Amphotericin B: How Much Is Enough?

The total curative dose of amphotericin B for any given fungal infection or specific patient is not precisely known. Prior to the availability of lipid formulations of amphotericin B (LFAB), dosing of amphotericin B was dictated by its associated toxicity. The unique pharmacokinetic features of each LFAB have led to differences in their recommended doses. Most published data have evaluated doses of 3–5 mg/kg/day, although niches exist for both higher and lower doses. Low-dose LFAB allows for intravenous broad-spectrum antifungal coverage without drug-drug interactions and with reduced toxicity. High-dose LFAB demonstrates increased fungal clearance in animal models, although this has not translated to improved clinical outcomes for most invasive fungal infections. Although available data do not demonstrate significant benefit associated with high-dose therapy, for liposomal amphotericin B, the data also demonstrate no significant harm. As such, the use of high-dose liposomal amphotericin B for salvage therapy may be a consideration.     

Conformational Analysis of Amphotericin B — Cholesterol Channel Complex

A molecular model of ionic channel formed by flexible molecules of amphotericin B and cholesterol is proposed. Complexes with axial symmetry from 5 to 11 were simulated. In contrast to the model of the channel formed from rigid molecules, flexible molecules form a tightly packed structure consolidated by both dispersive forces and intermolecular hydrogen bonds. Contributions of a lactone ring, polar heads, cholesterol and lipid environments to the global energy of the complex formation are discussed. Among the complexes capable of ionic transport, that of axial symmetry eight is preferable. Two types of complexes, differing by the number of intramolecular hydrogen bonds, are shown to be possible. Received: 25 April 1997/Revised: 20 November 1997     

Coccidioidal Meningitis—Intrathecal Treatment with Hyperbaric Amphotericin B

The localization of coccidioidal meningitis in the basilar regions, with resultant hydrocephalus and uniformly fatal outcome, has necessitated intrathecal injection of amphotericin B via cisternal puncture or subcutaneous ventricular reservoir for successful therapy. A simpler form of treatment is described here, whereby amphotericin B diluted in 10 percent glucose solution is injected via lumbar puncture, and delivered to the base of the skull by tilting the patient to a head-down position. A simultaneously performed hyperbaric cisternogram with ¹³¹I-serum albumin has demonstrated satisfactory migration of the injected bolus to the occiput. This method of administration resulted in successful suppressive treatment of one patient, including two years of follow-up without serious sequelae or relapse.     

Amphotericin B binds to amyloid fibrils and delays their formation: a therapeutic mechanism?

The membrane-active antifungal agent amphotericin B (AmB) is one of the few agents shown to slow the course of prion diseases in animals. Congo Red and other small molecules have been reported to directly inhibit amyloidogenesis in both prion and Alzheimer peptide model systems via specific binding. We propose that it is possible that AmB may act similarly to physically prevent conversion of the largely alpha-helical prion protein (PrP) to the pathological beta-sheet aggregate protease-resistant isoform (PrP(res)) in prion disease and by analogy prevent fibrillization in amyloid diseases. To assess whether AmB is capable of binding specifically to amyloid fibrils as does Congo Red, we have used the insulin fibril and Abeta 25-35 amyloid model fibril system. We find that AmB does bind strongly to both insulin (K(d) = 1.1 microM) and Abeta 25-35 amyloid (K(d) = 6.4 microM) fibrils but not to native insulin. Binding is characterized by a red-shifted AmB spectrum indicative of a more hydrophobic environment. Thus AmB seems to have a complementary face for amyloid fibrils but not the native protein. In addition, AmB interacts specifically with Congo Red, a known fibril-binding agent. In kinetic fibril formation studies, AmB was able to significantly kinetically delay the formation of Abeta 25-35 fibrils at pH 7.4 but not insulin fibrils at pH 2.     

Is There Still a Place for Conventional Amphotericin B in the Treatment of Neonatal Fungal Infections?

Neonatal invasive fungal infections (IFIs) remain an increasing problem associated with high rates of morbidity and mortality, as well as late-onset neurodevelopmental implications. Invasive candidiasis remains the leading neonatal IFI. Candida albicans is the fungal species most often affecting this population, although a changing epidemiologic incidence to non-albicans Candida species is reported in some neonatal intensive care units. Many treatment recommendations are extrapolated from adult populations, emphasizing the need to establish the optimal antifungal agent, dosage, and duration of therapy in neonates. Historically, conventional amphotericin B has been considered an efficient and safe treatment approach for most neonatal IFIs. More recently, lipid formulations of amphotericin B have been studied, used alone or in combination with other antifungal agents such as azoles or echinocandins. The aim of this article is to review the published experience in the use of amphotericin B formulations to treat neonatal IFIs.     

Peroral Amphotericin B Polymer Nanoparticles Lead to Comparable or Superior In Vivo Antifungal Activity to That of Intravenous Ambisome? or Fungizone?

Background

Despite advances in the treatment, the morbidity and mortality rate associated with invasive aspergillosis remains unacceptably high (70–90%) in immunocompromised patients. Amphotericin B (AMB), a polyene antibiotic with broad spectrum antifungal activity appears to be a choice of treatment but is available only as an intravenous formulation; development of an oral formulation would be beneficial as well as economical.

Methodology

Poly(lactide-co-glycolode) (PLGA) nanoparticles encapsulating AMB (AMB-NPs) were developed for oral administration. The AMB-NPs were 113±20 nm in size with ∼70% entrapment efficiency at 30% AMB w/w of polymer. The in vivo therapeutic efficacy of oral AMB-NPs was evaluated in neutropenic murine models of disseminated and invasive pulmonary aspergillosis. AMB-NPs exhibited comparable or superior efficacy to that of Ambisome® or Fungizone™ administered parenterally indicating potential of NPs as carrier for oral delivery.

Conclusions

The present investigation describes an efficient way of producing AMB-NPs with higher AMB pay-load and entrapment efficiency employing DMSO as solvent and ethanol as non-solvent. The developed oral formulation was highly efficacious in murine models of disseminated aspergillosis as well as an invasive pulmonary aspergillosis, which is refractory to treatment with IP Fungizone™and responds only modestly to AmBisome®.     

Broth Microdilution and Time–Kill Testing of Caspofungin, Voriconazole, Amphotericin B and their Combinations Against Clinical Isolates of Candida krusei

Treatment of invasive Candida krusei infections can be difficult due to its intrinsic fluconazole resistance and its reduced susceptibility to amphotericin B and flucytosine. Caspofungin (CAS) acts on a different cellular target, and its combination with voriconazole (VOR) or amphotericin B (AmB) appears promising. We evaluated the activity of CAS, VOR and AmB alone and in combination at 1/4, 1, 4xMIC concentrations by time–kill method against 30 C. krusei isolates. All isolates were susceptible to CAS and VOR; AmB MICs were 2 μg/ml for 50% of isolates by broth microdilution. CAS showed a fast killing activity at all concentrations; it was fungistatic at 1/4xMICs and fungicidal at 1-4xMICs in general. VOR displayed a concentration-independent fungistatic activity against all isolates. AmB exhibited a concentration-dependent activity; it was fungistatic at 1/4-1xMIC and fungicidal at 4xMIC. The most common interaction was indifference for both combinations. Frequency of synergic interaction for the VOR + CAS combination was 66.7% at 1/4xMIC after 48 h. The best results for CAS + AmB combination were obtained at 4xMIC in the first 4–8 h; synergic interaction was detected for 20 isolates (66.7%) at 4xMIC after 4 h. Consequently, VOR and CAS alone have been found effective, and high AmB MICs are remarkable against clinical C. krusei isolates in vitro. The combinations of CAS with VOR or AmB have exhibited promising results.     

Determination of free and liposomal Amphotericin B in human plasma by liquid chromatography–mass spectroscopy with solid phase extraction and protein precipitation techniques

Amphotericin B is available in various drug delivery systems such as cholesteryl sulfate complex, as lipid complex, and as liposomal formulation. The separation and measurement of free drug (drug which is not bound with liposomal lipids) and liposomal drug (drug which is entrapped in liposomes) in the human plasma after injection of liposomal Amphotericin B is of prime importance due to toxicity concerns. A robust, specific and sensitive method has been developed to effectively separate and then quantify the free drug and liposomal drug, present in human plasma. This method utilizes solid phase extraction Oasis HLB cartridges, which retains the free drug and the liposomal Amphotericin B was eluted from the cartridge in first step. The eluted liposomal Amphotericin B was then extracted from lipids by protein precipitation method using 2% dimethylsulfoxide (DMSO) in acetonitrile. After separation and extraction, the quantification of free and liposomal fractions of Amphotericin B was performed by HPLC–MS–MS technique. The chromatographic separation was performed using Chromolith Performance RP 18e column. The mobile phase composed of 5 mM ammonium acetate, methanol and acetonitrile and a gradient elution program was used. The calibration curves were found to be linear for free Amphotericin B (0.25–15.0 μg/ml) and liposomal Amphotericin B (1.0–100.0 μg/ml). The recovery was about 96% for free Amphotericin B and about 92% for liposomal Amphotericin B. Recoveries were consistent over the linearity ranges defined. The intra-batch and inter-batch accuracy and precision fulfilled the international requirements. The stability of free and liposomal Amphotericin B was assessed under different storage conditions.     

HIV-Associated Cryptococcal Meningitis Patients Treated with Amphotericin B Deoxycholate Plus Flucytosine under Routine Care Conditions in a Referral Center in São Paulo,Brazil

Mycopathologia - Cryptococcal meningitis remains a common cause of mortality in low- and middle-income countries, where amphotericin B deoxycholate (amphotericin) plus fluconazole is the most...     

A Mechanistic Study to Determine the Structural Similarities Between Artificial Membrane Strat-M™ and Biological Membranes and Its Application to Carry Out Skin Permeation Study of Amphotericin B Nanoformulations

Type of biological membrane used in skin permeation experiment significantly affects skin permeation and deposition potential of tested formulations. In this study, a comparative study has been carried out to evaluate the potential of a synthetic membrane (Strat-M?) with rat, human, and porcine ear skin to carry out skin permeation study of nanoformulations of a high molecular weight drug, amphotericin B. Results demonstrated that the permeation of this high molecular weight drug through Strat-M? showed close similitude to human skin. Value of correlation coefficient (R²) of log diffusion between Strat-M? and human skin was found to be 0.99 which demonstrated the similarities of Strat-M? membrane to the human skin. In similarity factor analysis, the value of f₂ was also found to be 85, which further demonstrated the similarities of Strat-M? membrane to human skin. Moreover, scanning electron microscopy (SEM), transmission electron microscopy (TEM), and Brunauer-Emmett-Teller (BET) analysis of synthetic and biological membranes depicted almost similar morphological features (thickness, pore size, surface morphology, and diameter) of synthetic membrane with human skin. The results of the study demonstrated Strat-M? as a better alternative to carry out skin permeation experiment due to the consistent results, reproducibility, easy availability, and minimum variability with human skin.     

阿扎霉素B(Azalomycin B)研究进展

介绍阿扎霉素B的生物学来源,研究历史,主要理化性质和结构确定,同时阐述了阿扎霉素B的生物合成途径,构效关系,生物学特性和应用前景。     

大鹏湾维生素B1、B12与赤潮

海湾及近海水域 ,因某些浮游生物爆发性繁殖引起的赤潮异常现象时有发生 ,已构成水产资源的严重破坏。为弄清赤潮发生的机理 ,已有许多作者进行过研究 ,现已知水温、盐度、溶解氧、ｐＨ、Ｎ、Ｐ ,以及Ｆｅ、Ｍｎ、Ｓｅ等微量元素都是发生赤潮的重要环境因子[1 ]。近年来通过生态实验研究 ,发现维生素Ｂ1 、Ｂ1 2 (以下简称Ｂ1 、Ｂ1 2 )亦有促进赤潮生物生长繁殖的作用[2 ]。本文报道 1 991年对大鹏湾海域水样中Ｂ1 、Ｂ1 2 含量的测定结果 ,并对赤潮发生与其相关性进行探讨。1　采样布点和分析方法1 .1　采样布点大鹏湾盐田海域的Ｓ0 、Ｓ1…     

Successful Treatment of Pulmonary Mucormycosis Caused by <Emphasis Type="Italic">Cunninghamella bertholletiae</Emphasis> with High-Dose Liposomal Amphotericin B (10 mg/kg/day) Followed by a Lobectomy in Cord Blood Transplant Recipients

Infection caused by Cunninghamella bertholletiae carries one of the highest mortality rates among mucormycosis, and there are no reported cases that survived from the infection in allogeneic hematopoietic stem cell transplantation recipients occurring before neutrophil engraftment. Here, we present two cases of pulmonary mucormycosis caused by C. bertholletiae occurring before neutrophil engraftment after cord blood transplantation. Both were successfully treated with high-dose liposomal amphotericin B (10 mg/kg/day) combined with micafungin, which was then followed by neutrophil recovery, reduction in immunosuppressive agents, and a subsequent lobectomy. The intensive antifungal therapy immediately administered upon suspicion of mucormycosis greatly suppressed the infection in its early stage and was well tolerated despite its prolonged administration and simultaneous use of nephrotoxic agents after transplantation. Although the synergic effect of micafungin remains unclear, these cases highlight the importance of prompt administration of high-dose lipid polyene when suspecting mucormycosis in highly immunocompromised patients, which enables subsequent diagnostic and therapeutic interventions, resulting in a favorable outcome.     

B.B.Brodie(1907～1989)

B.B.Brodie博土,一个先驱药理学家和美国国家科学院院士,1989年2月28日逝世。生前是美国国立卫生研究院心脏研究所化学药理实验室的创始人和第一任主任。     

Monoamine oxidase: To B or not to B?

That the enzyme, monoamine oxidase (E.C. 1.4.3.4. amine: O₂ oxidoreductase, MAO) exists in multiple forms was first suggested by Johnston (1) who studied the effects of the irreversible inhibitor clorgyline on MAO. It has been proposed that MAO can be classified into two types, A and B, according to their inhibitor sensitivity and substrate specificity. Type A MAO was found to be solely responsible for the deamination of 5-hydroxytryptamine (5-HT) and shows high sensitivity to clorgyline, while type B MAO metabolizes 2-phenethylamine (PEA) and benzylamine (BA) and is less sensitive to clorgyline. Subsequently, it was shown that type B MAO is highly sensitive to the irreversible inhibitor deprenyl (2).Recently, the “multiple forms” concept has been questioned (3–5) mainly because of increasing evidence which is contradictory to some earlier findings. As an alternative, another hypothesis was put forward insinuating that MAO is an enzyme with multiple binding sites but only one molecular entity (3,4,6,7). This account will focus on some experimental findings accumulated mainly since 1978 and which, although equivocal, strongly support the “one molecular entity” hypothesis of MAO.     

转录因子NF—КB／ⅠКB

可与kappa基因相结合的核因子NF-κB(nuclear factor-kappa gene binding)是研究得最为广泛的转录因子之一。该因子由Baltimore等人首先在B淋巴细胞发现,后来发现它广泛存在于其他类型细胞中。NF-κB具有如下特征:对外界信号的刺激反应迅速,控制广泛的基因表达,在免疫及炎症反应中起中心作用以及在胚胎发育中充当信号分子。本文就NF-κB/IκBα的结构、调节和功能作一综述。     

Liver Kinase B1 Suppresses Lipopolysaccharide-induced Nuclear Factor κB (NF-κB) Activation in Macrophages

Liver kinase B1 (LKB1), a serine/threonine kinase, is a tumor suppressor and metabolic regulator. Recent data suggest that LKB1 is essential in regulating homeostasis of hematopoietic cells and immune responses. However, its role in macrophages and innate immune system remains unclear. Here we report that macrophage LKB1 inhibits pro-inflammatory signaling in response to LPS. LPS-induced pro-inflammatory cytokines and pro-inflammatory enzymes were monitored in bone marrow-derived macrophages isolated from myeloid cell-specific LKB1 knock out mice and their wild type littermate control mice. LPS induced higher levels of pro-inflammatory cytokines and pro-inflammatory enzymes in bone marrow-derived macrophages from LKB1 KO than those from wild type mice. Consistently, LPS induced higher levels of NF-κB activation in LKB1-deficient macrophages than those in wild type. Further, LPS stimulation significantly increased LKB1 phosphorylation at serine 428, which promoted its binding to IκB kinaseβ (IKKβ), resulting in the inhibition of NF-κB. Finally, LPS injection caused higher levels of cytokine release and more severe tissue injury in the lung tissues of LKB1 KO mice than in those of control mice. We conclude that LKB1 inhibits LPS-induced NF-κB activation in macrophages.     

柯萨奇病毒B1,B3和B5以促衰退因子作为细胞受体

病毒复制起始于病毒吸附蛋白与宿主细胞表面受体的特异性结合及此后由细胞介导的病毒穿入,而这些受体的特异性决定宿主细胞范围。应用单克隆抗体ＭＡｂ８５４阻断,免疫沉淀法以及促衰退因子基因转染细胞等方法,发现细胞ＤＡＦ是宿主细胞吸附柯萨奇病毒Ｂ１、Ｂ３和Ｂ５的受体,但这些病毒要侵入细胞及在胞内进行复制尚需依赖其他因子的存在。     

Synthesis of 2′-Deoxyformycin B and 2′-Deoxyoxoformycin B

Abstract

3-β-D-Ribofuranosylpyazolo[4,3-d]pyrimidines (formycins)¹ modified in the heteroaromatic moiety are of biological interest as analogues of adenosine and guanosine, and have been the objects of intensive synthetic chemical effort by several groups.^2-9 2′-Deoxynucleosides^2c,2d,7b,13 and other analogties of the formycins modified in the sugar moiety^10-12 are also of potential interest, but have been less extensively studied. Examples of the 2′-deoxyribonucleoside type known to date include the 2′-deoxy-6-thioguanosine analogue 1, the 2′-deoxyadenosine (dAdo) analogue 2 (2′-deoxyformycin A),^10,13 and the 2-chloro-2′-deoxyadenosine analogue 3.^7b Compound 2 was found to be 10-15 times more potent than 2′-deoxyadenosine as an inhibitor of the growth of S49 cells, a murine lymphoma line of T-cell origin.¹³ Activity depended on 5′- phosphorylation, since mutants lacking the enzymes adenosine kinase (AK) and deoxycytidine kinase (dCK) were insensitive to the drug. Furthermore, activity was comparable in the presence and absence of an AK inhibitor, suggesting that 2, unlike dAdo, may be a poor substrate for adenosine deaminase. That 5′-phosphorylation of 2 was mediated by AK rather than dCK was indicated by the fact that miitants lacking only dCK retained sensitivity. This contrasted with the behavior of dAdo, which is known to be n substrate for both AK and dCK.¹⁴