The candidate, Brendan K. Podell, DVM, is pursuing a mentored research career development award to aid in his transition into a career as an independent biomedical researcher. Dr. Podell is a veterinary pathologist with career goals of pursuing research in infectious disease and immunology in an academic faculty position and will complete a PhD degree in May of 2014. Dr. Podell has established a career development plan that will facilitate a research career in tuberculosis pathogenesis, risk factors for tuberculosis, including diabetes, and investigation of novel treatment methods for both tuberculosis and diabetes. Expert faculty will facilitate Dr. Podell's development in advanced molecular biology, immunology and proteomic techniques and data interpretation. A development plan that emphasizes critical feedback from faculty in a newly established advisory committee, development of collaborative research, and achievement of excellence in grantsmanship and writing will ensure Dr. Podell's success during the award period. Dr. Podell will be mentored by Dr. Randall Basaraba, who is an accomplished researcher in tuberculosis pathogenesis and has established himself as a leader in the modeling and study of diabetic susceptibility to tuberculosis, a prioritized research topic with major impact on global tuberculosis control. The study of diabetes-tuberculosis comorbidity is the focus of the proposed research in this application and Dr. Basaraba represents the best-suited mentor at this institution. Dr. Edward Hoover will serve as co-mentor and through extensive experience mentoring veterinarians in research training and numerous K-awardees;he will support Dr. Podell's transition to independence. The CSU Mycobacterial Research Laboratories, a network of 21 internationally recognized investigators in mycobacterial disease, will provide an outstanding environment for development of the candidate. Diabetes is an established risk factor for tuberculosis (TB), however little is known about the pathogenesis of this comorbidity. Due to the rapidly growing prevalence of diabetes in developing countries with the highest incidence of TB, this combined burden of communicable and non-communicable diseases threatens global TB control. Diabetes is characterized by uncontrolled hyperglycemia, which accelerates the unregulated modification of macromolecules by sugars leading to the formation of advanced glycation end products (AGEs). AGEs promote a pro-inflammatory state by inducing signaling through the RAGE receptor, an underlying mechanism for development of diabetes-related complications. Since (1) hyperglycemia is linked to AGE formation in our animal models of DM-TB comorbidity;(2) hyperglycemia-induced AGE formation is associated with increased inflammation and pathology in these models;and (3) poorly controlled hyperglycemia and related glycation are associated with increased pro-inflammatory cytokines in Mycobacterium tuberculosis (Mtb) infected diabetic humans, we propose that AGE formation and RAGE signaling lead to a pro-inflammatory immune response that dictates more severe TB in diabetics. We have developed the first guinea pig model of type 2 diabetes and the only validated animal model of type 2 diabetes-tuberculosis comorbidity, which shows important similarities to what little is known about this disease complex in humans.
In Aim 1, we have developed a novel strategy to target this ligand-receptor interaction and determine if AGE-RAGE signaling worsens TB disease in diabetic guinea pigs. Along with collaborators, we have developed a novel and highly potent class of anti-AGE drugs that will reduce AGE formation in vivo. The RAGE receptor will be targeted using a recently developed, high affinity small molecule inhibitor proven to prevent RAGE signaling in vivo and will be interpreted in the context of isolated native guinea pig soluble RAGE (sRAGE), a soluble receptor isoform that sequesters ligands and prevents transmembrane RAGE signaling. Through this strategy, we will determine if AGE formation and/or RAGE signaling are responsible for more severe TB in diabetics. We have shown that RAGE expression along with pro-inflammatory cytokine expression, similar to humans with type 2 diabetes, are elevated in diabetic guinea pigs.
In Aim 2, we will determine if an amplified innate immune response due to RAGE signaling occurs early in Mtb infection and impairs the ability to control bacterial growth. Through use of the small molecule RAGE inhibitor and RNA interference, we will demonstrate alterations in the early cytokine response in vivo in diabetic guinea pigs as well as determine if the initial response and control of Mtb infection is impaired by RAGE-mediated amplification of the innate response in ex vivo isolated alveolar macrophages. We have also shown that diabetic guinea pigs have a delay in the adaptive immune response that is critical for control of Mtb. Since an early pro-inflammatory response impairs macrophage function and priming of adaptive immunity, and promotes destructive inflammation, in Aim 3, we will investigate the impact of RAGE and pro-inflammatory conditions on onset of adaptive immune function and damaging inflammation using novel intrapulmonary RNA interference techniques developed in our department. Successful completion of these aims will establish a novel mechanism responsible for heightened severity of TB in diabetics, which we will show can be targeted therapeutically with novel small molecules.
Diabetes is a recognized risk factor for tuberculosis and due to the growing global diabetes epidemic, is positioned to significantly hamper global tuberculosis control efforts. However, knowledge regarding the impact diabetes has on tuberculosis pathogenesis and areas for treatment intervention is limited. This study address these critical limitations through investigation of a novel pathway in diabetic susceptibility to infection with Mycobacterium tuberculosis, which involves well-characterized chemical modifications produced during diabetes that promote inflammation, known as advanced glycation end-products (AGEs). In this study, we will identify mechanisms of altered immune function in diabetes-tuberculosis comorbidity, which are mediated through AGEs and their receptor, and can be targeted therapeutically to reduce the burden of TB disease and control bacterial growth in diabetics.