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Biomedical subjects

Andreas Zimmer

Publications and source records attributed to Andreas Zimmer.

At least 19 recordsLinked to original sources
PubMed2006

Involvement of neuronal cannabinoid receptor CB1 in regulation of bone mass and bone remodeling.

The CB1 cannabinoid receptor has been implicated in the regulation of bone remodeling and bone mass. A high bone mass (HBM) phenotype was reported in CB1-null mice generated on a CD1 background (CD1(CB1-/-) mice). By contrast, our preliminary studies in cb1-/- mice, backcrossed to C57BL/6J mice (C57(CB1-/-) mice), revealed low bone mass (LBM). We therefore analyzed CB1 expression in bone and compared the skeletons of sexually mature C57(CB1-/-) and CD1(CB1-/-) mice in the same experimental setting. CB1 mRNA is weakly expressed in osteoclasts and immunoreactive CB1 is present in sympathetic neurons, close to osteoblasts. In addition to their LBM, male and female C57(CB1-/-) mice exhibit decreased bone formation rate and increased osteoclast number. The skeletal phenotype of the CD1(CB1-/-) mice shows a gender disparity. Female mice have normal trabecular bone with a slight cortical expansion, whereas male CD1(CB1-/-) animals display an HBM phenotype. We were surprised to find that bone formation and resorption are within normal limits. These findings, at least the consistent set of data obtained in the C57(CB1-/-) line, suggest an important role for CB1 signaling in the regulation of bone remodeling and bone mass. Because sympathetic CB1 signaling inhibits norepinephrine (NE) release in peripheral tissues, part of the endocannabinoid activity in bone may be attributed to the regulation of NE release from sympathetic nerve fibers. Several phenotypic discrepancies have been reported between C57(CB1-/-) and CD1(CB1-/-) mice that could result from genetic differences between the background strains. Unraveling these differences can provide useful information on the physiologic functional milieu of CB1 in bone.

Adrenergic Fibers↗
PubMed2006

Locus ceruleus degeneration promotes Alzheimer pathogenesis in amyloid precursor protein 23 transgenic mice.

Locus ceruleus (LC) degeneration and loss of cortical noradrenergic innervation occur early in Alzheimer's disease (AD). Although this has been known for several decades, the contribution of LC degeneration to AD pathogenesis remains unclear. We induced LC degeneration with N-(2-chloroethyl)-N-ethyl-bromo-benzylamine (dsp4) in amyloid precursor protein 23 (APP23) transgenic mice with a low amyloid load. Then 6 months later the LC projection areas showed a robust elevation of glial inflammation along with augmented amyloid plaque deposits. Moreover, neurodegeneration and neuronal loss significantly increased. Importantly, the paraventricular thalamus, a nonprojection area, remained unaffected. Radial arm maze and social partner recognition tests revealed increased memory deficits while high-resolution magnetic resonance imaging-guided micro-positron emission tomography demonstrated reduced cerebral glucose metabolism, disturbed neuronal integrity, and attenuated acetylcholinesterase activity. Nontransgenic mice with LC degeneration were devoid of these alterations. Our data demonstrate that the degeneration of LC affects morphology, metabolism, and function of amyloid plaque-containing higher brain regions in APP23 mice. We postulate that LC degeneration substantially contributes to AD development.

Alzheimer Disease↗
PubMed2006

Peripheral cannabinoid receptor, CB2, regulates bone mass.

The endogenous cannabinoids bind to and activate two G protein-coupled receptors, the predominantly central cannabinoid receptor type 1 (CB1) and peripheral cannabinoid receptor type 2 (CB2). Whereas CB1 mediates the cannabinoid psychotropic, analgesic, and orectic effects, CB2 has been implicated recently in the regulation of liver fibrosis and atherosclerosis. Here we show that CB2-deficient mice have a markedly accelerated age-related trabecular bone loss and cortical expansion, although cortical thickness remains unaltered. These changes are reminiscent of human osteoporosis and may result from differential regulation of trabecular and cortical bone remodeling. The CB2(-/-) phenotype is also characterized by increased activity of trabecular osteoblasts (bone-forming cells), increased osteoclast (the bone-resorbing cell) number, and a markedly decreased number of diaphyseal osteoblast precursors. CB2 is expressed in osteoblasts, osteocytes, and osteoclasts. A CB2-specific agonist that does not have any psychotropic effects enhances endocortical osteoblast number and activity and restrains trabecular osteoclastogenesis, apparently by inhibiting proliferation of osteoclast precursors and receptor activator of NF-kappaB ligand expression in bone marrow-derived osteoblasts/stromal cells. The same agonist attenuates ovariectomy-induced bone loss and markedly stimulates cortical thickness through the respective suppression of osteoclast number and stimulation of endocortical bone formation. These results demonstrate that the endocannabinoid system is essential for the maintenance of normal bone mass by osteoblastic and osteoclastic CB2 signaling. Hence, CB2 offers a molecular target for the diagnosis and treatment of osteoporosis, the most prevalent degenerative disease in developed countries.

Animals↗
PubMed2006

Immunostimulatory properties of CpG-oligonucleotides are enhanced by the use of protamine nanoparticles.

The aim of this paper was to investigate if the immunostimulatory effects of CpG-oligonucleotides (CpG-ODN) can be enhanced by the use of biodegradable protamine nanoparticles (proticles). We analyzed size, surface charge, and morphology of protamine nanoparticles containing CpG-ODN with photon correlation spectroscopy and transmission electron microscopy. Immunostimulatory effects of these nanoparticles on B cells, plasmacytoid dendritic cells (PDC), peripheral blood mononuclear cells, and whole blood were studied. Cytokine production, activation of the cells in terms of upregulation of surface molecules and uptake of nanoparticles were examined. We found that the use of protamine nanoparticles significantly increased (20-fold) CpG-ODN mediated interferon (IFN)-alpha production of PDC. ODN uptake in PDC was only marginally enhanced. CpG-ODN mediated IP-10 production in whole blood was strongly enhanced by the use of nanoparticles. Apart from a slight increase in CpG-ODN-induced interleukin (IL)-6 production in B cells, other parameters like the CpG-mediated activation of B cells and PDC as well as tumor necrosis factor (TNF)-alpha production of PDC remained largely unchanged. The use of control ODN indicated that the protamine nanoparticles themselves have no immunostimulatory properties. These results strongly support the use of particulate delivery systems like biodegradable protamine nanoparticles for the development of CpG-ODN-based therapeutics.

Adjuvants, Immunologic↗
PubMed2005

Visceral, inflammatory and neuropathic pain in glycine receptor alpha 3-deficient mice.

The alpha3-subunit of strychnine-sensitive glycine receptors is an important modulator of the pain-sensitizing effects of spinal prostaglandin prostaglandin E(2). Mice deficient for alpha3-subunit of strychnine-sensitive glycine receptors lack the prostaglandin E(2)-induced inhibition of glycinergic neurotransmission and recover faster from inflammation-induced hyperalgesia. It, however, remains unclear whether alpha3-subunit of strychnine-sensitive glycine receptors plays a role in other pain models involving prostaglandin synthesis, such as chemically induced pain or neuropathic pain. In this paper, we show a reduction of acetic acid-induced writhing responses in the absence of alpha3-subunit of strychnine-sensitive glycine receptors, but no changes in formalin-induced pain. Furthermore, alpha3-subunit of strychnine-sensitive glycine receptors-deficient mice develop normal thermal hyperalgesia and tactile allodynia. Thus, alpha3-subunit of strychnine-sensitive glycine receptors is involved in the modulation of moderate inflammatory acetic acid-induced pain responses, but neither in formalin-induced pain nor in neuropathic pain.

Acetic Acid↗
PubMed2005

Involvement of kappa/dynorphin system in WIN 55,212-2 self-administration in mice.

Self-administration procedures have not yet provided evidence that freely moving mice can reliably acquire and maintain an operant behavior to self-administer cannabinoid agonists. The aim of the present work was to establish a model of cannabinoid operant intravenous self-administration in freely moving mice given the relevance of this species for the use of genetically modified animals. In addition, the possible involvement of the kappa/dynorphin system in cannabinoid self-administration was evaluated by using pro-dynorphin knockout mice. Outbred CD1 wild-type mice as well as pro-dynorphin knockout and wild-type mice were trained to self-administer the cannabinoid receptor agonist WIN 55,212-2 under an FR1 schedule of reinforcement. Two cannabinoid training doses (6.25 and 12.5 microg/kg/infusion) were used in the acquisition studies in outbred mice. Animals acquired a reliable operant responding to self-administer WIN 55,212-2 (12.5 microg/kg/infusion), but required as many as 15 sessions to attain this behavior. Interestingly, when a previous injection of WIN 55,212-2 (0.1 mg/kg, i.p.) was administered in the home-cage 24 h before the first session, mice acquired operant responding for cannabinoid self-administration by the fourth session. When the kappa-opioid agonist antagonist nor-binaltorphimine (5 mg/kg s.c.) was administered 4 h before the first session, the time required to acquire a reliable cannabinoid self-administration was also significantly reduced. Finally, a shift to the left in the dose-intake curve to self-administer WIN 55,212-2 was observed in pro-dynorphin knockout mice when compared to wild-type mice. These results indicate that the activation of the kappa/dynorphin opioid system after WIN 55,212-2 administration could counteract cannabinoid rewarding effects.

Animals↗
PubMed2005

Cannabinoid receptor type 2 gene is associated with human osteoporosis.

Osteoporosis is one of the most common degenerative diseases. It is characterized by reduced bone mineral density (BMD) with an increased risk for bone fractures. There is a substantial genetic contribution to BMD, although the genetic factors involved in the pathogenesis of human osteoporosis are largely unknown. Mice with a targeted deletion of either the cannabinoid receptor type 1 (Cnr1) or type 2 (Cnr2) gene show an alteration of bone mass, and pharmacological modification of both receptors can regulate osteoclast activity and BMD. We therefore analyzed both genes in a systematic genetic association study in a human sample of postmenopausal osteoporosis patients and matched female controls. We found a significant association of single polymorphisms (P = 0.0014) and haplotypes (P = 0.0001) encompassing the CNR2 gene on human chromosome 1p36, whereas we found no convincing association for CNR1. These results demonstrate a role for the peripherally expressed CB2 receptor in the etiology of osteoporosis and provide an interesting novel therapeutical target for this severe and common disease.

Animals↗
PubMed2005

Incongruent pattern of neurokinin B expression in rat and mouse brains.

The expression patterns of Tac2 and NK3 mRNA and of pep2, the neurokinin B (NKB) precursor protein, were compared in rats and mice. Pep2 immunoreactivity was observed in fibers, terminals, and perikarya in the brains of both species, but the number of NKB-immunoreactive cells was generally smaller in mice than in the corresponding nuclei in rats. Congruent distribution patterns of Tac2 mRNA and NKB were found in many nuclei of the thalamus and hypothalamus (habenula, anterodorsal nucleus, preoptic area, arcuate nucleus, paraventricular nucleus). However, mice expressed Tac2 mRNA neither in the hippocampus nor in the nucleus of the lateral olfactory tract, in contrast to rats. Accordingly, mice showed no NKB in the projection areas of these nuclei, such as the olfactory tubercle, whereas a clear NKB signal was present in rat tissues. Surprisingly, we found nearly identical NK3 mRNA expression patterns in both species, despite the species differences in NKB expression. Thus, although the expression patterns of Tac2 and NKB are similar in rats and mice, noteworthy differences exist. Our results have important implications for the interpretation of behavioral results concerning the NKB/NK3 system in these species.

Amino Acid Sequence↗
PubMed2005

Interaction with vesicle luminal protachykinin regulates surface expression of delta-opioid receptors and opioid analgesia.

Opioid and tachykinin systems are involved in modulation of pain transmission in the spinal cord. Regulation of surface opioid receptors on nociceptive afferents is critical for opioid analgesia. Plasma-membrane insertion of delta-opioid receptors (DORs) is induced by stimulus-triggered exocytosis of DOR-containing large dense-core vesicles (LDCVs), but how DORs become sorted into the regulated secretory pathway is unknown. Here we report that direct interaction between protachykinin and DOR is responsible for sorting of DORs into LDCVs, allowing stimulus-induced surface insertion of DORs and DOR-mediated spinal analgesia. This interaction is mediated by the substance P domain of protachykinin and the third luminal domain of DOR. Furthermore, deletion of the preprotachykinin A gene reduced stimulus-induced surface insertion of DORs and abolished DOR-mediated spinal analgesia and morphine tolerance. Thus, protachykinin is essential for modulation of the sensitivity of nociceptive afferents to opioids, and the opioid and tachykinin systems are directly linked by protachykinin/DOR interaction.

Afferent Pathways↗
PubMed2005

The oral antidiabetic pioglitazone protects from neurodegeneration and amyotrophic lateral sclerosis-like symptoms in superoxide dismutase-G93A transgenic mice.

Amyotrophic lateral sclerosis (ALS) represents a fatal neurodegenerative disorder characterized by progressive death of the upper and lower motor neurons. Because accompanying inflammation may interact with and promote neurodegeneration, anti-inflammatory treatment strategies are being evaluated. Because peroxisome proliferator-activated receptor gamma (PPARgamma) agonists act as potent anti-inflammatory drugs, we tested whether superoxide dismutase (SOD1)-G93A transgenic mice, a mouse model of ALS, benefit from oral treatment with the PPARgamma agonist pioglitazone (Pio). Pio-treated transgenic mice revealed improved muscle strength and body weight, exhibited a delayed disease onset, and survived significantly longer than nontreated SOD1-G93A mice. Quantification of motor neurons of the spinal cord at day 90 revealed complete neuroprotection by Pio, whereas nontreated SOD1-G93A mice had lost 30% of motor neurons. This was paralleled by preservation of the median fiber diameter of the quadriceps muscle, indicating not only morphological but also functional protection of motor neurons by Pio. Activated microglia were significantly reduced at sites of neurodegeneration in Pio-treated SOD1-G93A mice, as were the protein levels of cyclooxygenase 2 and inducible nitric oxide synthase. Interestingly, mRNA levels of the suppressor of cytokine signaling 1 and 3 genes were increased by Pio, whereas both the mRNA and protein levels of endogenous mouse SOD1 and of transgenic human SOD1 remained unaffected.

Administration, Oral↗
PubMed2005

Oligonucleotide-protamine-albumin nanoparticles: Protamine sulfate causes drastic size reduction.

Nanoparticles prepared by self-assembly from oligonucleotides (ONs), protamine free base, and human serum albumin ("ternary proticles") are spheres of diameters around 200 nm. Substitution of the protamine free base by protamine sulfate leads to proticles of only around 40 nm in diameter with otherwise unchanged properties. The availability of drug delivery systems of very similar composition but grossly different size may be advantageous when dealing with cells which show size-dependent particle uptake. These nanoparticles are promising candidates for ON delivery to cells because of the following reasons: (1) They are stable for several hours in solutions of up to physiological ionic strength; (2) they are efficiently taken up by cells; (3) after cellular uptake, they easily release the ONs even when these are present as phosphorothioates.

Animals↗
PubMed2005

Low dose oral cannabinoid therapy reduces progression of atherosclerosis in mice.

Atherosclerosis is a chronic inflammatory disease, and is the primary cause of heart disease and stroke in Western countries. Derivatives of cannabinoids such as delta-9-tetrahydrocannabinol (THC) modulate immune functions and therefore have potential for the treatment of inflammatory diseases. We investigated the effects of THC in a murine model of established atherosclerosis. Oral administration of THC (1 mg kg(-1) per day) resulted in significant inhibition of disease progression. This effective dose is lower than the dose usually associated with psychotropic effects of THC. Furthermore, we detected the CB2 receptor (the main cannabinoid receptor expressed on immune cells) in both human and mouse atherosclerotic plaques. Lymphoid cells isolated from THC-treated mice showed diminished proliferation capacity and decreased interferon-gamma secretion. Macrophage chemotaxis, which is a crucial step for the development of atherosclerosis, was also inhibited in vitro by THC. All these effects were completely blocked by a specific CB2 receptor antagonist. Our data demonstrate that oral treatment with a low dose of THC inhibits atherosclerosis progression in the apolipoprotein E knockout mouse model, through pleiotropic immunomodulatory effects on lymphoid and myeloid cells. Thus, THC or cannabinoids with activity at the CB2 receptor may be valuable targets for treating atherosclerosis.

Animals↗
PubMed2005

Nicotine-induced antinociception, rewarding effects, and physical dependence are decreased in mice lacking the preproenkephalin gene.

It has been shown previously that the endogenous opioid system may be involved in the behavioral effects of nicotine. In the present study, the participation of endogenous enkephalins on nicotine responses has been investigated by using preproenkephalin knock-out mice. Acute nicotine-induced hypolocomotion remained unaffected in these mice. In contrast, antinociception elicited in the tail-immersion and hot-plate tests by acute nicotine administration was reduced in mutant animals. The rewarding properties of nicotine were then investigated using the place-conditioning paradigm. Nicotine induced a conditioned place preference in wild-type animals, but this effect was absent in knock-out mice. Accordingly, in vivo microdialysis studies revealed that the enhancement in dopamine extracellular levels in the nucleus accumbens induced by nicotine was also reduced in preproenkephalin-deficient mice. Finally, the somatic expression of the nicotine withdrawal syndrome precipitated in nicotine-dependent mice by mecamylamine was significantly attenuated in mutant animals. In summary, the present results indicate that endogenous opioid peptides derived from preproenkephalin are involved in the antinociceptive and rewarding properties of nicotine and participate in the expression of physical nicotine dependence.

Analgesics↗
PubMed2005

Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties, and intracellular distribution.

Oligodesoxynucleotides (ODNs) or the corresponding phosphorothioates (PTOs) spontaneously form spherical nanoparticles ("proticles") with protamine in aqueous solutions. The proticles can cross cellular membranes and release the ODNs within the cells. Thus, they represent a potential drug delivery system. The major disadvantages of this system are a lack of stability in salt solutions and its inability to also release PTOs. The present study shows, using PTOs and protamine free base, that these shortcomings can be eliminated by the addition of human serum albumin (HSA) as a third component to the starting mixture. The "ternary" proticles thus obtained contain maximally a few percent of the HSA that was originally present. Nevertheless, they differ from the previously studied "binary" proticles: (1) They are stable in salt solutions for at least several hours. (2) They show a high cellular uptake into murine fibroblasts, and they readily release the PTOs after uptake. The ternary proticles therefore represent a considerable improvement over binary proticles for use as drug delivery systems.

Albumins↗
PubMed2005

Albumin-protamine-oligonucleotide nanoparticles as a new antisense delivery system. Part 1: physicochemical characterization.

In this paper, a ternary system of albumin-protamine-oligonucleotide nanoparticles (AlPrO-NP) recently developed by Vogel et al. [V. Vogel, D. Lochmann, J. Weyermann, G. Mayer, C. Tziatzios, J.A. van den Broek, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles: preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which could serve as a potential drug delivery system for antisense oligonucleotides. Former studies of binary protamine-oligonucleotide nanoparticles showed two main disadvantages: (i) aggregation of the particles within a few minutes in the presence of salt; (ii) low intracellular dissociation between protamine and oligonucleotide, especially phosphorothioates. To overcome these problems, human serum albumin (HSA) as a non-toxic, biodegradable macromolecule was introduced as protective colloid. The assembly process of AlPrO-NP was investigated by small angle X-ray scattering (SAXS), fluorescence correlation spectroscopy (FCS), photon correlation spectroscopy (PCS) measurements and scanning electron microscopy (SEM). 'Initial complexes' of HSA and protamine sulphate with a mean hydrodynamic diameter (dh) of about 10-14 nm were found. After adding oligonucleotides (unmodified, phosphorothioate DNA and small interfering RNA), nanoparticles (NPs) were assembled in water and in isotonic media with a dh in a range of 230-320 nm for most preparations. The chemical composition of the particles was investigated by high performance liquid chromatography and fluorescence spectrometry. The whole amount of oligonucleotides (30 microg) was entrapped into the particles at a 1:2 mass ratio (oligonucleotide/protamine). Approximately 7-10% (w/w) of the HSA was bound to the particles. The surface charge of the particles ranged from about +12 to -60 mV depending on the protamine concentration and the ionic conditions. The size and the molecular weight of the components, initial complexes and two model NP preparations were calculated from FCS data. These data verified the PCS, SEM and SAXS measurements.

Chemical Phenomena↗
PubMed2005

Albumin-protamine-oligonucleotide-nanoparticles as a new antisense delivery system. Part 2: cellular uptake and effect.

Antisense oligonucleotides have been used as a specific tool to inhibit the expression of disease associated genes for many years. Unfortunately, oligonucleotides are polyanionic macromolecules which have a weak permeability through biological membranes and are rapidly degraded by nucleases. The purpose of this work is to characterise a new drug delivery system developed by [V. Vogel, D.Lochmann, J. Weyermann, G. Mayer, C. Tziatios, J.A. van der Brock, W. Haase, D. Wouters, U.S. Schubert, J. Kreuter, A. Zimmer, D. Schubert, Oligonucleotide-protamine-albumin nanoparticles preparation, physical properties and intracellular processing, J. Controlled Rel. (in press)] which allows an increased cellular uptake and an intracellular dissociation of the oligonucleotides. The new system based on nanoparticles (NPs) consists of human serum albumin, protamine sulphate and antisense-oligonucleotides (AlPrO). We tested these new nanoparticles on mouse fibroblasts which were stably transfected with a N-methyl-D-aspartate (NMDA) receptor (NR). This cell line enabled us to perform in vitro studies of cellular uptake, intracellular dissociation and effect of the antisense-oligonucleotide in a simple excitotoxicity model. We compared our findings with free oligonucleotides and a commercial available liposomal preparation (DOTAP). We found a 12-fold increased cellular uptake of oligonucleotides in comparison to free oligonucleotides while 100% of the cells were transfected. The AlPrO-NPs showed very low cytotoxic side effects during a 24 h application. We saw an antisense effect of about 35% in a functional assay as well as on the protein level (western blot). The results of the cell penetration and the antisense assay demonstrated that AlPrO nanoparticles are promising carriers for oligonucleotide administration.

Animals↗
PubMed2005

Cationic lipid-protamine-DNA (LPD) complexes for delivery of antisense c-myc oligonucleotides.

In the present study, cationic lipid-peptide-DNA-complexes (LPDs) consisting of AH-Chol-liposomes and protamine-phosphodiester-oligonucleotide-particles (proticles) were introduced as carriers for antisense therapy. The LPDs were physically characterized, and a possible mechanism for adsorption of oligonucleotides (ODNs) was suggested. An increase in stability of ODNs against DNase I and serum nuclease digestion by these carriers was demonstrated. The hydrodynamic diameter increased after incubation with FCS which could be attributed to a protein coating of the particle surface. However, in cell culture medium lower particle sizes of the complexes occurred. In an antisense c-myc in vitro model, the effect of LPDs was tested using U937 cells. The C-MYC level was reduced after treatment of these antisense ODN carrier complexes. Furthermore, no changes in target mRNA concentration of the treated cells was found by reverse transcription and competitive multiplex-PCR.

Culture Media↗