Biomedical subjects

Hongjiang Chen

Publications and source records attributed to Hongjiang Chen.

16 recordsLinked to original sources

PubMed2005

Identification of a homocysteine receptor in the peripheral endothelium and its role in proliferation.

BACKGROUND: Homocysteine, a risk factor for atherosclerosis, increases intimal hyperplasia after carotid endarterectomy with associated smooth muscle cell proliferation and modulation of cytokines. The N-methyl-D-aspartate receptor (NMDAr), a glutamate-gated ion channel receptor, is associated with homocysteine-induced cerebrovascular injury; however, the receptor has not been identified in peripheral vascular cells, nor has any interaction with homocysteine been clarified. Our objectives were first, to identify NMDAr in rat carotid artery and rat aorta endothelial cells (RAEC); and second, to determine whether homocysteine activates NMDAr in the endothelium. METHODS: NR1 and NR2A, two NMDAr subunits, were probed in rat carotid arteries by immunohistochemistry. RNA was isolated from RAECs, and expression of all NMDAr subunits (NR1, 2A, 2B, 2C, and 2D) were examined by RT-PCR and sequencing. For receptor protein expression, RAEC were incubated with different homocysteine concentrations and incubation times and also were treated with 50 microM homocysteine and/or preincubated with 50 microM dizocilpine MK-801, an NMDAr inhibitor. RESULTS: Both NR1 and NR2A were expressed in rat carotid arteries. All NMDAr subunits were expressed in the RAECs, and there was 92% to 100% similarity compared with rat NMDAr from the National Center for Biotechnology Information (NCBI) GenBank. Homocysteine upregulated NR1 expression and increased cell proliferation. RAEC pretreatment with MK-801 reduced homocysteine-mediated cell proliferation. CONCLUSION: This study is the first to show that NMDAr exists in the peripheral vasculature, and that homocysteine may act via NMDAr to increase intimal hyperplasia. CLINICAL RELEVANCE: Our objectives included the identification of a homocysteine receptor in the peripheral vasculature. The possible inhibition of a homocysteine receptor to prevent intimal hyperplasia rather than treat established stenosis would make a significant clinical impact. This will open further avenues of study in determining the role of homocysteine in the pathogenesis of intimal hyperplasia.

Animals↗

PubMed2005

Homocysteine-induced vascular dysregulation is mediated by the NMDA receptor.

Elevated plasma homocysteine accelerates myointimal hyperplasia and luminal narrowing after carotid endarterectomy. N-methyl D aspartate receptors (NMDAr) in rat cerebrovascular cells are involved in homocysteine uptake and receptor-mediated stimulation. In the vasculature, NMDAr subunits (NR1, 2A-2D) have been identified by sequence homology in rat aortic endothelial cells. Exposure of these cells to homocysteine increased expression of receptor subunits, an effect that was attenuated by dizocilpine (MK801), a noncompetitive NMDA inhibitor. The objective of this study was to investigate the existence of an NMDAr in rat vascular smooth muscle (A7r5) cells, and also the effect of homocysteine on vascular dysregulation as mediated by this receptor. Subunits of the NMDAr (NR1, 2A-2D) were detected in the A7r5 cells by using the reverse transcriptase polymerase chain reaction and Western blotting. Homocysteine induced an increase in A7r5 cell proliferation, which was blocked by MK801. Homocysteine, in a dose and time dependent manner, increased expression of matrix metallinoproteinase-9 and interleukin-1beta, which have been implicated in vascular smooth muscle cell migration and/or proliferation. Homocysteine reduced the vascular elaboration of nitric oxide and increased the elaboration of the nitric oxide synthase inhibitor, asymmetric dimethylarginine. All of these homocysteine mediated effects were inhibited by MK801. NMDAr exist in vascular smooth muscle cells and appear to mediate, at least in part, homocysteine-induced dysregulation of vascular smooth muscle cell functions.

Animals↗

PubMed2004

Cigarette smoke increases intimal hyperplasia and homocysteine in a rat carotid endarterectomy.

BACKGROUND: Homocysteine and smoking are independent risks for CVD; however their importance in post-CEA intimal hyperplasia is unclear. We performed a CEA in rats exposed to cigarette smoke with the hypothesis that smoking would increase intimal hyperplasia that may be associated with an elevated serum homocysteine. Folic acid (FA) and the homocysteine metabolic enzymes MTHFR and CBS were used to test for the significance of homocysteine elevation. MATERIALS AND METHODS: Rats underwent an open CEA. N = 13 rats received smoke exposure 2 weeks prior, and 2 weeks post-CEA and N = 12 received no smoke. Each group was divided into either control or an FA-added diet resulting in four groups. Rats were sacrificed at 2 weeks post-CEA; liver, urine, blood, and carotid arteries samples were obtained. RESULTS: Smoked rats had increased urinary peak and trough cotinine levels versus non-smoke rats, which decreased with FA. Smoke exposure increased intimal hyperplasia versus non-smoke controls by nearly 120% (57.8 +/- 6.2 versus 26.8 +/- 5.4% luminal stenosis, P = 0.005). Smoke-exposed rats had an increased serum homocysteine versus non-smoke controls (8.3 +/- 0.8 versus 5.7 +/- 0.8 microm, P = 0.014). Smoked rats given FA had decreased serum homocysteine compared to the smoke group. Along with reductions in homocysteine, FA eliminated the increase in intimal hyperplasia seen with smoke exposure (33.5 +/- 6.1 versus 57.8 +/- 6.2% luminal stenosis, P = 0.03). CBS activity decreased in smoked rats by nearly 20% versus non-smoke rats. FA supplementation in smoked rats both (1) increased CBS activity and (2) decreased MTHFR compared to control non-smoke-exposure levels. CONCLUSION: Smoking increases plasma homocysteine and post-CEA intimal hyperplasia. This suggests homocysteine has an etiological role in the intimal hyperplasia increase observed with smoking, since both were negated with FA.

Animals↗

PubMed2004

Plasma homocysteine measurements after carotid artery manipulation and clamping in a rat CEA model.

OBJECTIVE: The effect of a rat carotid endarterectomy (CEA) on homocysteine and the metabolic enzymes methylenetetrahydrofolate reductase (MTHFR) and cystathionine beta-synthase (CBS) was studied. METHODS: Rats were placed into 7 groups: (1) no anesthesia (NA), (2) anesthesia only (AO), (3) skin opened and closed (O/C), (4) skin opened with exposure of the carotid artery and closed (O/E/C), (5) carotid isolated and clamped (CO), (6) open CEA, and (7) open femoral endarterectomy (FEA). End points included homocysteine, hepatic MTHFR, and CBS activity. RESULTS: Homocysteine in the NA, AO, O/C, O/E/C, and FEA were low and not different. CEA produced a 6-fold increase in homocysteine when compared with non-CEA groups. Specifically, CEA produced an increase in homocysteine versus the AO group at 2 weeks (11.3 +/- 0.7 vs 2.1 +/- 0.9 micromol/L;P < .001), 4 weeks (8.9 +/- 0.7 vs 3.5 +/- 0.9 micromol/L; P = .004) and 6 weeks (7.7 +/- 0.9 vs 3.1 +/- 1.5 micromol/L; P = .03). The CO group had increased homocysteine versus the O/C, O/E/C, and FEA, but was lower than the CEA group. CEA produced an increase in MTHFR and CBS versus the AO group. CONCLUSIONS: CEA resulted in elevated levels of homocysteine; however, when broken down into its component parts, no elevation was observed except for a small increase with the CO procedure. Manipulation of the femoral artery did not raise homocysteine levels. The increase in homocysteine is possibly due to the combination of vessel wall damage and changes in cerebral blood flow dynamics.

Animals↗

PubMed2003

Eicosapentanoic acid inhibits hypoxia-reoxygenation-induced injury by attenuating upregulation of MMP-1 in adult rat myocytes.

BACKGROUND: Myocardial hypoxia-reoxygenation (H-R) is associated with upregulation of metalloproteinases (MMPs). Upregulation of MMPs is associated with cell injury. Previous studies have shown that fish oil can protect myocardium from injury induced by H-R. This study was designed to examine the effect of eicosapentanoic acid (EPA), one of the major components in fish oil, on the modulation of MMP-1 expression in response to H-R in cultured adult rat myocytes. METHODS AND RESULTS: Myocytes isolated from adult Sprague-Dawley rat hearts were cultured with or without EPA or arachidonic acid (AA) (10 and 50 microM) and exposed to 24 h of hypoxia followed by 3 h of reoxygenation (H-R). H-R resulted in myocyte injury (measured on LDH release), increase in p38MAPK phosphorylation (Western analysis), augmentation of lipid peroxidation, and upregulation of MMP-1 activity (zymography) and expression (RT-PCR and Western analysis) (all P<0.01 vs. control, n=5). Pretreatment of myocytes with EPA, but not AA, resulted in a reduction in LDH release, and attenuation of p38MAPK phosphorylation and MMP-1 activity and expression in response to H-R (all P<0.05 vs. H-R alone). Pretreatment of myocytes with EPA also reduced lipid peroxidation in myocytes exposed to H-R (P<0.05 vs. H-R alone). A high concentration of EPA (50 microM) was more potent than the lower concentration of EPA (10 microM). CONCLUSIONS: These observations suggest that EPA attenuates an increase in MMP-1 following H-R, which may be a basis of protection of myocytes from the adverse effects of H-R. p38MAPK phosphorylation may be an important signaling event in this process.

Animals↗

PubMed2003

Expression of lectin-like oxidized low-density lipoprotein receptors during ischemia-reperfusion and its role in determination of apoptosis and left ventricular dysfunction.

OBJECTIVES: The goal of this study was to determine the role of lectin-like oxidized low-density lipoprotein receptors (LOX-1), a recently identified oxidized low-density lipoprotein (ox-LDL) receptor, in ischemia-reperfusion injury to the heart. BACKGROUND: Reactive oxygen species (ROS) released during ischemia-reperfusion oxidize low-density lipoproteins; LOX-1 is upregulated by ox-LDL and ROS, and is involved in cell injury. METHODS: Anesthetized rats were subjected to left coronary artery ligation for 60 min (n = 10, ischemia group), or ischemia followed by 60 min of reperfusion (n = 30, ischemia-reperfusion group). Rats in the latter group were treated with saline, the LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat immunoglobulin G (IgG) (10 mg/kg). Ten other rats underwent thoracotomy without coronary ligation (sham control). RESULTS: Ischemia-reperfusion was associated with an increase in LOX-1 expression, lipid peroxidation and apoptosis, a large infarct area, and a decrease in left ventricular function (all, p < 0.01 vs. sham control and ischemia alone groups). Treatment of rats with LOX-1 antibody prevented ischemia-reperfusion-induced upregulation of LOX-1. Importantly, the LOX-1 antibody reduced apoptosis by 48%, lipid peroxidation by 39%, and myocardial infarct size by 45%, and improved left ventricular function (first derivative of pressure measured over time: -47% to -18%, p < 0.01). Nonspecific IgG had no effect. CONCLUSIONS: Lectin-like oxidized low-density lipoprotein receptors are upregulated during myocardial ischemia-reperfusion, and appear to be associated with apoptosis, necrosis, and left ventricular functional deterioration.

Animals↗

PubMed2003

LOX-1, an oxidized LDL endothelial receptor, induces CD40/CD40L signaling in human coronary artery endothelial cells.

BACKGROUND: Despite increasing appreciation that atherogenesis involves participation of inflammatory cells, information on mediators of communication between different constituents of atherosclerotic plaque remain incomplete. We examined the role of LOX-1, a receptor for oxidized (ox) LDL, in the expression of CD40/CD40L in cultured human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: We observed that ox-LDL increased the expression of CD40 and CD40L in a concentration (10 to 80 microg/mL)- and time (1 to 24 hours)- dependent manner. These effects of ox-LDL were mediated by activation of LOX-1, because pretreatment of HCAECs with a blocking antibody to LOX-1 (JTX92) prevented the expression of CD40 and CD40L in response to ox-LDL (P<0.01). In parallel experiments, HCAECs were incubated with the protein kinase C (PKC) inhibitor bisindolylmaleimide I, and the cells were then exposed to ox-LDL. Both LOX-1 antibody and the PKC inhibitor inhibited PKC activation in response to ox-LDL (P<0.01). The PKC inhibitor also blocked the effects of ox-LDL on the expression of CD40 and CD40L (P<0.01). In additional experiments, we found that it is the PKCalpha, but not PKCbeta and PKCgamma, isoform that mediated ox-LDL-induced CD40 and CD40L upregulation. Further experiments showed that upregulation of CD40 mediated induction of proinflammatory genes, because CD40 antibody markedly reduced ox-LDL-induced TNF-alpha generation and P-selectin expression, whereas nonspecific mouse IgG had no effect. CONCLUSIONS: These findings indicate that ox-LDL through its receptor LOX-1 triggers the CD40/CD40L signaling pathway that activates the inflammatory reaction in HCAECs. These observations provide novel insight into ox-LDL-mediated inflammation in atherosclerosis.

Arteriosclerosis↗

PubMed2003

LOX-1 mediates oxidized low-density lipoprotein-induced expression of matrix metalloproteinases in human coronary artery endothelial cells.

BACKGROUND: Oxidized LDL (ox-LDL) accumulation in the atherosclerotic region may enhance plaque instability. Both accumulation of ox-LDL and expression of its lectin-like receptor, LOX-1, have been shown in atherosclerotic regions. This study was designed to examine the role of LOX-1 in the modulation of metalloproteinases (MMP-1 and MMP-3) in human coronary artery endothelial cells (HCAECs). METHODS AND RESULTS: HCAECs were incubated with ox-LDL (10 to 80 micro g/mL) for 1 to 24 hours. Ox-LDL increased the expression of MMP-1 (collagenase) and MMP-3 (stromelysin-1) in a concentration- and time-dependent manner. Ox-LDL also increased collagenase activity. Ox-LDL did not significantly affect the expression of tissue inhibitors of metalloproteinases. Native LDL had no effect on the expression of MMPs. The effects of ox-LDL were mediated by its endothelial receptor, LOX-1, because pretreatment of HCAECs with a blocking antibody to LOX-1 (JTX92, 10 micro g/mL) prevented the expression of MMPs in response to ox-LDL (P<0.01). In parallel experiments, ox-LDL caused the activation of protein kinase C (PKC), which was inhibited by LOX-1 antibody. The PKC-beta isoform played a critical role in the expression of MMPs, because the PKC-beta inhibitor hispidin reduced ox-LDL-induced activation of PKC and the expression of MMPs. Other PKC subunits (alpha, gamma, and epsilon) did not affect the expression of MMPs. CONCLUSIONS: These findings indicate that ox-LDL, via LOX-1 activation, modulates the expression and activity of MMPs in HCAECs. In this process, activation of the PKC-beta subunit plays an important signaling role.

Cells, Cultured↗

PubMed2003

Oxidized-LDL through LOX-1 increases the expression of angiotensin converting enzyme in human coronary artery endothelial cells.

BACKGROUND AND OBJECTIVES: Our previous studies have shown that oxidized low-density lipoprotein (ox-LDL) and angiotensin II (Ang II) influence each other's action in endothelial cells. This study was designed to examine the regulation by ox-LDL of the expression of angiotensin converting enzyme (ACE) gene in human coronary artery endothelial cells (HCAECs). In addition, we studied the effect of the HMG CoA reductase inhibitor simvastatin on this interaction. METHODS AND RESULTS: Cultured HCAECs were incubated with ox-LDL (10-80 microg/ml) for 1-24 h. Ox-LDL increased the expression of ACE in a concentration- and time-dependent fashion. The upregulation of ACE expression in response to ox-LDL was mediated by its endothelial receptor LOX-1, since pretreatment of HCAECs with a blocking antibody to LOX-1 prevented the expression of ACE (P<0.01). Native-LDL had no significant effect on ACE expression. In this process, ox-LDL-induced activation of mitogen-activated protein kinase (MAPK p42/44) played an important role, since pretreatment of HCAECs with the MAPK p42/44 inhibitor (PD98059, 10 microM) inhibited MAPK activation and subsequently attenuated the expression of ACE (P<0.01 vs. ox-LDL alone). In other experiments, we pretreated HCAECs with simvastatin (10 microM) and then exposed the cells to ox-LDL. Simvastatin markedly attenuated ox-LDL-induced MAPK activation, and concurrently reduced ACE expression (P<0.01 vs. ox-LDL alone). CONCLUSIONS: Our observations provide direct evidence that ox-LDL via LOX-1 activation induces ACE gene expression in HCAECs, and MAPK activation plays a signal transduction role in this process. Simvastatin, which inhibits MAPK activation, also blocks ox-LDL-mediated upregulation of ACE.

Antibodies, Monoclonal↗

PubMed2003

EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules in human coronary artery endothelial cells via protein kinase B pathway.

Uptake of oxidized low-density lipoprotein (ox-LDL) by endothelial cells is a critical step for the initiation and development of atherosclerosis. Adhesion molecules are inflammatory makers, which are upregulated by ox-LDL and play a pivotal role in atherogenesis. A number of studies suggest that fish and its constituents can reduce inflammation and decrease atherosclerosis. We hypothesized that fish oil constituents namely docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA) may reduce expression of adhesion molecules induced by ox-LDL. Cultured human coronary artery endothelial cells (HCAECs) were incubated with ox-LDL for 24 h. Parallel groups of cells were pretreated with DHA or EPA (10 or 50 microM) overnight before incubation with ox-LDL. Ox-LDL markedly increased the expression of P-selectin and intracellular adhesion molecule-1 (ICAM-1) (both protein and mRNA) in HCAECs, and enhanced the adhesion of monocytes to the cultured HCAECs. Both EPA and DHA decreased ox-LDL-induced upregulation of expression of P-selectin and ICAM-1, and the enhanced adhesion of monocytes to HCAECs. To determine the role of protein kinase B (PKB) as an intracellular-signaling pathway, HCAECs were treated with the PKB upstream inhibitor wortmannin (100 nM) or transfected with plasmids encoding dominant-negative mutants of PKB (PKB-DN) before treatment with DHA. Ox-LDL alone downregulated the activity of PKB; DHA attenuated this effect of ox-LDL, and both wortmannin and PKB-DN blocked the effect of DHA. The present study in human coronary endothelial cells suggests that both EPA and DHA attenuate ox-LDL-induced expression of adhesion molecules, and the adhesion of monocytes to HCAECs by modulation of PKB activation. These effects may be important mechanisms of anti-atherosclerotic effects of fish and fish oils.

Arteries↗

PubMed2003

TGF-beta 1 attenuates myocardial ischemia-reperfusion injury via inhibition of upregulation of MMP-1.

Ischemia-reperfusion (I/R) is thought to upregulate the expression and activity of matrix metalloproteinases (MMPs), which regulate myocardial and vascular remodeling. Previous studies have shown that transforming growth factor-beta(1) (TGF-beta(1)) can attenuate myocardial injury induced by I/R. TGF-beta(1) is also reported to suppress the release of MMPs. To study the modulation of MMP-1 by TGF-beta(1) in I/R myocardium, Sprague-Dawley rats were given saline and subjected to 1 h of myocardial ischemia [total left coronary artery (LCA) ligation] followed by 1 h of reperfusion (n = 9). Parallel groups of rats were pretreated with recombinant TGF-beta(1) (rTGF-beta(1), 1 mg/rat, n = 9) before reperfusion or exposure to sham I/R (control group). I/R caused myocardial necrosis and dysfunction, indicated by decreased first derivative of left ventricular pressure, mean arterial blood pressure, and heart rate (all P < 0.01 vs. sham-operated control group). Simultaneously, I/R upregulated MMP-1 (P < 0.01). Treatment of rats with rTGF-beta(1) reduced the extent of myocardial necrosis and dysfunction despite I/R (all P < 0.01). rTGF-beta(1) treatment also inhibited the upregulation of MMP-1 in the I/R myocardium (P < 0.05). To determine the direct effect of MMP-1 on the myocardium, isolated adult rat myocytes were treated with active MMP-1, which caused injury and death of cultured myocytes, measured as lactate dehydrogenase release and trypan blue staining, in a dose- and time-dependent manner (P < 0.05). Pretreatment with PD-166793, a specific MMP inhibitor, attenuated myocardial injury and death induced by active MMP-1. The present study for the first time shows that MMP-1 can directly cause myocyte injury or death and that attenuation of myocardial I/R injury by TGF-beta(1) may, at least partly, be mediated by the inhibition of upregulation of MMP-1.

Animals↗

PubMed2002

Mixed tocopherol preparation is superior to alpha-tocopherol alone against hypoxia-reoxygenation injury.

Hypoxia-reoxygenation (H-R) is associated with alterations in oxidant-antioxidant balance and L-arginine-nitric oxide system. Tocopherols decrease the activity of reactive oxygen species (ROS) and yet are not beneficial in clinical trials. It has been proposed that mixed tocopherols as found in nature may be more tissue protective than alpha-tocopherol alone found in commercial preparations. We compared the effect of a mixed tocopherol preparation with that of alpha-tocopherol alone on superoxide dismutase (SOD) activity and iNOS expression in cultured myocytes exposed to H-R. Myocytes from Sprague-Dawley rat hearts were subjected to hypoxia for 24 h followed by reoxygenation for 3 h H-R. Parallel groups of myocytes were pretreated with alpha-tocopherol alone or a mixed-tocopherol preparation (containing alpha-, gamma-, and delta-tocopherols) (50 microM) for 30 min. H-R resulted in myocyte injury (determined by LDH release), a decrease in SOD activity and an upregulation of iNOS expression/activity. Both tocopherol preparations attenuated cell injury and markedly decreased the effects of H-R on SOD activity and iNOS expression/activity (all P < 0.05 vs H-R group, n = 5). However, mixed-tocopherol preparation was much superior to alpha-tocopherol in terms of myocyte protection from the adverse effect of H-R (P < 0.05). Lack of efficacy of commercial tocopherol preparations in clinical trials may reflect absence of gamma- and delta-tocopherols.

Animals↗

PubMed2002

Modulation of matrix metalloproteinase-1, its tissue inhibitor, and nuclear factor-kappa B by losartan in hypercholesterolemic rabbits.

Upregulation of angiotensin II receptor, may be involved in the initiation and progression of atherosclerosis. To examine the contribution of AT1 receptor in the expression of matrix metalloproteinase-1 (MMP-1) and its tissue inhibitor (TIMP-2) in lipid-deposited arterial tissues, New Zealand white rabbits were given high-cholesterol chow (with losartan 25 mg/d or vehicle) for 10 weeks. Losartan reduced the areas of sudanophilia in the aorta of rabbits fed high-cholesterol diet (p < 0.01 vs. control). Losartan also significantly decreased the enhanced mRNA expression of MMP-1 and TIMP-2 in aortas of rabbits with high-cholesterol diet. Losartan-treated rabbits revealed a reduction in immunohistochemical expression of MMP-1, whereas TIMP-2 expression became localized to the intima. In addition, losartan treatment reduced the activation of NF-kappa B by inhibiting the degradation of its inhibitor I kappa-B alpha. These observations demonstrate that AT1 receptor blockade with losartan reduces lipid deposition and exerts potent inhibitory effects on NF-kappa B activation and modulates the expression of MMP-1 and TIMP-2 in hypercholesterolemic rabbits.

Angiotensin II↗

PubMed2002

Statins modulate oxidized low-density lipoprotein-mediated adhesion molecule expression in human coronary artery endothelial cells: role of LOX-1.

LOX-1, a receptor for oxidized low-density lipoprotein (ox-LDL), plays a critical role in endothelial dysfunction and atherosclerosis. LOX-1 activation also plays an important role in monocyte adhesion to endothelial cells. A number of studies show that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) reduce total LDL cholesterol and exert a cardioprotective effect. We examined the modulation of LOX-1 expression and its function by two different statins, simvastatin and atorvastatin, in human coronary artery endothelial cells (HCAECs). We observed that ox-LDL (40 microg/ml) treatment up-regulated the expression of E- and P-selectins, VCAM-1 and ICAM-1 in HCAECs. Ox-LDL mediated these effects via LOX-1, since antisense to LOX-1 mRNA decreased LOX-1 expression and subsequent adhesion molecule expression. Pretreatment of HCAECs with simvastatin or atorvastatin (1 and 10 microM) reduced ox-LDL-induced expression of LOX-1 as well as adhesion molecules (all P < 0.05). A high concentration of statins (10 microM) was more potent than the low concentration (1 microM) (P < 0.05). Both statins reduced ox-LDL-mediated activation of the redox-sensitive nuclear factor-kappaB (NF-kappaB) but not AP-1. These observations indicate that LOX-1 activation plays an important role in ox-LDL-induced expression of adhesion molecules. Inhibition of expression of LOX-1 and adhesion molecules and activation of NF-kappaB may be another mechanism of beneficial effects of statins in vascular diseases.

Atorvastatin↗

PubMed2002

LOX-1 inhibition in myocardial ischemia-reperfusion injury: modulation of MMP-1 and inflammation.

A recently identified lectin-like oxidized low-density lipoprotein receptor (LOX-1) mediates endothelial cell injury and facilitates inflammatory cell adhesion. We studied the role of LOX-1 in myocardial ischemia-reperfusion (I/R) injury. Anesthetized Sprague-Dawley rats were subjected to 60 min of left coronary artery (LCA) ligation, followed by 60 min of reperfusion. Rats were treated with saline, LOX-1 blocking antibody JXT21 (10 mg/kg), or nonspecific anti-goat IgG (10 mg/kg) before I/R. Ten other rats underwent surgery without LCA ligation and served as a sham control group. LOX-1 expression was markedly increased during I/R (P < 0.01 vs. sham control group). Simultaneously, the expression of matrix metalloproteinase-1 (MMP-1) and adhesion molecules (P-selectin, VCAM-1, and ICAM-1) was also increased in the I/R area (P < 0.01 vs. sham control group). There was intense leukocyte accumulation in the I/R area in the saline-treated group. Treatment of rats with the LOX-1 antibody prevented I/R-induced upregulation of LOX-1 and reduced MMP-1 and adhesion molecule expression as well as leukocyte recruitment. LOX-1 antibody, but not nonspecific IgG, also reduced myocardial infarct size (P < 0.01 vs. saline-treated I/R group). To explore the link between LOX-1 and adhesion molecule expression, we measured expression of oxidative stress-sensitive p38 mitogen-activated protein kinase (p38 MAPK). The activity of p38 MAPK was increased during I/R (P < 0.01 vs. sham control), and use of LOX-1 antibody inhibited p38 MAPK activation (P < 0.01). These findings indicate that myocardial I/R upregulates LOX-1 expression, which through p38 MAPK activation increases the expression of MMP-1 and adhesion molecules. Inhibition of LOX-1 exerts an important protective effect against myocardial I/R injury.

Animals↗

PubMedDate not supplied

Effect of clopidogrel on platelet aggregation and intimal hyperplasia following carotid endarterectomy in the rat.

Intimal hyperplasia results in significant morbidity and mortality following vascular intervention. Both platelets and elevated homocysteine have been implicated in the development of intimal hyperplasia. We previously demonstrated that a locally applied antiplatelet agent decreases the development of intimal hyperplasia. We were therefore interested in a systemic antiplatelet agent, clopidogrel. We hypothesized that clopidogrel would decrease platelet aggregation and activity and intimal hyperplasia. Male Sprague-Dawley rats underwent carotid endarterectomy (CEA) and treatment with either placebo or varying regimens of clopidogrel, including chronic, pre-CEA bolus, chronic plus pre-CEA bolus, and chronic plus post-CEA bolus; a homocystine diet was used to elevate both plasma homocysteine and the degree of intimal hyperplasia. Platelet aggregation, platelet activity, and intimal hyperplasia were then assessed. Platelet aggregation was not decreased with chronic clopidogrel; however, it was decreased with pre-CEA bolus clopidogrel. Similarly, platelet activity was not inhibited by chronic clopidogrel but was inhibited by pre-CEA and chronic plus pre-CEA bolus clopidogrel. Neither chronic, pre-CEA bolus, chronic plus pre-CEA bolus, nor chronic plus post-CEA bolus clopidogrel resulted in a decrease in intimal hyperplasia. Although pre-CEA bolus clopidogrel resulted in a decrease in both platelet aggregation and activity, it was unable to decrease the development of intimal hyperplasia at any dose. Additional factors must therefore contribute to the pathologic development of intimal hyperplasia.

Animals↗