Nerve growth factor derivative NGF61/100 promotes outgrowth of primary sensory neurons with reduced signs of nociceptive sensitization.

Nerve Growth Factor (NGF) is being considered as a therapeutic candidate for Alzheimer's disease. However, the development of an NGF-based therapy is limited by its potent pain activity. We have developed a "painless" derivative form of human NGF (NGF61/100), characterized by identical neurotrophic properties but a reduced nociceptive sensitization activity in vivo. Here we characterized the response of rat dorsal root ganglia neurons (DRG) to the NGF derivative NGF61/100, in comparison to that of control NGF (NGF61), analyzing the expression of noxious pro-nociceptive mediators. NGF61/100 displays a neurotrophic activity on DRG neurons comparable to that of control NGF61, despite a reduced activation of PLCγ, Akt and Erk1/2. NGF61/100 does not differ from NGF61 in its ability to up-regulate Substance P (SP) and Calcitonin Gene Related Peptide (CGRP) expression. However, upon Bradykinin (BK) stimulation, NGF61/100-treated DRG neurons release a much lower amount of SP and CGRP, compared to control NGF61 pre-treated neurons. This effect of painless NGF is explained by the reduced up-regulation of BK receptor 2 (B2R), respect to control NGF61. As a consequence, BK treatment reduced phosphorylation of the transient receptor channel subfamily V member 1 (TRPV1) in NGF61/100-treated cultures and induced a significantly lower intracellular Ca2+ mobilization, responsible for the lower release of noxious mediators. Transcriptomic analysis of DRG neurons treated with NGF61/100 or control NGF allowed identifying a small number of nociceptive-related genes that constitute an "NGF pain fingerprint", whose differential regulation by NGF61/100 provides a strong mechanistic basis for its selective reduced pain sensitizing actions.

Dysregulated microRNAs in amyotrophic lateral sclerosis microglia modulate genes linked to neuroinflammation.

MicroRNAs (miRNAs) regulate gene expression at post-transcriptional level and are key modulators of immune system, whose dysfunction contributes to the progression of neuroinflammatory diseaseas such as amyotrophic lateral sclerosis (ALS), the most widespread motor neuron disorder. ALS is a non-cell-autonomous disease targeting motor neurons and neighboring glia, with microgliosis directly contributing to neurodegeneration. As limited information exists on miRNAs dysregulations in ALS, we examined this topic in primary microglia from superoxide dismutase 1-G93A mouse model. We compared miRNAs transcriptional profiling of non-transgenic and ALS microglia in resting conditions and after inflammatory activation by P2X7 receptor agonist. We identified upregulation of selected immune-enriched miRNAs, recognizing miR-22, miR-155, miR-125b and miR-146b among the most highly modulated. We proved that miR-365 and miR-125b interfere, respectively, with the interleukin-6 and STAT3 pathway determining increased tumor necrosis factor alpha (TNFα) transcription. As TNFα directly upregulated miR-125b, and inhibitors of miR-365/miR-125b reduced TNFα transcription, we recognized the induction of miR-365 and miR-125b as a vicious gateway culminating in abnormal TNFα release. These results strengthen the impact of miRNAs in modulating inflammatory genes linked to ALS and identify specific miRNAs as pathogenetic mechanisms in the disease.

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.

Distributed motor pattern underlying whole-body shortening in the medicinal leech.

Whole-body shortening was studied in the leech, Hirudo medicinalis, by a combination of videomicroscopy and multielectrode recordings. Video microscopy was used to monitor the animal behavior and muscle contraction. Eight suction pipettes were used to obtain simultaneous electrical recordings from fine roots emerging from ganglia. This vital escape reaction was rather reproducible. The coefficient of variation of the animal contraction during whole-body shortening was between 0.2 and 0.3. The great majority of all leech longitudinal motoneurons were activated during this escape reaction, in particular motoneurons 3, 4, 5, 8, 107, 108, and L. The firing pattern of all these motoneurons was poorly reproducible from trial to trial, and the coefficient of variation of their firing varied between 0.3 and 1.5 for different motoneurons. The electrical activity of pairs of coactivated motoneurons did not show any sign of correlation over a time window of 100 ms. Only the left and right motoneurons L in the same ganglion had a correlated firing pattern, resulting from their strong electrical coupling. As a consequence of the low correlation between coactivated motoneurons, the global electrical activity during whole-body shortening became reproducible with a coefficient of variation below 0.3 during maximal contraction. These results indicate that whole-body shortening is mediated by the coactivation of a large fraction of all leech motoneurons, i.e., it is a distributed process, and that coactivated motoneurons exhibit a significant statistical independence. Probably due to this statistical independence this vital escape reaction is smooth and reproducible.