KCNQ1 K+ Channels are Involved in Lipopolysaccharide-induced Apoptosis of Distal Kidney Cells

Abstract

Most bacteria initiate host inflammatory responses through interactions with epithelial cells. Lipopolysaccharide (LPS), a component of the bacterial cell wall is a major cause of septic shock in emergency care units and in the pathogenesis of acute renal failure. Kidney cells exposed to LPS undergo apoptotic changes, including cell volume decrease, phosphatidylserine exposure, caspase-3- and membrane K⁺ conductance -activation. Whole-cell configuration was used to identify K⁺ channels in primary and immortalized culture of mice distal convoluted tubules. LPS exposure induced a 3 fold increase in intracellular cAMP concentration and the activation of an outwardly rectifying K⁺ conductance in both immortalized and primary culture of distal cells. This LPS-induced current exhibited KCNQ1 K⁺ channel characteristics, i.e. inhibition by quinidine, chromanol293B and low dose of HMR1556 (IC50<1 µM) and insensitive to TEA and charybdotoxin. The background-like biophysical properties of the current suggest that the KCNQ1 pore-forming subunit is associated with a KCNE2 or KCNE3 ancillary subunit. RT-PCR experiments confirmed the presence of KCNQ1 and KCNE3 mRNA transcripts in primary culture of distal segments. Activation of the KCNQ1/KCNE3 K⁺ current appeared to be an essential step in the LPS-induced apoptosis process since HMR1556 blocked the LPS-induced- cell volume decrease, -caspase-3 activation and -phosphatidylserine exposure.