P0348THE DUAL ENDOTHELIN ETA AND ANGIOTENSIN AT1 RECEPTOR BLOCKER SPARSENTAN PROTECTS AGAINST THE DEVELOPMENT OF ALBUMINURIA AND GLOMERULOSCLEROSIS IN THE GDDY MOUSE MODEL OF IGA

Background and Aims gddY mice are an IgA nephropathy (IgAN)-prone mouse model that develops albuminuria by 8 weeks (wks) of age with glomerular IgA, IgG, and C3 deposits and progressive mesangioproliferative glomerulonephritis. A previous study in the ddY mouse model, the more genetically heterogeneous predecessor of gddY mice, using the endothelin type A receptor (ETAR) antagonist FR139317 resulted in amelioration of proteinuria and preservation of kidney function. Treatment of ddY mice with the angiotensin II type 1 receptor (AT1R) blocker valsartan resulted in significant protection from glomerulosclerosis (GS) without a significant prevention in proteinuria. Here we examined the effect of sparsentan (SP), a dual ETAR and AT1R blocker, currently in phase 3 trials for focal segmental glomerulosclerosis and IgAN, on the development of albuminuria and GS in gddY mice. Method gddY mice at 4 wks of age were fed with control (C) chow (n=5) or chow containing 900 ppm (n=10) or 1800 ppm (n=10) SP (approximately 180 and 360 mg/kg/day) for 8 wks. Albuminuria (U-Alb) was assessed at 4, 6, 8, and 12 wks of age and plasma levels of SP were determined at 8 am and 4 pm at wks 6, 8, and 12. Kidney biopsies were taken at the end of the study at 12 wks of age for processing and 30 glomeruli per animal were scored for the percentage of GS. Results gddY mice fed SP in the diet for 8 wks from 4 wks of age demonstrated significantly (*P<0.05) decreased U-Alb compared to mice fed the C diet in a dose-dependent manner (Figure 1). The development of GS in mice fed the diet containing 1800 ppm SP was significantly (*P<0.05) attenuated compared to C diet (Figure 2). Plasma levels of SP taken at 8 am and 4 pm after 8 wks of treatment were (mean±SD) 281±107 and 105±62 ng/ml for 900 ppm SP respectively, and 774±674 and 304±176 ng/ml for 1800 ppm SP, respectively. Weight gain in mice fed SP was not different from mice that received C diet. Conclusion Eight weeks of treatment with SP attenuated increases in albuminuria and GS associated with the development of IgAN in gddY mice. If translated to the clinic, these data support SP as a new approach to the treatment of IgAN.

Interaction between Angiotensin II and Insulin/IGF-1 Exerted a Synergistic Stimulatory Effect on ERK1/2 Activation in Adrenocortical Carcinoma H295R Cells

The cross talk between angiotensin II (Ang II) and insulin has been described mainly in cardiovascular cells, hepatocytes, adipocytes, and so forth, and to date no such cross talk was reported in adrenal. In this study, we examined the interaction between Ang II and insulin/IGF-1 in ERK and AKT signaling pathways and expression of steroidogenic enzymes in H295R cells. Compared to the control, 100 nM Ang II increased phospho-ERK1/2 approximately 3-fold. Insulin (100 nM) or IGF-1 (10 nM) alone raised phospho-ERK1/2 1.8- and 1.5-fold, respectively, while, after pretreatment with 100 nM Ang II for 30 min, insulin (100 nM) or IGF-1 (10 nM) elevated phospho-ERK1/2 level 8- and 7-fold, respectively. The synergistic effect of Ang II and insulin/IGF-1 on ERK1/2 activation was inhibited by selective AT1 receptor blocker, PKC inhibitor, and MEK1/2 inhibitor. Ang II marginally suppressed AKT activation under the basal condition, while it had no effect on phospho-AKT induced by insulin/IGF-1. Ang II significantly stimulated mRNA expression of CYP11B1 and CYP11B2, and such stimulatory effects were enhanced when cells were cotreated with insulin/IGF-1. We are led to conclude that Ang II in combination with insulin/IGF-1 had an evident synergistic stimulatory effect on ERK1/2 activation in H295R cells and the effect may be responsible for the enhanced steroid hormone production induced by Ang II plus insulin/IGF-1.