JMA Journal

Figure 1. Time-dependent changes in the mean arterial pressure (MAP) of angiotensin II (Ang II)-salt-induced hypertensive rats.
Male Sprague-Dawley rats with radio-telemetry pressure transducers underwent surgery for the subcutaneous implantation of either saline- or Ang II-filled osmotic minipump. They received an intracerebroventricular injection of either phosphate-buffered saline (PBS)- or clodronate-liposomes and were provided with a high-salt diet (2.0% NaCl). The saline-salt treatment groups are represented by a dotted line, with PBS-liposome (open triangle) or clodronate-liposome (open circle). The Ang II-salt treatment groups are represented by a solid line, with PBS-liposome (solid triangle) or clodronate-liposome (solid circle). The numbers in parentheses indicated the number of rats tested; *p < 0.05 versus the rats receiving saline-salt treatment with PBS-liposome or clodronate-liposome; #p < 0.05 versus the rats receiving Ang II-salt treatment with PBS-liposome.

Figure 2. The depressor response to acute ganglionic blockade in angiotensin II (Ang II)-salt-induced hypertensive rats.
A, Resting mean arterial pressure (MAP) of rats before the ganglionic blockade. Rats were treated with either saline or Ang II via subcutaneously implanted osmotic minipumps and received an intracerebroventricular injection of phosphate-buffered saline (PBS)-liposome or clodronate-liposome. B, Peak depressor response to acute ganglionic blockade. Following the same treatment paradigm, ganglionic blockade was performed to evaluate peak MAP reductions. C, MAP measured after ganglionic blockade. Post-blockade MAP was recorded in the same groups of rats. The numbers in parentheses indicate the number of rats tested; *p < 0.05 versus the rats receiving saline-salt treatment with an intracerebroventricular injection of PBS-liposome.

Figure 3. mRNA levels of inflammatory cytokines in the medulla oblongata of angiotensin II (Ang II)-salt-induced hypertensive rats.
Total RNA extracted from the homogenates of the medulla oblongata was analyzed by Real-time reverse transcription-polymerase chain reaction (RT-PCR) to assess the mRNA expression of interleukin (IL)-6 (A), transforming growth factor-beta (TGF-β) (B), tumor necrosis factor-alpha (TNF-α) (C), and IL-10 (D). Rats were treated with either saline or Ang II via subcutaneously implanted osmotic minipumps and received an intracerebroventricular injection of phosphate-buffered saline (PBS)-liposome or clodronate-liposome. Values are expressed as fold changes relative to the saline-salt treatment group with PBS-liposome. *p < 0.05 versus rats receiving saline-salt treatment with PBS-liposome; n = 4-5 animals per group.
a.u.: arbitrary unit.

Figure 4. Immunoreactivity of Iba1 in the rostral ventrolateral medulla (RVLM) of angiotensin II (Ang II)-salt-induced hypertensive rats.
A, Representative photo of Iba1 immunoreactivity in the RVLM of rats. The scale bar denotes 200 μm. B, The number of Iba1 positive cells in the RVLM. Rats were treated with either saline or Ang II via subcutaneously implanted osmotic minipumps and received an intracerebroventricular injection of PBS-liposome or clodronate-liposome. Iba1-positive cells were counted in two microscopic fields per rat. Individual data points are overlaid on the bar graphs. In the Ang II-salt treatment group receiving clodronate-liposomes, two data points overlapped at a value of 67. Data are presented as the mean ± standard error of the mean; n = 3 animals per group. n = 3 animals per group, two fields per rat were examined; *p < 0.05 versus the rats receiving saline-salt treatment with PBS-liposome.
ns: not significant.

Figure 5. Hypothetical illustration of cardiovascular regulatory areas in the brain.
These illustrations highlight cardiovascular regulatory regions in the brain and present our working hypothesis on the role of cerebrospinal fluid (CSF) macrophages in angiotensin II (Ang II)-induced neurogenic hypertension. CSF macrophages may relay inflammatory signals from peripheral Ang II to the brain parenchyma, promoting sympathetic overactivity via inflammation in these regulatory areas (left). Macrophage depletion via intracerebroventricular clodronate-liposome administration attenuates the development of Ang II-salt-induced neurogenic hypertension in rats (right).