IL-1 and IL-6 mediate increased production and synthesis by hepatocytes of acute-phase reactant mouse serum amyloid P-component (SAP)

Homologous lactoferrin triggers mobilization of the myelocytic lineage of bone marrow in experimental mice

The effects of lactoferrin (LF), an iron binding protein, on myelopoiesis have been studied extensively in vitro and in vivo in human and murine models over the past three decades. Due to the lack of high-quality homologous LFs, however, the conclusions are still unequivocal. Recently, both human and murine LFs have become available as recombinant products expressed in Chinese hamster ovary (CHO) cell lines showing mammalian type of glycosylation, thus apparently species compatible. In this study, we present the effects of homologous recombinant mouse LF (rmLF) on myelopoiesis in CBA mice. The myelocytic lineage has been assessed by their appearance in circulating blood and bone marrow, and induction of relevant mediators of inflammation. Intravenous injection of rmLF (100 μg/mouse) resulted in a significantly increased number of myelocytic cells in the circulating blood after 24 h. Mouse serum transferrin, used as a control protein, showed no stimulatory effect. The increase in output of neutrophil precursors, neutrophils, and eosinophils was correlated with a twofold increase of leukocyte concentrations. The analysis of the bone marrow sections confirmed increased myelopoiesis. The alterations in the bone marrow cell composition were statistically significant regarding mature neutrophils (10.8% vs. 27.7%), metamyelocytes (11.4% vs. 16.0%), and myelocytes (2.4% vs. 4.0%). The mobilization of the myelocytic cells in the bone marrow and the increased output of these cells into circulation were accompanied by elevated serum concentrations of interleukin-6 at 6 h and haptoglobin at 24 h following administration of rmLF. In conclusion, the homologous LF elicits significant and transient myelopoiesis in experimental mice.

Synergistic effects of hypertension and aging on cognitive function and hippocampal expression of genes involved in β-amyloid generation and Alzheimer's disease

Strong epidemiological and experimental evidence indicate that hypertension in the elderly predisposes to the development of Alzheimer's disease (AD), but the underlying mechanisms remain elusive. The present study was designed to characterize the additive/synergistic effects of hypertension and aging on the expression of genes involved in β-amyloid generation and AD in the hippocampus, an area of brain contributing to higher cognitive function, which is significantly affected by AD both in humans and in mouse models of the disease. To achieve that goal, we induced hypertension in young (3 mo) and aged (24 mo) C57BL/6 mice by chronic (4 wk) infusion of angiotensin II and assessed changes in hippocampal mRNA expression of genes involved in amyloid precursor protein (APP)-dependent signaling, APP cleavage, Aβ processing and Aβ-degradation, synaptic function, dysregulation of microtubule-associated τ protein, and apolipoprotein-E signaling. Aged hypertensive mice exhibited spatial memory impairments in the Y-maze and impaired performance in the novel object recognition assay. Surprisingly, hypertension in aging did not increase the expression of APP, β- and γ-secretases, or genes involved in tauopathy. These genes are all involved in the early onset form of AD. Yet, hypertension in aging was associated with changes in hippocampal expression of APP binding proteins, e.g., [Mint3/amyloid β A4 precursor protein-binding family A member 3 (APBA3), Fe65/amyloid β A4 precursor protein-binding family B member 1 (APBB1)], amyloid β (A4) precursor-like protein 1 (APLP1), muscarinic M1 receptor, and serum amyloid P component, all of which may have a role in the pathogenesis of late-onset AD. The hippocampal gene expression signature observed in aged hypertensive mice in the present study provides important clues for subsequent studies to elucidate the mechanisms by which hypertension may contribute to the pathogenesis and clinical manifestation of AD.

Characterization of Bglu3, a mouse fasting glucose locus, and identification of Apcs as an underlying candidate gene

Bglu3 is a quantitative trait locus for fasting glucose on distal chromosome 1 identified in an intercross between C57BL/6 (B6) and C3H/HeJ (C3H) apolipoprotein E-deficient (apoE(-/-)) mice. This locus was subsequently replicated in two separate mouse intercrosses. The objective of this study was to characterize Bglu3 through construction and analysis of a congenic strain and identify underlying candidate genes. Congenic mice were constructed by introgressing a genomic region harboring Bglu3 from C3H.apoE(-/-) into B6.apoE(-/-) mice. Mice were started with a Western diet at 6 wk of age and maintained on the diet for 12 wk. Gene expression in the liver was analyzed by microarrays. Congenic mice had significantly higher fasting glucose levels and developed more significant glucose intolerance compared with B6.apoE(-/-) mice on the Western diet. Microarray analysis revealed 336 genes to be differentially expressed in the liver of congenic mice. Further pathway analysis suggested a role for acute phase response signaling in regulating glucose intolerance. Apcs, encoding an acute phase response protein serum amyloid P (SAP), is located underneath the linkage peak of Bglu3. Multiple single nucleotide polymorphisms between B6 and C3H mice were detected within and surrounding Apcs. Apcs expression in the liver was significantly higher in congenic and C3H mice compared with B6 mice. The Western diet consumption led to a gradual rise in plasma SAP levels, which was accompanied by rising fasting glucose in both B6 and C3H apoE(-/-) mice. Expression of C3H Apcs in B6.apoE(-/-) mice aggravated glucose intolerance. Bglu3 is confirmed to be a locus affecting diabetes susceptibility, and Apcs is a probable candidate gene.

Pentraxins, anti-pentraxin antibodies, and atherosclerosis

Atherosclerosis is a disease of the vascular wall, which predominantly affects large and medium-sized arteries. It represents a leading cause of morbidity and mortality in the Western world. In the last few decades, it has been clearly shown that immune system plays a relevant role in atherogenesis. The effectors of both innate and adaptive immunity, including immune cells, cell or soluble receptors, cytokines, chemokines, complement components or coagulation systems, and autoantibodies are able to modulate atherosclerosis. Among proteins belonging to innate immunity, the highly conserved pentraxin family, which encompass C-reactive protein (CRP), serum amyloid P (SAP), and the long pentraxin 3 (PTX3) seems to be directly involved in the induction and progression of atherosclerosis. By immunohistochemical staining, pentraxins were found within the atherosclerotic plaques where they could play a key role interacting with atherogenic-modified lipoproteins, favoring the formation of foam cells, and exerting a proinflammatory action. Pentraxin serum levels have been shown to be associated with clinical and subclinical atherosclerosis in general population. Antibodies against pentraxins have been demonstrated in patients with autoimmune diseases, but their role in atherogenesis is still controversial.

Autoimmunity to protective molecules: is it the perpetuum mobile (vicious cycle) of autoimmune rheumatic diseases?

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload and might be involved in the initiation of an autoimmune response. The C1q protein and mannose-binding lectin are activators of the complement system. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein and serum amyloid P, and the long pentraxin family member, pentraxin 3, all of which are involved in innate immunity and in acute-phase responses. In addition to their role in innate immunity and inflammation, each of these proteins participates in the removal of damaged and apoptotic cells. In this article, we discuss the clinical significance of different levels of these proteins, their role in the induction of or protection against autoimmunity, and the presence of specific autoantibodies against them in various autoimmune diseases.

Protective Molecules–C-Reactive Protein (CRP), Serum Amyloid P (SAP), Pentraxin3 (PTX3), Mannose-Binding Lectin (MBL), and Apolipoprotein A1 (Apo A1), and Their Autoantibodies: Prevalence and Clinical Significance in Autoimmunity

Apoptotic defects and impaired clearance of cellular debris are considered key events in the development of autoimmunity, as they can contribute to autoantigen overload, and may initiate an autoimmune response. The pentraxins are a group of highly conserved proteins including the short pentraxins, C-reactive protein (CRP) and serum amyloid-P (SAP), and the long pentraxin-3 (PTX3), which are all involved in innate immunity and in acute-phase responses. Mannan-binding lectin (MBL) is an activator of the complement system, and Apolipoprotein A-1 (Apo A-1) is pivotal in the cholesterol homeostasis and has anti-inflammatory properties. In addition to their role in innate immunity and inflammation, each of these five proteins participates in the removal of damaged and apoptotic cells. In this review, we discuss the clinical significance of different levels of these proteins, their role in the induction or protection from autoimmunity, and the presence of specific autoantibodies against them in the different autoimmune diseases.

Serum amyloid P-component in murine tuberculosis: induction kinetics and intramacrophage Mycobacterium tuberculosis growth inhibition in vitro

Serum amyloid P-component (SAP), a pentraxin, is known to play an important role in innate immunity to microbial infections; however, nothing is known about it during tuberculosis (TB). Mice intratracheally infected with Mycobacterium tuberculosis Erdman, showed peak SAP levels (442+/-58.2 microg/ml) on day 21, which declined to background levels by day 60. Their serum interleukin-6 levels paralleled SAP levels, whereas, their serum transforming growth factor-beta levels were paradoxical. During the acute phase of infection, the SAP levels positively correlated with the lung mycobacterial load. Purified mouse SAP (1-50 microg/ml) treatment of M. tuberculosis-infected alveolar macrophages (AMs), in vitro, inhibited their intracellular mycobacterial growth; maximum inhibition (1.1 log10 CFU reduction) occurred at 10 microg/ml, and a 4-day treatment appeared optimal. Treatment of AMs with both rabbit anti-mouse SAP polyclonal antibody and mannose-derived simple sugars, separately, blocked the SAP-induced inhibition of mycobacterial growth. The mycobacterial growth inhibition appeared to be nitric oxide (NO)-dependent as NO synthase inhibitors, both aminoguanidine and N(G)-monomethyl-L-arginine, annulled it. Further, SAP treatment of infected AMs induced significant (P<0.05) elaboration of nitrite (72.1+/-8.3 nM/ml), compared to the controls, and these AMs showed augmented expression of inducible NO synthase. This first study demonstrates that during murine TB the SAP levels were increased, and purified mouse SAP inhibited the intra-AM M. tuberculosis growth, in vitro, apparently via NO-dependent mechanism(s). SAP may thus contribute both to the pathogenesis and pulmonary innate immunity in TB.

Serum amyloid P-component-mediated inhibition of the uptake of Mycobacterium tuberculosis by macrophages, in vitro

The effect of purified mouse serum amyloid P-component (SAP) treatment of mouse alveolar macrophages (AMs) on their uptake of Mycobacterium tuberculosis Erdman was investigated, in vitro. SAP (0.5-50.0 micro g/ml), in a concentration-dependent manner, inhibited the M. tuberculosis uptake by the AMs; maximum inhibition (33.43%) occurred at 10.0 micro g/ml. The inhibition of uptake could be observed as early as 30 min after the incubation of AMs with 10.0 micro g/ml SAP; however, an incubation of 60 min induced maximum inhibition beyond which the response became static. The SAP-mediated decreased uptake of M. tuberculosis also resulted in their reduced intramacrophage growth as determined by colony-forming unit counts. SAP inhibited the uptake of mycobacteria in the presence of Ca(2+), and at pH = 5.6, the inhibition was abrogated. Deglycosylation of purified SAP with N-glycanase, and not with O-glycanase, blocked the SAP-mediated inhibition of the uptake. Heat-inactivated (80 degrees C; 1 h; pH 7.0) SAP did not inhibit the uptake of M. tuberculosis by AMs. These data, apparently for the first time, indicate that purified mouse SAP, in a divalent cation- and N-linked oligosaccharide glycosylation-dependent manner, inhibited the in vitro uptake of M. tuberculosis Erdman by mouse AMs, which was also associated with their reduced intracellular growth.

Effects of lipopolysaccharide-stimulated inflammation and pyrazole-mediated hepatocellular injury on mouse hepatic Cyp2a5 expression

Murine hepatic cytochrome P450 2a5 (Cyp2a5) is induced during hepatotoxicity and hepatitis, however, the specific regulatory mechanisms have not been determined. We compared the influence of acute inflammation elicited in vivo by bacterial endotoxin lipopolysaccharide (LPS) and liver injury caused by the hepatotoxin pyrazole on hepatic Cyp2a5 expression in mice. Pyrazole treatment resulted in statistically significant increases in levels of Cyp2a5 mRNA, protein and catalytic activity by 540, 273 and 711%, respectively (P<0.05). In LPS-treated livers Cyp2a5 expression was significantly reduced compared to controls at the mRNA (46%) protein (35%), and activity (23%) levels (P<0.05). Treatment of mice with recombinant murine interleukin-1 beta and interleukin-6 had no significant effect on Cyp2a5 mRNA and protein levels. Liver injury, as assessed by serum alanine aminotransferase, was greater with pyrazole than with LPS treatment (609 vs 354% of control levels respectively). ER stress, determined by hepatic glucose regulated protein 78 (grp78) levels, was greater with pyrazole (185% of controls) than with LPS (128% of controls). In pyrazole-treated liver, overexpression of immunoreactive grp78 protein revealed that ER stress was localized to pericentral hepatocytes in which Cyp2a5 was induced. Evidence of glycogen loss and membrane damage in these cells was suggestive of oxidative damage. Moreover, vitamin E attenuated Cyp2a5 induction by pyrazole in vivo. These results suggest that induction of Cyp2a5 that has been observed in mouse models of hepatitis and hepatoxicity may be related to oxidative injury to the endoplasmic reticulum of pericentral hepatocytes rather than exposure to pro-inflammatory cytokines.

The major acute-phase protein, serum amyloid P component, in mice is not involved in endogenous resistance against tumor necrosis factor alpha-induced lethal hepatitis, shock, and skin necrosis

The proinflammatory cytokine tumor necrosis factor alpha (TNF-alpha) induces lethal hepatitis when injected into D-(+)-galactosamine-sensitized mice on the one hand or systemic inflammatory response syndrome (SIRS) in normal mice on the other hand. We studied whether serum amyloid P component (SAP), the major acute-phase protein in mice, plays a protective role in both lethal models. For this purpose, we used SAP(0/0) mice generated by gene targeting. We studied the lethal response of SAP(0/0) or SAP(+/+) mice to both lethal triggers but found no differences in the sensitivity of both types of mice. We also investigated whether SAP is involved in establishing two types of endogenous protection: one using a single injection of interleukin-1beta (IL-1beta) for desensitization and clearly involving a liver protein, the other by tolerizing mice for 5 days using small doses of human TNF-alpha. Although after IL-1beta or after tolerization the SAP levels in the serum had risen fourfold in the control mice and not in the SAP(0/0) mice, the same extents of desensitization and tolerization were achieved. Finally, we observed that the induction of hemorrhagic necrosis in the skin of mice by two consecutive local injections with TNF-alpha was not altered in SAP(0/0) mice. We conclude that the presence or absence of SAP has no influence on the sensitivity of mice to TNF-alpha-induced hepatitis, SIRS, and hemorrhagic necrosis or on the endogenous protective mechanisms of desensitization or tolerization.

Complement-dependent acute-phase expression of C-reactive protein and serum amyloid P-component

The acute-phase response (APR) is regulated by TNF-alpha, IL-1beta, and IL-6 acting alone, in combination, or in concert with hormones. The anaphylotoxin C5a, generated during complement activation, induces in vitro the synthesis of these cytokines by leukocytes and of acute-phase proteins by HepG2 cells. However, there is no clear evidence for a role of C5a or any other complement activation product in regulation of the APR in vivo. In this study, using human C-reactive protein (CRP) transgenic mice deficient in C3 or C5, we investigated whether complement activation contributes to induction of the acute-phase proteins CRP and serum amyloid P-component (SAP). Absence of C3 or C5 resulted in decreased LPS-induced up-regulation of the CRP transgene and the mouse SAP gene. Also, LPS induced both the IL-1beta and IL-6 genes in normocomplementemic mice, but in complement-deficient mice it significantly induced only IL-6. Like LPS injection, activation of complement by cobra venom factor led to significant elevation of serum CRP and SAP in normocomplementemic mice but not in complement-deficient mice. Injection of recombinant human C5a into human CRP transgenic mice induced the IL-1beta gene and caused significant elevation of both serum CRP and SAP. However, in human CRP transgenic IL-6-deficient mice, recombinant human C5a did not induce the CRP nor the SAP gene. Based on these data, we conclude that during the APR, C5a generated as a consequence of complement activation acts in concert with IL-6 and/or IL-1beta to promote up-regulation of the CRP and SAP genes.

Role of STAT3 and C/EBP in cytokine-dependent expression of the mouse serum amyloid P-component (SAP) and C-reactive protein (CRP) genes

Inflammation is accompanied by a rapid increase in blood levels of acute phase proteins synthesized by hepatocytes in response to cytokines. Although C-reactive protein (CRP) levels increase dramatically in most mammals, the major acute phase protein in the mouse is the homologous pentraxin, serum amyloid P-component (SAP), whereas CRP is a minor acute phase reactant. The molecular basis for the pronounced difference in SAP and CRP gene expression in the mouse is unknown. Transfection of ++/Li mouse hepatoma cells with CAT-reporter constructs containing the 5'-flanking region of the mouse CRP gene indicated that transcription was stimulated by either IL-6, or IL-6 plus IL-1, when > or =360 bp of the 5'-proximal DNA was present. Examination of the 5'-flanking region of the mouse SAP gene revealed that the region between -433 and -397 from the transcription start site responded to IL-1 and IL-6 by binding both STAT3 and C/EBPbeta. This responsive region consisted of two adjacent C/EBPbeta consensus sites that overlap with two STAT3 consensus sites and was found to bind C/EBPbeta at an upstream site of -427 to -409 and STAT3 at a downstream site of -415 to -397. By contrast, the 360 bp promoter of the CRP gene was bound only by STAT3 at consensus sites at -93, -142, -173, and -287 from the start site; however, a single consensus site for C/EBP at -75 was not recognized. STAT3 appears to be necessary for both mouse SAP and CRP gene transcription since overexpression of an inactive, deletion mutant of STAT3 inhibited transcription of both genes. The results indicate that both STAT3 and C/EBPbeta participate in mouse SAP gene expression, whereas only STAT3 is involved in mouse CRP gene expression. The findings for mouse SAP gene expression are consistent with the reported interaction between these two transcription factors for human CRP gene transcription.

Pharmacologic treatment options in patients with thrombocytopenia

Thrombocytopenia that results from chemotherapy has become an increasingly important issue in the treatment of cancer and remains a difficult clinical problem. The identification of a safe and effective platelet growth factor could significantly improve the management of severe chemotherapy-induced thrombocytopenia. Over the past decade, a number of hematopoietic growth factors with thrombopoietic activity have been identified, including stem-cell factor (c-kit ligand), interleukin (IL)-1, IL-3, IL-6, and IL-11, as well as thrombopoietin (TPO) and its derivatives. Only a few of these agents have shown acceptable tolerability and sufficient ability to stimulate thrombopoiesis to justify testing in randomized clinical trials. Currently, IL-11 is the only cytokine licensed in the United States for treatment of chemotherapy-induced thrombocytopenia. However, its thrombopoietic activity is modest and its use is often associated with unfavorable side effects. Identification of TPO, the c-Mpl ligand, as the primary physiologic regulator of megakaryocyte and platelet development offers important promise for treatment of thrombocytopenia. Preliminary clinical studies of recombinant human TPO (rhTPO), a full-length glycosylated molecule, indicate that it is safe and biologically active in reducing severe chemotherapy-induced thrombocytopenia. In addition to rhTPO, the future may see the development of novel genetically engineered, high-affinity cytokine receptor agonists and c-Mpl ligand mimetic peptides.

Increased production of acute-phase proteins corresponds to the peak parasitaemia of primary malaria infection

Recent studies have implicated non-specific mediators associated with CD4+ T cells of the T helper 1 subset in resistance to experimental malarias. As part of continuing studies into the multifactorial role of nitric oxide and other contributors to the innate immune response in control of acute-phase malaria infection, the production of the acute-phase proteins, caeruloplasmin and serum amyloid P, following infection of naive mice with blood stages of the rodent malaria parasite Plasmodium chabaudi was investigated. Levels of both acute-phase proteins in the serum of infected mice were significantly elevated on days 7-12 post-infection compared both to other times of infection, and to background levels detected in uninfected control mice. These times corresponded to the ascending and peak primary parasitaemia, when production of interferon-gamma, tumour necrosis factor-alpha and nitric oxide is known to be raised. Although it is not apparent whether the production of caeruloplasmin and serum amyloid P has a causal effect in reducing parasitaemia or is simply a by-product of innate immunity, the detection of increased levels of circulating acute-phase proteins may act as a useful surrogate marker of high level parasitaemia, and therefore, of blood-borne malaria pathology.

Testosterone and IL-6 Requirements for Human C-Reactive Protein Gene Expression in Transgenic Mice

In vitro, IL-6 is the main inducer of the human C-reactive protein (CRP) gene, and IL-1 and steroids can enhance this effect. However, in mice, IL-6 is necessary but not sufficient for induction of the human CRP transgene, and testosterone is required for its constitutive expression by males. To examine the relative contributions of testosterone and IL-6 in the regulation of CRP gene expression, we produced CRP-transgenic (CRPtg), IL-6-deficient (IL-6−/−) mice. Male CRPtg/IL-6−/− mice expressed CRP constitutively, but CRP levels were not increased after injection of LPS. However, acute-phase CRP levels were attained after injection of IL-6. In contrast, female CRPtg/IL-6−/− mice did not express CRP constitutively or after administration of LPS, IL-6, IL-1, or IL-6 plus IL-1. Like males, testosterone-treated CRPtg/IL-6−/− females expressed CRP constitutively, and their transgene responded to injection of IL-6. The endogenous acute-phase protein serum amyloid P (SAP) was expressed constitutively equally by male and female IL-6−/− mice, responded minimally to LPS, and did not respond to either IL-6 or IL-1 alone. Acute-phase levels of SAP were induced in IL-6−/− mice by injection of IL-6 together with IL-1 or LPS. We conclude that in vivo, both constitutive and IL-6-dependent acute-phase expression of the CRP transgene require testosterone. In contrast, testosterone is not required for expression of the SAP gene, which requires IL-1 plus IL-6 for acute-phase induction.

Effects of hormone replacement therapy on serum amyloid P component in postmenopausal women

The pentraxin serum amyloid P component (SAP) is a 9.5Sz1-glycoprotein and it has recently been found to be deposited in atherosclerotic lesions or neurofibrillary tangles, which are related to the aging process and Alzheimer's disease. The level of SAP was measured by micro single radial-immunodiffusion. Sample sera were obtained from 420 healthy humans, from newborn to 86 years old. The changes in SAP during the menstrual cycle were investigated in 6 women that were 20-21 years. Fifty of the postmenopausal women, suffering from climacteric symptoms, were administered either conjugated estrogen (E), or dehydroepiandrosterone (DHEA). The SAP levels increased with age, being 1.12 +/- 0.82 mg/dl (means +/- S.D.) in neonates, and 6.15 +/- 0.92 mg/dl in persons over 80 years. The SAP level in the females between 15 and 49 years (3.32 +/- 0.95 mg/dl) was significantly (P < 0.001) lower than that in the males in the same age group (5.19 +/- 1.25 mg/dl). The SAP level in the follicular phase was significantly (P < 0.01) lower than that in menstrual phase (menstrual: 4.36 +/- 0.90 mg/dl versus follicular: 2.61 +/- 0.99 mg/dl). In the post-menopausal women that were administered E (1.25 mg/day), the SAP decreased significantly (P < 0.001) from the prelevel of 5.64 +/- 1.40 mg/dl to 4.26 +/- 0.98 mg/dl on the 14th day. In the postmenopausal women that were administered DHEA (60 mg/day), the SAP increased rapidly from the prelevel of 4.97 +/- 0.76 mg/dl to 6.17 +/- 1.20 mg/dl on the 21st day. SAP seems to be a marker that can monitor the effect of hormone replacement therapy.

Response of interleukin-6-deficient mice to tumor necrosis factor-induced metabolic changes and lethality

Whether interleukin (IL)-6 contributes to tumor necrosis factor (TNF)-induced lethal shock or whether, on the contrary, it is part of a protective feedback system, remains unresolved. Here, we report experiments with IL-6 gene-disrupted mice (IL-6(0/0)). We have tested the susceptibility of these to TNF-induced metabolic changes and lethality in different models, and compared the results with those obtained with IL-6+/+ wild-type mice. We studied the response to TNF in three different models: (i) murine TNF administration; (ii) TNF in galactosamine (GalN)-sensitized mice; (iii) TNF in Bacillus Calmette-Guérin-sensitized mice. We observed no significant difference between the two types of mice in any of the three models. Furthermore, IL-6(0/0) mice could be equally well desensitized (by IL-1) to TNF/GalN-induced lethality and tolerized to TNF-induced shock as IL-6+/+ mice. We also observed that, in response to turpentine, TNF or IL-1, IL-6(0/0) mice produced significantly less acute phase proteins (APP) than IL-6+/+ mice. In IL-6(0/0) mice, less corticosterone was induced by TNF than in the control mice, while the response to adrenocorticotropic hormone was the same. The results indicate that IL-6 is not contributing in a major way to the pathogenesis leading to TNF-induced shock, and that neither IL-6 nor the APP studied are essential for a protective feedback system.

The major acute phase reactants: C-reactive protein, serum amyloid P component and serum amyloid A protein

Following an acute phase stimulus, such as infection or physical injury, many liver-derived plasma proteins are increased in concentration. These provide enhanced protection against invading micro-organisms, limit tissue damage and promote a rapid return to homeostasis. Diana Steel and Alexander Whitehead discuss the gene structure, regulation and possible clinical significance of the most dramatically induced acute phase reactants.

Interleukin-6 (IL-6) production in mice infected with Trypanosoma cruzi: effect of its paradoxical increase by anti-IL-6 monoclonal antibody treatment on infection and acute-phase and humoral immune responses

Trypanosoma cruzi infection of mice triggered endogenous production of interleukin-6 (IL-6) during the ascending phase of parasitemia. Injections of anti-IL-6 monoclonal antibody in infected mice at the time of the serum IL-6 peak paradoxically increased IL-6 levels to 60- to 80-fold those in infected mice receiving unrelated immunoglobulins. This early and transient increase in circulating IL-6 levels modified neither the immunoglobulin nor T. cruzi-specific antibody levels of immunoglobulin G1 (IgG1), IgG2a, IgG3, IgM, IgA, and IgE isotypes or the final outcome of infection nor the blood or tissular parasite levels. However, it tended to delay mortality of mice and to increase the levels of the acute-phase protein serum amyloid P component.

Protective effects of D-penicillamine and a thiazole derivative, SM-8849, on pristane-induced arthritis in mice

To evaluate the antiarthritic properties of a novel thiazole derivative, the drugs SM-8849, D-penicillamine and indomethacin were administered to pristane-injected DBA/1 mice. The mice were treated daily with the agents for 32 weeks, starting from the day of the pristane injection. Treatment with SM-8849 (50 mg/kg) resulted in an amelioration of arthritic disease, as assessed by clinical, radiographic, and histologic examinations. Similar results were obtained in mice treated with 50 mg/kg D-penicillamine, although this disease modifying antirheumatic drug was slightly less effective than the same dose of SM-8849. In contrast, indomethacin at the maximum tolerated dose of 2 mg/kg did not alter the course of the disease. SM-8849 and D-penicillamine were also shown to reduce serum levels of rheumatoid factors and the acute-phase reactant, serum amyloid P component. Indomethacin failed to affect either parameter. Flow cytometric analysis revealed an elevation in the T-cell population that expressed CD44, a marker of murine memory T-cells, in spleens from pristane-injected mice. SM-8849, but not D-penicillamine, prevented the increase in this cell population. These results led us to conclude that pristine-induced arthritis was a useful model for the evaluation of antirheumatic agents, in that using this model, we were able to distinguish disease modifying antirheumatic drugs from nonsteroidal anti-inflammatory drugs. Our findings also indicate that SM-8849 shows antiarthritic activity, with a unique mechanism of action, differing from that of D-penicillamine.

Cloning and tissue-specific expression of the gene for mouse C-reactive protein

C-reactive protein is a serum acute-phase reactant that increases several thousand-fold in concentration during inflammation in most mammals. However, mouse C-reactive protein is considered to be a minor acute-phase reactant, since its blood level increases only from approx. 0.1 to 1-2 micrograms/ml. A mouse genomic clone of approximately 5 kb was obtained to determine the molecular basis for the regulation of the expression of mouse C-reactive protein. Several cis-acting elements in the 5' flanking region that potentially regulate transcription were identified: two glucocorticoid-responsive elements, two CCAAT-enhancer-binding protein C (C/EBP) consensus elements that are required for the interleukin-1 responsiveness of some acute-phase reactant genes, an interleukin-6-responsive element, two hepatocyte nuclear factor-1 (HNF-1) elements and a single heat-shock element. Transfection of the hepatoma cell line Hep 3B.2 with a pCAT expression vector containing the 5' flanking sequence from -1083 to -3 bp from the transcriptional start site, and truncations of this sequence, localized elements that control the tissue-specific expression of mouse C-reactive protein to the two HNF-1 elements and a C/EBP, interleukin-1-responsive element located between -220 and -153, and -90 and -50 bp from the transcriptional start site. A constitutive nuclear protein from mouse-liver hepatocytes specifically binds to the HNF-1 elements. These findings explain the tissue-specific expression of the gene, as well as its limited expression during the acute-phase response.

Regulation of mouse serum amyloid P gene expression by cytokines in vitro

Inflammation is accompanied by an increase in the plasma levels of a number of proteins collectively known as acute-phase reactants (APRs). Serum amyloid P component (SAP) is a major mouse APR: hepatic SAP mRNA and plasma SAP protein concentrations increase by up to 20-fold in mice undergoing an inflammatory response. In-vitro studies, using primary hepatocyte cultures, have previously shown that SAP mRNA and protein levels increase in response to stimulation with a variety of cytokines such as monocyte-conditioned medium (MCM), interleukin 1 (IL-1), interleukin 6 (IL-6), tumor necrosis factor alpha (TNF-alpha) and transforming growth factor beta (TGF-beta). In this report, we have examined a mouse hepatoma cell line in which SAP gene regulation closely resembles that of primary hepatocytes. Accumulation of SAP mRNA in the +/+ Li mouse hepatoma cell line after stimulation with MCM, IL-1, IL-6 and the combination of IL-1 and IL-6 was demonstrated. This increase in the cellular content of SAP mRNA did not require new protein synthesis and was at least partially due to an increase in the transcription rate of the SAP gene.