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NF-kappaB mediated enhancement of potassium currents by the chemokine CXCL1/growth related oncogene in small diameter rat sensory neurons.

Yang RH, Strong JA, Zhang JM - Mol Pain (2009)

Bottom Line: We examined the direct effects of GRO/KC on small diameter DRG neurons, which are predominantly nociceptive.The amplitude of the fast inactivating component increased significantly with no large shifts in the voltage dependence of inactivation.The results suggest that GRO/KC has important effects in inflammatory processes via its direct actions on sensory neurons, and that activation of NF-kappaB is involved in the GRO/KC-induced enhancement of K currents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0531, USA. Rui-Hua.Yang@uc.edu

ABSTRACT

Background: Inflammatory processes play important roles in both neuropathic and inflammatory pain states, but the effects of inflammation per se within the sensory ganglia are not well understood. The cytokine growth-related oncogene (GRO/KC; CXCL1) shows strong, rapid upregulation in dorsal root ganglion (DRG) in both nerve injury and inflammatory pain models. We examined the direct effects of GRO/KC on small diameter DRG neurons, which are predominantly nociceptive. Whole cell voltage clamp technique was used to measure voltage-activated potassium (K) currents in acutely cultured adult rat small diameter sensory neurons. Fluorescently labeled isolectin B4 (IB4) was used to classify cells as IB4-positive or IB4-negative.

Results: In IB4-negative neurons, voltage-activated K current densities of both transient and sustained components were increased after overnight incubation with GRO/KC (1.5 nM), without marked changes in voltage dependence or kinetics. The average values for the slow and fast decay time constants at 20 mV were unchanged by GRO/KC. The amplitude of the fast inactivating component increased significantly with no large shifts in the voltage dependence of inactivation. The increase in K currents was completely blocked by co-incubation with protein synthesis inhibitor cycloheximide (CHX) or NF-kappaB inhibitors pyrrolidine dithiocarbamate (PDTC) or quinazoline (6-Amino-4-(4-phenoxypheny lethylamino;QNZ). In contrast, the voltage-activated K current of IB4-positive neurons was unchanged by GRO/KC. GRO/KC incubation caused no significant changes in the expression level of eight selected voltage-gated K channel genes in quantitative PCR analysis.

Conclusion: The results suggest that GRO/KC has important effects in inflammatory processes via its direct actions on sensory neurons, and that activation of NF-kappaB is involved in the GRO/KC-induced enhancement of K currents.

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Treatment with the protein synthesis inhibitor cycloheximide (CHX, 3.5 μM) blocked the effects of GRO/KC on K currents in IB4-negative cells. CHX had no effect on K currents in control cells (P = 0.755). CHX was added at the same time as GRO/KC and was present throughout the incubation period. GRO (N = 19) and GRO+CHX (N = 18) cells were from 9 cultures; 12 control cells and 8 CHX cells were from 2 cultures.
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Figure 6: Treatment with the protein synthesis inhibitor cycloheximide (CHX, 3.5 μM) blocked the effects of GRO/KC on K currents in IB4-negative cells. CHX had no effect on K currents in control cells (P = 0.755). CHX was added at the same time as GRO/KC and was present throughout the incubation period. GRO (N = 19) and GRO+CHX (N = 18) cells were from 9 cultures; 12 control cells and 8 CHX cells were from 2 cultures.

Mentions: The finding that GRO/KC enhanced the magnitude of K currents in IB4-negative cells, without marked shifts in voltage dependence of activation or kinetics suggested that the primary effect might be an increased number of K channels, and hence that protein synthesis might be required. To test this idea, we conducted experiments using the protein synthesis inhibitor cycloheximide. The results are shown in Figure 6. In general, cycloheximide prevented the GRO/KC-induced increases in K current density, without significantly affecting baseline current densities (P = 0.755). In IB4-negative cells, the only significant differences observed were between the GRO/KC treated groups and all other groups.


NF-kappaB mediated enhancement of potassium currents by the chemokine CXCL1/growth related oncogene in small diameter rat sensory neurons.

Yang RH, Strong JA, Zhang JM - Mol Pain (2009)

Treatment with the protein synthesis inhibitor cycloheximide (CHX, 3.5 μM) blocked the effects of GRO/KC on K currents in IB4-negative cells. CHX had no effect on K currents in control cells (P = 0.755). CHX was added at the same time as GRO/KC and was present throughout the incubation period. GRO (N = 19) and GRO+CHX (N = 18) cells were from 9 cultures; 12 control cells and 8 CHX cells were from 2 cultures.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2698898&req=5

Figure 6: Treatment with the protein synthesis inhibitor cycloheximide (CHX, 3.5 μM) blocked the effects of GRO/KC on K currents in IB4-negative cells. CHX had no effect on K currents in control cells (P = 0.755). CHX was added at the same time as GRO/KC and was present throughout the incubation period. GRO (N = 19) and GRO+CHX (N = 18) cells were from 9 cultures; 12 control cells and 8 CHX cells were from 2 cultures.
Mentions: The finding that GRO/KC enhanced the magnitude of K currents in IB4-negative cells, without marked shifts in voltage dependence of activation or kinetics suggested that the primary effect might be an increased number of K channels, and hence that protein synthesis might be required. To test this idea, we conducted experiments using the protein synthesis inhibitor cycloheximide. The results are shown in Figure 6. In general, cycloheximide prevented the GRO/KC-induced increases in K current density, without significantly affecting baseline current densities (P = 0.755). In IB4-negative cells, the only significant differences observed were between the GRO/KC treated groups and all other groups.

Bottom Line: We examined the direct effects of GRO/KC on small diameter DRG neurons, which are predominantly nociceptive.The amplitude of the fast inactivating component increased significantly with no large shifts in the voltage dependence of inactivation.The results suggest that GRO/KC has important effects in inflammatory processes via its direct actions on sensory neurons, and that activation of NF-kappaB is involved in the GRO/KC-induced enhancement of K currents.

View Article: PubMed Central - HTML - PubMed

Affiliation: Pain Research Center, Department of Anesthesiology, University of Cincinnati College of Medicine, Cincinnati, Ohio 45267-0531, USA. Rui-Hua.Yang@uc.edu

ABSTRACT

Background: Inflammatory processes play important roles in both neuropathic and inflammatory pain states, but the effects of inflammation per se within the sensory ganglia are not well understood. The cytokine growth-related oncogene (GRO/KC; CXCL1) shows strong, rapid upregulation in dorsal root ganglion (DRG) in both nerve injury and inflammatory pain models. We examined the direct effects of GRO/KC on small diameter DRG neurons, which are predominantly nociceptive. Whole cell voltage clamp technique was used to measure voltage-activated potassium (K) currents in acutely cultured adult rat small diameter sensory neurons. Fluorescently labeled isolectin B4 (IB4) was used to classify cells as IB4-positive or IB4-negative.

Results: In IB4-negative neurons, voltage-activated K current densities of both transient and sustained components were increased after overnight incubation with GRO/KC (1.5 nM), without marked changes in voltage dependence or kinetics. The average values for the slow and fast decay time constants at 20 mV were unchanged by GRO/KC. The amplitude of the fast inactivating component increased significantly with no large shifts in the voltage dependence of inactivation. The increase in K currents was completely blocked by co-incubation with protein synthesis inhibitor cycloheximide (CHX) or NF-kappaB inhibitors pyrrolidine dithiocarbamate (PDTC) or quinazoline (6-Amino-4-(4-phenoxypheny lethylamino;QNZ). In contrast, the voltage-activated K current of IB4-positive neurons was unchanged by GRO/KC. GRO/KC incubation caused no significant changes in the expression level of eight selected voltage-gated K channel genes in quantitative PCR analysis.

Conclusion: The results suggest that GRO/KC has important effects in inflammatory processes via its direct actions on sensory neurons, and that activation of NF-kappaB is involved in the GRO/KC-induced enhancement of K currents.

Show MeSH
Related in: MedlinePlus