The β-Hemolysin and Intracellular Survival of Streptococcus agalactiae in Human Macrophages

S. agalactiae (group B streptococci, GBS) is a major microbial pathogen in human neonates and causes invasive infections in pregnant women and immunocompromised individuals. The S. agalactiae β-hemolysin is regarded as an important virulence factor for the development of invasive disease. To examine the role of β-hemolysin in the interaction with professional phagocytes, the THP-1 monocytic cell line and human granulocytes were infected with a serotype Ia S. agalactiae wild type strain and its isogenic nonhemolytic mutant. We could show that the nonhemolytic mutants were able to survive in significantly higher numbers than the hemolytic wild type strain, in THP-1 macrophage-like cells and in assays with human granulocytes. Intracellular bacterial multiplication, however, could not be observed. The hemolytic wild type strain stimulated a significantly higher release of Tumor Necrosis Factor-α than the nonhemolytic mutant in THP-1 cells, while similar levels of the chemokine Interleukin-8 were induced. In order to investigate bacterial mediators of IL-8 release in this setting, purified cell wall preparations from both strains were tested and found to exert a potent proinflammatory stimulus on THP-1 cells. In conclusion, our results indicate that the β-hemolysin has a strong influence on the intracellular survival of S. agalactiae and that a tightly controlled regulation of β-hemolysin expression is required for the successful establishment of S. agalactiae in different host niches.     

Significance of myocardial eicosanoid production

Summary The precise role of eicosanoids in the development of myocardial injury during ischemia and reperfusion is still a matter of debate. Enhanced local production of these bioactive compounds appears to be a common response to tissue injury. Most likely, the cardiac tissue has the capacity to generate prostaglandins, thromboxanes as well as leukotrienes. Prostacyclin (PGI,) is the major eicosanoid produced by the jeopardized myocardium. In addition, at sites of tissue injury activation of platelets and infiltrating leukocytes results in the formation of considerable amounts of thromboxanes and leukotrienes. The production of eicosanoids requires prior release of arachidonic acid (AA) from phospholipids. Both ischemia and reperfusion are associated with a rise in the tissue level of AA. The absence of a proportional relationship between the tissue level of AA and the amounts of PGI, produced suggests that the sites of AA accumulation and PGI₂ formation are different. It is conceivable that AA accumulation is mainly confined to myocytes, whereas the capacity to synthesize PGI, mainly resides in vascular cells. Both beneficial and detrimental effects of eicosanoids on cardiac tissue have been described. Prostaglandins act as vasodilators. Besides, some of the prostaglandins, especially PGI,, are thought to possess cyto-protective properties. Thromboxanes and leukotrienes may impede blood supply by increasing smooth muscle tone. Besides, leukotrienes augment vascular permeability. Experimental studies, designed to evaluate the effect of pharmacological agents, like PGI₂-analogues and lipoxygenase and cyclo-oxygenase inhibitors, indicat that eicosanoids influence the outcome of myocardial injury. However, the delineation of the physiological significance of the locally produced eicosanoids is complicated by such factors as the wide variety of AA derivatives produced and the dose-dependency of their effects.     

Molecular characterization of a patient with del(1)(q23–q25)

Summary We report a patient (S.T.) with multiple congenital anomalies and developmental delay associated with an interstitial deletion of 1q23–1q25. Molecular analysis of the deletion was performed using DNA markers that map to 1q. Five DNA markers, MLAJ-1 (D1S61), CRI-L1054 (D1S42), HBI40 (D1S66), OS-6 (D1S75), and BH516 (D1S110), were demonstrated to be deleted. Informative polymorphisms demonstrated this to be a de novo deletion of the maternally derived chromosome. Deletion status was determined using restriction fragment length polymorphism (RFLP) analysis supplemented with densitometry in the experiments where RFLP analysis was not fully informative. Deletions were confirmed by Southern analysis using genomic DNA from a somatic cell hybrid retaining the del(1)(q23–q25) chromosome that was constructed from patient S.T. Flow karyotyping confirmed the deletion and estimated that the deletion encompassed 11,000–16,000 kb. The clinical and cytogenetic characteristics of S.T. are compared with those of ten previously described patients with monosomy 1q21–1q25.     

Hyperpolarization response of an identified neuron of Planobarius corneus mollusks to several cholinomimetic substances]

Two kinds of responses to cholinomimetics were found on the identified neuron (P-2) of Planorbarius corneus pedal ganglion using microelectrode technique. Nicotinomimetics caused depolization whereas some muscarinomimetics caused hyperpolarization of the neuron membrane. Acetylcholine usually depolarized the neuron membrane but after the blockade of nicotinic receptors with tubocurarine one can reveal a hyperpolarizing action of acetylcholine. These findings suggest that two kinds of receptors exist on the P-2 neuron membrane and these receptors differ both in pharmacological characteristics and in ionic permeability changes they control.     

The role of Brunner's glands in the mucosal protection of the proximal part of duodenum

In the course of a prospective study authors examined the role of the hyperplasia of Brunner's glands in the mucosal protection of proximal part of duodenum in patients with peptic ulcer, chronic pancreatitis and chronic renal insufficiency. Their method for this study was the histological examination of the endoscopic biopsy specimens. The hyperplasia of Brunner's glands occurs with significant frequency in all the three examined groups of patients, while we found it less frequently in the controls. Hyperplasia of Brunner's glands is one of the protective mechanisms of the organism, which serves the protection of the duodenal mucosa between the pyloric ring and the papilla of Vater, against the damaging effect of the hydrochloric acid.     

Proteus-typing by proticin production and susceptibility

A Proteus-typing method based on proticin production and proticin susceptibility (c.f. Senior, 1977) has been modified to increase its sensitivity. Proticins were prepared in fluid medium and applied to agar-plates shortly before seeding the plates with indicator bacteria. A given 10 proticin producer strains, which are responsible for the susceptibility patterns of the indicator-bacteria (S-types), form the foundation for this typing method. Using this producer-set an indicator-set (28 strains) was selected which was suitable for the typing of strains with different proticin activities (P-types). Standardization of the temperature for proticin production proved to be necessary. The degree of similarity between proticins was further elaborated by testing all indicator strains for susceptibility to proticin titrations. In the group of 148 clinical Proteus-isolates (four species) used for the development of the typing system 28 S-types and 34 P-types were observed. By combining the S- and P-type parameters 86 S-P-types were obtained for the 4 species combined. Seven strains were not typable. A separate group of 100 clinical Proteus-isolates was tested in order to prove the usefulness of the method. 39 new S-P-types were found. Repeated isolations from the same patients yielded the same patterns. Proteus S-P-typing is a useful method for the typing of Proteux vulgaris and Proteus mirabilis, but proves inadequate for the typing of Proteus rettgeri and Proteus morganii.     

Abiotic factors driving cyanobacterial biomass and composition under perennial bloom conditions in tropical latitudes

Hydrobiologia - While warming and eutrophication have increased the frequency and magnitude of harmful cyanobacterial blooms globally, the scenario for many eutrophic tropical freshwaters is a...     

Macrophage Specific Caspase-1/11 Deficiency Protects against Cholesterol Crystallization and Hepatic Inflammation in Hyperlipidemic Mice

Background & Aims

While non-alcoholic steatohepatitis (NASH) is characterized by hepatic steatosis combined with inflammation, the mechanisms triggering hepatic inflammation are unknown. In Ldlr^-/- mice, we have previously shown that lysosomal cholesterol accumulation in Kupffer cells (KCs) correlates with hepatic inflammation and cholesterol crystallization. Previously, cholesterol crystals have been shown to induce the activation of inflammasomes. Inflammasomes are protein complexes that induce the processing and release of pro-inflammatory cytokines IL-1b and IL-18 via caspase-1 activation. Whereas caspase-1 activation is independent of caspase-11 in the canonical pathway of inflammasome activation, caspase-11 was found to trigger caspase-1-dependent IL-1b and IL-18 in response to non-canonical inflammasome activators. So far, it has not been investigated whether inflammasome activation stimulates the formation of cholesterol crystals. We hypothesized that inflammasome activation in KCs stimulates cholesterol crystallization, thereby leading to hepatic inflammation.

Methods

Ldlr ^-/- mice were transplanted (tp) with wild-type (Wt) or caspase-1/11^-/- (dKO) bone marrow and fed either regular chow or a high-fat, high-cholesterol (HFC) diet for 12 weeks. In vitro, bone marrow derived macrophages (BMDM) from wt or caspase-1/11^-/- mice were incubated with oxLDL for 24h and autophagy was assessed.

Results

In line with our hypothesis, caspase-1/11^-/--tp mice had less severe hepatic inflammation than Wt-tp animals, as evident from liver histology and gene expression analysis in isolated KCs. Mechanistically, KCs from caspase-1/11^-/--tp mice showed less cholesterol crystals, enhanced cholesterol efflux and increased autophagy. In wt BMDM, oxLDL incubation led to disturbed autophagy activity whereas BMDM from caspase-1/11^-/- mice had normal autophagy activity.

Conclusion

Altogether, these data suggest a vicious cycle whereby disturbed autophagy and decreased cholesterol efflux leads to newly formed cholesterol crystals and thereby maintain hepatic inflammation during NASH by further activating the inflammasome.