Role of Legionella pneumophila outer membrane vesicles in host-pathogen interaction

Legionella pneumophila is an opportunistic intracellular pathogen that inhabits artificial water systems and can be transmitted to human hosts by contaminated aerosols. Upon inhalation, it colonizes and grows inside the alveolar macrophages and causes Legionnaires' disease. To effectively control and manage Legionnaires' disease, a deep understanding of the host-pathogen interaction is crucial. Bacterial extracellular vesicles, particularly outer membrane vesicles (OMVs) have emerged as mediators of intercellular communication between bacteria and host cells. These OMVs carry a diverse cargo, including proteins, toxins, virulence factors, and nucleic acids. OMVs play a pivotal role in disease pathogenesis by helping bacteria in colonization, delivering virulence factors into host cells, and modulating host immune responses. This review highlights the role of OMVs in the context of host-pathogen interaction shedding light on the pathogenesis of L. pneumophila. Understanding the functions of OMVs and their cargo provides valuable insights into potential therapeutic targets and interventions for combating Legionnaires' disease.

Effect of castration on acetyl salicylic acid metabolism in rabbits

OBJECTIVES

The biotransformation of acetyl salicylic acid (ASA) differs within species, and gender differences have been documented and attributed to the effect of sex hormones. Castration remains a standard therapy for men with advanced prostate cancer. We studied the effect of castration on the metabolism of ASA in rabbits to find out whether the metabolism of ASA is adversely affected after castration.

METHODS

ASA in doses of 12.5, 25, and 50 mg/kg body weight was given intravenously to male and female prepubertal and adult rabbits, castrated adult male rabbits, and castrated male rabbits given testosterone (3 animals per group). Blood samples were collected at 0, 10, 30, 60, 120, and 180 minutes. The high-performance liquid chromatography method was used for the quantitation of salicylic acid (SA) in serum. The percentage of SA not metabolized was determined by comparing the serum level at 10 and 180 minutes for each group.

RESULTS

At a dose of 50 mg/kg in the adult rabbits, the mean +/- SD of SA in serum at 10 and 180 minutes was 146.54 +/- 29.54 microg/mL and 19.12 +/- 5.93 microg/mL for males, 158.25 +/- 6.70 microg/mL and 33.24 +/- 2.78 microg/mL for females, 229.72 +/- 47.85 microg/mL and 44.33 +/- 5.64 microg/mL for castrated male rabbits, and 170.88 +/- 12.03 microg/mL and 68.1 +/- 37.54 microg/mL for castrated male rabbits given testosterone, respectively. Also, at 180 minutes, the percentage of SA not metabolized in adult male rabbits was 12.82% +/- 1.65% compared with 21.04% +/- 2.14% (P <0.01) in adult females, 19.53% +/- 1.73% (P <0.01) in castrated adult male rabbits, and 38.95% +/- 19.48% (P <0.001) in castrated male rabbits given testosterone. At all doses of ASA, the serum SA concentration in male and female prepubertal rabbits was not significantly different for each time point.

CONCLUSIONS

These results indicate that male rabbits are able to metabolize ASA faster than are females. After castration, this ability is significantly decreased. If these experimental results are confirmed in humans, men who are undergoing hormonal manipulation for advanced prostate cancer and who require high-dose ASA, such as in the treatment of stroke or rheumatoid arthritis or as an antioxidant, may need lower doses to reduce the possible toxic effects of ASA.

Acute 4-aminopyridine seizures increase the regional cerebral blood flow in the thalamus and neocortex, but not in the entire allocortex of the mouse brain

Systemic injections of 4-aminopyridine precipitate epileptiform generalized seizures characterized mainly by shivering of the body, tail movements and tonic-clonic convulsions in rats and mice. However, only few details are known as concerns which brain regions are possibly affected and stimulated by the compound. The aim of the present study was to investigate the changes in regional cerebral blood flow in mice by using the lipophilic compound technetium-99m-hexamethyl-propyleneamineoxime (99mTc-HMPAO). Whilst the uptake of 99mTc-HMPAO was increased significantly in the neocortex and thalamus following the induction of acute 4-aminopyridine seizures, no such changes were observed in the allocortex of the mice. The increases in uptake in the neocortex and thalamus were completely prevented by carbamazepine (which abolished the symptoms of the seizure, too). The primary involvement of the neocortex and thalamus points to the importance of thalamocortical circuits in the precipitation and maintenance of experimental 4-aminopyridine convulsions.

Placental binding and transfer of radiopharmaceuticals: technetium-99m d, 1-HMPAO

Placental binding and transfer of 99mTc d, 1-hexamethyl propyleneamine oxime (HMPAO) was studied in vitro using human placenta and pregnant guinea pigs.

MATERIALS AND METHODS

Five pieces of human placenta were incubated in 50 ml Earle's solution containing 1.85 MBq 99mTc d, 1-HMPAO. The percent binding of the tracer to the placenta per 1 ml standard solution was calculated. Pregnant guinea pigs representing first, second and third trimesters were each injected with 74 MBq 99mTc d, 1-HMPAO through the jugular or femoral vein after sedation was induced with pentabarbital sodium. Static images were obtained, the guinea pigs were killed, and the fetuses were removed, weighed and imaged separately. The placentas, maternal and fetal brains, lungs, livers and kidneys also were removed, and the radioactivity was assayed in a dose calibrator for each organ. The percent radioactivity in each organ was calculated.

RESULTS

The binding of 99mTc d, 1-HMPAO to human placenta ranged from 2.95% +/- 1.5% to 5.82% +/- 0.3% per 1 ml standard solution. Both the binding of 99mTc d, 1-HMPAO to guinea pig placenta and its transfer to the fetus increased with gestational age. The percent binding ranged from 0.09% +/- 0.06% to 0.43% +/- 0.05%, whereas that of transfer to the fetus ranged from 0.05% +/- 0.03% to 2.19% +/- 0.64%. Of the amount transfered to the fetus, the order of accumulation in the fetal organs was liver > blood >> brain > lungs > kidneys > heart.

CONCLUSION

Technetium-99m d, 1-HMPAO binds to the placenta, and a minimal amount crosses the placental barrier and is transfered into the fetal circulation, mostly in the liver but a measurable amount is found in brain tissue.