Chemotherapy Induced Sensory Neuropathy Depends on Non-Linear Interactions with Cancer

For the constellation of neurological disorders known as chemotherapy induced neuropathy, mechanistic understanding, and treatment remain deficient. In project one, I leveraged a multi-scale experimental approach to provide the first evidence that chronic sensory neuropathy depends on non-linear interactions between cancer and chemotherapy. Global transcriptional profiling of dorsal root ganglia revealed amplified differential expression, notably in regulators of neuronal excitability, metabolism and inflammatory responses, all of which were unpredictable from effects observed with either chemotherapy or cancer alone. Systemic interactions between cancer and chemotherapy also determined the extent of deficits in sensory encoding in vivo and ion channel protein expression by single mechanosensory neurons, with the potassium ion channel Kv3.3 emerging as candidate mechanisms explaining sensory neuron dysfunction. The sufficiency of this novel molecular mechanism was tested in an in silico biophysical model of mechanosensory function. Finally, validated measures of sensorimotor behavior in awake behaving animals confirmed that dysfunction after chronic chemotherapy treatment is exacerbated by cancer. Notably, errors in precise fore-limb placement emerged as a novel behavioral deficit unpredicted by our previous study of chemotherapy alone. These original findings identify novel contributors to peripheral neuropathy, and emphasize the fundamental dependence of neuropathy on the systemic interaction between chemotherapy and cancer across multiple levels of biological control. In project two, I extend study to multiple classes of mechanosensory neurons that are necessary for generating the information content (population code) needed for proprioception. I first tested the hypothesis that exacerbated neuronal dysfunction is conserved across multiple classes of mechanosensory neurons. Results revealed co-suppression of specific signaling parameters across all neuronal classes. To understand the consequences of corrupt population code, I employed a long-short-term memory neural network (LSTM), a deep-learning algorithm, to test how decoding of spatiotemporal features of movement are altered after chemotherapy treatment of cancer. Results indicate that spiking activity from the population of neurons in animals with cancer, treated by chemotherapy contain significantly less information about key features of movement including, e.g. timing, magnitudes, and velocity. I then modeled the central nervous systems (CNS) capacity to compensate for this information loss. Even under optimal learning conditions, the inability to fully restore predictive power suggests that the CNS would not be able to compensate and restore full function. Our results support our proposal that lasting deficits in mobility and perception experienced by cancer survivors can originate from sensory information that is corrupted and un-interpretable by CNS neurons or networks. Collectively, I present the first evidence that chronic cancer neuropathy cannot be explained by the effects of chemotherapy alone but instead depend on non-linear interactions with cancer. This understanding is a prerequisite for designing future studies and for developing effective treatments or preventative measures.Ph.D

Origins of eukaryotic excitability

This is the final version. Available on open access from the Royal Society via the DOI in this recordAll living cells interact dynamically with a constantly changing world. Eukaryotes in particular, evolved radically new ways to sense and react to their environment. These advances enabled new and more complex forms of cellular behavior in eukaryotes, including directional movement, active feeding, mating, or responses to predation. But what are the key events and innovations during eukaryogenesis that made all of this possible? Here we describe the ancestral repertoire of eukaryotic excitability and discuss five major cellular innovations that enabled its evolutionary origin. The innovations include a vastly expanded repertoire of ion channels, the emergence of cilia and pseudopodia, endomembranes as intracellular capacitors, a flexible plasma membrane, and the relocation of chemiosmotic ATP synthesis to mitochondria that liberated the plasma membrane for more complex electrical signaling involved in sensing and reacting. We conjecture that together with an increase in cell size, these new forms of excitability greatly amplified the degrees of freedom associated with cellular responses, allowing eukaryotes to vastly outperform prokaryotes in terms of both speed and accuracy. This comprehensive new perspective on the evolution of excitability enriches our view of eukaryogenesis and emphasizes behaviour and sensing as major contributors to the success of eukaryotes.European Commissio

Molecular and cellular characterization of cardiac overload-induced hypertrophy and failure

In neonatal rat ventricular cardiomyocytes (NRVCs), we activated integrins by RGD to test whether integrin stimulation produced hypertrophy. Effect of RGD was compared with pro-hypertrophic effects of phenylephrine (chapter 2). Ventricular failure is associated with disturbed collagen turnover. Myocardial collagen turnover can be assessed by plasma PINP, PIIINP, and ICTP representing collagen synthesis (PINP, PIIINP) or degradation (ICTP). We investigated the effects of cardiac resynchronization therapy (CRT) on collagen turnover in patients at baseline and after 6 months of CRT (chapter 3). Monocrotaline (MCT)-induced pulmonary arterial hypertension (PAH) and RV failure are associated with MMP activation in RV, we investigated whether NO plays role in RV hypertrophy and failure (chapter 4). In chapter 5 we reviewed novel approaches to treat experimental PAH. We investigated whether MCT-induced PAH and RV failure can be treated with mesenchymal stem cells (MSCs) from donor rats with PAH caused by MCT. At day 14 after MCT, recipient rats were treated with MSCs. In chapters 6,7 the effects of MSCs on pulmonary pathology and RV function were examined. Isolated cardiomyocytes were investigated for PAH-related changes in excitability. In chapter 8 we reported on excitability properties dependent on Kv-channel expression, proposed to play a role in arrhythmias.UBL - phd migration 201

Targeting Tight Junctions in Nanomedicine: a Molecular Modeling Perspective

Molecular Dynamics Simulations of Claudin Paracellular Channel

Neuroinflammation causes changes to the nodes of Ranvier in Multiple Sclerosis normal-appearing white matter.

Background: In addition to the focal demyelinating lesions in multiple sclerosis (MS), both imaging and neuropathological analyses have demonstrated the presence of a more diffuse pathology in both the white and grey matter, including changes to the structure of nodes of Ranvier in the normal-appearing white matter (NAWM). Objective: We have examined the expression of the paranodal axonal protein Caspr1, the voltage-gated channels Nav and Kv1.2 at nodes and juxtaparanodes respectively, and SMI32+ (dephosphorylated neurofilament) axons in NAWM areas from post-mortem progressive MS brains compared to controls. This axo-geometrical data on nodal changes was then integrated into a computational model of an axon developed with NEURON. To test our hypothesis, rats were injected into the cerebral subarachnoid space with lentiviral vectors for lymphotoxin-α and interferon-γ, and structural changes were examined 3 months later. Furthermore, a cerebellar tissue culture model was used to induce nodal pathology by the activation of microglia with TNF, interferon-γ, conditioned microglial medium and glutamate administration. Results: The paranodal domain in MS NAWM tissue was longer on average than in control and Kv1.2 channels appeared dislocated towards the paranode. These changes were associated with stressed axons and activation of microglia. When these changes were inserted into the computational model, a rapid decrease in velocity was observed as the paranodal peri-axonal space was increased, reaching conduction failure when the axons were less than 1mm of diameter. The same structural changes were observed in the corpus callosum of our rat model and were associated with microglia/astrocyte activation. TNF, interferon-γ, conditioned microglial medium and glutamate also generated paranodal elongation in the cerebellar cultures axons and was reversed/halted by an NMDA blocker. Conclusion: Microglia activated by pro-inflammatory cytokines may release high levels of glutamate, which triggers paranodal pathology in MS NAWM, contributing to axonal damage and subsequent conduction deficits.Open Acces

Structures Illuminate Cardiac Ion Channel Functions in Health and in Long QT Syndrome

The cardiac action potential is critical to the production of a synchronized heartbeat. This electrical impulse is governed by the intricate activity of cardiac ion channels, among them the cardiac voltage-gated potassium (Kv) channels KCNQ1 and hERG as well as the voltage-gated sodium (Nav) channel encoded by SCN5A. Each channel performs a highly distinct function, despite sharing a common topology and structural components. These three channels are also the primary proteins mutated in congenital long QT syndrome (LQTS), a genetic condition that predisposes to cardiac arrhythmia and sudden cardiac death due to impaired repolarization of the action potential and has a particular proclivity for reentrant ventricular arrhythmias. Recent cryo-electron microscopy structures of human KCNQ1 and hERG, along with the rat homolog of SCN5A and other mammalian sodium channels, provide atomic-level insight into the structure and function of these proteins that advance our understanding of their distinct functions in the cardiac action potential, as well as the molecular basis of LQTS. In this review, the gating, regulation, LQTS mechanisms, and pharmacological properties of KCNQ1, hERG, and SCN5A are discussed in light of these recent structural findings

Multiscale Model of Cerebral Blood Flow Control: Application to Small Vessel Disease and Cortical Spreading Depression

An in-time delivery of oxygen-rich blood into areas of high metabolic demand is pivotal in proper functioning of the brain and neuronal health. This highly precise communication between neuronal activity and cerebral blood flow (CBF) is termed as neurovascular coupling (NVC) or functional hyperemia. NVC is disrupted in major pathological conditions including Alzheimer’s disease, dementia, small vessel pathologies (SVD) and cortical spreading depression. Despite the utmost importance of NVC, its underlying mechanisms are not fully understood. This dissertation presents a multiscale mathematical modeling framework for studying unresolved mechanisms of NVC with major focus on K+ ions as a mediator of this process. To this end, models of single-cell electrophysiology are developed for endothelial (EC) and smooth muscle (SMC) cells of capillaries and parenchymal arterioles (PAs). Cells are electrically coupled, and large-scale geometrically-accurate models of microvascular networks are constructed. Model simulations predict an important role of capillary inward rectifying potassium channels (Kir) to sense neuronally-induced changes in extracellular potassium concentrations ([K+]o) and conduct hyperpolarizing signals over long distances to upstream PAs. Simulation results demonstrate a “tug-of-war” dynamic between Kir and voltage-gated potassium (Kv) channels in determining the Vm and myogenic tone of PA SMCs during NVC in SVD. Results also predict a key role of Kir channels in the experimentally observed multiphasic vascular response during high elevations of [K+]o in cortical spreading depression. The multiscale models presented in this study were able to accurately capture several experimentally observed responses during NVC and provided insights into their potential underlying mechanisms in health and disease. These models provide a theoretical platform where macroscale, tissue-level responses can be related to microscale, single-cell signaling pathways