NFκB-mediated CXCL1 production in spinal cord astrocytes contributes to the maintenance of bone cancer pain in mice

Abstract

BackgroundBone cancer pain (BCP) is one of the most disabling factors in patients suffering from primary bone cancer or bone metastases. Recent studies show several chemokines (for example, CCL2, CXCL10) in the spinal cord are involved in the pathogenesis of BCP. Here we investigated whether and how spinal CXCL1 contributes to BCP.MethodsMouse prostate tumor cell line, RM-1 cells were intramedullary injected into the femur to induce BCP. The mRNA expression of CXCL1 and CXCR2 was detected by quantitative real-time PCR. The protein expression and distribution of CXCL1, NFκB, and CXCR2 was examined by immunofluorescence staining and western blot. The effect of CXCL1 neutralizing antibody, NFκB antagonist, and CXCR2 antagonist on pain hypersensitivity was checked by behavioral testing.ResultsIntramedullary injection of RM-1 cells into the femur induced cortical bone damage and persistent (>21 days) mechanical allodynia and heat hyperalgesia. Tumor cell inoculation also produced CXCL1 upregulation in activated astrocytes in the spinal cord for more than 21 days. Inhibition of CXCL1 by intrathecal administration of CXCL1 neutralizing antibody at 7 days after inoculation attenuated mechanical allodynia and heat hyperalgesia. In cultured astrocytes, TNF-α induced robust CXCL1 expression, which was dose-dependently decreased by NFκB inhibitor. Furthermore, inoculation induced persistent NFκB phosphorylation in spinal astrocytes. Intrathecal injection of NFκB inhibitor attenuated BCP and reduced CXCL1 increase in the spinal cord. Finally, CXCR2, the primary receptor of CXCL1, was upregulated in dorsal horn neurons after inoculation. Inhibition of CXCR2 by its selective antagonist SB225002 attenuated BCP.ConclusionNFκB mediates CXCL1 upregulation in spinal astrocytes in the BCP model. In addition, CXCL1 may be released from astrocytes and act on CXCR2 on neurons in the spinal cord and be involved in the maintenance of BCP. Inhibition of the CXCL1 signaling may provide a new therapy for BCP management.

Minocycline attenuates bone cancer pain in rats by inhibiting NF-κB in spinal astrocytes

“…We demonstrated that NF-κB was specifically co-localized with astrocytes in the spinal cord of BCP rats, which is consistent with previous literature. For example, Xu et al [8] reported that NF-κB contributed to BCP via the mediation of CXCL1 production in spinal astrocytes; these authors also highlighted that an intrathecally injected inhibitor of NF-κB significantly attenuated nociceptive behavior. Similarly, other studies based on neuropathic pain have demonstrated that targeted blockades of NF-κB in the spinal cord alleviated pain perception [13,15] .…”

“…Over the previous few decades, BCP models have been successfully established [5] , and there is increasing evidence that indicates spinal astrocytes participate in the process [6,7] by releasing pro-inflammatory cytokines and chemokines [7][8][9] . Moreover, nuclear factor kappa B (NF-κB), an important transcriptional factor mediating cytokine production [8,10,11] , is activated in spinal astrocytes during a chronic pain state [8,12] .…”

“…Moreover, nuclear factor kappa B (NF-κB), an important transcriptional factor mediating cytokine production [8,10,11] , is activated in spinal astrocytes during a chronic pain state [8,12] .…”

Adrenergic signaling mediates mechanical hyperalgesia through activation of P2X3 receptors in primary sensory neurons of rats with chronic pancreatitis

“…Suramin or A317491 was intrathecally (it) injected once. Intrathecal injection was made with a 27 G needle between the L5 and L6 intervertebral space to deliver the reagents to the cerebral spinal fluid as described previously (21,45). Buto, Phen, or Prop was intraperitoneally injected once daily for 7 consecutive days for molecular expression experiments and once for behavioral test.…”

CXCR3: Latest evidence for the involvement of chemokine signaling in bone cancer pain

“…(6) The latest study also showed that NFκB mediated the release of CXCL1 from spinal astrocytes, which could act on CXCR2 on neurons in BCP mice. It suggested that CXCL1/CXCR2-mediated astroglia-neuron interaction plays a significant role in the maintenance of tumoral hypersensitivity (Xu et al, 2014). In conclusion, understanding the mechanisms of pro-inflammatory mediators in the context of BCP models is an ongoing effort that requires research attention.…”