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Biomedical subjects

S Pettersson

Publications and source records attributed to S Pettersson.

At least 37 records · Page 2Linked to original sources
PubMed2000

Bacterial adaptation to host innate immunity responses.

Several recent reports show that different bacterial components trigger innate and inflammatory responses in host organisms. In parallel, selected bacterial virulence factors have been identified that interfere with corresponding responses. In many cases, this involves interference with host proinflammatory signal transduction pathways, whereas in selected cases bacterial virulence factors interfere with host antibacterial mechanisms. This indicates that bacteria, besides activating cellular responses, also have the capacity to directly interact with branches of the innate defence.

Adaptation, Physiological↗
PubMed2000

The bacterial protein YopJ abrogates multiple signal transduction pathways that converge on the transcription factor CREB.

Bacterially encoded proteins are known to affect eukaryotic signalling pathways and thus cell growth and differentiation. The enteric pathogen Yersinia pseudotuberculosis (YP) can translocate Yersinia outer proteins (Yops) into eukaryotic cells. Recently, MKK proteins have been identified as tentative targets of YopJ-mediated inhibition of ligand receptor-dependent signal transduction in mammalian cells. These results prompted us to assess whether multiple signal transduction pathways and their downstream target genes would also be subject to regulation by YopJ. Here, we show that YopJ effectively blocks the lipopolysaccharide (LPS) receptor, the interleukin (IL)-1beta receptor and the UVC-induced activation of the transcription receptor cAMP response element-binding protein (CREB). In addition, by abrogating the phosphorylation of CREB and thus activating protein (AP)-1-dependent transcription, YopJ can block LPS-induced clonal expansion that is associated with an adaptive immune response. Thus, YopJ interferes with multiple pathways converging on the transcription factor CREB. Our data are discussed in the context of YopJ acting as an antagonist to circumvent innate and adaptive immune responses at multiple levels.

Bacterial Proteins↗
PubMed2000

Salmonella typhimurium mutants that downregulate phagocyte nitric oxide production.

To examine the potential and strategies of the facultative intracellular pathogen Salmonella typhimurium to increase its fitness in host cells, we applied a selection that enriches for mutants with increased bacterial growth yields in murine J774-A.1 macrophage-like cells. The selection, which was based on intracellular growth competition, rapidly yielded isolates that out-competed the wild-type strain during intracellular growth. J774-A.1 cells responded to challenge with S. typhimurium by mounting an inducible nitric oxide synthase (iNOS) mRNA and protein expression and a concomitant nitric oxide (NO) production. Inhibition of NO production with the use of the competitive inhibitor N-monomethyl-L-arginine (NMMA) resulted in a 20-fold increase in bacterial growth yield, suggesting that the NO response prevented bacterial intracellular growth. In accordance with this observation, five out of the nine growth advantage mutants isolated inhibited production of NO from J774-A.1 cells, despite an induction of iNOS mRNA and iNOS protein. Accompanying bacterial phenotypes included alterations in lipopolysaccharide structure and in the profiles of proteins secreted by invasion-competent bacteria. The results indicate that S. typhimurium has the ability to mutate in several different ways to increase its host fitness and that inhibition of iNOS activity may be a major adaptation.

Animals↗
PubMed2000

Bacterial regulation of intestinal immune responses.

If we understand pathological processess within the alimentary tract, it is apparent that the fundamental aspects of microbe-host interactions need to be examined in greater detail. Pathogenic bacteria have evolved strategies to alter and subvert the function of T cels and phagocytes in the gut wall, and exploiting these molecules may lead to new treatments for chronic inflammatory bowel diseases. The adaptation of microbes to their host must involve microbe-mediated interference of the host innate immune response. The recent demonstration that nonpathogenic E. coli have a beneficial effect in ulcerative colitis further supports the notion that normal flora may alter the expression of the innate immune receptors or recognize alternative receptors compared with pathogenic variants. Such differences may conceivably lead to beneficial and protective alterations to the host through cytokine and antimicrobial peptide expression. Perhaps the contact point between microbes and host cells lies with the pattern-recognition receptors such as TLRs. However, although much light has been shed on the downstream consequences of TLR activation, many more questions remain unsolved. For example, little is known about the expression profiles of the different TLRs throughout the gastrointestinal tract. Additionally, ambiguities remain over the natural ligands for TLRs. The discovery that the Drosophila Toll receptor acts downstream of the pathogen recognition event suggests that there are many more twists and turns to be revealed in the story of host-microbe interactions in the gastrointestinal tract.

Adhesins, Bacterial↗
PubMed1999

Cutting edge: Ig heavy chain 3' HS1-4 directs correct spatial position-independent expression of a linked transgene to B lineage cells.

The Ig H chain locus is regulated by a set of cis-acting elements. Hypersensitive sites (HS) located 3' of the IgH, HS1-4, has been suggested to act as a locus control region (LCR) in cell lines. To assess the proposed role of HS1-4 acting as an LCR, we generated transgenic mice harboring a VH promoter-beta-globin reporter gene linked to the Ig H chain HS1-4 3'regulatory sequences. Transgene expression is strictly confined to B lymphocytes, with no detectable expression outside the B cell lineage in all transgenic founder lines. Furthermore, reporter gene activity is integration independent but not copy number dependent. Thus, additional sequences are required to allow the HS1-4 regulatory region to act as a classical LCR in mice. Our data are discussed in the context of tissue-specific gene expression in B lineage cells.

3' Untranslated Regions↗
PubMed1999

Interference of eukaryotic signalling pathways by the bacteria Yersinia outer protein YopJ.

Upon contact with bacteria, eukaryotic cells activates a slurry of defence mechanisms via distinct signalling transduction pathways. However, some bacteria have evolved strategies to escape or inhibit these host defence systems. We have recently shown that the bacteria Yersinia pseudotuberculosis, which encodes the Yersinia outer protein (YopJ) appears to inhibit the activation of NF-kappaB by preventing the phosphorylation of IkappaB. In a subsequent series of experiments it has also been shown that YopJ blocks the phosphorylation of the p38 MAP kinase. Here the regulatory function of YopJ on eukaryotic signal transduction is discussed.

Bacterial Proteins↗
PubMed1999

Novel Salmonella typhimurium properties in host--parasite interactions.

Inflammatory bowel disease (IBD) comprises different diseases in the gastrointestinal tract in human, of which Crohn's disease (CD) and ulcerative colitis (UC) are the most prominent. A key factor in the etiology of IBD is the chronic inflammatory process, and a large body of evidence suggests that the transcription factor nuclear factor-kappa B (NF-kappaB) is the key regulator of responses determining the clinical inflammatory condition. Recent findings using antisense oligonucleotides provide direct evidence that the p65 subunit of NF-kappaB plays a central role in chronic intestinal inflammation. It has previously been shown that the Gram negative bacteria Yersinia pseudotubercolosis targets the eukaryotic signal transduction pathway(s) that lead to NF-kappaB activation (and thus avoid an anti-bacterial inflammatory response). In this paper, growth-based selected Salmonella typhimurium clones have been used to generate a clearer picture of the molecular mechanisms involved in host-parasite interactions. From the results presented here, S. typhimurium and Y. pseudotubercolosis may use the same mechanism to block NF-kappaB activation, following host cell infection. A new adaptational feature could also be shown, where a growth-based selected bacteria avoided the normally induced translocation of NF-kappaB in host cells.

Biological Transport↗
PubMed1999

Temporal expression of a V(H) promoter-Cmu transgene linked to the IgH HS1,2 enhancer.

Immunoglobulin heavy chain (IgH) gene expression is guided by cis-regulatory elements which direct correct temporal and spatial expression in B lineage cells. One of these cis-acting elements is the IgH HS1,2 enhancer and previous studies in transgenic mice have revealed a temporally restricted activity of an HS1,2 enhancer-linked human beta-globin reporter gene in B lineage cells. To assess whether this enhancer can impose strict temporal regulation onto a V(H)-promoter-Cmu reporter gene, transgenic mice were generated. These mice expressed high serum levels of protein from the transgene. Moreover, high levels of transgene expression were observed in spleen and thymus, while lower expression was found in heart and kidney and no expression was detected in liver and brain. Interestingly, transgene expression was confined to large, activated B cells and peritoneal B cells but not observed in small, resting splenic B cells or activated T cells. However, upon mitogenic stimulation of resting B cells with LPS, high levels of transgene expression was induced. Our data demonstrate that the HS1,2 enhancer can interact with a natural V(H) promoter in a strict temporal fashion and when provided with an appropriate activation signal, this V(H) promoter/enhancer construct can induce transgene expression in resting B, but not T lineage cells. Our data are compatible with a model whereby the regulation of IgH gene expression may be subject to regulation by distinct subsets of cis-regulatory elements acting at different stages of B lymphocyte development. Thus, Ig gene expression may be regulated via an interaction between the V(H) promoter and 3' enhancer elements (here typified by the HS1,2 enhancer) in terminally differentiated B lineage cells.

Animals↗
PubMed1999

Constitutive and inducible in vivo protein-DNA interactions at the tumor necrosis factor-alpha promoter in primary human T lymphocytes.

Tumor necrosis factor-alpha (TNF-alpha) is a key cytokine of lymphocytes with major regulatory functions in immunomodulation, chronic inflammation, and septic shock. However, only limited information on TNF promoter regulation in vivo in primary lymphocytes is available. To determine and compare protein-DNA interactions at the native TNF locus in primary lymphocytes, we analyzed the human TNF-alpha promoter by ligation-mediated polymerase chain reaction (LM-PCR) techniques. Accordingly, primary CD4+ T lymphocytes from peripheral blood were cultured in the presence of various stimuli and analyzed by LM-PCR. Inducible in vivo protein-DNA interactions at the TNF promoter were detected between -120 and -70 bp of the human TNF promoter relative to the transcriptional start site. This area includes binding sites for transcription factors such as ETS-1, NFAT, ATF-2/c-jun, SP-1/Egr-1, and NF-kappaB. In contrast, no protein-DNA interactions were observed at various binding sites with reported regulatory function in tumor cell lines such as the k2 element, the NFAT site at -160, the AP1 site at -50, and the SP1 site at -65. Additional mutagenesis and transfection studies demonstrated that NF-kappaB and CREB/AP-1 are important regulators of inducible TNF promoter activity in primary human T lymphocytes. These results provide novel insights into the complex regulation of TNF gene transcription in primary T lymphocytes in vivo by constitutive and inducible protein-DNA interactions that appear to be at least partially different compared to previously characterized tumor cell lines.

Base Sequence↗
PubMed1998

Cytokine gene transcription by NF-kappa B family members in patients with inflammatory bowel disease.

We examined the expression of the transcription factor NF-kappa B, a nuclear trans-acting factor known to play a key role in cytokine gene regulation, in patients with inflammatory bowel disease (IBD). It was found that LP macrophages in Crohn's disease (CD) and ulcerative colitis (UC) display high levels of NF-kappa B DNA-binding activity accompanied by an increased production of interleukin (IL)-1, IL-6, and tumor necrosis factor (TNF) alpha. Western blot studies showed an increased expression of the p50 and c-rel subunits of NF-kappa B; however, the most striking finding was an increased expression level of NF-kappa B p65 in patients with CD and UC. Selective downregulation of p65 in IBD macrophages by a specific antisense phosphorothioate oligonucleotide was sufficient to considerably reduce production of proinflammatory cytokines. These results demonstrate a characteristic increase of NF-kappa B binding levels in patients with IBD. The data suggest that antisense DNA targeting NF-kappa B p65 can be used as a novel molecular approach for the treatment of patients with IBD.

Adolescent↗
PubMed1998

In vivo 31P NMR OSIRIS of bioenergetic changes in rabbit kidneys during and after ischaemia: effect of pretreatment with an indeno-indole compound.

Changes in energy phosphates of rabbit kidneys subjected to ischaemia-reperfusion have been measured in vivo with volume selective 31P NMR spectroscopy. The effects of pretreatment with a new lipid peroxidation inhibitor (indeno-indol derivate--code name H290/51) on the bioenergetic changes were analysed. The left kidney was moved to a subcutaneous pocket to facilitate exact positioning over the surface coil. A 1H NMR image was acquired and a 3.5-mL cube selected for 31P NMR spectra. 31P NMR spectra were recorded before occlusion of the left renal artery, during 1 h of ischaemia and 2 hours of reperfusion. Ischaemia induced drastic changes in the levels of inorganic phosphates and ATP as well as intracellular acidosis. A normalization was observed during reperfusion. Two hours after reperfusion significantly higher values for beta-ATP/Pi and intracellular pH were recorded in the animals pretreated with H290/51. The present technique allows quantitative analyses of changes in kidney bioenergetics in vivo during different experimental conditions. The importance of ischaemia-reperfusion induced lipid peroxidation for mitochondrial function is emphasized.

Adenosine Triphosphate↗
PubMed1998

The yopJ locus is required for Yersinia-mediated inhibition of NF-kappaB activation and cytokine expression: YopJ contains a eukaryotic SH2-like domain that is essential for its repressive activity.

Upon exposure to bacteria, eukaryotic cells activate signalling pathways that result in the increased expression of several defence-related genes. Here, we report that the yopJ locus of the enteropathogen Yersinia pseudotuberculosis encodes a protein that inhibits the activation of NF-kappaB transcription factors by a mechanism(s), which prevents the phosphorylation and subsequent degradation of the inhibitor protein IkappaB. Consequently, eukaryotic cells infected with YopJ-expressing Yersinia become impaired in NF-kappaB-dependent cytokine expression. In addition, the blockage of inducible cytokine production coincides with yopJ-dependent induction of apoptosis. Interestingly, the YopJ protein contains a region that resembles a src homology domain 2 (SH2), and we show that a wild-type version of this motif is required for YopJ activity in suppressing cytokine expression and inducing apoptosis. As SH2 domains are found in several eukaryotic signalling proteins, we propose that YopJ, which we show is delivered into the cytoplasm of infected cells, interacts directly with signalling proteins involved in inductive cytokine expression. The repressive activity of YopJ on the expression of inflammatory mediators may account for the lack of an inflammatory host response observed in experimental yersiniosis. YopJ-like activity may also be a common feature of commensal bacteria that, like Yersinia, do not provoke a host inflammatory response.

Amino Acid Sequence↗
PubMed1998

How to select patients suitable for transurethral microwave thermotherapy: a systematic evaluation of potentially predictive variables.

OBJECTIVE: To identify clinical variables useful in predicting outcome after transurethral microwave thermotherapy (TUMT) of the prostate with Prostasoft v. 2.0. PATIENTS AND METHODS: Thirty-eight men with symptomatic benign prostatic hyperplasia (BPH) were treated with TUMT using the Prostatron device with the low-energy (v. 2.0) software. Before and 6 months after treatment symptoms were evaluated using the Madsen-Iversen (M-I) symptom score, a clinical examination and suprapubic pressure-flow measurement, free urinary peak flow rate (Qmax) and determination of post-void residual urine volume (PVR). Bladder outlet obstruction was assessed from urodynamic pressure-flow studies using the classification of Abrams and Griffiths, the obstruction grading of Schäfer, and calculation of other published factors, e.g. the urethral resistance, an obstruction index and the detrusor adjusted mean passive urethral resistance factor (DAMPF). Categories of M-I score (total, irritative and obstructive), PVR and Qmax were investigated to determine whether any could predict the outcome after low-energy TUMT. The values after treatment and changes in Qmax, M-I score and PVR were used as efficacy variables. RESULTS: Variables describing infravesical obstruction had predictive characteristics that may be useful in selecting patients for TUMT v. 2.0 and significantly better results were obtained in patients with a low to moderate obstruction as graded using the DAMPF classification of obstruction. The results also indicated that patients with a high irritative M-I score or a Qmax of 7-14 mL/s were those who fared best after TUMT. CONCLUSIONS: Variables expressing the obstruction grade seem to be useful in predicting outcome after TUMT (v. 2.0). Patients with a high obstruction index are probably unsuitable for TUMT (v. 2.0).

Aged↗
PubMed1998

A cost-effectiveness analysis of transurethral resection of the prostate and transurethral microwave thermotherapy for treatment of benign prostatic hyperplasia: two-year follow-up.

OBJECTIVE: To compare costs of transurethral prostatic resection (TURP) and transurethral microwave thermotherapy (TUMT) for symptomatic benign prostatic hyperplasia (BPH) in a randomized, controlled trial. METHODS: In 70 BPH patients all costs were calculated for management, including complications and repeat treatment, during TURP or TUMT and 24-month follow-up. Clinical outcome was judged from Madsen-Iversen symptom score, peak urinary flow and residual urine. The effect of changes in some critical variables was assessed by sensitivity analysis. A cost-effectiveness analysis was carried out to compare the two methods. RESULTS: Symptom reduction after 2 years was 92% in the TURP group and 83% in the TUMT group. The total costs over 2 years were SEK 24,234 and 14,830 in the respective groups. Costs for retreatments were higher after TUMT, while complication costs were higher in the TURP group. TUMT costs depend on the investment for the equipment, including disposable probes, and the degree of its utilization. TUMT was more cost-effective than TURP in relieving BPH-related symptoms during the 2-year follow-up. CONCLUSIONS: Primary treatment costs were lower for TUMT than for TURP. Complication costs were higher in the trial's TURP arm, while retreatment costs were greater in the TUMT arm. TUMT costs depend on investment in and utilization of the equipment and reuse of treatment probes. TUMT was more cost-effective than TURP in the 2-year study period.

Aged↗
PubMed1998

Stone fragmentation pattern of piezoelectric shockwave lithotripsy in vitro.

Whole stones (N = 64; largest diameter 5-15 mm) were treated in vitro with piezoelectric shockwaves using the Edap LT-01 lithotripter with 2.5 Hz at either 100% or 54% power. The number of fragments larger than 2 mm was counted after every 30 seconds. The stones were defined as totally broken when all fragments were < 2 mm. Total fragmentation time was correlated with the energy level and the size of the stone. The number of large fragments did not correlate with the energy level but rather with the original size of the stone.

Humans↗
PubMed1997

Evaluation of novel control elements by construction of eukaryotic expression vectors.

A novel mammalian eukaryotic expression vector for the production of immunoglobulin heavy chain (IgH) genes has been designed. This expression vector contains the variable heavy chain (VH) promoter, the IgH intron enhancer (muE) and the IgH 3' enhancer (3'E). This construct, designated pTIF-1, was stably transfected into the myeloma cell line J558L. A fivefold increase in the expression level of a rearranged IgH gene was observed when using the pTIF-1 vector containing the 3'E compared to an expression vector lacking this enhancer. Interestingly, this positive effect on the expression level of the 3' enhancer appears to be position independent. The introduction of two recently identified Ig control elements, HS3 and HS4, to the vector cassette did not further elevate the expression level in the cell line tested. The pTIF-1 vector can be used for expression of any antibody specificity, using PCR amplification of the VDJ region of interest. Furthermore, the constant region can easily be exchanged, which further facilitates studies to dissect different effector functions of IgH constant genes.

Animals↗