Expression of toll-like receptors in the Fusarium solani infected cornea

Itraconazole-Loaded Ufasomes: Evaluation, Characterization, and Anti-Fungal Activity against Candida albicans

Numerous obstacles challenge the treatment of fungal infections, including the uprising resistance and the low penetration of available drugs. One of the main active agents against fungal infections is itraconazole (ITZ), with activity against a broad spectrum of fungi while having few side effects. The aim of this study was to design ufasomes, oleic acid-based colloidal carriers, that could encapsulate ITZ to improve its penetration power. Employing a 2²3¹ factorial design, the effect of three independent factors (oleic acid amount, cholesterol concentration, and ITZ amount) was investigated and evaluated for the percentage encapsulation efficiency (%EE), particle size (PS), and zeta potential (ZP). Optimization was performed using Design^® expert software and the optimized ITZ-loaded ufasomes obtained had %EE of 99.4 ± 0.7%, PS of 190 ± 1 nm, and ZP of -81.6 ± 0.4 mV, with spherical unilamellar morphology and no aggregation. An in vitro microbiological study was conducted to identify the minimum inhibitory concentration of the selected formula against Candida albicans, which was found to be 0.0625 μg/mL. Moreover, the optimized formula reduced the expression of toll-like receptors-4 and pro-inflammatory cytokine IL-1β secretion in the C. albicans-infected fibroblasts, indicating that the proposed ITZ-loaded ufasomes are a promising drug delivery system for ITZ.

Roles of pattern recognition receptors in response to fungal keratitis

Fungal keratitis is one of the leading causes of blindness worldwide, which has become an increasingly serious threat to public ocular health, but no effective treatment strategies are available now. Pattern recognition receptors (PRRs) of the innate immune system are the first line of host defense against fungal infections. They could recognize pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) and trigger an array of inflammatory responses. Over the last decades, research has resulted in significant progress regarding the roles of PRRs in fungal keratitis. This review will highlight the importance of several pattern recognition receptors (C-type lectin-like receptors, Toll-like receptors, and NOD-like receptors) in regulating the innate immunity under fungal keratitis and describe the crosstalk and collaboration in PRRs contributing to disease pathology. Meanwhile, some potential therapy-based PRRs against corneal fungal infections are discussed.

Aspergillus niger lectin elicits MyD88 dependent proliferation and apoptosis at lower and higher doses in immortalized human corneal epithelial cells leading to pathogenesis

An L-fucose lectin, ANL from the corneal smears of a mycotic keratitis patient was reported earlier. Interaction of ANL with immortalized Human Corneal Epithelial Cells (HCECs) was studied in order to assign the role of ANL in pathogenesis. ANL showed strong binding to HCECs which could be blocked by L-fucose and mucin. At concentrations below 0.6 μg/mL ANL showed proliferative effect and highest at 0.07 μg/mL leading to expression of proinflammatory cytokines IL-6 and IL-8. ANL induced proinflammatory response is mediated by TLR-2,-4, MyD88, NFkB and C-Jun dependent signaling. In contrast, ANL at concentrations above 0.6 μg/mL showed growth inhibitory effect at 48 h with an IC₅₀ of 2.75 μg/mL. Western blot analysis revealed that HCECs treated with ANL at lower concentration induced the expression of proinflammatory signaling proteins TLR-2, 4, MyD88, NFkB and C-Jun which maintain high cell proliferating state. At higher concentration ANL induced apoptotic effect in HCECs with an increase in early apoptotic population as demonstrated by Annexin V-PI assay. ANL induced the expression of apoptotic proteins FADD, Caspase 8 and -3 mediated by MyD88. These findings demonstrate implication of ANL in pathogenesis and the findings are of clinical significance in developing strategy for controlling the infection leading to mycotic keratitis.

Therapeutic Effect of Corneal Crosslinking on Fungal Keratitis: Efficacy of Corneal Collagen Crosslinking as an Adjuvant Therapy for Fungal Keratitis in a Tertiary Eye Hospital in South India

PURPOSE

To evaluate the efficacy of CXL in treating fungal keratitis as an adjuvant therapy.

METHODS

Detailed clinical examination microbiological investigation was performed. Twenty fungal keratitis patients were recruited and randomized into two groups: group 1 (n= 11, standard antifungal), group 2 (n=9, corneal collagen crosslinking with standard antifungal). Corneal scraping and tear samples collected were subjected to real-time PCR targeting ITS, TLR analysis and cytokine analysis.

RESULTS

The mean time for complete resolution of ulcer for group 2 was significantly shorter compared to group 1 and the final mean BCVA was better for group 2. Expression of IL-1β, IL-8, IFN-γ significantly decreased immediately post CXL in group 2 patients. Significant downregulation of TLR 6, TLR-3, TLR-4 was observed 3-days post CXL compared to group 1 patients.

CONCLUSION

Adjuvant effect of CXL was significant in treating fungal keratitis compared to standalone antifungal treatment.

mRNA profiling reveals response regulators of decreased fungal keratitis symptoms in a tree shrew model

Fungal keratitis is a corneal disease with a high blindness rate caused by pathogenic fungal infections. The pathogenesis of fungal keratitis and the immune response after fungal infection are still unclear. Notably, the pathological features of fungal keratitis in tree shrews are similar to those in humans. In the present study, mRNA profiling of tree shrew corneas with fungal keratitis was performed. GO and KEGG enrichment analyses were performed on the differentially expressed mRNAs, and the GO biological process ontology was used to analyze functional trends in the differentially expressed mRNAs. In total, 151 downregulated and 71 upregulated mRNAs were shared among the 7-day, 14-day and 30-day infection groups. These differentially expressed mRNAs were significantly enriched in the GO category immune response (GO: 0002376) and the KEGG pathways cytokine receptor binding (KEGG ID: tup04060) and cell adhesion (KEGG ID: tup04514). The downregulated mRNAs were significantly enriched in the corneal epithelial cell adhesion function. Fifty-eight initially upregulated mRNAs gradually decreased in expression, and these mRNAs were significantly enriched in the functions lipopolysaccharide (LPS) and antibacterial polypeptide recognition, cell differentiation, and cell rearrangement. Zeta chain of T-cell receptor associated protein kinase 70 (ZAP70), lymphocyte cytosolic protein 2 (LCP2), C-C motif chemokine and its receptor showed high degrees of connectivity in the protein-protein interaction (PPI) network. We speculate that the decrease in symptoms of tree shrew fungal keratitis may be related to the upregulation of genes involved in immune regulation and macrophage colony stimulation. This study showed that the C-C motif chemokine and its receptor may play a key role in regulating tree shrew fungal keratitis, providing a theoretical basis for studying the pathogenesis of human fungal keratitis.

Evaluation of an Improved Chitosan Scaffold Cross-Linked With Polyvinyl Alcohol and Amine Coupling Through 1-Ethyl-3-(3-Dimethyl Aminopropyl)-Carbodiimide (EDC) and 2 N-Hydroxysuccinimide (NHS) for Corneal Applications

BACKGROUND:

Corneal blindness resulting from various medical conditions affects millions worldwide. The rapid developing tissue engineering field offers design of a scaffold with mechanical properties and transparency similar to that of the natural cornea.

AIM:

The present study aimed at to prepare and investigate the properties of PVA/chitosan blended scaffold by further cross-linking with 1-Ethyl-3-(3-dimethyl aminopropyl)-carbodiimide (EDC) and 2 N-Hydroxysuccinimide (NHS) as potential in vitro carrier for human limbal stem cells delivery.

MATERIAL AND METHODS:

Acetic acid dissolved chitosan was added to PVA solution, uniformly mixed with a homogenizer until the mixture was in a colloidal state, followed by H₂SO₄ and formaldehyde added and the sample was allowed to cool, subsequently it was poured into a tube and heated in an oven at 60°C for 50 minutes. Finally, samples were soaked in a cross-linking bath with EDC, NHS and NaOH in H₂O/EtOH for 24 h consecutively stirred to cross-link the polymeric chains, reduce degradation. After soaking in the bath, the samples were carefully washed with 2% glycine aqueous solution several times to remove the remaining amount of cross-linkers, followed by washed with water to remove residual agents. Later the cross-linked scaffold subjected for various characterization and biological experiments.

RESULTS:

After viscosity measurement, the scaffold was observed by Fourier transform infrared (FT-IR). The water absorbency of PVA/Chitosan was increased 361% by swelling. Compression testing demonstrated that by increasing the amount of chitosan, the strength of the scaffold could be increased to 16×10−1 MPa. Our degradation results revealed by mass loss using equation shows that scaffold degraded gradually imply slow degradation. In vitro tests showed good cell proliferation and growth in the scaffold. Our assay results confirmed that the membrane could increase the cells adhesion and growth on the substrate.

CONCLUSION:

Hence, we strongly believe the use of this improved PVA/chitosan scaffold has potential to cut down the disadvantages of the human amniotic membrane (HAM) for corneal epithelium in ocular surface surgery and greater mechanical strength in future after successful experimentation with clinical trials.

Role of Pattern Recognition Receptors in the Modulation of Antimicrobial Peptide Expression in the Corneal Epithelial Innate Response to F. solani

Purpose

Fusarium solani (F. solani) keratitis is a potentially sight-threatening fungal infection of the cornea. Antimicrobial peptides (AMPs), such as human β-defensins (hBDs) and cathelicidins, essential components of the immune system, likely have a protective role against F. solani keratitis. We examined the role of pattern recognition receptors (PRRs), Dectin-1, and TLR2 in F. solani–induced modulation of AMP expression in vitro.

Methods

Human corneal epithelial cells (HCECs) were exposed to heat-inactivated F. solani or pathogen-associated molecular patterns (PAMPs) of F. solani (Zymosan or Zymosan Depleted) for 6, 12, or 24 hours following which AMP mRNA and protein levels were determined. Involvement of TLR2 and Dectin-1 was confirmed by using siRNA knock-down (TLR2 and Dectin-1) or chemical inhibitor BAY 61-3606 (Dectin-1). The functional significance of AMP upregulation was tested using culture supernatant from F. solani or PAMP-treated HCECs against F. solani in the presence of hBD2 or LL37 neutralizing antibody.

Results

We confirm that HCECs express Dectin-1 and TLR2. HCECs demonstrated upregulation of AMPs hBD2 and cathelicidin LL37 following exposure to heat-inactivated F. solani or PAMPs. TLR2 and Dectin-1 knockdown and BAY 61-3606 treatment decreased AMP mRNA upregulation confirming PRR involvement. The culture supernatant from F. solani or PAMP-treated HCECs showed substantial killing of F. solani and hBD2 or LL37 neutralizing antibody significantly decreased this effect implicating involvement of these AMPs.

Conclusions

These findings demonstrate that Dectin-1 and TLR2 have an important role in regulating F. solani-induced AMP expression in corneal epithelial cells.

Toll-like receptor-associated keratitis and strategies for its management

Keratitis is an inflammatory condition, characterized by involvement of corneal tissues. Most recurrent challenge of keratitis is infection. Bacteria, virus, fungus and parasitic organism have potential to cause infection. TLR are an important class of protein which has a major role in innate immune response to combat with pathogens. In last past years, extensive research efforts have provided considerable abundance information regarding the role of TLR in various types of keratitis. This paper focuses to review the recent literature illustrating amoebic, bacterial, fungal and viral keratitis associated with Toll-like receptor molecules and summarize existing thoughts on pathogenesis and treatment besides future probabilities for prevention against TLR-associated keratitis.

Expression of Toll-like receptors 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, limbus, and conjunctiva

OBJECTIVE

Human corneal cells have detectable levels of TLRs 1-10. TLRs 2 and 4 are the major corneal receptors, recognizing the PAMPs associated with fungal invasion in humans. The conjunctiva and limbus contain TLRs 2, 4, and 9. Our purpose was to determine the expression of TLRs 2, 3, 4, 6, 9, and MD-2 in the normal equine cornea, conjunctiva, and limbus.

METHODS

Corneal, limbal, and conjunctival tissues were collected from seven euthanized horses having no evidence of ocular disease. RNA extraction with DNase-1 digestion was performed followed by RT-PCR to determine expression of TLRs 2, 3, 4, 6, 9, and MD-2. Products were resolved by electrophoresis on 1.5% agarose gels and visualized using ethidium bromide staining.

RESULTS

Expression of TLRs 2, 3, 4, 6, 9, and MD-2 was present in the cornea, limbus, and conjunctiva of each horse, except one horse, where TLR3 expression was unable to be demonstrated in the dorsal and ventral conjunctiva.

CONCLUSIONS

Confirming the expression of TLRs in equine ocular tissues is an initial step in identifying how they play a role in infectious keratitis, particularly fungal. The results further support the use of equine ocular tissues as a model for human fungal keratitis. Studies of the TLR expression together with their cytokine profile induced during equine fungal keratitis may help further clarify the pathogenesis of the disease and possibly lead to the development of new treatment protocols for both equines and humans.

Toll-like receptor activation modulates antimicrobial peptide expression by ocular surface cells

The ability of the ocular surface to respond to pathogens is in part attributed to toll-like receptors (TLRs) that recognize conserved motifs on various microbes. This study examines TLR expression on various ocular surface cells, if TLR agonists can modulate the expression of antimicrobial peptides (AMPs), human beta defensins (hBD) and cathelicidin (hCAP-18/LL-37) which maybe functionally active against Pseudomonas aeruginosa (PA) and if TLR agonists or AMPs can modulate TLR mRNA expression. TLR1-10 mRNA expression was examined in corneal epithelial, corneal stromal cells and conjunctival epithelial cells by RT-PCR. To confirm protein expression flow cytometry or immunostaining was performed for selected TLRs on some cell cultures. Ocular surface cells were cultured with a range of TLR agonists and then hBD-1, 2, 3, or hCAP-18 mRNA and protein expression was determined by RT-PCR and immunoblotting. In some experiments, cells were cultured with a cocktail of agonists for TLR3, 5 and 6/2 and the antimicrobial activity of the culture media was tested against PA. TLR mRNA expression was also examined in primary human corneal epithelial cells (HCEC) treated with either 3 μg/ml of hBD-2, 5 μg/ml of LL-37 or TLR4, 5 and 9 agonists. Overall, the ocular surface cells expressed mRNA for most of the TLRs but some differences were found. TLR2 was not detected in corneal fibroblasts, TLR4 was not detected in primary cultured or freshly isolated HCEC, TLR5 was not detected in conjunctival epithelial cells (IOBA-NHC) and corneal fibroblasts, TLR7 was not detected in freshly isolated HCEC and TLR10 was not detected in HCEC and IOBA-NHC. TLR8 mRNA was not expressed by any of the samples tested. Immunostaining of cadaver corneas revealed TLR5 and 9 expression throughout the cornea while TLR3 was significantly expressed only in the epithelium. Flow cytometry and immunostaining revealed cultured fibroblasts expressed TLR9 but had no significant TLR3 expression. hBD-2 expression was upregulated by TLR1/2, 3, 4, 5 and 6/2 agonists depending on the cell type, whereas only the TLR3 agonist upregulated the expression of hCAP-18 in primary HCEC. The combination of TLR3, 5 and 6/2 agonists in primary HCEC, upregulated hBD-2 and hCAP-18 mRNA and peptide expression and secretion into the culture media, which significantly killed PA. This antimicrobial activity was primarily attributed to LL-37. TLR agonists did not modulate TLR expression itself, however, LL-37 or hBD-2 downregulated TLR5, 7 and/or 9 mRNA depending on the cell type. TLRs are expressed on the ocular surface and TLR agonists trigger the production of LL-37 and hBD-2, with LL-37 being particularly important for protecting the ocular surface against PA infection.

Toll-like receptors in ocular surface disease

The ability of the ocular surface to mount an immune response is in part attributed to a family of proteins called toll-like receptors (TLRs). The latter are evolutionary conserved receptors that recognize and respond to various microbes and endogenous ligands. In addition to their recognition function, TLR activation triggers a complex signal transduction cascade that induces the production of inflammatory cytokines and co-stimulatory molecules, thus initiating innate and adaptive immunity. Toll-like receptor expression at the ocular surface is modulated during infection (e.g. Herpes simplex, bacterial keratitis and fungal keratitis) as well as during various inflammatory conditions (allergic conjunctivitis and dry-eye syndrome). Here recent findings regarding TLR expression and their involvement in various ocular surface diseases are discussed.

Toll-like receptors involved in the pathogenesis of experimental Candida albicans keratitis

Purpose. To investigate the expression and function of toll-like receptors (TLRs) during experimental keratomycosis. Methods. Scarified corneas of BALB/c mice were topically inoculated with Candida albicans and compared with control corneas by a murine gene microarray and immunostaining. Real-time reverse transcription polymerase chain reaction (RT-PCR) determined relative TLR gene expression in murine and human donor corneas. The scarified corneas of TLR2(-/-) mice, TLR4(-/-) mice, and C57BL/6J control mice were also inoculated with C. albicans, to determine relative severity, fungal load, and cytokine transcript levels. Results. TLR1, -2, -4, -6, and -13 were significantly upregulated (5- to 10-fold; P < 0.01) by microarray, and TLR1, -2, -4, and -13 were significantly increased (4- to 11-fold; P < 0.05) by real-time RT-PCR in BALB/c murine corneas. Similarly, TLR2, -6, and -13 were significantly upregulated (5- to 16-fold; P < or = 0.001) by real-time RT-PCR in C57BL/6J murine corneas the day after inoculation, and TLR2 and -13 remained significantly (P < 0.05) increased after 1 week. TLR2 transcript was also upregulated twofold (P = 0.04) in C. albicans-inoculated explanted human corneas. Although murine keratitis severity scores were similar, significantly more fungi were recovered from TLR2(-/-) mouse corneas (P = 0.04) than from TLR4(-/-) mouse corneas (P = 0.9). Tumor necrosis factor-alpha, interleukin 23, chemokine C-C ligands 3 and 4, and dectin-1 were significantly (P < 0.05) downregulated in C. albicans-infected corneas of TLR2(-/-) mice. Conclusions. TLR2 signals proinflammatory cytokines that control fungal growth during C. albicans keratitis. TLR13 may have an additional role in the innate immune response of murine corneal candidiasis.

Modulation of expression of Toll-like receptors in the human endometrium

PROBLEM

The purpose of the study was to investigate the different expressions of toll-like receptors (TLRs) in the proliferative and the secretory phase of endometrial tissue.

METHOD OF STUDY

Eight infertile women were included in this study. The endometrial tissues of proliferative and secretory phase were obtained from each woman. The tissues were evaluated for the expression of mRNA for TLR1-10 by reverse transcribed polymerase chain reaction (RT-PCR). The proteins of TLR2, 3, 4, and 9 were evaluated by Western blot. The mRNA and protein level of proliferative and secretory endometrial tissue from the same woman was compared. The data were analysed with SPSS15.0.

RESULTS

TLR1-7, 9, and 10 mRNA were expressed throughout the menstrual cycle, but in the same woman, the expression of TLR2-6, 9, and 10 mRNA was higher during the secretory phase than that in the proliferative phase. The Western blot also showed that the protein expression of TLR2, 3, 4, and 9 was stronger in the secretory phase than that in the proliferative phase in the same woman.

CONCLUSION

The expression of TLRs is cycle dependent in human endometrial tissue. The expressions of TLRs were higher in the secretory phase than that in the proliferative phase: this indicated that TLRs may be regulated by sex hormones throughout the menstrual cycle.