(585) CFTR Contributes to Chloride Homeostasis in Swine Sensory Neurons

Background: Cystic fibrosis (CF) phenotypes related to peripheral nerve dysfunction (neuropathy) are understudied, and their potential contribution to emerging CF complications in an aging patient population is unknown [1]. In addition to epithelial cells, CFTR is expressed across the nervous system [2–6]. The physiological role of CFTR in neurons remains largely unknown, but the development of peripheral neuropathy as an extrapulmonary complication of CF [1] suggests that it may be critical for neuronal function. Two pieces of evidence support the idea that neuropathy in CF is a direct consequence of CFTR dysfunction; first, CFTR-/- swine present polyneuropathy at birth [7]; and second, CFTR is involved in the control of chloride homeostasis and neuronal excitability in spinal motor neurons [8]. Therefore, in the current study, we investigated the cellular consequences of the lack of CFTR expression in sensory neurons from the dorsal root ganglia (DRG) in swine. This study aims to understand how CFTR may contribute to the development of neuropathy in CF.

Methods: We used DRG neurons from wild-type (WT) and CFTR-/- neonate swine. We studied excitability by patch-clamp electrophysiology, chloride homeostasis by MQAE live imaging, and the expression levels of the cotransporters Na-K-Cl 1 (NKCC1) and K-Cl 2 (KCC2), as well as the proteins of the WNK-SPAK/OSR1 pathway, by immunoblotting.

Results: DRG neurons from CFTR-/- swine had reduced excitability compared to WT. This was demonstrated by reduced action potential generation upon electrical stimulation and reduced capsaicin responses. The MQAE live imaging revealed that neurons from CFTR-/- swine had a lower intracellular chloride concentration than those from WT. These data were consistent with reduced expression levels of NKCC1, WNK1 and OSR1 in neurons from CFTR-/- swine. As expected, KCC2 was undetected in both genotypes.

Conclusions: Our data suggest that CFTR works together with NKCC1 to regulate chloride homeostasis in DRG neurons. Furthermore, the lack of CFTR expression in swine DRG neurons impaired cell excitability. Thus, our study supports an important role for CFTR in DRG neurons’ function, which may contribute to the development of peripheral neuropathy in CF.

Acknowledgements: This work was supported by CIHR, NSERC, and CF Canada.

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