STING Contributes to Cancer-Induced Bone Pain by Promoting M1 Polarization of Microglia in the Medial Prefrontal Cortex

Microglial STING activation alleviates nerve injury-induced neuropathic pain in male but not female mice

Microglia, resident immune cells in the central nervous system, play a role in neuroinflammation and the development of neuropathic pain. We found that the stimulator of interferon genes (STING) is predominantly expressed in spinal microglia and upregulated after peripheral nerve injury. However, mechanical allodynia, as a marker of neuropathic pain following peripheral nerve injury, did not require microglial STING expression. In contrast, STING activation by specific agonists (ADU-S100, 35 nmol) significantly alleviated neuropathic pain in male mice, but not female mice. STING activation in female mice leads to increase in proinflammatory cytokines that may counteract the analgesic effect of ADU-S100. Microglial STING expression and type I interferon-ß (IFN-ß) signaling were required for the analgesic effects of STING agonists in male mice. Mechanistically, downstream activation of TANK-binding kinase 1 (TBK1) and the production of IFN-ß, may partly account for the analgesic effect observed. These findings suggest that STING activation in spinal microglia could be a potential therapeutic intervention for neuropathic pain, particularly in males.

Edaravone dexborneol ameliorates cognitive impairment by regulating the NF-κB pathway through AHR and promoting microglial polarization towards the M2 phenotype in mice with bilateral carotid artery stenosis (BCAS)

Cerebral small vessel disease (CSVD) is one of the most important causes of stroke and vascular dementia, so exploring effective treatment modalities for CSVD is warranted. This study aimed to explore the anti-inflammatory effects of Edaravone dexborneol (C.EDA) in a CSVD model. Mice with CSVD showed distinct cognitive decline, as assessed by the Morris water maze (MWM). Pathological staining verified leakage across the blood‒brain barrier (BBB), microglial proliferation, neuronal loss and demyelination. Western blot analysis demonstrated that M1 microglia dominated prophase and released proinflammatory molecules; the aryl hydrocarbon receptor (AHR) was found to participate in modulating nuclear factor-kappa B (NF-κB) signalling activation through tumour necrosis factor receptor-associated factor-6 (TRAF6). C.EDA treatment resulted in the polarization of microglia from the M1 to the M2 phenotype. Mice sequentially treated with C.EDA exhibited a significant improvement in cognitive function; expression of the anti-inflammatory cytokines and modulatory proteins AHR and TRAF6 was upregulated, while the levels of pNF-κBp65 and pIΚBα were downregulated. C.EDA promoted microglial activation towards the M2 phenotype by upregulating AHR expression, which prevented TRAF6 ubiquitination, promoted NF-κB RelA/p65 protein degradation and inhibited subsequent NF-κB phosphorylation. Mechanistically, the anti-inflammatory effect of C.EDA alleviated neuronal loss and myelin damage, while at the functional level, C.EDA improved cognitive function and thus showed good application prospects.

Understanding the initiation, delivery and processing of bone cancer pain from the peripheral to the central nervous system

Bone cancer pain is a complex condition characterized by persistent, sudden, spontaneous pain accompanied by hyperalgesia that typically arises from bone metastases or primary bone tumors, causing severe discomfort and significantly diminishing cancer patients' quality of life and confidence in their ability to overcome the disease. It is widely known that peripheral nerves are responsible for detecting harmful stimuli, which are then transmitted to the brain via the spinal cord, resulting in the perception of pain. In the case of bone cancer, tumors and stromal cells within the bone marrow release various chemical signals, including inflammatory factors, colony-stimulating factors, chemokines, and hydrogen ions. Consequently, the nociceptors located at the nerve endings within the bone marrow sense these chemical signals, generating electrical signals that are then transmitted to the brain through the spinal cord. Subsequently, the brain processes these electrical signals in a complex manner to create the sensation of bone cancer pain. Numerous studies have investigated the transmission of bone cancer pain from the periphery to the spinal cord. However, the processing of pain information induced by bone cancer within the brain remains unclear. With the continuous advancements in brain science and technology, the brain mechanism of bone cancer pain would become more clearly understood. Herein, we focus on summarizing the peripheral nerve perception of the spinal cord transmission of bone cancer pain and provide a brief overview of the ongoing research regarding the brain mechanisms involved in bone cancer pain.

Vinorelbine causes a neuropathic pain-like state in mice via STING and MNK1 signaling associated with type I interferon induction

Type I interferons (IFNs) increase the excitability of dorsal root ganglion (DRG) neurons via activation of MNK-eIF4E translation signaling to promote pain sensitization in mice. Activation of STING signaling is a key component of type I IFN induction. Manipulation of STING signaling is an active area of investigation in cancer and other therapeutic areas. Vinorelbine is a chemotherapeutic that activates STING and has been shown to cause pain and neuropathy in oncology clinical trials in patients. There are conflicting reports on whether STING signaling promotes or inhibits pain in mice. We hypothesized that vinorelbine would cause a neuropathic pain-like state in mice via STING and signaling pathways in DRG neurons associated with type I IFN induction. Vinorelbine (10 mg/kg, i.v.) induced tactile allodynia and grimacing in WT male and female mice and increased p-IRF3 and type I IFN protein in peripheral nerves. In support of our hypothesis, vinorelbine-mediated pain was absent in male and female StingGt/Gt mice. Vinorelbine also failed to induce IRF3 and type I IFN signaling in these mice. Since type I IFNs engage translational control via MNK1-eIF4E in DRG nociceptors, we assessed vinorelbine-mediated p-eIF4E changes. Vinorelbine increased p-eIF4E in DRG in WT animals but not in StingGt/Gt or Mknk1-/- (MNK1 KO) mice. Consistent with these biochemical findings, vinorelbine had an attenuated pro-nociceptive effect in male and female MNK1 KO mice. Our findings support the conclusion that activation of STING signaling in the peripheral nervous system causes a neuropathic pain-like state that is mediated by type I IFN signaling to DRG nociceptors.

The bidirectional roles of the cGAS-STING pathway in pain processing: Cellular and molecular mechanisms

Pain is a common clinical condition. However, the mechanisms underlying pain are not yet fully understood. It is known that the neuroimmune system plays a critical role in the pathogenesis of pain. Recent studies indicated that the cyclic-GMP-AMP synthase-stimulator of interferon genes (cGAS-STING) pathway can activate the innate immune system by sensing both extrinsic and intrinsic double-stranded DNA in the cytoplasm, which is involved in pain processing. In this review, we summarise (1) the roles of the cGAS-STING pathway in different pain models, (2) the effect of the cGAS-STING pathway in different cells during pain regulation, and (3) the downstream molecular mechanisms of the cGAS-STING pathway in pain regulation. This review provides evidence that the cGAS-STING pathway has pro- and anti-nociceptive effects in pain models. It has different functions in neuron, microglia, macrophage, and T cells. Its downstream molecules include IFN-I, NF-κB, NLRP3, and eIF2α. The bidirectional roles of the cGAS-STING pathway in pain processing are mediated by regulating nociceptive neuronal sensitivity and neuroinflammatory responses. However, their effects in special brain regions, activation of astrocytes, and the different phases of pain require further exploration.

The cGAS-STING pathway promotes endometriosis by up-regulating autophagy

OBJECTIVE

To investigate the roles of the cGAS-STING signal pathway and autophagy in the disease progression of endometriosis and to explore the regulatory mechanism of the cGAS-STING signal pathway on autophagy.

DESIGN

A case-control experimental study, in vitro primary cell culture study, and in vivo animal research.

MAIN OUTCOME MEASURES

Immunohistochemistry, RT-PCR and Western Blot were used to detect cGAS-STING signal pathway and autophagy expression differences in human and rat models. The lentivirus was used to overexpress STING in cells. The expression level of autophagy in human endometrial stromal cells (HESCs) transfected with lv-STING was detected by Western Blot, RT-PCR, and immunofluorescence. Transwell migration and invasion assays were conducted to assess cellular motility. The STING antagonist was applicated in vivo to investigate the therapeutic effects.

RESULTS

The expression levels of the cGAS-STING signal pathway and autophagy in Human and Rat ectopic endometrium were increased. STING overexpression promotes the expression of autophagy in human endometrial stromal cells (HESCs). STING overexpression enhances the migration and invasion of the human endometrial stromal cells (HESCs), but the addition of autophagy antagonists could significantly reverse this. STING antagonists inhibited the expression of autophagy in vivo and reduced the volume of ectopic lesions.

CONCLUSION

The expression levels of the cGAS-STING signal pathway and autophagy were increased in endometriosis. cGAS-STING signal pathway promotes the development of endometriosis by upregulating autophagy.