THE PPARgamma ligand 15d-PGJ2 modulates macrophage activation after injury in a murine trauma model.

In macrophages, peroxisome proliferator-activated receptor gamma (PPARgamma) has been shown to be important for differentiation, and it serves as a negative regulator of activation. Major trauma/injury causes a dramatic host response that disrupts cellular immune homeostasis and initiates an inflammatory cascade that predisposes the injured host to subsequent infections. In prior studies using a murine trauma model consisting of femur fracture and hemorrhage, splenic macrophages from traumatized mice had significantly enhanced LPS-induced cyclooxygenase enzyme (subtype 2) and iNOS production as well as elevated levels of inflammatory cytokines at 1 week after injury compared with uninjured controls. These up-regulated cellular responses corresponded to increased mortality when animals were challenged with LPS or Candida. In the current study, we used the injury model to determine the effect of treatment of injured mice with the endogenous PPARgamma ligand 15-deoxy-Delta(12-, 14)-PGJ2 (15d-PGJ2). It was found that in vivo 15d-PGJ2 treatment significantly reduced the levels of inflammatory mediators produced by splenic macrophages 7 days after injury. The mechanism of inhibition is dependent on PPARgamma because concomitant treatment of animals with the PPARgamma antagonist GW9662 reversed the inhibitory effect of 15d-PGJ2. Endogenous PPARgamma modulated activation of LPS-induced p38 mitogen-activated protein kinase. Furthermore, treatment of injured mice with 15d-PGJ2 conferred a significant survival advantage after infectious challenge induced by cecal ligation and puncture. Thus, this PPARgamma ligands significantly attenuate the postinjury inflammatory response and improve survival after infectious challenge.

A critical stem-loop structure in the CR4-CR5 domain of mammalian telomerase RNA.

Telomerase is an enzyme that maintains telomere length by adding telomeric sequence repeats onto chromosome ends. The telomerase ribonucleoprotein complex consists of two essential components, a reverse transcriptase and an RNA molecule that provides the template for telomeric repeat synthesis. A common secondary structure of vertebrate telomerase RNA has been proposed based on a phylogenetic comparative analysis of 35 sequences. Here we report the identification of an additional essential base-paired region in the CR4-CR5 domain of mammalian telomerase RNA, termed P6.1. Mouse telomerase RNAs with mutations that disrupted base pairings in the P6.1 helix were unable to reconstitute telomerase activity in vivo. In contrast, an RNA mutant with compensatory mutations that restored base pairings in the P6.1 helix restored telomerase activity. In an in vitro reconstitution system stable base pairing of the P6.1 stem was required for the RNA-protein interaction between the CR4-CR5 domain and the telomerase reverse transcriptase (TERT) protein. Interestingly, two RNA mutations, one that extends the P6.1 stem and one that alters the conserved nucleotides of the L6.1 loop, allowed RNA-protein binding but significantly impaired telomerase activity. These data establish the presence of the P6.1 stem-loop and its importance for the assembly and enzymatic activity of the mammalian telomerase complex.

beta2 Adrenoreceptor blockade attenuates the hyperinflammatory response induced by traumatic injury.

BACKGROUND: Major operative injury initiates immunologic changes that may result in a systemic inflammatory response, leading to organ dysfunction/sepsis. Catecholamines seem to be key mediators. The effects of beta(2) receptor blockade in vitro and in vivo before and after operative injury were studied to clarify their role. METHODS: In vitro studies were done in RAW 264.7 cells using epinephrine (50 micromol/L) with or without alpha(2)- and beta(2)-receptor blockade. Comparative gene expression analysis on the Toll-like receptor (TLR)-4 receptor signaling pathway was performed between RAW cells pretreated with epinephrine with subsequent lipopolysaccharide (LPS) stimulation versus LPS alone. Confirmatory studies were performed by real-time reverse transcription polymerase chain reaction (RT-PCR). Tumor necrosis factor (TNF)-alpha gene and protein expression were determined via real time RT-PCR and enzyme-linked immunosorbent assay, respectively. In vivo, Balb/C mice received no treatment nor injury (group I). Group II received operative injury and vehicle injection, group III received ICI 118,551 (beta(2)-receptor antagonist) 30 minutes before or in separate studies after operative injury. At 7 days, splenic macrophages were harvested and cytokine production was measured with or without LPS. In separate experiments, cecal ligation and puncture (CLP) was done 7 days after operation and survival determined. RESULTS: In vitro studies demonstrated that epinephrine pretreatment significantly increased TNF-alpha production with LPS stimulation (P < .05). beta(2)-Receptor blockade significantly attenuated (P < .05) LPS stimulated TNF-alpha production. MD-2, an essential coactivator of TLR-4 signaling, gene expression was significantly elevated when cells were pretreated with epinephrine before LPS exposure (P < .001). In vivo studies demonstrated a significant decrease (P < .05) in TNF-alpha and interleukin-6 production in the ICI 118,551 group. Similar findings were demonstrated measuring monocyte chemoattractant protein-1 and interferon-gamma cytokine levels (P < .05) versus no treatment. ICI 118,551 treatment 30 minutes before operation demonstrated a 31% reduction in mortality after CLP (P < .05). CONCLUSION: This study demonstrates that beta(2)-receptor blockade reduces macrophage cytokine production and improves survival showing the critical importance of catecholamines to the immunologic response in surgery.

Haploinsufficiency of mTR results in defects in telomere elongation.

Telomeres are usually maintained about an equilibrium length, and the set point for this equilibrium differs between species and between strains of a given species. To examine the requirement for telomerase in mediating establishment of a new telomere length equilibrium, we generated interspecies crosses with telomerase mTR knockout mice. In crosses between C57BL/6J (B6) and either of two unrelated mouse species, CAST/Ei and SPRET/Ei, telomerase mediated establishment of a new telomere length equilibrium in wild-type mTR(+/+) mice. This new equilibrium was characterized by elongation of the short telomeres of CAST/Ei or SPRET/Ei origin. In contrast, mTR(-/-) offspring of interspecies crosses failed to elongate telomeres. Unexpectedly, haploinsufficiency was observed in mTR(+/-) heterozygous interspecies mice, which had an impaired ability to elongate short SPRET/Ei or CAST/Ei telomeres to the new equilibrium set point that was achieved in wild-type mTR(+/+) mice. These results demonstrate that elongation of telomeres to a new telomere set point requires telomerase and indicate that telomerase RNA may be limiting in vivo.