Effects of decentralization on the levels of GAP-43 and p38 (synaptophysin) in sympathetic adrenergic neurons: a semi-quantitative study using immunofluorescence and confocal laser scanning microscopy

Injury-induced gp130 cytokine signaling in peripheral ganglia is reduced in diabetes mellitus

Neuropathy is a major diabetic complication. While the mechanism of this neuropathy is not well understood, it is believed to result in part from deficient nerve regeneration. Work from our laboratory established that gp130 family of cytokines are induced in animals after axonal injury and are involved in the induction of regeneration-associated genes (RAGs) and in the conditioning lesion response. Here, we examine whether a reduction of cytokine signaling occurs in diabetes. Streptozotocin (STZ) was used to destroy pancreatic β cells, leading to chronic hyperglycemia. Mice were injected with either low doses of STZ (5×60mg/kg) or a single high dose (1×200mg/kg) and examined after three or one month, respectively. Both low and high dose STZ treatment resulted in sustained hyperglycemia and functional deficits associated with the presence of both sensory and autonomic neuropathy. Diabetic mice displayed significantly reduced intraepidermal nerve fiber density and sudomotor function. Furthermore, low and high dose diabetic mice showed significantly reduced tactile touch sensation measured with Von Frey monofilaments. To look at the regenerative and injury-induced responses in diabetic mice, neurons in both superior cervical ganglia (SCG) and the 4th and 5th lumbar dorsal root ganglia (DRG) were unilaterally axotomized. Both high and low dose diabetic mice displayed significantly less axonal regeneration in the sciatic nerve, when measured in vivo, 48h after crush injury. Significantly reduced induction of two gp130 cytokines, leukemia inhibitory factor and interleukin-6, occurred in diabetic animals in SCG 6h after injury compared to controls. Injury-induced expression of interleukin-6 was also found to be significantly reduced in the DRG at 6h after injury in low and high dose diabetic mice. These effects were accompanied by reduced phosphorylation of signal transducer and activator of transcription 3 (STAT3), a downstream effector of the gp130 signaling pathway. We also found decreased induction of several gp130-dependent RAGs, including galanin and vasoactive intestinal peptide. Together, these data suggest a novel mechanism for the decreased response of diabetic sympathetic and sensory neurons to injury.

Genistein inhibited retinal neovascularization and expression of vascular endothelial growth factor and hypoxia inducible factor 1alpha in a mouse model of oxygen-induced retinopathy

The effects of genistein on neovascularization, vascular endothelial growth factor (VEGF), and hypoxia inducible factor 1alpha (HIF1alpha) protein expression in a mouse model of oxygen-induced retinopathy were studied. The model of oxygen-induced retinal neovascularization was induced in newborn C57BL/6 mice by exposing 7-day-old mice to 75% oxygen for 5 days and then housing them in room air (relative hypoxia). Retinopathy was assessed by quantitation of vascular cell nuclei anterior to inner limiting membrane. Judged by relative fluorescence using a confocal scanning laser microscope coupled to a computer, VEGF and HIF1alpha protein expression were investigated. Genistein markedly inhibited the numbers of nuclei protruding above the inner limiting membrane under relative hypoxia conditions. The levels of nuclei numbers were suppressed by 50, 100, and 200 mg/kg body weight /day genistein to 87.4%, 72.0%, and 59.4%, respectively, compared to that untreated with genistein. VEGF protein was constitutively expressed in the preretinal area under normoxia conditions. Genistein markedly inhibited relative-hypoxia-elicited VEGF expression elevation in a dose-dependent manner. HIF1alpha expression was also observed in normoxia conditions. There was a 2.4-fold induction in preretinal HIF1alpha expression in oxygen-reared animals when compared to room-air-reared animals. Genistein dose-dependently suppressed HIF1alpha protein expression. These results indicated that the inhibition of VEGF and HIF1alpha protein expression by genistein may partly account for its effect on retinal neovascularization in vivo, and genistein could be an effective agent in the prevention and treatment of ocular neovascularization.

Genistein suppressed upregulation of vascular endothelial growth factor expression by cobalt chloride and hypoxia in rabbit retinal pigment epithelium cells

The time course changes of vascular endothelial growth factor (VEGF) protein expression induced by cobalt chloride (CoCl(2)) and hypoxia and the effects of genistein on CoCl(2)- and hypoxia-induced VEGF expression in rabbit retinal pigment epithelium (RPE) cells were studied. Judged by relative fluorescence using a confocal scanning laser microscope coupled to a computer, VEGF protein expression exposed for different periods to CoCl(2) or hypoxia was investigated. CoCl(2) was found to significantly elevate VEGF protein expression. At 4 h after CoCl(2) treatment, the expression of VEGF protein was about three times as much as that at the start of treatment. Genistein (50, 100 and 200 microM) inhibited VEGF protein expression elicited by CoCl(2) in a concentration-dependent manner. Hypoxia (5% CO(2)/95% N(2)) could markedly increase VEGF protein expression. The elevation of VEGF protein expression was gradual and time-dependently. At 6 h, the highest expression of VEGF protein was observed, it was about three times as much as that at the start of treatment. After preincubation with 50, 100, and 200 microM genistein respectively, the hypoxia-evoked VEGF expression was concentration-dependently suppressed. These results indicated that genistein could be an effective agent in the prevention and treatment of intraretinal and subretinal neovascularization.

Detection of JNK and p38 activation by flow cytometry analysis

JNK and p38 protein kinases are involved in the signal transduction of apoptotic stimulus. JNK and p38 are activated by dual phosphorylation on threonine and tyrosine residues. Different techniques such as Western blotting (WB) and confocal microscopy analysis have been developed to detect the activation by using antibodies that recognize the phosphorylated forms of both enzymes. However, these techniques are time consuming, not quantitative, and dependent on subjective interpretation. Herein, we describe a flow cytometry-based analysis to detect JNK and p38 activation. Using human primary lymphocytes and Jurkat CD4(+) T cells stimulated with PMA/ionomycin, we demonstrate activation (phosphorylation) of JNK and p38, which is further confirmed by two additional established techniques (WB and confocal microscopy). Flow cytometry analysis is shown to be more sensitive than WB to detect JNK and p38 activation, which can be quantitated and enables us to study their activation within cell populations.

Synaptic vesicle proteins and neuronal plasticity in adrenergic neurons

The neurons in the superior cervical ganglion are active in plasticity and re-modelling in order to adapt to requirements. However, so far, only a few studies dealing with synaptic vesicle related proteins during adaptive processes have been published. In the present paper, changes in content and expression of the synaptic vesicle related proteins in the neurons after decentralization (cutting the cervical sympathetic trunk) or axotomy (cutting the internal and external carotid nerves) were studied. Immunofluorescence studies were carried out using antibodies and antisera against integral membrane proteins, vesicle associated proteins, NPY, and the enzymes TH and PNMT. For colocalization studies, the sections were simultaneously double labelled. Confocal laser scanning microscopy was used for colocalization studies as well as for semi-quantification analysis, using the computer software. Westen blot analysis, in situ 3'-end DNA labelling, and in situ hybridization were also employed. After decentralization of the ganglia several of the synaptic vesicle proteins (synaptotagmin I, synaptophysin, SNAP-25, CLC and GAP-43) were increased in the iris nerve terminal network, but with different time patterns, while TH-immunoreactivity had clearly decreased. In the ganglia, these proteins had decreased at 1 day after decentralization, probably due to degeneration of the pre-ganglionic nerve fibres and terminals. At later intervals, these proteins, except SNAP-25, had increased in the nerve fibre bundles and re-appeared in nerve fibres outlining the principal neurons.

Spontaneous synaptogenesis in ex vivo sympathetic ganglion and the blockade by serum treatment

Central denervation for more than 1 month has been shown to cause an increase in the number of adrenergic synapses in sympathetic ganglia in vivo. Here, we report several lines of evidence that adrenergic synapses may be generated de novo in ex vivo superior cervical ganglion (SCG) of adult rats only several hours after the isolation. Structures immunoreactive for synaptophysin, a marker of presynaptic elements, were drastically decreased 6 days after the preganglionic denervation. A significant increase in number of synaptophysin positive boutons was observed over 3-8 hours in the denervated SCGs maintained ex vivo at 36 degrees C in oxygenated physiologic saline, and this increase was blocked by adding normal serum in the saline. Electron microscopic analysis confirmed that the number of adrenergic synapses specifically labeled with 5-hydroxydopamine was increased by several-fold under the same condition. Intracellular labeling of SCG neurons revealed an increase in the incidence (from 8 to 50%) of neurons having dendritic plexus after the in vitro incubation. No evidence of axonal sprouting within the ganglion was observed. Intracellular recordings from single neurons of denervated SCGs revealed that maximum amplitudes of inhibitory postsynaptic potentials, which were completely blocked by yohimbine, an alpha2-adrenoceptor antagonist, in response to focal stimulation were increased over the several hours. These results suggest that dendrites of SCG neurons rapidly develop and exhibit local efferent characteristics that underlie the inhibitory synaptic transmission once they are subjected to serum deprivation.

Unusual autonomic ganglia: connections, chemistry, and plasticity of pelvic ganglia

The pelvic ganglia provide the majority of the autonomic nerve supply to reproductive organs, urinary bladder, and lower bowel. Of all autonomic ganglia, they are probably the least understood because in many species their anatomy is particularly complex. Furthermore, they are unusual autonomic ganglia in many ways, including their connections, structure, chemistry, and hormone sensitivity. This review will compare and contrast the normal structure and function of pelvic ganglia with other types of autonomic ganglia (sympathetic, parasympathetic, and enteric). Two aspects of plasticity in the pelvic pathways will also be discussed. First, the influence of gonadal steroids on the maturation and maintenance of pelvic reflex circuits will be considered. Second, the consequences of nerve injury will be discussed, particularly in the context of the pelvic ganglia receiving distributed spinal inputs. The review demonstrates that in many ways the pelvic ganglia differ substantially from other autonomic ganglia. Pelvic ganglia may also provide a useful system in which to study many fundamental neurobiological questions of broader relevance.

Growth associated protein 43 (GAP-43) mRNA is upregulated in the rat superior cervical ganglia after preganglionic transection

Growth-associated protein 43 (GAP-43) is a growth-associated protein which is synthesised in high amounts in neurons during neuronal outgrowth. In a previous study we have shown that GAP-43 immunoreactivity is increased in neurons in superior cervical ganglia (SCG) and in nerve terminals in the irides after preganglionic denervation. We have now examined changes in GAP-43 mRNA using in situ hybridisation. GAP-43 mRNA was seen to be constitutively expressed by principal neurons of the rat superior cervical ganglion. Expression was increased further by section of the cervical sympathetic trunk, reaching a maximum (increased by about 30%) 3 days after decentralisation. The increased GAP-43 protein seen after decentralisation thus appears to be due to an upregulation of GAP-43 mRNA in the adrenergic neurons. The results imply that GAP-43 expression in the SCG is under presynaptic control, acting at least partly by control of mRNA levels.

SNAP25 and GAP-43 behave differently in decentralized rat superior cervical ganglia

The behaviour of synaptosome associated protein of mol. wt 25 kDa (SNAP25) in decentralized rat superior cervical ganglia (SCG) was investigated in order to observe its possible involvement in adrenergic postganglionic neuronal plasticity. Immunofluorescence and immunoblot results showed that the protein was increased in the nerve terminals in irides 8 days after operation. The intra-ganglionic nerve terminals and nerve fibres differed in their content of GAP-43 and SNAP25: GAP-43, which could not be observed at 1 day, appeared at 3 days after cutting the cervical sympathetic trunk, whilst SNAP25-immunoreactive material was still undetectable at this time. Immunoblot data also showed that SNAP25 did not reach control levels at 3 and 8 days after decentralization, in contrast to GAP-43. This observation may imply that SNAP25 is rapidly transported to its functional destinations immediately after synthesis and is possibly mainly involved in the remodelling of long projection pathways.

Clathrin light chain and synaptotagmin I in rat sympathetic neurons

Clathrin light chain (clathrin LC) and synaptotagmin I in sympathetic neurons in rat superior cervical ganglia (SCG) were studied using immunofluorescence and confocal microscopy. The distributions of clathrin LC and synaptotagmin I were compared with that of tyrosine hydroxylase (TH) and neuropeptide Y (NPY) in double label experiments. The influence of preganglionic regulation on the expression of clathrin LC and synaptotagmin I in post-ganglionic adrenergic neurons was investigated after cutting the cervical sympathetic trunk. In SCGs and irides of control animals, the calthrin LC- and synaptotagmin-I-positive structures were present in a granular pattern in nerve fibers and varicose terminals. In principal neurons, the two proteins were present in a perinuclear network (the Golgi complex). After decentralization, the synaptotagmin-I- and clathrin LC-positive granules normally present in preganglionic nerve terminals outlining the neuronal somata were no longer observed on day 1, but reappeared, and were increased above control in number and intensity, in axon bundles in the ganglia, on day 3 and up to day 28 post-decentralization. In irides, the fluorescence intensity and density of clathrin LC- and synaptotagmin-I-positive nerve terminals in the dilator plate, were semi-quantified using the confocal microscopy software. It was found that both proteins increased shortly after decentralization. Immunoblot data confirmed the immunohistochemical/confocal microscopy observations. Fast axonal transport of clathrin LC- and synaptotagmin I in preganglionic sympathetic neurons was demonstrated in crush-operated cervical sympathetic trunk. Both proteins rapidly accumulated proximally as well as distally to the crush, demonstrating fast anterograde and retrograde axonal transport (recycling). Thus, clathrin LC and synaptotagmin I are normally present in pre- as well as post-ganglionic sympathetic neurons. The colocalization of clathrin LC with synaptotagmin I in the Golgi complex of the adrenergic neurons may imply that clathrin participates in the synthesis/sorting of the fast transported materials in these neurons. Possible explanations for the increase of the two proteins after decentralization are discussed.

Synaptic vesicle proteins in cells of the sympathoadrenal lineage

The cells of sympathoadrenal lineage display different characteristics after differentiation, although they stem from the same neural crest precursor during embryonic development. In the present study we compared the distribution patterns of several synaptic vesicle proteins in the superior cervical ganglion (SCG) and the adrenal medulla. Using indirect immunofluorescence combined with confocal laser scanning microscopy, it was observed that antisera against integral synaptic vesicle membrane proteins (SV2, synaptotagmin I, synaptobrevin II and synaptophysin) induced strong immunoreactivities in these cells, but anti-synaptobrevin I caused only a faint fluorescence. Immunoreactivities of the synaptic vesicle-associated proteins Rab3a and SNAP25 were also observed in the cells. Synapsin-Ia-reactive material appeared absent from chromaffin cells but present in small amounts in sympathetic neurons in the SCG and iris terminals. On the other hand, synapsin IIa immunoreactive material was strong in most SCG neurons and in adrenergic iris terminals. The neural specific clatrin light chain was detected in the SCG cells and in ganglion cells of the adrenal, but only weak traces could be observed in chromaffin cells. One of the vesicular monoamine transmitter transporters, VMAT2, which is expressed in catecholamine neurons in the brain stem, was observed in most cells in the SCG and also in groups of cells in the adrenal medulla, where the VMAT2-positive small chromaffin cells were PNMT-negative. SIF cells in the SCG contained most of the synaptic vesicle proteins investigated. The results show that after differentiation, sympathetic neurons, SIF cells and adrenal chromaffin cells still share many vesicle proteins even though their physiology is different.