ABSTRACT
Background: The family of curcumin has biological functions, such as anti-oxidative and anti-inflammatory action. Recently, its inhibitory effect on angiogenesis in tumor has been suggested. However, it is not clear how curcumin (CUR) or its derivatives have such in vivo effects. Objective: To quantitatively examine the in vivo effects of CUR or its reduced derivative, tetrahydrocurcumin (THC), on neocapillarization in nude mouse tumors induced by hepatocellular carcinoma (HepG2) cells. Methods: In male BALB/c nude mice (20-25g b.w.), a dorsal skin-fold chamber was implanted, and 30 ml of 2 x 10⁶ human HepG2 cells were inoculated onto the upper layer. The mice were divided into 4 groups: control (CON) supplemented with 0.1% DMSO, HepG2-implanted mice supplemented with DMSO, CUR or THC groups supplemented with CUR or THC (3,000 mg/kg bw), respectively. On the day of the experiment, days 7 and 14, the microcirculation within the chamber was observed using fluorescence videomicroscopy. Based on the recorded video images, capillary vascularity (CV) was measured on the tumor surface. Results: The CV increased in tumors on days 7 and 14 in the HepG2-implanted mice. In the CUR and THC groups, the CV levels were lower than the control level. Furthermore, on day 14, the CV level of THC group was lower than the CV level of the age-matched group. This indicates that HepG2-induced neocapilllaries were reduced markedly by supplementation of THC. Conclusion: THC is potent for suppression of neocapillarization involved in tumor progression.
ABSTRACT
Background: Vitamin C is of clinical benefit for improvement of impaired endothelial functions in diabetes, but its direct effect on nitric oxide (NO) available in endothelial cells during diabetes as yet remains unclear. Objective: To examine the correlation between level of bioavailable NO and arteriolar vasodilation under the direct effect of vitamin C, using a novel NO-sensitive fluorescent indicator in diabetic rats. Methods: Male Spraque-Dawley rats (200-250g body weight) were used for the experiment. The rats were divided into control (CON) and diabetic rats (DM). The diabetes was induced in rats by injection of streptozotocin (STZ) (50 mg/kg body weight). The direct effects of vitamin C administration on NO bioavailability were examined using a buffer solution containing 4,5-diaminofluorescein-diacetate (DAF-2DA) and acetylcholine (Ach) with or without vitamin C in Krebs-Ringer solution. Twenty minutes after the buffer solution was superfused on the rat mesentery, the changes in DAF-2T fluorescence intensities were examined along the arteriolar walls. By visualizing the microcirculation using FITC-dextran, Ach-induced vasodilation of the arterioles (15 to 35 μm in diameter) was measured using Image Pro-Plus Software. The analysis was made after pre-constriction with norepinephrine, and after topical application of vitamin C (ascorbic acid) on the mesentery and following topical application of Ach. Results: DAF-2DF was a NO-sensitive fluorescent indicator that did not make the microvascular walls visible without endothelial activation by Ach. The administration of vitamin C increased Ach-evoked vasodilation in CON and DM groups. Twenty minutes after vitamin C administration, the DAF-2T fluorescence intensities increased significantly in both groups. Conclusion: Vitamin C improved diabetes-induced endothelial dysfunction by enhancing NO bioavailability. The level of bioavailable NO and endothelium-dependent vasodilation were highly correlated.
ABSTRACT
Objective: To determine the effects of vitamin C supplementation and low-intensity exercise training on diabetesinduced endothelial dysfunction. Methods: Male Spraque-Dawley rats were randomly divided into five groups: control (Con), diabetes (DM) (streptozotocin; 50 mg/kg BW, i.v.), diabetes with supplemented vitamin C (DM+Vit.C; 1 g/L mixed in drinking water), diabetes with low-intensity exercise-trained (DM+Ex; running 5 times/week with 13-15 m/min velocity for 30 minutes) and diabetes with supplemented vitamin C and exercisetrained (DM+Vit.C+Ex) groups. The number of leukocyte-endothelial cell (EC) interactions in mesenteric postcapillary venules was monitored using intravital fluorescence videomicroscopy. Liver malondialdehyde (MDA) level, an indicator for oxidative stress, was determined by using the thiobarbituric acid reaction. Results: At 24 weeks, the plasma vitamin C level was significantly increased (p
ABSTRACT
Background and objective: Antioxidants may be useful in preventing vascular diseases. Among the antioxidant agents, tetrahydrocurcumin (THC) has not yet been examined in regard to its effectiveness in ameliorating cerebral blood flow impairment in diabetes. The objective of this study is to examine the long-term effect of THC supplementation on the cerebral microcirculation in diabetes, using streptozotocin (STZ)-induced diabetic rats. Methods: Diabetes was induced in male Wistar Furth rats by a single intravenous injection of STZ (55 mg/kg BW). The rats were divided into control and diabetic groups either with or without THC supplementation. THC was supplemented at a dose of 100mg/kg BW for 24 weeks. The cerebral microcirculation was directly observed using fluorescence video microscopy. The regional cerebral blood flow (rCBF) was continuously measured using laser Doppler flowmetry. Leukocyte adhesion to endothelium was evaluated in cerebral post-capillary venules by counting the number of adherent cells labeled with rhodamine 6G. Results: Compared to non-diabetic rats, the diabetic rats demonstrated a significant reduction of the rCBF while leukocyte adhesion was significantly increased. In STZ rats with THC supplementation, the rCBF was significantly greater, whereas the leukocyte adhesion was significantly less than that in the STZ rats with no THC supplementation. Conclusion: Long-term supplementation of THC can markedly prevent cerebral blood-flow reduction as induced by diabetes.
ABSTRACT
Background: Due to technical difficulties of in vivo observation of blood flow and microvessels in bone, no study has been done concerning the role of blood flow in bone remodeling. Objective: To develop a new window chamber for microscopic observation of the microcirculation in living bone, and to examine the utility of the chamber using rat femur in health and diseases. Methods: A stainless chamber (19 mm in diameter and 5 mm in height) with a circular window (7.5 mm in diameter) for microscopic observation was developed. The chamber was put on rat femur which was exposed for direct observation of the microvasculature. Intravital observation was made of bone blood flow and microvessels, using fluorescence videomicroscopy and confocal laser microscopy. The utility of the chamber was examined based on images of microcirculation (normal and abnormal) in the femur bone. Results and conclusions: Images of rat femur microvasculature were enhanced in the quality by use of the femur window chamber. The new chamber provides a powerful tool for in vivo studies of the bone microcirculation in health and diseases.
ABSTRACT
Background: Estrogen synthesis decreases in the postmenopausal period inducing gingival periodontal disturbance. Estrogen replacement therapy has been used to reduce such gingival complications, although it has been limited by the adverse effect of estrogen. Objective: To investigate the effects of supplementation of genistein, a phytoestrogen derived from the soybean, on blood flow disturbance in the gingiva after menopause, using an ovariectomized rat model. Materials and methods: Female Wistar rats (220 - 280 g) were subjected to a bilateral ovariectomy (OVX rats). The rats were classified into four groups: sham-operated animals treated with vehicle (DMSO 100 μl/day,s.c) (Sham (veh); n = 6), OVX rats treated with vehicle (DMSO 100 μl/day,s.c) (OVX (veh); n = 6), OVX rats treated with 17β-estradiol (20 μg/kg/day,s.c) (OVX (E₂); n = 6) and OVX treated with genistein (0.25 mg/kg.BW/day,s.c) (OVX (gen); n = 6). Plasma estradiol, body weight, and gingival blood flow (GBF) were measured 3 weeks after OVX. For the GBF measurement, laser Doppler perfusion flowmetry was used. Results: Three weeks after OVX, plasma estradiol levels in three groups of OVX rats were significantly lower than the sham-operated control (p \< 0.05). Body weight increased in OVX (veh) and OVX (gen) groups (p \< 0.001). The GBF increased significantly in OVX (veh) compared to the Sham (veh) group (p \< 0.05), indicating that GBF disturbance due to the lack of estrogen was improved by oral supplemention of 17β-estradiol or genistein. Conclusion: Genistein supplementation improves disturbed gingival blood flow induced in ovariectomized-rats. Genistein might have oral health benefits after menopause.
ABSTRACT
Background: In a tumor, hypoxia-inducible factor-1α (HIF-1α) and vascular endothelial cell growth factor (VEGF) are induced to promote angiogenesis for the growth and metastasis of cells. There have been very few studies to examine in vivo relation between HIF-1α and VEGF during tumor progression. Objective: To study the relationship between HIF-1α and VEGF expressions under neovascularization induced by hepatocellular carcinoma cells (HepG2) implanted in nude mice. Methods: Male BALB/c-nude mice 8-10 weeks of age were used. A chamber was prepared on the dorsal skin in which HepG2 was transplanted to induce a tumor. On the day of the experiment, and on days 2, 7, and 14, microcirculation within the chamber was observed using fluorescence videomicroscopy. Based on the recorded video images, capillary vascularity (CV) was measured to examine tumor neovascularization. VEGF expression was measured in blood (serum) withdrawn, using enzyme immunoassay, while HIF-1α expression was measured on samples isolated from tumor tissue, using immunohistochemistry. Results: The measured CV significantly increased on day 7 and 14 compared to the aged-matched controls (p \< 0.05). HIF-1α markedly expressed on day 2, and the expression declined on day 7 and 14 post-inoculation. VEGF expression in serum increased more on day 7 and 14 than on day 2. HIF-1α expression decreased with the increase in VEGF expression from 2 to 14 days after HepG2 implantation, showing a reverse correlation. Conclusion: HIF-1α expression existed prior to both VEGF expression and neovascularization in the tumor. An inhibitor of HIF-1α might be a therapeutic agent for reducing neovascularization via adaptation to hypoxia in tumors.
ABSTRACT
Background: Many clinical reports have indicated that ascorbic acid (vitamin C) improves vasodilatory impairments in patients with diabetes mellitus, but there is very little in vivo evidence to demonstrate its effectiveness on the brain. Objective: To investigate long-term effects of oral vitamin C administration on the cerebral microvascular vasodilation in diabetes, using streptozotocin (STZ)-induced diabetic rats. Materials and methods: Diabetes was induced in male Wistar Furth rats by a single intravenous injection of STZ (55 mg/kg b.w). Ascorbic acid (vitamin C) was administered in drinking water (1g/l). The rats were divided into control and diabetic groups with or without administration of vitamin C. The cerebral microcirculation was observed at different times (12, 24 and 36 weeks) after vitamin C supplementation, using fluorescence videomicroscopy. Responses of cerebral arterioles to acetylcholine (ACh), adenosine-5 diphosphate (ADP) and nitroglycerine (NTG) were studied by measuring diameters of cerebral arterioles before and after topical application on the cortical surface. Results: The vasodilatory responses of cerebral arterioles to ACh and ADP were significantly decreased in diabetic rats, compared with non-diabetic (control) rats. The response to NTG was not altered in diabetic rats, indicating that the vasodilatory impairment involves at the endothelium. The impaired endothelium-dependent vasodilation was prevented by long-term vitamin C administration. Conclusion: Long-term oral vitamin C administration might be of clinical relevance in improving cerebral microvascular vasodilatory impairment in diabetes.