Secretion of rabbit C-reactive protein by transfected human cell lines is more rapid than by cultured rabbit hepatocytes

C-reactive protein (CRP) is a major acute phase protein in humans and rabbits. Its synthesis by the liver varies over a 1000-fold range depending on the presence and severity of inflammatory stimuli. In previous studies of synthesis and secretion of rabbit CRP, we showed that secretion becomes more efficient over the course of the acute phase response as CRP synthesis rates increase (Macintyre, S.S., Kushner, I., and Samols, D. (1985) J. Biol. Chem. 260, 4169-4173). The current studies were undertaken to help distinguish between two alternative explanations for this finding: 1) that secretion efficiency may simply be a property of the rate of synthesis and intracellular concentration of CRP or 2) that secretion may be regulated by separate intracellular mechanisms. A fusion gene containing the mouse metallothionein I promoter linked to the protein coding region of the rabbit CRP gene was introduced into the human hepatoma cell line, NPLC, and the nonliver cell line, HeLa. In this system a graded response of the mouse metallothionein I promoter following exposure to increasing zinc concentrations results in increasing CRP synthesis. Unlike hepatocytes from rabbits undergoing the acute phase response, we found that rabbit CRP was secreted by these transfected cell lines with a very high degree of efficiency which was independent of the rate of CRP synthesis. This finding implies that normal rabbit hepatocytes retard the secretion of CRP and that this inhibition is diminished as the acute phase response progresses. It further indicates that the relationship between changes in synthetic rate and efficiency of secretion of rabbit CRP is not a causal one and that synthesis and secretion of CRP by rabbit hepatocytes are regulated by independent intracellular mechanisms during the acute phase response.     

The effects of adrenal hormones, endotoxin and turpentine on serum components of the plaice (Pleuronectes platessa L.)

1. Within 24 hr of injection into plaice, cortisol, deoxycorticosterone, adrenalin or endotoxin cause an increase (P less than 0.001) in circulating C-reactive protein (CRP). Turpentine and soluble dexamethasone have no effect. 2. The increase in CRP with endotoxin is not enhanced with adrenalin or deoxycorticosterone, and in conjunction with cortisol the increase is additive. 3. Changes in CRP are independent of the amounts of serum amyloid P-component or total protein. 4. Turpentine, cortisol and adrenalin cause a rapid increase in circulating glucose. 5. It is concluded that some adrenal hormones stimulate the CRP acute phase response in plaice, without an apparent provoking agent.     

Induction in rainbow trout of an acute phase (C-reactive) protein by chemicals of environmental concern

1. Rainbow trout, Salmo gairdneri, produce elevated amounts of a serum acute phase (C-reactive) protein (CRP) when administered a variety of chemicals of environmental importance. 2. Compounds administered in doses which induce the cytochrome(s) P450 catalytic enzymes in trout hepatic microsomes also induce serum CRP. 3. However, an interferon-inducing virus does not induce CRP. Interferon induction by the virus is not significantly inhibited by chemicals which induce trout cytochrome(s) P450. 4. Simultaneous administration of chemicals and virus or virus alone results in depression of P450 protein production and only minor induction of CRP. 5. Thus, as with mammals, a reciprocating relationship appears to exist between the hemeprotein monooxygenase and immune systems of this freshwater teleost, and C-reactive protein appears to fit the reciprocating scheme closer to the cytochromes P450 response.     

Regulated export of a secretory protein from the ER of the hepatocyte: a specific binding site retaining C-reactive protein within the ER is downregulated during the acute phase response.

The half-time for secretion of the plasma protein C-reactive protein (CRP) by the hepatocyte decreases markedly in association with its increased synthesis during the acute phase response to tissue injury (Macintyre, S., D. Samols, and I. Kushner. 1985. J. Biol. Chem. 260:4169-4173). In studies in which subcellular fractions were prepared from cells incubated under pulse-chase conditions, CRP was found to be preferentially retained within the ER of normal hepatocytes, but secreted relatively efficiently in cells prepared from rabbits undergoing the acute phase response. On the basis of the detergent-dependency of specific binding of radiolabeled CRP, as well as EM visualization of biotinylated CRP identified with peroxidase-conjugated streptavidin, CRP was found to bind to the lumenal surface of permeabilized rough microsomes, while no binding was detected in Golgi fractions. As judged by both kinetic and equilibrium binding studies, rough microsomes from control rabbits were found to have two classes of specific binding sites for CRP; a high affinity site (Kd = 1 nM, Bmax = 1 pmol CRP/mg microsomal protein) as well as a much lower affinity (Kd = 140 nM) site. In contrast, only the lower affinity class was detected in microsomes isolated from rabbits undergoing the acute phase response. On nitrocellulose blots probed with radiolabeled CRP a 60-kD protein, distinct from BiP, was detected in extracts of rough microsomes isolated from control rabbits, but not in Golgi fractions or rough microsomes from stimulated animals. These findings correlate with previous observations of changes in secretion kinetics of CRP and are consistent with the hypothesis that the intracellular sorting of CRP could be rerouted by downregulation of a specific ER binding site during the acute phase response.     

Effect of C-reactive protein on peritoneal macrophages. II. Human C-reactive protein activates peritoneal macrophages of guinea pigs to release superoxide anion in vitro

The effect of human C-reactive protein (CRP) on macrophage function was studied in an assay of superoxide anion (O2-) production. Peritoneal exudate macrophages (PEM) of guinea pigs exposed in vitro to various doses of CRP for 72 hr resulted in the development of O2- production dose-dependently, measured by increases in superoxide dismutase-inhibitable nitro blue tetrazolium reduction. The O2--producing activity of PEM cultured without CRP, used as a control, decreased markedly in proportion to incubation time. The O2- production by PEM exposed to CRP for 18 hr when control PEM were still high in O2- production, was decreased by larger doses of CRP, while PEM cultured without CRP for 72 hr, when O2- production by control PEM was very low, followed by incubation with CRP for another 18 hr, produced O2- CRP-dose-dependently as in the case of that observed after 72-hr incubation with CRP. These results indicate that CRP is capable of activating macrophages and acts on macrophage function as a modulator. CRP possesses migration inhibitory factor (MIF)-like activity (as reported in the preceding paper) and also macrophage-activating factor (MAF)-like activity, indicating that CRP may play a functional role at the site of inflammation and tissue damage by accumulating and activating macrophages.     

Protective effect of C-reactive protein against the lethality induced by Vibrio vulnificus lipopolysaccharide

Vibrio vulnificus infection has attracted special interest because of its high mortality. A strong clinical association exists between hepatic dysfunction and increased morbidity and mortality from V. vulnificus infection. In this study, the effect of C-reactive protein (CRP), a typical hepatogenic acute phase protein, on the lethality induced by V. vulnificus lipopolysaccharide (LPS) was investigated in galactosamine-sensitized mice. The pretreatment of CRP, in a dose of at least 2 mg/kg, 2 hr before the challenge of LPS completely protected mice against the lethality by V. vulnificus LPS. The elevation of serum tumor necrosis factor-alpha (TNF-alpha) induced by LPS administration was not affected by CRP pretreatment. However, the LPS- or TNF-alpha-induced hepatotoxicity was completely prevented by CRP. These results indicate that CRP does not prevent the synthesis, but prevents the hepatotoxic action of TNF-alpha. The possibility that impaired production of acute phase proteins in patients with pre-existing hepatic dysfunction may predispose the higher risk of V. vulnificus infection needs to be evaluated further.     

Anaesthesia and the acute phase protein response in children undergoing circumcision

Concentrations of acute phase proteins (CRP: C-reactive protein, albumin) change during surgery. We investigated the acute phase response to circumcision and the effects of anaesthesia on this response. The children were divided into four groups; group 1 (intratracheal general anaesthesia, n=40), group 2 (general anaesthesia with mask, n=20), group 3 (ketamine, n=20), group 4 (local anaesthesia, n=35). Blood samples were obtained, 24 hours before circumcision, after premedication, and 24 hours after circumcision. CRP and albumin before circumcision were comparable for all groups. There was no increase in CRP, and albumin remained steady throughout the study. No difference was observed among the groups, and related to anaesthesia. No responsiveness may be explained with the size of injured tissue or anatomical and histological type of preputium.     

Blood clearance of Streptococcus pneumoniae by C-reactive protein

C-reactive protein (CRP) has long been known to be an acute phase protein associated with infection and various forms of tissue damage. Recent studies have shown that human CRP can be used to passively protect mice from lethal infection with Streptococci pneumoniae. In this study we have undertaken a detailed examination of the ability of human CRP and rabbit CRP (CxRP) to mediate the blood clearance of pneumococci in mice. We have shown that the optimal activity of these acute-phase proteins requires a functioning complement system, and it can take place even in the xid mouse, which has virtually no naturally occurring anti-pneumococcal antibody in its serum. These studies provide additional evidence that CRP may play a protective role in pneumococcal infections, and it may help postpone the development of fatal levels of pneumococci in the blood, long enough for an effective anti-pneumococcal antibody response to be generated.     

Linking long-term toxicity of xeno-chemicals with short-term biological adaptation

Understanding the mechanisms of long-term toxicities of chemicals is challenging. The present review discusses evidence suggesting that the biological adaptation to acute xenobiotic exposure could lead in the long run to toxic side effects. Upon acute exposure, hydrophobic xenobiotics are sequestered in the adipose tissue, which consequently protects other organs. However, this could also lead to the persistence of these xenochemicals and to a chronic low level internal exposure. The intrinsic properties of the xenobiotic detection and metabolism systems could also account for long-term toxicity. Indeed, hydrophobic xenochemicals are metabolized into more hydrophilic compounds; the first step of this pathway consists in the “activation” of the parent compound into a more reactive intermediate by cytochromes P450 activity. Those intermediates can be extremely reactive with DNA and proteins and thus could lead to toxic side effects that may become significant over time. Furthermore, recent evidence suggests that xenobiotic receptors also display endogenous functions. It is likely that repeated exposure to xenobiotics disrupts those endogenous functions with possibly dire cellular consequences. Altogether, The hypothesis presented here proposes that one mechanism for long-term toxicity stems from cumulative side effects due to the repeated activity of adaptive pathways triggered by acute intoxication.     

No reduction of atherosclerosis in C-reactive protein (CRP)-deficient mice

C-reactive protein (CRP), a phylogenetically highly conserved plasma protein, is the classical acute phase reactant in humans. Upon infection, inflammation, or tissue damage, its plasma level can rise within hours >1000-fold, providing an early, nonspecific disease indicator of prime clinical importance. In recent years, another aspect of CRP expression has attracted much scientific and public attention. Apart from transient, acute phase-associated spikes in plasma concentration, highly sensitive measurements have revealed stable interindividual differences of baseline CRP values in healthy persons. Strikingly, even modest elevations in stable baseline CRP plasma levels have been found to correlate with a significantly increased risk of future cardiovascular disease. These observations have triggered intense controversies about potential atherosclerosis-promoting properties of CRP. To directly assess potential effects of CRP on atherogenesis, we have generated CRP-deficient mice via gene targeting and introduced the inactivated allele into atherosclerosis-susceptible ApoE(-/-) and LDLR(-/-) mice, two well established mouse models of atherogenesis. Morphometric analyses of atherosclerotic plaques in CRP-deficient animals revealed equivalent or increased atherosclerotic lesions compared with controls, an experimental result, which does not support a proatherogenic role of CRP. In fact, our data suggest that mouse CRP may even mediate atheroprotective effects, adding a cautionary note to the idea of targeting CRP as therapeutic intervention against progressive cardiovascular disease.     

Inhibition of antibody responses to phosphocholine by C-reactive protein

C-reactive protein (CRP) is an acute phase serum protein in man that binds to the cell wall C-polysaccharide (PnC) of Streptococcus pneumoniae via phosphocholine (PC) determinants. We have previously shown that in mice CRP increases splenic clearance of PnC-coated autologous erythrocytes and S. pneumoniae, and increases survival after pneumococcal infection. Because CRP alters clearance of particulate PnC antigens, we tested its effect on immunization with pneumococci. Pretreatment of mice with 50 to 200 micrograms CRP 30 min before immunization with serotype 3 S. pneumoniae resulted in dose-dependent inhibition of the antibody response to PC. Both serum hemagglutinin and splenic PFC against PC were decreased in CRP-treated mice tested from 1 to 10 days after injection of antigen. CRP treatment had no effect on the antibody response to the serotype 3 capsular polysaccharide, another T-independent antigen. To determine whether CRP inhibition was related to altered processing of particulate antigen, mice were immunized with horse red blood cells (HRBC) conjugated with PC or PnC and the PFC responses to PC and HRBC were determined. CRP treatment resulted in specific inhibition of the PFC response to PC in both cases without affecting the response to HRBC. These results indicate that inhibition of the antibody response by CRP is not the result of altered antigen localization and processing, and that CRP may prevent immunization by masking determinants on bacterial or other surfaces.     

Stress-Induced Production of Biofilm in the Hyperthermophile Archaeoglobus fulgidus

Archaeoglobus fulgidus, an anaerobic marine hyperthermophile, forms a biofilm in response to environmental stresses. The biofilm is a heterogeneous, morphologically variable structure containing protein, polysaccharide, and metals. Production of the biofilm can be induced by nonphysiological extremes of pH and temperature, by high concentrations of metals, and by addition of antibiotics, xenobiotics, or oxygen. Cells within the biofilm show an increased tolerance to otherwise toxic environmental conditions. Metals sequestered within the biofilm stimulate growth of A. fulgidus cells in metal-depleted medium. These data suggest that cells may produce biofilm as a mechanism for concentrating cells and attaching to surfaces, as a protective barrier, and as a reserve nutrient. Because similar biofilms are formed by Archaeoglobus profundus, Methanococcus jannaschii, and Methanobacterium thermoautotrophicum, biofilm formation might be a common stress response mechanism among the archaea.     

C-reactive protein mediates protection from lipopolysaccharide through interactions with Fc gamma R

C-reactive protein (CRP) is a component of the acute phase response to infection, inflammation, and trauma. A major activity of acute phase proteins is to limit the inflammatory response. It has been demonstrated that CRP protects mice from lethal doses of LPS. In the mouse, CRP binds to the regulatory receptor, FcgammaRIIb, and to the gamma-chain-associated receptor, FcgammaRI. The goal ofthis study was to determine whether FcgammaRs are necessary for the protective effect of CRP. The ability of CRP to protect mice from a lethal dose of LPS was confirmed using injections of 500 and 250 micro g of CRP at 0 and 12 h. CRP treatment of FcgammaRIIb-deficient mice increased mortality after LPS challenge and increased serum levels of TNF and IL-12 in response to LPS. CRP did not protect FcR gamma-chain-deficient mice from LPS-induced mortality. Treatment of normal mice, but not gamma-chain-deficient mice, with CRP increased IL-10 levels following LPS injection. In vitro, in the presence of LPS, CRP enhanced IL-10 synthesis and inhibited IL-12 synthesis by bone marrow macrophages from normal, but not gamma-chain-deficient mice. The protective effect of CRP appears to be mediated by binding to FcgammaRI and FcgammaRII resulting in enhanced secretion of the anti-inflammatory cytokine IL-10 and the down-regulation of IL-12. These results suggest that CRP can alter the cytokine profile of mouse macrophages by acting through FcgammaR leading to a down-regulation of the inflammatory response.     

Acute-phase response of mRNAs for serum amyloid P component, C-reactive protein and prealbumin (transthyretin) in mouse liver

Acute-phase response of mRNAs for serum amyloid P component (SAP), C-reactive protein (CRP) and prealbumin was examined in C57BL/6 mouse liver by hybridization to specific cDNA probes. Although the level of SAP mRNAs in the unstimulated mouse was about one-tenth of that of CRP mRNAs, it increased up to 60-fold during the first 20 hr, and returned gradually to the original level at 69 hr after the administration of Escherichia coli lipopolysaccharide. On the other hand, the level of CRP mRNA rapidly increased up to 6-fold during the first 4 hr, and reverted to the original level as early as at 20 hr. In contrast, the level of mRNA for prealbumin decreased to about 0.5-fold during the first 20 hr, recovered and increased up to 1.6-fold of the original level during 32 to 69 hr.     

C反应蛋白与动脉粥样硬化

C反应蛋白（C-reactiveprotein,CRP）是人类非特异性急性期蛋白,是判断组织损伤和炎症反应的敏感指标之一。CRP的表达水平与动脉粥样硬化（atherosclerosis,AS）和心血管疾病的发生具有冠著的相关性。但是关于CRP是否是AS的独立危险因素并参与AS的发病机制,目前尚存在很大争议。新近的研究发现,CRP与某些特定的配体结合后,五聚体结构CRP可分离形成单体结构CRP。这一发现为研究CRP蛋白与AS的相互关系提供了新的线索,对CRP及其单体结构的深入研究,将有可能帮助人们找到治疗心血管疾病的有效方法。就炎性反应标志物CRP及其单体（monomeric CRP,mCRP）与动脉粥样硬化的相关研究进展进行综述,以探讨分析CRP在AS中的作用。     

C-reactive protein induced expression of adhesion molecules in cultured cerebral microvascular endothelial cells

Ischemic stroke can trigger an acute phase response resulting in a rise of plasma concentration of C-reactive protein (CRP). Clinical data about the relationship between CRP and prognosis suggest that CRP might be involved in the pathogenesis of cerebral ischemia. In the present work, a significant increase of circulating level of CRP was observed in an vivo rat brain ischemia model of middle cerebral artery occlusion. To determine the possible effects of CRP on brain microvessel endothelium, we performed a dose-dependent experiment in mouse brain microvascular endothelial cells (bEnd.3 cells) with emphasis on its relation to cell adhesions molecules. Incubation with CRP (1-75 mg/L) for 24 h significantly increased Lactate dehydrogenase (LDH) leakage from bEnd.3 cells (P<0.01) in a dose-dependent manner, and induced significant up-regulations of intercellular adhesion molecule-1 (ICAM-1) and vascular cell adhesion molecule-1 (VCAM-1) expressions analyzed by Western blotting (P<0.01). In contrast to earlier report, CRP also induced significant increase in ICAM-1 expression in the absence of serum (P<0.01). In conclusion, the present results suggest that CRP may be involved directly in the development of inflammation in response to cerebral ischemia.     

Appearance of C-reactive protein (CRP) in serum and liver cytosol of cadmium-treated rats

The possibility of stimulation of C-reactive protein (CRP) due to inflammation and necrosis caused by cadmium was investigated. Cadmium injection (less than 3 mg/kg body weight) in white rat was found to be associated with the appearance of CRP in liver cytosol after 8 hr and in serum after 18 hr of injection. Although, no definite dose-response relationship was found, yet CRP level was elevated drastically, varying from 1-4 mg/g wet weight liver and 0.3-0.7 mg/ml serum. CRP-positive serum from Cd-treated rats precipitated with normal rat serum on agarose-covered slides in the presence of 1 mM CaCl2. Evidences for raised level of CRP indicates acute tissue damage in the animal.