The Role of the Spleen in the Febrile Reponse

描述(由申请人提供)：尽管脾在宿主抵抗感染中的基本参与，但其在发热反应中的作用尚未得到系统的研究。我们最近报道，无论采用何种给药途径，脂多糖(LPS)诱导的发热的发生都与肝组织中内毒素的出现有时间上的相关性，脾切除显著增加了对内毒素的发热反应和肝脏(Kupffer细胞[KC])对内毒素的摄取。为了进一步探讨脾和肝在内毒素发热中的关系，我们结扎了脾和肝之间的连接，即豚鼠的脾静脉，并在7天和30天后用内毒素(LPS)腹腔内注射(Ip)刺激清醒动物。发热反应和KC对内毒素的摄取均增强，直至形成新的侧支静脉，提示正常情况下，脾可能是限制KC摄取内毒素的一个因素，从而调节发热反应。为进一步证实脾抑制因子的存在，我们制备了经脂多糖或无热原生理盐水处理的豚鼠脾提取液，匀浆和超滤后，静脉注射给经脂多糖处理的切除脾的豚鼠。结果证实了我们的假设，即内毒素处理的豚鼠的脾提取液抑制了Splex豚鼠的夸大发热反应，支持了脾抑制因子的假设。初步数据显示，S最有可能的因素是脂质。然而，可能被释放到脾静脉的脾因子(S)的身份仍然不确定，但活性成分通过标称分子量截止值为10,000 d的微孔过滤器的事实表明，它可能是前列腺素，例如前列腺素D_2、前列腺素E_2、前列腺素F_(11)、血栓素B_2或类固醇，如雌二醇。这些因素发生在脾，并影响KC的活动。因此，本研究的目的是通过分离这一因子，并证实脾巨噬细胞是其来源，从而证实脾参与了内毒素引起的发热。这项研究对于更好地理解脾如何调节发热反应以维护健康和减轻感染宿主高烧的潜在有害影响将是重要的。公共卫生关注点脾是人体的重要器官。它最关键的功能之一是帮助防止细菌和病毒感染。如果脾受损或被破坏(例如，在车祸中)，严重感染的风险就会变得更大，疾病甚至死亡的可能性也会更大。我们的实验室一直在研究脾是如何通过研究脾在发烧中的作用来保护我们免受感染的，发烧是对严重感染的第一反应。用从细菌细胞壁中提取的一种化学物质--脂多糖(LPS)处理实验动物，就会产生轻微的发热。在早期的实验中，我们发现，如果我们手术切除豚鼠的脾，内毒素引起的发烧比仍然有脾的动物高得多。为什么去脾会加重内毒素热？我们认为它牵涉到肝脏。正常情况下，内毒素会引起发烧，至少部分是通过刺激一种免疫细胞--库普弗细胞，这种细胞存在于肝脏中。内毒素从内部刺激库普弗细胞；也就是说，内毒素必须首先进入库普弗细胞，然后才能引起发烧。我们的数据表明，正常情况下，脾通过产生一种化学物质，通过血液进入肝脏，并告诉库普弗细胞不要摄取内毒素，从而保护我们免受发烧。当我们切除脾时，我们所说的这种脾因子是不可用的，库普弗细胞能够吸收更多的内毒素，并产生更高的发烧。本研究的目的是找出从脾释放的物质的身份，确认枯否细胞是脾因子的靶标，并确定其细胞来源。为了做到这一点，我们将用内毒素处理豚鼠，使脾产生脾因子，在麻醉下取出脾，然后提取脾。然后，我们将用脾提取物治疗去脾的豚鼠，看看这种提取物是否能保护它们免受过量的内毒素和脾切除动物的夸大发热反应的影响。用这种方法，我们应该能够从保护豚鼠免受内毒素影响的提取物中分离出脾因子。从长远来看，如果我们能确定这种脾因素，我们可能会发现一种可以退烧并保护患者免受感染危险影响的药物。

DESCRIPTION (provided by applicant): The role of the spleen in the febrile response has not been systematically investigated in spite of its fundamental participation in the host defenses against infections. We reported recently that the onset of lipopolysaccharide (LPS)-induced fever, irrespective of its route of administration, is temporally correlated with the appearance of LPS in the liver, and that splenectomy significantly increases both the febrile response to LPS and the uptake of LPS by the liver (Kupffer cells [KC]). To further evaluate the association between the spleen and the liver in LPS fever production, we ligated the connection between them, the splenic vein of guinea pigs and, 7 and 30 days later, challenged the conscious animals with LPS intraperitoneally (ip). Both the febrile response and the uptake of LPS by KC were augmented until new collateral veins developed, suggesting that the spleen may normally contribute a factor that limits the KC uptake of LPS and, thus, modulates the febrile response. To further verify the presence of a splenic inhibitory factor, we prepared an extract of spleens from guinea pigs pretreated ip with LPS or pyrogen-free saline, homogenized and ultrafiltered it, and injected it intravenously (iv) into splenectomized guinea pigs pre-treated with LPS ip. The results confirmed our presumption, viz., the splenic extract from LPS treated guinea pigs inhibited the exaggerated febrile response observed in the Splex guinea pigs, supporting the putative presence of a splenic inhibitory factor. Preliminary data indicates that the factor/s most likely is a lipid. The identity of the splenic factor(s) that may thus be released into the splenic vein, however, is (are) still uncertain, but the fact that the active principle passes through a microporous filter having a nominal molecular weight cutoff of 10,000 d suggests it could be a prostanoid, e.g., PGD2, PGE2, PGF11, thromboxane B2, or a steroid, such as estradiol. These factors occur in the spleen and influence KC activity. The purpose of the present study, therefore, is to substantiate the involvement of the spleen in LPS-induced fever by isolating this factor, and verifying that splenic macrophages are its source. This study will be important for better understanding how the febrile response may be regulated by the spleen to defend health and mitigate the potentially harmful effects of high fevers in infected hosts. PUBLIC HEALTH RELEVANCE The spleen is an important organ of the body. One of its most critical functions is to help prevent infection by bacteria and virus. If the spleen becomes damaged or destroyed (in an automobile accident, for example), the risk of a serious infection becomes much greater, as does the possibility of illness, disease, and even death. Our laboratory has been studying how the spleen protects us from infection by investigating the role of the spleen in the production of fever, one of the first responses to a serious infection. Mild fever can be produced in laboratory animals by treating them with lipopolysaccharide (LPS) a chemical extracted from the cell wall of bacteria. In earlier experiments we found that if we surgically removed the spleen of guinea pigs, LPS caused a much higher fever than it does in animals that still have a spleen. Why does removing the spleen potentiate LPS fever? We think that it involves the liver. Normally, LPS causes fever, at least in part, by stimulating a type of immune cell, the Kupffer cell, which is found in the liver. LPS stimulates Kupffer cells from the inside; that is, LPS must first be taken up into the Kupffer cell before it can cause fever. Our data indicate that the spleen normally protects us against fever by making a chemical that travels through the blood to the liver and tells the Kupffer cells NOT to take up LPS. When we remove the spleen, this splenic factor, as we call it, it not available and Kupffer cells are able to take up a lot more LPS and produce a much higher fever. The objective of our research is to discover the identity of the substance released from the spleen, confirm that Kupffer cells are the target of the splenic factor, and to identify its cell source. To accomplish this, we will treat guinea pigs with LPS to cause the spleen to make the splenic factor, remove the spleen under anesthesia, and then make extracts of the spleen. We will then treat splenectomized guinea pigs with the spleen extracts and see if the extract protects them against the excess of LPS and the exaggerated febrile response of splenectomized animals. With this approach, we should be able to isolate the splenic factor from the extracts that protect guinea pigs against the effects of LPS. In the longer term, if we can identify this splenic factor, we might be able to discover a drug that will reduce fever and protect patients from the dangerous effects of infection.