Modulation of cytokine and β-defensin 2 expressions in human gingival fibroblasts infected with Chlamydia pneumoniae

The immune function of dermal fibroblasts in skin defence against pathogens

Dermal fibroblasts are the main resident cells of the dermis. They have several significant functions related to wound healing, extracellular matrix production and hair cycling. Dermal fibroblasts can also act as sentinels in defence against infection. They express pattern recognition receptors such as toll-like receptors to sense pathogen components, followed by the synthesis of pro-inflammatory cytokines (including IL-6, IFN-β and TNF-α), chemokines (such as IL-8 and CXCL1) and antimicrobial peptides. Dermal fibroblasts also secrete other molecules-like growth factors and matrix metalloproteinases to benefit tissue repair from infection. Crosstalk between dermal fibroblasts and immune cells may amplify the immune response against infection. Moreover, the transition of a certain adipogenic fibroblasts to adipocytes protects skin from bacterial infection. Together, we discuss the role of dermal fibroblasts in the war against pathogens in this review. Dermal fibroblasts have important immune functions in anti-infection immunity, which should not be overlooked.

Essential immune functions of fibroblasts in innate host defense

The term fibroblast has been used generally to describe spindle-shaped stromal cells of mesenchymal origin that produce extracellular matrix, establish tissue structure, and form scar. Current evidence has found that cells with this morphology are highly heterogeneous with some fibroblastic cells actively participating in both innate and adaptive immune defense. Detailed analysis of barrier tissues such as skin, gut, and lung now show that some fibroblasts directly sense pathogens and other danger signals to elicit host defense functions including antimicrobial activity, leukocyte recruitment, and production of cytokines and lipid mediators relevant to inflammation and immunosuppression. This review will synthesize current literature focused on the innate immune functions performed by fibroblasts at barrier tissues to highlight the previously unappreciated importance of these cells in immunity.

A Review of Antimicrobial Activity of Dental Mesenchymal Stromal Cells: Is There Any Potential?

Antimicrobial defense is an essential component of host-microbial homeostasis and contributes substantially to oral health maintenance. Dental mesenchymal stromal cells (MSCs) possess multilineage differentiation potential, immunomodulatory properties and play an important role in various processes like regeneration and disease progression. Recent studies show that dental MSCs might also be involved in antibacterial defense. This occurs by producing antimicrobial peptides or attracting professional phagocytic immune cells and modulating their activity. The production of antimicrobial peptides and immunomodulatory abilities of dental MSCs are enhanced by an inflammatory environment and influenced by vitamin D3. Antimicrobial peptides also have anti-inflammatory effects in dental MSCs and improve their differentiation potential. Augmentation of antibacterial efficiency of dental MSCs could broaden their clinical application in dentistry.

Chlamydia pneumoniae is present in the dental plaque of periodontitis patients and stimulates an inflammatory response in gingival epithelial cells

Chlamydia pneumoniae is an airborne, Gram-negative, obligate intracellular bacterium which causes human respiratory infections and has been associated with atherosclerosis. Because individuals with periodontitis are at greater risk for atherosclerosis as well as respiratory infections, we in-vestigated the role of C. pneumoniae in inflammation and periodontal dis-ease. We found that C. pneumoniae was more frequently found in subgingival dental plaque obtained from periodontally diseased sites of the mouth versus healthy sites. The known periodontal pathogens, Porphyromonas gingivalis and Aggregatibacter actinomycetemcomitans, were also found in the plaque. In addition, C. pneumoniae could efficiently invade human gingival epithelial cells (GECs) in vitro, causing translocation of NF-κB to the nucleus along with increased secretion of mature IL-1β cytokine. Supernatants collected from C. pneumoniae-infected GECs showed increased activation of caspase-1 protein, which was significantly reduced when nlrp3 gene expression was silenced using shRNA lentiviral vectors. Our results demonstrate that C. pneumoniae was found in higher levels in periodontitis patients compared to control pa-tients. Additionally, C. pneumoniae could infect GECs, leading to inflammation caused by activation of NF-κB and the NLRP3 inflammasome. We propose that the presence of C. pneumoniae in subgingival dental plaque may contribute to periodontal disease and could be used as a potential risk indicator of perio-dontal disease.

Innate immune response of human epidermal keratinocytes and dermal fibroblasts to in vitro incubation of Trichophyton benhamiae DSM 6916

BACKGROUND

Superficial cutaneous infection caused by the zoophilic dermatophyte Trichophyton benhamiae is often associated with a highly inflammatory immune response. As non-professional immune cells, epidermal keratinocytes and dermal fibroblasts contribute to the first line of defence by producing pro-inflammatory cytokines and antimicrobial peptides (AMP).

OBJECTIVE

Purpose of this study was to gain a deeper understanding of the pathogenesis and the fungal-host interaction as not much is known about the innate immune response of these cutaneous cells against T. benhamiae.

METHODS

Using a dermatophytosis model of fibroblasts and keratinocytes incubated with T. benhamiae DSM 6916, analyses included determination of cell viability and cytotoxicity, effects on the innate immune response including expression and secretion of pro-inflammatory cytokines/chemokines and expression of AMP, as well as alterations of genes involved in cell adhesion.

RESULTS

Trichophyton benhamiae DSM 6916 infection led to severe cell damage and direct induction of a broad spectrum of pro-inflammatory cytokines and chemokines in both cutaneous cells. Only keratinocytes differentially up-regulated AMP genes expression after T. benhamiae DSM 6916 infection. Expression of AMPs in fibroblasts was not inducible by fungal infection, whereas their absences potentially contributed to a continuous increase in the fungal biomass on fibroblasts, which in turn was reduced in keratinocytes possibly due to the antimicrobial actions of induced AMPs. On mRNA level, T. benhamiae DSM 6916 infection altered cell-cell contact proteins in keratinocytes, indicating that targeting specific cell-cell adhesion proteins might be part of dermatophytes' virulence strategy.

CONCLUSION

This study showed that in addition to immune cells, keratinocytes and fibroblasts could participate in antimicrobial defence against an exemplary infection with T. benhamiae DSM 6916.

Cervicovaginal Levels of Human β-Defensin 1, 2, 3, and 4 of Reproductive-Aged Women With Chlamydia trachomatis Infection

OBJECTIVE

This study included women attending primary health care units in Botucatu, São Paulo, Brazil, to assess the cervicovaginal levels of human β-defensin (hBD) 1, 2, 3, and 4 during Chlamydia trachomatis infection.

PATIENTS AND METHODS

Cervicovaginal samples were collected for Pap testing and assessing the presence of infection by C. trachomatis, human papillomavirus, Neisseria gonorrhoeae, and Trichomonas vaginalis. Vaginal smears were taken to evaluate local microbiota. Human β-defensin levels were determined using enzyme-linked immunosorbent assay in cervicovaginal fluid samples. Seventy-four women with normal vaginal microbiota and no evidence of infection were included in hBD quantification assays; 37 tested positive for C. trachomatis and 37 were negative. Statistical analysis was performed using Mann-Whitney U test.

RESULTS

Women positive for C. trachomatis had significantly lower cervicovaginal hBD-1, hBD-2, and hBD-3 compared with those who tested negative (hBD-1: 0 pg/mL [0-2.1] vs 1.6 pg/mL [0-2.4], p < .0001; hBD-2: 0 pg/mL [0-3.9] vs 0.61 pg/mL [0-8.9], p = .0097; and hBD-3: 0 pg/mL [0-4.3] vs 0.28 pg/mL [0-8.4], p = .0076). Human β-defensin 4 was not detected.

CONCLUSIONS

Lower levels of hBD-1, hBD-2, and hBD-3 in cervicovaginal fluid were detected in the presence of C. trachomatis infection.

Fibroblasts: The Unknown Sentinels Eliciting Immune Responses Against Microorganisms

Fibroblasts are present in all tissues but predominantly in connective tissues. Some of their functions include contractility, locomotion, collagen and elastin fiber production, and the regulation and degradation of the extracellular matrix. Also, fibroblasts act as sentinels to produce inflammatory mediators in response to several microorganisms. There is evidence that fibroblasts can synthesize toll-like receptors (TLRs), antimicrobial peptides, proinflammatory cytokines, chemokines, and growth factors, which are important molecules involved in innate immune response against microorganisms. Fibroblasts can express TLRs (TLR-1 to TLR-10) to sense microbial components or microorganisms. They can synthesize antimicrobial peptides, such as LL-37, defensins hBD-1, and hBD-2, molecules that perform antimicrobial activity. Also, they can produce proinflammatory cytokines, such as TNFα, INFγ, IL-6, IL-12p70, and IL-10; other chemokines, such as CCL1, CCL2, CCL5, CXCL1, CXCL8, CXCL10, and CX3CL1; and the growth factors granulocyte/macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) to induce and recruit inflammatory cells. According to their immunological attributes, we can conclude that fibroblasts are sentinel cells that recognize pathogens, induce the recruitment of inflammatory cells via cytokines and growth factors, and release antimicrobial peptides, complying with the characteristics of real sentinels.

Chlamydia pneumoniae Clinical Isolate from Gingival Crevicular Fluid: A Potential Atherogenic Strain

Chlamydia pneumoniae has been associated to atherosclerotic cardiovascular diseases. The aim of our study was to characterize, for the first time, a C. pneumoniae strain isolated from the gingival crevicular fluid of a patient with chronic periodontitis, described as a risk factor for cardiovascular diseases. C. pneumoniae isolate was characterized and compared to the respiratory AR-39 strain by VD4-ompA genotyping and by investigating the intracellular growth in epithelial and macrophage cell lines and its ability to induce macrophage-derived foam cells. Inflammatory cytokine levels were determined in the gingival crevicular fluid sample. C. pneumoniae isolate showed a 99% similarity with the AR-39 strain in the VD4-ompA gene sequence and shared a comparable growth kinetic in epithelial cells and macrophages, as evidenced by the infectious progeny and by the number of chlamydial genomic copies. C. pneumoniae isolate significantly increased the number of foam cells as compared to uninfected and LDL-treated macrophages (45 vs. 6%, P = 0.0065) and to the AR-39 strain (45 vs. 30%, P = 0.0065). Significantly increased levels of interleukin 1-β (2.1 ± 0.3 pg/μL) and interleukin 6 (0.6 ± 0.08 pg/μL) were found. Our results suggest that C. pneumoniae may harbor inside oral cavity and potentially be atherogenic, even though further studies will be needed to clarify the involvement of C. pneumoniae in chronic periodontitis as a risk factor for cardiovascular diseases.

Human β-defensin messenger RNA is overexpressed in the cervical epithelia of patients with nongonococcal cervicitis

OBJECTIVE

Human β-defensin (hBD) is an innate immune mediator present in the mucosae. This study aimed to investigate whether hBD is implicated in nongonococcal cervicitis (NGC).

MATERIALS AND METHODS

Seventy-two patients with NGC and 64 healthy volunteers were consecutively enrolled between April 2010 and May 2011. Sensitive antimicrobial treatment was assigned to patients with NGC. Cervical tissues were sampled for the semiquantitative reverse transcription-polymerase chain reaction analyses of hBD-1, hBD-2, and hBD-3 messenger RNA (mRNA) expression.

RESULTS

The hBD-1, hBD-2, and hBD-3 mRNAs were comparably expressed in normal cervical tissues. The expression of hBD-1 mRNA was similar between patients with NGC and control subjects, whereas those of hBD-2 and hBD-3 mRNAs were significantly up-regulated in patients with NGC (1.25 [0.38] vs 1.08 [0.31], p = .005; 1.26 [0.35] vs 1.04 [0.30], p < .001). The relative expression level of hBD-1 mRNA remained unchanged in pathogen-eliminated patients, whereas those of hBD-2 mRNA (1.33 [0.42] vs 1.04 [0.36], p = .012) and hBD-3 mRNA (1.23 [0.32] vs 1.13 [0.26], p = .009) decreased significantly after the successful antimicrobial treatment.

CONCLUSIONS

Expressions of hBD-2 and hBD-3 mRNA are up-regulated in NGC, suggesting the role of mucosal immunity in NGC.

Effects of fruit and vegetable low molecular mass fractions on gene expression in gingival cells challenged with Prevotella intermedia and Actinomyces naeslundii

Low molecular mass (LMM) fractions obtained from extracts of raspberry, red chicory, and Shiitake mushrooms have been shown to be an useful source of specific antibacterial, antiadhesion/coaggregation, and antibiofilm agent(s) that might be used for protection towards caries and gingivitis. In this paper, the effects of such LMM fractions on human gingival KB cells exposed to the periodontal pathogens Prevotella intermedia and Actinomyces naeslundii were evaluated. Expression of cytokeratin 18 (CK18) and β4 integrin (β4INT) genes, that are involved in cell proliferation/differentiation and adhesion, and of the antimicrobial peptide β2 defensin (HβD2) in KB cells was increased upon exposure to either live or heat-killed bacteria. All LMM fractions tested prevented or reduced the induction of gene expression by P. intermedia and A. naeslundii depending on the experimental conditions. Overall, the results suggested that LMM fractions could modulate the effects of bacteria associated with periodontal disease in gingival cells.

Inducible expression of human β-defensin 2 by Chlamydophila pneumoniae in brain capillary endothelial cells

Defensins are an important family of natural antimicrobial peptides. Chlamydophila pneumoniae, a common cause of acute respiratory infection, has a tendency to cause persistent inflammatory diseases such as atherosclerosis, which may lead to cardiovascular disease or stroke. As endothelial cells are related to the physiopathology of stroke, the effects of in vitro C. pneumoniae infection on the expression of human β-defensin 2 (HBD-2) in brain capillary endothelial cells (BB19) was investigated. A time-dependent increase in HBD-2 mRNA was observed by means of real-time reverse transcription PCR (RT-PCR) in BB19 cells following C. pneumoniae infection, with a maximum increase at 24 h. A gradual induction of HBD-2 protein in the C. pneumoniae-infected endothelial cells was detected by immunoblotting. Immunofluorescence revealed the staining of HBD-2 in the cytoplasm of endothelial cells following C. pneumoniae infection. The secretion of HBD-2 (confirmed by ELISA) was significantly elevated 24 h after C. pneumoniae infection. These novel results indicate that HBD-2 is expressed and produced in the human brain capillary endothelial cells upon infection with C. pneumoniae, and provide evidence that HBD-2 plays a role in the early immune responses to C. pneumoniae and probably in the immunopathogenesis of atherosclerosis.

Immunomodulatory effects of Lactobacillus plantarum on human colon cancer cells

Probiotics, defined as live microbial food supplements which improve the health of the host, have obtained increasing medical importance. In the intestine they may prevent the overgrowth of pathogenic bacteria, increase the resistance of the gut to invasion by pathogens and ameliorate disease processes by inducting the secretion of soluble factors such as cytokines and antimicrobial beta-peptides. One important class of human antimicrobial peptides is the family of defensins. Human beta-defensin 2 (HBD-2) is a major inducible peptide which plays an important role in host defense and represents a link between innate and adaptive immune responses. This linkage is in part mediated through the recognition of conserved bacterial products or bacteria by Toll-like receptors (TLRs). The aim of this study was to investigate the effects of Lactobacillus plantarum on intestinal epithelial cells. We found that Caco-2 cells exposed to L. plantarum bacteria significantly induced HBD-2 mRNA expression and HBD-2 secretion in a dose- (16+/-1.4 pg/ml and 31.5+/-2.3 pg/ml at MOI 10 and 50, respectively) and time-dependent manner, but not HBD-3, compared to controls; in addition, when LPS was added to cells for 48 h, the interleukin (IL)-23 secretion (850+/-5.4 pg/ml) and IL-23 mRNA expression increased; while it was reduced when LPS was cocultured with L. plantarum (330+/-4.2 pg/ml). The L. plantarum-induced increase in HBD-2 expression is inhibited by anti-TLR-2 neutralizing antibodies, in the same way the pre-treatment with the anti-TLR-2 antibody inhibited the production of IL-23 induced by LPS in Caco-2 cells. The results of our study help to achieve a better understanding of how the intestinal epithelium participates in the innate immune response to commensal bacteria and pathogens in the gut.

Inducible expression of beta defensins by human respiratory epithelial cells exposed to Aspergillus fumigatus organisms

Background

Aspergillus fumigatus, a saprophytic mould, is responsible for life-threatening, invasive pulmonary diseases in immunocompromised hosts. The role of the airway epithelium involves a complex interaction with the inhaled pathogen. Antimicrobial peptides with direct antifungal and chemotactic activities may boost antifungal immune response.

Results

The inducible expression of defensins by human bronchial epithelial 16HBE cells and A549 pneumocyte cells exposed to A. fumigatus was investigated. Using RT-PCR and real time PCR, we showed an activation of hBD2 and hBD9 defensin genes: the expression was higher in cells exposed to swollen conidia (SC), compared to resting conidia (RC) or hyphal fragments (HF). The kinetics of defensin expression was different for each one, evoking a putative distinct function for each investigated defensin. The decrease of defensin expression in the presence of heat-inactivated serum indicated a possible link between defensins and the proteins of the host complement system. The presence of defensin peptide hBD2 was revealed using immunofluorescence that showed a punctual cytoplasmic and perinuclear staining. Quantification of the cells stained with anti hBD2 antibody demonstrated that SC induced a greater number of cells that synthesized hBD2, compared to RC or HF. Labelling of the cells with anti-hBD-2 antibody showed a positive immunofluorescence signal around RC or SC in contrast to HF. This suggests co-localisation of hBD2 and digested conidia. The HBD2 level was highest in the supernatants of cells exposed to SC, as was determined by sandwich ELISA. Experiments using neutralising anti-interleukine-1β antibody reflect the autocrine mechanism of defensin expression induced by SC. Investigation of defensin expression at transcriptional and post-transcriptional levels demonstrated the requirement of transcription as well as new protein synthesis during A. fumigatus defensin induction. Finally, induced defensin expression in primary culture of human respiratory cells exposed to A. fumigatus points to the biological significance of described phenomena.

Conclusion

Our findings provide evidence that respiratory epithelium might play an important role in the immune response during Aspergillus infection. Understanding the mechanisms of regulation of defensin expression may thus lead to new approaches that could enhance expression of antimicrobial peptides for potential therapeutic use during aspergillosis treatment.