Misfolded alpha-synuclein in amyotrophic lateral sclerosis: Implications for diagnosis and treatment

BACKGROUND

Alpha-synuclein (α-Syn) oligomers and fibrils have been shown to augment the aggregation of TAR DNA-binding Protein 43 (TDP-43) monomers in vitro, supporting the idea that TDP-43 proteinopathies such as ALS may be modulated by the presence of toxic forms of α-Syn. Recently, parkinsonian features were reported in a study of European patients and Lewy bodies have been demonstrated pathologically in a similar series of patients. Based on these and other considerations, we sought to determine whether seed-competent α-Syn can be identified in spinal fluid of patients with ALS including familial, sporadic, and Guamanian forms of the disease.

METHODS

Based on the finding that α-Syn has been found to be a prion-like protein, we have utilized a validated α-Synuclein seed amplification assay to determine if seed-competent α-Syn could be detected in the spinal fluid of patients with ALS.

RESULTS

Toxic species of α-Syn were detected in CSF in 18 of 127 ALS patients, 5 of whom were from Guam. Two out of twenty six samples from patients with C9orf72 variant ALS had positive seed-amplification assays (SAAs). No positive tests were noted in superoxide dismutase type 1 ALS subjects (n = 14). The SAA was negative in 31 control subjects.

CONCLUSIONS

Our findings suggest that a sub-group of ALS occurs in which self-replicating α-Syn is detectable and likely contributes to its pathogenesis. This finding may have implications for the diagnosis and treatment of this disorder.

α-Synuclein seed amplification assay as a diagnostic tool for parkinsonian disorders

INTRODUCTION

Synucleinopathies such as Parkinson's disease (PD) and multiple system atrophy (MSA) can be challenging to diagnose due to the symptom overlap with, for example, atypical parkinsonisms like progressive supranuclear palsy (PSP) and corticobasal degeneration (CBD). Seed amplification assays (SAA), developed for the detection of α-synuclein (αSyn) aggregates in CSF, have been successful when used as a biomarker evaluation for synucleinopathies. In this study, we investigated the potential of this assay to not only detect αSyn seeds in CSF, but also discriminate between movement disorders.

METHODS

The αSyn-SAA was tested in a Scandinavian cohort composed of 129 CSF samples from patients with PD (n = 55), MSA (n = 27), CBD (n = 7), and PSP (n = 16), as well as healthy controls (HC, n = 24).

RESULTS

The αSyn seed amplification assay (αSyn-SAA) was able to correctly identify all PD samples as positive (sensitivity of 100%) while also discriminating the PD group from HC (70.8% specificity, p < 0.0001) and tauopathies [CBD (71% specificity) and PSP (75% specificity), p < 0.0001)]. The αSyn-SAA was also able to identify almost all MSA samples as positive for αSyn aggregation (sensitivity of 92.6%). In general, this assay is able to discriminate between the synucleinopathies and tauopathies analyzed herein (p < 0.0001) despite the overlapping symptoms in these diseases.

CONCLUSION

These findings suggest the αSyn-SAA is a useful diagnostic tool for differentiating between different parkinsonian disorders, although further optimization may be needed.

Expression and functional significance of tumor necrosis factor receptors in human myocardium

BACKGROUND

Tumor necrosis factor-alpha (TNF-alpha), a proinflammatory cytokine with potent negative inotropic properties, is elaborated in septic shock, acute myocarditis, reperfusion injury, and congestive heart failure. TNF-alpha acts by binding to two specific receptors: TNFR1 and TNFR2. However, neither the presence nor the significance of TNF receptors has been studied in the adult mammalian heart.

METHODS AND RESULTS

In the present study, we showed that the adult heart expresses mRNA and receptor proteins for TNFR1 and TNFR2. Moreover, immunohistochemical staining studies localized TNFR1 and TNFR2 to the cardiac myocyte, providing a potential signaling pathway for the deleterious effects of TNF-alpha. The functional significance of the expression of TNFR1 and TNFR2 was explored with the use of a simple cell motion assay in which we assessed the effect(s) of TNF-alpha mutants known to bind selectively to human TNFR1 and TNFR2. We showed that the negative inotropic effect of wild-type TNF-alpha in isolated feline cardiac myocytes was mimicked by the TNF mutant that binds to TNFR1, whereas the TNF mutant that binds to TNFR2 had no significant effect on cell motion.

CONCLUSIONS

Results of the present study show that the adult human heart expresses both mRNA and receptor proteins for TNFR1 and TNFR2; moreover, the negative inotropic effects of TNF-alpha in adult cardiac myocytes appear to be initiated by activation of TNFR1.

The rat probasin gene promoter directs hormonally and developmentally regulated expression of a heterologous gene specifically to the prostate in transgenic mice

An expression cassette carrying 426 basepairs of the rat probasin (PB) gene promoter and 28 basepairs of 5'-untranslated region is sufficient to target the expression of the bacterial chloramphenicol acetyltransferase (CAT) gene specifically to the prostate in transgenic mice. The PB-CAT transgene was expressed in three of five (60%) independent lines of mice, and this expression, as reported previously for the endogenous rat gene, was male specific, restricted primarily to the lateral, dorsal, and ventral lobes of the prostate, with only very low levels of CAT activity detected in the anterior prostate and seminal vesicles. The developmental and hormonal regulation of the transgene also paralleled that reported for the rat gene, with a 70-fold increase in CAT activity in the mouse prostate observed between 2-7 weeks of age, a time corresponding to sexual maturation. PB-CAT activity in the prostate declined after castration to 3.5% of the precastration level, and the CAT activity in castrated males approached precastration levels when mice were supplemented with testosterone. Transgene expression in castrated males was not induced by dexamethasone. Coinjection of PB-CAT with a chicken lysozyme gene matrix attachment region resulted in their cointegration and further restricted the pattern of PB-CAT to the dorsolateral prostate, with suppressed expression observed in the ventral prostate. These studies demonstrate that a minimal rat probasin promoter can target heterologous gene expression specifically to the prostate in a developmentally and hormonally regulated fashion.

[3H]doxepin interactions with histamine H1-receptors and other sites in guinea pig and rat brain homogenates

[3H]Doxepin, a tricyclic antidepressant, binds to brain homogenates with two saturable components. The high affinity component, with a dissociation constant (KD) of 0.26 nM, is associated with histamine H1-receptors. This high affinity binding shows stereospecificity in that d-chlorpheniramine is 100 times more potent than the pharmacologically less active l-isomer. Its drug specificity and regional variation closely parallel those exhibited by [3H]mepyramine binding. The drug specificity of the low affinity component is distinct from that of histamine H1-receptors, with no stereospecificity for chlorpheniramine isomers. Furthermore, all the H1-histamine antagonists tested display micromolar potency at the low-affinity doxepin sites but nanomolar potency at the high-affinity doxepin sites associated with a physiological histamine H1-receptor. The drug specificity of the low affinity site does not correspond to that of any known neurotransmitter receptor. Tricyclic antidepressants display IC50 values of 30-600 nM for the inhibition of [3H]doxepin binding to the low-affinity component with most values in the 0.1-0.3 microM affinity range.

The preparation of leukocyte-poor red blood cells: a comparative study

Thirteen methods of prepararing leukocyte-poor red blood cells were compared for their effectiveness in removing leukocytes. When the starting material was six to ten days old, the residual leukocyte count was three to four times lower than when fresh material was used and no granulocytes could be found. The most effective manual procedure was a single upright sedimentation of six- to ten-day-old saline-diluted red cells. Inverted sedimentation was no more effective in leukocyte depletion than upright sedimentation. Automated cell processors were no more effective than several of the better manual methods. Freezing and deglycerolizing resulted in a ten-fold improvement in leukocyte removal with less red blood cell loss but at higher cost than the nonfreezing methods. The study indicates that unless the minimal leukocyte count of frozen red blood cells is essential, a single upright sedimentation of saline-diluted, six- to ten-day-old red blood cells is currently the most effective procedure for preparing leukocyte-poor red blood cells.

Familial balanced translocation 4p+/17q- as a suggested cause of primary trisomy-21 Down's syndrome

A case is presented in which a 4p+/17q- familial balanced reciprocal translocation in the mother produced a son with primary trisomy-21, as well as the structural chromosomal anomaly. A number of similar situations have been reported, suggesting that the two events are related. In practice, this (as well as other direct risks) should be taken into account when counseling those families in which one parent carries a balanced translocation. A hypothesis, based on experiments in Drosophila, has been put forward by Grell to explain the mechanism which links the balanced structural abnormality to an aneuploidy of chromosomes not taking part in the structural change, and this has been extended to similar human situations.