Chang-Xi Yu

Diabetic neuropathic pain (DNP), characterized by persistent spontaneous pain and evoked pain, poses clinical challenges including treatment resistance and frequent comorbidities with affective disorders such as anxiety and depression. Despite its clinical importance, the underlying mechanisms of DNP remain unclear. In our study, we reveal that hyperactivated astrocytes in the rostral ventromedial medulla (RVM) are functionally associated with both mechanical allodynia and anxiety-like behaviors in DNP. Chemogenetic inhibition of RVM astrocyte activity significantly alleviated mechanical allodynia and anxiety-like behaviors in DNP model rats. Conversely, targeted activation of RVM astrocytes in control rats induced neuropathic pain-like symptoms and pain-related aversion. Furthermore, we discovered that RVM astrocyte bidirectionally modulated glutamatergic neuronal activity; that is, astrocyte activation suppressed neuronal activity, whereas its inhibition increased neuronal excitability. These findings establish RVM astrocyte activation as a critical mediator of DNP pathogenesis, revealing a promising cellular target for the development of novel analgesics and providing therapeutic insights for DNP management.

Recent evidence highlights the importance of glutamatergic neurons in the basal forebrain (BF) in promoting cortical activity; however, whether BF glutamatergic neurons are involved in regulating general anesthesia and the underlying neural circuits remains unclear. Here, we showed that the activity of BF glutamatergic neurons decreased during the induction of isoflurane anesthesia and restored during the emergence in mice. Optogenetic activation of these neurons significantly enhanced cortical activation, accelerated behavioral emergence, and improved physiological indicators in both male and female mice under isoflurane anesthesia. Specifically, activation of BF glutamatergic neurons shortened emergence time from isoflurane anesthesia, decreased isoflurane sensitivity, and increased arousal scores of mice. Moreover, optogenetic activation of BF glutamatergic neurons decreased EEG delta power and burst suppression ratio, while increasing pupil size and respiration rate in mice during isoflurane anesthesia. Similar results were observed during the optogenetic activation of BF glutamatergic terminals in the ventral tegmental area (VTA). Additionally, we found that the activity of BF glutamatergic neurons and VTA glutamatergic neurons synchronously fluctuated during isoflurane anesthesia, and optogenetic activation of BF glutamatergic terminals in the VTA potently increased the calcium signals in VTA glutamatergic neurons during isoflurane anesthesia. Collectively, these findings demonstrate that BF glutamatergic neurons promote emergence from isoflurane anesthesia by activating VTA glutamatergic neurons.

Diabetic neuropathic pain (DNP) is a common chronic complication of diabetes mellitus and a clinically common form of neuropathic pain. The thalamus is an important center for the conduction and modulation of nociceptive signals. The paraventricular thalamic nucleus (PVT) is an important midline nucleus of the thalamus involved in sensory processing, but the specific role of PVT astrocytes and GABAergic neurons in DNP remains unclear. Here, we examined the activity of PVT astrocytes and neurons at various time points during the development of DNP by fluorescence immunohistochemistry and found that the activity of PVT astrocytes was significantly increased while that of PVT neurons was significantly decreased 14 d after streptozotocin injection in male rats. The inhibition of PVT astrocytes by chemogenetic manipulation relieved mechanical allodynia in male DNP model rats, whereas the activation of PVT astrocytes induced mechanical allodynia in normal male rats. Interestingly, chemogenetic activation of GABAergic neurons in the PVT alleviated mechanical allodynia in male DNP model rats, whereas chemogenetic inhibition of GABAergic neurons in the PVT induced mechanical allodynia in normal male rats. These data demonstrate the distinct roles of PVT astrocytes and GABAergic neurons in modulating DNP, revealing the mechanism of DNP pathogenesis and the role of the PVT in pain modulation.

Background: Recent evidence indicates that general anesthesia and sleep–wake behavior share some overlapping neural substrates. γ-Aminobutyric acid–mediated (GABAergic) neurons in the central amygdala have a high firing rate during wakefulness and play a role in regulating arousal-related behaviors. The objective of this study was to investigate whether central amygdala GABAergic neurons participate in the regulation of isoflurane general anesthesia and uncover the underlying neural circuitry. Methods: Fiber photometry recording was used to determine the changes in calcium signals of central amygdala GABAergic neurons during isoflurane anesthesia in Vgat-Cre mice. Chemogenetic and optogenetic approaches were used to manipulate the activity of central amygdala GABAergic neurons, and a righting reflex test was used to determine the induction and emergence from isoflurane anesthesia. Cortical electroencephalogram (EEG) recording was used to assess the changes in EEG spectral power and burst–suppression ratio during 0.8% and 1.4% isoflurane anesthesia, respectively. Both male and female mice were used in this study. Results: The calcium signals of central amygdala GABAergic neurons decreased during the induction of isoflurane anesthesia and were restored during the emergence. Chemogenetic activation of central amygdala GABAergic neurons delayed induction time (mean ± SD, vehicle vs. clozapine-N-oxide: 58.75 ± 5.42 s vs. 67.63 ± 5.01 s; n = 8; P = 0.0017) and shortened emergence time (385.50 ± 66.26 s vs. 214.60 ± 40.21 s; n = 8; P = 0.0017) from isoflurane anesthesia. Optogenetic activation of central amygdala GABAergic neurons produced a similar effect. Furthermore, optogenetic activation decreased EEG delta power (prestimulation vs. stimulation: 46.63 ± 4.40% vs. 34.16 ± 6.47%; n = 8; P = 0.0195) and burst–suppression ratio (83.39 ± 5.15% vs. 52.60 ± 12.98%; n = 8; P = 0.0003). Moreover, optogenetic stimulation of terminals of central amygdala GABAergic neurons in the basal forebrain also promoted cortical activation and accelerated behavioral emergence from isoflurane anesthesia. Conclusions: The results suggest that central amygdala GABAergic neurons play a role in general anesthesia regulation, which facilitates behavioral and cortical emergence from isoflurane anesthesia through the GABAergic central amygdala–basal forebrain pathway.

Introduction: Koumine (KME) is the most abundant active ingredient separated from Gelsemium elegans Benth and exhibits a significant therapeutic effect on rheumatoid arthritis (RA). It is a lipophilic compound with poor aqueous solubility, and there is an urgent need to develop novel dosage forms of KME and promote its clinical application for the treatment of RA. The aim of this study was to design and develop KME-loaded microemulsions (KME-MEs) for the effective management of RA. Methods: The composition of the microemulsion was selected by carrying out a solubility study and generating pseudoternary phase diagrams, and further optimized by D-Optimal design. The optimized KME-MEs was evaluated for particle size, viscosity, drug release, storage stability, cytotoxicity, cellular uptake, Caco-2 cell transport and everted gut sac investigations. In vivo fluorescence imaging and the therapeutic effects of KME and KME-MEs on collagen-induced arthritis (CIA) rats were also evaluated. Results: The optimized microemulsion contained 8% oil, 32% S_mix (surfactant/cosurfactant) and 60% water and was used for in vivo and in vitro studies. The optimal KME-MEs exhibited a small globule size of 18.5 ± 0.14 nm and good stability over 3 months, and the release kinetics followed a first-order model. These KME-MEs had no toxic effect on Caco-2 cells but were efficiently internalized into the cytoplasm. Compared to KME, the KME-MEs displayed significantly increased permeability and absorption in Caco-2 cell monolayer assay and ex vivo everted gut sac experiment. As expected, the KME-MEs attenuated the progression of RA in CIA rats and were more effective than free KME with a reduced frequency of administration. Conclusion: The KME-MEs improved the solubility and therapeutic efficacy of KME by employing formulation technology. These results provide a promising vehicle for the oral delivery of KME to treat RA and have attractive potential for clinical translation. Graphical Abstract: