TY - JOUR A1 - Lux, Thomas J. A1 - Hu, Xiawei A1 - Ben-Kraiem, Adel A1 - Blum, Robert A1 - Chen, Jeremy Tsung-Chieh A1 - Rittner, Heike L. T1 - Regional differences in tight junction protein expression in the blood−DRG barrier and their alterations after nerve traumatic injury in rats JF - International Journal of Molecular Sciences N2 - The nervous system is shielded by special barriers. Nerve injury results in blood–nerve barrier breakdown with downregulation of certain tight junction proteins accompanying the painful neuropathic phenotype. The dorsal root ganglion (DRG) consists of a neuron-rich region (NRR, somata of somatosensory and nociceptive neurons) and a fibre-rich region (FRR), and their putative epi-/perineurium (EPN). Here, we analysed blood–DRG barrier (BDB) properties in these physiologically distinct regions in Wistar rats after chronic constriction injury (CCI). Cldn5, Cldn12, and Tjp1 (rats) mRNA were downregulated 1 week after traumatic nerve injury. Claudin-1 immunoreactivity (IR) found in the EPN, claudin-19-IR in the FRR, and ZO-1-IR in FRR-EPN were unaltered after CCI. However, laser-assisted, vessel specific qPCR, and IR studies confirmed a significant loss of claudin-5 in the NRR. The NRR was three-times more permeable compared to the FRR for high and low molecular weight markers. NRR permeability was not further increased 1-week after CCI, but significantly more CD68\(^+\) macrophages had migrated into the NRR. In summary, NRR and FRR are different in naïve rats. Short-term traumatic nerve injury leaves the already highly permeable BDB in the NRR unaltered for small and large molecules. Claudin-5 is downregulated in the NRR. This could facilitate macrophage invasion, and thereby neuronal sensitisation and hyperalgesia. Targeting the stabilisation of claudin-5 in microvessels and the BDB barrier could be a future approach for neuropathic pain therapy. KW - tight junction KW - claudin-5 KW - neuropathic pain KW - nerve injury KW - dorsal root ganglion Y1 - 2019 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-285029 SN - 1422-0067 VL - 21 IS - 1 ER - TY - JOUR A1 - Chen, Jeremy Tsung-Chieh A1 - Schmidt, Lea A1 - Schürger, Christina A1 - Hankir, Mohammed K. A1 - Krug, Susanne M. A1 - Rittner, Heike L. T1 - Netrin-1 as a multitarget barrier stabilizer in the peripheral nerve after injury JF - International Journal of Molecular Sciences N2 - The blood–nerve barrier and myelin barrier normally shield peripheral nerves from potentially harmful insults. They are broken down during nerve injury, which contributes to neuronal damage. Netrin-1 is a neuronal guidance protein with various established functions in the peripheral and central nervous systems; however, its role in regulating barrier integrity and pain processing after nerve injury is poorly understood. Here, we show that chronic constriction injury (CCI) in Wistar rats reduced netrin-1 protein and the netrin-1 receptor neogenin-1 (Neo1) in the sciatic nerve. Replacement of netrin-1 via systemic or local administration of the recombinant protein rescued injury-induced nociceptive hypersensitivity. This was prevented by siRNA-mediated knockdown of Neo1 in the sciatic nerve. Mechanistically, netrin-1 restored endothelial and myelin, but not perineural, barrier function as measured by fluorescent dye or fibrinogen penetration. Netrin-1 also reversed the decline in the tight junction proteins claudin-5 and claudin-19 in the sciatic nerve caused by CCI. Our findings emphasize the role of the endothelial and myelin barriers in pain processing after nerve damage and reveal that exogenous netrin-1 restores their function to mitigate CCI-induced hypersensitivity via Neo1. The netrin-1-neogenin-1 signaling pathway may thus represent a multi-target barrier protector for the treatment of neuropathic pain. KW - neuropathic pain KW - netrin-1 KW - blood-nerve barrier KW - tight junction proteins Y1 - 2021 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-261695 SN - 1422-0067 VL - 22 IS - 18 ER - TY - JOUR A1 - Liu, Sheng A1 - Bonalume, Veronica A1 - Gao, Qi A1 - Chen, Jeremy Tsung-Chieh A1 - Rohr, Karl A1 - Hu, Jing A1 - Carr, Richard T1 - Pre-synaptic GABA\(_A\) in NaV1.8\(^+\) primary afferents is required for the development of punctate but not dynamic mechanical allodynia following CFA inflammation JF - Cells N2 - Hypersensitivity to mechanical stimuli is a cardinal symptom of neuropathic and inflammatory pain. A reduction in spinal inhibition is generally considered a causal factor in the development of mechanical hypersensitivity after injury. However, the extent to which presynaptic inhibition contributes to altered spinal inhibition is less well established. Here, we used conditional deletion of GABA\(_A\) in NaV1.8-positive sensory neurons (Scn10a\(^{Cre}\);Gabrb3\(^{fl/fl}\)) to manipulate selectively presynaptic GABAergic inhibition. Behavioral testing showed that the development of inflammatory punctate allodynia was mitigated in mice lacking pre-synaptic GABA\(_A\). Dorsal horn cellular circuits were visualized in single slices using stimulus-tractable dual-labelling of c-fos mRNA for punctate and the cognate c-Fos protein for dynamic mechanical stimulation. This revealed a substantial reduction in the number of cells activated by punctate stimulation in mice lacking presynaptic GABA\(_A\) and an approximate 50% overlap of the punctate with the dynamic circuit, the relative percentage of which did not change following inflammation. The reduction in dorsal horn cells activated by punctate stimuli was equally prevalent in parvalbumin- and calretinin-positive cells and across all laminae I–V, indicating a generalized reduction in spinal input. In peripheral DRG neurons, inflammation following complete Freund’s adjuvant (CFA) led to an increase in axonal excitability responses to GABA, suggesting that presynaptic GABA effects in NaV1.8\(^+\) afferents switch from inhibition to excitation after CFA. In the days after inflammation, presynaptic GABA\(_A\) in NaV1.8\(^+\) nociceptors constitutes an “open gate” pathway allowing mechanoreceptors responding to punctate mechanical stimulation access to nociceptive dorsal horn circuits. KW - GABA\(_A\) KW - presynaptic inhibition KW - NaV1.8 KW - spinal dorsal horn KW - punctate mechanical allodynia KW - c-fos KW - electrical excitability KW - activity-dependent slowing Y1 - 2022 U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-286081 SN - 2073-4409 VL - 11 IS - 15 ER -