Manus J. Donahue, Ph.D. - US grants

Infection of human and swine hosts by the intestinal parasite Ascaris represents a significant public health and economic problem world-wide. The adult organism is largely anaerobic, subsisting on available carbohydrate substrates during the host-feeding cycle and mobilizing endogenous glycogen during non-feeding periods. This investigator has established that 5-hydroxytryptamine (5-HT) is the hormone in Ascaris which initiates glycogenolysis in response to a failing energy charge in Ascaris. This application proposes to investigate the origin of the 5-HT. There are two viable possibilities for where the 5-HT is synthesized. One: the 5-HT is synthesized in the tissue of Ascaris. If this is true, the enzymes for the synthesis of 5-HT from tryptophan as well as the intermediate metabolites must be present. These questions will be investigated using both histochemical localization of 5-HT and biochemical analysis of the enzymes and metabolites. Second: the 5-HT is synthesized by the host and absorbed by the Ascaris. If this is true, 5-HT receptors must be present in Ascaris tissue for the uptake of the 5-HT. The application will investigate whether or not these receptors exist in Ascaris. These results will be correlated with and substantiated by the results obtained using an in situ perfusion system of Ascaris tissue developed by this investigator. The perfusion system permits a systematic variation in external metabolic signals in an attempt to correlate external stimuli with an internal biochemical event. This correlation will be utilized to provide an in-depth understanding of the regulation of 5-HT synthesis, utilization and metabolism and the significance of these events to the organism's survival. Collectively, the data will provide a biochemical basis for the development of chemotherapeutic agents which diminish the parasite's survival by selectively inhibiting the key regulation signal (5-HT) required for the initiation of glycogenolysis and, hence, energy production in this parasite.

DESCRIPTION (provided by applicant): The overall aim of this work is to assess the relationship between stroke risk and hemodynamic compensation strategies, as measured using a novel 3.0 Tesla MRI protocol, in patients with symptomatic intracranial (IC) steno-occlusive disease. Recent studies have shown high two-year ischemic stroke rates in symptomatic patients with IC arterial stenosis. Therapy for IC stenosis patients includes revascularization with angioplasty, IC stenting, or bypass, however identification of patients most likely to benefit from these more aggressive interventions, rather than medical management alone, has been problematic. Accurate measurements of hemodynamic compromise are likely required to better define stroke risk and guide treatment decisions. Specifically, in IC stenosis patients with compromised cerebral perfusion pressure (CPP), the extent of hemodynamic compromise reflects the autoregulatory capacity of vasculature to increase arterial cerebral blood volume (aCBV) and/or develop collaterals to supplement cerebral blood flow (CBF). The prevalence of CBF collateralization and aCBV autoregulation has been hypothesized to correlate uniquely with stroke risk; however the extent of this correlation has been debated. The critical barrier to stratifying stroke risk rests with a lack of i) methodology for measuring multiple hemodynamic factors with high specificity and (ii) noninvasive approaches capable of monitoring longitudinal progression of impairment. We have demonstrated the clinical utility of relatively new, noninvasive MRI approaches for assessing cerebrovascular reactivity (CVR), aCBV, and collateral CBF. We hypothesize that stroke risk can be more completely evinced from collective measurements of these parameters. Therefore, we propose to implement a novel, validated hemodynamic MRI protocol to assess tissue-level impairment and compensation strategies in patients with IC stenosis. Using a collective approach combining measurements of collateral CBF, aCBV and CVR in multiple brain regions, in conjunction with a statistical model incorporating the above variables as possible prognostic factors, we will quantify the extent to which two-year stroke risk is associated with hemodynamic compensation mechanisms. The noninvasive and multi-faceted scope of this investigation is intended to expand the diagnostic stroke infrastructure and elucidate new hemodynamic prognostic indicators of stroke in this high-risk population. PUBLIC HEALTH RELEVANCE: Recent studies have shown high stroke rates in patients with intracranial arterial stenosis, however conflicting reports regarding how best to manage these patients. To better understand stroke risk in these patients, we propose to apply novel, noninvasive magnetic resonance imaging approaches to obtain a more comprehensive measure of tissue viability and the prevalence of vascular compensation strategies in this at-risk population. Results from this study are anticipated to provide new information regarding the mechanisms by which the brain compensates for arterial stenosis and to describe the relationship between these mechanisms and stroke risk with the overreaching aims of reducing stroke and long-term disability.

DESCRIPTION (provided by applicant): This work will apply novel, noninvasive structural and functional magnetic resonance imaging (MRI) methods to patients with mild and moderate breast cancer-related lymphedema (BCRL) for the first time to test fundamental hypotheses about relationships between lymphatic compromise and imaging biomarkers that may portend disease progression and individualized therapy response. BCRL is a chronic, debilitating disease caused by lymphatic flow obstruction in the legs, arms, and shoulder regions. Lymphedema secondary to mastectomy and radiation therapy is a growing health concern and has been reported to occur, on average, in 20% of women within three years after breast cancer treatment and in as many as 94% of women five years after breast cancer treatment. While there is no cure for lymphedema, it has been shown that behavioral adjustments and aggressive therapeutic management of patients in early or subclinical disease stages can prevent or reduce long-term impairment. However, very limited information is available for identifying patients at highest risk for lymphedema. Several specialized imaging methods have demonstrated that reduced lymphatic flow velocity and related lymphatic contractility impairment may portend lymphedema risk, however these approaches require radioactive tracers and/or exogenous contrast agents, are generally only available in specialized centers, and are not performed in routine patient management. We have very recently demonstrated that arterial spin labeling (ASL), a popular and noninvasive MRI method for measuring blood flow, can be adapted to measure flow of lymphatic fluid to axillary lymph nodes, and furthermore that lymphatic velocities reported using this technique are consistent with similar measures using exogenous contrast agents. Additionally, we have shown that chemical exchange saturation transfer (CEST) MRI can be used to characterize interstitial protein accumulation in patients in preclinical BCRL stages prior to limb volume changes. Importantly, both spin labeling and CEST utilize standard MRI equipment available at most hospitals and therefore can easily be disseminated to clinical or research centers seeking to expand their abilities to characterize lymphatic compromise. Here, we propose to assess the ranges of lymphatic flow velocities and interstitial protein accumulation in healthy individuals (Aim 1) and BCRL patients in preclinical, mild, and moderate stages of impairment (Aim 2), and finally to assess how lymphatic system compromise changes in response to manual lymphatic drainage therapy and to what extent lymphatic flow velocity and interstitial protein accumulation may predict lymphedema progression (Aim 3). This work will for the first time apply a noninvasive, multi-modal MRI protocol, which has demonstrated clinical potential in neuroscience, liver, and breast applications, to the human lymphatic system to better characterize lymphatic dysfunction and lymphedema risk in the growing breast cancer survivor population.

Abstract The goal of this work is to apply novel neuroimaging methods in patients with Moyamoya syndrome to test fundamental hypotheses regarding hemodynamic compensation, stroke history, and symptomatology. Moyamoya disease (MMD) has unknown etiology and is characterized by steno-occlusion of the supraclinoid internal carotid arteries and proximal branches, development of collateral vessels, and a high risk of stroke. Idiopathic MMD is relatively rare, however moyamoya syndrome (MMS), which can arise secondary to Down syndrome, sickle cell disease, atherosclerosis, and radiotherapy shares many phenotypical characteristics as idiopathic MMD, yet is observed much more frequently. Patients with MMS are at high risk for stroke, and compared with atherosclerotic disease where preferred treatment regimens are outlined by recent clinical trial results, optimal MMS therapies are less clear and may comprise medical management and/or surgical revascularization. Owing to the dynamic course of MMS, which includes a wide variation of progressive steno- occlusion, abnormal expression of endothelial growth factors and inflammatory proteins, hemo-metabolic disturbances, intimal vessel wall thickening, and neoangiogensis, there is a pressing clinical need to understand the pathophysiology of these processes, how they relate to symptomatology and stroke incidence, and ultimately may be used to stratify patients for therapy or guide development of novel pharmaceuticals. The critical barrier to achieving this rests with a lack of optimal methods that can be implemented for mapping and surveillance. Here, in adults and children with MMS, we propose to implement new MRI methods developed in our center to test focused hypotheses regarding (Aim 1) relationships between endothelial dysfunction, stroke incidence, and symptomatology; (Aim 2) changes in vessel wall morphology, disease chronicity, and neurological symptoms; and (Aim 3) oxygen extraction fraction response to surgical revascularization therapy. The short-term significance of this work is that it will improve our understanding of the physiological processes that underlie how tissue responds to proximal non-atherosclerotic steno-occlusion and revascularization, which will serve as a prerequisite for utilizing functional neuroimaging to stratify patients with MMS for appropriate therapy. The longer-term goal is to use this information to guide the development of novel pharmaceuticals or early screening procedures that may enable therapies to be titrated to patients prior to irreversible tissue damage. Finally, methods implemented are translatable to other vascular diseases, and findings should have broader relevance for discerning pathophysiological differences between atherosclerotic and non- atherosclerotic hemodynamic compensation mechanisms.

ABSTRACT The goal of this work is to apply novel, noninvasive magnetic resonance imaging (MRI) methods for visualizing lymphatic circulation dysfunction to test fundamental hypotheses about lymphedema risk factors and therapies. Breast cancer treatment-related lymphedema (BCRL) arises secondary to surgical axillary lymph node (LN) dissection and irritation, and is a chronic and lifelong condition affecting a high 21.4% of patients receiving common breast cancer therapies. Reducing condition onset and improving management represent major unmet clinical needs for these 50,000 - 80,000 new patients per year, and emerging efforts focus on improving quality of life through more informed LN dissection and biopsy decisions, optimizing post-surgical complex decongestive therapy (CDT), and exploring novel pharmacological and surgical procedures. However, fundamental gaps in our knowledge persist regarding optimized implementation of these therapies and details of the physiological changes they elicit. The major underlying limitation is that there is a shortage of imaging methods available that can be used to evaluate lymphatic function directly, and there is currently no consensus regarding effective outcome measures for therapeutic efficacy evaluation. Rather, LN removal is frequently based on sentinel LN biopsy and additional subjectivity of the surgeon. Therapy evaluation is frequently based on coarse measurements such as changes in limb volume or patient-reported symptoms, which provide little information on underlying mechanistic changes that could be used to further refine these therapies. As part of our ongoing INFORM clinical trial of BCRL progression and therapy, we have demonstrated potential for new, noninvasive MRI approaches to identify BCRL risk in sub-clinical disease stages, as well as to visualize internal changes in lymphatic functioning as a result of emerging therapies. Here, we propose to extend these studies to improve abilities for BCRL theranostics. (Aim 1) Prevention. We will apply new anatomical and functional LN imaging approaches to identify LN profiles specific to biopsy-confirmed metastatic LNs; findings could be used to better inform LN dissection and reduce the incidence of benign LN removal. (Aim 2) Progression. We will improve our understanding of BCRL risk progression by testing the hypothesis that superficial tissue profiles and subcutaneous adipose accumulation are more prevalent in patients experiencing BCRL progression, and thereby could be used to triage patients for aggressive therapies prior to overt symptoms and irreversible damage. (Aim 3) Therapy. We will perform a repeated-measures cross-over trial to test the hypothesis that mobilization of protein enriched hardened tissue using graded negative pressure therapy in conjunction CDT is superior to standard CDT alone. The overall goal is to develop objective markers of lymphatic dysfunction that can be used in emerging therapeutic trials of cancer and BCRL therapies to reduce both the incidence and severity of symptoms associated with this prevalent and chronic condition.  

ABSTRACT Immunological and physiological studies have recently provided strong evidence in support of a central nervous system (CNS) lymphatic drainage system in vertebrate animals, which has more recently been implicated in amyloid beta (A?) plaque clearance disorders such as Alzheimer's disease (AD)-related dementias (ADRD). This system comprises (i) dural and meningeal lymphatic vessels that drain CSF and interstitial fluid (ISF) toward cervical lymph nodes and which may (ii) communicate with the recently-proposed glymphatic system, an aquaporin-4 (AQP4)-mediated system that facilitates CSF-ISF efflux from periarterial to perivenous spaces and ultimately to cervical lymphatic vessels and nodes. While multiple independent studies have speculated that the CNS lymphatic system may have relevance to clearance conditions of unknown etiology (including but not limited to A? clearance deficiency and Alzheimer's disease), limited direct information is available on the relevance of this system to CNS clearance disorders in humans. The critical barrier to addressing this problem in patients with these conditions rests with a general lack of imaging methods that can be applied to interrogate multiple aspects of the proposed human CNS lymphatic system in vivo. The parent study focuses on developing magnetic resonance imaging (MRI) methodologies to visualize lymphatic dysfunction in the periphery of patients with known lymphatic dysfunction. Very recently, we have translated these noninvasive MRI methods, optimized in prior work to evaluate peripheral blood and lymphatic circulatory dysfunction, to the CNS. These methods provide a foundation whereby novel, noninvasive metrics can be measured and quantified to understand CNS lymphatic function in healthy tissue and also in the presence of increased A? burden and ADRD. As such, the goal of this work is to apply novel MRI and established PET approaches, optimized for evaluating peripheral circulatory dysfunction and A? deposition, respectively, to evaluate relationships between CNS glymphatic function, A? burden, and cognitive impairment in older adults with and at risk for Alzheimer's disease. Study findings are intended to provide imaging biomarkers of CNS lymphatic dysfunction which can be recorded noninvasively in vivo using clinically-available imaging equipment. If successful, results will provide a new avenue for both understanding AD pathophysiology and evaluating novel glymphatic-based therapeutic avenues in patients with ADRD.

ABSTRACT Recent immunological and physiological studies have provided evidence in support of a central nervous system (CNS) lymphatic drainage system in vertebrate animals, which has more recently been implicated in brain amyloid beta (A?) plaque clearance disorders such as Alzheimer's disease (AD)-related dementias (ADRD). This system is believed to comprise (i) dural and meningeal lymphatic vessels that drain CSF and interstitial fluid (ISF) toward cervical lymph nodes and which may (ii) communicate with the recently-proposed glymphatic system, an aquaporin-4 (AQP4)-mediated system that facilitates CSF-ISF efflux from periarterial to perivenous spaces and ultimately to cervical lymphatic vessels and nodes. While multiple independent studies have speculated that the CNS lymphatic system may have relevance to clearance conditions of unknown etiology in humans (including but not limited to sleep disorders, CSF clearance disorders, multiple sclerosis, Parkinson's disease, and ADRD), limited direct information is available on the relevance of this system to these disorders in humans. The critical barrier to addressing this problem rests with a general lack of imaging methods that can be applied to interrogate multiple aspects of the proposed human CNS lymphatic system in vivo. As such, even basic knowledge about how this system changes with age, sex, and behavioral state remain debated, and these limitations preclude identification of pathological features in patients. Very recently, we have translated non-invasive magnetic resonance imaging (MRI) methods optimized in prior work for evaluating peripheral blood and lymphatic circulatory dysfunction to the CNS. We have quantified measures of intracranial glymphatic function in 61 older adults with Parkinson's disease (PD), with and without associated cognitive dysfunction, and have provided evidence that PD patients with amnestic mild cognitive impairment (aMCI) have significantly reduced markers of intracranial glymphatic function compared to age-matched patients without aMCI, and also that markers of glymphatic flow velocity inversely correlate with brain A? burden quantified from gold-standard PET imaging. These findings provide a foundation in which novel, non-invasive markers can be applied to understand lymphatic function in healthy tissue and also in the presence of increased brain A? burden. As such, the goal of this work is to apply novel MRI and established PET approaches to evaluate (i) how the CNS lymphatic system varies with age and sex for healthy aging, and subsequently the clinical relevance of CNS lymphatic function on (ii) brain A? burden and (ii) behavioral state in PD patients with cognitive impairment, a recognized ADRD. Study findings will provide fundamental insights into the behavior of the CNS lymphatic system in humans with and without ADRD. More broadly, the methods developed and refined will provide a support structure for the growing number of studies seeking to interrogate CNS lymphatic function, but where current imaging tools lack sufficient sensitivity.