In vitro and in vivo activities of leukotriene B4-loaded biodegradable microspheres

An all-silk-derived bilayer hydrogel for osteochondral tissue engineering

Osteochondral repair remains a challenge in clinical practice nowadays despite extensive advances in tissue engineering. The insufficient recruitment of endogenous cells in the early stage and incomplete cell differentiation in the later stage constitute the major difficulty of osteochondral repair. Here, a novel all-silk-derived multifunctional biomaterial platform for osteochondral engineering is reported. The bilayer methacrylated silk fibroin (SilMA) hydrogel was fabricated through stratified photocuring as the basic provisional matrix for tissue regeneration. Platelet-rich plasma (PRP) incorporation promoted the migration and pre-differentiation of the bone marrow mesenchymal stem cells (BMSCs) in the early stage of implantation. The long-term regulation of BMSCs chondrogenesis and osteogenesis was realized by the stratified anchoring of the silk fibroin (SF) microspheres respectively loaded with Kartogenin (KGN) and berberine (BBR) in the hydrogel. The composite hydrogels were further demonstrated to promote BMSCs chondrogenic and osteogenic differentiation under an inflammatory microenvironment and to achieve satisfying cartilage and subchondral bone regeneration with great biocompatibility after 8 weeks of implantation. Since all the components used are readily available and biocompatible and can be efficiently integrated via a simple process, this composite hydrogel scaffold has tremendous potential for clinical use in osteochondral regeneration.

Leukotriene B4 Loaded in Microspheres Inhibits Osteoclast Differentiation and Activation

To investigate osteoclast formation in vivo and if leukotriene B4 (LTB4) loaded in microspheres (MS) could be used as a therapeutical strategy to promote a sustained delivery of the mediator and prevent osteoclast differentiation. Methods: In vivo, apical periodontitis was induced in mice to investigate osteoclast differentiation and signaling in absence of 5-lipoxygenase (5-LO). In vitro, LTB4-MS were prepared using an oil-in-water emulsion solvent extraction-evaporation process. Characterization and efficiency of LTB4 encapsulation were investigated. J774A.1 macrophages were cultured in the presence of monocyte colony-stimulating factor (M-CSF) and ligand for receptor activator of nuclear factor kappa B (RANKL) and then stimulated with LTB4-MS. Cytotoxicity, in vitro MS-LTB4 uptake, osteoclast formation and gene expression were measured. Results: We found that 5-LO negatively regulates osteoclastic formation in vivo during apical periodontitis development. In vitro, LTB4-MS were up-taken by macrophages and were not cytotoxic to the cells. LTB4-MS inhibited osteoclast formation and the synthesis of osteoclastogenic genes Acp5, Mmp9, Calcr and Ctsk. LTB4-MS inhibited differentiation of macrophages into an osteoclastic phenotype and cell activation under M-CSF and RANKL stimulus.

Leukotriene B4 loaded in microspheres regulate the expression of genes related to odontoblastic differentiation and biomineralization by dental pulp stem cells

Background

Leukotriene B₄ (LTB₄) is a potent lipid mediator that stimulate the immune response. Because dental pulp inflammation and dentin repair are intrinsically related responses, the aim of this research was to investigate the potential of LTB₄ in inducing differentiation of dental pulp stem cells.

Methods

Microspheres (MS) loaded with LTB₄ were prepared using an oil emulsion solvent extraction evaporation process and sterility, characterization, efficiency of LTB₄ encapsulation and in vitro LTB₄ release assay were investigated. Mouse dental pulp stem cells (OD-21) were stimulated with soluble LTB₄ or MS loaded with LTB₄ (0.01 and 0.1 μM). Cytotoxicity and cell viability was determined by lactate dehydrogenase and methylthiazol tetrazolium assays. Gene expression were measured by quantitative reverse transcription polymerase chain reaction after 3, 6, 24, 48 and 72 h. Mineralized nodule formation was assessed after 28 days of OD-21 cell stimulation with LTB₄ in mineralized media or not. Groups were compared using one-way ANOVA test followed by Dunnett’s post-test (α = 0.05).

Results

Treatment with LTB₄ or MS loaded with LTB₄ (0.01 and 0.1 µm-μM) were not cytotoxic to OD-21 cells. Treatment with LTB₄ modulated the expression of the Ibsp (integrin binding sialoprotein) and Runx2 (runt-related transcription factor 2) genes differently depending on the experimental period analyzed. Interestingly LTB₄ loaded in microspheres (0.1 μM) allowed long term dental pulp cell differentiation and biomineralization.

Conclusion

LTB₄, soluble or loaded in MS, were not cytotoxic and modulated the expression of the Ibsp and Runx2 genes in cultured OD-21 cells. When LTB₄ was incorporated into MS, odontoblast differentiation and mineralization was induced in long term culture.

COVID-19: Integrating the Complexity of Systemic and Pulmonary Immunopathology to Identify Biomarkers for Different Outcomes

In the last few months, the coronavirus disease 2019 (COVID-19) pandemic has affected millions of people worldwide and has provoked an exceptional effort from the scientific community to understand the disease. Clinical evidence suggests that severe COVID-19 is associated with both dysregulation of damage tolerance caused by pulmonary immunopathology and high viral load. In this review article, we describe and discuss clinical studies that show advances in the understanding of mild and severe illness and we highlight major points that are critical for improving the comprehension of different clinical outcomes. The understanding of pulmonary immunopathology will contribute to the identification of biomarkers in an attempt to classify mild, moderate, severe and critical COVID-19 illness. The interface of pulmonary immunopathology and the identification of biomarkers are critical for the development of new therapeutic strategies aimed to reduce the systemic and pulmonary hyperinflammation in severe COVID-19.

Eicosanoids in Skin Wound Healing

Wound healing is an important process in the human body to protect against external threats. A dysregulation at any stage of the wound healing process may result in the development of various intractable ulcers or excessive scar formation. Numerous factors such as growth factors, cytokines, and chemokines are involved in this process and play vital roles in tissue repair. Moreover, recent studies have demonstrated that lipid mediators derived from membrane fatty acids are also involved in the process of wound healing. Among these lipid mediators, we focus on eicosanoids such as prostaglandins, thromboxane, leukotrienes, and specialized pro-resolving mediators, which are produced during wound healing processes and play versatile roles in the process. This review article highlights the roles of eicosanoids on skin wound healing, especially focusing on the biosynthetic pathways and biological functions, i.e., inflammation, proliferation, migration, angiogenesis, remodeling, and scarring.

Antileishmanial and Immunomodulatory Effect of Babassu-Loaded PLGA Microparticles: A Useful Drug Target to Leishmania amazonensis Infection

The immunological and the anti-Leishmania amazonensis activity of babassu-loaded poly(lactic-co-glycolic acid) [PLGA] microparticles was evaluated. The anti-Leishmania activity was evaluated against promastigotes or amastigotes forms, in Balb/c macrophages. The size of the microparticles ranged from 3 to 6.4 μm, with a zeta potential of −25 mV and encapsulation efficiency of 48%. The anti-Leishmania activity of the PLGA microparticles loaded with the aqueous extract of babassu mesocarp (MMP) (IC₅₀) was 10-fold higher than that free extract (Meso). MMP exhibited overall bioavailability and was very effective in eliminating intracellular parasites. MMP also reduced ex vivo parasite infectivity probably by the increased production of nitric oxide, hydrogen peroxide, and TNF-α indicating the activation of M1 macrophages. The overexpression of TNF-α did not impair cell viability, suggesting antiapoptotic effects of MMP. In conclusion, babassu-loaded microparticles could be useful for drug targeting in the treatment of leishmaniasis, due to the immunomodulatory effect on macrophage polarization and the increased efficacy as an anti-Leishmania product after the microencapsulation. These findings are of great relevance since the development of new drugs for the treatment of neglected diseases is desirable, mainly if we consider the high morbidity and mortality rates of leishmaniasis worldwide.

Lipoxin A4 encapsulated in PLGA microparticles accelerates wound healing of skin ulcers

Lipoxin A₄ (LXA₄) is involved in the resolution of inflammation and wound healing; however, it is extremely unstable. Thus, to preserve its biological activities and confer stability, we encapsulated LXA₄ in poly-lactic-co-glycolic acid (PLGA) microparticles (LXA₄-MS) and assessed its application in treating dorsal rat skin lesions. Ulcers were sealed with fibrin adhesive and treated with either LXA₄-MS, unloaded microparticles (Un-MS), soluble LXA₄, or PBS/glue (vehicle). All groups were compared at 0, 2, 7, and 14 days post-lesions. Our results revealed that LXA₄-MS accelerated wound healing from day 7 and reduced initial ulcer diameters by 80%. Soluble LXA₄, Un-MS, or PBS closed wounds by 60%, 45%, and 39%, respectively. LXA₄-MS reduced IL-1β and TNF-α, but increased TGF-β, collagen deposition, and the number of blood vessels. Compared to other treatments, LXA₄-MS reduced inflammatory cell numbers, myeloperoxidase (MPO) concentration, and metalloproteinase-8 (MMP8) mRNA in scar tissue, indicating decreased neutrophil chemotaxis. In addition, LXA₄-MS treatment increased macrophages and IL-4, suggesting a positive impact on wound healing. Finally, we demonstrated that WRW4, a selective LXA₄ receptor (ALX) antagonist, reversed healing by 50%, indicating that LXA₄ must interact with ALX to induce wound healing. Our results show that LXA₄-MS could be used as a pharmaceutical formulation for the treatment of skin ulcers.

Control of silk microsphere formation using polyethylene glycol (PEG)

A one step, rapid method to prepare silk microspheres was developed, with particle size controlled by the addition of polyethylene glycol (PEG). PEG molecular weight (4.0K-20.0KDa) and concentration (20-50wt%), as well as silk concentration (5-20wt%), were key factors that determined particle sizes varying in a range of 1-100μm. Addition of methanol to the PEG-silk combinations increased the content of crystalline β-sheet in the silk microspheres. To track the distribution and degradation of silk microspheres in vivo, 3-mercaptopropionic acid (MPA)-coated CdTe quantum dots (QDs) were physically entrapped in the silk microspheres. QDs tightly bound to the β-sheet domains of silk via hydrophobic interactions, with over 96% of the loaded QDs remaining in the silk microspheres after exhaustive extraction. The fluorescence of QDs-incorporated silk microspheres less stable in cell culture medium than in phosphate buffer solution (PBS) and water. After subcutaneous injection in mice, microspheres prepared from 20% silk (approx. 30μm diameter particles) still fluoresced at 24h, while those prepared from 8% silk (approx. 4μm diameter particles) and free QDs were not detectable, reflecting the QDs quenching and particle size effect on microsphere clearance in vivo. The larger microspheres were more resistant to cell internalization and degradation. Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.

STATEMENT OF SIGNIFICANCE

The work is of significance to the biomaterial and controlled release society because it provides a new option for fabricating silk microspheres in one simple step of mixing silk and polyethylene glycol (PEG), with the size and properties of microspheres controllable by PEG molecular weight as well as PEG and silk concentrations. Although fabrication of silk microspheres have been reported previously using spray-drying, liposome-templating, polyvinyl alcohol (PVA) emulsification, etc., applications were hindered due to harsh conditions (temperature, solvents, etc.) and complicated procedures used as well as low yield and less controllable particle size (usually <10μm). Since PEG is an FDA-approved polymer, and silk is FDA approved for some medical devices, the methods developed in the present study will be useful in a variety of biomedical applications where simple, rapid and scalable preparation of silk microspheres is required.

Hyaluronidase-loaded PLGA microparticles as a new strategy for the treatment of pulmonary fibrosis

The aim of this work was to develop an innovative tool for the treatment of pulmonary fibrosis based on our previous findings, which demonstrated that intranasally administered soluble bovine hyaluronidase (HYAL) increases the numbers of mesenchymal (MSC)-like cells in the bronchoalveolar fluid (BALF) and thus reduces the bleomycin-induced fibrosis. To this end, we developed poly(D,L-lactide-co-glycolide) (PLGA) microparticles (MPs) loaded with HYAL (HYAL-MP) to preserve the enzyme's biological activity and to facilitate its delivery to the lung. Nonloaded MPs (Control-MPs) and HYAL-MPs were prepared using the emulsion and solvent evaporation methods and thoroughly characterized. The HYAL-MPs and Control-MPs exhibited an average diameter of 4.3±2.1 and 4.4±1.5 μm, respectively. The encapsulation efficiency of the HYAL-MPs was 68%, and encapsulation led to a reduced release rate. Additionally, the HYAL-MPs were efficiently phagocytosed by J-774.1 cells. Compared with the soluble HYAL, the HYAL-MPs increased the proportion of MSC-like cells in the BALF of C57BL6 mice 96 h after treatment. The efficacy of the HYAL-MPs was also tested in C57BL6 mice that were previously exposed to 4 U/kg of bleomycin to induce lung fibrosis. The results demonstrated that the HYAL-MPs reduced neutrophil recruitment after bleomycin treatment more effectively than did the soluble HYAL, whereas the Control-MPs did not exhibit any effect. The HYAL-MPs also reduced the bleomycin-induced fibrosis more efficiently, and 134% of the collagen deposition in the lung compared with the soluble HYAL and the Control-MPs. In summary, our data indicate that HYAL-MPs are an effective delivery system that could feasibly be used in the treatment of pulmonary fibrosis.

Prostaglandin D2-loaded microspheres effectively activate macrophage effector functions

Biodegradable lactic-co-glycolic acid (PLGA) microspheres (MS) improve the stability of biomolecules stability and allow enable their sustained release. Lipid mediators represent a strategy for improving host defense; however, most of these mediators, such as prostaglandin D2 (PGD2), have low water solubility and are unstable. The present study aimed to develop and characterize MS loaded with PGD2 (PGD2-MS) to obtain an innovative tool to activate macrophages. PGD2-MS were prepared using an oil-in-water emulsion solvent extraction-evaporation process, and the size, zeta potential, surface morphology and encapsulation efficiency were determined. It was also evaluated in vitro the phagocytic index, NF-κB activation, as well as nitric oxide and cytokine production by alveolar macrophages (AMs) in response to PGD2-MS. PGD2-MS were spherical with a diameter of 5.0±3.3 μm and regular surface, zeta potential of -13.4±5.6 mV, and 36% of encapsulation efficiency, with 16-26% release of entrapped PGD2 at 4 and 48 h, respectively. PGD2-MS were more efficiently internalized by AMs than unloaded-MS, and activated NF-κB more than free PGD2. Moreover, PGD2-MS stimulated the production of nitric oxide, TNF-α, IL-1β, and TGF-β, more than free PGD2, indicating that microencapsulation increased the activating effect of PGD2 on cells. In LPS-pre-treated AMs, PGD2-MS decreased the release of IL-6 but increased the production of nitric oxide and IL-1β. These results show that the morphological characteristics of PGD2-MS facilitated interaction with, and activation of phagocytic cells; moreover, PGD2-MS retained the biological activities of PGD2 to trigger effector mechanisms in AMs. It is suggested that PGD2-MS represent a strategy for therapeutic intervention in the lungs of immunocompromised subjects.

Biodegradable microparticles containing crotamine isolated from Crotalus durissus terrificus display antileishmanial activity in vitro

BACKGROUND/AIMS

To evaluate antileishmanial activity of crotamine, a toxin isolated from Crotalus durissus terrificus, in solution form and encapsulated in biodegradable microparticles in vitro.

METHODS

Particles were analyzed on-chip by surface plasmon resonance and characterized by testing their diameters, zeta potential and encapsulation rate. The viability of promastigotes as well as murine macrophages was assessed. Furthermore, the phagocytic index was determined for macrophages, and cell supernatants were collected for the determination of TNF-α levels. An infection assay using Leishmania amazonensis-infected macrophages was also conducted.

RESULTS

The diameters and zeta potential of control particles (1.35 μm; -12.3 mV) and of those containing crotamine (3.09 μm; -20.9 mV) were adequate for the assays conducted. Crotamine-loaded particles were better captured by macrophages than control particles (increase of 12% in the phagocytic index), leading to increased TNF-α levels (196 pg/ml), and they also induced a significant decrease in the numbers of amastigotes compared to infected macrophages only.

CONCLUSION

The approach presented here opens the possibility of working with safe concentrations of encapsulated toxins to reach antileishmanial effects.

Therapeutic potential of biodegradable microparticles containing Punica granatum L. (pomegranate) in murine model of asthma

OBJECTIVE AND DESIGN

Among the options for treatment of diseases affecting the respiratory system, especially asthma, drug delivering systems for intranasal application represent an important therapeutic approach at the site of inflammation. The present study aimed to evaluate the therapeutic effect of biodegradable microparticles formed by poly lactic-co-glycolic acid (PLGA) containing encapsulated pomegranate extract on a murine model of asthma.

MATERIAL

The extract was acquired from the leaves of P. granatum and characterized qualitatively by HPLC. A w/o/w emulsion solvent extraction-evaporation method was chosen to prepare the microparticles containing pomegranate encapsulated extract (MP).

TREATMENT

OVA-sensitized BALB/c mice were used as asthma model and treated with dexamethasone and P. granatum extract in solution form or encapsulated into microparticles.

RESULTS

MP were able to inhibit leukocytes' recruitment to bronchoalveolar fluid, especially, eosinophils, decreasing cytokines (IL-1β and IL-5) and protein levels in the lungs.

CONCLUSIONS

This approach can be used as an alternative/supplementary therapy based on the biological effects of P. granatum for managing inflammatory processes, especially those with pulmonary complications.

The uptake of PLGA micro or nanoparticles by macrophages provokes distinct in vitro inflammatory response

Biodegradable micro/nanoparticles generated from PLGA have recently attracted attention due to their clinically proven biocompatibility, especially for immunization purposes. These polymeric particulate delivery systems are able to present antigens and activate both humoral and cellular responses. Many studies have discussed the ideal size of these particles in contributing to the generation of the different types of immune response. However, these studies do not demonstrate the effect of micro or nanoparticles, without any encapsulated bioactive, on phagocytic cells after the uptake process. In this context, the aim of this study was to analyze the in vitro inflammatory behavior of J774 murine macrophages after particles' uptake, since nano/microparticles per se can differently activate phagocytic cells, using or not appropriate receptors, inducing distinct inflammatory responses. An o/w emulsion solvent extraction-evaporation method was chosen to prepare the particles. We determined their diameters, zeta potential and morphology. Fluorescent particles' uptake by J774 murine "macrophage-like" cells was also analyzed. To evaluate the in vitro inflammatory profile of these cells after micro or nanoparticles' uptake, we conducted NF-κB translocation assay by confocal microscopy and also determined the pro-inflammatory cytokines production provoked by the particles.

Leukotriene B4-loaded microspheres as a new approach to enhance antimicrobial responses in Histoplasma capsulatum-infected mice

Histoplasmosis is a pulmonary disease characterised by chronic granulomatous and suppurative inflammatory reactions caused by Histoplasma capsulatum. Regarding new therapies to control fungal infections, the aim of this study was to investigate whether pulmonary administration of leukotriene B(4) (LTB(4))-loaded microspheres (MS) could confer protection to 5-lipoxygenase knockout (5-LO(-/-)) mice infected by H. capsulatum. In this study, MS containing LTB(4) were administered intranasally to mice infected by H. capsulatum. On Day 14 after the infection, fungal recovery from the lungs and histology were evaluated and inflammatory cytokines were measured. Pulmonary administration of LTB(4)-loaded MS was able to reduce fungal recovery from infected lungs. Production of important inflammatory cytokines related to host defence was augmented following MS administration to the lungs. Lung histology also showed that infected mice presented a clear reduction in the fungal burden following the pulmonary release of LTB(4) from MS. Our study provides evidence that the proposed biodegradable microparticulate system, which can release LTB(4) to the lungs, can be employed as therapy, enhancing the antimicrobial activity of host cells during histoplasmosis.

Leukotriene B4-loaded microspheres: a new therapeutic strategy to modulate cell activation

Background

Leukotriene B₄ (LTB₄) is a potent inflammatory mediator that also stimulates the immune response. In addition, it promotes polymorphonuclear leukocyte phagocytosis, chemotaxis, chemokinesis and modulates cytokines release. Regarding chemical instability of the leukotriene molecule, in the present study we assessed the immunomodulatory activities conferred by LTB₄ released from microspheres (MS). A previous oil-in-water emulsion solvent extraction-evaporation method was chosen to prepare LTB₄-loaded MS.

Results

In the mice cremasteric microcirculation, intraescrotal injection of 0.1 ml of LTB₄-loaded MS provoked significant increases in leukocyte rolling flux, adhesion and emigration besides significant decreases in the leukocyte rolling velocity. LTB₄-loaded MS also increase peroxisome proliferator-activated receptor-α (PPARα) expression by murine peritoneal macrophages and stimulate them to generate nitrite levels. Monocyte chemoattractant protein-1 (MCP-1) and nitric oxide (NO) productions were also increased when human umbilical vein and artery endothelial cells (HUVECs and HUAECs, respectively) were stimulated with LTB₄-loaded MS.

Conclusion

LTB₄-loaded MS preserve the biological activity of the encapsulated mediator indicating their use as a new strategy to modulate cell activation, especially in the innate immune response.

Prostaglandin E(2)-loaded microspheres as strategy to inhibit phagocytosis and modulate inflammatory mediators release

PGE(2), an arachidonic acid metabolite produced by various type of cells regulates a broad range of physiological activities in the endocrine, cardiovascular, gastrointestinal, and immune systems, and is involved in maintaining the local homeostasis. In the immune system, PGE(2) is mainly produced by APCs and it can suppress the Th1-mediated immune responses. The aim of this study was to develop PGE(2)-loaded biodegradable MS that prolong and sustain the in vivo release of this mediator. An o/w emulsion solvent extraction-evaporation method was chosen to prepare the MS. We determined their diameters, evaluated the in vitro release of PGE(2), using enzyme immunoassay and MS uptake by peritoneal macrophages. To assess the preservation of biological activities of this mediator, we determined the effect of PGE(2) released from MS on LPS-induced TNF-alpha release by murine peritoneal macrophages. We also analyzed the effect of encapsulated PGE(2) on inflammatory mediators release from HUVECs. Finally, we studied the effect of PGE(2) released from biodegradable MS in sepsis animal model. The use of this formulation can provide an alternative strategy for treating infections, by modulating or inhibiting inflammatory responses, especially when they constitute an exacerbated profile.

Blockade of avidity and focal clustering of beta 2-integrin by cysteinyl leukotriene antagonism attenuates eosinophil adhesion

BACKGROUND

Cysteinyl leukotriene (cysLT) antagonism attenuates migration of eosinophils into airways during immune challenge in human subjects and animal models. The intracellular signaling mechanism by which this occurs has not been elucidated.

OBJECTIVE

We sought to determine the relative efficacy and mechanism by which 5-lipoxygenase (5-LO) inhibition and cysLT(1) receptor (cysLT(1)R) antagonism block beta(2)-integrin adhesion in isolated human eosinophils in vitro.

METHODS

Human blood eosinophils were isolated by means of immunomagnetic separation. Upregulation of CD11b expression, active conformation of CD11b, and focal clustering of beta(2)-integrin caused by IL-5, eotaxin-1 or leukotriene (LT) B(4) was assessed by means of flow cytometry and confocal microscopy. The effect and mechanism of cysLT(1)R or 5-LO blockade on these components of beta(2)-integrin adhesion were determined.

RESULTS

Montelukast, a cysLT(1)R antagonist, and AA861, a 5-LO enzyme inhibitor, blocked (1) avidity of beta(2)-integrin, (2) beta(2)-integrin-mediated adhesion to intercellular adhesion molecule 1, and (3) focal clustering of CD11b elicited by LTB(4). However, adhesion caused by either IL-5 or eotaxin-1 was not attenuated for eosinophils pretreated with either montelukast or AA861.

CONCLUSION

Our data demonstrate that (1) LTB(4) causes autocrine upregulation of adhesion through secretion of cysLTs, and (2) blockade of cysLT(1)R blocks the avidity and focal clustering of CD11b/CD18 for eosinophils activated by LTB(4) but not by IL-5 or eotaxin-1.

CLINICAL IMPLICATIONS

Unlike cysLT-induced adhesion, adhesion caused by IL-5 or eotaxin-1 is not regulated through the cysLT(1)R, suggesting that cysLTs have specific but limited potential to upregulate eosinophil adhesion.