Activation of Nuclear Factor-κB via Endogenous Tumor Necrosis Factor α Regulates Survival of Axotomized Adult Sensory Neurons

Abstract

Embryonic dorsal root ganglion (DRG) neurons die after axonal damage in vivo, and cultured embryonic DRG neurons require exogenous neurotrophic factors that activate the neuroprotective transcription factor nuclear factor-kappaB (NF-kappaB) for survival. In contrast, adult DRG neurons survive permanent axotomy in vivo and in defined culture media devoid of exogenous neurotrophic factors in vitro. Peripheral axotomy in adult rats induces local accumulation of the cytokine tumor necrosis factor alpha (TNFalpha), a potent activator of NF-kappaB activity. We tested the hypothesis that activation of NF-kappaB stimulated by endogenous TNFalpha was required for survival of axotomized adult sensory neurons. Peripheral axotomy of lumbar DRG neurons by sciatic nerve crush induced a very rapid (within 2 h) and significant elevation in NF-kappaB-binding activity. This phenomenon was mimicked in cultured neurons in which there was substantial NF-kappaB nuclear translocation and a significant rise in NF-kappaB DNA-binding activity after plating. Inhibitors of NF-kappaB (SN50 or NF-kappaB decoy DNA) resulted in necrotic cell death of medium to large neurons (> or =40 microm) within 24 h (60 and 75%, respectively), whereas inhibition of p38 and mitogen-activated protein/extracellular signal-regulated kinase did not effect survival. ELISA revealed that these cultures contained TNFalpha, and exposure to an anti-TNFalpha antibody inhibited NF-kappaB DNA-binding activity by approximately 35% and killed approximately 40% of medium to large neurons within 24 h. The results show for the first time that cytokine-mediated activation of NF-kappaB is a component of the signaling pathway responsible for maintenance of adult sensory neuron survival after axon damage.

Activation of protein kinase CβI constitutes a new neurotrophic pathway for deafferented spiral ganglion neurons

“…When genistein (20 M), a tyrosine-specific kinase inhibitor (Akiyama et al, 1987), was included in the SG culture medium, the ability of PMA (100 nM) to increase SGN survival was significantly inhibited (control, 100±26%; PMA, 277±77%; genistein, 94±22%; PMA+genistein, 140±37%; n=9, P<0.001), a result that is consistent with previously described PKC/PYK2/PI3K signalling cascades (Sarkar et al, 2002;Sayed et al, 2000;Shi and Kehrl, 2001). As PKC␤ has been described as a component of the NF-B signalling axis (Saijo et al, 2002) and NF-B activity is of primary importance to sensory neuron survival (Fernyhough et al, 2005), we next sought to examine whether the Rel/NF-B family of transcription factors could play a role in PMAinduced survival of deafferented SGNs using two specific NF-B inhibitors, BAY 11-7082 (BAY) (Pierce et al, 1997) and sulfasalazine (SZ) (Wahl et al, 1998). Our experiments revealed that there was no difference (P>0.05) in the number of SGNs surviving after 24 hours in the presence of PMA (100 nM), either alone or with BAY (2 M) or SZ (1 mM) (Fig.…”

Receptor for Advanced Glycation End Products (RAGEs) and Experimental Diabetic Neuropathy

“…The role of NF-B is complex and depends on age and on injury type and timing (47,48). When diabetic peripheral nerve is exposed to ischemia followed by reperfusion, NF-B expression in Schwann cells of diabetic peripheral nerve rises (49).…”

New insights in diabetic autonomic neuropathy in children and adolescents

“…Several experimental studies have investigated direct insulin signaling of sensory neurons in diabetic or injury models (26)(27)(28)(29)(30)(31)(32)(33)(34)(35)(36)(37)(38)(39): the administration of local lowdose subhypoglycemic near nerve insulin reversed ipsilateral slowing of motor conduction velocity in diabetic rats without lowering plasma glucose levels. The local injections of insulin have no impact on changes of neuropathy in other territories of the same rat (contralateral side given carrier or in the caudal nerve) (27).…”

“…AGE ligation of RAGE inappropriately activates cellular second messengers (e.g. nuclear factor kappa B) (38)(39)(40). RAGE protein and mRNA are massively up-regulated in diabetic peripheral nerve and ganglia, whereas mice lacking RAGE are protected from neuropathy (41).…”