Koga Hiroyuki, Yang Hua, Haxhija Emir Q, Teitelbaum Daniel H
Section of Pediatric Surgery, Department of Surgery, C.S Mott Children's Hospital F3970, University of Michigan Medical School, Ann Arbor, MI 48109-0245, USA.
Pediatr Surg Int. 2008 Dec;24(12):1279-86. doi: 10.1007/s00383-008-2277-7.
We have previously shown that inhibition of angiotensin converting enzyme (ACE) significantly reduced intestinal epithelial cell (EC) apoptosis and improved morphometric intestinal adaptation in a mouse model of massive small-bowel resection (SBR). This study attempted to further examine the downstream signaling factors in this system by blocking the action of angiotensin II (ATII), hypothesizing that this would lead to similar improvement of intestinal adaptation after SBR.
Two groups of mice (C57BL/6J) underwent either a 60% mid-intestinal resection (SBR group) or a transection/re-anastomosis (Sham group). Because real-time PCR studies showed that only ATII receptor type 1a (ATII-1a) expression was significantly increased after SBR, compared to SHAM mice, we decided to use the specific ATII-1a receptor antagonist Losartan to block this signaling pathway. An additional two groups of mice received daily i.p. injections of Losartan (SBR + Losartan and Sham + Losartan group). At 7 days, the adaptive response was assessed in the remnant gut including villus height, crypt depth, EC apoptosis (TUNEL staining) and proliferation (BrdU incorporation). The apoptotic and proliferation signaling pathways were addressed by analysis of EC mRNA expression.
SBR (with and without Losartan) led to a significant increase in villus height and crypt depth. Losartan treatment did not significantly change EC proliferation, but did significantly reduce EC apoptosis rates as compared to the non-treated SBR group. Losartan treatment was associated with a significant reduction of the bax-to-bcl-2 ratio and TNF-alpha expression after SBR compared to non-treated groups. Interestingly, Losartan-treated groups showed a tremendous increase in proliferation of signaling factors EGFR, KGFR and IL7R, which may indicate an expanded potential for further intestinal adaptation also beyond 7 days after SBR.
This study showed that the ATII-1a receptor may be of crucial importance for the modulation of intestinal EC apoptosis, and for regulating the post-resectional EC adaptive response.
我们之前已经表明，在大规模小肠切除（SBR）小鼠模型中，抑制血管紧张素转换酶（ACE）可显著减少肠上皮细胞（EC）凋亡，并改善形态学上的肠道适应性。本研究试图通过阻断血管紧张素II（ATII）的作用，进一步研究该系统中的下游信号因子，推测这将导致SBR后肠道适应性得到类似改善。
两组小鼠（C57BL/6J）分别接受60%的中段肠切除（SBR组）或横断/重新吻合术（假手术组）。因为实时PCR研究表明，与假手术小鼠相比，SBR后仅1a型ATII受体（ATII-1a）表达显著增加，所以我们决定使用特异性ATII-1a受体拮抗剂氯沙坦来阻断该信号通路。另外两组小鼠每天腹腔注射氯沙坦（SBR + 氯沙坦组和假手术 + 氯沙坦组）。在第7天，评估残余肠道的适应性反应，包括绒毛高度、隐窝深度、EC凋亡（TUNEL染色）和增殖（BrdU掺入）。通过分析EC mRNA表达来研究凋亡和增殖信号通路。
SBR（使用和未使用氯沙坦）导致绒毛高度和隐窝深度显著增加。氯沙坦治疗并未显著改变EC增殖，但与未治疗的SBR组相比，确实显著降低了EC凋亡率。与未治疗组相比，氯沙坦治疗与SBR后bax与bcl-2比值及TNF-α表达的显著降低相关。有趣的是，氯沙坦治疗组显示信号因子EGFR、KGFR和IL7R的增殖大幅增加，这可能表明SBR后7天以上肠道仍有进一步适应性增强的潜力。
本研究表明，ATII-1a受体可能对调节肠EC凋亡及调控切除术后EC适应性反应至关重要。
