Genome expression analysis of nonproliferating intracellular Salmonella enterica serovar ty phimurium unravels an acid pH-dependent PhoP-PhoQ response essential for dormancy

Genome-wide expression analyses have provided clues on how Salmonella proliferates inside cultured macrophages and epithelial cells. However, in vivo studies show that Salmonella does not replicate massively within host cells, leaving the underlyingmechanisms of such growth control largely undefined. In vitro infection models based on fibroblasts or dendritic cells reveal limited proliferation of the pathogen, but it is presently unknown whether these phenomena reflect events occurring in vivo. Fibroblasts are distinctive, since they represent a nonphagocytic cell type in which S. enterica serovar Typhimurium actively attenuates intracellular growth. Here, we show in the mouse model that S. Typhimurium restrains intracellular growth within nonphagocytic cells positioned in the intestinal lamina propria. This response requires a functional PhoP-PhoQ system and is reproduced inprimary fibroblasts isolated from the mouse intestine. The fibroblast infection model was exploited to generate transcriptome data, which revealed that [H11011]2% (98 genes) of the S. Typhimurium genome is differentially expressed in nongrowing intracellular bacteria. Changes include metabolic reprogramming to microaerophilic conditions, induction of virulence plasmid genes,upregulation of the pathogenicity islands SPI-1 and SPI-2, and shutdown of flagella production and chemotaxis. Comparison of relative protein levels of several PhoP-PhoQ-regulated functions (PagN, PagP, and VirK) in nongrowing intra-cellular bacteria andextracellular bacteria exposed to diverse PhoP-PhoQ-inducing signals denoted a regulation responding to acidic pH. These data demonstrate that S. Typhimurium restrains intracellular growth in vivo and support a model in which dormant intracellular bacteriacould sense vacuolar acidification to stimulate the PhoP-PhoQ system for preventing intracellular overgrowth.Ministerio de Economía y Competitividad BIO2010-18885 CSD2008-00013-INTERMODS BIO2010-15023Junta de Andalucía P10-CVI-587

Genome expression analysis of nonproliferating intracellular Salmonella enterica serovar Typhimurium unravels an acid pH-dependent PhoP-PhoQ response essential for dormancy

Genome-wide expression analyses have provided clues on how Salmonella proliferates inside cultured macrophages and epithelial cells. However, in vivo studies show that Salmonella does not replicate massively within host cells, leaving the underlying mechanisms of such growth control largely undefined. In vitro infection models based on fibroblasts or dendritic cells reveal limited proliferation of the pathogen, but it is presently unknown whether these phenomena reflect events occurring in vivo. Fibroblasts are distinctive, since they represent a nonphagocytic cell type in which S. enterica serovar Typhimurium actively attenuates intracellular growth. Here, we show in the mouse model that S. Typhimurium restrains intracellular growth within nonphagocytic cells positioned in the intestinal lamina propria. This response requires a functional PhoP-PhoQ system and is reproduced in primary fibroblasts isolated from the mouse intestine. The fibroblast infection model was exploited to generate transcriptome data, which revealed that2% (98 genes) of the S. Typhimurium genome is differentially expressed in nongrowing intracellular bacteria. Changes include metabolic reprogramming to microaerophilic conditions, induction of virulence plasmid genes, upregulation of the pathogenicity islands SPI-1 and SPI-2, and shutdown of flagella production and chemotaxis. Comparison of relative protein levels of several PhoP-PhoQ-regulated functions (PagN, PagP, and VirK) in nongrowing intracellular bacteria and extracellular bacteria exposed to diverse PhoP-PhoQ-inducing signals denoted a regulation responding to acidic pH. These data demonstrate that S. Typhimurium restrains intracellular growth in vivo and support a model in which dormant intracellular bacteria could sense vacuolar acidification to stimulate the PhoP-PhoQ system for preventing intracellular overgrowth.This work was supported by grants BIO2010-18885 (to F.G-P.), CSD2008-00013-INTERMODS (to F.G.-P. and J.C.), and BIO2010-15023 (to J.C.) from the Spanish Ministry of Economy and Competitiveness and grant P10-CVI-5879 from the Junta of Andalucía (to J.C.). C.N.-H. and A.T. held fellowships from the Consejería de Educación de la Comunidad de MadridPeer Reviewe

Induction of PGC-1α expression can be detected in blood samples of patients with ST-segment elevation acute myocardial infarction.

Following acute myocardial infarction (MI), cardiomyocyte survival depends on its mitochondrial oxidative capacity. Cell death is normally followed by activation of the immune system. Peroxisome proliferator activated receptor γ-coactivator 1α (PGC-1α) is a transcriptional coactivator and a master regulator of cardiac oxidative metabolism. PGC-1α is induced by hypoxia and facilitates the recovery of the contractile capacity of the cardiac muscle following an artery ligation procedure. We hypothesized that PGC-1α activity could serve as a good molecular marker of cardiac recovery after a coronary event. The objective of the present study was to monitor the levels of PGC-1α following an ST-segment elevation acute myocardial infarction (STEMI) episode in blood samples of the affected patients. Analysis of blood mononuclear cells from human patients following an STEMI showed that PGC-1α expression was increased and the level of induction correlated with the infarct size. Infarct size was determined by LGE-CMR (late gadolinium enhancement on cardiac magnetic resonance), used to estimate the percentage of necrotic area. Cardiac markers, maximum creatine kinase (CK-MB) and Troponin I (TnI) levels, left ventricular ejection function (LVEF) and regional wall motion abnormalities (RWMA) as determined by echocardiography were also used to monitor cardiac injury. We also found that PGC-1α is present and active in mouse lymphocytes where its expression is induced upon activation and can be detected in the nuclear fraction of blood samples. These results support the notion that induction of PGC-1α expression can be part of the recovery response to an STEMI and could serve as a prognosis factor of cardiac recovery

PGC-1α regulates translocated in liposarcoma activity: role in oxidative stress gene expression.

UNLABELLED Translocated in liposarcoma (TLS) is a poorly characterized multifunctional protein involved in the genotoxic response. TLS regulates gene expression at several steps, including splicing and mRNA transport, possibly connecting transcriptional and posttranscriptional events. AIMS In this study we aimed to idenfity molecular targets and regulatory partners of TLS. RESULTS AND INNOVATION Here we report that TLS transcriptionally regulates the expression of oxidative stress protection genes. This regulation requires interaction with the transcriptional coactivator peroxisome proliferator activated receptor γ-coactivator 1α (PGC-1α), a master regulator of mitochondrial function that coordinately induces the expression of genes involved in detoxification of mitochondrial reactive oxygen species (ROS). Microarray gene expression analysis showed that TLS transcriptional activity is impaired in the absence of PGC-1α, and is thus largely dependent on PGC-1α. CONCLUSION These results suggest the existence of a regulatory circuit linking the control of ROS detoxification to the coordinated cross-talk between oxidative metabolism and the cellular response to genomic DNA damage.S

PGC-1α induction positively correlates with cardiac ventricular dysfunction.

<p><b>A)</b> LVEF and <b>B)</b> RWMA, were determined by ecocardiography. The estimated mean for patients that induced PGC-1α levels (PGC-1α 72 h/0 h ≥1) is compared to that of patients that did not induce PGC-1α (PGC-1α 72 h/0 h ≤1) after STEMI. <b>C)</b> Antero-lateral infarcts are associated to larger necrotic areas than inferior-posterior infarcts as determine by LGE on CRM. The graph shows mean LVEF and necrotic area (LGE) of patients with antero-lateral or inferior-posterior infarcts. Data are means +/−SD. (*) <i>p</i><0.05.</p

Demographic data, Biochemistry and CMR Characteristics of the Patients with and without PGC-1α Induction.

<p>Data are means +/−SD. n.s = non statistically significant. Significance: <i>p</i><0.05.</p

Patients that induce PGC-1α after STEMI have bigger necrotic areas.

<p><b>A)</b> Necrotic areas as estimated by late gadolinium enhancement (LGE). The infarct sizes, of the cohort of STEMI patients under survey, was determined by LGE on cardiac RMN (CMR). The estimated mean infarct size for patients that induced PGC-1α levels (PGC-1α 72 h/0 h ≥1) is compared to that of patients that did not induce PGC-1α (PGC-1α 72 h/0 h ≤1) after STEMI. <b>B–D)</b> PGC-1α induction positively correlates with cardiac necrosis as estimated by TnI_max (B), CKMB_max (C), and CRP plasma levels (D). TnI_max, CKMB_max, and CRP levels of the cohort of STEMI patients under survey The estimated mean for patients that induced PGC-1α levels (PGC-1α 72 h/0 h ≥1) is compared to that of patients that did not induce PGC-1α (PGC-1α 72 h/0 h ≤1) after STEMI. Data are means +/−SD. (*) <i>p</i><0.05.</p