Hull M A, Faluyi O O, Ko C W S, Holwell S, Scott D J, Cuthbert R J, Poulsom R, Goodlad R, Bonifer C, Markham A F, Coletta P L
Molecular Medicine Unit, University of Leeds, Leeds LS9 7TF, UK.
Carcinogenesis. 2006 Mar;27(3):382-91. doi: 10.1093/carcin/bgi236. Epub 2005 Oct 11.
Cyclooxygenase-2 (Cox-2) is expressed predominantly by stromal cells in intestinal adenomas from the Apc(Min/+) mouse model of familial adenomatous polyposis. We investigated the mechanistic basis of stromal cell Cox-2 expression in Apc(Min/+) mouse adenomas, as well as Cox-2 expression and activity in histologically normal (HN) Apc(Min/+) mouse intestine, in order to gain further insights into regulation of Cox-2 as a potential chemoprevention target. Upregulation of Cox-2 in intestinal tumours is not an intrinsic feature of Apc(Min/+) macrophages as bone marrow-derived Apc(Min/+) macrophages did not exhibit an abnormality in Cox-2 expression or activity. Intestinal permeability to lactulose or mannitol was similar in Apc(Min/+) mice and wild-type littermates, implying that macrophage activation by luminal antigen is unlikely to explain stromal cell Cox-2 induction. Moreover, stromal cells exhibited differential expression of Cox-2 and inducible nitric oxide synthase, suggesting 'alternative' (M2) rather than 'classical' (M1) macrophage activation. Flow cytometric sorting of isolated stromal mononuclear cells (SMNCs), on the basis of M-lysozyme and specific macrophage marker expression, demonstrated that macrophages, neutrophils and non-myelomonocytic cells all contributed to lamina propria prostaglandin (PG) E(2) synthesis. However, the majority of PGE(2) synthesis by macrophages was via a Cox-2-dependent pathway compared with predominant Cox-1-derived PGE(2) production by non-myelomonocytic cells. SMNCs from HN Apc(Min/+) intestinal mucosa exhibited similar levels of Cox-2 mRNA and protein, but produced more Cox-2-derived PGE(2) than wild-type cells at 70 days of age. There was an age-dependent decline in PGE(2) synthesis by Apc(Min/+) SMNCs, despite tumour progression. These data suggest that other Cox-2-independent factors also control PGE(2) levels during Apc(Min/+) mouse intestinal tumorigenesis. Regulation of macrophage Cox-2 expression and other steps in PGE(2) synthesis (e.g. PGE synthase) are valid targets for novel chemoprevention strategies that could minimize or avoid systemic COX-2 inhibition.
在家族性腺瘤性息肉病的Apc(Min/+)小鼠模型的肠道腺瘤中，环氧化酶-2（Cox-2）主要由基质细胞表达。我们研究了Apc(Min/+)小鼠腺瘤中基质细胞Cox-2表达的机制基础，以及组织学正常（HN）的Apc(Min/+)小鼠肠道中Cox-2的表达和活性，以便进一步深入了解作为潜在化学预防靶点的Cox-2的调控。肠道肿瘤中Cox-2的上调并非Apc(Min/+)巨噬细胞的固有特征，因为骨髓来源的Apc(Min/+)巨噬细胞在Cox-2表达或活性方面未表现出异常。Apc(Min/+)小鼠和野生型同窝小鼠对乳果糖或甘露醇的肠道通透性相似，这意味着管腔抗原激活巨噬细胞不太可能解释基质细胞Cox-2的诱导。此外，基质细胞表现出Cox-2和诱导型一氧化氮合酶的差异表达，提示“替代性”（M2）而非“经典”（M1）巨噬细胞激活。基于M-溶菌酶和特异性巨噬细胞标志物表达，对分离的基质单核细胞（SMNCs）进行流式细胞术分选，结果表明巨噬细胞、中性粒细胞和非髓单核细胞均参与固有层前列腺素（PG）E(2)的合成。然而，与非髓单核细胞主要通过Cox-1产生PGE(2)相比，巨噬细胞产生的大部分PGE(2)是通过Cox-2依赖性途径。来自HN Apc(Min/+)肠道黏膜的SMNCs在70日龄时Cox-2 mRNA和蛋白水平相似，但比野生型细胞产生更多的Cox-2衍生的PGE(2)。尽管肿瘤进展，但Apc(Min/+) SMNCs产生的PGE(2)随年龄下降。这些数据表明，在Apc(Min/+)小鼠肠道肿瘤发生过程中，其他不依赖Cox-2的因素也控制着PGE(2)水平。调节巨噬细胞Cox-2表达以及PGE(2)合成中的其他步骤（如PGE合酶）是新型化学预防策略的有效靶点，这些策略可最大限度减少或避免全身性COX-2抑制。
