Kyosuke Kazama

Omentin plays an anti-inflammatory role through inhibition of TNF-α-induced superoxide production in vascular smooth muscle cells.

Omentin is a recently identified adipocytokine and its effect in vasculature is largely unknown. Here we examined the effects of omentin on smooth muscle cells (SMCs) inflammatory states. Western blotting was performed to analyze inflammatory signal transduction in cultured SMCs. Phosphorylation of nuclear factor-κB (NF-κB), p38 and JNK, and expression of vascular cell adhesion molecule (VCAM)-1 and cyclooxygenase-2 were not induced by omentin (50-300ng/ml, 20min or 24h). On the other hand, tumor necrosis factor-α (TNF-α; 10ng/ml, 20min)-induced phosphorylation of p38 and JNK was significantly inhibited by omentin pretreatment in a concentration-dependent manner (50-300ng/ml, 30min). TNF-α (24h)-induced expression of VCAM-1 was also significantly inhibited by omentin pretreatment in a concentration-dependent manner. Both inhibitor of p38 (SB203580) and JNK (SP600125) significantly inhibited TNF-α-induced VCAM-1 expression. Omentin (300ng/ml, 30min) inhibited TNF-α (1h)-induced nicotinamide adenine dinucleotide phosphate oxidase activity as determined by lucigenin assay. An antioxidant drug, N-acetyl-l-cysteine significantly inhibited TNF-α-induced phosphorylation of p38 and JNK. Furthermore, omentin (300ng/ml, 30min) significantly inhibited TNF-α (24h)-induced monocytic cells adhesion to SMCs. In rat isolated thoracic aorta, omentin (300ng/ml, 30min) inhibited TNF-α (24h)-induced VCAM-1 expression. The present results demonstrate for the first time that omentin plays an anti-inflammatory role by preventing the TNF-α-induced VCAM-1 expression in SMCs. It is suggested that omentin inhibits TNF-α-induced VCAM-1 expression via preventing the activation of p38 and JNK at least in part through inhibition of superoxide production.

A novel adipocytokine, omentin, inhibits platelet-derived growth factor-BB-induced vascular smooth muscle cell migration through antioxidative mechanism

Omentin is a novel adipocytokine expressed in visceral adipose tissue. Secretion and blood concentration of omentin decrease in the obese subjects. We previously demonstrated that omentin is anti-inflammatory in vascular smooth muscle cells (SMCs). While vascular remodeling via migration of SMCs is also important for hypertension development, it remains to be clarified whether omentin affects this process. Here we examined whether omentin controls SMC migration. Omentin (300 ng/ml, 2 h) significantly inhibited platelet-derived growth factor (PDGF)-BB (10 ng/ml, 6 h)-induced migration of rat mesenteric arterial SMCs, as determined by Boyden chamber assay. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced phosphorylation of p38 and heat shock protein (HSP) 27. Omentin (300 ng/ml, 2 h) significantly inhibited PDGF-BB (10 ng/ml, 30 min)-induced NADPH oxidase (NOX) activation as determined by lucigenin assay. Omentin (300 ng/ml, 24 h) significantly inhibited fetal bovine serum (5%, 4 days)-induced SMC outgrowth from rat isolated mesenteric artery. In vivo, omentin significantly inhibited carotid intimal hyperplasia in mouse ligation model. In summary, we for the first time demonstrate that omentin prevents PDGF-BB-induced SMC migration by preventing NOX/O2(-)/p38/HSP27 pathways, which might be at least partly responsible for the preventive effects on neointimal hyperplasia. Our data suggest that omentin may be protective against hypertension development by inhibiting vascular structural remodeling.

A novel adipocytokine, omentin, inhibits monocrotaline-induced pulmonary arterial hypertension in rats

Omentin is a novel adipocytokine mainly expressed in visceral rather than subcutaneous adipose tissue. Several epidemiological studies demonstrated the negative relationship between blood omentin level and occurrence of obesity, type 2 diabetes and hypertension. Increases of inflammatory responses, contractile reactivity and structural remodeling of vascular wall contribute to hypertension development. Our in vitro studies previously demonstrated that omentin inhibited those hypertension-related pathological processes. In addition, our in vivo study demonstrated that intravenously injected omentin acutely inhibited agonists-induced increases of blood pressure in rats. However, the chronic effects of omentin on hypertension development are not determined. In the present study, we tested the hypothesis that chronic omentin treatment may inhibit pulmonary arterial (PA) hypertension (PAH). PAH was induced by a single intraperitoneal injection of monocrotaline (MCT: 60 mg/kg) to rats. Omentin (18 μg/kg/day) was intraperitoneally treated for 14 days. Chronic omentin treatment inhibited MCT-induced increases in PA pressure. Omentin inhibited MCT-induced right ventricular hypertrophy as well as increase of lung to body weight ratio. Histologically, omentin inhibited MCT-induced PA hyperplasia. Further, omentin inhibited the impairment of both endothelium-dependent and -independent relaxations mediated by acetylcholine and sodium nitroprusside, respectively. In conclusion, we for the first time demonstrate that chronic omentin treatment inhibits MCT-induced PAH in rats via inhibiting vascular structural remodeling and abnormal contractile reactivity.

Adipocytokine, omentin inhibits doxorubicin-induced H9c2 cardiomyoblasts apoptosis through the inhibition of mitochondrial reactive oxygen species.

Omentin is a relatively novel adipocyte-derived cytokine mainly expressed in visceral adipose tissues. Blood omentin level decreases in the patients with obesity, hypertension, type 2 diabetes and atherosclerosis. We have previously demonstrated that omentin inhibits key pathological processes for hypertension development, including vascular inflammatory responses, contractile reactivity and structural remodeling. In addition, there are several reports demonstrating that omentin prevents cardiac hypertrophy and myocardial ischemic injury. Doxorubicin (DOX) is an effective anti-cancer drug with cardiotoxic side effect. Here we tested the hypothesis that omentin may prevent DOX-induced cardiac cytotoxicity. H9c2 rat cardiomyoblasts were treated with DOX in the absence or presence of omentin. Omentin (300 ng/ml, 3 h pretreatment) significantly inhibited DOX (1 μM, 18 h)-induced decreases in living cell number as determined by a colorimetric cell counting assay. Omentin (300 ng/ml, 3 h) significantly inhibited DOX (1 μM, 12 h)-induced cleaved caspase-3 expression as determined by Western blotting. Omentin (300 ng/ml, 3 h) significantly inhibited DOX (1 μM, 6 h)-induced mitochondrial reactive oxygen species (ROS) production as determined by a MitoSOX Red fluorescent staining. In addition, a mitochondrial respiratory chain complex I inhibitor, rotenone (0.5 μM, 3 h pretreatment), significantly inhibited DOX (1 μM, 6-18 h)-induced decreases of living cell number, cleaved caspase-3 expression and mitochondrial ROS production. In summary, we for the first time demonstrate that omentin prevents DOX-induced H9c2 cells apoptosis through the inhibition of mitochondrial ROS production. These results indicate omentin as an attractive pharmaco-therapeautic target against DOX-induced cardiac side effect.

Chemerin promotes the proliferation and migration of vascular smooth muscle and increases mouse blood pressure

Blood chemerin concentration shows positive correlation not only with body mass index and serum triglyceride level but also with systolic blood pressure. While it seems likely that chemerin influences vascular smooth muscle cell (SMC) proliferation and migration, which are crucial to the development of hypertension, this remains to be clarified. In the present study, we investigated whether chemerin controls SMC proliferation and migration in vitro and also affects blood pressure in vivo. In vitro, chemerin significantly stimulated rat mesenteric arterial SMC proliferation and migration, as determined by a cell counting assay and Boyden chamber assay, respectively. The migratory effect of chemerin was confirmed in human aortic SMCs. Chemerin significantly increased ROS production in SMCs and phosphorylation of Akt (Ser(473)) and ERK, as measured by fluorescent staining and Western blot analysis, respectively. Various inhibitors (ROS inhibitor: N-acetyl-l-cysteine, phosphatidylinositol 3-kinase inhibitor: LY-294002, MAPKK inhibitor: PD-98059, NADPH oxidase inhibitor: gp91 ds-tat, and xanthine oxidase inhibitor: allopurinol) as well as chemokine-like receptor 1 small interfering RNA significantly inhibited chemerin-induced SMC proliferation and migration. Furthermore, chemerin-neutralizing antibody prevented carotid neointimal hyperplasia in the mouse ligation model. In vivo, chronic chemerin treatment (6 μg/kg, 6 wk) increased systolic blood pressure as well as phosphorylation of Akt and ERK in the mouse isolated aorta. In summary, we, for the first time, demonstrate that chemerin/chemokine-like receptor 1 stimulates SMC proliferation and migration via ROS-dependent phosphorylation of Akt/ERK, which may lead to vascular structural remodeling and an increase in systolic blood pressure.

Eukaryotic elongation factor 2 kinase mediates monocrotaline-induced pulmonary arterial hypertension via reactive oxygen species-dependent vascular remodeling

Pulmonary arterial (PA) hypertension (PAH) is a progressive and lethal disease that is caused by increased vascular contractile reactivity and structural remodeling. These changes contribute to increasing pulmonary peripheral vascular resistance, finally leading to right heart failure and death. Eukaryotic elongation factor 2 kinase (eEF2K) is a Ca(2+)/calmodulin-dependent protein kinase. We previously revealed that eEF2K protein increases in the mesenteric artery from spontaneously hypertensive rats and partly mediates the development of hypertension via a promotion of ROS-dependent vascular inflammatory responses and proliferation and migration of vascular smooth muscle cells. However, a role of eEF2K in the pathogenesis of PAH is unknown. In the present study, we tested the hypothesis that eEF2K may be involved in the pathogenesis of PAH. PAH was induced by a single intraperitoneal injection of monocrotaline (MCT; 60 mg/kg) to rats. A specific eEF2K inhibitor, A-484954 (2.5 mg·kg(-1)·day(-1)), was intraperitoneally injected for 14 days. Long-term A-484954 treatment inhibited MCT-induced increased PA pressure. It was revealed that A-484954 inhibited MCT-induced PA hypertrophy and fibrosis but not impairment of endothelium-dependent and -independent relaxation. Furthermore, A-484954 inhibited MCT-induced NADPH oxidase-1 expression and ROS generation as well as matrix metalloproteinase-2 activation. In conclusion, the present results suggest that eEF2K at least partly mediates MCT-induced PAH via stimulation of vascular structural remodeling perhaps through NADPH oxidase-1/ROS/matrix metalloproteinase-2 pathway.

Adipocytokine, progranulin, augments acetylcholine‐induced nitric oxide‐mediated relaxation through the increases of cGMP production in rat isolated mesenteric artery

Progranulin (PGRN) is a novel adipocytokine with anti‐inflammatory effects in vascular cells. The aim of this study was to clarify the effects of PGRN on reactivity of isolated blood vessel.