Effects of autoimmune NGF deprivation in the adult rabbit and offspring

An experimental autoimmune approach to the production of nerve growth factor deprivation, which we have previously described in the rat and guinea pig, has been applied to the rabbit. This species was chosen for study because of several potential advantages. The rabbit produces large litters and has a relatively short gestation period. More importantly, rabbits generate high titers of antibody against mouse NGF and large amounts of maternal antibody are passively transferred to the developing rabbit fetus compared to most other species, particularly the rat. The sympathetic nervous system of adult rabbit immunized against mouse NGF underwent degeneration with up to an 85% decrease in neuronal numbers in the superior cervical ganglion after 10 months of immunization, thus providing further evidence that NGF is required for the survival of mature sympathetic neurons. Despite the fact that newborn rabbits born to anti-NGF producing mothers had much higher titers of anti-NGF than did rats, the effects on the developing sympathetic and sensory nervous systems were not found to be any greater than in rats. Reductions in norepinephrine levels in the heart and spleen of adult rabbits born to anti-NGF producing mothers were greater than in small intestine. Prenatal exposure to maternal anti-NGF caused reductions (up to 70%) in the number of neurons in the dorsal root ganglia. Substance-P immunoreactivity was reduced in the substantia gelatinosa of the spinal cord of rabbit exposed to maternal anti-NGF. These changes, however, were not greater than seen in the rat. We conclide that although the rabbits offers some advantage in the study of the effects of NGF deprivation in the adult animal, it appears less well suited than the rat or guinea pig to the study of the effects of NGF deprivation on development.     

Effect of exposure to anti-NGF on sensory neurons of adult rats and guinea pigs

Nerve growth factor (NGF) deprivation was produced in adult rats and guinea pigs by immunization against mouse NGF. Exposure of adult animals to anti-NGF had no effect on sensory ganglion neuronal number or size-frequency histograms. However, the substance P content of sensory ganglia, spinal cord and hind paw skin decreased to as great an extent as was seen in animals exposed to anti-NGF in utero. We conclude that NGF has two separate effects on sensory neurons: adult sensory neurons require NGF for normal function whereas developing neurons require NGF for both survival and transmitter expression.     

Effects of nerve growth factor on the survival of primary cultured adult and aged mouse sensory neurons

This study investigated the effects of exogenous nerve growth factor (NGF) on the survival and differentiation in primary culture of sensory neurons isolated from adult (6 months) and aged (2 years) mice. For neurons prepared from adult mice, a concentration effect was evident during a 2 week culture period: Neuronal counts in cultures supplemented with 25 and 50 ng/ml NGF did not differ significantly from those of control cultures without exogenous NGF or those with anti-NGF included in the culture medium, whereas cultures supplemented with either 100 or 200 ng/ml NGF contained higher numbers of neurons throughout the culture period. Cultures prepared from aged mice contained less neurons than those from adult mice, although those supplemented with 100 ng/ml NGF retained higher neuronal numbers than cultures from aged mice which did not receive exogenous NGF. Neuronal diameters were measured to investigate whether specific subpopulations of neurons were more dependent on NGF; the results indicate that neurons of a medium-larger diameter were more prevalent than cells with a smaller diameter following NGF administration. A shape index was calculated for each culture regimen; with longer culture periods a higher proportion of spindle-shaped neurons was observed. © 1993 Wiley-Liss, Inc.     

A dual mechanism linking NGF/proNGF imbalance and early inflammation to Alzheimer's disease neurodegeneration in the AD11 anti-NGF mouse model

The neurotrophin Nerve Growth Factor (NGF) is essential for the maintenance and differentiation of basal forebrain cholinergic neurons. Since basal forebrain cholinergic neurons represent one major neuronal population affected and progressively degenerating in Alzheimer's disease (AD), interest has grown for NGF as a potential therapeutic agent in neurodegenerative disorders linked to aging, particularly for AD. However, no evidence was available, to link, in a cause-effect manner, deficits in NGF signalling to the broader activation in the Alzheimer's cascade, besides cholinergic deficits. The phenotypic analysis of the AD11 anti-NGF transgenic mouse, obtained by the "neuroantibodies" phenotypic protein knock out strategy, allowed demonstrating a direct causal link between NGF deprivation and AD pathology. Since then, extensive mechanistic studies on the AD11 model provided a new twist to the concept that alterations in NGF transport and signalling play a crucial role in sporadic Alzheimer's neurodegeneration, leading to the hypothesis of "Neurotrophic imbalance" as an upstream driver for sporadic AD. The results obtained with the AD11 anti-NGF mice highlight the fact that the particular mode of NGF neutralization, with an NGF antibody expressed in the brain, selectively interfering with mature NGF versus unprocessed proNGF, plays a major role in the mechanism of neurodegeneration, and could lead to new insights into the mechanisms of human sporadic AD. Here, we will review (1) the renewed neurotrophic imbalance hypothesis for AD and (2) the mechanisms underlying the neurodegenerative phenotype of AD11 anti-NGF mice.     

Immunochemical analysis of alpha-actinin of nemaline myopathy after two-dimensional electrophoresis

We analyzed alpha-actinin from human skeletal muscle by immunoblotting after two-dimensional electrophoresis. A monoclonal antibody, S alpha 5-17, was established after immunization in Balb/c mouse with crude alpha-actinin fraction from human soleus muscle. Western blotting and indirect immunofluorescence microscopy revealed that the antibody reacted selectively with alpha-actinin from human skeletal muscle and stained in a manner equivalent to that of type 1, 2A, 2B and 2C myofibers and cardiac atrial and ventricular muscles. No reactivity was observed in the arterial smooth muscle layer or in the central and peripheral nervous systems. The antibody exhibited 2 spots with different isoelectric points in a range more basic than that of actin upon immunoblotting after two-dimensional gel electrophoresis, suggesting the presence of 2 variants of alpha-actinin in human skeletal muscle. Analysis of type 2B-deficient muscle with nemaline myopathy or central core disease revealed that type 2B myofibers contained the basic variant, while type 1 and 2A myofibers contained only the acidic variant. Immunoblots performed after two-dimensional gel electrophoresis of muscles with nemaline myopathy revealed alpha-actinin variants indistinguishable from those of control muscles.     

Full-length dystrophin cDNA transfer into skeletal muscle of adult mdx mice by electroporation

We showed that a LacZ expression plasmid (pCAG-lacZ) injection followed by electroporation increased the expression of the LacZ gene in the skeletal muscles of adult mdx mice up to ninefold higher as compared with simple intramuscular DNA injection. When full-length mouse dystrophin plasmid (pCAG-dys) and pCAG-lacZ were co-transfected by electroporation, 56% of dystrophin-positive fibers were stained for beta-galactosidase activity suggesting most of these myofibers are not revertants but transfected ones. Our data indicate that electroporation in vivo could introduce large full-length dystrophin cDNA into skeletal muscle of adult mdx mice.     

Nerve growth factor depletion by autoimmunization produces thermal hypoalgesia in adult rats

Nerve growth factor (NGF) plays a role in mechanisms of inflammation and hyperalgesia in adult animals. We sought to determine if NGF depletion produced by autoimmunization of adult rats altered their thermal sensitivity to an acute noxious thermal stimulus. Anti-NGF IgG was not detected in the cerebrospinal fluid of any tested samples. Only those rats with the highest anti-NGF serum titers showed significant (P<0.05) thermal hypoalgesia measured using the hot plate test (52°C): the mean (±S.D.) hind paw lick latency of rats in the high anti-NGF titer group was 18.0±4.6 s compared to means of 10.8±4.3 s, 9.2±2.6 s and 10.1±3.0 s in the medium, low and control groups, respectively. Thus, NGF depletion by autoimmunization is a useful model for investigating the role of NGF in behavioral responses of adult rats to noxious stimuli, providing high titers of antibody are present.     

Dystrophin immunostaining and freeze-fracture studies of muscles of patients with early stage amyotrophic lateral sclerosis and Duchenne muscular dystrophy

We used polyclonal antibodies against dystrophin for the immunohistochemical localization of this protein in human skeletal muscle. Dystrophin was localized in the sarcolemma of the myofibers in 8 infantile and 11 adult normal control muscles and in 10 early stage patient muscles with amyotrophic lateral sclerosis (ALS). The protein was absent or markedly decreased in 8 early stage patients with Duchenne muscular dystrophy (DMD). Moreover the densities of sarcolemmal plasma membrane assemblies, orthogonal arrays and their pits were estimated by freeze-fracture electron microscopy studies in the same number of muscle samples in each disease and control case. The group median densities of orthogonal arrays and their pits in the ALS group and adult control group were 4.8 with a midrange of 1.1-13.5 (25-75%) and 7.5 with a midrange of 2.3-12.9, respectively (P greater than 0.1, Wilcoxon rank-sum test), whereas those of the DMD group and child control group were 0 with a midrange of 0-1.1 and 10.8 with a midrange of 5.4-16.7 respectively (P less than 0.01). The skeletal muscles of mdx mice and their controls were also investigated by the same techniques. In mdx mice, the absence or marked deficiency of dystrophin was also noted; however, the decrease of orthogonal arrays was not as severe as in DMD, which might relate to the milder clinical features in mdx mice as compared with those in DMD.     

Immunoreactivity of antibodies raised against synthetic peptide fragments predicted from mid portions of dystrophin cDNA

We synthesized 3 peptide fragments predicted by residues 2354-2368 (peptide I), 2310-2324 (peptide II) and 2255-2269 (peptide III) on the mid-portion of the human dystrophin cDNA map where the most frequent intragenic deletions occurred in Duchenne muscular dystrophy. Rabbit antibodies against these peptides were raised and cryosections of 47 biopsied muscles were studied immunohistochemically. The 47 biopsied muscles included the quadriceps femoris muscles of 8 Duchenne muscular dystrophy patients, 8 child and 5 adult normal controls, 1 facioscapulohumeral dystrophy, 2 limb girdle dystrophy, 3 myotonic dystrophy, 3 polymyositis, 1 mitochondrial myopathy, 1 nemaline myopathy, 3 amyotrophic lateral sclerosis and the extensor digitorum longus muscles of 6 mdx mice (C57BL/10ScSn-mdx) and 6 normal control mice (C57BL/10ScSn). The peptide I antiserum continuously stained the myofiber surface membranes in 8 child and 5 adult normal control muscles, and in 14 other muscles from various neuromuscular diseases, but failed to stain the surface membranes in normal control mice. The surface membranes of 8 Duchenne muscles were not stained by the peptide I antiserum except for a few myofibers. Although the ELISA titers of peptide I, II and III antibodies were high, immunostaining by peptide II antiserum showed no reaction in the myofibers of any of the biopsied muscles, and immunostaining by peptide III antiserum revealed faint reactions on the myofiber surface membranes of all biopsied muscles, including the mdx control mouse muscles except for the Duchenne and mdx myofibers.     

Growth of skeletal muscle from patients with amyotrophic lateral sclerosis transplanted into nude mice

We studied the fate of skeletal muscle obtained from patients with amyotrophic lateral sclerosis (ALS) after transplantation into immunodeficient nude mice. The transplanted muscle consistently survived in the nude mice without immunological rejection. The myofibers in these muscles underwent degeneration, followed by regeneration, maturation, and eventual functional innervation by the mouse motor neurons. The ability to grow diseased human muscle successfully over a prolonged period in nude mice offers an in vivo model to study the etiology of ALS and possibly of other neuromuscular disorders.     

NGF in experimental models of parkinson disease

We have now applied the enzyme immunoassay using anti-NGF monoclonal antibody (MAb) 27/21 and a blocking test validating the specificity of the immunoreactivity for NGF in serum samples to examine NGF levels in normal rat sera, hemiparkinsonian rat sera, normal monkey sera, and MPTP-treated monkey sera. The levels of NGF in treated animals showed reductions when compared with serum from normal animals. The NGF level alterations observed in lesioned animals and in human parkinsonian patients evidence a relationship between this neurotrophic factor and the neurodegenerative changes observed in Parkinson disease (PD).     

Acute cholinergic rescue of synaptic plasticity in the neurodegenerating cortex of anti-nerve-growth-factor mice

Deficits in cholinergic systems innervating cerebral cortex are associated with cognitive impairment during senescence and in age-related neurodegenerative pathologies. However, little is known about the role of cholinergic pathways in modulating cortical plasticity. Basal forebrain cholinergic neurons are a major target for nerve-growth factor (NGF). In order to investigate the relationship between cholinergic innervation and cortical synaptic plasticity, we exploited a transgenic mouse model in which the activity of NGF in the adult nervous system is neutralized by the expression of blocking antibodies to NGF itself (anti-NGF mice) [Ruberti, F. et al. (2000). J. Neurosci. 20, 2589-2601]. In 6-month-old anti-NGF mice, we show that the reduction in cholinergic innervation of the cortex is associated with different forms of synaptic plasticity impairment. A local, acute increase in the availability of acetylcholine rescues these synaptic plasticity deficits, thus indicating that a cholinergic system mediates the impairment of cortical plasticity at this early stage of the neurodegenerative process triggered by NGF neutralization. Our results represent an important step in unveiling the pivotal role of cholinergic transmission in modulating adult cortical plasticity.     

NGF in experimental models of parkinson disease

We have now applied the enzyme immunoassay using anti-NGF monoclonal antibody (MAb) 27/21 and a blocking test validating the specificity of the immunoreactivity for NGF in serum samples to examine NGF levels in normal rat sera, hemiparkinsonian rat sera, normal monkey sera, and MPTP-treated monkey sera. The levels of NGF in treated animals showed reductions when compared with serum from normal animals. The NGF level alterations observed in lesioned animals and in human parkinsonian patients evidence a relationship between this neurotrophic factor and the neurodegenerative changes observed in Parkinson disease (PD).     

Aciculin and its relation to dystrophin: immunocytochemical studies in human normal and Duchenne dystrophy quadriceps muscles

Aciculin is a novel adherens junction antigen extracted from human uterine smooth muscle that is reported to associate biochemically with dystrophin. We attempted to determine (i) the immunostainability of anti-aciculin antibody for the 6 histochemically normal human muscles and seven muscles from boys with Duchenne muscular dystrophy(DMD) and 11 disease control muscles, (ii) the ultrastructural localization of aciculin in normal skeletal myofibers, (iii) aciculin’s spacial relationship with dystrophin and β-spectrin, and (iv) if the aciculin is ultrastructurally colocalized with dystrophin, the distance from the aciculin epitope to the epitope of the dystrophin N- or C-terminal domain. For this, rabbit anti-aciculin antibody was generated against the synthetic peptide of aciculin fragment D [4]. Immunohistochemical staining showed that the immunostainability of DMD muscles for anti-aciculin antibody was markedly decreased as compared with normal and disease control muscles. Single and double immunogold labeling electron microscopy of 6 histochemically normal human quadriceps femoris muscles revealed that aciculin was present along the inner surface of muscle plasma membrane and that aciculin formed doublets more frequently with dystrophin (23.5 ± 1.8%; group mean ± SE) than with β-spectrin (12.8 ± 1.1%; P < 0.01 two tailed t test). Rabbit anti-aciculin antibody frequently formed doublets with monoclonal antibodies against the N- or C-terminal domain of dystrophin at the muscle cell surface. These results suggest that aciculin is associated with dystrophin and may interact with both the N- and C-terminal domains of dystrophin. Received: 2 June 1999 / Revised, accepted: 21 September 1999     

Sympathetic nerves in adult rats regenerate normally and restore pilomotor function during an anti-NGF treatment that prevents their collateral sprouting.

We have used anti-nerve growth factor (anti-NGF) [corrected] administration to study the NGF dependency of the reinnervation of denervated skin by sympathetic nerves in the adult rat. Sympathetic pilomotor fields were revealed by electrical stimulation of selected dorsal cutaneous nerves; the affected skin rapidly assumed a "gooseflesh" appearance, sharply demarcated from surrounding unstimulated skin. Examined 2-5 days after section of neighboring nerves, the "isolated" pilomotor field of the spared nerve was found to be coextensive with an area of amine-fluorescent fibers that were associated with pilomotor muscles and blood vessels. After its isolation, a pilomotor field begins to expand into the surrounding deprived territory, reaching a maximum size at approximately 40 days. Fluorescence studies confirmed that new sympathetic fiber growth had occurred into the expanded regions of such fields. Daily injections of polyclonal anti-NGF serum completely prevented these pilomotor field expansions. Following termination of the anti-NGF treatment, expansion proceeded normally. Finally, if the onset of anti-NGF treatment was delayed until pilomotor field expansion had already commenced, further expansion was halted. Regeneration of sympathetic fibers was evoked by crushing a selected nerve. Recovery of pilomotor function in the totally denervated skin was first detected at about 20 days postcrush, and the field progressively enlarged over the next 40 days. Although the imposed NGF deprivation is known to cause a demonstrable shrinkage, and presumably atrophy, of sympathetic ganglia, the anti-NGF treatment appeared to impair neither the restoration of a pilomotor field after nerve crush, nor its continued expansion into skin regions well beyond that originally supplied by the nerve, i.e., into territory whose invasion by collateral sprouts would have been totally prevented by the treatment. During such NGF deprivation, fluorescent regenerating fibers were visualized in the nerve trunk. We conclude that even though the regenerating and collaterally sprouting sympathetic fibers probably utilise the same degenerating dermal pathways to reach and functionally reinnervate the same denervated targets, only the collateral sprouting of the uninjured axons is dependent upon endogenous NGF. These findings extend the results described earlier for nociceptive fibers, and suggest that the contrasting dependencies upon growth factors of sprouting and regeneration might apply throughout the adult nervous system.     

Effects of pre- and postnatal administration of antibodies to nerve growth factor on the morphological and biochemical development of the rat adrenal medulla: a reinvestigation

Whether or not adrenal medullary (chromaffin) cells which respond to nerve growth factor (NGF) both in vitro and in vivo require NGF for their normal development is controversial. Systemic deprivation of endogenous NGF by injection of anti-NGF antibodies into rat fetuses or by transfer of anti-NGF to the offspring of autoimmunized mothers has provided conflicting results. We have reinvestigated the effects of a specific antiserum to NGF on the morphology, catecholamine (CA) and neuropeptide (Met-enkephalin, Met-ENK; substance P, SP) content, and choline acetyltransferase (ChAT) activity of the rat adrenal medulla. Fetuses were injected with anti-NGF antibodies on day 17 of gestation and postnatally at daily intervals for 7 days. The histological appearance of adrenal medullae of anti-NGF injected animals was not altered as compared to controls. Ultrastructurally, no degenerative changes or developmental retardation of chromaffin cells could be detected. However, numbers of chromaffin granules per micron 2 of cytoplasmic area were greater and the mean diameters of the cores of adrenaline storage granules were smaller in antibody-treated than in control animals. CA and SP content, ratios of adrenaline to noradrenaline and ChAT activities were identical in anti-NGF-treated and control animals. Anti-NGF antibodies caused a reduction of adrenal Met-ENK by 40% as compared to controls. Superior cervical ganglia from the same animals were used to document immunosympathectomy induced by the antiserum. They displayed the well-established structural alterations and a marked reduction of the CA content. We conclude that administration of anti-NGF antibodies to embryonic and early postnatal rats induces only subtle changes in the ultramorphology of chromaffin cells without altering the development of normal CA levels. The small, yet significant effects of anti-NGF antibodies on adrenal Met-ENK, however, may suggest a role for endogenous NGF in the regulation of opioid peptide metabolism in developing chromaffin cells.     

Nerve growth factor receptor-mediated transport from CSF labels cholinergic neurons: direct demonstration by a double-labeling study

It has recently been shown that, following intraventricular administration, a monoclonal antibody directed against rat nerve growth factor (NGF) receptor is specifically accumulated bilaterally by numerous neurons of the basal forebrain. The labeled neurons have a morphology and topography which are characteristic of the magnocellular cholinergic basal forebrain (CBF) system. This is also consistent with the evidence that CBF neurons have NGF receptors and respond to NGF in a variety of experimental situations. In the present report, a double-labeling technique is used to directly demonstrate that choline acetyltransferase-containing (and therefore cholinergic) neurons do in fact accumulate the anti-NGF receptor antibody from CSF.     

Continuous myofiber remodeling in uninjured extraocular myofibers: myonuclear turnover and evidence for apoptosis

Unlike normal mature limb skeletal muscles, in which satellite cells are quiescent unless the muscle is injured, satellite cells in mammalian adult extraocular muscles (EOM) are chronically activated. This is evidenced by hepatocyte growth factor, the myogenic regulatory factor, Pax-7, and the cell-cycle marker, Ki-67, localized to the satellite cell position using serial sections and the positional markers laminin and dystrophin. Bromodeoxyuridine (brdU) labeling combined with dystrophin immunostaining showed brdU-positive myonuclei, presumably the result of fusion of activated satellite cells into existing myofibers. One new myonucleus was added to every 1000 myofibers in cross-section using a 12-hour brdU-labeling paradigm. The EOM thus appear to retain a stable nuclear population by an opposing process of apoptosis that results in myonuclear removal as visualized by terminal deoxynucleotidyltransferase-mediated nick end labeling (TUNEL). Activated caspase-3 was present in localized cytoplasmic domains extending from 10 to 210 microm within individual myofibers, suggesting segmental cytoplasmic reorganization. Understanding the cellular mechanisms that maintain this process of continuous myonuclear addition and removal in normal adult EOM may suggest new hypotheses to explain the preferential involvement or sparing of these muscles in skeletal muscle disease.     

Naturally occurring antibodies against nerve growth factor in human and rabbit sera: comparison between control and herpes simplex virus-infected patients

Antibodies against nerve growth factor (NGF) in sera were detected by enzyme-linked immunosorbent assays (ELISA), by their isolation after passage of sera through NGF immunoadsorbent columns and by their specificity to bind and immunoprecipitate mouse NGF as well as to stain by immunohistochemical methods cellular sites of NGF synthesis. Increased levels of anti-NGF antibodies were found in sera of herpes simplex virus (HSV)-infected patients but not in HSV-inoculated rabbits. As HSV latency is known to be promoted by NGF in vitro, these results may suggest that anti-NGF antibodies modulate the cytokine function of NGF and thus might play a role in HSV infection. The biological function of circulating antibodies against NGF, in general, is now open to future investigation.