TRPV4 mutations causing mixed neuropathy and skeletal phenotypes result in severe gain of function.

OBJECTIVE: Distinct dominant mutations in the calcium-permeable ion channel TRPV4 (transient receptor potential vanilloid 4) typically cause nonoverlapping diseases of either the neuromuscular or skeletal systems. However, accumulating evidence suggests that some patients develop mixed phenotypes that include elements of both neuromuscular and skeletal disease. We sought to define the genetic and clinical features of these patients. METHODS: We report a 2-year-old with a novel R616G mutation in TRPV4 with a severe neuropathy phenotype and bilateral vocal cord paralysis. Interestingly, a different substitution at the same residue, R616Q, has been reported in families with isolated skeletal dysplasia. To gain insight into clinical features and potential genetic determinants of mixed phenotypes, we perform in-depth analysis of previously reported patients along with functional and structural assessment of selected mutations. RESULTS: We describe a wide range of neuromuscular and skeletal manifestations and highlight specific mutations that are more frequently associated with overlap syndromes. We find that mutations causing severe, mixed phenotypes have an earlier age of onset and result in more marked elevations of intracellular calcium, increased cytotoxicity, and reduced sensitivity to TRPV4 antagonism. Structural analysis of the two mutations with the most dramatic gain of ion channel function suggests that these mutants likely cause constitutive channel opening through disruption of the TRPV4 S5 transmembrane domain. INTERPRETATION: These findings demonstrate that the degree of baseline calcium elevation correlates with development of mixed phenotypes and sensitivity to pharmacologic channel inhibition, observations that will be critical for the design of future clinical trials for TRPV4 channelopathies.

Use of white cell count, age, and presence of other injuries in stratifying risk of intracranial injury in pediatric trauma.

The Pediatric Emergency Care Applied Research Network (PECARN) Head Injury/Trauma Algorithm is a well-validated decision rule used to identify patients at low risk of clinically important traumatic brain injuries who may not need head CT. In adult patients with mild head trauma, elevated serum glucose and white cell count (WCC) have been associated with abnormal head CT findings. Currently, glucose or WCC is not considered in pediatric patients. The objective of this study was to determine if elevations in glucose or WCC could be used as additional tools to risk-stratify pediatric trauma patients for intracranial injury (ICI). Data were abstracted from the Maryland Trauma Registry and from electronic medical records for patients at the Johns Hopkins Children's Center from 2017 to 2020. We evaluated 145 encounters that met the inclusion criteria. There were 33 cases of ICI on CT. In addition to higher median glucose and WCC, we found that patients with ICI had a younger median age and were less likely to have other clinically significant injuries than patients without ICI. Following multiple logistic regression analysis, WCC (OR 1.113, 95% CI 1.02 to 1.21), younger age (OR 0.89, 95% CI 0.8 to 0.98), and absence of other injuries (OR 0.41, 95% CI 0.23 to 0.73) were found to be associated with risk of ICI. The area under the curve for our model was 0.79. When used with the PECARN algorithm, our model could help determine which patients may avoid head CT or undergo a shorter observation period.

Pharmacokinetics and pharmacodynamics of a single dose Nilotinib in individuals with Parkinson's disease.

Nilotinib is a broad-based tyrosine kinase inhibitor with the highest affinity to inhibit Abelson (c-Abl) and discoidin domain receptors (DDR1/2). Preclinical evidence indicates that Nilotinib reduces the level of brain alpha-synuclein and attenuates inflammation in models of Parkinson's disease (PD). We previously showed that Nilotinib penetrates the blood-brain barrier (BBB) and potentially improves clinical outcomes in individuals with PD and dementia with Lewy bodies (DLB). We performed a physiologically based population pharmacokinetic/pharmacodynamic (popPK/PD) study to determine the effects of Nilotinib in a cohort of 75 PD participants. Participants were randomized (1:1:1:1:1) into five groups (n = 15) and received open-label random single dose (RSD) 150:200:300:400 mg Nilotinib vs placebo. Plasma and cerebrospinal fluid (CSF) were collected at 1, 2, 3, and 4 hours after Nilotinib administration. The results show that Nilotinib enters the brain in a dose-independent manner and 200 mg Nilotinib increases the level of 3,4-Dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA), suggesting alteration to dopamine metabolism. Nilotinib significantly reduces plasma total alpha-synuclein and appears to reduce CSF oligomeric: total alpha-synuclein ratio. Furthermore, Nilotinib significantly increases the CSF level of triggering receptors on myeloid cells (TREM)-2, suggesting an anti-inflammatory effect. Taken together, 200 mg Nilotinib appears to be an optimal single dose that concurrently reduces inflammation and engages surrogate disease biomarkers, including dopamine metabolism and alpha-synuclein.

Discoidin domain receptor inhibition reduces neuropathology and attenuates inflammation in neurodegeneration models.

The role of cell surface tyrosine kinase collagen-activated receptors known as discoidin domain receptors (DDRs) is unknown in neurodegenerative diseases. We detect up-regulation in DDRs level in post-mortem Alzheimer and Parkinson brains. Lentiviral shRNA knockdown of DDR1 and DDR2 reduces the levels of α-synuclein, tau, and ß-amyloid and prevents cell loss in vivo and in vitro. DDR1 and DDR2 knockdown alters brain immunity and significantly reduces the level of triggering receptor expressed on myeloid cells (TREM)-2 and microglia. These studies suggest that DDR1 and DDR2 inhibition is a potential target to clear neurotoxic proteins and reduce inflammation in neurodegeneration.