BCL3基因在嚴重敗血症病人的表現及預後的關聯性

Abstract

敗血症(sepsis)在重症的病患中是一個常導致嚴重併發症甚至死亡的重要原因。而合併器官功能失調(organ dysfunction)的嚴重敗血症病患(severe sepsis)，其30天的死亡率大約為30%。關於敗血症的致病機轉，除了病原體入侵病患之後所造成過度的免疫反應外，最近這些年也發現敗血症病人在疾病初期，其淋巴組織及周邊血液的淋巴球會出現大量細胞凋亡(lymphocyte apoptosis)的現象，而且疾病初期淋巴球細胞凋亡的程度與敗血症的嚴重度及預後有明顯關聯。至於敗血症病人淋巴球細胞凋亡的基因調控部分到目前為止仍然不是很清楚。在蔡等人的敗血症病患基因微陣列分析研究中，B-cell CLL/lymphoma 3基因(基因簡稱BCL3)，一個對於淋巴球生長具有重要調控作用的基因，無論在革蘭氏陽性細菌或革蘭氏陰性細菌所造成敗血症病患的周邊血液單核球細胞中的表現都比健康的對照組來得高。因此，我們假設BCL3基因在敗血症中可能對淋巴球的存活有重要的影響，進一步希望能分析基因表現對疾病嚴重度及預後的影響。 我們收集診斷為嚴重敗血症並且需要接受加護病房照護之病患，並於24小時之內抽取病患血液檢體，對照組則為至台大健康管理中心接受健檢且大於40歲的成人，之後利用同步定量聚合酶連鎖反應(Real-time Polymerase Chain Reaction, RT-PCR)的技術來分析敗血症病患及無敗血症病患周邊血液單核細胞內BCL3基因的表現，並分析敗血症病患周邊血液淋巴球細胞數量的變化。 臨床上分析的指標包括性別、年齡、白血球數目、急性生理及慢性健康評估評分(Acute Physiology and Chronic Health Evaluation II score, APACHE II score) 、器官功能失調數目、器官衰竭評估計分(Sequential Organ-Failure Assessment score, SOFA score)、休克的天數、是否須要接受透析治療、須要使用呼吸器和須要住在加護病房的天數、致病菌的種類及28天死亡率。 此研究包括51位嚴重敗血症的患者以及9位健康的對照組，在BCL3基因表現量的分析發現，敗血症組是健康組的16倍。即使是沒有過往疾病史的敗血症病患BCL3基因表現量也是比較高，是健康組的22倍，兩組間是達到統計上顯著的差異(P值小於0.05)。在敗血症疾病初期，患者的周邊血液淋巴球低下(lymphopenia)是非常普遍的(75.5%)，這樣的情形一週後會有改善(52.3%)，特別是在BCL3基因表現比較強的病人，在一週後會有較少病人(37.5%)持續淋巴球低下的狀況。在疾病嚴重度及預後的統計分析上，BCL3基因表現強的病人在疾病初期有較高的SOFA score，比較少的無休克天數(Shock-free day)和存活天數(28-day survival days)以及較高的死亡率(38.7%)。 此研究顯示在嚴重敗血症初期 BCL3基因的表現是明顯增加，而且在BCL3基因表現比較強的病人，他們周邊血液淋巴球低下的恢復會比基因表現比較弱的病人來得快，並且也證實基因表現和疾病嚴重度及預後的關聯，這將有利於未來臨床實驗利用細胞凋亡阻斷劑來治療嚴重敗血症之適當時機的一個很好依據。

Sepsis is the leading cause of morbidity and mortality in critically ill patients. The 30-day mortality in patients with severe sepsis is approximately 30%. In addition to excessive inflammatory response, unregulated apoptosis of peripheral circulating lymphocytes and splenocytes had been observed in patients with severe sepsis and may lead to immunosupression. However, the mechanism of lymphocyte apoptosis remains unclear. BCL3 gene encodes proteins which interact with p50 NF-kB homodimers and promote the survival of activated T-cell lymphocytes. We try to correlate the expression of BCL3 gene with the count of peripheral blood lymphocyte and other clinical variables. We investigated the expression of BCL3 gene by RT-PCR method in patients with severe sepsis, which required ICU admission. We also analyzed peripheral lymphocyte count and clinical parameters, including age, sex, infection source、white blood cell count、APACHE II score、SOFA score、number of organ dysfunction、duration of shock and mechanical ventilation、need for dialysis、ICU and hospital stay、microbiology and 28-day mortality。Univariate and multivariate analyses are performed using gene expression and clinical variables. A total of 51 patients with severe sepsis had been analyzed. Another 9 healthy people had been enrolled as control group. The mean BCL-3 gene expression (represented as 2-△CT BCL3-TBP) was 33.9 in septic group and 2.1 in control group (P=0.021). Lymphopenia was common on admission (75.5%) and subsided partially one week later (52.3%). The patients with higher BCL3 gene expression had shorter duration for recovery of peripheral blood lymphocytes. Kaplan-Meier analysis revealed that higher BCL3 gene expression was associated with poor prognosis in 28-day mortality (38.7% vs. 10.0%, P=0.022). Statistical analysis showed patients with higher BCL3 gene expression had less 28-day survival time (22.0±9.2 vs. 27.1±3.2 days, P=0.022), higher SOFA score on ICU admission (10.2±3.4 vs. 8.2±2.3, P=0.022), more 28-day shock-free duration (14.5±12.0 vs. 22.2±9.2 days, P=0.021) than those with lower BCL3 expression. In Cox proportional hazards regression model, higher BCL3 gene expression, APACHE II score and ventilator-free day were independent prognostic factors for 28-day mortality, with a hazard ratio of 26.1 (95%CI, 1.547-440.3, P=0.024), 1.156 (95%CI, 1.029-1.298, P=0.014) and 0.865 (95%CI, 0.763 – 0.982, P=0.025) for 28-day mortality, respectively. The study revealed that BCL3 gene expression was increased in the patients with severe sepsis. The patients with higher BCL-3 expression had shorter duration for the recovery of peripheral circulating lymphocytes, but it was correlated with poor short-term outcome.