Therapeutic interventions for intractable diseases using STAT3 inhibiting peptide and bilirubin-derived nanomedicine

Abstract

Intractable or incurable diseases refer to neoplastic, inflammatory, fibrotic, or autoimmune disorders that are difficult to treat with the established treatment means. While approximately 80% of incurable diseases are genetic disorders, some prevalent incurable conditions like pulmonary fibrosis (PF) and psoriasis affect many patients worldwide. Because these diseases have high mortality and recurrence rates, more often than not these conditions deteriorate the quality of life of the patients and their families. In order to address these problems that people face, many industry and academic entities put an effort to develop novel therapeutic agents but it was not very successful. In chapter 1, the current clinical challenges against pulmonary fibrosis and psoriasis will be discussed. In addition, the pathogenic role of signal transduction and activator 3 (STAT3) and reactive oxygen species (ROS) in the aforementioned diseases will be addressed. Lastly, nanomedicine used in the following studies will be introduced: Aptamer-mimicking peptide (Aptide) targeting STAT3 (APTstat3-9R) and bilirubin nanoparticles (BRNPs). In chapter 2, the development and therapeutic evaluation of STAT3-targeted peptides formulated with biomimetic lipid components against PF are demonstrated. The STAT3 pathway is vastly related to the pathogenesis of PF, evidenced by highly expressed phosphor-STAT3 in the lungs of PF patients. To specifically target STAT3 to hinder the progression of PF, the novel APTstat3-9R was utilized in a preclinical model of PF. Furthermore, the formulation of APTstat3-9R with biomimetic lipid elements yielded disc-shaped lipid nanocomplexes (APTstat3-9R@DLNPs), which displayed significant improvement in the lung delivery of APTstat3-9R through endogenous lung barrier and exerted encouraging therapeutic outcomes. The demonstrated works suggest that a non-invasive intratracheal delivery of APTstat3-9R@DLNPs may be a promising approach in treating PF. In chapter 3, BRNPs were used to suppress the progression of pulmonary fibrosis. Recently reported evidence proposes that bilirubin, an endogenous molecule that is a metabolite of heme, retains antioxidative and immunomodulatory effects. Nevertheless, pre-clinical and clinical applications using bilirubin were challenged due to its innate hydrophobicity. To address this, we have recently developed hydrophilic bilirubin by conjugating polyethylene glycol (PEG) to bilirubin, and the resulting amphiphilic molecule tends to form nanoparticles (BRNPs) in an aqueous solution. In a pre-clinical model of pulmonary fibrosis induced by bleomycin, systemically administered BRNPs were preferentially accumulated in the inflamed lungs and exerted a cytoprotective effect by lowering local oxidative stress. Furthermore, as a result of ROS downregulation, lungs of PF-induced animal subjects showed reduced immune cell infiltration, activation of macrophages, differentiation of epithelial cells and fibroblasts to myofibroblasts, and secretion of fibrosis-related cytokines. Collectively, BRNPs can be a viable option for PF for which there are currently limited treatments. In chapter 4, using the BRNPs used in chapter 3, the therapeutic effect and its mode of action were confirmed in psoriasis, an autoimmune skin disease. Psoriasis is reported to be predominant in all age groups and is known to be prevalent in at least 125 million individuals globally. Immunosuppressants and antihistamines are mostly used for managing the symptoms of the disease, but owing to the nature of recurrence, repetitive administration of these drugs can result in severe adverse effects. Based on the findings that oxidative stress within activated keratinocytes initiates the pathogenic loop of psoriasis, endogenous bilirubin-based antioxidative nanomedicine, BRNPs were topically applied on the psoriatic lesions for evaluation. BRNPs effectively infiltrated through the damaged skin barrier and reached the epidermis layer. BRNPs localized in the inflammation site effectively reduced the excess ROS and subsequent release of inflammatory chemokines and cytokines. As a result, local immune cell infiltration, maturation of antigen presenting cells (APCs), and differentiation of naïve CD4+ T cells to helper T cells were hindered. These findings emphasize the probability of BRNPs as a novel therapeutic agent that can alleviate the symptoms of psoriasis and other chronic skin diseases.