Translocator Protein 18 kDa (TSPO) as a Novel Therapeutic Target for Chronic Pain

Table 1

Role of TSPO and its ligands in chronic pain.

Model	TSPO/ligand	Mechanism	Reference(s)
SNL	TSPO	Inhibit CXCL1-CXCR2-dependent astrocyte-to-neuron signaling and central sensitization	[24, 27]
	Ro5-4864	Downregulate expression of TNF-α; alleviate mechanical allodynia and thermal hyperalgesia	[27, 28]
	FGIN-1-27	Downregulate expression of TNF-α, alleviate mechanical allodynia and thermal hyperalgesia	[27, 28]
CCI	Koumine	Downregulate the expression of TNF-α and IL-1β; inhibit microglia and astrocyte activation	[29, 30]
SNI	Ro5-4864	Downregulate the expression of p-ERK1/2 and BDNF in DRG; improve axonal regeneration and functional recovery	[31, 32]
SCI	PK11195	Assess the role of glial activation	[33]
	ZBD-2	Inhibit chronic activation of microglia and astrocytes; alleviate mechanical allodynia and thermal hyperalgesia	[34, 35]
	Progesterone	Reduce spinal expression of proinflammatory enzymes and cytokines	[36, 37]
CIBP	MZL	Inhibit the IL-6/sIL-6R trans-signaling pathway and MAPK ERK pathway; alleviate thermal hyperalgesia	[26, 38]; [39, 40]
CFA-induced	TSPO	Downregulate proinflammatory mediator IL-1β expression	[41–43]
Monoarthritic model	Ro5-4864	Alleviate mechanical allodynia and thermal hyperalgesia	[41, 44]

SNL: spinal nerve ligation; CCI: chronic constriction injury; SNI: sciatic nerve injury; SCI: spinal cord injury; CIBP: cancer-induced bone pain; CFA: Complete Freund’s adjuvant; TSPO: translocator protein; ZBD-2: N-benzyl-N-ethyl-2-(7,8-dihydro-7-benzyl-8-oxo-2-phenyl-9H-purin-9-yl) acetamide; MZL: midazolam; CXCL1: chemokine CXC motif ligand 1; CXCR2: chemokine CXC motif receptor 2; TNF-α: tumor necrosis factor-α; BDNF: brain-derived neurotrophic factor; DRG: dorsal root ganglion.