Br J Hosp Med (Lond)
October 2021
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View Article and Find Full Text PDFAlthough neural c-Jun is essential for successful peripheral nerve regeneration, the cellular basis of this effect and the impact of c-Jun activation are incompletely understood. In the current study, we explored the effects of neuron-selective c-Jun deletion, substitution of serine 63 and 73 phosphoacceptor sites with non-phosphorylatable alanine, and deletion of Jun N-terminal kinases 1, 2 and 3 in mouse facial nerve regeneration. Removal of the floxed c-jun gene in facial motoneurons using cre recombinase under control of a neuron-specific synapsin promoter (junΔS) abolished basal and injury-induced neuronal c-Jun immunoreactivity, as well as most of the molecular responses following facial axotomy.
View Article and Find Full Text PDFGeneration of new axonal sprouts plays an important role in neural repair. In the current study, we examined the appearance, composition and effects of gene deletions on intrabrainstem sprouts following peripheral facial nerve axotomy. Axotomy was followed by the appearance of galanin(+) and calcitonin gene-related peptide (CGRP)(+) sprouts peaking at day 14, matching both large, neuropeptide(+) subpopulations of axotomized facial motoneurons, but with CGRP(+) sprouts considerably rarer.
View Article and Find Full Text PDFActivation of Ras into the GTP-binding, 'ON' state is a key switch in the neurotrophin-mediated neuronal survival and neurite outgrowth, in vitro as well as in vivo. In the current study we explored changes in GTP-Ras levels following facial nerve injury and the ensuing regeneration and the effects of perturbing these changes in vivo using synapsin-promoter mediated neuronal expression of constitutively active Val12H-Ras (synRas). Quantification of GTP-Ras and total Ras revealed a precipitous drop in the relative GTP-Ras levels in the axotomized facial motor nucleus, to 40% of normal levels at 2 days after cut, followed by a partial recovery to 50-65% at 4-28 days.
View Article and Find Full Text PDFTransforming growth factor beta1 (TGFbeta1) is a pleiotropic cytokine with potent neurotrophic and immunosuppressive properties that is upregulated after injury, but also expressed in the normal nervous system. In the current study, we examined the regulation of TGFbeta1 and the effects of TGFbeta1 deletion on cellular response in the uninjured adult brain and in the injured and regenerating facial motor nucleus. To avoid lethal autoimmune inflammation within 3 weeks after birth in TGFbeta1-deficient mice, this study was performed on a T- and B-cell-deficient RAG2-/- background.
View Article and Find Full Text PDFNerve injury triggers numerous changes in the injured neurons and surrounding nonneuronal cells that ultimately result in successful target reinnervation or cell death. c-Jun is a component of the heterodimeric AP-1 transcription factor, and c-Jun is highly expressed in response to neuronal trauma. Here we have investigated the role of c-jun during axonal regeneration using mice lacking c-jun in the central nervous system.
View Article and Find Full Text PDFThe common neurotrophin receptor (p75NTR) is a member of the tumor necrosis factor receptor superfamily and binds the neurotrophins nerve growth factor, brain derived neurotrophic factor, neurotrophin-3, and neurotrophin-4. P75NTR is expressed on developing motoneurons and is reexpressed on adult motoneurons under pathological conditions such as nerve trauma or neurodegeneration. Here we examined the regulation and function of p75NTR during regeneration after peripheral transection of the facial nerve of adult mice.
View Article and Find Full Text PDFStudies using mouse axotomised facial motoneuron model show a strong and highly selective entry of CD3+ lymphocytes into the affected nucleus, with a maximum at Day 14, which coincides with the peak of neuronal cell death, microglial phagocytosis, and increased synthesis of interleukin-1 beta (IL1beta), tumour necrosis factor-alpha (TNFalpha) and interferon-gamma (IFNgamma). We explored the possible involvement of these cytokines during the main phase of lymphocyte recruitment into the axotomised facial motor nucleus 7-21 days after nerve cut using mice homozygously deficient for IL1 receptor type 1 (IL1R1-/-), TNF receptor type 1 (TNFR1-/-), type 2 (TNFR2-/-) and type 1 and 2 (TNFR1&2-/-), IFNgamma receptor type 1 (IFNgammaR1-/-), and the appropriate controls for the genetic background. Transgenic deletion of IL1R1 led to a 54% decrease and that of TNFR2 to a 44% reduction in the number of CD3+ T-cells in the axotomised facial motor nucleus, with a similar relative decrease at Day 7, 14, and 21.
View Article and Find Full Text PDFReduction in microglial branching is a common feature in brain pathology and culminates in the transformation into small, rounded, microglia-derived phagocytes in the presence of neural debris. The molecular factors responsible for this transformation are unknown. Here we explored the effect of different classes of intra- and extracellular stimuli in vitro on the morphology of ramified microglia cultured on a confluent astrocyte substrate.
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