Sepsis causes over 200,000 deaths yearly in the US; better treatments are urgently needed. Administering bone marrow stromal cells (BMSCs-also known as mesenchymal stem cells) to mice before or shortly after inducing sepsis by cecal ligation and puncture reduced mortality and improved organ function. The beneficial effect of BMSCs was eliminated by macrophage depletion or pretreatment with antibodies specific for interleukin-10 (IL-10) or IL-10 receptor. Monocytes and/ or macrophages from septic lungs made more IL-10 when prepared from mice treated with BMSCs versus untreated mice. Lipopolysaccharide (LPS)-stimulated macrophages produced more IL-10 when cultured with BMSCs, but this effect was eliminated if the BMSCs lacked the genes encoding Toll-like receptor 4, myeloid differentiation primary response gene-88, tumor necrosis factor (TNF) receptor-1a or cyclooxygenase-2. Our results suggest that BMSCs (activated by LPS or TNF-) reprogram macrophages by releasing prostaglandin E 2 that acts on the macrophages through the prostaglandin EP2 and EP4 receptors. Because BMSCs have been successfully given to humans and can easily be cultured and might be used without human leukocyte antigen matching, we suggest that cultured, banked human BMSCs may be effective in treating sepsis in high-risk patient groups. © 2008 Nature Publishing GroupCorrespondence should be addressed to E.M. (E-mail: mezeye@mail.nih.gov).. 6 These authors contributed equally to this work. AUTHOR CONTRIBUTIONS K.N., A.L., P.S.T.Y., R.A.S. and E.M. formulated the basic hypotheses and experimental design; K.N., A.L., E.M., P.S.T.Y. and R.A.S. collected and evaluated data on survival and organ injury; K.N. and A.L. performed the in vivo experiments; A.L., P.S.T.Y., A.P., K.D., K.L. and X.H. assisted in the in vivo experiments and histology; P.G.R. consulted on BMSC biology; K.N. formulated the molecular mechanism hypothesis and designed and performed in vitro and ex vivo assays; B.H.K. helped to test the involvement of the prostaglandin receptors; J.M.B. and B.M. contributed to testing the involvement of COX2; B.M. performed the measurements for tissue peroxidase; I.J. performed FACS experiments; E.M. wrote the initial manuscript and prepared the figures; all of the authors edited the manuscript.Note: Supplementary information is available on the Nature Medicine website. In the last few years, it has been discovered that BMSCs are potent modulators of immune responses 2-5 . We wondered whether such cells could bring the immune response back into balance, thus attenuating the underlying pathophysiology that eventually leads to severe sepsis, septic shock and death 6,7 . NIH Public AccessAs a model of sepsis, we chose cecal ligation and puncture (CLP), a procedure that has been used for more than two decades 8 . This mouse model closely resembles the human disease: it has a focal origin (cecum), is caused by multiple intestinal organisms, and results in septicemia with release of bacterial toxins into the circulation. With no treatment, the ma...

The pregnane X receptor (PXR) is the molecular target for catatoxic steroids such as pregnenolone 16␣-carbonitrile (PCN), which induce cytochrome P450 3A (CYP3A) expression and protect the body from harmful chemicals. In this study, we demonstrate that PXR is activated by the toxic bile acid lithocholic acid (LCA) and its 3-keto metabolite. Furthermore, we show that PXR regulates the expression of genes involved in the biosynthesis, transport, and metabolism of bile acids including cholesterol 7␣-hydroxylase (Cyp7a1) and the Na ؉ -independent organic anion transporter 2 (Oatp2). Finally, we demonstrate that activation of PXR protects against severe liver damage induced by LCA. Based on these data, we propose that PXR serves as a physiological sensor of LCA, and coordinately regulates gene expression to reduce the concentrations of this toxic bile acid. These findings suggest that PXR agonists may prove useful in the treatment of human cholestatic liver disease.

BRCA1 plays a critical role in homology-directed repair (HDR) of DNA double strand breaks, and the repair defect of BRCA1-mutant cancer cells is being targeted with platinum drugs and poly (ADP-ribose) polymerase (PARP) inhibitors. We have employed relatively simple and sensitive assays to determine the function of BRCA1 variants or mutants in two HDR mechanisms, homologous recombination (HR) and single strand annealing (SSA), and in conferring resistance to cisplatin and olaparib in human cancer cells. Our results define the functionality of the top 22 patient-derived BRCA1 missense variants and the contribution of different domains of BRCA1 and its E3 ubiquitin ligase activity to HDR and drug resistance. Importantly, our results also demonstrate that the BRCA1-PALB2 interaction dictates the choice between HR and SSA. These studies establish functional and mutational landscapes of BRCA1 for HDR and therapy resistance, while revealing novel insights into BRCA1 regulatory mechanisms and HDR pathway choice.

N-methyl-D-aspartate receptors (NMDARs) represent a subclass of glutamate receptors that play a critical role in neuronal development and physiology. We report here the generation of mice expressing only 5% of normal levels of the essential NMDAR1 (NR1) subunit. Unlike NR1 null mice, these mice survive to adulthood and display behavioral abnormalities, including increased motor activity and stereotypy and deficits in social and sexual interactions. These behavioral alterations are similar to those observed in pharmacologically induced animal models of schizophrenia and can be ameliorated by treatment with haloperidol or clozapine, antipsychotic drugs that antagonize dopaminergic and serotonergic receptors. These findings support a model in which reduced NMDA receptor activity results in schizophrenic-like behavior and reveals how pharmacological manipulation of monoaminergic pathways can affect this phenotype.

The P2X 7 receptor (P2X 7 R) is an ATP-gated ion channel expressed by monocytes and macrophages. To directly address the role of this receptor in interleukin (IL)-1␤ post-translational processing, we have generated a P2X 7 R-deficient mouse line. P2X 7 R ؊/؊ macrophages respond to lipopolysaccharide and produce levels of cyclooxygenase-2 and pro-IL-1␤ comparable with those generated by wild-type cells. In response to ATP, however, pro-IL-1␤ produced by the P2X 7 R ؊/؊ cells is not externalized or activated by caspase-1. Nigericin, an alternate secretion stimulus, promotes release of 17-kDa IL-1␤ from P2X 7 R ؊/؊ macrophages. In response to in vivo lipopolysaccharide injection, both wild-type and P2X 7 R ؊/؊ animals display increases in peritoneal lavage IL-6 levels but no detectable IL-1. Subsequent ATP injection to wild-type animals promotes an increase in IL-1, which in turn leads to additional IL-6 production; similar increases did not occur in ATPtreated, LPS-primed P2X 7 R ؊/؊ animals. Absence of the P2X 7 R thus leads to an inability of peritoneal macrophages to release IL-1 in response to ATP. As a result of the IL-1 deficiency, in vivo cytokine signaling cascades are impaired in P2X 7 R-deficient animals. Together these results demonstrate that P2X 7 R activation can provide a signal that leads to maturation and release of IL-1␤ and initiation of a cytokine cascade.

Thromboxane (Tx) A2 is a vasoconstrictor and platelet agonist. Aspirin affords cardioprotection through inhibition of TxA2 formation by platelet cyclooxygenase (COX-1). Prostacyclin (PGI2) is a vasodilator that inhibits platelet function. Here we show that injury-induced vascular proliferation and platelet activation are enhanced in mice that are genetically deficient in the PGI2 receptor (IP) but are depressed in mice genetically deficient in the TxA2 receptor (TP) or treated with a TP antagonist. The augmented response to vascular injury was abolished in mice deficient in both receptors. Thus, PGI2 modulates platelet-vascular interactions in vivo and specifically limits the response to TxA2. This interplay may help explain the adverse cardiovascular effects associated with selective COX-2 inhibitors, which, unlike aspirin and nonsteroidal anti-inflammatory drugs (NSAIDs), inhibit PGI2 but not TxA2.

Cystic fibrosis results from defects in the gene encoding a cyclic adenosine monophosphate-dependent chloride ion channel known as the cystic fibrosis transmembrane conductance regulator (CFTR). To create an animal model for cystic fibrosis, mice were generated from embryonic stem cells in which the CFTR gene was disrupted by gene targeting. Mice homozygous for the disrupted gene display many features common to young human cystic fibrosis patients, including failure to thrive, meconium ileus, alteration of mucous and serous glands, and obstruction of glandlike structures with inspissated eosinophilic material. Death resulting from intestinal obstruction usually occurs before 40 days of age.

Mice with a targeted disruption in the f32-microglobulin (f32m) gene, which lack major histocompatibility complex class I molecules and consequently fail to develop functional CD8 T cells, provided a useful model for assessing the role ofclass I-restricted T cells in resistance to infection with virulent Mycobacterium tuberculosis. Ofmutant P2m-/-mice infected with virulent 106 M. tuberculosis, 70% were dead or moribund after 6 weeks, while all control mice expressing the P2m gene remained alive for >20 weeks. Granuloma formation occurred in mutant and control mice, but far greater numbers of tubercle bacilli were present in the lungs ofmutant mice than in controls, and caseating necrosis was seen only in P2m -/-lungs. In contrast, no differences were seen in the course of infection of mutant and control mice with an avirulent vaccine strain, bacille Calmette-Guirin (BCG). Immunization with BCG vaccine prolonged survival of I2m-/-mice after challenge with M. tuberculosis for 4 weeks but did not protect them from death. These data indicate that functional CD8 T cells, and possibly T cells bearing y6 antigen receptor, are a necessary component of a protective immune response to M. tuberculosis in mice.