Angiopoietin growth factors and Tie receptor tyrosine kinases in renal vascular development

Angiopoietin-1 (Ang-1) is a secreted growth factor which binds to and activates the Tie-2 receptor tyrosine kinase. The factor enhances endothelial cell survival and capillary morphogenesis, and also limits capillary permeability. Ang-2 binds the same receptor but fails to activate it: hence, it is a natural inhibitor of Ang-1. Ang-2 destabilises capillary integrity, facilitating sprouting when ambient vascular endothelial growth factor (VEGF) levels are high, but causing vessel regression when VEGF levels are low. Tie-1 is a Tie-2 homologue but its ligands are unknown. Angiopoietin and Tie genes are expressed in the mammalian metanephros, the precursor of the adult kidney, where they may play a role in endothelial precursor growth. Tie-1-expressing cells can be detected in the metanephros when it first forms and, based on transplantation experiments, these precursors contribute to the generation of glomerular capillaries. During glomerular maturation, podocyte-derived Ang-1 and mesangial-cell-derived Ang-2 may affect growth of nascent capillaries. After birth, vasa rectae acquire their mature configuration and Ang-2 expressed by descending limbs of loops of Henle would be well placed to affect the growth of this medullary microcirculation. Finally, preliminary data implicate angiopoietins in deregulated vessel growth in Wilms’ kidney tumours and in vascular remodelling after nephrotoxicity. Received: 13 July 2000 / Revised: 6 September 2000 / Accepted: 11 September 2000     

Enhanced expression of tyrosine kinase receptor a in germ cells of rat testis with acute experimental testicular torsion

OBJECTIVE AND METHODS: To examine the involvement of neurotrophic factor receptors in the testis with acute experimental testicular torsion, the expression of tyrosine kinase receptors (trk) A and B, and p75 nerve growth factor receptor (NGFR) were studied in the rat testis with ischemia/reperfusion (I/R) injury, using Western blotting and immunohistochemistry. Apoptosis was detected using the terminal deoxynucleotidyl transferase-mediated dUTP nick end-labeling (TUNEL) method. RESULTS: There was a significant increase in TUNEL-positive reaction in spermatogonia in the seminiferous tubules in rat testes after testicular torsion. Western blot analysis showed that trk A expression reached a significant peak at 12 h after reperfusion (p < 0.01), as compared to sham-operated controls, whereas trk B was not increased in the testis after I/R. Constitutive expression of p75 NGFR was at or below the level detectable by Western blot analysis, and it remained unchanged in the testis after I/R. Immunohistochemistry demonstrated that after I/R trk A expression was increased in spermatocytes and spermatids in the seminiferous tubules, in contrast to the basal location of the TUNEL-positive reaction. Immunoreactivity of trk B was seen mainly in the interstitial cells in the sham-operated testis, and its localization was not changed after I/R. CONCLUSION: It is postulated that trk A and B, but not p75 NGFR, are involved differently in the survival of testicular cells during acute experimental testicular torsion. In particular, increased trk A seems to be related to germ cell survival following I/R.     

大鼠星形胶质瘤细胞系C6细胞μ受体的表达

目的 鉴定大鼠星形胶质瘤细胞系C6细胞μ受体的表达.方法 星形胶质瘤细胞系C6细胞培养、消化、传代后,接种于50 ml培养瓶中,待细胞生长至融合率达80%～90%时,采用RT-PCR法测定μ受体mRNA的表达,免疫组化SP法测定μ受体蛋白的表达.将C6细胞接种于无菌的盖玻片上,待细胞生长至融合率达40%～50%时,孵育、去脂后,随机分为5组:A组加入PBS 20μl;B组加入μ受体选择性激动剂DAMGO 1 μmol/L 20 μl;C组加入吗啡1 μmol/L20μl;D组先加入κ受体选择性抑制剂nor-Binaltorphimine 1 μmol/L 20μl,10 min后再加入吗啡1 μmol/L 20μl;E组先加入纳洛酮lμmol/L 20μl,10 min后再加入吗啡1 μmol/L 20μl.采用FV500型激光扫描共聚焦显微镜测定给予激动剂前、后细胞内游离钙离子浓度([Ca2+]j).结果 C6细胞存在μ受体mRNA,且μ受体主要分布于细胞膜及细胞浆;A组、B组和E组[Ca2+]i无变化(P>0.05),C组和D组[ca2+]i呈一过性升高(P<0.05).结论 标准条件下培养的大鼠星形胶质细胞系C6细胞膜表面可能存在μ3型受体.     

Inhibition of tyrosine kinases PDGFR and C-Kit by imatinib mesylate interferes with postnatal testicular development in the rat

The tyrosine kinase receptor c-kit and its interaction with the ligand, stem cell factor (SCF), play an essential role in the developing testis. C-kit is important for the development of the Leydig cells and for the migration, proliferation and survival of spermatogonia. Platelet-derived growth factor (PDGF) and its tyrosine kinase receptor (PDGFR) are important for the development of Leydig cells and myoid cells. The chemotherapeutic agent, imatinib mesylate (STI571, Glivec; Novartis) inhibits both of these tyrosine kinase receptors. Three-day treatment of immature male rats (SD) with imatinib (150 mg/kg) on postnatal days 5-7 delayed the formation of germ-line stem cell pool, reduced proliferation of type A spermatogonia and induced germ cell apoptosis. PDGFR-mediated proliferation of mesenchymal myoid precursors was also decreased and the length of the seminiferous cord was reduced. However, at the age of 11 weeks the exposed animals had normal epididymal sperm counts, whereas plasma levels of luteinizing hormone and follicle stimulating hormone were significantly increased. Imatinib serves as a good tool to study postnatal formation of the male germ-line stem cell pool and factors determining the final testicular size. As development of the human testis is controlled by the same mechanisms, further studies with primate and human models are needed to explore whether imatinib affects the testis in children as well.     

Regional variation in macrophage antigen expression by murine epididymal basal cells and their regulation by testicular factors

Factors controlling the appearance in the epididymis of basal cells and their expression of macrophage antigens were examined by ligating the efferent ducts to prevent the entry of spermatozoa in adult and juvenile mice. Fixation and antigen retrieval techniques were developed to preserve tissue morphology and expression of two macrophage antigens in paraffin-embedded epididymal tissue. A combination of periodate-lysine-phosphate fixation, low-temperature embedding and enzyme predigestion of sections permitted immunohistochemical detection of the mature macrophage antigen Mac-1, whereas the panmacrophage marker F4/80 required fixation in neutral-buffered formalin. Epididymal basal cells were immunostained for F4/80 and quantified with avidin-biotin-peroxidase. In the adult mouse, the total number of basal cells per millimeter length of tubule cross section perimeter and the percentage expressing the F4/80-antigen were significantly higher in the initial segment and caput region than in all other epididymal regions. In the initial segment, immunostained basal cells surrounded the tubule in a network, and some extended towards the lumen. Ligation of the efferent ducts to prevent inflow of testicular secretions significantly reduced the number of basal cells per cross section in the initial segment of the adult and juvenile; the percentage of basal cells expressing macrophage antigens in the initial segment and the caput epididymidis was also reduced. Since basal cells still appeared in the ligated postpubertal epididymis, it is concluded that testicular exocrine secretions entering the epididymal lumen around puberty are not the major influence on basal cell appearance in the murine epididymis, but they may modulate their expression of macrophage antigens.     

Immunohistochemical detection of receptor tyrosine kinases c-kit, EGF-R, and PDGF-R in colorectal adenocarcinomas

Purpose  

The selective inhibition of tyrosine kinases is a promising strategy in the treatment of several human malignancies. This study aimed to clarify expression patterns of therapeutically addressable receptor tyrosine kinases in colorectal cancer.     

G蛋白偶联受体激酶(GRKs)在肾脏功能调控中的作用

G蛋白信号转导通路是人体重要的信号转导途径.G蛋白偶联受体激酶(GRKs)属丝氨酸/酪氨酸蛋白激酶家族,其亚型广泛存存于各种组织,能特异地磷酸化G蛋白偶联受体(GPCRs)使其脱敏,从而使受体介导的信号转导效应消失或者降低.肾脏中存在多种G蛋白偶联受体,现就其中具有代表性的三个受体(多巴胺受体、血小板活化因子受体、血管...     

Nuclear androgen receptor dynamics in testicular peritubular and Sertoli cells

Nuclear androgen receptor dynamics were analyzed in peritubular cells and compared with those in cultured Sertoli cells. Nuclear receptors with a high affinity for [3H]dimethylnortestosterone (DMNT; mibolerone) exhibited equilibrium constants of 0.8 and 0.7 nmol, in Sertoli and peritubular cells, respectively. Time- and dose-dependent accumulation of nuclear bound receptors after exposure of whole cells to [3H]testosterone was similar for both cell types. Exogenously administered ligands demonstrated similar relative potencies as competitors with [3H]T for Sertoli and peritubular cell nuclear binding sites: DMNT greater than T greater than medroxyprogesterone acetate (MPA) greater than cyproterone acetate (CPA) tau hydroxyflutamide (OHF). Cells incubated with T or MPA showed increased nuclear androgen receptor concentrations compared to untreated controls, whereas those treated with CPA or OHF did not. These results demonstrate that the nuclear androgen receptor dynamics of peritubular cells are consistent with those of target cells. Since the dynamics are similar in Sertoli and peritubular cells, both cell types have the potential to respond to local androgen concentrations and may play important roles in androgen-dependent effects on seminiferous tubule function.     

Synthesis of extracellular matrix components by somatic testicular cells from immature and pubertal rats

Total testicular cells derived from immature and pubertal rats were cultured under long-term conditions. Somatic adherent cells proliferated in culture and produced collagen and proteoglycans. Collagen synthesis accounted for 25% and 5% of total protein synthesized by adherent cells derived from immature, and pubertal rats, respectively. Proteoglycan synthesis was higher in cells from immature than from pubertal rats. The proportion of different types of glycosaminoglycan chains (particularly hyaluronic acid and chondroitin sulphate) also varied according to the age of the donor. The results suggest that the synthesis of extracellular matrix components by somatic testicular cells is an age-related process which probably plays an active role in spermatogenesis.     

Calcium transport processes and their regulation in endocrine cells

Conclusion Calcium ions in trigger amounts are essential for activating a number of endocrine tisues to release their hormones. The cells are equipped with a number of processes for reestablishing the normal very low intracellular concentration of free calcium.     

Fas配体阳性睾丸细胞对共移植的胰岛细胞存活起全身和/或局部的免疫豁免作用

目的探讨Fas配体阳性睾丸细胞对共移植的胰岛细胞存活起全身和/或局部的免疫豁免作用。方法将同种大鼠胰岛细胞与不同数量的睾丸细胞同侧或两侧共移植于糖尿病受体肾包膜下,观察移植物功能和存活情况,以及移植物内淋巴细胞凋亡。结果单纯移植胰岛组(对照组)平均存活期为(4.6±1.1)天。睾丸细胞和胰岛细胞同侧共移植时,当睾丸细胞数为1×106(A组)时,胰岛细胞平均存活期为(23.8±4.6)天;睾丸细胞数增至1×107时(B组),胰岛细胞存活期大于(57.5±4.0)天,均较对照组明显延长(P<0.01)。两侧共移植时,当睾丸细胞数为1×105(C组),胰岛细胞平均存活期为(6.0±1.4)天,与对照组相似(P>0.05);睾丸细胞数增至1×106(D组),胰岛细胞存活期(11.5±3.1)天较对照组或C组延长(P<0.01);睾丸细胞数增至1×107(E组)时,胰岛细胞存活期(31.2±15.9)天延长更加明显(P<0.01)。相同剂量的睾丸细胞与胰岛细胞分别同侧和两侧共移植时发生移植排斥反应各自的病理表现是不同的,前者移植物内有淋巴细胞浸润,部分胰岛玻璃样变,抗胰岛素抗体染色仅见少量阳性细胞,而后者胰岛细胞移植物内有大量的淋巴细胞和少量的中性粒细胞浸润,抗胰岛素抗体阳性细胞较少,未见胰岛玻璃样变。原位细胞凋亡检测发现同侧共移植后的移植物与肾实质交界处有淋巴细胞凋亡。电镜检查发现胰岛移植物存活超过60d的标本可见大量存活的胰岛细胞团和睾丸Sertoli细胞,有散在的凋亡淋巴细胞。结论睾丸细胞与同种胰岛细胞移植后不仅可诱导局部免疫豁免,而且也具有一定的全身免疫保护作用,但较局部免疫豁免作用弱;这些作用可延长移植物的存活期,并具有剂量依赖性。     

胆管癌细胞层黏连素受体过表达上调Fas配体的研究

目的 探讨胆管癌细胞层黏连素受体(laminin receptor,LNR)过表达与Fas配体(Fas ligand,FasL)作用的关系.方法 采用脂质体转染法转染顺义、反义LNR寡核苷酸至胆管癌细胞QBC939中,用RT-PCR和细胞免疫组织化学方法检测两组细胞FasL及LNR的表达情况.结果 转染反义组LNR和FasL基因表达均较转染顺义组明显降低(t=14.136,25.161,P＜0.01).结论 LNR过表达在胆管癌免疫逃逸中的作用可能是通过Fas-FasL信号通路实现的.     

Identification of G protein alpha-subunits in RINm5F cells and their selective interaction with galanin receptor.

Galanin, an inhibitor of insulin secretion in pancreatic beta-cells, exerts its multiple effects through mechanisms that are sensitive to pertussis toxin (PTX). G proteins have been characterized in RINm5F cells. By ADP ribosylation and immunoblotting, the alpha-subunits of Gi1, Gi2, Gi3, and two forms of Go were identified, Gi alpha 2 being predominant. As expected from a G protein-linked receptor, GTP and its nonhydrolyzable analogue GTP-gamma-S decreased tracer galanin binding to cell membranes. This resulted from a change in receptor affinity without any modification in the number of sites. Selective antibodies against the COOH-terminal decapeptide of the alpha-subunits of the Gi and Go proteins were used to block G protein interaction before we studied galanin binding. Antibody AS, which selectively recognizes Gi alpha 1 and Gi alpha 2, decreased tracer galanin binding to membranes at concentrations where there were no effects of other antibodies specifically directed against Gi alpha 3 or G alpha o. These data suggest that Gi1 and/or Gi2 interact with the galanin receptor and probably mediate the effects of galanin in pancreatic beta-cells.     

Macrophage migration inhibitory factor (MIF) as a paracrine mediator in the interaction of testicular somatic cells

Originally the macrophage migration inhibitory factor (MIF) was described as a classical T-cell cytokine. Recently, a much broader tissue distribution for MIF has been revealed. We demonstrated that MIF protein and mRNA are present in the Leydig cells of the normal adult rat testis. Addition of recombinant MIF to cultures of rat seminiferous tubules resulted in decreased secretion of inhibin, whereas follistatin and activin levels remained unchanged, suggesting a paracrine role for MIF in Sertoli cell regulation. Furthermore, MIF showed unique compensatory production in the rat testis. Depletion of the original MIF source, the Leydig cells, by the specific toxin EDS prompted MIF expression by the previously negative Sertoli cells. Leydig cell re-population of the interstitial tissue by precursor cells resulted in a switch back to production by Leydig cells. Therefore, testicular MIF appears to be under very tight paracrine control. MIF has thus been identified as a new mediator in the cross-talk between Leydig cells and the somatic cells of the seminiferous tubules of the rat testis.     

Identification and characterization of a beta-adrenergic receptor in hamster Sertoli cells

Sertoli cells cultured from immature hamsters contain a beta-adrenergic receptor which is coupled to the cAMP second messenger system. Thus, isoproterenol, epinephrine, and norepinephrine, which act via beta-adrenergic receptors, all stimulate cAMP accumulation in Sertoli cells cultured for 4-5 days. This cAMP response to isoproterenol is inhibited stereospecifically by the beta-receptor blocker, propranolol. It is also sensitive to inhibition by beta-adrenergic antagonists in this order of potency: nonspecific beta receptor antagonists, propranolol, timolol, hydroxypindolol greater than beta 1 selective antagonists, oxyprenolol, metoprolol much much greater than beta 2 selective antagonist, butoxamine. Butoxamine was at least 1000-fold less sensitive than either the nonspecific or the beta 1 selective antagonists at inhibiting the response of either isoproterenol (nonspecific), dobutamine (beta 1 selective) or zinterol (beta 2 selective). The hamster Sertoli cell beta receptor is, therefore, predominantly of the B1 subtype. This beta receptor mediated increase in cAMP is sensitive to homologous desensitization and is stimulated synergistically by forskolin. In addition, Seroli cells freshly isolated from immature hamsters contain an active beta receptor. However, this beta receptor mediated increase in cAMP is dependent on the type of trypsin used in the cell preparation. In agreement with Kierszenbaum et al (1985), freshly isolated Sertoli cells from immature rats never responded to the catecholamines regardless of the type of trypsin used; indicating an important physiologic difference between rat and hamster Sertoli cells.     

趋化因子受体CXCR4与配体CXCL12在肝癌细胞迁移中的作用

目的 观察趋化因子受体CXCR4在肝细胞癌组织、肝癌MHCC97细胞中的表达,同时检测肝癌患者血清中CXCR4的配体CXCL12的含量.方法 利用半定量逆转录.聚合酶链反应(RT-PCR)和蛋白印迹方法检测MHCC97细胞、21例不同时期的肝细胞癌组织及17例正常肝组织中CXCR4的表达水平,同时用酶联免疫吸附实验(ELISA)检测18例肝癌患者血清中CXCL12的含量.以48孔微趋化板检测重组人CXCL12、肝细胞癌患者腹水对肝细胞癌细胞MHCC97的趋化影响.结果 在肝细胞癌组织、肝癌细胞株中,CXCR4在mRNA及蛋白水平的相对表达量分别为2.21±1.09、2.14±1.15及1.51±0.12、1.76±0.25,正常肝脏组织在mRNA及蛋白水平均未检测到CXCR4的表达.肝细胞癌患者腹水定量检查结果显示,CXCL12含量为783～8364 ng/L(中位数为6871 ng/L).重组人CXCL12可诱导MHCC97细胞的迁移,其趋化指数为3.9±1.2,与其对照1.0±0.4比较差异有统计学意义(P<0.05);肝细胞癌患者腹水可诱导MHCC97细胞的迁移,其趋化指数为1.9±0.8,与对照组(趋化指数为1.0±0.4)比较有统计学意义(P<0.05).结论 肝细胞癌组织和细胞中存在着CXCR4的高表达,但与肝癌临床分期明显相关(r=0.1,P>0.05),同时肝癌患者血清中存在CXCL12的含量升高,这些提示CXCR4可能在肝癌的转移中发挥重要的作用.     

Expression of Fas and Fas ligand in human testicular germ cell tumours

In the present study, we analysed the expression of Fas ligand (FasL) and its cognate receptor Fas in 14 seminomatous testicular germ cell tumours (TGCT) and six normal testicular tissues obtained following orchiectomy. Tissue samples have been processed to prepare either total RNA or protein extracts or fixed and embedded in paraffin for immunohistochemistry (IHC) experiments. Quantitative RT-PCR experiments demonstrated in TGCT a significant ( p  < 0.01) increase of the FasL mRNA expression of 21.1 ± 5.4 fold, with respect to normal tissues. On the contrary, in the same cancer tissues, the levels of Fas mRNA were significantly ( p  < 0.01) reduced to 0.27 ± 0.06 fold. These observations were confirmed in western blot experiments showing a significant increase of FasL and a concomitant decrease of Fas proteins in testicular cancer tissues, with respect to normal testis. Moreover, IHC experiments showed a strong FasL immuno-reactivity in six out of eight TGCT samples analysed, while Fas immuno-positivity was found in cancer cells of only two TGCT tissues. In addition, in all tumour samples, infiltrating lymphocytes were Fas positive. However, no correlation could be observed between Fas or FasL mRNA variations and clinical parameters such as patient's age, TNM stage or tumour size. We also compared the serum levels of soluble FasL (sFasL) of 15 patients affected by seminomatous TGCT, of four patients with non-seminomatous TGCT and six age-matched healthy males. No significant differences in sFasL serum level could be identified. In conclusion, our data demonstrated that the majority of seminomas are characterized by an increased expression of FasL and a concomitant reduction of Fas, with respect to human normal testis, and that sFasL serum level is not a tumour marker for patients affected by TGCT.