3′,4′-Dihydroxyflavonol improves post-ischaemic coronary endothelial function following 7days reperfusion in sheep

3',4'-Dihydroxyflavonol Inhibits Fibrotic Response in a Rabbit Model of Glaucoma Filtration Surgery

Post-operative fibrosis of the filtering bleb limits the success of glaucoma filtration surgery (GFS). To minimise subconjunctival scarring following GFS, treatment with antimetabolites such as Mitomycin C (MMC) has become standard practice; however, their use is associated with considerable side effects. This study aimed to investigate the anti-scarring properties of 3',4'-dihydroxyflavonol (DiOHF). GFS was performed in New Zealand white rabbits who received eye drops of DiOHF three times daily and vehicle eye drops after surgery (n = 5) or a single intraoperative treatment of MMC (n = 5). Blebs were imaged immediately following surgery and on days 7, 15, 21, and 28 for clinical examination. On day 28, eyes were harvested to assess collagen deposition, expression of α-SMA, oxidative stress, angiogenesis, fibroblast activity, and inflammation in the conjunctiva/Tenon's layer. At 7 and 28 days post-GFS, MMC-treated blebs were more ischaemic than DiOHF- or vehicle-treated blebs. On day 28, DiOHF treatment significantly suppressed collagen accumulation, CD31 expression, Vimentin expression, and CD45 expression compared to the vehicle control. No difference was observed in 3-Nitrotyrosine or αSMA expression between treatment groups. Treatment with DiOHF reduced conjunctival scarring and angiogenesis in rabbits with GFS, which was comparable to MMC. DiOHF may be a safer and more effective wound-modulating agent than conventional antifibrotic therapy in GFS.

Apoptosis of hippocampus and cerebellum induced with brain ischemia reperfusion prevented by 3',4'-dihydroxyflavonol (DiOHF)

The present study aimed to determine the effect of 3',4'-dihydroxyflavonol (DiOHF) on apoptosis in the cerebellum and hippocampus in rats with ischemia-reperfusion. A total of 38 Wistar albino male rats were used. Experimental groups were designed as Group 1-Sham; Group 2-Ischemia-reperfusion (IR), in which animals were anesthetized and carotid arteries ligated for 30 minutes (ischemia) and reperfused 30 minutes; Group 3- IR + DiOHF (10 mg/kg); Group 4- Ischemia + DiOHF (10 mg/kg) + reperfusion; Group 5-DiOHF + IR. DiOHF was supplemented as 10 mg/kg by intraperitoneal injection 30 minutes before IR. Following application, the animals were sacrificed under general anesthetic by cervical dislocation, and the cerebellum and hippocampus tissues were analyzed for apoptosis. IR significantly increased hippocampus and cerebellum apoptosis activity, confirmed by Hematoxylin-Eosin, TUNEL labeling, and Caspase-8 activity. However, these values were significantly suppressed by the administration of DiOHF, especially when used before the ischemia and reperfusion. The results of the study show that increased apoptosis in the cerebellum and hippocampus tissue was inhibited by intraperitoneal DiOHF supplementation.

NP202 treatment improves left ventricular systolic function and attenuates pathological remodelling following chronic myocardial infarction

AIMS

Myocardial injury is a major contributor to left ventricular (LV) remodelling activating neurohormonal and inflammatory processes that create an environment of enhanced oxidative stress. This results in geometric and structural alterations leading to reduced LV systolic function. In this study we evaluated the efficacy of NP202, a synthetic flavonol, on cardiac remodelling in a chronic model of myocardial infarction (MI).

MAIN METHODS

A rat model of chronic MI was induced by permanent surgical ligation of the coronary artery. NP202 treatment was commenced 2 days post-MI for 6 weeks at different doses (1, 10 and 20 mg/kg/day) to determine efficacy. Cardiac function was assessed by echocardiography prior to treatment and at week 6, and pressure-volume measurements were performed prior to tissue collection. Tissues were analysed for changes in fibrotic and inflammatory markers using immunohistochemistry and gene expression analysis.

KEY FINDINGS

Rats treated with NP202 demonstrated improved LV systolic function and LV geometry compared to vehicle treated animals. Furthermore, measures of hypertrophy and interstitial fibrosis were attenuated in the non-infarct region of the myocardium with NP202 at the higher dose of 20 mg/kg (P < 0.05). At the tissue level, NP202 reduced monocyte chemoattractant protein-1 expression (P < 0.05) and tended to attenuate active caspase-3 expression to similar levels observed in sham animals (P = 0.075).

SIGNIFICANCE

Improved LV function and structural changes observed with NP202 may be mediated through inhibition of inflammatory and apoptotic processes in the MI setting. NP202 could therefore prove a useful addition to standard therapy in patients with post-MI LV dysfunction.

Current state and future perspective of cardiovascular medicines derived from natural products

The contribution of natural products (NPs) to cardiovascular medicine has been extensively documented, and many have been used for centuries. Cardiovascular disease (CVD) is the leading cause of morbidity and mortality worldwide. Over the past 40 years, approximately 50% of newly developed cardiovascular drugs were based on NPs, suggesting that NPs provide essential skeletal structures for the discovery of novel medicines. After a period of lower productivity since the 1990s, NPs have recently regained scientific and commercial attention, leveraging the wealth of knowledge provided by multi-omics, combinatorial biosynthesis, synthetic biology, integrative pharmacology, analytical and computational technologies. In addition, as a crucial part of complementary and alternative medicine, Traditional Chinese Medicine has increasingly drawn attention as an important source of NPs for cardiovascular drug discovery. Given their structural diversity and biological activity NPs are one of the most valuable sources of drugs and drug leads. In this review, we briefly described the characteristics and classification of NPs in CVDs. Then, we provide an up to date summary on the therapeutic potential and the underlying mechanisms of action of NPs in CVDs, and the current view and future prospect of developing safer and more effective cardiovascular drugs based on NPs.

7‑Difluoromethyl‑5,4'‑dimethoxygenistein exerts anti‑angiogenic effects on acute promyelocytic leukemia HL‑60 cells by inhibiting the TLR4/NF‑κB signaling pathway

Angiogenesis plays an important role in the development and metastasis of tumors, and anti-angiogenesis agents are used to treat tumors. For example, the acute promyelocytic leukemia (APL) may be treated with arsenic trioxide. Angiogenesis in APL is a multi-step dynamic equilibrium process coordinated by various angiogenic stimulators and inhibitors, which play key roles in the occurrence, progression and chemosensitivity of this disease. Our research group previously synthesized 7-difluoromethyl-5,4′-dimethoxygenistein (DFMG), and found that it inhibits angiogenesis during atherosclerotic plaque formation. In the present study, the effect and mechanism of DFMG in angiogenesis induced by APL HL-60 cells was investigated using a chick embryo chorioallantoic membrane model and Matrigel tubule formation assays. The results obtained revealed an anti-angiogenesis effect of DFMG towards HL-60 cells. When the Toll-like receptor 4/nuclear factor-κB (TLR4/NF-κB) signaling pathway was inhibited, the anti-angiogenic effect of DFMG was further enhanced. However, when the TLR4/NF-κB signaling pathway was activated, the anti-angiogenic effect of DFMG was attenuated. These results demonstrated that DFMG inhibits angiogenesis induced by APL HL-60 cells, and provides insights into the mechanism by which DFMG inhibits the TLR4/NF-κB signaling pathway. In conclusion, in the present study, the anti-angiogenesis effect of DFMG on APL has been reported, and the mechanism by which DFMG induced the anti-angiogenesis effect was explored. These findings have provided a potential new drug candidate for the treatment of patients with APL.

Flavonols in the Prevention of Diabetes-induced Vascular Dysfunction

As flavonols are present in fruits and vegetables, they are consumed in considerable amounts in the diet. There is growing evidence that the well-recognized antioxidant, anti-inflammatory, and vasorelaxant actions of flavonols may, at least in part, result from modulation of biochemical signaling pathways and kinases. It is well established that diabetes is associated with increased cardiovascular morbidity and mortality. Despite clinical management of blood glucose levels, diabetes often results in cardiovascular disease. There is good evidence that endothelial dysfunction contributes significantly to the progression of diabetic cardiovascular diseases. This review describes the biological actions of flavonols that may ameliorate adverse cardiovascular events in diabetes. We discuss evidence that flavonols may be developed as novel pharmacological agents to prevent diabetes-induced vascular dysfunction.

Treatment with quercetin and 3',4'-dihydroxyflavonol inhibits platelet function and reduces thrombus formation in vivo

Flavonols are polyphenolic compounds with reported cardiovascular benefits and have been shown to exhibit antiplatelet properties in vitro. While some studies have shown inhibition of platelet aggregation following dietary supplementation with flavonol rich foods, few studies have assessed the ability of flavonols to inhibit platelet mediated thrombus generation in vivo. Furthermore, the duration of benefit and the influence of different dosing regimens remain unclear. In this study we investigate the ability of two structurally related flavonols; quercetin (Que) and 3',4'-dihydroxyflavonol (DiOHF) to inhibit platelet aggregation, platelet granule exocytosis and vessel occlusion in a well characterized mouse model of platelet mediated arterial thrombosis. We investigated the effect of a single 6 mg/kg intravenous bolus and daily 6 mg/kg intraperitoneal doses over seven consecutive days. Carotid artery blood flow after injury was better maintained in mice treated with both Que and DiOHF when compared to the vehicle for both dosage regimens. This improved blood flow corresponded to inhibition of platelet aggregation and platelet dense granule exocytosis following chemical stimulation of PAR4. We therefore provide evidence of inhibition of platelet-mediated arterial thrombosis by flavonols in vivo, and demonstrate that this effect persists for at least 24 h after the last intraperitoneal dose. These data suggest a potential clinical role for flavonols as anti-platelet therapy.

Cardioprotective 3',4'-dihydroxyflavonol attenuation of JNK and p38(MAPK) signalling involves CaMKII inhibition

DiOHF (3',4'-dihydroxyflavonol) is cardioprotective against I/R (ischaemia/reperfusion) injury. The biological activities of flavonols are associated with kinase modulation to alter cell signalling. We thus investigated the effects of DiOHF on the activation of MAPKs (mitogen-activated protein kinases) that regulate the cardiac stress response. In an ovine model of I/R, JNK (c-Jun N-terminal kinase), p38(MAPK), ERK (extracellular-signal-regulated kinase) and Akt were activated, and NP202, a pro-drug of DiOHF, reduced infarct size and inhibited JNK and p38(MAPK) activation, whereas ERK and Akt phosphorylation were unaltered. Similarly, in cultured myoblasts, DiOHF pre-treatment preserved viability and inhibited activation of JNK and p38(MAPK), but not ERK in response to acute oxidative and chemotoxic stress. Furthermore, DiOHF prevented stress-activation of the direct upstream regulators MKK4/7 (MAPK kinase 4/7) and MKK3/6 respectively. We utilized small-molecule affinity purification and identified CaMKII (Ca(2+)/calmodulin-dependent protein kinase II) as a kinase targeted by DiOHF and demonstrated potent CaMKII inhibition by DiOHF in vitro. Moreover, the specific inhibition of CaMKII with KN-93, but not KN-92, prevented oxidative stress-induced activation of JNK and p38(MAPK). The present study indicates DiOHF inhibition of CaMKII and attenuation of MKK3/6→p38(MAPK) and MKK4/7→JNK signalling as a requirement for the protective effects of DiOHF against stress stimuli and myocardial I/R injury.

Anti-neoplastic activity of two flavone isomers derived from Gnaphalium elegans and Achyrocline bogotensis

Over 4000 flavonoids have been identified so far and among these, many are known to have antitumor activities. The basis of the relationships between chemical structures, type and position of substituent groups and the effects these compounds exert specifically on cancer cells are not completely elucidated. Here we report the differential cytotoxic effects of two flavone isomers on human cancer cells from breast (MCF7, SK-BR-3), colon (Caco-2, HCT116), pancreas (MIA PaCa, Panc 28), and prostate (PC3, LNCaP) that vary in differentiation status and tumorigenic potential. These flavones are derived from plants of the family Asteraceae, genera Gnaphalium and Achyrocline reputed to have anti-cancer properties. Our studies indicate that 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays potent activity against more differentiated carcinomas of the colon (Caco-2), and pancreas (Panc28), whereas 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) cytototoxic action is observed on poorly differentiated carcinomas of the colon (HCT116), pancreas (Mia PaCa), and breast (SK-BR3). Both flavones induced cell death (>50%) as proven by MTT cell viability assay in these cancer cell lines, all of which are regarded as highly tumorigenic. At the concentrations studied (5-80 µM), neither flavone demonstrated activity against the less tumorigenic cell lines, breast cancer MCF-7 cells, androgen-responsive LNCaP human prostate cancer line, and androgen-unresponsive PC3 prostate cancer cells. 5,7-dihydroxy-3,6,8-trimethoxy-2-phenyl-4H-chromen-4-one (5,7-dihydroxy-3,6,8-trimethoxy flavone) displays activity against more differentiated carcinomas of the colon and pancreas, but minimal cytotoxicity on poorly differentiated carcinomas of these organs. On the contrary, 3,5-dihydroxy-6,7,8-trimethoxy-2-phenyl-4H-chromen-4-one (3,5-dihydroxy-6,7,8-trimethoxy flavone) is highly cytotoxic to poorly differentiated carcinomas of the colon, pancreas, and breast with minimal activity against more differentiated carcinomas of the same organs. These differential effects suggest activation of distinct apoptotic pathways. In conclusion, the specific chemical properties of these two flavone isomers dictate mechanistic properties which may be relevant when evaluating biological responses to flavones.

3',4'-Dihydroxyflavonol reduces superoxide and improves nitric oxide function in diabetic rat mesenteric arteries

Background

3',4'-Dihydroxyflavonol (DiOHF) is an effective antioxidant that acutely preserves nitric oxide (NO) activity in the presence of elevated reactive oxygen species (ROS). We hypothesized that DiOHF treatment (7 days, 1 mg/kg per day s.c.) would improve relaxation in mesenteric arteries from diabetic rats where endothelial dysfunction is associated with elevated oxidant stress.

Methodology/Principal Findings

In mesenteric arteries from diabetic rats there was an increase in ROS, measured by L-012 and 2',7'-dichlorodihydrofluorescein diacetate fluorescence. NADPH oxidase-derived superoxide levels, assayed by lucigenin chemiluminescence, were also significantly increased in diabetic mesenteric arteries (diabetes, 4892±946 counts/mg versus normal 2486±344 counts/mg, n = 7–10, p<0.01) associated with an increase in Nox2 expression but DiOHF (2094±300 counts/mg, n = 10, p<0.001) reversed that effect. Acetylcholine (ACh)-induced relaxation of mesenteric arteries was assessed using wire myography (pEC₅₀ = 7.94±0.13 n = 12). Diabetes significantly reduced the sensitivity to ACh and treatment with DiOHF prevented endothelial dysfunction (pEC₅₀, diabetic 6.86±0.12 versus diabetic+DiOHF, 7.49±0.13, n = 11, p<0.01). The contribution of NO versus endothelium-derived hyperpolarizing factor (EDHF) to ACh-induced relaxation was assessed by evaluating responses in the presence of TRAM-34+apamin+iberiotoxin or N-nitro-L-arginine+ODQ respectively. Diabetes impaired the contribution of both NO (maximum relaxation, R_max diabetic 24±7 versus normal, 68±10, n = 9–10, p<0.01) and EDHF (pEC₅₀, diabetic 6.63±0.15 versus normal, 7.14±0.12, n = 10–11, p<0.01) to endothelium-dependent relaxation. DiOHF treatment did not significantly affect the EDHF contribution but enhanced NO-mediated relaxation (R_max 69±6, n = 11, p<0.01). Western blotting demonstrated that diabetes also decreased expression and increased uncoupling of endothelial NO synthase (eNOS). Treatment of the diabetic rats with DiOHF significantly reduced vascular ROS and restored NO-mediated endothelium-dependent relaxation. Treatment of the diabetic rats with DiOHF also increased eNOS expression, both in total and as a dimer.

Conclusions/Significance

DiOHF improves NO activity in diabetes by reducing Nox2-dependent superoxide production and preventing eNOS uncoupling to improve endothelial function.

Cardioprotection from ischaemia-reperfusion injury by a novel flavonol that reduces activation of p38 MAPK

Oxidative stress, activation of intracellular protein kinases and cardiomyocyte apoptosis are known mediators of cardiac ischaemia/reperfusion injury. The sites at which NP202, a novel water soluble pro-drug of 3',4'-dihydroxyflavonol (DiOHF), acts in this cascade to cause cardioprotection are unknown. In this study we examined the ability of NP202 to reduce infarct size after a prolonged period of ischaemia and reperfusion. In addition, we tested whether NP202 inhibits pro-apoptotic signalling, apoptosis and inflammation following myocardial ischaemia and reperfusion. Sheep were anaesthetised, the heart exposed and the 2nd branch of the left anterior descending coronary artery isolated. The artery was occluded for 3h and, five minutes before 3h of reperfusion was commenced, sheep were treated with intravenous vehicle or NP202. At the end of reperfusion infarct size was measured and normal left ventricle, non-infarcted area-at-risk and infarcted myocardium were collected to identify polymorphonuclear leukocytes (PMN) or apoptotic cells (TUNEL-positive), or assessed for activation of mitogen-activated protein kinase (MAPK) pathways by Western blot analysis. Compared with vehicle treatment, NP202 reduced infarct size (-20 ± 4%, P<0.05) and decreased the number of PMNs and TUNEL-positive cells in the area-at-risk (-35 ± 16% and -52 ± 19%, respectively) and infarcted tissue (-57 ± 9 and -81 ± 5%, respectively, P<0.05). Furthermore, NP202 significantly reduced I/R-induced elevated p38 MAPK phosphorylation (by 67 ± 4%, P<0.05) in the area-at-risk zone. In conclusion, the novel aqueous flavonol NP202 provided significant cardioprotection from clinically relevant prolonged myocardial ischaemia when administered just before reperfusion. Efficacy of NP202 was also associated with reduced p38 MAPK activation, inflammation and apoptotic cell death.