Ps-bpb05-9: dual deletion of guanylyl cyclase-a and p38 mapk in podocytes with aldosterone administration causes glomerular intracapillary thrombi

Objective: Previously, we demonstrated that uninephrectomized aldosterone-infused, high salt-fed podocyte-specific guanylyl cyclase-A (GC-A) conditional KO (pod-GC-A cKO) mice exhibit glomerular injury and that pharmacological inhibition of p38 MAPK ameliorates podocyte damage. However, the effects of genetic deletion of p38 MAPK in podocytes of pod-GC-A cKO mice have been unknown. By generating podocyte-specific p38 MAPK and GC-A double cKO mice, the study investigated the effects of p38 MAPK deletion in podocytes on glomerular injury with aldosterone and a high salt diet in mice. Design and method: We generated p38 MAPK(fl/fl);Nephrin-Cre (pod-p38 MA- PK cKO) mice and p38 MAPK(fl/fl);GC-A(fl/fl);Nephrin-Cre (pod-p38MAPK/GC-A double cKO) mice. For induction of glomerular injury, we treated them with aldosterone and high salt at 2 months of age for 3 weeks without nephrectomy (B-ALDO). In vitro, firstly, we examined human podocytes which p38 MAPK was deleted by Crispr/Cas9 system and GC-A was suppressed by siRNA. Secondly, we used a transwell co-culture system to investigate changes of wild-type human umbilical vein endothelial cells (HUVEC) mRNA in the lower layer culture with immortalized p38 MAPK-null podocytes transfected with si-GC-A in the upper layer. Results: Unexpectedly, aldosterone-infused, and high salt-fed (B-ALDO)-treated pod-p38 MAPK/GC-A double cKO mice resulted in significant elevation of serum Cr (0.29 ± 0.04 mg/dL), massive albuminuria (42,0541 ± 8,493 μg/mgCr) and severe foot process effacement in addition to intracapillary fibrin thrombi which indicated endothelial damage. In vitro, knockout of p38 MAPK and suppression of GC-A in human cultured podocytes induced podocyte damage. Deletion of p38 MAPK and inhibition of GC-A in podocytes in the upper layer upregulated TGFB1 and FN1 in the HUVEC in the lower layer, indicating that some humoral factors derived from podocytes could work as cell-to-cell mediators, especially for HUVEC. Conclusions: Genetic dual deletion of p38 MAPK and GC-A in podocytes accelerates both podocyte and endothelium injuries, suggesting that p38 MAPK in podocytes has an essential role in maintaining podocyte-endothelial interactions, especially under diseased conditions.