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Downregulation of Renal G Protein – Coupled Receptor Kinase Type 4 Expression via Ultrasound ‐ Targeted Microbubble Destruction Lowers Blood Pressure in Spontaneously Hypertensive Rats

View Article: PubMed Central - PubMed

ABSTRACT

Background: G protein–coupled receptor kinase type 4 (GRK4) plays a vital role in the long‐term control of blood pressure (BP) and sodium excretion by regulating renal G protein–coupled receptor phosphorylation, including dopamine type 1 receptor (D1R). Ultrasound‐targeted microbubble destruction (UTMD) is a promising method for gene delivery. Whether this method can deliver GRK4 small interfering RNA (siRNA) and lower BP is not known.

Methods and results: BP, 24‐hour sodium excretion, and urine volume were measured after UTMD‐targeted GRK4 siRNA delivery to the kidney in spontaneously hypertensive rats. The expression levels of GRK4 and D1R were determined by immunoblotting. The phosphorylation of D1R was investigated using immunoprecipitation. The present study revealed that UTMD‐mediated renal GRK4 siRNA delivery efficiently reduced GRK4 expression and lowered BP in spontaneously hypertensive rats, accompanied by increased sodium excretion. The increased sodium excretion might be accounted for by the UTMD regulation of D1R phosphorylation and function in spontaneously hypertensive rats. Further analysis showed that, although UTMD had no effect on D1R expression, it reduced D1R phosphorylation in spontaneously hypertensive rats kidneys and consequently increased D1R‐mediated natriuresis and diuresis.

Conclusions: Taken together, these study results indicate that UTMD‐targeted GRK4 siRNA delivery to the kidney effectively reduces D1R phosphorylation by inhibiting renal GRK4 expression, improving D1R‐mediated natriuresis and diuresis, and lowering BP, which may provide a promising novel strategy for gene therapy for hypertension.

No MeSH data available.


Effects of ultrasound‐targeted microbubble destruction (UTMD)–mediated G protein–coupled receptor kinase type 4 (GRK4) small interfering RNA (siRNA) delivery on dopamine type 1 receptor (D1R) phosphorylation and D1R‐mediated natriuresis. A and B, Effects of UTMD‐mediated GRK4 siRNA delivery for 20 days on renal D1R expression (A) and phosphorylation (B) in spontaneously hypertensive rats (SHRs) (n=5, *P<0.05 vs control). C and D, Effects of fenoldopam, a D1‐like receptor agonist, on sodium excretion and urine volumes in the UTMD (20 days)‐treated SHRs (n=5, *P<0.05 vs control).
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jah31805-fig-0006: Effects of ultrasound‐targeted microbubble destruction (UTMD)–mediated G protein–coupled receptor kinase type 4 (GRK4) small interfering RNA (siRNA) delivery on dopamine type 1 receptor (D1R) phosphorylation and D1R‐mediated natriuresis. A and B, Effects of UTMD‐mediated GRK4 siRNA delivery for 20 days on renal D1R expression (A) and phosphorylation (B) in spontaneously hypertensive rats (SHRs) (n=5, *P<0.05 vs control). C and D, Effects of fenoldopam, a D1‐like receptor agonist, on sodium excretion and urine volumes in the UTMD (20 days)‐treated SHRs (n=5, *P<0.05 vs control).

Mentions: As mentioned above, D1R is the major target of GRK4 in the kidney. We determined whether GRK4 siRNA via UTMD in the kidney regulates D1R phosphorylation and function in SHRs. Our results revealed that, although there was no difference in the D1R protein expression between the UTMD treatment group and the control group (Figure 6A), GRK4 siRNA via UTMD decreased the phosphorylation of D1R compared with the control group (Figure 6B). Moreover, UTMD‐mediated delivery of GRK4 siRNA also led to an improvement in D1R‐mediated natriuresis in SHRs because fenoldopam, a D1‐like receptor agonist, led to a greater increase in sodium excretion and urine volume in the UTMD treatment group than the control group (Figure 6C and 6D). These results suggest that silencing GRK4 expression via UTMD improves renal D1R function.


Downregulation of Renal G Protein – Coupled Receptor Kinase Type 4 Expression via Ultrasound ‐ Targeted Microbubble Destruction Lowers Blood Pressure in Spontaneously Hypertensive Rats
Effects of ultrasound‐targeted microbubble destruction (UTMD)–mediated G protein–coupled receptor kinase type 4 (GRK4) small interfering RNA (siRNA) delivery on dopamine type 1 receptor (D1R) phosphorylation and D1R‐mediated natriuresis. A and B, Effects of UTMD‐mediated GRK4 siRNA delivery for 20 days on renal D1R expression (A) and phosphorylation (B) in spontaneously hypertensive rats (SHRs) (n=5, *P<0.05 vs control). C and D, Effects of fenoldopam, a D1‐like receptor agonist, on sodium excretion and urine volumes in the UTMD (20 days)‐treated SHRs (n=5, *P<0.05 vs control).
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jah31805-fig-0006: Effects of ultrasound‐targeted microbubble destruction (UTMD)–mediated G protein–coupled receptor kinase type 4 (GRK4) small interfering RNA (siRNA) delivery on dopamine type 1 receptor (D1R) phosphorylation and D1R‐mediated natriuresis. A and B, Effects of UTMD‐mediated GRK4 siRNA delivery for 20 days on renal D1R expression (A) and phosphorylation (B) in spontaneously hypertensive rats (SHRs) (n=5, *P<0.05 vs control). C and D, Effects of fenoldopam, a D1‐like receptor agonist, on sodium excretion and urine volumes in the UTMD (20 days)‐treated SHRs (n=5, *P<0.05 vs control).
Mentions: As mentioned above, D1R is the major target of GRK4 in the kidney. We determined whether GRK4 siRNA via UTMD in the kidney regulates D1R phosphorylation and function in SHRs. Our results revealed that, although there was no difference in the D1R protein expression between the UTMD treatment group and the control group (Figure 6A), GRK4 siRNA via UTMD decreased the phosphorylation of D1R compared with the control group (Figure 6B). Moreover, UTMD‐mediated delivery of GRK4 siRNA also led to an improvement in D1R‐mediated natriuresis in SHRs because fenoldopam, a D1‐like receptor agonist, led to a greater increase in sodium excretion and urine volume in the UTMD treatment group than the control group (Figure 6C and 6D). These results suggest that silencing GRK4 expression via UTMD improves renal D1R function.

View Article: PubMed Central - PubMed

ABSTRACT

Background: G protein&ndash;coupled receptor kinase type 4 (GRK4) plays a vital role in the long&#8208;term control of blood pressure (BP) and sodium excretion by regulating renal G protein&ndash;coupled receptor phosphorylation, including dopamine type 1 receptor (D1R). Ultrasound&#8208;targeted microbubble destruction (UTMD) is a promising method for gene delivery. Whether this method can deliver GRK4 small interfering RNA (siRNA) and lower BP is not known.

Methods and results: BP, 24&#8208;hour sodium excretion, and urine volume were measured after UTMD&#8208;targeted GRK4 siRNA delivery to the kidney in spontaneously hypertensive rats. The expression levels of GRK4 and D1R were determined by immunoblotting. The phosphorylation of D1R was investigated using immunoprecipitation. The present study revealed that UTMD&#8208;mediated renal GRK4 siRNA delivery efficiently reduced GRK4 expression and lowered BP in spontaneously hypertensive rats, accompanied by increased sodium excretion. The increased sodium excretion might be accounted for by the UTMD regulation of D1R phosphorylation and function in spontaneously hypertensive rats. Further analysis showed that, although UTMD had no effect on D1R expression, it reduced D1R phosphorylation in spontaneously hypertensive rats kidneys and consequently increased D1R&#8208;mediated natriuresis and diuresis.

Conclusions: Taken together, these study results indicate that UTMD&#8208;targeted GRK4 siRNA delivery to the kidney effectively reduces D1R phosphorylation by inhibiting renal GRK4 expression, improving D1R&#8208;mediated natriuresis and diuresis, and lowering BP, which may provide a promising novel strategy for gene therapy for hypertension.

No MeSH data available.