Discriminatory ability of next-generation tau PET tracers for Alzheimer's disease

A next generation of tau PET tracers for the imaging of Alzheimer’s disease and other dementias has recently been developed. Whilst the new compounds have now entered clinical studies, there is limited information available to assess their suitability for clinical applications. Head-to-head comparisons are urgently needed to understand differences in the radiotracer binding profiles. We characterized the binding of the tau tracers PI2620, RO948, MK6240 and JNJ067 in human post-mortem brain tissue from a cohort of 25 dementia cases and age-matched controls using quantitative phosphorimaging with tritium-labelled radiotracers in conjunction with phospho-tau specific immunohistochemistry. The four radiotracers depicted tau inclusions composed of paired helical filaments with high specificity, both in cases with Alzheimer’s disease and in primary tauopathy cases with concomitant Alzheimer’s disease pathology. In contrast, cortical binding to primary tauopathy in cases without paired helical filament tau was found to be within the range of age-matched controls. Off-target binding to monoamine oxidase B has been overcome, as demonstrated by heterologous blocking studies in basal ganglia tissue. The high variability of cortical tracer binding within the Alzheimer’s disease group followed the same pattern with each tracer, suggesting that all compounds are suited to differentiate Alzheimer’s disease from other dementias.

B Cell Synovitis and Clinical Phenotypes in Rheumatoid Arthritis: Relationship to Disease Stages and Drug Exposure

OBJECTIVE

To define the relationship of synovial B cells to clinical phenotypes at different stages of disease evolution and drug exposure in rheumatoid arthritis (RA).

METHODS

Synovial biopsy specimens and demographic and clinical data were collected from 2 RA cohorts (n = 329), one of patients with untreated early RA (n = 165) and one of patients with established RA with an inadequate response to tumor necrosis factor inhibitors (TNFi-IR; n = 164). Synovial tissue was subjected to hematoxylin and eosin and immunohistochemical staining and semiquantitative assessment for the degree of synovitis (on a scale of 0-9) and of CD20+ B cell infiltrate (on a scale of 0-4). B cell scores were validated by digital image analysis and B cell lineage-specific transcript analysis (RNA-Seq) in the early RA (n = 91) and TNFi-IR (n = 127) cohorts. Semiquantitative CD20 scores were used to classify patients as B cell rich (≥2) or B cell poor (<2).

RESULTS

Semiquantitative B cell scores correlated with digital image analysis quantitative measurements and B cell lineage-specific transcripts. B cell-rich synovitis was present in 35% of patients in the early RA cohort and 47.7% of patients in the TNFi-IR cohort (P = 0.025). B cell-rich patients showed higher levels of disease activity and seropositivity for rheumatoid factor and anti-citrullinated protein antibody in early RA but not in established RA, while significantly higher histologic synovitis scores in B cell-rich patients were demonstrated in both cohorts.

CONCLUSION

We describe a robust semiquantitative histologic B cell score that closely replicates the quantification of B cells by digital or molecular analyses. Our findings indicate an ongoing B cell-rich synovitis, which does not seem to be captured by standard clinimetric assessment, in a larger proportion of patients with established RA than early RA.

Reduced colonic smooth muscle cholinergic responsiveness is associated with impaired bowel motility after chronic experimental high-level spinal cord injury

The mechanisms underlying bowel dysfunction after high-level spinal cord injury (SCI) are poorly understood. However, impaired supraspinal sympathetic and parasympathetic control is likely a major contributing factor. Disruption of the descending autonomic pathways traversing the spinal cord was achieved by a T3 complete spinal cord transection, and colonic function was examined in vivo and ex vivo four weeks post-injury. Total gastrointestinal transit time (TGTT) was reduced and contractility of the proximal and distal colon was impaired due to reduced M₃ receptor sensitivity. These data describe a clinically relevant model of bowel dysfunction after SCI.

Development of an Algorithm to Perform a Comprehensive Study of Autonomic Dysreflexia in Animals with High Spinal Cord Injury Using a Telemetry Device

Spinal cord injury (SCI) is a debilitating neurological condition characterized by somatic and autonomic dysfunctions. In particular, SCI above the mid-thoracic level can lead to a potentially life-threatening hypertensive condition called autonomic dysreflexia (AD) that is often triggered by noxious or non-noxious somatic or visceral stimuli below the level of injury. One of the most common triggers of AD is the distension of pelvic viscera, such as during bladder and bowel distension or evacuation. This protocol presents a novel pattern recognition algorithm developed for a JAVA platform software to study the fluctuations of cardiovascular parameters as well as the number, severity and duration of spontaneously occurring AD events. The software is able to apply a pattern recognition algorithm on hemodynamic data such as systolic blood pressure (SBP) and heart rate (HR) extracted from telemetry recordings of conscious and unrestrained animals before and after thoracic (T3) complete transection. With this software, hemodynamic parameters and episodes of AD are able to be detected and analyzed with minimal experimenter bias.

Rigid and remodelled: cerebrovascular structure and function after experimental high-thoracic spinal cord transection

High-thoracic or cervical spinal cord injury (SCI) is associated with several critical clinical conditions related to impaired cerebrovascular health, including: 300-400% increased risk of stroke, cognitive decline and diminished cerebral blood flow regulation. The purpose of this study was to examine the influence of high-thoracic (T3 spinal segment) SCI on cerebrovascular structure and function, as well as molecular markers of profibrosis. Seven weeks after complete T3 spinal cord transection (T3-SCI, n = 15) or sham injury (Sham, n = 10), rats were sacrificed for either middle cerebral artery (MCA) structure and function assessments via ex vivo pressure myography, or immunohistochemical analyses. Myogenic tone was unchanged, but over a range of transmural pressures, inward remodelling occurred after T3-SCI with a 40% reduction in distensibility (both P < 0.05), and a 33% reduction in vasoconstrictive reactivity to 5-HT trending toward significance (P = 0.09). After T3-SCI, the MCA had more collagen I (42%), collagen III (24%), transforming growth factor β (47%) and angiotensin II receptor type 2 (132%), 27% less elastin as well as concurrent increased wall thickness and reduced lumen diameter (all P < 0.05). Sympathetic innervation (tyrosine hydroxylase-positive axon density) and endothelium-dependent dilatation (carbachol) of the MCA were not different between groups. This study demonstrates profibrosis and hypertrophic inward remodelling within the largest cerebral artery after high-thoracic SCI, leading to increased stiffness and possibly impaired reactivity. These deleterious adaptations would substantially undermine the capacity for regulation of cerebral blood flow and probably underlie several cerebrovascular clinical conditions in the SCI population.

Transient receptor potential channels in bladder function

The transient receptor potential (TRP) superfamily of cationic ion channels includes proteins involved in the transduction of several physical and chemical stimuli to finely tune physiological functions. In the urinary bladder, they are highly expressed in, but not restricted to, primary afferent neurons. The urothelium and some interstitial cells also express several TRP channels. In this review, we describe the expression and the known roles of some members of TRP subfamilies, namely TRPV, TRPM and TRPA, in the urinary bladder. The therapeutic interest of modulating the activity of TRP channels to treat bladder dysfunctions is also discussed.

Sequestration of brain derived nerve factor by intravenous delivery of TrkB-Ig2 reduces bladder overactivity and noxious input in animals with chronic cystitis

Brain derived nerve factor (BDNF) is a trophic factor belonging to the neurotrophin family. It is upregulated in various inflammatory conditions, where it may contribute to altered pain states. In cystitis, little is known about the relevance of BDNF in bladder-generated noxious input and bladder overactivity, a matter we investigated in the present study. Female rats were intraperitoneally (i.p.) injected with cyclophosphamide (CYP; 200 mg/kg). They received saline or TrkB-Ig(2) via intravenously (i.v.) or intravesical administration. Three days after CYP-injection, animals were anaesthetized and cystometries performed. All animals were perfusion-fixed and the spinal cord segments L6 collected, post-fixed and processed for c-Fos and phosphoERK immunoreactivity. BDNF expression in the bladder, as well as bladder histology, was also assessed. Intravesical TrkB-Ig(2) did not change bladder reflex activity of CYP-injected rats. In CYP-animals treated with i.v. TrkB-Ig(2) a decrease in the frequency of bladder reflex contractions, in comparison with saline-treated animals, was observed. In spinal sections from the latter group of animals, the number of phosphoERK and c-Fos immunoreactive neurons was lower than in sections from saline-treated CYP-animals. BDNF immunoreactivity was higher during cystitis but was not changed by TrkB-Ig(2) i.v. treatment. Evaluation of the bladder histology showed similar inflammatory signs in the bladders of inflamed animals, irrespective of the treatment. Data show that i.v. but not intravesical administration of TrkB-Ig(2) reduced bladder hyperactivity in animals with cystitis to levels comparable to those observed in unirritated rats. Since i.v. TrkB-Ig(2) also reduced spinal extracellular signal-regulated kinase (ERK) activation, it is possible that BDNF contribution to inflammation-induced bladder hyperactivity is via spinal activation of the ERK pathway. Finally, the reduction in c-Fos expression indicates that TrkB-Ig(2) also reduced bladder-generated noxious input. Our results show that sequestration of BDNF may be considered a new therapeutic strategy to treat chronic cystitis.