Per Andrén - Academia.edu (original) (raw)

Papers by Per Andrén

npj Parkinson's Disease

L-DOPA administration is the primary treatment for Parkinson’s disease (PD) but long-term adminis... more L-DOPA administration is the primary treatment for Parkinson’s disease (PD) but long-term administration is usually accompanied by hyperkinetic side-effects called L-DOPA-induced dyskinesia (LID). Signaling neuropeptides of the basal ganglia are affected in LID and changes in the expression of neuropeptide precursors have been described, but the final products formed from these precursors have not been well defined and regionally mapped. We therefore used mass spectrometry imaging to visualize and quantify neuropeptides in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine exposed parkinsonian and LID Macaca mulatta brain samples. We found that dyskinesia severity correlated with the levels of some abnormally processed peptides — notably, des-tyrosine dynorphins, substance P (1-7), and substance P (1-9) — in multiple brain regions. Levels of the active neuropeptides; dynorphin B, dynorphin A (1-8), α-neoendorphin, substance P (1-11), and neurokinin A, in the globus pallidus and substantia...

Neurobiology of Disease, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of The American Society for Mass Spectrometry, 2018

Frontiers in pharmacology, 2018

The trace amine-associated receptor 1 (TAAR1) is expressed by dopaminergic neurons, but the preci... more The trace amine-associated receptor 1 (TAAR1) is expressed by dopaminergic neurons, but the precise influence of trace amines upon their functional activity remains to be fully characterized. Here, we examined the regulation of tyrosine hydroxylase (TH) by tyramine and beta-phenylethylamine (β-PEA) compared to 3-iodothyronamine (TAM). Immunoblotting and amperometry were performed in dorsal striatal slices from wild-type (WT) and TAAR1 knockout (KO) mice. TAM increased TH phosphorylation at both Serand Ser, actions that should promote functional activity of TH. Indeed, HPLC data revealed higher rates of L-dihydroxyphenylalanine (DOPA) accumulation in WT animals treated with TAM after the administration of a DOPA decarboxylase inhibitor. These effects were abolished both in TAAR1 KO mice and by the TAAR1 antagonist, EPPTB. Further, they were specific inasmuch as Serphosphorylation of the post-synaptic GluA1 AMPAR subunit was unaffected. The effects of TAM on TH phosphorylation at both...

British journal of pharmacology, Jan 13, 2015

In pharmaceutical research, understanding the biodistribution, accumulation and metabolism of dru... more In pharmaceutical research, understanding the biodistribution, accumulation and metabolism of drugs in tissue plays a key role during drug discovery and development. In particular, information regarding pharmacokinetics, pharmacodynamics and transport properties of compounds in tissues is crucial during early screening. Historically, the abundance and distribution of drugs have been assessed by well-established techniques such as quantitative whole body autoradiography (WBA) or tissue homogenisation with liquid chromatography-mass spectrometry (LC/MS) analysis. However, WBA does not distinguish active drug from its metabolites and LC/MS, while highly sensitive, does not report spatial distribution. Mass spectrometry imaging (MSI) can discriminate drug and its metabolites and endogenous compounds, while simultaneously reporting their distribution. MSI data are influencing drug development and currently used in investigational studies in areas such compound toxicity. In in vivo studie...

Neurobiology of disease, 2014

A role for enhanced peptidergic transmission, either opioidergic or not, has been proposed for th... more A role for enhanced peptidergic transmission, either opioidergic or not, has been proposed for the generation of l-3,4-dihydroxyphenylalanine (l-DOPA)-induced dyskinesia (LID) on the basis of in situ hybridization studies showing that striatal peptidergic precursor expression consistently correlates with LID severity. Few studies, however, have focused on the actual peptides derived from these precursors. We used mass-spectrometry to study peptide profiles in the putamen and globus pallidus (internalis and externalis) collected from 1-methyl-4-phenyl-1,2,4,6-tetrahydropyridine treated macaque monkeys, acutely or chronically treated with l-DOPA. We identified that parkinsonian and dyskinetic states are associated with an abnormal production of proenkephalin-, prodynorphin- and protachykinin-1-derived peptides in both segments of the globus pallidus. Moreover, we report that peptidergic processing is dopamine-state dependent and highly structure-specific, possibly explaining the failu...

Neuron, 2014

Current neuroimaging techniques have very limited abilities to directly identify and quantify neu... more Current neuroimaging techniques have very limited abilities to directly identify and quantify neurotransmitters from brain sections. We have developed a molecular-specific approach for the simultaneous imaging and quantitation of multiple neurotransmitters, precursors, and metabolites, such as tyrosine, tryptamine, tyramine, phenethylamine, dopamine, 3-methoxytyramine, serotonin, GABA, glutamate, acetylcholine, and L-alpha-glycerylphosphorylcholine, in histological tissue sections at high spatial resolutions. The method is employed to directly measure changes in the absolute and relative levels of neurotransmitters in specific brain structures in animal disease models and in response to drug treatments, demonstrating the power of mass spectrometry imaging in neuroscience.

Rapid Communications in Mass Spectrometry, 2003

In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass ... more In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass spectrometry was used to study the processing of LVV-hemorphin-7, an endogenous decapeptide with opioid activity, in rat brain and blood. A microdialysis probe (flow rate 0.4 microL/min) was used to both introduce LVV-hemorphin-7 into the striatum of the brain (1.0 pmol/microL) or the venous blood (10 pmol/microL) and to collect the metabolic products. LVV-hemorphin-7 was extracellularly metabolized in the striatum to form C-terminal fragments 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, and N-terminal fragments 1-9, 1-8, 1-6. Infusion of the aminopeptidase inhibitor amastatin (1.0 pmol/microL) into the striatum, together with LVV-hemorphin-7, decreased the processing of LVV-hemorphin-7 to form C-terminal fragments 2-10, 3-10, 4-10, but increased the relative levels of fragment 5-10 and N-terminal fragments 1-9, 1-8 and 1-6. The major metabolic product from LVV-hemorphin-7 in the striatum was the C-terminal fragment 5-10, which may be processed by an endopeptidase not sensitive to amastatin. The LVV-hemorphin-7 infusion to the venous blood produced the C-terminal fragments 2-10, 3-10, 4-10, and 5-10, N-terminal fragment 1-9, and internal fragments 4-7 and 4-9. It is concluded that the combination of microdialysis and electrospray mass spectrometry provides a powerful tool for the study of extracellular metabolism and kinetic processes of complex reaction systems in vivo.

Psychopharmacology, 1989

Leu- and Metenkephalin (Lenk and Menk) and their more stable analogues D-Ala-Leu- and D-Ala-Meten... more Leu- and Metenkephalin (Lenk and Menk) and their more stable analogues D-Ala-Leu- and D-Ala-Metenkephalin (DALenk and DAMenk) as well as D-Ala-D-Leu- and D-Ala-D-Metenkephalin (DADLenk and DADMenk) were infused bilaterally into substantia nigra in awake rats and oral movements were recorded for 90 min. DADLenk and DADMenk elicited dose-dependent biting dyskinesias with a chewing rate of about 90 jaw movements/min. DALenk produced a similar but weaker effect, whereas DAMenk, Lenk and Menk were ineffective in the doses given. These findings suggest a possible enkephalinergic mechanism underlying neuroleptic-induced tardive dyskinesias.

PROTEOMICS, 2011

The hypothalamus is the central regulatory region of the brain that links the nervous system to t... more The hypothalamus is the central regulatory region of the brain that links the nervous system to the endocrine system via the pituitary gland. It synthesizes and secretes neuropeptide hormones, which in turn act to stimulate or inhibit the secretion of pituitary hormones. We have undertaken a detailed MS investigation of the peptides present in the bovine hypothalamus by adapting a novel heat stabilization methodology, which improved peptide discovery to direct our studies into the molecular mechanisms involved in bovine reproduction. The untreated samples contained large numbers of protein degradation products that interfered with the analysis of the neuropeptides. In the thermally stabilized samples, we were able to identify many more neuropeptides that are known to be expressed in the bovine hypothalamus. Furthermore, we have characterized a range of post-translational modifications that indicate the presence of processed intact mature neuropeptides in the stabilized tissue samples, whereas we detected many trimmed or truncated peptides resulting from post-mortem degradation in the untreated tissue samples. Altogether, using an optimized workflow, we were able to identify 140 candidate neuropeptides. We also nominate six new candidate neuropeptides derived from proSAAS, secretogranin-2 and proTRH.

Preparative Biochemistry and Biotechnology, 1997

Two enzymes with substance P degrading activity were purified from the membrane bound fraction of... more Two enzymes with substance P degrading activity were purified from the membrane bound fraction of the rat spinal cord. The purified enzymes were characterized with regard to biochemical and kinetic properties. One of the enzymes exhibited close similarity to neutral endopeptidase 24.11 (NEP, EC 3.4.24.11), while the other resembled a substance P converting endopeptidase (SPE), which has previously been identified and purified from human cerebrospinal fluid (CSF). Detergent treated spinal cord homogenates from male Sprague Dawley rats were purified by anion-exchange chromatography (DEAE-sepharose CL-6B), hydrophobic-interaction chromatography (phenyl-sepharose CL-4B) and molecular sieving (Sephadex G-50). Two fractions with enzymes differing in size were recovered and allowed for further purification to apparent homogeneity by ion-exchange chromatography and molecular sieving on a micro-purification system (SMART). The enzyme activities were monitored by following the conversion of synthetic substance P using a radioimmunoassay specific for the heptapeptide product, substance P (1-7). By SDS-polyacrylamide gel electrophoresis of the purified enzymes molecular weights of 43 and 70 kDa were estimated for the SPE-like and NEP-like activity, respectively. A K(m) of 5 microM was determined for the conversion of substance P to its (1-7) fragment by the SPE-like activity. Reversed-phase HPLC together with mass spectrometry permitted identification of all fragments released from substance P by the peptidases. The released fragments were for both enzymes identified as substance P (1-7), substance P (8-11), substance P (1-8), substance P (9-11). The NEP-like enzyme preparation also gave substance P (1-6) as a major product.

PLoS ONE, 2008

L-3,4-dihydroxypheylalanine (L-dopa)-induced dyskinesia represent a debilitating complication of ... more L-3,4-dihydroxypheylalanine (L-dopa)-induced dyskinesia represent a debilitating complication of therapy for Parkinson's disease (PD) that result from a progressive sensitization through repeated L-dopa exposures. The MPTP macaque model was used to study the proteome in dopamine-depleted striatum with and without subsequent acute and chronic L-dopa treatment using two-dimensional difference in-gel electrophoresis (2D-DIGE) and mass spectrometry. The present data suggest that the dopamine-depleted striatum is so sensitive to de novo L-dopa treatment that the first ever administration alone would be able (i) to induce rapid post-translational modification-based proteomic changes that are specific to this first exposure and (ii), possibly, lead to irreversible protein level changes that would be not further modified by chronic L-dopa treatment. The apparent equivalence between first and chronic L-dopa administration suggests that priming would be the direct consequence of dopamine loss, the first L-dopa administrations only exacerbating the sensitization process but not inducing it.

Neuropsychopharmacology, 2013

Mass spectrometry imaging is a powerful tool for directly determining the distribution of protein... more Mass spectrometry imaging is a powerful tool for directly determining the distribution of proteins, peptides, lipids, neurotransmitters, metabolites and drugs in neural tissue sections in situ. Molecule-specific imaging can be achieved using various ionization techniques that are suited to different applications but which all yield data with high mass accuracies and spatial resolutions. The ability to simultaneously obtain images showing the distributions of chemical species ranging from metal ions to macromolecules makes it possible to explore the chemical organization of a sample and to correlate the results obtained with specific anatomical features. The imaging of biomolecules has provided new insights into multiple neurological diseases, including Parkinson's and Alzheimer's disease. Mass spectrometry imaging can also be used in conjunction with other imaging techniques in order to identify correlations between changes in the distribution of important chemical species and other changes in the properties of the tissue. Here we review the applications of mass spectrometry imaging in neuroscience research and discuss its potential. The results presented demonstrate that mass spectrometry imaging is a useful experimental method with diverse applications in neuroscience.

Neuropharmacology, 2012

Open access under CC BY-NC-ND license. Open access under CC BY-NC-ND license.

Molecular & Cellular Proteomics, 2013

The chronic use of nicotine, the main psychoactive ingredient of tobacco smoking, alters diverse ... more The chronic use of nicotine, the main psychoactive ingredient of tobacco smoking, alters diverse physiological processes and consequently generates physical dependence. To understand the impact of chronic nicotine on neuropeptides, which are potential molecules associated with dependence, we conducted qualitative and quantitative neuropeptidomics on the rat dorsal striatum (DS), an important brain region implicated in the preoccupation/craving phase of drug dependence. We used extensive LC-FT-MS/MS analyses for neuropeptide identification and LC-FT-MS in conjunction with stable isotope addition for relative quantification. The treatment with chronic nicotine for three months led to moderate changes in the levels of endogenous DS peptides. Five enkephalin opioid peptides were upregulated, while no change was observed for dynorphin peptides. Specially, nicotine altered levels of 9 non-opioid peptides derived from precursors including somatostatin and cerebellin, which potentially modulate neurotransmitter release and energy metabolism. This broad but selective impact on the multiple peptidergic systems suggests that apart from the opioid peptides, several other peptidergic systems are involved in the preoccupation/craving phase of drug dependence. Our finding permits future evaluation of the neurochemical circuits modulated by chronic nicotine exposure and provides a number of novel molecules that could serve as potential therapeutic targets for treating drug dependence.

Journal of Proteome Research, 2012

Mass spectrometry-based neuropeptidomics is one of the most powerful approaches for identificatio... more Mass spectrometry-based neuropeptidomics is one of the most powerful approaches for identification of endogenous neuropeptides in the brain. Until now, however, the identification rate of neuropeptides in neuropeptidomics is relatively low and this severely restricts insights into their biological function. In the present study, we developed a high accuracy mass spectrometry-based approach to enhance the identification rates of neuropeptides from brain tissue. Our integrated approach used mixing on column for loading aqueous and organic extracts to reduce the loss of peptides during sample treatment and used charge state-directed tandem mass spectrometry to increase the number of peptides subjected to high mass accuracy fragmentation. This approach allowed 206 peptides on average to be identified from a single mouse brain sample that was prepared using 15 μL of solutions per 1 mg of tissue. In total, we identified more than 500 endogenous peptides from mouse hypothalamus and whole brain samples. Our identification rate is about two to four times higher compared to previously reported studies conducted on mice or other species. The hydrophobic peptides, such as neuropeptide Y and galanin, could be presented and detected with hydrophilic peptides in the same LC−MS run, allowing a high coverage of peptide characterization over an organism. This will advance our understanding of the roles of diverse peptides and their links in the brain functions.

Journal of Proteome Research, 2009

We have applied a recently developed label-free mass spectrometry based peptidomic approach to id... more We have applied a recently developed label-free mass spectrometry based peptidomic approach to identify and quantify a variety of endogenous peptides from rat nucleus accumbens following withdrawal in naloxoneprecipitated, morphine-dependent rats of two separate strains. We focused on maturated, partially processed and truncated peptides derived from the peptide precursors proenkephalin, prodynorphin and preprotachykinin. The expression of several identified peptides was dependent on strain and was affected during morphine withdrawal.

Journal of Proteome Research, 2007

Differential quantification of proteins and peptides by LC-MS is a promising method to acquire kn... more Differential quantification of proteins and peptides by LC-MS is a promising method to acquire knowledge about biological processes, and for finding drug targets and biomarkers. However, differential protein analysis using LC-MS has been held back by the lack of suitable software tools. Large amounts of experimental data are easily generated in protein and peptide profiling experiments, but data analysis is time-consuming and laborintensive. Here, we present a fully automated method for scanning LC-MS/MS data for biologically significant peptides and proteins, including support for interactive confirmation and further profiling. By studying peptide mixtures of known composition, we demonstrate that peptides present in different amounts in different groups of samples can be automatically screened for using statistical tests. A linear response can be obtained over almost 3 orders of magnitude, facilitating further profiling of peptides and proteins of interest. Furthermore, we apply the method to study the changes of endogenous peptide levels in mouse brain striatum after administration of reserpine, a classical model drug for inducing Parkinson disease symptoms.

Journal of Proteome Research, 2013

Journal of Proteome Research, 2012

Neuropeptide identification in mass spectrometry experiments using database search programs devel... more Neuropeptide identification in mass spectrometry experiments using database search programs developed for proteins is challenging. Unlike proteins, the detection of the complete sequence using a single spectrum is required to identify neuropeptides or prohormone peptides. This study compared the performance of three open-source programs used to identify proteins, OMSSA, X!Tandem and Crux, to identify prohormone peptides. From a target database of 7850 prohormone peptides, 23550 query spectra were simulated across different scenarios. Crux was the only program that correctly matched all peptides regardless of p-value and at pvalue < 1 × 10 −2 , 33%, 64%, and >75%, of the 5, 6, and ≥7 amino acid-peptides were detected. Crux also had the best performance in the identification of peptides from chimera spectra and in a variety of missing ion scenarios. OMSSA, X!Tandem and Crux correctly detected 98.9% (99.9%), 93.9% (97.4%) and 88.7% (98.3%) of the peptides at E-or p-value < 1 × 10 −6 (< 1 × 10 −2), respectively. OMSSA and X! Tandem outperformed the other programs in significance level and computational speed, respectively. A consensus approach is not recommended because some prohormone peptides were only identified by one program.

npj Parkinson's Disease

L-DOPA administration is the primary treatment for Parkinson’s disease (PD) but long-term adminis... more L-DOPA administration is the primary treatment for Parkinson’s disease (PD) but long-term administration is usually accompanied by hyperkinetic side-effects called L-DOPA-induced dyskinesia (LID). Signaling neuropeptides of the basal ganglia are affected in LID and changes in the expression of neuropeptide precursors have been described, but the final products formed from these precursors have not been well defined and regionally mapped. We therefore used mass spectrometry imaging to visualize and quantify neuropeptides in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine exposed parkinsonian and LID Macaca mulatta brain samples. We found that dyskinesia severity correlated with the levels of some abnormally processed peptides — notably, des-tyrosine dynorphins, substance P (1-7), and substance P (1-9) — in multiple brain regions. Levels of the active neuropeptides; dynorphin B, dynorphin A (1-8), α-neoendorphin, substance P (1-11), and neurokinin A, in the globus pallidus and substantia...

Neurobiology of Disease, 2020

This is a PDF file of an article that has undergone enhancements after acceptance, such as the ad... more This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. Please note that, during the production process, errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Journal of The American Society for Mass Spectrometry, 2018

Frontiers in pharmacology, 2018

The trace amine-associated receptor 1 (TAAR1) is expressed by dopaminergic neurons, but the preci... more The trace amine-associated receptor 1 (TAAR1) is expressed by dopaminergic neurons, but the precise influence of trace amines upon their functional activity remains to be fully characterized. Here, we examined the regulation of tyrosine hydroxylase (TH) by tyramine and beta-phenylethylamine (β-PEA) compared to 3-iodothyronamine (TAM). Immunoblotting and amperometry were performed in dorsal striatal slices from wild-type (WT) and TAAR1 knockout (KO) mice. TAM increased TH phosphorylation at both Serand Ser, actions that should promote functional activity of TH. Indeed, HPLC data revealed higher rates of L-dihydroxyphenylalanine (DOPA) accumulation in WT animals treated with TAM after the administration of a DOPA decarboxylase inhibitor. These effects were abolished both in TAAR1 KO mice and by the TAAR1 antagonist, EPPTB. Further, they were specific inasmuch as Serphosphorylation of the post-synaptic GluA1 AMPAR subunit was unaffected. The effects of TAM on TH phosphorylation at both...

British journal of pharmacology, Jan 13, 2015

In pharmaceutical research, understanding the biodistribution, accumulation and metabolism of dru... more In pharmaceutical research, understanding the biodistribution, accumulation and metabolism of drugs in tissue plays a key role during drug discovery and development. In particular, information regarding pharmacokinetics, pharmacodynamics and transport properties of compounds in tissues is crucial during early screening. Historically, the abundance and distribution of drugs have been assessed by well-established techniques such as quantitative whole body autoradiography (WBA) or tissue homogenisation with liquid chromatography-mass spectrometry (LC/MS) analysis. However, WBA does not distinguish active drug from its metabolites and LC/MS, while highly sensitive, does not report spatial distribution. Mass spectrometry imaging (MSI) can discriminate drug and its metabolites and endogenous compounds, while simultaneously reporting their distribution. MSI data are influencing drug development and currently used in investigational studies in areas such compound toxicity. In in vivo studie...

Neurobiology of disease, 2014

A role for enhanced peptidergic transmission, either opioidergic or not, has been proposed for th... more A role for enhanced peptidergic transmission, either opioidergic or not, has been proposed for the generation of l-3,4-dihydroxyphenylalanine (l-DOPA)-induced dyskinesia (LID) on the basis of in situ hybridization studies showing that striatal peptidergic precursor expression consistently correlates with LID severity. Few studies, however, have focused on the actual peptides derived from these precursors. We used mass-spectrometry to study peptide profiles in the putamen and globus pallidus (internalis and externalis) collected from 1-methyl-4-phenyl-1,2,4,6-tetrahydropyridine treated macaque monkeys, acutely or chronically treated with l-DOPA. We identified that parkinsonian and dyskinetic states are associated with an abnormal production of proenkephalin-, prodynorphin- and protachykinin-1-derived peptides in both segments of the globus pallidus. Moreover, we report that peptidergic processing is dopamine-state dependent and highly structure-specific, possibly explaining the failu...

Neuron, 2014

Current neuroimaging techniques have very limited abilities to directly identify and quantify neu... more Current neuroimaging techniques have very limited abilities to directly identify and quantify neurotransmitters from brain sections. We have developed a molecular-specific approach for the simultaneous imaging and quantitation of multiple neurotransmitters, precursors, and metabolites, such as tyrosine, tryptamine, tyramine, phenethylamine, dopamine, 3-methoxytyramine, serotonin, GABA, glutamate, acetylcholine, and L-alpha-glycerylphosphorylcholine, in histological tissue sections at high spatial resolutions. The method is employed to directly measure changes in the absolute and relative levels of neurotransmitters in specific brain structures in animal disease models and in response to drug treatments, demonstrating the power of mass spectrometry imaging in neuroscience.

Rapid Communications in Mass Spectrometry, 2003

In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass ... more In vivo microdialysis in combination with liquid chromatography/electrospray time-of-flight mass spectrometry was used to study the processing of LVV-hemorphin-7, an endogenous decapeptide with opioid activity, in rat brain and blood. A microdialysis probe (flow rate 0.4 microL/min) was used to both introduce LVV-hemorphin-7 into the striatum of the brain (1.0 pmol/microL) or the venous blood (10 pmol/microL) and to collect the metabolic products. LVV-hemorphin-7 was extracellularly metabolized in the striatum to form C-terminal fragments 2-10, 3-10, 4-10, 5-10, 6-10, 7-10, and N-terminal fragments 1-9, 1-8, 1-6. Infusion of the aminopeptidase inhibitor amastatin (1.0 pmol/microL) into the striatum, together with LVV-hemorphin-7, decreased the processing of LVV-hemorphin-7 to form C-terminal fragments 2-10, 3-10, 4-10, but increased the relative levels of fragment 5-10 and N-terminal fragments 1-9, 1-8 and 1-6. The major metabolic product from LVV-hemorphin-7 in the striatum was the C-terminal fragment 5-10, which may be processed by an endopeptidase not sensitive to amastatin. The LVV-hemorphin-7 infusion to the venous blood produced the C-terminal fragments 2-10, 3-10, 4-10, and 5-10, N-terminal fragment 1-9, and internal fragments 4-7 and 4-9. It is concluded that the combination of microdialysis and electrospray mass spectrometry provides a powerful tool for the study of extracellular metabolism and kinetic processes of complex reaction systems in vivo.

Psychopharmacology, 1989

Leu- and Metenkephalin (Lenk and Menk) and their more stable analogues D-Ala-Leu- and D-Ala-Meten... more Leu- and Metenkephalin (Lenk and Menk) and their more stable analogues D-Ala-Leu- and D-Ala-Metenkephalin (DALenk and DAMenk) as well as D-Ala-D-Leu- and D-Ala-D-Metenkephalin (DADLenk and DADMenk) were infused bilaterally into substantia nigra in awake rats and oral movements were recorded for 90 min. DADLenk and DADMenk elicited dose-dependent biting dyskinesias with a chewing rate of about 90 jaw movements/min. DALenk produced a similar but weaker effect, whereas DAMenk, Lenk and Menk were ineffective in the doses given. These findings suggest a possible enkephalinergic mechanism underlying neuroleptic-induced tardive dyskinesias.

PROTEOMICS, 2011

The hypothalamus is the central regulatory region of the brain that links the nervous system to t... more The hypothalamus is the central regulatory region of the brain that links the nervous system to the endocrine system via the pituitary gland. It synthesizes and secretes neuropeptide hormones, which in turn act to stimulate or inhibit the secretion of pituitary hormones. We have undertaken a detailed MS investigation of the peptides present in the bovine hypothalamus by adapting a novel heat stabilization methodology, which improved peptide discovery to direct our studies into the molecular mechanisms involved in bovine reproduction. The untreated samples contained large numbers of protein degradation products that interfered with the analysis of the neuropeptides. In the thermally stabilized samples, we were able to identify many more neuropeptides that are known to be expressed in the bovine hypothalamus. Furthermore, we have characterized a range of post-translational modifications that indicate the presence of processed intact mature neuropeptides in the stabilized tissue samples, whereas we detected many trimmed or truncated peptides resulting from post-mortem degradation in the untreated tissue samples. Altogether, using an optimized workflow, we were able to identify 140 candidate neuropeptides. We also nominate six new candidate neuropeptides derived from proSAAS, secretogranin-2 and proTRH.

Preparative Biochemistry and Biotechnology, 1997

Two enzymes with substance P degrading activity were purified from the membrane bound fraction of... more Two enzymes with substance P degrading activity were purified from the membrane bound fraction of the rat spinal cord. The purified enzymes were characterized with regard to biochemical and kinetic properties. One of the enzymes exhibited close similarity to neutral endopeptidase 24.11 (NEP, EC 3.4.24.11), while the other resembled a substance P converting endopeptidase (SPE), which has previously been identified and purified from human cerebrospinal fluid (CSF). Detergent treated spinal cord homogenates from male Sprague Dawley rats were purified by anion-exchange chromatography (DEAE-sepharose CL-6B), hydrophobic-interaction chromatography (phenyl-sepharose CL-4B) and molecular sieving (Sephadex G-50). Two fractions with enzymes differing in size were recovered and allowed for further purification to apparent homogeneity by ion-exchange chromatography and molecular sieving on a micro-purification system (SMART). The enzyme activities were monitored by following the conversion of synthetic substance P using a radioimmunoassay specific for the heptapeptide product, substance P (1-7). By SDS-polyacrylamide gel electrophoresis of the purified enzymes molecular weights of 43 and 70 kDa were estimated for the SPE-like and NEP-like activity, respectively. A K(m) of 5 microM was determined for the conversion of substance P to its (1-7) fragment by the SPE-like activity. Reversed-phase HPLC together with mass spectrometry permitted identification of all fragments released from substance P by the peptidases. The released fragments were for both enzymes identified as substance P (1-7), substance P (8-11), substance P (1-8), substance P (9-11). The NEP-like enzyme preparation also gave substance P (1-6) as a major product.

PLoS ONE, 2008

L-3,4-dihydroxypheylalanine (L-dopa)-induced dyskinesia represent a debilitating complication of ... more L-3,4-dihydroxypheylalanine (L-dopa)-induced dyskinesia represent a debilitating complication of therapy for Parkinson's disease (PD) that result from a progressive sensitization through repeated L-dopa exposures. The MPTP macaque model was used to study the proteome in dopamine-depleted striatum with and without subsequent acute and chronic L-dopa treatment using two-dimensional difference in-gel electrophoresis (2D-DIGE) and mass spectrometry. The present data suggest that the dopamine-depleted striatum is so sensitive to de novo L-dopa treatment that the first ever administration alone would be able (i) to induce rapid post-translational modification-based proteomic changes that are specific to this first exposure and (ii), possibly, lead to irreversible protein level changes that would be not further modified by chronic L-dopa treatment. The apparent equivalence between first and chronic L-dopa administration suggests that priming would be the direct consequence of dopamine loss, the first L-dopa administrations only exacerbating the sensitization process but not inducing it.

Neuropsychopharmacology, 2013

Mass spectrometry imaging is a powerful tool for directly determining the distribution of protein... more Mass spectrometry imaging is a powerful tool for directly determining the distribution of proteins, peptides, lipids, neurotransmitters, metabolites and drugs in neural tissue sections in situ. Molecule-specific imaging can be achieved using various ionization techniques that are suited to different applications but which all yield data with high mass accuracies and spatial resolutions. The ability to simultaneously obtain images showing the distributions of chemical species ranging from metal ions to macromolecules makes it possible to explore the chemical organization of a sample and to correlate the results obtained with specific anatomical features. The imaging of biomolecules has provided new insights into multiple neurological diseases, including Parkinson's and Alzheimer's disease. Mass spectrometry imaging can also be used in conjunction with other imaging techniques in order to identify correlations between changes in the distribution of important chemical species and other changes in the properties of the tissue. Here we review the applications of mass spectrometry imaging in neuroscience research and discuss its potential. The results presented demonstrate that mass spectrometry imaging is a useful experimental method with diverse applications in neuroscience.

Neuropharmacology, 2012

Open access under CC BY-NC-ND license. Open access under CC BY-NC-ND license.

Molecular & Cellular Proteomics, 2013

The chronic use of nicotine, the main psychoactive ingredient of tobacco smoking, alters diverse ... more The chronic use of nicotine, the main psychoactive ingredient of tobacco smoking, alters diverse physiological processes and consequently generates physical dependence. To understand the impact of chronic nicotine on neuropeptides, which are potential molecules associated with dependence, we conducted qualitative and quantitative neuropeptidomics on the rat dorsal striatum (DS), an important brain region implicated in the preoccupation/craving phase of drug dependence. We used extensive LC-FT-MS/MS analyses for neuropeptide identification and LC-FT-MS in conjunction with stable isotope addition for relative quantification. The treatment with chronic nicotine for three months led to moderate changes in the levels of endogenous DS peptides. Five enkephalin opioid peptides were upregulated, while no change was observed for dynorphin peptides. Specially, nicotine altered levels of 9 non-opioid peptides derived from precursors including somatostatin and cerebellin, which potentially modulate neurotransmitter release and energy metabolism. This broad but selective impact on the multiple peptidergic systems suggests that apart from the opioid peptides, several other peptidergic systems are involved in the preoccupation/craving phase of drug dependence. Our finding permits future evaluation of the neurochemical circuits modulated by chronic nicotine exposure and provides a number of novel molecules that could serve as potential therapeutic targets for treating drug dependence.

Journal of Proteome Research, 2012

Mass spectrometry-based neuropeptidomics is one of the most powerful approaches for identificatio... more Mass spectrometry-based neuropeptidomics is one of the most powerful approaches for identification of endogenous neuropeptides in the brain. Until now, however, the identification rate of neuropeptides in neuropeptidomics is relatively low and this severely restricts insights into their biological function. In the present study, we developed a high accuracy mass spectrometry-based approach to enhance the identification rates of neuropeptides from brain tissue. Our integrated approach used mixing on column for loading aqueous and organic extracts to reduce the loss of peptides during sample treatment and used charge state-directed tandem mass spectrometry to increase the number of peptides subjected to high mass accuracy fragmentation. This approach allowed 206 peptides on average to be identified from a single mouse brain sample that was prepared using 15 μL of solutions per 1 mg of tissue. In total, we identified more than 500 endogenous peptides from mouse hypothalamus and whole brain samples. Our identification rate is about two to four times higher compared to previously reported studies conducted on mice or other species. The hydrophobic peptides, such as neuropeptide Y and galanin, could be presented and detected with hydrophilic peptides in the same LC−MS run, allowing a high coverage of peptide characterization over an organism. This will advance our understanding of the roles of diverse peptides and their links in the brain functions.

Journal of Proteome Research, 2009

We have applied a recently developed label-free mass spectrometry based peptidomic approach to id... more We have applied a recently developed label-free mass spectrometry based peptidomic approach to identify and quantify a variety of endogenous peptides from rat nucleus accumbens following withdrawal in naloxoneprecipitated, morphine-dependent rats of two separate strains. We focused on maturated, partially processed and truncated peptides derived from the peptide precursors proenkephalin, prodynorphin and preprotachykinin. The expression of several identified peptides was dependent on strain and was affected during morphine withdrawal.

Journal of Proteome Research, 2007

Differential quantification of proteins and peptides by LC-MS is a promising method to acquire kn... more Differential quantification of proteins and peptides by LC-MS is a promising method to acquire knowledge about biological processes, and for finding drug targets and biomarkers. However, differential protein analysis using LC-MS has been held back by the lack of suitable software tools. Large amounts of experimental data are easily generated in protein and peptide profiling experiments, but data analysis is time-consuming and laborintensive. Here, we present a fully automated method for scanning LC-MS/MS data for biologically significant peptides and proteins, including support for interactive confirmation and further profiling. By studying peptide mixtures of known composition, we demonstrate that peptides present in different amounts in different groups of samples can be automatically screened for using statistical tests. A linear response can be obtained over almost 3 orders of magnitude, facilitating further profiling of peptides and proteins of interest. Furthermore, we apply the method to study the changes of endogenous peptide levels in mouse brain striatum after administration of reserpine, a classical model drug for inducing Parkinson disease symptoms.

Journal of Proteome Research, 2013

Journal of Proteome Research, 2012

Neuropeptide identification in mass spectrometry experiments using database search programs devel... more Neuropeptide identification in mass spectrometry experiments using database search programs developed for proteins is challenging. Unlike proteins, the detection of the complete sequence using a single spectrum is required to identify neuropeptides or prohormone peptides. This study compared the performance of three open-source programs used to identify proteins, OMSSA, X!Tandem and Crux, to identify prohormone peptides. From a target database of 7850 prohormone peptides, 23550 query spectra were simulated across different scenarios. Crux was the only program that correctly matched all peptides regardless of p-value and at pvalue < 1 × 10 −2 , 33%, 64%, and >75%, of the 5, 6, and ≥7 amino acid-peptides were detected. Crux also had the best performance in the identification of peptides from chimera spectra and in a variety of missing ion scenarios. OMSSA, X!Tandem and Crux correctly detected 98.9% (99.9%), 93.9% (97.4%) and 88.7% (98.3%) of the peptides at E-or p-value < 1 × 10 −6 (< 1 × 10 −2), respectively. OMSSA and X! Tandem outperformed the other programs in significance level and computational speed, respectively. A consensus approach is not recommended because some prohormone peptides were only identified by one program.