Prostate specific antigen enhances the innate defence of prostatic epithelium against Escherichia coli infection.

BACKGROUND: This study investigated whether the increase in serum prostate specific antigen (PSA) typically seen during male urinary tract infection (UTI) is incidental or reflects an innate defence mechanism of the prostate. The protective roles of the whey-acid-motif-4-disulphide core (WFDC) proteins, secretory leukoproteinase inhibitor (SLPI) and WFDC2, in the prostate were also examined. METHODS: UTI recurrence was assessed retrospectively in men following initial UTI by patient interview. PSA, SLPI, and WFDC2 gene expression were assessed using biopsy samples. LNCaP and DU145 in vitro prostate cell models were utilized to assess the effects of an Escherichia coli challenge on PSA and WFDC gene expression, and bacterial invasion of the prostate epithelium. The effects of PSA on WFDC antimicrobial properties were studied using recombinant peptides and time-kill assays. RESULTS: Men presenting with PSA >4 ng/ml at initial UTI were less likely to have recurrent (r) UTI than those with PSA <4 ng/ml [2/15 (13%) vs. 7/10 (70%), P < 0.01]. Genes encoding PSA, SLPI and WFDC2, were expressed in prostatic epithelium, and the PSA and SLPI proteins co-localized in vivo. Challenging LNCaP (PSA-positive) cells with E. coli increased PSA, SLPI, and WFDC2 gene expression (P < 0.05), and PSA synthesis (P < 0.05), and reduced bacterial invasion. Pre-incubation of DU145 (PSA-negative) cells with PSA also decreased bacterial invasion. In vitro incubation of recombinant SLPI and WFDC2 with PSA resulted in peptide proteolysis and increased E. coli killing. CONCLUSIONS: Increased PSA during UTI appears protective against rUTI and in vitro is linked to proteolysis of WFDC proteins supporting enhanced prostate innate defences.

The interaction of the antimicrobial peptide cLEAP-2 and the bacterial membrane.

Chicken Liver Expressed Antimicrobial Peptide-2 (cLEAP-2) is known to have killing activities against Salmonella spp., but the mechanism by which killing occurs remains to be elucidated. The ability of cLEAP-2 to disrupt the outer membrane of several Salmonella spp. was assessed using the fluorescent probe N-phenyl-1-naphthylamine (NPN). A rapid dose-dependent permeabilization of the outer membranes of Salmonella enterica serovar Typhimurium phoP, and S. enterica serovar Typhimurium SL1344 was observed although no significant permeabilisation of the S. enteriditis membrane was detected. These data suggested that the ability of the mature cLEAP-2 peptide to permeabilise the Salmonella outer membrane is important in mediating its killing activities. The ability of the peptide to kill Gram-positive bacteria, specifically Streptococcus spp. and Staphylococcus spp. was also investigated using recombinant peptide and a time-kill assay. Of the strains analysed the Streptococcus pyogenes M1 strain appeared the most resistant to LEAP-2 killing although S. pyogenes mutants deficient in Sortase and M1 activities showed increased sensitivity to the mature peptide. This suggested the involvement of specific Streptococcus cell wall proteins including M1 in the resistance of the bacteria to cLEAP-2 killing. cLEAP-2 showed no significant toxicity towards mammalian erythrocytes indicating selectivity for bacterial over eukaryote cell membranes. These data provide further support for mature cLEAP-2 functioning in protecting the chicken against microbial attack.

Maintaining a sterile urinary tract: the role of antimicrobial peptides.

PURPOSE: The normally sterile urinary tract is constantly challenged by microbial invasion leading to a high prevalence of isolated, recurrent and catheter associated urinary tract infection. The continuous emergence of bacterial resistance following overuse of traditional antibiotics requires the urgent development of alternative treatment strategies. The involvement of innate immune mechanisms in host defense is an emerging field of microbiological research with recent work focusing on the urinary tract. We performed a comprehensive literature review to establish the current level of knowledge concerning the role of innate immunity and specifically antimicrobial peptides within the human urinary tract. MATERIALS AND METHODS: A systematic review of the literature was performed by searching PubMed from January 1988 to September 2008. Electronic searches were limited to the English language using the key words antimicrobial, peptide and urinary. Reference lists from relevant reviews were hand searched and appropriate articles were retrieved. The proceedings of conferences held in the last 2 years by the American Urological Association, European Association of Urology and British Association of Urological Surgeons were also searched. RESULTS: Several defensive mechanisms have evolved in response to the threat of urinary infection, comprising physical factors and innate immune responses characterized by the expression of antimicrobial peptides. Antimicrobial peptides are small (less than 10 kDa), cationic and amphipathic peptides of variable length, sequence and structure with broad spectrum killing activity against a wide range of microorganisms including gram-positive and gram-negative bacteria. Several antimicrobial peptides have been identified in the urinary tract, and the amount and type of antimicrobial peptides expressed vary according to tissue source and disease state. These differences may reflect altered levels of innate response and, hence, susceptibility to infection. Antimicrobial peptides are already being exploited therapeutically for skin and endovascular catheter infection, and prospects for useful application in the urinary tract are emerging. CONCLUSIONS: Although investigation of antimicrobial peptide function in the human urinary tract is at an early stage, it is clear that there is considerable potential for the future design of novel therapeutic strategies. More knowledge is needed concerning the pathway of involvement of antimicrobial peptides in the maintenance of urinary tract sterility and the ways in which this is altered during active infection.

The novel avian protein, AWAK, contains multiple domains with homology to protease inhibitory modules.

We report the purification of a 3.5kDa peptide with antimicrobial activity from the mucosa and epithelial cells of chicken intestine. The peptide contains a pattern of cysteines characteristic of a whey acidic protein (WAP) domain and was identified as the carboxy terminal fragment of a novel 767 amino acid avian protein which has a proposed molecular weight of 81kDa. Using the conserved domain database (CDD) we identified this 81kDa protein to contain multiple amino acid motifs with homology to WAP domains and an amino acid motif with homology to a Kunitz proteinase inhibitor domain. We propose to call this avian protein AWAK (Avian WAP motif containing, Kunitz domain containing). The presence of WAP and Kunitz modules suggests that AWAK has proteinase inhibitor activity. RT-PCR analyses demonstrated expression of the AWAK gene in the chicken intestine.

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 ß-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 ß-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.

The chicken host peptides, gallinacins 4, 7, and 9 have antimicrobial activity against Salmonella serovars.

The gallinacin genes clustered on chromosome 3 of the chicken (Gallus gallus domesticus) genome encode a group of cationic antimicrobial peptides characteristic of the beta-defensins. In this study, gallinacins 4, 7, and 9, all predicted to contain the conserved pattern of cysteines typical of beta-defensins but differing in their charge and hydrophobicity, were characterised for their in vivo gene expression patterns and in vitro antimicrobial activities against Salmonella serovars. Reverse-transcription PCR analyses of chicken epithelial tissues indicated gallinacin (Gal) 7 expression to be ubiquitous while Gal 4 and Gal 9 expression appeared localized to specific epithelial tissues including the ovary, trachea, and lung, respectively. In addition Gal 7, but neither Gal 4 nor Gal 9, expression was identified in tissues taken from the non-domesticated bird species, Parus caeruleus, Larus argentatus, and Columba palambus. Analysis of Gal 7 expression in chickens in response to an oral challenge with either Salmonella enterica serovar Typhimurium SL1344 or Salmonella enteriditis indicated no significant increase in small intestinal Gal 7 mRNA expression although a significant increase (p <0.05) was detected in the liver, suggesting that, in response to Salmonella infection Gal 7 expression is inducible in the liver. Neither Gal 4 nor Gal 9 expression was induced in the chicken small intestine in response to the oral Salmonella infection. The antimicrobial capabilities of Gals 4, 7, and 9 against Salmonella serovars including S. typhimurium SL1344 and S. enteriditis were investigated in vitro using recombinant His-tagged peptides and a time-kill assay. The antimicrobial activity data indicated the potency of the recombinant gallinacins against the Salmonella serovars to be in the order Gal 9> or=4>7, and provided evidence for the synergistic interaction of Gals 7 and 9 against S. enteriditis. These results support in silico data that Gals 4, 7, and 9 are part of the innate defences of the chicken and function in microbial killing activities.

Induction of cationic chicken liver-expressed antimicrobial peptide 2 in response to Salmonella enterica infection.

Cationic antimicrobial peptides constitute part of the innate immune system and provide an essential role in the defense against infection. At present there is a paucity of information regarding the antimicrobial profile of the chicken (Gallus gallus). Using in silico studies, an expressed sequence tag (EST) clone was identified which encodes a novel cationic antimicrobial peptide, chicken liver-expressed antimicrobial peptide 2 (cLEAP-2). The predicted amino acid sequence composed a prepropeptide, and the active peptide contained four conserved cysteine amino acids. The gene was localized to chromosome 13, and analysis of the genome revealed three exons separated by two introns. The cLEAP-2 gene was expressed in a number of chicken epithelial tissues including the small intestine, liver, lung, and kidney. Northern analysis identified liver-specific cLEAP-2 splice variants, suggesting some degree of tissue-specific regulation. To investigate whether cLEAP-2 expression was constitutive or induced in response to microbial infection, 4-day-old birds were orally infected with Salmonella. Analyses of cLEAP-2 expression by semiquantitative reverse transcription-PCR indicated that cLEAP-2 mRNA was upregulated significantly in the small intestinal tissues and the liver, indicative of direct and systemic responses. The antimicrobial activity of cLEAP-2 against Salmonella was analyzed in vitro with a time-kill assay and recombinant cLEAP-2. Interestingly Salmonella enterica serovar Typhimurium SL1344 showed increased susceptibility to the active cationic peptide (amino acids 37 to 76) compared to S. enterica serovar Typhimurium C5 and Salmonella enteritidis. Taken together, these data suggest that cationic cLEAP-2 is part of the innate host defense mechanisms of the chicken.