Anti-Proliferative Actions of T-Type Calcium Channel Inhibition in Thy1 Nephritis

Aberrant proliferation of mesangial cells (MCs) is a key finding in progressive glomerular disease. TH1177 is a small molecule that has been shown to inhibit low-voltage activated T-type Ca2+ channels (TCCs). The current study investigates the effect of TH1177 on MC proliferation in vitro and in vivo . The effect of Ca2+ channel inhibition on primary rat MC proliferation in vitro was studied using the microculture tetrazolium assay and by measuring bromodeoxyuridine incorporation. In vivo , rats with Thy1 nephritis were treated with TH1177 or vehicle. Glomerular injury and average glomerular cell number were determined in a blinded fashion. Immunostaining for Ki-67 and phosphorylated ERK were also performed. The expression of TCC isoforms in healthy and diseased tissue was investigated using quantitative real-time PCR. TCC blockade caused a significant reduction in rat MC proliferation in vitro , whereas L-type inhibition had no effect. Treatment of Thy1 nephritis with TH1177 significantly reduced glomerular injury ( P < 0.005) and caused a 49% reduction in glomerular cell number ( P < 0.005) compared to the placebo. TH1177 also reduced Ki-67-positive and pERK-positive cells per glomerulus by 52% ( P < 0.01 and P < 0.005, respectively). These results demonstrate that TH1177 inhibits MC proliferation in vitro and in vivo , supporting the hypothesis that TCC inhibition may be a useful strategy for studying and modifying MC proliferative responses to injury.