Small cell lung cancer (SCLC) is one of the most lethal human malignancies. To investigate the cellular origin(s) of this cancer, we assessed the effect of Trp53 and Rb1 inactivation in distinct cell types in the adult lung using adenoviral vectors that target Cre recombinase to Clara, neuroendocrine (NE), and alveolar type 2 (SPC-expressing) cells. Using these cell type-restricted Adeno-Cre viruses, we show that loss of Trp53 and Rb1 can efficiently transform NE and SPC-expressing cells leading to SCLC, albeit SPC-expressing cells at a lesser efficiency. In contrast, Clara cells were largely resistant to transformation. The results indicate that although NE cells serve as the predominant cell of origin of SCLC a subset of SPC-expressing cells are also endowed with this ability.

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Cytoglobin and neuroglobin are recently discovered members of the globin family. In situ hybridization localized neuroglobin mainly in brain and retina, while cytoglobin was expressed ubiquitously in all analyzed tissues. In the present study, polyclonal antibodies were raised against both proteins and the distribution of them was studied by immunocytochemistry at tissue and subcellular level. Cytoglobin immunoreactivity was uniformly distributed and found in all tissues studied. At the subcellular level, cytoglobin immunoreactivity was exclusively detected in the cell nucleus. In contrast, neuroglobin immunoreactivity was detected in specific brain regions with varying intensities and in the islet of Langerhans in the pancreas. The immunoreactivity was restricted to the cytoplasm of neurons and endocrine beta cells. The nuclear localization of cytoglobin opens new perspectives for possible function(s) of globinfolded proteins as transcriptional regulators.The widespread occurrence of hemoglobins (Hbs) 1 in virtually all kingdoms indicates that the gene for Hb is very ancient and that Hbs may serve functions other than simple O 2 carriers (1-4). The actual function of the proteins of this superfamily is mainly associated with O 2 transport/storage. However, the reported involvement of bacterial (5), invertebrate (6) and vertebrate Hbs/myoglobins (Mbs) (7,8) in the detoxification of NO, might illustrate a more primitive function of these molecules (3). Involvement in other functions as O 2 scavenger (4), O 2 sensor (9), O 2 consuming enzymes (10), or shadow pigments (11) have been suggested and may illustrate the coincidental use of a stable protein fold during evolution.Recently, two new members of the vertebrate globin family, namely neuroglobin (Ngb) and cytoglobin (Cygb), have been discovered (12)(13)(14)(15)(16). Both are monomeric (151 and 190 amino acid residues, respectively), intracellular proteins, displaying all determinants of the globin fold. Sequence analyses reveal low sequence identity with vertebrate Hb and Mb (20 -25%), as well as a very ancient origin, i.e. much older than Mb (16). The heme-iron atom of Ngb and Cygb is hexacoordinated, showing a His-Fe-His binding scheme, both histidines being the proximal and the distal histidine, respectively (13,15,17). Ngb has a high recombination rate (k on ) and a slow dissociation rate (k off ), indicating a high intrinsic affinity for the ligands (O 2 / CO). Before binding, the external ligands must compete with the internal sixth ligand, resulting in an observed O 2 affinity of the recombinant proteins similar to that of Mb (1 torr at 37°C).The function of Ngb and Cygb is a matter of debate. In response to hypoxia, Ngb is up-regulated in vivo and in vitro and protects the neurons against hypoxic damage (18). High concentrations (ϳ100 M) of Ngb are observed in the retina and its subcellular distribution correlates with the localization of the mitochondria (19). Both observations suggest a role in intracellular O 2 supply.A protein, identical to Cygb a...

The neurotransmitters/modulators involved in the interaction between pulmonary neuroepithelial bodies (NEBs) and the vagal sensory component of their innervation have not yet been elucidated. Because P2X(3) purinoreceptors are known to be strongly expressed in peripheral sensory neurons, the aim of the present study was to examine the localization of nerve endings expressing P2X(3) purinoreceptors in the rat lung in general and those contacting pulmonary NEBs in particular. Most striking were intraepithelial arborizations of P2X(3) purinoceptor-immunoreactive (IR) nerve terminals, which in all cases appeared to ramify between calcitonin gene-related peptide (CGRP)- or calbindin D28k (CB)-labeled NEB cells. However, not all NEBs received nerve endings expressing P2X(3) receptors. Using CGRP and CB staining as markers for two different sensory components of the innervation of NEBs, it was revealed that P2X(3) receptor and CB immunoreactivity were colocalized, whereas CGRP-IR fibers clearly formed a different population. The disappearance of characteristic P2X(3) receptor-positive nerve fibers in contact with NEBs after infranodosal vagal crush and colocalization of tracer and P2X(3) receptor immunoreactivity in vagal nodose neuronal cell bodies in retrograde tracing experiments further supports our hypothesis that the P2X(3) receptor-IR nerve fibers contacting NEBs have their origin in the vagal sensory nodose ganglia. Combination of quinacrine accumulation in NEBs, suggestive of the presence of high concentrations of adenosine triphosphate (ATP) in their secretory vesicles, and P2X(3) receptor staining showed that the branching intraepithelial P2X(3) receptor-IR nerve terminals in rat lungs were exclusively associated with quinacrine-stained NEBs. We conclude that ATP might act as a neurotransmitter/neuromodulator in the vagal sensory innervation of NEBs via a P2X(3) receptor-mediated pathway. Further studies are necessary to determine whether the P2X(3) receptor-expressing neurons, specifically innervating NEBs in the rat lung, belong to a population of P2X(3) receptor-IR nociceptive vagal nodose neurons.

Innervated groups of neuroendocrine cells, called neuroepithelial bodies (NEBs), are diffusely spread in the epithelium of intrapulmonary airways in many species. Our present understanding of the morphology of NEBs in mammalian lungs is comprehensive, but none of the proposed functional hypotheses have been proven conclusively. In recent reviews on airway innervation, NEBs have been added to the list of presumed physiological lung receptors. Microscopic data on the innervation of NEBs, however, have given rise to conflicting interpretations. Using neuronal tracing, denervation, and immunostaining, we recently demonstrated that the innervation of NEBs is much more complex than the almost unique vagal nodose sensory innervation suggested by other authors. The aim of the present work is to summarize our present understanding about the origin and chemical coding of the profuse nerve terminals that selectively contact pulmonary NEBs. A thorough knowledge of the complex interactions between the neuroendocrine cells and at least five different nerve fiber populations is essential for defining the position Key words: NEBs; neuroepithelial bodies; innervation; airway receptors; lung; rat Highly specialized neuroepithelial bodies (NEBs) , which consist of extensively innervated groups of pulmonary neuroendocrine cells (PNECs), are normal components of the epithelium of intrapulmonary airways in humans, mammals, and all air-breathing vertebrate species investigated so far.The pulmonary neuroendocrine system was first reported more than 50 years ago (Fröhlich, 1949), but especially over the last 25 years detailed information has been provided about the distribution, ontogeny, and microscopic morphology of NEBs (for reviews see Scheuermann, 1987;Sorokin and Hoyt, 1989;Adriaensen and Scheuermann, 1993;Sorokin et al., 1997).PNECs belong to the diffuse neuroendocrine system (DNES) (Pearse and Takor Takor, 1979), members of which have been assigned important roles in the peripheral control of various organs. The pulmonary DNES in healthy lungs appears to be characterized by the production of amines and several neuropeptides, including serotonin (5-HT), bombesin (gastrin-releasing peptide), calcitonin gene-related peptide (CGRP), calcitonin, enkephalin, somatostatin, cholecystokinin, and substance P (SP) (for reviews see Sorokin and Hoyt, 1989; Scheuermann et al., 1992;Adriaensen and Scheuermann, 1993). These bioactive substances are stored in secretory granules (60 -200 nm diameter) with typical endocrine-like characteristics, the so-called dense-cored vesicles (DCVs).Interestingly, PNECs are by far the first cell type to fully differentiate in the human airway epithelium (before