The neuroprotective effect of overexpression of calbindin-D(28k) in an animal model of Parkinson's disease

Differential expression of calbindin in nigral dopaminergic neurons in two mice strains with differential susceptibility to 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine

Parkinson's disease (PD) affects the A9 dopaminergic (DA) neurons of substantia nigra pars compacta (SNpc) whereas other DA neuronal subtypes are spared. The role of calbindin in this differential vulnerability has been long elicited, and is seen in the MPTP induced mice models of PD. A peculiar feature of mice models is the strain specific differences in the susceptibility to MPTP. Here, calbindin-D28K expression in DA neurons of SNpc of MPTP susceptible C57BL/6 mice and MPTP resistant CD-1 mice was studied as a susceptibility marker of degeneration. Unbiased stereological estimation of immunoperoxidase stained midbrain sections revealed significantly higher number of calbindin immunoreactive cells in SNpc of CD-1 mice compared to that of C57BL/6 strain. Western blotting showed minimal differences in the levels. Calbindin-tyrosine hydroxylase immunofluorescence co-labeling was performed to map the calbindin immunoreactive DA neurons in SNpc and ventral tegmental area (VTA) and to quantify the calbindin expression at cellular level. While the levels were comparable in VTA of both mice strains, the SNpc of CD-1 mice showed significantly higher calbindin expression. Within the SNpc, the medial and dorsal subdivisions showed higher calbindin expression in CD-1. The expression in the ventrolateral SNpc of both strains remained comparable. Our observations clearly point at overall higher levels and sizeable percentage of cells expressing more calbindin in SNpc of CD-1 mice, which might confer neuroprotection against MPTP, while its lower expression makes C57BL/6 mice more susceptible. Similar mechanism may be attributed to the phenomenon of differential prevalence of PD in different ethnic populations.

ERK1, 2, and 5 expression and activation in dopaminergic brain regions during postnatal development

Degeneration and dysfunctioning of dopaminergic neurons in the midbrain have been associated with serious neurodegenerative and neuropsychiatric disorders. Elucidating the underlying neurobiology of these neurons during early postnatal development may provide important information regarding the etiology of these disorders. Cellular signaling pathways have been shown to regulate postnatal neuronal development. Among several signaling pathways, extracellular-regulated mitogen kinases (ERK) 1, 2, and 5 have been shown to be crucial for the survival and function of dopaminergic neurons. In this study, the basal expression and activation of ERK1, 2, and 5 were studied during postnatal development in regions rich in DA cells and terminals. In the striatum (STR) and ventral mesencephalon regions of the substantia nigra (SN) and ventral tegmental area (VTA), ERK5 expression and activation were high during early postnatal days and declined with aging. Interestingly, sharp increases in phosphorylated or activated ERK1 and ERK2 were observed at postnatal day (PND) 7 in the SN and VTA. In contrast, in the STR, the levels of phosphorylated ERK1 and 2 were significantly higher at PND0 than at any other PND examined. Overall, the understanding of alterations in ERK signaling in regions rich in DA cells and DA terminals during postnatal neuronal development may provide information about their role in regulation of dopamine neuronal development which may ultimately provide insight into the underlying mechanisms of dopamine neurodegeneration.

Drosophila Cbp53E Regulates Axon Growth at the Neuromuscular Junction

Calcium is a primary second messenger in all cells that functions in processes ranging from cellular proliferation to synaptic transmission. Proper regulation of calcium is achieved through numerous mechanisms involving channels, sensors, and buffers notably containing one or more EF-hand calcium binding domains. The Drosophila genome encodes only a single 6 EF-hand domain containing protein, Cbp53E, which is likely the prototypic member of a small family of related mammalian proteins that act as calcium buffers and calcium sensors. Like the mammalian homologs, Cbp53E is broadly though discretely expressed throughout the nervous system. Despite the importance of calcium in neuronal function and growth, nothing is known about Cbp53E's function in neuronal development. To address this deficiency, we generated novel null alleles of Drosophila Cbp53E and examined neuronal development at the well-characterized larval neuromuscular junction. Loss of Cbp53E resulted in increases in axonal branching at both peptidergic and glutamatergic neuronal terminals. This overgrowth could be completely rescued by expression of exogenous Cbp53E. Overexpression of Cbp53E, however, only affected the growth of peptidergic neuronal processes. These findings indicate that Cbp53E plays a significant role in neuronal growth and suggest that it may function in both local synaptic and global cellular mechanisms.

Comparison of immunoreactivities of calbindin-D28k, calretinin and parvalbumin in the striatum between young, adult and aged mice, rats and gerbils

Calcium binding proteins play important roles in all aspects of neural functioning in the central nervous system. In the present study, we examined age-related changes of three different calcium binding proteins calbindin-D28k (CB), calretinin (CR) and parvalbumin (PV) immunoreactivities in the striatum of young (1 month), adult (6 months) and aged (24 months) ages in three species of rodents (mouse, rat and gerbil) using immunohistochemistry and Western blotting. Our results show that the number of CB-immunoreactive neurons was highest in the adult mouse and rat; however, in the gerbil, the number of CB-immunoreactive neurons was not significantly different from each group although the CB immunoreactivity was significantly decreased in the aged group compared with the adult group. The number of CR-immunoreactive neurons in the striatum was significantly highest in all the adult groups, and, especially, the number of CR-immunoreactive neurons and CR immunoreactivity in the aged gerbil were significantly decreased in the aged group compared with the other groups. Finally, we did not found any significant difference in the number of PV-immunoreactive neurons in the striatum with age among the three rodents. On the other hand, we found that protein levels of three calcium binding proteins in all the mouse groups were similar to the immunohistochemical data. These results indicate that the distribution pattern of calcium binding proteins is different according to age; the adult might show an apparent tendency of high expression in the striatum.

In vitro models for neurotoxicology research

The nervous system has a highly complex organization, including many cell types with multiple functions, with an intricate anatomy and unique structural and functional characteristics; the study of its (dys)functionality following exposure to xenobiotics, neurotoxicology, constitutes an important issue in neurosciences.

Calbindin content and differential vulnerability of midbrain efferent dopaminergic neurons in macaques

Calbindin (CB) is a calcium binding protein reported to protect dopaminergic neurons from degeneration. Although a direct link between CB content and differential vulnerability of dopaminergic neurons has long been accepted, factors other than CB have also been suggested, particularly those related to the dopamine transporter. Indeed, several studies have reported that CB levels are not causally related to the differential vulnerability of dopaminergic neurons against neurotoxins. Here we have used dual stains for tyrosine hydroxylase (TH) and CB in 3 control and 3 MPTP-treated monkeys to visualize dopaminergic neurons in the ventral tegmental area (VTA) and in the dorsal and ventral tiers of the substantia nigra pars compacta (SNcd and SNcv) co-expressing TH and CB. In control animals, the highest percentages of co-localization were found in VTA (58.2%), followed by neurons located in the SNcd (34.7%). As expected, SNcv neurons lacked CB expression. In MPTP-treated animals, the percentage of CB-ir/TH-ir neurons in the VTA was similar to control monkeys (62.1%), whereas most of the few surviving neurons in the SNcd were CB-ir/TH-ir (88.6%). Next, we have elucidated the presence of CB within identified nigrostriatal and nigroextrastriatal midbrain dopaminergic projection neurons. For this purpose, two control monkeys received one injection of Fluoro-Gold into the caudate nucleus and one injection of cholera toxin (CTB) into the postcommissural putamen, whereas two more monkeys were injected with CTB into the internal division of the globus pallidus (GPi). As expected, all the nigrocaudate- and nigroputamen-projecting neurons were TH-ir, although surprisingly, all of these nigrostriatal-projecting neurons were negative for CB. Furthermore, all the nigropallidal-projecting neurons co-expressed both TH and CB. In summary, although CB-ir dopaminergic neurons seem to be less prone to MPTP-induced degeneration, our data clearly demonstrated that these neurons are not giving rise to nigrostriatal projections and indeed CB-ir/TH-ir neurons only originate nigroextrastriatal projections.

Transient neuroprotection by SRY upregulation in dopamine cells following injury in males

Emerging evidence suggest sex-specific regulation of dopamine neurons may underlie susceptibility of males to disorders such as Parkinson's disease (PD). In healthy male dopamine neurons, the Y-chromosome gene product, the sex-determining region on the Y chromosome (SRY) modulates dopamine biosynthesis and motor function. We investigated the regulation and function of SRY in a model of dopamine cell injury. Treatment with the dopaminergic toxin, 6-hydroxydopamine (6-OHDA), significantly elevated SRY mRNA expression (9-fold) in human male dopamine M17 cells. SRY up-regulation occurred via the p-quinone pathway, associated with a 3.5-fold increase in expression of GADD45γ, a DNA damage inducible factor gene and known SRY regulator. In turn, a signaling cascade involving GADD45γ/p38-MAPK/GATA activated the SRY promoter. Knockdown of SRY mRNA in 6-OHDA-treated M17 cells was deleterious, increasing levels of reactive oxygen species (ROS), pro-apoptotic marker PUMA mRNA, and cell injury (+25%, +32% and +34%, respectively). Conversely, ectopic over-expression of SRY in 6-OHDA-treated female SH-SY5Y cells was protective, decreasing ROS, PUMA, and cell injury (-40%, -46%, and -30%, respectively). However, the 6-OHDA-induced increase in SRY expression was diminished with higher concentrations of toxins or with chronic exposure to 6-OHDA. We conclude that SRY upregulation after dopamine cell injury is initially a protective response in males, but diminishes with gradual loss in dopamine cells. We speculate that dysregulation of SRY may contribute the susceptibility of males to PD.

Interleukin-1 receptor antagonist promotes survival of ventral horn neurons and suppresses microglial activation in mouse spinal cord slice cultures

Secondary damage after spinal cord injury (SCI) induces neuronal demise through neurotoxicity and inflammation, and interleukin (IL)-1β is a key inflammatory mediator. We hypothesized that IL-1β is released in spinal cord slice cultures (SCSC) and aimed at preventing the potentially neurotoxic effects of IL-1β by using interleukin-1 receptor antagonist (IL1RA). We hypothesized that IL1RA treatment enhances neuronal survival and suppresses microglial activation. SCSC were cultured up to 8 days in vitro (DIV) in the presence of IL1RA or without, either combined with trophic support using neurotrophin (NT)-3 or not. Four groups were studied: negative control, IL1RA, NT-3, and IL1RA + NT-3. IL-1β concentrations in supernatants were measured by ELISA. SCSC were immunohistochemically stained for NeuN and α-neurofilament, and microglial cells were visualized with isolectin B4 . After 8 DIV, ventral horn neurons were significantly more numerous in the IL1RA, NT-3, and IL1RA + NT-3 groups compared with negative controls. Activated microglial cells were significantly less numerous in the IL1RA, NT-3, and IL1RA + NT-3 groups compared with negative controls. Axons expanded into the collagen matrix after treatment with IL1RA, NT-3, or IL1RA + NT-3, but not in negative controls. IL-1β release from cultures peaked after 6 hr and was lowest in the IL1RA + NT-3 group. We conclude that IL-1β is released in traumatized spinal cord tissue and that IL1RA could exert its neuroprotective actions by blocking IL-1-receptors. IL1RA thereby sustains neuronal survival irrespective of the presence of additional trophic support. Microglial activation is suppressed in the presence of IL1RA, suggesting decreased inflammatory activity. IL1RA treatment approaches may have substantial impact following SCI.

Calbindin-D28K immunoreactivity in the human cerebellar cortex

Calbindin-D28k (CB) is a calcium-binding protein largely distributed in the cerebellum of various species of vertebrates. As regards the human cerebellar cortex, precise data on the distribution of CB have not yet been reported. Aim of the present work was to analyze the distribution of CB in postmortem samples of human cerebellar cortex using light microscopy immunohistochemical techniques. Immunoreactivity to CB was detected within neuronal bodies and processes distributed in all cortex layers. In the molecular layer, the immunoreactivity was observed in subpopulations of stellate and basket neurons. In the Purkinje neuron layer, the immunoreactivity was observed in practically all the Purkinje neurons. In the granular layer, the immunoreactivity was observed in subpopulations of granules, of Golgi neurons, and also of other types of large neurons (candelabrum, Lugaro neurons, etc.). Immunoreactivity to CB was also observed in axon terminals distributed throughout the cortex according to layer-specific patterns of distribution. The qualitative and quantitative patterns of distribution of CB showed no difference among the different lobes of the cerebellar cortex. This study reports that CB is expressed by different neuron types, both inhibitory (GABAergic) and excitatory (glutamatergic), involved in both intrinsic and extrinsic circuits of the human cerebellar cortex. The study provides further insights on the functional role of CB and on the neuronal types of the cerebellar cortex in which it is expressed.

Embryonic and postnatal development of calcium-binding proteins immunoreactivity in the anterior thalamus of the guinea pig

Our recent studies have shown that the distribution of calretinin (CR) in the anterior thalamic nuclei (ATN) changes significantly during the development of the guinea pig. The present study was designed to reveal the distribution pattern of calcium-binding proteins, i.e. calbindin (CB) and parvalbumin (PV), as well as the colocalization pattern of all three proteins, including CR, in the ATN of guinea pigs ranging from the 40th embryonic day (E40) to the 80th postnatal day (P80). According to these patterns, CB appears exclusively in the perikarya of the anteromedial nucleus (AM) not before P20 and always colocalizes with CR. Moreover, CB and CR colocalize in fibers of thin bundles traversing the anteroventral nucleus (AV) since E50. The ATN also display CB-positive neuropil in all studied stages, especially a strong one in the ventral part of the AV. PV was not observed in the perikarya of the ATN in all the stages, but was abundantly present in the neuropil of the anterodorsal nucleus (AD). No colocalizations exist between PV and the rest of the studied proteins. In conclusion, our study reveals that the distribution of the studied proteins differs greatly. Nevertheless, the postnatal coexistence of CB and CR in the AM perikarya may indicate the cooperation of both of the proteins in some functions of the nucleus. Parvalbumin is limited mostly to the neuropil of the AD, suggesting different functions in comparison to CB and CR.

Changes in expression of calbindin 28 kDa in the small intestine of red kidney bean (Phaseolus vulgaris) lectin-treated suckling piglets

Calbindin (CB) is a calcium binding protein playing a role in calcium uptake and anti-apoptotic cellular protection. The expression of CB was immunohistochemically studied in the small intestine of normal and red bean kidney lectin-treated suckling piglets. In the duodenum and jejunum (but not ileum) of lectin-treated animals overexpression of CB was noted in chromogranin A-immunoreactive (CgA-IR) neuroendocrine (NE) cells. In both control and experimental group a small population of CB-IR NE cells exhibited the presence of somatostatin (but not serotonin, histamine or CRF). After the lectin treatment, an increased (however not statistically significant) immunoreactivity to CB was found in a small subpopulation of neurons of outer submucous (but not inner submucous and myenteric) plexus. It is suggested that there is a functional interaction between lectin administration and CB-expression in the porcine small intestine. Future studies will be needed to clarify this processes.

Paternal deprivation affects the functional maturation of corticotropin-releasing hormone (CRH)- and calbindin-D28k-expressing neurons in the bed nucleus of the stria terminalis (BNST) of the biparental Octodon degus

While the critical role of maternal care on the development of brain and behavior of the offspring has been extensively studied, our knowledge about the importance of paternal care for brain development of his offspring is still comparatively scarce. The aim of this study in the biparental caviomorph rodent Octodon degus was to analyze the impact of paternal care on the development of corticotropin-releasing hormone (CRH)-expressing neurons in the bed nucleus of the stria terminalis (BNST) and hypothalamic paraventricular nucleus (PVN). Both brain areas are key players in neuronal circuits that regulate hypothalamic–pituitary–adrenal axis (HPA) activity. At the age of postnatal day (PND) 21, we found that paternal deprivation resulted in a decreased density of CRH-containing neurons in the medial, but not in the lateral BNST, whereas no changes were observed in the PVN. These deprivation-induced changes were still prominent in adulthood. At PND 21, the density of Ca-binding protein calbindin D28K (CaBP-D28K)-expressing neurons was specifically increased in the medial, but not lateral BNST of father-deprived animals. In contrast, adult father-deprived animals show significantly decreased density of CaBP-D28K-expressing neurons in the lateral, but not medial BNST. Taken together, these results may have important implications for our understanding of the experience-driven development of neural circuits that regulate HPA activity mediating acute responses to stress and chronic anxiety.