Biomedical subjects

Martin Schaller

Publications and source records attributed to Martin Schaller.

At least 37 records · Page 2Linked to original sources

PubMed2005

Candida albicans-secreted aspartic proteinases modify the epithelial cytokine response in an in vitro model of vaginal candidiasis.

Secreted aspartyl proteinases (Saps) are important virulence factors of Candida albicans during mucosal and disseminated infections and may also contribute to the induction of an inflammatory host immune response. We used a model of vaginal candidiasis based on reconstituted human vaginal epithelium (RHVE) to study the epithelial cytokine response induced by C. albicans. In order to study the impact of the overall proteolytic activity and of distinct Sap isoenzymes, we studied the effect of the proteinase inhibitor pepstatin A on the immune response and compared the cytokine expression pattern induced by the wild-type strain SC5314 with the pattern induced by Sap-deficient mutants. Infection of RHVE with the C. albicans wild-type strain induced strong interleukin 1alpha (IL-1alpha), IL-1beta, IL-6, IL-8, IL-10, granulocyte-macrophage colony-stimulating factor, gamma interferon, and tumor necrosis factor alpha responses in comparison with cytokine expression in noninfected tissue. Addition of the aspartyl proteinase inhibitor pepstatin A strongly reduced the cytokine response of RHVE. Furthermore, SAP-null mutants lacking either SAP1 or SAP2 caused reduced tissue damage and had a significantly reduced potential to stimulate cytokine expression. In contrast, the vaginopathic and cytokine-inducing potential of mutants lacking SAP4 to SAP6 was similar to that of the wild-type strain. These data show that the potential of specific Saps to cause tissue damage correlates with an epithelium-induced proinflammatory cytokine response, which may be crucial in controlling and managing C. albicans infections at the vaginal mucosa in vivo.

Aspartic Acid Endopeptidases↗

PubMed2005

Virulence of the fungal pathogen Candida albicans requires the five isoforms of protein mannosyltransferases.

The PMT gene family in Candida albicans encodes five isoforms of protein mannosyltransferases (Pmt proteins Pmt1p, Pmt2p, Pmt4p, Pmt5p, and Pmt6p) that initiate O mannosylation of secretory proteins. We compared virulence characteristics of pmt mutants in two complex, three-dimensional models of localized candidiasis, using reconstituted human epithelium (RHE) and engineered human oral mucosa (EHOM); in addition, mutants were tested in a mouse model of hematogenously disseminated candidiasis (HDC). All pmt mutants showed attenuated virulence in the HDC model and at least one model of localized candidiasis. The pmt5 mutant, which lacks in vitro growth phenotypes, was less virulent in the EHOM and HDC assays but had no consistent phenotype in the RHE assay. In contrast, the pmt4 and pmt6 mutants were less virulent in the RHE and HDC assays but not in the EHOM assay. The results stress the contribution of all Pmt isoforms to the virulence of C. albicans and suggest that the importance of individual Pmt isoforms may differ in specific host niches. We propose that Pmt proteins may be suitable targets for future novel classes of antifungal agents.

Animals↗

PubMed2005

Peroxisome proliferator-activated receptors and their ligands: entry into the post-glucocorticoid era of skin treatment?

Glucocorticoids have remained one of the most frequently used classes of drugs for the treatment of skin diseases since their introduction more than 50 years ago. As a result of the discovery of new members of the nuclear hormone receptor (NR) superfamily, alternative therapeutic interventions that target retinoid and vitamin D receptors have been developed. Peroxisome proliferator-activated receptors (PPARs) comprise another important NR subfamily, consisting of three different isotypes: PPARalpha, PPARdelta (PPARbeta) and PPARgamma. These NRs are activated by a variety of natural and synthetic ligands such as fatty acids, eicosanoids, and antidiabetic and antihyperlipidaemic agents. While these receptors are established as regulators of gene expression in lipid and glucose homeostasis, evidence is now accumulating that PPARs also play a crucial role in cutaneous biology. Results from in vitro and in vivo studies have indicated the involvement of PPARs in epidermal maturation, proliferation and differentiation, as well as in immune and inflammatory responses, carcinogenesis, hyperpigmentation and skin wound healing. Furthermore, treatment of psoriatic patients with PPARgamma activators (thiazolidinediones) has been shown to induce beneficial effects. However, the effects of PPAR ligands should be carefully evaluated to determine whether they are in fact mediated via PPAR-dependent mechanisms. Nonetheless, PPARs seem to have significant potential as therapeutic targets in skin inflammatory disorders.

Animals↗

PubMed2005

[Desmoglein 1-negative, desmoglein 3-positive pemphigus herpetiformis with involvement of oral mucous membranes].

A 46-year-old woman presented with a two year history of pruritic erythematous plaques with blisters, as well as oral erosions. Even though the cutaneous lesions fit best with dermatitis herpetiformis, bullous pemphigoid or pemphigoid gestationis, the histologic examination revealed eosinophilic spongiosis, most compatible with some form of pemphigus. The identification of intercellular IgG deposition on direct immunofluorescence and circulating IgG pemphigus antibodies on indirect immunofluorescence microscopy led to diagnosis of pemphigus herpetiformis. This rare form of pemphigus does not often involve the oral mucosa. In our patient, the explanation is that she had antibodies against desmoglein 3 but not desmoglein 1. Treatment with prednisolone and azathioprine caused rapid and complete healing.

Azathioprine↗

PubMed2004

Bartonella adhesin a mediates a proangiogenic host cell response.

Bartonella henselae causes vasculoproliferative disorders in humans. We identified a nonfimbrial adhesin of B. henselae designated as Bartonella adhesin A (BadA). BadA is a 340-kD outer membrane protein encoded by the 9.3-kb badA gene. It has a modular structure and contains domains homologous to the Yersinia enterocolitica nonfimbrial adhesin (Yersinia adhesin A). Expression of BadA was restored in a BadA-deficient transposon mutant by complementation in trans. BadA mediates the binding of B. henselae to extracellular matrix proteins and to endothelial cells, possibly via beta1 integrins, but prevents phagocytosis. Expression of BadA is crucial for activation of hypoxia-inducible factor 1 in host cells by B. henselae and secretion of proangiogenic cytokines (e.g., vascular endothelial growth factor). BadA is immunodominant in B. henselae-infected patients and rodents, indicating that it is expressed during Bartonella infections. Our results suggest that BadA, the largest characterized bacterial protein thus far, is a major pathogenicity factor of B. henselae with a potential role in the induction of vasculoproliferative disorders.

Adhesins, Bacterial↗

PubMed2004

Induction of nuclear factor- kappa B and c-Jun/activator protein-1 via toll-like receptor 2 in macrophages by antimycotic-treated Candida albicans.

We examined the role of Toll-like receptors (TLRs) by using TLR2-deficient (TLR2(-/-)), TLR4-defective (TLR4(d/d)), and double-knockout murine macrophages and human embryonic kidney (HEK) 293 cells transfected with human TLR2 or TLR4 expression plasmids after stimulation with different preparations of the human pathogenic fungus Candida albicans. Compared with wild-type macrophages, TLR2(-/-) and TLR4(d/d) macrophages had impaired recognition of viable C. albicans, whereas antimycotic (AM)-treated C. albicans solely used TLR2 in a TLR4- and interferon- gamma -independent manner. In human HEK293 cells, AM-treated C. albicans elicited mainly TLR2-dependent activation. The differences in responsiveness to viable C. albicans, compared with C. albicans treated with cytoplasmic membrane-interacting AMs, suggest specific recognition of different pathogen-associated patterns by TLRs in innate antifungal responses. Our analyses of signal transduction after stimulation of wild-type macrophages with AM-treated C. albicans demonstrated involvement of the transcription factors nuclear factor- kappa B and c-Jun/activator protein-1 and of the mitogen-activated protein kinases p38, extracellular-related kinase, and c-Jun NH(2)-terminal kinase.

Animals↗

PubMed2004

Toll-like receptors and innate antifungal responses.

The mammalian Toll-like receptors (TLRs) are homologues of Drosophila Toll and constitute a novel protein family involved in the mediation of innate immunity and the activation of adaptive immunity. Analysis of infection with human pathogenic fungi Candida albicans and Aspergillus fumigatus implicated TLR2 and TLR4 in elicitation of immune responses. Cryptococcus neoformans is recognized by a process that uses TLR4. C. albicans induces immunostimulation through causative agents, such as mannan or its structural derivatives (e.g. phospholipomannan), which are recognized by the immune system as pathogen-associated molecular patterns and are located in the cell wall of fungi. Secreted aspartic proteinases represent a key virulence factor that contributes to the ability of C. albicans to cause mucosal and disseminated infections, and might be a further potential stimulator of TLRs. Simultaneous activation of other pattern recognition receptors collaborating with TLRs illustrates the cooperation of various chains within ligand-specific receptor complexes for the recognition of fungal pathogens and their cell wall components.

Animals↗

PubMed2004

[Use of Lactobacillus as a probiotic factor to treat urogenital and intestinal infections as well as to prevent and treat allergic diseases].

Lactobacilli are probiotic micro-organisms that are part of the oral, intestinal and urogenital commensal flora. The beneficial effect of these bacterial strains, especially the eradication of or protection against pathogenic bacteria and yeasts, was shown by several studies. The preventive and therapeutic effect of lactobacilli applies to diarrhoea and urogenital infections in particular. Lactobacilli also seem to have a protective influence on the development and treatment of atopic disease.

Female Urogenital Diseases↗

PubMed2004

Toll-like receptors as key mediators in innate antifungal immunity.

The Toll protein of Drosophila is a transmembrane receptor involved in dorsoventral polarization during embryonic development and recognition of infection. In mammals, Toll-like receptors (TLRs) constitute a novel protein family involved in innate immunity and respond to a wide spectrum of microorganisms, including fungi, bacteria, viruses, and protozoa. Specific agonists for nine of the ten members of the human TLR family have been described to date. TLRs as well as the TLR-associated adaptor molecule MyD88 have been implicated in the recognition of the fungal pathogens Candida albicans, Aspergillus fumigatus, Cryptococcus neoformans and Pneumocystis carinii. Moreover, several pathogen associated molecular patterns (PAMPs) located in the cell wall or cell surface of fungi have been identified as potential ligands. Yeast zymosan activates TLR2/ TLR6 heterodimers, whereas Saccharomyces cerevisiae- and C. albicans-derived mannan seems to be detected by TLR4. Phospholipomannan, present in the cell surface of C. albicans has been shown to be recognized by TLR2, while TLR4 mainly interacts with glucuronoxylomannan, the major capsular polysaccharide of C. neoformans. MyD88 has been implicated in TLR signalling of linear (1 --> 3)-beta-D-glucan, and of beta-glucan from P. carinii. These data point towards the ability of the innate immune system to utilize TLRs that are specific to different types and components of pathogenic fungi. Recent evidence further suggests that TLRs cooperate with other immune receptors involved in fungal recognition and that the selective induction of adaptor proteins finally leads to distinct signalling events upon fungal challenge.

Adaptor Proteins, Signal Transducing↗

PubMed2004

Candida albicans PLD I activity is required for full virulence.

Phospholipase D1 (PLD1) mutants of Candida albicans are defective in important in vivo and in vitro virulence factors. PLD1 mutants colonize the murine alimentary tract as well as PLD1 sufficient strains. In comparison to PLD1 sufficient strains, the PLD1 mutants: (i) are unable to survive in internal organs after intravenous challenge; (ii) do not decrease the body weights of mice after oral challenge; and (iii) are not lethal for immunodeficient mice after oral challenge. In vitro, the PLD1 mutants show a drastically reduced capacity to penetrate epithelial monolayers and they fail to develop hyphae when grown on solid Spider medium. The morphogenic switch from yeast to hyphae is controlled by multiple parallel signaling pathways that couple specific stimuli to the regulation of several transcription factors. Our data suggest that PLD1 functions in at least one of these pathways regulating morphogenesis in vitro and that while the mutants are able to form hyphae in vivo, the hyphae are defective in their ability to cause oroesophageal and gastric candidiasis and to kill the C. albicans-colonized mice.

Animals↗

PubMed2004

Polymorphonuclear leukocytes (PMNs) induce protective Th1-type cytokine epithelial responses in an in vitro model of oral candidosis.

The immune response and the anticandidal activity of keratinocytes and polymorphonuclear leukocytes (PMNs) play a key role in host defence against localized Candida albicans infection. An established model of oral candidosis based on reconstituted human oral epithelium (RHE) was supplemented with PMNs to study the effect of these immune cells during experimental oral candidosis. Infection of RHE with C. albicans induced a strong expression of the chemokine interleukin-8 (IL-8) and the cytokine granulocyte-macrophages colony-stimulating factor (GM-CSF), and a moderate stimulation of interleukin-1alpha (IL-1alpha), interleukin-1beta (IL-1beta), interleukin-6 (IL-6), interferon gamma (IFN-gamma) and tumour necrosis factor alpha (TNF-alpha) by keratinocytes. This immune response was associated with chemoattraction of PMNs to the site of infection, whereas uninfected RHE failed to induce cytokine expression or to attract PMNs. Growth of the pathogen and tissue damage of C. albicans-infected RHE were significantly reduced when PMNs were applied to the apical epithelial surface or when PMNs migrated through a perforated basal polycarbonate filter of the model. Notably, protection against epithelial tissue damage was also observed when PMNs were placed on the basal side of non-perforated filters, which prevented PMN migration into the RHE. Addition of PMNs enhanced a Th1-type immune response (IFN-gamma, TNF-alpha), down-regulated the expression of the Th2-type cytokine interleukin-10 (IL-10), and was associated with protection against Candida-induced tissue damage. This PMN-supplemented model of oral candidosis mimics the in vivo situation, and provides a promising tool for studying the immunological interactions between keratinocytes and C. albicans, as well as the influence of PMNs on C. albicans pathogenesis.

Candida albicans↗

PubMed2004

Yersinia enterocolitica induces apoptosis and inhibits surface molecule expression and cytokine production in murine dendritic cells.

Yersinia enterocolitica evades innate immunity by expression of a variety of pathogenicity factors. Therefore, adaptive immunity including CD4(+) T cells plays an important role in defense against Y. enterocolitica. We investigated whether Y. enterocolitica might target dendritic cells (DC) involved in adaptive T-cell responses. For this purpose, murine DC were infected with Y. enterocolitica wild-type and mutant strains prior to incubation with ovalbumin (OVA) as antigen and 5-(6)-carboxyfluorescein diacetate N-succinimidyl ester-labeled OVA-specific T cells from DO11.10 mice. While T-cell proliferation was partially affected by infection of DC with plasmid-cured and YopP-deficient Yersinia mutant strains, no T-cell proliferation occurred after infection of DC with wild-type Y. enterocolitica. Infection of DC with Y. enterocolitica wild type resulted in decreased up-regulation of major histocompatibility complex class II, CD54 (intercellular adhesion molecule 1), CD 80, and CD86 expression. Experiments with plasmid-cured Y. enterocolitica or a YopP-deficient mutant strain revealed that YopP accounts for inhibition of surface molecule expression. Wild-type Y. enterocolitica suppressed the release of KC, tumor necrosis factor alpha, interleukin-10 (IL-10), and IL-12 by DC, while infection of DC with plasmid-cured Y. enterocolitica or with the YopP-deficient mutant resulted in the production of these cytokines. Moreover, infection with wild-type Y. enterocolitica induced apoptosis in DC mediated by YopP. Apoptosis occurred despite translocation of NF-kappaB to the nucleus, as demonstrated by electromobility shift assays. Together, these data demonstrate that Y. enterocolitica targets functions of murine DC that are required for T-cell activation. This might contribute to evasion of adaptive immune responses by Y. enterocolitica.

Animals↗

PubMed2003

Demodex abscesses: clinical and therapeutic challenges.

A 53-year-old man had a 6-week history of confluent erythematous papules, pustules, and abscesses of the face initially limited to the right nasolabial fold. Histologic investigation revealed a perifollicular infiltrate with lymphocytes, histiocytes, and many Demodex folliculorum mites. A large number of mites were seen in skin scrapings. The skin manifestations progressed and persisted for the following 5 years and were unresponsive to numerous antiparasitic treatments, including repeated oral administration of ivermectin and external application of lindane, permethrin, and benzoyl benzoate. Therapy with oral administration of 250 mg metronidazole 3 times a day for 2 weeks resulted in rapid and lasting recovery. Demodex folliculitis remains a diagnostic and therapeutic challenge. Antiparasitic therapies used against lice or scabies may fail in control of D folliculorum mites. In the presence of clinical and microscopic findings typical of Demodex folliculitis or abscesses, treatment failure with acaricidal agents does not exclude the diagnosis. Oral metronidazole seems to work in the management of this chronic mite infestation.

Administration, Oral↗

PubMed2003

Effect of antimycotic agents on the activity of aspartyl proteinases secreted by Candida albicans.

The inhibitory effect of human immunodeficiency virus (HIV) proteinase inhibitors amprenavir and saquinavir and antifungal agents terbinafine, ketoconazole, amphotericin B and ciclopiroxolamine on aspartyl proteinases (Saps) secreted by Candida albicans was tested in an in vitro spectophotometric assay. As expected, both HIV proteinase inhibitors showed a significant inhibitory effect on Sap activity, which was comparable to that of the classical aspartyl proteinase inhibitor pepstatin A (P < 0.001). Antifungal drugs such as ketoconazole, terbinafine and amphotericin B had no, or only minor, inhibitory effects on proteolytic activity. In contrast, a significant reduction in Sap activity could be demonstrated during treatment with the antifungal agent ciclopiroxolamine (P < 0.001). These results point to a multiple effect of this antimycotic agent and might explain the reduced adherence of C. albicans to human epithelial cells at subinhibitory doses.

Antifungal Agents↗

PubMed2003

Reduced expression of the hyphal-independent Candida albicans proteinase genes SAP1 and SAP3 in the efg1 mutant is associated with attenuated virulence during infection of oral epithelium.

The transition of Candida albicans from a yeast to a hyphal form is controlled by several transcriptional factors, including the key regulators Cph1 and Efg1, and is considered an important virulence attribute. These factors, especially Efg1, regulate the expression of hyphal-associated genes e.g. SAP4-SAP6. In order to investigate the relevance of these transcriptional regulators for hyphal-independent SAP genes, recently constructed cph1 and efg1 single mutants and a cph1/efg1 double mutant lacking these factors were tested during interaction with oral epithelium and polymorphonuclear neutrophils. In contrast to the parental wild-type strain and the cph1 mutant, the efg1 and the cph1/efg1 mutants did not produce hyphal forms in all experiments and were less capable of damaging epithelial cells and neutrophil granulocytes. The attenuated epithelial lesions of these mutants were correlated not only with reduced expression of the hyphal-associated gene SAP4, but also with the lack of SAP1 and SAP3 expression previously shown to be important for oral infections. An efg1 mutant strain carrying a plasmid-borne copy of the EFG1 gene regained hyphal growth, damage of keratinocytes, granulocytes and the expression of SAP1 and SAP3. Although efg1 and cph1/efg1 mutants did not produce germ tubes during infection, expression of the hyphal-associated genes SAP5 and SAP6 was not completely abolished. A reduced capacity to stimulate an epithelial immune response manifested by a delayed onset of IL-1beta, IL-8 and TNF expression was only observed in the cph1/efg1-infected tissue. These results provide further evidence for a combined regulation of different virulence factors, such as dimorphism and expression of SAP genes. Furthermore, it could be demonstrated that the lack of Efg1 also caused reduced expression of hyphal-independent SAP genes. Both the EFG1 and the CPH1 gene products are necessary for adequate induction of an immune response.

Aspartic Acid Endopeptidases↗

PubMed2003

Ciclopirox olamine treatment affects the expression pattern of Candida albicans genes encoding virulence factors, iron metabolism proteins, and drug resistance factors.

The hydroxypyridone ciclopirox olamine belongs to the antimycotic drugs used for the treatment of superficial mycoses. In contrast to the azoles and other antimycotic drugs, its specific mode of action is only poorly understood. To investigate the mode of action of ciclopirox olamine on fungal viability, pathogenicity, and drug resistance, we examined the expression patterns of 47 Candida albicans genes in cells grown in the presence of a subinhibitory concentration (0.6 micro g/ml) of ciclopirox olamine by reverse transcription-PCR. In addition, we used suppression-subtractive hybridization to further identify genes that are up-regulated in the presence of ciclopirox olamine. The expression of essential genes such as ACT1 was not significantly modified in cells exposed to ciclopirox olamine. Most putative and known virulence genes such as genes encoding secreted proteinases or lipases had no or only moderately reduced expression levels. In contrast, exposure of cells to ciclopirox olamine led to a distinct up- or down-regulation of genes encoding iron permeases or transporters (FTR1, FTR2, FTH1), a copper permease (CCC2), an iron reductase (CFL1), and a siderophore transporter (SIT1); these effects resembled those found under iron-limited conditions. Addition of FeCl(3) to ciclopirox olamine-treated cells reversed the effect of the drug. Addition of the iron chelator bipyridine to the growth medium induced similar patterns of expression of distinct iron-regulated genes (FTR1, FTR2). While serum-induced yeast-to-hyphal phase transition of C. albicans was not affected in ciclopirox olamine-treated cells in the presence of subinhibitory conditions, a dramatic increase in sensitivity to oxidative stress was noted, which may indicate the reduced activities of iron-containing gene products responsible for detoxification. Although the Candida drug resistance genes CDR1 and CDR2 were up-regulated, no change in resistance or increased tolerance could be observed even after an incubation period of 6 months. This was in contrast to control experiments with fluconazole, in which the MICs for cells incubated with this drug had noticeably increased after 2 months. These data support the view that the antifungal activity of ciclopirox olamine may at least be partially caused by iron limitation. Furthermore, neither the expression of certain multiple-drug resistance genes nor other resistance mechanisms caused C. albicans resistance to this drug even after long-term exposure.

2,2'-Dipyridyl↗

PubMed2003

The secreted aspartyl proteinases Sap1 and Sap2 cause tissue damage in an in vitro model of vaginal candidiasis based on reconstituted human vaginal epithelium.

Secreted aspartyl proteinases (Saps) contribute to the ability of Candida albicans to cause mucosal and disseminated infections. A model of vaginal candidiasis based on reconstituted human vaginal epithelium (RHVE) was used to study the expression and role of these C. albicans proteinases during infection and tissue damage of vaginal epithelium. Colonization of the RHVE by C. albicans SC5314 did not cause any visible epithelial damage 6 h after inoculation, although expression of SAP2, SAP9, and SAP10 was detected by reverse transcriptase PCR. However, significant epithelial damage was observed after 12 h, concomitant with the additional expression of SAP1, SAP4, and SAP5. Additional transcripts of SAP6 and SAP7 were detected at a later stage of the artificial infection (24 h). Similar SAP expression profiles were observed in three samples isolated from human patients with vaginal candidiasis. In experimental infection, secretion of antigens Sap1 to Sap6 by C. albicans was confirmed at the ultrastructural level by using polyclonal antisera raised against Sap1 to Sap6. Addition of the aspartyl proteinase inhibitors pepstatin A and the human immunodeficiency virus proteinase inhibitors ritonavir and amprenavir strongly reduced the tissue damage of the vaginal epithelia by C. albicans cells. Furthermore, SAP null mutants lacking either SAP1 or SAP2 had a drastically reduced potential to cause tissue damage even though SAP3, SAP4, and SAP7 were up-regulated in these mutants. In contrast the vaginopathic potential of mutants lacking SAP3 or SAP4 to SAP6 was not reduced compared to wild-type cells. These data provide further evidence for a crucial role of Sap1 and Sap2 in C. albicans vaginal infections.

Aspartic Acid Endopeptidases↗

PubMed2003

[Facial foreign body granulomas after dermal injection of a polylactate-based implant for wrinkles].

New methods are constantly introduced for soft tissue augmentation to correction of scars and wrinkles. Each method has its advantages and disadvantages. A 48 year old woman developed visible and palpable plaques and papules after treatment of the nasolabial and glabella folds with a poly L-lactic acid implant. Histological examination revealed a foreign body granuloma, while electron microscopy showed remnants of the implant material, demonstrating that poly L-lactic acid can also induce a foreign body reaction.

Facial Dermatoses↗