C-reactive protein: a pentraxin with anti-acetylcholine activity.

Purified C-reactive protein (CRP) diminished effects of acetylcholine (ACh) on the vascular tone and the heart rate of rats in vivo. In vitro CRP inhibited breakdown of ACh by acetylcholinesterase (AChE) while did not interact with AChE itself. CRP appears to bind ACh. CRP did not modify the cardiovascular effects of adenosine, another vasorelaxant. The data suggest that there is a new line of cross-talk between the inflammation and cholinergic regulation with CRP acting on endothelium via the ACh-dependent pathway.

The influence of cholinergic agents on histamine release from HMC-1 human mast cell line stimulated with IgG, C-reactive protein and compound 48/80.

AIMS: The aim of this work is to study the role of acetylcholine (ACh) receptors (AChRs) in the regulation of FcγR activity in human mast cells (MC) activated by aggregated IgG (aIgG) and CRP. MC, the key regulators at the interface of innate and acquired immunity, have abundant Fc receptors for IgG (FcγRII) which indicate the role of their ligands, IgG and C-reactive protein (CRP), in regulating MC activity. Cholinergic control of FcγR-dependent MC functions is poorly defined. MAIN METHODS: HMC-1 culture of human MC; cell incubations with cholinergic drugs and FcγR ligands such as heat aggregated human IgG or purified human CRP; compound 48/80, a known histamine liberator employing G protein-coupled receptors, was used as a positive control of MC degranulation; assessment of histamine release. KEY FINDINGS: Both nAChR and mAChR antagonists (hexamethonium and methacine, respectively), per se, elevated histamine-releasing activity of the HMC-1 and suppressed the MC responses to most of investigated activators (carbachol, compound 48/80, and to a lesser extent aIgG). Two blockers together should be applied to aIgG-stimulated cells in order to obtain appreciable suppression of histamine release. The FcγR-mediated HMC-1 cell response to CRP was the least sensitive to attenuation by ACh signaling. SIGNIFICANCE: The data obtained suggest the involvement of ACh in the functioning of other receptor systems. Our results indicate that AChRs are closely associated with G protein-coupled receptor-induced reactions of MC and optionally with FcγR-dependent functions. CONCLUSION: The data presented demonstrate that AChRs and endogenous ACh are involved in regulating mast cell degranulation and histamine release by affecting the functions of receptors to compound 48/80 and, less, FcγRs.

Complement and Reactants of Acute Phase of Inflammation in the Processes of Functional Activity of Non-Specific Resistance and Immunoregulation.

Complement system is a family comprising of 20 plasma and membrane proteins, acting in concord by cascade principle. The investigators display great interest to C4b-binding protein (C4bp) which is the main regulatory protein of complement system, regulating of C3 convertase activity in classical way of complement activation. The major regulatory function of C4bp is related to its interaction with activated form of the forth complement component, C4b. C4bp may also interact with one of pentraxins, serum amyloid P component (SAP) that inhibits complement-regulatory functions of C4bp. C4bp forms tight complexes with protein S and SAP. Pentraxin family (proteins with five-ray symmetry, such as C-reactive protein and SAP) became more numerous. Protein PTX3, synthesized by endothelial cells, macrophages and leukocytes, and considered to be local regulator of reaction of non-specific resistance in tissues; serum acute phase protein TSG-14; neuronal pentraxin - protein of cerebellum, hippocampus and brain cortex neurons, binding typoxin of snake venom; Narp (neuronal activity-regulated pentraxin) protein; apexin, acrosomal protein of spermatozoa; female hamster protein; pentraxin XL-PXN1 from Xenopus laevis - are all examples of new pentraxins. Pro-inflammatory cytokines, IL-1 and IL-6, may induce expression of pentraxin genes. Pentraxins are closely integrated not only to non-specific resistance, but to the system of immunoregulation and take part in its key events.

Interactions of C-Reactive Protein and Serum Amyloid P Component with Interleukin-8 and Their Role in Regulation of Neutrophil Functions.

C-reactive protein (CRP) and serum amyloid P component (SAP) are acute phase proteins, whose concentrations increase within 24 h of inflammation along with concentration of IL-8. Polymorphonuclear neutrophil leukocytes (PMNs) form the earliest barrier protecting an injured organ during acute phase response. The aim of present work was to study interactions between CRP, SAP and IL-8, and to estimate the role of these interactions in regulation of neutrophil transendothelial migration. The results have shown that IL-8 binds to immobilized but not to free CRP. Binding of IL-8 to immobilized SAP was less strong. SAP like IL-8 increased CD11/CD18 integrin expression. IL-8 did not abolish the effect of SAP, and the mixture of IL-8 and SAP has stimulated CD11/CD18 expression. CRP upregulated CD18 but not CD11b expression. Under simultaneous action of CRP and IL-8, the stimulatory effect on CD11b and CD18 was abolished. The expression of fibronectin receptor was reduced by either IL-8 or CRP but increased by SAP. Effect of each protein was downregulated after following preincubations: CRP+SAP, CRP+IL-8 or SAP+IL-8. The mixtures of CRP with SAP, CRP with IL-8 or SAP with IL-8 showed no chemotactic activity, although each of the proteins was chemoattractive. Thus, acute phase proteins and IL-8 can act as anti-inflammatory factors upon binding each other. In summary, CRP and SAP influence PMN adhesion, migration and expression of CD11b/CD18 and fibronectin receptors, and can modulate the action of IL-8 on PMN attachment to endothelium and fibronectin, and on PMN traffic through the extracellular matrix during transendothelial migration.