Cigarette Smoke Extract Disturbs Mitochondria-Regulated Airway Epithelial Cell Responses to Pneumococci.

Cells. 2022;11(11)
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Cigarette smoking can affect airway epithelial cells, causing overproduction of mucus, damage, and inflammation, which may result in the progression of airway diseases. Airway epithelial cells (AEC) rely on mitochondria for energy, and mitochondrial dysfunction may affect innate immunity and the integrity of the airway epithelium. Cigarette smoking is found to accelerate mitochondrial damage within AEC. Maintaining a normal microbial composition within the respiratory tract is essential for maintaining immunity. There is evidence that smoking cigarettes disrupts the microbial composition and increases the spread of pathogenic bacteria such as Streptococcus pneumoniae (Sp) which causes inflammation. By exposing 16HBE cells to Sp and cigarette smoke extract (CSE), this study investigated the effect of cigarette smoking on mitochondrial dysfunction in ACE in an in vitro model. Additionally, the study examined the direct and indirect pathways involved in cigarette smoking-induced mitochondrial dysfunction and altered innate immune response to Sp infection. CSE exposure decreases mitochondrial complex protein levels and mitochondrial membrane potential, which affects energy production. It also increases mitochondrial oxidative stress and mitochondrial degradation. All these factors lead to mitochondrial dysfunction in ACE. CSE exposure to ACE was associated with altered gene expression in the tight and adherence junctions that serve as a protective barrier against pathogens and pollutants and reduced type I interferon immune responses to Sp. Using the results of this study, healthcare professionals can gain a better understanding of the impact of cigarette smoking on mitochondrial dysfunction and how it increases susceptibility to Sp-related immune responses. It is necessary to conduct further studies to evaluate the effects of cigarette smoking on mitochondrial dysfunction, microbial composition disruption, and the interaction between AECs and elevated immune responses.

Abstract

Mitochondrial functionality is crucial for the execution of physiologic functions of metabolically active cells in the respiratory tract including airway epithelial cells (AECs). Cigarette smoke is known to impair mitochondrial function in AECs. However, the potential contribution of mitochondrial dysfunction in AECs to airway infection and airway epithelial barrier dysfunction is unknown. In this study, we used an in vitro model based on AECs exposed to cigarette smoke extract (CSE) followed by an infection with Streptococcus pneumoniae (Sp). The levels of oxidative stress as an indicator of mitochondrial stress were quantified upon CSE and Sp treatment. In addition, expression of proteins associated with mitophagy, mitochondrial content, and biogenesis as well as mitochondrial fission and fusion was quantified. Transcriptional AEC profiling was performed to identify the potential changes in innate immune pathways and correlate them with indices of mitochondrial function. We observed that CSE exposure substantially altered mitochondrial function in AECs by suppressing mitochondrial complex protein levels, reducing mitochondrial membrane potential and increasing mitochondrial stress and mitophagy. Moreover, CSE-induced mitochondrial dysfunction correlated with reduced enrichment of genes involved in apical junctions and innate immune responses to Sp, particularly type I interferon responses. Together, our results demonstrated that CSE-induced mitochondrial dysfunction may contribute to impaired innate immune responses to Sp.

Lifestyle medicine

Environmental Inputs : Xenobiotics ; Microorganisms
Personal Lifestyle Factors : Environment
Functional Laboratory Testing : Tissue biopsy

Methodological quality

Jadad score : Not applicable
Allocation concealment : Not applicable

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