Peri-sciatic administration of recombinant rat TNF-alpha induces mechanical allodynia via upregulation of TNF-alpha in dorsal root ganglia and in spinal dorsal horn: the role of NF-kappa B pathway.
Previous studies have shown that tumor necrosis factor-alpha (TNF-alpha) and TNF receptor 1 (TNFR1) in dorsal root ganglia (DRG) and in spinal dorsal horn are upregulated after nerve injury and that many TNF-alpha-containing neurons overexpress TNFR1. In the present study, we found that peri-sciatic administration of rat recombinant TNF-alpha (rrTNF) at the concentrations of 10, 100 and 1000 pg/ml (daily for 2 days) induced mechanical allodynia in bilateral hindpaws, lasting for about 20 days. The immunoreactivity (IR) of TNF-alpha and TNFR1 in the ipsilateral (but not in the contralateral) L4 and L5 DRGs increased significantly on day 1 and day 3 after administration of rrTNF, respectively. Double immunofluorescence staining revealed that in DRGs the increased TNF-alpha-IR was mainly in neuronal cells and with a lesser extent in satellite glial cells, while the upregulation of TNFR1-IR was almost restricted at neuronal cells. TNF-alpha-IR but not TNFR1-IR also increased in bilateral lumbar spinal dorsal horn from day 3 to day 14, which was observed in astrocytes, microglias and neurons. In addition, a progressive infiltration of monocyte/macrophages and T lymphocytes in the ipsilateral L5 DRG and sciatic nerve was observed, starting on day 2 following administration of rrTNF. Intrathecal delivery of PDTC (8.2 ng in 10 microl volume), a nuclear factor-kappa B (NF-kappaB) inhibitor, 30 min before each rrTNF administration blocked mechanical allodynia completely and inhibited the upregulation of TNF-alpha-IR and TNFR1-IR substantially. The results suggest that peri-sciatic administration of rrTNF may induce mechanical allodynia by an autocrine mechanism via activation of the NF-kappaB pathway.
Wei
Xu-Hong
XH
Pain Research Center, Department of Physiology, Zhongshan Medical School of Sun Yat-Sen University, 74 Zhongshan Rd. 2, Guangzhou, PR China.
Zang
Ying
Y
Wu
Chang-You
CY
Xu
Ji-Tian
JT
Xin
Wen-Jun
WJ
Liu
Xian-Guo
XG
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects; D005727:Ganglia, Spinal / Q000187:drug effects / Q000378:metabolism*; D007150:Immunohistochemistry; D007267:Injections; D008264:Macrophages / Q000502:physiology; D008297:Male; D009000:Monocytes / Q000502:physiology; D016328:NF-kappa B / Q000502:physiology*; D010146:Pain / Q000139:chemically induced* / Q000209:etiology; D010523:Peripheral Nervous System Diseases / Q000139:chemically induced / Q000150:complications / Q000473:pathology; D020671:Posterior Horn Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D011994:Recombinant Proteins / Q000008:administration & dosage / Q000494:pharmacology; D012584:Sciatic Nerve / Q000502:physiology*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology; D013601:T-Lymphocytes / Q000502:physiology; D047990:TNF Receptor-Associated Factor 1 / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage / Q000096:biosynthesis* / Q000494:pharmacology*; D015854:Up-Regulation / Q000187:drug effects
D016328:NF-kappa B; D011994:Recombinant Proteins; D047990:TNF Receptor-Associated Factor 1; D014409:Tumor Necrosis Factor-alpha