Sensitivity of prostate cells to TRAIL-induced apoptosis increases with tumor progression: DR5 and caspase 8 are key players

BACKGROUND: As advanced prostate cancers are resistant to currently available chemotherapies, we evaluated the cytotoxic effect of TNF-related apoptosis-inducing ligand (TRAIL) and characterized the involvement of its five receptors DR4, DR5, DcR1, DcR2, and osteoprotegerin (OPG) and of the death-inducing signaling complex (DISC)-forming proteins caspase 8 and c-FLIP in prostate cell lines. METHODS: We used six prostate cell lines, each corresponding to a particular stage in prostate tumorigenesis, and analyzed TRAIL sensitivity in relation to TRAIL receptors' expression. RESULTS: TRAIL sensitivity was correlated with tumor progression and DR5 expression levels and apoptosis was exclusively mediated by DR5. DcR2 was significantly more abundant in tumor cells than in non-neoplastic ones and may contribute to partial resistance to TRAIL in some prostate tumor cells. Conversely, non-tumoral cells secreted high levels of OPG, which can protect them from apoptosis. Finally, caspase 8 expression levels were as DR5 directly correlated to TRAIL sensitivity in prostate tumor cells. CONCLUSION: TRAIL-induced apoptosis is closely related to the balanced expression of its different receptors in prostate cancer cells and their modulation could be of potential clinical value for advanced tumor treatment.     

培养麻醉专业学生科研能力的探索

为了适应新世纪我国高等医学教育的要求，改变目前我国高等教育传统的思维模式，树立创新教育观念，提高教育质量，全面推进素质教育。《高等教育法》规定，大学的基本任务是培养具有创新精神和实践能力的高级专门人才。因此，在培养高级医学人才的过程中，提出了更高、更新的要求，其核心是创新精神和实践能力。学生通过参与科研活动，培养学生的科研思维和创新能力，提高学生的综合素质，就显得非常重要，也是医学院校教学改革的重要内容之一。     

婴幼儿下呼吸道SIgA变化规律及其与唾液SIgA相关性的探讨

对74例正常婴幼儿和70例患下呼吸道感染的婴幼儿同时测定下呼吸道分泌物(LRS)及唾液中SIgA的含量。两组检测对象在性别和年龄分组上无明显差异。结果表明:1LRS和唾液的SIgA含量都与年龄呈正性相关,各年龄组之间SIgA含量也存在着显著性差异(P<0.01);②感染婴幼儿组及其各年龄组的SIgA含量均明显高于正常婴幼儿组及其各年龄组(P<0.01);③LRS的SIgA含量与唾液SIgA含量之间存在密切的相关性(P<0.01)。作者认为婴幼儿下呼吸道感染后局部SIgA增高是一种正常的免疫应答反应,有助于控制感染;SIgA的变化规律可作为鉴别免疫缺陷的指标;应用测定唾液中SIgA间接反映LRS中SIgA水平的方法将推进临床免疫研究开展。     

VPAC2 receptors mediate vasoactive intestinal peptide-induced neuroprotection against neonatal excitotoxic brain lesions in mice

Prepro-vasoactive intestinal peptide (VIP) mRNA codes for two neuropeptides: VIP and peptide histidine isoleucine (PHI). Two VIP receptors, shared with a similar affinity by pituitary adenylate cyclase-activating polypeptide (PACAP), have been cloned: VPAC(1) and VPAC(2). PHI binds to these receptors with a lower affinity. VPAC receptors are classically associated with a cAMP-dependent pathway, although other pathways, including calcium mobilization and protein kinase C activation have been described. We previously showed that intracerebral administration of the glutamate agonist ibotenate to postnatal day 5 mice induces white matter lesions mimicking human periventricular leukomalacia. In this model, coinjection of VIP protects against white matter lesions. This neuroprotection is independent from cAMP and is mediated by protein kinase C. Using this model, this study aimed to determine the receptor involved in VIP-induced neuroprotection. VIP effects were mimicked with a similar potency by VPAC(2) agonists and PHI but not by VPAC(1) agonists, PACAP 27, or PACAP 38. VIP neuroprotective effects were lost in mice lacking VPAC(2) receptor. In situ hybridization confirmed the presence of VPAC(2) mRNA in the postnatal day 5 white matter. When analyzed between embryonic life and adulthood, VIP-specific binding site density peaked at postnatal day 5. These data suggest that, in this model, VIP-induced neuroprotection is mediated by VPAC(2) receptors. The pharmacology of this VPAC(2) receptor seems unconventional because 1) PACAP does not mimic VIP effects, 2) PHI acts with a comparable potency, and 3) PACAP 27 modestly inhibited the VIP-specific binding, whereas for PHI or VIP, inhibition was complete.     

Distribution of the mRNAs encoding the thyrotropin-releasing hormone (TRH) precursor and three TRH receptors in the brain and pituitary of Xenopus laevis: effect of background color adaptation on TRH and TRH receptor gene expression

In amphibians, thyrotropin-releasing hormone (TRH) is a potent stimulator of alpha-melanotropin (alpha-MSH) secretion, so TRH plays a major role in the neuroendocrine regulation of skin-color adaptation. We have recently cloned a third type of TRH receptor in Xenopus laevis (xTRHR3) that has not yet been characterized in any other vertebrate species. In the present study, we have examined the distribution of the mRNAs encoding proTRH and the three receptor subtypes (xTRHR1, xTRHR2, and xTRHR3) in the frog CNS and pituitary, and we have investigated the effect of background color adaptation on the expression of these mRNAs. A good correlation was generally observed between the expression patterns of proTRH and xTRHR mRNAs. xTRHRs, including the novel receptor subtype xTRHR3, were widely expressed in the telencephalon and diencephalon, where two or even three xTRHR mRNAs were often simultaneously observed within the same brain structures. In the pituitary, xTRHR2 was expressed selectively in the distal lobe, and xTRHR3 was found exclusively in the intermediate lobe. Adaptation of frog skin to background illumination had no effect on the expression of proTRH and xTRHRs in the brain. In contrast, adaptation of the animals to a white background provoked an 18-fold increase in xTRHR3 mRNA concentration in the intermediate lobe of the pituitary. These data demonstrate that, in amphibians, the effect of TRH on alpha-MSH secretion is mediated through the novel receptor subtype xTRHR3.     

Production of the antiviral proteins 2'5'oligoadenylate synthetase,PKR and Mx in interstitial cells and spermatogonia

We report an in vitro analysis of the spatial pattern of production of three antiviral proteins (2'5'oligoadenylate synthetase, 2'5'AS; double-stranded RNA-activated protein kinase, PKR; and Mx protein, Mx) in the rat testis, in basal conditions and following stimulation with interferon (IFN) or Sendai virus. The two major constituents of interstitial tissue--Leydig cells and macrophages--constitutively produce 2'5' oligoadenylate synthetase (2'5'AS), PKR and Mx. Production of an isoform of 2'5'AS was induced following Leydig cells stimulation by the Sendai virus. The most immature germ cells, spermatogonia, were devoid of 2'5'AS whatever the type of stimulation, whereas IFN treatment induced Mx production and increased PKR production in this cell type. IFN stimulation strongly increased PKR production in all three cell types. This new set of data extends our previous investigations and demonstrates that the testis possesses an anti-viral defense system involving IFNs and IFN-induced anti-viral proteins.     

Microchimerism and transmission of porcine endogenous retrovirus from a pig cell line or specific pathogen-free pig islets to mouse tissues and human cells during xenografts in nude mice

AIMS/HYPOTHESIS: Pig islets could transmit porcine endogenous retroviruses (PERV) to diabetic patients. Our previous work showed that pig islets expressed low levels of PERV mRNA and were not likely to transmit PERV to human cells in vitro. The real risk of infection during pig tissue xenografts can only be evaluated by in vivo experiments. METHODS: Nude mice bearing tumours containing human 293 cells were grafted with specific pathogen-free pig islets or PERV-producing pig PK15 cells to determine whether pig cells could transmit PERV to mouse and human cells in vivo. Infection was monitored by PCR, long PCR, RT-PCR and long RT-PCR. As detection of PERV sequences could be due to the presence of residual pig cells, we looked for pig mitochondrial (mt) DNA. Quantitative PCR for PERV and pig mt DNA was done to compare the PERV-to-pig mt (P-to-M) ratio of each sample with the reference ratio for grafted pig cells. RESULTS: Among 78 mouse tissues from PK15-grafted mice, 54 and 72 were positive for gag and pig mt DNA, respectively. Human tumours developed in these mice were positive for PERV (78%) and pig mt (89%). The P-to-M ratios for mouse tissues and PERV-positive human tumours from PK15-grafted mice were higher than the ratio in PK15 cells. Among 41 tissues from pig islet cell-grafted mice, 7 were positive for PERV (3 lymph nodes, 1 kidney, 2 salivary glands, 1 ovary), and 14 were positive for pig mt DNA. Three of these samples (1 lymph node, 1 kidney and 1 salivary gland) were positive for gag DNA, but negative for pig mt DNA. One human tumour in these mice was positive for PERV DNA. P-to-M reference ratio in grafted islet cells was 0.05+/-0.03. The three PERV-positive lymph nodes contained 78 gag/3 mt copies (P-to-M: 26), 101 gag/3 mt copies (P-to-M: 34), and 4 gag/0 mt copies. The two PERV-positive salivary glands contained 14 gag/1 mt copies, and 28 gag/0 mt copies. The ovary and the kidney contained 46 gag/3 mt and 69 gag/0 mt copies, respectively. The PERV-positive human tumour contained 47 gag/3 mt copies. CONCLUSIONS/INTERPRETATION: Microchimerism and PERV transmission were frequently observed in both mouse and human tissues during grafting of pig PK15 cells into nude mice bearing human tumours, and sometimes during pig islet xenograft in this model. This strengthens the notion that there is a risk of transmitting PERV during pig islet xenograft.     

Seasonal variations in sex steroids and male sexual characteristics in Scyliorhinus canicula

Concentrations of testosterone, progesterone, Delta4-androstenedione, dihydrotestosterone, 11-ketotestosterone, estrone, estradiol-17beta, 5alpha-androstane, 3alpha, 17beta-diol, and 17alpha-hydroxy, 20beta-dihydroprogesterone were determined by radioimmunoassays in the blood plasma and testicular homogenates of Scyliorhinus canicula. Samples were collected almost every month for 27 months. The weights and sizes of reproductive organs and sperm reserves were also measured over the same period. Quantitatively, testosterone was the principal steroid present. Testicular and epididymal weights, sperm reserves, and clasper size varied throughout the year, but not always in a synchronous fashion. Most of the testicular steroids had an annual peak, generally in February, except for progesterone. The plasma concentrations of progesterone, Delta4-androstenedione, and androgens presented various degrees of fluctuation over the year, but were not synchronized: maxima occurred during autumn-winter for androgens and progesterone, during spring for Delta4-androstenedione. Thus, various aspects of S. canicula reproductive function appear to be influenced by season, the sea temperature being, most probably, a major determinant in this respect.