Pharmacological Preconditioning with Vitamin C Attenuates Intestinal Injury via the Induction of Heme Oxygenase-1 after Hemorrhagic Shock in Rats

Pre-induction of heme oxygenase (HO)-1, which is regarded as an effective method of “organ preconditioning”, exerts beneficial effects during hemorrhagic shock (HS). However, the available HO-1 inducers exhibit disadvantages such as toxicity or complex technical requirements. Therefore, a safe and convenient HO-1 inducer would be promising and could be exploited in the treatment of foreseeable hemorrhaging, such as prior to major surgery. Here we investigated the effect of vitamin C (VitC), a common antioxidant, on intestinal HO-1 expression and examined whether VitC pretreatment prevented HS related intestinal tissue injuries after HO-1 induction. First, we conducted an in vitro study and found that HO-1 expression in rat intestinal epithelial cells (IEC-6) was induced by non-toxic VitC in a time and concentration dependent manner, and the mechanism was related to the activation of extracellular signal-regulated kinase 1/2 (ERK1/2). Next, we conducted an in vivo study and found that VitC induced intestinal HO-1 protein expression (mainly observed in the intestinal epithelial cells) and HO-1 activity in normal SD rats, and that these HO-1 levels were further enhanced by VitC in a rat model of HS. The HS related intestinal injuries, including histological damage, pro-inflammatory cytokine levels (tumor necrosis factor and interleukin-6), neutrophil infiltration and apoptosis decreased after VitC pretreatment, and this alleviating of organ injuries was abrogated after the inhibition of HO-1 activity by zinc protoporphyrin-IX. It was of note that VitC did little histological damage to the intestine of the sham rats. These data suggested that VitC might be applied as a safe inducer of intestinal HO-1 and that VitC pretreatment attenuated HS related intestinal injuries via the induction of HO-1.

血红素加氧酶-1（heme oxygenase-1，HO-1）的预诱导被视为“器官预处理”的有效策略，在失血性休克（hemorrhagic shock，HS）进程中可发挥保护作用。然而，现有HO-1诱导剂存在毒性较高或技术要求繁琐等缺陷。因此，开发一种安全便捷的HO-1诱导剂，有望用于可预见的出血性病症的临床治疗，例如大型手术前的预防性预处理。本研究针对常见抗氧化剂维生素C（vitamin C，VitC）对肠道HO-1表达的调控作用展开探讨，并考察了VitC预处理是否能在HO-1诱导后，减轻失血性休克引发的肠道组织损伤。首先，我们开展了体外实验，结果显示无毒浓度的VitC可呈时间、浓度依赖性诱导大鼠肠上皮细胞（IEC-6）的HO-1表达，其分子机制与细胞外信号调节激酶1/2（extracellular signal-regulated kinase 1/2，ERK1/2）的激活密切相关。随后，我们进行了体内实验，发现VitC可在正常SD大鼠中诱导肠道HO-1蛋白表达（主要表达于肠上皮细胞）并提升HO-1活性；在失血性休克大鼠模型中，VitC可进一步上调上述HO-1的表达与活性水平。VitC预处理可缓解失血性休克相关的肠道损伤，包括组织学损伤、促炎细胞因子（肿瘤坏死因子tumor necrosis factor、白细胞介素-6interleukin-6）水平升高、中性粒细胞浸润及细胞凋亡；而使用锌原卟啉IX（zinc protoporphyrin-IX）抑制HO-1活性后，这种脏器损伤的缓解效应被完全抵消。值得注意的是，VitC对假手术大鼠的肠道几乎无明显组织学损伤。上述研究结果表明，VitC可作为一种安全的肠道HO-1诱导剂，且VitC预处理通过诱导HO-1表达，减轻失血性休克相关的肠道组织损伤。