ABSTRACT
OBJECTIVE: Adenosine modulates inflammation and prevents associated organ injury by activation of its receptors. During sepsis, the extracellular adenosine concentration increases rapidly, but the underlying mechanism in humans is unknown. We aimed to determine the changes in adenosine metabolism and signaling both in vivo during experimental human endotoxemia and in vitro. DESIGN: We studied subjects participating in three different randomized double-blind placebo-controlled trials. In order to prevent confounding by the different pharmacological interventions in these trials, analyses were performed on data of placebo-treated subjects only. SETTING: Intensive care research unit at the Radboud University Nijmegen Medical Center. SUBJECTS: In total, we used material of 24 healthy male subjects. INTERVENTIONS: Subjects received 2 ng/kg Escherichia coli endotoxin (lipopolysaccharide) intravenously. MEASUREMENTS AND MAIN RESULTS: Following experimental endotoxemia, endogenous adenosine concentrations increased. Expression of 5'ectonucleotidase messenger RNA was upregulated (p = .01), whereas adenosine deaminase messenger RNA was downregulated (p = .02). Furthermore, both adenosine deaminase and adenosine kinase activity was significantly diminished (both p ≤ .0001). A2a and A2b receptor messenger RNA expression was elevated (p = .02 and p = .04, respectively), whereas messenger RNA expression of A1 and A3 receptors was reduced (both, p = .03). In vitro, lipopolysaccharide dose-dependently attenuated the activity of both adenosine deaminase and adenosine kinase (both p ≤ .0001). CONCLUSIONS: Adenosine metabolism and signaling undergo adaptive changes during human experimental endotoxemia promoting higher levels of adenosine thereby facilitating its inflammatory signaling.
Subject(s)
Adenosine/metabolism , Cytokines/metabolism , Endotoxemia/metabolism , Endotoxins , Receptors, Purinergic P1/metabolism , Adenosine/analysis , Analysis of Variance , Cells, Cultured , Down-Regulation , Endotoxemia/blood , Gene Expression Regulation , Human Experimentation , Humans , Leukocytes, Mononuclear/cytology , Leukocytes, Mononuclear/metabolism , Lipopolysaccharides/pharmacology , Lymphocytes , Male , RNA, Messenger/analysis , Real-Time Polymerase Chain Reaction , Receptors, Purinergic P1/genetics , Reference Values , Sampling Studies , Systemic Inflammatory Response Syndrome/metabolism , Systemic Inflammatory Response Syndrome/physiopathology , Young AdultABSTRACT
New engineering possibilities allow biomaterials to serve as active orchestrators of the molecular and cellular events of tissue regeneration. Here, the molecular control of tissue regeneration for calcium phosphate (CaP)-based materials is established by defining the parameters critical for tissue induction and those are linked to the molecular circuitry controlling cell physiology. The material properties (microporosity, ion composition, protein adsorption) of a set of synthesized osteoinductive and noninductive CaP ceramics are parameterized and these properties are correlated to a transcriptomics profile of osteogenic cells grown on the materials in vitro. Using these data, a genetic network controlling biomaterial-induced bone formation is built. By isolating the complex material properties into single-parameter test conditions, it is verified that a subset of these genes is indeed controlled by surface topography and ions released from the ceramics, respectively. The gene network points to a decisive role for extracellular matrix deposition in osteoinduction by genes such as tenascin C and hyaluronic acid synthase 2, which are controlled by calcium and phosphate ions as well as surface topography. This work provides insight into the biomaterial composition and material engineering aspects of bone void filling and can be used as a strategy to explore the interface between biomaterials and tissue regeneration.