Identification of potential inhibitors against FemX of Staphylococcus aureus: A hierarchial in-silico drug repurposing approach.

Staphylococcus aureus causes a wide range of common diseases in both community-acquired and hospital-acquired environments. The treatment becomes challenging due to the emergence of multi-drug resistant strains such as Methicillin-Resistant Staphylococcus aureus (MRSA). This study aims to find some drugs that can be used in repurposing. Virtual screening has been performed against S. aureus FemX using 1,918 FDA-approved drugs, which provides the top 10 drugs with good binding affinity. These drugs are re-docked to understand their interaction patterns with FemX. Docking study shows a high score for three drugs, Lumacaftor, Dihydroergocornine and Olaparib, and they are selected for molecular dynamics and quantum mechanical analysis. Molecular dynamics calculation shows that drug-FemX forms a stable structure compared to apo-FemX. Besides, the free energy landscape reveals that drug-protein complexes possess a single global minimum indicating their thermodynamic stability. MM/GBSA calculations show that Lumacaftor, Dihydroergocornine and Olaparib have the binding free energy of -30.03, -19.22 and -16.54 kcal/mol, respectively. The analysis of the wavefunctions from quantum chemical calculations reveals the presence of non-covalent interactions between drug and receptor, dominated by aromatic π-π interactions. The drug-receptor interaction energy estimated from quantum mechanical methods suggests an important role of dispersion interactions in stabilizing the drug molecules with FemX. The hierarchy of computational methods of increasing accuracy employed in this work finds Lumacaftor to be the most potent inhibitor against FemX.

Identification and human pharmacokinetics of dihydroergotoxine metabolites in man: preliminary results.

Dihydroergotoxine is a mixture of semi-synthetic ergot alkaloids mainly used for age-related cognitive impairment. In this study, dihydroergotoxine (30 microM) was added to incubates of rat and bovine liver microsomes, and the resulting major metabolites were identified as hydroxy-dihydroergocornine, hydroxy-dihydroergocryptine and hydroxy-dihydroergocristine on the basis of molecular mass measurements, determined with a time-of-flight mass spectrometer. The relevance of these to humans was then investigated by simultaneously monitoring dihydroergotoxine and its hydroxy-metabolites in human plasma by LC-MS/MS after oral dosing of dihydroergotoxine mesylate (27 mg) to a healthy volunteer (male, age 45, height 1.93 m, weight 103 kg). In this preliminary approach, the peaks (C(max)) of dihydroergocornine, dihydroergocryptine and dihydroergocristine were about 0.04 microg/l. The peaks (C(max)) of their hydroxy-metabolites were 0.98, 0.53 and 0.30 microg/l, respectively. In conclusion, in this preliminary approach it was found that hydroxy-dihydroergocornine, hydroxy-dihydroergocryptine and hydroxy-dihydroergocristine were one order of magnitude higher in concentration than their parents in human plasma.

Contractile responses to ergotamine and dihydroergotamine in the perfused middle cerebral artery of rat.

The vasomotor effects of ergotamine and dihydroergotamine (DHE) on the middle cerebral artery (MCA) of rats were studied using the pressurised arteriography method and in vitro myographs. MCAs from Sprague-Dawley rats were mounted on two glass micropipettes using the arteriograph, pressurised to 85 mmHg and luminally perfused. All vessels used attained spontaneous contractile tone (34.9+/-1.8% of resting tone) and responded to luminal adenosine triphosphate (ATP) with dilatation (24.1+/-4.0%), which showed functioning endothelium. Luminally added ergotamine or DHE induced maximal contractions of 16.8+8% and 22.4+/-0.9%, respectively, compared to the resting diameter, with a pEC(50) of 8.7+/-0.1 for ergotamine and 9.0+/-0.1 for DHE. Abluminal application of ergotamine and DHE also caused concentration-dependent contractions of the perfused MCA by 21.4+/-2.1% and 23.1+/-7.0%, respectively, with pEC(50) values of 7.6+/-0.2 for ergotamine and 8.4+/-0.5 for DHE. The responses were blocked by the 5-HT(2A) receptor antagonist ketanserin (concentration 10(-12) to 10(-5) M) and partially with the 5-HT(1B) receptor antagonist BRL-11557PM-B. The 5-HT(1D) receptor antagonist SB-224289-A had no significant effect. Using a myograph technique, isolated ring segments of the MCA with intact endothelium were mounted on two metal wires. Neither agonist caused relaxation of resting vessels, however, they both responded by weak contractile responses (26+/-3% of submaximal contractile capacity relative to 60 mM potassium). The contractions were typically slow in on and off set (about 30-60 min). The long duration of ergots should be investigated further in an attempt to design drugs with less recurrence.

Placebo adverse events in headache trials: headache as an adverse event of placebo.

We analysed the adverse events of placebo in acute and preventive randomized, double-blind, placebo-controlled studies for migraine treatment. Fifty-seven trials (oral triptans, non-steroidal anti-inflammatory drugs, nasal ergot alkaloids and preventive agents) were included. From 10 to 30% of subjects reported adverse events after placebo. Most common were features associated with a migraine attack, such as nausea, phono- and photophobia. Other frequent complaints resembled those of the active drug (e.g. chest pressure in triptan trials). A third group of adverse events appeared to be coincidental (e.g. sleep disturbance). Adverse events following placebo are probably related to the drug under study and the symptomatology of migraine; some have no obvious explanation.