Vylkova Slavena, Nayyar Namrata, Li Wansheng, Edgerton Mira
Department of Oral Biology, State University of New York at Buffalo, Buffalo, NY 14214, USA.
Antimicrob Agents Chemother. 2007 Jan;51(1):154-61. doi: 10.1128/AAC.00478-06. Epub 2006 Oct 30.
Human beta-defensin 2 (hBD-2) and hBD-3 have potent fungicidal activity in the micromolar range. Although little is known about their mechanism of action against Candida species, some similarities to the antifungal mechanism of salivary peptide histatin 5 (Hst 5) seem to exist. Since hBD-2 and hBD-3 have been reported to cause direct disruption of target cell membranes, we compared the effects of hBD-2 and hBD-3 on Candida albicans membrane integrity. Incubation of calcein-loaded C. albicans cells with a dose of hBD-2 lethal for 90% of the strains tested (LD(90)) resulted in a maximal dye efflux of only 10.3% +/- 2.8% at 90 min, similar to that induced by Hst 5. In contrast, an LD(90) of hBD-3 more than doubled calcein release from cells yet did not result in more than 24% of total release, showing that neither peptide caused gross membrane damage. As for Hst 5, killing of C. albicans cells by hBD-2 and hBD-3 was salt sensitive; however, Ca(2+) and Mg(2+) inhibited hBD-2 but not hBD-3 fungicidal activity. Pretreatment of C. albicans cells with sodium azide resulted in significantly decreased ATP release and susceptibility of cells to hBD-2 and hBD-3. However, hBD-3 killing was partially restored at concentrations of > or =0.8 microM, showing energy-independent mechanisms at higher doses. C. glabrata resistance to Hst 5, hBD-2, and hBD-3 is not a result of loss of expression of cell wall Ssa proteins. The candidacidal effects of hBD-2-hBD-3 and Hst 5-hBD-2 were additive, while the index of interaction between Hst 5 and hBD-3 was 0.717 (P < 0.05). Thus, the candidacidal action of hBD-2 shows many similarities to that of Hst 5 in terms of salt sensitivity, ion selectivity, and energy requirements while hBD-3 exhibits biphasic concentration-dependent mechanisms of candidacidal action complementary to those of Hst 5.
人β-防御素2（hBD-2）和hBD-3在微摩尔范围内具有强大的杀真菌活性。尽管对它们针对念珠菌属的作用机制了解甚少，但似乎与唾液肽组蛋白5（Hst 5）的抗真菌机制存在一些相似之处。由于已有报道称hBD-2和hBD-3会导致靶细胞膜的直接破坏，我们比较了hBD-2和hBD-3对白色念珠菌膜完整性的影响。用对90%受试菌株具有致死性的剂量（LD(90)）的hBD-2孵育负载钙黄绿素的白色念珠菌细胞，在90分钟时最大染料外流量仅为10.3%±2.8%，与Hst 5诱导的情况相似。相比之下，hBD-3的LD(90)使细胞中钙黄绿素释放量增加了一倍多，但总释放量未超过24%，表明这两种肽均未导致严重的膜损伤。与Hst 5一样，hBD-2和hBD-3对白色念珠菌细胞的杀伤作用对盐敏感；然而，Ca(2+)和Mg(2+)抑制hBD-2的杀真菌活性，但不抑制hBD-3的杀真菌活性。用叠氮化钠预处理白色念珠菌细胞会导致ATP释放显著减少以及细胞对hBD-2和hBD-3的敏感性降低。然而，在浓度≥0.8 microM时，hBD-3的杀伤作用部分恢复，表明在较高剂量下存在能量非依赖机制。光滑念珠菌对Hst 5、hBD-2和hBD-3的耐药性不是细胞壁Ssa蛋白表达缺失的结果。hBD-2 - hBD-3和Hst 5 - hBD-2的杀念珠菌作用是相加的，而Hst 5与hBD-3之间的相互作用指数为0.717（P < 0.05）。因此，hBD-2的杀念珠菌作用在盐敏感性、离子选择性和能量需求方面与Hst 5有许多相似之处，而hBD-3表现出与Hst 5互补的双相浓度依赖性杀念珠菌作用机制。
