Comparative Effects of Recombinant Acid Sphingomyelinase Administration by Different Routes in Niemann-Pick Disease Mice

Blood-brain barrier delivery for lysosomal storage disorders with IgG-lysosomal enzyme fusion proteins

The majority of lysosomal storage diseases affect the brain. Treatment of the brain with intravenous enzyme replacement therapy is not successful, because the recombinant lysosomal enzymes do not cross the blood-brain barrier (BBB). Biologic drugs, including lysosomal enzymes, can be re-engineered for BBB delivery as IgG-enzyme fusion proteins. The IgG domain of the fusion protein is a monoclonal antibody directed against an endogenous receptor-mediated transporter at the BBB, such as the insulin receptor or the transferrin receptor. This receptor transports the IgG across the BBB, in parallel with the endogenous receptor ligand, and the IgG acts as a molecular Trojan horse to ferry into brain the lysosomal enzyme genetically fused to the IgG. The IgG-enzyme fusion protein is bi-functional and retains both high affinity binding for the BBB receptor, and high lysosomal enzyme activity. IgG-lysosomal enzymes are presently in clinical trials for treatment of the brain in Mucopolysaccharidosis.

Targeting drug delivery in the vascular system: Focus on endothelium

The bloodstream is the main transporting pathway for drug delivery systems (DDS) from the site of administration to the intended site of action. In many cases, components of the vascular system represent therapeutic targets. Endothelial cells, which line the luminal surface of the vasculature, play a tripartite role of the key target, barrier, or victim of nanomedicines in the bloodstream. Circulating DDS may accumulate in the vascular areas of interest and in off-target areas via mechanisms bypassing specific molecular recognition, but using ligands of specific vascular determinant molecules enables a degree of precision, efficacy, and specificity of delivery unattainable by non-affinity DDS. Three decades of research efforts have focused on specific vascular targeting, which have yielded a multitude of DDS, many of which are currently undergoing a translational phase of development for biomedical applications, including interventions in the cardiovascular, pulmonary, and central nervous systems, regulation of endothelial functions, host defense, and permeation of vascular barriers. We discuss the design of endothelial-targeted nanocarriers, factors underlying their interactions with cells and tissues, and describe examples of their investigational use in models of acute vascular inflammation with an eye on translational challenges.

Enzyme replacement therapy for Farber disease: Proof-of-concept studies in cells and mice

A series of studies were carried out in Farber disease (OMIM #228000) cells and mice to evaluate the feasibility of enzyme replacement therapy (ERT) for this disorder. Media from Chinese hamster ovary (CHO) cells overexpressing human recombinant acid ceramidase (rhAC) was used to treat fibroblasts from a Farber disease patient, leading to significantly reduced ceramide. We also found that chondrocytes from Farber disease mice had a markedly abnormal chondrogenic phenotype, and this was corrected by rhAC as well. Acute dosing of rhAC in Farber mice confirmed the enzyme's bioactivity in vivo, and showed that it could be safely administered at doses up to 50 mg/kg. These studies also revealed little or no re-accumulation of ceramide in tissues for at least 7 days after enzyme administration. Once weekly administration of rhAC moderately improved survival of the mice, which could be enhanced by starting enzyme administration at an earlier age (3 days vs. 3 weeks). Repeat administration of the enzyme also led to normalization of spleen size, significantly reduced plasma levels of monocyte chemoattractant protein 1 (MCP-1), reduced infiltration of macrophages into liver and spleen, and significantly reduced ceramide and sphingosine in tissues. Overall, we conclude that ERT should be further developed for this debilitating and life-threatening disorder.

Targeted endothelial nanomedicine for common acute pathological conditions

Endothelium, a thin monolayer of specialized cells lining the lumen of blood vessels is the key regulatory interface between blood and tissues. Endothelial abnormalities are implicated in many diseases, including common acute conditions with high morbidity and mortality lacking therapy, in part because drugs and drug carriers have no natural endothelial affinity. Precise endothelial drug delivery may improve management of these conditions. Using ligands of molecules exposed to the bloodstream on the endothelial surface enables design of diverse targeted endothelial nanomedicine agents. Target molecules and binding epitopes must be accessible to drug carriers, carriers must be free of harmful effects, and targeting should provide desirable sub-cellular addressing of the drug cargo. The roster of current candidate target molecules for endothelial nanomedicine includes peptidases and other enzymes, cell adhesion molecules and integrins, localized in different domains of the endothelial plasmalemma and differentially distributed throughout the vasculature. Endowing carriers with an affinity to specific endothelial epitopes enables an unprecedented level of precision of control of drug delivery: binding to selected endothelial cell phenotypes, cellular addressing and duration of therapeutic effects. Features of nanocarrier design such as choice of epitope and ligand control delivery and effect of targeted endothelial nanomedicine agents. Pathological factors modulate endothelial targeting and uptake of nanocarriers. Selection of optimal binding sites and design features of nanocarriers are key controllable factors that can be iteratively engineered based on their performance from in vitro to pre-clinical in vivo experimental models. Targeted endothelial nanomedicine agents provide antioxidant, anti-inflammatory and other therapeutic effects unattainable by non-targeted counterparts in animal models of common acute severe human disease conditions. The results of animal studies provide the basis for the challenging translation endothelial nanomedicine into the clinical domain.

Targeted Drug Delivery to Endothelial Adhesion Molecules

Endothelial cells represent important targets for therapeutic and diagnostic interventions in many cardiovascular, pulmonary, neurological, inflammatory, and metabolic diseases. Targeted delivery of drugs (especially potent and labile biotherapeutics that require specific subcellular addressing) and imaging probes to endothelium holds promise to improve management of these maladies. In order to achieve this goal, drug cargoes or their carriers including liposomes and polymeric nanoparticles are chemically conjugated or fused using recombinant techniques with affinity ligands of endothelial surface molecules. Cell adhesion molecules, constitutively expressed on the endothelial surface and exposed on the surface of pathologically altered endothelium—selectins, VCAM-1, PECAM-1, and ICAM-1—represent good determinants for such a delivery. In particular, PECAM-1 and ICAM-1 meet criteria of accessibility, safety, and relevance to the (patho)physiological context of treatment of inflammation, ischemia, and thrombosis and offer a unique combination of targeting options including surface anchoring as well as intra- and transcellular targeting, modulated by parameters of the design of drug delivery system and local biological factors including flow and endothelial phenotype. This review includes analysis of these factors and examples of targeting selected classes of therapeutics showing promising results in animal studies, supporting translational potential of these interventions.

Pulmonary delivery of recombinant acid sphingomyelinase improves clearance of lysosomal sphingomyelin from the lungs of a murine model of Niemann-Pick disease

Systemic administration of recombinant acid sphingomyelinase (rhASM) into ASM deficient mice (ASMKO) results in hydrolysis of the abnormal storage of sphingomyelin in lysosomes of the liver, spleen and lung. However, the efficiency with which the substrate is cleared from the lung, particularly the alveolar macrophages, appears to be lower than from the other visceral tissues. To determine if delivery of rhASM into the air spaces of the lung could enhance clearance of pulmonary sphingomyelin, enzyme was administered to ASMKO mice by intranasal instillation. Treatment resulted in a significant and dose-dependent reduction in sphingomyelin levels in the lung. Concomitant with this reduction in substrate levels was a decrease in the amounts of the pro-inflammatory cytokine, MIP-1alpha, in the bronchoalveolar lavage fluids and an improvement in lung pathology. Maximal reduction of lung sphingomyelin levels was observed at 7 days post-treatment. However, reaccumulation of the substrate was noted starting at day 14 suggesting that repeated treatments will be necessary to effect a sustained reduction in sphingomyelin levels. In addition to reducing the storage abnormality in the lung, intranasal delivery of rhASM also resulted in clearance of the substrate from the liver and spleen. Hence, pulmonary administration of rhASM may represent an alternative route of delivery to address the visceral pathology associated with ASM deficiency.

Les sphingolipides : vecteurs d’agents pathogènes et cause de maladies génétiques

Sphingolipids are present in all eukaryotic cells and share a sphingoid base : sphingosine. They were first discovered in 1884 and for a long time they were thought to participate to membrane structure only. Recently it has been established that they are mainly located in particular areas of the membrane called rafts which are signalling platforms. It has also been demonstrated that sphingolipids are receptors and second messengers. They play a crucial role in cellular functioning and are necessary to maintenance and developing of living organisms. However due to their receptor properties, they are also gateway for penetration of pathogenic agents such as virus (Ebola, HIV) or toxins (botulinium, tetanus). These agents first bind to glycosphingolipids or proteins mainly located in rafts. The complex so formed is required for the crossing of the membrane by the pathogenic agent. Sphingolipids metabolism is regulated by numerous enzymes. A failure in the activity of one of them induces an accumulation of sphingolipids known as sphingolipidoses. These are genetic diseases having severe consequences for the survival of the organism. The precise mechanisms of the sphingolipidoses are still mainly unknown which explains why few therapeutic strategies are available. These particular properties of lipids rafts and sphingolipids explain why a growing number of studies in the medical and scientific fields are devoted to them.