Down-regulation of iNOS and TNF-α expression by kaempferol via NF-κB inactivation in aged rat gingival tissues

Abstract

The primary objective of this study was to evaluate the ability and mechanism of action of kaempferol, which is contained in extracts from Nelumbo nucifera, a well-known Oriental herb used in traditional medicine, with regard to the inhibition of iNOS and TNF-alpha expression in aged rat gingival tissues. We conducted an investigation into the age-related effects of kaempferol on reactive oxygen species (ROS) and GSH oxidative status in samples of aged gingival tissues. Western blotting was conducted in order to determine the expression of iNOS, TNF-alpha, p38 MAPK, NIK/IKK, p65 and IkappaBalpha in the sample tissues. Electrophoretic mobility shift assays (EMSA) were conducted in an effort to characterize the binding activities of NF-kappaB transcription factors in the aged rat gingival nuclear extracts. Our results indicate that kaempferol reduced ROS levels and augmented GSH levels in a dose-dependent manner in the aged gingival tissues. Kaempferol was shown to effect a significant reduction in iNOS and TNF-alpha protein levels, as compared to control gingival tissue samples. The results of Western blot analysis revealed that kaempferol treatment effected the reduction of iNOS and TNF-alpha expression, decreased nuclear p65 and increased cytosolic p65, down-regulation of Erk, p38, JNK and NIK/IKK expression. The EMSA results also indicated that kaempferol, when administered to the rat tissues, attenuated the NF-kappaB nuclear binding activity. Kaempferol may inhibit ROS generation via the inhibition of iNOS and TNF-alpha expression in aged gingival tissues, via the modulation of the NF-kappaB and mitogen-activated protein kinase (MAPK) pathways.