Effects of rikkunshito on renal fibrosis and inflammation in angiotensin II-infused mice

The underlying pathogenesis of chronic kidney disease involves an activated renin-angiotensin system and systemic inflammation which ultimately develop renal injury. Rikkunshito (RKT) has been reported to exert anti-fibrotic and anti-inflammatory effects through enhancement of ghrelin signaling pathway. In this study, we investigated the effects of RKT on renal fibrosis and inflammation in angiotensin II (Ang II)-induced renal injury model. Ang II-infused mice exhibited hypertension, cardiac hypertrophy, increases in blood urea nitrogen and serum creatinine, moderate albuminuria and renal pathological changes such as mild urinary cast, interstitial macrophage infiltration and modest interstitial fibrosis. RKT had no evident effects on the Ang II-induced renal functional insufficiency and fibrosis, but attenuated renal interstitial macrophage infiltration. In addition, RKT significantly restored the Ang II-induced alteration in the expression of renal fibrosis- and inflammation-related genes such as type 3 collagen, transforming growth factor-β, monocyte chemoattractant protein-1 and interleukin-6. Furthermore, although RKT did not affect the expression of renal ghrelin receptor, an Ang II-induced decrease in renal sirtuin 1 expression, a critical down-stream pathway of the ghrelin receptor, was restored by RKT. These findings suggest that RKT potentially has a renal anti-inflammatory effect in the development of renal injury, and this effect could be mediated by the ghrelin signaling pathway.