Guanidiniocarbonylpyrrole-aryl derivatives: structure tuning for spectrophotometric recognition of specific DNA and RNA sequences and for antiproliferative activity

We present a systematic study of different guanidiniocarbonylpyrrole-aryl derivatives designed to interact with DNA or RNA both through intercalation of an aromatic moiety into the base stack of the nucleotide and through groove binding of a guanidiniocarbonylpyrrole cation. We varied 1) the size of the aromatic ring (benzene, naphthalene, pyrene and acridine), 2) the length and flexibility of the linker connecting the two binding groups, and 3) the total number of positive charges present at different pH values. The compounds and their interactions with DNA and RNA were studied by UV/Vis, fluorescence and CD spectroscopy. Antiproliferative activities against human tumour cell lines were also determined. Our studies show that efficient interaction with, for example, DNA requires a significantly large aromatic ring (pyrene) connected through a flexible linker to the pyrrole moiety. However, a positive charge, as in 12, is also needed. Compound 12 allows for base-pair-selective recognition of ds-DNA at physiological pH values. The antiproliferative activities of these compounds correlate with their binding affinities towards DNA, suggesting that their biological effects are most probably due to DNA binding.

A novel Respiratory Health Score (RHS) supports a role of acute lung damage and pig breed in the course of an Actinobacillus pleuropneumoniae infection

Background

Bacterial lung infections are a major cause of economic losses in the pig industry; they are responsible for approximately 50% of the antibiotics used in pigs and, therefore, also present an increasing concern to consumer protection agencies. In response to this changing market we investigated the feasibility of an old approach aimed at the breeding selection of more resistant pigs. As a first step in this direction we applied a new respiratory health score system to study the susceptibility of four different pig breeding lines (German Landrace, Piétrain, Hampshire, Large White) towards the respiratory tract pathogen Actinobacillus (A.) pleuropneumoniae.

Results

A controlled experimental aerosol infection with an A. pleuropneumoniae serotype 7 isolate was performed using 106 weaning pigs of defined breeding lines from the breeds German Landrace, Piétrain, Hamphire, and Large White. Pigs were clinically assessed on days 4 and 20 post infection following a novel scoring system, the Respiratory Health Score (RHS), which combines clinical, sonographic and radiographic examination results. The ranking on day 4 was significantly correlated with the ranking based on the pathomorphological Lung Lesion Score (LLS; Spearman Rank Correlation Coefficient of 0.86 [p < 0.0001]). Based on their RHS pigs were assigned to the different quartiles independent of the breeding line. The RHS-based rankings of pigs on day 4 and on day 20 were highly correlated (Spearman Rank Correlation Coefficient of 0.82 [p < 0.0001]) independent of the breeding line. Pigs of the Hampshire line were predominantly found in the lowest scoring quartile (47.6%) and absent in the highest scoring quartile. In contrast, pigs of the German Landrace and Piétrain breeding lines were predominantly found in the highest scoring quartile (32.3% and 35.7%, respectively).

Conclusion

These results demonstrate that the RHS obtained from live pigs shows a highly significant correlation to the lung lesion score considered as a "gold standard". The correlation of the ranking at days 4 and 20 post infection implies that the course of disease is highly dependent on the acute lung damage. The different severity of signs among the tested pig breeding lines clearly suggests a genetic difference in the susceptibility of pigs to A. pleuropneumoniae infection.

[Comparison of the diagnostic significance of clinical, radiographic and ultrasonographic results after an experimental aerosol infection of pigs with Actinobacillus pleuropneumoniae]

Scoring schemes for clinical, ultrasonographic and radiographic findings in pigs were developed based upon a standardized animal model for Actinobacillus pleuropneumoniae infection.The results of these methods were compared to each other as well as with the corresponding pathomorphological findings during necropsy. Altogether 69 pigs of different breeding lines (Hampshire, Pietrain and German Landrace were examined. Positive correlations were found between the results of all three methods as well as with the necropsy scores (p <0.0001). Different pathomorphological findings were detected either by radiographic or by ultrasonographic examination dependent upon the type of lung tissue alterations: Alterations of the pleura as well as sequestration of lung tissue on the lung surface could be clearly identified during the ultrasonographic examination while deep tissue alterations with no contact to the lung surface could be detected reliably by radiographic examination. Both methods complement each other, and the application of a combined ultrasonographic and radiographic examination of the thorax allows a comprehensive inspection of the lung condition. Particularly during the acute phase of the disease the extent of lung tissue damage can be estimated more precisely than by clinical examination alone.

[Functional genome analysis investigating resistance to respiratory tract disease in a porcine Actinobacillus pleuropneumoniae infection model]

Here we present the work of the multidisciplinary consortium IRAS (Development of Genetic Markers for Immune Defence and Resistance in the Porcine Respiratory Tract) which includes different commercial and research institutions and was formed as a response to the call "Functional Genome Analysis in the Animal Organism (FUGATO)" by the German Ministry of Education and Research. IRAS started work in the fall of 2005 and--using the experimental infection of pigs with Actinobacillus pleuropneumoniae as model pathogen--aims at i) characterizing the course of infection by clinical as well as advanced laboratory tools (phenotypic-genetic approach) and ii) defining the diversity and distribution of allels known to be associated with immune defence in mouse and man (homolog-genetic approach). The intention is to identify genetic markers for increased resistance to infection thereby providing additional tools for the estimation of breeding values to the pig industry.

Synthesis and self-association properties of flexible guanidiniocarbonylpyrrole-carboxylate zwitterions in DMSO: intra- versus intermolecular ion pairing

We have synthesized a new class of flexible zwitterions 6a-e, in which a carboxylate is linked via an alkyl chain with variable length (one to five methylene groups) to a guanidiniocarbonylpyrrole cation. The self-association properties of these zwitterions were determined by NMR dilution studies in DMSO and by ESI-MS experiments. The stability and hence also the size of the aggregates formed via self-assembly is critically dependent on the length and therefore flexibility of the spacer. Whereas the smallest zwitterion 6a forms large aggregates already at low concentrations, the more flexible zwitterions only form small oligomers (6b) or dimers (6c-e) at much larger concentrations. The differences between the five zwitterions can be explained based on the different extent of intramolecular ion pairing within the monomers. Any intramolecular ion pairing, which becomes possible with increasing linker length, stabilizes the monomer and therefore destabilizes any oligomer.

Amplified fragment length polymorphism of Streptococcus suis strains correlates with their profile of virulence-associated genes and clinical background

Amplified fragment length polymorphism (AFLP) typing was applied to 116 Streptococcus suis isolates with different clinical backgrounds (invasive/pneumonia/carrier/human) and with known profiles of virulence-associated genes (cps1, -2, -7 and -9, as well as mrp, epf and sly). A dendrogram was generated that allowed identification of two clusters (A and C) with different subclusters (A1, A2, C1 and C2) and two heterogeneous groups of strains (B and D). For comparison, three strains from each AFLP subcluster and group were subjected to multilocus sequence typing (MLST) analysis. The closest relationship and lowest diversity were found for patterns clustering within AFLP subcluster A1, which corresponded with sequence type (ST) complex 1. Strains within subcluster A1 were mainly invasive cps1 and mrp+ epf+ (or epf*) sly+ cps2+ strains of porcine or human origin. A new finding of this study was the clustering of invasive mrp* cps9 isolates within subcluster A2. MLST analysis suggested that A2 correlates with a single ST complex (ST87). In contrast to A1 and A2, subclusters C1 and C2 contained mainly pneumonia isolates of genotype cps7 or cps2 and epf- sly-. In conclusion, this study demonstrates that AFLP allows identification of clusters of S. suis strains with clinical relevance.

Prevalence of Streptococcus suis genotypes in wild boars of Northwestern Germany

Invasive serotype 2 (cps2+) strains of Streptococcus suis cause meningitis in pigs and humans. Four case reports of S. suis meningitis in hunters suggest transmission of S. suis through the butchering of wild boars. Therefore, the objective of this study was to investigate the prevalence of potentially human-pathogenic S. suis strains in wild boars. S. suis was isolated from 92% of all tested tonsils (n=200) from wild boars. A total of 244 S. suis isolates were genotyped using PCR assays for the detection of serotype-specific genes, the hemolysin gene sly, and the virulence-associated genes mrp and epf. The prevalence of the cps2+ genotype among strains from wild boars was comparable to that of control strains from domestic pig carriers. Ninety-five percent of the cps2+ wild boar strains were positive for mrp, sly, and epf*, the large variant of epf. Interestingly, epf* was significantly more frequently detected in cps2+ strains from wild boars than in those from domestic pigs; epf* is also typically found in European S. suis isolates from humans, including a meningitis isolate from a German hunter. These results suggest that at least 10% of wild boars in Northwestern Germany carry S. suis strains that are potentially virulent in humans. Additional amplified fragment length polymorphism analysis supported this hypothesis, since homogeneous clustering of the epf* mrp+ sly+ cps2+ strains from wild boars with invasive human and porcine strains was observed.

Virulence-associated gene profiling of Streptococcus suis isolates by PCR

Definition of virulent Streptococcus suis strains is controversial. One successful approach for identification of virulent European strains is differentiation of capsular serotypes (or the corresponding cps types) and subsequent detection of virulence-associated factors, namely the extracellular factor (EF, epf), the muramidase-released protein (MRP, mrp) and the hemolysin suilysin (SLY, sly). In this work we present a novel multiplex PCR (MP-PCR) and an mrp variant PCR for identification and characterization of virulent S. suis strains. These new methods were used to identify association of disease with particular profiles of virulence-associated genes. The MP-PCR allowed identification of S. suis through detection of the housekeeping gene gdh, differentiation of four cps types (1, 2, 7 and 9), and detection of epf, mrp, sly and arcA (arginine deiminase from S. suis). Furthermore, this study describes the first PCR assay for differentiation of at least six mrp variants. Expression of the corresponding size variants of MRP was shown for four of the six mrp variants, but was undetectable for the two larger mrp variants in the particular strains investigated. The results of this study suggest that cps7 strains are associated with pneumonia and that variation of mrp is very pronounced among these strains. Gene profiles of invasive, pneumonia and carrier S. suis isolates by combination of PCR assays allowed differentiation of 24 different genotypes among cps1, 2, 7 and 9 strains. Forty-five percent of the invasive S. suis diseases investigated in this study were caused by only two of these genotypes, namely cps2/mrp+/epf+/sly+ and cps9/mrp(*)/epf-/sly+. Thus, this study demonstrates for the first time a uniform profile of the particular virulence-associated genes for the vast majority of the investigated invasive cps9 strains.

Ion pair driven self-assembly of a flexible bis-zwitterion in polar solution: formation of discrete nanometer-sized cyclic dimers

The self-complementary flexible bis-zwitterion 1 forms discrete nanometer-sized cyclic dimers via ion pair driven self-assembly even in polar solvents. The existence of such dimers was confirmed by DOSY NMR, FAB-MS, and scattering experiments (DLS, SANS) which all indicate the concentration-dependent formation of cyclic dimers with a hydrodynamic radius of rH approximately 2.5 nm in solution.

[Eradication of paratuberculosis in dairy herds: determination of the initial herd prevalence and modelling of prevalence development]

A prerequisite for the success of any eradication programme is the accurate determination of the initial herd prevalence as well as a herd-specific prediction of prevalence development. This prerequisite is not currently given for the eradication of paratuberculosis in infected herds. In the work presented a method to predict the initial paratuberculosis prevalence in infected herds is presented; it is based on the formation of two groups (ELISA-positive and negative) and the determination of generally applicable factors (positive predictive value [ppvn] of the ELISA and sensitivity of fecal culture in the ELISA-negative group [senF]). The ppvn of the ELISA was determined to be 0.6 based on the cultural examination of the ileocaecal lymph node of 64 ELISA-positive animals; the value for senF was set to be 0.64 based on the cultural examination of feces and ileocaecal lymph nodes of 40 ELISA-negative animals. To calculate the initial herd prevalence the number of animals in each of the groups was multiplied with the ppvn of the ELISA or with the reciprocal value of senF (1.5). The values were added and divided by the size of the herd. The practicability of this model was examined on nine herds with a total of 708 animals. The development of herd prevalence was modelled based on the examination scheme given in the paratuberculosis control programme of the "Niedersächsische Tierseuchenkasse" (local board for infectious disease control in food animals in the state of Lower Saxony, Germany). For the calculation a yearly turnover-rate of 33% with restocking from within the herd and a possibility of paratuberculosis diagnosis only in animals two years and older were assumed. The development of herd prevalence is exemplarily presented for four herds with different initial prevalences.

Chalcone derivatives antagonize interactions between the human oncoprotein MDM2 and p53

The oncoprotein MDM2 inhibits the tumor suppressor protein p53 by binding to the p53 transactivation domain. The p53 gene is inactivated in many human tumors either by mutations or by binding to oncogenic proteins. In some tumors, such as soft tissue sarcomas, overexpression of MDM2 inactivates an otherwise intact p53, disabling the genome integrity checkpoint and allowing cell cycle progression of defective cells. Disruption of the MDM2/p53 interaction leads to increased p53 levels and restored p53 transcriptional activity, indicating restoration of the genome integrity check and therapeutic potential for MDM2/p53 binding antagonists. Here, we show by multidimensional NMR spectroscopy that chalcones (1,3-diphenyl-2-propen-1-ones) are MDM2 inhibitors that bind to a subsite of the p53 binding cleft of human MDM2. Biochemical experiments showed that these compounds can disrupt the MDM2/p53 protein complex, releasing p53 from both the p53/MDM2 and DNA-bound p53/MDM2 complexes. These results thus offer a starting basis for structure-based drug design of cancer therapeutics.

Pituitary androgen receptors and the resistance of long-term castrated rams to the androgenic control of luteinizing hormone (LH) secretion

Luteinizing hormone (LH) responses of short-term (24 h) and long-term (6 mo) castrated rams to testosterone replacement therapy were investigated. Testosterone filled Silastic capsules which maintained physiological concentrations of testosterone in blood (approximately 3.2 ng/ml) prevented the post-castration rise in serum LH of short-term castrated rams but failed to effectively reduce the established elevated serum LH levels in long-term castrated rams. The LH response to exogenous LHRH was also suppressed in the short-term castrated rams, whereas the response was increased in direct proportion to basal LH levels in long-term castrates. The possibility that a change in pituitary androgen receptors may explain the resistance of long-term castrates to testosterone feedback was examined. For this purpose, a cytosolic androgen receptor binding assay was developed using tritiated methyltrienolone (R 1881) as the labeled ligand and dextran-charcoal to separate free and protein-bound steroid. Stable, high affinity (Kd = 0.3-1.5 nM), saturable binding of R 1881 was demonstrated in pituitary cytosol from both intact and castrate rams. Relative binding specificities in intact rams, however, suggested partial binding to a progestin-binding component, whereas receptor binding in long-term castrates was androgen specific. For this reason, androgen receptor binding was studied after addition of triamcinolone acetonide to occupy apparent progestin binding sites. We observed no differences in either androgen receptor concentration (4.10 +/- 0.70 versus 3.23 +/- 0.45 fmol/mg protein; Mean +/- SD) nor ligand affinity at 0 degrees C (Kd = 0.66 +/- 0.34 versus 0.40 +/- 0.08 nM) in 6 mo compared to 24-h castrate rams. These data indicate that the inability of androgens to suppress gonadotropin secretion in long-term castrate rams is unlikely to be related to specific changes in pituitary cytosol androgen receptors.