Lipocalin-2 is a Sensitive and Specific Marker of Bacterial Infection in Children

IntroductionBacterial infection is the leading cause of death in children globally. Clinical algorithms to identify children who are likely to benefit from antimicrobial treatment remain suboptimal. Biomarkers that accurately identify serious bacterial infection (SBI) could improve diagnosis and clinical management. Lipocalin 2 (LCN2) and neutrophil collagenase (MMP-8) are neutrophil-derived biomarkers associated with bacterial infection.MethodsWe evaluated LCN2 and MMP-8 as candidate biomarkers in 40 healthy controls and 151 febrile children categorised confirmed SBI, probable SBI, or viral infection. The diagnostic performance of LCN2 and MMP-8 to predict SBI was estimated by the area under the receiver operating characteristic curve (AUROC) and compared to the performance of C-reactive protein (CRP).ResultsPlasma LCN2 and MMP-8 concentration were predictive of SBI. The AUROC (95% CI) for LCN2, MMP8 and CRP to predict SBI was 0.88 (0.82-0.94); 0.80 (0.72-0.87) and 0.89 (0.84-0.94), respectively. The diagnostic performance of LCN2 in combination with CRP was significantly superior to either marker alone: AUROC 0.92 (95% CI: 0.88-0.96).ConclusionLCN2 is a sensitive and specific predictor of SBI in children which could be used to improve clinical management and antimicrobial stewardship. LCN2 should be further evaluated in prospective clinical studies.

Differences in genetic signaling, and not mechanical properties of the wall, are linked to ascending aortic aneurysms in fibulin-4 knockout mice

Fibulin-4 is an extracellular matrix protein that is essential for proper assembly of arterial elastic fibers. Mutations in fibulin-4 cause cutis laxa with thoracic aortic aneurysms (TAAs). Sixty percent of TAAs occur in the ascending aorta (AA). Newborn mice lacking fibulin-4 ( Fbln4−/−) have aneurysms in the AA, but narrowing in the descending aorta (DA), and are a unique model to investigate locational differences in aneurysm susceptibility. We measured mechanical behavior and gene expression of AA and DA segments in newborn Fbln4−/− and Fbln4+/+ mice. Fbln4−/− AA has increased diameters compared with Fbln4+/+ AA and Fbln4−/− DA at most applied pressures, confirming genotypic and locational specificity of the aneurysm phenotype. When diameter compliance and tangent modulus were calculated from the mechanical data, we found few significant differences between genotypes, suggesting that the mechanical response to incremental diameter changes is similar, despite the fragmented elastic fibers in Fbln4−/− aortas. Fbln4−/− aortas showed a trend toward increased circumferential stretch, which may be transmitted to smooth muscle cells (SMCs) in the wall. Gene expression data suggest activation of pathways for SMC proliferation and inflammation in Fbln4−/− aortas compared with Fbln4+/+. Additional genes in both pathways, as well as matrix metalloprotease-8 ( Mmp8), are upregulated specifically in Fbln4−/− AA compared with Fbln4+/+ AA and Fbln4−/− DA. Mmp8 is a neutrophil collagenase that targets type 1 collagen, and upregulation may be necessary to allow diameter expansion in Fbln4−/− AA. Our results provide molecular and mechanical targets for further investigation in aneurysm pathogenesis.

Inhibition of Neutrophil Collagenase/MMP-8 and Gelatinase B/MMP-9 and Protection against Endotoxin Shock

Endotoxin shock is a life-threatening disorder, associated with the rapid release of neutrophil enzymes, including neutrophil collagenase/matrix metalloproteinase-8 (MMP-8) and gelatinase B/matrix metalloproteinase-9 (MMP-9). After activation, these enzymes cleave extracellular matrix components and cytokines and thus may contribute to shock syndrome development. MMP inhibitors have been suggested as immunotherapy of endotoxin shock. However, little is known about the therapeutic time window of MMP inhibition. Here, a sublethal endotoxin shock mouse model was used to evaluate the effect of an MMP inhibiting peptide (P2) after intravenous or intraperitoneal injection and to study the time window between LPS and inhibitor injections. With the use of a specific ELISA the plasma P2 concentrations were monitored. Whereas we corroborated the treatment strategy of MMP targeting in endotoxin shock with a new inhibitor, we also demonstrated that the time window, within which effective MMP inhibition increased the survival rates, is rather limited.

Role of Matrix Metalloproteinase-8 in Atherosclerosis

Plaque rupture is the main cause of acute myocardial infarction and stroke. Atherosclerotic plaques have been described to be vulnerable and more prone to rupture when they are characterized by thin, highly inflamed, and collagen-poor fibrous caps and contain elevated levels of proteases, including metalloproteinases (MMPs). Initiation of collagen breakdown in plaques requires interstitial collagenases, a MMP subfamily consisting of MMP-1, MMP-8, and MMP-13. Previous reports demonstrated that MMP-1 and MMP-13 might be overexpressed in both human and experimental atherosclerosis. Since neutrophils have been only recently reported in atherosclerotic plaques, the role of MMP-8 (formerly known as “neutrophil collagenase”) was only marginally evaluated. In this paper, we will update and comment on evidence of the most relevant regulatory pathways and activities mediated by MMP-8 in atherogenesis.

NHE3 modulates the severity of colitis in IL-10-deficient mice

NHE3, the major intestinal Na+/H+exchanger, was shown to be downregulated and/or inhibited in patients with inflammatory bowel disease (IBD), a phenomenon believed to contribute to inflammation-associated diarrhea. NHE3−/−mice spontaneously develop colitis and demonstrate high susceptibility to dextran sulfate-induced mucosal injury. We investigated the effects of NHE3 deficiency on the development of chronic colitis in an IL-10 knockout (KO) mouse model of Crohn's disease. NHE3−/−mice were first backcrossed to 129/SvEv mice for >10 generations, with no apparent changes in their survival or phenotype. These mice were crossed with IL-10−/−mice on the same genetic background, and the phenotypes of 10-wk-old wild-type (WT), IL-10−/−, NHE3−/−, and IL-10−/−/NHE3−/−(double-KO) mice were studied. Histological and immunohistochemical examination of the colon established important architectural alterations, including increased neutrophilic and mononuclear cell infiltration in double- compared with single-KO mice. Double-KO mice demonstrated increased colonic expression of neutrophil collagenase matrix metalloproteinase-8 and the chemokines macrophage inflammatory protein-2, CXCL1, CXCL10, and CXCL11. Colonic IFNγ, IL-17, and IL-12/23 p40 protein secretion was significantly increased in double- compared with single-KO mice. IL-10−/−/NHE3−/−mouse colonic epithelium exhibited increased hallmarks of apoptosis, including a significantly increased number of cleaved caspase-3-positive surface epithelial cells. These results highlight the importance of NHE3 in the maintenance of intestinal barrier integrity and in modulating the inflammatory process in IL-10-deficient mice. Chronic NHE3 inhibition or underexpression observed in IBD may therefore contribute to the pathogenesis of IBD by influencing the extent of the epithelial barrier defect and affect the ultimate degree of inflammation.