(411) Insulin-like growth factor binding protein (IGFBP-6) as a novel regulator of inflammatory response in Cystic Fibrosis airway cells

Background: Cystic Fibrosis (CF) patients are prone to contracting bacterial lung infections with opportunistic pathogens, especially Pseudomonas aeruginosa. Prolonged P. aeruginosa infections have been linked to chronic inflammation in the CF lung, whose hallmarks are increased levels of cytokines (i.e., TNF-α, IL-1β, IL-6) and neutrophil attraction by chemokines, like IL-8. Recently, insulin-like growth factor binding protein 6 (IGFBP-6) has been shown to play a putative role in the immune system and was found at higher levels in the sera and synovial tissue of rheumatoid arthritis patients. Moreover, it has been demonstrated that IGFBP-6 has chemoattractant properties towards cells of the innate (neutrophils, monocytes) and adaptive (T cells) immunity. However, it is not known the precise role of IGFBP-6 in airway epithelial cells in pathophysiology, in particular in CF under infection/inflammatory conditions.

Methods: We used qRT-PCR, ELISA and immunoblots to determine the IGFBP-6 expression in non-CF (Wt-CFTR CFBE) and CF (F508del-CFTR CFBE) cells lines and primary nasal epithelial cells. Moreover, we investigated the effect of IGFBP-6 on CFTR using the FLIPR membrane potential dye assay to measure CFTR activity in CFBE cell line.

Results: we first measured the basal IGFBP-6 mRNA and protein basal levels in bronchial epithelial cells lines (Wt and F508del-CFTR CFBE), finding they both are upregulated in F508del-CFTR CFBE cells. Interestingly, LPS and TNF-α, IL-1β treatments increased the IGFBP-6 mRNA level, that was reduced after treatment with an anti-inflammatory (Dimethyl Fumarate) in CFBE cell line and in patient derived nasal epithelial cultures. Lastly, we demonstrated that IGFBP-6 reduced the level of pro-inflammatory cytokines in both CFBE and primary nasal epithelial cells, without affecting rescued CFTR expression and function.

Conclusions: Together, these data suggest that IGFBP-6 may play a direct role in the CF-associated inflammation. Moreover, IGFBP-6 represents a novel mediator in CF airway inflammation, and our data suggest a negative feedback autoregulator of the inflammatory response of airway epithelial cells

Acknowledgements: This work was supported by operating grants awarded to O.L by University of Foggia (LASELVA PRA2020) and Micro Synergy Grant through the CF Canada-Sick Kids Program in Individual Therapy (CFIT) with funding provided by the Sick Kids Foundation and Cystic Fibrosis Canada.

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