| Summary: | Objective To explore the role of Dickkopf-related protein 1 (DKK1) in hypertension and its effect on urinary sodium excretion. Methods Twelve rats with normal blood pressure (Wister Kyoto rats, WKY), and 12 primary hypertension rats (spontaneously hypertensive rats, SHRs), all male, at an age of 8~10 weeks, weighing 190~210 g, were employed in this study. The expression of DKK1 and β-catenin in the kidney of WKY and SHR rats was detected by Western blotting. Then 12 WKY rats were randomly divided into WKY+DKK1 group and WKY control group (n=6), and so were the 12 SHR rats. Recombinant protein DKK 16 ng/(g·d) was pumped into the rats from the DKK1 groups via micro-syringe. The blood pressure of all the rats was measured by non-invasive tail-cuff method. And the urine was collected by metabolic cages for 24-hour urinary volume and urinary sodium, which were adjusted with their weight. The expression of DKK1 and β-catenin protein in renal proximal tubule epithelial (RPT) cells (WKY-RPT and SHR-RPT) was detected by Western blotting. After intervention with recombinant protein DKK1, DKK1 siRNA (siDKK1), and β-catenin nuclear signal inhibitor (inhibitor of β-catenin-responsive transcription, ICRT 14), inhibitor of GSK3β (6-bromoindirubin-3′-oxime, BIO), the expression of DKK1 and β-catenin and the activity of Na+-K+-ATPase were measured. Results The expression level of DKK1 was lower, while that of β-catenin (indicating Wnt/β-catenin was activated) was higher in the renal tissue of SHR rats than of WKY rats. When the SHR+ DKK1 group was compared with the SHR group, the systolic blood pressure was significantly decreased at 2 weeks after implantation (145.21±2.83 vs 156.07±3.08 mmHg, P < 0.05), and both urine volume (37.40±3.76 vs 27.24±2.30 mL/kg, P < 0.05) and urinary sodium excretion (0.79±0.09 vs 0.51±0.09 mmol/kg, P < 0.05) within 24 h were increased. There were no significant differences in above indexes between WKY+DKK1 group and WKY group. The expression of DKK1 was lower in the SHR-RPT cells than the WKY-RPT cells, and that of β-catenin was opposite. Intervention of DKK1 expression would cause the change of β-catenin (indicating the alteration of Wnt/β-catenin pathway), and thus affect the activity of Na+-K+-ATPase, and the activity of Na+-K+-ATPase was negatively correlated with DKK1. Conclusion DKK1 can reduce Na+-K+-ATPase activity at least partially by inhibiting the Wnt/β-catenin pathway, promote urinary sodium excretion and lower blood pressure.
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