Chitin Analog AVR-25 Prevents Experimental Bronchopulmonary Dysplasia

Chitin Derived Small Molecule AVR-48 Reprograms the Resting Macrophages to an Intermediate Phenotype and Decrease Pseudomonas aeruginosa Mouse Lung Infection

AVR-48 is a structural derivative of chitin previously shown by our laboratory to significantly decrease lung injury parameters in LPS, hyperoxia and sepsis-induced rodent models. The current study objectives are to determine the cellular mechanism of action and demonstrate efficacy in a mouse bacterial lung infection model. For in vitro receptor binding and macrophage polarization studies, C57Bl/6J mouse derived spleens and human peripheral blood mononuclear cells (hPBMCs) were treated with AVR-48 ± LPS or biotin conjugated AVR-48. Different macrophage types were determined using flow cytometry and secreted cytokines were measured using ELISA. In vivo, a CD-1 mouse Pseudomonas aeruginosa lung infection was treated with AVR-48, assessing bacterial colony forming unit (CFU), IL-10 and IL-17A levels in lung and blood samples. AVR-48 binds to both the toll-like receptor 4 (TLR4) and the CD163 receptor on mouse monocytes. In hPBMCs, frequency of intermediate macrophages increased upon AVR-48 treatment for 72 h. Increased bacterial phagocytosis/intracellular killing were observed in THP-1 cells and reduction in CFU in CD-1 mouse lungs. Binding of AVR-48 to both TLR4 and CD163 receptors bring the macrophages to an intermediary stage, resulting in increased phagocytosis and decreased inflammation, altogether providing an optimal immune balance for treating lung injury and infection.

Chitin-Derived AVR-48 Prevents Experimental Bronchopulmonary Dysplasia (BPD) and BPD-Associated Pulmonary Hypertension in Newborn Mice

Bronchopulmonary dysplasia (BPD) is the most common complication of prematurity and a key contributor to the large health care burden associated with prematurity, longer hospital stays, higher hospital costs, and frequent re-hospitalizations of affected patients through the first year of life and increased resource utilization throughout childhood. This disease is associated with abnormal pulmonary function that may lead to BPD-associated pulmonary hypertension (PH), a major contributor to neonatal mortality and morbidity. In the absence of any definitive treatment options, this life-threatening disease is associated with high resource utilization during and after neonatal intensive care unit (NICU) stay. The goal of this study was to test the safety and efficacy of a small molecule derivative of chitin, AVR-48, as prophylactic therapy for preventing experimental BPD in a mouse model. Two doses of AVR-48 were delivered either intranasally (0.11 mg/kg), intraperitoneally (10 mg/kg), or intravenously (IV) (10 mg/kg) to newborn mouse pups on postnatal day (P)2 and P4. The outcomes were assessed by measuring total inflammatory cells in the broncho-alveolar lavage fluid (BALF), chord length, septal thickness, and radial alveolar counts of the alveoli, Fulton’s Index (for PH), cell proliferation and cell death by immunostaining, and markers of inflammation by Western blotting and ELISA. The bioavailability and safety of the drug were assessed by pharmacokinetic and toxicity studies in both neonatal mice and rat pups (P3-P5). Following AVR-48 treatment, alveolar simplification was improved, as evident from chord length, septal thickness, and radial alveolar counts; total inflammatory cells were decreased in the BALF; Fulton’s Index was decreased and lung inflammation and cell death were decreased, while angiogenesis and cell proliferation were increased. AVR-48 was found to be safe and the no-observed-adverse-effect level (NOAEL) in rat pups was determined to be 100 mg/kg when delivered via IV dosing with a 20-fold safety margin. With no reported toxicity and with a shorter half-life, AVR-48 is able to reverse the worsening cardiopulmonary phenotype of experimental BPD and BPD-PH, compared to controls, thus positioning it as a future drug candidate.

Chitin and Chitosan Derivatives as Biomaterial Resources for Biological and Biomedical Applications

Chitin is a long-chain polymer of N-acetyl-glucosamine, which is regularly found in the exoskeleton of arthropods including insects, shellfish and the cell wall of fungi. It has been known that chitin can be used for biological and biomedical applications, especially as a biomaterial for tissue repairing, encapsulating drug for drug delivery. However, chitin has been postulated as an inducer of proinflammatory cytokines and certain diseases including asthma. Likewise, chitosan, a long-chain polymer of N-acetyl-glucosamine and d-glucosamine derived from chitin deacetylation, and chitosan oligosaccharide, a short chain polymer, have been known for their potential therapeutic effects, including anti-inflammatory, antioxidant, antidiarrheal, and anti-Alzheimer effects. This review summarizes potential utilization and limitation of chitin, chitosan and chitosan oligosaccharide in a variety of diseases. Furthermore, future direction of research and development of chitin, chitosan, and chitosan oligosaccharide for biomedical applications is discussed.