Department for Molecular Biomedical Research, VIB, B-9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, B-9052 Ghent, Belgium.
Department for Molecular Biomedical Research, VIB, B-9052 Ghent, Belgium; Department of Biomedical Molecular Biology, Ghent University, B-9052 Ghent, Belgium.
Nitric Oxide. 2014 Jan 30;36:36-43. doi: 10.1016/j.niox.2013.11.001. Epub 2013 Nov 21.
Sepsis and septic shock result from an exacerbated systemic inflammatory reaction to infection. Their incidence is rising, and they have recently become the main cause of death in intensive care units. Septic shock is defined as sepsis accompanied by life-threatening refractory hypotension, for which excessive nitric oxide (NO), produced by inducible NO synthase iNOS, is thought responsible. LPS, a vital outer membrane component of Gram-negative bacteria, mimics most of the septic effects and is widely used as a model for septic shock. TLR4 is the signal-transducing receptor for LPS, evidenced by the resistance of TLR4-deficient C3H/HeJ and C57BL/10ScNJ mice. As expected, we found that TLR4 deficiency precludes LPS-induced cytokine production, independent of the purity of the LPS preparation. However, various conventional LPS preparations induced NO in TLR4-deficient mice to the same level as in control animals, while ultrapure LPS did not, indicating the presence of NO-producing contaminant(s). Nevertheless, despite identical iNOS induction pattern and systemic NO levels, the contaminant does not cause hypotension, hypothermia, or any other sign of morbidity. Using mice deficient for TLR2, TRL3, TLR4, TRL2x4, TLR9, MyD88 or TRIF, we found that the contaminant signals via TLR2 and MyD88. In conclusion, conventional LPS preparations generally used in endotoxic shock research contain TLR2 agonists that induce iNOS and high levels of systemic NO as such, and synergize with LPS towards the production of pro-inflammatory cytokines, morbidity and mortality. Surprisingly, the excessive iNOS-derived systemic NO production induced by impure LPS in TLR4⁻/⁻ is not accompanied by hypotension or morbidity.
脓毒症和感染性休克是由感染引起的全身炎症反应过度加剧所致。它们的发病率正在上升，最近已成为重症监护病房死亡的主要原因。感染性休克的定义是伴有危及生命的难治性低血压的败血症，认为过量的一氧化氮（NO），由诱导型一氧化氮合酶（iNOS）产生，对此负责。LPS 是革兰氏阴性菌的重要外膜成分，模拟了大部分脓毒症的作用，被广泛用作感染性休克的模型。TLR4 是 LPS 的信号转导受体，这一点已被 TLR4 缺陷型 C3H/HeJ 和 C57BL/10ScNJ 小鼠的抗性所证明。不出所料，我们发现 TLR4 缺陷可防止 LPS 诱导的细胞因子产生，而与 LPS 制剂的纯度无关。然而，各种常规 LPS 制剂在 TLR4 缺陷型小鼠中诱导产生的 NO 与对照动物相同，而超纯 LPS 则没有，表明存在产生 NO 的污染物。尽管诱导 iNOS 的模式和全身 NO 水平相同，但该污染物不会引起低血压、低体温或任何其他病态迹象。使用 TLR2、TLR3、TLR4、TLR2x4、TLR9、MyD88 或 TRIF 缺陷型小鼠，我们发现该污染物通过 TLR2 和 MyD88 信号传递。总之，一般用于内毒素休克研究的常规 LPS 制剂含有 TLR2 激动剂，可诱导 iNOS 和高水平的全身 NO，并且与 LPS 协同产生促炎细胞因子、病态和死亡率。令人惊讶的是，TLR4⁻/⁻ 中不纯 LPS 诱导的过度 iNOS 衍生的全身 NO 产生并不伴有低血压或病态。
