibiotics

Surfaces of higher eukaryotes such as plants, invertebrates, and vertebrates, including humans, are normally covered with microorganisms but usually are not infected by them. The reason, apart from physical barriers, is the production of gene-encoded antimicrobial peptides by epithelial cells. Many novel antimicrobial peptides have been discovered recently in the epithelia of plants, insects, amphibians, and cattle, and, more recently, also in humans. In situ hybridization studies indicate a rather organ-specific expression of the genes for peptide antibiotics, which, due to their antimicrobial spectrum and conditions of expression, may also define the physiologic microflora. Some epithelial antimicrobial peptides are constitutively expressed; others are inducible, either by the presence of microorganisms via as of yet not well characterized elicitor receptors or by endogenous proinflammatory cytokines. Most antimicrobial peptides kill microorganisms by forming pores in the cell membrane, and the sensitivity of some peptide antibiotics towards cholesterol, a major mammalian cell membrane constituent, may indicate why these peptide antibiotics are not toxic for mammalian cells. Thus, it seems to be difficult for microorganisms to acquire resistance, making these peptides very attractive for therapeutic use as antibiotics. The first clinical studies are very promising, and after solving the problems of a large-scale biotechnical synthesis, which is more complicated due to the principally suicidal activity of these peptides, a number of new natural structure-based peptides may be developed. Furthermore, discovery of the inducibility of many antimicrobial peptides may also lead to the development of compounds that elicit epithelial defense reactions by stimulating the synthesis of endogenous peptide antibiotics.

Role of CFTR in airway disease

Role of CFTR in Airway Disease. Physiol. Rev. 79, Suppl.: S215-S255, 1999. - Cystic fibrosis (CF) is caused by mutations in the gene encoding the CF transmembrane conductance regulator (CFTR), which accounts for the cAMP-regulated chloride conductance of airway epithelial cells. Lung disease is the chief cause of morbidity and mortality in CF patients. This review focuses on mechanisms whereby the deletion or impairment of CFTR chloride channel function produces lung disease. It examines the major themes of the channel hypothesis of CF, which involve impaired regulation of airway surface fluid volume or composition. Available evidence indicates that the effect of CFTR deletion alters physiological functions of both surface and submucosal gland epithelia. At the airway surface, deletion of CFTR causes hyperabsorption of sodium chloride and a reduction in the periciliary salt and water content, which impairs mucociliary clearance. In submucosal glands, loss of CFTR-mediated salt and water secretion compromises the clearance of mucins and a variety of defense substances onto the airway surface. Impaired mucociliary clearance, together with CFTR-related changes in the airway surface microenvironment, leads to a progressive cycle of infection, inflammation, and declining lung function. Here, we provide the details of this pathophysiological cascade in the hope that its understanding will promote the development of new therapies for CF.

The role of enterocytes in gut dysfunction

Stem cells in the intestinal epithelium give rise to enterocytes, goblet cells, enteroendocrine cells, and Paneth cells. Each of these cell lines plays a role in cytoprotection of the intestinal mucosa. In particular, it has been demonstrated that mature enterocytes can act as antigen presenting cells. Parenteral and enteral nutrition are used to nourish critically ill patients. However, these regimens are unfortunately associated with gut atrophy. Glutamine, the preferred intestinal nutrient, reverses this gut atrophy and plays a key role in maintaining the barrier function of the gut. Specific nutrients (putrescine, spermidine, spermine) have been used to modulate intestinal adaption. In addition, ornithine has been shown to act as a regulator of intestinal adaption. In this review, we discuss the relationship between the biology of enterocytes and failure of the gut barrier.

Production of beta-defensins by human airway epithelia

Human beta-defensins (HBDs) are antimicrobial peptides that may play a role in mucosal defense. Diminished activity of these peptides has been implicated in the pathogenesis of cystic fibrosis (CF) lung disease. We show that HBD-1 and HBD-2 mRNAs are expressed in excised surface and submucosal gland epithelia from non-CF and CF patients. The pro-inflammatory cytokine interleukin-1beta stimulated the expression of HBD-2 but not HBD-1 mRNA and peptide in primary cultures of airway epithelia. HBD-1 was found in bronchoalveolar lavage (BAL) fluid from normal volunteers, CF patients, and patients with inflammatory lung diseases, whereas HBD-2 was detected in BAL fluid from patients with CF or inflammatory lung diseases, but not in normal volunteers. Both HBD-1 and HBD-2 were found in BAL fluid in concentrations of several ng/ml, and both recombinant peptides showed salt-sensitive bactericidal activity. These data suggest that in the lung HBD-2 expression is induced by inflammation, whereas HBD-1 may serve as a defense in the absence of inflammation.

The lipopolysaccharide of Bordetella bronchiseptica acts as a protective shield against antimicrobial peptides

Resistance profiles of the two Bordetella species B. bronchiseptica and B. pertussis against various antimicrobial peptides were determined in liquid survival and agar diffusion assays. B. bronchiseptica exhibited significantly higher resistance against all tested peptides than B. pertussis. The most powerful agents acting on B. bronchiseptica were, in the order of their killing efficiencies, cecropin P > cecropin B > magainin-II-amide > protamine > melittin. Interestingly, for B. bronchiseptica, the resistance level was significantly affected by phase variation, as a bvgS deletion derivative showed an increased sensitivity to these peptides. Tn5-induced protamine-sensitive B. bronchiseptica mutants, which were found to be very susceptible to most of the cationic peptides, were isolated. In two of these mutants, the genetic loci inactivated by transposon insertion were identified as containing genes highly homologous to the wlbA and wlbL genes of B. pertussis that are involved in the biosynthesis of lipopolysaccharide (LPS). In agreement with this finding, the two peptide-sensitive mutants revealed structural changes in the LPS, resulting in the loss of the O-specific side chains and the prevalence of the LPS core structure. This demonstrates that LPS plays a major role in the resistance of B. bronchiseptica against the action of antimicrobial peptides and suggests that B. pertussis is much more susceptible to these peptides due to the lack of the highly charged O-specific sugar side chains.

Epithelial antimicrobial peptides: review and significance for oral applications

Epithelial tissues provide the first line of defense between an organism and the environment. Disruption of this barrier leads to bacterial invasion and subsequent inflammation. This is precisely the situation existing in the human oral cavity, where tissues are constantly exposed to a variety of microbial challenges that can lead to bacterially induced periodontal diseases, and to infections of the oral mucosa by bacteria, fungi, and viruses. With the recent discoveries of host-derived peptide antibiotics in mammalian mucosal epithelium, a new line of investigation is emerging to test the hypothesis that one class of these peptides, called "beta-defensins", functions to protect the host against microbial pathogenesis at these critical, confrontational sites. In that light, impairment of beta-defensin activity has recently been implicated in chronic bacterial infections in cystic fibrosis patients. The first direct evidence of expression of defensin peptides in the oral mucosa was the identification of a novel epithelial beta-defensin in mammalian tongue. It was shown to be upregulated in inflammation, suggesting that it participates in host defense. It is theorized that epithelial cell-derived antimicrobial peptides function to keep the natural flora of micro-organisms in a steady state in different niches such as the skin, the intestines, the airway, the endocervix, and the mouth. There is now evidence indicating that normal gingival epithelial cells and tissues express two beta-defensins, hBD-1 and the newly described hBD-2. In addition, a cathelin-class antimicrobial peptide, designated LL-37 and found in human neutrophils, is also expressed in skin and gingiva. It is highly likely that these and/or other epithelial antimicrobial peptides play an important role in determining the outcome of the host-pathogen interaction at the oral mucosal barrier, and that they may have important future applications in antibiotic treatment.

Inhibition of Activation of the Classical Pathway of Complement by Human Neutrophil Defensins

Defensins are small, cationic antimicrobial peptides that are present in the azurophilic granules of neutrophils. Earlier studies have shown that defensins may influence complement activation by specific interaction with activated C1, C1q, and C1-inhibitor. In the present study, we show that the defensin human neutrophil peptide-1 (HNP-1) is able to inhibit activation of the classical complement pathway by inhibition of C1q hemolytic activity. The binding site for HNP-1 on C1q is most likely located on the collagen-like stalks, as a clear, dose-dependent binding of HNP-1 to either intact C1q or to the collagen-like stalks of C1q was demonstrated using enzyme-linked immunosorbent assay (ELISA). Besides binding of HNP-1 to C1q, also a limited binding to C1 and to a mixture of C1r and C1s was observed, whereas no binding to C1-inhibitor was found. Because binding of HNP-1 to C1-inhibitor has been suggested in earlier studies, we also assessed the binding of HNP-1 to mixtures of C1-inhibitor with either C1r/ C1s or C1. No binding was found. Using a competition ELISA, it was found that HNP-1, but not protamine, inhibited binding of biotin-labeled HNP-1 to C1q in a dose-dependent fashion. In the fluid phase, preincubation of HNP-1 with C1q resulted in complex formation of HNP-1 and C1q and generation of stable complexes. In conclusion, HNP-1 is able to bind to C1q in the fluid phase and inhibits the classical complement pathway. This mechanism may be involved in the control of an inflammatory response in vivo.

Inhibition of Activation of the Classical Pathway of Complement by Human Neutrophil Defensins

Defensins are small, cationic antimicrobial peptides that are present in the azurophilic granules of neutrophils. Earlier studies have shown that defensins may influence complement activation by specific interaction with activated C1, C1q, and C1-inhibitor. In the present study, we show that the defensin human neutrophil peptide-1 (HNP-1) is able to inhibit activation of the classical complement pathway by inhibition of C1q hemolytic activity. The binding site for HNP-1 on C1q is most likely located on the collagen-like stalks, as a clear, dose-dependent binding of HNP-1 to either intact C1q or to the collagen-like stalks of C1q was demonstrated using enzyme-linked immunosorbent assay (ELISA). Besides binding of HNP-1 to C1q, also a limited binding to C1 and to a mixture of C1r and C1s was observed, whereas no binding to C1-inhibitor was found. Because binding of HNP-1 to C1-inhibitor has been suggested in earlier studies, we also assessed the binding of HNP-1 to mixtures of C1-inhibitor with either C1r/ C1s or C1. No binding was found. Using a competition ELISA, it was found that HNP-1, but not protamine, inhibited binding of biotin-labeled HNP-1 to C1q in a dose-dependent fashion. In the fluid phase, preincubation of HNP-1 with C1q resulted in complex formation of HNP-1 and C1q and generation of stable complexes. In conclusion, HNP-1 is able to bind to C1q in the fluid phase and inhibits the classical complement pathway. This mechanism may be involved in the control of an inflammatory response in vivo.

Antimicrobial peptides: an emerging concept in cutaneous biology

Antimicrobial peptides are part of the host defense systems of plants, insects, fish, amphibia, birds, and mammals. These small proteins were previously thought of as an evolutionarily ancient system of immune protection with little relevance to the normal function of human skin. Recent developments have found that mammalian skin expresses these gene-encoded peptide antibiotics during inflammatory events such as wound repair, contact dermatitis, and psoriasis. The presence of these peptides in the skin forms a barrier for innate host protection against microbial pathogenesis. Furthermore, antimicrobial peptides also act on animal cells by stimulating them to change behaviors such as syndecan expression, chemotaxis, and chloride secretion. The combination of effects on host cells with antimicrobial action in a single molecule represents an efficient defense and response system against injury. Understanding the action of antimicrobial peptides in skin may yield further insight into the mechanism of innate cutaneous disease control and provide new approaches to therapy of wounds and inflammatory dermatitis.

Expression of the peptide antibiotic human beta-defensin 1 in cultured gingival epithelial cells and gingival tissue

Human beta-defensin-1 (hBD-1) is a member of the family of small cationic antimicrobial peptides that have been identified in several mucosal epithelia. Because human gingival epithelium is a site that is constantly challenged by oral microorganisms, we examined the expression of hBD-1 in human gingival epithelial and fibroblast cell cultures and tissue samples. Cell cultures were challenged with cell wall extracts of Porphyromonas gingivalis or Fusobacterium nucleatum, Escherichia coli lipopolysaccharide, tumor necrosis factor alpha, or phorbol myristate acetate. hBD-1 mRNA was detected in unstimulated and stimulated cultures by reverse transcription (RT)-PCR using several primer sets specific for hBD-1. Gingival epithelial cells, but not gingival fibroblasts, expressed a product of the predicted size for hBD-1 mRNA. The sequence of the PCR product was identical to that of hBD-1. hBD-1 mRNA expression was not significantly modulated by any of the stimulants tested. Human gingival tissues from noninflamed and inflamed sites were also analyzed by RT-PCR. hBD-1 mRNA was expressed in all tissue samples. The relative expression of hBD-1 mRNA was similar in noninflamed and inflamed tissues obtained from each of four patients undergoing treatment for periodontitis. However, the relative expression of hBD-1 mRNA varied in gingival biopsies obtained from 15 different normal individuals, and the relative hBD-1 expression was unrelated to interleukin-8 expression. Our findings show the constitutive expression of hBD-1 mRNA in cultured epithelial cells and gingival tissues but not gingival fibroblasts. These findings suggest that expression of hBD-1 may play a role as part of the innate host defenses in maintaining normal gingival health.

Antibacterial peptides in bronchoalveolar lavage fluid

Defensins and other antimicrobial peptides act in the innate host defense of epithelial surfaces. Human beta defensin 1 (hBD-1) has recently been shown to be expressed in airway epithelial cells and so has been implicated as a primary component of antibacterial activity in human lung. We attempted to purify these molecules from bronchoalveolar lavage fluid (BALF). Extraction of BALF on SepPak C-18 cartridges, followed by continuous acid-urea polyacrylamide gel electrophoresis and reverse-phase high-performance liquid chromatography yielded one fraction with antibacterial activity associated with factors of < 6.5 kD. N-terminal amino acid sequencing identified these peptides as human neutrophil defensins (HD) 1 through 3. No hBD-1 was detected. Together with lysozyme, it appears that HD-1 through -3 are the most prominent antimicrobial factors in BALF. The contribution of epithelial defensins such as hBD-1 to antibacterial defense of human airway in vivo remains to be elucidated.

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

Defensins are antimicrobial peptides which play a key role in innate immunity. High levels of human beta defensin-1 (hBD-1) have previously been detected in the kidney and pancreas, but the cell-specific location of hBD-1 mRNA has not been determined. The expression of hBD-1 mRNA has been examined in fetal and adult pancreas and kidney by mRNA in situ hybridization. In fetal pancreas, hBD-1 expression was detected in the developing acini and in adult pancreas in the acini, but not in the pancreatic ducts. In both fetal and adult kidney, hBD-1 expression was detected in the collecting ducts and in the loops of Henle in adult kidney. Expression of hBD-1 mRNA in the pancreas and kidney from early development and in the acini of the adult pancreas, rather than in the pancreatic ducts, may indicate that in these tissues, hBD-1 fulfils physiological functions in addition to host defence.

Loss of CFTR chloride channels alters salt absorption by cystic fibrosis airway epithelia in vitro

Cystic fibrosis (CF) is caused by the loss of functional CFTR Cl- channels. However, it is not understood how this defect disrupts salt and liquid movement in the airway or whether it alters the NaCl concentration in the thin liquid film covering the airway surface. Using a new approach, we found that CF airway surface liquid had a higher NaCl concentration than normal. Both CF and non-CF epithelia absorbed salt and liquid; however, expression of CFTR Cl- channels was required for maximal absorption. Thus, loss of CFTR elevates the salt concentration in CF airway surface liquid and in sweat by related mechanisms; the elevated NaCl concentration is due to a block in transcellular Cl- movement. The high NaCl may predispose CF airways to bacterial infections by inhibiting endogenous antibacterial defenses.

Identification of human beta-defensin-2 in respiratory tract and plasma and its increase in bacterial pneumonia

Human beta-defensin-2 (hBD-2), a novel antimicrobial peptide, was originally isolated from human skin. We found that synthetic hBD-2 has high bactericidal activity against Escherichia coli under conditions nearly the same as in human bronchial airway surface liquid. We prepared an antiserum against hBD-2 and established a highly sensitive radioimmunoassay (RIA). Reverse-phase high-performance liquid chromatography coupled with the RIA showed that hBD-2 in patients with human lung, bronchoalveolar lavage flid, and plasma. The plasma concentration of hBD-2 in patients with bacterial pneumonia was 32.1 +/- 3.7 fmol/ml (mean +/- SE), 3.9-fold that of normal individuals. By reverse transcription-polymerase chain reaction, the hBD-2 gene transcript was detected in the respiratory epithelial surface of human lung. Human beta-defensin-2 seems to function in airway mucosal defense. Our findings provide a clue to elucidate its pathophysiological significance in respiratory infection.

Polymorphisms of the human beta-defensin-1 gene

Defensins are antimicrobial peptides that play an important role in innate immunity. The authors have searched for intragenic polymorphisms of the recently cloned human beta-defensin-1 gene (HBD-1) whose gene product is expressed in the lung and whose function seems to be compromised in cystic fibrosis. Four frequent restriction fragment length polymorphisms in the HBD-1 cDNA sequence are described here, three of them being located in the 5'-UTR and one in the 3'-UTR. The minor alleles of the three polymorphisms of the 5'-UTR had allele frequencies of 0.39, 0.34 and 0.27, respectively, and the minor allele of the 3'-UTR polymorphism had a relative frequency of 0.13 in a cohort of 103 random German blood donors. The variants described in this report should be useful as single nucleotide polymorphisms in linkage and association studies of respiratory and other diseases.

Human beta-defensin-1: an antimicrobial peptide of urogenital tissues

Antimicrobial peptides are widely distributed mediators of innate host defense in animals and plants. A 36 amino acid antimicrobial peptide belonging to the defensin family, and named human beta-defensin-1 (HBD-1), was purified recently from hemodialysate fluid, but its tissue sources were not identified. By Northern blotting, we found the highest concentrations of HBD-1 mRNA in the kidney and the female reproductive tract. In situ hybridization localized the HBD-1 mRNA in the epithelial layers of the loops of Henle, distal tubules, and the collecting ducts of the kidney and the epithelial layers of the vagina, ectocervix, endocervix, uterus, and fallopian tubes in the female reproductive tract. Using a novel technique designed to detect cationic peptides in urine, we recovered several forms of HBD-1 ranging in length from 36 to 47 amino acid (aa) residues and differing from each other by amino terminal truncation. The total concentration of HBD-1 forms in voided urine was estimated at 10-100 microg/liter, with individual variations in the total amount of HBD-1 peptides and the relative proportion of HBD-1 forms. Multiple forms of HBD-1 (size 36-47 aa) were also found in the blood plasma, bound to carrier macromolecules that released the peptide under acid conditions, and in vaginal mucosal secretions (39, 40, and 44 aa). By immunostaining, HBD-1 was located in the kidney within the lumen of the loops of Henle, but no intracellular storage sites were identified in renal or female reproductive tissues. Recombinant HBD-1 forms (36, 39, and 42 aa) and natural HBD-1 forms were antimicrobial to laboratory and clinical strains of Escherichia coli at micromolar concentrations. HBD-1 activity was not changed appreciably by low pH, but was inhibited by high salt conditions. Some of the HBD-1 peptides retained their activity against E. coli in unconcentrated (low conductance) urine, and the 36 aa form was microbicidal even in normal (high conductance) urine. Production of HBD-1 in the urogenital tract could contribute to local antimicrobial defense.