Distortion of endothelial repair. The effect of hypercholesterolaemia on regeneration of aortic endothelium following injury by endotoxin. A scanning electron microscope study

Advances in the Detection, Mechanism and Therapy of Chronic Kidney Disease

Chronic Kidney Disease (CKD) is characterized by the gradual loss of renal mass and functions. It has become a global health problem, with hundreds of millions of people being affected. Both its incidence and prevalence are increasing over time. More than $20,000 are spent on each patient per year. The economic burden on the patients, as well as the society, is heavy and their life quality worsen over time. However, there are still limited effective therapeutic strategies for CKD. Patients mainly rely on dialysis and renal transplantation, which cannot prevent all the complications of CKD. Great efforts are needed in understanding the nature of CKD progression as well as developing effective therapeutic methods, including pharmacological agents. This paper reviews three aspects in the research of CKD that may show great interests to those who devote to bioanalysis, biomedicine and drug development, including important endogenous biomarkers quantification, mechanisms underlying CKD progression and current status of CKD therapy.

CD34+ circulating cells display signs of immune activation in patients with acute coronary syndrome

Bone marrow-derived endothelial progenitor cells (EPC) are released into the peripheral blood in situations of vascular repair/angiogenesis. Regulation of vascular repair and angiogenesis by EPC depends not only on the number of circulating EPC but also on their functionality. As endothelial cells can act as antigen-presenting cells in coronary artery disease (CAD), we postulated that EPC can be immune activated here as well. CD34⁺-EPC were isolated from peripheral blood of patients with ST-elevation myocardial infarction (STEMI, n = 12), non-STEMI/unstable angina (UA, n = 15), and stable CAD (SA, n = 18). Expression of HLA-DR, adhesion and costimulatory molecules by isolated CD34⁺-EPC were compared with levels in healthy controls (n = 18). There were no significant differences in VCAM-1 and CD80 expression by peripheral circulating CD34⁺-EPC between the four groups, yet expression of CD86 was highest in UA (p < 0.05). ICAM-1 expression was lowest in SA (p < 0.01). CD34⁺-EPC constitutively expressed HLA-DR across all groups. Of note, patients pretreated with HMG-CoA reductase inhibitors exhibited lower expression of VCAM-1 by CD34⁺-EPC throughout all patient groups; furthermore, statins significantly limited ex vivo-induced upregulation of ICAM-1 by TNF-alpha. To the best of our knowledge, this is the first study to examine the expression of immune markers in peripheral circulating CD34⁺-EPC ex vivo. We demonstrate that CD34⁺-EPC display different patterns of adhesion and costimulatory molecules in various states of CAD. Expression levels were affected by pretreatment with statins. Hence, immune activity of peripheral circulating CD34⁺ cells might play a pathophysiologic role in evolution of CAD.

Circulating Bacterial Fragments as Cardiovascular Risk Factors in CKD

Cardiovascular disease (CVD) is a major cause of mortality and morbidity in patients with CKD. In the past decade, intestinal dysbiosis and altered gut epithelial barrier function are increasingly recognized in CKD. Uremic patients have slow intestinal transit time, impaired protein assimilation, and decreased consumption of dietary fiber. The use of multiple medications also may contribute to the proliferation of dysbiotic bacteria, which affect the barrier function of intestinal epithelium. In addition, fluid overload and uremic toxins per se directly reduce the gut barrier function. The major consequence of these alterations, the translocation of bacterial fragments from bowel lumen to systemic circulation, can lead to diverse biologic effects and probably represents an important nontraditional CVD risk factor in CKD. Among all bacterial fragments, endotoxin is the most well studied. Plasma endotoxin levels are markedly elevated in both patients with CKD and those on dialysis, and are associated with the systemic inflammatory state, accelerated atherosclerosis, and clinical CVD in patients on dialysis. Optimization of BP control and the use of ultrapure dialysate can reduce plasma endotoxin levels, with probable metabolic and cardiovascular benefits. The benefit of synbiotic therapy is not confirmed, although results from animal studies are impressive. The biologic effects and clinical relevance of other bacterial fragments, such as bacterial DNA fragments, are less well defined. Further studies are needed to delineate the pathogenic relation between circulating bacterial fragments and CVD, and to define the role of the plasma bacterial fragment level as a prognostic indicator of CKD.

Gut microbiome in chronic kidney disease: challenges and opportunities

More than 100 trillion microbial cells that reside in the human gut heavily influence nutrition, metabolism, and immune function of the host. Gut dysbiosis, seen commonly in patients with chronic kidney disease (CKD), results from qualitative and quantitative changes in host microbiome profile and disruption of gut barrier function. Alterations in gut microbiota and a myriad of host responses have been implicated in progression of CKD, increased cardiovascular risk, uremic toxicity, and inflammation. We present a discussion of dysbiosis, various uremic toxins produced from dysbiotic gut microbiome, and their roles in CKD progression and complications. We also review the gut microbiome in renal transplant, highlighting the role of commensal microbes in alteration of immune responses to transplantation, and conclude with therapeutic interventions that aim to restore intestinal dysbiosis.

Role of the Gut Microbiome in Uremia: A Potential Therapeutic Target

Also known as the "second human genome," the gut microbiome plays important roles in both the maintenance of health and the pathogenesis of disease. The symbiotic relationship between host and microbiome is disturbed due to the proliferation of dysbiotic bacteria in patients with chronic kidney disease (CKD). Fermentation of protein and amino acids by gut bacteria generates excess amounts of potentially toxic compounds such as ammonia, amines, thiols, phenols, and indoles, but the generation of short-chain fatty acids is reduced. Impaired intestinal barrier function in patients with CKD permits translocation of gut-derived uremic toxins into the systemic circulation, contributing to the progression of CKD, cardiovascular disease, insulin resistance, and protein-energy wasting. The field of microbiome research is still nascent, but is evolving rapidly. Establishing symbiosis to treat uremic syndrome is a novel concept, but if proved effective, it will have a significant impact on the management of patients with CKD.

The gut microbiome, kidney disease, and targeted interventions

The human gut harbors >100 trillion microbial cells, which influence the nutrition, metabolism, physiology, and immune function of the host. Here, we review the quantitative and qualitative changes in gut microbiota of patients with CKD that lead to disturbance of this symbiotic relationship, how this may contribute to the progression of CKD, and targeted interventions to re-establish symbiosis. Endotoxin derived from gut bacteria incites a powerful inflammatory response in the host organism. Furthermore, protein fermentation by gut microbiota generates myriad toxic metabolites, including p-cresol and indoxyl sulfate. Disruption of gut barrier function in CKD allows translocation of endotoxin and bacterial metabolites to the systemic circulation, which contributes to uremic toxicity, inflammation, progression of CKD, and associated cardiovascular disease. Several targeted interventions that aim to re-establish intestinal symbiosis, neutralize bacterial endotoxins, or adsorb gut-derived uremic toxins have been developed. Indeed, animal and human studies suggest that prebiotics and probiotics may have therapeutic roles in maintaining a metabolically-balanced gut microbiota and reducing progression of CKD and uremia-associated complications. We propose that further research should focus on using this highly efficient metabolic machinery to alleviate uremic symptoms.

The association between periodontitis and dyslipidemia based on the Fourth Korea National Health and Nutrition Examination Survey

AIMS

The aim of this study was to examine whether dyslipidemia is associated with periodontitis in a representative sample of Korean adults who were involved in the Fourth Korea National Health and Nutrition Examination Survey (KNHANES).

MATERIALS AND METHODS

A total of 18,210 subjects over 19 years of age who participated in KNHANES were examined. Dyslipidemia is defined according to the definition proposed by the Korean Society of Lipidology and Atherosclerosis. The periodontal status of the patients was assessed by the Community Periodontal Index (CPI). Multivariate logistic regression analysis was carried out and adjusted for socio-demographics, oral health behaviours and status and general health behaviour. All analyses considered a complex sampling design, and multivariate analysis was also performed in the subgroups (age, gender and current smoking status).

RESULTS

Multivariate logistic regression analysis revealed significant associations between dyslipidemia except pre-hypercholesterolemia and periodontitis. In the subgroup analysis, periodontitis was significantly associated with hypo-HDL-cholesterolemia and had a potential association with hyper- triglycerides (TG) in subjects younger than 40 years. The adjusted ORs were greater in the present smoker group than the non-smoker group.

CONCLUSIONS

Dyslipidemia except pre-hypercholesterolemia is associated with periodontitis.

Chronic infection in the etiology of atherosclerosis--the case for Chlamydia pneumoniae

Established cardiovascular risk factors do not fully explain the variations in the prevalence and severity of coronary heart disease. Recent evidence suggests that common chronic infections may contribute, either by direct or indirect mechanisms, to the etiology and/or progression of coronary atherosclerosis. Of the candidate infectious agents implicated, Chlamydia pneumoniae has emerged as the most likely pathogen to have a causal role. Evidence for this is based on seroepidemiologic, pathologic, and laboratory-based evidence, in addition to recent small-scale antibiotic intervention studies. Concerted efforts are now focused on the design of large prospective trials with antibiotics active against C. pneumoniae in the secondary prevention of coronary heart disease.

Impaired graft healing due to hypercholesterolemia is prevented by dietary supplementation with alpha-tocopherol

OBJECTIVE

The patency of prosthetic grafts is partly limited by incomplete endothelial cell coverage and development of anastomotic intimal hyperplasia. The goal of this study was to determine the effect of elevated cholesterol on prosthetic graft healing and the ability of alpha-tocopherol to improve healing.

METHODS

Rabbits were placed on one of four diets: chow, chow plus 1% cholesterol, chow plus alpha-tocopherol, or chow plus 1% cholesterol and alpha-tocopherol. After 2 weeks, expanded polytetrafluoroethylene grafts (12-cm long, 4-mm internal diameter) were implanted in the abdominal aorta. Grafts were removed after 6 weeks and analyzed for cholesterol and alpha-tocopherol content, endothelial coverage, anastomotic intimal thickness, and cellular composition of the neointima.

RESULTS

At the time of graft implantation, plasma cholesterol was 34 +/- 4 mg/dL in the chow group and 689 +/- 30 mg/dL in the 1% cholesterol group (P < .05). Grafts removed from hypercholesterolemic rabbits had marked intimal thickening, with an intima/graft thickness ratio of 0.76 +/- 0.29 compared with 0.14 +/- 0.06 in chow animals (P < .05). Macrophage infiltrate was increased to 45 +/- 11 macrophages/0.625 mm(2) in grafts from hypercholesterolemic rabbits compared with 0 +/- 0.4 in controls (P < .05). Endothelialization of grafts was lower in hypercholesterolemic rabbits than in the chow group, with endothelial cells covering 46% +/- 7% and 62% +/- 7% of the graft surface, respectively (P = .05). When alpha-tocopherol was added to the 1% cholesterol diet, the macrophage count decreased to 12 +/- 8, the intimal/graft thickness ratio decreased to 0.17 +/- 0.09, and endothelial coverage increased to 70% +/- 7% (P < .05 compared with the high-cholesterol group).

CONCLUSION

Anastomotic intimal hyperplasia is dramatically increased and endothelialization is reduced in rabbits on a high-cholesterol diet, but alpha-tocopherol supplementation blocks the augmented neointimal thickening and improves endothelial cell coverage.

Stem cells and scaffolds for vascularizing engineered tissue constructs

The clinical impact of tissue engineering depends upon our ability to direct cells to form tissues with characteristic structural and mechanical properties from the molecular level up to organized tissue. Induction and creation of functional vascular networks has been one of the main goals of tissue engineering either in vitro, for the transplantation of prevascularized constructs, or in vivo, for cellular organization within the implantation site. In most cases, tissue engineering attempts to recapitulate certain aspects of normal development in order to stimulate cell differentiation and functional tissue assembly. The induction of tissue growth generally involves the use of biodegradable and bioactive materials designed, ideally, to provide a mechanical, physical, and biochemical template for tissue regeneration. Human embryonic stem cells (hESCs), derived from the inner cell mass of a developing blastocyst, are capable of differentiating into all cell types of the body. Specifically, hESCs have the capability to differentiate and form blood vessels de novo in a process called vasculogenesis. Human ESC-derived endothelial progenitor cells (EPCs) and endothelial cells have substantial potential for microvessel formation, in vitro and in vivo. Human adult EPCs are being isolated to understand the fundamental biology of how these cells are regulated as a population and to explore whether these cells can be differentiated and reimplanted as a cellular therapy in order to arrest or even reverse damaged vasculature. This chapter focuses on advances made toward the generation and engineering of functional vascular tissue, focusing on both the scaffolds - the synthetic and biopolymer materials - and the cell sources - hESCs and hEPCs.

Endothelial progenitor cells in the natural history of atherosclerosis

Atherosclerotic diseases are responsible for a significant part of morbidity and mortality in western countries. According to the classical views, atherosclerotic lesions develop as the result of an inflammatory process initiated by endothelial damage. The discovery that bone marrow-derived cells participate in endothelial repair and new vessel growth has changed the pathogenetic models of cardiovascular disease. These cells, termed endothelial progenitor cells (EPCs), represent the endogenous endothelial regenerative capacity and the ability to form new collateral vessels. In this review we describe how quantitative and qualitative alterations of EPCs have a significant role in virtually all stages of the atherosclerotic process and in the clinical manifestations of the diseases: starting from the impact of risk factors on EPCs, through the mechanisms that link EPC reduction/dysfunction to plaque formation, and finally to the clinical syndromes. An attempt to diverge our attention from the vessel wall to the bloodstream reveals a central role of EPCs in atherogenesis.

LPS-Induced Release of IL-1β, IL-1Ra, IL-6, and TNF-αin Whole Blood from Patients with Familial Hypercholesterolemia: No Effect of Cholesterol-Lowering Treatment

Proinflammatory cytokines, such as interleukin-1beta (IL-1beta), IL-6, and tumor necrosis factor-alpha (TNF-alpha), are suggested to have an important role in the process of atherosclerosis. Patients with heterozygous familial hypercholesterolemia (FH) have a marked elevation in the plasma level of low-density lipoproteins (LDL), and they show early development of atherosclerosis. The aim of the present study was to test with a whole blood culture system if hyperlipoproteinemia is associated with increased cytokine production capacity in these patients and if treatment with 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors influences this production capacity of blood cells, at both the protein and mRNA levels. The capacity of blood cells in a whole blood culture to produce IL-1beta, IL-6, TNF-alpha, IL-12, IL-18, and IL-1 receptor antagonist (IL-1Ra) in response to lipopolysaccharide (LPS) appeared to be similar for heterozygous FH patients and healthy volunteers. Furthermore, the capacity to produce IL-1beta, IL-6, and TNF-alpha in response to LPS was not modified by cholesterol synthesis inhibitors at the level of mRNA expression or at the level of release. On the other hand, the release of IL-1Ra was significantly increased after treatment with HMG-CoA reductase inhibitors, although only at the protein level. This suggests a possible beneficial anti-inflammatory role for this therapy.

Periodontal diseases and the risk of coronary heart and cerebrovascular diseases: a meta-analysis

BACKGROUND

This meta-analysis was conducted to examine the relationship between periodontal diseases and coronary heart diseases (CHD) and cerebrovascular diseases (CVD) in observational studies.

METHODS

This study was based on seven cohort studies and four studies of other designs that met prestated inclusion criteria. Information on study design, year of publication, study location, sample size, study population, participant characteristics, measurement of risk factors, exposure and outcome measures, matching, controlling for confounders, and risk estimates was abstracted independently by two investigators using a standard protocol.

RESULTS

Subjects with periodontitis had an overall adjusted risk of CHD that was 1.15 times (95% confidence interval [CI]: 1.06 to 1.25; P = 0.001) the risk for healthy subjects. There was no heterogeneity among the studies in the overall relative risk estimate (P = 0.472). As compared to healthy subjects, those with periodontitis had an overall adjusted relative risk of CVD of 1.13 (95% CI: 1.01 to 1.27; P = 0.032).

CONCLUSIONS

Findings indicated that periodontal infection increases the risk of CHD and CVD. However, this meta-analysis provided no evidence for the existence of strong associations between periodontitis and CHD and CVD. Larger and better-controlled studies involving socially homogeneous populations and measuring specific periodontal pathogens are required to identify a definite association between periodontal disease and the risk of coronary heart disease and cerebrovascular disease.

Recurrent perivascular inflammation induced by lipopolysaccharide (endotoxin) results in the formation of atheromatous lesions in vivo

Bacteria and viruses are suspected to induce arteriosclerosis; however, most investigators have focused on coincidences rather than causal relationships. The aim of this work was to establish a rabbit model in which the vessel reaction to local perivascular injection of defined bacterial products can be analyzed. A total of 23 rabbits were randomized to four groups. Groups A and B were fed a normal diet, groups C and D were fed a cholesterol-enriched diet. Groups A and C were treated with a single perivascular injection of bacterial lipopolysaccharide (LPS, endotoxin) placed next to auricular, carotid and femoral arteries, and sodium chloride placed next to the contralateral arteries (control). Group B and D animals were treated with repeated perivascular injections over 90 days. Vascular tissues (n=116 treated segments of 23 rabbits) were analyzed using morphometry at histology, and using immunohistochemistry to detect macrophages, lymphocytes and vascular smooth muscle cells. LPS treatment resulted in transient focal intima thickening. After single LPS application, no increase in atheromatous lesion formation was observed in comparison with controls (group C, lesion area index 0.031+/-0.012 vs 0.015+/-0.006, P=1.0). Repeated LPS application resulted in significant atheromatous lesion formation compared with saline control (group D, lesion area index 0.148+/-0.049 vs 0.008+/-0.006, P=0.003) in hypercholesterolemic rabbits. Repeated LPS inflammation in normocholesterolemic did not lead to atheromatous lesion formation (intima media ratio 0.04+/-0.01 vs 0.04+/-0.007, P=1.0). Single perivascular administration of low-dose bacterial LPS resulted in transient focal intimal thickening, while significant increase in lesion formation occurred after repeated LPS application in cholesterol-fed animals. In conclusion, this animal model will allow the assessment of the impact of defined dosages of different bacterial pathogens onto the vascular wall in the context of atherogenesis. The atheromatous lesion-promoting effect of repeated perivascular administration of LPS supports the hypothesis that bacterial pathogens may be involved in atherogenesis.

Immunopathogenesis of atherosclerosis: endotoxin accelerates atherosclerosis in rabbits on hypercholesterolemic diet

BACKGROUND

On the basis of our concept that atherosclerosis has an immunopathological background, we tested whether activation of the innate immune system influences its progression.

METHODS AND RESULTS

Hypercholesterolemic (0.5% wt/wt diet) rabbits received either repeated intravenous injections of endotoxin (Escherichia coli lipopolysaccharide 1.25 to 2.5 microg, once per week) or a self-limiting cutaneous Staphylococcus aureus infection with or without a quinolone antibiotic. Measured laboratory parameters, including LDL and HDL cholesterols, were similar in the different groups of hypercholesterolemic animals. All endotoxin-treated animals developed transient episodes of fever after endotoxin administration. The extent of atherosclerosis was evaluated by computer-assisted morphometry in the aortas en face (Sudan IV) and by histology at 8 weeks after start of the experiments. Endotoxin-treated animals exhibited significantly accelerated atherosclerosis compared with control animals (141+/-38 versus 45+/-16 mm(3) total lesion volume, n=7 to 9 rabbits each, P<0.001).

CONCLUSIONS

Nonspecific stimulation of the innate immune system accelerates cholesterol-induced atherosclerosis. These data support the concept that atherosclerosis has an immunopathological component and render it improbable that a single infectious agent should assume particular importance in its initiation or progression.

Lipopolysaccharide enhances oxidative modification of low density lipoprotein by copper ions, endothelial and smooth muscle cells

The effect of lipopolysaccharide (LPS, endotoxin) on low density lipoprotein (LDL) oxidative modification by copper ions, endothelial and smooth muscle cells was studied by determination of the level of lipid peroxidation products (thiobarbituric acid reactive substances or TBARS), the diene level and the electrophoretic mobility of the LDL particle. LPS 25-75 microg/ml induced a dose-dependent increase in LDL oxidation by copper ions, endothelial and smooth muscle cells. At 75 microg LPS/ml, the TBARS content was 1.9, 1.6, and 1.8-fold increased, respectively. The LDL degradation by J774 macrophage-like cells was concomitantly stimulated. Preincubation of the LDL particle with LPS induced a marked increase in the subsequent LDL oxidative modification either by copper ions or by endothelial and smooth muscle cells. In addition, pretreatment of endothelial and smooth muscle cells with LPS also induced an enhancement of LDL oxidative modification performed in the absence of LPS. This effect was accompanied by a parallel increase in superoxide anion release by the cells. These results point at one of the mechanisms involved in the described association between bacterial infection and acute myocardial infarction as well as coronary heart disease.

Increased interleukin-1alpha and interleukin-1beta production by macrophages of low-density lipoprotein receptor knock-out mice stimulated with lipopolysaccharide is CD11c/CD18-receptor mediated

Immune mechanisms, including production of pro-inflammatory cytokines such as interleukin-1 (IL-1) and tumour necrosis factor (TNF), play an important role in early atherogenesis. The study of the mechanisms responsible for the increased cytokine production capacity of hypercholesterolemic hosts is therefore crucial for finding new strategies aimed to stop the development of atherosclerosis. We assessed the lipopolysaccharide (LPS)-induced cytokine production of macrophages from low-density lipoproteins (LDL)-receptor knock-out (LDLR-/-) mice, which have a seven- to ninefold higher plasma LDL concentration. Macrophages of LDLR-/- mice produced approximately twofold more IL-1alpha and IL-1beta in response to LPS when compared with macrophages of control mice (LDLR+/+). TNF-alpha synthesis was only slightly increased. Removal of CD14 by phospholipase C treatment of cells decreased cytokine production by 50% (IL-1) to 80% (TNF), but the differences between LDLR-/- and LDLR+/+ remained the same. In contrast, treatment of cells with anti-CD11c monoclonal antibody inhibited the IL-1alpha and IL-1beta production in LDLR-/- mice towards normal values, while no effect could be seen on TNF. In conclusion, LDLR-/- macrophages stimulated with LPS synthesize more IL-1alpha and IL-1beta than controls and this phenomenon is mediated by the CD11c/CD18 receptor.

LPS-induced cytokine production and expression of LPS-receptors by peripheral blood mononuclear cells of patients with familial hypercholesterolemia and the effect of HMG-CoA reductase inhibitors

Inflammatory processes play an important role in atherogenesis, and proinflammatory cytokines such as interleukin-1beta (IL-1beta), IL-6, and tumour necrosis factor alpha (TNFalpha) are thought to be mediators in this phenomenon. We have previously established that peritoneal macrophages of LDL-receptor knock-out mice, which are hypercholesterolemic and are prone to atherosclerosis, have an increased LPS-induced cytokine production capacity, ex vivo. The aim of the present study was to investigate whether the process leading to atherosclerosis in patients with familial hypercholesterolemia (FH) is associated with increased cytokine production capacity of peripheral blood mononuclear cells (PBMC) and/or increased expression of adhesion molecules on monocytes and lymphocytes. Furthermore, we assessed the effect of cholesterol lowering on the production capacity of PBMC, as these drugs are beneficial with regard to cardiovascular diseases. LPS-induced IL-1beta and TNFalpha production by PBMCs of 21 heterozygous FH patients appeared to be similar to the production by PBMCs of 21 healthy volunteers. In addition, expression of the LPS-receptors CD14 and beta2-integrins in nine patients and controls did not differ either. In a second series of experiments, HMG-CoA synthesis inhibitors were ineffective to change the LPS-induced production by PBMC of IL-1alpha, IL-1beta, IL-1 receptor antagonist (IL-1ra), IL-6, and TNFalpha. In conclusion, cytokine production capacity of blood cells or the expression of LPS-receptors on circulating PBMC do not deviate in subjects with FH and also do not change as a result of treatment with cholesterol synthesis inhibitors.

Deamination of methylamine and angiopathy; toxicity of formaldehyde, oxidative stress and relevance to protein glycoxidation in diabetes

Semicarbazide-sensitive amine oxidase (SSAO) is located in the vascular smooth muscles, retina, kidney and the cartilage tissues, and it circulates in the blood. The enzyme activity has been found to be significantly increased in blood and tissues in diabetic patients and animals. Methylamine and aminoacetone are endogenous substrates for SSAO. The deaminated products are formaldehyde and methylglyoxal respectively, as well as H2O2 and ammonia, which are all potentially cytotoxic. Formaldehyde and methylglyoxal are cytotoxic towards endothelial cells. Excessive SSAO-mediated deamination may directly initiate endothelial injury and plaque formation, increase oxidative stress, which can potentiate oxidative glycation, and/or LDL oxidation and damage vascular systems. Formaldehyde is also capable of exacerbating advanced glycation, and thus increase the complexity of protein cross-linking. Uncontrolled SSAO-mediated deamination may be involved in the acceleration of the clinical complications in diabetes.

Is vasospasm related to proliferative arteriopathy?

Although proliferative arteriopathy has been postulated to play a role in the etiology of vasospasm after subarachnoid hemorrhage (SAH), histological and morphological studies examining cerebral vasospasm have produced conflicting results. To help settle this controversy, the authors used an in vivo label of cell division, bromodeoxycytidine, to assess cell proliferation in a primate model of SAH. Fifteen cynomolgus monkeys received a clot of either whole blood (11 animals) or red blood cells (four animals) placed around the right middle cerebral artery (MCA). On the day of surgery continuous intravenous infusion of bromodeoxycytidine was begun and continued until the animal was sacrificed immediately after arteriography on Day 7, 12, or 27 following surgery. Sections from the right and left MCA's were stained with a monoclonal antibody against bromodeoxcytidine, and labeled cells were counted. Arteriographic evidence of vasospasm occurred in nine monkeys on Day 7. On Day 12 and Day 27 no monkeys had persistent vasospasm. Placement of subarachnoid clot around the right MCA increased proliferative activity across all layers of the arterial wall. Most of the labeled cells were in the adventitia and the endothelium. Although there were more dividing cells in all layers of the right MCA than the left MCA (p < 0.01), the number of stained cells per section was limited (range 0.1 to 21.2, mean 8) and the occurrence of vasospasm was not associated with the number of dividing cells in the right MCA on Day 7, 12, 27, or for all days combined (p > 0.6). Cerebral vasospasm after SAH was not associated with the extent of proliferation of cells in the vessel wall, nor could the intensity of the limited proliferative changes have been responsible for narrowing of the vessel diameter.

Enhancement of migration in bovine endothelial cells by eicosapentaenoic acid pretreatment

It has been recognized that endothelial cell migration is an important process in the regeneration of injury in blood vessels. In this study, we examined the effects of polyunsaturated fatty acids on the migration of cultured endothelial cells using a modified Boyden chamber. When endothelial cells isolated from bovine carotid artery were pretreated for 2 days with 5 micrograms/ml of either arachidonic acid, eicosapentaenoic acid or docosahexaenoic acid, every polyunsaturated fatty acid was incorporated substantially into cellular phospholipids. The content of arachidonic acid increased from 9.27 to 23.9% by the arachidonic acid pretreatment, and that of eicosapentaenoic acid and docosahexaenoic acid increased from 9.57 to 11.85% by the eicosapentaenoic acid pretreatment and from 5.56 to 18.40% by the docosahexaenoic acid pretreatment, respectively. Pretreatment of the cells with 0.5-5.0 micrograms/ml of eicosapentaenoic acid resulted in a dose-dependent increase in endothelial migration in response to fetal bovine serum. In contrast, pretreatment of the cells with arachidonic acid and docosahexaenoic acid had no effects on the cell migration. If eicosapentaenoic acid, however, was added directly to the migration assay system instead of the pretreatment, it did not show a profile of chemotactic factor. The eicosapentaenoic acid pretreatment also potentiated cell migration activity in response to several other chemotactic factors such as basic fibroblast growth factor, tumor necrosis factor-alpha and leukotriene C4. The effect of eicosapentaenoic acid on porcine smooth muscle cell migration was also examined. Although eicosapentaenoic acid was similarly incorporated into cellular phospholipids of smooth muscle cells by the pretreatment for 2 days, no stimulative effect was observed in the migration of smooth muscle cells at any doses (0.5-5.0 microns/ml).(ABSTRACT TRUNCATED AT 250 WORDS)

Immunological and microbiological factors in the pathogenesis of atherosclerosis

Among the several pathological events that lead to the formation of an atheromatous lesion, endothelial cell damage, smooth muscle cell proliferation, and foam cell formation, are considered as particularly significant. In this review we summarize data suggesting that immunological and microbial factors may cause, directly or indirectly, these pathological events. Binding of immunocomplexes to endothelial cells, phagocytic cells, platelets, or erythrocytes could be the starting point for a variety of circuits leading to endothelial cell cytotoxicity and to the release of a variety of mediators, including cell proliferative factors. Endothelial cell toxicity could also be induced, directly or indirectly, by endotoxin; however, the possibility that endotoxin and other microbial factors may induce abnormalities in lipid metabolism at the monocyte/macrophage level which eventually result in intracellular accumulation of cholesterol (particularly if cholesterol levels are elevated) is specially attractive as a potential pathogenic mechanism. The various pathologic pathways discussed in this review appear plausible on the basis of our current knowledge and point to the need to investigate the potential role of infectious processes, autoimmune reactions, and administration of antigenic compounds as possible risk factors for the development of atherosclerosis.

Endothelial regeneration in hypertensive and genetically hypercholesterolemic rats

Endothelial regeneration after a narrow, superficial aortic injury was studied in rats with chronic Goldblatt hypertension, genetic hypercholesterolemia, or a combination of hypertension and genetic hypercholesterolemia. In all groups, endothelial continuity was restored within 24 to 36 hours by a combination of endothelial migration and proliferation. A line of increased endothelial density covering the previous wound was seen through 16 weeks after injury. Intimal thickening after injury did not occur in any of the groups. These results indicate that hypertension and hypercholesterolemia neither delay endothelial regeneration nor cause intimal thickening after a small injury in the rat.

Narrow superficial injury to rabbit aortic endothelium. The healing process as observed by scanning electron microscopy

A study was made of the healing of aortic endothelium in rabbits following the production of a defined superficial injury. This was induced using a fine nylon filament which removed the endothelial cells without producing significant damage to underlying structures. The morphology of the injury and subsequent repair was observed using light microscopy and scanning and transmission electron microscopy. Two forms of injury were produced (a) a longitudinal injury along the full length of the aorta which was 50-80 microns wide (about 5-8 cell widths), (b) a circumferential injury approximately 80 microns wide (about 2 cell lengths). Thirty minutes after injury the exposed tissue was almost devoid of adherent cells, but after 4 h became covered by a sparse monolayer of platelets. Occasional leukocytes were also present from 7 h after injury. Injury tracks were found to repair very quickly; re-endothelialisation being complete by 48 h and there being no sign of injury by 7 days.

Effects of traumatic manipulations on grafts, sutures, and host arteries during vascular surgery procedures. Experiments on dogs

Scanning electron microscopy was used to diagnose incidents of trauma and the pattern of healing following surgical implantation of microporous blood vessel substitutes. Vascular reconstruction procedures using autogenous or synthetic prosthetic material inflict damage to the adjacent tissues as well as the prosthesis. This affects the thrombotic behavior and healing pattern of the area. The prognosis for long-term success are, as a consequence, directly influenced. Various vessel-occluding devices were evaluated in canine models with respect to their ability to damage blood vessels at the clamped site. The impact of suture needles on tissues and prosthetic materials was also considered. Of the various vessel-clamping devices which are commercially available, those which have elastomeric shields on the clamping components were found to be most satisfactory. The development of less traumatic surgical devices is discussed with the aim of further reducing surgical trauma.

Heparin and atherosclerosis. A review of old and recent findings

This article reviews the experimental and clinical evidence regarding heparin therapy in the prophylaxis of coronary heart disease. The actions of heparin take place at the vascular endothelium where injected heparin concentrates, and within the bloodstream. At the endothelium heparin acts to prevent endothelial injury, prevent thrombin generation, prevent platelet adhesion to endothelium, and to decrease uptake of serum lipoproteins. Within the bloodstream heparin increases lipoprotein lipase activity and reduces the concentration of atherogenic very low-density lipoproteins. The reduction in lipemia enhances oxygen transfer from blood to the tissues, and decreases thrombin or ADP-induced platelet aggregation. Heparin increases the concentration of high-density lipoproteins. It decreases hypercoagulability and inhibits overactivation of serum complement. Heparin reduced atherosclerosis in most studies in cholesterol-fed animals. In human subjects who had a myocardial infarct at least one year before the onset of treatment, long-term intermittent heparin therapy significantly decreased cardiovascular deaths as compared to control groups.