Inhibition of 5-lipoxygenase as anti-inflammatory mode of action of Plectranthus zeylanicus Benth and chemical characterization of ingredients by a mass spectrometric approach

Ethnopharmacological relevance

The perennial herb Plectranthus zeylanicus Benth is extensively used in traditional medicine in Sri Lanka and South India for treating inflammatory conditions, but pharmacological features of Plectranthus zeylanicus are hardly explored in order to understand and rationalize its use in ethnomedicine. As 5-lipoxygenase (5-LO) is a key enzyme in inflammatory disorders such as asthma or atherosclerosis, we investigated 5-LO inhibition by Plectranthus zeylanicus extracts and analyzed relevant constituents.

Materials and methods

We applied cell-free and cell-based assays to investigate suppression of 5-LO activity. Cell viability, radical scavenger activities, and inhibition of reactive oxygen species formation (ROS) in neutrophils were analysed to exclude unspecific cytotoxic or antioxidant effects. Constituents of the extracts were characterized by bioassay-guided fractionation and by analysis using gas or liquid chromatography coupled to mass spectrometric (Orbitrap) analysis.

Results

Extracts of Plectranthus zeylanicus prepared with n-hexane or dichloromethane potently suppressed 5-LO activity in stimulated human neutrophils (IC₅₀=6.6 and 12 µg/ml, respectively) and inhibited isolated human recombinant 5-LO (IC₅₀=0.7 and 1.2 µg/ml, respectively). In contrast, no significant radical scavenging activity or suppression of ROS formation was observed, and neutrophil viability was unaffected. Besides ubiquitously occurring ingredients, coleone P, cinncassiol A and C, and callistric acid were identified as constituents in the most active fraction.

Conclusions

Together, potent inhibition of 5-LO activity, without concomitant anti-oxidant activity and cytotoxic effects, rationalizes the ethnopharmacological use of Plectranthus zeylanicus as anti-inflammatory remedy. Modern chromatographic/mass spectrometric analysis reveals discrete chemical structures of relevant constituents.     

Simplicity within complexity: Seasonality and predictability of hospital admissions in the province of Ontario 1988–2001, a population-based analysis

Background  

Seasonality is a common feature of communicable diseases. Less well understood is whether seasonal patterns occur for non-communicable diseases. The overall effect of seasonal fluctuations on hospital admissions has not been systematically evaluated.     

The use of radiolabeled and fluorescein-labeled antiglobulins in assays to predict platelet transfusion outcome

We used both radiolabeled and fluorescein-labeled antiglobulins in assays to detect antibodies against platelets in multiply transfused patients to determine the value of these tests in predicting the outcome of platelet transfusion in such patients. In 15 allosensitized patients, we studied 68 single-donor platelet transfusions, 43 (63%) of which had a poor outcome, defined as a corrected count increment (CCI), less than 10,000. The results obtained with either test were significantly correlated with the CCI following transfusion (p less than 0.001), but the assay using the radiolabeled antiglobulin had slightly better sensitivity, specificity, and predictive value. When the assays were used in combination, there was again significant correlation with the CCI of the transfusion, p less than 0.001. When both assays predicted failure of the transfusions, 31/31 (100%) such transfusions resulted in a CCI of less than 10,000, and when both assays predicted success of the transfusions, 14/15 (93%) such transfusions resulted in a CCI of greater than 10,000. Both assays are useful in predicting the outcome of the platelet transfusions; when the assay results were concordant, almost total predictive accuracy was obtained.     

Quantitation and properties of the active and latent plasminogen activator inhibitors in cultures of human endothelial cells

Human endothelial cells release two forms of a plasminogen activator- specific inhibitor: an active form that readily binds to and inhibits plasminogen activators and an inactive or latent form that has no anti- activator activity but which can be activated by denaturation. Latent and active forms of plasminogen activator-specific inhibitor were measured in cultures of human umbilical vein endothelial cells. Latent inhibitor was activated by treatment with 1% sodium dodecyl sulfate (SDS), and both forms were assayed by the 125I-fibrin plate method. After 16 hours, the conditioned medium contained 104.6 U/mL latent inhibitor activity and 2.6 U/mL active inhibitor. The level of each form in the culture medium increased with time although the activity associated with the latent form rose more rapidly: the ratio of latent to active inhibitor activity was 12 at four hours (10.3 U/mL v 0.86 U/mL) and reached 56 at 24 hours (155.3 U/mL v 2.80 U/mL). Intracellular inhibitor activity was associated with the active form only; no additional inhibitor activity was observed following SDS treatment of cell extracts. A decline in active inhibitor activity occurred during incubation at 37 degrees C with a 50% reduction in activity occurring in two hours. Treatment of conditioned medium with 10 U/mL thrombin also resulted in a loss of active inhibitor activity. The latent inhibitor, however, was not affected by either of these conditions. The inhibitor activity lost during incubation at 37 degrees C or thrombin treatment could be regenerated by SDS treatment, suggesting that the loss of the active inhibitor activity represented a conversion of this form to its latent counterpart. Thus, the concentration, stability, and regulation of these two forms of plasminogen activator inhibitor in human endothelial cell cultures differ significantly.     

Post-infection fatigue syndrome following Q fever

In 1989, 147 individuals in the West Midlands, UK, were infected with Q fever. Five years later, following anecdotal reports of fatigue, we used a questionnaire-based case-control study to determine the prevalence of chronic fatigue syndrome symptoms in this group. Replies from 71 patients were compared with those from 142 age- and sex-matched controls. Increased sweating (52.9% vs. 31.6%, p = 0.006), breathlessness (50.7% vs. 30.6%, p = 0.006), blurred vision (34.3% vs. 17.8%, p = 0.016) and undue tiredness (68.7% vs. 51.5%, p = 0.03) were found in controls compared to cases. These findings were similar to those in Australian abbatoir workers occupationally exposed to Q fever. CDC criteria for chronic fatigue syndrome were fulfilled by 42.3% of cases and 26% of controls. Using visual analogue scores, symptoms were more severe in cases than in controls. Our findings support the existence of a chronic fatigue state following acute Q fever, in a group of patients exposed just once to the organism, and in circumstances free of such confounding factors as lawsuits over compensation.      

Monitoring of the neonate undergoing MR imaging: technical considerations. Work in progress

Instrument monitoring of vital signs in neonates undergoing magnetic resonance (MR) imaging can be difficult because of the unique environmental restrictions imposed by the imager. The authors present their experience with monitoring more than 50 newborn infants and discuss the interaction of monitoring devices with the MR imager. Several MR-compatible monitors allow continuous evaluation of body temperature, heart rate, blood pressure, and auscultation of heart sounds and respiration in mechanically ventilated infants. Signal-to-noise (S/N) ratio measurements taken during imaging of the head of an infant with these monitors in place did not differ appreciably from the ratio obtained during imaging without monitors. Tip angles should be optimized to account for widely varying head size among neonates, since adverse monitoring effects are significantly compounded by improper tip angle adjustment.