Reduced phagocytosis of colloidal carriers using soluble CD47

Suppressing or Enhancing Macrophage Engulfment through the Use of CD47 and Related Peptides

Foreign particles and microbes are rapidly cleared by macrophages in vivo, although many key aspects of uptake mechanisms remain unclear. "Self" cells express CD47 which functions as an anti-phagocytic ligand for SIRPα on macrophages, particularly when pro-phagocytic ligands such as antibodies are displayed in parallel. Here, we review CD47 and related "Self" peptides as modulators of macrophage uptake. Nanoparticles conjugated with either CD47 or peptides derived from its SIRPα binding site can suppress phagocytic uptake by macrophages in vitro and in vivo, with similar findings for CD47-displaying viruses. Drugs, dyes, and genes as payloads thus show increased delivery to targeted cells. On the other hand, CD47 expression by cancer cells enables such cells to evade macrophages and immune surveillance. This has motivated development of soluble antagonists to CD47-SIRPα, ranging from blocking antibodies in the clinic to synthetic peptides in preclinical models. CD47 and peptides are thus emerging as dual-use phagocytosis modulators against diseases.

Less phagocytosis of viral vectors by tethering with CD47 ectodomain

Many viral vectors, which are effective when administrated in situ, lack efficacy when delivered intravenously. The key reason for this is the rapid clearance of the viruses from the blood circulation via the immune system before they reach target sites. Therefore, avoiding their clearance by the immune system is essential. In this study, lentiviral vectors were tethered with the ectodomain of self-marker protein CD47 to suppress phagocytosis via interacting with SIRPα on the outer membrane of macrophage cells. CD47 ectodomain and core-streptavidin fusion gene (CD47ED-coreSA) was constructed into pET-30a(+) plasmid and transformed into Lemo21 (DE3) competent E. coli cells. The expressed CD47ED-coreSA chimeric protein was purified by cobalt-nitrilotriacetate affinity column and characterized by SDS-PAGE and western blot. The purified chimeric protein was anchored on biotinylated lentivirus via biotin-streptavidin binding. The CD47ED-capped lentiviruses encoding GFP were used to infect J774A.1 macrophage cells to assess the impact on phagocytosis. Our results showed that the overexpressed CD47ED-coreSA chimeric protein was purified and bound on the surface of biotinylated lentivirus which was confirmed via immunoblotting assay. The process to produce biotinylated lentivirus did not affect native viral infectivity. It was shown that the level of GFP expression in J774A.1 macrophages transduced with CD47ED-lentiviruses was threefold lower in comparison to control lentiviruses, indicating an antiphagocytic effect triggered by the interaction of CD47ED and SIRPα. Through the test of blocking antibodies against CD47ED and/or SIRPα, it was confirmed that the phagocytosis inhibition was mediated through the CD47ED-SIRPα axis signaling. In conclusion, surface immobilization of CD47ED on lentiviral vectors inhibits their phagocytosis by macrophages. The chimeric protein of CD47 ectodomain and core-streptavidin is effective in mediating the surface binding and endowing the lentiviral nanoparticles with the antiphagocytic property.

The regulation of CD47-SIRPα signaling axis by microRNAs in combination with conventional cytotoxic drugs together with the help of nano-delivery: a choice for therapy?

CD47, a member of the immunoglobulin superfamily, is an important "Don't Eat-Me" signal in phagocytosis process [clearance of apoptotic cells] as well as a regulator of the adaptive immune response. The lower level of CD47 on the cell surface leads to the clearance of apoptotic cells. Dysregulation of CD47 plays a critical role in the development of disorders, particularly cancers. In cancers, recognition of CD47 overexpression on the surface of cancer cells by its receptor, SIRPα on the phagocytic cells, inhibits phagocytosis of cancer cells. Thus, blocking of CD47-SIRPα signaling axis might be as a promising therapeutic target, which promotes phagocytosis of cancer cells, antigen-presenting cell function as well as adaptive T cell-mediated anti-cancer immunity. In this respect, it has been reported that CD47 expression can be regulated by microRNAs (miRNAs). MiRNAs can regulate phagocytosis of macrophages apoptotic process, drug resistance, relapse of disease, radio-sensitivity, and suppress cell proliferation, migration, and invasion through post-transcriptional regulation of CD47-SIRPα signaling axis. Moreover, the regulation of CD47 expression by miRNAs and combination with conventional cytotoxic drugs together with the help of nano-delivery represent a valuable opportunity for effective cancer treatment. In this review, we review studies that evaluate the role of miRNAs in the regulation of CD47-SIRPα in disorders to achieve a novel preventive, diagnostic, and therapeutic strategy.Please confirm if the author names are presented accurately and in the correct sequence (given name, middle name/initial, family name). Also, kindly confirm the details in the metadata are correct. Confirmed.Journal standard instruction requires a structured abstract; however, none was provided. Please supply an Abstract with subsections..Not confirmed. This is a review article. According to submission guidelines: "The abstract should be presented divided into subheadings (unless it is a mini or full review article)". Kindly check and confirm whether the corresponding authors and mail ID are correctly identified. Confirmed.

In vivo blockade of mononuclear phagocyte system with solid nanoparticles: Efficiency and affecting factors

Smart nanomaterials, contrast nanoparticles and drug nanocarriers of advanced targeting architecture were designed for various biomedical applications. Most of such agents demonstrate poor pharmacokinetics in vivo due to rapid elimination from the bloodstream by cells of the mononuclear phagocyte system (MPS). One of the promising methods to prolong blood circulation of the nanoparticles without their modification is MPS blockade. The method temporarily decreases macrophage endocytosis in response to uptake of a low-toxic non-functional material. The effect of different factors on the efficiency of macrophage blockade in vivo induced by solid nanomaterials has been studied here. Those include: blocker nanoparticle size, ζ-potential, surface coating, dose, mice strain, presence of tumor or inflammation. We found that the blocker particle coating type had the strongest effect on MPS blockade efficiency, which allowed to prolong functional particle blood circulation half-life 18 times. The mechanisms capable of regulation of the MPS blockade have been demonstrated, which can promote application of this phenomenon in medicine for improving delivery of diagnostic and therapeutic nanomaterials.

Efficient Expression of Soluble Recombinant Protein Fused with Core-Streptavidin in Bacterial Strain with T7 Expression System

The limited amount of fusion protein transported into cytosol milieu has made it challenging to obtain a sufficient amount for further applications. To avoid the laborious and expensive task, T7 promoter-driving pET-30a(+) coding for chimeric gene of thymidine phosphorylase and core streptavidin as a model system was constructed and transformed into a variety of E. coli strains with T7 expression system. Our results demonstrated that the pET-30a(+)-TP-coreSA/Lemo21(DE3) system is able to provide efficient expression of soluble TP-coreSA fusion protein for purification. Moreover, the eluted TP-coreSA fusion protein tethered on biotinylated A549 carcinoma cells could effectively eliminate these malignant cells after administrating prodrug 5′-DFUR.

Effect of soluble cleavage products of important receptors/ligands on efferocytosis: Their role in inflammatory, autoimmune and cardiovascular disease

Efferocytosis, the clearance of apoptotic cells (ACs), is a physiologic, multifaceted and dynamic process and a fundamental mechanism for the preservation of tissue homeostasis by avoiding unwanted inflammation and autoimmune responses through special phagocytic receptors. Defective efferocytosis is associated with several disease states, including cardiovascular disease and impaired immune surveillance, as occurs in cancer and autoimmune disease. A major cause of defective efferocytosis is non-functionality of surface receptors on either the phagocytic cells or the ACs, such as TAM family tyrosine kinase, which turns to a soluble form by cleavage/shedding or alternative splicing. Recently, soluble forms have featured prominently as potential biomarkers, indicative of prognosis and enabling targeted therapy using several commonly employed drugs and inhibitors, such as bleomycin, dexamethasone, statins and some matrix metalloproteinase inhibitors such as TAPI-1 and BB3103. Importantly, to design drug carriers with enhanced circulatory durability, the adaptation of soluble forms of physiological receptors/ligands has been purported. Research has shown that soluble forms are more effective than antibody forms in enabling targeted treatment of certain conditions, such as autoimmune diseases. In this review, we sought to summarize the current knowledge of these soluble products, how they are generated, their interactions, roles, and their potential use as biomarkers in prognosis and treatment related to inflammatory, cardiovascular, and autoimmune diseases.

Block Copolymer Micelles in Nanomedicine Applications

Polymeric micelles are demonstrating high potential as nanomedicines capable of controlling the distribution and function of loaded bioactive agents in the body, effectively overcoming biological barriers, and various formulations are engaged in intensive preclinical and clinical testing. This Review focuses on polymeric micelles assembled through multimolecular interactions between block copolymers and the loaded drugs, proteins, or nucleic acids as translationable nanomedicines. The aspects involved in the design of successful micellar carriers are described in detail on the basis of the type of polymer/payload interaction, as well as the interplay of micelles with the biological interface, emphasizing on the chemistry and engineering of the block copolymers. By shaping these features, polymeric micelles have been propitious for delivering a wide range of therapeutics through effective sensing of targets in the body and adjustment of their properties in response to particular stimuli, modulating the activity of the loaded drugs at the targeted sites, even at the subcellular level. Finally, the future perspectives and imminent challenges for polymeric micelles as nanomedicines are discussed, anticipating to spur further innovations.

The Diverse Range of Possible Cell Membrane Interactions with Substrates: Drug Delivery, Interfaces and Mobility

The cell membrane has gained significant attention as a platform for the development of bio-inspired nanodevices due to its immune-evasive functionalities and copious bio-analogs. This review will examine several uses of cell membranes such as (i) therapeutic delivery carriers with or without substrates (i.e., nanoparticles and artificial polymers) that have enhanced efficiency regarding copious cargo loading and controlled release, (ii) exploiting nano-bio interfaces in membrane-coated particles from the macro- to the nanoscales, which would help resolve the biomedical issues involved in biological interfacing in the body, and (iii) its effects on the mobility of bio-moieties such as lipids and/or proteins in cell membranes, as discussed from a biophysical perspective. We anticipate that this review will influence both the development of novel anti-phagocytic delivery cargo and address biophysical problems in soft and complex cell membrane.

Co-coating of receptor-targeted drug nanocarriers with anti-phagocytic moieties enhances specific tissue uptake versus non-specific phagocytic clearance

Nanocarriers (NCs) help improve the performance of therapeutics, but their removal by phagocytes in the liver, spleen, tissues, etc. diminishes this potential. Although NC functionalization with polyethylene glycol (PEG) lowers interaction with phagocytes, it also reduces interactions with tissue cells. Coating NCs with CD47, a protein expressed by body cells to avoid phagocytic removal, offers an alternative. Previous studies showed that coating CD47 on non-targeted NCs reduces phagocytosis, but whether this alters binding and endocytosis of actively-targeted NCs remains unknown. To evaluate this, we used polymer NCs targeted to ICAM-1, a receptor overexpressed in many diseases. Co-coating of CD47 on anti-ICAM NCs reduced macrophage phagocytosis by ∼50% for up to 24 h, while increasing endothelial-cell targeting by ∼87% over control anti-ICAM/IgG NCs. Anti-ICAM/CD47 NCs were endocytosed via the CAM-mediated pathway with efficiency similar (0.99-fold) to anti-ICAM/IgG NCs. Comparable outcomes were observed for NCs targeted to PECAM-1 or transferrin receptor, suggesting broad applicability. When injected in mice, anti-ICAM/CD47 NCs reduced liver and spleen uptake by ∼30-50% and increased lung targeting by ∼2-fold (∼10-fold over IgG NCs). Therefore, co-coating NCs with CD47 and targeting moieties reduces macrophage phagocytosis and improves targeted uptake. This strategy may significantly improve the efficacy of targeted drug NCs.

Peptide-based strategies for enhanced cell uptake, transcellular transport, and circulation: Mechanisms and challenges

Peptides are emerging as a new tool in drug and gene delivery. Peptide-drug conjugates and peptide-modified drug delivery systems provide new opportunities to avoid macrophage recognition and subsequent phagocytosis, cross endothelial and epithelial barriers, and enter the cytoplasm of target cells. Peptides are relatively small, low-cost, and are stable in a wide range of biological conditions. In this review, we summarize recent work in designing peptides to enhance penetration of biological barriers, increase cell uptake, and avoid the immune system. We highlight recent successes and contradictory results, and outline common emerging concepts and design rules. The development of sequence-structure-function relationships and standard protocols for benchmarking will be a key to progress in the field.

Purification of CD47-streptavidin fusion protein from bacterial lysate using biotin-agarose affinity chromatography

CD47 is a widely expressed transmembrane glycoprotein that modulates the activity of a plethora of immune cells via its extracellular domain. Therefore, CD47 plays important roles in the regulation of immune responses and may serve as targets for the development of immunotherapeutic agents. To make sure CD47 functionality is intact under the process of protein conjugation, CD47-streptavidin fusion protein was expressed and purified because it can easily bind to biotin-tagged materials via the unique biotin-streptavidin affinity. In this study, gene sequences of CD47 extracellular domain (CD47ECD) and core streptavidin (coreSA) with a total 834 bp were inserted into pET20b plasmid to construct recombinant plasmid encoding CD47-SA fusion gene. After bacteria transformation, the CD47-SA fusion protein was expressed by isopropyl-β-d-thiogalactopyranoside (IPTG) induction. The collected bacteria lysate was loaded on biotinylated agarose to proceed the purification of CD47-SA fusion protein. Due to the unexpected high affinity between biotin and coreSA, standard washing and elution approaches (e.g., varying pH, using biotin, and applying guanidine hydrochloride) reported for biotin-streptavidin affinity chromatography were not able to separate the target fusion protein. Instead, using low concentration of the non-ionic detergent Triton X-100 followed with alkaline buffer could efficiently weaken the binding between biotin and coreSA, thereby eluting out CD47-SA fusion protein from the biotin agarose column. The purified CD47-SA fusion protein was further characterized by molecular biology methods and its antiphagocytic functionality was confirmed by the phagocytosis assay. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:949-958, 2016.

Nanobiotechnology for the Therapeutic Targeting of Cancer Cells in Blood

During metastasis, circulating tumor cells migrate away from a primary tumor via the blood circulation to form secondary tumors in distant organs. Mounting evidence from clinical observations indicates that the number of circulating tumor cells (CTCs) in the blood correlates with the progression of solid tumors before and during chemotherapy. Beyond the well-established role of CTCs as a fluid biopsy, however, the field of targeting CTCs for the prevention or reduction of metastases has just emerged. Conventional cancer therapeutics have a relatively short circulation time in the blood which may render the killing of CTCs inefficient due to reduced exposure of CTCs to drugs. Nevertheless, over the past few decades, the development of nanoparticles and nanoformulations to improve the half-life and release profile of drugs in circulation has rejuvenated certain traditional medicines in the emerging field of CTC neutralization. This review focuses on how the principles of nanomedicine may be applied to target CTCs. Moreover, inspired by the interactions between CTCs and host cells in the blood circulation, novel biomimetic approaches for targeted drug delivery are presented.

Liposome-like Nanostructures for Drug Delivery

Liposomes are a class of well-established drug carriers that have found numerous therapeutic applications. The success of liposomes, together with recent advancements in nanotechnology, has motivated the development of various novel liposome-like nanostructures with improved drug delivery performance. These nanostructures can be categorized into five major varieties, namely: (1) polymer-stabilized liposomes, (2) nanoparticle-stabilized liposomes, (3) core-shell lipid-polymer hybrid nanoparticles, (4) natural membrane-derived vesicles, and (5) natural membrane coated nanoparticles. They have received significant attention and have become popular drug delivery platforms. Herein, we discuss the unique strengths of these liposome-like platforms in drug delivery, with a particular emphasis on how liposome-inspired novel designs have led to improved therapeutic efficacy, and review recent progress made by each platform in advancing healthcare.

Engineering antiphagocytic biomimetic drug carriers

Drug-delivery carriers have the potential to not only treat but also diagnose many diseases; however, they still lack the complexity of natural-particulate systems. Cell-based therapies using tumor-targeting T cells and tumor-homing mesenchymal stem cells have given researchers a means to exploit the characteristics exhibited by innate-biological entities. Similarly, immune evasion by pathogens has inspired the development of natural polymers to cloak drug carriers. The 'marker-of-self' CD47 protein, which is found ubiquitously on mammalian cell surfaces, has been used for evading phagocyte clearance of drug carriers. This review will focus on the recent progress of drug carriers co-opting the tricks that cells in nature use to hide safely under the radar of the body's innate immune system.

Surface functionalization of gold nanoparticles with red blood cell membranes

Gold nanoparticles are enclosed in cellular membranes derived from natural red blood cells (RBCs) by a top-down approach. The gold nanoparticles exhibit a complete membrane surface layer and biological characteristics of the source cells. The combination of inorganic gold nanoparticles with biological membranes is a compelling way to develop biomimetic gold nanostructures for future applications, such as those requiring evasion of the immune system.

'Marker-of-self' functionalization of nanoscale particles through a top-down cellular membrane coating approach

We investigate the 'marker-of-self' functionalization of nanoparticles through coating of natural RBC membranes. The membrane translocation approach is shown to be highly efficient and bestows nanoparticles with correctly oriented and functional immunomodulatory proteins such as CD47 at equivalent density to natural RBCs.

Small molecule-gold nanorod conjugates selectively target and induce macrophage cytotoxicity towards breast cancer cells

Gold nanoparticles are known to activate anti-tumor potential in macrophage immune cells; however, the subsequent effects of these cells on others nearby are poorly understood. A novel gold-nanoparticle conjugate that selectively targets and induces cytotoxic activity of tumor-associated macrophages towards breast cancer cells in co-culture is synthesized. These constructs are promising new tools for studying fundamental biological interactions with nanoscale materials and candidates for emerging macrophage-mediated delivery applications.

Erythrocyte-inspired delivery systems

Herein recent progress in developing red blood cell (RBC)-inspired delivery systems is reviewed, with an emphasis on how our growing understanding of fundamental biological properties of natural RBCs has been applied in the design and engineering of these delivery systems. Specifically, progress achieved in developing carrier RBCs, a class of delivery vehicles engineered by directly loading natural RBCs with therapeutic agents, will be reviewed. Then alternative approaches to engineering synthetic vehicles through mimicking the mechanobiological and chemico-biological properties of natural RBCs will be considered. The synthesis and application of RBC membrane-derived vesicles, of which the natural RBC membranes are collected and directly utilized to prepare drug carriers, will then be discussed. Finally, a recent approach in engineering RBC membrane-camouflaged nanoparticle systems that combine advantages of natural RBCs and synthetic biomaterials will be highlighted. These developments indicate that RBC-inspired delivery systems will result in next-generation nanomedicine with extensive medical applications.

MicroRNA profiling of multiple sclerosis lesions identifies modulators of the regulatory protein CD47

We established microRNA profiles from active and inactive multiple sclerosis lesions. Using laser capture microdissection from multiple sclerosis lesions to pool single cells and in vitro cultures, we assigned differentially expressed microRNA to specific cell types. Astrocytes contained all 10 microRNA that were most strongly upregulated in active multiple sclerosis lesions, including microRNA-155, which is known to modulate immune responses in different ways but so far had not been assigned to central nervous system resident cells. MicroRNA-155 was expressed in human astrocytes in situ, and further induced with cytokines in human astrocytes in vitro. This was confirmed with astrocyte cultures from microRNA-155-|-lacZ mice. We matched microRNA upregulated in phagocytically active multiple sclerosis lesions with downregulated protein coding transcripts. This converged on CD47, which functions as a 'don't eat me' signal inhibiting macrophage activity. Three microRNA upregulated in active multiple sclerosis lesions (microRNA-34a, microRNA-155 and microRNA-326) targeted the 3'-untranslated region of CD47 in reporter assays, with microRNA-155 even at two distinct sites. Our findings suggest that microRNA dysregulated in multiple sclerosis lesions reduce CD47 in brain resident cells, releasing macrophages from inhibitory control, thereby promoting phagocytosis of myelin. This mechanism may have broad implications for microRNA-regulated macrophage activation in inflammatory diseases.

Perfluorohexane-loaded macrophages as a novel ultrasound contrast agent: a feasibility study

PURPOSE

We investigated in vitro the potential of macrophages to act as targeted vehicle for ultrasound molecular imaging.

PROCEDURES

Murine bone marrow-derived macrophages (BMM), incubated for 3 h with different concentrations of perfluorohexane (PFH) emulsions, were monitored by microscopy, flow cytometry, and ultrasound. Effects of PFH loading on BMM adhesion molecule (PSGL-1, VLA-4, Mac-1, LFA-1) expression were analyzed by flow cytometry. Static adhesion of PFH loaded BMM to unstimulated and TNF-alpha stimulated b.End5 endothelial cells was assessed by microscopy.

RESULTS

Incubation of BMM with PFH emulsions resulted in dose-dependent uptake and increased echogenicity (max. 17 dB). Flow cytometry analyses revealed no down-regulation related to PFH loading of BMM adhesion molecule expression. Endothelial adhesion remained functional, even after 24 h, although PFH loading dose-dependently attenuated static adhesion.

CONCLUSION

PFH loaded BMM may potentially serve as ultrasound contrast agent for noninvasive detection of atherogenic hotspots in arteries.

CD47 is expressed at normal levels in patients with autoimmune haemolytic anaemia and/or immune thrombocytopenia

CD47 deficiency results in lethal autoimmune haemolytic anaemia (AIHA) and mild spontaneous thrombocytopenia in non-obese diabetic mice. It is unknown whether CD47 has an impact on AIHA of the warm type or autoimmune thrombocytopenia (ITP) in humans. Healthy blood donors (n= 11), patients with AIHA (n= 13), patients with ITP (n= 18) and one patient with Rh(null) phenotype were investigated. CD47 expression on red blood cells (RBC), platelets, granulocytes and lymphocytes and in plasma was determined by quantitative flow cytometry. All types of blood cells studied were found to carry CD47. Although CD47 expression on Rh(null) RBCs was decreased, there was no significant difference between CD47 expression on RBCs of healthy blood donors and on those of patients with AIHA or ITP. Similarly, CD47 was detectable in the plasma of the studied subjects. No evidence for a pathogenetic role of CD47 in autoimmune haemolysis or thrombocytopenia in humans could be demonstrated.