The pentraxin family of proteins includes C-reactive protein (CRP), a canonical marker for the acute phase inflammatory response. As compared to normal physiological conditions in human serum,... Show moreThe pentraxin family of proteins includes C-reactive protein (CRP), a canonical marker for the acute phase inflammatory response. As compared to normal physiological conditions in human serum, under conditions associated with damage and inflammation, such as acidosis and the oxidative burst, CRP exhibits modulated biochemical properties that may have a structural basis. Here, we explore how pH and ligand binding affect the structure and biochemical properties of CRP. Cryo-electron microscopy was used to solve structures of CRP at pH 7.5 or pH 5 and in the presence or absence of the ligand phosphocholine (PCh), which yielded 7 new high-resolution structures of CRP, including pentameric and decameric complexes. Structures previously derived from crystallography were imperfect pentagons, as shown by the variable angles between each subunit, whereas pentameric CRP derived from cryoEM was found to have C5 symmetry, with subunits forming a regular pentagon with equal angles. This discrepancy indicates flexibility at the interfaces of monomers that may relate to activation of the complement system by the C1 complex. CRP also appears to readily decamerise in solution into dimers of pentamers, which obscures the postulated binding sites for C1. Subtle structural rearrangements were observed between the conditions tested, including a putative change in histidine protonation that may prime the disulphide bridges for reduction and enhanced ability to activate the immune system. Enzyme-linked immunosorbent assays showed that CRP had markedly increased association to the C1 complex and immunoglobulins under conditions associated with acidosis, whilst a reduction in the Ca2+ concentration lowered this pH-sensitivity for C1q, but not immunoglobulins, suggesting different modes of binding. These data suggest a model whereby a change in the ionic nature of CRP and immunological proteins can make it more adhesive to potential ligands without large structural rearrangements. Show less
Background: Diagnosing pneumonia can be challenging in general practice but is essential to distinguish from other respiratory tract infections because of treatment choice and outcome prediction.... Show moreBackground: Diagnosing pneumonia can be challenging in general practice but is essential to distinguish from other respiratory tract infections because of treatment choice and outcome prediction. We determined predictive signs, symptoms and biomarkers for the presence of pneumonia in patients with acute respiratory tract infection in primary care.Methods: From March 2012 until May 2016 we did a prospective observational cohort study in three radiology departments in the Leiden-The Hague area, The Netherlands. From adult patients we collected clinical characteristics and biomarkers, chest X ray results and outcome. To assess the predictive value of C-reactive protein (CRP), procalcitonin and midregional pro-adrenomedullin for pneumonia, univariate and multivariate binary logistic regression were used to determine risk factors and to develop a prediction model.Results: Two hundred forty-nine patients were included of whom 30 (12%) displayed a consolidation on chest X ray. Absence of runny nose and whether or not a patient felt ill were independent predictors for pneumonia. CRP predicts pneumonia better than the other biomarkers but adding CRP to the clinical model did not improve classification (- 4%); however, CRP helped guidance of the decision which patients should be given antibiotics.Conclusions: Adding CRP measurements to a clinical model in selected patients with an acute respiratory infection does not improve prediction of pneumonia, but does help in giving guidance on which patients to treat with antibiotics. Our findings put the use of biomarkers and chest X ray in diagnosing pneumonia and for treatment decisions into some perspective for general practitioners. Show less
Ypma, P.F.; Geloven, N. van; Kerkhoffs, J.L.H.; Boekhorst, P. te; Zwaginga, J.J.; Beckers, E.A.M.; ... ; Eikenboom, J.C.J. 2019
Osteoarthritis (OA) mainly affects the articular cartilage covering the bones. In this thesis we investigated the relation between levels of inflammatory mediators, genes involved in their... Show moreOsteoarthritis (OA) mainly affects the articular cartilage covering the bones. In this thesis we investigated the relation between levels of inflammatory mediators, genes involved in their regulation and the disease status of OA. We investigated the role of genetic variation at the interleukin(IL)-1 gene cluster in the innate bio-availability of IL-1beta. A haplotype that associated to low innate bio-availability also associated to higher hand OA scores. Although this is counterintuitive with respect to the generally accepted hypothesis that a pro-inflammatory status is detrimental to the cartilage it underlines a complex relationship between inflammation and OA. For the C-reactive protein we identified a haplotype associated to high CRP levels as well as to severe hand OA, which is more in line with expected directions of associations. Analysis of baseline cytokine and chemokine levels indicated that chemokine levels associated to hand OA scores, again with low levels associated to high OA scores. In a follow up functional genomic analysis of a previously identified OA susceptibility gene (DIO2) in our studies we show that the risk allele of this gene is transcribed at higher levels as compared to the non-risk allele. Furthermore, we showed increased DIO2 protein presence in OA affected cartilage. Show less
In the first of this thesis, results are summarized of a randomised crossover trial on the effects of aspirin on markers of inflammation, coagulation and number of endothelial progenitor cells in... Show moreIn the first of this thesis, results are summarized of a randomised crossover trial on the effects of aspirin on markers of inflammation, coagulation and number of endothelial progenitor cells in type 2 diabetic patients without cardiovascular disease. In the second part, results of two systematic reviews on prevalence and clinical relevance of aspirin resistance are reported. Furthermore, we describe time-dependent mechanisms by which aspirin may reduce bloodpressure. Show less
The aim of this thesis was to explore the relation between visceral obesity and the accompanying metabolic disturbances, systemic inflammation and the atherosclerotic process. A newly developed... Show moreThe aim of this thesis was to explore the relation between visceral obesity and the accompanying metabolic disturbances, systemic inflammation and the atherosclerotic process. A newly developed magnetic resonance vessel wall imaging technique was implemented in phenotyping patients and as a therapeutic endpoint in a randomised controlled setting. A three step approach was chosen for this purpose. First, the magnetic resonance black blood vessel wall imaging technique at the magnetic field strength of 3 Tesla was developed and validated. Secondly, phenotyping of viscerally obese subjects was performed with special attention for the role of systemic inflammation and atherosclerosis. Finally, in the setting of a randomised controlled trial, the impact of reducing visceral obesity and systemic inflammation with lifestyle intervention and rosiglitazone treatment (PPARg agonist) on the progression of atherosclerosis was assessed. Show less
Ischemia-reperfusion injury (IRI) is a pathophysiological event that occurs in many clinical conditions, ranging from surgery, acute artery occlusion to transplantation. Complement activation is... Show moreIschemia-reperfusion injury (IRI) is a pathophysiological event that occurs in many clinical conditions, ranging from surgery, acute artery occlusion to transplantation. Complement activation is thought to be a crucial step in IRI, because complement inhibition and complement deficiency considerably attenuate irreversible injury. However, the specific complement pathway remains unclear. All three complement pathways: the classical, the alternative, and the mannose-binding lectin dependent pathway may be involved in the development of IRI, depending on the model, the tissue, and the time course of inflammation. Ischemia leads to the exposition of neoantigens on the jeopardized tissues, which could be recognized by C-reactive protein (CRP) and natural IgM antibodies. The binding of CRP and IgM to these neoepitopes is followed by complement activation. In this thesis, we demonstrated that both proteins bind to jeopardized tissues and activate the complement system, in particular intestines from rats subjected to IRI. Furthermore, it was shown that IgM levels against altered phospholipids correlated with the levels of inflammatory mediators in patients subjected to tissue damage suggesting that IgM participates in amplification of inflammation. The development of strategies to prevent binding of CRP and/or IgM is an attractive approach for a therapy for reducing IRI. Show less
