Alterations in the expression, molecular composition, and localization of voltage-gated sodium channels play major roles in a broad range of neurological disorders. Recent evidence identifies sodium channel proteolysis as a key early event after ischemia and traumatic brain injury, further expanding the role of the sodium channel in neurological diseases. In this study, we investigate the protease responsible for proteolytic cleavage of voltage-gated sodium channels (NaChs). NaCh proteolysis occurs after protease activation in rat brain homogenates, pharmacological disruption of ionic homeostasis in cortical cultures, and mechanical injury using an in vitro model of traumatic brain injury. Proteolysis requires Ca 2+ and calpain activation but is not influenced by caspase-3 or cathepsin inhibition. Proteolysis results in loss of the full-length α-subunits, and the creation of fragments comprising all domains of the channel that retain interaction even after proteolysis. Cell surface biotinylation after mechanical injury indicates that proteolyzed NaChs remain in the membrane before noticeable evidence of neuronal death, providing a mechanism for altered action potential initiation, propagation, and downstream signaling events after Ca 2+ elevation.

Increases in cytosolic calcium ([Ca 2+ ] i ) following mechanical injury are often considered a major contributing factor to the cellular sequelae in traumatic brain injury (TBI). However, very little is known on how developmental changes may affect the calcium signaling in mechanically injured neurons. One key feature in the developing brain that may directly impact its sensitivity to stretch is the reduced inhibition which results in spontaneous [Ca 2+ ] i oscillations. In this study, we examined the mechanism of stretch-induced ] i response to stretch is initiated, and how reduced inhibition -a feature of the developing brain -may affect the sensitivity of the immature brain to trauma.

NMDA receptors are essential for neurotransmission and key mediators of synaptic signaling, but they can also trigger deleterious degenerative processes that lead to cell death. Growing evidence suggests that selective blockade of the heterogeneous subunits that comprise the NMDA receptor may enable better control of pharmacotherapies for treating neurological diseases and injuries. We investigated the relationship between NMDAR activation, MAPK signaling, and mitochondrial shape following an excitotoxic insult. NR2A- and NR2B-containing NMDARs differentially mediated acute changes in cytosolic calcium, alterations in mitochondrial morphology, and phosphorylation of the MAPKs ERK and JNK. Activation of NR2A-containing NMDARs was associated with JNK phosphorylation that was neuroprotective in neuronal cultures subjected to excitotoxicity. In contrast, activation of NR2B-containing NMDARs triggered calcium accumulation in mitochondria that was strongly associated with mitochondrial swelling and neuronal cell death. Indeed, while blockade of NR2B-containing receptors was neuroprotective, this protection was lost when NR2A-initiated JNK phosphorylation was inhibited. Given the modest selectivity of the NR2A inhibitor, NVP-AAM077, the results highlight the significance of the relative, rather than absolute, activation of these two NMDA subtypes in modulating cell death pathways. Therefore, the balance between concurrent activation of NR2B-containing and NR2A-containing NMDARs dictates neuronal fate following excitotoxicity.

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Congenital hyperinsulinism (HI) is the most frequent cause of severe, persistent hypoglycemia in newborn babies and children. There are many areas of need for HI research. Some of the most critical needs include describing the natural history of the disease, research leading to new and better treatments, and identifying and managing hypoglycemia before it is prolonged and causes brain damage or death. Patient-reported data provides a basis for understanding the day-to-day experience of living with HI. Commonly identified goals of registries include performing natural history studies, establishing a network for future product and treatment studies, and supporting patients and families to offer more successful and coordinated care. Congenital Hyperinsulinism International (CHI) created the HI Global Registry (HIGR) in October 2018 as the first global patient-powered hyperinsulinism registry. The registry consists of thirteen surveys made up of questions about the patient’s experience with HI over their lifetime. An international team of HI experts, including family members of children with HI, advocates, clinicians, and researchers, developed the survey questions. HIGR is managed by CHI and advised by internationally recognized HI patient advocates and experts. This paper aims to characterize HI through the experience of individuals who live with it. This paper includes descriptive statistics on the birthing experience, hospitalizations, medication management, feeding challenges, experiences with glucose monitoring devices, and the overall disease burden to provide insights into the current data in HIGR and demonstrate the potential areas of future research. As of January 2022, 344 respondents from 37 countries consented to participate in HIGR. Parents or guardians of individuals living with HI represented 83.9% of the respondents, 15.3% were individuals living with HI. Data from HIGR has already provided insight into access challenges, patients’ and caregivers’ quality of life, and to inform clinical trial research programs. Data is also available to researchers seeking to study the pathophysiology of HI retrospectively or to design prospective trials related to improving HI patient outcomes. Understanding the natural history of the disease can also guide standards of care. The data generated through HIGR provides an opportunity to improve the lives of all those affected by HI.