Measurement of the concentration of amphotericin B in brain tissue of scrapie-infected hamsters with a simple and sensitive method

Amphotericin B-loaded natural latex dressing for treating Candida albicans wound infections using Galleria mellonella model

Amphotericin B (AmB) is the gold standard for antifungal drugs. However, AmB systemic administration is restricted because of its side effects. Here, we report AmB loaded in natural rubber latex (NRL), a sustained delivery system with low toxicity, which stimulates angiogenesis, cell adhesion and accelerates wound healing. Physicochemical characterizations showed that AmB did not bind chemically to the polymeric matrix. Electronic and topographical images showed small crystalline aggregates from AmB crystals on the polymer surface. About 56.6% of AmB was released by the NRL in 120 h. However, 33.6% of this antifungal was delivered in the first 24 h due to the presence of AmB on the polymer surface. The biomaterial's excellent hemo- and cytocompatibility with erythrocytes and human dermal fibroblasts (HDF) confirmed its safety for dermal wound application. Antifungal assay against Candida albicans showed that AmB-NRL presented a dose-dependent behavior with an inhibition halo of 30.0 ± 1.0 mm. Galleria mellonella was employed as an in vivo model for C. albicans infection. Survival rates of 60% were observed following the injection of AmB (0.5 mg.mL-1) in G. mellonella larvae infected by C. albicans. Likewise, AmB-NRL (0.5 mg.mL-1) presented survival rates of 40%, inferring antifungal activity against fungus. Thus, NRL adequately acts as an AmB-sustained release matrix, which is an exciting approach, since this antifungal is toxic at high concentrations. Our findings suggest that AmB-NRL is an efficient, safe, and reasonably priced ($0.15) dressing for the treatment of cutaneous fungal infections.

Stimulation of monocytes, macrophages, and microglia by amphotericin B and macrophage colony-stimulating factor promotes remyelination

Approaches to stimulate remyelination may lead to recovery from demyelinating injuries and protect axons. One such strategy is the activation of immune cells with clinically used medications, since a properly directed inflammatory response can have healing properties through mechanisms such as the provision of growth factors and the removal of cellular debris. We previously reported that the antifungal medication amphotericin B is an activator of circulating monocytes, and their tissue-infiltrated counterparts and macrophages, and of microglia within the CNS. Here, we describe that amphotericin B activates these cells through engaging MyD88/TRIF signaling. When mice were subjected to lysolecithin-induced demyelination of the spinal cord, systemic injections of nontoxic doses of amphotericin B and another activator, macrophage colony-stimulating factor (MCSF), further elevated the representation of microglia/macrophages at the site of injury. Treatment with amphotericin B, particularly in combination with MCSF, increased the number of oligodendrocyte precursor cells and promoted remyelination within lesions; these pro-regenerative effects were mitigated in mice treated with clodronate liposomes to reduce circulating monocytes and tissue-infiltrated macrophages. Our results have identified candidates among currently used medications as potential therapies for the repair of myelin.

Therapeutic approaches to prion diseases

Prion diseases are unique in that they comprise sporadic, genetic, and iatrogenically or environmentally acquired forms. When disease is acquired by peripheral route, neuroinvasion occurs via at least two different neural pathways (vague and splanchnic nerves) and is usually preceded by prion propagation in secondary lymphoid organs. Conversely, in the other etiologic forms, PrPSc formation occurs within, and is apparently limited to, the CNS. Longitudinal studies on experimental scrapie indicate that substantial neuropathologic changes (i.e., glial activation and nerve cell degeneration) already are present before the onset of symptoms and are topographically related to PrPSc deposits. Accordingly, any effective intervention should start during the preclinical stage of disease, and be aimed at preventing neuroinvasion or PrPSc propagation in the CNS. Unfortunately, no tests are available currently to detect presymptomatic individuals, except for carriers of pathogenic mutations of the PRNP gene. Inhibition of PrPSc formation can be achieved through (1) abrogation of PrPC synthesis or prevention of its transport to the cell surface; (2) stabilization of the PrPC structure to make its conformational change unfavorable; (3) sequestration of PrPSc; (4) reversion of PrPSc to a protease-sensitive form; or (5) interference with the interaction between PrPC, PrPSc, and other macromolecules that feature in the conversion process. The compounds that have some effectiveness in in vitro, cell culture, or animal models of prion disease seem to operate through one of these mechanisms (see Table 1); however, even the most effective drugs only work when administered at the time of infection or very short thereafter, and these conditions are incurable at present. The heterogeneity and complexity of the etiopathogenesis of prion diseases suggest that various strategies and a combination of several compounds with different modes of actions are likely necessary for prevention and treatment. Major efforts should be focused on the development of preclinical diagnostic tests in conjunction with immunization strategies for diseases acquired by peripheral route and identification of more effective compounds for the other etiological forms.

Late treatment with polyene antibiotics can prolong the survival time of scrapie-infected animals

Amphotericin B (AmB) is one of the few drugs able to prolong survival times in experimental scrapie and delays the accumulation of PrPres, a specific marker of this disease in the brain in vivo. Previous reports showed that the AmB effect is observed only if the drug is administered around the time of infection. In the present study, intracerebrally infected mice were treated with AmB or one of its derivatives, MS-8209, between 80 and 140 days postinoculation. We observed an increased incubation time and a delay in PrPres accumulation and glial fibrillary acidic protein gene expression. Treatment starting at 80 days postinoculation was as efficient as long-term treatment starting the day of inoculation. Our results indicate that polyene antibiotics may interfere, throughout the course of the experimental disease, with the propagation of the scrapie agent.

New high-performance liquid chromatographic method for amphotericin B analysis using an internal standard

A simple and reproducible HPLC method for the analysis of amphotericin B (AmB) in serum, lung and liver using natamycin as the internal standard was developed. AmB and natamycin were extracted from serum, lung and liver and were separated using an isocratic elution from C18 reversed-phase column. The mobile phase consisted of acetonitrile-10 mM acetate buffer pH 4.0 (37:63, v/v). The HPLC system had two detectors in series. One was set at 303 nm and the other at 383 nm for the detection of natamycin and AmB, respectively. The retention times of AmB and natamycin were 15 and 6 min, respectively. The recovery efficiency was 96%-70%. The limit of quantification was 0.1 microgram/ml. The assay was reproducible, the within-day coefficient of variation (n = 6) was < 8% for serum, lungs and liver. The between-day variability (n = 6) was < 7.7% for serum, liver and lungs at 1 microgram/ml or 1 microgram/g tissue concentration. The assay was linear within the range 1-40 micrograms/ml (r2 = 0.99).

Amphotericin B treatment dissociates in vivo replication of the scrapie agent from PrP accumulation

Scrapie and related animal and human disorders are neurodegenerative diseases characterized by the formation of a modified, partly proteinase-resistant protein (PrP) of the host, which tends to aggregate as amyloid fibrils and accumulate in the brain of infected individuals. There is a general consensus that the pathological form of PrP (PrPSc) is essential for the clinical appearance of the disease, but whether it is part of the scrapie agent or a by-product of viral infection is still controversial. Here we report that treatment of scrapie-infected hamsters with amphotericin B delays the accumulation in the brain of the proteinase-resistant portion of PrPSc by about 30 days without affecting scrapie replication. The consequence is that hamsters treated with amphotericin B developed clinical signs of disease later than infected controls. We argue that the proteinase-resistant portion of PrPSc is necessary for the development of the disease but that it is unlikely to be essential for scrapie replication.