Research Project Leaders
Aminoglycosides (AG) have broad antibiotic spectra against aerobic gram-positive and gram-negative bacteria as well as mycobacterial pathogens. AG toxicities include kidney tubular necrosis, vertigo, and, most notably, hearing loss. AG are used to treat multidrug-resistant tuberculosis (MDR-TB) and Mycobacterium abscessus complex (MABSC) infected patients (e.g. cystic fibrosis, bronchiectasis or chronic obstructive pulmonary disease). Studies have shown that 55-58% of patients infected with MDR-TB who received amikacin as part of their therapy, experienced hearing loss due to its ototoxic effects. Likewise, up to 27% of cystic fibrosis patients infected with M. abscessus who received AG therapy experienced hearing loss. To date, there is no FDA-approved therapy available to prevent or treat hearing loss. A reduced reliance on AG therapy in mycobacterial infections will minimize hearing loss for patients infected with drug-resistant M. tb strains and nontuberculous mycobacteria. We have discovered a novel series of small molecules (indole-2-carboxamides and acetamides) that have potent activity against a panel of mycobacteria. Two of our lead candidates had poor oral absorption yet achieved efficacy in a mouse model of M. abscessus infection. We propose to discover and develop anti-mycobacterial inhibitors with potent activity with improved pharmacokinetic profiles and no ototoxicity. Using ligand-based drug design and computer aided drug design. In vitro bioavailability and toxicity profiles will also be determined. Finally, potent anti-NTM agents with optimized bioavailability and toxicity profiles will be subjected to macromolecular mechanism of action studies, ensuring future compounds remain on target as MmpL inhibitors. Our lab has developed novel MmpL3 (Mycobacterium membrane protein Large 3) inhibitors showing excellent promise for the treatment of mycobacterial infections, including Mycobacterium tuberculosis, the causative pathogen for tuberculosis. The design and synthesis of a novel series of MmpL3 inhibitors led us to identify a number of analogs with 0.06-8 µg/mL potency against various slow- and fast-growing mycobacterial pathogens of clinical interest. Consistent with earlier findings in M. tuberculosis, our preliminary evidence indicates that ICs (Indole-2-carboxamide) kill Mycobacterium abscessus isolates through the inhibition of the essential mycolic acid transporter, MmpL3. Mycolic acids, which are long α-alkylated β-hydroxylated fatty acids, are primary constituents of the mycobacterial outer membrane (also referred to as mycomembrane) and inhibition of translocation across the plasma membrane through the inhibition of MmpL3 has a rapid bactericidal effect on the cells. We believe MmpL3 inhibitors are an important discovery of a new chemotype that can be used for the treatment of mycobacterial infections.
Hidden hearing loss is damage to the cochlear nerve fibers connecting the sensory cell receptors of the inner ear to the brain, that occur before changes in hearing thresholds, and is likely a major contributor to difficulties understanding speech in a noisy environment as well as tinnitus and hyperacusis. Tinnitus is the ringing noise that some people experience in their ears that others cannot hear which is caused by underlining conditions such as age-related hearing loss. Hyperacusis is when people experience normal noises as being too loud and loud noises cause extreme pain and discomfort. We will to examine the effect of fractalkine exposure and macrophage depletion in preserving or restoring nerve fiber connections after noise trauma. Such knowledge will advance our understanding on the role of immune system in damaged ears and is essential to developing novel therapeutic strategies to reconnect nerve fibers to sensory cells and restore hearing function.
Exposure to alcohol during pregnancy produces fetal alcohol spectrum disorders (FASD) that are associated with sensory and cognitive deficits. Individuals with FASD have impaired auditory processing and also frequently exhibit atypical auditory behaviors. It is therefore important to determine the molecular mechanisms that govern auditory processing in normal and developmentally abnormal brain. We will examine auditory processing in mice prenatally exposed to alcohol, perform in vivo imaging in the primary auditory cortex to track AMPARs α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid.) and dendritic spines over days, and perform electrophysiological recordings to study AMPAR-mediated synaptic transmission. The goal of this study is to provide a mechanistic basis for the altered auditory processing observed in FASD and examine the therapeutic potential of the BDNF-TrkB (Brain-Derived Neurotrophic Factor-tyrosine kinase receptor B) signaling to preserve or restore central auditory processing following prenatal alcohol exposure.