Ludo Van Den Bosch - Academia.edu (original) (raw)

Papers by Ludo Van Den Bosch

Chemistry (Weinheim an der Bergstrasse, Germany), 2017

Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals du... more Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Herein, the synthesis of ten new benzohydroxamic acids, constructed by employing the tetrahydrobenzothiazepine core as a privileged pharmacophoric unit, is described. This is the first report on the synthesis and isolation of octahydrodibenzothiazepines and octahydro-6H-benzocycloheptathiazepines, which were then used to develop a new class of HDAC6 inhibitors. Evaluations of their HDAC-inhibiting activity resulted in the identification of cis-N-(4-hydroxycarbamoylbenzyl)-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide and cis-N-(4-hydroxycarbamoylbenzyl)-7-trifluoromethyl-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide as highly potent and selective HDAC6 inhibitors with activity in the low nanomolar range, which also show excel...

J Biol Phys, 2009

Selective motor neuron death during amyotrophic lateral sclerosis (ALS) is a non-cell autonomous ... more Selective motor neuron death during amyotrophic lateral sclerosis (ALS) is a non-cell autonomous process in which non-neuronal cells induce and/or contribute to the disease process. The non-neuronal cells that are clearly involved in the pathogenesis of the disease are the surrounding astrocytes. Under normal conditions, astrocytes remove glutamate from the synaptic cleft and release trophic factors. In addition, these cells determine the functional characteristics of motor neurons. Recent evidence suggests that activation of astrocytes in a degenerative disease like ALS disturbs the crosstalk between astrocytes and motor neurons, which could contribute to and/or accelerate selective motor neuron death. These new insights may contribute to the development of therapeutic approaches to slow this fatal neurodegenerative disease.

Org. Biomol. Chem., 2016

The synthesis of novel isoform-selective HDAC inhibitors is considered to be an important, emergi... more The synthesis of novel isoform-selective HDAC inhibitors is considered to be an important, emerging field in medicinal chemistry. In this paper, the preparation and assessment of thirteen selective HDAC6 inhibitors is disclosed, elaborating on a previously developed thiaheterocyclic Tubathian series. All compounds were evaluated in vitro for their ability to inhibit HDAC6, and a selection of five potent compounds was further screened toward all HDAC isoforms (HDAC1-11). The capability of these Tubathian analogs to inhibit α-tubulin deacetylation was assessed as well, and ADME/Tox data were collected. This thorough SAR evaluation revealed that the oxidized, para-substituted hydroxamic acids can be recognized as valuable lead structures in the pursuit of novel potent and selective HDAC6 inhibitors.

Progress in clinical and biological research

Journal of Biological Chemistry

Annals of the New York Academy of Sciences

Eukaryotic cells express one or more isoforms of a sarco(endo)plasmic reticulum (SERCA) and of a ... more Eukaryotic cells express one or more isoforms of a sarco(endo)plasmic reticulum (SERCA) and of a plasma membrane (PMCA) Ca2+ pump. Both the SERCA and PMCA gene transcripts are subject to alternative processing in a differentiation stage-dependent and tissue-dependent manner. The Ca2+ pump isoforms thus generated may present different functional properties. This is exemplified by the SERCA2a and SERCA2b isoforms which differ in their Ca2+ sensitivity. Analysis of the cDNA structures for PMCA1 predicts protein isoforms with variant calmodulin- and phospholipid-binding domains. A comparative study of the tissue-specific mechanisms governing SERCA-PMCA transcript processing and a more detailed study of the functional implication of the PMCA pumps isoform diversity will be challenging subjects for future studies.

Journal of Biological Chemistry

BMC Neuroscience, 2015

GABAA receptor-mediated neurotransmission is greatly influenced by cation-chloride cotransporter ... more GABAA receptor-mediated neurotransmission is greatly influenced by cation-chloride cotransporter activity during developmental stages. In embryonic neurons Na-K-2Cl (NKCC1) cotransporters mediate active chloride uptake, thus increasing the intracellular chloride concentration associated with GABA-induced depolarization. At fetal stages near term, oxytocin-induced NKCC1 downregulation has been implicated in the developmental shift from depolarizing to hyperpolarizing GABA action. Mature dorsal root ganglion neurons (DRGN), however, express high NKCC1 levels and maintain high intracellular chloride levels with consequent GABA-induced depolarization. Gramicidin-perforated patch-clamp recordings were used to assess the developmental change in chloride homeostasis in rat cultured small DRGN at the embryonic day 16 (E16) and 19 (E19). The results were compared to data previously obtained in fetal DRGN at E14 and in mature cells. A significant NKCC1 downregulation, leading to reduction in excitatory GABAergic transmission, was observed at E16 and E19. These results indicate that NKCC1 activity transiently decreases in DRGN at fetal stages near term. This developmental shift in GABAergic transmission may contribute to fetal analgesia and neuroprotection at birth.

Chem. Commun., 2015

A small library of 3-[(4-hydroxycarbamoylphenyl)aminomethyl]benzothiophenes was prepared and asse... more A small library of 3-[(4-hydroxycarbamoylphenyl)aminomethyl]benzothiophenes was prepared and assessed as a novel class of HDAC6 inhibitors, leading to the identification of three representatives as potent and selective HDAC6 inhibitors. Further tests with regard to inflammatory responses indicated that HDAC6 inhibition can be uncoupled from transcriptional inhibition at the level of activated NF-κB, AP-1, and GR.

Molecular and cellular endocrinology, Jan 5, 2017

The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic act... more The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic actions on several tissues, including bone. The off-target effects of tamoxifen are one of the most widely recognized pitfalls of tamoxifen-inducible Cre recombinases (CreERs), potentially confounding the phenotypic findings. Still, the validation of tamoxifen induction schemes that minimize the side effects of the drug has not been addressed. Here, we compared the side effects on the skeleton and other androgen-responsive targets of a shortened tamoxifen regimen (2 doses of 190 mg/kg body weight by oral gavage) to a standard protocol (4 doses) and determined their efficiency in inducing CreER-mediated gene deletion. In addition, both a vehicle- and a 10-dose group, which served as a positive control for tamoxifen side effects, were also included. For this purpose, we generated male mice with a floxed androgen receptor (AR) and a neuron-specifically expressed CreER. Treatment with two doses...

The Biochemical journal, Jan 15, 1997

Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca2+-ATPase (SERC... more Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2) requires activation of an inefficient optional splice process at the 3' end of the primary gene transcript. The sequence elements required for this regulated splice event were studied by modifying a minigene containing the 3' end of the SERCA2 gene. An important requirement appears to be a strong muscle-specific acceptor site, as replacing it by a weak one prevented the induction of muscle-type splicing during myogenic differentiation. The induction of muscle-type splicing did not depend on positive cis-active sequences in the muscle-specific exon. On the other hand, replacement of a broad region around the acceptor site dramatically deregulated the expression pattern, as this modification strongly induced muscle-type splicing in undifferentiated muscle cells and in fibroblasts. This cis-active region is also involved in the suppression of the neuronal type of splicing. Furth...

The Biochemical journal, 1996

We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ s... more We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ stores in permeabilized A7r5 cells. The decrease in the content of stored Ca2+ in the presence of 2 microM thapsigargin deviated from a single-exponential curve in the initial phase of the efflux. The deviation persisted after correcting this efflux for passively bound Ca2+. The non-single-exponential nature of the spontaneous release also occurred when the initial store Ca2+ content was reduced to 40% of its original value by pretreatment with 200 nM inositol 1,4,5-trisphosphate (InsP3). The passive Ca2+ leak could be modelled by two exponential curves with discrete rate constants of 0.06 min-1 and 0.98 min-1, and not by any other type of non-exponential decay. We concluded that individual store units are heterogeneous with respect to their passive Ca2+ permeability. This non-exponential nature of the passive Ca2+ release is unrelated to the non-single-exponential InsP3-induced Ca2+ rele...

The Biochemical journal, 1996

Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SE... more Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2) requires activation of an otherwise inefficient splice process at the 3'-end of the primary gene transcript. We provide evidence that SERCA2 splicing is a specifically regulated process, rather than the result of an increase in general splice efficiency or a decrease in polyadenylation efficiency at the 5'-most polyadenylation site. This is indicated by the fact that changes in general splice and polyadenylation efficiency, as observed during B-cell maturation, did not affect SERCA2 splicing. Furthermore, expression and overexpression studies did not support the hypothesis that changes in the level of the alternative splice factor ASF/SF2 or other arginine and serine rich proteins are sufficient to obtain the regulation of muscle- and neuronal-specific splicing.

The Biochemical journal, 1994

Ca(2+)-uptake experiments in microsomal fractions from transfected COS-1 cells have revealed a fu... more Ca(2+)-uptake experiments in microsomal fractions from transfected COS-1 cells have revealed a functional difference between the non-muscle SERCA2b Ca2+ pump and its muscle-specific SERCA2a splice variant. Structurally, the two pumps differ only in their C-terminal tail. The last four amino acids of SERCA2a are replaced in SERCA2b by a 49-residue-long peptide chain containing a very hydrophobic stretch which could be an additional transmembrane segment. The functionally important subdomains in the SERCA2b tail were analysed by constructing three SERCA2b deletion mutants lacking 12, 31 or 49 amino acids. The mutants and the parental SERCA2 pumps were expressed in COS-1 cells and analysed for functional difference. SERCA2b had a twofold higher Ca2+ affinity, a twofold lower turnover rate and a 10-fold lower vanadate-sensitivity than SERCA2a and the mutants. Since each of the three truncated versions of SERCA2b acquire the characteristic properties of SERCA2a, it is concluded that the ...

The Biochemical journal, 1994

Tissue-specific alternative processing of sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) tr... more Tissue-specific alternative processing of sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) transcripts generates functionally different Ca2+ pump isoforms in muscle compared with non-muscle tissues. In non-muscle cells, the SERCA2 pre-mRNA can be polyadenylated at a site located between the donor and acceptor splice site of an intron which is only removed in muscle tissues. To define the cis-active elements involved in differential processing, we constructed a minigene (pCM beta SERCA2) containing the 3' end of the SERCA2 gene. When stably transfected into a myogenic cell line, minigene transcripts were differentially processed depending on the differentiation state of the cells. This proves that the essential elements required for regulated processing are present in the construct. Furthermore, co-transfection of the pCM beta SERCA2 minigene and a myogenin expression vector in a fibroblast cell line induced muscle-specific splicing of transcripts from pCM beta SERCA2. This s...

Advances in Molecular and Cell Biology, 1997

ABSTRACT

... mutant superoxide dismutase. Exp Neurol 220, 267-275. Gowing, G., Philips, T., Van Wijmeersch... more ... mutant superoxide dismutase. Exp Neurol 220, 267-275. Gowing, G., Philips, T., Van Wijmeersch, B., Audet, JN, Dewil, M., Van Den Bosch, L., Billiau, AD, Robberecht, W., and Julien, JP (2008). Ablation of proliferating microglia ...

Biocomputing 2007 - Proceedings of the Pacific Symposium, 2007

Chemistry (Weinheim an der Bergstrasse, Germany), 2017

Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals du... more Selective inhibitors of histone deacetylase 6 (HDAC6) are an emerging class of pharmaceuticals due to the involvement of HDAC6 in different pathways related to neurodegenerative diseases, cancer, and immunology. Herein, the synthesis of ten new benzohydroxamic acids, constructed by employing the tetrahydrobenzothiazepine core as a privileged pharmacophoric unit, is described. This is the first report on the synthesis and isolation of octahydrodibenzothiazepines and octahydro-6H-benzocycloheptathiazepines, which were then used to develop a new class of HDAC6 inhibitors. Evaluations of their HDAC-inhibiting activity resulted in the identification of cis-N-(4-hydroxycarbamoylbenzyl)-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide and cis-N-(4-hydroxycarbamoylbenzyl)-7-trifluoromethyl-1,2,3,4,4a,5,11,11a-octahydrodibenzo[b,e][1,4]thiazepine-10,10-dioxide as highly potent and selective HDAC6 inhibitors with activity in the low nanomolar range, which also show excel...

J Biol Phys, 2009

Selective motor neuron death during amyotrophic lateral sclerosis (ALS) is a non-cell autonomous ... more Selective motor neuron death during amyotrophic lateral sclerosis (ALS) is a non-cell autonomous process in which non-neuronal cells induce and/or contribute to the disease process. The non-neuronal cells that are clearly involved in the pathogenesis of the disease are the surrounding astrocytes. Under normal conditions, astrocytes remove glutamate from the synaptic cleft and release trophic factors. In addition, these cells determine the functional characteristics of motor neurons. Recent evidence suggests that activation of astrocytes in a degenerative disease like ALS disturbs the crosstalk between astrocytes and motor neurons, which could contribute to and/or accelerate selective motor neuron death. These new insights may contribute to the development of therapeutic approaches to slow this fatal neurodegenerative disease.

Org. Biomol. Chem., 2016

The synthesis of novel isoform-selective HDAC inhibitors is considered to be an important, emergi... more The synthesis of novel isoform-selective HDAC inhibitors is considered to be an important, emerging field in medicinal chemistry. In this paper, the preparation and assessment of thirteen selective HDAC6 inhibitors is disclosed, elaborating on a previously developed thiaheterocyclic Tubathian series. All compounds were evaluated in vitro for their ability to inhibit HDAC6, and a selection of five potent compounds was further screened toward all HDAC isoforms (HDAC1-11). The capability of these Tubathian analogs to inhibit α-tubulin deacetylation was assessed as well, and ADME/Tox data were collected. This thorough SAR evaluation revealed that the oxidized, para-substituted hydroxamic acids can be recognized as valuable lead structures in the pursuit of novel potent and selective HDAC6 inhibitors.

Progress in clinical and biological research

Journal of Biological Chemistry

Annals of the New York Academy of Sciences

Eukaryotic cells express one or more isoforms of a sarco(endo)plasmic reticulum (SERCA) and of a ... more Eukaryotic cells express one or more isoforms of a sarco(endo)plasmic reticulum (SERCA) and of a plasma membrane (PMCA) Ca2+ pump. Both the SERCA and PMCA gene transcripts are subject to alternative processing in a differentiation stage-dependent and tissue-dependent manner. The Ca2+ pump isoforms thus generated may present different functional properties. This is exemplified by the SERCA2a and SERCA2b isoforms which differ in their Ca2+ sensitivity. Analysis of the cDNA structures for PMCA1 predicts protein isoforms with variant calmodulin- and phospholipid-binding domains. A comparative study of the tissue-specific mechanisms governing SERCA-PMCA transcript processing and a more detailed study of the functional implication of the PMCA pumps isoform diversity will be challenging subjects for future studies.

Journal of Biological Chemistry

BMC Neuroscience, 2015

GABAA receptor-mediated neurotransmission is greatly influenced by cation-chloride cotransporter ... more GABAA receptor-mediated neurotransmission is greatly influenced by cation-chloride cotransporter activity during developmental stages. In embryonic neurons Na-K-2Cl (NKCC1) cotransporters mediate active chloride uptake, thus increasing the intracellular chloride concentration associated with GABA-induced depolarization. At fetal stages near term, oxytocin-induced NKCC1 downregulation has been implicated in the developmental shift from depolarizing to hyperpolarizing GABA action. Mature dorsal root ganglion neurons (DRGN), however, express high NKCC1 levels and maintain high intracellular chloride levels with consequent GABA-induced depolarization. Gramicidin-perforated patch-clamp recordings were used to assess the developmental change in chloride homeostasis in rat cultured small DRGN at the embryonic day 16 (E16) and 19 (E19). The results were compared to data previously obtained in fetal DRGN at E14 and in mature cells. A significant NKCC1 downregulation, leading to reduction in excitatory GABAergic transmission, was observed at E16 and E19. These results indicate that NKCC1 activity transiently decreases in DRGN at fetal stages near term. This developmental shift in GABAergic transmission may contribute to fetal analgesia and neuroprotection at birth.

Chem. Commun., 2015

A small library of 3-[(4-hydroxycarbamoylphenyl)aminomethyl]benzothiophenes was prepared and asse... more A small library of 3-[(4-hydroxycarbamoylphenyl)aminomethyl]benzothiophenes was prepared and assessed as a novel class of HDAC6 inhibitors, leading to the identification of three representatives as potent and selective HDAC6 inhibitors. Further tests with regard to inflammatory responses indicated that HDAC6 inhibition can be uncoupled from transcriptional inhibition at the level of activated NF-κB, AP-1, and GR.

Molecular and cellular endocrinology, Jan 5, 2017

The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic act... more The selective estrogen receptor modulator tamoxifen exerts estrogen agonistic or antagonistic actions on several tissues, including bone. The off-target effects of tamoxifen are one of the most widely recognized pitfalls of tamoxifen-inducible Cre recombinases (CreERs), potentially confounding the phenotypic findings. Still, the validation of tamoxifen induction schemes that minimize the side effects of the drug has not been addressed. Here, we compared the side effects on the skeleton and other androgen-responsive targets of a shortened tamoxifen regimen (2 doses of 190 mg/kg body weight by oral gavage) to a standard protocol (4 doses) and determined their efficiency in inducing CreER-mediated gene deletion. In addition, both a vehicle- and a 10-dose group, which served as a positive control for tamoxifen side effects, were also included. For this purpose, we generated male mice with a floxed androgen receptor (AR) and a neuron-specifically expressed CreER. Treatment with two doses...

The Biochemical journal, Jan 15, 1997

Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca2+-ATPase (SERC... more Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca2+-ATPase (SERCA2) requires activation of an inefficient optional splice process at the 3' end of the primary gene transcript. The sequence elements required for this regulated splice event were studied by modifying a minigene containing the 3' end of the SERCA2 gene. An important requirement appears to be a strong muscle-specific acceptor site, as replacing it by a weak one prevented the induction of muscle-type splicing during myogenic differentiation. The induction of muscle-type splicing did not depend on positive cis-active sequences in the muscle-specific exon. On the other hand, replacement of a broad region around the acceptor site dramatically deregulated the expression pattern, as this modification strongly induced muscle-type splicing in undifferentiated muscle cells and in fibroblasts. This cis-active region is also involved in the suppression of the neuronal type of splicing. Furth...

The Biochemical journal, 1996

We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ s... more We have investigated the detailed kinetics of the passive Ca2+ leak from non-mitochondrial Ca2+ stores in permeabilized A7r5 cells. The decrease in the content of stored Ca2+ in the presence of 2 microM thapsigargin deviated from a single-exponential curve in the initial phase of the efflux. The deviation persisted after correcting this efflux for passively bound Ca2+. The non-single-exponential nature of the spontaneous release also occurred when the initial store Ca2+ content was reduced to 40% of its original value by pretreatment with 200 nM inositol 1,4,5-trisphosphate (InsP3). The passive Ca2+ leak could be modelled by two exponential curves with discrete rate constants of 0.06 min-1 and 0.98 min-1, and not by any other type of non-exponential decay. We concluded that individual store units are heterogeneous with respect to their passive Ca2+ permeability. This non-exponential nature of the passive Ca2+ release is unrelated to the non-single-exponential InsP3-induced Ca2+ rele...

The Biochemical journal, 1996

Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SE... more Expression of the muscle-specific 2a isoform of the sarco/endoplasmic reticulum Ca(2+)-ATPase (SERCA2) requires activation of an otherwise inefficient splice process at the 3'-end of the primary gene transcript. We provide evidence that SERCA2 splicing is a specifically regulated process, rather than the result of an increase in general splice efficiency or a decrease in polyadenylation efficiency at the 5'-most polyadenylation site. This is indicated by the fact that changes in general splice and polyadenylation efficiency, as observed during B-cell maturation, did not affect SERCA2 splicing. Furthermore, expression and overexpression studies did not support the hypothesis that changes in the level of the alternative splice factor ASF/SF2 or other arginine and serine rich proteins are sufficient to obtain the regulation of muscle- and neuronal-specific splicing.

The Biochemical journal, 1994

Ca(2+)-uptake experiments in microsomal fractions from transfected COS-1 cells have revealed a fu... more Ca(2+)-uptake experiments in microsomal fractions from transfected COS-1 cells have revealed a functional difference between the non-muscle SERCA2b Ca2+ pump and its muscle-specific SERCA2a splice variant. Structurally, the two pumps differ only in their C-terminal tail. The last four amino acids of SERCA2a are replaced in SERCA2b by a 49-residue-long peptide chain containing a very hydrophobic stretch which could be an additional transmembrane segment. The functionally important subdomains in the SERCA2b tail were analysed by constructing three SERCA2b deletion mutants lacking 12, 31 or 49 amino acids. The mutants and the parental SERCA2 pumps were expressed in COS-1 cells and analysed for functional difference. SERCA2b had a twofold higher Ca2+ affinity, a twofold lower turnover rate and a 10-fold lower vanadate-sensitivity than SERCA2a and the mutants. Since each of the three truncated versions of SERCA2b acquire the characteristic properties of SERCA2a, it is concluded that the ...

The Biochemical journal, 1994

Tissue-specific alternative processing of sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) tr... more Tissue-specific alternative processing of sarco/endoplasmic reticulum Ca(2+)-ATPase 2 (SERCA2) transcripts generates functionally different Ca2+ pump isoforms in muscle compared with non-muscle tissues. In non-muscle cells, the SERCA2 pre-mRNA can be polyadenylated at a site located between the donor and acceptor splice site of an intron which is only removed in muscle tissues. To define the cis-active elements involved in differential processing, we constructed a minigene (pCM beta SERCA2) containing the 3' end of the SERCA2 gene. When stably transfected into a myogenic cell line, minigene transcripts were differentially processed depending on the differentiation state of the cells. This proves that the essential elements required for regulated processing are present in the construct. Furthermore, co-transfection of the pCM beta SERCA2 minigene and a myogenin expression vector in a fibroblast cell line induced muscle-specific splicing of transcripts from pCM beta SERCA2. This s...

Advances in Molecular and Cell Biology, 1997

ABSTRACT

... mutant superoxide dismutase. Exp Neurol 220, 267-275. Gowing, G., Philips, T., Van Wijmeersch... more ... mutant superoxide dismutase. Exp Neurol 220, 267-275. Gowing, G., Philips, T., Van Wijmeersch, B., Audet, JN, Dewil, M., Van Den Bosch, L., Billiau, AD, Robberecht, W., and Julien, JP (2008). Ablation of proliferating microglia ...

Biocomputing 2007 - Proceedings of the Pacific Symposium, 2007