Matrix metalloproteinases induction by pseudomonal virulence factors and inflammatory cytokines in vitro

A Pilot Study to Evaluate Genipin in Staphylococcus aureus and Pseudomonas aeruginosa Keratitis Models: Modulation of Pro-Inflammatory Cytokines and Matrix Metalloproteinases

Infectious keratitis is a vision-threatening microbial infection. The increasing antimicrobial resistance and the fact that severe cases often evolve into corneal perforation necessitate the development of alternative therapeutics for effective medical management. Genipin, a natural crosslinker, was recently shown to exert antimicrobial effects in an ex vivo model of microbial keratitis, highlighting its potential to serve as a novel treatment for infectious keratitis. This study aimed to evaluate the antimicrobial and anti-inflammatory effects of genipin in an in vivo model of Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) keratitis. Clinical scores, confocal microscopy, plate count, and histology were carried out to evaluate the severity of keratitis. To assess the effect of genipin on inflammation, the gene expression of pro- and anti-inflammatory factors, including matrix metalloproteinases (MMPs), were evaluated. Genipin treatment alleviated the severity of bacterial keratitis by reducing bacterial load and repressing neutrophil infiltration. The expression of interleukin 1B (IL1B), interleukin 6 (IL6), interleukin 8 (IL8), interleukin 15 (IL15), tumor necrosis factor-α (TNF-α), and interferon γ (IFNγ), as well as MMP2 and MMP9, were significantly reduced in genipin-treated corneas. Genipin promoted corneal proteolysis and host resistance to S. aureus and P. aeruginosa infection by suppressing inflammatory cell infiltration, regulating inflammatory mediators, and downregulating the expression of MMP2 and MMP9.

Predatory bacteria can reduce Pseudomonas aeruginosa induced corneal perforation and proliferation in a rabbit keratitis model

PURPOSE

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

METHODS

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic ΔlasR mutant and co-injected with PBS or B. bacteriovorus. After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

RESULTS

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n = 24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n = 25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The ΔlasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus.

CONCLUSION

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Predatory Bacteria can Reduce Pseudomonas aeruginosa Induced Corneal Perforation and Proliferation in a Rabbit Keratitis Model

Purpose

Pseudomonas aeruginosa keratitis is a severe ocular infection that can lead to perforation of the cornea. In this study we evaluated the role of bacterial quorum sensing in generating corneal perforation and bacterial proliferation and tested whether co-injection of the predatory bacteria Bdellovibrio bacteriovorus could alter the clinical outcome. P. aeruginosa with lasR mutations were observed among keratitis isolates from a study collecting samples from India, so an isogenic lasR mutant strain of P. aeruginosa was included.

Methods

Rabbit corneas were intracorneally infected with P. aeruginosa strain PA14 or an isogenic Δ lasR mutant and co-injected with PBS or B. bacteriovorus . After 24 h, eyes were evaluated for clinical signs of infection. Samples were analyzed by scanning electron microscopy, optical coherence tomography, sectioned for histology, and corneas were homogenized for CFU enumeration and for inflammatory cytokines.

Results

We observed that 54% of corneas infected by wild-type PA14 presented with a corneal perforation (n=24), whereas only 4% of PA14 infected corneas that were co-infected with B. bacteriovorus perforate (n=25). Wild-type P. aeruginosa proliferation was reduced 7-fold in the predatory bacteria treated eyes. The Δ lasR mutant was less able to proliferate compared to the wild-type, but was largely unaffected by B. bacteriovorus .

Conclusion

These studies indicate a role for bacterial quorum sensing in the ability of P. aeruginosa to proliferate and cause perforation of the rabbit cornea. Additionally, this study suggests that predatory bacteria can reduce the virulence of P. aeruginosa in an ocular prophylaxis model.

Endogenous α1-antitrypsin levels in the perilymphatic fluid correlates with severity of hearing loss

OBJECTIVES

To determine the levels of endogenous α1-antitrypsin in the perilymph of patients undergoing cochlear implant (CI), and its reverse association with the severity of hearing loss.

STUDY DESIGN

Retrospective study.

SETTING

Tertiary care university hospital.

PARTICIPANTS

The study includes 38 patients undergoing CI surgery, 11 patients diagnosed with congenital deafness and 27 non-congenital deafness, eight patients diagnosed with moderate hearing loss (N = 8; PTA = 70 dB), severe hearing loss (N = 11; PTA 70-90 dB) and profound hearing loss (N = 19; PTA > 90 dB).

MAIN OUTCOME AND MEASURE

1 to 12 μL perilymphatic fluids were collected by micropipette. α1-antitrypsin levels were determined, and current and historic audiological parameters were obtained.

RESULTS

The congenital and non-congenital group exhibited AAT concentrations of 2.5 ± 1.9 × 10⁶ LFQ and 3.2 ± 1.2 × 10⁶ LFQ, respectively (mean ± SD; P = .38). Mean levels of α1-antitrypsin in the perilymph fluid within the moderate group was 3.64 × 10⁶  ± 2.1 × 10⁶ LFQ vs 3.5 × 10⁶  ± 1.2 × 10⁶ in severe hearing loss (P = .81) and 2.4 × 10⁶  ± 1.1 × 10⁶ LFQ in the profound hearings loss group (P = .06). The difference in levels of AAT in samples from the severe hearings loss group vs the profound hearings loss group reached statistical significance (P = .04).

CONCLUSION

Insufficiency in α1-antitrypsin levels in the perilymph fluid of the inner ear appears to display a relationship with the severity of hearing loss. The prospect of introducing clinical-grade plasma-purified α1-antitrypsin directly onto the site of cochlear injury deserves thorough investigation.

A Novel Silver Bioactive Glass Elicits Antimicrobial Efficacy Against Pseudomonas aeruginosa and Staphylococcus aureus in an ex Vivo Skin Wound Biofilm Model

Biofilm infection is now understood to be a potent contributor to the recalcitrant nature of chronic wounds. Bacterial biofilms evade the host immune response and show increased resistance to antibiotics. Along with improvements in antibiotic stewardship, effective new anti-biofilm therapies are urgently needed for effective wound management. Previous studies have shown that bioactive glass (Bg) is able to promote healing with moderate bactericidal activity. Here we tested the antimicrobial efficacy of a novel BG incorporating silver (BgAg), against both planktonic and biofilm forms of the wound-relevant bacteria Pseudomonas aeruginosa and Staphylococcus aureus. BgAg was stable, long lasting, and potently effective against planktonic bacteria in time-kill assays (6-log reduction in bacterial viability within 2 h) and in agar diffusion assays. BgAg reduced bacterial load in a physiologically relevant ex vivo porcine wound biofilm model; P. aeruginosa (2-log reduction) and S. aureus (3-log reduction). BgAg also conferred strong effects against P. aeruginosa biofilm virulence, reducing both protease activity and virulence gene expression. Co-culture biofilms appeared more resistant to BgAg, where a selective reduction in S. aureus was observed. Finally, BgAg was shown to benefit the host response to biofilm infection, directly reducing host tissue cell death. Taken together, the findings provide evidence that BgAg elicits potent antimicrobial effects against planktonic and single-species biofilms, with beneficial effects on the host tissue response. Further investigations are required to elucidate the specific consequences of BG administration on polymicrobial biofilms, and further explore the effects on host-microbe interactions.

Ex vivo Caprine Model to Study Virulence Factors in Keratitis

Purpose:

To develop an infectious keratitis model using caprine (goat) corneas and to investigate the expression of virulence factors during infection.

Methods:

Goat eyes were surface-sterilized and dissected, and the corneas were placed on an agarose-gelatin solid support (0.5% in phosphate-buffered saline) in a 12-well culture plate containing 10% fetal bovine serum-supplemented culture medium for 3 weeks. Cell viability tests (trypan blue and MTT) were performed on the cultured corneas. Corneas were infected with Pseudomonas aeruginosa and Fusarium solani separately. Infection progression was observed via histological analysis and hematoxylin and eosin (H-E) staining. For Pseudomonas-infected corneas, expression of eight virulence genes (exoS, exoT, exoY, alpR, prpL, lasA, lasB, and algD) was determined via quantitative real-time PCR (qRT-PCR) at 48-h and 72-h time-points. For Fusarium-infected corneas, expression of five proteases (C7Z0E6, C7ZFW9, C7Z7U2, C7ZNV5, and C7YY94) was quantified via qRT-PCR at 2, 4, and 8 days after infection. Protease from infected corneas was detected via gelatin zymography.

Results:

Goat corneas with a viable epithelium could be maintained for 15 days. Pseudomonas infection progressed rapidly, and complete corneal degradation was observed on day 4 after infection. Fusarium infection progressed more slowly. Histological analysis and H-E staining of Fusarium-infected cornea revealed mycelia penetrating all layers of the cornea. qRT-PCR revealed expression of all eight virulence factors, and statistically significant difference in expression of prpL and alpR in Pseudomonas-infected corneas. Expression of C7ZNV5 was highest in Fusarium-infected corneas.

Conclusion:

Goat corneas can be used to evaluate the expression of virulence factors involved in Pseudomonas and Fusarium infection.

A tale of two risks: smoking, diabetes and the subgingival microbiome

Although smoking and diabetes have been established as the only two risk factors for periodontitis, their individual and synergistic impacts on the periodontal microbiome are not well studied. The present investigation analyzed 2.7 million 16S sequences from 175 non-smoking normoglycemic individuals (controls), smokers, diabetics and diabetic smokers with periodontitis as well as periodontally healthy controls, smokers and diabetics to assess subgingival bacterial biodiversity and co-occurrence patterns. The microbial signatures of periodontally healthy smokers, but not diabetics, were highly aligned with the disease-associated microbiomes of their respective cohorts. Diabetics were dominated by species belonging to Fusobacterium, Parvimonas, Peptostreptococcus, Gemella, Streptococcus, Leptotrichia, Filifactor, Veillonella, TM7 and Terrahemophilus. These microbiomes exhibited significant clustering based on HbA1c levels (pre-diabetic (<6.5%), diabetic (6.5–9.9%), diabetics >10%). Smokers with periodontitis evidenced a robust core microbiome (species identified in at least 80% of individuals) dominated by anaerobes, with inter-individual differences attributable largely to the ‘rare biosphere’. Diabetics and diabetic smokers, on the other hand, were microbially heterogeneous and enriched for facultative species. In smokers, microbial co-occurrence networks were sparse and predominantly congeneric, while robust inter-generic networks were observed in diabetics and diabetic smokers. Smoking and hyperglycemia impact the subgingival microbiome in distinct ways, and when these perturbations intersect, their synergistic effect is greater than what would be expected from the sum of each effect separately. Thus, this study underscores the importance of early intervention strategies in maintaining health-compatible microbiomes in high-risk individuals, as well as the need to personalize these interventions based on the environmental perturbation.

Identification of SlpB, a Cytotoxic Protease from Serratia marcescens

The Gram-negative bacterium and opportunistic pathogen Serratia marcescens causes ocular infections in healthy individuals. Secreted protease activity was characterized from 44 ocular clinical isolates, and a higher frequency of protease-positive strains was observed among keratitis isolates than among conjunctivitis isolates. A positive correlation between protease activity and cytotoxicity to human corneal epithelial cells in vitro was determined. Deletion of prtS in clinical keratitis isolate K904 reduced, but did not eliminate, cytotoxicity and secreted protease production. This indicated that PrtS is necessary for full cytotoxicity to ocular cells and implied the existence of another secreted protease(s) and cytotoxic factors. Bioinformatic analysis of the S. marcescens Db11 genome revealed three additional open reading frames predicted to code for serralysin-like proteases noted here as slpB, slpC, and slpD. Induced expression of prtS and slpB, but not slpC and slpD, in strain PIC3611 rendered the strain cytotoxic to a lung carcinoma cell line; however, only prtS induction was sufficient for cytotoxicity to a corneal cell line. Strain K904 with deletion of both prtS and slpB genes was defective in secreted protease activity and cytotoxicity to human cell lines. PAGE analysis suggests that SlpB is produced at lower levels than PrtS. Purified SlpB demonstrated calcium-dependent and AprI-inhibited protease activity and cytotoxicity to airway and ocular cell lines in vitro. Lastly, genetic analysis indicated that the type I secretion system gene, lipD, is required for SlpB secretion. These genetic data introduce SlpB as a new cytotoxic protease from S. marcescens.

Non-invasive assessment of upper and lower airway infection and inflammation in CF patients

BACKGROUND

The upper (UAW) and lower (LAW) airways of patients with cystic fibrosis (CF) have the same ion-channel defects, but little is known about similarities and differences in host immunological responses at the two levels.

AIM

Identification and comparison of both levels' pathogen colonization and resulting immunological host responses.

METHODS

The UAW and LAW of 40 CF patients were non-invasively assessed by nasal lavage and induced sputum. Pathogen colonization, cytology, and the concentrations of inflammatory mediators (TNF-α, MPO, matrix metalloprotease (MMP)-9, tissue inhibitor of metalloprotease (TIMP)-1, regulated upon activation, normal T-cell expressed and presumably secreted (RANTES), and interleukin (IL)-1β, -5, -6, -8, and -10) were measured.

RESULTS

Inflammatory responses were more pronounced in the LAW than the UAW. Pseudomonas aeruginosa LAW colonization is accompanied by a significantly enhanced neutrophil (PMN)-dominated response (P = 0.041) and IL-8 concentration (P = 0.01) not observed in P. aeruginosa UAW colonization. In contrast, sinonasal P. aeruginosa colonization resulted in elevated RANTES (P = 0.039) and reduced MMP-9 (P = 0.023) and TIMP-1 (P = 0.035) concentrations. Interestingly, LAW P. aeruginosa colonization was associated with reduced sinonasal concentrations of MMP-9 (P = 0.01) and TIMP-1 (P = 0.02), a finding independent of UAW colonization for MMP-9.

CONCLUSION

CF UAW and LAW show distinct inflammatory profiles and differentiated responses upon P. aeruginosa colonization. Assessment of UAW colonization and MMP-9 are predictive of chronic pulmonary colonization with P. aeruginosa. Thus, this linkage between CF UAW and LAW can provide new clinical and scientific implications.

Pseudomonas aeruginosa small protease (PASP), a keratitis virulence factor

PURPOSE

The virulence contribution of Pseudomonas aeruginosa small protease (PASP) during experimental keratitis was studied by comparing a PASP-deficient mutant with its parent and rescue strains.

METHODS

The pasP gene of P. aeruginosa was replaced with the tetracycline resistance gene via allelic exchange. A plasmid carrying the pasP gene was introduced into the PASP-deficient mutant to construct a rescue strain. The PASP protein in the culture supernatants was determined by Western blot analysis. Corneal virulence was evaluated in rabbit and mouse keratitis models by slit lamp examination (SLE), bacterial enumeration, and/or histopathological analysis. Various host proteins and the rabbit tear film were analyzed for their susceptibility to PASP degradation.

RESULTS

The PASP-deficient mutant produced a significantly lower mean SLE score when compared with the parent or rescue strain (P ≤ 0.03) at 29 hours postinfection (PI). All of the strains grew equally in the rabbit cornea (P = 0.971). Corneas infected with the PASP-deficient mutant showed moderate histopathology compared with those infected with the parent or rescue strain, which produced severe pathology inclusive of epithelial erosions, corneal edema, and neutrophil infiltration. In the mouse model, eyes inoculated with the PASP-deficient mutant had a significantly lower mean SLE score at 24 hours PI than the eyes inoculated with the parent or rescue strain (P ≤ 0.007). PASP was found to degrade complement C3, fibrinogen, antimicrobial peptide LL-37, and constituents of the tear film.

CONCLUSIONS

PASP is a commonly secreted protease of P. aeruginosa that contributes significantly to the pathogenesis of keratitis.

Effect of fluoroquinolones on the expression of matrix metalloproteinase in debrided cornea of rats

Matrix metalloproteinases (MMPs) are implicated in regenerative and healing processes in corneal injuries. Based upon reports that topical fluoroquinolones (FQs) may cause perforations during corneal healing by modulating MMPs, this study evaluated the comparative effects of commercially available FQs eye drops on the expression of MMP-2 and MMP-9 in the cornea after ethanol injury. Uniform corneal epithelial defects were created using 70% ethanol in the right eye of the rats (n = 6). The groups studied were (I) sham, (II) normal saline with benzalkonium chloride (NS-BKC), (III) norfloxacin 0.3%, (IV) ciprofloxacin 0.3%, (V) lomefloxacin 0.3%, (VI) sparfloxacin 0.3%, (VII) gatifloxacin 0.3%, and (VIII) moxifloxacin 0.5%. Each treatment was instilled six times/day up to 48 h and rats were sacrificed using excess of anesthesia. The corneas were excised to study the expression of MMP-2 and MMP-9 using gelatin zymography and real-time PCR. All the FQs significantly increased the expression of MMP-2 and MMP-9 as compared to the sham and NS-BKC-treated group. NS-BKC did not show a significant effect on MMPs expression compared to the sham group. Among the studied FQs, ciprofloxacin was observed to exhibit maximal induction of MMP-2 and MMP-9, whereas lomefloxacin exhibited an equivocal effect on both MMP-2 and MMP-9 expression. Findings of the present study demonstrate that topical application of FQs may induce the expression of MMP-2 and MMP-9 in debrided corneal epithelium and, therefore, may delay corneal wound healing. Thus, it can be concluded that selecting a FQ for ophthalmic use having minimal effect on MMPs may impact wound healing in injured or vulnerable cornea.

Collagen-based wound dressing for doxycycline delivery: in-vivo evaluation in an infected excisional wound model in rats

Objectives

A novel collagen-based dressing consisting of 2,3-dihydroxybenzoic-acid-modified gelatin microspheres loaded with doxycycline has previously been reported to address both infection and matrix degradation. In the present study the potential benefits of the dressing were investigated in an excisional wound model in rats challenged with Pseudomonas aeruginosa.

Methods

A full-thick excisional wound (1.5 times 1.5 cm) was created on the dorsum of the rats and infection induced by injecting 105 colony-forming units (CFU) of P. aeruginosa. The healing pattern was assessed from wound reduction, matrix metalloprotease (MMP) levels, CFU reduction and histological and biochemical analysis.

Key findings

The treated group exhibited complete healing by day 15, compared with day 24 in the control group. Early subsidence of infection (99.9% by day 9) resulted in faster epidermal resurfacing and fibroplasias, whereas the microbial load exceeded 103 CFU even on day 15 in the control group and caused severe inflammation. Biochemical analysis showed that the expression of both collagen and hexosamine was significantly increased in the treated group. Gelatin zymography revealed prolonged expression of MMPs 2, 8 and 9 in the control group compared with the treated group.

Conclusions

The study indicates that the developed dressing attenuated both infection and metalloprotease levels, and may therefore have potential application in wound healing.

Rifaximin-induced alteration of virulence of diarrhoea-producing Escherichia coli and Shigella sonnei

Rifaximin shortens the duration of travellers' diarrhoea without important alteration of colonic flora. This study investigated the expression of virulence factors [heat-stable (ST) and heat-labile (LT) enterotoxins, surface adhesion factors (CS2/CS3, CS6) and matrix metalloproteinase-9 (MMP-9)] as well as the interleukin (IL)-8 induction potential of diarrhoeagenic Escherichia coli and Shigella sonnei strains exposed to rifaximin (8, 32 and 64mg/L) for 4, 8, 18 and 24h. Following exposure to rifaximin, enterotoxigenic E. coli (ETEC) isolates did not express ST/LT, CS2/CS3 or CS6, whereas enteroaggregative E. coli (EAEC) and S. sonnei isolates did not produce detectable amounts of MMP-9. Moreover, induction of IL-8 was undetectable. At subinhibitory concentrations, rifaximin alters the virulence of ETEC, EAEC and S. sonnei isolates. These findings help explain the efficacy of rifaximin despite minimal alteration of colonic flora.

Role of the corneal epithelial basement membrane in ocular defense against Pseudomonas aeruginosa

Pseudomonas aeruginosa can invade corneal epithelial cells and translocates multilayered corneal epithelia in vitro, but it does not penetrate the intact corneal epithelium in vivo. In healthy corneas, the epithelium is separated from the underlying stroma by a basement membrane containing extracellular matrix proteins and pores smaller than bacteria. Here we used in vivo and in vitro models to investigate the potential of the basement membrane to defend against P. aeruginosa. Transmission electron microscopy of infected mouse corneas in vivo showed penetration of the stroma by P. aeruginosa only where the basement membrane was visibly disrupted by scratch injury, suggesting that the intact basement membrane prevented penetration. This hypothesis was explored using an in vitro Matrigel Transwell model to mimic the corneal basement membrane. P. aeruginosa translocation of multilayered corneal epithelia grown on Matrigel was approximately 100-fold lower than that of cells grown without Matrigel (P < 0.005, t test). Matrigel did not increase transepithelial resistance. Matrigel-grown cells blocked translocation by a P. aeruginosa protease mutant. Without cells, Matrigel also reduced traversal of P. aeruginosa and the protease mutant. Fluorescence microscopy revealed a relative accumulation of bacteria at the superficial epithelium of cells grown on Matrigel at 3 h compared to cells grown on uncoated filters. By 5 h, bacteria accumulated beneath the cells, suggesting direct trapping by the Matrigel. These findings suggest that the basement membrane helps defend the cornea against infection via physical barrier effects and influences on the epithelium and that these roles could be compromised by P. aeruginosa proteases.

Efficiency of controlled topical delivery of silver sulfadiazine in infected burn wounds

The present study is designed to assess the potential benefits of controlled delivery of silver sulfadiazine from collagen scaffold (SSDM-CS) in infected deep partial thickness burn wounds in which epidermis is lost completely and the entire papillary dermis and most of the recticular layer of the dermis is lost. Infection induced by inoculating 10(7) colony forming units (cfu) of Pseudomonas aeruginosa caused significant increase in wound size (20%) till day 15, which decreased significantly from day 9 by SSDM-CS treatment, showing complete healing by day 27 (control > or = 37 days). Early subsidence of infection (<10(2) cfu, day 9) by SSDM-CS resulted in faster epidermal resurfacing and fibroplasia, whereas heavy microbial load (>10(7) cfu, day 9) in controls caused severe inflammatory cellular infiltration. Persistent infection triggered early expression of proinflammatory cytokines intereukin-6, intereukin 1-beta, and tumor necrosis factor-alpha, lasting until day 9, whereas cytokine level decreased in SSDM-CS-treated group by day 6. Infection exacerbated expression of active matrix metalloproteinases (MMPs)-2 and -9 in controls (day 15), while SSDM-CS positively modulated MMP-2 and -9 with faster decline in their levels (day 12). Inherent nature of the dressing to maintain drug level at equilibrium therapeutic concentration (51.2 microg/mL) for prolonged time (72 h), below systemic toxic limits (20 microg/dL, serum level), accelerated the magnitude and sequence of reparative events.

Delayed local inflammatory response induced by Thalassophryne nattereri venom is related to extracellular matrix degradation

Symptoms evoked by Thalassophryne nattereri fish envenomation include local oedema, severe pain and intense necrosis with strikingly inefficient healing, continuing for several weeks or months. Investigations carried out in our laboratory showed that, in the venom-induced acute inflammation, thrombosis in venules and constrictions in arterioles were highly visible, in contrast to a notable lack of inflammatory cell. Nevertheless, the reason that the venom toxins favour delayed local inflammatory response is poorly defined. In this study, we analysed the movement of leucocytes after T. nattereri venom injection in the intraplantar region of Swiss mice, the production of pro-inflammatory mediators and the venom potential to elicit matrix metalloproteinase production and extracellular matrix degradation. Total absence of mononuclear and neutrophil influx was observed until 14 days, but the venom stimulates pro-inflammatory mediator secretion. Matrix metalloproteinases (MMP)-2 and MMP-9 were detected in greater quantities, accompanied by tissue degradation of collagenous fibre. An influx of mononuclear cells was noted very late and at this time the levels of IL-6, IL-1beta and MMP-2 remained high. Additionally, the action of venom on the cytoskeletal organization was assessed in vitro. Swift F-actin disruption and subsequent loss of focal adhesion was noted. Collectively these findings show that the altered specific interaction cell-matrix during the inflammatory process creates an inadequate environment for infiltration of inflammatory cells.

Modulation of corneal and stromal matrix metalloproteinase by the mannose-induced Acanthamoeba cytolytic protein

The involvement of the mannose-induced Acanthamoeba cytopathic protein (MIP-133) in tissue injury and activation of metalloproteinase of corneal and stromal cells was examined in vitro. Activation of MMP-1, MMP-2, MMP-3, and MMP-9 induced by MIP-133 on human corneal epithelial and stromal cell cultures was examined by reverse transcriptase polymerase chain reaction (RT-PCR) and ELISA. MMP-1, MMP-2, MMP-3, and MMP-9 mRNA were expressed in both cultured human corneal epithelial and stromal cells. When the epithelial cells were exposed to MIP-133 protein, the mRNA expression for MMP-1 and MMP-9 was unchanged. However, the transcript for MMP-2 and MMP-3 was decreased by 2-fold. By contrast, the expression of MMP-2 and MMP-3 was significantly upregulated (2- to 4-fold) in the corneal stromal cells 1, 4, and 8h after MIP-133 stimulation. At the protein level, there was no significant difference in the level of MMPs between the corneal epithelial cells before and after stimulation with MIP-133. By contrast, the levels of MMP-2 and MMP-3 were significantly higher in the corneal stromal cells stimulated with MIP-133. The supernatants from corneal stromal cells stimulated with MIP-133 were incubated with PMSF and MIP-133 antibody and the level of MMP-2 was measured by ELISA. Activation of MMP-2 by MIP-133 was inhibited in the supernatants pretreated with the serine protease inhibitor, PMSF, and anti-MIP-133. Supernatants pretreated with the cysteine protease inhibitor E6 or control antibody produced the same amount of MMP-2 as the untreated supernatants. To verify possible homology between MMPs and Acanthamoeba castellanii proteases, the mRNA from A. castellanii was prepared and analyzed for the expression of MMP genes by PT-PCR. The results showed that A. castellanii did not express mRNA for MMP-1, MMP-2, MMP-3, or MMP-9. Thus, A. castellanii mRNA does not cross-react with human MMPs. Furthermore, ELISA was used to determine the cross-reactivity of MMP antibodies with the MIP-133 protein. Monoclonal antibodies against MMPs did not cross-react with either the MIP-133 protein or BSA (negative control antigen). The results indicate that the MIP-133 protein modulates MMP-2 and -3 expression differently in human corneal epithelial and stromal cells.

Gastric gelatinase B/matrix metalloproteinase-9 is rapidly increased in Helicobacter felis-induced gastritis

It has previously been shown that matrix metalloproteinase-9 (MMP-9) levels, originating from macrophages, are considerably increased in human Helicobacter pylori-associated gastritis. Here, the early kinetics of the MMP-9 response resulting from Helicobacter infection in C57BL/6 and MMP-9 knock-out mice using the murine Helicobacter felis model were examined. H. felis infection induced severe gastritis in the murine stomach at just 2 weeks after infection. Before gastritis, an increase was observed in MMP-9-positive cells detected by immunohistochemistry in the basal lamina propria. This finding was corroborated by gelatin zymography of stomach samples. As the gastritis increased so did the concentration of MMP-9 and the incidence of gastric MMP-9-positive cells, their location corresponding to that of macrophages. In contrast, systemic levels of MMP-9 remained unchanged. When MMP-9-deficient mice were infected with H. felis, no significant difference in gastritis development was detected compared with disease development in wild-type animals. We conclude that MMP-9 production is an early event in the response to gastric Helicobacter infection, a feature that may favor the recruitment of immune cells early during infection. At later stages, however, the increased levels of MMP-9 may damage the integrity of the stomach mucosa.

Inflammatory response to fungal keratitis

Ocular fungal infections occur worldwide and are important contributors to vision loss. While many aspects of the microbe and host interaction involved in fungal keratitis remain undefined, two aspects known to affect susceptibility are disruption of the epithelial barrier and immunosuppression of the host. Our recent pathogenesis studies using an experimental murine model have provided insight into the influence of these factors on keratomycosis. Increased susceptibility was associated with greater neutrophilic infiltration, greater fungal invasion of the corneal stroma, up-regulation of matrix metalloproteinase-9, and morphogenic switching from yeast to hyphae. Understanding the pathogenic events of fungal keratitis will identify potential targets for therapeutic intervention of these sight-threatening infections.

Life at the front: dissecting bacterial-host interactions at the ocular surface

The ocular surface usually looks quiet, presenting a general impression of biological inactivity. Yet, the ability of the cornea to maintain health while continually exposed to environmental insults, and in the relative absence of immune strategies afforded by other body sites, reflects its complexity. Because it is critical for transparency and, therefore, our survival, the fine structure of the cornea has likely provided the driving force for the evolution of what appears to be a truly remarkable system. While several molecules are now known to participate, we are only beginning to obtain the knowledge to fully explain the mechanisms involved in corneal resistance to infection. Full explanation will require a better understanding of the interplay between microbes and various components of the ocular surface, and of the critical factors determining health as the usual outcome. To understand infectious disease, we need to consider how the scenario changes in conditions associated with susceptibility. What we learn in the process could yield a wealth of potential therapies for a wide variety of diseases of the eye and of other sites.

Expression of Matrix Metalloproteinases 2 and 9 in Experimental Corneal Injury and Fungal Keratitis

PURPOSE

Levels of matrix metalloproteinases (MMPs) can be modulated during corneal infection, but little is known about MMP profiles during fungal keratitis. The purpose of this study was to determine the effect of corneal trauma and immunosuppressive treatment on the expression kinetics of MMP-2 and MMP-9 during experimental keratomycosis.

METHODS

Corneas of immunocompetent and cyclophosphamide-treated adult BALB/c mice were topically inoculated with 1 x 10 culturable units of Fusarium solani or mock-inoculated with or without superficial corneal scarification. Eyes were scored daily for disease severity and processed for zymography after 1.5 hours, 6 hours, 1 day, 4 days, or 8 days. Gelatinase activity was densitometrically quantitated and normalized to MMP-2 and MMP-9 controls.

RESULTS

MMP-9 levels in nontraumatized eyes transiently increased at 6 hours after fungal exposure, but this increase was inhibited by cyclophosphamide treatment. Corneal injury significantly induced early MMP-9 expression that returned to baseline levels within 4 days. Cyclophosphamide pretreatment reduced and delayed MMP-9 after scarification. Fusarium exposure dampened the MMP-9 response to corneal trauma in immunocompetent and cyclophosphamide-treated animals. Ocular levels of MMP-2 were not affected by scarification, fungal exposure, or immunosuppressive treatment.

CONCLUSIONS

Ocular MMP-9 levels, but not MMP-2 levels, increased soon after corneal injury. A similar, although muted, MMP-9 response occurs during early filamentous fungal keratitis, with a kinetic profile similar to corneal disease progression. The early stage of ulcerative keratitis may involve selective regulation of corneal matrix metalloproteinases, suggesting an initial opportunity for therapeutic intervention.

Regulation of matrix metalloproteinases and tissue inhibitors of matrix metalloproteinases by Porphyromonas gingivalis in an engineered human oral mucosa model

Under physiological conditions, matrix metalloproteinases (MMPs) are involved in the remodeling and turnover of periodontal tissue and their activity is tightly regulated by tissue inhibitors of metalloproteinases (TIMPs). Disturbances in the balance between MMPs and TIMPs may result in excessive tissue destruction. We previously used an engineered human oral mucosa (EHOM) model to demonstrate that Porphyromonas gingivalis, a major etiological agent of periodontitis, infiltrates connective tissue and induces significant loss of attachment of the stratified epithelium from the basement membrane. The aim of the present study was to investigate the effect of P. gingivalis on the expression and production of MMP-2, MMP-9, TIMP-1, and TIMP-2 by oral fibroblasts and epithelial cells. The EHOM model was infected with P. gingivalis ATCC 33277 or its derivative gingipain-null mutant (KDP128) for different periods of time. MMP and TIMP mRNA expression was evaluated by reverse transcription-polymerase chain reaction (RT-PCR) analysis, while protein secretion into the culture medium was assessed by enzyme-linked immunosorbent assays. P. gingivalis significantly up-regulated MMP-2 and MMP-9 mRNA expression by oral epithelial cells. This MMP gene activation was paralleled by TIMP-2 gene activation. However, only MMP-9 mRNA expression was significantly enhanced by the gingipain-null mutant. At 8 and 24 h post-infection, P. gingivalis increased significantly the MMP-9 protein level compared to the uninfected EHOM model. The present study reports the ability of P. gingivalis to regulate MMP and TIMP production by oral cells, a phenomenon that may contribute to tissue destruction.

The role of prostaglandins in the mechanism of lipopolysaccharide-induced proMMP9 secretion from human placenta and fetal membrane cells

The abnormal degradation of the extracellular matrix by matrix metalloproteinases (MMPs) in the fetal membranes has been proposed as a central event in preterm premature rupture of the membranes (pPROM). Prostaglandins (PGs) are thought to increase the risk of preterm premature rupture of the fetal membranes by causing matrix degradation. The aim of this study was to assess the mediating role of PGs on lipopolysaccharide (LPS)-induced MMP9 secretion in vitro. ELISA, zymography, and Western blotting were performed on cells and medium from cultures of purified chorion trophoblasts (CTs) and syncytiotrophoblasts (STs) from the human placenta and fetal membranes treated with LPS, meloxicam, (a selective prostaglandin-endoperoxide synthase 2 [PTGS2, previously known as cyclooxygenase 2] inhibitor), or replacement PGE(2) or PGF(2alpha). LPS significantly (P < 0.01) increased proMMP9 secretion and prostaglandin E(2) (PGE(2)) output by cultured CTs and STs, but there was no effect on tissue inhibitor of matrix metalloproteinase 1 (TIMP1) secretion. In these cells, meloxicam significantly blocked LPS-induced proMMP9 secretion and PGE(2) output (P < 0.01). Exogenous PGE(2) and PGF(2alpha) significantly reversed the reduction in proMMP9 secretion caused by meloxicam in a dose-dependent manner (P < 0.01). The expression of PTGS2 protein in CTs and STs was increased dramatically after LPS treatment, but there was no significant effect on the expression of PTGS1 (previously known as cyclooxygenase 1), membrane-associated prostaglandin E synthases (membrane-associated PTGES, previously known as mPGES) 1 and 2, or cytosolic prostaglandin E synthase (cytosolic PTGES, previously knows as cPGES) proteins. Our results suggest that PGs may mediate the selective increase in MMP9 after exposure of trophoblast cells to LPS. There was no effect of LPS on TIMP1. Understanding this relationship may help in developing strategies for the prevention and management of pPROM and preterm labor.

Induction of matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs correlates with outcome of acute experimental pseudomonal keratitis

This study aimed to investigate expressions and sources of matrix metalloproteinases (MMP)-2 and MMP-9, and of tissue inhibitors of MMP (TIMP)-1 and TIMP-2 in experimental Pseudomonas aeruginosa keratitis in rabbits. Pseudomonal keratitis was induced in New Zealand white rabbits, and macroscopic and microscopic examinations were performed at appropriate time points (3, 9, 12, 18, 24, 72 h). Expressions and sources of MMP-2, 9, and TIMP-1, 2 were determined using immunohistochemistry, gelatin zymography, ELISA, and RT-PCR. A typical corneal ulcer with a ring abscess was observed 12-72 h post-infection (p.i.) with P. aeruginosa. In microscopic examinations, massive inflammatory cell (mostly polymorphonuclear leukocytes, PMNs) infiltration and liquefactive necrosis were characteristic features. MMP-2 was constitutively expressed in keratocytes, and its expression was not apparently enhanced after pseudomonal infection as evidenced by zymography, immunostaining, and RT-PCR. However, MMP-9 and its activated form were induced, and were significantly enhanced 12-24 h p.i. MMP-9 appeared to derive from PMNs rather than from resident corneal cells. TIMP-1 was expressed in PMNs, macrophages, and keratocytes, and its expression was enhanced 72 h p.i. Although TIMP-2 was constitutively expressed as seen by immunostaining and RT-PCR, its concentration was below detection limits during the experiments. We demonstrated that MMP-9 was one of the important factors for corneal tissue destruction, because it was induced and significantly expressed in keratocytes and inflammatory cells after pseudomonal infection. Although TIMP-1 was expressed in later stages of infection, enhancement and activation of MMP-9 were much faster and stronger than those of TIMP-1, thereby facilitating tissue destruction leading to corneal ulceration.

Gelatinolytic matrix metalloproteinases-2 and -9 in tracheobronchial lavage fluid obtained from calves with concurrent infections of Pasteurella multocida and Mycoplasma bovirhinis

OBJECTIVE

To study gelatinolytic matrix metalloproteinases (MMPs) in tracheobronchial lavage fluid (TBLF) obtained from clinically normal calves and calves with Pasteurella multocida infection.

SAMPLE POPULATION

Samples of TBLF obtained from 11 calves with clinical signs of respiratory tract disease and growth of P multocida and Mycoplasma spp during culture of TBLF and samples of TBLF from 6 clinically normal calves with no bacterial growth during culture of TBLF.

PROCEDURE

MMPs in TBLF were analyzed by use of gelatin zymography. Gelatinases were identified on the basis of molecular weights and inhibition by EDTA.

RESULTS

The main gelatinolytic MMPs detected were the proform (90 to 110 kd) and active form (75 to 85 kd) of MMP-9 (gelatinase B) and the proform (67 to 75 kd) and active form (< 65 kd) of MMP-2 (gelatinase A). Increased amounts of active MMP-2 and MMP-9 were detected in TBLF of calves with respiratory tract disease, compared with amounts of active MMP-2 and MMP-9 in TBLF of clinically normal calves. Concurrent infection with Mycoplasma bovirhinis in calves with pneumonia attributable to P multocida was associated with higher concentrations of MMP-9.

CONCLUSIONS AND CLINICAL RELEVANCE

The host response to P multocida includes increases in MMP-2 and MMP-9 concentrations in TBLF. Greater amounts of MMPs detected in calves with concurrent M bovirhinis and P multocida infection indicates synergism between these organisms.

The pathophysiology of Acanthamoeba keratitis

Acanthamoeba keratitis is a sight-threatening infection of the ocular surface that is produced by several free-living amebae of the genus Acanthamoeba. Infection is usually initiated by Acanthamoeba-contaminated contact lenses and produces exquisite pain and ulceration of the ocular surface. The pathophysiology of this infection involves an intricate series of sequential events that includes the production of several pathogenic proteases that degrade basement membranes and induce cytolysis and apoptosis of the cellular elements of the cornea, culminating in dissolution of the collagenous corneal stroma. Targeting such proteases could lead to the development of vaccines that target the disease process rather than the pathogen itself.

Role of cytokines and chemokines in pseudomonal keratitis

Pseudomonal keratitis usually progresses rapidly, often resulting in corneal perforation and blindness. Remarkable events in pseudomonal keratitis include massive polymorphonuclear leukocyte infiltration in the cornea and various degrees of tissue destruction. With regard to initiation of these inflammatory events, various inflammatory cytokines and chemokines appear to be key substances and have been the subject of several studies. Inflammatory cytokines and chemokines believed to be important in pseudomonal keratitis include interleukin (IL)-1 beta, IL-6, macrophage inflammatory protein (MIP)-2 (homologous to human IL-8), macrophage inhibitory factor (MIF), IL-12, IL-18, interferon (IFN)-gamma, and tumor necrosis factor (TNF)-alpha. In this article, current concepts related to the role of inflammatory cytokines and chemokines in pseudomonal keratitis are reviewed.

Secretion of matrix metalloproteinase-9 by macrophages, in vitro, in response to Helicobacter pylori

We have previously shown that matrix metalloproteinase-9 (MMP-9) activity is greatly enhanced within the active chronic inflammation of Helicobacter pylori infected individuals, of which a major fraction derives from macrophages in the tissue. Here, we have investigated the ability of macrophages to secrete MMPs in response to H. pylori. Human macrophages secrete MMP-9 in response to live and inactivated H. pylori, as well as to specific bacterial products. Protein kinase C, phosphatiolylinositol 3-kinase and calcium uptake channels all play a role in MMP-9 secretion, whereas neither tumour necrosis factor alpha, interleukin-8, nor interleukin-1beta autocrine stimulation appear to contribute. We conclude that human macrophages have the ability to react directly against several H. pylori derived factors, utilising several signalling pathways.

Serum amyloid A stimulates matrix-metalloproteinase-9 upregulation via formyl peptide receptor like-1-mediated signaling in human monocytic cells

In the present study, we found that serum amyloid A (SAA) stimulated matrix-metalloproteinase-9 (MMP-9) upregulation at the transcription and translational levels in THP-1 cells. SAA stimulated the activation of nuclear factor kappaB (NF-kappaB), which was required for the MMP-9 upregulation by SAA. The signaling events induced by SAA included the activation of ERK and intracellular calcium rise, which were found to be required for MMP-9 upregulation. Formyl peptide receptor like 1 (FPRL1) was found to be involved in the upregulation of MMP-9 by SAA. Among several FPRL1 agonists, including Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm), SAA selectively stimulated MMP-9 upregulation. With respect to the molecular mechanisms involved in the differential action of SAA and WKYMVm, we found that SAA could not competitively inhibit the binding of 125I-labeled WKYMVm to FPRL1. Taken together, we suggest that SAA plays a role in the modulation of inflammatory and immune responses via FPRL1, by inducing MMP-9 upregulation in human monocytic cells.

Role of bacterial proteases in pseudomonal and serratial keratitis

Pseudomonas aeruginosa and Serratia marcescens can cause refractory keratitis resulting in corneal perforation and blindness. These bacteria produce various kinds of proteases. In addition to pseudomonal elastase (LasB) and alkaline protease, LasA protease and protease IV have recently been found to be more important virulence factors of P. aeruginosa . S. marcescens produces a cysteine protease in addition to metalloproteases. These bacterial proteases have a number of biological activities, such as degradation of tissue constituents and host defense-oriented proteins, as well as activation of zymogens (Hageman factor, prekallikrein and pro-matrix metalloproteinases) through limited proteolysis. In this article, the properties of these bacterial proteases are reviewed and the pathogenic roles of these proteases in pseudomonal keratitis are discussed.

Molecular mechanism for activation and regulation of matrix metalloproteinases during bacterial infections and respiratory inflammation

Matrix metalloproteinases (MMPs) are critical mediators of tissue remodeling. Inappropriate regulation of MMPs causes many pathological events, including microbial invasion and inflammatory tissue damage. Some of the bacterial exoproteinases can effectively activate pro-MMPs (inactive zymogens) via limited proteolysis around their autoinhibitory domains. In addition, overproduction of nitric oxide (NO) may contribute to respiratory inflammation via the formation of reactive nitrogen species (RNS). Several studies have identified regulatory properties of NO/RNS on biomolecules due to functional modification of their cysteine residues. In fact, NO/RNS can mediate activation and expression of MMPs, because RNS can interact with a cysteine switch in the autoinhibitory domain, thus converting proMMPs into their active forms without proteolysis. Many studies have indicated that NO/RNS can participate in expression of various genes that affect immune-inflammatory responses, including MMPs. Although NO in some cases upregulates MMPs, S -nitrosothiols downregulate MMP-9 expression by suppressing the NF-kappaB pathway. While microbial proteinases cause excessive activation of MMPs and contribute to microbial pathogenesis, NO/RNS may modulate expression and activation of MMPs as well as various inflammatory mediators, depending on the redox status at sites of inflammation. Therefore, appropriate regulation of MMPs may be of potential therapeutic value for various infections and inflammatory lung diseases.

Proapoptotic effect of proteolytic activation of matrix metalloproteinases by Streptococcus pyogenes thiol proteinase (Streptococcus pyrogenic exotoxin B)

Streptococcus pyogenes thiol proteinase, also known as streptococcal pyrogenic exotoxin B (SpeB), has been suggested to be a major virulence factor in S. pyogenes infection. SpeB was reported to induce apoptosis of host cells, but its mechanism of action is not yet fully understood. In this study, we examined the involvement of matrix metalloproteinases (MMPs) in SpeB-induced apoptosis. We first developed a large-scale preparation of recombinant SpeB and precursors of human MMP-9 and -2 (proMMPs) by using Escherichia coli Rosetta (DE3)pLysS and baculovirus-insect cell expression systems, respectively. Treatment with SpeB induced effective proteolytic activation of both proMMP-9 and -2. When RAW264 murine macrophages were incubated with SpeB-activated proMMP-9, the level of tumor necrosis factor alpha (TNF-alpha) in conditioned medium (CM), assessed by an enzyme immunoassay, was elevated. This increase was completely inhibited by addition of the MMP inhibitor SI-27 to the cell culture. The CM also produced marked induction of apoptosis of U937 human monocytic cells. Similarly, soluble Fas ligand (sFasL) was detected in CM of cultures of SW480 cells expressing FasL after treatment with SpeB-activated proMMPs; this CM also induced apoptosis in U937 cells. SpeB had a direct effect as well and caused the release of TNF-alpha and sFasL from the cells. SpeB-dependent production of MMP-9 and -2 and proapoptotic molecules (TNF-alpha and sFasL) was evident in a murine model of severe invasive S. pyogenes infection. These results suggest that SpeB or SpeB-activated MMPs contribute to tissue damage and streptococcal invasion in the host via extracellular release of TNF-alpha and sFasL.

Increased production of matrix metalloproteinases in Helicobacter pylori-associated human gastritis

BACKGROUND AND AIMS

Helicobacter pylori infection results in an active, chronic inflammation of the gastric mucosa. Previous studies have highlighted the importance of matrix metalloproteinases (MMPs) in diseases involving mucosal inflammation, prompting us to investigate MMP activity in H. pylori-induced gastritis.

METHODS

Gastric biopsies were obtained from H. pylori-infected and uninfected volunteers, and MMP activity was assessed using substrate gel electrophoresis. MMP production was also evaluated by immunohistochemistry and real time-polymerase chain reaction. In parallel, tissue inhibitors of MMPs (TIMP) levels and TIMP-MMP complexes were examined in corresponding tissues using enzyme-linked immunosorbent assays and Western blotting. Finally, MMP production by gastric macrophages was determined after stimulation with H. pylori.

RESULTS

Antral mucosa of H. pylori-infected subjects demonstrated a 19-fold higher MMP-9 activity than that of uninfected individuals. MMP-2 was present at lower levels, but was also increased in H. pylori-infected individuals, while there was no difference in the total levels of TIMP-1 and TIMP-2 between the groups of volunteers. Significant numbers of MMP-9-containing cells were only found in the H. pylori-infected antral mucosa. Tissue-resident macrophages were significantly increased in H. pylori-infected individuals, and double-staining showed MMP-9 colocalized to macrophages. Furthermore, gastric macrophages secreted MMP-9 in response to H. pylori bacteria. A corresponding 10-fold increase of gene expression of MMP-9 was seen in patients infected with H. pylori compared to uninfected individuals.

CONCLUSIONS

Helicobacter pylori infection results in a substantial increase in MMP-9 and MMP-2 activity in the gastric mucosa, probably contributed to in large part by tissue-resident macrophages, while no changes were seen in the TIMP levels. The net increase in gastric MMP activity is likely to contribute to tissue damage during H. pylori-associated gastritis.

Calcium and magnesium enhance the production of Pseudomonas aeruginosa protease IV, a corneal virulence factor

The effect of calcium and magnesium on protease IV production during the growth of Pseudomonas aeruginosa was investigated. Strain PA103 was grown to stationary phase in medium containing various concentrations of either calcium or magnesium. Culture supernatants were concentrated, standardized relative to cell density, and the pyoverdine concentrations were measured. Overall extracellular protease activity and specific protease IV (lysine endoproteinase) activity were measured with or without TLCK, a serine protease inhibitor effective against protease IV activity. Protease IV activity was also observed by casein zymography. Calcium and magnesium were quantified in the corneas and aqueous humor of rabbits that were inoculated intrastromally with strain PA103. Pyoverdine production was not significantly different in cultures grown in medium with added calcium or magnesium, but extracellular caseinase activity increased in these cultures. Susceptibility of caseinase activity to TLCK inhibition and a specific assay for protease IV indicated that protease IV activity increased in cultures grown in calcium or magnesium. Casein zymography supported the observation that protease IV activity increased in the cultures with added calcium and magnesium. Addition of calcium or magnesium to the protease IV-specific assay had no effect on the catalytic activity of pure protease IV. Infection of rabbit corneas with PA103 did not change the magnesium concentration in either corneas or aqueous humor, but significantly increased the concentration of calcium in corneas. These results indicate that calcium and magnesium enhance the production of protease IV, but not pyoverdine production. Calcium increases in the cornea following infection with P. aeruginosa could favor production of protease IV.

Alpha 1-antitrypsin and ilomastat inhibit inflammatory proteases present in human middle ear effusions

OBJECTIVES

Proteases of both the serine and metalloproteinase families have been shown to play a role in the pathogenesis of otitis media (OM). Inhibitors of proteases from each of these families have been shown to beneficially impact disease progression in a number of related chronic inflammatory conditions, but their use has not been studied in OM. The purpose of this study was to assess the activity of the protease inhibitors recombinant alpha 1-antitrypsin (rAAT) and ilomastat on inflammatory proteases present in human middle ear effusions (MEEs), with a view to their potential utility in the treatment of OM.

STUDY DESIGN

Prospective and ex vivo.

METHODS

MEEs were collected from 100 patients presenting for middle ear surgery, most commonly tympanostomy tube placement or treatment of acute posttympanostomy otorrhea (APTO). MEEs were analyzed for the presence of matrix metalloproteinases (MMPs) and human neutrophil elastase (HNE) and the inhibitory activity of rAAT and ilomastat on these proteases, respectively.

RESULTS

MMP levels were highest in APTO, and HNE was highest in chronic suppurative OM and APTO. High levels of MMP and HNE (>3 mAU/min) were found in 52% and 37% of MEEs, respectively. Ilomastat and rAAT demonstrated significant inhibition of MMP and HNE activity (>30% reduction), respectively, in 80% and 82% of MEEs with high levels of activity.

CONCLUSIONS

Proteases are commonly found in OM. Ilomastat and rAAT are potent inhibitors of proteases in MEEs across a wide range of OM in humans. Investigation into the potential therapeutic benefits of these protease inhibitors is warranted.

N-terminal E-cadherin peptides act as decoy receptors for Listeria monocytogenes

The observation that E-cadherin is the principal epithelial receptor for the bacterial pathogen Listeria monocytogenes led us to investigate whether N-terminal fragments of E-cadherin containing the L. monocytogenes binding domain could inhibit entry of the bacteria into cultured epithelial cells. Here we demonstrate that a conditioned medium from a gastric cancer cell line (Kato III) that carries a truncating CDH-1 mutation 3' of the L. monocytogenes binding domain can inhibit the uptake of the bacteria into Caco-2 cells. The inhibitory activity of the Kato III conditioned medium could be mimicked by incubation of the bacteria with a recombinant 26-kDa N-terminal E-cadherin peptide prior to infection. Furthermore, these data suggest that cleavage of the 80-kDa extracellular domain of E-cadherin from the cell surface may provide an innate form of pathogen defense by acting as a decoy receptor for L. monocytogenes.

Pulmonary matrix metalloproteinase excess in hospital-acquired pneumonia

In hospital-acquired pneumonia, extracellular matrix destruction is common and may be caused by excessive activity of matrix metalloproteinases (MMPs). Thirty patients with hospital-acquired pneumonia and 16 control subjects were studied. We evaluated the concentrations of MMP-8, MMP-9, and tissue inhibitor of metalloproteinase-1 in mini-bronchoalveolar lavage fluid (mini-BALF) and blood using zymography and specific immunoassays. In patients with hospital-acquired pneumonia concentrations of MMP-8 and MMP-9 in mini-BALF were increased 10-fold, whereas their specific inhibitor tissue inhibitor of metalloproteinase-1 was not concomitantly increased. In 80% of patients with pneumonia, but in none of the control subjects, the active form of MMP-9 was detected by zymography. Zymography furthermore showed the banding pattern of neutrophil-derived MMP-9, indicating that neutrophils were the main source of MMP-9. Comparison of neutrophils from blood and mini-BALF showed higher basal release of MMPs by pulmonary neutrophils. Stimulation analysis indicated that pulmonary neutrophils were already maximally activated. In patients with detection of potentially pathogenic microorganisms, concentrations of MMPs were fivefold increased compared with patients with negative cultures. Furthermore, MMP-levels were related to clinical severity. These are the first data suggesting that neutrophil-derived MMPs are increased in hospital-acquired pneumonia in association to the detection of causative microorganisms and clinical severity.

Microarray analysis of global gene expression in mucoid Pseudomonas aeruginosa

Pseudomonas aeruginosa is the dominant pathogen causing chronic respiratory infections in cystic fibrosis (CF). After an initial phase characterized by intermittent infections, a chronic colonization is established in CF upon the conversion of P. aeruginosa to the mucoid, exopolysaccharide alginate-overproducing phenotype. The emergence of mucoid P. aeruginosa in CF is associated with respiratory decline and poor prognosis. The switch to mucoidy in most CF isolates is caused by mutations in the mucA gene encoding an anti-sigma factor. The mutations in mucA result in the activation of the alternative sigma factor AlgU, the P. aeruginosa ortholog of Escherichia coli extreme stress sigma factor sigma(E). Because of the global nature of the regulators of mucoidy, we have hypothesized that other genes, in addition to those specific for alginate production, must be induced upon conversion to mucoidy, and their production may contribute to the pathogenesis in CF. Here we applied microarray analysis to identify on the whole-genome scale those genes that are coinduced with the AlgU sigmulon upon conversion to mucoidy. Gene expression profiles of AlgU-dependent conversion to mucoidy revealed coinduction of a specific subset of known virulence determinants (the major protease elastase gene, alkaline metalloproteinase gene aprA, and the protease secretion factor genes aprE and aprF) or toxic factors (cyanide synthase) that may have implications for disease in CF. Analysis of promoter regions of the most highly induced genes (>40-fold, P < or = 10(-4)) revealed a previously unrecognized, putative AlgU promoter upstream of the osmotically inducible gene osmE. This newly identified AlgU-dependent promoter of osmE was confirmed by mapping the mRNA 5' end by primer extension. The recognition of genes induced in mucoid P. aeruginosa, other than those associated with alginate biosynthesis, reported here revealed the identity of previously unappreciated factors potentially contributing to the morbidity and mortality caused by mucoid P. aeruginosa in CF.