- 學位論文
治療性用藥對粘多糖體誘發大白鼠敗血性休克的抑制作用
Inhibitory effect of therapeutic agent in LPS-induced septic shock in rats
摘要
敗血症（Septicemia），可由革蘭氏陰性菌（Gram negative bacteria）細胞壁上結構物質－黏多醣（lipopolysaccharide，LPS）所引起，藉由一氧化氮（NO）的生成，使血壓急劇下降和器官灌流不足時，引致敗血症休克（septic shock），嚴重時可致造成死亡。本實驗之目的是要探討在臨床上常用於治療敗血症的數種藥物，可能的作用機轉；藉由注射老鼠LPS模擬敗血症前，先給予Minocycline，Clindamycin，Cyclosporin，Platonin等藥物治療，評估藥物的改善狀況，同時觀察血壓、心跳、動物存活時間及偵測體內NO的生成量，來比較給葯與否之差異，且針對變化的可能原因來探討。 首先，選用四環素中的Minocycline（10mg/kg）此藥能與細菌體內核糖體30S結合，可抑制細菌蛋白質的合成。結果發現，Minocycline會改善LPS引起的低血壓現象，同時，降低體內NO的生成；此乃可能因Minocycline抑制NO的合成，以致血壓不會受LPS的作用影響。Clindamycin與Minocycline同樣會與細菌體核糖體30S結合，抑制蛋白質的合成。Clindamycin（10mg/kg），可抑制LPS所誘發的低血壓，且體內NO的合成亦同時被抑制。由此可知Minocycline與Clindamycin抗菌機轉類似，其改善LPS所誘發的低血壓現象，也具有相當的療效。Cyclosporin是一種免疫抑制劑，可抑制T-－細胞所促成反應發生，並會抑制Lymphokine產生及釋放。在給LPS後30分鐘，隨即給予Cyclosporin（15mg/kg），實驗顯示，Cyclosporin並不影響LPS誘發的低血壓且NO的生成量仍有增加的趨勢，因此Cyclosporin不能改善LPS引起的低血壓作用，可能與Cyclosporin無法法抑制NO的產生量有關。Platonin為一種細胞感光色素，具有消炎及組織再生作用。在給予Platonin（10mg/kg）治療後，LPS的低血壓作用獲得改善，此時NO的合成也被減緩。由實驗證實LPS造成的低血壓反應可以給予Minocycline，Clindamycin，Platonin被改善，主要的可能原因為Minocycline等三藥會抑制NO的生合成，導致緩解敗血症休克的低血壓現象。Cyclosporin則無法改變LPS的降血壓作用，亦不會改變體內NO的合成。 在心跳方面，LPS注射至老鼠體內後，因血壓逐漸下降，導致產生代償性心搏加速。在給予Minocycline，Clindamycin，Platonin後，因體內NO合成量減少，血壓上升，使得心跳加速的現象減緩。Cyclosporin因無法改善LPS的血壓下降，以致心跳持續加快。另外，在給予Minocycline，Clidamycin，Platonin後，雖有改善LPS造成的低血壓現象，但仍然沒有增加老鼠的存活時間，因此，推測可能與LPS引起的發燒反應影響下視丘的體溫調控，因Minocycline等三藥物不能改變體溫的調節，導致體溫上升，動物死亡。再者，Minocycline等三藥可降低NO的產生，但尚無法獲知體內其他傷害性介質的變化的狀況。 綜合以上的結果，Minocycline，Clindamycin，Platonin能改善LPS誘發的低血壓作用，減緩心搏過速現象同時可降低體內NO的合成。Cyclosporin則無法治療LPS的低血壓現象，亦不會改變體內NO的合成。不管藥物是否可改變LPS的低血壓狀況，皆無法延長老鼠的存活時間。所以，由本實驗可應用在臨床上對於敗血症休克時，選用治療藥物的一項參考指標。並且，期望在敗血症發生的早期投予適當的藥物。預防併發症的產生。
並列摘要
Abstract Background Septicemia is generally caused by a cell wall component in Gram negative bacterias called lipopolysaccharide (LPS). It promotes the synthesis of nitric oxide (NO), which induces drastic blood pressure fall, tissue hypoperfusion, (a state known as “septic shock”), and even death. Objective and Methods To evaluate mechanisms of drugs commonly used in the treatment of septicemia, giving antibiotics including Minocycline (10 mg/kg), Clindamycin (10 mg/kg), Cyclosporin (15 mg/kg) and Platonin (10 mg/kg) to septicemic rat injected with LPS. Clinical improvement, blood pressure, heart rate, survival time are assessed, and the amount of endogenous NO production is determined. Difference between whether or not drug therapy was given, and possible causative factors were discussed. Results First of all, we choose minocycline (10 mg/kg), which has the ability of binding to the 30S of the ribosomes in the cytoplasm of the bacterial cell, inhibiting the synthesis of bacterial proteins. As a result, Minocycline blocks the hypotensive effect induced by LPSs, and at the same time, decreases the production of endogenous NO. Therefore, Minocycline’s blood-pressure stabilizing effect may be due to its inhibitory mechanism to the synthesis of NO. Clindamycin has the same affinity of binding to the 30S in bacterial ribosome. Giving this drug at the dose of 10 mg/kg, LPS-induced hypotension and the endogenous production of NO were effectively blocked simultaneously. We can conclude that both minocycline and clindamycin posses the same antimicrobial mechanism, effectively reversing the hypotensive phenomena induced by LPSs. Cyclosporin on the other hand, is a potent immunologic agent, acting as inhibitor of T-cell reactions, and of lymphokine production and its delivery. Our experiment showed that the administration of Cyclosporin (15 mg/kg) 30 minutes before LPS injection did not affect LPS-induced hypotension, and the production of NO even increased. Consequently, Cyclosporin’s inability of controlling LPS-induced hypotension is possibly due to its lack of inhibitory properties in NO synthesis. Platonin , a cyanine photosentizing dye, is a cellular photosensitive substance with anti-inflammatory and tissue regeneration effects. Its administration (10 mg/kg) also effectively controls the LPS-induced hypotension, and slows down the generation of NO free radicals. Other than causing hypotension, LPS induces compensatory tachycardia. By giving Minocycline, Clindamycin and Platonin, NO radicals production decreases, the blood pressure climbs up, therefore the heart rate slows down. Since Cyclosporin was unable to control LPS-induced hypotension, tachycardia persists. Although Minocycline, Clindamycin and Platonin were effective in controlling LPS-induced hypotension, survival time did not increase. This might be related to reactive fever caused by hypothalamic LPS stimulation, because these agents could not regulate body temperatures, leading to animal’s hyperthermia and death. Moreover, other biological mediators may have influential effects on decreasing the production of NO radicals. These three drugs have no effects upon other harmful substances despite decreasing the production of NO radicals. Conclusion Minocycline, Clindamycin and Platonin can effectively control LPS-induced hypotension, compensatory tachycardia, by reducing NO radicals production. Cyclosporin though, has no preventive effect against LPS-induced hypotension, due to its lack of ability in slowing down the production of NO radicals. Regardless of whether or not these drugs control LPS-induced hypotension, survival length of laboratory animals showed no improvement. The present experiment offers some parameters for choosing an effective therapeutic agent in the treatment of septicemia, especially in its early stages, in order to prevent the occurrence of complications.