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Growth/differentiation factor−15 (Gdf-15) is a member of the transforming growth factor-β (Tgf-β) superfamily and has been shown to be a potent neurotrophic factor for midbrain dopaminergic (DAergic) neurons both in vitro and in vivo. Gdf-15 has also been shown to be involved in inflammatory processes. The aim of this study was to identify the role of endogenous Gdf-15 in the MPTP (1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine) mouse model of Parkinson’s disease (PD) by comparing Gdf-15 +/+ and Gdf-15 −/− mice. At 4 days and 14 days post-MPTP administration, both Gdf-15 +/+ and Gdf-15 −/− mice showed a similar decline in DAergic neuron numbers and in striatal dopamine (DA) levels. This was followed by a comparable restorative phase at 90 days and 120 days, indicating that the absence of Gdf-15 does not affect the susceptibility or the recovery capacity of the nigrostriatal system after MPTP administration. The MPTP-induced microglial and astrocytic response was not significantly altered between the two genotypes. However, pro-inflammatory and anti-inflammatory cytokine profiling revealed the differential expression of markers in Gdf-15 +/+ and Gdf-15 −/− mice after MPTP administration. Thus, the MPTP mouse model fails to uncover a major role of endogenous Gdf-15 in the protection of MPTP-lesioned nigrostriatal DAergic neurons, in contrast to its capacity to protect the 6-hydroxydopamine-intoxicated nigrostriatal system.

The neural-crest-derived sympathoadrenal cell lineage gives rise to sympathetic neurons and to endocrine chromaffin cells of the adrenal medulla. Both cell types express a largely overlapping set of genes, including those coding for the molecular machinery related to the synthesis and exocytotic release of catecholamines. During their early development, sympathetic neurons and chromaffin cells rely on a shared transcription factor network that controls the establishment of these common features. Despite many similarities, mature sympathetic neurons and chromaffin cells significantly differ regarding their morphology and function. Most prominently, sympathetic neurons possess axons that are absent in mammalian adrenal chromaffin cells. The molecular mechanism underlying the divergent development of sympathoadrenal cells into neuronal and endocrine cells remains elusive. Mutational inactivation of the ribonuclease dicer hints at the importance of microRNAs in this diversification. We show here that miR-124 is detectable in developing sympathetic neurons but absent in chromaffin cell precursors. We further demonstrate that miR-124 promotes neurite elongation when transfected into cultured chromaffin cells indicating its capability to support the establishment of a neuronal morphology in non-neuronal sympathoadrenal cells. Our results also show that treatment of PC12 cells with the neurotrophin nerve growth factor leads to an upregulation of miR-124 expression and that inhibition of miR-124 reduces nerve-growth-factor-induced neurite outgrowth in PC12 cells. Thus, our data indicate that miR-124 contributes to the establishment of specific neuronal features in developing sympathoadrenal cells.

Growth/differentiation factor-15 (GDF-15) is a distant member of the transforming growth factor beta (TGF-β) superfamily. It is widely distributed in the nervous system, where it has been shown to play an important role in neuronal maintenance. The present study investigates the role of endogenous GDF-15 in sciatic nerve (SN) lesions using wild-type (WT) and GDF-15 knock-out (KO) mice. SN of 5-6-month-old mice were crushed or transected. Dorsal root ganglia (DRG) and nerve tissue were analyzed at different time points from 6 h to 9 weeks post-lesion. Both crush and transection induced GDF-15 mRNA and protein in the distal portion of the nerve, with a peak at day 7. DRG neuron death did not significantly differ between the genotypes; similarly, remyelination of regenerating axons was not affected by the genotype. Alternative macrophage activation and macrophage recruitment were more pronounced in the KO nerve. Protrusion speed of axons was similar in the two genotypes but WT axons showed better maturation, as indicated by larger caliber at 9 weeks. Furthermore, the regenerated WT nerve showed better performance in the electromyography test, indicating better functional recovery. We conclude that endogenous GDF-15 is beneficial for axon regeneration following SN crush.

The pan-neurotrophin receptor p75NTR is expressed in the adult brain in a discrete pattern. Although numerous studies have addressed its implications for hippocampal functions, the generated sets of data are surprisingly conflicting. We have therefore set out to re-investigate the impact of a deletion of the full-length p75NTR receptor on several parameters of the dentate gyrus (DG), including neurogenesis and hippocampus-related behavior by using p75NTR(ExIII) knockout mice. Moreover, we investigated further parameters of the DG (cholinergic innervation, dendritic spines). In addition, we analyzed on the morphological level the impact of aging by comparing adult and aged p75NTR(ExIII) mice and their age-matched littermates. Adult (4-6 months old), but not aged (20 months old), p75NTR(ExIII) knockout mice display an enhanced volume of the DG. However, adult neurogenesis within the adult DG was unaffected in both adult and aged p75NTR(ExIII) knockout mice. We could further demonstrate that the change in the volume of the DG was accompanied by an increased cholinergic innervation and increased spine densities of granule cells in adult, but not aged p75NTR deficient mice. These morphological changes in the adult p75NTR deficient mice were accompanied by specific alterations in their behavior, including altered behavior in the Morris water maze test, indicating impairments in spatial memory retention.

The superfamily of transforming growth factor-βs (TGF-βs) constitutes one of the most versatile families of signaling molecules, being involved in a broad range of biological processes spanning from development, cell death and maintenance, to aging and disease. The field has made impressive progress during the past decade. Novel signaling pathways and contextual mechanisms have been discovered. New insights into the roles of TGF-βs in tumor initiation and progression have been achieved. Numerous associations of TGF-βs with various diseases have been newly discovered or elucidated in much more detail than before, including atherosclerosis, acute and chronic liver and kidney disease, osteoarthritis and neurodegenerative diseases. This Special Issue highlights several of the recent advances in the TGF-β field. The purpose of this collection of reviews is not to present a comprehensive overview of the current status of knowledge on TGF-βs. Rather, it is the guest editors’ concept to focus on recent progress seen from the perspective of dynamic cell performances, signaling and complex disease states. A brief overview of articles in this Special Issue

Transforming growth factor-beta (TGF-beta) and glial-cell-line-derived neurotrophic factor (GDNF) have been shown to synergize in several paradigms of neuronal survival. We have previously shown that cerebellar granule neurons (CGN) degenerate in low potassium via ERK1/2 (extra-cellular-regulated kinase)-dependent plasma membrane (PM) damage and caspase-3-dependent DNA fragmentation. Here, we have investigated the putative synergistic function of GDNF and TGF-beta in CGN degeneration. GDNF alone prevents low-potassium-induced caspase-3 activation and DNA fragmentation but does not affect either low-potassium-induced ERK activation or PM damage. TGF-beta alone does not affect low-potassium-induced DNA fragmentation but potentiates low-potassium-induced PM damage. This effect of TGF-beta is independent of ERK1/2 activation but dependent on p38-MAPK (mitogen-activated protein kinase) activation. When co-applied with TGF-beta, GDNF paradoxically antagonizes TGF-beta-induced potentiation of PM damage by inhibiting TGF-beta-induced p38-MAPK activation. In addition, PI3K (phosphatidylinositol 3-kinase) inhibitors abolish the GDNF effect. This study thus demonstrates a differential mechanism of action of GDNF and TGF-beta on CGN degeneration. GDNF inhibits caspase-3-dependent DNA fragmentation but does not affect ERK-dependent PM damage. However, GDNF can attenuate TGF-beta-induced p38-MAPK-dependent PM damage via the PI3K pathway.

Growth differentiation factor-15/macrophage inhibitory cytokine-1 (GDF-15/MIC-1) is a new member of the transforming growth factor beta (TGF-beta) superfamily, which has most recently been found in activated macrophages (MPhi). We have now investigated GDF-15/MIC-1 in human MPhi after exposure to oxidized low-density lipoproteins (oxLDL) related mediators in vitro and in arteriosclerotic carotid arteries. Using RT-PCR and Western blotting a pronounced induction of GDF-15/MIC-1 expression by oxLDL, C6-ceramide, tumor necrosis factor (TNFalpha) and hydrogen peroxide (H2O2) was found in cultured human MPhi. In 11 human arteriosclerotic carotid arteries, immunohistochemical analyses supported by computer-assisted morphometry and regression analyses demonstrated a significant colocalization of GDF-15/MIC-1 immunoreactivity (IR) with oxLDL IR and manganese superoxide dismutase (MnSOD) IR in CD68 immunoreactive (ir) MPhi, which were also expressing AIF-IR (apoptosis-inducing factor), caspase-3-IR (CPP32), PARP-IR, c-Jun/AP-1-IR and p53-IR. Our data suggest that GDF-15/MIC-1 is inducible in human MPhi by oxLDL and its mediators in vitro and is supposed to contribute to oxidative stress dependent consequences in arteriosclerotic plaques, e.g. modulating apoptosis and inflammatory processes in activated MPhi.

Andreas Oksche Coordinating Editor of Cell & Tissue Research from 1978 to 1995, and Co-Editor for the section “Neuroendocrinology” for many years, will celebrate his ninetieth birthday on 27 July 2016. We, the Editors, Springer Nature Publishing Group, and many friends and former colleagues congratulate him on this occasion and wish him health and vitality for the years to come. Andreas Oksche is known as an eminent figure in neuroendocrinology with a world-wide reputation, as a leading anatomist in Germany and beyond and as a prominent personality in national science policy. He was born in Riga, Latvia, and received his training in anatomy and neuroscience at the University of Marburg under the guidance of Professors Benninghoff and Niessing. His MD thesis on the “Organon frontale” of the grass frog established the foundation of his successful career in neuroendocrinology. Andreas Oksche’s Habilitation addressed secretory features of glia, with special reference to the subcommissural organ, thereby expanding the list of cells with a secretory capacity in the brain and anticipating the functions of astroglia, which have only recently been analysed in detail. Following postdoctoral work with Ernst and Berta Scharrer, two prominent pioneers in neuroendocrinology and hypothalamic-pituitary neurosecretion, at the Albert Einstein College of Medicine, he moved to the University of Kiel, where, in the late 1940s, Wolfgang Bargmann had established a centre for research on hypothalamic neurosecretion. The concept of neurons having a secretory identity had been initially met with profound scepticism. Proceeding from the hypothalamus to the pineal gland and circumventricular organs, Andreas Oksche’s contributions were essential to the broadening of the perception of the brain as having secretory capacities and of the neural–endocrine hybrid character of neurons. The discovery that such neuroendocrine cells could simultaneously act as photoreceptors and the elucidation of their fine structure was the culmination of the search for mechanisms underlying the regulation of Andreas Oksche (by courtesy of Dr. Alexander Oksche)

Numbers of catecholaminergic neurons are known to decline with aging. Whether projections of these neurons to the forebrain are similarly affected is not known. High densities of tyrosine hydroxylase-immunoreactive (TH-ir) fibers are found in the hippocampal formation (CA1-3, dentate gyrus) and in the amygdala of normal adult mice. We report here that densities of TH-ir fibers in the amygdala and hippocampus in aged mice (21-26 months) decrease dramatically and in a subregion-specific fashion. There is a reduction of 35% in the dentate gyrus, while hippocampal regions CA1 through CA3 are almost entirely spared. In the amygdala the lateral, basolateral, basomedial, and central nucleus were affected, with fiber reduction ranging from 19% to 34%. These results indicate that the age-related decline of TH-ir catecholaminergic cell bodies in the substantia nigra and the ventral tegmental area induces substantial losses of TH-ir fibers in the amygdala and dentate gyrus, but not in other areas of the hippocampal formation. This suggests that region-specific factors may be implicated in the regulation of maintenance vs. degeneration of TH-ir fibers during aging.

Glial cell line-derived neurotrophic factor (GDNF), an important factor for developing and lesioned pre- and postganglionic sympathetic neurons, and its congeners signal through a receptor complex consisting of the tyrosine kinase c-Ret and a lipid-anchored alpha receptor (GFR alpha 1-4). Using in situ hybridization we show now that the mRNA for GFR alpha-2 is abundant in the adult rat adrenal medulla and its chromaffin cells. Coexpression of c-Ret and GFR alpha-1 mRNA's is restricted to a scarce subpopulation of medullary sympathetic neurons. Both GFR alpha-1 and GFR alpha-2 mRNA's are associated with preganglionic nerve trunks in the adrenal cortex. It is conceivable therefore that GDNF and related factors may activate chromaffin and preganglionic Schwann cells through a GFR-alpha receptor in absence of c-Ret.

We have cloned a novel member of the transforming growth factor-beta (TGF-beta) superfamily from a human placental cDNA library. The sequence is identical to five very recently published sequences, of which only one (macrophage inhibitory cytokine-1, MIC-1) has been characterized in terms of function. In light of the present data demonstrating the wide distribution of the mRNA and putative multifunctionality, we propose to name this molecule growth/differentiation factor-15/MIC-1 (GDF-15/MIC-1). The deduced amino acid sequence reveals typical features of a secreted molecule. The epithelium of the choroid plexus is the only site in the adult brain expressing detectable levels of GDF-15/MIC-1 mRNA. Many epithelia of non-neural tissues including those of the prostate and intestinal mucosa, bronchi and bronchioli, secretory tubuli of the submandibular gland, and lactating mammary gland are prominent sites of GDF-15/MIC-1 synthesis. GDF-15/MIC-1 is also strongly expressed by macrophages in the adrenal gland. Thus, GDF-15/MIC-1, like many other members of the TGF-beta superfamily, is widely distributed in adult tissues, being most strongly expressed in epithelial cells and macrophages.

Neurotrophins and their trk receptors constitute major classes of signaling molecules with important actions in the developing and adult nervous system. With regard to the sympathoadrenal cell lineage, which gives rise to sympathetic neurons and chromaffin cells, neurotrophin-3 (NT-3) and nerve growth factor (NGF) are thought to influence developing sympathetic neurons. Neurotrophin requirements of chromaffin cells of the adrenal medulla are less well understood than those for NGF. In order to provide the bases for understanding of putative functions of neurotrophins for the development and maintenance of chromaffin cells and their preganglionic innervation, in situ hybridization has been used to study the expression of brain-derived neurotrophic factor (BDNF) and NT-3, together with their cognate receptors trkB and trkC, in the adrenal gland and in the intermediolateral column (IML) of the spinal cord. BDNF is highly expressed in the embryonic adrenal cortex and later in cells of the cortical reticularis zone. Adrenal medullary chromaffin cells fail to express detectable levels of mRNAs for BDNF, NT-3, and their cognate receptors trkB and trkC. Neurons in the IML express BDNF and trkB, and low levels of NT-3 and trkC. Our data make it unlikely that BDNF and NT-3 serve as retrograde trophic factors for IML neurons but suggest roles of BDNF and NT-3 locally within the spinal cord and possibly for sensory nerves of the adrenal cortex.

Embryonic day 14 rat midbrain cultures were kept for 7 days in vitro and then intoxicated with radical donors iron and sodium-nitroprusside for 24 h. Tyrosine-hydroxylase positive neurons in cultures which were additionally treated with growth/differentiation factor-5 (GDF-5) survived to a significantly higher percentage as compared to sister cultures without factor supplementation. Since the degeneration of TH positive cells is a key feature in Parkinson's disease, GDF-5 might be a putative therapeutical agent for this disorder.

Macrophages are widely distributed in lymphohaemopoietic and many other mammalian tissues, where they are mainly involved in host defence mechanisms, phagocytosis, wound repair, and secretion of growth factors. Increasing evidence suggests that secretory products of macrophages can influence adrenal gland functions. In the present study, we have used specific antibodies to ED1 (cytoplasmic antigen), ED2 (membrane antigen), ED8 (membrane antigen), and OX-6 (MHC class II/membrane antigen) as markers for macrophages to examine their distribution within the adult rat adrenal gland. ED2 and OX-6 recognize distinct subpopulations of adrenal gland macrophages, whereas macrophages immunoreactive (-ir) for ED1 and ED8 could not be detected. OX-6-ir macrophages were most numerous in the cortical reticularis and glomerulosa zones, while only few cells were found in the zona fasciculata and in the adrenal medulla. Macrophages immunoreactive for ED2 were restricted to the adrenal medulla. The majority of these macrophages were associated with vascular sinuses or chromaffin cells. By double-immunolabelling we found that most of ED2-ir medullary macrophages contain neurotrophin-4 (NT-4)-like ir. Attempts to clarify whether macrophages take up NT-4 from NT-4-ir chromaffin cells indicated that medullary macrophages are immunonegative for chromogranin A and neuropeptide Y, two major secretory products of chromaffin cells. In situ hybridizations and immunofluorescence showed expression of the neurotrophin receptor TrkA, but not TrkB in the adrenal medulla. In vitro studies indicated that NT-4, similar to nerve growth factor, can induce c-fos-ir in chromaffin cells. We conclude that chromaffin cells are putative targets for adrenal medullary NT-4, whose functions remain to be clarified.

The Alzheimer amyloid precursor protein (APP) is cleaved by several proteases, the most studied, but still unidentified ones, are those involved in the release of a fragment of APP, the amyloidogenic beta-protein A beta. Proteolysis by gamma-secretase is the last processing step resulting in release of A beta. Cleavage occurs after residue 40 of A beta [A beta(1-40)], occasionally after residue 42 [A beta(1-42)]. Even slightly increased amounts of this A beta(1-42) might be sufficient to cause Alzheimer's disease (AD) (reviewed in ref. 1, 2). It is thus generally believed that inhibition of this enzyme could aid in prevention of AD. Unexpectedly we have identified in neurons the endoplasmic reticulum (ER) as the site for generation of A beta(1-42) and the trans-Golgi network (TGN) as the site for A beta(1-40) generation. It is interesting that intracellular generation of A beta seemed to be unique to neurons, because we found that nonneuronal cells produced significant amounts of A beta(1-40) and A beta(1-42) only at the cell surface. The specific production of the critical A beta isoform in the ER of neurons links this compartment with the generation of A beta and explains why primarily ER localized (mutant) proteins such as the presenilins could induce AD. We suggest that the earliest event taking place in AD might be the generation of A beta(1-42) in the ER.

The neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), and neurotrophin-3 (NT-3) are important for the regulation of survival and differentiation of distinct, largely non-overlapping populations of embryonic sensory neurons. We show here that the multifunctional cytokine transforming growth factor-beta (TGF-beta) fails to maintain sensory neurons cultured from embryonic day (E) 8 chick dorsal root ganglia (DRG), although DRG neurons are immunoreactive for the TGF-beta receptor type II, which is essential for TGF-beta signaling. However, in combination with various concentrations of NT-3 and NT-4, but not NGF, TGF-beta 3 causes a further significant increase in neuron survival. In DRG cell cultures treated with NGF, NT-3, and NT-4, a neutralizing antibody to TGF-beta decreases neuron survival suggesting that endogenous TGF-beta in these cultures affects the efficacies of neurotrophins. Consistent with this notion and a modulatory role of TGF-beta in neurotrophin functions is the observation that TGF-beta 2 and -beta 3 immunoreactivities and TGF-beta 3 mRNA are located in embryonic chick DRG in close association with neurons from E5 onwards. We also show that leukemia inhibitory factor (LIF) significantly decreases NGF-mediated DRG neuron survival. Together, these data indicate that actions and efficacies of neurotrophins are under distinct control by TGF-beta and LIF in vitro, and possibly also in vivo.

Adult bovine and young rat chromaffin cells cultured in serum-free medium were examined for their survival and differentiation following exposure to various additives, trophic agents and conditioned media. Adrenal chromaffin cells dissociated from 8 day old rats were maintained by dexamethasone, NGF and CNTF or without any additives in an N1-supplemented medium in similar numbers as in serum-containing medium for up to 6 days. Neuritic growth elicited by NGF or CNTF was enhanced in the absence of serum. Medium conditioned by purified bovine chromaffin cells improved cell survival and caused neurite outgrowth in a dose-dependent manner. The activiti(es) was sensitive to heat and trypsin and not blocked by the addition of anti-NGF antibodies. Bovine chromaffin cell survival was reduced by 30% when cells were maintained for one week in the absence as compared to the presence of serum. Addition of insulin, the N1 supplement, dexamethasone or dbcAMP single or in combinations improved the survival to different extents. A combination of insulin (5 micrograms/ml) and dexamethasone (5 X 10(-6) M) proved to be optimal in this respect. However, these supplements failed to restore the cellular catecholamine, noradrenaline and adrenaline contents to levels seen in the presence of serum. This was also true for a chromaffin cell-conditioned medium, which improved survival without elevating the catecholamine contents. Conditioned medium, however, partly restored a more physiological adrenaline-noradrenaline-ratio.

The innervation of the chicken ovary was investigated with special emphasis on adrenergic nerves in the follicular wall. Quantitative determinations of catecholamines (CA) by high-performance liquid chromatography and electrochemical detection (hplc-ed) revealed 15.4 +/- 3.3 ng/mg protein of norepinephrine (NE) and 3.14 ng/mg protein of epinephrine (E), with even larger amounts in the cranial part of the ovary close to the adrenal gland. Serial sections that had been processed for the visualisation of aminergic nerves (Falck-Hillarp- or glyoxylic acid techniques) showed CA localized in nerve-fibre bundles; cell bodies of chromaffin and sympathetic neurons were only found at the ovarian-adrenal junction suggesting that ovarian nerves stored considerable quantities of E. An antiserum against bovine phenylethanolamine N-methyltransferase (PNMT, the E-synthesizing enzyme) produced no immunostaining in chicken ovary or adrenal gland, due to a lack of cross-reactivity between the antiserum and chicken PNMT. Serial sections processed alternately for the visualisation of aminergic nerves and myosin (from chicken gizzard) immunoreactivity revealed a scarce nerve supply of contractile cells in the theca externa compared to an extraordinarily dense innervation of the endocrine interstitial tissue of the theca interna. This distribution pattern of nerve fibres in the follicular wall was confirmed by electron microscopy in ovarian tissue that had been pretreated with 5- or 6-hydroxydopamine (HDA). More than 90% of the terminal axons were specifically labeled by these false adrenergic transmitters. Many of these terminals were seen in close contact (20 nm) with steroidogenic cells suggesting a neuromodulatory function of CA in hormone synthesis and/or release. It is yet unclear whether E and NE are stored in separate or identical axon moieties and within the same organelles. Choline acetyltransferase activity, which was taken as a measure for a cholinergic nerve component in the ovary, amounted to only 7% of its adrenal activity. It is suggested that the chicken ovary may serve as an excellent model to investigate the modulatory role of nerves in the endocrine function of the ovary.

The present study investigates the innervation of the embryonic chick ovary with regard to (i) development and compartmentalization of catecholaminergic nerves, and (ii) presence of adrenoceptors on steroidogenic target cells of catecholaminergic nerve terminals. Catecholaminergic nerve fibers visualized by glyoxylic acid-induced histofluorescence first appeared at embryonic day (E) 13. From E15 through E21 the density of fluorescent aminergic nerves increased markedly in parallel with the concentration of catecholamines and numbers of nerve bundles and single axons seen at the electron-microscopic level. Catecholaminergic nerves were confined to the ovarian medulla and closely associated with interstitial cells. Nerve terminals approached interstitial cells up to a distance of 20 nm and, in their majority, exhibited uptake of the false adrenergic transmitter 5-hydroxydopamine. Although adrenaline amounted to 14% of the total catecholamine content at E21, adrenaline immunoreactivity was only detected in adrenal chromaffin cells, but not in nerve fibers or cell bodies within the ovary. Interstitial cells structurally matured between E15 and E21 as documented by an increase of smooth endoplasmic reticulum and tubular mitochondria. Monoclonal antibodies mAB 120 and BRK 2 raised against avian beta 1- and mammalian beta 2-adrenergic receptors revealed the presence of beta 2-adrenoceptor-like immunoreactivity on the surface of interstitial cells, but not on any other cell type. The results are consistent with the notion of a dense adrenergic innervation of the embryonic chick ovarian medulla and its steroidogenic interstitial cells, and suggest the chick ovary as an excellent model for elucidating the functional role of a neural input to steroidogenic cells during development.

The effects of a single high dose (10mg/kg) of vinblastine (vb) sulfate (“Velbe”, Lilly) on the ultrastructure, catecholamine (CA) content and activity of CA-synthesizing enzymes of the rat adrenal medulla were studied for up to 120h after intravenous injection of the drug.