585 Cystic fibrosis transmembrane conductance regulator 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, CF transmembrane conductance regulator (CFTR) is expressed across the nervous system [2-6].The physiological role of CFTR in neurons is largely unknown, but 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; CFTR-/-swine present polyneuropathy at birth [7], and CFTR is involved in control of chloride homeostasis and neuronal excitability in spinal motor neurons [8].Therefore, in the current study, we investigated the cellular consequences of 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 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 N-(Ethoxycarbonylmethyl)-6-methoxyquinolinium bromide (MQAE) live imaging and 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 less excitability than WT, as evidenced by less action potential generation upon electrical stimulation and lower capsaicin responses.MQAE live imaging revealed that neurons from CFTR-/-swine had a lower intracellular chloride concentration than those from WT-consistent with lower expression levels of NKCC1, WNK1, and OSR1 in neurons from CFTR-/-swine.As expected, KCC2 was not detected in either genotype.Conclusions: Our data suggest that CFTR works with NKCC1 to regulate chloride homeostasis in DRG neurons.Furthermore, lack of CFTR expression in swine DRG neurons impaired cell excitability.Thus, our study supports an important role for CFTR in DRG neuron function, which may contribute to development of peripheral neuropathy in CF.