Laboratory of Pharmaceutical Microbiology, Ghent University, Ghent, Belgium.
Antimicrob Agents Chemother. 2012 May;56(5):2290-4. doi: 10.1128/AAC.05106-11. Epub 2012 Feb 21.
Previous research has shown that 1% to 10% of sessile Candida albicans cells survive treatment with high doses of miconazole (a fungicidal imidazole). In the present study, we investigated the involvement of sphingolipid biosynthetic intermediates in this survival. We observed that the LCB4 gene, coding for the enzyme that catalyzes the phosphorylation of dihydrosphingosine and phytosphingosine, is important in governing the miconazole resistance of sessile Saccharomyces cerevisiae and C. albicans cells. The addition of 10 nM phytosphingosine-1-phosphate (PHS-1-P) drastically reduced the intracellular miconazole concentration and significantly increased the miconazole resistance of a hypersusceptible C. albicans heterozygous LCB4/lcb4 mutant, indicating a protective effect of PHS-1-P against miconazole-induced cell death in sessile cells. At this concentration of PHS-1-P, we did not observe any effect on the fluidity of the cytoplasmic membrane. The protective effect of PHS-1-P was not observed when the efflux pumps were inhibited or when tested in a mutant without functional efflux systems. Also, the addition of PHS-1-P during miconazole treatment increased the expression levels of genes coding for efflux pumps, leading to the hypothesis that PHS-1-P acts as a signaling molecule and enhances the efflux of miconazole in sessile C. albicans cells.
先前的研究表明，在高剂量咪康唑（一种杀真菌咪唑）的治疗下，1%到 10%的静止念珠菌细胞能够存活。在本研究中，我们研究了鞘脂生物合成中间体在此存活过程中的参与情况。我们观察到，LCB4 基因编码催化二氢神经酰胺和植物神经酰胺磷酸化的酶，对于调控静止型酿酒酵母和白色念珠菌细胞的咪康唑耐药性非常重要。添加 10 nM 植物鞘氨醇-1-磷酸（PHS-1-P）可大大降低细胞内咪康唑浓度，并显著增加高度敏感的白色念珠菌杂合 LCB4/lcb4 突变体的咪康唑耐药性，表明 PHS-1-P 对静止细胞中咪康唑诱导的细胞死亡具有保护作用。在该 PHS-1-P 浓度下，我们未观察到其对细胞质膜流动性有任何影响。当抑制外排泵或在没有功能外排系统的突变体中进行测试时，未观察到 PHS-1-P 的保护作用。此外，在咪康唑处理过程中添加 PHS-1-P 会增加编码外排泵的基因的表达水平，这导致了 PHS-1-P 作为信号分子并增强了静止型白色念珠菌细胞中咪康唑的外排的假设。
