Proresolving and Tissue-Protective Actions of Annexin A1–Based Cleavage-Resistant Peptides Are Mediated by Formyl Peptide Receptor 2/Lipoxin A4 Receptor

Authors

Jesmond Dalli, Angelo P. Consalvo, Vicki Ray, Clara Di Filippo, Michele D’Amico, Nozer Mehta and Mauro Perretti

Abstract

Endogenous mechanisms regulating the host response during inflammation resolution are critical in ensuring disposal of noxious stimuli and return to homeostasis. In this article, we engineered novel Annexin A1 (AnxA1)–based peptides, AnxA12–50, that displayed specific binding to the AnxA1 receptor (formyl peptide receptor 2/Lipoxin A4 receptor [FPR2/ALX]; IC50 ∼4 nM). Intravenous administration of AnxA12–50 markedly reduced (>60%) leukocyte adhesion to postcapillary venules in wild type and Fpr1−/−, but not Fpr2/Alx−/−, mice. Generation of a metabolically stable form of this peptide (CR-AnxA12–50), engineered by substituting a cleavage site shared by human proteinase 3 and neutrophil elastase, yielded an agonist that was resistant to neutrophil-mediated cleavage and displayed enhanced proresolving actions: accelerated resolution of self-limited inflammation and enhanced macrophage efferocytosis after sterile injury, when compared with AnxA12–50. These actions were retained with human primary leukocytes where CR-AnxA12–50 decreased neutrophil–endothelial interactions (∼25–45%), and stimulated neutrophil apoptosis and macrophage efferocytosis (∼45%). In murine cardiac ischemia/reperfusion injury, CR-AnxA12–50 elicited tissue-protective actions reducing infarct size (∼60%) and incidence of 24-h death. These results identify AnxA12–50 and CR-AnxA12–50 as FPR2/ALX agonists that harness the proresolving actions of AnxA1, and thus may represent therapeutic tools for treatment of inflammatory conditions.

Link to Article

http://dx.doi.org/10.4049/immunol.1203000

Mice Lacking Pten in Osteoblasts Have Improved Intramembranous and Late Endochondral Fracture Healing

Authors

Travis A. Burgers, Martin F. Hoffmann, Caitlyn J. Collins, Juraj Zahatnansky, Martin A. Alvarado, Michael R. Morris, Debra L. Sietsema, James J. Mason, Clifford B. Jones, Heidi L. Ploeg, Bart O. Williams

Abstract

The failure of an osseous fracture to heal (development of a non-union) is a common and debilitating clinical problem. Mice lacking the tumor suppressor Pten in osteoblasts have dramatic and progressive increases in bone volume and density throughout life. Since fracture healing is a recapitulation of bone development, we investigated the process of fracture healing in mice lacking Pten in osteoblasts (Ocn-cretg/+;Ptenflox/flox). Mid-diaphyseal femoral fractures induced in wild-type and Ocn-cretg/+;Ptenflox/flox mice were studied via micro-computed tomography (µCT) scans, biomechanical testing, histological and histomorphometric analysis, and protein expression analysis. Ocn-cretg/+;Ptenflox/flox mice had significantly stiffer and stronger intact bones relative to controls in all cohorts. They also had significantly stiffer healing bones at day 28 post-fracture (PF) and significantly stronger healing bones at days 14, 21, and 28 PF. At day 7 PF, the proximal and distal ends of the Pten mutant calluses were more ossified. By day 28 PF, Pten mutants had larger and more mineralized calluses. Pten mutants had improved intramembranous bone formation during healing originating from the periosteum. They also had improved endochondral bone formation later in the healing process, after mature osteoblasts are present in the callus. Our results indicate that the inhibition of Pten can improve fracture healing and that the local or short-term use of commercially available Pten-inhibiting agents may have clinical application for enhancing fracture healing.

Link to Article

http://dx.doi.org/10.1371/journal.pone.0063857

Roquin Promotes Constitutive mRNA Decay via a Conserved Class of Stem-Loop Recognition Motifs

Authors

Kathrin Leppek, Johanna Schott, Sonja Reitter, Fabian Poetz, Ming C. Hammond, Georg Stoecklin

Abstract

Tumor necrosis factor-α (TNF-α) is the most potent proinflammatory cytokine in mammals. The degradation of TNF-α mRNA is critical for restricting TNF-α synthesis and involves a constitutive decay element (CDE) in the 3′ UTR of the mRNA. Here, we demonstrate that the CDE folds into an RNA stem-loop motif that is specifically recognized by Roquin and Roquin2. Binding of Roquin initiates degradation of TNF-α mRNA and limits TNF-α production in macrophages. Roquin proteins promote mRNA degradation by recruiting the Ccr4-Caf1-Not deadenylase complex. CDE sequences are highly conserved and are found in more than 50 vertebrate mRNAs, many of which encode regulators of development and inflammation. In macrophages, CDE-containing mRNAs were identified as the primary targets of Roquin on a transcriptome-wide scale. Thus, Roquin proteins act broadly as mediators of mRNA deadenylation by recognizing a conserved class of stem-loop RNA degradation motifs.

Link to Article

http://dx.doi.org/10.1016/j.cell.2013.04.016

Liver X receptor activation inhibits osteoclastogenesis by suppressing NF-κB activity and c-Fos induction and prevents inflammatory bone loss in mice

Authors

Hyun-Ju Kim, Kyung-Ae Yoon, Hye-Jin Yoon, Jung Min Hong, Min-Jung Lee, In-Kyu Lee and Shin-Yoon Kim

Abstract

LXRs are nuclear receptors that function as important regulators of lipid homeostasis and inflammatory responses. LXR activation has been shown to suppress RANKL-induced osteoclast differentiation, but its underlying mechanisms and its influence on inflammatory bone destruction remain unclear. In this study, we report that the LXR agonists T0901317 and GW3965 inhibit osteoclastogenesis from primary BMMs in a dose-dependent manner. LXR activation suppressed RANKL-induced transcriptional activity of NF-κB without affecting IκBα degradation and the phosphorylation of p38. LXR agonists significantly suppressed RANKL-induced expression of c-Fos and NFATc1, which are crucial transcription factors for osteoclastogenesis. The activation of LXRs also inhibited RANKL-mediated AP-1 transcriptional activity. Furthermore, LXR activation attenuated PPARγ ligand-induced c-Fos expression, and LXR suppressed AP-1 promoter activity by PPARγ. The inhibitory effect of LXR activation on osteoclastogenesis was reversed by overexpression of c-Fos, suggesting that c-Fos is a downstream target of the antiosteoclastogenic action of LXRs. In addition to osteoclast differentiation, LXR activation accelerated apoptosis in mature osteoclasts by the induction of caspase-3 and -9 activity and Bim expression. Consistent with the in vitro effects we observed, the administration of a LXR agonist protected from bone loss induced by LPS in vivo. Together, our data provide evidence that LXRs may have potential as therapeutic targets for bone resorption-associated diseases.

Link to Article

http://dx.doi.org/10.1189/jlb.1112601

Birth outcome measures and maternal exposure to heavy metals (lead, cadmium and mercury) in Saudi Arabian population

Authors

Iman Al-Saleh, Neptune Shinwari, Abdullah Mashhour, Abdullah Rabah

Abstract

This cross-sectional study was conducted to assess the association between exposure to heavy metals (lead, cadmium and mercury) during pregnancy and birth outcomes in 1578 women aged 16–50 years who delivered in Al-Kharj hospital, Saudi Arabia, in 2005 and 2006. The levels of lead, cadmium and mercury were measured in umbilical cord blood, maternal blood and the placenta. Outcome variables were anthropometric measures taken at birth, along with the risk of being small-for-gestational age (SGA). We selected the 10th percentile as the cutoff for dichotomizing measures of birth outcome. Cadmium, despite its partial passage through the placenta had the most prominent effect on several measures of birth outcome. After adjustment for potential confounders, logistic regression models revealed that crown-heel length (p = 0.034), the Apgar 5-minute score (p = 0.004), birth weight (p = 0.015) and SGA (p = 0.049) were influenced by cadmium in the umbilical cord blood. Significant decreases in crown-heel length (p = 0.007) and placental thickness (p = 0.022) were seen with higher levels of cadmium in maternal blood. As placental cadmium increased, cord length increased (p = 0.012) and placental thickness decreased (p = 0.032). Only lead levels in maternal blood influenced placental thickness (p = 0.011). Mercury in both umbilical cord and maternal blood was marginally associated with placental thickness and placental weight, respectively. Conversely, placental mercury levels significantly influenced head circumference (p = 0.017), the Apgar 5-minute score (p = 0.01) and cord length (p = 0.026). The predictions of these models were further assessed with the area under the curve (AUC) of the receiver operating curves (ROCs), which were modest (larger than 0.5 and smaller than 0.7). The independence of gestational age or preterm births on the observed effect of metals on some measures of birth outcome, suggested detrimental effects of exposure on fetal development. The magnitude of the estimated effects might not necessarily be of clinical significance for infants but may have a considerable public-health relevance given the high prevalence of exposure to heavy metals. Further research should be conducted to confirm these findings and to evaluate their long-term risks, if any.

Link to Article

http://dx.doi.org/10.1016/j.ijheh.2013.04.009

Uridine Prodrug Improves Memory in Tg2576 and TAPP Mice and Reduces Pathological Factors associated with Alzheimer's Disease in Related Models

Authors

Joel A. Saydoff, Ana Olariu, Jin Sheng, Zhongyi Hu, Qin Li, Rolando Garcia, Jiong Pei, Grace Y. Sun, Reid von Borstel

Abstract

Uridine prodrug PN401 has been shown to have neuroprotective effects in models of Parkinson's disease and Huntington's disease. These age-related neurodegenerative diseases including Alzheimer's disease (AD) are associated with mitochondrial dysfunction, oxidative stress, and inflammation. Attenuation of these pathological factors in AD, in addition to amyloid fibrils and neurofibrillary tangles, is critical to prevent cognitive impairment. The effects of PN401 treatment were tested in the Tg2576 and Tg2576 X P301L (TAPP) mouse models of AD. Treatment with PN401 reduced impairments in the Tg2576 mice in contextual fear conditioning and novel object recognition. In the TAPP mice, PN401 reduced the impairments in novel object recognition and social transmission of food preference. PN401 also improved motor behavior and reduced anxiety-like behavior in the TAPP mice. TAPP mouse hippocampal tau phosphorylation and lipid peroxidation were reduced by PN401 treatment. Increased tau phosphorylation was significantly correlated with worsening novel object recognition memory. PN401 did not affect amyloid plaque area in the AD mice. In other AD-related animal studies, PN401 treatment reduced blood-brain barrier damage due to intracortical LPS, elevation of serum TNFα due to systemic LPS, and hippocampal CA1 neuronal loss in the gerbil stroke model. Uridine dose-dependently protected cells from chemical hypoxia and ceramide, and decreased formation of reactive oxygen species and mitochondrial DNA damage due to hydrogen peroxide. These protective effects were achieved by raising uridine levels to at least 25–50 μM and serum uridine levels in this range in humans were obtained with oral PN401.

Link to Article

http://dx.doi.org/10.3233/JAD-130059