Schisanhenol Attenuates OxLDL-Induced Endothelial Dysfunction via an AMPK-Dependent Mechanism

Atherosclerotic cardiovascular diseases, commonly known as the formation of fibrofatty lesions in the artery wall, are the leading causes of death globally. Oxidized low-density lipoprotein (oxLDL) is one of the major components of atherosclerotic plaques. It is evident that dietary supplementation containing sources of antioxidants can prevent atherogenic diseases. Schisanhenol (SAL), a dibenzocyclooctene lignin, has been shown to attenuate oxLDL-induced apoptosis and the generation of reactive oxygen species (ROS) in endothelial cells. However, the underlying molecular mechanisms are still largely unknown. In this study, human umbilical vein endothelial cells (HUVECs) were pre-treated with SAL and oxLDL. Our results showed that adenosine monophosphate-activated protein kinase (AMPK) phosphorylation was enhanced in cells pre-treated with SAL in time-dependent and dose-dependent manners. Subsequently, oxLDL-induced AMPK dephosphorylation and protein kinase C (PKC) phosphorylation were significantly reversed in the presence of SAL. In addition, SAL treatment led to an inhibiting effect on the oxLDL-induced membrane assembly of NADPH oxidase subunits, and a similar effect was observed in ROS generation. This effect was further confirmed using knockdown AMPK with small interfering RNA (siRNA) and pharmaceutical reagents, such as the AMPK activator (AICAR), PKC inhibitor (Gö 6983), and ROS inhibitor (DPI). Furthermore, the oxLDL-induced intracellular calcium rise and the potential collapse of the mitochondrial membrane reduced the Bcl-2/Bax ratio, and released cytochrome c from the mitochondria, leading to the subsequent activation of caspase-3 in HUVECs, which were also markedly suppressed by SAL pretreatment. The results mentioned above may provide additional insights into the possible molecular mechanisms underlying the cardiovascular protective effects of SAL.

Schisanhenol ameliorates oxLDL-caused endothelial dysfunction by inhibiting LOX-1 signaling

Atherosclerotic lesions play a critical role in leading cardiovascular diseases. Oxidized low-density lipoprotein (OxLDL) is a vital risk factor for atherosclerosis since it acts a crucial role in endothelial dysfunction and foam cell formation. Schisanhenol, a composition extracted from the fruit of Schisandra rubriflora, has been reported to have antioxidative effects on human LDL oxidation. This study investigates whether Schisanhenol protects against oxLDL-mediated endothelial damage by modulating the lectin-like oxLDL receptor-1 (LOX-1)-mediated inflammatory processes. Human umbilical vein endothelial cells (HUVECs) were pre-treated with 10 or 20 μM Schisanhenol for 2 h and then exposed to 150 μg/mL oxLDL. We revealed that Schisanhenol reduced oxLDL-enhanced LOX-1 expression. We also found that oxLDL down-regulated endothelial nitric oxide synthase (eNOS) as well as activated inducible NOS (iNOS), thereby enhancing the generation of nitric oxide (NO). Moreover, oxLDL elevated the expression levels of phosphorylated-p38MAPK, subsequently promoting NF-κB-modulated inflammatory responses. Pretreatment with Schisanhenol exerted significant cytoprotective function in all the above-mentioned detrimental events. Results from this present study reveal that Schisanhenol has a potential therapeutic effect on preventing oxLDL-induced endothelial injuries.

Quercetin Mitigates Cisplatin-Induced Oxidative Damage and Apoptosis in Cardiomyocytes through Nrf2/HO-1 Signaling Pathway

Cisplatin is massively used to treat solid tumors. However, several severe adverse effects, such as cardiotoxicity, are obstacles to its clinical application. Cardiotoxicity may lead to congestive heart failure and even sudden cardiac death in patients receiving cisplatin. Therefore, finding a novel therapeutic strategy for the prevention of cisplatin-induced cardiotoxicity is urgent. Quercetin is a flavonol compound that can be found in dietary fruits and vegetables. The antioxidant function and anti-inflammatory capacity of quercetin have been reported. However, whether quercetin could protect against cisplatin-caused apoptosis and cellular damage in cardiomyocytes is still unclear. H9c2 cardiomyocytes were treated with cisplatin (40 μM) for 24 h to induce cellular damage with or without quercetin pretreatment. We found that quercetin activates Nrf2 and HO-1 expression, thereby mitigating cisplatin-caused cytotoxicity in H9c2 cells. Quercetin also increases SOD levels, maintains mitochondrial function, and reduces oxidative stress under cisplatin stimulation. Quercetin attenuates cisplatin-induced apoptosis and inflammation in H9c2 cardiomyocytes; however, these cytoprotective effects were diminished by silencing Nrf2 and HO-1. In conclusion, this study reports that quercetin has the potential to antagonize cisplatin-caused cardiotoxicity by reducing ROS-mediated mitochondrial damage and inflammation via the Nrf2/HO-1 and p38MAPK/NF-[Formula: see text]Bp65/IL-8 signaling pathway. This study provided the theoretical basis and experimental proof for the clinical application of quercetin as a new effective strategy to relieve chemotherapy-induced cardiotoxicity.

Low-level laser prevents doxorubicin-induced skeletal muscle atrophy by modulating AMPK/SIRT1/PCG-1α-mediated mitochondrial function, apoptosis and up-regulation of pro-inflammatory responses

Background

Doxorubicin (Dox) is a widely used anthracycline drug to treat cancer, yet numerous adverse effects influencing different organs may offset the treatment outcome, which in turn affects the patient’s quality of life. Low-level lasers (LLLs) have resulted in several novel indications in addition to traditional orthopedic conditions, such as increased fatigue resistance and muscle strength. However, the mechanisms by which LLL irradiation exerts beneficial effects on muscle atrophy are still largely unknown.

Results

The present study aimed to test our hypothesis that LLL irradiation protects skeletal muscles against Dox-induced muscle wasting by using both animal and C2C12 myoblast cell models. We established SD rats treated with 4 consecutive Dox injections (12 mg/kg cumulative dose) and C2C12 myoblast cells incubated with 2 μM Dox to explore the protective effects of LLL irradiation. We found that LLL irradiation markedly alleviated Dox-induced muscle wasting in rats. Additionally, LLL irradiation inhibited Dox-induced mitochondrial dysfunction, apoptosis, and oxidative stress via the activation of AMPK and upregulation of SIRT1 with its downstream signaling PGC-1α. These aforementioned beneficial effects of LLL irradiation were reversed by knockdown AMPK, SIRT1, and PGC-1α in C2C12 cells transfected with siRNA and were negated by cotreatment with mitochondrial antioxidant and P38MAPK inhibitor. Therefore, AMPK/SIRT1/PGC-1α pathway activation may represent a new mechanism by which LLL irradiation exerts protection against Dox myotoxicity through preservation of mitochondrial homeostasis and alleviation of oxidative stress and apoptosis.

Conclusion

Our findings may provide a novel adjuvant intervention that can potentially benefit cancer patients from Dox-induced muscle wasting.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13578-021-00719-w.

The molecular mechanisms underlying arecoline-induced cardiac fibrosis in rats

The areca nut is one of the most commonly consumed psychoactive substances worldwide, with an estimated consumption by approximately 10% of the world’s population, especially in some regions of South Asia, East Africa, and the tropical Pacific. Arecoline, the major areca nut alkaloid, has been classified as carcinogenic to humans as it adversely affects various organs, including the brain, heart, lungs, gastrointestinal tract, and reproductive organs. Earlier studies have established a link between areca nut chewing and cardiac arrhythmias, and yet research pertaining to the mechanisms underlying cardiotoxicity caused by arecoline is still preliminary. The main purpose of this study is to test the hypothesis that arecoline causes cardiac fibrosis through transforming growth factor-β (TGF-β)/Smad-mediated signaling pathways. Male Wistar rats were injected intraperitoneally with low (5 mg/kg/day) or high (50 mg/kg/day) doses of arecoline for 3 weeks. Results from Masson’s trichrome staining indicated that arecoline could induce cardiac fibrosis through collagen accumulation. Western blot analysis showed that TGF-β and p-Smad2/3 protein expression levels were markedly higher in the arecoline-injected rat hearts than in those of the control rats. Moreover, arecoline upregulated other fibrotic-related proteins, including SP1-mediated connective tissue growth factor expression. Tissue-type plasminogen activator and its inhibitor, plasminogen activator inhibitor, and matrix metalloproteinase (MMP) 9 were upregulated, and the inhibitor of MMP9 was downregulated. This study provides novel insight into the molecular mechanisms underlying arecoline-induced cardiac fibrosis. Taken together, the areca nut is a harmful substance, and the detrimental effects of arecoline on the heart are similar to that caused by oral submucous fibrosis.

Cordycepin Attenuates Palmitic Acid-Induced Inflammation and Apoptosis of Vascular Endothelial Cells through Mediating PI3K/Akt/eNOS Signaling Pathway

A well-known medicinal mushroom in the field of traditional Chinese medicine, Cordyceps sinensis, is a rare natural-occurring entomopathogenic fungus, and it typically grows at high altitudes on the plateau of the Himalayan. Previous studies indicated that cordycepin, the main bioactive chemical of Cordyceps sinensis, has very potent anticancer, anti-oxidant and anti-inflammatory activities. However, its protective effects against atherosclerotic changes in vascular endothelial cells have not been fully elucidated. In this study, we showed that pretreatment with cordycepin significantly attenuated palmitic acid (PA)-induced cytotoxicity, reactive oxygen species (ROS) generation, and inflammatory responses. We found that PA decreased phosphorylation of Akt, eNOS, and bioavailability of nitric oxide (NO), which in turn activated NF-[Formula: see text]B and the downstream inflammatory responses. All these detrimental events were markedly blocked by pretreatment with cordycepin. Moreover, cordycepin ameliorated destabilization of mitochondrial permeability, cytosolic calcium rises, and apoptotic features caused by PA. In addition, all these anti-inflammatory and anti-apoptosis effects of cordycepin were found to be inhibited by the PI3K and eNOS inhibitor, suggesting that its anti-atherosclerotic effects may partially be mediated by the PI3K/Akt/eNOS signaling pathway.

Epigallocatechin Gallate Reduces Homocysteine-Caused Oxidative Damages through Modulation SIRT1/AMPK Pathway in Endothelial Cells

Elevated plasma concentration of total homocysteine is a pathological condition that causes vascular endothelial injury and subsequently leads to the progression of endothelial apoptosis in atherosclerosis. Epigallocatechin gallate (EGCG), a well-known anti-oxidant in green tea, has been reported with benefits on metabolic and cardiovascular diseases. This study aimed to explore that EGCG ameliorates homocysteine-induced endothelial cell apoptosis through enhancing the sirtuin 1 (SIRT1)/AMP-activated protein kinase (AMPK) survival signaling pathway. Human umbilical endothelial cells were treated with homocysteine in the presence or absence of EGCG. We found that EGCG significantly increased the activities of SIRT1 and AMPK. EGCG diminished homocysteine-mediated nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation by inhibiting protein kinase C activation as well as reactive oxygen species (ROS) generation and recovered the activity of the endogenous antioxidant enzyme, superoxidase dismutase (SOD). Besides, EGCG also restores homocysteine-mediated dephosphorylation of Akt and decreases endothelial NO synthase (eNOS) expression. Furthermore, EGCG ameliorates homocysteine-activated pro-apoptotic events. The present study shows that EGCG prevents homocysteine-induced endothelial cell apoptosis via enhancing SIRT1/AMPK as well as Akt/eNOS signaling pathways. Results from this study indicated that EGCG might have some benefits for hyperhomocysteinemia.

Protective effects of luteolin against oxidative stress and mitochondrial dysfunction in endothelial cells

BACKGROUND AND AIMS

Luteolin is a common flavonoid that is abundantly present in various edible plants, it is known to exhibit beneficial effects on cardiovascular system. However, the mechanisms which underlie the protective effects of luteolin on endothelial cell damage caused by oxidative stress remains unclear. The purpose of this study is to test the hypothesis which states that luteolin protects against H₂O₂-induced oxidative stress via modulating ROS-mediated P38 MAPK/NF-κB and calcium-evoked mitochondrial apoptotic signalling pathways.

METHODS AND RESULTS

Human umbilical vein endothelial cells (HUVECs) were pretreated with luteolin prior to being stimulated by 600 μM H₂O₂ for another 24 h. The expression of native and phosphorylated-P38, IκB, NF-κB, native eNOS, phosphorylated-eNOS, iNOS and several apoptosis-related proteins were analyzed by Western blot. In addition, intracellular calcium was determined by fura-2 AM and mitochondrial membrane potential was examined by using JC1. Using the data gathered, we found indications that H₂O₂ induced P38 MAPK/NF-κB activation. H₂O₂ downregulated the expression of eNOS and upregulated iNOS, which in turn contribute to an elevated NO generation and protein nitrosylation. However, pretreatment with luteolin markedly reversed all of these alterations dose-dependently. Additionally, an intracellular calcium rise and subsequent mitochondrial membrane potential collapse, P53 phosphorylation, reduced BcL-2/Bax ratio in the mitochondrial membrane, release cytochrome c from mitochondria, leading to the subsequent activation of caspase 3 activation by H₂O₂ were all markedly suppressed in the presence of luteolin.

CONCLUSION

Results from this study may provide the possible molecular mechanisms underlying cardiovascular protective effects of luteolin.

Deep sea minerals ameliorate diabetic-induced inflammation via inhibition of TNFα signaling pathways

It has been well-documented that the consumption of deep sea water (DSW) has beneficial effects on myocardial hypertrophy and cardiac apoptosis induced by hypercholesterolemia. However, the molecular mechanisms for the anti-inflammatory effects of DSW on diabetic cardiomyopathy are still largely unclear. The main purpose of this present study was to test the hypothesis that DSW exerts anti-inflammatory effects through the suppression of the TNF-α-mediated signaling pathways. IP injection of streptozotocin (STZ) at the dose of 65 mg/kg was used to establish a diabetes rat model. DSW mineral extracts that diluted in desalinated water were prepared in three different dosages and administered to the rats through gavages for 4 weeks. These dosages are DSW-1X (equivalent to 37 mg Mg²⁺ /kg/day), 2X (equivalent to 74 mg Mg²⁺ /kg/day) and 3X (equivalent to 111 mg Mg²⁺ mg/kg/day). Immunofluorescence staining and Western blot showed that the protein expression level of TNF-α was markedly higher in the STZ-induced diabetic rat hearts than in the control group. Consequently, the phosphorylation levels of the TNF-α-modulated downstream signaling molecules and P38 mitogen-activated protein kinases (MAPKs) were notably elevated in heart tissues of STZ-induced diabetes. These higher phosphorylation levels subsequently upregulated NF-κB-modulated inflammatory mediators, such as cyclooxygenase (COX)-II and inducible nitric oxide synthase (iNOS). However, treatment with DSW as well as MgSO₄ , the main mineral in DSW, significantly reversed all the alterations. These findings suggest that DSW has potential as a therapeutic agent for preventing diabetes-related cardiovascular diseases.

Anti-Apoptotic Effects of Diosgenin in D-Galactose-Induced Aging Brain

The purpose of this study was to evaluate the effects of diosgenin on the D-galactose-induced cerebral cortical widely dispersed apoptosis. Male 12-week-old Wistar rats were divided into four groups: Control (1mg/kg/day of saline, i.p.), DD0 (150mg/kg/day of D-galactose, i.p.), DD10, and DD50 (D-galactose+10 or 50mg/kg/day of diosgenin orally). After eight weeks, histopathological analysis, positive TUNEL and Western blotting assays were performed on the excised cerebral cortex from all four groups. The TUNEL-positive apoptotic cells, the components of Fas pathway (Fas, FADD, active caspase-8 and active caspase-3), and mitochondria pathway (t-Bid, Bax, cytochrome c, active caspase-9 and active caspase-3) were increased in the DD0 group compared with the control group, whereas they were decreased in the DD50 group. The components of survival pathway (p-Bad, Bcl-2, Bcl-xL, IGF-1, p-PI3K and p-AKT) were increased in the DD50 group compared to the control group, whereas the levels of Bcl-xL, p-PI3K, and p-AKT were also compensatorily increased in the DD0 group compared to the control group. Taken together, diosgenin suppressed D-galactose-induced neuronal Fas-dependent and mitochondria-dependent apoptotic pathways and enhanced the Bcl-2 family associated pro-survival and IGF-1-PI3K-AKT survival pathways, which might provide neuroprotective effects of diosgenin for prevention of the D-galactose-induced aging brain.

Neuroprotective Effect of Rhodiola crenulata in D-Galactose-Induced Aging Model

The medicinal plant Rhodiola crenulata grows at high altitudes in the Arctic and mountainous regions and is commonly used in phytotherapy in Eastern European and Asian countries. In the present study, we investigated the anti-apoptotic effect of Rhodiola crenulata and its neuroprotective mechanism of action in a rat model of D-galactose-induced aging. Two groups of twelve-week-old male Wistar rats received a daily injection of D-galactose (150mg/kg/day, i.p.) and orally administered Rhodiola crenulata (0, 248mg/kg/day) for eight weeks, while a control group received a saline injection (1ml/kg/day, i.p.). We examined apoptosis in the cortex and hippocampus of three groups of rats based on a terminal deoxynucleotide transferase-mediated deoxy uridine triphosphate nick-end labeling (TUNEL) positive assay. The expression levels of apoptotic and anti-apoptotic proteins in excised brains were analyzed by Western blotting. Our findings indicated that D-galactose caused marked neuronal apoptosis via activation of both extrinsic-dependent and mitochondrial-dependent apoptotic pathways. When compared to the control group, the protein levels of Fas receptor, Fas ligand, Fas-associated death domain (FADD), and activated caspase-8 (Fas-dependent apoptotic pathways), as well as those of t-Bid, Bax, cytochrome c, activated caspase-9, and activated caspase-3 (mitochondrial-dependent apoptotic pathways), were significantly increased in the D-galactose treated group. In addition, D-galactose impaired the phosphorylation of PI3K/Akt, an important survival signaling event in neurons. Rhodiola crenulata, however, protected against all these neurotoxicities in aging brains. The present study suggests that neuronal survival promoted by Rhodiola crenulata may be a potentially effective method to enhance the resistance of neurons to age-related disorders.

Deep ocean minerals inhibit IL-6 and IGFIIR hypertrophic signaling pathways to attenuate diabetes-induced hypertrophy in rat hearts

We previously reported that deep sea water (DSW) prolongs the life span of streptozotocin (STZ)-induced diabetic rats by the compensatory augmentation of the insulin like growth factor (IGF)-I survival signaling and inhibition of apoptosis. Here, we investigated the effects of DSW on cardiac hypertrophy in diabetic rats. Cardiac hypertrophy was induced in rats by using STZ (65 mg/kg) administered via IP injection. DSW was prepared by mixing DSW mineral extracts and desalinated water. Different dosages of DSW-1X (equivalent to 37 mg Mg²⁺·kg^-1·day^-1), 2X (equivalent to 74 mg Mg²⁺·kg^-1·day^-1) and 3X (equivalent to 111 mg Mg²⁺·kg^-1·day^-1) were administered to the rats through gavage for 4 wk. Cardiac hypertrophy was evaluated by the heart weight-to-body weight ratio and the cardiac tissue cross-sectional area after hematoxylin and eosin staining. The protein levels of the cardiac hypertrophy signaling molecules were determined by Western blot. Our results showed that the suppressive effects of the DSW treatment on STZ-induced cardiac hypertrophy were comparable to those of MgSO₄ administration and that the hypertrophic marker brain natriuretic peptide (BNP) was decreased by DSW. In addition, DSW attenuated both the eccentric hypertrophy signaling pathway, IL-6-MEK-STAT3, and the concentric signaling pathway, IGF-II-PKCα-CaMKII, in DM rat hearts. The cardiac hypertrophy-associated activation of extracellular signal-regulated kinase (ERK) and the upregulation of the transcription factor GATA binding protein 4 (GATA4) were also negated by treatment with DSW. The results from this study suggest that DSW could be a potential therapeutic agent for the prevention and treatment of diabetic cardiac hypertrophy.NEW & NOTEWORTHY Deep sea water, containing high levels of minerals, improve cardiac hypertrophy in diabetic rats through attenuating the eccentric signaling pathway, IL-6-MEK5-STAT3, and concentric signaling pathway, IGF2-PKCα-CaMKII. The results from this study suggest that deep sea water could be a potential therapeutic agent for the prevention and treatment of diabetic cardiac hypertrophy.

Galectin-3 aggravates ox-LDL-induced endothelial dysfunction through LOX-1 mediated signaling pathway

Galectin-3, a biomarker linking oxidative stress and inflammation, participates in different mechanisms related to atherothrombosis, such as inflammation, proliferation, or macrophage chemotaxis. Accumulating evidence indicates that galectin-3 may also promote atherogenesis through inducing endothelial dysfunction. Lectin-like oxidized low-density lipoprotein (oxLDL) receptor-1 (LOX-1), a receptor for oxLDL uptake, contributes to oxLDL-induced endothelial dysfunction. Whether galectin-3 induces endothelial dysfunction through modulation of LOX-1-mediated signaling remains unclear. In the present study, we explored the mechanisms underlying galectin-3 enhanced cytotoxicity of oxLDL in human umbilical vein endothelial cells (HUVECs) and the role of LOX-1. Incubation of HUVECs with galectin-3 increased the expression of LOX-1 in RNA and protein levels. In addition, the expression of LOX-1 induced by oxLDL was promoted by galectin-3. However, pretreatment of LOX-1 antibody reduced LOX-1 mRNA expression level in cells with oxLDL plus galectin-3 incubation. Compared to cells treated with oxLDL alone, reactive oxygen species (ROS) generation via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activation and subsequent activation of p38 mitogen-activated protein kinases followed by nuclear factor kappa B (NF-κB) activation and related inflammatory responses including adhesion molecule expression, adhesiveness of monocytic cells, and IL-8 release were also aggravated in cells treated with galectin-3 combined with oxLDL. Compared to cells treated with galectin-3 plus oxLDL group. We found that LOX-1 antibody mitigated NADPH oxidase activity, p-38 up-regulation, NF-κB activation, and proinflammatory responses in cells treated with galectin-3 combined with oxLDL. We conclude that galectin-3 enhances endothelial LOX-1 expression and propose a new mechanism by which galectin-3 may promote endothelial dysfunction by inducing inflammation via LOX-1/ROS/p38/NF-κB-mediated signaling pathway.

Fucoxanthin Protects against oxLDL-Induced Endothelial Damage via Activating the AMPK-Akt-CREB-PGC1α Pathway

SCOPE

Atherosclerotic cardiovascular disease is the most prevalent cause of mortality and morbidity. Fucoxanthin (FX) possesses anti-hypertensive and anti-obesity properties. However, the molecular mechanisms underlying the inhibitory effects of FX on oxidized low-density lipoprotein (oxLDL)-induced oxidative injuries in human endothelial cells are still largely unknown. This study aims to test the hypothesis that FX protects against oxLDL-induced oxidative stress by upregulating AMP-activated protein kinase (AMPK) and to explore the roles of cAMP response element binding protein (CREB) and peroxisome proliferator-activated receptor gamma coactivator-1α (PGC-1α).

METHODS AND RESULTS

Human umbilical vein endothelial cells are treated with oxLDL in the presence or absence of FX. FX significantly increases AMPK phosphorylation. In addition, FX diminishes oxLDL-mediated nicotinamide adenine dinucleotide phosphate oxidase activation by inhibiting protein kinase C and subsequently inducing reactive oxygen species generation and impairing the activity of the endogenous antioxidant enzyme superoxidase dismutase. Furthermore, FX restores oxLDL-mediated dephosphorylation of phosphoinositide-3-kinase/Akt and decreases CREB and PGC-1α expression to nearly normal levels. Moreover, FX ameliorates the oxLDL-mediated suppression of mitochondrial function and apoptosis.

CONCLUSION

These findings provide new insights into the possible molecular mechanisms by which FX mitigates oxLDL-induced endothelial oxidative stress and mitochondrial dysfunction.

Luteolin: A Natural Flavonoid Enhances the Survival of HUVECs against Oxidative Stress by Modulating AMPK/PKC Pathway

Oxidative stress has been implicated in the pathogenesis of atherosclerotic cardiovascular diseases. Dietary supplementation of anti-oxidants has been reported to have beneficial effects on the prevention of atherogenic diseases. Luteolin (a natural flavonoid) has been shown to possess antimutagenic, antitumorigenic, anti-oxidant and anti-inflammatory properties. However, the effects and underlying molecular mechanisms of luteolin on cardiovascular systems are poorly explored. Therefore, the aim of the present study was to test whether luteolin could protect against oxidative stress-induced endothelial cell injury and explore the underlying mechanisms. In this study, human umbilical vein endothelial cells (HUVECs) were pre-treated with luteolin followed by hydrogen peroxide induction (H₂O₂). Our results showed that luteolin protected against H₂O₂-induced oxidative stress and ameliorated ROS and superoxide generation. In addition, we found that luteolin treatment inhibited the H₂O₂-induced membrane assembly of NADPH oxidase subunits, which was further confirmed by specifically inhibiting NADPH oxidase using DPI treatment. Furthermore, pAMPK protein expression was enhanced and p-PKC isoforms were significantly down-regulated by luteolin treatment in a dose-dependent manner, and a similar effect was observed upon DPI treatment. However, co-treatment with the specific inhibitor of AMPK (Compound C) restored p-PKC levels suggesting the role of AMPK signaling in regulating p-PKC expression under oxidative stress condition in HUVECs. Finally, we confirmed using siRNAs and specific inhibitor and/or activator of AMPK (AICAR) that luteolin treatment induced AMPK is a key player and regulator of activated expression of PKC isoforms and thereby confers protection against H₂O₂-induced oxidative stress in HUVECs.

Protective effect of HDL on NADPH oxidase-derived super oxide anion mediates hypoxia-induced cardiomyocyte apoptosis

Cardiovascular diseases are the leading cause of death of death in Taiwan. Atherosclerosis can lead to serious problems, including heart attack, stroke, or even death. Coronary heart disease (CHD) occurs when plaque builds up in the coronary arteries to cause the ischemic heart disease which will enhance myocardial remodeling and also induce myocardial hypoxia. High density lipoprotein (HDL) has been proposed to have cardio-protective effects. Under hypoxic conditions (1%O₂ for 24hr), in H9c2 cells, reactive oxygen species (ROS) is induced which leads to cardiomyocyte apoptosis and cardiac dysfunction. Therefore, the present study described the protective effect of HDL on hypoxia-induced cardiomyocyte damage. We investigated the NADPH oxidase-produced ROS-related signaling pathways and apoptosis in cardiomyocytes under hypoxia conditions. Results showed that the ROS mediated cardiac damage might occur via AT1 and PKC activation. Furthermore, hypoxia downregulated the survival protein (p-AKT^ser473) and anti-apoptotic protein (BCL₂), whereas pro-apoptotic protein, Bax and caspase 3 were upregulated. These detrimental effects by ROS and apoptosis were prevented by HDL pretreatment. Our findings revealed the underlying molecular mechanism by which HDL suppresses the hypoxia-induced cardiomyocyte dysfunction. Further, we elucidated the role of HDL on preventing hypoxia induced cardiomyocyte apoptosis is mediated through the inhibition of NADPH oxidase-derived ROS.

Prior experience but not size of error improves motor learning on the split-belt treadmill in young children

Children can modify learned motor skills, such as walking, to adapt to new environments. Movement errors in these new situations drive the learning. We used split-belt walking to determine whether size of the error affects the degree of learning. Twenty-two children (aged 2–5 y) walked on the split-belt treadmill on two separate days spaced 1 week apart. Twenty-eight adults served as controls. On Day 1, children experienced an abrupt change in belt speeds (from 1∶1 to 2∶1 differential) resulting in large errors, or a gradual change (same change in speed over 12–15 min), resulting in small errors. Learning was measured by the size of the aftereffect upon return to a 1∶1 differential. On Day 2 (1 week later), the leg on the fast belt was reversed, as was the method of introducing the speed differential. We found that the error size did not affect learning. Unexpectedly, learning was greater on Day 2 compared to Day 1, especially for children under 4 y of age, despite the fact that the task was opposite to that of Day 1, and did not influence learning in adults. Hence, 11 additional children under 4 y of age were tested with belts running at the same speed on Day 1, and with a 2∶1 speed differential (abrupt introduction) on Day 2. Surprisingly, learning was again greater on Day 2. We conclude that size of error during split-belt walking does not affect learning, but experience on a treadmill does, especially for younger children.

Diallyl trisulfide and diallyl disulfide ameliorate cardiac dysfunction by suppressing apoptotic and enhancing survival pathways in experimental diabetic rats

Cardiovascular disease is one of the major causes of mortality in diabetic patients. Mounting studies have shown that garlic exhibits, possibly through its antioxidant potential, diverse biological activities. In this study, we investigated the alleviating effects of garlic oil (GO) and its two major components, diallyl disulfide (DADS) and diallyl trisulfide (DATS), on diabetic cardiomyopathy in rats. Physiological cardiac parameters were obtained using echocardiography. Apoptotic cells were evaluated using TUNEL and DAPI staining. Protein expression levels were determined using Western blotting analysis. Our findings indicated that in diabetic rat hearts significantly decreased fractional shortening percentage, increased levels of nitrotyrosine, an elevated number of TUNEL-positive cells, enhanced levels of caspase 3 expression, and decreased PI3K-Akt signaling pathway activities were observed. Furthermore, all of these alterations were reversed following both GO and DATS (or DADS) administrations through increasing PI3K-Akt signaling pathway activities and inhibiting both the death receptor-dependent and the mitochondria-dependent apoptotic pathways. In conclusion, this study shows that DATS and DADS, with the efficacy order DATS > DADS, have the therapeutic potential for ameliorating diabetic cardiomyopathy. Furthermore, the therapeutic effects of GO on diabetic cardiomyopathy should be mainly from DATS and DADS.

Ginkgo biloba extract attenuates oxLDL-induced endothelial dysfunction via an AMPK-dependent mechanism

Atherosclerosis is a complex inflammatory arterial disease, and oxidized low-density lipoprotein (oxLDL) is directly associated with chronic vascular inflammation. Previous studies have shown that Ginkgo biloba extract (GbE) acts as a therapeutic agent for neurological and cardiovascular disorders. However, the mechanisms mediating the actions of GbE are still largely unknown. In the present study, we tested the hypothesis that GbE protects against oxLDL-induced endothelial dysfunction via an AMP-activated protein kinase (AMPK)-dependent mechanism. Human umbilical vein endothelial cells were treated with GbE, followed by oxLDL, for indicated time periods. Results from Western blot showed that GbE inhibited the membrane translocation of the NADPH oxidase subunits p47(phox) and Rac-1 and attenuated the increase in protein expression of membrane subunits gp91 and p22(phox) caused by oxLDL-induced AMPK dephosphorylation and subsequent PKC activation. AMPK-α(1)-specific small interfering RNA-transfected cells that had been exposed to GbE followed by oxLDL revealed elevated levels of PKC and p47(phox). In addition, exposure to oxLDL resulted in reduced AMPK-mediated Akt/endothelial nitric oxide (NO) synthase signaling and the induction of phosphorylation of p38 mitogen-activated protein kinase, which, in turn, activated NF-κB-mediated inflammatory responses, such as the release of interleukin-8, the expression of the adhesion molecule, and the adherence of monocytic cells to human umbilical vein endothelial cells. Furthermore, oxLDL upregulated the expression of inducible NO synthase, thereby augmenting the formation of NO and protein nitrosylation. Pretreatment with GbE, however, exerted significant cytoprotective effects in a dose-dependent manner. Results from this study may provide insight into a possible molecular mechanism by which GbE protects against oxLDL-induced endothelial dysfunction.

Ergothioneine protects against neuronal injury induced by β-amyloid in mice

β-Amyloid peptides (Aβ) are neurotoxic and contribute to the development of Alzheimer's disease (AD). Ergothioneine (EGT) has been shown to protect against loss of memory and learning abilities in mice. In this study, mice were orally fed EGT (0.5 or 2 mg/kg body weight) for 16 days before treatment (i.c.v) with a single dose of Aβ1-40 in the hippocampus. After resting for 12 days to restore the body weight, the mice were again fed EGT for additional 39 days. Active avoidance tests were conducted on days 37-39 (short-memory avoidance) and on days 37, 44 and 51 (long-memory avoidance). Water maze task was used to evaluate learning and memory abilities by acquisition test and retention test. In both long-memory avoidance and water maze tests, EGT significantly decreased the escape latency and increased the frequency of successful avoidance. Furthermore, EGT significantly prevented Aβ accumulation in the hippocampus and brain lipid peroxidation, restored acetylcholinesterase (AChE) activity, maintained glutathione/glutathione disulfide ratio and superoxide dismutase activity in brain tissues of Aβ1-40-teated mice. Thus, EGT can protect against Aβ-induced loss of memory and learning abilities in mice. Further studies are required to confirm the protective effects of EGT on the development or progression of AD.

Vinorelbine-induced oxidative injury in human endothelial cells mediated by AMPK/PKC/NADPH/NF-κB pathways

Vinorelbine tartrate (VNR), a semi-synthetic vinca alkaloid acquired from vinblastine, has extensively been used as an anticancer agent. However, VNR-induced oxidative damage may cause several side effects, such as venous irritation, vascular pain, and necrotizing vasculitis, thereby repressing clinical treatment efficiency. The molecular mechanisms underlying the induced oxidative stress in endothelial cells are still largely unknown. This study was designed to test the hypothesis that VNR induces oxidative injury through modulation of AMP-activated protein kinase (AMPK) and possible mechanisms were then explored. Human umbilical vein endothelial cells (HUVECs) were treated with VNR (5-0.625 μM) to produce oxidative damage. The VNR-mediated AMPK, PKC, and NADPH oxidase expressions were investigated by western blotting. Furthermore, several oxidative stress-induced oxidative damage markers as well as pro-inflammatory responses were also investigated. VNR treatment resulted in dephosphorylation of AMPK, which in turn led to an activation of NADPH oxidase by PKC; however, the phenomena were repressed by AICAR (an agonist of AMPK). Furthermore, VNR suppressed Akt/eNOS and enhanced p38 mitogen-activated protein kinase (MAPK), which in turn activated the NF-κB pathway. Furthermore, VNR facilitated several pro-inflammatory events, such as the adherence of monocytic THP-1 cells to HUVECs, pro-inflammatory cytokines release, and overexpression of adhesion molecular. Our results highlight a possible molecular mechanism for VNR-mediated endothelial dysfunction.

Proliferative Effects of Chishao on Schwann Cells are FGF-uPA, and ERK- and JNK-Dependent

This study evaluated the proliferative effects of chishao on RSC96, Schwann cells. A dose-dependent proliferative effect of chishao was obtained by methylthiazol tetrazolium (MTT), proliferating cell nuclear antigen (PCNA) Western blotting, and wound healing assays in Schwann cells administered with chishao (0–500 mg/ml), except at 500 mg/ml concentration. The chishao-treated cells also showed a dose-dependent activated fibroblast growth factor-2 (FGF-2) signaling with increased urokinase plasminogen activator (uPA) and decreased plasminogen activator inhibitor-1 (PAI-1), enhanced proliferative proteins, extracellular signal regulated kinase (ERK) and c-Jun N-terminal kinase (JNK)-signaling. Using mitogen-actvated protein kinase (MAPK)-signaling chemical inhibitors, U0126, SB203580, and SP600125, the proliferative effects of chishao on RSC cells were identified to be ERK- and JNK- signaling dependent. Based on the results, applying appropriate doses of chishao to Schwann cells would be a potential approach for enhancing neuron regeneration.

Exercise training enhances cardiac IGFI-R/PI3K/Akt and Bcl-2 family associated pro-survival pathways in streptozotocin-induced diabetic rats

BACKGROUND

Increased myocyte apoptosis in diabetic hearts has been previously reported. The purpose of this study was to evaluate the effects of exercise training on cardiac survival pathways in streptozotocin (STZ)-induced diabetic rats.

METHODS

Forty-eight male Wistar rats were randomly divided into control group (Control), STZ-induced (65 mg/kg, i.p.) diabetes (DM), and DM rats with moderate aerobic exercise training (DM-EX) on a treadmill 60 min/day, 5 days/week, for 10 weeks. Histopathological analysis, positive TUNEL assays and Western blotting were performed on the excised cardiac left ventricles from all three groups.

RESULTS

The components of cardiac survival pathway (insulin-like growth factor I (IGFI), IGFI-receptor (IGFI-R), phosphatidylinositol 3'-kinase (PI3K), and Akt) and the pro-survival Bcl-2 family proteins (Bcl-2, Bcl-xL, and p-BAD) were all significantly decreased in the DM group compared with the Control group whereas they were increased in the DM-EX group. In addition, the abnormal myocardial architecture, enlarged interstitial space and increased cardiac TUNEL-positive apoptotic cells were observed in the DM group, but they were reduced in the DM-EX group. The apoptotic key component, caspase-3, was significantly increased in the DM group relative to the Control group whereas it was decreased in the DM-EX group.

CONCLUSIONS

Exercise training enhances cardiac IGFI-R/PI3K/Akt and Bcl-2 family associated pro-survival pathways, which provides one of the new beneficial effects for exercise training in diabetes.

Aspirin prevents resistin-induced endothelial dysfunction by modulating AMPK, ROS, and Akt/eNOS signaling

BACKGROUND

Resistin, an adipocytokine, plays a potential role in cardiovascular disease and may contribute to increased atherosclerotic risk by modulating the activity of endothelial cells. A growing body of evidence suggests that aspirin is a potent antioxidant. We investigated whether aspirin mitigates resistin-induced endothelial dysfunction via modulation of reactive oxygen species (ROS) generation and explored the role that AMP-activated protein kinase (AMPK), a negative regulator of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, plays in the suppressive effects of aspirin on resistin-induced endothelial dysfunction.

METHODS

Human umbilical vein endothelial cells (HUVECs) were pretreated with various doses of aspirin (10-500 μg/mL) for 2 hours and then incubated with resistin (100 ng/mL) for an additional 48 hours. Fluorescence produced by the oxidation of dihydroethidium (DHE) was used to quantify the production of superoxide in situ; superoxide dismutase (SOD) and catalase activities were determined by an enzymatic assay; and protein levels of AMPK-mediated downstream signaling were investigated by Western blot.

RESULTS

Treatment of HUVECs with resistin for 48 hours resulted in a 2.9-fold increase in superoxide production; however, pretreatment with aspirin resulted in a dose-dependent decrease in production of superoxide (10-500 μg/mL; n = 3 experiments; all P < .05). Resistin also suppressed the activity of superoxide dismutase and catalase by nearly 50%; that result, however, was not observed in HUVECs that had been pretreated with aspirin at a concentration of 500 μg/mL. The membrane translocation assay showed that the levels of NADPH oxidase subunits p47(phox)and Rac-1 in membrane fractions of HUVECs were threefold to fourfold higher in cells that had been treated with resistin for 1 hour than in untreated cells; however, pretreatment with aspirin markedly inhibited resistin-induced membrane assembly of NADPH oxidase via modulating AMPK-suppressed PKC-α activation. Application of AMPKα1-specific siRNA resulted in increased activation of PKC-α and p47(phox). In addition, resistin significantly decreased AMPK-mediated downstream Akt/endothelial nitric oxide synthase (eNOS)/nitric oxide (NO) signaling and induced the phosphorylation of p38 mitogen-activated protein kinases, which in turn activated NF-κB-mediated inflammatory responses such as the release of interleukin (IL)-6 and IL-8, the overexpression of adhesion molecules, and stimulation of monocytic THP-1 cell attachment to HUVECs (2.5-fold vs control; n = 3 experiments). Furthermore, resistin downregulated eNOS and upregulated inducible NO synthase (iNOS) expression, thereby augmenting the formation of NO and protein nitrosylation. Pretreatment with aspirin, however, exerted significant cytoprotective effects in a dose-dependent manner (P < .05).

CONCLUSIONS

Our findings suggest a direct connection between adipocytokines and endothelial dysfunction and provide further insight into the protective effects of aspirin in obese individuals with endothelial dysfunction.

A novel mechanism of coenzyme Q10 protects against human endothelial cells from oxidative stress-induced injury by modulating NO-related pathways

BACKGROUND

Atherosclerosis is a chronic inflammatory disease of the vessel wall associated with oxidized low-density lipoprotein (oxLDL)-induced apoptosis of endothelial cells. Coenzyme Q10 (CoQ10), a potent antioxidant and a critical intermediate of the electron transport chain, has been reported to inhibit LDL oxidation and thus the progression of atherosclerosis. However, its molecular mechanisms on endothelial cells remain still unclarified.

METHODS

In this study, primary human umbilical vein endothelial cell cultures treated with oxLDL were used to explore the protective effects of CoQ10.

RESULTS

Our results showed that CoQ10 attenuated the oxLDL-induced generation of reactive oxygen species and improved the antioxidant capacity. CoQ10 also attenuated the oxLDL-mediated down-regulation of endothelial nitric oxide synthase (eNOS) and up-regulation of inducible nitric oxide synthase (iNOS). In addition, CoQ10 suppressed oxLDL-activated NF-κB and downstream inflammatory mediators, including expression of adhesion molecules, release of proinflammatory cytokines and the adherence of monocytic THP-1 cells. Moreover, CoQ10 attenuated oxLDL-altered proapoptotic responses. The inhibitor of eNOS (L-NIO 10 μM) and iNOS (1400W 10 μM) as well as NO enhancer (SNP 10 μM) were used to clean up the mechanism.

CONCLUSION

These results provide new insight into the possible molecular mechanisms by which CoQ10 protects against atherogenesis by NO-related pathways.

Ellagic acid inhibits oxidized low-density lipoprotein (OxLDL)-induced metalloproteinase (MMP) expression by modulating the protein kinase C-α/extracellular signal-regulated kinase/peroxisome proliferator-activated receptor γ/nuclear factor-κB (PKC-α/ERK/PPAR-γ/NF-κB) signaling pathway in endothelial cells

Previous studies have shown that vascular endothelium-derived matrix metalloproteinases (MMPs) contribute to the destabilization of atherosclerotic plaques, a key event triggering acute myocardial infarction. In addition, studies have reported that the PKC-MEK-PPARγ signaling pathway is involved in oxidized low-density lipoprotein (oxLDL)-induced expression of MMPs. Ellagic acid, a phenolic compound found in fruits and nuts, has potent antioxidant, anti-inflammatory, and anticancerous properties. However, the molecular mechanisms underlying its antiatherogenic effects remain to be clarified. This study aimed to assess whether the effects of ellagic acid on the fibrotic markers MMP-1 and MMP-3 are modulated by the PKC-ERK-PPAR-γ signaling pathway in human umbilical vein endothelial cells (HUVECs) that have been exposed to oxLDL. It was found that ellagic acid significantly inhibited oxLDL-induced expressions of MMP-1 and MMP-3. Pretreatment with ellagic acid and DPI, a well-known ROS inhibitor, attenuated the oxLDL-induced expression and activity of PKC-α. In addition, ellagic acid as well as pharmacological inhibitors of ROS, calcium, and PKC strongly suppressed the oxLDL-induced phosphorylation of extracellular signal-regulated kinase (ERK) and NF-κB activation. Moreover, ellagic acid ameliorated the oxLDL-induced suppression of PPAR-γ expression. In conclusion, the data suggest that ellagic acid elicits its protective effects by modulating the PKC-α/ERK/PPAR-γ/NF-κB pathway, resulting in the suppression of ROS generation and, ultimately, inhibition of MMP-1 and MMP-3 expression in HUVECs exposed to oxLDL.

Ergothioneine protects against neuronal injury induced by cisplatin both in vitro and in vivo

The neuroprotective effects of ergothioneine (EGT) against cisplatin toxicity were investigated both in vitro and in vivo. For in vitro study, two types of neuronal cells, primary cortical neuron (PCN) cells and rat pheochromocytoma (PC12) cells, were incubated with EGT (0.1-10.0 μM) for 2 h followed by incubation with 0.5 μM cisplatin for 72 h. Results show that cisplatin markedly decreased the proliferation of PC12 cells and strongly inhibited the growth of axon and dendrite of PCN cells, but these effects were significantly prevented by EGT. For in vivo study, CBA mice were orally administered with 2 or 8 mg EGT/kg body weight for 58 consecutive days and were injected i.p. with 5mg cisplatin/kg body weight on days 7, 9 and 11. We found that EGT significantly restored the learning and memory deficits in mice treated with cisplatin evaluated by active and passive avoidance tests. EGT also significantly prevented brain lipid peroxidation, restored acetylcholinesterase (AChE) activity and maintained glutathione/glutathione disulfide ratio in brain tissues of mice treated with cisplatin. These results demonstrate that EGT protects against cisplatin-induced neuronal injury and enhances cognition, possibly through the inhibition of oxidative stress and restoration of AChE activity in neuronal cells.

Cardiac contractile dysfunction and apoptosis in streptozotocin-induced diabetic rats are ameliorated by garlic oil supplementation

Previous studies have suggested that garlic oil could protect the cardiovascular system. However, the mechanism by which garlic oil protects diabetes-induced cardiomyopathy is unclear. In this study, streptozotocin (STZ)-induced diabetic rats received garlic oil (0, 10, 50, or 100 mg/kg of body weight) by gastric gavage every 2 days for 16 days. Normal rats without diabetes were used as control. Cardiac contractile dysfunction examined by echocardiography and apoptosis evaluated by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) assay were observed in diabetic rat hearts. Additionally, a shift in cardiac myosin heavy chain (MHC) gene expression from α- to β-MHC isoform, decreased levels of superoxide dismutase-1 (SOD-1) and cardiac α-actin, and elevated cardiac thiobarbituric acid reactive substances (TBARS) and caspase- and p38-NFκB-leading apoptosis signaling activities were demonstrated in diabetic hearts. However, these diabetes-related cardiac dysfunctions were almost dose-dependently ameliorated by garlic oil administration. In conclusion, garlic oil possesses significant potential for protecting hearts from diabetes-induced cardiomyopathy.

Ellagic acid inhibits oxidized LDL-mediated LOX-1 expression, ROS generation, and inflammation in human endothelial cells

BACKGROUND

LOX-1, a lectin-like receptor on endothelial cells, facilitates the uptake of oxidized low-density lipoprotein (oxLDL). Expression of LOX-1 is involved in the pathobiological effects of oxLDL in endothelial cells, including reactive oxygen species (ROS) generation, suppression of endothelial nitric oxide synthase (eNOS) activity, and leukocytic adhesion. Moderate consumption of phenolic-enriched food may have a protective effect against the development of atherosclerosis via the antioxidant capacity of phenolic compounds at the endothelial level. In this study, we determined whether ellagic acid, a polyphenolic compound widely distributed in fruits and nuts, protects against oxLDL-induced endothelial dysfunction by modulating the LOX-1-mediated signaling pathway.

METHODS

Human umbilical vein endothelial cells (HUVECs) were pretreated with ellagic acid at doses of 5, 10, 15, and 20 μM for 2 hours and then incubated with oxLDL (150 μg/mL) for an additional 24 hours.

RESULTS

LOX-1 protein expression was markedly lower after exposure to oxLDL in HUVECs pretreated with ellagic acid or diphenyleneiodonium, a well-known inhibitor of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase, than in HUVECs exposed to oxLDL alone, suggesting that ellagic acid deactivates NADPH oxidase. We also found that oxLDL activated the membrane assembly of p47phox, Rac1, gp91 and p22phox, and the subsequent induction of ROS generation; however, ROS generation was markedly suppressed in cells pretreated with ellagic acid or anti-LOX-1 monoclonal antibody. In addition, oxLDL down-regulated eNOS and up-regulated inducible NO synthase (iNOS), thereby augmenting the formation of NO and protein nitrosylation. Furthermore, oxLDL induced the phosphorylation of p38 mitogen-activated protein kinase, activated the NF-κB-mediated inflammatory signaling molecules interleukin-(IL) 6 and IL-8 and the adhesion molecules intercellular adhesion molecule-1, vascular cell adhesion molecule-1, and E-selectin, and stimulated the adherence of THP-1 (a human acute monocytic leukemia cell line) to HUVECs. Pretreatment with ellagic acid, however, exerted significant cytoprotective effects in all events.

CONCLUSION

Findings from this study may provide insight into a possible molecular mechanism by which ellagic acid inhibits LOX-1-induced endothelial dysfunction. Our data indicate that ellagic acid exerts its protective effects by inhibiting NADPH oxidase-induced overproduction of superoxide, suppressing the release of NO by down-regulating iNOS, enhancing cellular antioxidant defenses, and attenuating oxLDL-induced LOX-1 up-regulation and eNOS down-regulation.

EGCG protects against oxidized LDL-induced endothelial dysfunction by inhibiting LOX-1-mediated signaling

Lectin-like oxidized low-density lipoprotein receptor-1 (LOX-1), originally identified as the major receptor for oxidized low-density lipoprotein (oxLDL) in endothelial cells, plays a major role in the pathology of vascular diseases. Green tea consumption is associated with reduced cardiovascular mortality in some epidemiological studies. In the present study, we hypothesized that the most abundant polyphenolic compound in tea, epigallocatechin-3-gallate (EGCG), can downregulate parameters of endothelial dysfunction by modulating LOX-1-regulated cell signaling. In cultured human umbilical vein endothelial cells (HUVECs), exposure to oxLDL (130 microg/ml), which led to an increase in LOX-1 expression at the RNA and protein levels, was abrogated by addition of EGCG or DPI, a well-known inhibitor of flavoproteins, suggesting the involvement of NADPH oxidase. Furthermore, oxLDL rapidly activated the membrane translocation of Rac-1 and p47phox and the subsequent induction of ROS generation, which was suppressed markedly by pretreatment with EGCG or anti-LOX-1 monoclonal antibody. OxLDL also increased p38 MAPK phosphorylation and decreased phosphorylation of the amino-terminal region of Akt, with maximal induction at about 30 min, and NF-kappaB phosphorylation within 1 h, resulting in redox-sensitive signaling. In addition, oxLDL diminished the expression of endothelial nitric oxide synthase (eNOS), enhanced the expression of endothelin-1 and adhesion molecules (ICAM, E-selectin, and monocyte chemoattractant protein-1), and increased the adherence of monocytic THP-1 cells to HUVECs. Pretreatment with EGCG, however, exerted significant cytoprotective effects in all events. These data suggest that EGCG inhibits the oxLDL-induced LOX-1-mediated signaling pathway, at least in part, by inhibiting NADPH oxidase and consequent ROS-enhanced LOX-1 expression, which contributes to further ROS generation and the subsequent activation of NF-kappaB via the p38 MAPK pathway. Results from this study may provide insight into a possible molecular mechanism by which EGCG suppresses oxLDL-mediated vascular endothelial dysfunction.

Sesamin mitigates inflammation and oxidative stress in endothelial cells exposed to oxidized low-density lipoprotein

Sesamin, a lignan from sesame oil, has been shown to have antihypertensive and antioxidative properties. This study examined the effects of sesamin on oxidized low-density lipoprotein (oxLDL)-induced endothelial dysfunction. Oxidative stress was determined by measuring the generation of intracellular reactive oxygen species (ROS) and by measuring the expression levels of superoxide dismutase (SOD) and endothelial nitric oxide synthase (eNOS). To assess the pro-inflammatory effects of oxLDL, ELISA was used to detect IL-8 expression, endothelin-1 (ET-1) secretion, and nuclear factor-kappaB (NF-kappaB) activation. The expression of adhesion molecules (ICAM-1, VCAM-1, and E-selectin) was examined by flow cytometry. In addition, several apoptotic signaling pathways were also investigated. The data showed that sesamin significantly ameliorated oxLDL-induced ROS generation and SOD-1 inactivation. Sesamin also attenuated the oxLDL-induced activation of NF-kappaB, suggesting that the inhibitory effects of sesamin on IL-8 and ET-1 release, adhesion molecule expression, and the adherence of THP-1 cells were at least partially through the blockade of NF-kappaB activation. Furthermore, sesamin attenuated oxLDL-induced apoptotic features, such as intracellular calcium accumulation and the subsequent collapse of mitochondrial membrane potential, release of cytochrome c, and activation of caspase-3. Results from this study may provide insight into possible molecular mechanisms underlying sesamin's beneficial effects against oxLDL-mediated vascular endothelial dysfunction.

Crude extracts of Solanum lyratum protect endothelial cells against oxidized low-density lipoprotein-induced injury by direct antioxidant action

BACKGROUND

Oxidized low-density lipoprotein (oxLDL) is a proatherogenic molecule that accumulates in the vascular wall and contributes to the pathogenesis of vascular dysfunction early in the development of atherosclerosis. The whole plant of Solanum lyratum is a traditional Chinese medicine that has been used for centuries to treat cancer, tumors, and herpes. However, the cellular and molecular mechanisms of its antioxidant effects are still largely unknown. This study tested the hypothesis that Solanum lyratum Thunberg extract (SLE) could block oxLDL-induced endothelial dysfunction in cultured human umbilical vein endothelial cells (HUVECs). Possible mechanisms were explored.

METHODS

Antioxidative activities of SLE were assayed by measuring the scavenging of 1,1-diphenyl-2-picryl-hydrazyl (DPPH) free radical and the inhibition of copper-mediated or cell-mediated LDL oxidation. Production of reactive oxygen species (ROS) and the expression of adhesion molecules were evaluated in HUVECs after exposure to oxLDL and treatment with SLE. Several apoptotic signaling pathways were investigated.

RESULTS

SLE scavenged DPPH and also delayed the kinetics of LDL oxidation in a dose-dependent manner. SLE attenuated the level of oxLDL-induced ROS generation, diminished the expression of endothelial NO synthase (eNOS), and enhanced the expression of adhesion molecules (vascular cellular adhesion molecule-1, E-selectin, and monocyte chemotactic protein-1) and the adherence of monocytic THP-1 cells to HUVECs. OxLDL increased the concentration of intracellular calcium, disturbed the balance of the Bcl-2 protein family, destabilized the mitochondrial membrane potential, increased the amount of cytochrome c released into the cytosol, and increased the activation of caspase 3. These detrimental effects were ameliorated dose-dependently by SLE (P < .05).

CONCLUSION

Crude extracts of Solanum lyratum protect against oxLDL-induced injury in endothelial cells by direct antioxidant action.

CLINICAL RELEVANCE

Atherosclerosis is a chronic inflammatory disease characterized by lipid-laden lesions within arterialblood vessel walls. Inhibiting the oxidation of low-density lipoprotein may be an effective way to prevent or delay theprogression of atherosclerosis. This study underscores the potential clinical benefits and application of Solanum lyratumextract in controlling oxidized low-density lipoprotein-associated vascular injury and cardiovascular disease.

Ginkgo biloba extract attenuates oxLDL-induced oxidative functional damages in endothelial cells

Atherosclerosis is a chronic inflammatory process with increased oxidative stress in vascular endothelium. Ginkgo biloba extract (GbE), extracted from Ginkgo biloba leaves, has commonly been used as a therapeutic agent for cardiovascular and neurological disorders. The aim of this study was to investigate how GbE protects vascular endothelial cells against the proatherosclerotic stressor oxidized low-density lipoprotein (oxLDL) in vitro. Human umbilical vein endothelial cells (HUVECs) were incubated with GbE (12.5–100 μg/ml) for 2 h and then incubated with oxLDL (150 μg/ml) for an additional 24 h. Subsequently, reactive oxygen species (ROS) generation, antioxidant enzyme activities, adhesion to monocytes, cell morphology, viability, and several apoptotic indexes were assessed. Our data show that ROS generation is an upstream signal in oxLDL-treated HUVECs. Cu,Zn-SOD, but not Mn-SOD, was inactivated by oxLDL. In addition, oxLDL diminished expression of endothelial NO synthase and enhanced expression of adhesion molecules (ICAM, VCAM, and E-selectin) and the adherence of monocytic THP-1 cells to HUVECs. Furthermore, oxLDL increased intracellular calcium, disturbed the balance of Bcl-2 family proteins, destabilized mitochondrial membrane potential, and triggered subsequent cytochrome c release into the cytosol and activation of caspase-3. These detrimental effects were ameliorated dose dependently by GbE ( P < 0.05). Results from this study may provide insight into a possible molecular mechanism underlying GbE suppression of the oxLDL-mediated vascular endothelial dysfunction.

Metabolic syndrome abating the beneficial effect of pravastatin treatment on adhesion of endothelium by monocytes in subjects with hypercholesterolemia

Statin, a potent lipid-lowering agent, ameliorates the interaction of monocytes and endothelium, a critical step in the atherosclerotic process. However, it remains unclear whether this effect of statin depends on different doses or the presence of metabolic syndrome. In this prospectively double-blind study, 21 hypercholesterolemia subjects, with low-density lipoprotein cholesterol between 130 and 170 mg/dL, received low-dose (10 mg/d) or high-dose (40 mg/d) pravastatin treatment for 8 weeks. We assessed the reduction of monocyte adhesion to cultured endothelium between different-dose groups and the relationship to metabolic syndrome. Total cholesterol and low-density lipoprotein cholesterol were significantly decreased after 40-mg pravastatin treatment (-23.3% +/- 3.7%, P < .001 and -28.8% +/- 3.0%, P < .001), and the reductions were greater than those in the 10-mg group (P = .041 and P = .045, respectively). There was no significant difference in monocyte adhesion between high-dose and low-dose pravastatin treatment. When all subjects were divided into an improvement group and a no improvement group, according to the median of change percentage of monocyte adhesion after pravastatin treatment, there were significantly more subjects with metabolic syndrome in the no improvement than the improvement group (6 vs 1 person, P =.024). Using logistic regression analysis, metabolic syndrome, rather than dose effect of pravastatin, was an independent predictor of interaction between monocytes and endothelium (95% confidence interval = 0.001-0.865, P = .041). Attenuating adhesion between monocytes and endothelium is altered by the presence of metabolic syndrome when hypercholesterolemia subjects receive pravastatin treatment.

Plasma interleukin-1beta, -6, -8 and tumor necrosis factor-alpha as highly informative markers of pelvic inflammatory disease

BACKGROUND

The role of proinflammatory cytokines in pelvic inflammatory disease (PID) is unclear. We therefore determined whether plasma proinflammatory cytokines, interleukin-1beta (IL-1beta), IL-6, IL-8 and tumor necrosis factor-alpha (TNF-alpha) were useful plasma markers in PID patients.

METHODS

Multiplex bead array analysis was used to measure the plasma levels of proinflammatory cytokines in 50 healthy controls as well as in 41 PID patients before and after routine protocol treatments.

RESULTS

IL-1beta, IL-6, IL-8 and TNF-alpha were significantly elevated in PID patients before antibiotic treatment than after treatment. However, IL-8 was not significantly different between healthy controls and PID patients. The relative increase in ratio of IL-6 was significantly correlated with white blood cell count (r=0.448, p=0.003), neutrophil count (r=0.472, p=0.002) and C-reactive protein level (r=0.412, p=0.008).

CONCLUSIONS

IL-1beta, IL-6, IL-8 and TNF-alpha may play an important role in the pathogenesis of PID. These biomarkers, particularly IL-6, could be useful adjuncts for the clinical diagnosis of PID.

Effect of weight loss on proinflammatory state of mononuclear cells in obese women

In order to investigate whether weight loss can lead to improvement of the mononuclear cell (MNC) proinflammatory state, 21 nondiabetic obese women with mean age 34+/-2 years (mean+/-s.e.m.) and BMI 32.5+/-1.2 kg/m2 were enrolled in a 12-week caloric restriction and light exercise-based weight loss program. Ten lean women served as controls. Reverse transcription-PCR of proinflammatory cytokines and adipocytokines as well as homeostasis model assessment of insulin resistance (HOMA-IR) were determined before and after weight reduction. Nuclear factor kappaB (NF-kappaB) binding to DNA and inhibitors of NF-kappaB (IkappaB-alpha and IkappaB-beta) obtained from peripheral MNCs were measured. Overall, subjects lost a mean of 4.0+/-0.4 kg (5.0+/-0.3% of their initial body weight) (P<0.01). In addition to significant reductions in BMI, fasting glucose and insulin concentrations, mean serum high-sensitivity C-reactive protein (hs-CRP), migration inhibitor factor (MIF), leptin and visfatin levels decreased by 49.0, 66.6, 17.2, and 50.2%, respectively (all P<0.05), while adiponectin concentrations rose by 33.9% (P<0.05). The DNA binding of the transcriptionally active NF-kappaB from (p65/p50) decreased by 38.1% (P<0.05). Elevated levels of mRNA of NF-kappaB related proinflammatory genes, tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), MIF, and matrix metalloproteinase-9 (MMP-9), decreased significantly after weight loss. Although mRNA expression of Rel-A, p105, IkappaB-alpha, IkappaB-beta decreased significantly, their protein levels did not change after weight loss. As a group, NF-kappaB binding activity correlated with HOMA-IR (r=0.332, P=0.049) and marginally with values of BMI (r=0.308, P=0.059). In conclusion, weight loss by 5% of initial weight in nondiabetic obese women led to significant improvement in activated intranuclear NF-kappaB binding as well as several transcriptions of proinflammatory genes regulated by NF-kappaB.

Protective effects of magnolol against oxidized LDL-induced apoptosis in endothelial cells

Magnolol, a compound extracted from the Chinese medicinal herb Magnolia officinalis, has several biological effects. However, its protective effects against endothelial injury remain unclear. In this study, we examined whether magnolol prevents oxidized low density lipoprotein (oxLDL)-induced vascular endothelial apoptosis. Incubation of oxLDL with magnolol (2.5-20 microM) inhibited copper-induced oxidative modification via diene formation, thiobarbituric acid reactive substances (TBARS) assay and electrophoretic mobility assay. Apoptotic cell death as characterized by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain. We measured the production of reactive oxygen species (ROS) by using the fluorescent probe 2',7'-dichlorofluorescein acetoxymethyl ester (DCF-AM), and observed the activity of antioxidant enzymes. Furthermore, several apoptotic signaling pathways which showed NF-kappaB activation, increased cytosolic calcium, alteration of mitochondrial membrane potential, cytochrome c release and activation of caspase 3 were also investigated. We demonstrated that magnolol prevented the copper-induced oxidative modification of LDL. Magnolol attenuated the oxLDL-induced ROS generation and subsequent NF-kappaB activation. Furthermore, intracellular calcium accumulation and subsequent mitochondrial membrane potential collapse, cytochome c release and activation of caspase 3 caused by oxLDL were also inhibited by magnolol. Our results suggest that magnolol may have clinical implications in the prevention of atherosclerotic vascular disease through decreasing the oxLDL-induced ROS production.

Protective effects of eugenol against oxidized LDL-induced cytotoxicity and adhesion molecule expression in endothelial cells

Eugenol, a natural constituent of a number of aromatic plants and their essential oil fractions, has several biological effects. However, its protective effects against endothelial injury remain unclarified. This study investigates how eugenol affects human umbilical vein endothelial cells (HUVECs) dysfunction mediated by oxidized low density lipoprotein (oxLDL). Our results showed that the suppression of endothelial NO synthase (eNOS) expression, enhancement of adhesion molecules (ICAM, VCAM, and E-selectin) expression, and adherence of monocytic THP1 cells caused by a non-cytotoxic concentration (100 microg/ml) of oxLDL were ameliorated following a eugenol treatment (12.5-100 microM) in HUVECs. Eugneol also inhibited the reactive oxygen species (ROS) generation, intracellular calcium accumulation, and the subsequent mitochondrial membrane potential collapse, cytochrome c release and caspase-3 activation induced by oxLDL. The cytotoxicity and apoptotic features induced by a cytotoxic concentration (200 microg/ml) of oxLDL was also attenuated by eugenol. Our results suggest that eugenol may protect against the oxLDL-induced dysfunction in endothelial cells.

Protective effects of honokiol against oxidized LDL-induced cytotoxicity and adhesion molecule expression in endothelial cells

Honokiol, a compound extracted from Chinese medicinal herb Magnolia officinalis, has several biological effects. However, its protective effects against endothelial injury remain unclarified. In this study, we examined whether honokiol prevented oxidized low-density lipoprotein (oxLDL)-induced vascular endothelial dysfunction. Incubation of oxLDL with honokiol (2.5-20 microM) inhibited copper-induced oxidative modification as demonstrated by diene formation, thiobarbituric acid reactive substances (TBARS) assay and electrophoretic mobility assay. Expression of adhesion molecules (ICAM, VCAM and E-selectin) and endothelial NO synthase (eNOS) affected by oxLDL was investigated by flow cytometry and Western blot. We also measured the production of reactive oxygen species (ROS) using the fluorescent probe 2',7'-dichlorofluorescein acetoxymethyl ester (DCF-AM). Furthermore, several apoptotic phenomena including increased cytosolic calcium, alteration of mitochondrial membrane potential, cytochrome c release and activation of caspase-3 were also investigated. Apoptotic cell death was characterized by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain. The results showed that honokiol prevented the copper-induced oxidative modification of LDL. Honokiol also ameliorated the oxLDL-diminished eNOS protein expression and reduced the oxLDL-induced adhesion molecules and the adherence of THP-1 cells to HUVECs. Furthermore, honokiol attenuated the oxLDL-induced cytotoxicity, apoptotic features, ROS generation, intracellular calcium accumulation and the subsequent mitochondrial membrane potential collapse, cytochrome c release and activation of caspase-3. Our results suggest that honokiol may have clinical implications in the prevention of atherosclerotic vascular disease.

Rosiglitazone inhibits endothelial proliferation and angiogenesis

Rosiglitazone, an insulin sensitizer, is known to offer beneficial effects in retarding atherosclerotic vascular diseases. Since proliferation and angiogenesis are involved in initiation and plaque instability, two critical steps in the cardiovascular events, this study was designed to evaluate the mechanisms of rosiglitazone on endothelial proliferation and angiogenesis. Rosiglitazone-treated human umbilical vein endothelial cells were analyzed for growth rate by use of cell number counting, 3-[4,5-Dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide assay as well as 3H-thymidine incorporation. Cell cycle analysis was detected by flow cytometry and cell cycle-related proteins were measured by Western blot. Effects of rosiglitazone on angiogenesis were assessed by vascular endothelial growth factor (VEGF)-induced tube formation and wound-healing migration. Furthermore, effects of rosiglitazone on actin stress fiber were observed under confocal microscopy. Our data showed that rosiglitazone inhibits endothelial proliferation in a dose-dependent manner. Rosiglitazone caused endothelial arrest at G1 phase via affecting several cell cycle-related proteins that led to attenuate phosphorylation of retinoblastoma protein. Rosiglitazone markedly decreased VEGF-induced tube formation and endothelial cell migration, which might be explained by a disorganization of the actin cytoskeleton. Our data suggest that both anti-proliferative and anti-angiogenic activities in endothelial cells might account for the greater than expected beneficial effects of rosiglitazone for the treatment and prevention of atherosclerosis.

Exercise paradoxically modulates oxidized low density lipoprotein-induced adhesion molecules expression and trans-endothelial migration of monocyte in men

Physical exercise can affect the risk of cardiovascular disease. Oxidized-low density lipoprotein (ox-LDL) promotes transendothelial migration (TEM) of monocyte, thereby accelerating the pathogenesis of atherosclerosis. This study investigated how exercise intensity affects monocyte/EC interactions under ox-LDL-mediated condition. Light- (LIE), moderate- (MIE) and high- (HIE) intensity exercise (i.e., 40%, 60%, and 80% VO2max, respectively) on a bicycle ergometer in 18 sedentary healthy men were performed on three separate occasions. Before and immediately after exercise, ox-LDL-promoted expressions of monocyte adhesion molecules and TEM of monocyte, as well as oxidation of LDL and amounts of soluble adhesion molecules in plasma were measured. Analytical results showed that (1) ox-LDL furthered monocyte L-selectin shedding and Mac-1 expression, and an attendant increase in TEM of monocyte, while treating the monocyte with Mac-1 antibody inhibited the ox-LDL-promoted TEM of monocyte; (2) under ox-LDL-treated condition, MIE increased monocyte Mac-1 and LFA-1 expressions, enhancing the TEM of monocyte, whereas HIE downregulated monocyte Mac-1 expression, suppressing the TEM of monocyte; (3) LIE decreased basal LFA-1 expression as well as basal and ox-LDL-promoted TEM of monocyte; and (4) MIE and HIE, but not LIE, elevated plasma ox-LDL level, while there were no significant changes in sL-selectin, sE-selectin, sICAM-1, and sVCAM-1 following these exercises. Therefore, we conclude that monocyte activation and subsequent TEM promoted by ox-LDL are changed by short-term exercise in an intensity-dependent manner. These findings provide a new insight into the may aid the development of suitable exercise intensity enable people to prevent early atherogenesis.

Hypercholesterolemia, not metabolic syndrome, related to adhesion of monocytes to cultured endothelium in nondiabetic subjects

The interaction of leukocytes and endothelium plays an important role in the development of atherosclerosis. Previous studies found that adhesion of leukocytes to endothelium is greater in subjects with hypercholesterolemia. It is not clear if metabolic syndrome, a contributing risk factor of cardiovascular disease, is related to this adhesion. Therefore, we conducted a study, in which 48 nondiabetic subjects were enrolled, to determine the relationship between leukocyte adhesion and the components of metabolic syndrome. After a 12-hour overnight fast, subjects' fasting blood was obtained for measurement of lipoprotein concentrations and glucose and insulin levels. Results of the number of monocyte adhesion to human umbilical vein endothelial cells were divided into high monocyte adhesion group and low monocyte adhesion group (n=24 in each group). Plasma concentrations of total cholesterol (245 +/- 5 vs 229+/- 4 mg/dL, P=.021) and low-density lipoprotein cholesterol (LDL-C) (162+/- 4 vs 146+/- 3 mg/dL, P=.003) were both higher in the high monocyte adhesion group than in the low monocyte adhesion group. Monocyte adhesion was significantly correlated to plasma concentrations of LDL-C (r=0.407, P=.002) but not to the total cholesterol (r=0.202, P=.085). However, there was no difference in monocyte adhesion to endothelium between subjects with or without metabolic syndrome, based on the modified criteria from the Adult Treatment Panel III of the National Cholesterol Education Program. Insulin resistance index, presented as homeostasis model assessment insulin resistance, and glucose or insulin responses to oral glucose tolerance test were similar between groups. Our study demonstrated that monocyte adhesion to endothelium has a stronger relationship with the plasma concentration LDL-C than with characteristics of metabolic syndrome.

Resveratrol, a polyphenolic compound in red wine, protects against oxidized LDL-induced cytotoxicity in endothelial cells

BACKGROUND

Resveratrol, a polyphenolic constituent of red wine, has antioxidant effects. However, its protective effects against oxLDL-induced endothelial injury remained unclarified.

METHODS

Primary human umbilical vein endothelial cell cultures (HUVECs) treated with oxLDL (200 microg/ml) were used to explore the protective effect of resveratrol. Cytotoxicity of oxLDL on HUVECs was studied by measuring lactate dehydrogenase (LDH) release, methylthiazol tetrazolium (MTT) and apoptotic cell death as characterized by terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) stain. We also measured the production of reactive oxygen species (ROS) by using the fluorescnet probe 2', 7'-dichlorofluorescein acetoxymethyl ester (DCF-AM), and observed the activity of antioxidant enzymes. Furthermore, several apoptotic signaling pathway with increased cytosolic calcium, alteration of mitochondrial membrane potential, cytochrome c release and activation of caspase 3 were also investigated.

RESULTS

Resveratrol attenuated oxLDL-induced cytotoxicity, apoptotic features, generation of ROS and intracellular calcium accumulation. OxLDL-induced mitochondria membrane potential collapase, cytochrome c release and activation of caspase 3 in HUVECs were also suppressed by resveratrol pretreatment.

CONCLUSIONS

Red wine intake may protect against oxLDL-induced dysfunction of endothelial cells.

Protective effect of nicotinamide on neuronal cells under oxygen and glucose deprivation and hypoxia/reoxygenation

Nicotinamide (vitamin B(3)) reduces the infarct volume following focal cerebral ischemia in rats; however, its mechanism of action has not been reported. After cerebral ischemia and/or reperfusion, reactive oxygen species (ROS) and reactive nitrogen species may be generated by inflammatory cells through several cellular pathways, which can lead to intracellular calcium influx and cell damage. Therefore, we investigated the mechanisms of action of nicotinamide in neuroprotection under conditions of hypoxia/reoxygenation. Results showed that nicotinamide significantly protected rat primary cortical cells from hypoxia by reducing lactate dehydrogenase release with 1 h of oxygen-glucose deprivation (OGD) stress. ROS production and calcium influx in neuronal cells during OGD were dose-dependently diminished by up to 10 mM nicotinamide (p < 0.01). This effect was further examined with OGD/reoxygenation (H/R). Cells were stained with the fluorescent dye 4,6-diamidino-2-phenylindole (DAPI) or antibodies against anti-microtubule-associated protein-2 and cleaved caspase-3. Apoptotic cells were studied using Western blotting of cytochrome c and cleaved caspase-3. Results showed that vitamin B(3) reduced cell injury, caspase-3 cleavage and nuclear condensation (DAPI staining) in neuronal cells under H/R. In addition, nicotinamide diminished c-fos and zif268 immediate-early gene expressions following OGD. Taken together, these results indicate that the neuroprotective effect of nicotinamide might occur through these mechanisms in this in vitro ischemia/reperfusion model.

Neuroprotective MK801 is associated with nitric oxide synthase during hypoxia/reoxygenation in rat cortical cell cultures

The neuroprotective effect of MK801 against hypoxia and/or reoxygenation-induced neuronal cell injury and its relationship to neuronal nitric oxide synthetase (nNOS) expression were examined in cultured rat cortical cells. Treatment of cortical neuronal cells with hypoxia (95% N(2)/5% CO(2)) for 2 h followed by reoxygenation for 24 h induced a release of lactate dehydrogenase (LDH) into the medium, and reduced the protein level of MAP-2 as well. MK801 attenuated the release of LDH and the reduction of the MAP-2 protein by hypoxia, suggesting a neuroprotective role of MK801. MK801 also diminished the number of nuclear condensation by hypoxia/reoxygenation. The NOS inhibitors 7-nitroindazole (7-NI) and N (G)-nitro-L-arginine methyl ester (L-NAME), as well as the Ca(2+) channel blocker nimodipine, reduced hypoxia-induced LDH, suggesting that nitric oxide (NO) and calcium homeostasis contribute to hypoxia and/or the reoxygenation-induced cell injury. The levels of nNOS immunoactivities and mRNA by RT-PCR were enhanced by hypoxia with time and, down regulated following 24 h reoxygenation after hypoxia, and were attenuated by MK801. In addition, the reduction of nNOS mRNA levels by hypoxia/reoxygenation was also diminished by MK801. Further delineation of the mechanisms of NO production and nNOS regulation are needed and may lead to additional strategies to protect neuronal cells against hypoxic/reoxygenation insults.