REVIEW article

Front. Mol. Neurosci., 04 January 2023

Sec. Pain Mechanisms and Modulators

Volume 15 - 2022 | https://doi.org/10.3389/fnmol.2022.1081288

Mechanism and effects of STING–IFN-I pathway on nociception: A narrative review

  • 1. Department of Anesthesiology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

  • 2. Department of Obstetrics and Gynecology, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

  • 3. Department of Integrated Traditional Chinese and Western Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

  • 4. Department of Pain, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

  • 5. Institute of Anesthesia and Critical Care Medicine, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, China

Abstract

Since the discovery of STING in 2008, numerous studies have investigated its functions in immunity, inflammation, and cancer. STING activates downstream molecules including IFN-I, NLRP3, and NF-κB. The STING–IFN-I pathway plays a vital role in nociception. After receiving the upstream signal, STING is activated and induces the expression of IFN-I, and after paracrine and autocrine signaling, IFN-I binds to IFN receptors. Subsequently, the activity of ion channels is inhibited by TYK2, which induces an acute antinociceptive effect. JAK activates PIK3 and MAPK–MNK–eIF4E pathways, which sensitize nociceptors in the peripheral nervous system. In the mid-late stage, the STING–IFN-I pathway activates STAT, increases pro-inflammatory and anti-inflammatory cytokines, inhibits ER-phagy, and promotes microglial M1-polarization in the central nervous system, leading to central sensitization. Thus, the STING–IFN-I pathway may exert complex effects on nociception at various stages, and these effects require further comprehensive elucidation. Therefore, in this review, we systematically summarized the mechanisms of the STING–IFN-I pathway and discussed its function in nociception.

Introduction

Pain is defined by the International Association for the Study of Pain as an unpleasant sensory and emotional experience associated with actual or potential tissue or other damage (). After sensing physical and chemical stimuli, nociceptors produce and transmit information to the central nervous system(CNS). Notably, the brain can generate pain without a message from nociceptors or the spinal cord, such as in phantom limb pain (; ). Multiple molecules are involved in the production of pain, such as G protein-coupled receptors, cyclic nucleotides, capsaicin, and acid ().

Stimulator of interferon genes (also called STING, MITA, MPYS, ERIS, and TMEM173) was first discovered in 2008 (; ). STING could regulate antimicrobial response, autoimmune disease, and cancer progression (; ; ). The stimulator of interferon genes (STING)–interferon-I (IFN-I) pathway can control nociception (; ). In neuropathic pain models including bone cancer pain, chemotherapy-induced peripheral neuropathy, and nerve injury, administration of STING agonists activates STING, increases the expression of IFN-I, and inhibits the excitability of nociceptors in the peripheral nervous system (PNS) (). These effects induce transient, short-term, and dose-dependent antinociception at an early stage (). However, the antinociceptive effect was not substantial 11 days after the injection (). Similarly, activation of the STING–IFN-I pathway induces nociception or neuropathic pain at a late stage (; ). The exact effects of STING–IFN-I remain controversial, and its differential role in different sexes, neuropathic pain models, cells, and stages requires further research. Previous studies hypothesized that this pathway might be a potential therapeutic target for pain management.

In this review, we systematically summarize the mechanisms of the STING–IFN-I pathway and discuss its function in nociception.

Structure and properties of STING and IFN-I

STING is located in the endoplasmic reticulum (ER) (; ). In human cells, STING comprises 379 amino acids and contains five putative transmembrane regions (). The N-terminal of STING, consisting of four transmembrane regions, is responsible for membrane anchoring. The C-terminal protrudes into the cytoplasm and contains a domain that binds with cyclic dinucleotides (CDNs) (; ; ). STING can directly detect bacterial CDNs and activate immune responses (; ). In addition, it can detect cytosolic double-stranded DNA (dsDNA) released by tumor and dead cells via cyclic guanosine monophosphate–adenosine monophosphate (cyclic GMP–AMP or cGAMP) synthase (cGAS) activity (). Moreover, leakage of mitochondrial DNA can activate STING in adjacent phagocytic cells (). After STING activation, the expression of IFN-I, NOD-like receptor protein 3 (NLRP3), and nuclear factor-κB (NF-κB) increases (; ; ).

IFN-I was first discovered in 1957 and is composed of IFN-α, IFN-β, IFN-δ, IFN-ε, IFN-κ, IFN-τ, and IFN-ω (; ). IFN-I participates in the antiviral response, cell proliferation, apoptosis, inflammation, and adaptive immunity (; ; ).

Research progress of STING–IFN-I pathway

Antimicrobial response

Microbial DNA invasion triggers a series of immune responses. STING is essential for detecting exogenous microbial DNA (). Activation of STING consequently activates the transcription factors NF-κB and interferon regulatory factor 3 (IRF3) to induce cytokines and IFN-I expression (). STING is required by fibroblasts, macrophages, dendritic cells, and myeloid cells to induce IFN-I production against vaccinia virus (VACV), cytomegalovirus (HCMV), baculovirus, several strains of herpes simplex virus-1 (HSV1), and Listeria monocytogenes (; ).

Autoimmune disease

In addition to exogenous DNA, STING can detect self-DNA. Undigested DNA from apoptotic cells triggers DNA sensors, which increase the expression of cytokines and result in autoimmune diseases (; ). The exonuclease, three prime repair exonuclease 1 (TREX1), degrades cytosolic DNA (; ) and its deficiency leads to multiple inflammatory and autoimmune diseases such as systemic lupus erythematosus, Aicardi–Goutieres syndrome, and familial chilblain lupus (). In a TREX1-deficient rat model, cGAS activated STING through cGAMP production and mediated inflammatory disease and death in mice (). Similarly, STING triggered by apoptotic or necrotic DNA promoted the expression of cytokines, whereas its deficiency abrogated the production of cytokines activated by self-DNA in a DNase II-deficient model ().

Cancer progression

Nuclear and mitochondrial DNA are easily damaged in tumor cells, inducing IFN-I through the cGAS–STING–IRF3-dependent pathway (; ; ). IFN-I is a mediator of STING and exerts adaptive antitumor effects (). It can promote cross-presentation by stimulating the maturation of DCs, slowing down the endosome–lysosome acidification process to prevent phagocytic tumor antigen clearance, and increasing the expression of cell surface MHC I molecules, which accelerates DC migration to lymph nodes to cross-trigger tumor-specific CD8+ T cells (; ; ; ). In addition, IFN-I can induce the expression of multiple chemokines (; ). For instance, CXCL9 and CXCL10 are involved in cytotoxic T lymphocyte transfer and infiltration, whereas CCL5 and CXCL10 promote the recruitment and activation of NK cells and T cells in tumors (; ). By contrast, the cGAS–STING pathway can induce the senescence-associated secretory phenotype (SASP) (). The SASP factor induces immune surveillance and acts as a tumor suppressor. However, continuous exposure to SASP may cause tissue damage and chronic inflammation associated with tumor growth (). Nevertheless, long-term activation of STING may promote tumor growth and metastasis, and this effect is associated with tumor stage, CIN status, and the degree of STING activation (). STING agonists including cyclic dinucleotides and their derivatives, DMXAA and its analogs, and small-molecule agonists are widely studied as cancer treatment agents (; ; ).

Mechanism of STING–IFN-I pathway with respect to pain

Peripheral nociceptors and pain

Cell bodies of nociceptors are distributed in the dorsal root ganglia (DRG) and trigeminal ganglion (). Most nociceptors contain unmyelinated C fibers (). However, initial and acute pain is mediated by nociceptors with A fibers (). After sensing physical and chemical stimuli, peripheral nociceptors are activated to produce pain through different signal transduction pathways (; ). Particularly, TRP channels recognize noxious heat, and the ENaC/DEG channel family senses mechanical stimuli (; ). Nociceptors can convert receptor potentials into action potentials through voltage-gated channels (including sodium, calcium, and potassium channels) (). Primary nociceptors transmit noxious stimuli to projection neurons located in the cornu dorsalis medullae spinalis (). Harmful information is transmitted to the somatosensory cortex through the thalamus, indicating the location and intensity of the pain (). Other projection neurons contact the cingulate gyrus and insular cortex through the brain stem and amygdala, forming emotional elements of pain experiences ().

Pattern recognition receptors in nociception

Pattern recognition receptors (PRRs) recognize pathogen-associated molecular patterns (PAMPs) and damage-associated molecular patterns (DAMPs) to induce the transcription of genes involved in inflammatory responses (). PRRs include toll-like, RIG-I-like, NOD-like, and DNA receptors (cytosolic sensors for DNA) (; ). Both immune cells and peripheral nociceptors express PRRs (; ; ). Cytosolic DNA sensors such as the cGAS–STING pathway are highly expressed in nociceptive neurons (; ; ). PRRs on immune cells recognize DAMPs/PAMPs and release cytokines/chemokines and inflammatory mediators to react with nociceptor terminals (). Meanwhile, the terminals of nociceptors can directly detect PAMPs/DAMPs and danger signals (). The indirect and direct pathways can regulate the function of sodium (e.g., Nav1.7, Nav1.8, and Nav1.9), calcium, and transient receptor potential channels. Thus, the excitability and activity of nociceptors are altered (; ; ; Figure 1).

FIGURE 1

Upstream signals of STING

cGAS, a cytosolic sensor for DNA, can activate STING through cGAMP production (; ; ; ). STING directly detects bacterial cytoplasmic CDNs including cyclic-di-GMP, cyclic-di-AMP, and 3′,3′-cGAMP (; ; ; ). Aside from cGAS, DNA-dependent activators of interferon regulatory factors, IFN-γ-inducible protein 16, and DEAD box polypeptide 41 can also recognize cytosolic DNA and activate STING (; ; ; Figure 2). Intracellular dsDNA and dsRNA can induce IFN-I-dependent antinociception; however, only the dsDNA-dependent pathway requires the cGAS–STING pathway ().

FIGURE 2

Downstream signals of STING

After binding with CDNs, STING is transferred from the ER to the Golgi complex via perinuclear vesicles (). STING forms oligomers in the ER–Golgi membrane and exposes its C terminal (; ). The C terminal of STING recruits TANK-binding kinase 1 (TBK1), and the STING dimer accesses the active site of TBK1 for its phosphorylation (; ). In addition, two TBK1 dimers can be mutually activated via transautophosphorylation (). The phosphorylated tail of STING recruits IRF3 and transports it to TBK1 for phosphorylation (; ). Notably, the interaction between STING and TBK1 enhances the binding of TBK1 and IRF3 (; ; ). Phosphorylated IRF3 dimers access the nucleus and activate the transcription of IFN and inflammatory factor genes (; ). Thus, IFN-I synthesis increases notably. After paracrine and autocrine signaling, IFN-I binds with IFN receptors on sensory neurons to generate nociceptive effects (; ). IFN receptors comprise IFNAR1 and IFNAR2 (). IFNAR1 plays a vital role in acute nociceptive functions (; ). Inhibition of tyrosine kinase (TYK2) eliminates the analgesic effect of IFN-β (). Thus, TYK2 associated with IFNAR1 inhibits the activity of sodium (Nav1.7) and calcium channels (; ). Furthermore, the low excitability of nociceptors is attributed to the loss of function of sodium (Nav1.7) and calcium channels (; ). Therefore, IFN-I can induce acute and short-term antinociception via TYK2.

Conversely, IFNAR2 is associated with Janus-activated kinases (JAKs) (; ). After activation of JAKs, the mitogen-activated protein kinase (MAPK)–interacting kinase (MNK)–eukaryotic translation initiation factor 4E (eIF4E) pathway and PIK3 are activated, causing nociceptor sensitization in the PNS at a later stage (). In the mid-late stage, IFN-I activates STAT to induce the expression of pro-inflammatory and anti-inflammatory cytokines, inhibits ER-phagy, and promotes microglial M1-polarization, which generates delayed nociceptive effects in the CNS (Figure 2; ; ; ; ).

Regulatory mechanism of STING–IFN-I pathway

Regulation of the STING–IFN-I pathway mostly depends on STING activity. Posttranslational modifications including phosphorylation, ubiquitination, and palmitoylation play vital roles in regulating STING activity (). Activation of STING requires palmitoylation in the Golgi complex (; ). After recruiting TBK1 and activating IRF3, negative feedback is triggered. STING is subsequently phosphorylated by serine/threonine UNC-51-like kinase, and IRF3 activity is inhibited ().

Among posttranslational modifications, ubiquitination is essential for STING activity. Some molecules have been shown to play essential roles in STING regulation. AMFR facilitates K27-linked polyubiquitination of STING through the ER membrane protein INSIG1 and promotes the recruitment and activation of TBK1 (). EIF3S5, OTUD5, CYLD, and ubiquitin-specific protease (USP) 44 (USP44) are deubiquitinases that remove K48-linked polyubiquitination to maintain the stability of STING (; ; ; ). TRIM32 promotes K63-linked polyubiquitination of STING and increases the production of IFN-I (). iRhom2 recruits the translocon-associated protein (TRAPβ) and the deubiquitination enzyme (EIF3S5) to promote STING trafficking from the ER to perinuclear microsomes (). USP13 deconjugates polyubiquitin chains on STING to prevent recruitment of TBK1 (), while USP21 hydrolyzes the K27/63-linked polyubiquitin chain on STING to negatively regulate the production of IFN-I (Table 1; ). The regulatory mechanism of STING is complex and warrants further investigation.

TABLE 1

MoleculesMechanismFunction
AMFRFacilitates K27-linked Polyubiquitination through INSIG1Promotes recruitment and activation of TBK1
EIF3S5


Remove K48-linked Polyubiquitination



Maintain stabilization of STING
OTUD5
CYLD
USP44
TRIM32Promotes K63-linked
Polyubiquitination
Increases production of IFN-I
iRhom2Recruits translocon-associated
Protein TRAPβ and EIF3S5
Promote transmitting of STING from ER to perinuclear
microsomes and maintain stabilization of STING
USP13Deconjugates polyubiquitin chains on STINGPrevent recruitment of TBK1
USP21Hydrolyzes K27/63-linked
Polyubiquitin chain on STING
Decreases production of IFN-I

Summary of molecules associated with ubiquitination of STING and regulation of STING activity.

AMFR, EIF3S5, OTUD5, CYLD, USP44, TRIM32, and iRhom2 are positive regulators. USP13 and USP21 are negative regulators.

Effects of STING–IFN-I pathway on nociception

Limited studies indicated that the STING–IFN-I pathway has dual effects on nociception (Table 2).

TABLE 2

ReferencesStudy designAnimal/
Population
ModelReagent injectedInjection methodTesting timeMechanism (location)ResultsEffect
Animal experimentC56BL/6 miceChemotherapy-induced peripheral neuropathy model
Nerve injury model
Bone cancer pain model
DMXAA (STING agonists)Intrathecal injection of 35 nmol DXMAA on day 0, day 3, day 6, day 9, and day 12Tests conducted 4h after each injectionActivated STING-IFN-I pathway
Restrained activity of ion channels
Inhibit excitability of nociceptors (DRG/PNS)
Activation of STING-IFN-Ipathway in sensory neurons was sufficient to induce antinociception (DRG)Positive
Animal experimentC56BL/6 miceLewis lung carcinoma cells induced bone cancer painDMXAA (STING agonist)20 mg/kg injected intraprtitoneally twice on day 3 and day 7 after inoculationTests conducted 10 and 14 days after LLC inoculationActivated STING-IFN-I pathway
Inhibited osteoclastogenesis
Reduced tumor burden (DRG/PNS)
Activation of STING-IFN-I pathway attenuated bone cancer painPositive
Animal experimentC57BL/6 male mice aged between 8 and 12 weeksChronic constriction injuryH-151 and 7-BIAIntrathecal injection of 10 nM H-151 on day 7 after CCI
Intraperitoneal injection of 7-BIA (10 or 20 mg/kg) on day 7 after CCI
Tests conducted 1.5, 6, 24, and 48 h after injectionLack of protein tyrosine phosphatase receptor type D
Activation of STING-IFN-I pathway (DRG/PNS)
Knockdown of protein tyrosine phosphatase receptor type D attenuated neuropathic pain via STING-IFN I pathwayPositive
Animal experimentMale eIF4ES209A and MNK1–/– mice, C57BL/6J wild-type (WT) mice aged 8 and 12 weeksViral infectionIFN-α and IFN-βIntraplantar administration of IFN-α (300 U/25 μl) or IFN-β (300 U/25 μl)Tests conducted 1 h, 3 h, 24 h, 3 days, 6 days, 10 days after injectionActivation of MNK-eIF4E pathway
Nociceptor hyperexcitability
Mechanical pain sensitization (DRG/PNS)
Peripheral administration of IFN-I induced pain behavior in rats model in a short-termNegative
Animal experimentAdult male Sprague–Dawley rats (200–220 g)Spared nerve injuryRU.521 and C-176 (STING antagonist)Consecutively intrathecal injection of 10 μM RU.521 and 5 μM C-176 on days 7–11 after SNITests conducted 6 h after each injectionActivation of spinal cGAS/STING pathway
Microglial M1-polarization
(spinal cord/CNS)
Inhibition of cGAS-STING pathway suppressed microglial M1-polarizarion in the spinal cord and attenuated neuropathic painNegative
Animal experimentMale Sprague Dawley (SD) rats (180–230 g)Spinal nerve ligation2′3′-cGAMP (STING agonist)
Ketamine; Dexmedetomidine
Intrathecal injections of 10 μg 2′3′-cGAMP on days 2, 4, and 6 after operation
Intraperitoneal injection of 20 mg/kg ketamine and 20 μg/kg dexmedetomidine on postoperative days 2, 4, and 6
Tests conducted on days 3, 5, 7 after operationActivation of STING/TBK pathway
Inhibition of ER-phagy
Enhancement of ER stress
(Spinal cord/CNS)
Dexmedetomidine and ketamine attenuated neuropathic pain via STING pathway to induce ER-phagyNegative
Clinical trial
(Prospective study)
372 HCV patientsCombinatory antiviral therapy (IFN-α-2beta + ribavirin)1.5 μg of peg IFN-α-2beta per kilogram of body weight subcutaneously once weekly, and 600–800 mg of ribavirin daily for 24 weeksNeurotoxicity Rating Scale (NRS) for somatic symptoms at baseline and at the 2nd, 4th, 8th, 12th, 16th, 20th, and 24th week/IFN-α therapy induces significant somatic pain symptoms as early as the 2nd week of treatment in HCV patientsNegative
Clinical trial
(Case series)
11 pediatric patientsPatients with COVID-19-related skin lesionsParacetamolage- and weight-adjusted paracetamol 15 mg/kg per dose, to a maximum of 750 mg per dose, every 6 – 8 h, with a maximum of 3,000 mgs daily for 10 days/In young patients, the IFN-1 response induces microangiopathic changes and produces a chilblain LE-like eruption with vasculitic neuropathic pain featuresNegative

Studies on the STING–IFN-I pathway and pain.

STING–IFN-I pathway has complex effects in different neuropathic pain models, effective time, and location of nerve system (see “Supplementary Appendix” for the search flow, method, and results).

Positive effect

The STING–IFN-I pathway is associated with acute antinociceptive effects. In a rat model, deficiency of the STING–IFN-I pathway increased the excitability of nociceptors (). In the chronic constriction injury model of rats, knockdown of the D-type protein tyrosine phosphatase receptor increased the expression of STING and IFN-α, which attenuated pain (). STING agonists can relieve neuropathic pain in peripheral neuropathy induced by paclitaxel chemotherapy () and pain induced by nerve injury (). Similarly, they may inhibit bone cancer pain and maintain motor function by reducing tumor burden and inhibiting cancer-induced osteoclast generation (; ). Moreover, STING agonists can attenuate fracture-induced pain in tumor-free mice (). Notably, after injecting STING agonists in rats, IFN-I levels in serum, DRG tissues, and bone marrow lysates were significantly upregulated 1000-fold in 4 h and maintained for up to 24 h (; ; ). Therefore, the STING–IFN-I pathway may promote short-term antinociception.

Negative effect

Several studies have also reported contradictory results, wherein the STING–IFN-I pathway exerted negative effects. A case series reported that IFN-I induced by STING causes neuropathic pain in young patients (). Similarly, in patients with hepatitis C virus infection, the use of IFN-α leads to somatic pain ().

Intraplantar administration of IFN-α (300 U/25 μL) or IFN-β (300 U/25 μL) can activate the MNK-eIF4E pathway via the STING–IFN-I pathway (). Subsequently, this pathway induces nociceptor hyperexcitability and mechanical pain sensitization at the DRG level for a short period of time (). Pain induction was not significant 3 days after peripheral injection (). Thus, the effects of IFN-I may be acute or transient.

In the spared nerve injury (SNI) model, inhibiting the cGAS–STING pathway can restrain microglial M1-polarization and attenuate neuropathic pain (). M1-polarization microglia express CD16 and induce TNF-α and IL-1β synthesis, which may cause central sensitization (). In a rat SNL model, ketamine and dexmedetomidine induced ER-phagy and alleviated ER stress to provide antianxiety and antinociceptive effects by inhibiting the STING–TBK pathway in the spinal cord ().

Underlying reasons for the dual effects

There are several possible explanations for these contradictions. First, the sex of the animals may have caused this discrepancy. This pathway more likely has a negative effect on male rats (). Second, animal experiments were used to create different neuropathic pain models to explore its effects. However, different animal models may exhibit various neuropathies. Third, different injection methods may also have caused bias. Peripheral administration of IFN-I induced pain behavior in rat models (). However, intrathecal injection of IFN-α inhibited mechanical hypersensitivity caused by intraplantar (). Fourth, the different effective times influenced the results. Short-term activation of this pathway led to transient and acute antinociception, which was maintained for up to 24 h (). However, consecutive and repeated administration of STING agonists caused central sensitization and nociception (). Fifth, the STING–IFN-I pathway does not participate in the physiological regulation of pain sensitivity and is only involved in the regulation of pain after nerve injury (; ). Therefore, observing a positive effect in normal rat models injected with STING agonists or IFN-I is challenging. Finally, the STING–IFN-I pathway may play distinct roles in different parts of the PNS and CNS. A study has demonstrated that after STING agonist DMXAA treatment in mouse models, bone cancer-induced cold and mechanical allodynia were reduced at an early stage but not at the mid-late stage (). Therefore, at an early stage, it induces antinociception and reduces pain by restraining the activity of ion channels and the excitability of nociceptors in the PNS. Subsequently, this pathway may induce nociceptor sensitization via the MAPK–MNK–eIF4E pathway and PIK3. At the mid-late stage, it can cause central sensitization in several ways (Figure 3).

FIGURE 3

STING agonists compared with opiates

Since the isolation of morphine in 1805, opioids have been widely used for pain management (). Opioids, including morphine, interact with μ, κ, and δ receptors to produce analgesic effects, respiratory depression, and euphoria addiction. After binding with opioid receptors, opioids cause antinociception through the same mechanism as enkephalin, which involves hyperpolarization of interneurons and reduction of transmitters associated with pain (; ). In addition, morphine can react with opioid receptors in supraspinal structures to activate the supraspinal system (). By contrast, STING agonists produce acute and short-term antinociception via the STING–IFN-I pathway in the PNS. Furthermore, opioids are highly addictive, which is caused by a reduction in the inhibitory function of GABAergic synapses in the neurons of the central amygdala and brain reward/motivational mesocorticolimbic circuitry (; ). In contrast, the repeated use of STING agonists does not cause addiction and attenuates SNI-induced astrogliosis (). In non-human primates, intrathecal administration of STING agonists produces longer lasting analgesic effects at lower doses than morphine (3 vs. 100 nmol) (; ; ). Naloxone, a nonselective and short-acting opioid receptor antagonist, can reverse the analgesic effect of morphine (; ). By contrast, STING agonist-mediated analgesia is not affected by naloxone ().

Previous studies have suggested that STING agonists have potential advantages including strong efficacy at low doses, a longer lasting effect, and non-addictive. However, the exact effects of STING–IFN-I on nociception remain unclear and require further investigation.

Discussion

Apart from inducing antimicrobial response, mediating autoimmune disease, and regulating tumor growth, the STING–IFN-I pathway can induce acute antinociception for a short period of time. Therefore, the STING–IFN-I pathway may be a potential therapeutic target for pain management.

However, the effects of STING on nociception have several issues that need to be discussed. First, demonstrated that STING agonists reduced bone cancer pain. However, suggested that mitochondrial DNA triggers the STING pathway, leading to peripheral neuroinflammation and sensitization (). In the early stage, the STING–IFN-I pathway was dominant, which reduced bone cancer pain. In the mid-late stage, the MAPK–MNK–eIF4E pathway was activated, and the STING–NF-κB pathway increased bone cancer pain via IL-1β, IL-6, and TNF-α (; ). In addition, STING agonists have been shown to reduce bone cancer pain through immune and neuronal modulation, reducing tumor burden and inhibiting osteoclastogenesis (; ). Therefore, it is difficult to determine the true effects of STING agonists in bone cancer pain models. Second, the STING–IFN-I pathway may influence central sensitization through ER-phagy and microglial M1-polarization. Further studies are needed to confirm this hypothesis and to determine how the STING–IFN-I pathway regulates ER-phagy and microglial M1-polarization. Third, previous studies have only discussed one downstream pathway in a neuropathic pain model. However, STING has various downstream signaling components, including IFN-I, NF-κB, and NLPRS. Studies that include all downstream signals of STING are still lacking. Lastly, STING–IFN-I exists not only in peripheral and central neurons but also in immune cells. Whether STING agonists interact with these cell types to cause nociception requires further studies ().

The current clinical use of STING agonists focuses on cancer immunotherapy. Several combination therapies are currently available in clinical trials (). Few studies have indicated the effectiveness of STING in nociception; however, the use of STING for nociception remains controversial and warrants further extensive and comprehensive studies.

Conclusion

At an early stage, the STING–IFN-I pathway can induce short-term antinociceptive effects by activating TYK2, restraining the activity of calcium and sodium channels, and inhibiting the excitability of nociceptors in the PNS. Subsequently, it activates the JAK–MAPK–MNK–eIF4E pathway and PIK3, which cause nociceptor sensitization. At the mid-late stage, it promotes microglial M1-polarization, inhibits ER-phagy, activates STAT, and increases the expression of pro-inflammatory and anti-inflammatory cytokines in the CNS, which leads to central sensitization. Thus, the STING–IFN-I pathway at various stages has a dual effect on nociception.

Statements

Author contributions

JY wrote the manuscript and made illustrations. HD, BS, and YZ (Fifth author) provided advice for the manuscript. YZ (Fourth author) provided the supervision and comments on the manuscript. All the authors read and approved the final manuscript.

Funding

The work was supported by the National Natural Science Foundation of China (grant no. 81901144).

Conflict of interest

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Publisher’s note

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article, or claim that may be made by its manufacturer, is not guaranteed or endorsed by the publisher.

Supplementary material

The Supplementary Material for this article can be found online at: https://www.frontiersin.org/articles/10.3389/fnmol.2022.1081288/full#supplementary-material

Supplementary Data Sheet 1

Search process for cited articles. Forty-seven articles were found initially. After excluding ineligible articles, only eight articles were included.

References

Summary

Keywords

nociception, stimulator of interferon genes, interferon-I, peripheral nerve system (PNS), central nerve system (CNS)

Citation

Yang J, Ding H, Shuai B, Zhang Y and Zhang Y (2023) Mechanism and effects of STING–IFN-I pathway on nociception: A narrative review. Front. Mol. Neurosci. 15:1081288. doi: 10.3389/fnmol.2022.1081288

Received

27 October 2022

Accepted

05 December 2022

Published

04 January 2023

Volume

15 - 2022

Edited by

Xiaodong Sheldon Liu, Beijing University of Chinese Medicine, China

Reviewed by

Qiuyi Lv, Beijing University of Chinese Medicine, China; Jianjun Zhang, Institute of Psychology (CAS), China; Simin Pan, Texas A&M University, College Station, United States

Updates

Copyright

*Correspondence: Yan Zhang,

†These authors have contributed equally to this work and share first authorship

This article was submitted to Pain Mechanisms and Modulators, a section of the journal Frontiers in Molecular Neuroscience

Disclaimer

All claims expressed in this article are solely those of the authors and do not necessarily represent those of their affiliated organizations, or those of the publisher, the editors and the reviewers. Any product that may be evaluated in this article or claim that may be made by its manufacturer is not guaranteed or endorsed by the publisher.

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