[Show abstract][Hide abstract] ABSTRACT: Primary Familial Brain Calcification (PFBC), a neurodegenerative disease characterized by progressive pericapillary calcifications, has recently been linked to heterozygous mutations in PDGFB and PDGFRB genes. Here, we functionally analyzed several of these mutations in vitro. All six analyzed PDGFB mutations led to complete loss of PDGF-B function either through abolished protein synthesis or through defective binding and/or stimulation of PDGF-Rβ. The three analyzed PDGFRB mutations had more diverse consequences. Whereas PDGF-Rβ autophosphorylation was almost totally abolished in the PDGFRB L658P mutation, the two sporadic PDGFRB mutations R987W and E1071V caused reductions in protein levels and specific changes in the intensity and kinetics of PLCγ activation, respectively. Since at least some of the PDGFB mutations were predicted to act through haploinsufficiency, we explored the consequences of reduced Pdgfb or Pdgfrb transcript and protein levels in mice. Heterozygous Pdgfb or Pdgfrb knockouts, as well as double Pdgfb+/-;Pdgfrb+/- mice did not develop brain calcification, nor did Pdgfrbredeye/redeye mice, which show a 90% reduction of PDGFRβ protein levels. In contrast, Pdgfbret/ret mice, which have altered tissue distribution of PDGF-B protein due to loss of a proteoglycan binding motif, developed brain calcifications. We also determined pericyte coverage in calcification-prone and non-calcification-prone brain regions in Pdgfbret/ret mice. Surprisingly and contrary to our hypothesis, we found that the calcification-prone brain regions in Pdgfbret/ret mice model had a higher pericyte coverage and a more intact blood-brain barrier (BBB) compared to non-calcification-prone brain regions. While our findings provide clear evidence that loss-of-function mutations in PDGFB or PDGFRB cause PFBC, they also demonstrate species differences in the threshold levels of PDGF-B/PDGF-Rβ signaling that protect against small-vessel calcification in the brain. They further implicate region-specific susceptibility factor(s) in PFBC pathogenesis that are distinct from pericyte and BBB deficiency.
[Show abstract][Hide abstract] ABSTRACT: Despite its known expression in both the vascular endothelium and the lung epithelium, until recently the physiological role of the adhesion receptor Gpr116/ADGRF5 has remained elusive. We generated a new mouse model of constitutive Gpr116 inactivation, with a large genetic deletion encompassing exon 4 to exon 21 of the Gpr116 gene. This model allowed us to confirm recent results defining Gpr116 as necessary regulator of surfactant homeostasis. The loss of Gpr116 provokes an early accumulation of surfactant in the lungs, followed by a massive infiltration of macrophages, and eventually progresses into an emphysema-like pathology. Further analysis of this knockout model revealed cerebral vascular leakage, beginning at around 1.5 months of age. Additionally, endothelial-specific deletion of Gpr116 resulted in a significant increase of the brain vascular leakage. Mice devoid of Gpr116 developed an anatomically normal and largely functional vascular network, surprisingly exhibited an attenuated pathological retinal vascular response in a model of oxygen-induced retinopathy. These data suggest that Gpr116 modulates endothelial properties, a previously unappreciated function despite the pan-vascular expression of this receptor. Our results support the key pulmonary function of Gpr116 and describe a new role in the central nervous system vasculature.
[Show abstract][Hide abstract] ABSTRACT: Calcifications in the basal ganglia are a common incidental finding and are sometimes inherited as an autosomal dominant trait (idiopathic basal ganglia calcification (IBGC)). Recently, mutations in the PDGFRB gene coding for the platelet-derived growth factor receptor β (PDGF-Rβ) were linked to IBGC. Here we identify six families of different ancestry with nonsense and missense mutations in the gene encoding PDGF-B, the main ligand for PDGF-Rβ. We also show that mice carrying hypomorphic Pdgfb alleles develop brain calcifications that show age-related expansion. The occurrence of these calcium depositions depends on the loss of endothelial PDGF-B and correlates with the degree of pericyte and blood-brain barrier deficiency. Thus, our data present a clear link between Pdgfb mutations and brain calcifications in mice, as well as between PDGFB mutations and IBGC in humans.
[Show abstract][Hide abstract] ABSTRACT: Cell-penetrating peptides (CPPs) are short transport peptides with a well-established ability for delivery of bioactive cargoes inside the cells both, in vitro and in vivo. CPPs enter unselectively in a wide variety of cell lines, this is a desirable property for most in vitro applications, however, in vivo e.g. in tumor models, specific targeted accumulation is required. In order to achieve tumor targeting, a known CPP, YTA4, was modified by prolonging it C-terminally with mainly negatively charged amino acids. Additionally, a matrix metalloproteinase-2 cleavage site was introduced between the CPP and the inactivating sequence. This new peptide, named NoPe, is an inactive pro-form of YTA4. It can be selectively cleaved and thereby activated by MMPs. We have conjugated an imaging agent, fluoresceinyl carboxylic acid, and a cytostatic agent methotrexate, to this activable pro-form. NoPe activation was demonstrated in vitro by recombinant MMP-2 cleavage and the cleavage of the attenuating sequence was abolished with MMP-2 specific inhibitor. Furthermore, the fluoresceinyl-NoPe is selectively accumulated in the tumor tissue in MDA-MB-231 tumor bearing mice after intravenous injection. Thus, this strategy proves to be successful for in vivo tumor imaging.
Full-text · Article · Dec 2012 · International Journal of Peptide Research and Therapeutics
[Show abstract][Hide abstract] ABSTRACT: The neurovascular unit (NVU), consisting of endothelial cells, basement membrane, pericytes, astrocytes and microglial cells, couples local neuronal function to local cerebral blood flow and regulates transport of blood-borne molecules across the blood-brain barrier (BBB). The building blocks and the phenotype of the NVU are well-established but the intercellular signaling between the different components remains elusive. A better understanding of the cellular interactions and signaling within the NVU is critical for the development of efficient therapeutics for the treatment of a variety of brain diseases, such as brain cancer, stroke, neuroinflammation and neurodegeneration. This review gives an overview about the current in vivo knowledge of the NVU and the communication between its different cellular constituents. We also discuss the usefulness of various model organisms for studies of the brain vasculature.
No preview · Article · Aug 2011 · Current pharmaceutical design
[Show abstract][Hide abstract] ABSTRACT: "Once the regulation of brain endothelial transcytosis is understood at the molecular level, it should be possible to exploit these mechanisms as targets for facilitated CNS drug delivery".
No preview · Article · Apr 2011 · Therapeutic delivery
[Show abstract][Hide abstract] ABSTRACT: Finding suitable nonviral delivery vehicles for nucleic acid-based therapeutics is a landmark goal in gene therapy. Cell-penetrating peptides (CPPs) are one class of delivery vectors that has been exploited for this purpose. However, since CPPs use endocytosis to enter cells, a large fraction of peptides remain trapped in endosomes. We have previously reported that stearylation of amphipathic CPPs, such as transportan 10 (TP10), dramatically increases transfection of oligonucleotides in vitro partially by promoting endosomal escape. Therefore, we aimed to evaluate whether stearyl-TP10 could be used for the delivery of plasmids as well. Our results demonstrate that stearyl-TP10 forms stable nanoparticles with plasmids that efficiently enter different cell-types in a ubiquitous manner, including primary cells, resulting in significantly higher gene expression levels than when using stearyl-Arg9 or unmodified CPPs. In fact, the transfection efficacy of stearyl-TP10 almost reached the levels of Lipofectamine 2000 (LF2000), however, without any of the observed lipofection-associated toxicities. Most importantly, stearyl-TP10/plasmid nanoparticles are nonimmunogenic, mediate efficient gene delivery in vivo, when administrated intramuscularly (i.m.) or intradermally (i.d.) without any associated toxicity in mice.
Full-text · Article · Feb 2011 · Molecular Therapy
[Show abstract][Hide abstract] ABSTRACT: Cell-penetrating peptides (CPPs) are a promising group of delivery vectors for various therapeutic agents but their application is often hampered by poor stability in the presence of serum. Different strategies to improve peptide stability have been exploited, one of them being "retro-inversion" (RI) of natural peptides. With this approach the stability of CPPs has been increased, thereby making them more efficient transporters. Several RI-CPPs were here assessed and compared to the corresponding parent peptides in different cell-lines. Surprisingly, treatment of cells with these peptides induced trypsin insensitivity and rapid severe toxicity in contrast to L-peptides. This was measured as reduced metabolic activity and condensed cell nuclei, in parity with the apoptosis inducing agent staurosporine. Furthermore, effects on mitochondrial network, focal adhesions, actin cytoskeleton and caspase-3 activation were analyzed and adverse effects were evident at 20 μM peptide concentration within 4 h while parent L-peptides had negligible effects. To our knowledge this is the first time RI peptides are reported to cause cellular toxicity, displayed by decreased metabolic activity, morphological changes and induction of apoptosis. Considering the wide range of research areas that involves the use of RI-peptides, this finding is of major importance and needs to be taken under consideration in applications of RI-peptides.
Full-text · Article · Nov 2010 · Biochimica et Biophysica Acta
[Show abstract][Hide abstract] ABSTRACT: The blood-brain barrier (BBB) consists of specific physical barriers, enzymes and transporters, which together maintain the necessary extracellular environment of the central nervous system (CNS). The main physical barrier is found in the CNS endothelial cell, and depends on continuous complexes of tight junctions combined with reduced vesicular transport. Other possible constituents of the BBB include extracellular matrix, astrocytes and pericytes, but the relative contribution of these different components to the BBB remains largely unknown. Here we demonstrate a direct role of pericytes at the BBB in vivo. Using a set of adult viable pericyte-deficient mouse mutants we show that pericyte deficiency increases the permeability of the BBB to water and a range of low-molecular-mass and high-molecular-mass tracers. The increased permeability occurs by endothelial transcytosis, a process that is rapidly arrested by the drug imatinib. Furthermore, we show that pericytes function at the BBB in at least two ways: by regulating BBB-specific gene expression patterns in endothelial cells, and by inducing polarization of astrocyte end-feet surrounding CNS blood vessels. Our results indicate a novel and critical role for pericytes in the integration of endothelial and astrocyte functions at the neurovascular unit, and in the regulation of the BBB.
[Show abstract][Hide abstract] ABSTRACT: Short nucleic acids targeting biologically important RNAs and plasmids have been shown to be promising future therapeutics; however, their hydrophilic nature greatly limits their utility in clinics and therefore efficient delivery vectors are greatly needed. Cell-penetrating peptides (CPPs) are relatively short amphipathic and/or cationic peptides that are able to transport various biologically active molecules inside mammalian cells, both in vitro and in vivo, in a seemingly non-toxic fashion. Although CPPs have proved to be appealing drug delivery vehicles, their major limitation in nucleic acid delivery is that most of the internalized peptide-cargo is entrapped in endosomal compartments following endocytosis and the bioavailability is therefore severely reduced. Several groups are working towards overcoming this obstacle and this review highlights the evidence that by introducing chemical modification in CPPs, the bioavailability of delivered nucleic acids increases significantly.
No preview · Article · Nov 2009 · Expert Opinion on Drug Delivery
[Show abstract][Hide abstract] ABSTRACT: Aberrations in splicing patterns play a significant role in several diseases, and splice correction, together with other forms of gene regulation, is consequently an emerging therapeutic target. In order to achieve successful oligonucleotide transfection, efficient delivery vectors are generally necessary. In this study we present one such vector, the chemically modified cell-penetrating peptide (CPP) TP10, for efficient delivery of a splice-correcting 2'-OMe RNA oligonucleotide. Utilizing a functional splice correction assay, we assessed the transfection efficiency of non-covalent complexes of oligonucleotides and stearylated or cysteamidated CPPs. Stearylation of the CPPs Arg9 and penetratin, as well as cysteamidation of MPG and TP10, did not improve transfection, whereas the presence of an N-terminal stearyl group on TP10 improved delivery efficiency remarkably compared to the unmodified peptide. The splice correction levels observed with stearyl-TP10 are in fact in parity with the effects seen with the commercially available transfection agent Lipofectamine 2000. However, the inherent toxicity associated with cationic lipid-based transfections can be completely eliminated when using the stearylated TP10, making this vector highly promising for non-covalent delivery of negatively charged oligonucleotides.
Full-text · Article · Mar 2009 · Journal of Controlled Release
[Show abstract][Hide abstract] ABSTRACT: The major drawbacks with conventional cancer chemotherapy are the lack of satisfactory specificity towards tumor cells and
poor antitumor activity. In order to improve these characteristics, chemotherapeutic drugs can be conjugated to targeting
moieties e.g. to peptides with the ability to recognize cancer cells. We have previously reported that combining a tumor homing
peptide with a cell-penetrating peptide yields a chimeric peptide with tumor cell specificity that can carry cargo molecules
inside the cells. In the present study, we have used a linear breast tumor homing peptide, CREKA, in conjunction with a cell-penetrating
peptide, pVEC. This new chimeric peptide, CREKA–pVEC, is more convenient to synthesize and moreover it is better in translocating cargo molecules inside cancer cells as compared
to previously published PEGA–pVEC peptide. This study demonstrates that CREKA–pVEC is a suitable vehicle for targeted intracellular delivery of a DNA alkylating agent, chlorambucil, as the chlorambucil–peptide
conjugate was substantially better at killing cancer cells invitro than the anticancer drug alone.
No preview · Article · Feb 2009 · International Journal of Peptide Research and Therapeutics
[Show abstract][Hide abstract] ABSTRACT: Chemotherapy is often limited by toxicity to normal cells. Therefore, an ideal anticancer drug should discriminate between normal tissue and tumors. This would require a target receptor molecule mostly present in tumors. The cyclic peptide cCPGPEGAGC (PEGA) is a homing peptide that has previously been shown to accumulate in breast tumor tissue in mice. PEGA peptide does not cross the plasma membrane per se; however, when attached to the cell-penetrating peptide pVEC, the conjugate is taken up by different breast cancer cells in vitro. Additionally, the homing capacity of the PEGA- pVEC is conserved in vivo, where the conjugate mainly accumulates in blood vessels in breast tumor tissue and, consequently is taken up. Furthermore, we show that the efficacy of the anticancer drug, chlorambucil, is increased more than 4 times when the drug is conjugated to the PEGA- pVEC chimeric peptide. These data demonstrate that combining a homing sequence with a cell-penetrating sequence yields a peptide that combines the desirable properties of the parent peptides. Such peptides may be useful in diagnostics and delivery of therapeutic agents to an intracellular location in a specific tumor target tissue.
Full-text · Article · Feb 2008 · Bioconjugate Chemistry
[Show abstract][Hide abstract] ABSTRACT: The tumor suppressor p14ARF is widely deregulated in many types of cancers and is believed to function as a failsafe mechanism, inhibiting proliferation and inducing apoptosis as cellular response to a high oncogene load. We have found that a 22-amino-acid-long peptide derived from the N-terminal part of p14ARF, denoted ARF(1-22), which has previously been shown to mimic the function of p14ARF, has cell-penetrating properties. This peptide is internalized to the same extent as the cell-penetrating peptide (CPP) TP10 and dose-dependently decreases proliferation in MCF-7 and MDA MB 231 cells. Uptake of the ARF(1-22) peptide is associated with low membrane disturbance, measured by deoxyglucose and lactate dehydrogenase (LDH) leakage, as compared to its scrambled peptide. Also, flow cytometric analysis of annexin V/propidium iodide (PI) binding and Hoechst staining of nuclei suggest that ARF(1-22) induces apoptosis, whereas scrambled or inverted peptide sequences have no effect. The ARF(1-22) peptide mainly translocates cells through endocytosis, and is found intact inside cells for at least 3 hours. To our knowledge, this is the first time a CPP having pro-apoptopic activity has been designed from a protein.
No preview · Article · Feb 2008 · Molecular Therapy
[Show abstract][Hide abstract] ABSTRACT: High molecular weight biomolecules are becoming more and more important in the development of new therapeutic drugs. However, the hydrophilic nature of such molecules creates a major limitation for their application--poor penetration through biological membranes. In 1994, a new class of peptides--cell-penetrating peptides (CPPs)--was discovered. CPPs seem to greatly facilitate the delivery of hydrophilic macromolecules over the plasma membrane, both in vitro and in vivo, and show promise for therapeutic purposes. One such example--suppressor of cytokine signalling 3 protein--was shown to act as an effective inhibitor of acute inflammation in vivo owing to its successful delivery by CPPs.
No preview · Article · Nov 2006 · Current Opinion in Pharmacology
[Show abstract][Hide abstract] ABSTRACT: Cells are protected from the surrounding environment by plasma membrane which is impenetrable for most hydrophilic molecules. In the last 10 years cell-penetrating peptides (CPPs) have been discovered and developed. CPPs enter mammalian cells and carry cargo molecules over the plasma membrane with a molecular weight several times their own. Known transformation methods for plant cells have relatively low efficiency and require improvement. The possibility to use CPPs as potential delivery vectors for internalisation in plant cells has been studied in the present work. We analyse and compare the uptake of the fluorescein-labeled CPPs, transportan, TP10, penetratin and pVEC in Bowes human melanoma cells and Nicotiana tabacum cultivar (cv.) SR-1 protoplasts (plant cells without cell wall). We study the internalisation efficiency of CPPs with fluorescence microscopy, spectrofluorometry and fluorescence-activated cell sorter (FACS). All methods indicate, for the first time, that these CPPs can internalise into N. tabacum cv. SR-1 protoplasts. Transportan has the highest uptake efficacy among the studied peptides, both in mammalian cells and plant protoplast. The internalisation of CPPs by plant protoplasts may open up a new effective method for transfection in plants.
Full-text · Article · Jun 2005 · Biochimica et Biophysica Acta