Secretory Leucoprotease Inhibitor (SLPI) Promotes Survival during Acute Pseudomonas aeruginosa Infection by Suppression of Inflammation Rather Than Microbial Killing.

Secretory leucoprotease inhibitor (SLPI) has multifaceted functions, including inhibition of protease activity, antimicrobial functions, and anti-inflammatory properties. In this study, we show that SLPI plays a role in controlling pulmonary Pseudomonas aeruginosa infection. Mice lacking SLPI were highly susceptible to P. aeruginosa infection, however there was no difference in bacterial burden. Utilising a model of P. aeruginosa LPS-induced lung inflammation, human recombinant SLPI (hrSLPI) administered intraperitoneally suppressed the recruitment of inflammatory cells in the bronchoalveolar lavage fluid (BALF) and resulted in reduced BALF and serum levels of inflammatory cytokines and chemokines. This anti-inflammatory effect of hrSLPI was similarly demonstrated in a systemic inflammation model induced by intraperitoneal injection of LPS from various bacteria or lipoteichoic acid, highlighting the broad anti-inflammatory properties of hrSLPI. Moreover, in bone-marrow-derived macrophages, hrSLPI reduced LPS-induced phosphorylation of p-IkB-α, p-IKK-α/ß, p-P38, demonstrating that the anti-inflammatory effect of hrSLPI was due to the inhibition of the NFκB and MAPK pathways. In conclusion, administration of hrSLPI attenuates excessive inflammatory responses and is therefore, a promising strategy to target inflammatory diseases such as acute respiratory distress syndrome or sepsis and could potentially be used to augment antibiotic treatment.

Human serum albumin nanoparticles as nanovector carriers for proteins: Application to the antibacterial proteins "neutrophil elastase" and "secretory leukocyte protease inhibitor".

The use of proteins and defined amino acid sequences as therapeutic drugs have gained a certain interest in the past decade. However, protein encapsulation within protein nanoparticles was never endeavored. For this reason, human serum albumin (HSA) nanoparticles were prepared by nanoprecipitation method. The process was optimized, and particles were obtained with a size of 120 nm and zeta potential of -25 mV. Neutrophil elastase (NE) and secretory leukocyte protease inhibitor (SLPI) were encapsulated separately within HSA nanoparticles. Gel electrophoresis and western blot studies demonstrate the successful encapsulation and the stability of the particles. On the other hand, enzymatic assays show that encapsulated NE lost its proteolytic activity, whereas encapsulated SLPI maintained its inhibitory property. In addition, the antibacterial studies showed that both formulations were able to drastically reduce bacterial growth of Pseudomonas aeruginosa. This work showed the possibility of using both NE and SLPI as anti-bacterial agents through encapsulation within HSA nanoparticles.

Thymic stromal lymphopoetin-induced expression of the endogenous inhibitory enzyme SLPI mediates recovery from colonic inflammation.

Thymic stromal lymphopoetin (TSLP) influences numerous immune functions, including those in the colonic mucosa. Here we report that TSLP-deficient (Tslp(-/-)) mice did not exhibit increased inflammation during dextran sodium sulfate (DSS)-induced colitis but failed to recover from disease, resulting in death. Increased localized neutrophil elastase (NE) activity during overt inflammation was observed in Tslp(-/-) mice and was paralleled by reduced expression of an endogenous inhibitor, secretory leukocyte peptidase inhibitor (SLPI). Pharmacological inhibition of NE or treatment with rSLPI reduced DSS-induced mortality in Tslp(-/-) mice. Signaling through TSLPR on nonhematopoietic cells was sufficient for recovery from DSS-induced colitis. Expression of the receptor occurred on intestinal epithelial cells (IEC), with stimulation inducing SLPI expression. Therefore, TSLP is critical in mediating mucosal healing after insult and functions in a nonredundant capacity that is independent of restraining T helper 1 (Th1) and Th17 cell cytokine production.

The effect of liposome encapsulation on the pharmacokinetics of recombinant secretory leukocyte protease inhibitor (rSLPI) therapy after local delivery to a guinea pig asthma model.

PURPOSE: Inhaled recombinant Secretory Leukocyte Protease Inhibitor (rSLPI) has shown potential for treatment of inflammatory lung conditions. Rapid inactivation of rSLPI by cathepsin L (Cat L) and rapid clearance from the lungs have limited clinical efficacy. Encapsulation of rSLPI within 1,2-Dioleoyl-sn-Glycero-3-[Phospho-L-Serine]:Cholesterol liposomes (DOPS-rSLPI) protects rSLPI against Cat L inactivation in vitro. We aimed to determine the effect of liposomes on rSLPI pharmacokinetics and activity in vitro and after local delivery to the airways in vivo. METHODS: Transport of DOPS-rSLPI and free-rSLPI across a polarised air-liquid epithelial monolayer was measured. An asthma guinea pig model was administered either DOPS-rSLPI liposomes or free-rSLPI by intratracheal instillation. RESULTS: Apparent permeability (P(app)) of free-rSLPI was significantly higher at 4.9 x 10⁻6 cm/s than for DOPS-rSLPI, P(app) of 2.05 x 10⁻7 cm/s, confirmed by in vivo studies. Plasma rSLPI concentrations were highest in free-rSLPI-treated animals compared with those treated with DOPS-rSLPI; there also appeared to be a trend for higher intracellular rSLPI content in animals dosed with DOPS-rSLPI compared to free-rSLPI. Eosinophil influx was recorded as a measure of inflammation. Pre-dosing with either free-rSLPI or DOPS-rSLPI prevented inflammatory response to antigen challenge to levels comparable to control animals. CONCLUSION: Encapsulation of rSLPI in DOPS:Chol liposomes improves stability, reduces clearance and increases residence time in the lungs after local delivery.

A dry powder formulation of liposome-encapsulated recombinant secretory leukocyte protease inhibitor (rSLPI) for inhalation: preparation and characterisation.

Inhaled recombinant secretory leukocyte protease inhibitor (rSLPI) has shown potential for the treatment of inflammatory lung conditions. Rapid inactivation of rSLPI by cathepsin L (Cat L) and rapid clearance from the lungs has limited clinical efficacy to date. Previous studies by us have shown that encapsulation of rSLPI within1,2-dioleoyl-sn-glycero-3-[phospho-L-serine]/cholesterol (DOPS/Chol) liposomes protects rSLPI against Cat L inactivation in vitro. Liquid DOPS-rSLPI preparations were found to be unstable upon long-term storage and nebulisation. The aim of this study was therefore to develop a method of manufacture for preparing DOPS-rSLPI liposomes as a dry powder for inhalation. DOPS-rSLPI dry powders were lyophilised and subsequently micronised with a novel micronisation aid. The effects of formulation and processing on rSLPI stability, activity, and uniformity of content within the powders were characterised. Using D-mannitol as the micronisation aid, dry powder particles in the inhalable size range (<5 µm) were prepared. By optimising process parameters, up to 54% of rSLPI was recovered after micronisation, of which there was no significant loss in anti-neutrophil elastase activity and no detectable evidence of protein degradation. Aerosolisation was achieved using a dry powder inhaler, and mass median aerodynamic diameter (MMAD) was evaluated after collection in a cascade impactor. Aerosolisation of the DOPS-rSLPI dry powder yielded 38% emitted dose, with 2.44 µm MMAD. When challenged with Cat L post-aerosolisation, DOPS-rSLPI dry powder was significantly better at retaining a protective function against Cat L-induced rSLPI inactivation compared to the aqueous DOPS-rSLPI liposome dispersion and was also more stable under storage.

Delivery of rSLPI in a liposomal carrier for inhalation provides protection against cathepsin L degradation.

Secretory leukocyte protease inhibitor (SLPI) is an endogenous serine protease inhibitor that protects the lungs from excessive tissue damage caused by leukocyte proteases released during inflammation. Recombinant SLPI (rSLPI) has shown potential as a treatment for inflammatory lung conditions. To date, its clinical application has been limited by rapid enzymatic cleavage by cathepsins and rapid clearance from the lungs after inhalation. In this study, rSLPI was encapsulated in 1,2-Dioleoyl-sn-Glycero-3-[Phospho-L-Serine] : Cholesterol (DOPS : Chol) liposomes for inhalation. Incubation of rSLPI with cathepsin L leads to complete loss of activity while encapsulation of rSLPI in DOPS : Chol liposomes retained 92.6% of its activity after challenge with cathepsin L. rSLPI-loaded liposomes were aerosolized efficiently using a standard nebulizer with a minimal loss of activity and stability. This formulation was biocompatible and encapsulation did not appear to diminish access to intracellular sites of action in in vitro cell culture studies. Liposome encapsulation of rSLPI therefore improves stability and potentially reduces the level and frequency of dosing required for therapeutic effect after inhalation.

Antileukoproteinase protects against hepatic inflammation, but not apoptosis in the response of D-galactosamine-sensitized mice to lipopolysaccharide.

BACKGROUND AND PURPOSE: There is major evidence for the strong bi-directional interrelation of parenchymal cell apoptosis and leukocyte accumulation and inflammation in acute liver injury. Therefore, the aim of this in vivo study was to investigate the anti-apoptotic and anti-inflammatory potential of antileukoproteinase (ALP) in a murine model of acute liver failure. EXPERIMENTAL APPROACH: C57BL/6J mice were given galactosamine (D-GalN) and E. coli lipopolysaccharide (LPS) followed by administration of saline or ALP. Besides survival rate, hepatic tissue damage and inflammatory response were analyzed by intravital fluorescence microscopy 6 hours after treatment. In addition, immunohistochemical analysis of NFkappaB-p65 and hepatocellular apoptosis, plasma levels of AST/ALT, TNF-alpha and IL-10 were determined. KEY RESULTS: Administration of D-GalN/LPS provoked hepatic damage, including marked leukocyte recruitment and microvascular perfusion failure, as well as hepatocellular apoptosis and enzyme release. NFkappaB-p65 became increasingly detectable in hepatocellular nuclei, accompanied by a rise of TNF-alpha and IL-10 plasma levels. ALP markedly reduced intrahepatic leukocyte accumulation, nuclear translocation of NFkappaB and plasma levels of TNF-alpha and IL-10. Moreover, liver enzyme levels indicated the absence of necrotic parenchymal cell death. In contrast, ALP failed to block both apoptosis and caspase-3 levels and the mortality rate of ALP-treated animals was comparable to that of saline-treated mice. CONCLUSIONS AND IMPLICATIONS: ALP could effectively prevent D-GalN/LPS-associated intrahepatic inflammatory responses by inhibition of NFkappaB activity, but not apoptosis-driven mortality. Thus, a protease-inactivating approach such as application of ALP seems to be inadequate in damaged liver where apoptosis represents the predominant mode of cell death.