Analgesic Effect of Intrathecal 2R， 6R-HNK on Neuropathic Pain in Female Mice / 中山大学学报(医学科学版)

ObjectiveTo investigate the analgesic action and mechanism of intrathecal 2R， 6R-hydroxynorketamine （2R， 6R-HNK） on spared nerve injury （SNI）-induced chronic neuropathic pain （CNP） in female mice. MethodsSNI was used to establish acute and chronic CNP models in female mice. The mice were randomly divided into different groups with administration of vehicle， 2R， 6R-HNK or S-ketamine （10 mg/kg intraperitoneal injection/i.p. or 7， 21 μmol/L intrathecal injection/i.t.） at 3 weeks after or 30 min/1 d before operation （n = 3 - 7 mice/group）. The curative or preventive effect of 2R， 6R-HNK was evaluated by mechanical paw withdrawal threshold （PWT） and the analgesic efficiency. Finally， immunofluorescence and RT-PCR of dorsal root ganglion （DRG） and spinal dorsal horn （SDH） were used to explore the possible mechanisms. ResultsCompared with vehicle， intrathecal injection of 2R， 6R-HNK largely reversed SNI-induced bilateral mechanical allodynia in a delayed-and-dose-dependent way. Among them， 21 μmol/L 2R， 6R-HNK reached its maximum analgesic efficiency （75.32±7.69） % at 2 d. Pre-intrathecal delivery of 2R， 6R-HNK also delayed the development of bilateral mechanical hypersensitivity 2 - 3 d induced by SNI. Mechanically， 2R， 6R-HNK reversed not only the abnormal excitability of neurons in bilateral DRG and superficial SDH， but also the upregulation of calcitonin gene-related peptide （CGRP） and brain-derived nerve growth factor （BDNF） in DRG. ConclusionIntrathecal administration of 2R， 6R-HNK exerts an analgesic effect against CNP， probably via suppressing abnormal neuronal excitability in ascending pain pathway as well as down-regulating CGRP and BDNF expression in DRG neurons.

Sexual Dimorphism in Mechanical Hypersensitivity Induced by Subcutaneous Injection of M-CSF / 中山大学学报(医学科学版)

ObjectiveTo investigate whether there exists gender differences in mechanical pain hypersensitivity induced by the subcutaneous injection of macrophage colony-stimulating factor （M-CSF） in normal mice and to explore the preliminary mechanism. MethodsThirty 10-week-old C57BL/6J mice were randomly divided into three groups， (n = 10 mice/group, half male and half female). The albumin control group （BSA， 0.3 μg）， low dose M-CSF group （L M-CSF， 0.075 μg） and high dose M-CSF group （H M-CSF， 0.3 μg） received 50 μL BSA or M-CSF injected subcutaneously into the left medial thigh once daily for 3 consecutive days. Before and after drug administration， von-Frey mechanical sensitivity test was used to detect the mechanical paw withdrawal threshold （PWT） in each group. Immunofluorescence was performed to examine the expression changes of Ionized calcium-binding adaptor molecule 1 (Iba1) in skin， calcitonin gene-related peptide （CGRP） and phosphorylated ERK1/2 （p-ERK） in L5-L6 DRG and lumbar spinal dorsal horn. ResultsIn female mice， only high dose of M-CSF caused mechanical allodynia， whereas in male mice both doses produced marked allodynia. Mechanically， high-dose M-CSF induced massive aggregation of subcutaneous macrophages （marked by Iba1） in male and female mice， but more dramatic dependence in female mice. Similar gender differences were also found in the increase of p-ERK and CGRP expression in dorsal root ganglion （DRGs）. Notably， CGRP expression was especially elevated in the fibers of DRG in male mice. Correspondingly， the expressions of p-ERK and CGRP+ terminals in the superficial spinal dorsal horn of male mice were significantly higher than those of female mice after M-CSF treatment. ConclusionSubcutaneous injection of M-CSF triggers sexual dimorphism in mechanical pain hypersensitivity, which is related with differential changes in peripheral macrophage expansion and sensitization of the nociceptive pathway.

Modified Trizol Method for Extracting RNA from Mouse Skin / 中山大学学报(医学科学版)

@#【Objective】Due to the tough nature of skin tissue and a high presence of RNases，the isolation of skin RNA by the classical Trizol method presents a challenge. Therefore，we adapted and tested different sample treatment protocols to improve the Trizol method for high- quality extraction of skin RNA.【Methods】In this study，normal skin of mice processed by different treatments（Tri：submersion Trizol；Pro：RNA sample protector；Cry：cryopreservation in liquid nitrogen frozen and then - 80 ℃ refrigerator；LNG：liquid nitrogen grinding；Cut：scissor cutting）were used as the experimental groups. Spinal cord tissue（Sp）was used as the reference group，and skin tissue of mouse psoriasis model induced by imiquimod（IMQ）was used as the validation group. We compared skin RNA concentration，purity and integrity， as well as IL- 1β mRNA expression extracted by conventional Trizol methods（1-Tri，Nor）and modified Trizol methods（2-Tri，LNG-Tri，Tri-Cut，Pro），which were determined by UV spectrophotometry，agar gel electrophoresis and quantitative reverse transcription PCR（qRT- PCR）.【Results】① Compared with spinal cord（Sp），the total RNA of normal skin tissue extracted with the same classical Trizol method（1-Tri）was with lower yields，more obvious DNA contamination and 5S RNA bands，and higher IL-1β mRNA relative expression，suggesting that skin tissue was relatively special and the classical Trizol methods of skin RNA extraction should be improved. ② Among the different treatment methods of skin tissue，2-Tri and LNG-Tri methods resulted in higher RNA concentrations，lower RNA degradation and lower DNA contamination，and the expression of IL-1β mRNA was closer to normal levels. More importantly，the skin RNA samples extracted by the 2-Tri method can reflect more realistically the variation of IL-1β mRNA expression between normal and psoriasiform groups.【Conclusion】Improved 2-Tri or LNG-Tri method has the advantage of high quality of total RNA，and 2-Tri can more reliably reflect the mRNA expression pattern under physiological and pathological conditions.

A modified protocol of mouse hippocampal primary microglia culture by using manual dissociation, magnetic activated cell sorting and TIC medium / 生理学报

In this study, we improved the culture method of mouse hippocampal primary microglia to obtain hippocampal ramified microglia with high activity and purity, which were resemble to the resting status of normal microglia in healthy brain in vivo. Hippocampal tissue was excised from 2-4-week-old SPF C57BL/6J mice and cut into pieces after PBS perfusion, and then manually dissociated into the single-cell suspension by using Miltenyi Biotec's Adult Brain Dissociation Kit. The tissue fragments such as myelin in the supernatant were removed by debris removal solution in the kit. The cell suspension was incubated with CD11b immunomagnetic beads for 15 min at 4 °C. To obtain high-purity microglia, we used two consecutive cell-sorting steps by magnetic activated cell sorting (MACS). After centrifugation, the cells were resuspended and seeded in a 24-well culture plate. The primary microglia were cultured with complete medium (CM) or TIC medium (a serum-free medium with TGF-β, IL-34 and cholesterol as the main nutritional components) for 4 days, and then were used for further experiments. The results showed that: (1) The cell viability was (56.03 ± 2.10)% by manual dissociation of hippocampus; (2) Compared with immunopanning, two-step MACS sorting allowed for efficient enrichment of microglia with higher purity of (86.20 ± 0.68)%; (3) After being incubated in TIC medium for 4 d, microglia exhibited branching, quiescent morphology; (4) The results from qRT-PCR assay showed that the levels of TNF-α, IL-1β and CCL2 mRNA in TIC cultured-microglia were similar to freshly isolated microglia, while those were much higher in CM cultured-microglia after incubation for 4 d and 7 d (P < 0.05). Taken together, compared to the conventional approaches, this modified protocol of mouse hippocampal primary microglia culture by using MACS and TIC medium enables the increased yield and purity of microglia in the quiescent state, which is similar to normal ramified microglia in healthy brain in vivo.