Ayami Ikeda

Exaggerated Blood Pressure Variability Superimposed on Hypertension Aggravates Cardiac Remodeling in Rats via Angiotensin II System-Mediated Chronic Inflammation

Hypertensive patients with large blood pressure variability (BPV) have aggravated end-organ damage. However, the pathogenesis remains unknown. We investigated whether exaggerated BPV aggravates hypertensive cardiac remodeling and function by activating inflammation and angiotensin II–mediated mechanisms. A model of exaggerated BPV superimposed on chronic hypertension was created by performing bilateral sinoaortic denervation (SAD) in spontaneously hypertensive rats (SHRs). SAD increased BPV to a similar extent in Wistar Kyoto rats and SHRs without significant changes in mean blood pressure. SAD aggravated left ventricular and myocyte hypertrophy and myocardial fibrosis to a greater extent and impaired left ventricular systolic function in SHRs. SAD induced monocyte chemoattractant protein-1, transforming growth factor-&bgr;, and angiotensinogen mRNA upregulations and macrophage infiltration of the heart in SHRs. The effects of SAD on cardiac remodeling and inflammation were much smaller in Wistar Kyoto rats compared with SHRs. Circulating levels of norepinephrine, the active form of renin, and inflammatory cytokines were not affected by SAD in Wistar Kyoto rats and SHRs. A subdepressor dose of candesartan abolished the SAD-induced left ventricular/myocyte hypertrophy, myocardial fibrosis, macrophage infiltration, and inductions of monocyte chemoattractant protein-1, transforming growth factor-&bgr;, and angiotensinogen and subsequently prevented systolic dysfunction in SHRs with SAD. These findings suggest that exaggerated BPV induces chronic myocardial inflammation and thereby aggravates cardiac remodeling and systolic function in hypertensive hearts. The cardiac angiotensin II system may play a role in the pathogenesis of cardiac remodeling and dysfunction induced by a combination of hypertension and exaggerated BPV.

Inhibition of Intrinsic Interferon-γ Function Prevents Neointima Formation After Balloon Injury

It is still controversial whether intrinsic interferon (IFN)-&ggr; promotes or attenuates vascular remodeling in hyperproliferative vascular disorders, such as neointima formation after balloon injury. Thus, we investigated whether inhibition of intrinsic IFN-&ggr; function prevents neointima formation. For this purpose, naked DNA plasmid encoding a soluble mutant of IFN-&ggr; receptor &agr;-subunit (sIFN&ggr;R; an IFN-&ggr; inhibitory protein) or mock plasmid was injected into the thigh muscle of male Wistar rats 2 days before balloon injury (day −2). sIFN&ggr;R gene transfer significantly elevated serum levels of sIFN&ggr;R protein for 2 weeks. In mock-treated rats, balloon injury induced smooth muscle cell proliferation in the neointima with a peak at day 7 and produced thick neointima at day 14. sIFN&ggr;R treatment reduced the number of proliferating intimal smooth muscle cells by 50% at day 7 and attenuated neointima formation with a 45% reduction of the intima/media area ratio at day 14. In mock-treated rats, at day 7, balloon injury induced phosphorylation of signal transducer and activator of transcription-1 and upregulations of IFN regulatory factor-1 (a transcription factor mediating IFN-&ggr; signal). Balloon injury also upregulated the key molecules of neointima formation, such as intercellular adhesion molecule-1 and platelet-derived growth factor &bgr;-receptor. These changes were suppressed by sIFN&ggr;R treatment. In conclusion, it is suggested that intrinsic IFN-&ggr; promotes neointima formation probably through IFN regulatory factor-1/intercellular adhesion molecule-1–mediated and platelet-derived growth factor–mediated mechanisms. Thus, inhibition of IFN-&ggr; signaling may be a new therapeutic target for prevention of neointima formation of hyperproliferative vascular disorders.

Selective gene expression analysis of muscular and vascular components in hearts using laser microdissection method.

Background. The heart consists of various kinds of cell components. However, it has not been feasible to separately analyze the gene expression of individual components. The laser microdissection (LMD) method, a new technology to collect target cells from the microscopic regions, has been used for malignancies. We sought to establish a method to selectively collect the muscular and vascular regions from the heart sections and to compare the marker gene expressions with this method. Methods and Results. Frozen left ventricle sections were obtained from Wistar-Kyoto rats (WKY) and stroke-prone spontaneously hypertensive rats (SHR-SP) at 24 weeks of age. Using the LMD method, the muscular and vascular regions were selectively collected under microscopic guidance. Real-time RT-PCR analysis showed that brain-type natriuretic peptide (BNP), a marker of cardiac myocytes, was expressed in the muscular samples, but not in the vascular samples, whereas α-smooth muscle actin, a marker of smooth muscle cells, was detected only in the vascular samples. Moreover, SHR-SP had significantly greater BNP upregulation than WKY (P < 0.05) in the muscular samples. Conclusions. The LMD method enabled us to separately collect the muscular and vascular samples from myocardial sections and to selectively evaluate mRNA expressions of the individual tissue component.