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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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Effect of GRO/KC treatment on voltage-dependence of K current activation in IB4-negative cells. Data from Figure 2 were converted to conductance values using the calculated value of the K Nernst potential. Data were fitted with the Boltzmann equation. Top: the transient component showed a small but significant leftward shift of V1/2, from 14.3 mV in control cells to 8.8 mV in GRO/KC treated cells (p < 0.0005). The Hill slope values were 10.3 and 11.7 mV, respectively (for e-fold change; difference not significant). Bottom: there was no significant change in the voltage dependence of activation of the sustained component. Best-fit shared parameters were -9.3 mV for V1/2 and 15.1 mV for Hill slope.
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Figure 3: Effect of GRO/KC treatment on voltage-dependence of K current activation in IB4-negative cells. Data from Figure 2 were converted to conductance values using the calculated value of the K Nernst potential. Data were fitted with the Boltzmann equation. Top: the transient component showed a small but significant leftward shift of V1/2, from 14.3 mV in control cells to 8.8 mV in GRO/KC treated cells (p < 0.0005). The Hill slope values were 10.3 and 11.7 mV, respectively (for e-fold change; difference not significant). Bottom: there was no significant change in the voltage dependence of activation of the sustained component. Best-fit shared parameters were -9.3 mV for V1/2 and 15.1 mV for Hill slope.

Mentions: The current densities of both transient (P < 0.001) and sustained components (P < 0.001) were increased after overnight incubation with GRO/KC (1.5 nM) in IB4-negative neurons (Figure 2). Two-way repeated-measures analysis of variance indicated that the effect of GRO/KC was significant at all points above 10 mV in IB4-negative cells. These effects were primarily due to increased amplitude of the current, without any large changes in the voltage dependence of activation (Figure 3); however, the activation curve for the transient component showed a small (5.5 mV) but significant leftward shift after GRO/KC incubation.


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)

Effect of GRO/KC treatment on voltage-dependence of K current activation in IB4-negative cells. Data from Figure 2 were converted to conductance values using the calculated value of the K Nernst potential. Data were fitted with the Boltzmann equation. Top: the transient component showed a small but significant leftward shift of V1/2, from 14.3 mV in control cells to 8.8 mV in GRO/KC treated cells (p < 0.0005). The Hill slope values were 10.3 and 11.7 mV, respectively (for e-fold change; difference not significant). Bottom: there was no significant change in the voltage dependence of activation of the sustained component. Best-fit shared parameters were -9.3 mV for V1/2 and 15.1 mV for Hill slope.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Effect of GRO/KC treatment on voltage-dependence of K current activation in IB4-negative cells. Data from Figure 2 were converted to conductance values using the calculated value of the K Nernst potential. Data were fitted with the Boltzmann equation. Top: the transient component showed a small but significant leftward shift of V1/2, from 14.3 mV in control cells to 8.8 mV in GRO/KC treated cells (p < 0.0005). The Hill slope values were 10.3 and 11.7 mV, respectively (for e-fold change; difference not significant). Bottom: there was no significant change in the voltage dependence of activation of the sustained component. Best-fit shared parameters were -9.3 mV for V1/2 and 15.1 mV for Hill slope.
Mentions: The current densities of both transient (P < 0.001) and sustained components (P < 0.001) were increased after overnight incubation with GRO/KC (1.5 nM) in IB4-negative neurons (Figure 2). Two-way repeated-measures analysis of variance indicated that the effect of GRO/KC was significant at all points above 10 mV in IB4-negative cells. These effects were primarily due to increased amplitude of the current, without any large changes in the voltage dependence of activation (Figure 3); however, the activation curve for the transient component showed a small (5.5 mV) but significant leftward shift after GRO/KC incubation.

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