Is cellular senescence involved in cystic fibrosis?

Abstract

Pulmonary disease is the main cause of the morbidity and mortality of patients affected by cystic fibrosis (CF). The lung pathology is dominated by excessive recruitment of neutrophils followed by an exaggerated inflammatory process that has also been reported to occur in the absence of apparent pathogenic infections. Airway surface dehydration and mucus accumulation are the driving forces of this process. The continuous release of reactive oxygen species and proteases by neutrophils contributes to tissue damage, which eventually leads to respiratory insufficiency. CF has been considered a paediatric problem for several decades. Nevertheless, during the last 40 years, therapeutic options for CF have been greatly improved, turning CF into a chronic disease and extending the life expectancy of patients. Unfortunately, chronic inflammatory processes, which are characterized by a substantial release of cytokines and chemokines, along with ROS and proteases, can accelerate cellular senescence, leading to further complications in adulthood. The alterations and mechanisms downstream of CFTR functional defects that can stimulate cellular senescence remain unclear. However, while there are correlative data suggesting that cellular senescence may be implicated in CF, a causal or consequential relationship between cellular senescence and CF is still far from being established. Senescence can be both beneficial and detrimental. Senescence may suppress bacterial infections and cooperate with tissue repair. Additionally, it may act as an effective anticancer mechanism. However, it may also promote a pro-inflammatory environment, thereby damaging tissues and leading to chronic age-related diseases. In this review, we present the most current knowledge on cellular senescence and contextualize its possible involvement in CF.

Keywords: Cellular senescence; Cystic fibrosis; SASP.

Fig. 1

Hypothesis of cellular senescence in CF airways. Signal transduction pathways are commonly activated in CF epithelial cells (left) and are hypothesized to be involved in senescent CF cells (right) upon defective senescence immunosurveillance. CF senescent cells might promote further recruitment of neutrophils (PMNs) into the bronchial lumen through the activation of ROS and mitochondrial stress signalling, which in turn increase SASP release, worsening the lung inflammatory process and activating pro-tumoural pathways. DDR, DNA damage response; SAHF, senescence-associated heterochromatin foci