THE ROLE OF THE CYSTIC FIBROSIS TRANSMEMBRANE REGULATOR (CFTR) IN CHLORIDE HOMEOSTASIS AND EXCITABILITY IN SWINE SENSORY NEURONS

Cystic Fibrosis (CF) is a common fatal disorder associated with mutations of recessive inheritance in the gene that encodes for the cystic fibrosis transmembrane regulator (CFTR) protein. In the past, the life expectancy of patients with CF was 6 months due to respiratory failure and gastrointestinal (GI) complications. However, with current advances in the treatment and management of the disease, the life expectancy of CF has improved drastically. As a consequence, now adult CF patients are exposed to previously unknown chronic complications of CF such a peripheral neuropathy. Initially, peripheral neuropathy was considered a consequence of malnutrition and vitamin E deficiency, however, later studies showed that CFTR is widely expressed in the nervous system and may be an important regulator of chloride homeostasis in neurons. Unfortunately, the role of CFTR in neurons and its relevance in CF neuropathology has not been studied in detail. Therefore, this project aimed to investigate the cellular consequences of the lack of CFTR function in dorsal root ganglion (DRG) neurons. First, we quantified chloride levels in DRG primary cultures from WT and CFTR-/- swine using a chloride sensitive dye (i.e., MQAE) and perforated patch-clamp electrophysiology. We found that CFTR-/- DRG neurons have a lower intracellular concentration of chloride compared to WT neurons. Second, we used a CFTR inhibitor (i.e., CFTR (inh)-172) and current-clamp electrophysiology to determine if short-term inhibition of CFTR had abnormal effects in DRG neuronal excitability and GABA mediated inhibition of action potentials. We observed that CFTR inhibition in DRG neurons had no effect on DRG neuronal excitability. Moreover, our findings indicate that GABA did not modulate action potential firing in DRG neurons from swine. Taken together, our data suggest that CFTR has an active role in the regulation of chloride transport in DRG neurons. However, if these changes have a significant effect on neuronal excitability remain to be studied in more detail