Changes in Gap Junction Permeability, Gap Junction Number, and Connexin43 Expression in Lindane-Treated Rat Liver Epithelial Cells

Abstract

The pesticide lindane (gamma-hexachlorocyclohexane) is a mammalian neurotoxin and hepatocarcinogen. Lindane can inhibit gap junctional intercellular communication (GJIC) and this effect may contribute to its toxic properties. The mechanism of inhibition of GJIC by lindane in WB-F344 rat liver epithelial cells was studied to determine if altered gap junction permeability, gap junction number, and/or gap junction protein (connexin43) expression were involved. GJIC was monitored by fluorescent Lucifer Yellow CH dye microinjection (dye-coupling). Gap junction number was quantified visually after indirect immunostaining of gap junctions using an anti-connexin43 monoclonal antibody. Connexin43 mRNA and protein levels were determined by Northern and Western blotting, respectively. Short-term treatment (10-30 min) with lindane (50 microM) resulted in the rapid (within 10 min), nearly complete loss of dye-coupling but no changes in gap junction number of connexin43 mRNA or protein levels. Medium-term treatment (1-4 hr) resulted in the loss of dye-coupling, gap junctions, and phosphorylated connexin43 proteins. Long-term treatment (1-14 days) led to reductions in dye-coupling, total connexin43 protein, and connexin43 mRNA. Nuclear run-on assays indicated that transcription of the connexin43 gene was reduced nonspecifically by lindane. These data indicate that reductions in gap junction permeability, number, and expression may be involved in the inhibition of GJIC depending on pesticide treatment duration.