3',4'-Dihydroxyflavonol down-regulates monocyte chemoattractant protein-1 in smooth muscle: role of focal adhesion kinase and PDGF receptor signalling

3',4'-Dihydroxyflavonol Attenuates Lipopolysaccharide-Induced Neuroinflammatory Responses of Microglial Cells by Suppressing AKT-mTOR and NF-κB Pathways

Microglia-related neuroinflammation contributes to the pathogenesis of a variety of neurodegenerative disorders such as Alzheimer's disease. The synthetic flavonoid, 3',4'-dihydroxyflavonol (3,3',4'-trihydroxyflavone), has been shown to protect brain or myocardial ischemia reperfusion-induced cell death and prevent the aggregation of amyloid-β protein, a process that causes progressive neurodegeneration in Alzheimer's disease. Here, we explored the anti-neuroinflammatory ability of 3',4'-dihydroxyflavonol in lipopolysaccharide (LPS)-activated MG6 microglial cells. 3',4'-Dihydroxyflavonol attenuated LPS-induced tumor necrosis factor-α and nitric oxide secretion in MG6 cells. LPS-induced phosphorylation of mammalian target of rapamycin (mTOR), nuclear factor-κB (NF-κB), and protein kinase B (AKT) (which are all associated with the neuroinflammatory response in microglia) were attenuated by 3',4'-dihydroxyflavonol treatment. Treatment with the mTOR inhibitor, rapamycin, NF-κB inhibitor, caffeic acid phenethyl ester, or AKT inhibitor, LY294002, also attenuated LPS-induced tumor necrosis factor-α and nitric oxide secretion in MG6 cells. LY294002 treatment attenuated LPS-induced phosphorylation of mTOR and NF-κB in MG6 cells. Hence, our study suggests that 3',4'-dihydroxyflavonol can attenuate the neuroinflammatory response of microglial cells by suppressing the AKT-mTOR and NF-κB pathways.

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.

Prevention and management of type II diabetes chronic complications: the role of polyphenols (Mini-Review)

The numerous complications of diabetes may be at least in part generated by the oxidative stress associated with the constant state of hyperglycemia. Polyphenols are plant based secondary metabolites that have high potentials in the prevention and treatment of some diseases, in particular those that involve oxidative stress, such as complications of diabetes. The purpose of this narrative review is to show the main evidence regarding the role of polyphenols in treating and preventing these complications. For the bibliographic research, the papers published up to March 15, 2021 were considered and the search terms included words relating to polyphenols, their classes and some more known compounds, in association with the complications of diabetes. There are numerous studies showing how polyphenols are active against endothelial damage induced by diabetes, oxidative stress and hyperinflammatory states that are at the origin of the complications of diabetes. Compounds such as flavonoids, but also anthocyanins, stilbenes or lignans slow the progression of kidney damage, prevent ischemic events and diabetic nephropathy. Many of these studies are preclinical, in cellular or animal models. The role of polyphenols in the prevention and treatment of diabetes complications is undoubtedly promising. However, more clinical trials need to be implemented to understand the real effectiveness of these compounds.

Butanolic Extract of Noni Inhibits Proliferation, Inflammation, and Proprotein Convertase Subtilisin Kexin Type 9 (PCSK9) Expression in Cultured Smooth Muscle Cells

Platelet-derived growth factor-BB (PDGF-BB) plays a central role in smooth muscle cell (SMC) proliferation and inflammation, being involved in atherosclerotic cardiovascular disease. We have previously found that butanolic extract of noni, a tropical plant belonging to the family Rubiaceae, exerts anti-inflammatory effects on endothelial cells exposed to advanced glycation end products (AGEs). Here, we examined the effects of noni extract on oxidative stress production, growth, and inflammatory reactions in PDGF-BB or AGE-exposed SMCs. Reactive oxygen species (ROS) generation, cell proliferation, and adhesion were measured by a fluorescent dye, a colorimetric agent, and labeled THP-1 cells, respectively. Gene and protein expression was evaluated by real-time reverse transcription-polymerase chain reaction and Western blot analysis. Butanolic extract of noni reduced ROS production, monocyte chemoattractant protein-1, intercellular adhesion molecule-1, and proprotein convertase subtilisin kexin type 9 (PCSK9) expression, and proliferation in, and THP-1 cell adhesion to, PDGF-BB-exposed SMCs. Gene expression and protein level of receptor for AGEs (RAGE) were significantly decreased by noni extract in SMCs. Furthermore, AGEs significantly increased PCSK9 mRNA and protein levels in SMCs, which were inhibited by noni extract or an antioxidant N-acetylcysteine. Our present study suggests that butanolic extract of noni not only inhibits the PDGF-BB-induced proliferation and inflammatory reactions in SMCs through its antioxidative properties but also reduces PCSK9 levels in AGE-exposed SMCs via suppression of RAGE expression. Butanolic extract of noni may play a protective role against atherosclerosis.

Macrophage-stimulated microRNA expression in mural cells promotes transplantation-induced neointima formation

In this study, we tested the possibility that macrophages might contribute to neointima formation by stimulating microRNA expressions in mural cells. Thoracic aortas from F344 rats were transplanted into recipient Lewis rats. Clodronate liposome was used for in vivo macrophage depletion. Using miR-21 as a prototypic example of vascular enriched microRNA, we showed that macrophage depletion reduced the expression level of miR-21, which was upregulated in the allograft. This effect of macrophage depletion was accompanied by attenuations in neointimal hyperplasia and transplantation-induced vascular inflammation. Using in vitro assays, we identified that macrophages might stimulate miR-21 expression in smooth muscle cells and adventitial fibroblasts via the release of tumor necrosis factor-α. We also showed that silencing of miR-21 suppressed tumor necrosis factor-induced proliferation, migration, and inflammatory responses in mural cells. Our results suggest that macrophage may promote transplantation-induced neointima formation by stimulating miR-21 expression in vascular mural cells, which promotes mural cell proliferation, migration and/or inflammation. Moreover, we have established that tumor necrosis factor-α has a major role in mediating this paracrine process.

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.

The antioxidant compound tert-butylhydroquinone activates Akt in myocardium, suppresses apoptosis and ameliorates pressure overload-induced cardiac dysfunction

Tert-butylhydroquinone (TBHQ) is an antioxidant compound which shows multiple cytoprotective actions. We evaluated the effects of TBHQ on pathological cardiac remodeling and dysfunction induced by chronic overload. Pressure overload was created by transverse aortic constriction (TAC) in male C57BL/6 mice. TBHQ was incorporated in the diet and administered for 4 weeks. TBHQ treatment prevented left ventricular dilatation and cardiac dysfunction induced by TAC, and decreased the prevalence of myocardial apoptosis. The beneficial effects of TBHQ were associated with an increase in Akt activation, but not related to activations of Nrf2 or AMP-activated protein kinase. TBHQ-induced Akt activation was accompanied by increased phosphorylation of Bad, glycogen synthase kinase-3β (GSK-3β) and mammalian target of rapamycin (mTOR). Mechanistically, we showed that in cultured H9c2 cells and primary cardiac myocytes, TBHQ stimulated Akt phosphorylation and suppressed oxidant-induced apoptosis; this effect was abolished by wortmannin or an Akt inhibitor. Blockade of the Akt pathway in vivo accelerated cardiac dysfunction, and abrogated the protective effects of TBHQ. TBHQ also reduced the reactive aldehyde production and protein carbonylation in stressed myocardium. We suggest that TBHQ treatment may represent a novel strategy for timely activation of the cytoprotective Akt pathway in stressed myocardium.

TRAIL/DR5 signaling promotes macrophage foam cell formation by modulating scavenger receptor expression

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL/Apo2L) has been shown to have protective effects against atherosclerosis. However, whether TRAIL has any effects on expression of macrophage scavenger receptors and lipid uptake has not yet been studied. Macrophage lines RAW264.7 and THP-1, and mouse primary peritoneal macrophages, were cultured in vitro and treated with recombinant human TRAIL. Real-time PCR and western blot were performed to measure mRNA and protein expressions. Foam cell formation was assessed by internalization of acetylated and oxidized low-density lipoproteins (LDL). Apoptosis was measured by terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling. We found that TRAIL treatment increased expression of scavenger receptor (SR)-AI and SR-BI in a time- and dose-dependent manner, and this effect was accompanied by increased foam cell formation. These effects of TRAIL were abolished by a TRAIL neutralizing antibody or in DR5 receptor-deficient macrophages. The increased LDL uptake by TRAIL was blocked by SR-AI gene silencing or the SR-AI inhibitor poly(I:C), while SR-BI blockade with BLT-1 had no effect. TRAIL-induced SR-AI expression was blocked by the inhibitor of p38 mitogen-activated protein kinase, but not by inhibitors of ERK1/2 or JNK. TRAIL also induced apoptosis in macrophages. In contrast to macrophages, TRAIL showed little effects on SR expression or apoptosis in vascular smooth muscle cells. In conclusion, our results demonstrate that TRAIL promotes macrophage lipid uptake via SR-AI upregulation through activation of the p38 pathway.

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.

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.