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Biomedical subjects

R Sandbrink

Publications and source records attributed to R Sandbrink.

At least 19 recordsLinked to original sources
PubMed2006

Blockade of chemokine signaling in patients with multiple sclerosis.

We assessed the safety and efficacy of orally administered CC chemokine receptor 1 (CCR1) antagonist in 105 patients with relapsing/remitting MS (RRMS) in a 16-week, randomized, double-blind, placebo-controlled trial. The primary endpoint was the cumulative number of newly active lesions on serial MRI scans. Other MRI, immunologic, and clinical outcomes were also explored. No significant treatment difference was observed for any tested MRI variable. CCR1 does not contribute to initial leukocyte infiltration in RRMS.

Central Nervous System↗
PubMed2006

Treatment with interferon beta-1b delays conversion to clinically definite and McDonald MS in patients with clinically isolated syndromes.

OBJECTIVE: To assess efficacy, safety, and tolerability of every-other-day interferon beta-1b treatment in patients with a first clinical event suggestive of multiple sclerosis (MS) (clinically isolated syndrome). METHODS: We conducted a multicenter, randomized, double-blind, placebo-controlled trial. Patients with a first clinical demyelinating event and at least two clinically silent brain MRI lesions were randomized to interferon beta-1b (IFNB-1b) 250 mug subcutaneously (SC) every other day (EOD) (n = 292) or placebo (n = 176), until clinically definite MS (CDMS) was diagnosed or they had been followed for 24 months. RESULTS: After 2 years, 45% of placebo patients had converted to CDMS (Kaplan-Meier estimate; primary outcome measure) and 85% fulfilled the McDonald criteria (co-primary outcome measure). Overall interferon beta-1b delayed the time to diagnosis of CDMS (p < 0.0001) and McDonald MS (p < 0.00001). Hazard ratios (95% CI) were 0.50 (0.36 to 0.70) for CDMS and 0.54 (0.43 to 0.67) for McDonald MS favoring treatment with IFNB-1b. Treatment was well tolerated, as indicated by the low rate of patients dropping out of the study before CDMS was reached (6.6% overall, 7.2% in the IFNB-1b group). CONCLUSIONS: Interferon beta-1b 250 mug subcutaneously every other day delayed conversion to clinically definite multiple sclerosis, and should be considered as a therapeutic option in patients presenting with a first clinical event suggestive of multiple sclerosis.

Adult↗
PubMed2003

Oral interferon beta-1a in relapsing-remitting multiple sclerosis: a double-blind randomized study.

BACKGROUND: Interferon beta (IFNB) is available in parenteral formulations for treatment of multiple sclerosis (MS). The purpose of this study was to evaluate safety, tolerability and effects on MRI lesions of three different doses of oral IFNB-1a compared with placebo over six months in relapsing-remitting (RR) MS patients. METHODS: In this multicenter; double-blind randomized trial, RR-MS patients received 0.06, 0.6 or 6 million international units (MIU) IFNB-1a or placebo every other day for up to six months. Gadolinium DTPA-enhanced brain MRI scans were performed at screening and monthly during treatment. The primary variable was the cumulative number of newly active lesions. Secondary variables included volume of enhancing lesions on T1-weighted images each month and lesion volume on T2-weighted images at months three and six. Safety measures included adverse events, laboratory variables, vital signs, ECG, physical examination, EDSS and number of relapses. Neopterin was measured in 21 patients and neutralizing antibodies in 24 patients. RESULTS: Of 194 screened patients, 173 were randomized (42-44 patients per group) in 15 centers. Median cumulative numbers of newly active lesions over six months were 4.0 in the placebo and 0.6 MIU groups, compared with 7.5 and 9.0 in the 0.06 and 6 MIU groups (no significant differences). Secondary efficacy endpoints showed small and inconsistent differences between groups. Adverse events showed no notable group differences. Approximately two-thirds of patients in each group remained relapse free. No patients showed neutralizing antibodies. Neopterin levels were comparable between groups. CONCLUSION: Oral IFNB-1a showed neither beneficial effects in RRMS nor any systemic biological effects. Treatment was safe and well tolerated.

Adjuvants, Immunologic↗
PubMed1997

Expression of the APP gene family in brain cells, brain development and aging.

The Alzheimer's beta A4-amyloid protein precursor (APP) and the APP-like proteins (APLPs) are transmembrane glycoproteins with a similar modular domain structure. Alternatively spliced exons found in both genes comprise a Kunitz protease inhibitor domain encoding exon, and another exon within the divergent regions adjacent to the transmembrane domain, i.e. exon 15 of the APP gene and an exon encoding 12 residues in APLP2. Omission of the latter exons in L-APP and L-APLP2 isoforms, respectively, generates a functional recognition sequence for xylosyltransferase-mediated addition of glycosaminoglycans and proteoglycan formation. In this paper, we summarize our analyses of the regulated expression of these alternatively spliced exons in APP and APLP2 in primary cultured rat brain cells, rat brain development and aging. In conjunction with additional data for the human brain, these data provide important clues for understanding the functional significance of alternative splicing and glycosylation in APP biology. On the basis of recent results showing a higher amyloidogenicity of exon 15 encoding APP than L-APP isoforms, we further discuss the potential significance of the low levels of L-APP in neurons for the susceptibility of the brain towards Alzheimer's disease.

Aging↗
PubMed1996

Analysis of heterogeneous A4 peptides in human cerebrospinal fluid and blood by a newly developed sensitive Western blot assay.

The betaA4 peptide, a major component of senile plaques in Alzheimer's disease (AD) brain, has been found in cerebrospinal fluid (CSF) and blood of both AD patients and normal subjects. Although betaA4 1-40 is the major form produced by cell metabolism and found in CSF, recent observations suggest that the long-tailed betaA4 1-42 plays a more crucial role in AD pathogenesis. Here, we established new monoclonal antibodies against the C-terminal end of betaA4 1-40 and 1-42, and used them for the specific Western blot detection. After optimizing the assay conditions, these antibodies detected low picogram amount of betaA4, and both betaA4 1-40 and 1-42 levels in CSF could be determined by direct loading of the samples. Blood levels of betaA4 1-40 and 1-42 were also determined by specific immunoprecipitation followed by Western blot detection. We found that CSF betaA4 1-42 level is lower in AD patients compared with non-demented controls, although there was a significant overlap between the groups. The level of betaA4 1-40 in CSF, and of betaA4 1-40 as well as betaA4 1-42 in plasma, were not different between AD patients and controls. Besides the 4-kDa full-length betaA4 band, we could also detect several N-terminal variants of betaA4 in CSF and plasma of both AD patients and controls. Two N-terminally truncated betaA4 species migrating at the position of 3.3 and 3.7 kDa were found in CSF, while 3.7- and 5-kDa forms were found in plasma. The relative abundance of these various species were considerably different in the CSF and plasma, suggesting that the cellular source and/or clearance of betaA4 is different in these two compartments.

Aged↗
PubMed1996

Alzheimer's disease betaA4 protein release and amyloid precursor protein sorting are regulated by alternative splicing.

We show here that alternative splicing influences the polarized secretion of amyloid precursor protein (APP) as well as the release of its proteolytic 3-4-kDa fragments betaA4 and p3. In Madin-Darby canine kidney II cells stably transfected with various APP isoforms and APP mutants, APPsec was consistently secreted basolaterally. In contrast, Madin-Darby canine kidney II cells transfected with L-APP677, which occurs naturally by alternative splicing of exon 15, secreted this isoform both apically and basolaterally, while maintaining the basolateral sorting of endogenous APPsec. This suggests that the alternative splicing of APP exon 15 modulates the polarized sorting of secretory APP. The same alternative splicing event also decreased the production of betaA4 relative to p3. This is the first example of alternative splicing regulating polarized trafficking of a secretory protein.

Alternative Splicing↗
PubMed1996

APP gene family. Alternative splicing generates functionally related isoforms.

The Alzheimer's beta A4-amyloid protein precursor (APP) and the APP-like proteins (APLPs) are transmembrane glycoproteins with a similar modular domain structure. APP exists in 8 isoforms generated by alternative splicing of exons 7, 8, and 15, of which the L-APP mRNAs lacking exon 15 are ubiquitously expressed in rat tissues but not in neurons. Rat APLP2, the nearest relative of APP, is similarly expressed in 4 different isoforms due to alternative splicing of inserts encoding a Kunitz protease inhibitor domain (KPI, homologous to exon 7 of APP) and a divergent region of 12 amino acids on the NH2-terminal side of the transmembrane domain (12 aa exon). KPI-APLP2 transcripts are highly expressed in neurons, in contrast to KPI-APPs, while L-APLP2 mRNA isoforms lacking the 12 aa exon are predominantly expressed in non-neuronal rat tissues, similar to L-APPs. Further examination of the divergent domains in APP and APLP2 harboring the similarly alternatively spliced APP exon 15 and the 12 aa exon of APLP2 revealed some structural similarities of the amino acid sequences and the predicted secondary structures. In both L-APLP2 and L-APP, a putative xylosyl-transferase recognition site for chondroitin sulfate glycosaminoglycan attachment is present that is interrupted in APP and APLP2 isoforms expressing APP exon 15 or the 12 aa exon of APLP2. Thus, a related function of the divergent domains and the corresponding alternatively spliced APP and APLP2 isoforms in regulation of the binding properties of the ectodomain is suggested. Additionally, beta-secretase cleavage of APP might be sterically hindered selectively in proteoglycan L-APP but not in APP lacking the proteoglycan attachment site. Neurons which have a uniquely low portion of L-APP and high content of APP might therefore be especially susceptible to beta A4-protein liberation. This could explain the selective vulnerability of neurons that is observed in Alzheimer's disease.

Alternative Splicing↗
PubMed1996

Genes contributing to Alzheimer's disease.

We propose that Alzheimer's disease (AD) is a single disease with a common metabolic APP-beta A4-amyloid pathway. The multiple genetic and other factors already identified to induce this pathway are reviewed. The molecular genetics of AD has been successfully studied within the last years, and we now can account for the genetic and molecular alterations underlying the majority of familial AD cases inherited with an autosomal dominant pattern of complete penetrance. AD in these pedigrees can be caused by missense mutations within the recently identified PS1 (S182) gene on chromosome 14 (AD3 locus) and the PS2 (STM2/E5-1) gene on chromosome 1, in addition to previously described point mutations of the beta A4-amyloid protein precursor (APP) gene on chromosome 21 (AD1 locus). The majority of AD cases, however, appears to be sporadic or 'familial' in terms of an increased family-associated AD-probability. Genetic risk factors contributing to AD in these cases have also been identified. On chromosome 19, allelic segregation of the APOE gene with both late onset 'familial' (AD2) and sporadic AD has been demonstrated, with the APOE epsilon 4 allele conferring a relatively higher risk of developing AD at an earlier age. Several other risk factors have also been proposed, including the alpha 1-antichymotrypsin allele A (ACT-A), the 5-repeat allele of the VLDL-receptor (VLDL-R) gene, the A2 allele of the HLA-A locus, and possibly yet unknown mitochondrial mutations. All these findings are discussed against the background of what is known about APP metabolism leading to beta A4 amyloid formation, a process that is also modified by APP expression level, alternative splicing of APP exon 15, extracellular signalling and intracellular sorting.

Alzheimer Disease↗
PubMed1995

Extracellular matrix influences the biogenesis of amyloid precursor protein in microglial cells.

During axotomy studies, we discovered that the beta A4-amyloid precursor protein (APP) participates in immune responses of the central nervous system. Since microglia constitute the main immune effector cell population of this response, we used the murine microglial cell line BV-2 to analyze immune response-related APP expression. We show that interaction of microglia with the extracellular environment, particularly components of the extracellular matrix, affects APP secretion as well as intracellular APP biogenesis and catabolism. Fibronectin enhanced APP secretion and decreased the level of cellular mature transmembrane APP, whereas laminin and collagen caused a decrease in secretion and an accumulation of cellular mature APP and APP fragments. Our results demonstrate that APP plays a fundamental role in the regulation of microglial mobility, i.e. migration, initial target recognition, and binding. The decrease in APP secretion and the concomitant increase in cellular mature APP were accompanied by an accumulation of C-terminal APP fragments. Enrichment of APP and APP fragments is assumedly based on inhibition of catabolic processes that is caused by a disorganization of the actin microfilament network. These observations provide evidence that microglia, which are closely associated with certain amyloid deposits in the brain of Alzheimer patients, can play a key role in initial events of amyloidogenesis by initiating accumulation of APP and also of amyloidogenic APP fragments in response to physiological changes upon brain injury.

Alzheimer Disease↗
PubMed1994

Complete nucleotide and deduced amino acid sequence of rat amyloid protein precursor-like protein 2 (APLP2/APPH): two amino acids length difference to human and murine homologues.

We present the cDNA sequence of the rat amyloid precursor-like protein 2 (APLP2) comprising the complete coding sequence of 765 amino acid residues. By alternative splicing of two exons, transcripts encoding for 753, 709 and 697 amino acids are also generated. The derived amino acid sequence displays a sequence identity to human APLP2 of approx. 92% and to murine CDEI binding protein of approx. 95%, but differs from both by a deletion of 2 amino acids and an insertion of 4 amino acids within the acidic domain.

Alternative Splicing↗
PubMed1994

Similar alternative splicing of a non-homologous domain in beta A4-amyloid protein precursor-like proteins.

The beta A4-amyloid protein precursor (APP) is a transmembrane glycoprotein that is the source of the characteristic beta A4-amyloid deposits found in Alzheimer brains. It is expressed in several isoforms generated by alternative splicing of exons 7, 8, and 15, of which the leukocyte-derived APP mRNAs lacking exon 15 are significantly expressed in non-neuronal tissues, but not in neurons. The recent finding of APP-like proteins prompted us to analyze alternative splicing of the nearest relative of APP, the amyloid protein precursor homologue (APPH) or amyloid precursor-like protein 2 (APLP2). We were able to show that there are two alternatively spliced inserts, i.e. the Kunitz protease inhibitor domain and a 12-amino-acid-encoding region on the NH2-terminal side of the transmembrane domain, which is part of the region of highest divergence between APP and APLP2/APPH. Analysis of the tissue-specific differential expression of the resulting four APLP2/APPH mRNA isoforms revealed that isoforms lacking the latter, non-homologous insert are highly expressed in non-neuronal tissues, but only weakly in neurons. While this resembles the tissue-specific alternative splicing of exon 15 of APP, expression of the Kunitz protease inhibitor-encoding exon of APLP2/APPH is abundant in both neuronal and non-neuronal tissues and thus differs from APP. Because of the similar regulation of alternative splicing of exon 15 of APP and the described APLP2/APPH insert, and because of structural similarities of the sequences and the predicted secondary structures, a functional homology of alternatively spliced isoforms of APP and APLP2/APPH is suggested.

Alternative Splicing↗
PubMed1994

Transforming growth factor beta mediates increase of mature transmembrane amyloid precursor protein in microglial cells.

By using the immortalized microglial cell line BV-2, we show that the high expression of the beta A4 amyloid precursor protein (APP), its biogenesis and metabolism is modulated by TGF beta, a cytokine with immunosuppressive activity, and by the microglia-stimulating agent LPS. TGF beta induces accumulation of cellular mature APP, the putative precursor of the amyloid subunit of Alzheimer's disease. LPS leads to an increase in cellular immature, non-amyloidogenic APP and secretion of also non-amyloidogenic APP fragments. We also demonstrate a functional involvement of ECM molecules in the regulation of microglial APP expression at mRNA and protein level by TGF beta and LPS.

Amyloid beta-Protein Precursor↗
PubMed1994

Beta A4-amyloid protein precursor mRNA isoforms without exon 15 are ubiquitously expressed in rat tissues including brain, but not in neurons.

The beta A4-amyloid protein precursor (APP), the source of the beta A4-amyloid deposits found in Alzheimer brains, constitutes a family of transmembrane glycoproteins generated by alternative splicing. While exon 7 and exon 8 are well known to be alternatively spliced, APP mRNA isoforms without exon 15 were only recently identified in leukocytes and rat brain microglial cells and therefore denoted as L-APP mRNAs. In order to perform a detailed analysis of individual L-APP mRNA isoforms in perfused rat tissues, we developed a quantitative polymerase chain reaction assay from reverse transcribed RNA allowing us to analyze the alternatively spliced region in between exon 6 and 16. In all peripheral tissues examined, L-APP mRNA isoforms were detected comprising between 25% (skeletal muscle) and about 70% (aorta, pancreas) of total APP transcripts. All four possible APP mRNA isoforms without exon 15 were shown to exist, i.e. L-APP752, L-APP733, L-APP696, and L-APP677. L-APP expression in the central nervous system (approximately 4% of total APP mRNA) was then studied in more detail by analyzing different brain regions and tissues and primary cultured brain cells. The only cell type which was shown not to express L-APP mRNA to a detectable level is the neuronal cell. Ubiquitous expression of APP mRNAs lacking exon 15 except for neurons indicates an important function in non-neuronal cells and is especially remarkable since neurons are the primarily affected cells in Alzheimer's disease.

Alternative Splicing↗
PubMed1994

APP gene family: unique age-associated changes in splicing of Alzheimer's betaA4-amyloid protein precursor.

The betaA4-amyloid protein precursor (APP) is a transmembrane glycoprotein that is the source of the characteristic betaA4-amyloid deposits of Alzheimer brains. It exists in eight isoforms generated by alternative splicing of exons 7, 8 and 15, of which the L-APP mRNAs lacking exon 15 are significantly expressed in non-neuronal cells and tissues, but not in neurones. Recently, it was shown that APP is a member of a multigene family of which the amyloid precursor-like protein 2 (APLP2) is the nearest relative. Analysis of APLP2 expression revealed regulated alternative splicing of the Kunitz protease inhibitor domain (KPI, homologous to exon 7 of APP) and a non-homologous insert of 12 amino acids on the NH2-terminal side of the transmembrane domain. While expression of the KPI encoding exon of APLP2 is abundant in neurones and thus differs from APP, L-APLP2 mRNA isoforms lacking the latter, non-homologous insert show a tissue-specific expression pattern similar to that of exon 15 of APP. Comparison of alternatively spliced APP and APLP2 mRNA isoforms in rat brain regions from early post-natal and adult rats revealed significantly higher relative amounts of KPI-encoding APP isoforms in the adult rat brain and an even more pronounced augmentation of L-APP mRNAs. Both effects were not observed for APLP2. This indicates an APP-specific age-associated regulation pattern within the APP gene family which has intriguing implications for the development of Alzheimer's disease in humans.

Age Factors↗