Lysophosphatidylcholine (lysoPC), an atherogenic lysophospholipid, is known to induce the proliferation of vascular smooth muscle cells (VSMCs). Naringin is a flavonoid in grapes and grapefruits and has anti-inflammatory as well as antioxidative effects. We investigated whether naringin could protect VSMCs from the effect of lysoPC. Additionally, we investigated the changes of nuclear translocation of nuclear factor-κB (NF-κB).

VSMCs were prepared from the aorta of Sprague-Dawley rats. Near-confluent VSMCs were preincubated in media containing 0, 10, 100 micrometer naringin, and incubated with 0, 10, 20, 100 micrometer lysoPC. The degree of proliferation of VSMCs was evaluated with [H3]-thymidine incorporation and MTT assay. The changes of nuclear translocation of NF-κB in VSMCs were investigated with EMSA.

LysoPC promoted the growth of VSMCs, whereas naringin inhibited the proliferative effect of lysoPC on VSMCs. MTT assay showed a 63±24% and 89±17% increase of cellular growth in the 10 and 20 micrometer lysoPC groups, respectively, as compared with the control group with media only (p<0.01). [H3]-thymidine incorporation assay also showed 61±25% and 92±25% increase in the 10 and 20 micrometer lysoPC groups, respectively (p<0.01). However, the growth of VSMCs was suppressed in the 100 micrometer lysoPC group (p<0.01). Naringin inhibited the proliferative effects of lysoPC on VSMCs by 34±5% (MTT assay) and 35±5% ([H3]-thymidine incorporation assay) in the 100 micrometer naringin group (p=0.01). The nuclear translocation of NF-κB was stimulated by lysoPC and suppressed by naringin.

LysoPC promoted the growth of VSMCs, whereas naringin inhibited the proliferative effect of lysoPC on VSMCs. These effects of lysoPC and naringin are associated with the regulation of nuclear translocation of NF-κB.