P0552EXPRESSION OF CNDP1 PROTEIN IS REGULATED BY AGE-DEPENDENT AND AKI-RELATED ASTRAGALUS MEMBRANACEOUS EFFECTS IN MICE
Authors: Kajiwara Kagemasa , Arai Makoto , Nakada Yoshinobu , Nagashima Go , Kinoue Takeaki 
Published: June 2020

Abstract

Background and Aims
Astragalus membranaceus (AM) is widely used for herbal medicine in Asia (see http://nccih.nih.gov/health/astragalus). Until now, numerous findings about the AM effects have been provided in various tissues and organs; however, the therapeutic effects of AM against chronic kidney disease (CKD) remain unclear. Recent findings suggest that acute kidney injury (AKI), which has been previously believed to heal completely, is a promoting factor for CKD pathogenesis or progression. Our recent findings have been observed that susceptibility to AKI as well as AM effects against AKI was significant in old mice, suggesting that AM effects exert an age-dependent manner in kidney. Therefore, we further examined the therapeutic effect of AM against age-dependent AKI pathogenicity.

Method
Female C57BL/6 mice were collected blood in advance (0.2 ml as normal), separated to two groups, and administered with AM powder-mixed sterilized 0.5% methylcellulose 400 (w/v) (AM-administered group) or with sterilized 0.5% methylcellulose 400 (control group), respectively by two hours before surgery. Left renal artery was exposed and occluded by non-traumatic small clips for 20 minutes. Twenty hours after the renal reperfusion, we collected blood (0.2 ml as reaction) and acquired kidney from each mouse. These serum samples were measured to detect serum creatinine and urea nitrogen. The dissected kidneys were used for Western blot analysis to determine the expression of AM-target protein candidates, which were selected as both age-dependent and renal disease-related factors from research data base (NCBI, Bethesda MD USA).

Results
Sorting with the data base, we isolated a metabolic product, carnosine (beta-alanyl-L-histidine), which is abundant in young human blood samples and exerted a scavenger effects against the anti-oxidative stress. Carnosine is degraded by carnosinase encoded by CNDP1 gene, and its metabolism revealed renoprotective characterization including scavenger of reactive oxygens in various tissues. Furthermore, recent epidemiologic studies showed association between pathogenesis of diabetic nephropathy and CNDP1 gene polymorphism. Therefore, here we examined the levels of CNDP1 protein by Western blot analysis. CNDP1 protein was upregulated in ischemia-reperfusion kidneys significantly from old mice (52 weeks old), compared to those from young mice (6-8 weeks old) which showed little increased levels. The levels of CNDP1 protein were down-regulated by AM administration prior to ischemia-reperfusion in both old and young kidneys. These findings suggest that pharmacological effects of AM normalized carnosine metabolism by regulating expression of CNDP1, which plays a critical role in AKI pathogenesis of aged kidney.

Conclusion
AM administration can reduce day-to-day generated AKI by carnosine upregulation at least in part. The AM effects involved in carnosine metabolism would play a critical role in prolonging activity of aged kidney.