Induces C-reactive Protein Expression Research Articles

Effect of nattokinase on the pathological conditions in streptozotocin induced diabetic rats

Nattokinase (NK), also known as subtilisin NAT (EC 3.4.21.62), is a serine protease produced by Bacillus subtilis natto that has anti-inflammatory and fibrinolytic properties. To study whether NK prevents the progression of pathological changes in diabetes as an inflammatory disease, we examined the effect of NK on pathological conditions in streptozotocin (STZ)-induced diabetic rats using the following parameters: fasting blood glucose (glucose), total plasma protein (TP), creatinine, histopathology of renal corpuscles and tubules, advanced glycation end products (AGEs), and C-reactive protein (CRP). STZ-administered rats were maintained on a basic diet (CE-2) as control, low-NK diet (containing 0.2 mg NK/g diet), and high-NK diet (0.6 mg NK/g diet) for 14 days. High-dose NK significantly inhibited both glycogen deposition in the renal tubules and increase in the circulating AGE levels without downregulating glucose levels. Compared with the control group, the group treated with the high-NK diet presented a significant inhibition of the increase in the circulating CRP level on day 7 after the beginning of the treatment. However, the CRP level in the NK-H group reached the same level as that in the control group on Day 14. AGEs are known to induce CRP expression in hepatocytes, but the increase in CRP levels in our animal model was independent on the circulating AGE levels. In contrast, low-dose NK did not suppress changes in these parameters. Our present study suggests that NK suppresses glycogen deposition in renal tubules in a dose-dependent manner by the downregulation of AGE formation under hyperglycaemia in the rats with STZ-induced short-term diabetes. However, it is unclear whether this downregulation is caused by intact NK or peptides derived from NK during its digestion in the digestive tract.

IL-6 regulates induction of C-reactive protein gene expression by activating STAT3 isoforms

C-reactive protein (CRP) is synthesized in hepatocytes. The serum concentration of CRP increases dramatically during the acute phase response. In human hepatoma Hep3B cells, maximal CRP expression occurs in cells treated with the combination of IL-6 and IL-1β. IL-6 induces transcription of the CRP gene and IL-1β synergistically enhances the effects of IL-6. We investigated the role of IL-6-activated transcription factor STAT3, also known as STAT3α, in inducing CRP expression since we identified four consensus STAT3-binding sites centered at positions − 72, − 108, − 134 and − 164 on the CRP promoter. It has been shown previously that STAT3 binds to the site at − 108 and induces CRP expression. We found that STAT3 also bound to the other three sites, and several STAT3-containing complexes were formed at each site, suggesting the presence of STAT3 isoforms and additional transcription factors in the complexes. Mutation of the STAT3 sites at − 108, − 134 or − 164 resulted in decreased CRP expression in response to IL-6 and IL-1β treatment, although the synergy between IL-6 and IL-1β was not affected by the mutations. The STAT3 site at − 72 could not be investigated employing mutagenesis. We also found that IL-6 activated two isoforms of STAT3 in Hep3B cells: STAT3α which contains both a DNA-binding domain and a transactivation domain and STAT3β which contains only the DNA-binding domain. Taken together, these findings raise the possibility that IL-6 not only induces CRP expression but also regulates the induction of CRP expression by activating STAT3 isoforms and by utilizing all four STAT3 sites.

Fibrinopeptide A induces C-reactive protein expression through the ROS-ERK1/2/p38-NF-κB signal pathway in the human umbilical vascular endothelial cells.

Atherosclerosis is a chronic inflammatory disease of the arterial wall. Inflammation causes endothelial injury and dysfunction, which is an initial step of atherosclerosis. Fibrinopeptide A (FPA) is a biomarker of the activation of the coagulation system, and a high concentration of FPA in the blood occurs in patients with ischemic cardiocerebrovascular diseases. The present research observed that FPA stimulated the generation of C-reactive protein (CRP), IL-1β, and IL-6 in human umbilical vascular endothelial cells (HUVECs); and anti-IL-1 β and anti-IL-6 neutralizing antibodies did not alter FPA-induced CRP expression in HUVECs. The subchronic administration of FPA into rats increased the plasma FPA and CRP levels. Further studies showed that FPA stimulated superoxide anion generation, activated ERK1/2 and p38, promoted nuclear factor κB (NF-κB) nuclear translocation, and raised the NF-κB level in the nuclei of HUVECs. Antioxidant N-acetylcysteine (NAC), complex II inhibitor thenoyltrifluoroacetone (TTFA), and NADPH oxidase inhibitor diphenyleneiodonium (DPI) inhibited FPA-stimulated generation of superoxide anion, and NAC reduced FPA-induced expressions of the phosphorylated ERK1/2 and p38. NAC, TTFA, DPI, inhibitors of ERK1/2, p38, and NF-κB all downregulated FPA-induced CRP expression. These results indicate that FPA induces CRP expression in HUVECs via the ROS-ERK1/2/p38-NF-κB signal pathway. Moreover, this is the first report that FPA produces a proinflammatory effect on the vascular endothelial cells.

C-Reactive Protein and Inflammatory Cytokines during Percutaneous Coronary Intervention

Background: C-reactive protein (CRP) is significantly associated with cardiovascular diseases; however, whether CRP plays a causal role in coronary artery disease has yet to be determined. In addition, the relationship between CRP, atherosclerosis, and inflammation remains controversial. Methods and Results: Serum interleukin (IL)-6, IL-1β, and CRP levels were determined in 160 patients at time points around percutaneous coronary intervention (PCI) with drug-eluting stent implantation. The levels were found to be at peak at 24 h post-PCI and gradually declined to the level before PCI at day 30 post-PCI. These inflammation markers around PCI have no statistical difference in the different postdilation pressures (≤14, 14-18, and ≥18 atm) and stent number (1 and ≥2 stents) groups. Treatment of cultured human vascular smooth muscle cells (VSMCs) with a combination of IL-6 and IL-1β at concentrations associated with PCI did not result in any significant change in the CRP mRNA levels. The IL-6-augmented CRP expression in human internal mammary arteries (IMAs) stretched with a mechanical strength of 3 g was blocked by the nuclear factor-κB (NF-κB) peptide inhibitor SN50 and not by the inactive SN50 analog SN50M. IL-6 treatment increased NF-κB activity in human IMAs stretched with 3 g, and this effect was further blocked by stretch-activated channel (SAC) inhibitors (streptomycin or GdCl₃) and SN50. Conclusions: The current study provides evidence that increased serum IL-6, IL-1β, and CRP levels around PCI are not different between different postdilation pressure and stent number groups. The combination of IL-6 and IL-1β at concentrations associated with PCI cannot induce CRP expression in human VSMCs, but they can augment mechanical strain-induced CRP synthesis via the SAC-NF-κB pathway in human IMAs.

Aldosterone induces C-reactive protein expression via MR-ROS-MAPK-NF-κB signal pathway in rat vascular smooth muscle cells

Atherosclerosis is a chronic inflammatory disease in the vessel. As a representative inflammatory cytokine, C-reactive protein (CRP) participates in atherogenesis. Although hyperaldosteronism is known to evoke inflammatory response in several tissues and cell types, there is no direct evidence to demonstrate the proinflammatory effect of aldosterone on vascular smooth muscle cells (VSMCs) through CRP. In this study, we observed the effect of aldosterone on CRP expression and the molecular mechanisms in rat VSMCs. The results showed that aldosterone induced CRP expression in VSMCs in vitro and in vivo. Mineralocorticoid receptor (MR) antagonist spironolactone abolished aldosterone-induced CRP expression. In addition, aldosterone stimulated generation of reactive oxygen species (ROS) and activated ERK1/2 phosphorylation, whereas spironolactone inhibited aldosterone-stimulated ROS generation and ERK1/2 phosphorylation. Antioxidant NAC decreased aldosterone-induced CRP expression and ERK1/2 phosphorylation. The further study confirmed that ERK1/2 inhibitor PD98059 and NF-κB inhibitor pyrrolidine dithiocarbamate both depressed aldosterone-induced CRP expression. These demonstrate that aldosterone is able to induce CRP expression via MR-ROS-ERK1/2-NF-κB signal pathway in VSMCs, which provides a new evidence for the proinflammatory and proatherosclerotic effects of aldosterone.

Inflammatory lipid sphingosine-1-phosphate upregulates C-reactive protein via C/EBPβ and potentiates breast cancer progression

A crucial role of the inflammatory lipid sphingosine-1-phosphate (S1P) in breast cancer aggressiveness has been reported. Recent clinical studies have suggested that C-reactive protein (CRP) has a role in breast cancer development. However, limited information is available on the molecular basis for the expression of CRP and its functional significance in breast cell invasion. The present study aimed to elucidate the molecular link between S1P and CRP during the invasive process of breast epithelial cells. This is the first report showing that transcription of CRP was markedly activated by S1P in breast cells. Our data suggest that not only S1P treatment but also the endogenously produced S1P may upregulate CRP in breast carcinoma cells. Transcription factors CCAAT/enhancer-binding protein beta and c-fos were required for S1P-induced CRP expression. Coupling of S1P3 to heterotrimeric Gαq triggered the expression of CRP, utilizing signaling pathways involving reactive oxygen species (ROS), Ca(2+) and extracellular signal-related kinases (ERKs). S1P-induced CRP expression was crucial for the transcriptional activation of matrix metalloproteinase-9 through ERKs, ROS and c-fos, leading to breast cell invasion. Using a xenograft mice tumor model, we demonstrated that S1P induced CRP expression both in vitro and in vivo. Taken together, our findings have revealed a molecular basis for S1P-induced transcriptional activation of CRP and its functional significance in the acquisition of the invasive phenotype of human breast epithelial cells under inflammatory conditions. Our findings may provide useful information on the identification of useful therapeutic targets for inflammatory breast cancer.

Angiotensin II Induces C-Reactive Protein Expression via AT1-ROS-MAPK-NF-κB Signal Pathway in Hepatocytes

Background: C-reactive protein (CRP) participates in development of inflammatory diseases. Hepatocytes are a major contributor of circulating CRP. Although angiotensin II (Ang II) is known to evoke inflammatory response, it remains unknown whether Ang II induces CRP expression in hepatocytes. The present study observed effect of Ang II on CRP expression and the related signal pathway in hepatocytes. Methods: mRNA and protein expressions in human hepatocytes were determined with RT-PCR and Western blot respectively. Reactive oxygen species (ROS) was measured using a fluorescence probe. CRP in liver and serum of rats was determined by immunohistochemistry and ELISA respectively. Results: Ang II induced mRNA and protein expression of CRP in hepatocytes and increased CRP production in liver and CRP level in serum. Losartan reduced Ang II- induced CRP expression in hepatocytes. Losartan and thenoyltrifluoroacetone decreased Ang II-stimulated ROS production. N-acetylcysteine antagonized Ang II-induced CRP expression. Losartan and N-acetylcysteine inhibited Ang II-activated ERK1/2. Unlike ERK1/2, only losartan inhibited Ang II-activated JNK. Furthermore, pyrrolidine dithiocarbamate abolished Ang II-induced CRP expression. Conclusion: Ang II has ability to induce CRP expression in hepatocytes in vitro and in vivo through AT1 receptor followed by ROS, MAPK and NF-κB signal pathway.

Nicotine induces the expression of C-reactive protein via MAPK-dependent signal pathway in U937 macrophages.

Atherosclerosis is an inflammatory disease in the vessel wall. Nicotine, a major component of cigarette smoke, is an independent risk factor for cardiovascular diseases including atherosclerosis. As an inflammatory molecule, C- reactive protein (CRP) participates in atherogenesis. Although it has been confirmed that CRP level in smoking patient is significantly higher than non-smokers and cigarette withdrawal, it is unknown whether nicotine induces CRP expression in macrophages. The present study was to observe effect of nicotine on CRP production and the related signal pathway in U937 macrophages. The results showed that nicotine significantly increased mRNA and protein expression of CRP in U937 macrophages in time- and concentration-dependent ways. Nicotinic acetylcholine receptor (nAChR) blocker hexamethonium, MEK1/2 inhibitor PD98059, p38 MAPK inhibitor SB203580 and NF-κB inhibitor PDTC almost completely abolished nicotineinduced CRP expression in mRNA and protein levels in U937 macrophages. The further study indicated that hexamethonium, PD98059, and SB203580 significantly inhibited ERK1/2 and p38 MAPK phosphorylation. These demonstrate that nicotine has ability to induce CRP expression in macrophages through nAChR-ERK1/2/p38 MAPK-NF-κB signal pathway, which contributes to better understanding of the pro-inflammatory and pro-atherosclerotic effects of nicotine in cigarette smokers.

Oct-1 acts as a transcriptional repressor on the C-reactive protein promoter

C-reactive protein (CRP), a plasma protein of the innate immune system, is produced by hepatocytes. A critical regulatory region (−42 to −57) on the CRP promoter contains binding site for the IL-6-activated transcription factor C/EBPβ. The IL-1β-activated transcription factor NF-κB binds to a κB site located nearby (−63 to −74). The κB site overlaps an octamer motif (−59 to −66) which is the binding site for the constitutively active transcription factor Oct-1. Oct-1 is known to function both as a transcriptional repressor and as an activator depending upon the promoter context. Also, Oct-1 can regulate gene expression either by binding directly to the promoter or by interacting with other transcription factors bound to the promoter. The aim of this study was to investigate the functions of Oct-1 in regulating CRP expression. In luciferase transactivation assays, overexpressed Oct-1 inhibited (IL-6+IL-1β)-induced CRP expression in Hep3B cells. Deletion of the Oct-1 site from the promoter drastically reduced the cytokine response because the κB site was altered as a consequence of deleting the Oct-1 site. Surprisingly, overexpressed Oct-1 inhibited the residual (IL-6+IL-1β)-induced CRP expression through the promoter lacking the Oct-1 site. Similarly, deletion of the Oct-1 site reduced the induction of CRP expression in response to overexpressed C/EBPβ, and overexpressed Oct-1 inhibited C/EBPβ-induced CRP expression through the promoter lacking the Oct-1 site. We conclude that Oct-1 acts as a transcriptional repressor of CRP expression and it does so by occupying its cognate site on the promoter and also via other transcription factors by an as yet undefined mechanism.

Carbon monoxide, a reaction product of heme oxygenase-1, suppresses the expression of C-reactive protein by endoplasmic reticulum stress through modulation of the unfolded protein response

The expression of C-reactive protein (CRP) rises rapidly in response to inflammation. The endoplasmic reticulum (ER) stress has been reported to cause CRP expression. Carbon monoxide (CO), a reaction product of heme oxygenase, exerts anti-inflammatory effects. In this study, we aimed to examine the role of CO in modulating ER stress-induced CRP expression. In HepG2 cells, ER stress triggered by tunicamycin, thapsigargin and homocysteine markedly induced CRP expression and the activation of protein kinase R-like endoplasmic reticulum kinase (PERK), inositol-requiring transmembrane kinase/endonuclease 1α (IRE1α), activating transcription factor 6 (ATF6), and hepatocyte-specific cyclic AMP response element binding protein H (CREBH). A CO-releasing molecule (CORM) inhibited ER stress-induced CRP expression. While CORM attenuated ER stress-induced activation of IRE1α, ATF6 and CREBH, it augmented PERK activation, which was associated with its inhibition of CRP expression. CORM also inhibited CRP expression in response to the pro-inflammatory cytokine IL-6 that was found to induce ER stress response in HepG2 cells. Moreover, in mice treated with the ER stress inducer tunicamycin, CORM administration reduced serum levels of CRP and the expression of CRP mRNA in the liver. Collectively, our findings suggest that CO may attenuate ER stress-induced CRP expression through modulation of the unfolded protein response.

Angiotensin II Induces the Expression of C-reactive Protein via MAPK-Dependent Signal Pathway in U937 Macrophages

Atherosclerosis is an inflammatory disease in the vessel wall. As an inflammatory molecule, C-reactive protein (CRP) participates in all stages of atherosclerotic process. Although angiotensin II (Ang II) can stimulate the vascular cells to produce CRP, it is unknown whether Ang II induces CRP expression in macrophages. The present study was to observe effect of Ang II on CRP production and the related signal pathway in U937 macrophages so as to provide more evidence for the proinflammatory action of Ang II. The results showed that Ang II significantly increased mRNA and protein expression of CRP in U937 macrophages in time- and concentration-dependent manners. AT₁ receptor blocker losartan blocked Ang II -induced CRP expression in mRNA and protein levels in U937 macrophages. Losartan and complex II inhibitor TIFA decreased Ang II -stimulated reactive oxygen species (ROS) generation, and antioxidant NAC completely abolished Ang II -induced CRP expression in U937 macrophages. The further study indicated that losartan, NAC, MEK1/2 inhibitor PD98059, p38MAPK inhibitor SB203580 obviously inhibited ERK1/2 and p38MAPK phosphorylation, and PD98059, SB203580 and NF-ĸB inhibitor PDTC reduced Ang II -induced mRNA and protein expression of CRP in U937 macrophages. These demonstrate that Ang II is capable of inducing CRP generation in macrophages via AT₁-ROS-ERK1/2/p38MAPK-NF-ĸB signal pathway, which contributes to better understanding of the proinflammatory and proatherosclerotic actions of Ang II.

Angiotensin II induces C-reactive protein expression through ERK1/2 and JNK signaling in human aortic endothelial cells

BackgroundAtherosclerosis is an inflammatory disease in the vessel. As an inflammatory cytokine, C-reactive protein (CRP) participates in atherogenesis. Although angiotensin II (AngII) is known to evoke inflammatory response in vascular endothelial cells (VECs), there is no direct evidence to demonstrate the proinflammatory effect of AngII on VECs through CRP. The present study focused on effect of AngII on CRP expression and the signal pathway in human aortic endothelial cells (HAECs). Methods and resultsmRNA and protein expression was identified by RT-PCR and Western blot, respectively. Reactive oxygen species (ROS) were observed by a fluorescence microscope. The results showed that AngII significantly increased mRNA and protein expression of CRP in HAECs in time- and concentration-dependent ways. Anti-IL-1β and anti-IL-6 neutralizing antibodies did not affect AngII-induced CRP expression. Losartan reduced AngII-induced CRP expression in mRNA and protein levels in HAECs. Losartan and TIFA decreased AngII-stimulated ROS generation, and antioxidant NAC completely abolished AngII-induced CRP expression in HAECs. The further study indicated that losartan, NAC, PD98059, SP600125 significantly inhibited ERK1/2 and JNK phosphorylation, and PD98059, SP600125, PDTC completely antagonized AngII-induced CRP expression in HAECs. ConclusionsThe present study demonstrates that AngII has ability to induce CRP expression in HAECs through AT1-ROS-ERK1/2 and JNK-NF-κB signal pathway, which strengthens understanding of the proinflammatory and proathroscerotic actions of AngII.

Mechanical Strain Induces Expression of C-Reactive Protein in Human Blood Vessels

C-reactive protein (CRP) is a powerful independent risk factor for cardiovascular diseases. Elevated mechanical strain on vessels induces the local expression of proinflammatory cytokines. We hypothesized that mechanical strain on vessels may induce local CRP expression. Human saphenous vein and internal mammary artery (IMA) rings were stretched in vitro with a mechanical strength of 1, 3, or 5 g. Reverse transcription-polymerase chain reaction and enzyme-linked immunosorbent assay results showed that mechanical stretching significantly induced CRP mRNA and protein expression in the saphenous vein and IMA rings in a strength-dependent manner reaching a maximum at a mechanical strength of 3 g, but CRP expression returned at strengths of >5 g. In vessels, mechanical strain-induced CRP expression was blocked by two stretch-activated ion channel (SAC) blockers: GdCl(3) and streptomycin. Mechanical strain also increased activation of nuclear factor kappaB (NF-kappaB), which was detected with a nonradioactive NF-kappaB p50/p65 EZ-TFA transcription factor assay. Mechanical strain-induced NF-kappaB activation was blocked by SAC blockers and the NF-kappaB inhibitor (SN50, H-Ala-Ala-Val-Ala-Leu-Leu-Pro-Ala-Val-Leu-Leu-Ala-Leu-Leu-Ala-Pro-Val-Gln-Arg-Lys-Arg-Gln-Lys-Leu-Met-Pro-OH). SN50 also blocked mechanical strain-induced CRP expression in vessels. In conclusion, mechanical strain induces CRP expression in IMAs and saphenous veins by activating the SAC-induced NF-kappaB pathway.

Interleukin-17 Stimulates C-reactive Protein Expression in Hepatocytes and Smooth Muscle Cells via p38 MAPK and ERK1/2-dependent NF-κB and C/EBPβ Activation

Elevated systemic levels of the acute phase C-reactive protein (CRP) are predictors of future cardiovascular events. There is evidence that CRP may also play a direct role in atherogenesis. Here we determined whether the proinflammatory interleukin (IL)-17 stimulates CRP expression in hepatocytes (Hep3B cell line and primary hepatocytes) and coronary artery smooth muscle cells (CASMC). Our results demonstrate that IL-17 potently induces CRP expression in Hep3B cells independent of IL-1beta and IL-6. IL-17 induced CRP promoter-driven reporter gene activity that could be attenuated by dominant negative IkappaBalpha or C/EBPbeta knockdown and stimulated both NF-kappaB and C/EBP DNA binding and reporter gene activities. Targeting NF-kappaB and C/EBPbeta activation by pharmacological inhibitors, small interfering RNA interference and adenoviral transduction of dominant negative expression vectors blocked IL-17-mediated CRP induction. Overexpression of wild type p50, p65, and C/EBPbeta stimulated CRP transcription. IL-17 stimulated p38 MAPK and ERK1/2 activation, and SB203580 and PD98059 blunted IL-17-mediated NF-kappaB and C/EBP activation and CRP transcription. These results, confirmed in primary human hepatocytes and CASMC, demonstrate for the first time that IL-17 is a potent inducer of CRP expression via p38 MAPK and ERK1/2-dependent NF-kappaB and C/EBPbeta activation and suggest that IL-17 may mediate chronic inflammation, atherosclerosis, and thrombosis.

Leptin Induces C-Reactive Protein Expression in Vascular Endothelial Cells

There is increasing evidence of an association between leptin and increased cardiovascular risk. Higher leptin levels are associated with increased levels of C-reactive protein (CRP), which itself elicits proatherogenic effects in the vascular endothelium. We tested the hypothesis that leptin induces CRP expression in human coronary artery endothelial cells (HCAECs). We confirmed the presence of both long and short isoforms of the leptin receptor in cultured HCAECs. Leptin but not IFNalphaA/D nor tumor necrosis factor (TNF) alpha, induced expression of CRP. A dose dependent increase of CRP mRNA and protein was observed with increasing concentration of leptin (0 to 400 ng/mL). This increased CRP expression was attenuated in the presence of anti-leptin receptor antibodies and also by inhibition of ERK1/2 by PD98059 (20 to 40 micromol/L). Time (0 to 60 minutes) and leptin concentration (0 to 200 ng/mL)-dependence of ERK1/2 phosphorylation were evident in response to leptin treatment. Leptin also elicited ROS generation. Inhibition of ROS by catalase (200 microg/mL) prevented ERK1/2 phosphorylation and CRP mRNA transcription. Leptin induces CRP expression in HCAECs via activation of the leptin receptor, increased ROS production, and phosphorylation of ERK1/2. These studies suggest a mechanism for the proatherogenic effects of leptin.

Effect of wine phenolics on cytokine-induced C-reactive protein expression.

Elevation of C-reactive protein (CRP) levels in blood was recognized as one of the cardiac disease risk factors. Consumption of wine is shown to reduce the risk from heart disease and improve longevity. In the present study, we evaluated the effect of various wine polyphenolic compounds and several active synthetic derivatives of resveratrol on the inflammatory cytokines (IL-1beta + IL-6)-induced CRP expression in Hep3B cells. Among the wine phenolics tested, quercetin and resveratrol, in a dose-dependent manner, suppressed cytokine-induced CRP expression. Two of the synthetic derivatives of resveratrol, R3 and 7b, elicited a fiftyfold higher suppressive effect compared with resveratrol. The inhibitory effects of resveratrol and its derivatives on CRP expression were at the level of mRNA production. Investigation of signaling pathways showed that the cytokines induced the phosphorylation of p38 and p44/42 MAP kinases. Inhibitors of p38 and p44/42 mitogen-activated protein kinase (MAPK) activation inhibited CRP expression, implicating the involvement of both pathways in cytokine-induced CRP expression. These data revealed a previously unrecognized role of the p44/42 MAPK signaling pathway in CRP expression. Wine polyphenolics or the synthetic compounds of resveratrol did not affect cytokine-activated phosphorylation of these MAPKs. Wine phenolics inhibit CRP expression; however, to do so, they do not utilize the MAPK pathways.

CRP—Marker or Maker of Cardiovascular Disease?

C-reactive protein (CRP) has emerged as an interesting novel and potentially clinically useful marker for increased cardiovascular risk.1,2 This is an attractive concept because atherosclerosis is a disease characterized by chronic arterial inflammation3,4 and suggests the possibility that subclinical states of atherosclerosis can be identified by an increase in circulating markers of inflammation before acute events occur. Based on data obtained primarily from in vitro studies it has also been proposed that CRP in itself is actively contributing to disease progression and that it should be considered as true risk factor and consequently as a target for intervention. However, in the present issue of Arteriosclerosis, Thrombosis, and Vascular Biology , two independent reports demonstrate that transgenic overexpression of CRP does not affect the development of atherosclerosis in mice, suggesting that this is not the case. See pages 1635 and 1641 The association between moderately elevated CRP levels and an increased risk for development of cardiovascular disease is well established. Although the increase in risk may have been overestimated in initial studies, recent meta-analysis comprising >7000 patients with coronary events shows that subjects with CRP in the upper tertile have a 50% increased risk for development of acute cardiovascular events.2 There are several possible explanations for this association (Figure). (1) The inflammatory process in arterial tissue affected by atherosclerosis results in release of cytokines into the circulation that subsequently activates expression of CRP in the liver. Plasma CRP levels would then reflect the severity of atherosclerosis and, as a consequence, the risk for development of clinical events. If CRP in addition …

Expression of C-Reactive Protein in Human Lung Epithelial Cells and Upregulation by Cytokines and Carbon Particles

C-reactive protein (CRP) is the prototypic human acute-phase protein and is found at increased levels in the blood during episodes of inflammation. CRP was generally thought to be produced only by hepatocytes; however, several studies have shown extrahepatic synthesis of CRP. A previous study showed that PM10 and ultrafine carbon black (ufCB) were able to induce CRP expression in A549 cells. This study aims to examine the factors that lead to the production of CRP in A549 cells. A549 human lung epithelial cells were treated with cytokines (interleukin 6, tumor necrosis factor α, interferon γ, or interleukin 1β) or carbon particles (CB and ufCB) for 18 h. It was found that CRP could be expressed within the cells and that CRP was secreted from the cells particularly with tumor necrosis factor α, CB and ufCB treatments. It was also found that this expression of CRP with CB and ufCB treatments was dependent on nuclear factor kappa B (NFκB). The expression of CRP in A549 cells may indicate an important role for CRP expression and secretion from lung epithelial cells in response to inflammatory stimuli.

Fibrates down-regulate IL-1–stimulated C-reactive protein gene expression in hepatocytes by reducing nuclear p50-NFκB–C/EBP-β complex formation

C-reactive protein (CRP) is a major acute-phase protein in humans. Elevated plasma CRP levels are a risk factor for cardiovascular disease. CRP is predominantly expressed in hepatocytes and is induced by interleukin-1 (IL-1) and IL-6 under inflammatory situations, such as the acute phase. Fibrates are hypolipidemic drugs that act through the nuclear receptor peroxisome proliferator-activated receptor-alpha (PPAR-alpha). Fibrates have been shown to reduce elevated CRP levels in humans, but the molecular mechanism is unknown. In this study, we demonstrate that different PPAR-alpha activators suppress IL-1-induced, but not IL-6-induced, expression of CRP in primary human hepatocytes and HuH7 hepatoma cells. Induction of CRP expression by IL-1 occurs at the transcriptional level. Site-directed mutagenesis experiments show that IL-1 induces CRP expression through 2 overlapping response elements, the binding sites for CCAAT-box/enhancer-binding protein-beta (C/EBP-beta) and p50-nuclear factor-kappaB (p50-NFkappaB). Cotransfection of C/EBP-beta and p50-NFkappaB enhances CRP promoter activity, and coimmunoprecipitation experiments indicate that the increase in CRP promoter activity by IL-1 is related to the generation and nuclear accumulation of C/EBP-beta-p50-NFkappaB complexes. Interestingly, PPAR-alpha activators reduce the formation of nuclear C/EBP-beta-p50-NFkappaB complexes, and thereby CRP promoter activity, by 2 mechanisms. First, PPAR-alpha increases IkappaB-alpha expression and thus prevents p50-NFkappaB translocation to the nucleus. Second, fibrates decrease hepatic C/EBP-beta and p50-NFkappaB protein levels in mice in a PPAR-alpha-dependent way. Our findings identify C/EBP-beta and p50-NFkappaB as novel targets for PPAR-alpha and provide a molecular explanation for the reduction of plasma CRP levels by fibrates.

The Rel family member P50 mediates cytokine-induced C-reactive protein expression by a novel mechanism.

Transcription of C-reactive protein (CRP) in Hep 3B cells is induced by IL-6, acting through C/EBP isoforms and STAT3. IL-1beta, which alone has no effect, greatly enhances IL-6-induced transcription by unknown mechanisms. Because IL-1beta activates the NF-kappaB system, we explored the effects of overexpressed Rel family members on CRP expression. Unexpectedly, transactivation assays in transiently transfected Hep 3B cells showed p50 overexpression to markedly induce CRP transcription, acting in a region 3' to -86. In the presence of overexpressed p50, IL-1beta induced a 3-fold increase in CRP expression, and responses to IL-6 and to IL-6 plus IL-1beta were 4-fold greater than seen in cells without p50 overexpression. In contrast, overexpressed p65 abolished CRP induction by p50 and by cytokines. EMSA studies demonstrated that recombinant p50 bound to a nonconsensus kappaB site overlapping the proximal C/EBP binding site on the CRP promoter. Mutation of a polypyrimidine tract in the p50-binding site inhibited the transactivating effect of cytokines. P50- but not p65-containing dimers were found in nuclei of Hep 3B cells 18 h after stimulation with IL-1beta, when C/EBPbeta is greatly activated, in the presence or absence of IL-6. These findings suggest that IL-1beta induces nuclear translocation of p50-containing dimers and that p50 interacts with C/EBPbeta activated by both IL-6 and IL-1beta to induce CRP expression.