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

Emerging Roles of Lysophosphatidic Acid in Macrophages and Inflammatory Diseases

Lysophosphatidic acid (LPA) is a bioactive phospholipid that regulates physiological and pathological processes in numerous cell biological functions, including cell migration, apoptosis, and proliferation. Macrophages are found in most human tissues and have multiple physiological and pathological functions. There is growing evidence that LPA signaling plays a significant role in the physiological function of macrophages and accelerates the development of diseases caused by macrophage dysfunction and inflammation, such as inflammation-related diseases, cancer, atherosclerosis, and fibrosis. In this review, we summarize the roles of LPA in macrophages, analyze numerous macrophage- and inflammation-associated diseases triggered by LPA, and discuss LPA-targeting therapeutic strategies.

5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone Inhibits LPS-Induced Vascular Inflammation by Targeting the Cav1 Protein

Vascular inflammation is directly responsible for atherosclerosis. 5,2′-Dibromo-2,4′,5′-trihydroxydiphenylmethanone (TDD), a synthetic bromophenol derivative, exhibits anti-atherosclerosis and anti-inflammatory effects. However, the underlying pathways are not yet clear. In this study, we first examined the effects of TDD on toll-like receptor-4 (TLR4) activity, the signaling receptor for lipopolysaccharide (LPS), and found that TDD does not inhibit LPS-induced TLR4 expression in EA.hy926 cells and the vascular wall in vivo. Next, we investigated the global protein alterations and the mechanisms underlying the action of TDD in LPS-treated EA.hy926 cells using an isobaric tag for the relative and absolute quantification technique. Western blot analysis revealed that TDD inhibited NF-κB activation by regulating the phosphorylation and subsequent degradation IκBα. Among the differentially expressed proteins, TDD concentration-dependently inhibited Caveolin 1(Cav1) expression. The interaction between Cav1 and TDD was determined by using biolayer interference assay, UV-vis absorption spectra, fluorescence spectrum, and molecular docking. We found that TDD can directly bind to Cav1 through hydrogen bonds and van der Waals forces. In conclusion, our results showed that TDD inhibited LPS-induced vascular inflammation and the NF-κB signaling pathway by specifically targeting the Cav1 protein. TDD may be a novel anti-inflammatory compound, especially for the treatment of atherosclerosis.

N-Docosahexaenoylethanolamine Attenuates Neuroinflammation and Improves Hippocampal Neurogenesis in Rats with Sciatic Nerve Chronic Constriction Injury

Chronic neuropathic pain is a condition that causes both sensory disturbances and a variety of functional disorders, indicating the involvement of various brain structures in pain pathogenesis. One of the factors underlying chronic neuropathic pain is neuroinflammation, which is accompanied by microglial activation and pro-inflammatory factor release. N-docosahexaenoylethanolamine (DHEA, synaptamide) is an endocannabinoid-like metabolite synthesized endogenously from docosahexaenoic acid. Synaptamide exhibits anti-inflammatory activity and improves neurite outgrowth, neurogenesis, and synaptogenesis within the hippocampus. This study aims to evaluate the effects of synaptamide obtained by the chemical modification of DHA, extracted from the Far Eastern raw material Berryteuthis magister on neuroinflammatory response and hippocampal neurogenesis changes during neuropathic pain. The study of microglial protein and cytokine concentrations was performed using immunohistochemistry and ELISA. The brain lipid analysis was performed using the liquid chromatography-mass spectrometry technique. Behavioral experiments showed that synaptamide prevented neuropathic pain-associated sensory and behavioral changes, such as thermal allodynia, impaired locomotor activity, working and long-term memory, and increased anxiety. Synaptamide attenuated microglial activation, release of proinflammatory cytokines, and decrease in hippocampal neurogenesis. Lipid analysis revealed changes in the brain N-acylethanolamines composition and plasmalogen concentration after synaptamide administration. In conclusion, we show here that synaptamide may have potential for use in preventing or treating neuropathic cognitive pain and emotional effects.

Expression of Nik-related kinase in smooth muscle cells attenuates vascular inflammation and intimal hyperplasia

Inflammation of the vascular microenvironment modulates distinct types of vascular cells, and plays important roles in promoting atherosclerosis, stenosis/restenosis, and vascular-related diseases. Nik-related kinase (Nrk), a member of the Ste20-type kinase family, has been reported to be selectively expressed in embryonic skeletal muscle. However, whether Nrk is expressed in adult vascular smooth muscle, and if it influences intimal hyperplasia is unclear. Here, we found that Nrk is abundantly expressed in cultured vascular smooth muscle cells (VSMC) and mouse arterial intima. Treatment of mouse VSMCs with lipopolysaccharide (LPS) or platelet-derived growth factor significantly reduced Nrk expression. In addition, expression of Nrk was significantly reduced in regions of neointimal formation caused by guide-wire carotid artery injuries in mice, as well as in human atherosclerotic tissues, when compared to normal vessels. We identified that expression of matrix metalloproteinases (MMP3, MMP8 and MMP12) and inflammatory cytokines/chemokines (CCL6, CCL8, CCL11, CXCL1, CXCL3, CXCL5 and CXCL9) are synergistically induced by Nrk siRNA in LPS-treated mouse VSMCs. Moreover, we found that resveratrol significantly impaired LPS- and Nrk siRNA-induced expression of MMP3, CCL8, CCL11, CXCL3 and CXCL5. These results suggested that Nrk may play important roles in regulating pathological progression of atherosclerosis or neointimal- hyperplasia-related vascular diseases.

5,2'-dibromo-2,4',5'-trihydroxydiphenylmethanone attenuates LPS-induced inflammation and ROS production in EA.hy926 cells via HMBOX1 induction

Inflammation and reactive oxygen species (ROS) are important factors in the pathogenesis of atherosclerosis (AS). 5,2′‐dibromo‐2,4′,5′‐trihydroxydiphenylmethanone (TDD), possess anti‐atherogenic properties; however, its underlying mechanism of action remains unclear. Therefore, we sought to understand the therapeutic molecular mechanism of TDD in inflammatory response and oxidative stress in EA.hy926 cells. Microarray analysis revealed that the expression of homeobox containing 1 (HMBOX1) was dramatically upregulated in TDD‐treated EA.hy926 cells. According to the gene ontology (GO) analysis of microarray data, TDD significantly influenced the response to lipopolysaccharide (LPS); it suppressed the LPS‐induced adhesion of monocytes to EA.hy926 cells. Simultaneously, TDD dose‐dependently inhibited the production or expression of IL‐6, IL‐1β, MCP‐1, TNF‐α, VCAM‐1, ICAM‐1 and E‐selectin as well as ROS in LPS‐stimulated EA.hy926 cells. HMBOX1 knockdown using RNA interference attenuated the anti‐inflammatory and anti‐oxidative effects of TDD. Furthermore, TDD inhibited LPS‐induced NF‐κB and MAPK activation in EA.hy926 cells, but this effect was abolished by HMBOX1 knockdown. Overall, these results demonstrate that TDD activates HMBOX1, which is an inducible protective mechanism that inhibits LPS‐induced inflammation and ROS production in EA.hy926 cells by the subsequent inhibition of redox‐sensitive NF‐κB and MAPK activation. Our study suggested that TDD may be a potential novel agent for treating endothelial cells dysfunction in AS.

JNK1 Mediates Lipopolysaccharide-Induced CD14 and SR-AI Expression and Macrophage Foam Cell Formation

Foam cell formation is the key process in the development of atherosclerosis. The uptake of oxidized low-density lipoprotein (oxLDL) converts macrophages into foam cells. We recently reported that lipopolysaccharide (LPS)-induced foam cell formation is regulated by CD14 and scavenger receptor AI (SR-AI). In this study, we employed pharmaceutical and gene knockdown approaches to determine the upstream molecular mediators, which control LPS-induced foam cell formation. Our results demonstrated that the specific c-Jun N-terminal kinase (JNK) pathway inhibitor, SP600125, but neither the specific inhibitor of extracellular signaling-regulated kinase (ERK) kinase MEK1/2, U0126, nor the specific inhibitor of p38 MAPK, SB203580, significantly blocks LPS-induced oxLDL uptake, suggesting that the JNK pathway is the upstream mediator of LPS-induced oxLDL uptake/foam cell formation. To address whether JNK pathway mediates LPS-induced oxLDL uptake is due to JNK pathway-regulated CD14 and SR-AI expression, we assessed whether the pharmaceutical inhibitor of JNK influences LPS-induced expression of CD14 and SR-AI. Our results indicate that JNK pathway mediates LPS-induced CD14 and SR-AI expression. To conclusively address the isoform role of JNK family, we depleted JNK isoforms using the JNK isoform-specific siRNA. Our data showed that the depletion of JNK1, but not JNK2 blocked LPS-induced CD14/SR-AI expression and foam cell formation. Taken together, our results reveal for the first time that JNK1 is the key mediator of LPS-induced CD14 and SR-AI expression in macrophages, leading to LPS-induced oxLDL uptake/foam cell formation. We conclude that the novel JNK1/CD14/SR-AI pathway controls macrophage oxLDL uptake/foam cell formation.

CD14 is a key mediator of both lysophosphatidic acid and lipopolysaccharide induction of foam cell formation

Macrophage uptake of oxidized low-density lipoprotein (oxLDL) plays an important role in foam cell formation and the pathogenesis of atherosclerosis. We report here that lysophosphatidic acid (LPA) enhances lipopolysaccharide (LPS)-induced oxLDL uptake in macrophages. Our data revealed that both LPA and LPS highly induce the CD14 expression at messenger RNA and protein levels in macrophages. The role of CD14, one component of the LPS receptor cluster, in LPA-induced biological functions has been unknown. We took several steps to examine the role of CD14 in LPA signaling pathways. Knockdown of CD14 expression nearly completely blocked LPA/LPS-induced oxLDL uptake in macrophages, demonstrating for the first time that CD14 is a key mediator responsible for both LPA- and LPS-induced oxLDL uptake/foam cell formation. To determine the molecular mechanism mediating CD14 function, we demonstrated that both LPA and LPS significantly induce the expression of scavenger receptor class A type I (SR-AI), which has been implicated in lipid uptake process, and depletion of CD14 levels blocked LPA/LPS-induced SR-AI expression. We further showed that the SR-AI-specific antibody, which quenches SR-AI function, blocked LPA- and LPS-induced foam cell formation. Thus, SR-AI is the downstream mediator of CD14 in regulating LPA-, LPS-, and LPA/LPS-induced foam cell formation. Taken together, our results provide the first experimental evidence that CD14 is a novel connecting molecule linking both LPA and LPS pathways and is a key mediator responsible for LPA/LPS-induced foam cell formation. The LPA/LPS-CD14-SR-AI nexus might be the new convergent pathway, contributing to the worsening of atherosclerosis.

A Novel ASK Inhibitor AGI-1067 Inhibits TLR-4-Mediated Activation of ASK1 by Preventing Dissociation of Thioredoxin from ASK1

The cell type that normally limits the inflammatory and atherosclerotic process is the vascular endothelial cell (EC) that can be regulated by proinflammatory and various stresses. Toll-like receptor-4 (TLR4) plays an important role in the pathogenesis of atherosclerosis, in part, by activating apoptosis signal-regulating kinase 1 (ASK1) to initiate the activation of MAP kinases pathways and the expression of inflammatory genes. In the present study, we test the hypothesis that AGI-1067 acts as an anti-inflammatory agent by inhibiting the activation of ASK1 in human EC. Pretreatment of human aortic endothelial cells with AGI-1067 inhibits TLR4 ligand (LPS)-induced activation of ASK1 and the downstream p38 and c-Jun N-terminal kinase (JNK) MAP kinases. LPS dissociates two endogenous inhibitors thioredoxin-1 (Trx1) and 14-3-3 from ASK1, leading to ASK1 autoactivation. Interestingly, AGI-1067 inhibits the dissociation of Trx1, but not 14-3-3, from ASK1. However, inhibition of Trx1 dissociation from ASK1 by AGI-1067 is sufficient to suppress LPS-mediated phosphorylation of the transcription factors c-Jun and activating transcription factor 2, and inhibit LPS-induced inflammatory genes including vascular cell adhesion molecule 1, E-selectin, IL-6 and monocyte chemoattractant protein 1. Our findings suggest that AGI-1067 as a unique ASK1 inhibitor to inhibit TLR4-mediated ASK1 activation, contributing to its anti-inflammatory properties.

Danger signaling in atherosclerosis

All aspects of the pathogenesis of atherosclerosis are critically influenced by the inflammatory response in vascular plaques. Research in the field of innate immunity from the past 2 decades has uncovered many novel mechanisms elucidating how immune cells sense microbes, tissue damage, and metabolic derangements. Here, we summarize which triggers of innate immunity appear during atherogenesis and by which pathways they can contribute to inflammation in atherosclerotic plaques. The increased understanding gained from studies assessing how immune activation is associated with the pathogenesis of atherosclerosis has provided many novel targets for potential therapeutic intervention. Excitingly, the concept that inflammation may be the core of cardiovascular disease is currently being clinically evaluated and will probably encourage further studies in this area.

A rabbit model of spontaneous thrombosis induced by lipopolysaccharide

AIM

Inflammation plays a critical role in the development of atherosclerotic plaque, and lipopolysaccharide (LPS) is a potentially important source of inflammation. The aim of this study was to develop a rabbit model of spontaneous thrombosis mimicking the pathophysiological and morphological characteristics of atherosclerotic plaque in humans.

METHODS

The rabbits were randomized into four groups: group A (n=10) received a normal diet; group B (n=10) received a regular diet and weekly LPS injections (1 μg/kg, Escherichia coli); group C (n=15) received a cholesterol-enriched diet before and after sustaining a balloon injury to the right common carotid artery; and group D (n=15) was treated the same as group C in addition to receiving LPS injections. The morphological characteristics of the resulting lesions were evaluated using optical coherence tomography (OCT) and histology.

RESULTS

No significant atherosclerotic plaque was observed in groups A or B. Group D exhibited a higher incidence of spontaneous luminal thrombi than group C or B (60% vs. 20% vs. 10%, p<0.05). All of the thrombi detected with OCT were confirmed on histology. A good correlation between the fibrous cap thickness and thrombus arc was obtained on OCT and the histological evaluations.

CONCLUSIONS

A rabbit model of LPS-induced spontaneous thrombosis was developed in which OCT was used to follow changes in plaque morphology.

Lipopolysaccharide-induced proliferation of the vasa vasorum in a rabbit model of atherosclerosis as evaluated by contrast-enhanced ultrasound imaging and histology

Whether lipopolysaccharide (LPS) can promote vasa vasorum (VV) proliferation for atherosclerosis in vivo is unclear. Eighteen rabbits with atherosclerosis were randomly assigned into one of three groups of six. Group A received biweekly injections of 10 mL saline after 2 weeks of balloon injury. Groups B and C received biweekly intravenous injections of 3.0 μg LPS in 10 mL saline at weeks 10 and 4, respectively, until study termination. LPS significantly increased the levels of triglycerides and C-reactive protein and decreased the level of high-density lipoprotein cholesterol. Group C had significant larger plaques and more macrophages than group A (p = 0.01 and p < 0.001, respectively). Contrast enhancement ultrasound imaging and histological detection demonstrated that plaques in group C had a significantly higher VV density than that in group A (p = 0.009 and p = 0.002, respectively). In summary, VV proliferation for plaque destabilization can be accelerated by LPS-induced systemic inflammation and changes in lipid profiles.

Arginase I Attenuates Inflammatory Cytokine Secretion Induced by Lipopolysaccharide in Vascular Smooth Muscle Cells

Objective—

Inflammation plays an important role in atherosclerosis. Arginase I (Arg I) promotes the proliferation of vascular smooth muscle cells; however, the effect of Arg I on inflammation remains unknown. The present study investigated the role of Arg I in inflammation in vitro and in vivo.

Methods and Results—

Quantitative reverse transcription–polymerase chain reaction and Western blot analysis demonstrated that Arg I inhibited tumor necrosis factor-α production induced by lipopolysaccharide in human aortic smooth muscle cells. Inducible nitric oxide synthase substrate competition and nuclear factor-κB activation were main contributors to lipopolysaccharide-mediated inflammatory cytokine generation. However, Arg I could attenuate the function of inducible nitric oxide synthase and inhibit the subsequent nuclear factor-κB activation, leading to inhibition of tumor necrosis factor-α generation. Furthermore, upregulation of Arg I significantly decreased macrophage infiltration and inflammation in atherosclerotic plaque of rabbits, whereas downregulation of Arg I aggravated these adverse effects.

Conclusion—

The results indicate the antiinflammatory effects of Arg I and suggest an unexpected beneficial role of Arg I in inflammatory disease.

Housefly maggots (Musca domestica) protein-enriched fraction/extracts (PE) inhibit lipopolysaccharide-induced atherosclerosis pro-inflammatory responses

AIM

To investigate the effects of housefly maggot (Musca domestica) protein-enriched fraction/extracts (PE) on lipopolysaccharide (LPS)-induced atherosclerosis (AS) pro-inflammatory responses in mice and macrophages.

METHODS

The mouse model of AS was established by feeding a cholesterol-enriched diet and inducing by LPS. Changes in the levels of blood lipids (total cholesterol (TC), triglyceride (TG), low-density lipoprotein cholesterol (LDL) and high-density lipoprotein cholesterol (HDL)) and pro-inflammatory cytokines (interferon-gamma (IFNγ), tumor necrosis factor alpha (TNFα) and interleukin-1alpha (IL-1α)) were determined. Histomorphometric analysis of the pathological condition of the artery was also carried out. The macrophages were stimulated by LPS in the presence or absence of PE, and then the levels of TNFα, IL-1α and monocyte chemotactic protein 1 (MCP-1) in cell culture supernatant were measured.

RESULTS

Compared with the negative control group, the levels of three pro-inflammatory cytokines were significantly enhanced in the PE treatment group (p< 0.01). The concentrations of TC, TG and LDL were lower in the PE treatment group than in the negative control group (p< 0.01). HDL concentration in the PE treatment group was higher than in the negative control group (p< 0.01). Histomorphometric analysis showed that the thickness of the intima and media area, as well as the area ratio of the intima to media in the PE treatment group were lower than in the negative control group (p< 0.01). The expression of TNFα, IL-1α and MCP-1 in LPS-induced macrophages was inhibited by different concentrations of PE (p< 0.01).

CONCLUSION

These results indicate that PE potently inhibited multiple pro-inflammatory responses in experimental atherosclerosis lesions in vivo, and possessed anti-pro-inflammatory properties in vitro.

The capacity of foodstuffs to induce innate immune activation of human monocytes in vitro is dependent on food content of stimulants of Toll-like receptors 2 and 4

The ingestion of fatty meals is associated with a transient, low-grade systemic inflammatory response in human subjects, involving the activation of circulating monocytes and the secretion of pro-inflammatory cytokines. However, it is not yet clear how different foodstuffs may promote inflammatory signalling. In a screen of forty filter-sterilised soluble extracts from common foodstuffs, seven were found to induce the secretion of TNF-α and IL-6 from human monocytes in vitro. To investigate what may differentiate inflammatory from non-inflammatory food extracts, stimulants of Toll-like receptor (TLR) 2 and TLR4 were quantified using human embryonic kidney-293 cells transfected with each TLR, and calibrated with defined bacterial lipopeptide (BLP) and lipopolysaccharide (LPS) standards. These assays revealed that while most foods contained undetectable levels of TLR2 or TLR4 stimulants, all TNF-α-inducing foods contained stimulants of either TLR2 (up to 1100 ng BLP-equivalent/g) or TLR4 (up to 2700 ng LPS-equivalent/g) in both the soluble and insoluble fractions. TLR stimulants were present mainly in meat products and processed foods, but were minimal or undetectable in fresh fruit and vegetables. The capacity of food extracts to induce TNF-α secretion in monocytes correlated with the content of both TLR2 (r 0·837) and TLR4 stimulants (r 0·748), and was completely abolished by specific inhibition of TLR2 and TLR4. LPS and BLP were found to be highly resistant to typical cooking times and temperatures, low pH and protease treatment. In conclusion, apparently unspoiled foodstuffs can contain large quantities of stimulants of TLR2 and TLR4, both of which may regulate their capacity to stimulate inflammatory signalling.

Carotid artery brain aneurysm model: in vivo molecular enzyme-specific MR imaging of active inflammation in a pilot study

PURPOSE

To demonstrate the feasibility of using a myeloperoxidase (MPO)-specific paramagnetic magnetic resonance (MR) contrast agent to identify active inflammation in an animal model of common carotid artery (CCA) aneurysm.

MATERIALS AND METHODS

All animal experiments were approved by the institutional animal care and use committee. Elastase-induced saccular aneurysms were created at the root of the right CCA in 16 New Zealand white rabbits. Intramural and perivascular injection of Escherichia coli lipopolysaccharide (LPS) was performed with an endovascular approach to induce aneurysm inflammation. After intraarterial injection of an MPO-specific (di-5-hydroxytryptamide of gadopentetate dimeglumine, 0.1 mmol per kilogram of bodyweight) or a non-MPO-specific (di-tyrosine of gadopentetate dimeglumine, 0.1 mmol/kg) contrast agent, animals underwent 3-T MR imaging. Intramural presence of MPO in aneurysms in which LPS had been injected was confirmed at immunohistologic analysis. Active MPO activity was verified by measuring the spectrophotometric oxidation of guaiacol.

RESULTS

Endovascular injection of LPS resulted in inflammatory cell infiltration into the aneurysm wall, and there was a difference in active MPO expression between aneurysms in which LPS had been injected and control aneurysms (20.3 ng of MPO per milligram of tissue vs 0.12 ng of MPO per milligram of tissue, respectively; P < .002). MR imaging with di-5-hydroxytryptamide of gadopentetate dimeglumine revealed a difference in enhancement ratio between inflamed aneurysms in which LPS had been injected and control aneurysms (1.55 +/- 0.05 vs 1.16 +/- 0.10, respectively; P < .02). In inflamed aneurysms, di-5-hydroxytryptamide of gadopentetate dimeglumine exhibited delayed washout kinetics compared with the kinetics of di-tyrosine of gadopentetate dimeglumine. This finding enabled the verification of MPO specificity.

CONCLUSION

The findings of this pilot study established the feasibility of an animal model of saccular aneurysm inflammation that can be seen with clinical-field-strength MR imaging and use of the enzyme-sensitive MR contrast agent di-5-hydroxytryptamide of gadopentetate dimeglumine, which is a paramagnetic MPO substrate that specifically enhances MR signal.

Translational mini-review series on immunology of vascular disease: inflammation, infections and Toll-like receptors in cardiovascular disease

Cardiovascular disease, in which atherosclerosis is the major underlying cause, is currently the largest cause of death in the world. Atherosclerosis is an inflammatory disease characterized by the formation of arterial lesions over a period of several decades at sites of endothelial cell dysfunction. These lesions are composed of endothelial cells, vascular smooth muscle cells, monocytes/macrophages and T lymphocytes (CD4(+)). As the lesions progress some can become unstable and prone to disruption, resulting in thrombus formation and possibly a myocardial infarction or stroke depending upon the location. Although the exact triggers for plaque disruption remain unknown, much recent evidence has shown a link between the incidence of myocardial infarction and stroke and a recent respiratory tract infection. Interestingly, many reports have also shown a link between a family of pattern recognition receptors, the Toll-like receptors, and the progression of atherosclerosis, suggesting that infections may play a role in both the progression of atherosclerosis and in inducing the more severe complications associated with the disease.

Chronic perivascular inoculation with Chlamydophila pneumoniae results in plaque formation in vivo

Hypercholesterolemic and normocholesterolemic rabbit models of chronic arterial Chlamydophila (Chlamydia) pneumoniae (CPN) inoculation were established and the role of both viable and inactivated bacteria was investigated in atherogenesis. A total of 29 rabbits were randomized to four groups. Groups A and B were fed a cholesterol-enriched diet, and groups C and D were fed a normal diet. Arterial segments of group A and C animals were inoculated in vivo using viable CPN chronically using repeated perivascular applications. Contralateral arteries were treated using heat-inactivated CPN. Group B and D animals were treated with repeated perivascular injections of bacterial lipopolysaccharide (LPS) and saline (control). Additional hypercholesterolemic rabbits were treated by repeated injections using viable and inactivated CPN, each controlled by saline injections. To compare the effects of this chronic inoculation model, additional animals received single injections of either viable CPN, inactivated CPN, LPS, or saline. Vascular tissues (n=162 treated arteries of 29 rabbits) were analyzed using morphometry at histology. CPN was detected by fluorescence-immunohistochemistry and nested polymerase chain reaction. Only in hypercholesterolemic, but not in normocholesterolemic rabbits, chronic perivascular infection of all bacterial components, viable and heat-inactivated CPN, as well as LPS resulted in a significant increase in atheromatous lesion formation (lesion area index: 0.23+/-0.08, 0.25+/-0.09, and 0.15+/-0.05) when compared to controls (lesion area index 0.01+/-0.01, P=0.002). CPN persisted in atheromatous lesions and vascular tissues. Single perivascular infection using CPN or inactivated CPN was not able to induce lesion formation (lesion area index: 0.03+/-0.03, 0.03+/-0.02 vs 0.03+/-0.02 after single saline inoculation, P=0.965). In conclusion, chronic vascular infection with CPN or CPN components acts as a cofactor requiring other major atherogenic stimuli, rather than as a causative agent.

Relationship of coffee consumption with risk factors of atherosclerosis in rats

AIMS

In experimental animals we investigated the relationship of coffee consumption with risk factors of atherosclerosis such as cholesterol, homocysteine, oxidative stress and inflammatory cytokines.

METHODS

Forty-eight male Wistar rats were assigned to 3 treatment groups (a control diet group, 0.62% coffee diet group, and 1.36% coffee diet group), and animals were maintained on the experimental diets for 140 days.

RESULTS

Coffee diets led to an increase in the caffeine concentration to 0.53 +/- 0.11 and 1.77 +/- 0.22 microg/ml, respectively, although caffeine in serum was not detected in rats fed the control diet. It also led to slightly increased total serum levels of homocysteine and cholesterol, but no significant differences were found between the control and coffee diet groups. Coffee intake did not affect the production of IL-6 and TNF-alpha induced by LPS, which contributes to the atheroma-promoting effect of recurrent bacterial infection. Regarding the biomarkers of oxidative stress, the serum level of 15-isoprostane F(2t), which was significantly increased by LPS injection, was not altered by coffee intake. In contrast, urinary 8-hydroxy-2-deoxyguanosine was significantly increased in the coffee diet groups (p < 0.05). On the other hand, serum glutathione peroxidase (GPx) activity tended to decrease in the coffee groups compared with the control group, but no significant difference was found between the control and coffee diet groups. Interestingly, a significant negative correlation was observed between GPx activity and homocysteine levels in the sera from control and coffee diet groups (r = -0.403, p < 0.05).

CONCLUSIONS

This report is the first animal study on the relationship of coffee consumption with risk factors for atherosclerosis. From these results, we conclude that moderate coffee intake is not a risk factor for atherogenesis.