Drug-loaded mesoporous carbon with sustained drug release capacity and enhanced antifungal activity to treat fungal keratitis

Platelet membrane-camouflaged PLGA loaded natamycin improve the prognosis of fungal keratitis

Fungal keratitis (FK) is a severe infectious corneal disease and a common cause of blindness. At present, natamycin (NATA) is the most commonly prescribed drug for fungal keratitis. However, these disadvantages, including poor water solubility, poor stability, and significant corneal irritation, limit its effect in clinical application. In this study, we innovatively prepare platelet membranes (PLTm) which are a unique population of cellular fragments that adhere to a variety of pathogens camouflaged with fabulous biocompatibility poly (lactic-co-glycolic acid) (PLGA) loaded NATA. PLTm can help NATA adhere to the fungal surface, increase the ocular surface retention, and achieve a double sustained-release effect, significantly increasing the antifungal effect of NATA. And platelet membrane-camouflaged PLGA loaded NATA (PLTm@PLGA-NATA) has better antifungal ability. Compared with pure NATA, PLTm@PLGA-NATA significantly improved the therapeutic effect on FK in vivo experiments. Moreover, in vitro, platelet membrane-camouflaged PLGA (PLTm@PLGA) can exert anti-inflammatory effects by reducing inflammatory cytokines caused by fungal stimulation. Therefore, this study provides a therapeutic strategy with a novel antifungal drug delivery system (DDS). Platelet membrane biomimetic nanoparticles play a promising role in treating FK.

Piperine inhibits fungal growth and protects against pyroptosis in Aspergillus fumigatus keratitis by regulating the mTOR/HIF-1α pathway

PURPOSE

To confirm the antifungal ability of piperine (PIP) and to assess its therapeutic potential in the treatment of Aspergillus fumigatus (A. fumigatus) keratitis.

METHODS

The toxicity of PIP was measured to determine the optimal therapeutic concentration both in human corneal epithelial cells (HCECs), RAW264.7 cells and mice fungal keratitis models. The antifungal efficacy of PIP was confirmed through the minimum inhibitory concentration (MIC) test, biofilm formation inhibition test, Calcofluor white and PI staining, and anti-adhesion of A. fumigatus conidia test. Hematoxylin-eosin (HE) staining, corneal fungal load assay, RT-qPCR, western blot, and Elisa were used to assess the therapeutic effect and anti-inflammatory ability of PIP in fungal keratitis. The significance of the mTOR/HIF-1α signal pathway after PIP treatment of A. fumigatus keratitis was evaluated.

RESULTS

PIP had no obvious toxicity to HCECs, RAW 264.7 cells, or mouse cornea at the concentration of 30 µg/mL. PIP effectively inhibited A. fumigatus from growing and showed synergistic effects when combined with NATA. PIP not only reduced fungal load and the aggregation of inflammatory cells, but also dramatically reduced the expression levels of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β, which were linked to pyroptosis. Additionally, PIP decreased mTOR phosphorylation and HIF-1α expression. The pretreatment with mTOR agonists reversed the inhibition of NLRP3, caspase-1, cleaved caspase-1, GSDMD, GSDMD-N, IL-18, and IL-1β protein levels caused by PIP.

CONCLUSION

PIP exhibited antifungal and anti-inflammatory properties, and alleviated pyroptosis in A. fumigatus keratitis via inhibiting the mTOR/HIF-1α signaling pathway.

Hydroxytyrosol downregulates inflammatory responses via Nrf2/HO-1 axis during fungal keratitis and exerts antifungal effects

PURPOSE

This study aims to explore the protective effect and underlying mechanism of hydroxytyrosol (HT) in fungal keratitis.

METHODS

Mouse models with Aspergillus fumigatus (A. fumigatus) keratitis, human corneal epithelial cells (HCECs) and RAW 264.7 cells were used in this study. Methods employed included MIC assay, biofilm formation test, hyphal immunofluorescence staining and adhesion test to assess the antifungal activity of HT. The severity of keratitis was evaluated using slit-lamp examination and HE staining. Draize eye test was used to measure corneal tolerance to HT. Corneal macrophages were detected by immunofluorescence staining. Reactive oxygen species (ROS) production in cytoplasm was quantified using DCFH-DA. Mitochondrial membrane potential was detected by JC-1. RT-PCR, ELISA and western blot were used to measure the expression of cytokines, as well as Nrf2 and HO-1 levels.

RESULTS

HT inhibited A. fumigatus growth, biofilm formation and conidial adhesion, and downregulated the expression of genes related to cell-wall assembly and morphogenesis. In fungal keratitis mouse models, HT significantly alleviated corneal inflammation, decreased the expression of cytokines and the accumulation of macrophages. In vitro, HT attenuated A. fumigatus-induced cytokine overexpression in HCECs or RAW 264.7 cells, and this effect was counteracted by an Nrf2 inhibitor. In RAW 264.7 cells stimulated with A. fumigatus, HT downregulated M1 markers expression, upregulated M2 markers expression, reduced ROS production, and restored mitochondrial membrane potential. Notably, these effects of HT were negated by pretreatment with an Nrf2 inhibitor.

CONCLUSIONS

This study underscores HT's efficacy against A. fumigatus growth and corneal invasion, its ability to mitigate fungi-induced inflammation, and its capacity to eliminate ROS via activation of the Nrf2/HO-1 signaling pathway. These findings suggest that HT holds therapeutic promise for fungal keratitis.

Macrophage Membrane-Coated Nanoparticles for the Delivery of Natamycin Exhibit Increased Antifungal and Anti-Inflammatory Activities in Fungal Keratitis

This study aims to explore the efficacy and safety of macrophage membrane-coated nanoparticles for the delivery of natamycin (NAT) in the therapy of fungal keratitis (FK). Macrophage membranes were isolated and identified by immunofluorescence staining (IFS). NAT was encapsulated into poly(lactic-co-glycolic acid) (PLGA). Fungal stimulated macrophage membranes (M1) or unstimulated membranes (M) were separately mixed and sonicated with PLGA nanoparticles. The biocompatible nanoparticles (PLGA-NAT, PLGA-NAT@M, and PLGA-NAT@M1) were characterized with zeta-sizer analysis, transmission electron microscopy (TEM), and Western blot. Drug encapsulation and loading efficiency and the release of NAT in the nanoparticles were detected by ultraviolet spectrophotometry. The cytotoxicity, ocular surface toxicity and irritability, and systemic safety of nanoparticles with different concentrations were assessed. In vitro, we examined the antifungal properties of the nanoparticles. The eye surface retention time, drug release, and curative effects on FK were evaluated in vitro and in vivo. IFS results showed the separation of the macrophage membrane and nucleus. The prepared nanoparticles had a typical "core-shell" structure and uniform nanometer size, and the membrane proteins were retained on the membrane allowing to exert functional effects of macrophage. The loading efficiencies of PLGA-NAT@M and PLGA-NAT@M1 were 7.6 and 6.7%, respectively. The encapsulation efficiencies of PLGA-NAT@M and PLGA-NAT@M1 were 51.2 and 41.5%, respectively. PLGA-NAT@M and PLGA-NAT@M1 could gradually release NAT and reduce the clearance of the ocular surface. Macrophage membranes enhanced the antifungal activity of PLGA-NAT. Furthermore, the membrane coated with macrophage increased the biocompatibility and decreased the corneal toxicity of nanoparticles. In vivo, PLGA-NAT@M1 significantly alleviated the severity of FK. In vitro, PLGA@M and PLGA@M1 reduced the protein levels of inflammatory cytokines after fungal stimulation. The prepared PLGA-NAT@M1 has good physical properties and biosafety. It could evade ocular surface clearance, release NAT gradually, and achieve high antifungal and anti-inflammatory efficiencies to FK. Macrophage membrane-coated nanoparticles clinically have high application potential to the treatment of FK.

Oriented cellulose hydrogel: Directed tissue regeneration for reducing corneal leukoplakia and managing fungal corneal ulcers

Fungal corneal ulcer is one of the leading causes of corneal blindness in developing countries. Corneal scars such as leukoplakia are formed due to inflammation, oxidative stress and non-directed repair, which seriously affect the patients' subsequent visual and life quality. In this study, drawing inspiration from the oriented structure of collagen fibers within the corneal stroma, we first proposed the directional arrangement of CuTA-CMHT hydrogel system at micro and macro scales based on the 3D printing extrusion method combined with secondary patterning. It played an antifungal role and induced oriented repair in therapy of fungal corneal ulcer. The results showed that it effectively inhibited Candida albicans, Aspergillus Niger, Fusarium sapropelum, which mainly affects TNF, NF-kappa B, and HIF-1 signaling pathways, achieving effective antifungal functions. More importantly, the fibroblasts interacted with extracellular matrix (ECM) of corneal stroma through formation of focal adhesions, promoted the proliferation and directional migration of cells in vitro, induced the directional alignment of collagen fibers and corneal stromal orthogonally oriented repair in vivo. This process is mainly associated with MYLK, MYL9, and ITGA3 molecules. Furthermore, the downregulation the growth factors TGF-β and PDGF-β inhibits myofibroblast development and reduces scar-type ECM production, thereby reducing corneal leukoplakia. It also activates the PI3K-AKT signaling pathway, promoting corneal healing. In conclusion, the oriented CuTA-CMHT hydrogel system mimics the orthogonal arrangement of collagen fibers, inhibits inflammation, eliminates reactive oxygen species, and reduces corneal leukoplakia, which is of great significance in the treatment of fungal corneal ulcer and is expected to write a new chapter in corneal tissue engineering.

Solubilization techniques used for poorly water-soluble drugs

About 40% of approved drugs and nearly 90% of drug candidates are poorly water-soluble drugs. Low solubility reduces the drugability. Effectively improving the solubility and bioavailability of poorly water-soluble drugs is a critical issue that needs to be urgently addressed in drug development and application. This review briefly introduces the conventional solubilization techniques such as solubilizers, hydrotropes, cosolvents, prodrugs, salt modification, micronization, cyclodextrin inclusion, solid dispersions, and details the crystallization strategies, ionic liquids, and polymer-based, lipid-based, and inorganic-based carriers in improving solubility and bioavailability. Some of the most commonly used approved carrier materials for solubilization techniques are presented. Several approved poorly water-soluble drugs using solubilization techniques are summarized. Furthermore, this review summarizes the solubilization mechanism of each solubilization technique, reviews the latest research advances and challenges, and evaluates the potential for clinical translation. This review could guide the selection of a solubilization approach, dosage form, and administration route for poorly water-soluble drugs. Moreover, we discuss several promising solubilization techniques attracting increasing attention worldwide.

Zeolitic Imidazolate Framework-8 Offers an Anti-Inflammatory and Antifungal Method in the Treatment of Aspergillus Fungal Keratitis in vitro and in vivo

Background

Fungal keratitis is a serious blinding eye disease. Traditional drugs used to treat fungal keratitis commonly have the disadvantages of low bioavailability, poor dispersion, and limited permeability.

Purpose

To develop a new method for the treatment of fungal keratitis with improved bioavailability, dispersion, and permeability.

Methods

Zeolitic Imidazolate Framework-8 (ZIF-8) was formed by zinc ions and 2-methylimidazole linked by coordination bonds and characterized by Scanning electron microscopy (SEM), X-ray diffraction (XRD), and Zeta potential. The safety of ZIF-8 on HCECs and RAW 264.7 cells was detected by Cell Counting Kit-8 (CCK-8). Safety evaluation of ZIF-8 on mice corneal epithelium was conducted using the Draize corneal toxicity test. The effects of ZIF-8 on fungal growth, biofilm formation, and hyphae structure were detected by Minimal inhibit concentration (MIC), crystal violet staining, Propidium Iodide (PI) testing, and calcofluor white staining. The anti-inflammatory effects of ZIF-8 on RAW 246.7 cells were evaluated by Quantitative Real-Time PCR Experiments (qPCR) and Enzyme-linked immunosorbent assay (ELISA). Clinical score, Colony-Forming Units (CFU), Hematoxylin-eosin (HE) staining, and immunofluorescence were conducted to verify the therapeutic effect of ZIF-8 on C57BL/6 female mice with fungal keratitis.

Results

In vitro, ZIF-8 showed outstanding antifungal effects, including inhibiting the growth of Aspergillus fumigatus over 90% at 64 μg/mL, restraining the formation of biofilm, and destroying cell membranes. In vivo, treatment with ZIF-8 reduced corneal fungal load and mitigated neutrophil infiltration in fungal keratitis, which effectively reduced the severity of keratitis in mice and alleviated the infiltration of inflammatory factors in the mouse cornea. In addition, ZIF-8 reduces the inflammatory response by downregulating the expression of pro-inflammatory cytokines TNF-α, IL-6, and IL-1β after Aspergillus fumigatus infection in vivo and in vitro.

Conclusion

ZIF-8 has a significant anti-inflammatory and antifungal effect, which provides a new solution for the treatment of fungal keratitis.

Formononetin protects against Aspergillus fumigatus Keratitis: Targeting inflammation and fungal load

PURPOSE

To investigate the potential treatment of formononetin (FMN) on Aspergillus fumigatus (A. fumigatus) keratitis with anti-inflammatory and antifungal activity.

METHODS

The effects of FMN on mice with A. fumigatus keratitis were evaluated through keratitis clinical scores, hematoxylin-eosin (HE) staining, and plate counts. The expression of pro-inflammatory factors was measured using RT-PCR, ELISA, or Western blot. The distribution of macrophages and neutrophils was explored by immunofluorescence staining. The antifungal properties of FMN were assessed through minimum inhibitory concentration (MIC), propidium iodide (PI) staining, fungal spore adhesion, and biofilm formation assay.

RESULTS

In A. fumigatus keratitis mice, FMN decreased the keratitis clinical scores, macrophages and neutrophils migration, and the expression of TNF-α, IL-6, and IL-1β. In A. fumigatus-stimulated human corneal epithelial cells (HCECs), FMN reduced the expression of IL-6, TNF-α, IL-1β, and NLRP3. FMN also decreased the expression of thymic stromal lymphopoietin (TSLP) and thymic stromal lymphopoietin receptor (TSLPR). Moreover, FMN reduced the levels of reactive oxygen species (ROS) induced by A. fumigatus in HCECs. Furthermore, FMN inhibited A. fumigatus growth, prevented spore adhesion and disrupted fungal biofilm formation in vitro. In vivo, FMN treatment reduced the fungal load in mice cornea at 3 days post infection (p.i.).

CONCLUSION

FMN demonstrated anti-inflammatory and antifungal properties, and exhibited a protective effect on mouse A. fumigatus keratitis.

Mesoporous zinc oxide-based drug delivery system offers an antifungal and immunoregulatory strategy for treating keratitis

Fungal keratitis is a refractory eye disease that is prone to causing blindness. Fungal virulence and inflammatory responses are two major factors that accelerate the course of fungal keratitis. However, the current antifungal drugs used for treatment usually possess transient residence time on the ocular surface and low bioavailability deficiencies, which limit their therapeutic efficacy. In this work, natamycin (NATA)-loaded mesoporous zinc oxide (Meso-ZnO) was synthesized for treating Aspergillus fumigatus keratitis with excellent drug-loading and sustained drug release capacities. In addition to being a carrier for drug delivery, Meso-ZnO could restrict fungal growth in a concentration-dependent manner, and the transcriptome analysis of fungal hyphae indicated that it inhibited the mycotoxin biosynthesis, oxidoreductase activity and fungal cell wall formation. Meso-ZnO also promoted cell migration and exhibited anti-inflammatory role during fungal infection by promoting the activation of autophagy. In mouse models of fungal keratitis, Meso-ZnO/NATA greatly reduced corneal fungal survival, alleviated tissue inflammatory damage, and reduced neutrophils accumulation and cytokines expression. This study suggests that Meso-ZnO/NATA can be a novel and effective treatment strategy for fungal keratitis.

Dimethyl fumarate ameliorates fungal keratitis by limiting fungal growth and inhibiting pyroptosis

PURPOSE

We aimed to investigate the therapeutic role of dimethyl fumarate (DMF) in fungal keratitis.

METHODS

Human corneal epithelial cells (HCECs) and mouse models of fungal keratitis were used in this study. The antifungal effect of DMF on Aspergillus fumigatus (A. fumigatus) was confirmed by examining the minimum inhibitory concentration (MIC), biofilm formation, conidial adherence and corneal fungal loads. Slit-lamp photography, haematoxylin and eosin staining and immunostaining were used to assess the severity of corneal impairment. RT-PCR, western blot, ELISA, immunohistochemistry and immunostaining were performed to examine the effects of DMF on the expression of the inflammatory mediators during fungal infection.

RESULTS

In vitro, DMF limited A. fumigatus growth, biofilm formation, and conidial adherence and reduced the mRNA levels of AldA, GlkA, GAPDH, HxkA, PgkA, Sdh2, GelA and ChsF in A. fumigatus. In vivo, DMF effectively decreased corneal fungal loads. DMF attenuated corneal inflammatory impairment by suppressing inflammatory cell accumulation and downregulating cytokine expression. DMF notably downregulated the high expression of NLRP3, cleaved GSDMD, cleaved caspase-1, mature IL-1β and mature IL-18 induced by fungi. The production of Nrf2 and HO-1 could be further increased by DMF in infected HCECs. Nrf2 siRNA pretreatment counteracted DMF-mediated downregulation of the expression of the active forms of IL-18, IL-1β, caspase-1 and GSDMD.

CONCLUSION

DMF limits fungal growth by suppressing biofilm formation, conidial adherence and respiratory metabolism. It also exerts an anti-inflammatory effect on fungal keratitis by inhibiting pyroptosis, which could be regulated by Nrf2. Our results suggest that DMF plays a therapeutic role in fungal keratitis.