Prophylactic therapies to treat septic shock - Tolerance to LPS-induced microvascular change in mouse skin

皮下注射脂多糖（LPS）可增加小鼠皮肤中的血浆渗漏。用LPS预处理条件下小鼠耐受LPS诱导的血浆渗漏。一氧化氮（NO）已被认为是参与这些LPS的影响。采用诱导型一氧化氮合酶（iNOS）缺陷小鼠研究了诱导型一氧化氮合酶（iNOS）在LPS诱导的血浆渗漏中的特定作用。据推测，LPS的大部分生物活性来自脂质A部分。我们研究了脂质A类似物（ONO-4007）在增加血浆渗漏中的作用。皮下注射LPS的小鼠预先静脉注射Pontamine天蓝染料产生了剂量相关的增加，在iNOS缺陷型和野生型小鼠的染料泄漏与约40%，减少iNOS缺陷型小鼠的染料泄漏。NOS抑制剂和LPS预处理均不能抑制iNOS缺陷小鼠LPS诱导的染料渗漏。这些研究表明，LPS诱导的染料渗漏是由iNOS产生的NO、前列腺素（PG）、组胺和TNF-α介导的。对LPS诱导的血管通透性改变的耐受可能是通过诱导iNOS来介导的。ONO-4007的皮下注射诱导染料渗漏的剂量依赖性增加。在iNOS缺陷型小鼠中，ONO-4007增加染料渗漏。NO、TNF-α和IL-1α在ONO-4007诱导的血浆渗漏增加中起作用，而PG或组胺不起作用。虽然ONO-4007模拟LPS增加血管通透性，但ONO-4007引起的通透性变化机制与LPS的机制不同。ONO-4007诱导对由LPS、ONO-4007和炎症介质引起的血浆渗漏的瞬时耐受。内源性皮质酮，至少部分地，在耐受性的发展中起作用。LPS诱导的免疫耐受可能为脓毒症的治疗提供了潜在的基础，脂质A类似物可能作为脓毒症休克的预防性治疗。

Subcutaneous injection of lipopolysaccharide (LPS) increases plasma leakage in mouse skin. Pretreatment with LPS conditions mice tolerant to the LPS-induced plasma leakage. Nitric oxide (NO) has been suggested to be involved in these LPS effects. A specific role of inducible NO synthase (iNOS) was investigated in the LPS-induced plasma leakage using iNOS deficient mice. It has been postulated that most biological activities of LPS are derived from lipid A moiety. We examined the effect of lipid A analog (ONO-4007) in increasing plasma leakage. Subcutaneous injection of LPS in mice that were preinjected I.v. with Pontamine sky blue dye produced a dose-related increase in dye leakage in both iNOS deficient and wild-type mice with about 40% less dye leakage in iNOS deficient mice. The LPS-induced dye leakage was not inhibited by inhibitors of NOS and LPS pretreatment in iNOS deficient mice. These studies indicate that LPS-induced dye leakage is mediated by NO produced by iNOS, prostaglandin (PG), histamine and TNF-α. The tolerance against LPS-induced vascular permeability change may be mediated by iNOS induction. Subcutaneous injection of ONO-4007 induced a dose-dependent increase in dye leakage. In iNOS deficient mice, ONO-4007 increased the dye leakage. A constitutive NOS-derived NO, TNF-α and IL-1α but not PG or histamine play a role in ONO-4007-induced increase in plasma leakage. Although ONO-4007 mimics LPS in increasing vascular permeability, mechanisms of permeability change elicited by ONO-4007 were not identical to those of LPS. ONO-4007 induced transient tolerance to plasma leakage elicited by LPS, ONO-4007 and inflammatory mediators. Endogenous corticosterone, at least in part, plays a role in development of tolerance. The tolerance induced by LPS may provide a potential basis for the treatment of sepsis, lipid A analog may be useful as a prophylactic therapy of septic shock.