Enhanced cardiac inflammation and fibrosis in ovariectomized hypertensive rats: a possible mechanism of diastolic dysfunction in postmenopausal women.

Diastolic dysfunction is more prevalent in individuals with hypertension, particularly postmenopausal women; however, the pathogenesis of diastolic dysfunction remains unknown. Pressure overload activates cardiac inflammation, which induces myocardial fibrosis and diastolic dysfunction in rats with a suprarenal aortic constriction (AC). Therefore, we examined the effects of bilateral ovariectomy (OVX) on left ventricle (LV) remodeling, diastolic dysfunction and cardiac inflammation in hypertensive female rats. Rats were randomized to OVX+AC, OVX and AC groups as well as a Control group receiving sham operations for both the procedures. Rats underwent OVX at 6 weeks and AC at 10 weeks (Day 0). At Day 28, OVX did not appear to affect arterial pressure, cardiac hypertrophy or LV fractional shortening in AC rats. However, OVX increased myocardial fibrosis, elevated LV end-diastolic pressure and reduced the transmitral Doppler spectra early to late filling velocity ratio in AC rats. AC-induced transient myocardial monocyte chemoattractant protein-1 expression and macrophage infiltration, both of which peaked at Day 3 and were augmented and prolonged by OVX. At Day 28, dihydroethidium staining revealed superoxide generation in the intramyocardial arterioles in the OVX+AC group but not in the AC group. NOX1, a functional subunit of nicotinamide adenine dinucleotide phosphate oxidase, was upregulated only in the OVX+AC group at Day 28. Chronic 17ß-estradiol replacement prevented the increases in macrophage infiltration, NOX1 upregulation, myocardial fibrosis and diastolic dysfunction in OVX+AC rats. In conclusion, we suggest that estrogen deficiency augments cardiac inflammation and oxidative stress and thereby aggravates myocardial fibrosis and diastolic dysfunction in hypertensive female rats. The findings provide insight into the mechanism underlying diastolic dysfunction in hypertensive postmenopausal women.

Mutant MCP-1 therapy inhibits tumor angiogenesis and growth of malignant melanoma in mice.

We investigated whether blocking of monocyte chemoattractant-1 (MCP-1) function would inhibit recruitment of tumor-associated macrophages (TAMs) and prevent tumor angiogenesis and tumor growth of human malignant melanoma. B16-F1 melanoma cells were implanted onto the back of C57BL/6 mice (Day 0). At Day 7, a dominant negative MCP-1 mutant (7ND) gene was transfected in the thigh muscle to make overexpressed 7ND protein secreted into systemic circulation. 7ND treatment inhibited TAM recruitment and partially reduced tumor angiogenesis and tumor growth. Also, 7ND treatment attenuated inductions of tumor necrosis factor-alpha (TNFalpha), interleukin-1alpha (IL-1alpha), and vascular endothelial growth factor (VEGF) in the stroma and tumor. Melanoma cells expressed not only MCP-1 but also its receptor CCR2. Accordingly, it was suggested that MCP-1 would enhance tumor angiogenesis and early tumor growth in the early stages by inducing TNFalpha, IL-1alpha, and VEGF through TAM recruitment and probably the direct autocrine/paracrine effects on melanoma cells.

Inhibition of progression and stabilization of plaques by postnatal interferon-gamma function blocking in ApoE-knockout mice.

A role of interferon-gamma is suggested in early development of atherosclerosis. However, the role of interferon-gamma in progression and destabilization of advanced atherosclerotic plaques remains unknown. Thus, the aim of this study was to determine whether postnatal inhibition of interferon-gamma signaling could inhibit progression of atherosclerotic plaques and stabilize the lipid- and macrophage-rich advanced plaques. Atherosclerotic plaques were induced in ApoE-knockout (KO) mice by feeding high-fat diet from 8 weeks old (w). Interferon-gamma function was postnatally inhibited by repeated gene transfers of a soluble mutant of interferon-gamma receptors (sIFNgammaR), an interferon-gamma inhibitory protein, into the thigh muscle every 2 weeks. When sIFNgammaR treatment was started at 12 w (atherosclerotic stage), sIFNgammaR not only prevented plaque progression but also stabilized advanced plaques at 16 w: sIFNgammaR decreased accumulations of the lipid and macrophages and increased fibrotic area with more smooth muscle cells. Moreover, sIFNgammaR downregulated expressions of proinflammatory cytokines, chemokines, adhesion molecules, and matrix metalloproteinases but upregulated procollagen type I. sIFNgammaR did not affect serum cholesterol levels. In conclusion, postnatal blocking of interferon-gamma function by sIFNgammaR treatment would be a new strategy to inhibit plaque progression and to stabilize advanced plaques through the antiinflammatory effects.

Nitric oxide mediates cyclosporine-induced impairment of the blood-brain barrier in cocultures of mouse brain endothelial cells and rat astrocytes.

The present study was designed to clarify the involvement of nitric oxide (NO) signaling in the adverse effect of cyclosporine on the blood-brain barrier. Cyclosporine increased the permeability of sodium-fluorescein and the cellular accumulation of rhodamine 123, a substrate of P-glycoprotein, in mouse brain endothelial (MBEC4) cells. This effect was markedly enhanced two- to threefold when MBEC4 cells were cocultured with rat astrocytes or C6 glioma cells. Direct and continuous electrochemical measurement of NO demonstrated that cyclosporine dose-dependently increased histamine- and phenylephrine-evoked NO production in MBEC4 cells and astrocytes, respectively. A NO synthase inhibitor (NG-monomethyl-L-arginine) blocked slightly and markedly cyclosporine-induced impairment of the endothelial barrier in the monolayer and coculture system, respectively. These findings suggest that cyclosporine impairs the brain endothelial barrier function by accelerating NO production in the brain endothelial and astroglial cells. This event may be interpreted as triggering the occurrence of cyclosporine neurotoxicity.

Soybean isoflavones eliminate nifedipine-induced flushing of tail skin in ovariectomized mice.

Hot flushes are one of the most frequent symptoms in menopausal women. We investigated effect of soybean isoflavones (Soyaflavone HG) on nifedipine-induced flushing in ovariectomized mice. Ovariectomy markedly aggravated nifedipine-induced increase in tail skin temperature. Soyaflavone HG (10 mg/kg, p.o., once a day for 5 days) inhibited nifedipine-induced flushing in ovariectomized mice. The inhibitory effect of Soyaflavone HG was significantly reversed by an estrogen-receptor antagonist, ICI 182,780, suggesting that Soyaflavone HG prevents nifedipine-induced flushing partially through estrogen receptors. We presented the experimental evidence suggesting that soybean isoflavones including Soyaflavone HG have the benefits for menopausal hot flushes.

Ovariectomy aggravates nifedipine-induced flushing of tail skin in mice.

Flushing is one of the most common vasodilation-related adverse effects associated with Ca(2+) channel antagonist treatment. This symptom is known to occur more frequently in women than men. The present study aimed at investigating the effect of ovariectomy on nifedipine-induced flushing in mice. Ovariectomy markedly increased the tail skin temperature, a parameter of skin flushing, induced by nifedipine at a dose showing no influence on blood pressure. This event was blocked by estradiol replacement. Estrogen withdrawal is, therefore, included in the risk factors for nifedipine-induced flushing and this risk is lessened by estrogen replacement.

Subchronic treatment with cyclosporin A decreases the binding properties of the GABAA receptor in ovariectomized rats.

In this study, we investigated the effect of cyclosporin A on the binding properties of the GABAA receptor in the hippocampus, known to be responsible for the induction of seizures, to clarify the mechanism of cyclosporin A-inhibited GABA neurotransmission in ovariectomized rats, as a climacterium model. The effects of single and subchronic treatments with cyclosporin A were examined on [3H]muscimol binding to hippocampal synaptosomal membranes in sham, ovariectomized, and estradiol/ovariectomized rats. A single treatment with cyclosporin A (40 mg/kg, i.p.) failed to change [3H]muscimol binding in the 3 groups, when compared with each corresponding vehicle-treated group. Subchronic treatment with cyclosporin A (40 mg/kg, i.p., once a day for 5 days) significantly decreased the amount of [3H]muscimol binding in ovariectomized rats. However, this inhibitory effect was not observed in sham or estradiol/ovariectomized rats. These results demonstrated that the binding activity of the GABAA receptor was decreased in ovariectomized rats after subchronic cyclosporin A treatment. This study supports the hypothesis that ovariectomy elevates the susceptibility to cyclosporin A-induced convulsions by accelerating the inhibitory actions of cyclosporin A on GABA neurotransmission in the hippocampus.