ABSTRACT
Aims: Angiotensin receptor-neprilysin inhibitor (ARNI) is an established treatment for heart failure. However, whether ARNI has renoprotective effects beyond renin-angiotensin system inhibitors alone in cardiorenal syndrome (CRS) has not been fully elucidated. Here, we examined the effects of ARNI on the heart and kidneys of CRS model mice with overt albuminuria and identified the mechanisms underlying ARNI-induced kidney protection. Methods and results: C57BL6 mice were subjected to chronic angiotensin II infusion, nephrectomy, and salt loading (ANS); they developed CRS phenotypes and were divided into the vehicle treatment (ANS-vehicle), sacubitril/valsartan treatment (ANS-ARNI), and two different doses of valsartan treatment (ANS-VAL M, ANS-VAL H) groups. Four weeks after treatment, the hearts and kidneys of each group were evaluated. The ANS-vehicle group showed cardiac fibrosis, cardiac dysfunction, overt albuminuria, and kidney fibrosis. The ANS-ARNI group showed a reduction in cardiac fibrosis and cardiac dysfunction compared with the valsartan treatment groups. However, regarding the renoprotective effects characterized by albuminuria and fibrosis, ARNI was less effective than valsartan. Kidney transcriptomic analysis showed that the ANS-ARNI group exhibited a significant enhancement in the phosphoinositide 3-kinase (PI3K)-AKT signalling pathway compared with the ANS-VAL M group. Adding PI3K inhibitor treatment to ARNI ameliorated kidney injury to levels comparable with those of ANS-VAL M while preserving the superior cardioprotective effect of ARNI. Conclusion: PI3K pathway activation has been identified as a key mechanism affecting remnant kidney injury under ARNI treatment in CRS pathology, and blockading the PI3K pathway with simultaneous ARNI treatment is a potential therapeutic strategy for treating CRS with overt albuminuria.
ABSTRACT
In the sexual reproduction of flowering plants, two independent fertilization events occur almost simultaneously: two identical sperm cells fuse with either the egg cell or the central cell, resulting in embryo and endosperm development to produce a seed. GCS1/HAP2 is a sperm cell membrane protein essential for plasma membrane fusion with both female gametes. Other sperm membrane proteins, DMP8 and DMP9, are more important for egg cell fertilization than that of the central cell, suggesting its regulatory mechanism in GCS1/HAP2-driving gamete membrane fusion. To assess the GCS1/HAP2 regulatory cascade in the double fertilization system of flowering plants, we produced Arabidopsis transgenic lines expressing different GCS1/HAP2 variants and evaluated the fertilization in vivo. The fertilization pattern observed in GCS1_RNAi transgenic plants implied that sperm cells over the amount of GCS1/HAP2 required for fusion on their surface could facilitate membrane fusion with both female gametes. The cytological analysis of the dmp8dmp9 sperm cell arrested alone in an embryo sac supported GCS1/HAP2 distribution on the sperm surface. Furthermore, the fertilization failures with both female gametes were caused by GCS1/HAP2 secretion from the egg cell. These results provided a possible scenario of GCS1/HAP2 regulation, showing a potential scheme for capturing additional GCS1/HAP2-interacting proteins.