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Key role for spinal dorsal horn microglial kinin B1 receptor in early diabetic pain neuropathy.

Talbot S, Chahmi E, Dias JP, Couture R - J Neuroinflammation (2010)

Bottom Line: Inhibition of microglia was confirmed by confocal microscopy with the specific marker Iba-1.Effects of intrathecal and/or systemic administration of B1R agonist (des-Arg9-BK) and antagonists (SSR240612 and R-715) were measured on neuropathic pain manifestations.The enhanced mRNA expression (B1R, IL-1beta, TNF-alpha, TRPV1) and Iba-1 immunoreactivity in the STZ spinal cord were normalized by fluorocitrate or minocycline, yet B1R binding sites were reduced by 38%.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, Faculty of Medicine, Université de Montréal, C,P, 6128, Succursale Downtown, Montréal, Québec, H3C 3J7, Canada.

ABSTRACT

Background: The pro-nociceptive kinin B1 receptor (B1R) is upregulated on sensory C-fibres, astrocytes and microglia in the spinal cord of streptozotocin (STZ)-diabetic rat. This study aims at defining the role of microglial kinin B1R in diabetic pain neuropathy.

Methods: Sprague-Dawley rats were made diabetic with STZ (65 mg/kg, i.p.), and 4 days later, two specific inhibitors of microglial cells (fluorocitrate, 1 nmol, i.t.; minocycline, 10 mg/kg, i.p.) were administered to assess the impact on thermal hyperalgesia, allodynia and mRNA expression (qRT-PCR) of B1R and pro-inflammatory markers. Spinal B1R binding sites ((125I)-HPP-desArg10-Hoe 140) were also measured by quantitative autoradiography. Inhibition of microglia was confirmed by confocal microscopy with the specific marker Iba-1. Effects of intrathecal and/or systemic administration of B1R agonist (des-Arg9-BK) and antagonists (SSR240612 and R-715) were measured on neuropathic pain manifestations.

Results: STZ-diabetic rats displayed significant tactile and cold allodynia compared with control rats. Intrathecal or peripheral blockade of B1R or inhibition of microglia reversed time-dependently tactile and cold allodynia in diabetic rats without affecting basal values in control rats. Microglia inhibition also abolished thermal hyperalgesia and the enhanced allodynia induced by intrathecal des-Arg9-BK without affecting hyperglycemia in STZ rats. The enhanced mRNA expression (B1R, IL-1beta, TNF-alpha, TRPV1) and Iba-1 immunoreactivity in the STZ spinal cord were normalized by fluorocitrate or minocycline, yet B1R binding sites were reduced by 38%.

Conclusion: The upregulation of kinin B1R in spinal dorsal horn microglia by pro-inflammatory cytokines is proposed as a crucial mechanism in early pain neuropathy in STZ-diabetic rats.

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Effect of microglia inhibitors administered 3 h earlier on tail-flick reaction time (MPE %) in control and 4-day STZ-diabetic rats. Shown are the maximal responses measured 1 min after intrathecal injection of either aCSF, 9.6 nmol des-Arg9-BK or 6.6 nmol SP. Data are the mean ± S.E.M. of 5 rats in each group. Within groups, statistical comparison to aCSF is indicated by ††P < 0.01, while statistical comparison to the same agonist in the control group (*) or in STZ + vehicle (+) is indicated by * + P < 0.05; ++ ††P < 0.01; ***P < 0.001.
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Figure 5: Effect of microglia inhibitors administered 3 h earlier on tail-flick reaction time (MPE %) in control and 4-day STZ-diabetic rats. Shown are the maximal responses measured 1 min after intrathecal injection of either aCSF, 9.6 nmol des-Arg9-BK or 6.6 nmol SP. Data are the mean ± S.E.M. of 5 rats in each group. Within groups, statistical comparison to aCSF is indicated by ††P < 0.01, while statistical comparison to the same agonist in the control group (*) or in STZ + vehicle (+) is indicated by * + P < 0.05; ++ ††P < 0.01; ***P < 0.001.

Mentions: As shown in Figure 5, control rats treated with SP (6.6 nmol, i.t.) showed a significant decrease in reaction time to thermal stimulation at 1 min post-injection (-35%) in comparison with aCSF. This response was not significantly increased (-40%) in STZ-diabetic rats. Whereas des-Arg9-BK (9.6 nmol, i.t.) had no significant effect in control rats, a significant decrease in reaction time (-30%) occurred at 1 min post-injection in STZ-diabetic rats. A 3 h pre-treatment with fluorocitrate (1 nmol, i.t.) or minocycline (10 mg/kg, i.p.) abolished the hyperalgesic response to des-Arg9-BK (-5% and + 2%, respectively). Both fluorocitrate and minocycline reduced significantly SP-induced hyperalgesia in STZ-diabetic rats. This result indicates that microglia inhibition may partly contribute to SP-induced hyperalgesia in STZ-diabetic rats. Baseline values of the thermal nociceptive threshold in control rats (9.04 ± 0.79; n = 5) were not affected (P > 0.05) at this early stage of STZ-induced diabetes (9.16 ± 0.45; n = 5) neither by fluorocitrate (9.07 ± 0.93; n = 5) nor minocycline (9.12 ± 0.73; n = 5) treatment.


Key role for spinal dorsal horn microglial kinin B1 receptor in early diabetic pain neuropathy.

Talbot S, Chahmi E, Dias JP, Couture R - J Neuroinflammation (2010)

Effect of microglia inhibitors administered 3 h earlier on tail-flick reaction time (MPE %) in control and 4-day STZ-diabetic rats. Shown are the maximal responses measured 1 min after intrathecal injection of either aCSF, 9.6 nmol des-Arg9-BK or 6.6 nmol SP. Data are the mean ± S.E.M. of 5 rats in each group. Within groups, statistical comparison to aCSF is indicated by ††P < 0.01, while statistical comparison to the same agonist in the control group (*) or in STZ + vehicle (+) is indicated by * + P < 0.05; ++ ††P < 0.01; ***P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2913947&req=5

Figure 5: Effect of microglia inhibitors administered 3 h earlier on tail-flick reaction time (MPE %) in control and 4-day STZ-diabetic rats. Shown are the maximal responses measured 1 min after intrathecal injection of either aCSF, 9.6 nmol des-Arg9-BK or 6.6 nmol SP. Data are the mean ± S.E.M. of 5 rats in each group. Within groups, statistical comparison to aCSF is indicated by ††P < 0.01, while statistical comparison to the same agonist in the control group (*) or in STZ + vehicle (+) is indicated by * + P < 0.05; ++ ††P < 0.01; ***P < 0.001.
Mentions: As shown in Figure 5, control rats treated with SP (6.6 nmol, i.t.) showed a significant decrease in reaction time to thermal stimulation at 1 min post-injection (-35%) in comparison with aCSF. This response was not significantly increased (-40%) in STZ-diabetic rats. Whereas des-Arg9-BK (9.6 nmol, i.t.) had no significant effect in control rats, a significant decrease in reaction time (-30%) occurred at 1 min post-injection in STZ-diabetic rats. A 3 h pre-treatment with fluorocitrate (1 nmol, i.t.) or minocycline (10 mg/kg, i.p.) abolished the hyperalgesic response to des-Arg9-BK (-5% and + 2%, respectively). Both fluorocitrate and minocycline reduced significantly SP-induced hyperalgesia in STZ-diabetic rats. This result indicates that microglia inhibition may partly contribute to SP-induced hyperalgesia in STZ-diabetic rats. Baseline values of the thermal nociceptive threshold in control rats (9.04 ± 0.79; n = 5) were not affected (P > 0.05) at this early stage of STZ-induced diabetes (9.16 ± 0.45; n = 5) neither by fluorocitrate (9.07 ± 0.93; n = 5) nor minocycline (9.12 ± 0.73; n = 5) treatment.

Bottom Line: Inhibition of microglia was confirmed by confocal microscopy with the specific marker Iba-1.Effects of intrathecal and/or systemic administration of B1R agonist (des-Arg9-BK) and antagonists (SSR240612 and R-715) were measured on neuropathic pain manifestations.The enhanced mRNA expression (B1R, IL-1beta, TNF-alpha, TRPV1) and Iba-1 immunoreactivity in the STZ spinal cord were normalized by fluorocitrate or minocycline, yet B1R binding sites were reduced by 38%.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Physiology, Faculty of Medicine, Université de Montréal, C,P, 6128, Succursale Downtown, Montréal, Québec, H3C 3J7, Canada.

ABSTRACT

Background: The pro-nociceptive kinin B1 receptor (B1R) is upregulated on sensory C-fibres, astrocytes and microglia in the spinal cord of streptozotocin (STZ)-diabetic rat. This study aims at defining the role of microglial kinin B1R in diabetic pain neuropathy.

Methods: Sprague-Dawley rats were made diabetic with STZ (65 mg/kg, i.p.), and 4 days later, two specific inhibitors of microglial cells (fluorocitrate, 1 nmol, i.t.; minocycline, 10 mg/kg, i.p.) were administered to assess the impact on thermal hyperalgesia, allodynia and mRNA expression (qRT-PCR) of B1R and pro-inflammatory markers. Spinal B1R binding sites ((125I)-HPP-desArg10-Hoe 140) were also measured by quantitative autoradiography. Inhibition of microglia was confirmed by confocal microscopy with the specific marker Iba-1. Effects of intrathecal and/or systemic administration of B1R agonist (des-Arg9-BK) and antagonists (SSR240612 and R-715) were measured on neuropathic pain manifestations.

Results: STZ-diabetic rats displayed significant tactile and cold allodynia compared with control rats. Intrathecal or peripheral blockade of B1R or inhibition of microglia reversed time-dependently tactile and cold allodynia in diabetic rats without affecting basal values in control rats. Microglia inhibition also abolished thermal hyperalgesia and the enhanced allodynia induced by intrathecal des-Arg9-BK without affecting hyperglycemia in STZ rats. The enhanced mRNA expression (B1R, IL-1beta, TNF-alpha, TRPV1) and Iba-1 immunoreactivity in the STZ spinal cord were normalized by fluorocitrate or minocycline, yet B1R binding sites were reduced by 38%.

Conclusion: The upregulation of kinin B1R in spinal dorsal horn microglia by pro-inflammatory cytokines is proposed as a crucial mechanism in early pain neuropathy in STZ-diabetic rats.

Show MeSH
Related in: MedlinePlus