Glucocerebrosidase expression patterns in the non-human primate brain

Glucocerebrosidase (GCase) is a lysosomal enzyme encoded by the GBA1 gene. Mutations in GBA1 gene lead to Gaucher’s disease, the most prevalent lysosomal storage disorder. GBA1 mutations reduce GCase activity, therefore promoting the aggregation of alphasynuclein, a common neuropathological finding underlying Parkinson’s disease (PD) and dementia with Lewy bodies. However, it is also worth noting that a direct link between GBA1 mutations and alpha-synuclein aggregation indicating cause and effect is still lacking, with limited experimental evidence to date. Bearing in mind that a number of strategies increasing GCase expression for the treatment of PD are currently under development, here we sought to analyze the baseline expression of GCase in the brain of Macaca fascicularis, which has often been considered as the gold-standard animal model of PD. Although as with other lysosomal enzymes, GCase is expected to be ubiquitously expressed, here a number of regional variations have been consistently found, together with several specific neurochemical phenotypes expressing very high levels of GCase. In this regard, the most enriched expression of GCase was constantly found in cholinergic neurons from the nucleus basalis of Meynert, dopaminergic cells in the substantia nigra pars compacta, serotoninergic neurons from the raphe nuclei, as well as in noradrenergic neurons located in the locus ceruleus. Moreover, it is also worth noting that moderate levels of expression were also found in a number of areas within the paleocortex and archicortex, such as the entorhinal cortex and the hippocampal formation, respectively

Mitochondrial angiotensin receptors in dopaminergic neurons. Role in cell protection and aging-related vulnerability to neurodegeneration

The renin-angiotensin system (RAS) was initially considered as a circulating humoral system controlling blood pressure, being kidney the key control organ. In addition to the \u27classical\u27 humoral RAS, a second level in RAS, local or tissular RAS, has been identified in a variety of tissues, in which local RAS play a key role in degenerative and aging-related diseases. The local brain RAS plays a major role in brain function and neurodegeneration. It is normally assumed that the effects are mediated by the cell-surface-specific G-protein-coupled angiotensin type 1 and 2 receptors (AT1 and AT2). A combination of in vivo (rats, wild-type mice and knockout mice) and in vitro (primary mesencephalic cultures, dopaminergic neuron cell line cultures) experimental approaches (confocal microscopy, electron microscopy, laser capture microdissection, transfection of fluorescent-tagged receptors, treatments with fluorescent angiotensin, western blot, polymerase chain reaction, HPLC, mitochondrial respirometry and other functional assays) were used in the present study. We report the discovery of AT1 and AT2 receptors in brain mitochondria, particularly mitochondria of dopaminergic neurons. Activation of AT1 receptors in mitochondria regulates superoxide production, via Nox4, and increases respiration. Mitochondrial AT2 receptors are much more abundant and increase after treatment of cells with oxidative stress inducers, and produce, via nitric oxide, a decrease in mitochondrial respiration. Mitochondria from the nigral region of aged rats displayed altered expression of AT1 and AT2 receptors. AT2-mediated regulation of mitochondrial respiration represents an unrecognized primary line of defence against oxidative stress, which may be particularly important in neurons with increased levels of oxidative stress such as dopaminergic neurons. Altered expression of AT1 and AT2 receptors with aging may induce mitochondrial dysfunction, the main risk factor for neurodegeneratio

Nigral and striatal regulation of angiotensin receptor expression by dopamine and angiotensin in rodents: implications for progression of Parkinson's disease

The basal ganglia have a local renin-angiotensin system and it has been shown that the loss of dopaminergic neurons induced by neurotoxins is amplified by local angiotensin II (AII) via angiotensin type 1 receptors (AT1) and nicotinamide adenine dinucleotide phosphate (NADPH) complex activation. Recent studies have revealed a high degree of counter-regulatory interactions between dopamine and AII receptors in non-neural cells such as renal proximal tubule cells. However, it is not known if this occurs in the basal ganglia. In the striatum and nigra, depletion of dopamine with reserpine induced a significant increase in the expression of AT1, angiotensin type 2 receptors (AT2) and the NADPH subunit p47(phox) , which decreased as dopamine function was restored. Similarly, 6-hydroxydopamine-induced chronic dopaminergic denervation induced a significant increase in expression of AT1, AT2 and p47(phox) , which decreased with L-dopa administration. A significant reduction in expression of AT1 mRNA was also observed after administration of dopamine to cultures of microglial cells. Transgenic rats with very low levels of brain AII showed increased AT1, decreased p47 (phox) and no changes in AT2 expression, whereas mice deficient in AT1 exhibited a decrease in the expression of p47 (phox) and AT2. The administration of relatively high doses of AII (100 nm) decreased the expression of AT1, and the increased expression of AT2 and p47(phox) in primary mesencephalic cultures. The results reveal an important interaction between the dopaminergic and local renin-angiotensin system in the basal ganglia, which may be a major factor in the progression of Parkinson's disease

Estrogen and angiotensin interaction in the substantia nigra. Relevance to postmenopausal Parkinson's disease

Epidemiological studies have reported that the incidence of Parkinson's disease (PD) is higher in postmenopausal than in premenopausal women of similar age. Several laboratory observations have revealed that estrogen has protective effects against dopaminergic toxins. The mechanism by which estrogen protects dopaminergic neurons has not been clarified, although estrogen-induced attenuation of the neuroinflammatory response plays a major role. We have recently shown that activation of the nigral renin-angiotensin system (RAS), via type 1 (AT1) receptors, leads to NADPH complex and microglial activation and induces dopaminergic neuron death. In the present study we investigated the effect of ovariectomy and estrogen replacement on the nigral RAS and on dopaminergic degeneration induced by intrastriatal injection of 6-OHDA. We observed a marked loss of dopaminergic neurons in ovariectomized rats treated with 6-OHDA, which was significantly reduced by estrogen replacement or treatment with the AT1 receptor antagonist candesartan. We also observed that estrogen replacement induces significant downregulation of the activity of the angiotensin converting enzyme as well as downregulation of AT1 receptors, upregulation of AT2 receptors and downregulation of the NADPH complex activity in the substantia nigra in comparison with ovariectomized rats. The present results suggest that estrogen-induced down-regulation of RAS and NADPH activity may be associated with the reduced risk of PD in premenopausal women, and increased risk in conditions causing early reduction in endogenous estrogen, and that manipulation of brain RAS system may be an efficient approach for the prevention or coadjutant treatment of PD in estrogen-deficient women

Estrogen and angiotensin interaction in the substantia nigra. Relevance to postmenopausal Parkinson's disease

Epidemiological studies have reported that the incidence of Parkinson's disease (PD) is higher in postmenopausal than in premenopausal women of similar age. Several laboratory observations have revealed that estrogen has protective effects against dopaminergic toxins. The mechanism by which estrogen protects dopaminergic neurons has not been clarified, although estrogen-induced attenuation of the neuroinflammatory response plays a major role. We have recently shown that activation of the nigral renin-angiotensin system (RAS), via type 1 (AT1) receptors, leads to NADPH complex and microglial activation and induces dopaminergic neuron death. In the present study we investigated the effect of ovariectomy and estrogen replacement on the nigral RAS and on dopaminergic degeneration induced by intrastriatal injection of 6-OHDA. We observed a marked loss of dopaminergic neurons in ovariectomized rats treated with 6-OHDA, which was significantly reduced by estrogen replacement or treatment with the AT1 receptor antagonist candesartan. We also observed that estrogen replacement induces significant downregulation of the activity of the angiotensin converting enzyme as well as downregulation of AT1 receptors, upregulation of AT2 receptors and downregulation of the NADPH complex activity in the substantia nigra in comparison with ovariectomized rats. The present results suggest that estrogen-induced down-regulation of RAS and NADPH activity may be associated with the reduced risk of PD in premenopausal women, and increased risk in conditions causing early reduction in endogenous estrogen, and that manipulation of brain RAS system may be an efficient approach for the prevention or coadjutant treatment of PD in estrogen-deficient women

Location of prorenin receptors in primate substantia nigra: effects on dopaminergic cell death

Angiotensin II acts via angiotensin type 1 receptors and is a major inducer of inflammation and oxidative stress. Local renin-angiotensin systems play a major role in the development of age-related disorders in several tissues. These processes are delayed, but not totally abolished, by blockade of angiotensin signaling. A specific receptor for renin and its precursor prorenin has recently been identified. We previously showed that neurotoxin-induced dopaminergic (DA) cell loss is decreased by inhibition of angiotensin receptors, but the location and functional effects of prorenin receptor (PRR) in the brain, including the DA system, are unknown. In the substantia nigra of Macaca fascicularis and in rat primary mesencephalic cultures, double immunofluorescence analysis revealed PRR immunoreactivity in neurons (including DA neurons) and microglia, but not in astrocytes. Administration of the PRR blocker, handle region peptide, led to a significant decrease in 6-hydroxydopamine-induced DA cell death in the cultures,whereas administration of renin with simultaneous blockade of angiotensin receptors led to an increase in 6-hydroxydopamine-induced cell death. These results suggest that active agent angiotensin II-independent PRR intracellular signaling may contribute to exacerbation of DA cell death in vivo. Therefore, potential neuroprotective strategies for DA neurons in Parkinson disease should address both angiotensin and PRR signaling

Location of prorenin receptors in primate substantia nigra: effects on dopaminergic cell death

Angiotensin II acts via angiotensin type 1 receptors and is a major inducer of inflammation and oxidative stress. Local renin-angiotensin systems play a major role in the development of age-related disorders in several tissues. These processes are delayed, but not totally abolished, by blockade of angiotensin signaling. A specific receptor for renin and its precursor prorenin has recently been identified. We previously showed that neurotoxin-induced dopaminergic (DA) cell loss is decreased by inhibition of angiotensin receptors, but the location and functional effects of prorenin receptor (PRR) in the brain, including the DA system, are unknown. In the substantia nigra of Macaca fascicularis and in rat primary mesencephalic cultures, double immunofluorescence analysis revealed PRR immunoreactivity in neurons (including DA neurons) and microglia, but not in astrocytes. Administration of the PRR blocker, handle region peptide, led to a significant decrease in 6-hydroxydopamine-induced DA cell death in the cultures,whereas administration of renin with simultaneous blockade of angiotensin receptors led to an increase in 6-hydroxydopamine-induced cell death. These results suggest that active agent angiotensin II-independent PRR intracellular signaling may contribute to exacerbation of DA cell death in vivo. Therefore, potential neuroprotective strategies for DA neurons in Parkinson disease should address both angiotensin and PRR signaling

Glucocerebrosidase expression patterns in the non-human primate brain

Glucocerebrosidase (GCase) is a lysosomal enzyme encoded by the GBA1 gene. Mutations in GBA1 gene lead to Gaucher’s disease, the most prevalent lysosomal storage disorder. GBA1 mutations reduce GCase activity, therefore promoting the aggregation of alphasynuclein, a common neuropathological finding underlying Parkinson’s disease (PD) and dementia with Lewy bodies. However, it is also worth noting that a direct link between GBA1 mutations and alpha-synuclein aggregation indicating cause and effect is still lacking, with limited experimental evidence to date. Bearing in mind that a number of strategies increasing GCase expression for the treatment of PD are currently under development, here we sought to analyze the baseline expression of GCase in the brain of Macaca fascicularis, which has often been considered as the gold-standard animal model of PD. Although as with other lysosomal enzymes, GCase is expected to be ubiquitously expressed, here a number of regional variations have been consistently found, together with several specific neurochemical phenotypes expressing very high levels of GCase. In this regard, the most enriched expression of GCase was constantly found in cholinergic neurons from the nucleus basalis of Meynert, dopaminergic cells in the substantia nigra pars compacta, serotoninergic neurons from the raphe nuclei, as well as in noradrenergic neurons located in the locus ceruleus. Moreover, it is also worth noting that moderate levels of expression were also found in a number of areas within the paleocortex and archicortex, such as the entorhinal cortex and the hippocampal formation, respectively

Expression of the mRNA coding the cannabinoid receptor 2 in the pallidal complex of Macaca fascicularis

The putative presence of the cannabinoid receptor type 2 (CB(2)-R) in the central nervous system is still a matter of debate. Although first described in peripheral and immune tissues, evidence suggesting the existence of CB(2)-Rs in glial cells and even neurons has been made available more recently. By taking advantage of newly designed CB(2)-R mRNA riboprobes, we have demonstrated by in situ hybridization and PCR the existence of CB2-R transcripts in a variety of brain areas of the primate Macaca fascicularis, including the cerebral cortex and the hippocampus, as well as in the external and internal divisions of the globus pallidus, both pallidal segments showing the highest abundance of CB(2)-R transcripts. In this regard, the presence of the messenger coding CB(2)-Rs within the pallidal complex highlights their consideration as potential targets for the treatment of movement disorders of basal ganglia origin

Detection of cannabinoid receptors CB1 and CB2 within basal ganglia output neurons in macaques: changes following experimental parkinsonism

Abstract Although type 1 cannabinoid receptors (CB1- Rs) are expressed abundantly throughout the brain, the presence of type 2 cannabinoid receptors (CB2Rs) in neurons is still somewhat controversial. Taking advantage of newly designed CB1R and CB2R mRNA riboprobes, we demonstrate by PCR and in situ hybridization that transcripts for both cannabinoid receptors are present within labeled pallidothalamic-projecting neurons of control and MPTP-treated macaques, whereas the expression is markedly reduced in dyskinetic animals. Moreover, an in situ proximity ligation assay was used to qualitatively assess the presence of CB1Rs and CB2Rs, as well as CB1R–CB2R heteromers within basal ganglia output neurons in all animal groups (control, parkinsonian and dyskinetic macaques). A marked reduction in the number of CB1Rs, CB2Rs and CB1R–CB2R heteromers was found in dyskinetic animals, mimicking the observed reduction in CB1R and CB2R mRNA expression levels. The fact that chronic levodopa treatment disrupted CB1R–CB2R heteromeric complexes should be taken into consideration when designing new drugs acting on cannabinoid receptor heteromers