J. Ruth Gallimore

Low grade inflammation and coronary heart disease : prospective study and updated meta-analyses

Abstract Objective: To assess associations between baseline values of four different circulating markers of inflammation and future risk of coronary heart disease, potential triggers of systemic inflammation (such as persistent infection), and other markers of inflammation. Design: Nested case-control comparisons in a prospective, population based cohort. Setting: General practices in 18 towns in Britain. Participants: 506 men who died from coronary heart disease or had a non-fatal myocardial infarction and 1025 men who remained free of such disease until 1996 selected from 5661 men aged 40–59 years who provided blood samples in 1978-1980. Main outcome measures: Plasma concentrations of C reactive protein, serum amyloid A protein, and serum albumin and leucocyte count. Information on fatal and non-fatal coronary heart disease was obtained from medical records and death certificates. Results: Compared with men in the bottom third of baseline measurements of C reactive protein, men in the top third had an odds ratio for coronary heart disease of 2.13 (95% confidence interval 1.38 to 3.28) after age, town, smoking, vascular risk factors, and indicators of socioeconomic status were adjusted for. Similar adjusted odds ratios were 1.65 (1.07 to 2.55) for serum amyloid A protein; 1.12 (0.71 to 1.77) for leucocyte count; and 0.67 (0.43 to 1.04) for albumin. No strong associations were observed of these factors with Helicobacter pylori seropositivity, Chlamydia pneumoniae IgG titres, or plasma total homocysteine concentrations. Baseline values of the acute phase reactants were significantly associated with one another (P<0.0001), although the association between low serum albumin concentration and leucocyte count was weaker (P=0.08). Conclusion: In the context of results from other relevant studies these findings suggest that some inflammatory processes, unrelated to the chronic infections studied here, are likely to be involved in coronary heart disease.

Targeting C-reactive protein for the treatment of cardiovascular disease

Complement-mediated inflammation exacerbates the tissue injury of ischaemic necrosis in heart attacks and strokes, the most common causes of death in developed countries. Large infarct size increases immediate morbidity and mortality and, in survivors of the acute event, larger non-functional scars adversely affect long-term prognosis. There is thus an important unmet medical need for new cardioprotective and neuroprotective treatments. We have previously shown that human C-reactive protein (CRP), the classical acute-phase protein that binds to ligands exposed in damaged tissue and then activates complement, increases myocardial and cerebral infarct size in rats subjected to coronary or cerebral artery ligation, respectively. Rat CRP does not activate rat complement, whereas human CRP activates both rat and human complement. Administration of human CRP to rats is thus an excellent model for the actions of endogenous human CRP. Here we report the design, synthesis and efficacy of 1,6-bis(phosphocholine)-hexane as a specific small-molecule inhibitor of CRP. Five molecules of this palindromic compound are bound by two pentameric CRP molecules, crosslinking and occluding the ligand-binding B-face of CRP and blocking its functions. Administration of 1,6-bis(phosphocholine)-hexane to rats undergoing acute myocardial infarction abrogated the increase in infarct size and cardiac dysfunction produced by injection of human CRP. Therapeutic inhibition of CRP is thus a promising new approach to cardioprotection in acute myocardial infarction, and may also provide neuroprotection in stroke. Potential wider applications include other inflammatory, infective and tissue-damaging conditions characterized by increased CRP production, in which binding of CRP to exposed ligands in damaged cells may lead to complement-mediated exacerbation of tissue injury.

C-Reactive Protein, Insulin Resistance, Central Obesity, and Coronary Heart Disease Risk in Indian Asians From the United Kingdom Compared With European Whites

Background—Indian Asians in the United Kingdom have increased coronary heart disease (CHD) mortality compared with European whites, but the causes are not well understood. Increased circulating concentrations of C-reactive protein (CRP) are an independent risk factor for CHD. Therefore, we investigated this marker of inflammation in healthy UK Indian Asian and European white men. Methods and Results—We measured serum CRP concentrations and conventional CHD risk factors in 1025 healthy male subjects (518 Indian Asians and 507 European whites) aged 35 to 60 years who were recruited at random from general practitioner lists. The geometric mean CRP concentration was 17% higher (95% confidence interval, 3% to 33%) in Indian Asians compared with European whites. CRP values were strongly associated with conventional CHD risk factors, measures of obesity, and metabolic disturbances associated with insulin resistance in both racial groups. The difference in CRP concentrations between Indian Asians and European whites remained after adjustment for conventional CHD risk factors but was eliminated by an adjustment for central obesity and insulin resistance score in Asians. On the basis of these results, we estimate that the processes underlying elevated CRP and/or increased CRP production itself are associated with an ≈14% increase in population CHD risk among Indian Asians compared with European whites. Conclusions—CRP concentrations are higher in healthy Indian Asians than in European whites and are accounted for by greater central obesity and insulin resistance in Indian Asians. Our results suggest that inflammation or other mechanisms underlying elevated CRP values may contribute to the increased CHD risk among Indian Asians.

Enhanced Inflammatory Response to Coronary Angioplasty in Patients With Severe Unstable Angina

BACKGROUND Systemic markers of inflammation have been found in unstable angina. Disruption of culprit coronary stenoses may cause a greater inflammatory response in patients with unstable than those with stable angina. We assessed the time course of C-reactive protein (CRP), serum amyloid A protein (SAA), and interleukin-6 (IL-6) after single-vessel PTCA in 30 patients with stable and 56 patients with unstable angina (protocol A). We also studied 12 patients with stable and 15 with unstable angina after diagnostic coronary angiography (protocol B). METHODS AND RESULTS Peripheral blood samples were taken before and 6, 24, 48, and 72 hours after PTCA or angiography. In protocol A, baseline CRP, SAA, and IL-6 levels were normal in 87% of stable and 29% of unstable patients. After PTCA, CRP, SAA, and IL-6 did not change in stable patients and unstable patients with normal baseline levels but increased in unstable patients with raised baseline levels (all P<0.001). In protocol B, CRP, SAA, and IL-6 did not change in stable angina patients after angiography but increased in unstable angina patients (all P<0.05). Baseline CRP and SAA levels correlated with their peak values after PTCA and angiography (all P<0.001). CONCLUSIONS Our data suggest that plaque rupture per se is not the main cause of the acute-phase protein increase in unstable angina and that increased baseline levels of acute-phase proteins are a marker of the hyperresponsiveness of the inflammatory system even to small stimuli. Thus, an enhanced inflammatory response to nonspecific stimuli may be involved in the pathogenesis of unstable angina.

Antibodies to human serum amyloid P component eliminate visceral amyloid deposits

Accumulation of amyloid fibrils in the viscera and connective tissues causes systemic amyloidosis, which is responsible for about one in a thousand deaths in developed countries. Localized amyloid can also have serious consequences; for example, cerebral amyloid angiopathy is an important cause of haemorrhagic stroke. The clinical presentations of amyloidosis are extremely diverse and the diagnosis is rarely made before significant organ damage is present. There is therefore a major unmet need for therapy that safely promotes the clearance of established amyloid deposits. Over 20 different amyloid fibril proteins are responsible for different forms of clinically significant amyloidosis and treatments that substantially reduce the abundance of the respective amyloid fibril precursor proteins can arrest amyloid accumulation. Unfortunately, control of fibril-protein production is not possible in some forms of amyloidosis and in others it is often slow and hazardous. There is no therapy that directly targets amyloid deposits for enhanced clearance. However, all amyloid deposits contain the normal, non-fibrillar plasma glycoprotein, serum amyloid P component (SAP). Here we show that administration of anti-human-SAP antibodies to mice with amyloid deposits containing human SAP triggers a potent, complement-dependent, macrophage-derived giant cell reaction that swiftly removes massive visceral amyloid deposits without adverse effects. Anti-SAP-antibody treatment is clinically feasible because circulating human SAP can be depleted in patients by the bis-d-proline compound CPHPC, thereby enabling injected anti-SAP antibodies to reach residual SAP in the amyloid deposits. The unprecedented capacity of this novel combined therapy to eliminate amyloid deposits should be applicable to all forms of systemic and local amyloidosis.

Plasma Protein Acute-Phase Response in Unstable Angina Is Not Induced by Ischemic Injury

BACKGROUND Elevated levels of C-reactive protein (CRP) are associated with an unfavorable clinical outcome in patients with unstable angina. To determine whether ischemia-reperfusion injury causes this acute-phase response, we studied the temporal relation between plasma levels of CRP and ischemic episodes in 48 patients with unstable angina and 20 control patients with active variant angina, in which severe myocardial ischemia is caused by occlusive coronary artery spasm. METHODS AND RESULTS Blood samples were taken on admission and subsequently at 24, 48, 72, and 96 hours. All patients underwent Holter monitoring for the first 24 hours and remained in the coronary care unit under ECG monitoring until completion of the study. On admission, CRP was significantly higher in unstable angina than in variant angina patients (P < .001). In unstable angina, 70 ischemic episodes (1.5 +/- 2 per patient) and in variant angina 192 ischemic episodes (9.6 +/- 10.7 per patient) were observed during Holter monitoring (P < .001), for a total ischemic burden of 14.8 +/- 30.2 and 44.4 +/- 57.2 minutes per patient, respectively (P < .001). The plasma concentration of CRP did not increase in either group during the 96 hours of study, even in patients who had episodes of ischemia lasting > 10 minutes. CONCLUSIONS The normal levels of CRP in variant angina, despite a significantly larger number of ischemic episodes and greater total ischemic burden, and the failure of CRP values to increase in unstable angina indicate that transient myocardial ischemia, within the range of duration observed, does not itself stimulate an appreciable acute-phase response.

Incremental prognostic value of serum levels of troponin T and C-reactive protein on admission in patients with unstable angina pectoris

Management of unstable angina is largely determined by symptoms, yet some symptomatic patients stabilize, whereas others develop myocardial infarction after waning of symptoms. Therefore, markers of short-term risk, available on admission, are needed. The value of 4 prognostic indicators available on admission (pain in the last 24 hours, electrocardiogram [ECG], troponin T, and C-reactive protein [CRP]), and of Holter monitoring available during the subsequent 24 hours was analyzed in 102 patients with Braunwald class IIIB unstable angina hospitalized in 4 centers. The patients were divided into 3 groups: group 1, 27 with pain during the last 24 hours and ischemic electrocardiographic changes; group 2, 45 with pain or electrocardiographic changes; group 3, 30 with neither pain nor electrocardiographic changes. Troponin T, CRP, ECG on admission, and Holter monitoring were analyzed blindly in the core laboratory. Fifteen patients developed myocardial infarction: 22% in group 1, 13% in group 2, and 10% in group 3. Twenty-eight patients underwent revascularization: 37% in group 1, 35% in group 2, and 7% in group 2 (p <0.01 between groups 1 or 2 vs group 3). Myocardial infarction was more frequent in patients with elevated troponin T (50% vs 9%, p=0.001) and elevated CRP (24% vs 4%, p= 0.01). Positive troponin T or CRP identified all myocardial infarctions in group 3. Only 1 of 46 patients with negative troponin T and CRP developed myocardial infarction. Among the indicators available on admission, multivariate analysis showed that troponin T (p=0.02) and CRP (p=0.04) were independently associated with myocardial infarction. Troponin T had the highest specificity (92%), and CRP the highest sensitivity (87%). Positive results on Holter monitoring were also associated with myocardial infarction (p=0.003), but when added to troponin T and CRP, increased specificity and positive predictive value by only 3%. Thus, in patients with class IIIB unstable angina, among data potentially available on admission, serum levels of troponin T and CRP have a significantly greater prognostic accuracy than symptoms and ECGs. Holter monitoring, available 24 hours later, adds no significant information.

Inflammation and Endothelial Function Direct Vascular Effects of Human C-Reactive Protein on Nitric Oxide Bioavailability

Background—Circulating concentrations of the sensitive inflammatory marker C-reactive protein (CRP) predict future cardiovascular events, and CRP is elevated during sepsis and inflammation, when vascular reactivity may be modulated. We therefore investigated the direct effect of CRP on vascular reactivity. Methods and Results—The effects of isolated, pure human CRP on vasoreactivity and protein expression were studied in vascular rings and cells in vitro, and effects on blood pressure were studied in rats in vivo. The temporal relationship between changes in CRP concentration and brachial flow-mediated dilation was also studied in humans after vaccination with Salmonella typhi capsular polysaccharide, a model of inflammatory endothelial dysfunction. In contrast to some previous reports, highly purified and well-characterized human CRP specifically induced hyporeactivity to phenylephrine in rings of human internal mammary artery and rat aorta that was mediated through physiological antagonism by nitric oxide (NO). CRP did not alter endothelial NO synthase protein expression but increased protein expression of GTP cyclohydrolase-1, the rate-limiting enzyme in the synthesis of tetrahydrobiopterin, the NO synthase cofactor. In the vaccine model of inflammatory endothelial dysfunction in humans, increased CRP concentration coincided with the resolution rather than the development of endothelial dysfunction, consistent with the vitro findings; however, administration of human CRP to rats had no effect on blood pressure. Conclusions—Pure human CRP has specific, direct effects on vascular function in vitro via increased NO production; however, further clarification of the effect, if any, of CRP on vascular reactivity in humans in vivo will require clinical studies using specific inhibitors of CRP.

Obesity Is an Important Determinant of Baseline Serum C-Reactive Protein Concentration in Monozygotic Twins, Independent of Genetic Influences

Background—C-reactive protein (CRP) values predict atherothrombotic cardiovascular disease and type 2 diabetes mellitus. Associations between CRP and obesity, predominantly assessed anthropometrically, may partly explain these observations. Previous studies have been unable to control for genetic influences on CRP and obesity. The aim of this study was to examine the relationship between CRP and accurately measured body fat, lipids, apolipoproteins, blood pressure, and environmental and behavioral factors, independent of genetic influences. Methods and Results—One hundred ninety-four healthy female twins (age 57.2±7 years) were studied after excluding pairs with CRP values >10 mg/L. Total body fat and central abdominal fat (CAF) were measured by dual-energy x-ray absorptiometry. CRP concentration was strongly related to surrogate and direct measures of body fat (r =0.31 to 0.54, P <0.001), diastolic blood pressure (r =0.20, P =0.003), and lipid and apolipoprotein levels (r =0.21 to 0.51, P <0.008). Light-to-moderate alcohol consumers and nonusers of hormone replacement therapy (HRT) had lower CRP levels than abstainers and HRT users, respectively. In stepwise multiple regression analysis, CAF, triglycerides, apolipoprotein B, and HRT use explained 46% of the variance in circulating CRP. In analyses controlling for genetic influences in monozygotic twins, within-pair differences in CRP were associated with within-pair differences in total body fat (r =0.39, P <0.001), CAF (r =0.34, P =0.002), diastolic blood pressure (r =0.24, P =0.03), apolipoprotein AI (r =−0.33, P =0.01), HDL cholesterol (r =−0.42, P =0.001), and triglycerides (r =0.35, P =0.007). Conclusions—CRP was strongly related to total and central abdominal obesity, blood pressure, and lipid levels, independent of genetic influences. These relationships are likely to contribute significantly to prospective associations between CRP and type 2 diabetes and coronary events.

Enhanced inflammatory response in patients with preinfarction unstable angina.

OBJECTIVES We assessed the extent and the time course of the acute phase response following myocardial cell necrosis and its relationship with the presence of preinfarction unstable angina (UA). BACKGROUND Elevated levels of acute phase proteins have been reported in patients with UA and in patients with acute myocardial infarction (MI). METHODS C-Reactive Protein (CRP), serum amyloid A protein (SAA) and interleukin-6 (IL-6) were measured in 36 patients with MI admitted within 3 h from symptoms onset. All patients had normal levels of creatine kinase and of troponin T on admission, rising above diagnostic levels within 6 to 12 h. Blood samples for CRP, SAA and IL-6 measurements were taken on admission, at 6, 24, 48, 72 h and at discharge. RESULTS Twenty of the 36 patients studied presented an unheralded MI (Group 1); the remaining 16 patients had symptoms of unstable angina in the preceding 7 days (Group 2). Group 2 patients have much higher levels of CRP and SAA on admission (median values 8.8 vs. 3 mg/L and 28 vs. 3.4 mg/L, respectively, all p<0.001). Following the necrotic insult, despite similar infarct size and clinical signs of reperfusion, Group 2 patients had strikingly higher peaks of IL-6 (median values 85.2 vs. 19 pg/ml, p<0.05), CRP (50 vs. 31.4 mg/L, p<0.05) and SAA (228 vs. 45 mg/L, p<0.001). CONCLUSIONS Our data demonstrated that the acute phase response is greatly enhanced in patients with preinfarction UA compared with those presenting with an unheralded MI. The significant differences in acute phase response observed in these two clinical presentations of MI indicate a major difference in their underlying pathogenetic components.