Design, Synthesis and Antiparasitic Evaluation of Click Phospholipids

A library of seventeen novel ether phospholipid analogues, containing 5-membered heterocyclic rings (1,2,3-triazolyl, isoxazolyl, 1,3,4-oxadiazolyl and 1,2,4-oxadiazolyl) in the lipid portion were designed and synthesized aiming to identify optimised miltefosine analogues. The compounds were evaluated for their in vitro antiparasitic activity against Leishmania infantum and Leishmania donovani intracellular amastigotes, against Trypanosoma brucei brucei and against different developmental stages of Trypanosoma cruzi. The nature of the substituents of the heterocyclic ring (tail) and the oligomethylene spacer between the head group and the heterocyclic ring was found to affect the activity and toxicity of these compounds leading to a significantly improved understanding of their structure-activity relationships. The early ADMET profile of the new derivatives did not reveal major liabilities for the potent compounds. The 1,2,3-triazole derivative 27 substituted by a decyl tail, an undecyl spacer and a choline head group exhibited broad spectrum antiparasitic activity. It possessed low micromolar activity against the intracellular amastigotes of two L. infantum strains and T. cruzi Y strain epimastigotes, intracellular amastigotes and trypomastigotes, while its cytotoxicity concentration (CC50) against THP-1 macrophages ranged between 50 and 100 μM. Altogether, our work paves the way for the development of improved ether phospholipid derivatives to control neglected tropical diseases.

Pentamidine enhances photosensitization of Acinetobacter baumannii using diode lasers with emission of light at wavelength of ʎ = 405 nm and ʎ = 635 nm

Antimicrobial photodynamic inactivation is currently one of the most promising trends in the modern bactericidal protocols. Under the conditions defined in our studies, we found that in vitro photosensitization of A. baumannii with 5-ALA as a precursor of protoporphyrin IX (photosensitizer) reduces the concentration of viable cells in planktonic cultures, and this process can be strongly enhanced by pentamidine. Diode lasers with the peak-power wavelength of ʎ = 405 nm (radiation intensity of 26 mW cm^-2) and ʎ = 635 nm (radiation intensity of 55 mW cm^-2) were used in this study. It was found that a blue laser light (energy fluence of 64 J cm^-2; no external photosensitizer) in the presence of pentamidine resulted in a reduction of CFU of 99.992 % compared to 99.97 % killing without pentamidine. When a red laser light was used in the experiments (energy fluence of 136 J cm^-2; no external photosensitizer), the mortality rate was 99.98 % in the presence of pentamidine compared to 99.93 % of those killed without the addition of this drug. The lethal effect with 5-ALA was achieved under blue light fluence of 16 J cm^-2 (in the presence of pentamidine) and 32 J cm^-2 (without pentamidine). In the case of laser light of 635 nm, the lethal effect with 5-ALA was attained with energy fluence of 51 J cm^-2 (with pentamidine) and 102 J cm^-2 (without pentamidine). The possible roles of pentamidine in enhancing photodynamic inactivation of A. baumannii have been discussed.

Clinical pharmacokinetics of inhaled antimicrobials

Administration of inhaled antimicrobials affords the ability to achieve targeted drug delivery into the respiratory tract, rapid entry into the systemic circulation, high bioavailability and minimal metabolism. These unique pharmacokinetic characteristics make inhaled antimicrobial delivery attractive for the treatment of many pulmonary diseases. This review examines recent pharmacokinetic trials with inhaled antibacterials, antivirals and antifungals, with an emphasis on the clinical implications of these studies. The majority of these studies revealed evidence of high antimicrobial concentrations in the airway with limited systemic exposure, thereby reducing the risk of toxicity. Sputum pharmacokinetics varied widely, which makes it challenging to interpret the result of sputum pharmacokinetic studies. Many no vel inhaled antimicrobial therapies are currently under investigation that will require detailed pharmacokinetic studies, including combination inhaled antimicrobial therapies, inhaled nanoparticle formulations of several antibacterials, inhaled non-antimicrobial adjuvants, inhaled antiviral recombinant protein therapies and semi-synthetic inhaled antifungal agents. Additionally, the development of new inhaled delivery devices, particularly for mechanically ventilated patients, will result in a pressing need for additional pharmacokinetic studies to identify optimal dosing regimens.

Theoretical study on binding of S100B protein

S100B protein is one of the factors involved in the down-regulation of tumor suppressor protein p53, a transcription activator that signals for cycle arrest and apoptosis. As the inactivation of normal p53 functions is found in over half of human cancers, restoration of normal p53 functions through the destruction or prevention of S100B--p53 complexes represents a possible approach for the development of anti-cancer drugs. The aim of this work was to propose the S100B binding interface through an examination of the literature and use of molecular modeling (MM) techniques with AutoDock program and the AMBER force field. We propose two residues in the S100B binding pocket (Val56, Phe76) and two residues on the protein surface (Val52, Ala83) are essential for ligand binding. The data presented here indicate that interactions with these four residues are necessary for a reduction in the incidence of the S100B--p53 complex. Additionally, we have tried to explain a mechanism for the action of pentamidine, the best-known S100B ligand, and have proposed two S100B--pentamidine structures. The results presented here may be useful for the efficient design of new S100B ligands.

Effects of long-term aerosol pentamidine for Pneumocystis carinii prophylaxis on pulmonary function

OBJECTIVE

The purpose of the study was to evaluate the long-term effects of aerosolized pentamidine (AP) on the pulmonary function of HIV-positive individuals receiving AP for Pneumocystis carinii pneumonia (PCP) prophylaxis.

DESIGN

A retrospective analysis of serial pulmonary function tests (PFTs) performed on a cohort of HIV-positive patients who had received AP for >2 years.

METHODS

Of the 1,787 HIV-positive patients receiving AP prophylaxis in our database, 380 patients had been receiving AP for at least 24 months. Of these 380 patients, the PFTs at baseline and at 24 months after starting AP therapy were documented in 179. We compared the baseline PFTs of these 179 patients with results obtained 24 months later to evaluate if there was any change in pulmonary function parameters.

RESULTS

Baseline and 24-month PFT parameters (total lung capacity [TLC], FVC, residual volume [RV], FEV1, FEV1/FVC, maximum midexpiratory flow rate at 50% of vital capacity [MEF50], diffusion of carbon monoxide [DLCO]) were all within the normal ranges. However, AP therapy over 24 months was associated with a modest decline in lung volume parameters (TLC, FVC, RV), a slight reduction in flow rates (FEV1, FEV1/FVC, and MEF50), but no change in DLCO. The mean treatment duration was 23.8 months (range, 21 to 27 months).

CONCLUSIONS

Long-term AP therapy is associated with a mild combined restrictive and obstructive pulmonary defect. Since 24-month PFT parameters remained within the normal ranges, this level of decline is of unclear clinical significance. Overall, AP has good pulmonary tolerance when used up to 24 months for PCP prophylaxis in patients with normal baseline pulmonary function.

Pneumocystis carinii

Improved understanding of Pneumocystis carinii, in particular the widespread use of chemoprophylaxis, has resulted in a declining incidence of infection in patients infected with HIV since the late 1980s. Despite these advances, P. carinii pneumonia continues to represent an important cause of pulmonary disease in HIV-seropositive individuals who do not receive chemoprophylaxis or when breakthrough episodes occur. This article reviews the history, biology, clinical manifestations, prognostic markers, therapy, and chemoprophylaxis of P. carinii pneumonia in HIV-seropositive patients.

Crystal structure of gamma-oxapentamidine complexed with d(CGCGAATTCGCG)2. The effects of drug structural change on DNA minor-groove recognition

The crystal structure of the complex of gamma-oxapentamidine and the DNA dodecamer d(CGCGAATTCGCG)2 has been determined to a resolution of 0.22 nm and an R factor of 18.9%. The gamma-oxapentamidine ligand interacts with the dodecamer by classic minor groove binding via interactions within the A+T-rich region of the minor groove. A chain of solvent molecules lies along the mouth of the minor groove on the outside of the bound ligand. The structural details of the complex are discussed and compared with the closely analogous complex with pentamidine bound to the same dodecamer [Edwards, K. J., Jenkins, T. C. & Neidle, S. (1992) Biochemistry 31, 7104-7109]. The amidinium groups of the ligand do not hydrogen bond to bases, but are in close contact with O4' sugar ring atoms. This in part explains the reduced DNA binding affinity of this ligand compared to pentamidine.

Selective effects of pentamidine on cytosolic and granule-associated enzyme release from zymosan-activated human neutrophilic granulocytes

Therapeutic concentrations (0.3-1.5 mgL-1) of pentamidine isethionate, normally obtainable in-vivo after parenteral administration of the drug, did not affect the in-vitro activity of the enzymes lysozyme, beta-glucuronidase or myeloperoxidase released from zymosan-activated human neutrophilic granulocytes. At concentrations of 0.7, 1.1 and 1.5 mgL-1, activity of cytosolic enzymes lactate dehydrogenase and glucose-6-phosphate dehydrogenase were reduced relative to untreated cells (P < 0.001 and P < 0.01, respectively), but not in a dose-dependent fashion. Cell viability, as determined by dye-exclusion remained unaffected.

Crystal structure of d(CGCGAATTCGCG) complexed with propamidine, a short-chain homologue of the drug pentamidine

The crystal structure of the complex between propamidine and the self-complementary DNA dodecamer d(CGCGAATTCGCG) duplex has been determined to a resolution of 2.1 A and a R-factor of 17.4%. The propamidine binds to the DNA within the minor groove, with specific hydrogen-bonding interactions from the amidinium groups to the bases and sugar groups of the DNA, via a 4-base-pair binding site. A network of water molecules lies over the mouth of the minor groove. The structure provides a rationale for the superior DNA-binding properties of propamidine as compared to pentamidine [cf. Edwards, K. J., Jenkins, T. C. & Neidle, S. (1992) Biochemistry 31, 7104-7109]. This is seen to result from (i) decreased minor groove width at the binding site and (ii) reduced mobility of the bound propamidine molecule.