Cell death, proliferation and repair in human myocarditis responding to immunosuppressive therapy

In this study, we evaluate cell death, proliferation and repair in left ventricular endomyocardial biopsies from 20 patients with active lymphocytic myocarditis worsening or recovering from cardiac dysfunction after 6-months immunosuppression. Apoptosis and necrosis were assessed by in situ ligation of hairpin probes, proliferation by Ki67 and MCM5 labelling of myocytes, repair by electron microscopy, morphometric study of percent myofibrillar area and real-time polymerase chain reaction of alpha-and beta-Myosin Heavy Chain (MHC). Apoptosis and necrosis decreased in post- vs pretreatment biopsies by 85 and 62%, respectively in responders, while increased by 42 and 46% in nonresponders. Ki67 and MCM5-positive myocytes were higher vs controls at baseline and increased by 43 and 38% at follow-up in responders and by 75 and 63% in nonresponders. Myofibrillar area reduced in pretreatment samples, increased by 33% at follow-up in responders, correlated with percent enhancement of ejection fraction and was associated with increased alpha-MHC expression and alpha/beta-MHC ratio. In follow-up biopsies of nonresponders, myofibrillar area diminished by 36% and correlated with percent decrease of ejection fraction. Our results suggest that recovery of cardiac function in myocarditis responding to immunosuppression is associated with inhibition of cell death, activation of cell proliferation and with newly synthesized contractile material.

Increased apoptosis, Huntingtin inclusions and altered differentiation in muscle cell cultures from Huntington's disease subjects

Mutated huntingtin (htt) is ubiquitously expressed in tissues of Huntington's disease (HD) patients. In the brain, the mutated protein leads to neuronal cell dysfunction and death, associated with formation of htt-positive inclusions. Given increasing evidence of abnormalities in HD skeletal muscle, we extensively analyzed primary muscle cell cultures from seven HD subjects (including two unaffected mutation carriers). Myoblasts from presymptomatic and symptomatic HD subjects showed cellular abnormalities in vitro, namely mitochondrial depolarization, cytochrome c release, increased caspase-3, -8, and -9 activities, and defective cell differentiation. Another notable feature was the formation of htt inclusions in differentiated myotubes. This study helps to advance current knowledge about the downstream effects of the htt mutation in human tissues. Further applications may include drug screening using this human cellular model.

Re-evaluation of the distinction between type I and type II cells: The necessary role of the mitochondria in both the extrinsic and intrinsic signaling pathways upon fas receptor activation

Cyclosporin A (CyA) and bongkrekic acid (BK) prevented Fas-induced apoptosis in two type I cell lines (H9 and SKW6.4) and two type II cell lines (Jurkat and CEM). CyA and BK inhibited the release of cytochrome c in all four cell lines. In type I cells and in CEM cells, CyA and BK did not prevent the translocation of Bax to the mitochondria. In these same cells, full-length Bid decreased in the mitochondria and cytosol. The cleavage product of Bid, tBid, appeared in the cytosol and to a lesser extent in the mitochondria. In Jurkat cells, Bid also decreased in the cytosol, but increased in the mitochondria. Similar to the other cells, tBid appeared in the mitochondria and cytosol. In the type I H9 and SKW6.4 cells and type II Jurkat cells, the caspase-8 inhibitor Z-Ile-Glu(OMe)-Thr-Asp(OMe)-CH2F (IETD) prevented the cell killing. In the type I cells, IETD prevented the translocation of Bax, the degradation of Bid and the accumulation of tBid. By contrast, IETD only marginally protected the type II CEM cells. In these cells in the presence of IETD, Bax translocated to the mitochondria, in the absence of any degradation of Bid or accumulation of tBid. In the type I H9 cells, IETD produced a depletion of ATP, an effect that did not occur in the type II CEM cells. It is concluded that in type I cells the extrinsic signaling pathway is mitochondrial dependent to the same extent as is the intrinsic pathway in type II cells.

Severe ultrastructural mitochondrial changes in lymphoblasts homozygous for Huntington disease mutation

Mutated huntingtin is expressed in nervous and non nervous system included lymphoblasts. Eneregetic metabolism is impaired in Huntington's disease (HD) and other neurodegenerative diseases. Human HD lymphoblasts have provided clear-cut data on mitochondnal disruption. Here we report morphological, morphometric and membrane potential differences in mitochondria from lymphoblasts obtained from patients homozygous and heterozygous for the CAG mutation, and controls. Homozygotes, who despite a similar age at onset show a more aggressive phenotype than heterozygotes, had giant mitochondria and a reduced membrane potential. We argue that early mitochondrial impairment at basal level may affect the severity of HD progression in patients.

Laser Microdissection in Clinical Cardiovascular Research

Laser microdissection (LMD) is an accurate and fast method to procure pure populations of cells from complex, heterogeneous tissues under direct microscopic visualization. It can be applied to a wide range of cell preparation, including paraffin-embedded material. The morphology of the captured cells is retained, and DNA, RNA, and proteins can be extracted for molecular analysis. The potential applications of LMD to human cardiovascular research are multiple, including viral/autoimmune myocarditis and arteritis, atherosclerotic lesions, and myocardial and vascular cell proliferation and death. Molecular and genetic analysis of LMD-procured cells in cardiac and vascular tissues may provide a better understanding of several cardiac diseases.

C3-induced 3LL cell proliferation is mediated by C kinase

It has been demonstrated that the third component of complement (C3)(1) and its peptides increase normal and tumour cell proliferation. However, the signal cascade responsible for this phenomenon is still unknown. In this study, we elucidate some of the mechanisms involved in the signalling of C3 stimulation of cell proliferation. We have first investigated the in and out traffic of C3 peptides, then we have identified the subcellular localisation of internalised C3 and, finally, we have explored the role of protein phosphorylation in C3 traffic and in the proliferation of the Lewis lung carcinoma (3LL) cells. Our results indicate that traffic of C3 is not dependent on cytoskeletal integrity and requires protein kinase C-dependent phosphorylation. In addition, proliferation of 3LL cells stimulated by C3 depends on both C3 internalisation and protein-kinase C phosphorylation.

Intramyocyte Detection of Epstein-Barr Virus Genome by Laser Capture Microdissection in Patients With Inflammatory Cardiomyopathy

Background— The causal role of Epstein-Barr virus (EBV) in inflammatory cardiomyopathy (IC) is still unclear, because this virus is present in latently infected circulating B lymphocytes in 90% of adults. Laser capture microdissection (LCM) has been applied on endomyocardial biopsy samples from patients with IC to assess the presence of EBV genome in separately dissected lymphocytes and myocytes.

Methods and Results— Among 142 patients with cardiac dilation and dysfunction and a histological and immunohistochemical diagnosis of myocarditis, 44 had a myocardial viral infection detected by polymerase chain reaction on frozen endomyocardial biopsy samples. In 9 of them, the virus detected was EBV. LCM was performed on 5-μm-thick paraffin sections of EBV-infected hearts. Lymphocytes and myocytes were microdissected and analyzed separately by polymerase chain reaction analysis on DNA extracted from the collected cells. Blood and myocardial samples from patients with positive and negative serology for EBV were used as controls. EBV genome was detected in myocytes but not in infiltrating lymphocytes of patients, nor in myocardial samples from controls. Despite full conventional antifailure therapy, a progressive cardiac dilation and dysfunction was documented in patients with EBV-related IC at a mean of 31±14 months of follow-up.

Conclusions— Intramyocyte detection of EBV can be obtained by LCM in up to 6.3% of patients with IC. This supports a cytopathic EBV role and suggests the opportunity for an antiviral/immunomodulatory therapy.

Oxytocin Modulates Nitric Oxide Generation by Human Fetal Membranes at Term Pregnancy

PROBLEM

Nitric oxide (NO), an important mediator of the inflammatory response, is involved in several reproductive processes including pregnancy and labor. Uterus, placenta and fetal membranes are significant sources of NO. Presently, there is no information on factors regulating NO production by fetal membranes.

METHOD OF STUDY

Human fetal membranes at term gestation were cultured for 24 hr in the presence of oxytocin. The concentrations of NO metabolites nitrites in culture medium were determined by the Griess reaction. The presence of inducible nitric oxide synthase (iNOS) was determined by reverse transcriptase-polymerase chain reaction and Western blot.

RESULTS

Oxytocin increased nitrite release by fetal membranes. Messenger ribonucleic acid iNOS expression was also enhanced by oxytocin. These effects were more marked in tissues obtained after labor than before labor.

CONCLUSIONS

Oxytocin exerts an overall stimulatory effect on NO release by fetal membranes. This action might be of relevance in the biomolecular processes leading to parturition.

An hypothesis on the consolidation and PGE1-induced deconsolidation of a platelet plug

Consolidation is the final stage in haemostasis in which a platelet plug blocking a bleeding area of a vessel: (a) becomes impermeable to circulating plasma proteins and (b) contracts to resist blood pressure.

HYPOTHESIS

The impermeabilization step of consolidation is accomplished through fluid uptake by the platelets from a hydrated intercellular glue formed during thrombin activation. Dehydration occurs through inhibition of the Na+,K+-ATPase of platelets with sodium and water uptake. However, and uniquely, due to the high cellular density of the platelet plug, access of peripheral plasma fluids to the plug is limited forcing the platelets to take up preferentially the fluid of interplatelet space. The increased adhesion properties of the dehydrated glue simultaneously furthers a decreased hydraulic permeability and an improved coupling of the contractile forces among platelets. In 'Deconsolidation', the fluid uptake process can be reversed and amplified by agents that increase cAMP, reactivating the Na+,K+-ATPase and expressing CFTR or equivalent Cl- secretory channels that force the extrusion of fluid from the platelets, with rehydration of the intercellular polymer and a large increase in the interplatelet space.

Oestrogens and selective oestrogen receptor (ER) modulators regulate EGF receptor gene expression through human ER alpha and beta subtypes via an Sp1 site

Through the analysis of the transient expression of the luciferase reporter gene in HeLa cells, an evaluation has been made of the transcriptional activity of oestrogens and of selective oestrogen receptor (ER) modulators (SERMs), mediated by the alpha and beta isoforms of the ER, on the epidermal growth factor receptor gene promoter. Oestrogen-activated ERbeta presents a lower transcriptional activity compared with ERalpha, probably due to structural differences in the AF-1 regions of the receptors. Also SERMs induce different responses depending on the receptor isoform bound. Indeed, the phyto-oestrogens, genistein and daidzein, act as weak agonists of the oestrogenic activity via ERalpha, but as full agonists when bound to ERbeta. The synthetic SERM 4OH-tamoxifen, on the other hand, displays an opposite behaviour since it exerts a full agonist action through ERalpha, but acts as a full antagonist via ERbeta. As we have previously shown for ERalpha, an ERbeta/Sp1 functional synergism has also been highlighted, by means of gel mobility shift assays. Moreover, our results show that the sensitivity of target tissues to oestrogens and SERMs can be affected by coexpression of ERs, depending on the formation of appropriate levels of homo- and heterodimers, thus providing a useful approach to predict the effects of hormonal treatment.

Regulation of intracellular pH mediates Bax activation in HeLa cells treated with staurosporine or tumor necrosis factor-alpha

Induction of apoptosis in HeLa cells with staurosporine produced a rise in the intracellular pH (pH(i)). Intracellular alkalinization was accompanied by translocation of Bax to the mitochondria, cytochrome c release, and cell death. The chloride channel inhibitor furosemide prevented intracellular alkalinization, Bax translocation, cytochrome c release, and cell death. Translocation of full-length Bid to the mitochondria was also prevented by furosemide. The cleavage product of Bid degradation (truncated Bid, tBid) was not detectable in the mitochondria. Its accumulation in the cytosol was prevented by furosemide. Apoptosis induced by tumor necrosis factor-alpha (TNF) lowered pH(i), an effect also accompanied by Bax translocation, cytochrome c release, and cell killing. Furosemide prevented all of these events. TNF induced a depletion of full-length Bid from the mitochondria and the cytosol but induced an accumulation of mitochondrial tBid. Furosemide only delayed full-length Bid depletion and tBid accumulation. The caspase 8 inhibitor IETD did not prevent the translocation of Bax. Although IETD did inhibit the cleavage of Bid and the accumulation of tBid, cell killing was reduced only slightly. It is concluded that with either staurosporine or TNF a furosemide-sensitive change in pH(i) is linked to Bax translocation, cytochrome c release, and cell killing. With TNF Bax translocation occurs as Bid is depleted and can be dissociated from the accumulation of tBid. With staurosporine a role for full-length Bid in Bax translocation cannot be excluded but is not necessary as evidenced by the data with TNF.

Akt induces enhanced myocardial contractility and cell size in vivo in transgenic mice

The serine-threonine kinase Akt seems to be central in mediating stimuli from different classes of receptors. In fact, both IGF-1 and IL6-like cytokines induce hypertrophic and antiapoptotic signals in cardiomyocytes through PI3K-dependent Akt activation. More recently, it was shown that Akt is involved also in the hypertrophic and antiapoptotic effects of beta-adrenergic stimulation. Thus, to determine the effects of Akt on cardiac function in vivo, we generated a model of cardiac-specific Akt overexpression in mice. Transgenic mice were generated by using the E40K, constitutively active mutant of Akt linked to the rat alpha-myosin heavy chain promoter. The effects of cardiac-selective Akt overexpression were studied by echocardiography, cardiac catheterization, histological and biochemical techniques. We found that Akt overexpression produced cardiac hypertrophy at the molecular and histological levels, with a significant increase in cardiomyocyte cell size and concentric LV hypertrophy. Akt-transgenic mice also showed a remarkable increase in cardiac contractility compared with wild-type controls as demonstrated by the analysis of left ventricular (dP/dt(max)) in an invasive hemodynamic study, although with graded dobutamine infusion, the maximum response was not different from that in controls. Diastolic function, evaluated by left ventricular dP/dt(min), was not affected at rest but was impaired during graded dobutamine infusion. Isoproterenol-induced cAMP levels, beta-adrenergic receptor (beta-AR) density, and beta-AR affinity were not altered compared with control mice. Moreover, studies on signaling pathway activation from myocardial extracts demonstrated that glycogen synthase kinase3-beta is phosphorylated, whereas p42/44 mitogen-activated protein kinases is not, indicating that Akt induces hypertrophy in vivo by activating the glycogen synthase kinase3-beta/GATA 4 pathway. In summary, our results not only demonstrate that Akt regulates cardiomyocyte cell size in vivo, but, importantly, show that Akt modulates cardiac contractility in vivo without directly affecting beta-AR signaling capacity.

REN: a novel, developmentally regulated gene that promotes neural cell differentiation

Expansion and fate choice of pluripotent stem cells along the neuroectodermal lineage is regulated by a number of signals, including EGF, retinoic acid, and NGF, which also control the proliferation and differentiation of central nervous system (CNS) and peripheral nervous system (PNS) neural progenitor cells. We report here the identification of a novel gene, REN, upregulated by neurogenic signals (retinoic acid, EGF, and NGF) in pluripotent embryonal stem (ES) cells and neural progenitor cell lines in association with neurotypic differentiation. Consistent with a role in neural promotion, REN overexpression induced neuronal differentiation as well as growth arrest and p27Kip1 expression in CNS and PNS neural progenitor cell lines, and its inhibition impaired retinoic acid induction of neurogenin-1 and NeuroD expression. REN expression is developmentally regulated, initially detected in the neural fold epithelium of the mouse embryo during gastrulation, and subsequently throughout the ventral neural tube, the outer layer of the ventricular encephalic neuroepithelium and in neural crest derivatives including dorsal root ganglia. We propose that REN represents a novel component of the neurogenic signaling cascade induced by retinoic acid, EGF, and NGF, and is both a marker and a regulator of neuronal differentiation.

Hormonal regulation of cytokine release by human fetal membranes at term gestation: effects of oxytocin, hydrocortisone and progesterone on tumour necrosis factor-alpha and transforming growth factor-beta 1 output

Inflammatory cytokines can play an important role in the biomolecular processes leading to labour by regulating prostaglandin production in intrauterine tissues. In the setting of intrauterine infection, an increased production of these cytokines by placenta, decidua and fetal membranes occurs and is responsible for the onset and maintenance of preterm labour. However, the factors involved in the control of cytokine release by these tissues in normal pregnancy at term are still largely unknown. We investigated the possibility that the synthesis and release of tumour necrosis factor-alpha (TNF-alpha) and transforming growth factor-beta1 (TGF-beta1) by human fetal membranes at term gestation is regulated by several hormones potentially involved either in the maintenance of pregnancy or in the parturitional process. In the present study, the effects of hydrocortisone, progesterone and oxytocin on TNF-alpha and TGF-beta1 release by explants of fetal membranes at term gestation were evaluated. Reverse transcriptase-polymerase chain reaction (RT-PCR) was used to assess the effect of the above hormones on mRNA expression; TNF-alpha and TGF-beta1 release in culture medium was quantitifed by ELISA assays. Results show that both tissue mRNA expression for TNF-alpha and TNF-alpha release in culture medium were significantly increased by oxytocin, but not by hydrocortisone and progesterone. On the contrary, all the hormones tested increased both tissue TGF-beta1 mRNA expression and release in culture medium. These findings suggest that TNF-alpha and TGF-beta1 production by human fetal membranes in uncomplicated pregnancy at term is selectively modulated by oxytocin, hydrocortisone and progesterone.

The course of etoposide-induced apoptosis from damage to DNA and p53 activation to mitochondrial release of cytochrome c

Treatment of L929 fibroblasts by the topoisomerase II inhibitor etoposide killed 50% of the cells within 72 h. The cell killing was preceded by the release of cytochrome c from the mitochondria. Simultaneous treatment of the cells with wortmannin, cycloheximide, furosemide, cyclosporin A, or decylubiquinone prevented the release of cytochrome c and significantly reduced the loss of viability. Etoposide caused the phosphorylation of p53 within 6 h, an effect prevented by wortmannin, an inhibitor of DNA-dependent protein kinase (DNA-PK). The activation of p53 by etoposide resulted in the up-regulation of the pro-apoptotic protein Bax, a result that was prevented by the protein synthesis inhibitor cycloheximide. The increase in the content of Bax was followed by the translocation of this protein from the cytosol to the mitochondria, an event that was inhibited by furosemide, a chloride channel inhibitor. Stably transfected L929 fibroblasts that overexpress Akt were resistant to etoposide and did not translocate Bax to the mitochondria or release cytochrome c. Bax levels in these transfected cells were comparable with the wild-type cells. The release of cytochrome c upon translocation of Bax has been attributed to induction of the mitochondrial permeability transition (MPT). Cyclosporin A and decylubiquinone, inhibitors of MPT, prevented the release of cytochrome c without affecting Bax translocation. These data define a sequence of biochemical events that mediates the apoptosis induced by etoposide. This cascade proceeds by coupling DNA damage to p53 phosphorylation through the action of DNA-PK. The activation of p53 increases Bax synthesis. The translocation of Bax to the mitochondria induces the MPT, the event that releases cytochrome c and culminates in the death of the cells.

Cytochrome c release upon Fas receptor activation depends on translocation of full-length bid and the induction of the mitochondrial permeability transition

In Jurkat cells Bid was cleaved upon activation of the Fas receptor with an anti-Fas antibody. The caspase-8 inhibitor benzyloxycarbonyl-Ile-Glu(OMe)-Thr-Asp(OMe)-CH(2)F (IETD) prevented the cleavage of Bid and the loss of viability. The nuclear enzyme poly(ADP-ribose)polymerase (PARP) was also cleaved upon the activation of caspases, and IETD similarly prevented PARP cleavage. The PARP inhibitor 3-aminobenzamide (3-AB) restored the cell killing in the presence of IETD, an effect that occurred without restoration of the cleavage of Bid or PARP. In the presence of 3-AB and IETD, translocation occurred of full-length Bid to the mitochondria. The induction of the mitochondrial permeability transition (MPT) was documented by the cyclosporin A (CyA) sensitivity of the release of cytochrome c, the release of malate dehydrogenase from the mitochondrial matrix, the loss of the mitochondrial membrane potential, and the pronounced swelling of these organelles, as assessed by electron microscopy. In addition to preventing all evidence of the MPT, CyA prevented the loss of cell viability, without effect on the cleavage of either Bid or PARP. The prevention of PARP cleavage by inhibition of caspase-3 resulted in a 10-fold activation of the enzyme and a resultant depletion of NAD and ATP. The PARP inhibitor 3-AB prevented the loss of NAD and ATP. Depletion of ATP by metabolic inhibitors similarly prevented the cell killing. It is concluded that the cleaving of PARP in Fas-mediated apoptosis allowed expression of an energy-dependent cell death program that included the translocation of full-length Bid to the mitochondria with induction of the MPT.

Heart-targeted overexpression of caspase3 in mice increases infarct size and depresses cardiac function

Up-regulation of proapoptotic genes has been reported in heart failure and myocardial infarction. To determine whether caspase genes can affect cardiac function, a transgenic mouse was generated. Cardiac tissue-specific overexpression of the proapoptotic gene Caspase3 was induced by using the rat promoter of alpha-myosin heavy chain, a model that may represent a unique tool for investigating new molecules and antiapoptotic therapeutic strategies. Cardiac-specific Caspase3 expression induced transient depression of cardiac function and abnormal nuclear and myofibrillar ultrastructural damage. When subjected to myocardial ischemia-reperfusion injury, Caspase3 transgenic mice showed increased infarct size and a pronounced susceptibility to die. In this report, we document an unexpected property of the proapoptotic gene caspase3 on cardiac contractility. Despite inducing ultrastructural damage, Caspase3 does not trigger a full apoptotic response in the cardiomyocyte. We also implicate Caspase3 in determining myocardial infarct size after ischemia-reperfusion injury, because its cardiomyocyte-specific overexpression increases infarct size.

Expression of neurotrophin receptors in the developing and adult testis

Nerve growth factor (NGF) and the other members of the family of neurotrophic factors (the neurotrophin) are essential for neuronal development and differentiation. Neurotrophins interact with two types of cell surface receptors: a low-affinity receptor (p75 NGF-R) and a high-affinity tyrosine kinase receptor belonging to the trk proto-oncogene family, both expressed in the nervous system and in certain non-neuronal tissues. Recently, NGF immunoreactivity and mRNA have been detected in the testis of the adult mouse, rat and human. In the present report we demonstrate the expression of p75 NGF-R during early gonadal development, by mesenchymal cells of the embryonic mouse and rat testis. In the embryonic testis p75 NGF-R-positive cells are spread through the interstitial compartment; during postnatal development they become organized in a cellular layer that surrounds differentiating myoid cells of the seminiferous tubule. Our results also show the expression in the peripuberal and adult mouse and rat testis, of an abundant and shorter transcript of 3.2 kb that cross-hybridizes to the receptor mRNA (3.7 kb). This new mRNA species, which appears at the beginning of spermatogenesis, is expressed by pachytene spermatocytes and round spermatids.

Mesenchymal cell precursors of peritubular smooth muscle cells of the mouse testis can be identified by the presence of the p75 neurotrophin receptor

In the mouse embryo, at approximately 11.5 days postcoitum (dpc), cells migrate from the mesonephros into the developing testis to contribute to the somatic population of the interstitial compartment (i.e., peritubular myoid cells, Leydig cells, and endothelial cells). Studies from this laboratory have shown that the interstitial population of mesenchymal cells in fetal and newborn mouse testis express the p75 neurotrophin receptor (p75NTR, formerly known as the low-affinity nerve growth factor receptor); part of the cell population progressively congregates around testis cords, later to be replaced by contractile peritubular myoid cells, which express smooth muscle cell markers. In the present study, we show that the migrating cells and the p75NTR-expressing cells are the same population. We also show that the neurotrophin receptor is a useful endogenous marker to follow cell migration within the urogenital ridge and to identify and isolate mesenchymal precursors of myoid cells. A time-course immunolocalization study of the location of p75NTR-bearing cells within the urogenital ridge of mouse embryos between 10.5 and 12.5 dpc showed that the interstitium of the fetal testis was progressively occupied by p75NTR+ cells. The progressive increase of p75NTR expression within the developing testis was confirmed by immunoblot analysis of proteins isolated from the fetal gonads. Organ cultures of isolated testes or testis-mesonephros grafts confirmed that p75NTR+ cells do not appear in the testis unless a mesonephros is attached to it. Cells bearing the p75NTR receptor, purified from 12.5-dpc male mouse mesonephroi by immunomagnetic sorting, were able to differentiate in vitro into myoid cells. Immunofluorescence analysis of postnatal testis sections confirmed the presence around the tubules of cells coexpressing p75NTR and alpha-smooth muscle actin. The ability to identify and purify precursors of myoid cells may be of considerable help for studying the mechanisms regulating their differentiation.

Identification of an estrogen-mediated deoxyribonucleic acid-binding independent transactivation pathway on the epidermal growth factor receptor gene promoter

To investigate the estrogenic effects on the transcriptional regulation of the epidermal growth factor (EGF) receptor (EGFR) gene, we assayed its promoter ability to direct transcription of the luciferase reporter gene after transfection into HeLa cells. Our studies demonstrated a dose-dependent activation of the EGFR gene transcription by ligand-bound estrogen receptor alpha (ERalpha). This action was retained by the 36-bp core promoter fragment and did not require the receptor DNA binding domain, as demonstrated by analyzing the role of ERalpha deletion mutants on EGFR gene promoter-derived constructs. The 36-bp promoter fragment does not contain an estrogen response element but an imperfect thyroid hormone response element half-site that overlaps the Sp1 binding site. ERalpha does not bind this imperfect thyroid hormone response element half-site but is able to enhance binding of Sp1 to its site, in gel mobility shift assays, suggesting that the mechanism by which the receptor stimulated the transcription involved protein-protein interactions that replaced DNA binding. To explain this action, we propose a model in which induction of the EGFR gene expression by estrogens in HeLa cells is dependent upon the formation of a transcriptionally active ERalpha-Sp1 complex that binds to the GC-rich (Sp1) region of the minimal promoter.

Surface expression of the IFN-gamma R2 chain is regulated by intracellular trafficking in human T lymphocytes

The surface and cytoplasmic expressions of the transducing chain (IFN-gamma R2) of the heterodimeric IFN-gamma receptor on human T lymphocytes have been investigated. We show that its surface expression is low, whereas high cytoplasmic levels are found in both resting and PHA-activated T lymphocytes. This low expression does not prevent activated T cells from responding to IFN-gamma, because it induces IFN-regulatory factor 1 expression. Low surface IFN-gamma R2 expression appears to be due to recycling between cytoplasmic stores and the cell surface, which does not depend on signals mediated by endogenous IFN-gamma, because IFN-gamma R2 surface expression is low, and its internalization is equally observed in patients with inherited IFN-gamma R1 gene deficiency and in healthy donors. Moreover, IFN-gamma R2 internalization in T lymphoblasts from healthy donors was not affected by the presence of anti-IFN-gamma-neutralizing or anti-IFN-gamma R1-blocking mAb. In conclusion, these data illustrate a new mechanism whereby human T cells limit the surface expression of IFN-gamma R2 in a ligand-independent manner.

Spatiotemporal patterns of expression of neurotrophins and neurotrophin receptors in mice suggest functional roles in testicular and epididymal morphogenesis

Several reports have established that the action of neurotrophins is not restricted to the nervous system but can affect a broad range of non-neuronal cells. Nerve growth factor (NGF) is present in adult testis and has been suggested as a potential regulator of meiosis in rat seminiferous epithelium. Here we present an extensive immunohistochemical study on neurotrophins and their receptors (p75 and trk) in the developing mouse testis and epididymis, and in fetal human testis. During the early steps of testicular and epididymal organization in the mouse, strong p75 immunoreactivity is detectable in the gonadal ridge in the mesenchyme that is excluded from the evolving testicular cords, and in the mesenchymal cells of the mesonephros. Later in organogenesis, most of the p75-positive interstitial cells of the testis coexpress neurotrophin-3 (NT-3) and the truncated trk B receptor in a developmentally regulated pattern. Our Western blot data confirm the expression of these molecules. These findings suggest that neurotrophin receptors play a role in early inductive events during critical periods of testicular and epididymal development. During fetal and postnatal histogenesis, an increasing number of NT-3- and p75-positive mesenchymal cells start to express alpha-smooth muscle isoactin, suggesting a role for the so-called neurotrophic system in the differentiation of testicular myoid cells and epididymal smooth muscle cells. In the testis of an 18-wk gestational-age human fetus, immunohistochemical analysis has shown intense immunoreactivity of mesenchymal cells to antibodies for neurotrophin receptors p75, trk A, and trk C, and their ligands NGF and NT-3. In addition, we found that in the human fetal testis, the interstitial cells that are differentiating into peritubular myoid cells are associated with a dense network of nerve fibers. Our data suggest that neurotrophins and their receptors are involved in a multifunctional system that regulates cell differentiation and innervation in the developing testis and epididymis.