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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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Time-course of the inhibitory effect of B1R antagonists administered in the periphery (A, C) or intrathecally (B, D) on paw withdrawal response frequency (%) to cold stimulation in control and 4-day STZ-diabetic rats. All treatments were given at time 0 h. Data represent the mean ± S.E.M. of 4 to 12 rats in each group. Statistical comparison to control + vehicle (*) and STZ + vehicle (+) is indicated by ++P < 0.01; *** +++P < 0.001.
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Figure 8: Time-course of the inhibitory effect of B1R antagonists administered in the periphery (A, C) or intrathecally (B, D) on paw withdrawal response frequency (%) to cold stimulation in control and 4-day STZ-diabetic rats. All treatments were given at time 0 h. Data represent the mean ± S.E.M. of 4 to 12 rats in each group. Statistical comparison to control + vehicle (*) and STZ + vehicle (+) is indicated by ++P < 0.01; *** +++P < 0.001.

Mentions: STZ-diabetic rats presented significant tactile (Figures 6, 7) and cold allodynia (Figures 8,9) in comparison with vehicle-matched control rats. These responses were stable when the tests were performed over a period of 24 h. The B1R antagonists, SSR240612 and R-715, administered systemically blocked in a transient and reversible manner cold and tactile allodynia between 3 and 6 h post-treatment in STZ-diabetic rats. Intrathecal treatments with B1R antagonists provided more rapid and shorter inhibition of allodynia (1-3 h) than systemic treatments (3-6 h). Fluorocitrate and minocycline caused a similar pattern of inhibition on tactile allodynia at 1 and 3 h post-treatment while the inhibition of cold allodynia with microglia inhibitors lasted at least up to 6 h post-treatment. The same treatments with B1R antagonists or microglia inhibitors had no consequence on baseline values in control rats.


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)

Time-course of the inhibitory effect of B1R antagonists administered in the periphery (A, C) or intrathecally (B, D) on paw withdrawal response frequency (%) to cold stimulation in control and 4-day STZ-diabetic rats. All treatments were given at time 0 h. Data represent the mean ± S.E.M. of 4 to 12 rats in each group. Statistical comparison to control + vehicle (*) and STZ + vehicle (+) is indicated by ++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 8: Time-course of the inhibitory effect of B1R antagonists administered in the periphery (A, C) or intrathecally (B, D) on paw withdrawal response frequency (%) to cold stimulation in control and 4-day STZ-diabetic rats. All treatments were given at time 0 h. Data represent the mean ± S.E.M. of 4 to 12 rats in each group. Statistical comparison to control + vehicle (*) and STZ + vehicle (+) is indicated by ++P < 0.01; *** +++P < 0.001.
Mentions: STZ-diabetic rats presented significant tactile (Figures 6, 7) and cold allodynia (Figures 8,9) in comparison with vehicle-matched control rats. These responses were stable when the tests were performed over a period of 24 h. The B1R antagonists, SSR240612 and R-715, administered systemically blocked in a transient and reversible manner cold and tactile allodynia between 3 and 6 h post-treatment in STZ-diabetic rats. Intrathecal treatments with B1R antagonists provided more rapid and shorter inhibition of allodynia (1-3 h) than systemic treatments (3-6 h). Fluorocitrate and minocycline caused a similar pattern of inhibition on tactile allodynia at 1 and 3 h post-treatment while the inhibition of cold allodynia with microglia inhibitors lasted at least up to 6 h post-treatment. The same treatments with B1R antagonists or microglia inhibitors had no consequence on baseline values in control rats.

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