CX3CR1 Mediates Nicotine Withdrawal-Induced Hyperalgesia via Microglial P38 MAPK Signaling
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Previously, we reported that nicotine withdrawal (NT) significantly increased pain sensitivity in rats. Recent reports suggest that fractalkine is involved in the spinal cord neuron-to-microglia activation via CX3CR1 signaling. However, its contribution to NT-induced hyperalgesia and the underlying mechanisms have yet to be elucidated. In the present study, a rat model of NT was used to test the changes in CX3CR1 expression in the spinal cord. We also evaluated the effect of the CX3CR1 neutralizing antibody on spinal microglial activity, the expression of phosphorylated p38-mitogen-activated protein kinase (p-p38-MAPK) and heat-induced pain responses. We established a NT model via subcutaneous injection of pure nicotine (3 mg/kg), three times daily for 7 days. The expression of CX3CR1 was studied by Western blot and immunofluorescence staining. Following NT, the rats received daily intrathecal injections of CX3CR1 neutralizing antibody for 3 days. The change in paw withdrawal latency (PWL) was observed. The activation of microglia and the expression of p-p38-MAPK were investigated by Western blot and immunofluorescence staining. The expression of CX3CR1 was significantly increased after NT and co-localized with IBA-1. NT rats treated with CX3CR1 neutralizing antibody showed significantly increased PWL on day 4 after NT. Furthermore, the activation of microglia and the expression of p-p38-MAPK in the spinal cord were suppressed. These results indicate that microglial CX3CR1/p38MAPK pathway is critical for the development of pain hypersensitivity after NT.
KeywordsNicotine withdrawal Hyperalgesia CX3CR1 Microglia p38 MAP kinase
Chemokine CX3C motif receptor
Phosphorylation of p38-mitogen-activated protein kinase
Cold pressor test
Protein kinase A
Protein kinase C
Calcium/calmodulin-dependent protein kinase II
- p38 MAPK
p38-mitogen-activated protein kinase
Ionized calcium binding adapter molecule-1
Glial fibrillary acidic protein
Paw withdrawal latency
Polyvinylidene fluoride membrane
Spared nerve injury
Toll-like receptor 4
This work was supported by grants from National Natural Science of China (81471134). Our great thanks also go to the critical scientific opinions of Prof. Li-Cai Zhang from Xuzhou Medical College.
ZWZ conceived and designed the study. YHD performed the animal surgery, behavioral testing and data analysis. WHS carried out the immunohistochemistry and Western blot. GNX, ALY and QHW participated in behavioral testing and immunohistochemistry experiments. All authors read and approved the final manuscript.
Compliance with Ethical Standards
Conflict of interest
The authors report no financial or other conflict of interest relevant to the subject of this manuscript.
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