The role of endogenous antibiotics, Cathelicidin in liver regeneration

脊椎动物的宿主防御机制包括获得性免疫系统和先天免疫系统。前者是脊椎动物的特定系统。免疫球蛋白或T细胞受体对病原体的识别具有特异性。另一方面，后者普遍存在于昆虫等低等动物中。它对宿主与病原体的一线防御具有重要作用。Cathelicidins是哺乳动物内源性抗生素，作为先天免疫的效应分子，诱导跨膜硫酸肝素蛋白多糖的合成，参与表皮生长因子受体（EGFR）的辅助因子在皮肤创面愈合中的作用。先前我们揭示了宿主防御在皮肤感染模型中的重要性（Nature,2001）和cathelicidin表达缺乏是特应性皮炎继发感染的原因（N Engl J Med,2002）。猪抗菌肽、PR-39可诱导大鼠心肌梗死模型血管生成。巨噬细胞中存在较多的抗菌肽，脂多糖（LPS）刺激诱导抗菌肽通过Toll样受体（TLR）表达。最近报道了库普弗细胞在肝脏再生中的重要性。我们推测Kupffer细胞中的cathelicidin可直接或间接诱导肝细胞增殖。实际上我们通过RTPCR发现了正常肝组织中TLR-3至8和10 mRNA的表达。然而，我们可以发现，在正常肝组织中，cathelicidin在募集中性粒细胞而不是库普弗细胞中的表达信号。因此，为了研究和评价抗菌活性和组织愈合活性，我们利用小鼠皮肤感染模型，培育了两只抗菌素转基因小鼠。抗菌肽是哺乳动物先天免疫防御的效应器。人类和老鼠只有一个抗菌肽基因，而驯化的哺乳动物如猪、牛和马有多个抗菌肽基因。我们假设多种抗菌肽基因的进化为这些动物提供了增强的抗感染能力。为了验证这一点，我们通过在体外结合合成的抗菌肽，在培养物中产生过表达抗菌肽的人角质形成细胞，或在体内产生组成性过表达抗菌肽的转基因小鼠，来研究添加抗菌肽的影响。猪抗菌肽PR-39与人抗菌肽LL-37联合杀灭A组链球菌（GAS）。慢病毒递送PR-39增强人角质形成细胞对GAS的杀伤作用。最后，在K14启动子的影响下，表达PR-39的转基因小鼠对GAS皮肤感染的抵抗力增强（坏死溃疡缩小50%，存活细菌减少60%）。设计过表达其天然抗菌肽的类似构建的转基因小鼠没有显示出增加的耐药性。这些发现表明，外源抗菌肽的靶向基因转移赋予抗感染能力，并表明在抗菌肽的进化中复制和分化的好处。少

The mechanism of host defense of Vertebrates consists of both acquired and innate immune systems. The former is the specific system of Vertebrates. The recognition of pathogens by immunoglobulin or T cell receptor is specific. On the other hand the later exists universally in the lower animals such as insect. It has the important role for the host defense with the front line of pathogens. Cathelicidins are mammalian endogenous antibiotic, which works as the effecter molecule of innate immunity, induces the synthesis of a transmembrane heparin sulphate proteoglycan involved in co-factor of epidermal growth factor receptor (EGFR) in skin wound healing. Previously we revealed that the importance of the host defense in skin infection model (Nature,2001) and the lack of the expression of cathelicidin is the cause of secondary infection in atopic dermatitis (N Engl J Med,2002). Furthermore, porcine cathelicidin, PR-39 induce angiogenesis in model of rat myocardial infarction. Existence of ca … More thelicidin in macrophage, and stimuli by lipopolysacchaloid (LPS) induce the expression of cathelicidin via Toll like receptor (TLR). Recently the importance of Kupffer cells in liver regeneration is reported. We hypotheses that cathelicidin in Kupffer cell could induce proliferation of hepatocytes directly and indirectly. Actually we revealed that the expression of mRNA of TLR-3 to 8 and 10 in normal liver tissue by RTPCR. However we could reveal that the signals of expression of cathelicidin in recruiting neutrophils but not Kupffer cells in normal liver tissue. Therefore for investigation and evaluation of bactericidal activity and tissue healing activity, we used mouse skin infection model and generated two cathelicidin transgenic mice.Cathelicidin antimicrobial peptides are effectors of innate immune defense in mammals. Humans and mice have only one cathelicidin gene, whereas domesticated mammals such as the pig, cow, and horse have multiple cathelicidin genes. We hypothesized that the evolution of multiple cathelicidin genes provides these animals with enhanced resistance to infection. To test this, we investigated the effects of the addition of cathelicidins by combining synthetic cathelicidin peptides in vitro, by producing human keratinocytes that overexpress cathelicidins in culture, or by producing transgenic mice that constitutively overexpress cathelicidins in vivo. The porcine cathelicidin peptide PR-39 acted additively with human cathelicidin LL-37 to kill group A Streptococcus (GAS). Lentiviral delivery of PR-39 enhanced killing of GAS by human keratinocytes. Finally, transgenic mice expressing PR-39 under the influence of a K14 promoter showed increased resistance to GAS skin infection (50% smaller necrotic ulcers and 60% fewer surviving bacteria). Similarly constructed transgenic mice designed to overexpress their native cathelicidin did not show increased resistance. These findings demonstrate that targeted gene transfer of a xenobiotic cathelicidin confers resistance against infection and suggests the benefit of duplication and divergence in the evolution of antimicrobial peptides. Less