Hussain Roslinah Mohamad, Razak Zayan Nabilah Rasyidah Abd, Saad Wan Mazlina Md, Mustakim Maimunah
Department of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA (UiTM), Selangor, Malaysia.
Department of Medical Laboratory Technology, Faculty of Health Sciences, Universiti Teknologi MARA (UiTM), Selangor, Malaysia.
Asian Pac J Trop Med. 2017 Jul;10(7):685-695. doi: 10.1016/j.apjtm.2017.07.009. Epub 2017 Jul 29.
To investigate the effects of Andrographis paniculata (Burm.f.) Wall. Ex Nees (A. paniculata) on expressions and activities of catalase, superoxide dismutase and alkylhydroperoxide reductase C in Staphylococcus aureus (S. aureus) with respect to its survival in vitro.
Antioxidative property of methanolic leaves extract of A. paniculata (0.06 mg/mL). Minimum inhibitory concentration (MIC) was determined by its ability to reduce hydrogen peroxide (HO) toxicity against S. aureus ATCC 25923 [(3.8 × 10) cfu/mL]. Effects of the extract on expressions of katA (encoding catalase), sodA and sodM [encoding superoxide dismutases (SODs)], and ahpC [encoding alkylhydroperoxide reductase C (AhpC)] in S. aureus were determined by RT-qPCR and corresponding enzyme activity assays were performed. Nitroblue tetrazolium reduction (NBT) assay was performed to determine effects of the extract on intracellular and extracellular levels of O in S. aureus.
Cells challenged with 7.5 mmol/L HO showed 0% survival in 30 min whereas 25% survived after treatment with the extract and HO. Cells that were treated with the extract alone had 43% survival in the same exposure period. Expressions of sodA and sodM genes in extract-treated cells were lowered 0.8-fold and 0.7-fold, respectively with decrease in total SOD activity of 26.8 U compared to untreated cells, 32.4 U (P < 0.05). In contrast, extract-treated S. aureus cells showed 3.3-fold increase in katA expression with corresponding increase in catalase activity of 1.828 U compared to untreated cells which was 1.248 U, (P < 0.05). More profoundly, ahpC expression was increased 61-fold in extract-treated cells, (P < 0.05) with corresponding increase in AhpC activity of 0.018 U compared to untreated cells, 0.012 U, (P < 0.05). Extract-treated cells had significantly lower intra- and extracellular O levels with absorbance readings (A) of 0.340 and 0.524 compared to untreated cells which were 0.516 and 0.928 (P < 0.05), respectively.
Taken together these results suggest that the low MIC of A. paniculata methanolic leaves extract (0.06 mg/mL) reduce HO toxicity and more importantly, was in itself effectively inhibitory against S. aureus. Further, our observations suggest that a probable mode of its inhibitory mechanism against S. aureus is by reducing total SOD activity through downregulation of sodA and sodM expressions.
研究穿心莲对金黄色葡萄球菌过氧化氢酶、超氧化物歧化酶及烷基过氧化氢还原酶C表达和活性的影响，以及其在体外的生存情况。
采用穿心莲甲醇叶提取物（0.06 mg/mL）进行抗氧化性能研究。通过其降低过氧化氢（HO）对金黄色葡萄球菌ATCC 25923[（3.8×10）cfu/mL]毒性的能力来确定最低抑菌浓度（MIC）。通过RT-qPCR测定提取物对金黄色葡萄球菌中katA（编码过氧化氢酶）、sodA和sodM[编码超氧化物歧化酶（SOD）]以及ahpC[编码烷基过氧化氢还原酶C（AhpC）]表达的影响，并进行相应的酶活性测定。采用氮蓝四唑还原（NBT）试验来确定提取物对金黄色葡萄球菌细胞内和细胞外O水平的影响。
用7.5 mmol/L HO处理的细胞在30分钟内存活率为0%，而用提取物和HO处理后25%存活。仅用提取物处理的细胞在相同暴露时间内存活率为43%。与未处理细胞相比，提取物处理细胞中sodA和sodM基因的表达分别降低了0.8倍和0.7倍，总SOD活性从32.4 U降至26.8 U（P<0.05）。相比之下，提取物处理的金黄色葡萄球菌细胞中katA表达增加了3.3倍，过氧化氢酶活性从1.248 U增加到1.828 U（P<0.05）。更显著的是，提取物处理细胞中ahpC表达增加了61倍（P<0.05），AhpC活性从0.012 U增加到0.018 U（P<0.05）。与未处理细胞的吸光度读数（A）分别为0.516和0.928相比，提取物处理细胞的细胞内和细胞外O水平显著降低，分别为0.340和0.524（P<0.05）。
这些结果表明，穿心莲甲醇叶提取物的低MIC（0.06 mg/mL）降低了HO毒性，更重要的是，其本身对金黄色葡萄球菌具有有效抑制作用。此外，我们的观察结果表明，其对金黄色葡萄球菌的抑制机制可能是通过下调sodA和sodM表达来降低总SOD活性。
