Shp-2 knockdown prevents l-dopa-induced dyskinesia in a rat model of Parkinson's disease

BACKGROUND

Dyskinesia, the major side effect of l-dopa therapy in PD, is mainly associated with nonphysiological stimulation of denervated receptors in the striatum. In particular, DA D1 receptor-mediated aberrant extracellular signal-regulated protein kinases 1 and 2 activation have been associated with striatal changes leading to dyskinesia. We recently identified the tyrosine phosphatase Shp-2 as a crucial effector transmitting D1 receptor signaling to extracellular signal-regulated protein kinases 1 and 2 activation and reported the involvement of the D1 receptor/Shp-2/extracellular signal-regulated protein kinases 1 and 2 pathway in the development of l-dopa-induced dyskinesia.

OBJECTIVES

In this study, the role of Shp-2 in l-dopa-induced dyskinesia development was investigated by in vivo silencing of Shp-2 in the striatum of the 6-hydroxy-dopamine rat model of PD.

METHODS

Lentiviral particles delivering short hairpin RNA were used to obtain long-term striatal Shp-2 downregulation. Rats were then treated with l-dopa and analyzed for both the improvement of akinesia and the development of l-dopa-induced dyskinesia.

RESULTS

The results show that Shp-2 knockdown remarkably decreased extracellular signal-regulated protein kinases 1 and 2 phosphorylation and attenuated the severity of l-dopa-induced dyskinesia likely without compromising the therapeutic efficacy of l-dopa.

CONCLUSION

These data suggest that the striatal D1 receptor/Shp-2 complex may represent a promising novel target for the development of antidyskinetic drugs.

Chronic glutamate treatment selectively modulates AMPA RNA editing and ADAR expression and activity in primary cortical neurons

Adenosine-to-inosine RNA editing is a post-transcriptional process, catalyzed by ADAR enzymes, with an important role in diversifying the number of proteins derived from a single gene. In neurons, editing of ionotropic AMPA glutamate receptors has been shown to be altered under several experimental conditions, including severe pathologies, thus highlighting the potential significance of its modulation. In this study, we treated rat primary cortical cell cultures with a sub-lethal dose of glutamate (10 μM), focusing on RNA editing and ADAR activity. We found that chronic glutamate treatment down-regulates RNA editing levels at the R/G site of GluA2-4 subunits of AMPA receptors and at the K/E site of CYFIP2. These changes are site-specific since they were not observed either for the GluA2 Q/R site or for other non-glutamatergic sites. Glutamate treatment also down-regulates the protein expression levels of both ADAR1 and ADAR2 enzymes, through a pathway that is Ca(2+)- and calpain-dependent. Given that AMPA receptors containing unedited subunits show a slower recovery rate from desensitization compared to those containing edited forms, the reduced editing at the R/G site may, at least in part, compensate for glutamate over-stimulation, perhaps through the reduced activation of postsynaptic receptors. In summary, our data provide direct evidence of the involvement of ADAR1 and ADAR2 activity as a possible compensatory mechanism for neuronal protection following glutamate over-stimulation.

The D3 dopamine receptor: From structural interactions to function

Novel structural and functional aspects of the dopamine (DA) D3 receptors (D3R) have been recently described. D3R expressed in dopaminergic neurons have been classically considered to play the role of autoreceptors inhibiting, as the D2R, DA release. However, evidence for D3R-mediated neurotrophic and neuroprotective effects on DA neurons suggests their involvement in preventing pathological alterations leading to neurodegeneration. On the other hand, given its localization and functional role at postsynaptic striatal levels, the D3R may also be involved in the pathogenesis of movement disorders and psychiatric diseases. Functional interactions of D3R with other receptor systems are crucial for the modulation of several physiological events. On this line, the discovery that the D3R can form heteromers with other receptors has opened the possibility of uncover novel molecular mechanisms of brain functions and dysfunctions. This paper summarizes the functional and physical interactions of D3R with other receptors both at pre-synaptic sites, where it is co-expressed with the D2R and nicotinic receptors, and at post-synaptic sites where it interacts with the DA D1 receptors (D1R). The biochemical and functional properties of the D1R-D3R heteromer will be especially discussed. Both D1R and D3R have been in fact implicated in several disorders, including schizophrenia and motor dysfunctions. Therefore, the D1R-D3R heteromer may represent a potential drug target for the treatment of these diseases.

Diet Quality and Risk of Melanoma in an Italian Population

BACKGROUND

Some results from laboratory and epidemiologic studies suggest that diet may influence the risk of melanoma, but convincing evidence for a role of single nutrients or food items is lacking. Diet quality, which considers the combined effect of multiple food items, may be superior for examining this relation.

OBJECTIVE

We sought to assess whether diet quality, evaluated with the use of 4 different dietary indexes, is associated with melanoma risk.

METHODS

In this population-based case-control study, we analyzed the relation between 4 diet quality indexes, the Healthy Eating Index 2010 (HEI-2010), Dietary Approaches to Stop Hypertension (DASH) index, Greek Mediterranean Index (GMI), and Italian Mediterranean Index (IMI), and melanoma risk in a northern Italian community, with the use of data from 380 cases and 719 matched controls who completed a semiquantitative food frequency questionnaire.

RESULTS

In the overall sample, we found an inverse association between disease risk and the HEI-2010 and DASH index, but not the Mediterranean indexes, adjusting for potential confounders (skin phototype, body mass index, energy intake, sunburn history, skin sun reaction, and education). However, in sex stratified analyses, the association appeared only in women (P-trend: 0.10 and 0.04 for the HEI-2010 and DASH index, respectively). The inverse relations were stronger in women younger than age 50 y than in older women, for whom the GMI and IMI scores also showed an inverse association with disease risk (P-trend: 0.05 and 0.02, respectively).

CONCLUSIONS

These results suggest that diet quality may play a role in cutaneous melanoma etiology among women.

Variation in the X-linked EFHC2 gene is associated with social cognitive abilities in males

Females outperform males on many social cognitive tasks. X-linked genes may contribute to this sex difference. Males possess one X chromosome, while females possess two X chromosomes. Functional variations in X-linked genes are therefore likely to impact more on males than females. Previous studies of X-monosomic women with Turner syndrome suggest a genetic association with facial fear recognition abilities at Xp11.3, specifically at a single nucleotide polymorphism (SNP rs7055196) within the EFHC2 gene. Based on a strong hypothesis, we investigated an association between variation at SNP rs7055196 and facial fear recognition and theory of mind abilities in males. As predicted, males possessing the G allele had significantly poorer facial fear detection accuracy and theory of mind abilities than males possessing the A allele (with SNP variant accounting for up to 4.6% of variance). Variation in the X-linked EFHC2 gene at SNP rs7055196 is therefore associated with social cognitive abilities in males.

MURC/cavin-4 Is Co-Expressed with Caveolin-3 in Rhabdomyosarcoma Tumors and Its Silencing Prevents Myogenic Differentiation in the Human Embryonal RD Cell Line

The purpose of this study was to investigate whether MURC/cavin-4, a plasma membrane and Z-line associated protein exhibiting an overlapping distribution with Caveolin-3 (Cav-3) in heart and muscle tissues, may be expressed and play a role in rhabdomyosarcoma (RMS), an aggressive myogenic tumor affecting childhood. We found MURC/cavin-4 to be expressed, often concurrently with Cav-3, in mouse and human RMS, as demonstrated through in silico analysis of gene datasets and immunohistochemical analysis of tumor samples. In vitro expression studies carried out using human cell lines and primary mouse tumor cultures showed that expression levels of both MURC/cavin-4 and Cav-3, while being low or undetectable during cell proliferation, became robustly increased during myogenic differentiation, as detected via semi-quantitative RT-PCR and immunoblotting analysis. Furthermore, confocal microscopy analysis performed on human RD and RH30 cell lines confirmed that MURC/cavin-4 mostly marks differentiated cell elements, colocalizing at the cell surface with Cav-3 and labeling myosin heavy chain (MHC) expressing cells. Finally, MURC/cavin-4 silencing prevented the differentiation in the RD cell line, leading to morphological cell impairment characterized by depletion of myogenin, Cav-3 and MHC protein levels. Overall, our data suggest that MURC/cavin-4, especially in combination with Cav-3, may play a consistent role in the differentiation process of RMS.

The "in situ" proximity ligation assay to probe protein-protein interactions in intact tissues

The proximity ligation assay (PLA) is a sensitive and specific technique to visualize proteins, their posttranslational modifications and activation state as well as protein-protein interactions. The assay is based on the employment of proximity probes, composed by oligonucleotide-conjugated antibodies, to recognize a couple of specific targets. The binding of probes in close proximity allows for their hybridization by connector oligonucleotides, that can form a circular DNA strand. These DNA circles can then be amplified by polymerase chain reaction. Finally, the conjugation of fluorescence-labelled oligonucleotides with the amplification product allows for the localized detection of individual or interacting proteins in cells and tissues. Here, we describe the use of "in situ" PLA to visualize the localization of protein-protein interactions in intact tissues.

Receptor heteromers in Parkinson's disease and L-DOPA-induced dyskinesia

Parkinson's disease (PD) and L-DOPA-induced dyskinesia, a major complication of treatment of PD, are associated with molecular and functional alterations occurring into the medium spiny neurons (MSNs) of the dorsal striatum, a key areas involved in the control of motor activity. MSNs are regulated by several neurotransmitter systems including dopamine, glutamate and adenosine via activation of distinct receptors. Increasing evidence suggest that interactions among systems are mediated by different mechanisms including the formation of receptor heterodimers. The current view of G protein-coupled receptors organization, in fact, assumes that they do not work as monomeric units, but are part of heterodimeric complexes or of high order heteromers, where other receptors and ancillary proteins are coclustered. This organization implies that the pharmacological and signalling properties of these receptors may depend on the molecular composition of the receptor heteromers where they are clustered and may be differentially modulated in physiological or pathological conditions. Here, we provide an overview of the functional implications of physical interactions among dopamine, glutamate and adenosine receptors, their relevance for striatal MSNs activity and their involvement in the physiopathology of PD and dyskinesia.

Kainate receptor RNA editing is markedly altered by acute spinal cord injury

We have previously observed changes in the RNA editing of AMPA receptors after acute spinal cord injury (SCI); this implies that post-transcriptional modifications are capable of affecting the physiological properties of glutamate receptor channels and related signal transduction in this neurodegenerative condition. Here, we report that the editing of the ionotropic KAR is markedly decreased at both GluK1 and GluK2 Q/R sites in the epicenter of the lesion and with distinct magnitude and kinetics also in the caudal and rostral portions of the injured cord. These effects are persistent, being observed as late as 30 days after lesioning. In addition, also the I/V and Y/C sites of GluK2 were severely affected after SCI. These findings add novel information to the relevance of editing of glutamate receptors following acute SCI, thus expanding the recently emerged role of post-transcriptional mechanisms under these experimental conditions.

Recognition of face and non-face stimuli in autistic spectrum disorder

The ability to remember faces is critical for the development of social competence. From childhood to adulthood, we acquire a high level of expertise in the recognition of facial images, and neural processes become dedicated to sustaining competence. Many people with autism spectrum disorder (ASD) have poor face recognition memory; changes in hairstyle or other non-facial features in an otherwise familiar person affect their recollection skills. The observation implies that they may not use the configuration of the inner face to achieve memory competence, but bolster performance in other ways. We aimed to test this hypothesis by comparing the performance of a group of high-functioning unmedicated adolescents with ASD and a matched control group on a "surprise" face recognition memory task. We compared their memory for unfamiliar faces with their memory for images of houses. To evaluate the role that is played by peripheral cues in assisting recognition memory, we cropped both sets of pictures, retaining only the most salient central features. ASD adolescents had poorer recognition memory for faces than typical controls, but their recognition memory for houses was unimpaired. Cropping images of faces did not disproportionately influence their recall accuracy, relative to controls. House recognition skills (cropped and uncropped) were similar in both groups. In the ASD group only, performance on both sets of task was closely correlated, implying that memory for faces and other complex pictorial stimuli is achieved by domain-general (non-dedicated) cognitive mechanisms. Adolescents with ASD apparently do not use domain-specialized processing of inner facial cues to support face recognition memory.

Importance of the inverted control in measuring holistic face processing with the composite effect and part-whole effect

Holistic coding for faces is shown in several illusions that demonstrate integration of the percept across the entire face. The illusions occur upright but, crucially, not inverted. Converting the illusions into experimental tasks that measure their strength – and thus index degree of holistic coding – is often considered straightforward yet in fact relies on a hidden assumption, namely that there is no contribution to the experimental measure from secondary cognitive factors. For the composite effect, a relevant secondary factor is size of the “spotlight” of visuospatial attention. The composite task assumes this spotlight can be easily restricted to the target half (e.g., top-half) of the compound face stimulus. Yet, if this assumption were not true then a large spotlight, in the absence of holistic perception, could produce a false composite effect, present even for inverted faces and contributing partially to the score for upright faces. We review evidence that various factors can influence spotlight size: race/culture (Asians often prefer a more global distribution of attention than Caucasians); sex (females can be more global); appearance of the join or gap between face halves; and location of the eyes, which typically attract attention. Results from five experiments then show inverted faces can sometimes produce large false composite effects, and imply that whether this happens or not depends on complex interactions between causal factors. We also report, for both identity and expression, that only top-half face targets (containing eyes) produce valid composite measures. A sixth experiment demonstrates an example of a false inverted part-whole effect, where encoding-specificity is the secondary cognitive factor. We conclude the inverted face control should be tested in all composite and part-whole studies, and an effect for upright faces should be interpreted as a pure measure of holistic processing only when the experimental design produces no effect inverted.

Persistent activation of the D1R/Shp-2/Erk1/2 pathway in l-DOPA-induced dyskinesia in the 6-hydroxy-dopamine rat model of Parkinson's disease

Prolonged l-3,4-dihydroxyphenylalanine (l-DOPA) administration, the gold standard therapy for Parkinson's disease (PD) is associated with serious motor complications, known as l-DOPA-induced dyskinesia (LID). One of the major molecular changes associated with LID is the increased activity of the extracellular signal-regulated kinases 1/2 (Erk1/2) signaling in the medium spiny neurons of the striatum induced by malfunctioning in the dopamine D1 receptor (D1R)-mediated transmission. We have previously established that in the striatum, activation of Shp-2, an intracellular tyrosine phosphatase associated with the D1R, is a requisite for the D1R to activate Erk1/2. In this study, we investigated the role of striatal D1R/Shp-2 complex in the molecular event underlying LID in the 6-OHDA-lesioned rat model of PD. We found that in hemiparkinsonian rats experiencing LID, the physiological interaction between D1R and Shp-2 in the striatum was preserved. In these animals, the chronic activation of D1R either by l-DOPA or by the selective D1R agonist SKF 38393 induced both dyskinesia and Shp-2/Erk1/2 activation. These effects were prevented by the selective D1R-antagonist SCH23390 suggesting the involvement of striatal D1R/Shp-2 complex, via Erk1/2 activation, in the molecular events underlying LID. Interestingly, we found that D1R-mediated Shp-2-Erk1/2 activation was persistently detected in the striatum of dyskinetic rats during l-DOPA washout, with a close correlation between LID severity and the extent of long term activation of both Shp-2 and Erk1/2. Taken together, our data show that in hemiparkinsonian rats developing dyskinesia, the aberrant phosphorylation of Shp-2 by D1R activation, represents an upstream molecular event leading to the persistent phosphorylation of Erk1/2 and therefore a novel therapeutic target to counteract LID development and maintenance during l-DOPA therapy.

Association between dietary vitamin C and risk of cutaneous melanoma in a population of Northern Italy

Cutaneous melanoma incidence has been increasing during the last few years, and diet has been suggested as one of the lifestyle factors responsible for this increase. Since antioxidant nutrients such as ascorbic acid might prevent skin carcinogenesis, we investigated the risk of cutaneous melanoma related to vitamin C intake in a population-based case-control study in Northern Italy based on 380 melanoma patients and 719 matched controls, to whom we administered a semiquantitative food-frequency questionnaire. After adjusting for potential confounders, odds ratio of melanoma were 0.86 (95 % confidence interval 0.65 - 1.15) and 0.59 (95 % confidence interval 0.37 - 0.94) in the intermediate and highest categories of vitamin C dietary intake respectively, compared with the bottom one. The association between vitamin C and decreased risk persisted after adjustment for some potential confounders. In age- and gender-stratified analyses, this association was seen in young females (< 60 years old), and was found to be enhanced in subjects with phototypes II and III. These results suggest a possible protective activity of vitamin C intake against cutaneous melanoma in specific subgroups of this population of Northern Italy.

A robust method of measuring other-race and other-ethnicity effects: the Cambridge Face Memory Test format

Other-race and other-ethnicity effects on face memory have remained a topic of consistent research interest over several decades, across fields including face perception, social psychology, and forensic psychology (eyewitness testimony). Here we demonstrate that the Cambridge Face Memory Test format provides a robust method for measuring these effects. Testing the Cambridge Face Memory Test original version (CFMT-original; European-ancestry faces from Boston USA) and a new Cambridge Face Memory Test Chinese (CFMT-Chinese), with European and Asian observers, we report a race-of-face by race-of-observer interaction that was highly significant despite modest sample size and despite observers who had quite high exposure to the other race. We attribute this to high statistical power arising from the very high internal reliability of the tasks. This power also allows us to demonstrate a much smaller within-race other ethnicity effect, based on differences in European physiognomy between Boston faces/observers and Australian faces/observers (using the CFMT-Australian).