Rhein reverses Klotho repression via promoter demethylation and protects against kidney and bone injuries in mice with chronic kidney disease.

Rhein is an anthraquinone compound isolated from the medicinal plant rhubarb and mainly used in the clinical treatment of diabetic nephropathy. Rhein exhibits various renoprotective functions, but the underlying mechanisms are not fully determined. However, its renoprotective properties recapitulate the role of Klotho, a renal-specific antiaging protein critical for maintaining kidney homeostasis. Here we explored the connections between rhein renoprotection and Klotho in a mouse model of adenine-induced chronic kidney disease. In addition to being an impressive Klotho upregulator, rhein remarkably reversed renal Klotho deficiency in adenine-treated mice. This effect was associated with significant improvement in disturbed serum biochemistry, profibrogenic protein expression, and kidney and bone damage. Further investigation of the molecular basis of Klotho loss revealed that these kidneys displayed marked inductions of DNA methyltransferase DNMT1/DNMT3a and Klotho promoter hypermethylation, whereas rhein treatment effectively corrected these alterations. The renal protective effects of rhein were largely abolished when Klotho was knocked-down by RNA interferences, suggesting that rhein reversal of Klotho deficiency is essential for its renoprotective actions. Thus, our study clarifies how rhein regulation of Klotho expression contributes to its renoprotection and brings new insights into Klotho-targeted strategy for the treatment of kidney diseases of various etiologies.

Sinomenine attenuates renal fibrosis through Nrf2-mediated inhibition of oxidative stress and TGFß signaling.

Renal fibrosis is the common feature of chronic kidney disease and mainly mediated by TGFß-associated pro-fibrogenic signaling, which causes excessive extracellular matrix accumulation and successive loss of kidney functions. Sinomenine (SIN), an alkaloid derived from medicinal herb extensively used in treatment of rheumatoid arthritis and various inflammatory disorders, displays renal protective properties in experimental animals; however its pharmacological potency against renal fibrosis is not explored. In this study we report that SIN possesses strong anti-renal fibrosis functions in kidney cell and in mouse fibrotic kidney. SIN beneficially modulated the pro-fibrogenic protein expression in TGFß-treated kidney cells and attenuated the renal fibrotic pathogenesis incurred by unilateral ureteral obstruction (UUO), which correlated with its activation of Nrf2 signaling - the key defender against oxidative stress with anti-fibrotic potentials. Further investigation on its regulation of Nrf2 downstream events revealed that SIN significantly balanced oxidative stress via improving the expression and activity of anti-oxidant and detoxifying enzymes, and interrupted the pro-fibrogenic signaling of TGFß/Smad and Wnt/ß-catenin. Even more impressively SIN achieved its anti-fibrotic activities in an Nrf2-dependent manner, suggesting that SIN regulation of Nrf2-associated anti-fibrotic activities constitutes a critical component of SIN's renoprotective functions. Collectively our studies have demonstrated a novel anti-fibrotic property of SIN and its upstream events and provided a molecular basis for SIN's potential applications in treatment of renal fibrosis-associated kidney disorders.

Sinomenine activation of Nrf2 signaling prevents hyperactive inflammation and kidney injury in a mouse model of obstructive nephropathy.

Sinomenine is originally derived from medicinal herb and used preferentially in treatment of rheumatoid diseases in Far East regions. SIN has strong anti-inflammatory and immune-regulatory properties, acting mainly through inhibiting NF-kB signaling. Although the upstream target through which SIN affects NF-kB activity is unknown, evidence suggests that SIN might regulate inflammation through Nrf2 signaling. In this study we explored the role of Nrf2 in mediating SIN's anti-inflammation and kidney protection in a mouse model of obstructive nephropathy. We found that SIN is an activator of Nrf2 signaling. It markedly increased Nrf2 protein level, Nrf2 nuclear translocation, Nef2 transcription capacity, and the downstream protein expression. We further demonstrated that SIN activation of Nrf2 is likely due to its repression of the Nrf2 inhibitor Keap1 since it drastically reduced Keap1 protein through the PKC-sensitive ubiquitination-proteasomal degradation. SIN treatment of nephropathy mice effectively reduced the kidney damage and inflammatory responses, balanced renal oxidative stress, and improved the pathological protein expression in an Nrf2 dependent manner. In addition, SIN also Nrf2-dependently modulated macrophage M1/M2 polarization and inhibited the IkBα phosphorylation and NF-kB nuclear translocation, hence revealing an important upstream event that contributed to its anti-inflammation and tissue protection. Taken together our study has identified a novel pathway through which SIN exerts its anti-inflammation and renal protective functions, and provided a molecular basis for SIN potential applications in the treatment of kidney and other inflammatory disorders.