Characterization of persistent hyperemic foci and their role in photocarcinogenes

描述(由申请人提供)：慢性炎症促进覆盖上皮细胞的DNA损伤，并经常与肿瘤疾病有关。此外，DNA对上皮组织的损伤会导致大量细胞因子和趋化因子的释放，从而促进炎症反应。尤其是，导致细胞衰老的持续性DNA损伤反应(PDDR)在产生持续来源的促炎介质方面尤其有效；这种反应被称为衰老相关分泌表型(SASP)。因此，DNA损伤/SASP和炎症的自我持续循环可能会导致覆盖上皮细胞持续的突变压力，这似乎是合理的。我们建议的研究将检验这种联系。这是可能的，因为一种新的生物成像方法，监测真皮微血管血红蛋白(HGB)的含量。我们发现，在小鼠皮肤上应用化学致癌物或紫外线(UV)后，会出现局部充血。充血在肿瘤形成之前，肿瘤总是发生在这些充血的区域，这些区域被认为在最初的致癌紫外线暴露停止后持续并扩大。只有充血增加的区域才与表皮增生和真皮炎症有关。此外，塞来昔布，一种已知的抗炎药，被证明可以抑制这些区域的充血以及随后的肿瘤形成。我们假设，最初的致癌暴露在上皮或真皮细胞中诱导了PDDR偶联的SASP，然后驱动在肿瘤发生之前的DNA损伤/真皮炎性血管生成的自我持续循环。我们将利用我们独特的生物成像策略在两个目标上检验这一想法。在第一个目标中，我们将把小鼠暴露在有限时间的致癌剂量的紫外线下，然后绘制出微血管血液供应的早期变化。然后我们将验证充血区域对应于微观或宏观肿瘤性疾病之前的炎性血管生成区。我们还将确定这些充血区是否表现出SASP特有的炎症介质的浓缩。在第二个目标中，我们将检查覆盖在早期充血区域的表皮是否表现出关键的DNA损伤调节因子p53的突变增加，这是已知的增强SASP反应的突变。此外，我们将确定充血灶早期的真皮成纤维细胞或表皮角质形成细胞是否存在衰老标记物异染色质蛋白1g(HP1g)以及双链DNA断裂标记物gH2AX和p53BP1。此外，使用转基因小鼠模型(大蓝鼠)，我们将确定充血区域是否与表皮突变频率增加有关，以及在没有进一步紫外线暴露的情况下，这种突变压力是否持续。在这两个目标中，我们将研究两种抗炎药(塞来昔布和CXCR2受体拮抗剂)抑制充血灶形成的能力，以及与炎症、衰老和表皮突变压力增加相关的特征。

DESCRIPTION (provided by applicant): Chronic inflammation promotes DNA damage to overlying epithelium and is frequently associated with neoplastic disease. In addition, DNA damage to epithelial tissues results in the release of a number of cytokines and chemokines that promote an inflammatory response. In particular, a persistent DNA damage response (PDDR) leading to cellular senescence is particularly potent in producing a sustained source of pro- inflammatory mediators; this response has been called the senescence associated secretory phenotype (SASP). It would therefore seem reasonable that a self-perpetuating cycle of DNA damage/SASP and inflammation could occur that would lead to continuing mutation pressure in overlying epithelium. Our proposed studies will examine this linkage. This is possible due to a novel bioimaging approach that monitors dermal microvascular hemoglobin (Hgb) content. We show that focal areas of hyperemia occur following the application of chemical carcinogens or ultraviolet (UV) light to mouse skin. Hyperemia preceded tumor formation, tumors were found to invariably occur in these areas of hyperemia, and these areas were seen to persist and expand following the cessation of an initial carcinogenic UV exposure. Only areas with increased hyperemia were associated with epidermal hyperplasia and dermal inflammation. Moreover, celecoxib, a known anti-inflammatory agent, was shown to suppress these areas of hyperemia along with subsequent tumor formation. We hypothesize that initial carcinogenic exposures elicit a PDDR coupled SASP in epithelial or dermal cells that then drive a self- perpetuating cycle of DNA damage/dermal inflammatory angiogenesis that precedes neoplastic development. We will utilize our unique bioimaging strategy to examine this idea in two aims. In the first aim, we will expose mice to a carcinogenic dose of UV of limited duration, then map out early changes in microvascular blood supply. We will then verify that hyperemic areas correspond to zones of inflammatory angiogenesis that precede microscopic or macroscopic neoplastic disease. We will also determine whether these hyperemic zones exhibit enrichment for characteristic SASP inflammatory mediators. In the second aim, we will examine whether the epidermis overlying early hyperemic areas exhibit increased mutations of the key DNA damage regulator, p53, which is known to augment the SASP response. Moreover, we will determine whether dermal fibroblasts or epidermal keratinocytes in early hyperemic foci exhibit a senescence marker, heterochromatin protein 1g (HP1g), and markers of double stranded DNA breaks, gH2AX and p53BP1. In addition, using a transgenic mouse model (Big Blue mice), we will determine whether hyperemic areas are associated with increased epidermal mutation frequency and whether this mutation pressure persists in the absence of further UV exposures. In both aims, we will examine the capacity of two anti-inflammatory agents (celecoxib and a CXCR2 receptor antagonist) to suppress the formation of hyperemic foci and the associated features of inflammation, senescence and increased epidermal mutation pressure.