Fotinos Nicolas, Convert Maruska, Piffaretti Jean-Claude, Gurny Robert, Lange Norbert
Department of Pharmaceutics and Biopharmaceutics, School of Pharmaceutical Sciences, University of Geneva, University of Lausanne, 30 Quai Ernest Ansermet, Geneva 1211, Switzerland.
Antimicrob Agents Chemother. 2008 Apr;52(4):1366-73. doi: 10.1128/AAC.01372-07. Epub 2008 Jan 14.
Due mainly to the extensive use of antibiotics, the spread of multiresistant bacterial strains is one of the most worrying threats to public health. One strategy that can be used to overcome potential shortcomings might be the inactivation of these microorganisms by 5-aminolevulinic acid (5-ALA) or 5-ALA derivative-mediated photodynamic therapy (PDT). 5-ALA has no photoactive properties, but when it is given exogenously, it acts as a precursor of photosensitive porphyrins predominantly in tissues or organisms that are characterized by a high metabolic turnover, such as tumors, macrophages, and bacteria. However, the weak ability of 5-ALA to cross biological barriers has led to the introduction of more lipophilic derivatives, such as methyl aminolevulinate or hexyl aminolevulinate, which display improved capacities to reach the cytoplasm. Starting from the hypothesis that more lipophilic compounds carrying only a permanent positive charge under physiological conditions may more easily cross the bacterial multilayer barrier, we have tested the efficacies of some 5-ALA n-alkyl esters for the inactivation of bacteria. For this purpose, different bacterial strains were incubated with 5-ALA or its corresponding esters of different lipophilicities. Then, the bacteria were irradiated with light and the numbers of CFU post-PDT were counted and compared to those for the controls, which were kept in the dark. Furthermore, the total amount of accumulated porphyrins was quantified by high-pressure liquid chromatography analysis. In our studies, analysis of the bacterial extracts revealed the presence of all the porphyrins involved in heme biosynthesis, from uroporphyrin to protoporphyin IX. The efficacy of bacterial inactivation was a function of the total amount of porphyrins produced, independently of their nature. The 5-ALA methyl and butyl esters were the most effective compounds with respect to the photodynamic inactivation of bacteria. We observed significant differences in terms of the optimal drug concentration, bactericidal activities, and porphyrin production.
主要由于抗生素的广泛使用，多重耐药细菌菌株的传播是对公众健康最令人担忧的威胁之一。一种可用于克服潜在缺点的策略可能是通过5-氨基乙酰丙酸（5-ALA）或5-ALA衍生物介导的光动力疗法（PDT）使这些微生物失活。5-ALA本身没有光活性，但当外源性给予时，它主要在代谢周转率高的组织或生物体（如肿瘤、巨噬细胞和细菌）中作为光敏卟啉的前体。然而，5-ALA穿越生物屏障的能力较弱，这导致了更具亲脂性的衍生物的引入，如甲基氨基乙酰丙酸或己基氨基乙酰丙酸，它们具有更好的进入细胞质的能力。基于在生理条件下仅带有永久正电荷的亲脂性更强的化合物可能更容易穿越细菌多层屏障这一假设，我们测试了一些5-ALA正烷基酯对细菌失活的效果。为此，将不同的细菌菌株与5-ALA或其不同亲脂性的相应酯一起孵育。然后，用光照细菌，并计算光动力疗法后每毫升菌落形成单位（CFU）的数量，并与保存在黑暗中的对照进行比较。此外，通过高压液相色谱分析对积累的卟啉总量进行定量。在我们的研究中，对细菌提取物的分析揭示了血红素生物合成中涉及的所有卟啉的存在，从尿卟啉到原卟啉IX。细菌失活的效果是所产生的卟啉总量的函数，与其性质无关。就细菌的光动力失活而言，5-ALA甲酯和丁酯是最有效的化合物。我们在最佳药物浓度、杀菌活性和卟啉产生方面观察到了显著差异。
