Down-regulation of L-type calcium channel in pups born to 52 kDa SSA/Ro immunized rabbits

Congenital heart block is considered a model of passively acquired autoimmune disease in which the mother generates anti-SSA/Ro and/or anti-SSB/La antibodies that cross the placenta and presumably injure the heart of developing fetus. CHB is accompanied by ECG abnormalities including AV block, sinus bradycardia, and ventricular dysfunction. Our previous data indicate that these abnormalities are caused by maternal autoantibody-mediated disturbance of L-type Ca channels. To investigate the consequence of chronic exposure of L-type Ca channels in newborn pups to maternal autoantibodies during pregnancy, we immunized female rabbits with human 52 kDa-SSA/Ro (Ro52) recombinant protein. ECG revealed that pups from the immunized group had varying degrees of conduction defects. In addition, ICaL density and protein were reduced in hearts of pups from the immunized group. Sera and purified IgG from immunized rabbits inhibited IBa recorded from oocytes with expressed α1C and β2a subunits of L-type Ca channel. Pups ...