Faculty Bibliography

Advances in closed-loop neural interfaces and neuromodulation have offered a potentially effective and non-addictive treatment for chronic pain. These interfaces link neural sensors with device outputs to provide temporally precise stimulation. We discuss challenges and trends of state-of-the-art neural interfaces for treating pain in animal models and human pilot trials.

Oral cancer is notoriously painful. Activation of protease-activated receptor 2 (PAR₂, encoded by F2RL1) by proteases in the cancer microenvironment is implicated in oral cancer pain. PAR₂ is a G protein-coupled receptor (GPCR) expressed on neurons and cells in the cancer microenvironment. Sustained signaling of PAR₂ from endosomes of neurons mediates sensitization and nociception. We focused on the differential contribution of PAR₂ on oral cancer cells and neurons to oral cancer pain and whether encapsulation of a PAR₂ inhibitor, AZ3451 in nanoparticles (NP) more effectively reverses PAR₂ activation. We report that F2RL1 was overexpressed in human oral cancers and cancer cell lines. Deletion of F2RL1 on cancer cells reduced cancer-associated mechanical allodynia. A third-generation polyamidoamine dendrimer, functionalized with cholesterol was self-assembled into NPs encapsulating AZ3451. NP encapsulated AZ3451 (PAMAM-Chol-AZ NPs) more effectively reversed activation of PAR₂ at the plasma membrane and early endosomes than free drug. The PAMAM-Chol-AZ NPs showed greater efficacy in reversing nociception than free drug, with respect to both level and duration, in three preclinical mouse models of oral cancer pain. The antinociceptive efficacy was confirmed with an operant orofacial assay. Genetic deletion of F2RL1 on cancer cells or F2rl1 on neurons each partially reversed mechanical cancer allodynia. The remaining nociception could be effectively reversed by PAMAM-Chol-AZ NPs. These findings suggest that PAR₂ on oral cancer cells and neurons contribute to oral cancer nociception and NPs loaded with a PAR₂ antagonist provide increased antinociception and improved oral function compared to free drug.

Professor Alessandro Zuddas, from the University of Cagliari (Italy), passed away prematurely in July 2022. As a prominent figure in child and adolescent neuropsychiatry, he substantially influenced the fields of neurodevelopmental disorders and neuropsychopharmacology both nationally and internationally. Professor Zuddas was a renowned expert in basic and clinical research in child and adolescent psychopharmacology, an enlightened and stimulating educator, and a mentor to many students, residents, and senior colleagues. With his enthusiasm and unique ability to network, he contributed enormously to trace a path in the field that we continue to follow. His name will remain in the textbooks and articles he authored. Here, as colleagues and friends who had the honor to work with him, we provide our personal views of Alessandro's impact and legacy, which go far beyond his publications.

INTRODUCTION/BACKGROUND:It is unclear how early neuronal deficits occur in tauopathies, if these are associated with changes in neuronal network activity, and if they can be alleviated with therapies. METHODS:imaging in tauopathy mice at 6 versus 12 months, compared to controls, and treated the younger animals with a tau antibody. RESULTS:Neuronal function was impaired at 6 months but did not deteriorate further at 12 months, presumably because cortical tau burden was comparable at these ages. At 6 months, neurons were mostly hypoactive, with enhanced neuronal synchrony, and had dysregulated responses to stimulus. Ex vivo, electrophysiology revealed altered synaptic transmission and enhanced excitability of motor cortical neurons, which likely explains the altered network activity. Acute tau antibody treatment reduced pathological tau and gliosis and partially restored neuronal function. DISCUSSION/CONCLUSIONS:Tauopathies are associated with early neuronal deficits that can be attenuated with tau antibody therapy. HIGHLIGHTS/CONCLUSIONS:Neuronal hypofunction in awake and behaving mice in early stages of tauopathy. Altered network activity disrupted local circuitry engagement in tauopathy mice. Enhanced neuronal excitability and altered synaptic transmission in tauopathy mice. Tau antibody acutely reduced soluble phospho-tau and improved neuronal function.

Legumain is a cysteine protease broadly associated with inflammation. It has been reported to cleave and activate protease-activated receptor 2 to provoke pain associated with oral cancer. Outside of gastric and colon cancer, little has been reported on the roles of legumain within the gastrointestinal tract. Using a legumain-selective activity-based probe, LE28, we report that legumain is activated within colonocytes and macrophages of the murine colon, and that it is upregulated in models of acute experimental colitis. We demonstrated that loss of legumain activity in colonocytes, either through pharmacological inhibition or gene deletion, had no impact on epithelial permeability in vitro. Moreover, legumain inhibition or deletion had no obvious impacts on symptoms or histological features associated with dextran sulfate sodium-induced colitis, suggesting its proteolytic activity is dispensable for colitis initiation. To gain insight into potential functions of legumain within the colon, we performed field asymmetric waveform ion mobility spectrometry-facilitated quantitative proteomics and N-terminomics analyses on naïve and inflamed colon tissue from wild-type and legumain-deficient mice. We identified 16 altered cleavage sites with an asparaginyl endopeptidase signature that may be direct substrates of legumain and a further 16 cleavage sites that may be indirectly mediated by legumain. We also analyzed changes in protein abundance and proteolytic events broadly associated with colitis in the gut, which permitted comparison to recent analyses on mucosal biopsies from patients with inflammatory bowel disease. Collectively, these results shed light on potential functions of legumain and highlight its potential roles in the transition from inflammation to colorectal cancer.

The astrocyte, a major glial cell type in the central nervous system (CNS), is widely regarded as a functionally diverse mediator of homeostasis. During development and throughout adulthood, astrocytes have essential roles, such as providing neuron metabolic support, modulating synaptic function, and maintaining the blood-brain barrier (BBB). Recent evidence continues to underscore their functional heterogeneity and importance for CNS maintenance, as well as how these cells ensure optimal CNS and immune responses to disease, acute trauma, and infection. Advances in our understanding of neuroimmune interactions complement our knowledge of astrocyte functional heterogeneity, where astrocytes are now regarded as key effectors and propagators of immune signaling. This shift in perspective highlights the role of astrocytes not merely as support cells, but as active participants in CNS immune responses.

Chronic pain affects one in five adults. It is not only a major cause of disability for individual patients but also a driver of costs for entire healthcare systems. Treatment of pain remains a challenge, and the use of opioids has further led to a concurrent opioid epidemic. In this review, we discuss current standard treatment options for chronic pain, including pharmacological, behavioral, and interventional treatments. In addition, we review ongoing research in different areas that will potentially unlock new therapies.

PURPOSE/OBJECTIVE:maps from fewer echoes. METHODS:mapping was evaluated in seven experiments. RESULTS:estimation. CONCLUSIONS:estimation from fewer echoes allows for increased volumetric coverage and/or higher slice resolution without prolonging total scan times.

Across species, navigation is crucial for finding both resources and shelter. In vertebrates, the hippocampus supports memory-guided goal-directed navigation, whereas in arthropods the central complex supports similar functions. A growing literature is revealing similarities and differences in the organization and function of these brain regions. We review current knowledge about how each structure supports goal-directed navigation by building internal representations of the position or orientation of an animal in space, and of the location or direction of potential goals. We describe input pathways to each structure - medial and lateral entorhinal cortex in vertebrates, and columnar and tangential neurons in insects - that primarily encode spatial and non-spatial information, respectively. Finally, we highlight similarities and differences in spatial encoding across clades and suggest experimental approaches to compare coding principles and behavioral capabilities across species. Such a comparative approach can provide new insights into the neural basis of spatial navigation and neural computation.

The COVID-19 pandemic was an unparalleled stressor that enhanced isolation. Loneliness has been identified as an epidemic by the US Surgeon General. This study aimed to: (1) characterize longitudinal trajectories of loneliness during the acute phase of the COVID-19 pandemic; (2) identify longitudinal mediators of the relationship of loneliness with anxiety and depression; and (3) examine how loneliness naturally clusters and identify factors associated with high loneliness. Two hundred and twenty-nine adults (78% female; mean age = 39.5 ± 13.8) completed an abbreviated version of the UCLA Loneliness Scale, Perceived Stress Scale, Emotion Regulation Questionnaire, State Anxiety Inventory, and Patient Health Questionnaire-8 longitudinally between April 2020 and 2021. Trajectory analyses demonstrated relatively stable loneliness over time, while anxiety and depression symptoms declined. Longitudinal analyses indicated that loneliness effects on anxiety and depression were both partially mediated by perceived stress, while emotion regulation capacity only mediated effects on anxiety. Three stable clusters of loneliness trajectories emerged (high, moderate, and low). The odds of moderate or high loneliness cluster membership were positively associated with higher perceived stress and negatively associated with greater cognitive reappraisal use. Our results demonstrate the important interconnections between loneliness and facets of mental health throughout the early phases of the pandemic and may inform targeted future interventions for loneliness work.