Antinociceptive effects of IL-6R vs. glucocorticoid receptors during rat hind paw inflammatory pain

Valproate attenuates somatic hyperalgesia induced by orofacial inflammation combined with stress through inhibiting spinal IL-6 and STAT1 phosphorylation

Temporomandibular disorder (TMD) and fibromyalgia syndrome (FMS) may present as comorbid conditions, but treatment options are ineffective. The purpose of this study was to investigate whether valproate (VPA) attenuates somatic hyperalgesia induced by orofacial inflammation combined with stress, which represents a model of pain associated with TMD and FMS comorbidity, and to explore the potential mechanisms. The results showed that VPA inhibited somatic hyperalgesia induced by orofacial inflammation combined with stress, and down-regulated the interleukin-6 (IL-6) expression in the L4-L5 spinal dorsal horn of female rats. The anti-nociceptive effect of VPA was blocked by single or 5 consecutive day intrathecal administration of recombinant rat IL-6. Orofacial inflammation combined with stress up-regulated the ratio of phosphorylated signal transducer and activator of transcription 1 (p-STAT1) to STAT1 (p-STAT1/STAT1) in the spinal cord. VPA did not affect the STAT1 expression, while it down-regulated the ratio of p-STAT1/STAT1. The expression of STAT3 and the ratio of p-STAT3/STAT3 were not affected by orofacial inflammation combined with stress and VPA treatment. Intrathecal administration of exogenous IL-6 up-regulated the ratio of p-STAT1/STAT1. These data indicate that VPA attenuated somatic hyperalgesia induced by orofacial inflammation combined with stress via inhibiting spinal IL-6 in female rats, and the mechanism may involve the alteration of activation status of spinal STAT1. Thus, VPA may be a new candidate analgesic that targets IL-6 and STAT1 for the treatment of pain associated with the comorbidity of TMD and FMS.

Dexamethasone inhibits IL-8 via glycolysis and mitochondria-related pathway to regulate inflammatory pain

BACKGROUND

Dexamethasone (Dexa) has been recently found to exert an analgesic effect, whose action is closely related to IL-8. However, whether dexamethasone induces antinociception via glycolysis and mitochondria-related pathways is still unclear.

METHODS

Right hind paw inflammatory pain in mice was induced by intraplantar injection of Freund's Complete Adjuvant (FCA). Von Frey test was then used to measure the paw withdrawal threshold. The detection of glycolysis and mitochondrial pathway-related proteins and IL-8 were determined by Western blot and ELISA. The potential interaction between Dexa and fructose-1,6-bisphosphate (FBP, a PKM2 activator) was examined by simulation predictions using molecular docking.

RESULTS

Intrathecal administration of Dexa (20 µg/20 µL) had an obvious analgesic effect in FCA-treated mice, which was counteracted by the glycolysis inhibitor 2-deoxyglucose (2-DG, 5 mg/20 µL) or the mitochondria-related pathway inhibitor oligomycin complex (Oligo, 5 µg/20 µL). In the glycolysis pathway, Dexa decreased GLUT3 and had no impact on HIF-1α expression during FCA-induced inflammation. Additionally, Dexa further increased the PKM2 level, accompanied by the formation of hydrogen bonds between Dexa and the PKM2 activator fructose-1,6-bisphosphate (FBP). In the mitochondrial pathway, Dexa downregulated the expression of Mfn2 protein but not the PGC-1α and SIRT-1 levels in the spinal cord. Moreover, both 2-DG and Oligo decreased Mfn2 expression. Finally, IL-8 level was reduced by the single or combined administration of Dexa, 2-DG, and Oligo.

CONCLUSION

Dexa attenuated IL-8 expression via glycolysis and mitochondrial pathway-related proteins, thus mediating the analgesic effect during inflammatory pain.

Evaluation of antinociceptive effect and pharmacological mechanisms of thiocyanoacetamide in rats

OBJECTIVE

Acute pain is the most common type of pain. The aim of the present work was carried out to study the antinociceptive effect and pharmacological mechanisms of thiocyanoacetamide (Thm) in rats exposed to thermal pain stimulus.

MATERIALS AND METHODS

The anti-nociceptive effect of the newly synthesized compound, Thm was studied in comparison to that of paracetamol (Para), dexamethasone (Dex), and morphine (Morph) at different doses using a hot plate test at a constant temperature of 48.0 ± 0.5°C. During this test, the latency time (LT) was measured when rats express pain behavior. Then, the pharmacological mechanisms were determined using receptor-antagonist drugs.

RESULTS

Firstly, the obtained result showed pain modulation of the pretreated rats with Thm at 10 mg/kg dose proved by the delay of latency time during the thermal test. This significant antinociceptive activity of the thiocyanoacetamide was more effective than that of paracetamol or dexamethasone and less than that of morphine. Second, the pretreatment with acebutolol or risperidone antagonist drugs of, respectively, adrenergic and serotonin receptors demonstrated the elimination of pain modulation with Thm 10 mg/kg dose proved by a short latency time of rat's response in hot plate test. In this case, the pharmacological mechanism of Thm was characterized by the involvement of adrenergic and serotoninergic systems.

CONCLUSIONS

It may be concluded that Thm constitutes a promising antinociceptive drug including beta-adrenergic and serotoninergic targets. The present study warrants further investigation to determine the side effects of this compound.

SARS-CoV-2 airway infection results in the development of somatosensory abnormalities in a hamster model

Although largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and chronic phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster model to characterize and compare the effects of infection with SARS-CoV-2 and influenza A virus (IAV) on the sensory nervous system. We detected SARS-CoV-2 transcripts but no infectious material in the cervical and thoracic spinal cord and dorsal root ganglia (DRGs) within the first 24 hours of intranasal virus infection. SARS-CoV-2-infected hamsters exhibited mechanical hypersensitivity that was milder but prolonged compared with that observed in IAV-infected hamsters. RNA sequencing analysis of thoracic DRGs 1 to 4 days after infection suggested perturbations in predominantly neuronal signaling in SARS-CoV-2-infected animals as opposed to type I interferon signaling in IAV-infected animals. Later, 31 days after infection, a neuropathic transcriptome emerged in thoracic DRGs from SARS-CoV-2-infected animals, which coincided with SARS-CoV-2-specific mechanical hypersensitivity. These data revealed potential targets for pain management, including the RNA binding protein ILF3, which was validated in murine pain models. This work elucidates transcriptomic signatures in the DRGs triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities.

A network pharmacology approach to predict potential targets and mechanisms of "Ramulus Cinnamomi (cassiae) - Paeonia lactiflora" herb pair in the treatment of chronic pain with comorbid anxiety and depression

BACKGROUND

Traditional Chinese medicine (TCM) prescriptions have multiple bioactive properties. "Gui Zhi-Shao Yao" herb pair is widely used to treat chronic pain (CP), as well as anxiety and depression. However, its related targets and underlying mechanisms have not been deciphered.

METHODS

In this study, the network pharmacology method was used to explore the bioactive components and targets of "Gui Zhi-Shao Yao" herb pair and further elucidate its potential biological mechanisms of action in the treatment of CP with comorbid anxiety disorder (AD) and mental depression (MD).

RESULTS

Following a series of analyses, we identified 15 active compounds, hitting 130 potential targets. After the intersections the targets of this herb pair and CP, AD and MD - sorted by the value of degree - nine targets were identified as the vital ones: Akt1, IL6, TNF, PTGS2, JUN, CASP3, MAPK8, PPARγ and NOS3. Gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis results demonstrated 11 pathways, such as AGE-RAGE signalling pathway, IL-17 signalling pathway, TNF signalling pathway, which primarily participate in the pathological processes.

CONCLUSIONS

This study preliminarily predicted and verified the pharmacological and molecular mechanisms of "Gui Zhi-Shao Yao" herb pair for treating CP with comorbid AD and MD from a holistic perspective. In vivo and in vitro experiments will be required to further investigate the mechanisms.KEY MESSAGEA network pharmacology approach was applied to identify key targets and molecular mechanisms.Nine targets were regarded as the vital targets for chronic pain with comorbid anxiety and depression.Predicted 11 pathways were the potential therapy targets and pharmacological mechanism of "Gui Zhi-Shao Yao" herb pair.

Dexamethasone and potassium canrenoate alleviate hyperalgesia by competitively regulating IL-6/JAK2/STAT3 signaling pathway during inflammatory pain in vivo and in vitro

Background

Dexamethasone (Dexa) and potassium canrenoate (Cane) modulate nociceptive behavior via glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) by two mechanisms (genomic and nongenomic pathways). This study was designed to investigate the Dexa‐ or Cane‐mediated nongenomic and genomic effects on mechanical nociception and inflammation‐induced changes in interleukin‐6 (IL‐6) mediated signaling pathway in rats.

Methods

Freund's complete adjuvant (FCA) was used to trigger an inflammation of the right hind paw in male Sprague–Dawley rats. First, the mechanical nociceptive behavioral changes were examined following intraplantar administration of GR agonist Dexa and/or MR antagonist Cane in vivo. Subsequently, the protein levels of IL‐6, IL‐6Rα, JAK2, pJAK2, STAT3, pSTAT3^Ser727, migration inhibitory factor, and cyclooxygenase‐2 were assessed by Western blot following intraplantar injection of Dexa or Cane or the combination. Moreover, the molecular docking studies determined the interaction between Dexa, Cane, and IL‐6. The competition binding assay was carried out using enzyme‐linked immunosorbent assays (ELISA).

Results

Administration of Dexa and Cane dose‐dependently attenuated FCA‐induced inflammatory pain. The sub‐additive effect of Dexa/Cane combination was elucidated by isobologram analysis, accompanied by decrease in the spinal levels of IL‐6, pJAK2, and pSTAT3^Ser727. The molecular docking study demonstrated that both Dexa and Cane displayed a firm interaction with THR¹³⁸ binding site of IL‐6 via a strong hydrogen bond. ELISA revealed that Dexa has a higher affinity to IL‐6 than Cane.

Conclusions

There was no additive or negative effect of Dexa and Cane, and they modulate the IL‐6/JAK2/STAT3 signaling pathway through competitive binding with IL‐6 and relieves hypersensitivity during inflammatory pain.

SARS-CoV-2 Airway Infection Results in Time-dependent Sensory Abnormalities in a Hamster Model

Despite being largely confined to the airways, SARS-CoV-2 infection has been associated with sensory abnormalities that manifest in both acute and long-lasting phenotypes. To gain insight on the molecular basis of these sensory abnormalities, we used the golden hamster infection model to characterize the effects of SARS-CoV-2 versus Influenza A virus (IAV) infection on the sensory nervous system. Efforts to detect the presence of virus in the cervical/thoracic spinal cord and dorsal root ganglia (DRGs) demonstrated detectable levels of SARS-CoV-2 by quantitative PCR and RNAscope uniquely within the first 24 hours of infection. SARS-CoV-2-infected hamsters demonstrated mechanical hypersensitivity during acute infection; intriguingly, this hypersensitivity was milder, but prolonged when compared to IAV-infected hamsters. RNA sequencing (RNA-seq) of thoracic DRGs from acute infection revealed predominantly neuron-biased signaling perturbations in SARS-CoV-2-infected animals as opposed to type I interferon signaling in tissue derived from IAV-infected animals. RNA-seq of 31dpi thoracic DRGs from SARS-CoV-2-infected animals highlighted a uniquely neuropathic transcriptomic landscape, which was consistent with substantial SARS-CoV-2-specific mechanical hypersensitivity at 28dpi. Ontology analysis of 1, 4, and 30dpi RNA-seq revealed novel targets for pain management, such as ILF3. Meta-analysis of all SARS-CoV-2 RNA-seq timepoints against preclinical pain model datasets highlighted both conserved and unique pro-nociceptive gene expression changes following infection. Overall, this work elucidates novel transcriptomic signatures triggered by SARS-CoV-2 that may underlie both short- and long-term sensory abnormalities while also highlighting several therapeutic targets for alleviation of infection-induced hypersensitivity.

One Sentence Summary

SARS-CoV-2 infection results in an interferon-associated transcriptional response in sensory tissues underlying time-dependent hypersensitivity.

LOXG473A induces the formation of osteoclasts in RAW264.7 cells via IL-6/JAK2/STAT3 signaling

Formation of osteoclasts is known to be closely associated with osteoporosis progression. LOX is a key enzyme that catalyzes the synthesis of collagen, which is the new mediator in osteoclast formation. However, the effect of LOXG473A on of osteoclast formation needs to be explored. Thereby, we sought to explore the effect of LOX_G473A on formation of osteoclasts and its underlying mechanism. To investigate the function of LOX_G473A in osteoclast formation, Raw264.7 cells were stably transfected with LOX-WT or LOX-MUT (LOX_G473A). Real-time PCR and western blotting were used to detect the relative levels of osteoclast formation related genes and proteins. TRAP staining and immunofluorescence staining were used to test the ability of Raw264.7 cells to form osteoclasts and the ability of cells to form rings, respectively. Bone erosion assay was used to test bone resorptive activity. The data indicated that LOX_G473A significantly enhanced the ability of osteoclasts forming, ring-forming and bone resorpting in Raw264.7 cells. Mechanically, LOX_G473A upregulated the expressions of NFATC1, ACP5, CTSK, IL-6, and the proportion of p-JAK2/JAK2 and p-STAT3/STAT3, thereby promoting the formation of osteoclasts. In conclusion, we have verified that LOX_G473A induces the proliferation of osteoclasts in Raw264.7 cells via IL-6/JAK2/STAT3 signaling, suggesting a novel strategy for studying osteoporosis.