Cellular Basis Of Action Of Gastrointestinal Peptides/Growth factors

最近的研究表明，胃肠激素/生长因子可能通过刺激细胞内多个酪氨酸磷酸化(TyrP)信号通路以及反式激活生长因子受体而导致细胞生长。然而，目前对许多胃肠激素/生长因子激活这些级联反应的能力知之甚少。在一项针对肺癌细胞的研究中，我们研究了神经降压素的G蛋白偶联受体刺激其生长的能力。我们发现其机制涉及EGF受体的反式激活以及刺激活性氧物种、基质金属蛋白酶和Src的激活。针对NT受体1的SI RNA降低了NTS1拮抗剂SR48692抑制肺癌细胞生长的能力。拮抗剂增强了吉非替尼的抑制作用。神经内分泌肿瘤细胞也进行了类似的研究，不同的胃肠激素(蛙皮素、神经张力、PACAP)以类似的方式调节生长效应。这些结果提示，胃肠激素抑制EGFR信号转导通路可能是一种有效的治疗方法。 与西班牙马德里的N.Gonzalez博士合作，我们探索了BNR受体BRS-3调节脂肪和胰岛素代谢的细胞机制。对正常、肥胖或糖尿病受试者分散的心肌细胞中的BRS-3信号进行了研究。Brs3激动剂增加MAPK、p90RSK1、PKB、PI3K和P70sgK的活性。它还能刺激糖原合成酶a的活性和糖原合成。肥胖症或糖尿病患者的肌细胞更敏感。 胰腺星状细胞在胰腺炎和胰腺癌中都具有重要作用，它们可被多种细胞因子和G蛋白偶联受体激活，但对它们在胰腺炎发病中的作用和信号转导机制知之甚少。与日本福冈的伊藤教授合作进行了两项研究，调查它们在胰腺炎中的信号转导。在一项研究中，研究了细胞因子Fractalkine(CXCL1)在胰腺炎中的作用，发现它是由星状细胞通过涉及金属蛋白酶的MPK机制分泌的，这可能有助于星状细胞在引起胰腺炎中的信号转导作用。在第二项研究中，在星状细胞上发现了GLP1的受体。这一点可能特别重要，因为这些药物被广泛用于治疗糖尿病，而它们不想要的副作用之一是胰腺炎，其机制尚不清楚。我们发现GLP1R受体在胰腺炎期间数量增加，在星状细胞中，它们激活MAPK级联并导致这些细胞的生长，提示它们可能参与了GLP1-R使用的这种副作用。在最后一项研究中，我们用三种不同的方法详细研究了胃肠激素CCK在胰腺腺泡细胞中激活Src激酶的作用：通过腺病毒过度表达SFK激动剂或抑制物。这些结果表明，SFK参与了许多重要的细胞过程，包括生长、分泌、运动以及这些细胞对胰腺炎等病理过程的反应。

Recent studies show that gastrointestinal hormones/growth factors may cause cell growth by stimulating multiple intracellular tyrosine phosphorylation (TyrP) signaling cascades as well as by transactivating growth factor receptors. However at present little is known about the ability of many gastrointestinal hormones/growth factors to activate these cascades. In a study on lung cancer cells we investigated the ability of the G-protein coupled receptors for neurotensin to stimulate their growth. We found that the mechanism involved transactivation of the EGF receptor as well as stimulating activation of reactive oxygen species, matrix metalloproteinases and Src. SI RNA for NT receptors 1 reduced the ability the NTS1 anatagonist,SR48692, to inhibit the growth of the lung cancer cells. THe antagonist potentiated the inhibitory action of gefitinib. Similar studies were performed with neuroendocrine tumor cells and the growth effects of various GI hormones (bombesin, Neurotenisn, PACAP) were mediated in a similar manner. These results suggest inhibition of the EGFR signaling cascade by GI hormones may be a useful therapeutic approach. In collaboration with Dr N.Gonzalez(Madrid, Spain) we explored the cellular mechanisms by which the BnR receptor, BRS-3 regulates fat and insulin metabolism. BRS-3 signaling was investigated in dispersed myocytes form normal, obese, or diabetic subjects. BRS3 agonists increased activity of MAPK,p90RSK1, PKB, PI3K,and P70sgK. It also stimualted glycogen synthetase a activity and glycogen synthesis.. Myocytes from obesity or diabetic patients were mor sensitive. Pancreatic stellate cells are important in both pancreatitis and pancreatic cancer and they are activated by a number of cytokines and G-protein coupled receptors however little is known of their signaling or importance in causing pancreatitis. Two studies in collaboration with Prof Ito, Fukuoka, Japan were performed investigating their signaling in pancreatitis. In one study, the role of the cytokine fractalkine (CXCL1) in pancreatitis was investigate and it was found to be secreted by stellate cells though a MPK mechanism involving metalloproteinase, and this could contribute to the role of stellate cells signaling in causing pancreatitis. In a second study receptors for the GLP1 were found on stellate cells. This could be particularly important because these agents are widely used to treat diabetes and one of their unwanted side-effect is pancreatitis, the mechanism of which is unknown. We found GLP1R receptor increase in number during pancreatitis, in the stellate cells, they activate the MAPK cascade and can cause growth of these cells suggesting they may be involve in this side-effect of GLP1-R usage. In a final study the role of Src kinase activation by the GI hormone CCk was studied in detail in pancreatic acinar cells using three different approaches.: a specific SFK inhibitor with inactive control, over expression by adenovirus of SFK stimulants or inhibitors. These resulted demonstrated that SFK were involved in a number of cellular processes important in growth, secretion, movement and in the response of these cells to pathological processes such as pancreatitis.