Increased monocyte adhesion to aortic endothelium in rats with hyperhomocysteinemia: role of chemokine and adhesion molecules

Sex-specific implications of inflammation in covert cerebral small vessel disease

BACKGROUND

The relationship between inflammation and covert cerebral small vessel disease (SVD) with regards to sex difference has received limited attention in research. We aim to unravel the intricate associations between inflammation and covert SVD, while also scrutinizing potential sex-based differences in these connections.

METHODS

Non-stroke/dementia-free study population was from the I-Lan longitudinal Aging Study. Severity and etiology of SVD were assessed by 3T-MRI in each participant. Systemic and vascular inflammatory-status was determined by the circulatory levels of high-sensitivity C-reactive protein (hsCRP) and homocysteine, respectively. Sex-specific multivariate logistic regression to calculate odds ratios (ORs) and interaction models to scrutinize women-to-men ratios of ORs (RORs) were used to evaluate the potential impact of sex on the associations between inflammatory factors and SVD.

RESULTS

Overall, 708 participants (62.19 ± 8.51 years; 392 women) were included. Only women had significant associations between homocysteine levels and covert SVD, particularly in arteriosclerosis/lipohyalinosis SVD (ORs[95%CI]: 1.14[1.03-1.27] and 1.15[1.05-1.27] for more severe and arteriosclerosis/lipohyalinosis SVD, respectively). Furthermore, higher circulatory levels of homocysteine were associated with a greater risk of covert SVD in women compared to men, as evidenced by the RORs [95%CI]: 1.14[1.01-1.29] and 1.14[1.02-1.28] for more severe and arteriosclerosis/lipohyalinosis SVD, respectively. No significant associations were found between circulatory hsCRP levels and SVD in either sex.

CONCLUSION

Circulatory homocysteine is associated with covert SVD of arteriosclerosis/lipohyalinosis solely in women. The intricacies underlying the sex-specific effects of homocysteine on SVD at the preclinical stage warrant further investigations, potentially leading to personalized/tailored managements.

TRIAL REGISTRATION

Not applicable.

In vitro and in vivo exposure of endothelial cells to dibutyl phthalate promotes monocyte adhesion

The effect of endothelial cells' exposure to dibutyl phthalate (DBP) on monocyte adhesion is largely unknown. We evaluated monocyte adhesion to DBP-exposed endothelial cells by combining three approaches: short-term exposure (24 h) of EA.hy926 cells to 10-6, 10-5, and 10-4 M DBP, long-term exposure (12 weeks) of EA.hy926 cells to 10-9, 10-8, and 10-7 M DBP, and exposure of rats (28 and 90 days) to 100, 500, and 5000 mg DBP/kg food. Monocyte adhesion to human EA.hy926 and rat aortic endothelial cells, expression of selected cellular adhesion molecules and chemokines, and the involvement of extracellular signal-regulated kinase 1/2 (ERK1/2) were analyzed. We observed increased monocyte adhesion to DBP-exposed EA.hy926 cells in vitro and to rat aortic endothelium ex vivo. ERK1/2 inhibitor prevented monocyte adhesion to DBP-exposed EA.hy926 cells in short-term exposure experiments. Increased ERK1/2 phosphorylation in rat aortic endothelium and transient decrease in ERK1/2 activation following long-term exposure of EA.hy926 cells to DBP were also observed. In summary, exposure of endothelial cells to DBP promotes monocyte adhesion, thus suggesting a possible role for this phthalate in the development of atherosclerosis. ERK1/2 signaling could be the mediator of monocyte adhesion to DBP-exposed endothelial cells, but only after short-term high-level exposure.

Homocysteine and Glaucoma

Elevated levels of homocysteine (Hcy), a non-proteinogenic amino acid, may lead to a host of manifestations across the biological systems, particularly the nervous system. Defects in Hcy metabolism have been associated with many neurodegenerative diseases including glaucoma, i.e., the leading cause of blindness. However, the pathophysiology of elevated Hcy and its eligibility as a risk factor for glaucoma remain unclear. We aimed to provide a comprehensive review of the relationship between elevated Hcy levels and glaucoma. Through a systemic search of the PubMed and Google Scholar databases, we found that elevated Hcy might play an important role in the pathogenesis of glaucoma. Further research will be necessary to help clarify the specific contribution of elevated Hcy in the pathogenesis of glaucoma. A discovery and conceptual understanding of Hcy-associated glaucoma could be the keys to providing better therapeutic treatment, if not prophylactic treatment, for this disease.

Natural lactucopicrin alleviates importin-α3-mediated NF-κB activation in inflammated endothelial cells and improves sepsis in mice

Lactucopicrin, a bitter sesquiterpene lactone of leafy vegetables, such as chicory, curly escarole, and lettuce, possesses anti-malarial, anti-cancer and analgesic properties. However, it remains unknown whether lactucopicrin could inhibit vascular endothelial nuclear factor-κB (NF-κB) activation, a hallmark of vascular inflammatory diseases including sepsis. In tumor necrosis factor-α-stimulated human or mouse aortic endothelial cells, lactucopicrin dose-dependently inhibited NF-κB activation, and concomitantly repressed both vascular cell adhesion molecule 1 (VCAM-1) and intercellular adhesion molecule 1 (ICAM-1)-mediated monocyte adhesion. The lactucopicrin effect was not due to modulation of inhibitor of NF-κB kinases (IKK) α/β/γ, inhibitor of NF-κB alpha (IκBα), and NF-κB/p65 DNA binding activity. Instead, lactucopicrin inhibited importin-α3 expression by destabilization of its mRNA, an effect mediating the lactucopicrin effect on NF-κB activity. More importantly, in lipopolysaccharide (LPS)-elicited septic mice, oral gavage with lactucopicrin decreased mortality by 30.5% as compared with the control treatment. This effect was associated with inhibited importin-α3 expression, suppressed NF-κB activation and VCAM-1/ICAM-1 expression, and inhibited leukocyte influx in the vascular endothelium of both lung and aorta. Collectively, our novel data suggest that dietary supplementation with lactucopicrin inhibits endothelial NF-κB activation by down-regulation of importin-α3 and thereby improves sepsis.

The impact of reactive oxygen species in the development of cardiometabolic disorders: a review

Oxidative stress, an alteration in the balance between reactive oxygen species (ROS) generation and antioxidant buffering capacity, has been implicated in the pathogenesis of cardiometabolic disorders (CMD). At physiological levels, ROS functions as signalling mediators, regulates various physiological functions such as the growth, proliferation, and migration endothelial cells (EC) and smooth muscle cells (SMC); formation and development of new blood vessels; EC and SMC regulated death; vascular tone; host defence; and genomic stability. However, at excessive levels, it causes a deviation in the redox state, mediates the development of CMD. Multiple mechanisms account for the rise in the production of free radicals in the heart. These include mitochondrial dysfunction and uncoupling, increased fatty acid oxidation, exaggerated activity of nicotinamide adenine dinucleotide phosphate oxidase (NOX), reduced antioxidant capacity, and cardiac metabolic memory. The purpose of this study is to discuss the link between oxidative stress and the aetiopathogenesis of CMD and highlight associated mechanisms. Oxidative stress plays a vital role in the development of obesity and dyslipidaemia, insulin resistance and diabetes, hypertension via various mechanisms associated with ROS-led inflammatory response and endothelial dysfunction.

Probucol decreases homocysteine-stimulated CRP production in rat aortic smooth muscle cells via regulating HO-1/NADPH oxidase/ROS/p38 pathway

The elevated homocysteine level is an independent risk factor for atherosclerosis, which is characterized as a chronic inflammatory disease associated with oxidative stress. We have confirmed that homocysteine can stimulate the production of C-reactive protein (CRP) in rat aortic smooth muscle cells (RASMCs). In the present study, we investigated the role of probucol in homocysteine-induced CRP expression in cultured RASMCs and high-methionine-diet-induced hyperhomocysteinemic rats. The results showed that probucol decreased homocysteine-induced CRP mRNA and protein expression in RASMCs in a concentration-dependent manner. In addition, the animal experiment showed that probucol not only inhibited CRP expression in the vessel wall but also reduced the circulating CRP level in hyperhomocysteinemic rats. Further investigations revealed that probucol markedly increased heme oxygenase-1 activity, suppressed nicotinamide adenine dinucleotide phosphate (NADPH) oxidase activity, diminished superoxide anion generation, and decreased p38 phosphorylation in RASMCs and hyperhomocysteinemic rat aorta. These data demonstrate that probucol can inhibit homocysteine-induced CRP generation by interfering with the NADPH oxidase/p38 signal pathway in RASMCs, which will provide new evidence for the anti-inflammatory and anti-atherosclerotic effects of probucol.

Effects of ketoisocaproic acid and inflammation on glucose transport in muscle cells

Branched-chain amino acids (BCAAs) are regulators of protein metabolism. However, elevated levels of BCAAs and their metabolites are linked to insulin resistance. We previously demonstrated that the leucine metabolite, α-ketoisocaproate (KIC), inhibited insulin-stimulated glucose transport in myotubes. Like KIC, inflammatory factors are implicated in the development of insulin resistance. Here, we analyzed the effect of KIC and inflammatory factors (homocysteine [50 μM], TNF-α [10 ng/ml], and interleukin 6 (IL-6) [10 ng/ml]) on myotubes. Although KIC suppressed insulin-stimulated glucose transport, addition of the inflammatory factors did not worsen this effect. Depletion of branched-chain aminotransferase 2, the enzyme that catalyzes the conversion of leucine into KIC, abrogated the effect of KIC and the inflammatory factors. The effect of insulin on AKTS473 and S6K1T389 phosphorylation was not modified by treatments. There were no treatment effects on glycogen synthase phosphorylation. Depletion of E1α subunit of branched-chain α-keto acid dehydrogenase, the enzyme that catalyzes the oxidative decarboxylation of KIC, suppressed insulin-stimulated glucose transport, especially in cells incubated in KIC. Thus, defects in BCAA catabolism are contributory to insulin resistance of glucose transport in myotubes, especially in the presence of KIC. Interventions that increase BCAA catabolism may promote muscle glucose utilization and improve insulin resistance and its sequelae.

Ischemia-Reperfusion Injury Reduces Kidney Folate Transporter Expression and Plasma Folate Levels

Acute or chronic kidney disease can cause micronutrient deficiency. Patients with end-stage renal disease, kidney transplantation or on dialysis have reduced circulating levels of folate, an essential B vitamin. However, the molecular mechanism is not well understood. Reabsorption of folate in renal proximal tubules through folate transporters is an important process to prevent urinary loss of folate. The present study investigated the impact of acute kidney injury (AKI) on folate transporter expression and the underlying mechanism. AKI was induced in Sprague-Dawley rats that were subjected to kidney ischemia (45 min)-reperfusion (24 h). Both male and female rats displayed kidney injury and low plasma folate levels compared with sham-operated rats. The plasma folate levels were inversely correlated to plasma creatinine levels. There was a significant increase in neutrophil gelatinase-associated lipocalin (NGAL) and IL-6 mRNA expression in the kidneys of rats with ischemia-reperfusion, indicating kidney injury and increased inflammatory cytokine expression. Ischemia-reperfusion decreased mRNA and protein expression of folate transporters including folate receptor 1 (FOLR1) and reduced folate carrier (RFC); and inhibited transcription factor Sp1/DNA binding activity in the kidneys. Simulated ischemia-reperfusion through hypoxia-reoxygenation or Sp1 siRNA transfection in human proximal tubular cells inhibited folate transporter expression and reduced intracellular folate levels. These results suggest that ischemia-reperfusion injury downregulates renal folate transporter expression and decreases folate uptake by tubular cells, which may contribute to low folate status in AKI. In conclusion, ischemia-reperfusion injury can downregulate Sp1 mediated-folate transporter expression in tubular cells, which may reduce folate reabsorption and lead to low folate status.

Inhibition of Inflammatory Cytokine Expression Prevents High-Fat Diet-Induced Kidney Injury: Role of Lingonberry Supplementation

Chronic low-grade inflammation is a major stimulus for progression of chronic kidney disease (CKD) in individuals consuming high-fat diet. Currently, there are limited treatment options for CKD other than controlling the progression rate and its associated complications. Lingonberry (Vaccinium vitis-idaea L.) is rich in anthocyanins with demonstrated anti-inflammatory effect. In the current study, we investigated the potential renal protective effect of lingonberry and its anthocyanin (cyanidin-3-glucoside) in high-fat diet fed obese mice and in human proximal tubular cells. Prolonged consumption of high-fat diets is strongly associated with obesity, abnormal lipid and glucose metabolism. Mice (C57BL/6J) fed a high-fat diet (62% kcal fat) for 12 weeks developed renal injury as indicated by an elevation of blood urea nitrogen (BUN) level as well as an increase in renal kidney injury molecule-1 (KIM-1), neutrophil gelatinase-associated lipocalin (NGAL) and renin expression. Those mice displayed an activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB) and increased expression of inflammatory cytokines-monocyte chemoattractant-1 (MCP-1), tumor necrosis factor alpha (TNF-α), interleukin-6 (IL-6) in the kidneys. Mice fed a high-fat diet also had a significant elevation of inflammatory cytokine levels in the plasma. Dietary supplementation of lingonberry for 12 weeks not only attenuated high-fat diet-induced renal inflammatory response but also reduced kidney injury. Such a treatment improved plasma lipid and glucose profiles, reduced plasma inflammatory cytokine levels but did not affect body weight gain induced by high-fat diet feeding. Lingonberry extract or its active component cyanidin-3-glucoside effectively inhibited palmitic acid-induced NF-κB activation and inflammatory cytokine expression in proximal tubular cells. These results suggest that lingonberry supplementation can reduce inflammatory response and prevent chronic kidney injury. Such a renal protective effect by lingonberry and its active component may be mediated, in part, through NF-κB signaling pathway.

Serum/plasma homocysteine levels in patients with systemic lupus erythematosus: a systematic review and meta-analysis

Published studies have shown contradictory results in the association of serum/plasma levels of homocysteine (HCY) with systemic lupus erythematosus (SLE). This study is to systematically evaluate the association of serum/plasma HCY levels in SLE. A search was done using PubMed, Embase, Web of Science, and ScienceDirect databases up to 7 April 2019. Thirty-six articles including 2919 SLE patients and 3120 healthy controls were finally included in this meta-analysis. The HCY levels were significantly higher in SLE patients than in healthy controls (P < 0.001). The subgroup analysis revealed that Asian, African, Arab, Mixed, White and others as well as ages (< 35 and ≥ 35) had significant higher HCY levels in SLE patients than in the healthy controls. The study indicated that patients with disease activity index scores < 8 (P < 0.001) and ≥ 8 (P = 0.003) of SLE had significant higher HCY levels as compared with the healthy controls. It was also revealed that disease duration in SLE patients for < 10 and ≥ 10 years (P < 0.001) had significant higher HCY levels as compared with the healthy controls. A significant higher HCY level for body mass index (< 23 and ≥ 23) was found as well as measurement type in SLE patients than healthy controls. This meta-analysis demonstrated higher HCY levels in patients with SLE than healthy controls, suggesting a possible role of HCY in the disease.Key Points• Homocysteine (HCY) is closely related to the mechanisms of systemic lupus erythematosus (SLE).• This study reveals a significant correlation between HCY levels and the various indexes of disease activity.• This study reveals that medication may influence HCY levels in SLE.• This study also discovers that the subgroup analysis of all the factors influences the HCY levels in SLE patients.

The immunomodulatory mechanism of brain injury induced by hyperhomocysteinemia in spontaneously hypertensive rats

BACKGROUND

Elevated plasma homocysteine (Hcy) concentration is considered as the diagnostic criteria of Hyperhomocysteinemia (HHcy), which is associated with the inflammatory response and blood-brain barrier disruption. Previous studies have proposed that HHcy with hypertension was associated with the brain injury by enhancing the cerebrovascular permeability, however, the immune mechanism remains obscure. The purpose of the study is to explore the immunomodulatory mechanism of brain injury in spontaneously hypertensive rats (SHRs) induced by HHcy.

MATERIALS AND METHODS

Sixty SHRs were randomly assigned to three groups: SHR-C (control group), SHR-M (methionine group) and SHR-T (treatment group). Physical examination of body weight, systolic blood pressure (SBP) and plasma Hcy content was measured every 4 weeks. Besides, T-helper cell 17 and regulatory T cells (Treg)-related inflammatory cytokines (interleukin [IL]-6, IL-17, IL-10, and transforming growth factor beta [TGF-β]) and genes (RORγt and FoxP3) were detected by enzyme-linked immunosorbent assay, quantitative polymerase chain reaction , Western blot, and immunohistochemistry.

RESULTS

High methionine diet could cause weight loss, SBP rising, and plasma Hcy content significantly elevated. IL-16 and IL-17A levels in peripheral blood and in brain tissue both lifted, while IL-10 and TGF-β levels dropped; RORγt expression raised in brain, nevertheless, FoxP3 levels were the opposite. After the intervention with vitamin B6, B12, and folic acid in SHR-T group, these trends would be eased or completely changed. Furthermore, brain tissue slices showed that IL-17-positive cells tended to decrease, and IL-10-positive cells increased in SHR-T group, which was reversed in SHR-M group.

CONCLUSIONS

HHcy may promote inflammation that can lead to brain lesions and down-regulate immune response to protect the brain.

High methionine, low folate and low vitamin B6/B12 (HM-LF-LV) diet causes neurodegeneration and subsequent short-term memory loss

Methionine is an essential amino acid found in rich quantities in average American diet such as meats, fish and eggs. Excessive consumption of such food often exceeds the normal requirement of the methionine in our body; which found to be related to the development of neurodegenerative disorders. However, the mechanistic pathways of methionine's influence on the brain are unclear. The present study is focus on the effects of high methionine, low folate and low vitamin B6/B12 (HM-LF-LV) diet on the dysfunction of neuronal and vascular specific markers in the brain. C57BL6/J male mice (8-10 week old) were fed with HM-LF-LV diet for a 6 week period. Cognitive function of mice was determine by measuring short-term memory using a Novel Object Recognition test (NORT). Neuronal dysfunction were evaluate by measuring the levels of Neuronal nuclear antigen (NeuN), Neuron-specific-enolase (NSE) and Fluoro-jade C(FJC) fluorescence; while cerebrovascular disruption were evaluate by assessing levels of endothelial junction proteins Vascular Endothelial-Cadherin (VE-Cadherin) and Claudin-5 in harvested brain tissue. Cerebrovascular permeability was assess by evaluating microvascular leakage of fluorescently labeled albumin in vivo. Endothelial and Neuronal Nitric Oxide Synthase (eNOS, nNOS) regulation and vascular inflammation (ICAM: intercellular adhesion molecules) were also evaluate in brain tissue. All assessments were conduct at weekly intervals throughout the study duration. NORT showed a significant temporal decrease in short-term memory of mice fed on HM-LF-LV diet for 6 weeks compared to the wild-type control group. Our experimental data showed that neuronal dysfunction (decreased NeuN levels and increased FJC positive neurons in brain) was more prominent in HM-LF-LV diet fed mice compared to normal diet fed control mice. In experimental mice, cerebrovascular disruption was found to be elevated as evident from increased pial venular permeability (microvascular leakage) and decreased in VE-Cadherin expression compared to control. Slight decrease in nNOS and increase in eNOS in experimental mice suggest a trend towards the decrease in potential for neuronal development due to the long-term HM-LF-LV diet fed. Collectively, our results suggest that a diet containing high methionine, low folate and low vitamin B6/B12 results in increased neuronal degeneration and vascular dysfunction, leading to short-term memory loss. Interestingly, significant neuronal damage precedes vascular dysfunction.

The metabolism and significance of homocysteine in nutrition and health

An association between arteriosclerosis and homocysteine (Hcy) was first demonstrated in 1969. Hcy is a sulfur containing amino acid derived from the essential amino acid methionine (Met). Hyperhomocysteinemia (HHcy) was subsequently shown in several age-related pathologies such as osteoporosis, Alzheimer's disease, Parkinson's disease, stroke, and cardiovascular disease (CVD). Also, Hcy is associated with (but not limited to) cancer, aortic aneurysm, hypothyroidism and end renal stage disease to mention some. The circulating levels of Hcy can be increased by defects in enzymes of the metabolism of Met, deficiencies of vitamins B6, B12 and folate or by feeding Met enriched diets. Additionally, some of the pharmaceuticals currently in clinical practice such as lipid lowering, and anti-Parkinsonian drugs are known to elevate Hcy levels. Studies on supplementation with folate, vitamins B6 and B12 have shown reduction in Hcy levels but concomitant reduction in certain associated pathologies have not been definitive. The enormous importance of Hcy in health and disease is illustrated by its prevalence in the medical literature (e.g. > 22,000 publications). Although there are compelling data in favor of Hcy as a modifiable risk factor, the debate regarding the significance of Hcy mediated health effects is still ongoing. Despite associations between increased levels of Hcy with several pathologies being well documented, whether it is a causative factor, or an effect remains inconclusive. The present review though not exhaustive, is focused on several important aspects of Hcy metabolism and their relevance to health.

Vascular protective effects of Astragalus membranaceus and its main constituents in rats with chronic hyperhomocysteinemia

Hyperhomocysteinemia (HHcy) is an important factor in cardiovascular disease. However, is currently no cure available in western medicine for HHcy-evoked cardiovascular disease. The present study explored the vascular protective effects of Astragalus membranaceus (AM), a traditional Chinese medicine. Rats with HHcy were induced by feeding high-methionine diets and treated with total extract of AM (TEA) and its constituents, including Astragalus saponins (ASP), Astragalus total flavonoids (ATF) and Astragalus polysaccharides (APS). Examination of the rats indicated that TEA and ASP controlled blood pressure and ameliorated HHcy-induced impairment of endothelium-dependent vasorelaxation by increasing the nitric oxide content and nitric oxide synthase activity of the abdominal aorta. Furthermore, they decreased the accumulation of hydrogen peroxide and superoxide anion, and attenuated the inhibition of superoxide dismutase and catalase activities in rats with HHcy. Additionally, TEA and ASP attenuated the HHcy-induced increases of matrix metalloproteinase (MMP)-2 and -9 concentrations. However, similar effects were not observed for ATF and APS. In conclusion, TEA and ASP are beneficial to vascular disease, and their effects may be attributed to protective actions against oxidation, activity of the MMPs and endothelial dysfunction.

NLRP3 inflammasome as a novel target for docosahexaenoic acid metabolites to abrogate glomerular injury

The nucleotide-binding oligomerization domain-like receptor containing pyrin domain 3 (NLRP3) inflammasome has been implicated in podocyte injury and glomerular sclerosis during hyperhomocysteinemia (hHcys). However, it remains unclear whether the NLRP3 inflammasome can be a therapeutic target for treatment of hHcys-induced kidney injury. Given that DHA metabolites-resolvins have potent anti-inflammatory effects, the present study tested whether the prototype, resolvin D1 (RvD1), and 17S-hydroxy DHA (17S-HDHA), an intermediate product, abrogate hHcys-induced podocyte injury by targeting the NLRP3 inflammasome. In vitro, confocal microscopy demonstrated that 17S-HDHA (100 nM) and RvD1 (60 nM) prevented Hcys-induced formation of NLRP3 inflammasomes, as shown by reduced colocalization of NLRP3 with apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) or caspase-1. Both DHA metabolites inhibited Hcys-induced caspase-1 activation and interleukin-1β production. However, DHA had no significant effect on these Hcys-induced changes in podocytes. In vivo, DHA lipoxygenase metabolites substantially inhibited podocyte NLRP3 inflammasome formation and activation and consequent glomerular sclerosis in mice with hHcys. Mechanistically, RvD1 and 17S-HDHA were shown to suppress Hcys-induced formation of lipid raft redox signaling platforms and subsequent O₂^·- production in podocytes. It is concluded that inhibition of NLRP3 inflammasome activation is one of the important mechanisms mediating the beneficial action of RvD1 and 17S-HDHA on Hcys-induced podocyte injury and glomerular sclerosis.

Monocyte Induction of E-Selectin-Mediated Endothelial Activation Releases VE-Cadherin Junctions to Promote Tumor Cell Extravasation in the Metastasis Cascade

Tumor cells interact with blood constituents and these interactions promote metastasis. Selectins are vascular receptors facilitating interactions of tumor cells with platelets, leukocytes, and endothelium, but the role of endothelial E-selectin remains unclear. Here we show that E-selectin is a major receptor for monocyte recruitment to tumor cell-activated endothelium. Experimental and spontaneous lung metastasis using murine tumor cells, without E-selectin ligands, were attenuated in E-selectin-deficient mice. Tumor cell-derived CCL2 promoted endothelial activation, resulting in enhanced endothelial E-selectin expression. The recruitment of inflammatory monocytes to metastasizing tumor cells was dependent on the local endothelial activation and the presence of E-selectin. Monocytes promoted transendothelial migration of tumor cells through the induction of E-selectin-dependent endothelial retractions and a subsequent modulation of tight junctions through dephosphorylation of VE-cadherin. Thus, endothelial E-selectin shapes the tumor microenvironment through the recruitment, adhesion, and activation of monocytes that facilitate tumor cell extravasation and thereby metastasis. These findings provide evidence that endothelial E-selectin is a novel factor contributing to endothelial retraction required for efficient lung metastasis. Cancer Res; 76(18); 5302-12. ©2016 AACR.

Atherogenesis: hyperhomocysteinemia interactions with LDL, macrophage function, paraoxonase 1, and exercise

Despite great strides in understanding the atherogenesis process, the mechanisms are not entirely known. In addition to diet, cigarette smoking, genetic predisposition, and hypertension, hyperhomocysteinemia (HHcy), an accumulation of the noncoding sulfur-containing amino acid homocysteine (Hcy), is a significant contributor to atherogenesis. Although exercise decreases HHcy and increases longevity, the complete mechanism is unclear. In light of recent evidence, in this review, we focus on the effects of HHcy on macrophage function, differentiation, and polarization. Though there is need for further evidence, it is most likely that HHcy-mediated alterations in macrophage function are important contributors to atherogenesis, and HHcy-countering strategies, such as nutrition and exercise, should be included in the combinatorial regimens for effective prevention and regression of atherosclerotic plaques. Therefore, we also included a discussion on the effects of exercise on the HHcy-mediated atherogenic process.

Simulated microgravity promotes monocyte adhesion to rat aortic endothelium via nuclear factor-κB activation

Microgravity-induced vascular remodelling may play an important role in post-spaceflight orthostatic intolerance. In this study, we aimed to investigate the effects of simulated microgravity on monocyte adhesion to aortic endothelium in hindlimb unweighted rats and to elucidate the underlying mechanisms associated with this event. Sprague-Dawley rats were subjected to 4-week hindlimb unweighting to simulate microgravity. The recruitment of monocytes to the abdominal aorta was investigated by en face immunofluorescence staining and monocyte binding assays. The expression of the adhesion molecules E-selectin and vascular cell adhesion molecule-1 as well as the cytokine monocyte chemoattractant protein (MCP)-1 was evaluated by immunohistochemical staining, western blot, and quantitative reverse transcription polymerase chain reaction analyses. Additionally, nuclear factor-κB (NF-κB) activation and the messenger RNA expression levels of E-selectin, vascular cell adhesion molecule-1, and MCP-1 were assessed with the administration of an NF-κB inhibitor, pyrrolidine dithiocarbamate. Results showed that simulated microgravity significantly increased monocyte recruitment to the aortic endothelium, protein expression of E-selectin and MCP-1, and NF-κB activation in the abdominal aorta of rats. Pyrrolidine dithiocarbamate treatment not only significantly inhibited NF-κB activity but also reduced the messenger RNA levels of E-selectin, vascular cell adhesion molecule-1, and MCP-1 as well as monocyte recruitment in the abdominal aorta of hindlimb unweighted rats. These results suggest that simulated microgravity increases monocyte adhesion to rat aortic endothelium via the NF-κB-mediated expression of the adhesion molecule E-selectin and the cytokine MCP-1. Therefore, an NF-κB-mediated inflammatory response may be one of the cellular mechanisms responsible for arterial remodelling during exposure to microgravity.

Endothelial dysfunction: the link between homocysteine and hydrogen sulfide

High level of homocysteine (hyperhomocysteinemia, HHcy) is associated with increased risk for vascular disease. Evidence for this emerges from epidemiological studies which show that HHcy is associated with premature peripheral, coronary artery and cerebrovascular disease independent of other risk factors. Possible mechanisms by which homocysteine causes vascular injury include endothelial injury, DNA dysfunction, proliferation of smooth muscle cells, increased oxidative stress, reduced activity of glutathione peroxidase and promoting inflammation. HHcy has been shown to cause direct damage to endothelial cells both in vitro and in vivo. Clinically, this manifests as impaired flow-mediated vasodilation and is mainly due to a reduction in nitric oxide synthesis and bioavailability. The effect of impaired nitric oxide release can in turn trigger and potentiate atherothrombogenesis and oxidative stress. Endothelial damage is a crucial aspect of atherosclerosis and precedes overt manifestation of disease. In addition, endothelial dysfunction is also associated with hypertension, diabetes, ischemia reperfusion injury and neurodegenerative diseases. Homocysteine is a precursor of hydrogen sulfide (H2S) which is formed by transulfuration process catalyzed by the enzymes, cystathionine β-synthase and cystathionine γ-lyase. H2S is a gasotransmitter that has emerged recently as a novel mediator in cardiovascular homeostasis. As a potent vasodilator, it plays several roles which include regulation of vessel diameter, protection of endothelium from redox stress, ischemia reperfusion injury and chronic inflammation. However, the precise mechanism by which it mediates these beneficial effects is complex and still remains unclear. Current evidence indicates H2S modulates cellular functions by a variety of intracellular signaling processes. In this review, we summarize the mechanisms of HHcy-induced endothelial dysfunction and the metabolism and physiological functions of H2S as a protective agent.

Redox regulation of NLRP3 inflammasomes: ROS as trigger or effector?

SIGNIFICANCE

Inflammasomes are multiprotein complexes localized within the cytoplasm of the cell that are responsible for the maturation of proinflammatory cytokines such as interleukin-1β (IL-1β) and IL-18, and the activation of a highly inflammatory form of cell death, pyroptosis. In response to infection or cellular stress, inflammasomes are assembled, activated, and involved in host defense and pathophysiology of diseases. Clarification of the molecular mechanisms leading to the activation of this intracellular inflammatory machinery may provide new insights into the concept of inflammation as the root of and route to human diseases.

RECENT ADVANCES

The activation of inflammasomes, specifically the most fully characterized inflammasome-the nucleotide-binding oligomerization domain (NOD)-like receptor containing pyrin domain 3 (NLRP3) inflammasome, is now emerging as a critical molecular mechanism for many degenerative diseases. Several models have been developed to describe how NLRP3 inflammasomes are activated, including K(+) efflux, lysosome function, endoplasmic reticulum (ER) stress, intracellular calcium, ubiquitination, microRNAs, and, in particular, reactive oxygen species (ROS).

CRITICAL ISSUES

ROS may serve as a "kindling" or triggering factor to activate NLRP3 inflammasomes as well as "bonfire" or "effector" molecules, resulting in pathological processes. Increasing evidence seeks to understand how this spatiotemporal action of ROS occurs during NLRP3 inflammasome activation, which will be a major focus of this review.

FUTURE DIRECTIONS

It is imperative to know how this dual action of ROS works during NLRP3 inflammation activation on different stimuli and what relevance such spatiotemporal redox regulation of NLRP3 inflammasomes has in cell or organ functions and possible human diseases.

The role of homocysteine-lowering B-vitamins in the primary prevention of cardiovascular disease

Cardiovascular disease (CVD) is the leading cause of mortality in the Western world. The effort of research should aim at the primary prevention of CVD. Alongside statin therapy, which is maintained to be an effective method of CVD prevention, there are alternative methods such as vitamin B substitution therapy with folic acid (FA), and vitamins B12 and B6 . B-vitamins may inhibit atherogenesis by decreasing the plasma level of homocysteine (Hcy)-a suspected etiological factor for atherosclerosis-and by other mechanisms, primarily through their antioxidant properties. Although Hcy-lowering vitamin trials have failed to demonstrate beneficial effects of B-vitamins in the prevention of CVD, a meta-analysis and stratification of a number of large vitamin trials have suggested their effectiveness in cardiovascular prevention (CVP) in some aspects. Furthermore, interpretation of the results from these large vitamin trials has been troubled by statin/aspirin therapy, which was applied along with the vitamin substitution, and FA fortification, both of which obscured the separate effects of vitamins in CVP. Recent research results have accentuated a new approach to vitamin therapy for CVP. Studies undertaken with the aim of primary prevention have shown that vitamin B substitution may be effective in the primary prevention of CVD and may also be an option in the secondary prevention of disease if statin therapy is accompanied by serious adverse effects. Further investigations are needed to determine the validity of vitamin substitution therapy before its introduction in the protocol of CVD prevention.

Homocysteine induces the expression of C-reactive protein via NMDAr-ROS-MAPK-NF-κB signal pathway in rat vascular smooth muscle cells

OBJECTIVE

Homocysteine (Hcy) is known as an independent risk factor for atherosclerosis. C-reactive protein (CRP) directly participates in initiation and progression of atherosclerosis. However, there is no direct evidence to demonstrate pro-inflammatory effect of Hcy on vascular smooth muscle cells (VSMCs) through CRP. In the present study, we examined the effect of Hcy on CRP expression and investigated the related mechanism in VSMCs.

METHODS AND RESULTS

Protein expression and secretion were detected by Western blot and ELISA, respectively. mRNA expression was detected by RT-PCR. Superoxide anion was detected by lucigenin chemiluminometry and the immunofluorescence staining was observed by a fluorescence microscope. The results revealed that Hcy significantly induced mRNA and protein expressions of CRP in VSMCs both in vitro and in vivo, and anti-IL-1β or anti-IL-6 neutralizing antibody alone or in combination partially reduced Hcy-induced CRP expression. Hcy increased the expression of NR1 subunit of N-methyl-d-aspartate receptor (NMDAr), and MK-801 alleviated Hcy-induced CRP expression in VSMCs. Further studies showed that Hcy-stimulated superoxide anion generation in VSMCs. Nevertheless, pretreatment of the cells with MK-801, TTFA and DPI significantly reduced Hcy-stimulated superoxide anion generation, and antioxidant NAC decreased Hcy-induced CRP expression in VSMCs. Additionally, PD98059, SB205380 or PDTC antagonized Hcy-induced CRP expression, and MK-801, NAC, PD98059 or SB205380 inhibited Hcy-activated phosphorylations of ERK1/2 and p38.

CONCLUSION

The present study demonstrates that Hcy is able to initiate an inflammatory response in VSMCs by stimulating CRP production, which is mediated through NMDAr-ROS-ERK1/2/p38-NF-κB signal pathway. These findings provide new evidence for a role of Hcy in pathogenesis of atherosclerosis.

Effect of homocysteine on intestinal permeability in rats with experimental colitis, and its mechanism

OBJECTIVE

To investigate the effect of homocysteine (Hcy) on intestinal permeability in rats with TNBS/ethanol-induced colitis and elucidate its mechanism.

METHODS

Sprague-Dawley rats were divided into four groups: normal, normal + Hcy injection, TNBS model, and TNBS model + Hcy injection. Experimental colitis was induced by trinitrobenzene sulfonic acid (TNBS) in 50% ethanol; rats were injected subcutaneously with Hcy from the first day after the induction of experimental colitis on 30 consecutive days. To determine the severity of colitis, the disease activity index (DAI) was evaluated; colon tissues were collected for the detection of the activity of myeloperoxidase (MPO) and the contents of MDA, IL-1β, IL-6, TNF-α, MMP-2, and MMP-9. Intestinal epithelial permeability was assessed with Evans blue (EB) dye. The levels of Hcy in plasma and colon mucosa were measured by high-performance liquid chromatography-fluorescence detection (HPLC-FD).

RESULTS

Compared with the normal group, the DAI scoring and MPO activity, contents of MDA, IL-1β, IL-6, TNF-α, MMP-2, MMP-9 in the colon and EB in the small intestine were significantly increased in the TNBS group (P < 0.01). Compared with the TNBS model group, the DAI scoring, plasma and colonic mucosa Hcy levels, MPO activity and contents of MDA, IL-1β, IL-6, TNF-α, MMP-2, MMP-9 in colon and EB in small intestine were significantly increased in the TNBS-induced colitis rats with simultaneous Hcy injection (P < 0.01).

CONCLUSION

Hcy can increase intestinal permeability and aggravate inflammatory damage in rats with TNBS-induced colitis, the underlying mechanisms of which may be attributed to its effects of promoting the expression of MMP-2 and MMP-9, leading to injury of the intestinal barrier.

Effects of allicin on hyperhomocysteinemia-induced experimental vascular endothelial dysfunction

This study was designed to investigate the effect and mechanism of allicin on hyperhomocysteinemia-induced experimental vascular endothelial dysfunction in rats. Fifty male Wistar rats were randomly divided into five groups: the normal control rats (NC), the high-methionine-diet rats (Met), the high-methionine-diet rats treated with folic acid, vitaminB₆ and vitaminB₁₂ (Met+F), or with low-dose allicin (Met+L), or with high-dose allicin (Met+H). After 6 weeks, we collected blood samples of all groups to determine plasma endothelin (ET), serum homocysteine (Hcy), nitric oxide (NO), superoxide dismutase (SOD), malondialdehyde (MDA), and detected the expression of basic fibroblast growth factors (bFGF), transforming growth factor beta (TGF-β), tumor necrosis factor-alpha (TNF-α), and intercellular adhesion molecule-1 (ICAM-1) in the aorta. The Hcy and the expression of TGF-β in both the Met+L and Met+H groups were significantly lower than the Met and Met+F groups. The ET, ET/NO ratio and the MDA levels of the Met+L and Met+H groups were significantly lower than the Met group. The SOD and NO levels and the expression of bFGF, TNF-α and ICAM-1 of the Met+L and Met+H groups were significantly higher than the Met group. Our data indicate that allicin inhibits lipid peroxidation induced by hyperhomocysteinemia and regulates the excretion and equilibrium of ET and NO, and suggest that allicin might be useful in the prevention of endothelial dysfunction caused by hyperhomocysteinemia.

Zc3h12c inhibits vascular inflammation by repressing NF-κB activation and pro-inflammatory gene expression in endothelial cells

Endothelial activation characterized by the expression of multiple chemokines and adhesive molecules is a critical initial step of vascular inflammation, which results in recruitment of leucocytes into the sub-endothelial layer of the vascular wall and triggers vascular inflammatory diseases such as atherosclerosis. Although inhibiting endothelial inflammation has already been well recognized as a therapeutic strategy in vascular inflammatory diseases, the therapeutic targets are still elusive. In the present study we found that Zc3h12c (zinc finger CCCH-type-containing 12C), a recently discovered CCCH zinc finger-containing protein, significantly inhibited the endothelial cell inflammatory response in vitro. Overexpression of Zc3h12c significantly attenuated TNFα (tumour necrosis factor α)-induced expression of chemokines and adhesive molecules, and thus reduced monocyte adherence to HUVECs (human umbilical vein endothelial cells). Conversely, siRNA (small interfering RNA)-mediated knockdown of Zc3h12c increased the TNFα-induced expression of chemokines and adhesive molecules in HUVECs. Furthermore, forced expression of Zc3h12c decreased TNFα-induced IKKα/β [IκB (inhibitor of nuclear factor κB) kinase α/β], IκBα phosphorylation and p65 nuclear translocation, suggesting that Zc3h12c exerted its anti-inflammatory function probably by suppressing the NF-κB (nuclear factor κB) pathway. Thus Zc3h12c is an endogenous inhibitor of TNFα-induced inflammatory signalling in HUVECs and might be a therapeutic target in vascular inflammatory diseases.

NADPH oxidase-mediated triggering of inflammasome activation in mouse podocytes and glomeruli during hyperhomocysteinemia

AIM

Our previous studies have shown that NOD-like receptor protein (NALP3) inflammasome activation is importantly involved in podocyte dysfunction and glomerular sclerosis induced by hyperhomocysteinemia (hHcys). The present study was designed to test whether nicotinamide adenine dinucleotide phosphate (NADPH) oxidase-mediated redox signaling contributes to homocysteine (Hcys)-induced activation of NALP3 inflammasomes, an intracellular inflammatory machinery in podocytes in vitro and in vivo.

RESULTS

In vitro confocal microscopy and size-exclusion chromatography revealed that upon NADPH oxidase inhibition by gp91(phox) siRNA, gp91ds-tat peptide, diphenyleneiodonium, or apocynin, aggregation of inflammasome proteins NALP3, apoptosis-associated speck-like protein (ASC), and caspase-1 was significantly attenuated in mouse podocytes. This NADPH oxidase inhibition also resulted in diminished Hcys-induced inflammasome activation, evidenced by reduced caspase-1 activity and interleukin-1β production. Similar findings were observed in vivo where gp91(phox-/-) mice and mice receiving a gp91ds-tat treatment exhibited markedly reduced inflammasome formation and activation. Further, in vivo NADPH oxidase inhibition protected the glomeruli and podocytes from hHcys-induced injury as shown by attenuated proteinuria, albuminuria, and glomerular sclerotic changes. This might be attributed to the fact that gp91(phox-/-) and gp91ds-tat-treated mice had abolished infiltration of macrophages and T-cells into the glomeruli during hHcys.

INNOVATION

Our study for the first time links NADPH oxidase to the formation and activation of NALP3 inflammasomes in podocytes.

CONCLUSION

Hcys-induced NADPH oxidase activation is importantly involved in the switching on of NALP3 inflammasomes within podocytes, which leads to the downstream recruitment of immune cells, ultimately resulting in glomerular injury and sclerosis.

Site-specific antioxidative therapy for prevention of atherosclerosis and cardiovascular disease

Oxidative stress has been implicated in pathophysiology of aging and age-associated disease. Antioxidative medicine has become a practice for prevention of atherosclerosis. However, limited success in preventing cardiovascular disease (CVD) in individuals with atherosclerosis using general antioxidants has prompted us to develop a novel antioxidative strategy to prevent atherosclerosis. Reducing visceral adipose tissue by calorie restriction (CR) and regular endurance exercise represents a causative therapy for ameliorating oxidative stress. Some of the recently emerging drugs used for the treatment of CVD may be assigned as site-specific antioxidants. CR and exercise mimetic agents are the choice for individuals who are difficult to continue CR and exercise. Better understanding of molecular and cellular biology of redox signaling will pave the way for more effective antioxidative medicine for prevention of CVD and prolongation of healthy life span.

Effects of ghrelin on homocysteine-induced dysfunction and inflammatory response in rat cardiac microvascular endothelial cells

Ghrelin is a well-characterized hormone that has protective effects on endothelial cells. Elevated HCY (homocysteine) can be a cardiovascular risk factor, but it is not known whether ghrelin can inhibit HCY-induced dysfunction and inflammatory response in rat CMECs (cardiac microvascular endothelial cells). We found that HCY treatment for 24 h inhibited proliferation and NO (nitric oxide) secretion, but with increased cell apoptosis and secretion of cytokines in CMECs. In contrast, ghrelin pretreatment significantly improved proliferation and NO secretion, and inhibited cell apoptosis and secretion of cytokines in HCY-induced CMECs. In addition, Western blot assay showed that NF-κB (nuclear factor κB) and cleaved-caspase 3 expression were elevated, and PCNA (proliferating cell nuclear antigen) and eNOS (endothelial nitric oxide synthase) expression were decreased after treatment with HCY, which was significantly reversed by pretreatment with ghrelin. The data suggest that ghrelin inhibits HCY-induced CMEC dysfunction and inflammatory response, probably mediated by inhibition of NF-κB activation.

Caffeic acid inhibits acute hyperhomocysteinemia-induced leukocyte rolling and adhesion in mouse cerebral venules

OBJECTIVE

To investigate the effects and possible mechanisms of CA on acute HHcy-induced leukocyte rolling and adhesion in mouse cerebral venules.

METHODS

Male C57 BL/6J mice were injected with DL-Hcy (50 mg/kg) and CA (10 mg/kg). The effect of CA on HHcy-induced leukocyte rolling and adhesion in cerebral vessels was assessed using intravital microscopy. Plasma cytokines and chemokines were evaluated by cytometric bead array. ROS production in HUVECs and adhesion molecule expression on leukocytes were determined by flow cytometry. E-selectin and ICAM-1 expression in cerebrovascular endothelium was detected by immunohistochemistry. CD18 phosphorylation and the Src/PI3K/Akt pathway in leukocytes were determined by confocal microscopy and Western blot.

RESULTS

CA inhibited HHcy-elicited leukocyte rolling and adhesion, decreased ROS production in HUVECs, and reduced plasma KC, MIP-2, and MCP-1 levels. CA reduced the E-selectin and ICAM-1 expression on cerebrovascular endothelium and CD11b/CD18 on leukocytes caused by HHcy. Of notice, CA depressed CD18 phosphorylation and the Src/PI3K/Akt pathway in leukocytes.

CONCLUSIONS

CA inhibited HHcy-provoked leukocyte rolling and adhesion in cerebral venules, ameliorating adhesion molecule expression and activation, which is related to the suppression of the Src/PI3K/Akt pathway in leukocytes.

The effects of berberine on hyperhomocysteinemia and hyperlipidemia in rats fed with a long-term high-fat diet

Background

The study was undertaken to examine the effects of berberine (BBR) on serum homocysteine, lipids and the aortic lesion in Sprague–Dawley (SD) rats fed with a long-term high-fat diet (HFD).

Methods

Healthy male SD rats weighing 190-210 g received randomly standard diet or a high-fat diet for 24 weeks. After 8 weeks of feeding, rats fed with HFD were randomized to receive berberine (200 mg · kg-1· day-1) or vehicle by gavage for 16 weeks. After overnight fasting, all rats were sacrificed and total blood samples were also collected for determinant of fasting serum homocysteine (Hcy), total cholesterol (TC) and low density lipoprotein cholesterol (LDL-c) levels. The aorta was stained with hematoxylin and eosin (HE) and Sudan Ш to evaluate aortic lesion. The livers were dissected out and snap-frozen in liquid nitrogen for hepatic TC content and molecular analysis. 3-hydroxy-3-methyl-glutaryl-CoA reductase (HMGR), Lipoprotein receptors and apolipoproteins gene expression in the liver were determined by real-time PCR.

Results

Intragastrical administration with berberine for 16 weeks lowered serum Hcy in rats fed with a high-fat diet. In parallel, it also decreased body weight and improved serum TC and LDL-c. Berberine also tended to decrease hepatic cholesterol. Consistently, berberine also upregulated LDL receptor (LDLR) mRNA level and suppressed HMGR gene expression. Meanwhile, upon berberine-treated rats, there was a significant increase in apolipoprotein E (apoE) mRNA, but no change in apoAI and scavenger receptor (SR) mRNA in the liver. Further, no atherosclerotic lesions were developed in berberine-treated rats for 16 weeks.

Conclusion

Berberine can counteract HFD-elicited hyperhomocysteinemia and hyperlipidemia partially via upregulating LDLR and apoE mRNA levels and suppressing HMGR gene expression.

E-selectin mediates Porphyromonas gingivalis adherence to human endothelial cells

Porphyromonas gingivalis, a major periodontal pathogen, may contribute to atherogenesis and other inflammatory cardiovascular diseases. However, little is known about interactions between P. gingivalis and endothelial cells. E-selectin is a membrane protein on endothelial cells that initiates recruitment of leukocytes to inflamed tissue, and it may also play a role in pathogen attachment. In the present study, we examined the role of E-selectin in P. gingivalis adherence to endothelial cells. Human umbilical vein endothelial cells (HUVECs) were stimulated with tumor necrosis factor alpha (TNF-α) to induce E-selectin expression. Adherence of P. gingivalis to HUVECs was measured by fluorescence microscopy. TNF-α increased adherence of wild-type P. gingivalis to HUVECs. Antibodies to E-selectin and sialyl Lewis X suppressed P. gingivalis adherence to stimulated HUVECs. P. gingivalis mutants lacking OmpA-like proteins Pgm6 and -7 had reduced adherence to stimulated HUVECs, but fimbria-deficient mutants were not affected. E-selectin-mediated P. gingivalis adherence activated endothelial exocytosis. These results suggest that the interaction between host E-selectin and pathogen Pgm6/7 mediates P. gingivalis adherence to endothelial cells and may trigger vascular inflammation.

Homocysteinylated albumin promotes increased monocyte-endothelial cell adhesion and up-regulation of MCP1, Hsp60 and ADAM17

Rationale

The cardiovascular risk factor homocysteine is mainly bound to proteins in human plasma, and it has been hypothesized that homocysteinylated proteins are important mediators of the toxic effects of hyperhomocysteinemia. It has been recently demonstrated that homocysteinylated proteins are elevated in hemodialysis patients, a high cardiovascular risk population, and that homocysteinylated albumin shows altered properties.

Objective

Aim of this work was to investigate the effects of homocysteinylated albumin - the circulating form of this amino acid, utilized at the concentration present in uremia - on monocyte adhesion to a human endothelial cell culture monolayer and the relevant molecular changes induced at both cell levels.

Methods and Results

Treated endothelial cells showed a significant increase in monocyte adhesion. Endothelial cells showed after treatment a significant, specific and time-dependent increase in ICAM1 and VCAM1. Expression profiling and real time PCR, as well as protein analysis, showed an increase in the expression of genes encoding for chemokines/cytokines regulating the adhesion process and mediators of vascular remodeling (ADAM17, MCP1, and Hsp60). The mature form of ADAM17 was also increased as well as Tnf-α released in the cell medium. At monocyte level, treatment induced up-regulation of ICAM1, MCP1 and its receptor CCR2.

Conclusions

Treatment with homocysteinylated albumin specifically increases monocyte adhesion to endothelial cells through up-regulation of effectors involved in vascular remodeling.

Oxidative stress as pathogenesis of cardiovascular risk associated with metabolic syndrome

Metabolic syndrome (MetS) is characterized by accumulation of visceral fat associated with the clustering of metabolic and pathophysiological cardiovascular risk factors: impaired glucose tolerance, dyslipidemia, and hypertension. Although the definition of MetS is different among countries, visceral obesity is an indispensable component of MetS. A growing body of evidence suggests that increased oxidative stress to adipocytes is central to the pathogenesis of cardiovascular disease in MetS. Increased oxidative stress to adipocytes causes dysregulated expression of inflammation-related adipocytokines in MetS, which contributes to obesity-associated vasculopathy and cardiovascular risk primarily through endothelial dysfunction. The purpose of present review is to unravel the mechanistic link between oxidative stress and cardiovascular risk in MetS, focusing on insulin resistance, hypertension, and atherosclerosis. Then, therapeutic opportunities translated from the bench to bedside will be provided to develop novel strategies to cardiovascular risk factors in MetS.

Homocysteine induces phosphatidylserine exposure in cardiomyocytes through inhibition of Rho kinase and flippase activity

AIMS

Increased levels of homocysteine (Hcy) form an independent risk factor for cardiovascular disease. In a previous study we have shown that Hcy induced phosphatidylserine (PS) exposure to the outer leaflet of the plasma membrane in cardiomyocytes, inducing a pro-inflammatory phenotype. In the present study the mechanism(s) involved in Hcy-induced PS exposure were analyzed.

METHODS

H9c2 rat cardiomyoblasts were subjected to 2.5 mM D,L-Hcy and analyzed for RhoA translocation and activity, Rho Kinase (ROCK) activity and expression and flippase activity. In addition, the effect of ROCK inhibition with Y27632 on Hcy-induced PS exposure and flippase activity was analyzed. Furthermore, GTP and ATP levels were determined.

RESULTS

Incubation of H9c2 cells with 2.5 mM D,L-Hcy did not inhibit RhoA translocation to the plasma membrane. Neither did it inhibit activation of RhoA, even though GTP levels were significantly decreased. Hcy did significantly inhibit ROCK activation, but not its expression, and did inhibit flippase activity, in advance of a significant decrease in ATP levels. ROCK inhibition via Y27632 did not have significant added effects on this.

CONCLUSION

Hcy induced PS exposure in the outer leaflet of the plasma membrane in cardiomyocytes via inhibition of ROCK and flippase activity. As such Hcy may induce cardiomyocytes vulnerable to inflammation in vivo in hyperhomocysteinaemia patients.

Hyperhomocysteinemia inhibited cardiac stem cell homing into the peri-infarcted area post myocardial infarction in rats

BACKGROUND

Hyperhomocysteinemia (HHcy) has been reported as an independent risk factor for coronary artery disease; however it is not clear regarding the action of HHcy on the homing of cardiac stem cells (CSCs) to the damaged myocardium and the consequent CSCs-mediated cardiac repair post myocardial infarction.

METHODS

Sprague-Dawley (SD) rats were divided into 4 groups. HHcy was induced in the rats by a 6-week high-methionine diet. Rat heart MI model was developed by left coronary artery ligation. Immunofluorescence was used to examine the CSCs migration in vivo via injecting BrdU-labeled CSCs into AV-groove followed by a coronary ligation. Immunohistochemistry, western blot and ELISA analysis were carried out to detect the expression of stem cell factor (SCF) protein, and RT-PCR was conducted for the expression of SCF mRNA.

RESULTS

On day 5 of MI model creation, accumulation of CSCs was significantly increased in the peri-infarcted area by the non-hyperhomocysteinemic rats, which led to an improvement of cardiac function at 3 weeks after MI. however, the accumulation of CSCs was markedly decreased by the hyperhomocysteinemic rats followed with the decline of cardiac function. SCF expression was also significantly decreased in the peri-infarcted area by the hyperhomocysteinemic rats compared to the non-hyperhomocysteinemic rats. The experiments in vitro confirmed that homocysteine (Hcy) decreased SCF expression via inhibition of TNF-α-induced activity of NF-κB, further reduced the migration of CSCs.

CONCLUSION

It demonstrated that hyperhomocysteinemia may significantly contribute to restrain CSCs-mediated cardiac repair by reducing SCF-induced homing of CSCs.

Homocysteine enhances transmigration of rat monocytes through a brain capillary endothelial cell monolayer via ICAM-1

Increased homocysteine (Hcy) levels contribute to a variety of cardiovascular and cerebrovascular diseases including stroke and Alzheimer's disease. Recent data has shown that elevated levels of Hcy can lead to the blood-brain barrier (BBB) dysfunction and activation. However, the mechanism for Hcy-mediated dysfunction remains unclear. The aim of this study is to characterize the effects of moderate Hcy administration in rat brain capillary endothelial cells (BCECs), which serve as a simple model to study blood-brain barrier (BBB) functions. This present study shows that addition of 20 microM Hcy for 6 days did not significantly affect BCEC survival, as measured by acridine orange staining, propidium iodide staining, and nitrite content. However, addition of 20 microM Hcy for 6 days did elevate lactate dehydrogenase (LDH) activity released into the supernatant of BCECs, as well as significantly enhance the transmigration of monocytes across the BCEC in a time-dependent manner. In addition, TNFalpha levels in BCEC were also elevated by Hcy, whereas inflammatory markers MIP3alpha and RANTES were significantly reduced. Finally, this study also shows that intercellular adhesion molecule-1 (ICAM-1) expression is significantly enhanced by 20 microM Hcy treatment compared to control conditions. These results suggest that moderate levels of homocysteine can affect proinflammatory patterns expressed by BCECs ultimately leading to BBB activation and dysfunction through enhanced monocyte transmigration and ICAM-1 expression.

Folic acid supplementation inhibits NADPH oxidase-mediated superoxide anion production in the kidney

Hyperhomocysteinemia, a condition of elevated blood homocysteine (Hcy) levels, is a metabolic disease. It is a common clinical finding in patients with chronic kidney diseases and occurs almost uniformly in patients with end-stage renal disease. Hyperhomocysteinemia is also a risk factor for cardiovascular disease. Our recent studies indicate that hyperhomocysteinemia can lead to renal injury by inducing oxidative stress. Oxidative stress is one of the important mechanisms contributing to Hcy-induced tissue injury. Folic acid supplementation is regarded as a promising approach for prevention and treatment of cardiovascular disease associated with hyperhomocysteinemia due to its Hcy-lowering effect. However, its effect on the kidney is not clear. The aim of this study was to examine the effect of folic acid supplementation on Hcy-induced superoxide anion production via nicotinamide adenine dinucleotide phosphate (NADPH) oxidase in the kidney during hyperhomocysteinemia. Hyperhomocysteinemia was induced in male Sprague-Dawley rats fed a high-methionine diet for 12 wk with or without folic acid supplementation. A group of rats fed a regular diet was used as control. There was a significant increase in levels of superoxide anions and lipid peroxides in kidneys isolated from hyperhomocysteinemic rats. Activation of NADPH oxidase was responsible for hyperhomocysteinemia-induced oxidative stress in the kidney. Folic acid supplementation effectively antagonized hyperhomocysteinemia-induced oxidative stress via its Hcy-lowering and Hcy-independent effect. In vitro study also showed that 5-methyltetrahydrofolate, an active form of folate, effectively reduced Hcy-induced superoxide anion production via NADPH oxidase. Xanthine oxidase activity was increased and superoxide dismutase (SOD) activity was decreased in the kidney of hyperhomocysteinemic rats, which might also contribute to an elevation of superoxide anion level in the kidney. Folic acid supplementation attenuated xanthine oxidase activity and restored SOD activity in the kidney of hyperhomocysteinemic rats. These results suggest that folic acid supplementation may offer renal protective effect against oxidative stress.

Homocysteine and Hypertension in Diabetes: Does PPARgamma Have a Regulatory Role?

Dysfunction of macro- and microvessels is a major cause of morbidity and mortality in patients with cardio-renovascular diseases such as atherosclerosis, hypertension, and diabetes. Renal failure and impairment of renal function due to vasoconstriction of the glomerular arteriole in diabetic nephropathy leads to renal volume retention and increase in plasma homocysteine level. Homocysteine, which is a nonprotein amino acid, at elevated levels is an independent cardio-renovascular risk factor. Homocysteine induces oxidative injury of vascular endothelial cells, involved in matrix remodeling through modulation of the matrix metalloproteinase (MMP)/tissue inhibitor of metalloproteinase (TIMP) axis, and increased formation and accumulation of extracellular matrix protein, such as collagen. In heart this leads to increased endothelial-myocyte uncoupling resulting in diastolic dysfunction and hypertension. In the kidney, increased matrix accumulation in the glomerulus causes glomerulosclerosis resulting in hypofiltration, increased renal volume retention, and hypertension. PPARγ agonist reduces tissue homocysteine levels and is reported to ameliorate homocysteine-induced deleterious vascular effects in diabetes. This review, in light of current information, focuses on the beneficial effects of PPARγ agonist in homocysteine-associated hypertension and vascular remodeling in diabetes.

Hyperlipidemia induces endothelial-derived foam cells in culture

Endothelial cells (ECs) play a major role in the pathophysiology of various diseases, conditions in which stress proteins are most probably involved. Both in humans and in experimental models, hyperlipidemia induces early alterations of plasma components that in turn have a profound effect on EC. Activated ECs change their basal characteristics becoming more permeable to lipoproteins, increasing the synthesis of their basal lamina, and express new adhesion molecules; the cells are "activated". In lesion-prone areas, the ECs are the first cells to experience the impact of hyperlipidemia. In this study, human ECs were activated by exposure to serum from hyperlipidemic human subjects. In this condition, the EC gradually become loaded with lipid droplets and turn into endothelial-derived foam cells. The EC-derived foam cells express adhesion molecules (VCAM-1, VLA-4), show enhanced intracellular Ca(2+) release, and demonstrate high level of heat shock proteins (Hsp27, Hsp70, and Hsp90). In this study, we bring evidence that the EC-derived foam cells in culture proved to be an useful model to identify the multiple changes induced in activated ECs under hyperlipidemic stress. On the basis of these considerations, future studies using this model system will help to elucidate the molecular basis of the modulator role of molecular chaperones (Hsp) in atherosclerosis under various environmental conditions.

Increased inflammatory markers in brain and blood of rats subjected to acute homocysteine administration

Hyperhomocysteinemia plays an etiologic role in the pathogenesis of disorders, including homocystinuria and neurodegenerative and cardiovascular diseases. In the present study, we studied the effect of acute administration of homocysteine, similar to that found in homocystinuria, on parameters of inflammation such as cytokines (TNF-alpha, IL-1beta and IL-6), chemokine CCL2 (MCP-1), nitrite and acute phase-proteins (C-reactive protein and alpha(1)-Acid glycoprotein) levels in brain and blood of rats. In addition, a differential count of blood leukocytes was performed. Wistar rats, aged 29 days, received a single subcutaneous injection of saline (control) or homocysteine (0.6 micromol/g body weight). Fifteen minutes, 1 h, 6 h or 12 h after the injection, the rats were sacrificed and serum, hippocampus and cerebral cortex were used. Results showed that homocysteine significantly increased proinflammatory cytokines (TNF-alpha, IL-1beta and IL-6) and chemokine CCL2 (MCP-1) in serum, hippocampus and cerebral cortex. Nitrite levels also increased in hippocampus and cerebral cortex at 15 min, 1 h and 6 h, but not 12 h after homocysteine administration. Acute phase-protein levels were not altered by homocysteine. The percentage of neutrophils and monocytes significantly increased in blood at 15 min and 1 h, but not at 6 h and 12 h after acute hyperhomocysteinemia, when compared to the control group. Our results showed that acute administration of homocysteine increased inflammatory parameters, suggesting that inflammation might be associated, at least in part, with the neuronal and cardiovascular dysfunctions observed in homocystinuric patients.

Induction of hepatic cyclooxygenase-2 by hyperhomocysteinemia via nuclear factor-κB activation

Hyperhomocysteinemia, an elevation of blood homocysteine (Hcy), is a metabolic disorder associated with dysfunction of multiple organs. Apart from endothelial dysfunction, Hcy can cause hepatic lipid accumulation and liver injury. However, the mechanism responsible for Hcy-induced liver injury is poorly understood. The aim of this study was to investigate the regulation of cyclooxygenase-2 (COX-2), a proinflammatory factor, expression in the liver during the initial phase of hyperhomocysteinemia. Sprague-Dawley rats were fed a high-methionine diet for 1 or 4 wk. Serum and liver concentrations of Hcy were significantly elevated after 1 or 4 wk of dietary treatment. COX-2 mRNA and protein levels were significantly elevated in the liver of hyperhomocysteinemic rats. The induction of COX-2 expression was more prominent in 1-wk hyperhomocysteinemic rats than that in the 4-wk group. EMSA revealed an activation of NF-κB in the same liver tissue in which COX-2 was induced. Administration of a NF-κB inhibitor to hyperhomocysteinemic rats effectively abolished hepatic COX-2 expression, inhibited the formation of inflammatory foci, and improved liver function. Further investigation revealed that oxidative stress due to increased superoxide generation was responsible for increased phosphorylation and degradation of IκBα leading to NF-κB activation in the liver. Administration of 4-hydroxy-tetramethyl-piperidine-1-oxyl, an SOD mimetic, to hyperhomocysteinemic rats not only inhibited NF-κB activation but also prevented hepatic COX-2 induction and improved liver function. These results suggest that hyperhomocysteinemia-induced COX-2 expression is mediated via NF-κB activation. Increased oxidative stress and inflammatory response may contribute to liver injury associated with hyperhomocysteinemia.

White blood cell count is associated with plasma total homocysteine in Japanese men

White blood cell (WBC) count has been related to risk for coronary heart disease. The relationship may be due to the association between WBC count and cardiovascular risk factors. So far, it has been shown that WBC count is associated with body mass index, total cholesterol, triglyceride, glucose, blood pressure and some lifestyle factors. It is not known, however, whether WBC count is associated with other risk factors such as total homocysteine or gamma-glutamyl transferase. The association between WBC count, total homocysteine and gamma-glutamyl transferase was analyzed cross-sectionally in middle-aged Japanese men. In a univariate regression analysis WBC count was associated positively with total homocysteine (beta (standard regression coefficient) = 0.112; p<0.001) but not with gamma-glutamyl transferase (beta = 0.033; p = 0.309). In a multivariate analysis which included cigarette smoking, physical activity, ethanol consumption, vegetable intake and body mass index, the association between WBC count and total homocysteine remained significant (beta = 0.062; p = 0.026). The association may partially explain the reported association between elevated WBC count and cardiovascular disease.

The genomic basis of cerebral palsy: a HuGE systematic literature review

Cerebral palsy has been associated with a number of candidate genes. To date, no systematic review has been conducted to synthesise genetic polymorphism associations with cerebral palsy. We apply the HuGE NET guidelines to search PubMed and EMBASE databases for publications investigating single nucleotide polymorphisms (SNPs) and cerebral palsy outcome. 22 papers were identified and are discussed in this review. Candidate genes were grouped as (1) thrombophilic, (2) cytokine, (3) apolipoprotein E or (4) other SNPs, largely related to cardiovascular physiology/pathophysiology and the functioning of the immune system. Of the studies identified, cohorts were usually small, without adequate control and ethnically diverse, making direct comparison between studies difficult. The most promising candidate genes include factor V Leiden, methylenetetrahydrofolate reductase, lymphotoxin-alpha, tumour necrosis factor-alpha, eNOS and mannose binding lectin. Large case-control studies are needed to confirm these candidates with attention given to cohort ethnicity, cerebral palsy subtype analysis and possible multiple gene and gene-environment interactions.

Genetic or nutritional disorders in homocysteine or folate metabolism increase protein N-homocysteinylation in mice

Genetic disorders of homocysteine (Hcy) or folate metabolism or high-methionine diets elevate plasma Hcy and its atherogenic metabolite Hcy-thiolactone. In humans, severe hyperhomocysteinemia due to genetic alterations in cystathionine beta-synthase (Cbs) or methylenetetrahydrofolate reductase (Mthfr) results in neurological abnormalities and premature death from vascular complications. In mouse models, dietary or genetic hyperhomocysteinemia results in liver or brain pathological changes and accelerates atherosclerosis. Hcy-thiolactone has the ability to form isopeptide bonds with protein lysine residues, which generates modified proteins (N-Hcy-protein) with autoimmunogenic and prothrombotic properties. Our aim was to determine how N-Hcy-protein levels are affected by genetic or nutritional disorders in Hcy or folate metabolism in mice. We found that plasma N-Hcy-protein was elevated 10-fold in mice fed a high-methionine diet compared with the animals fed a normal commercial diet. We also found that inactivation of Cbs, Mthfr, or the proton-coupled folate transporter (Pcft) gene resulted in a 10- to 30-fold increase in plasma or serum N-Hcy-protein levels. Liver N-Hcy-protein was elevated 3.4-fold in severely and 11-fold in extremely hyperhomocysteinemic Cbs-deficient mice, 3.6-fold in severely hyperhomocysteinemic Pcft mice, but was not elevated in mildly hyperhomocysteinemic Mthfr-deficient animals, suggesting that mice have a capacity to prevent accumulation of N-Hcy-protein in their organs. These findings provide evidence that N-Hcy-protein is an important metabolite associated with Hcy pathophysiology in the mouse.