Upregulation of AT1 Receptor Mediates a Pressor Effect Through ROS-SAPK/JNK Signaling in Glutamatergic Neurons of Rostral Ventrolateral Medulla in Rats With Stress-Induced Hypertension

Figures

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  FIGURE 1. The changes of systolic blood pressure (SBP) (A), heart rate (HR) (B), and body weight (C) in stress-induced hypertension (SIH) and control group. n = 10, ∗P < 0.05 vs. control (Student’s t-test); #P < 0.05 vs. baseline (paired t-test) (third day prior to stress).

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  FIGURE 2. Localization of AT1R and VGLUT2 in the rostral ventrolateral medulla (RVLM) of SIH rat (A) and chromatogram of amino acids in the IML in control (B) and SIH rats (C) the red (cy3), green (FAM) areas represented the staining of glutamatergic neurons and AT1R, respectively. Scale bars = 25 μm. The baseline release of glutamate increased in SIH rats compared with control rats (D). n = 8, ∗P < 0.05 vs. control (Student’s t-test). Glu, glutamate; Gln, glutamine.

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  FIGURE 3. The protein levels of phosphorylation or total SAPK/JNK (A), ERK1/2 (B), and p38MAPK (C) in the RVLM in the SIH group 15 and 30 min after RVLM microinjection of Ang II (50 pmol). Densitometry values were determined as indicated. n = 4, ∗P < 0.05 vs. control; #P < 0.05 vs. SIH (one-way ANOVA with Tukey post hoc test).

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  FIGURE 4. Effects of candesartan (CAN) on the production of Reactive oxygen species (ROS) and phosphorylation of SAPK/JNK, ERK1/2, and p38MAPK in the RVLM in SIH and control groups. The production of ROS in the RVLM detected at 20 min after microinjection of apocynin APO (2 nmol) or CAN (2 nmol) into the RVLM (A); n = 6. The protein levels of phosphorylated SAPK/JNK, ERK1/2, and p38MAPK were detected 30 min after microinjection of CAN (2 nmol) into the RVLM, bilaterally (B,C); n = 4. ∗P < 0.05 vs. control + aCSF; #P < 0.05 vs. SIH + aCSF (one-way ANOVA with Tukey post hoc test).

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  FIGURE 5. Effects of APO on MAPK activation in the RVLM in the SIH and control group. Immunohistochemistry for p-SAPK/JNK (A), p-ERK1/2 (B), or p-p38MAPK (C) in control and SIH groups treated with or without APO (D). Scale bars = 50 μm in a1, b1, c1; 25 μm in a2, b2, c2. n = 4, ∗P < 0.05 vs. control + aCSF; #P < 0.05 vs. SIH + aCSF (one-way ANOVA with Tukey post hoc test).

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  FIGURE 6. Effects of the inhibitors of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, SAPK/JNK, ERK1/2, and p38MAPK on AT1R expression in the RVLM and Mean arterial blood pressure (MABP) in rats with SIH. The mRNA levels of AT1R in the RVLM (n = 4) (A), and change in MABP (n = 6) (C) in response to microinjection of APO (2 nmol), SP600125 (500 nmol), U0126 (500 nmol), or SB203580 (500 nmol) into the RVLM of rats with SIH. Representative gels or densitometric analysis of AT1R protein in the RVLM (n = 5) (B), and change in MABP (n = 6) (D) of SIH group after intracerebroventricular infusion (ICV) of aCSF, APO (0.45 mol/L), SP600125 (0.6 mol/L), U0126 (0.6 mol/L), or SB203580 (0.6 mol/L) for 14 days in stress-induced hypertensive rats (SIHR). ∗P < 0.05 vs. control + aCSF; #P < 0.05 vs. SIH + aCSF (one-way ANOVA with Tukey post hoc test, A,B,D; Student’s t-test, C).

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  FIGURE 7. Schematic diagram showing the mechanism by which AT1R mediates pressor effect in the glutamatergic neurons of the RVLM of SIHR. Ang II triggers the activation of NADPH oxidase derived ROS-SAPK pathway via AT1R in the glutamatergic neurons of the RVLM of SIHR, then may activate activator protein (AP)-1 to evoke gene transcription and increase AT1R expression, which promotes the release of glutamate in the IML and eventually increases BP and HR.