Abstract
Respiratory viruses disrupt normal homeostasis of airway epithelial cells and induceinflammation, injury, and repair processes. MicroRNAs (miRNAs) are crucial regulators of
various physiological and pathological conditions. Particularly miR-149-5p is predicted to
target inflammatory (e.g interleukin-6 (IL-6)) and wound repair markers (e.g tumour protein
63 (p63)). However, the role of miR-149-5p in airway epithelium remains unclear. This
study examined the effect of viral pathogen-associated molecular patterns (PAMPs),
polyinosinic:polycytidylic acid (poly (I:C)), on cell viability and IL-6 release from bronchial
(BEAS-2B) and alveolar (A549) epithelial cells in different culture conditions. This study
also explored the role of miR-149-5p in modulating IL-6 and p63 expression in airway
epithelial cells in response to poly (I:C) or severe acute respiratory syndrome coronavirus 2
(SARS-CoV-2) spike protein 1 or 2 (S1 or S2) subunits. The outcomes indicated that BEAS-
2B cells incubated with poly (I:C) exhibited reduced cell viability and increased IL-6 release
in serum-free conditions compared to complete media, with no significant effects observed
in A549 cells. Further, poly (I:C) suppressed miR-149-5p levels, which correlated with the
increased release of IL-6 and expression of p63 and toll-like receptor (TLR)-3, a poly (I:C)
receptor, in BEAS-2B cells. Poly (I:C) also downregulated miR-149-5p and upregulated IL-
6 expression in A549 cells; however, p63 and TLR3 were undetectable. In addition, ectopic
overexpression of miR-149-5p in BEAS-2B cells inhibited IL-6 and p63 mRNA expression
and suppressed poly (I:C)-mediated IL-6 and p63 expression. Moreover, miR-149-5p
directly targeted the IL-6 mRNA in BEAS-2B cells. The S1 or S2 subunit did not affect miR-
149-5p expression in either cell type; however, the S1 subunit induced IL-6 release in BEAS-
2B cells uniquely expressing the S1 subunit receptor, TLR2. These findings suggested that
different culture conditions affected cell viability and IL-6 release from BEAS-2B cells in
response to poly (I:C). This study highlighted that TLR3 and TLR2 expression differences
at baseline may contribute to the distinct responses of BEAS-2B cells to poly (I:C) and S1
subunit compared with A549 cells. These findings also indicated that TLR3-mediated miR-
149-5p dysregulation significantly increased IL-6 and p63 expression in BEAS-2B cells.
These outcomes elucidated the specific regulatory mechanisms of miR-149-5p in airway
epithelial cells, highlighting its potential as a therapeutic target for managing viral-induced
airway inflammation and injury.
Date of Award | 11 Dec 2024 |
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Original language | English |
Awarding Institution |
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Supervisor | Fatemeh Moheimani (Supervisor) |