Impaired Regulatory Volume Decrease and Characterization of Underlying Volume-Activated Currents in Cystic Fibrosis...

Area of Science:

• Cellular Physiology
• Ion Transport
• Epithelial Biology

Background:

• Volume-activated chloride channels (VACC) are crucial for cell volume regulation and secretion.
• Regulatory volume decrease (RVD) is impaired in primary cystic fibrosis (CF) mouse cholangiocytes.
• The role of CFTR defect in VACC and RVD in human cholangiocytes remains unclear.

Purpose of the Study:

• To investigate the effect of CFTR defect on VACC and RVD in CF human immortalized cholangiocyte cell (HBDC).
• To compare VACC and RVD function in CF HBDC versus normal HBDC.

Main Methods:

• Cell volume measurement to assess RVD.
• Whole-cell patch clamp techniques to analyze ion currents.
• Chloride concentration-dependent electrophysiological recordings.

Main Results:

• CF HBDC exhibited impaired RVD.
• Volume-activated chloride channel (VACC) amplitude was greater in CF HBDC compared to normal HBDC.
• Volume-activated potassium current amplitude was lower in CF HBDC.

Conclusions:

• RVD is impaired in CF human cholangiocytes due to augmented VACC activity and decreased volume-activated potassium current.
• CFTR may exert inhibitory effects on VACC and regulatory effects on volume-activated potassium current.
• These findings elucidate a fundamental pathophysiologic mechanism underlying impaired RVD in CF cholangiocytes.