Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 （C-C motif chemokine ligand 2） has been shown ...Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 （C-C motif chemokine ligand 2） has been shown to enhance N-methyl-D-aspartate （NMDA）-induced currents in spinal outer lamina II （Iio） neurons. However, the exact molecular, synaptic, and cellular mechanisms by which CCL2 modulates central sensitization are still unclear. We found that spinal injection of the CCR2 antagonist RS504393 attenuated CCL2- and inflammation-induced hyperalgesia. Single-cell RT-PCR revealed CCR2 expres- sion in excitatory vesicular glutamate transporter subtype 2-positive （VGLUT2＋） neurons. CCL2 increased NMDA- induced currents in CCR2＋/VGLUT2＋ neurons in lamina IIo; it also enhanced the synaptic NMDA currents evoked by dorsal root stimulation; and furthermore, it increased the total and synaptic NMDA currents in somatostatin- expressing excitatory neurons. Finally, intrathecal RS504393 reversed the long-term potentiation evoked in the spinal cord by C-fiber stimulation. Our findings suggest that CCL2 directly modulates synaptic plasticity in CCR2- expressing excitatory neurons in spinal lamina Iio, and this underlies the generation of central sensitization in patho- logical pain.展开更多
Previous studies have shown that CCL2(C-C motif chemokine ligand 2)induces chronic pain,but the exact mechanisms are still unknown.Here,we established models to explore the potential mechanisms.Behavioral experiments ...Previous studies have shown that CCL2(C-C motif chemokine ligand 2)induces chronic pain,but the exact mechanisms are still unknown.Here,we established models to explore the potential mechanisms.Behavioral experiments revealed that an antagonist of extracellular signal-regulated kinase(ERK)inhibited not only CCL2-induced inflammatory pain,but also pain responses induced by complete Freund’s adjuvant.We posed the question of the intracellular signaling cascade involved.Subsequent experiments showed that CCL2 up-regulated the expression of phosphorylated ERK(pERK)and N-methyl D-aspartate receptor[NMDAR]subtype 2B(GluN2B);meanwhile,antagonists of CCR2 and ERK effectively reversed these phenomena.Whole-cell patchclamp recordings revealed that CCL2 enhanced the NMDAR-induced currents via activating the pERK pathway,which was blocked by antagonists of GluN2B and ERK.In summary,we demonstrate that CCL2 directly interacts with CCR2 to enhance NMDAR-induced currents,eventually leading to inflammatory pain mainly through the CCL2-CCR2-pERK-GluN2B pathway.展开更多
Recent studies have shown that the chemokine receptor CXCR3 and its ligand CXCL10 in the dorsal root ganglion mediate itch in experimental allergic contact dermatitis （ACD）. CXCR3 in the spinal cord also con- tribut...Recent studies have shown that the chemokine receptor CXCR3 and its ligand CXCL10 in the dorsal root ganglion mediate itch in experimental allergic contact dermatitis （ACD）. CXCR3 in the spinal cord also con- tributes to the maintenance of neuropathic pain. However, whether spinal CXCR3 is involved in acute or chronic itch remains unclear. Here, we report that Cxcr3-/- mice showed normal scratching in acute itch models but reduced scratching in chronic itch models of dry skin and ACD. In contrast, both formalin-induced acute pain and complete Freund＇s adjuvant-induced chronic inflammatory pain were reduced in Cxcr3-/- mice. In addition, the expression of CXCR3 and CXCL10 was increased in the spinal cord in the dry skin model induced by acetone and diethyl ether followed by water （AEW）. Intrathecal injection of a CXCR3 antagonist alleviated AEW-induced itch. Further- more, touch-elicited itch （alloknesis） after compound 48/80 or AEW treatment was suppressed in Cxcr3-/- mice. Finally, AEW-induced astrocyte activation was inhibited in Cxcr3-/- mice. Taken together, these data suggest that spinal CXCR3 mediates chronic itch and alloknesis, and targeting CXCR3 may provide effective treatment for chronic pruritus.展开更多
基金supported by grants from the National Natural Science Foundation of China(31400949,81502102,31471059,81371498,and 31371121)NIH R01,USA Grants(DE17794,DE22743,and NS87988)
文摘Mounting evidence supports an important role of chemokines, produced by spinal cord astrocytes, in promoting central sensitization and chronic pain. In particular, CCL2 （C-C motif chemokine ligand 2） has been shown to enhance N-methyl-D-aspartate （NMDA）-induced currents in spinal outer lamina II （Iio） neurons. However, the exact molecular, synaptic, and cellular mechanisms by which CCL2 modulates central sensitization are still unclear. We found that spinal injection of the CCR2 antagonist RS504393 attenuated CCL2- and inflammation-induced hyperalgesia. Single-cell RT-PCR revealed CCR2 expres- sion in excitatory vesicular glutamate transporter subtype 2-positive （VGLUT2＋） neurons. CCL2 increased NMDA- induced currents in CCR2＋/VGLUT2＋ neurons in lamina IIo; it also enhanced the synaptic NMDA currents evoked by dorsal root stimulation; and furthermore, it increased the total and synaptic NMDA currents in somatostatin- expressing excitatory neurons. Finally, intrathecal RS504393 reversed the long-term potentiation evoked in the spinal cord by C-fiber stimulation. Our findings suggest that CCL2 directly modulates synaptic plasticity in CCR2- expressing excitatory neurons in spinal lamina Iio, and this underlies the generation of central sensitization in patho- logical pain.
基金grants from the National Natural Science Foundation of China(81870867,31671088,31471059,and 81502102)the Natural Science Foundation of Shaanxi Province,China(2019SF-071 and 2017ZDJC-01)。
文摘Previous studies have shown that CCL2(C-C motif chemokine ligand 2)induces chronic pain,but the exact mechanisms are still unknown.Here,we established models to explore the potential mechanisms.Behavioral experiments revealed that an antagonist of extracellular signal-regulated kinase(ERK)inhibited not only CCL2-induced inflammatory pain,but also pain responses induced by complete Freund’s adjuvant.We posed the question of the intracellular signaling cascade involved.Subsequent experiments showed that CCL2 up-regulated the expression of phosphorylated ERK(pERK)and N-methyl D-aspartate receptor[NMDAR]subtype 2B(GluN2B);meanwhile,antagonists of CCR2 and ERK effectively reversed these phenomena.Whole-cell patchclamp recordings revealed that CCL2 enhanced the NMDAR-induced currents via activating the pERK pathway,which was blocked by antagonists of GluN2B and ERK.In summary,we demonstrate that CCL2 directly interacts with CCR2 to enhance NMDAR-induced currents,eventually leading to inflammatory pain mainly through the CCL2-CCR2-pERK-GluN2B pathway.
基金supported by Grants from the National Natural Science Foundation of China(31371121,81300954,and 31671091)the Priority Academic Program Development of Jiangsu Higher Education Institutions,China
文摘Recent studies have shown that the chemokine receptor CXCR3 and its ligand CXCL10 in the dorsal root ganglion mediate itch in experimental allergic contact dermatitis （ACD）. CXCR3 in the spinal cord also con- tributes to the maintenance of neuropathic pain. However, whether spinal CXCR3 is involved in acute or chronic itch remains unclear. Here, we report that Cxcr3-/- mice showed normal scratching in acute itch models but reduced scratching in chronic itch models of dry skin and ACD. In contrast, both formalin-induced acute pain and complete Freund＇s adjuvant-induced chronic inflammatory pain were reduced in Cxcr3-/- mice. In addition, the expression of CXCR3 and CXCL10 was increased in the spinal cord in the dry skin model induced by acetone and diethyl ether followed by water （AEW）. Intrathecal injection of a CXCR3 antagonist alleviated AEW-induced itch. Further- more, touch-elicited itch （alloknesis） after compound 48/80 or AEW treatment was suppressed in Cxcr3-/- mice. Finally, AEW-induced astrocyte activation was inhibited in Cxcr3-/- mice. Taken together, these data suggest that spinal CXCR3 mediates chronic itch and alloknesis, and targeting CXCR3 may provide effective treatment for chronic pruritus.
