ABSTRACT
Peripheral nerve injury-induced mechanical allodynia is often accompanied by abnormalities in the higher cortical regions, yet the mechanisms underlying such maladaptive cortical plasticity remain unclear. Here, we show that in male mice, structural and functional changes in the primary somatosensory cortex (S1) caused by peripheral nerve injury require neuron-microglial signaling within the local circuit. Following peripheral nerve injury, microglia in the S1 maintain ramified morphology and normal density but up-regulate the mRNA expression of brain-derived neurotrophic factor (BDNF). Using in vivo two-photon imaging and Cx3cr1CreER;Bdnfflox mice, we show that conditional knockout of BDNF from microglia prevents nerve injury-induced synaptic remodeling and pyramidal neuron hyperactivity in the S1, as well as pain hypersensitivity in mice. Importantly, S1-targeted removal of microglial BDNF largely recapitulates the beneficial effects of systemic BDNF depletion on cortical plasticity and allodynia. Together, these findings reveal a pivotal role of cerebral microglial BDNF in somatosensory cortical plasticity and pain hypersensitivity.
Subject(s)
Brain-Derived Neurotrophic Factor/physiology , Brain/metabolism , Hyperalgesia/physiopathology , Microglia/metabolism , Neuronal Plasticity/physiology , Peripheral Nerve Injuries/metabolism , Animals , Brain-Derived Neurotrophic Factor/biosynthesis , Brain-Derived Neurotrophic Factor/genetics , Mice , Mice, Knockout , Peripheral Nerve Injuries/physiopathologyABSTRACT
Homeostasis of neural firing properties is important in stabilizing neuronal circuitry, but how such plasticity might depend on alternative splicing is not known. Here we report that chronic inactivity homeostatically increases action potential duration by changing alternative splicing of BK channels; this requires nuclear export of the splicing factor Nova-2. Inactivity and Nova-2 relocation were connected by a novel synapto-nuclear signaling pathway that surprisingly invoked mechanisms akin to Hebbian plasticity: Ca2+-permeable AMPA receptor upregulation, L-type Ca2+ channel activation, enhanced spine Ca2+ transients, nuclear translocation of a CaM shuttle, and nuclear CaMKIV activation. These findings not only uncover commonalities between homeostatic and Hebbian plasticity but also connect homeostatic regulation of synaptic transmission and neuronal excitability. The signaling cascade provides a full-loop mechanism for a classic autoregulatory feedback loop proposed â¼25 years ago. Each element of the loop has been implicated previously in neuropsychiatric disease.
Subject(s)
Large-Conductance Calcium-Activated Potassium Channels/metabolism , Long-Term Potentiation/physiology , Nerve Tissue Proteins/metabolism , RNA-Binding Proteins/metabolism , Action Potentials/physiology , Alternative Splicing/genetics , Alternative Splicing/physiology , Animals , Calcium-Calmodulin-Dependent Protein Kinase Type 1/metabolism , Calcium-Calmodulin-Dependent Protein Kinases/metabolism , Female , HEK293 Cells , Homeostasis/physiology , Humans , Large-Conductance Calcium-Activated Potassium Channels/genetics , Male , Mice , Mice, Inbred C57BL , Nerve Tissue Proteins/physiology , Neuro-Oncological Ventral Antigen , Neuronal Plasticity/physiology , Neurons/metabolism , RNA-Binding Proteins/physiology , Rats , Rats, Sprague-Dawley , Signal Transduction , Synapses/metabolism , Synaptic Transmission/physiologyABSTRACT
Endothelin-1 (ET-1) plays important roles in endothelial dysfunction, vascular physiology, inflammation, and atherosclerosis. Nonetheless, the role of ET-1 (EDN1) gene variants on coronary artery disease (CAD) risk remains poorly understood. The aim of the present study was to evaluate the role of EDN1 gene polymorphisms on individual susceptibility to CAD. We genotyped five tagSNPs (single-nucleotide polymorphisms) (rs6458155, rs4145451, rs9369217, rs3087459, and rs2070699) within EDN1 gene in 525 CAD patients and 675 control subjects. In a multivariate logistic regression analysis, we detected an association of rs6458155 in EDN1 gene with the CAD risk; compared with the TT homozygotes, the CT heterozygotes (odds ratio (OR) = 1.53, 95% confidence interval (CI) = 1.02-2.29, P=0.040) and the CC homozygotes (OR = 1.55, 95% CI = 1.01-2.36, P=0.043) were statistically significantly associated with the increased risk for CAD. A similar trend of the association was found in dominant model (OR = 1.53, 95% CI = 1.05-2.25, P=0.029). Consistently, the haplotype rs6458155C-rs4145451C containing rs6458155 C allele exhibited the increased CAD risk (OR = 1.22, 95% CI = 1.03-1.43, and P=0.018). In addition, CT genotype of rs6458155 conferred the increased plasma ET-1 levels compared with TT genotype (P<0.05). No association of the other four tagSNPs in EDN1 gene with CAD risk was observed. In conclusion, our study provides the first evidence that EDN1 tagSNP rs6458155 is associated with CAD risk in the Chinese Han population, which is probably due to the influence of the circulating ET-1 levels.
