Incidence of Orbital Exenteration: A Nationwide Study in France over the 2006-2017 Period

PURPOSE

Orbital exenteration is a radical and disfiguring surgery mainly performed for treating orbital malignancies. Recently, several studies found favorable results in terms of overall survival with eye-sparing surgeries combined with targeted therapies and/or radiotherapy. The aim of this study was to assess the incidence of orbital exenteration and its evolution in France between 2006 and 2017.

METHODS

A national observational cohort study was conducted in France between January 2006 and December 2017. Data were collected from the national PMSI (Programme de Médicalisation des Systèmes d'Information) database provided by the CNAM (Caisse Nationale de l'Assurance Maladie). All patients undergoing orbital exenteration over the study period in France were included.

RESULTS

One thousand and fifty-seven patients were included. The mean annual number of orbital exenterations was 88.1 (63-117), corresponding to a mean incidence of 0.1/100,000 inhabitants/year. A male predominance was noted (n = 626, 59.2%). Exenteration was mainly performed between 75 and 79 years. The underlying etiology was available for 821 patients (77.7%): malignancies were the most common (n = 755; 92.0%) followed by infectious diseases (n = 16; 1.9%). Over the study period, no statistical difference in the mean incidence of orbital exenteration was found (p = .132).

CONCLUSION

The mean annual incidence of orbital exenteration was 0.1/100,000 inhabitants in France and was not significantly modified during the study period.

[Does orbital exenteration still has a place in 2019?]

INTRODUCTION

Orbital exenteration is a radical anatomically and psychologically disfiguring procedure. It is mostly performed for management of orbital cancers or cancers with orbital involvement. The lack of benefit in terms of overall survival and the development of new molecular therapies (targeted therapies, immunotherapy) in recent years leads us to question its use. The goal of our review is to answer to the following question: is orbital exenteration a viable procedure in 2019?

MATERIALS AND METHODS

A literature review was performed using the PUBMED and MEDLINE databases. The following terms were used then crossed with each other: "orbital exenteration", "exenterated socket", "overall survival", "life expectancy", "orbital reconstruction", "socket reconstruction". Oncology articles from the past 15 years were included and separated into those in the oculoplastic literature and those in the ENT literature.

RESULTS

Nineteen articles were included in this review. Eyelid tumours represent the main etiology of orbital exenteration. Basal cell carcinoma is the most frequently incriminated tumor, while sebaceous carcinoma and conjunctival squamous cell carcinoma are the most frequently encountered in Asian series. Non-conservative orbital exenteration is the most prevalent surgery performed. Orbital reconstruction depends on the surgeon's speciality: healing by secondary intention and split thickness skin grafts are mostly performed by oculoplastic surgeons, whereas regional or free flaps are mostly performed by ENT surgeons. Cerebrospinal fluid leakage is the most common intraoperative complication, encountered in 0 to 13 % of cases. The most common postoperative complications are ethmoid fistula and infection of the operative site, encountered in 0 to 50 % and 0 to 43 % of cases respectively. Orbital exenteration allows surgical resection of R0 tumors in 42.5 % to 97 % of cases. Overall survival following orbital exenteration is 83 % (50.5-97) and 65 % (37-92) at 1 and 5 years respectively. Identified risk factors for poor overall survival are: age, tumor histology (worse prognosis with choroidal melanoma, better prognosis with basal cell carcinoma), non-R0 surgical resection, locally advanced tumors (size>20mm, BCVA<20/400 and the presence of metastases at diagnosis). Recent studies have demonstrated favorable outcomes when managing locally advanced basal cell carcinoma, lacrimal gland cancer and conjunctival melanoma with targeted therapies or immunotherapies without performing orbital exenteration.

CONCLUSION

Orbital exenteration remains a major part of our therapeutic arsenal. Although orbital exenteration has failed to demonstrate any overall survival benefit, it allows satisfactory local control of the disease with an increasingly less invasive procedure. The development of targeted therapies and immunotherapies may change our therapeutic decisions in the future.

Hypoxia and MITF control metastatic behaviour in mouse and human melanoma cells

Melanomas are very aggressive neoplasms with notorious resistance to therapeutics. It was recently proposed that the remarkable phenotypic plasticity of melanoma cells allows for the rapid development of both resistance to chemotherapeutic drugs and invasive properties. Indeed, the capacity of melanoma cells to form distant metastases is the main cause of mortality in melanoma patients. Therefore, the identification of the mechanism controlling melanoma phenotype is of paramount importance. In the present report, we show that deletion of microphthalmia-associated transcription factor (MITF), the master gene in melanocyte differentiation, is sufficient to increase the metastatic potential of mouse and human melanoma cells. MITF silencing also increases fibronectin and Snail, two mesenchymal markers that might explain the increased invasiveness in vitro and in vivo. Furthermore, ablation of this population by Forskolin-induced differentiation or MITF-forced expression significantly decreases tumour and metastasis formation, suggesting that eradication of low-MITF cells might improve melanoma treatment. Moreover, we demonstrate that a hypoxic microenvironment decreases MITF expression through an indirect, hypoxia-inducible factor 1 (HIF1)α-dependant transcriptional mechanism, and increases the tumourigenic and metastatic properties of melanoma cells. We identified Bhlhb2, a new factor in melanoma biology, as the mediator of hypoxia/HIF1α inhibitory effect on MITF expression. Our results reveal a hypoxia-HIF1α-BHLHB2-MITF cascade controlling the phenotypic plasticity in melanoma cells and favouring metastasis development. Targeting this pathway might be helpful in the design of new anti-melanoma therapies.

Mitf is the key molecular switch between mouse or human melanoma initiating cells and their differentiated progeny

In melanoma, as well as in other solid tumors, the cells within a given tumor exhibit strong morphological, functional and molecular heterogeneity that might reflect the existence of different cancer cell populations, among which are melanoma-initiating cells (MICs) with 'stemness' properties and their differentiated, fast-growing progeny. The existence of a slow-growing population might explain the resistance of melanoma to classical chemotherapies that target fast growing cells. Therefore, elucidating the biologic properties of MICs and, more importantly, the molecular mechanisms that drive the transition between MICs and their proliferating progeny needs to be addressed to develop an efficient melanoma therapy. Using B16 mouse melanoma cells and syngeneic mice, we show that the inhibition of microphthalmia-associated transcription factor (Mitf), the master regulator of melanocyte differentiation, increases the tumorigenic potential of melanoma cells and upregulates the stem cell markers Oct4 and Nanog. Notably, p27, the CDK inhibitor, is increased in Mitf-depleted cells and is required for exacerbation of the tumorigenic properties of melanoma cells. Further, a slow-growing population with low-Mitf level and high tumorigenic potential exists spontaneously in melanoma. Ablation of this population dramatically decreases tumor formation. Importantly, these data were confirmed using human melanoma cell lines and freshly isolated human melanoma cell from lymph node and skin melanoma metastasis. Taken together our data, identified Mitf and p27 as the key molecular switches that control the transition between MICs and their differentiated progeny. Eradication of low-Mitf cells might be an appealing strategy to cure melanoma.

Essential role of microphthalmia transcription factor for DNA replication, mitosis and genomic stability in melanoma

Malignant melanoma is an aggressive cancer known for its notorious resistance to most current therapies. The basic helix-loop-helix microphthalmia transcription factor (MITF) is the master regulator determining the identity and properties of the melanocyte lineage, and is regarded as a lineage-specific 'oncogene' that has a critical role in the pathogenesis of melanoma. MITF promotes melanoma cell proliferation, whereas sustained supression of MITF expression leads to senescence. By combining chromatin immunoprecipitation coupled to high throughput sequencing (ChIP-seq) and RNA sequencing analyses, we show that MITF directly regulates a set of genes required for DNA replication, repair and mitosis. Our results reveal how loss of MITF regulates mitotic fidelity, and through defective replication and repair induces DNA damage, ultimately ending in cellular senescence. These findings reveal a lineage-specific control of DNA replication and mitosis by MITF, providing new avenues for therapeutic intervention in melanoma. The identification of MITF-binding sites and gene-regulatory networks establish a framework for understanding oncogenic basic helix-loop-helix factors such as N-myc or TFE3 in other cancers.

Ciglitazone negatively regulates CXCL1 signaling through MITF to suppress melanoma growth

We have previously demonstrated that the thiazolidinedione ciglitazone inhibited, independently of PPARγ activation, melanoma cell growth. Further investigations now show that ciglitazone effects are mediated through the regulation of secreted factors. Q-PCR screening of several genes involved in melanoma biology reveals that ciglitazone inhibits expression of the CXCL1 chemokine gene. CXCL1 is overexpressed in melanoma and contributes to tumorigenicity. We show that ciglitazone induces a diminution of CXCL1 level in different human melanoma cell lines. This effect is mediated by the downregulation of microphthalmia-associated transcription factor, MITF, the master gene in melanocyte differentiation and involved in melanoma development. Further, recombinant CXCL1 protein is sufficient to abrogate thiazolidinedione effects such as apoptosis induction, whereas extinction of the CXCL1 pathway mimics phenotypic changes observed in response to ciglitazone. Finally, inhibition of human melanoma tumor development in nude mice treated with ciglitazone is associated with a strong decrease in MITF and CXCL1 levels. Our results show that anti-melanoma effects of thiazolidinediones involve an inhibition of the MITF/CXCL1 axis and highlight the key role of this specific pathway in melanoma malignancy.

Involvement of FKHRL1 in melanoma cell survival and death

Melanoma is a highly aggressive tumour characterized by a strong resistance to apoptotic stimuli that give rise to a selective advantage for tumour progression and metastasis formation. Therefore, it is of paramount importance to better understand the mechanisms involved in this resistance to apoptosis. In this report, we focused our attention on FKHRL1, a member of the forkhead family of transcription factors, which controls expression of genes involved in cell cycle progression and apoptosis. In melanoma cells, we show that IGF1, which exerts pro-survival properties, induces the phosphorylation and nuclear exclusion of FKHRL1 in a PI3K/AKT-dependent pathway. Moreover, we observe that over-expression of a non-phosphorylable mutant of FKHRL1 (FKHRL1-TM), constitutively localized to the nucleus, promotes apoptotic cell death of melanoma cells. Finally, we find that FKHRL1-TM decreases the expression of survivin, a member of the inhibitor of apoptosis protein and that survivin re-expression partially rescues the deleterious effects of FKHRL1. Taken together, these findings reveal, in melanoma cells, that endogenous FKHRL1 is a downstream target of the PI3K/AKT pathway and suggest that the phosphorylation of this transcription factor may be involved in the pro-survival effects of growth factors such as IGF1. On the other hand, forced nuclear localization of FKHRL1 decreases melanoma cell growth and may serve as a therapeutic strategy against melanoma.

PI3K mediates protection against TRAIL-induced apoptosis in primary human melanocytes

Melanocytes are cells of the epidermis that synthesize melanin, which is responsible for skin pigmentation. Transformation of melanocytes leads to melanoma, a highly aggressive neoplasm, which displays resistance to apoptosis. In this report, we demonstrate that TNF-related apoptosis-inducing ligand (TRAIL), which was thought to kill only transformed cells, promotes very efficiently apoptosis of primary human melanocytes, leading to activation of caspases 8, 9 and 3, and the cleavage of vital proteins. Further, we show that stem cell factor (SCF), a physiologic melanocyte growth factor that activates both the phosphatidyl-inositol-3 kinase (PI3K) and the extracellular regulated kinase (ERK) pathways, strongly protects melanocytes from TRAIL and staurosporine killing. Interestingly, inhibition of PI3K or its downstream target AKT completely blocks the antiapoptotic effect of SCF, while inhibition of ERK has only a moderate effect. Our data indicate that protection evoked by SCF/PI3K/AKT cascade is not mediated by an increase in the intracellular level of FLIP. Further, only a sustained PI3K activity can protect melanocytes from apoptosis, thereby indicating that the PI3K/AKT pathway plays a pivotal role in melanocyte survival. The results gathered in this report bring new information on the molecular mechanisms involved in primary melanocyte apoptosis and survival that would help to better understand the process by which melanomas acquire their resistance to apoptosis.

Cultured pancreatic ductal cells undergo cell cycle re-distribution and beta-cell-like differentiation in response to glucagon-like peptide-1

The intestinal hormone glucagon-like peptide-1 (GLP-1) has been shown to promote an increase in pancreatic beta-cell mass via proliferation of islet cells and differentiation of non-insulin-secreting cells. In this study, we have characterized some of the events that lead to the differentiation of pancreatic ductal cells in response to treatment with human GLP-1. Rat pancreatic ductal (ARIP) cells were cultured in the presence of GLP-1 and analyzed for cell counting, cell cycle distribution, expression of cyclin-dependent-kinase (Cdk) inhibitors, transcription of beta-cell-specific genes, loss of ductal-like phenotype and acquisition of beta-cell-like gene expression profile. Exposure of ARIP cells to 10 nM GLP-1 induced a significant reduction in the cell replication rate and a significant decrease in the percentage of cells in S phase of the cell cycle. This was associated with an increase in the number of cells in G0-G1 phase and a reduction of cells in G2-M phase. Western blot analysis for the Cdk inhibitors, kinase inhibitor protein 1 (p27(Kip1)) and Cdk-interacting protein 1 (p21(Cip1)), demonstrated a significant increase in p27(Kip1) and p21(Cip1) levels within the first 24 h from the beginning of GLP-1 treatment. As cells slowed down their proliferation rate, GLP-1 also induced a time-dependent expression of various beta-cell-specific mRNAs. The glucose transporter GLUT-2 was the first of those factors to be expressed (24 h treatment), followed by insulin (44 h) and finally by the enzyme glucokinase (56 h). In addition, immunocytochemistry analysis showed that GLP-1 induced a time-dependent down-regulation of the ductal marker cytokeratin-20 (CK-20) and a time-dependent induction of insulin expression. Finally, GLP-1 promoted a glucose-dependent secretion of insulin, as demonstrated by HPLC and RIA analyses of the cell culture medium. The present study has demonstrated that GLP-1 induces a cell cycle re-distribution with a decrease in cell proliferation rate prior to promoting the differentiation of cells towards an endocrine-like phenotype.

T and B leukemic cell lines exhibit different requirements for cell death: correlation between caspase activation, DFF40/DFF45 expression, DNA fragmentation and apoptosis in T cell lines but not in Burkitt's lymphoma

The execution phase of apoptosis occurs through the activation and function of caspases which cleave key substrates that orchestrate the death process. Here, we have compared the sensitivity of various T and B cell lines to death receptor or staurosporine-induced apoptosis. First, we found a lack of correlation between death receptor expression and sensitivity to Fas or Trail. By contrast, a correlation between caspase activation, DNA fragmentation and cell death in T cell lines was evidenced. Among T cells, CEM underwent apoptosis in response to CH11 but were resistant to Trail in agreement with the absence of Trail receptors (DR4 and DR5) on their surface. The B cell line SKW 6.4 was sensitive to CH11 and staurosporine but resistant to Trail. As B cell lines expressed significant levels of DR4 and DR5, resistance to Trail in SKW 6.4 is likely due to the expression of the decoy receptor DcR1. Burkitt's lymphoma such as RPMI 8866 and Raji did not exhibit DNA fragmentation in response to CH11, Trail or staurosporine but showed long-term caspase-dependent loss of viability upon effector treatment. The B cell lines used in this study express very weak or undetectable levels of DFF40 and relatively high levels of DFF45. Interestingly, cytosolic extracts from RPMI 88.66 but not other B lymphoma exhibit altered levels of cytochrome c-dependent caspase activation. Taken together, our results show that: (1) death receptor expression does not correlate with sensitivity to apoptosis; (2) the very low ratio of DFF40 vs. DFF45 is unlikely to explain by itself the lack of DNA fragmentation observed in certain B cell lines; and (3) a defective cytochrome c-dependent caspase activation might account at least in part for the insensitivity of certain Burkitt's lymphoma (RPMI 88.66) to apoptosis. Thus it seems that resistance of Burkitt's lymphoma to apoptosis is not governed by a general mechanism, but is rather multifactorial and differs from one cell line to another.

BMP-2 stimulates tyrosinase gene expression and melanogenesis in differentiated melanocytes

Cells of the vertebrate neural crest (crest cells) differentiate in vitro to melanocytes and sympathoadrenal (SA) progenitor cells. We have shown previously, using primary J. quail neural crest cultures, the combinatorial effect of bone morphogenetic protein-2 (BMP-2) and cAMP signaling on SA cell development. Herein, we report that in primary J. quail neural crest cultures, BMP-2 and cAMP signaling similarly exert a combinatorial effect on melanocyte development. We demonstrate that BMP-2 treatment of neural crest cells increases melanogenesis by promoting the synthesis of melanin. This increased melanin synthesis by BMP-2 is effected by the selective increase in the transcription of the tyrosinase gene, encoding the rate-limiting enzyme of the melanin biosynthetic pathway. By contrast, BMP-2 exerts no effect on the expression of the tyrosine-related proteins 1 and 2 (Tyrpl and Dct), also involved in the melanin biosynthetic process, or on the expression of microphalmia (Mitf) gene, supporting the fact that BMP-2 does not affect melanocyte differentiation. Employing transient transfection analysis of tyrosinase-reporter constructs in B16 melanoma cells, we demonstrate that the BMP-2 response-element is localized between 900 and 1,100 bp upstream from the tyrosinase transcriptional start site. These studies support a role for BMP-2 in melanogenesis by selectively targeting the expression of the tyrosinase gene involved in melanin biosynthesis.

Differential requirements for ERK1/2 and P38 MAPK activation by thrombin in T cells. Role of P59Fyn and PKCε

Activation of the mitogen-activated protein kinase (MAPK) cascade is a well documented mechanism for the G-protein-coupled receptors. Here, we have analysed the requirements for ERKs and p38 MAPK activation by thrombin in Jurkat T cells. We show that thrombin-mediated ERKs activation requires both PTK and PKC activities, whereas p38 MAPK activation is dependent only on PTKs. Thrombin-induced ERK and p38 MAPK activation was more pronounced in p56Lck deficient cells indicating that this PTK exerts a negative control on MAPK activity. Accordingly, overexpression of p50 Csk a kinase that inactivates p56Lck induced constitutive activation of ERKs. Requirement for a Src kinase was evidenced by expression of a constitutively active form of p59Fyn in Jurkat cells. Besides its effect on tyrosine phosphorylation events, thrombin also triggered a rapid and robust redistribution of PKCepsilon and delta from the cytosol to the membrane. Expression of constitutively active and dominant negative PKCepsilon demonstrates the pivotal role of this PKC isoform in ERKs activation by thrombin. These data are consistent with a model where thrombin induces ERK activation via both PKC-dependent and independent pathways, whereas p38 MAPK activation requires only PTKs. The PKC-independent pathway requires Src kinases other than p56Lck more likely p59Fyn, while the PKC-dependent mechanism depends on PKCepsilon

A Jurkat T cell variant resistant to death receptor-induced apoptosis. Correlation with heat shock protein (Hsp) 27 and 70 levels

Ligation of Fas induces an apoptotic program in Jurkat cells (Jd). We describe a Jurkat T cell variant (Jr) which shows total resistance to Fas-mediated apoptosis but which exhibits sensitivity to non-death-receptor pro-apoptotic stimuli such as staurosporine. Resistance to Fas-induced apoptosis in Jr cells is correlated with high expression of Hsps. A prior heat-shock increases Hsp27 and 70 expression and protects Jd and Jr cells from Fas- and staurosporine-induced apoptosis. Staurosporine, but not the anti-Fas antibody CH11, abrogates constitutive Hsp70 expression at 37 degrees C and staurosporine also inhibit Hsp27 expression in Jd and Jr cells at 42 degrees C. These data suggest that constitutive expression of Hsp27 inhibits Fas-mediated apoptosis, but only induced expression of Hsp70 can protect T cells from staurosporine-induced apoptosis. Thus, Hsp27 could play a role in the regulation of death receptor-mediated apoptosis, while Hsp70 could regulate mitochondrial-dependent cell death.

Protein kinase C theta and epsilon promote T-cell survival by a rsk-dependent phosphorylation and inactivation of BAD

Both MAPK and protein kinase C (PKC) signaling pathways promote cell survival and protect against cell death. Here, we show that 12-O-tetradecanoylphorbol-13-acetate (TPA) prevents Fas-induced apoptosis in T lymphocytes. The effect of TPA was specifically abolished by the PKC inhibitor GF109203X and by dominant negative PKCtheta, PKCepsilon, and PKCalpha, suggesting that novel and conventional PKC isoforms mediate phorbol ester action. Moreover, TPA stimulated phosphorylation of BAD at serine 112, an effect abrogated by GF109203X but not by the MEK inhibitor PD98059. Expression of constitutively active PKC increased the phosphorylation of BAD at serine 112 but not at serine 136. Additionally, Fas-mediated cell death was enhanced by overexpression of a catalytically inactive form of p90Rsk (Rsk2-KN). Finally, Rsk2-KN abolished the protective effect of constitutively active PKC and totally blocked phosphorylation of BAD on serine 112. Thus, novel PKCtheta and PKCepsilon rescue T lymphocytes from Fas-mediated apoptosis via a p90Rsk-dependent phosphorylation and inactivation of BAD.

Cleavage of the serum response factor during death receptor-induced apoptosis results in an inhibition of the c-FOS promoter transcriptional activity

The c-FOS protooncogene is rapidly induced by a wide variety of extracellular stimuli including mitogenic signals. Regulation of c-FOS expression is tightly dependent on the serum response element localized within its promoter. Two transcription factors, the serum response factor (SRF) and the ternary complex factor, bind to the serum response element and play a key role in the regulation of the c-FOS promoter activity. In the present study, we show that two death effectors (CH11 and TRAIL) severely impaired the transcriptional activity of the c-FOS promoter in Jurkat T cells. This inhibition can be accounted for by the specific cleavage by caspase 3 of the SRF both in vitro and in vivo, since acetyl-DEVD-aldehyde prevented SRF cleavage and abolished the inhibitory effect of CH11 and TRAIL on the c-FOS promoter activity. Moreover, phorbol myristate acetate, a potent anti-apoptotic effector, was found to protect SRF completely from cleavage by caspase 3 and also to prevent the inhibition of the c-FOS promoter activity by death effectors. Survival factors play an essential function in the regulation of cell growth mainly by regulating the expression of immediate early gene such as c-FOS. In this line, cleavage of SRF at the onset of apoptosis could abrogate the ability of the cell to induce inappropriate survival pathways. All together, our results are consistent with a role of SRF at the interface between cell survival and death pathways.

TFE3, a transcription factor homologous to microphthalmia, is a potential transcriptional activator of tyrosinase and TyrpI genes

Microphthalmia gene encodes a basic helix-loop-helix-leucine zipper (bHLH-Zip) transcription factor involved in the development of the melanocyte lineage and plays a key role in the transcriptional regulation of the melanogenic enzymes, tyrosinase and TyrpI. Recently, we have shown that Microphthalmia mediates the melanogenic effects elicited by alphaMSH that up-regulates the expression of tyrosinase through the activation of the cAMP pathway. Therefore, Microphthalmia appears as a principal gene in melanocyte development and functioning. Among the transcription factors of the bHLH-Zip family, TFE3 and TFEB show a remarkably elevated homology with Microphthalmia. These observations prompted us to investigate the role of TFE3 and TFEB in the regulation of tyrosinase and TyrpI gene transcription. We show in this report that overexpression of TFE3 stimulates the tyrosinase and TyrpI promoter activities, while TFEB acts only on the TyrpI promoter. TFE3 and TFEB elicit their effects mainly through the binding to Mbox (AGTCATGTGCT) and Ebox motifs (CATGTG) of tyrosinase and TyrpI promoters. In B16 melanoma cells, the high basal expression of TFE3 is down-regulated by forskolin and by alphaMSH. Interestingly, endogenous TFE3 cannot bind as homodimers to the Mbox, and we did not detect TFE3/Mi heterodimers. According to these data, TFE3 is clearly endowed with the capacity to regulate tyrosinase and TyrpI gene expression. However, TFE3 binding to the melanogenic gene promoters is hindered, thereby preventing its potential melanogenic action. In specific physiological or pathological conditions, the recovery of its binding function would make TFE3 an important element in melanogenesis regulation.

Differential development of cholinergic-like neurons in the superior olive: a light microscopic study

To better understand the development of cholinergic-like neurons within the superior olivary complex, we investigated the onset and distribution of two well-known markers of cholinergic-like neurons in hamsters: choline acetyltransferase (ChAT) and acetylcholinesterase (AChE). From embryonic day (E) 14 through postnatal day (P) 0, olivary cells immunopositive for ChAT were restricted to the rostral periolivary (RPO) area. Between P0 and P3, ChAT-positive cells are found in progressively more caudal and ventral periolivary locations. Although rostral and ventral periolivary cells exhibited an early onset of ChAT expression, stable numbers were not reached until P4. In contrast, ChAT expression within the lateral superior olive (LSO) is not visible until after P0 and higher numbers of ChAT-positive cells are obtained by P5. The AChE expression lags several days but follows roughly the same pattern of onset as for ChAT. Additionally in rostral and ventral periolivary regions as well as in the LSO, there were fewer AChE-labeled cells than ChAT-labeled cells. The observed temporal relationships in cholinergic-like expression within olivary cells suggest that different cholinergic-like populations may be defined on the basis of the onset of neurotransmitter-related enzymes: RPO cells are first, cells in ventral periolivary regions are second, and cells associated with the LSO are last. The differences observed in the onset of ChAT and AChE expression may reflect differences in the timing of target innervation as well as differences in synaptogenesis.

Tumor necrosis factor alpha-mediated inhibition of melanogenesis is dependent on nuclear factor kappa B activation

Melanogenesis is a physiological process resulting in the synthesis of melanin pigments which play a crucial protective role against skin photocarcinogenesis. In vivo, solar ultraviolet light triggers the secretion of numerous keratinocyte-derived factors that are implicated in the regulation of melanogenesis. Among these, tumor necrosis factor alpha (TNFalpha), a cytokine implicated in the pro-inflammatory response, down-regulates pigment synthesis in vitro. In this report, we aimed to determine the molecular mechanisms by which this cytokine inhibits melanogenesis in B16 melanoma cells. First, we show that TNFalpha inhibits the activity and protein expression of tyrosinase which is the key enzyme of melanogenesis. Further, we demonstrate that this effect is subsequent to a down-regulation of the tyrosinase promoter activity in both basal and cAMP-induced melanogenesis. Finally, we present evidence indicating that the inhibitory effect of TNFalpha on melanogenesis is dependent on nuclear factor kappa B (NFkappaB) activation. Indeed, overexpression of this transcription factor in B16 cells is sufficient to inhibit tyrosinase promoter activity. Furthermore, a mutant of inhibitory kappa B (IkappaB), that prevents NFkappaB activation, is able to revert the effect of TNFalpha on the tyrosinase promoter activity. Taken together, our results clarify the mechanisms by which TNFalpha inhibits pigmentation and point out the key role of NFkappaB in the regulation of melanogenesis.

Microphthalmia gene product as a signal transducer in cAMP-induced differentiation of melanocytes

Melanocyte differentiation characterized by an increased melanogenesis, is stimulated by alpha-melanocyte-stimulating hormone through activation of the cAMP pathway. During this process, the expression of tyrosinase, the enzyme that controls melanin synthesis is upregulated. We previously showed that cAMP regulates transcription of the tyrosinase gene through a CATGTG motif that binds microphthalmia a transcription factor involved in melanocyte survival. Further, microphthalmia stimulates the transcriptional activity of the tyrosinase promoter and cAMP increases the binding of microphthalmia to the CATGTG motif. These observations led us to hypothesize that microphthalmia mediates the effect of cAMP on the expression of tyrosinase. The present study was designed to elucidate the mechanism by which cAMP regulates microphthalmia function and to prove our former hypothesis, suggesting that microphthalmia is a key component in cAMP-induced melanogenesis. First, we showed that cAMP upregulates the transcription of microphthalmia gene through a classical cAMP response element that is functional only in melanocytes. Then, using a dominant-negative mutant of microphthalmia, we demonstrated that microphthalmia is required for the cAMP effect on tyrosinase promoter. These findings disclose the mechanism by which cAMP stimulates tyrosinase expression and melanogenesis and emphasize the critical role of microphthalmia as signal transducer in cAMP-induced melanogenesis and pigment cell differentiation.

Involvement of microphthalmia in the inhibition of melanocyte lineage differentiation and of melanogenesis by agouti signal protein

In mouse follicular melanocytes, production of eumelanins (brown-black pigments) and pheomelanins (yellow-brownish pigments) is under the control of two intercellular signaling molecules that exert opposite actions, alpha-melanocyte-stimulating hormone (alphaMSH) which preferentially increases the synthesis of eumelanins, and agouti signal protein (ASP) whose expression favors the production of hair containing pheomelanins. In this study, we report that ASP does not only affect mature melanocytes but can also inhibit the differentiation of melanoblasts. We show that both alphaMSH and forskolin promote the differentiation of murine melanoblasts into mature melanocytes and that ASP inhibits this process. We present evidence that the expression of a specific melanogenic transcription factor, microphthalmia, and its binding to an M box regulatory element, is inhibited by ASP. We also show that, in B16 murine melanoma cells, ASP inhibits alphaMSH-stimulated expression of tyrosinase, tyrosine-related proteins 1 and 2 through an inhibition of the transcription activity of their respective promoters. Further, ASP inhibits alphaMSH-induced expression of the microphthalmia gene and reduces the level of microphthalmia in the cells. Our data demonstrate that ASP can regulate both melanoblast differentiation and melanogenesis, pointing out the key role of microphthalmia in the control of these processes.

Choline acetyltransferase expression during a putative developmental waiting period

The relationship between the cholinergic expression, morphological development, and target cell innervation of olivocochlear (OC) efferent neurons was investigated in the postnatal hamster. Similar to what was found in previous studies, tracer injections into the contralateral cochlea labeled cells bodies retrogradely in periolivary regions and labeled cell bodies only rarely in the lateral superior olive (LSO). Few morphological differences were found among cell bodies labeled between postnatal day 1 (P1) and P30. Tracer injections into the crossed OC bundles within the brainstem anterogradely labeled terminals below the inner hair cells of the cochlea prior to P5 and labeled terminals below outer hair cells after P5, consistent with a period of transient innervation, as hypothesized previously. Within the superior olive, choline acetyltransferase (ChAT) was expressed differentially. In periolivary regions, ChAT was expressed as early as P0. ChAT-immunoreactive cell bodies in periolivary regions were similar morphologically to retrogradely labeled OC neurons. In contrast, within the LSO, ChAT was not expressed until after P2. Consistent with a medical OC projection to the cochlea at early postnatal ages, ChAT immunoreactivity was detected below inner hair cells as early as P2 but was not detected below outer hair cells until after P6. Our results suggest that medial OC neurons not only provide transient connections to inner hair cells but also may express ChAT when they are below inner hair cells. Furthermore, these results raise the possibility that OC neurons may be capable of acetylcholine synthesis and release prior to or simultaneous with their innervation of the cochlea.

Inhibition of Rho is required for cAMP-induced melanoma cell differentiation

Up-regulation of the cAMP pathway by forskolin or alpha-melanocyte stimulating hormone induces melanocyte and melanoma cell differentiation characterized by stimulation of melanin synthesis and dendrite development. Here we show that forskolin-induced dendricity is associated to a disassembly of actin stress fibers. Since Rho controls actin organization, we studied the role of this guanosine triphosphate (GTP)-binding protein in cAMP-induced dendrite formation. Clostridium botulinum C3 exotransferase, which inhibits Rho, mimicked the effect of forskolin in promoting dendricity and stress fiber disruption, while the Escherichia coli toxin cytotoxic necrotizing factor-1 (CNF-1), which activates Rho and the expression of a constitutively active Rho mutant, blocked forskolin-induced dendrite outgrowth. In addition, overexpression of a constitutively active form of the Rho target p160 Rho-kinase (P160(ROCK)) prevented the dendritogenic effects of cAMP. Our results suggest that inhibition of Rho and of its target p160(ROCK) are required events for cAMP-induced dendrite outgrowth in B16 cells. Furthermore, we present evidence that Rho is involved in the regulation of melanogenesis. Indeed, Rho inactivation enhanced the cAMP stimulation of tyrosinase gene transcription and protein expression, while Rho constitutive activation impaired these cAMP-induced effects. This reveals that, in addition to controlling dendricity, Rho also participates in the regulation of melanin synthesis by cAMP.

Inhibition of the mitogen-activated protein kinase pathway triggers B16 melanoma cell differentiation

In B16 melanoma cells, mitogen-activated protein (MAP) kinases are activated during cAMP-induced melanogenesis (Englaro, W., Rezzonico, R., Durand-Clément, M., Lallemand, D., Ortonne, J. P., and Ballotti, R. (1995) J. Biol. Chem. 270, 24315-24320). To establish the role of the MAP kinases in melanogenesis, we studied the effects of a specific MAP kinase kinase (MEK) inhibitor PD 98059 on different melanogenic parameters. We showed that PD 98059 inhibits the activation of MAP kinase extracellular signal-regulated kinase 1 by cAMP, but does not impair the effects of cAMP either on the morphological differentiation, characterized by an increase in dendrite outgrowth, or on the up-regulation of tyrosinase that is the key enzyme in melanogenesis. On the contrary, PD 98059 promotes by itself cell dendricity and increases the tyrosinase amount and activity. Moreover, down-regulation of the MAP kinase pathway by PD 98059, or with dominant negative mutants of p21(ras) and MEK, triggers a stimulation of the tyrosinase promoter activity and enhances the effect of cAMP on this parameter. Conversely, activation of the MAP kinase pathway, using constitutive active mutants of p21(ras) and MEK, leads to an inhibition of basal and cAMP-induced tyrosinase gene transcription. These results demonstrate that the MAP kinase pathway activation is not required for cAMP-induced melanogenesis. Furthermore, the inhibition of this pathway induces B16 melanoma cell differentiation, while a sustained activation impairs the melanogenic effect of cAMP-elevating agents.

In B16 melanoma cells, the inhibition of melanogenesis by TPA results from PKC activation and diminution of microphthalmia binding to the M-box of the tyrosinase promoter

In B16 melanoma cells, cAMP-induced melanogenesis is inhibited by the tumor promoting phorbol ester, TPA. However, the role of PKC activation or depletion in the inhibition of melanogenesis by TPA remains controversial. In this report, using specific PKC inhibitors, we demonstrated that PKC inhibition does not impair cAMP-induced melanin synthesis and tyrosinase expression. Further, the inhibition of melanogenesis by TPA results from a decrease of the tyrosinase promoter transcriptional activity and this effect is mimicked by over-expression of a constitutively active form of PKC alpha. These findings clearly demonstrate that PKC activation accounts for the inhibition of melanin synthesis by TPA. Additional experiments were undertaken to elucidate the mechanism by which TPA inhibits the tyrosinase gene transcription. Deletions and mutation in the tyrosinase promoter showed that TPA acts on a M-box which is involved in tissue-specific expression and regulation by cAMP of the tyrosinase gene. We showed that TPA decreases the binding of microphthalmia, a basic helix-loop-helix transcription factor, to the M-box. Since microphthalmia, strongly stimulates the transcriptional activity of the promoter we propose that TPA, through PKC activation, decreases microphthalmia binding to the M-box of the tyrosinase promoter, thereby leading to a reduced tyrosinase expression and melanogenesis inhibition.

Different cis-acting elements are involved in the regulation of TRP1 and TRP2 promoter activities by cyclic AMP: pivotal role of M boxes (GTCATGTGCT) and of microphthalmia

In melanocytes and in melanoma cells, cyclic AMP (cAMP)-elevating agents stimulate melanogenesis and increase the transcription of tyrosinase, the rate-limiting enzyme in melanin synthesis. However, two other enzymes, tyrosinase-related protein 1 (TRP1) and TRP2, are required for a normal melanization process leading to eumelanin synthesis. In B16 melanoma cells, we demonstrated that stimulation of melanogenesis by cAMP-elevating agents results in an increase in tyrosinase, TRP1, and TRP2 expression. cAMP, through a cAMP-dependent protein kinase pathway, stimulates TRP1 and TRP2 promoter activities in both B16 mouse melanoma cells and normal human melanocytes. Regulation of the TRP1 and TRP2 promoters by cAMP involves a M box and an E box. Further, a classical cAMP response element-like motif participates in the cAMP responsiveness of the TRP2 promoter, demonstrating that the TRP2 gene is subjected to different regulatory processes, which could account for its different expression patterns during embryonic development or under specific physiological and pathological conditions. We also found that microphthalmia, a basic helix-loop-helix transcription factor, strongly stimulates the transcriptional activities of the TRP1 and TRP2 promoters, mainly through binding to the M boxes. Additionally, we demonstrated that cAMP increases microphthalmia expression and thereby its binding to TRP1 and TRP2 M boxes. These convergent and compelling results disclose at least a part of the molecular mechanism involved in the regulation of melanogenic gene expression by cAMP and emphasize the pivotal role of microphthalmia in this process.

Inhibition of the phosphatidylinositol 3-kinase/p70(S6)-kinase pathway induces B16 melanoma cell differentiation

alpha-Melanocyte-stimulating hormone and cAMP-elevating agents are known to induce B16 cell differentiation, characterized by increased melanin synthesis and dendrite outgrowth. In order to elucidate intracellular signaling pathways involved in this differentiation process, we focused our interest on the phosphatidylinositol 3-kinase/p70(S6)-kinase pathway. The specific inhibition of phosphatidylinositol 3-kinase by LY294002 markedly stimulated dendrite outgrowth, thus mimicking the action of cAMP-elevating agents on B16 cell morphology. In addition, LY294002 and rapamycin, a specific p70(S6)-kinase inhibitor, were found to independently stimulate tyrosinase expression, thus increasing melanin synthesis. In an attempt to better dissect the molecular mechanisms triggered by cAMP to induce melanoma cell differentiation, we examined the effects of a cAMP-elevating agent forskolin, on both phosphatidylinositol 3-kinase and p70(S6)-kinase activities. Specific kinase assays revealed that forskolin partially inhibited phosphatidylinositol 3-kinase activity and completely blocked p70(S6)-kinase activity and phosphorylation. In conclusion, our results clearly demonstrate that the inhibition of phosphatidylinositol 3-kinase and p70(S6)-kinase is involved in the regulation of B16 cell differentiation. Furthermore, we provide evidence which suggests that cAMP-induced melanogenesis and dendricity are, at least partially, mediated by the cAMP inhibition of the phosphatidylinositol 3-kinase/p70(S6)-kinase signaling pathway.

Regulation of tyrosinase gene expression by cAMP in B16 melanoma cells involves two CATGTG motifs surrounding the TATA box: implication of the microphthalmia gene product

In melanocytes and in melanoma cells, upregulation of melanogenesis, by cAMP elevating agents, results from a stimulation of tyrosinase activity that has been ascribed to an increase in tyrosinase protein and messenger amount. However, the mechanism by which cAMP elevating agents increase tyrosinase mRNA remains to be elucidated. In this study, using a luciferase reporter plasmid containing the 2.2-kb fragment 5' of the transcriptional start site of the mouse tyrosinase gene, we showed that cAMP elevating agents lead to a strong stimulation (20-fold) of transcriptional activity of the tyrosinase promoter. Deletions and mutations in the mouse tyrosinase promoter showed that the M-box 70-bp upstream from the TATA-box and the E-box located downstream the TATA-box, near to the initiator site, are involved in the regulation of the tyrosinase promoter activity by cAMP. Additionally, we showed that microphthalmia, a b-HLH transcription factor associated with pigmentation disorders in mouse, binds to these regulatory elements and modulates the transcriptional activity of the tyrosinase promoter. Since cAMP stimulates the binding of microphthalmia to the M-box and to the E-box; it is tempting to propose that microphthalmia, through its interaction with cis-acting elements surrounding the TATA-box, plays a key role in the regulation of the mouse tyrosinase gene expression by cAMP.

Age-related changes in soma size of neurons in the spinal cord motor column of the cat

The present study was undertaken to examine the effect of the aging process on the soma size and number of motoneurons and interneurons in the motor column of the spinal cord of old cats. Neurons in the motor column were divided into small and large populations based on a bimodal distribution of their soma cross-sectional areas. A 17% decrease in the cross-sectional area of small neurons was observed, this decrease was statistically significant (P < 0.0001). The cross-sectional area of large neurons decreased by only 6%, which was statistically significant (P < 0.05). On the other hand, there was no significant difference in the number of large, small or of these combined population of ventral horn neurons in the aged cats compared with the control animals. This data suggest that neurons in the motor column are not uniformly affected by the aging process because morphological changes are proportionally greater in small neurons than in large neurons.

Morphological gradients in sensory hair cells of the amphibian papilla of the frog, Rana pipiens pipiens

The sensory hair cells of the amphibian papilla (AP) of the northern leopard frog were examined in a light-microscopic analysis. Hair cell length and cross-sectional area were found to vary systematically along the rostro-caudal axis of the endorgan. The AP was readily divided into three morphological regions. Rostrally-located hair cells are tall, cylindrically-shaped cells with large cross-sectional areas and long stereocilia; caudally-located hair cells are short, goblet-shaped cells with small cross-sectional areas and short stereocilia. In the middle region, hair cells exhibit features intermediate to those of hair cells located at the AP extremes. The detailed pattern of changes in hair cell morphology along the endorgan correlates well with its observed tonotopy and may have implications for the intrinsic tuning of the AP.

[The first isolation of Torulopsis glabrata (Anderson) Lodder from dental granulomas]

Three Torulopsis have been isolated from two hundred or so dental granulomas. Torulopsis glabrata has been observed in cases of ophthalmopathy, infections of the oral cavity, lung infections, endocarditis and septicaemia. Apical lesions due to Torulopsis glabrata are not typical of mycosis but are generic of dental granulomas. The histological granulomatous character prevails. Experimental infections have been obtained from this fungus. Human infections by Torulopsis glabrata have been described. These infections are induced particularly in subjects with their immunity systems depressed by prolonged cortisone therapy. Their systematic position and morphology in optical microscopy have been examined in accordance with current views.

Innervation of the amphibian and basilar papillae in the leopard frog: reconstructions of single labeled fibers

Amphibians have two auditory organs specialized for reception of airborne sounds: the amphibian papilla and the basilar papilla. In this report we examine the morphology of the ganglion cells and the afferent innervation of the sensory epithelium in both auditory organs of the leopard frog, Rana pipiens pipiens. Extracellular injections of either biocytin or horseradish peroxidase (HRP) were made into the VIII nerve; they labeled ganglion cells, their axons, and their terminal fibers within the papillae. Ganglion cells that projected to either the amphibian papilla or basilar papilla had cell bodies that were morphologically distinct from other labeled cells. In the amphibian papilla thick fibers terminated in the rostral portion and thin fibers terminated in the caudal portion. Labeled fibers in the rostral portion traveled short distances before making contacts with up to nine hair cells whereas labeled fibers in the caudal portion traveled longer distances and contacted no more than five hair cells. In the basilar papilla labeled fibers were thick (around 4 microns) and terminated on as many as nine hair cells. Consistent with studies from the bullfrog, Rana catesbeiana, our results suggest that the amphibian papilla of R. pipiens pipiens has a convergent innervation (i.e., multiple hair cells provide input to a single ganglion cell) and is topographically organized. However, in contrast to reports in other ranid species, a highly convergent innervation like that found in the amphibian papilla is also found in the basilar papilla.

[The first isolation of Cladosporium cladosporioides (Fres.) de Vries from dental granulomas]

Thirteen Cladosporium have been isolated from 221 dental granulomas. Cases have been observed of cerebral lesions both in man and cats. Also various types of lesions, encapsulated abscesses, etc. to be classified under the group of pheoifomycoses. Cutaneous allergies and cases of keratitis and chromoblastomycosis have been observed, too Cladosporium cladosporioides is very resistant to mercuric and phenolic compounds and radiations. The systematic position and morphology of Cladosporium have been fully examined in accordance to the latest scientific views.

Some aspects of the structural organization of the spinal cord of Gymnotus carapo (Teleostei, Gymnotiformes). I. The electromotor neurons

The spinal electromotor neurons (EMNs) of Gymnotus carapo from a distinct column dorsal to the central canal. When massively retrograde-labeled with horseradish peroxidase, these neurons show a well-developed dendritic arborization. Dendrites run along the longitudinal axis of the cord and also project toward the dorsal gray and dorsolateral funiculi. Input to the EMNs is mediated by scarce synaptic contacts which show the fine structural characteristics of the so-called "morphologically mixed" junctions. Serial section reconstructions of the junctional areas revealed the occurrence of "gap junctions," dense membranes facing cumuli of microvesicles, and relatively large zones of undifferentiated membranes. Comparative electrophysiological and morphological data suggest that EMN activity may be mediated by electrical transmission. Since neither dendro-dendritic nor dendro-somatic junctions have been observed, other circuitry alternatives are proposed to account for the expected synchronized firing of the EMNs.

[Morphologic characteristics of leukoplakias of the oral cavity and review of case material]

Cases of oral mucosa leukoplakias are presented. The authors discuss histologic features, clinical and prognostic findings.