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

Cardiovascular manifestations of inflammatory bowel diseases and the underlying pathogenic mechanisms

Inflammatory bowel disease (IBD), consisting of ulcerative colitis and Crohn's disease, mainly affects the gastrointestinal tract but is also known to have extraintestinal manifestations because of long-standing systemic inflammation. Several national cohort studies have found that IBD is an independent risk factor for the development of cardiovascular disorders. However, the molecular mechanisms by which IBD impairs the cardiovascular system are not fully understood. Although the gut-heart axis is attracting more attention in recent years, our knowledge of the organ-to-organ communication between the gut and the heart remains limited. In patients with IBD, upregulated inflammatory factors, altered microRNAs and lipid profiles, as well as dysbiotic gut microbiota, may induce adverse cardiac remodeling. In addition, patients with IBD have a three- to four times higher risk of developing thrombosis than people without IBD, and it is believed that the increased risk of thrombosis is largely due to increased procoagulant factors, platelet count/activity, and fibrinogen concentration, in addition to decreased anticoagulant factors. The predisposing factors for atherosclerosis are present in IBD and the possible mechanisms may involve oxidative stress system, overexpression of matrix metalloproteinases, and changes in vascular smooth muscle phenotype. This review focuses mainly on 1) the prevalence of cardiovascular diseases associated with IBD, 2) the potential pathogenic mechanisms of cardiovascular diseases in patients with IBD, and 3) adverse effects of IBD drugs on the cardiovascular system. Also, we introduce here a new paradigm for the gut-heart axis that includes exosomal microRNA and the gut microbiota as a cause for cardiac remodeling and fibrosis.

NEIL3-deficiency increases gut permeability and contributes to a pro-atherogenic metabolic phenotype

Atherosclerosis and its consequences cause considerable morbidity and mortality world-wide. We have previously shown that expression of the DNA glycosylase NEIL3 is regulated in human atherosclerotic plaques, and that NEIL3-deficiency enhances atherogenesis in Apoe-/- mice. Herein, we identified a time point prior to quantifiable differences in atherosclerosis between Apoe-/-Neil3-/- mice and Apoe-/- mice. Mice at this age were selected to explore the metabolic and pathophysiological processes preceding extensive atherogenesis in NEIL3-deficient mice. Untargeted metabolomic analysis of young Apoe-/-Neil3-/- mice revealed significant metabolic disturbances as compared to mice expressing NEIL3, particularly in metabolites dependent on the gut microbiota. 16S rRNA gene sequencing of fecal bacterial DNA indeed confirmed that the NEIL3-deficient mice had altered gut microbiota, as well as increased circulating levels of the bacterially derived molecule LPS. The mice were challenged with a FITC-conjugated dextran to explore gut permeability, which was significantly increased in the NEIL3-deficient mice. Further, immunohistochemistry showed increased levels of the proliferation marker Ki67 in the colonic epithelium of NEIL3-deficient mice, suggesting increased proliferation of intestinal cells and gut leakage. We suggest that these metabolic alterations serve as drivers of atherosclerosis in NEIL3-deficient mice.

Lipoproteins and Cardiovascular Redox Signaling: Role in Atherosclerosis and Coronary Disease

SIGNIFICANCE

Lipoproteins, such as low-density lipoprotein, play a causal role in the development of atherosclerosis and coronary disease. Recent Advances: Lipoproteins can stimulate vascular production of reactive oxygen species, which act as important signaling molecules in the cardiovascular system contributing to the pathophysiology of endothelial dysfunction, hypertension, and atherosclerosis.

CRITICAL ISSUES

Modified lipoproteins have emerged as important regulators of redox signaling, such as oxidized or carbamylated low-density lipoprotein or modified high-density lipoproteins, that contain oxidized lipids, an altered protein cargo, and associated small molecules, such as symmetric dimethylarginine.

FUTURE DIRECTIONS

In this review, we provide an overview on signaling pathways stimulated by modified lipoproteins in the cardiovascular system and their potential role in cardiovascular disease development. Moreover, we highlight novel aspects of how gut microbiome-related mechanisms-a growing research field-may contribute to lipoprotein modification with subsequent impact on cardiovascular redox signaling. Antioxid. Redox Signal. 29, 337-352.

[Gut microbiota and immune crosstalk in metabolic disease]

The aim of the review is to discuss about the role played by the defence crosstalk between the gut microbiota and the intestinal immune system, in the development of metabolic disease focusing on obesity and diabetes. Starting from physiological and pathological stand points and based on the latest published data, this review is addressing how the concept of the hologenome theory of evolution can drive the fate of metabolic disease. The notion of "metabolic infection" to explain the "metabolic inflammation" is discussed. This imply comments about the process of bacterial translocation and impaired intestinal immune defense against commensals. Eventually this review sets the soil for personalized medicine. The monthly increase in the number of publications on the gut microbiota to intestinal immune defense and the control of metabolism demonstrate the importance of this field of investigation. The notion of commensal as "self or non-self" has to be reevaluated in the light of the current data. Furthermore, data demonstrate the major role played by short chain fatty acids, secondary bile acids, LPS, peptidoglycans, indole derivatives, and other bacteria-related molecules on the shaping of cells involved in the intestinal protection against commensals is now becoming a central player in the incidence of metabolic diseases. The literature demonstrates that the onset of metabolic diseases and some specific co-morbidities can be explained by a gut microbiota to intestinal immune system crosstalk. Therefore, one should now consider this avenue of investigation as a putative source of biomarkers and therapeutic targets to personalize the treatment of metabolic disease and its co-morbidities. Gut microbiota is considered as a major regulator of metabolic disease. This reconciles the notion of metabolic inflammation and the epidemic development of the disease. In addition to evidence showing that a specific gut microbiota characterizes patients with obesity, type 2 diabetes, and hepatic steatosis, the mechanisms causal to the disease could be related to the translocation of microbiota from the gut to the tissues, which induces inflammation. The mechanisms regulating such a process are based on the crosstalk between the gut microbiota and the host immune system. The hologenome theory of evolution supports this concept and implies that therapeutic strategies aiming to control glycemia should take into account both the gut microbiota and the host immune system. This review discusses the latest evidence regarding the bidirectional impact of the gut microbiota on host immune system crosstalk for the control of metabolic disease, hyperglycemia, and obesity. To avoid redundancies with the literature, we will focus our attention on the intestinal immune system, identifying evidence for the generation of novel therapeutic strategies, which could be based on the control of the translocation of gut bacteria to tissues. Such novel strategies should hamper the role played by gut microbiota dysbiosis on the development of metabolic inflammation. Recent evidence in rodents allows us to conclude that an impaired intestinal immune system characterizes and could be causal in the development of metabolic disease. The fine understanding of the molecular mechanisms should allow for the development of a first line of treatment for metabolic disease and its co-morbidities.

Risk of cardiovascular disease in inflammatory bowel disease

Cardiovascular disease (CVD) can arise because of chronic inflammation and inflammatory bowel disease (IBD) is one such disease where the risk for CVD and eventual heart failure is increased considerably. The incidence of IBD, which refers to both ulcerative colitis and Crohn's disease, has been on the increase in several countries and is a potential risk factor for CVD. Although IBD can potentially cause venous thromboembolism, its significance in arterial stiffening, atherosclerosis, ischemic heart disease and myocardial infarction is only being realized now and it is currently under debate. However, several studies with large groups of patients have demonstrated the association of IBD with heart disease. It has been suggested that systemic inflammation as observed in IBD patients leads to oxidative stress and elevated levels of inflammatory cytokines such as tumor necrosis factor-α (TNF-α), which lead to phenotypic changes in smooth muscle cells and sets into motion a series of events that culminate in atherosclerosis and CVD. Besides the endogenous factors and cytokines, it has been suggested that due to the compromised intestinal mucosal barrier, endotoxins and bacterial lipopolysaccharides produced by intestinal microflora can enter into circulation and activate inflammatory responses that lead to atherosclerosis. Therapeutic management of IBD-associated heart diseases cannot be achieved with simple anti-inflammatory drugs such as corticosteroids and anti-TNF-α antibodies. Treatment with existing medications for CVDs, aspirin, platelet aggregation inhibitors and statins is found to be acceptable and safe. Nevertheless, further research is needed to assess their efficacy in IBD patients suffering from heart disease.

Gut microbiota and immune crosstalk in metabolic disease

Background

Gut microbiota is considered as a major regulator of metabolic disease. This reconciles the notion of metabolic inflammation and the epidemic development of the disease. In addition to evidence showing that a specific gut microbiota characterizes patients with obesity, type 2 diabetes, and hepatic steatosis, the mechanisms causal to the disease could be related to the translocation of microbiota from the gut to the tissues, inducing inflammation. The mechanisms regulating such a process are based on the crosstalk between the gut microbiota and the host immune system. The hologenome theory of evolution supports this concept and implies that therapeutic strategies aiming to control glycemia should take into account both the gut microbiota and the host immune system.

Scope of review

This review discusses the latest evidence regarding the bidirectional impact of the gut microbiota on host immune system crosstalk for the control of metabolic disease, hyperglycemia, and obesity. To avoid redundancies with the literature, we will focus our attention on the intestinal immune system, identifying evidence for the generation of novel therapeutic strategies, which could be based on the control of the translocation of gut bacteria to tissues. Such novel strategies should hamper the role played by gut microbiota dysbiosis on the development of metabolic inflammation.

Major conclusions

Recent evidence in rodents allows us to conclude that an impaired intestinal immune system characterizes and could be causal in the development of metabolic disease. The fine understanding of the molecular mechanisms should allow for the development of a first line of treatment for metabolic disease and its co-morbidities.

This article is part of a special issue on microbiota.

Cardiovascular complications in inflammatory bowel disease

Over the past years, a growing number of studies have indicated that patients suffering from inflammatory bowel disease (IBD) have an increased risk of developing cardiovascular disease. Both are chronic inflammatory diseases and share certain pathophysiological mechanisms that may influence each other. High levels of cytokines, C-reactive protein (CRP), and homocysteine in IBD patients may lead to endothelial dysfunction, an early sign of atherosclerosis. IBD patients, in general, do not show the typical risk factors for cardiovascular disease but changes in lipid profiles similar to the ones seen in cardiovascular events have been reported recently. Higher levels of coagulation factors frequently occur in IBD which may predispose to arterial thromboembolic events. Finally, the gut itself may have an impact on atherogenesis during IBD through its microbiota. Microbial products are released from the inflamed mucosa into the circulation through a leaky barrier. The induced rise in proinflammatory cytokines could contribute to endothelial damage, artherosclerosis and cardiovascular events. Although large retrospective studies favor a link between IBD and cardiovascular diseases, the mechanisms behind still remain to be determined.

Cardiovascular complications in inflammatory bowel disease

Over the past years, a growing number of studies have indicated that patients suffering from inflammatory bowel disease (IBD) have an increased risk of developing cardiovascular disease. Both are chronic inflammatory diseases and share certain pathophysiological mechanisms that may influence each other. High levels of cytokines, C-reactive protein (CRP), and homocysteine in IBD patients may lead to endothelial dysfunction, an early sign of atherosclerosis. IBD patients, in general, do not show the typical risk factors for cardiovascular disease but changes in lipid profiles similar to the ones seen in cardiovascular events have been reported recently. Higher levels of coagulation factors frequently occur in IBD which may predispose to arterial thromboembolic events. Finally, the gut itself may have an impact on atherogenesis during IBD through its microbiota. Microbial products are released from the inflamed mucosa into the circulation through a leaky barrier. The induced rise in proinflammatory cytokines could contribute to endothelial damage, artherosclerosis and cardiovascular events. Although large retrospective studies favor a link between IBD and cardiovascular diseases, the mechanisms behind still remain to be determined.

Metabolic syndrome in pediatric cancer survivors: a mechanistic review

Pediatric cancer survivors have increased risk of obesity, hypertension, dyslipidemia, and type 2 diabetes, leading to premature cardiovascular disease (CVD). Multiple tissues that are involved in glucose homeostasis and lipid metabolism are adversely affected by chemotherapy. This review highlights the relevant tissue and molecular end-organ effects of therapy exposures and synthesizes the current understanding of the mechanisms underlying CVD risk in this vulnerable population. The review also approaches the topic from a developmental perspective, with the goal of providing a translational approach to identifying the antecedents of overt CVD among survivors of pediatric cancer.

Gut microbiota and diabetes: from pathogenesis to therapeutic perspective

More than several hundreds of millions of people will be diabetic and obese over the next decades in front of which the actual therapeutic approaches aim at treating the consequences rather than causes of the impaired metabolism. This strategy is not efficient and new paradigms should be found. The wide analysis of the genome cannot predict or explain more than 10-20% of the disease, whereas changes in feeding and social behavior have certainly a major impact. However, the molecular mechanisms linking environmental factors and genetic susceptibility were so far not envisioned until the recent discovery of a hidden source of genomic diversity, i.e., the metagenome. More than 3 million genes from several hundreds of species constitute our intestinal microbiome. First key experiments have demonstrated that this biome can by itself transfer metabolic disease. The mechanisms are unknown but could be involved in the modulation of energy harvesting capacity by the host as well as the low-grade inflammation and the corresponding immune response on adipose tissue plasticity, hepatic steatosis, insulin resistance and even the secondary cardiovascular events. Secreted bacterial factors reach the circulating blood, and even full bacteria from intestinal microbiota can reach tissues where inflammation is triggered. The last 5 years have demonstrated that intestinal microbiota, at its molecular level, is a causal factor early in the development of the diseases. Nonetheless, much more need to be uncovered in order to identify first, new predictive biomarkers so that preventive strategies based on pre- and probiotics, and second, new therapeutic strategies against the cause rather than the consequence of hyperglycemia and body weight gain.

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.