The preservation of cellular homeostasis requires the synthesis of new proteins (proteostasis) and organelles, and the effective removal of misfolded or impaired proteins and cellular debris. This cellular homeostasis involves two key proteostasis mechanisms, the ubiquitin proteasome system and the autophagy–lysosome pathway. These catabolic pathways have been known to be involved in respiratory exacerbations and the pathogenesis of various lung diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), idiopathic pulmonary fibrosis (IPF), acute lung injury (ALI), acute respiratory distress syndrome (ARDS), and coronavirus disease-2019 (COVID-19). Briefly, proteostasis and autophagy processes are known to decline over time with age, cigarette or biomass smoke exposure, and/or influenced by underlying genetic factors, resulting in the accumulation of misfolded proteins and cellular debris, elevating apoptosis and cellular senescence, and initiating the pathogenesis of acute or chronic lung disease. Moreover, autophagic dysfunction results in an impaired microbial clearance, post-bacterial and/or viral infection(s) which contribute to the initiation of acute and recurrent respiratory exacerbations as well as the progression of chronic obstructive and restrictive lung diseases. In addition, the autophagic dysfunction-mediated cystic fibrosis transmembrane conductance regulator (CFTR) immune response impairment further exacerbates the lung disease. Recent studies demonstrate the therapeutic potential of novel autophagy augmentation strategies, in alleviating the pathogenesis of chronic obstructive or restrictive lung diseases and exacerbations such as those commonly seen in COPD, CF, ALI/ARDS and COVID-19.

Introduction. Cigarette smoke (CS) exposure is the leading risk factor for COPD-emphysema pathogenesis. A common characteristic of COPD is impaired phagocytosis that causes frequent exacerbations in patients leading to increased morbidity. However, the underlying mechanism is unclear. Hence, we investigated if CS exposure causes autophagy impairment as a mechanism for diminished bacterial clearance via phagocytosis by utilizing murine macrophages (RAW264.7 cells) and Pseudomonas aeruginosa (PA01-GFP) as an experimental model. Methods. Briefly, RAW cells were treated with cigarette smoke extract (CSE), chloroquine (autophagy inhibitor), TFEB-shRNA, CFTR(inh)-172, and/or fisetin prior to bacterial infection for functional analysis. Results. Bacterial clearance of PA01-GFP was significantly impaired while its survival was promoted by CSE (p<0.01), autophagy inhibition (p<0.05; p<0.01), TFEB knockdown (p<0.01; p<0.001), and inhibition of CFTR function (p<0.001; p<0.01) in comparison to the control group(s) that was significantly recovered by autophagy-inducing antioxidant drug, fisetin, treatment (p<0.05; p<0.01; and p<0.001). Moreover, investigations into other pharmacological properties of fisetin show that it has significant mucolytic and bactericidal activities (p<0.01; p<0.001), which warrants further investigation. Conclusions. Our data suggests that CS-mediated autophagy impairment as a critical mechanism involved in the resulting phagocytic defect, as well as the therapeutic potential of autophagy-inducing drugs in restoring is CS-impaired phagocytosis.

Background: Cystic fibrosis (CF) is challenged with pathophysiological barriers for effective airway drug-delivery. Hence, we standardized the therapeutic efficacy of the novel dendrimer-based autophagy-inducing anti-oxidant drug, cysteamine. Research design and methods: Human primary-CF epithelial-cells, CFBE41o-cells were used to standardize the efficacy of the dendrimer-cystamine in correcting impaired-autophagy, rescuing ΔF508-CFTR and Pseudomonas-aeruginosa (Pa) infection. Results: We first designed a novel cystamine-core dendrimer formulation (G4-CYS) that significantly increases membrane-ΔF508CFTR expression in CFBE41o-cells (p < 0.05) by forming its reduced-form cysteamine, in vivo. Additionally, G4-CYS treatment corrects ΔF508-CFTR-mediated impaired-autophagy as observed by a significant decrease (p < 0.05) in Ub-LC3-positive aggresome-bodies. Next, we verified that in non-permeabilized CFBE41o-cells, G4-CYS significantly (p < 0.05) induces ΔF508-CFTR’s forward-trafficking to the plasma membrane. Furthermore, cysteamine’s known antibacterial and anti-biofilm properties against Pa were enhanced as our findings demonstrate that both G4-CYS and its control DAB-core dendrimer, G4-DAB, exhibited significant (p < 0.05) bactericidal-activity against Pa. We also found that both G4-CYS and G4-DAB exhibit marked mucolytic-activity against porcine-mucus (p < 0.05). Finally, we demonstrate that G4-CYS not only corrects the autophagy-impairment by rescuing ΔF508-CFTR in CFBE41o-cells but also corrects the intrinsic phagocytosis defect (p < 0.05). Conclusions: Overall, our data demonstrates the efficacy of novel cystamine-dendrimer formulation in rescuing ΔF508-CFTR to the plasma membrane and inhibiting Pa bacterial-infection by augmenting autophagy.

The respiratory system is one of the critical organ systems in our body that performs the life-supporting role of providing oxygen and eliminating the toxic carbon dioxide (Santus et al. 2014). The extraordinarily large surface area of the lungs renders them highly prone to being exposed to a variety of prooxidants and toxic agents (Santus et al. 2014). The airways are knowingly or unknowingly being bombarded with environmental gaseous and particulate matter present in air pollution (Liu et al. 2009; Valavanidis et al. 2013), tobacco smoke (Valavanidis et al. 2009), or occupational settings (Kaushik et al. 2012) leading to generation of inflammation and oxidative stress. Thankfully, our lungs are fairly robust, as they are capable of managing a certain threshold level of inflammatory–oxidative stress that prevents or delays the onset of acute and chronic pulmonary diseases via a healthy antioxidant defense mechanism (Comhair and Erzurum 2002). A breach of this critical threshold leads to an imbalance of prooxidants and antioxidant factors resulting in unabated inflammatory–oxidative stress that forms the basis of numerous debilitating lung conditions such as acute lung injury (ALI), acute respiratory distress syndrome (ARDS), bronchopulmonary dysplasia (BPD), asthma, chronic bronchitis, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), and idiopathic pulmonary fibrosis (IPF) (Park et al. 2009; Holguin 2013). The leading deleterious agents known to cause oxidative damage are the reactive oxygen species (ROS) and reactive nitrogen species (RNS), both contributing to initiation and progression of various lung diseases (Holguin 2013). Moreover, numerous types of inflammatory cells that infiltrate the pulmonary vasculature upon any external insult are activated by the cell surface receptors–ligand interaction (Lao et al. 2014). These ligands include secreted factors such as cytokines (Lao et al. 2014), chemokines (Lao et al. 2014), and the proteases–antiproteases (Bodas et al. 2012) that regulate pulmonary immune responses. The activated immune cells are also the major source of the ROS/RNS (Domej et al. 2014; Lao et al. 2014). Once generated, these ROS/RNS undergo complex chemical interactions with biomolecules and inflict oxidative damage to proteins, DNA, and/or lipids (Domej et al. 2014), thus targeting key cellular homeostatic processes such as cell proliferation (Matés et al. 2008), protease/antiprotease balance (Bodas et al. 2012), inflammation and proteostasis/autophagy (Holguin 2013), and so on. The perturbations in these critical cellular 373mechanisms contribute to initiation and progression of pathophysiological changes leading to lung diseases (Comhair and Erzurum 2002; Holguin 2013). Thus, subduing the elevated inflammatory–oxidative stress forms the basis of numerous therapeutic strategies utilized for management of several lung disorders, where there is a clear and urgent need to address the progression of acute and chronic lung diseases (Lao et al. 2014). Although various therapeutic compounds are being developed, they have significant side effects (Kawada et al. 2012). Thus, bringing major transformations in our regular diet (lifestyle) supplemented with nutraceuticals—based on prevention and treatment of lung diseases—seems promising (Sharafkhaneh et al. 2007; Sorkness 2009). This strategy may well become the choice of both medical fraternity and the common man, aptly supported by the intriguing understanding of the gut–lung axis and its role in modulating immune responses (Marsland et al. 2015).