Staphylococcus aureus is a Gram-positive bacterium responsible for a variety of mild to life-threatening infections including bone infections such as osteomyelitis. This bacterium is able to invade and persist within non-professional phagocytic cells such as osteoblasts. In the present study, four different S. aureus strains, namely, 2SA-ST239-III (ST239), 5SA-ST5-II (ST5), 10SA-ST228-I (ST228), and 14SA-ST22-IVh (ST22), were tested for their ability to modulate cell viability in MG-63 osteoblast-like cells following successful invasion and persistence. Methicillin-sensitive S. aureus (MSSA) ATCC-12598-ST30 (ST30) was used as control strain. Despite being proven that ST30, ST239, and ST22 have a similar ability to internalize and persist in MG-63 osteoblast-like cells under our experimental conditions, we demonstrated that the observed decrease in cell viability was due to the different behavior of the considered strains, rather than the number of intracellular bacteria. We focused our attention on different biochemical cell functions related to inflammation, cell metabolism, and oxidative stress during osteoblast infections. We were able to show the following: (1) ST30 and ST239 were the only two clones able to persist and maintain their number in the hostile environment of the cell during the entire period of infection; (2) ST239 was the only clone able to significantly increase gene expression (3 and 24 h post-infection (p.i.)) and protein secretion (24 h p.i.) of both interleukin-6 (IL-6) and tumor necrosis factor alpha (TNF-α) in MG-63 osteoblast-like cells; (3) the same clone determined a significant up-regulation of the transforming growth factorbeta 1 (TGF-β1) and of the metabolic marker glyceraldehyde 3-phosphate dehydrogenase (GAPDH) mRNAs at 24 h p.i.; and (4) neither the MSSA nor the four methicillin-resistant S. aureus (MRSA) strains induced oxidative stress phenomena in MG-63 cells, although a high degree of variability was observed for the different clones with regard to the expression pattern of nuclear factor E2-related factor 2 (Nrf2) and its downstream gene heme oxygenase 1 (HO-1) activation. Our results may pave the way for an approach to S. aureus-induced damage, moving towards individualized therapeutic strategies that take into account the differences between MSSA and MRSA as well as the distinctive features of the different clones. This approach is based on a change of paradigm in antibiotic therapy involving a case-based use of molecules able to counteract pro-inflammatory cytokines activity such as selective cytokine signaling inhibitors (IL-6, TNF-α).

中文翻译：

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四种耐甲氧西林金黄色葡萄球菌克隆对MG-63成骨细胞样细胞的不同调节作用

金黄色葡萄球菌是革兰氏阳性细菌，负责多种轻度至危及生命的感染，包括骨骼感染，如骨髓炎。该细菌能够侵袭并在非专业吞噬细胞（例如成骨细胞）中持续存在。在本研究中，四种不同的金黄色葡萄球菌菌株分别为2SA-ST239-III（ST239），5SA-ST5-II（ST5），10SA-ST228-I（ST228）和14SA-ST22-IVh（ST22）在成功侵袭和持久后，测试了它们在MG-63成骨细胞样细胞中调节细胞活力的能力。甲氧西林敏感的金黄色葡萄球菌（MSSA）ATCC-12598-ST30（ST30）用作对照菌株。尽管已证明在我们的实验条件下ST30，ST239和ST22具有类似的内在化能力并在MG-63成骨细胞样细胞中持续存在，但我们证明观察到的细胞活力下降是由于所考虑菌株的行为不同，而不是细胞内细菌的数量。我们将注意力集中在成骨细胞感染期间与炎症，细胞代谢和氧化应激有关的不同生化细胞功能上。我们能够证明以下几点：（1）在整个感染期间，ST30和ST239是仅有的两个能够在细胞的敌对环境中保持并维持其数量的克隆；（2）ST239是唯一能够显着提高基因表达的克隆（感染后3和24 h（p。i。））和MG-63成骨细胞样细胞中白介素6（IL-6）和肿瘤坏死因子α（TNF-α）的蛋白质分泌（pi 24小时）；（3）同一克隆在感染后24小时检测到转化生长因子β1（TGF-β1）和代谢标志物甘油醛3-磷酸脱氢酶（GAPDH）mRNA的显着上调；（4）无论是MSSA还是四种耐甲氧西林的药尽管观察到不同克隆在核因子E2相关因子2（Nrf2）及其下游基因的表达模式上存在高度差异，但金黄色葡萄球菌（MRSA）菌株在MG-63细胞中诱导了氧化应激现象。血红素加氧酶1（HO-1）激活。我们的结果可能为解决金黄色葡萄球菌引起的损伤铺平道路，朝着考虑到MSSA和MRSA之间的差异以及不同克隆的独特特征的个性化治疗策略迈进。这种方法基于抗生素治疗模式的改变，涉及基于案例的能够对抗促炎性细胞因子活性的分子（例如选择性细胞因子信号传导抑制剂（IL-6，TNF-α））的使用。