Age-related neurochemical and behavioural changes in D409V/WT GBA1 mouse: Relevance to lewy body dementia.

Heterozygous mutations in GBA1, the gene which encodes the lysosomal enzyme glucocerebrosidase (GCase), are a strong genetic risk factor for the development of Lewy body dementia (LBD). Until this point however, recapitulation of the symptoms and pathology of LBD has been limited to a homozygous GBA1 mouse model which genetically and enzymatically reflects the lysosomal storage disorder Gaucher's disease. This study reports for the first time cognitive impairment by two independent behavioural tests in heterozygous GBA1 mutant mice (D409V/WT) which demonstrate significant cognitive impairment by the age of 12 months. Furthermore, reductions in GBA1 GCase enzyme activity within the brain reflects levels seen in sporadic and GBA1 mutant LBD patients. While there is no overt deposition of Lewy bodies within the hippocampus, alterations to cholinergic machinery and glial proliferation are evident, both pathological features of LBD. Interestingly, we also describe the novel finding of significantly reduced GBA2 GCase enzyme activity specifically within the hippocampus. This suggests that reduced GBA1 GCase enzyme activity dis-equilibrates the finely balanced glycosphingolipid metabolism pathway and that reductions in GBA2 GCase enzyme could contribute to the pathological and behavioural effects seen. Overall, this study presents evidence to suggest that pathological hallmarks associated with LBD specifically affecting brain regions intrinsically linked with cognition are present in the D409V/WT mice. In the absence of Lewy body deposition, the D409V/WT mice could be considered an early pre-clinical model of LBD with potential for drug discovery. Since few robust pre-clinical models of LBD currently exist, with further characterization, the mouse model described here may contribute significantly to developments in the LBD field.

Clinical trials of dementia with Lewy bodies and Parkinson's disease dementia.

Despite the frequency and importance of dementia associated with Parkinson's disease (PDD) and dementia with Lewy bodies (DLB), there is relatively little evidence on which to base treatment. Evidence from meta-analysis suggests that rivastigmine can improve cognition and functioning in PDD and also reduce risk of falling. There is also evidence supporting its use in DLB. Recent evidence suggests that memantine may also be effective, particularly for PDD, although evidence is more conflicting. Memantine may also improve parkinsonism and dyskinesias. Few clinical trials of cognition in PD without dementia exist, but there is preliminary evidence for atomoxetine, memantine, and piribedil. There is a lack of systematic evidence for the treatment of visual hallucinations and depression in PDD and DLB. In addition, there is a need for studies of whether potentially disease-modifying agents can prevent or delay the progression to dementia in PD.

Antiparkinsonian potential of targeting group III metabotropic glutamate receptor subtypes in the rodent substantia nigra pars reticulata.

BACKGROUND AND PURPOSE: Increased firing of the glutamatergic pathway between the subthalamic nucleus and substantia nigra pars reticulata (SNpr) contributes to the abnormal firing of motor circuits and subsequent motor deficits seen in Parkinson's disease. Broad spectrum agonist-induced activation of presynaptic group III metabotropic glutamate (mGlu) receptors within the SNpr reduced glutamate release and reversed akinesia in the reserpine-treated rat model of Parkinson's disease. Here, we have sought to identify which subtypes of group III mGlu receptor in the SNpr were responsible for these beneficial effects. EXPERIMENTAL APPROACH: The ability of the mGlu(4) positive allosteric modulator, N-phenyl-7-(hydroxyminocyclopropa[b]chromen-1a-carboxamide) (PHCCC), the mGlu(7) allosteric agonist, N,N'-dibenzhydrylethane-1,2-diamine dihydrochloride (AMN082) and the mGlu(8) -selective agonist (S)-3,4-dicarboxyphenylglycine [(S)-3,4-DCPG] to inhibit KCl-evoked [(3) H]-D-aspartate release was examined in vitro in rat nigral prisms. Reversal of akinesia in reserpine-treated rats was also assessed following intranigral injection of these agents. KEY RESULTS: PHCCC and AMN082 inhibited [(3) H]-D-aspartate release by 42% and 53%, respectively when given alongside a sub-threshold concentration of the broad spectrum group III agonist, L-2-amino-4-phosphonobutyrate (L-AP4; 1 µM). In contrast (S)-3,4-DCPG failed to inhibit [(3) H]-D-aspartate release. All three agents also reversed reserpine-induced akinesia although only the effects of PHCCC and AMN082 were inhibited by pre-treatment with the group III antagonist (RS)-α-cyclopropyl-4-phosphonophenylglycine (CPPG). CONCLUSIONS AND IMPLICATIONS: These findings reveal that targeting SNpr mGlu(4) or mGlu(7) receptors, but not mGlu(8) receptors, provided relief from akinesia in the reserpine-treated rat model of Parkinson's disease, most likely reflecting inhibition of excess glutamate release in this region.

Symptomatic and neuroprotective effects following activation of nigral group III metabotropic glutamate receptors in rodent models of Parkinson's disease.

BACKGROUND AND PURPOSE: Increased glutamatergic innervation of the substantia nigra pars reticulata (SNpr) and pars compacta (SNpc) may contribute to the motor deficits and neurodegeneration, respectively, in Parkinson's disease (PD). This study aimed to establish whether activation of pre-synaptic group III metabotropic glutamate (mGlu) receptors reduced glutamate release in the SN, and provided symptomatic or neuroprotective relief in animal models of PD. EXPERIMENTAL APPROACH: Broad-spectrum group III mGlu receptor agonists, O-phospho-l-serine (l-SOP) and l-2-amino-4-phosphonobutyrate (l-AP4), were assessed for their ability to inhibit KCl-evoked [(3)H]-d-aspartate release in rat nigral prisms or inhibit KCl-evoked endogenous glutamate release in the SNpr in vivo using microdialysis. Reversal of akinesia in reserpine-treated rats was assessed following intranigral injection of l-SOP and l-AP4. Finally, the neuroprotective effect of 7 days' supra-nigral treatment with l-AP4 was examined in 6-hydroxydopamine (6-OHDA)-lesioned rats. KEY RESULTS: l-SOP and l-AP4 inhibited [(3)H]-d-aspartate release by 33 and 44% respectively. These effects were blocked by the selective group III mGlu antagonist (RS)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG). l-SOP also reduced glutamate release in the SNpr in vivo by 48%. Injection of l-SOP and l-AP4 into the SNpr reversed reserpine-induced akinesia. Following administration above the SNpc, l-AP4 provided neurochemical, histological and functional protection against 6-OHDA lesion of the nigrostriatal tract. Pretreatment with CPPG inhibited these effects. CONCLUSIONS AND IMPLICATIONS: These findings highlight group III mGlu receptors in the SN as potential targets for providing both symptomatic and neuroprotective relief in PD, and indicate that inhibition of glutamate release in the SN may underlie these effects.

Psychological consequences of predictive genetic testing: a systematic review.

The aim of this systematic literature review is to describe the psychological consequences of predictive genetic testing. Five databases were searched for studies using standardised outcome measures and statistical comparison of groups. Studies were selected and coded by two independent researchers. From 899 abstracts, 15 papers, describing 11 data sets, met the selection criteria for the review. The studies were of predictive genetic testing for Huntington's disease, hereditary breast and ovarian cancer, familial adenomatous polyposis and spinocerebellar ataxia. One involved children; the rest were of adults. None of the 15 papers reported increased distress (general and situational distress, anxiety and depression) in carriers or non-carriers at any point during the 12 months after testing. Both carriers and non-carriers showed decreased distress after testing; this was greater and more rapid amongst non-carriers. Test result (ie being a carrier or non-carrier) was rarely predictive of distress more than one month after testing (predictive in two of 14 analyses). Pre-test emotional state was predictive of subsequent distress in 14 of 27 analyses. There is a lack of informative studies in this field. The studies reviewed suggest that those undergoing predictive genetic testing do not experience adverse psychological consequences. However, the studies are of self-selected populations who have agreed to participate in psychological studies and have been followed up for no more than three years. Most research has been of testing for Huntington's Disease and included follow-up of no more than one year. The results suggest that testing protocols should include a pre-test assessment of emotional state so that post-test counselling can be targeted at those more distressed before testing. None of the studies experimentally manipulated the amount or type of counselling provided. The relationship between counselling and emotional outcome is therefore unclear and awaits empirical study.

The psychological consequences of offering mutation searching in the family for those at risk of hereditary breast and ovarian cancer--a pilot study.

AIM: To describe the short and longer-term psychological consequences of waiting for the results of mutation searching (MS) amongst those at risk of hereditary breast and ovarian cancer (HBOC). DESIGN: A prospective study, with measures before the offer of a mutation search, and 1 week, 6 months and 12 months afterwards. SAMPLE: 21 unaffected women at risk of HBOC offered MS in an affected relative at one of two UK regional genetics centres. OUTCOME MEASURES: Standardized questionnaire measures of general anxiety, general distress, distress about cancer in the family and cancer-specific worries. RESULTS: Mutation searches were initiated in 15 of 21 families; two received results within 12 months. For the 13 still waiting for results, levels of anxiety and distress were within normal ranges at all time-points. They reported reduced worries about cancer 6 and 12 months post-search offer compared with earlier assessments, but experienced an increase in general anxiety 12 months since the search offer. These changes over time were not found in those not waiting for the results of a mutation search. CONCLUSION: The majority of women were without a result 12 months after being offered MS. Whilst these women were less worried about cancer in the 6 months after initiating the testing process, their anxiety levels increased 12 months since the offer of a mutation search. Seeing a specialist seems to reduce cancer worries. There may, however, be long-term psychological costs of offering tests that are unlikely to give results in a foreseeable future.

Evaluation and impact of promotion of a cancer helpline to cancer patients through their specialists.

Four hundred and sixty four cancer patients attending their first outpatient consultation (96% of those eligible) were given a pamphlet promoting a cancer helpline by their participating specialist. Calls to the helpline during and six weeks following the study period were made relating to 4% (95% CI: 2.1%-5.6%) of patients or family members receiving the pamphlet. Whilst this response is small, the willingness of cancer specialists to distribute the pamphlet identifies them as a valuable channel for linking patients with complementary services.