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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 B1R binding sites in the thoracic spinal cord of control and 4-day STZ-diabetic rats. Shown in (A) are autoradiograms of Control (I), Non-specific (II), STZ (III) and STZ + fluorocitrate (IV), and in (B) are the quantification of specific densities of B1R binding sites in spinal dorsal horn (Laminae I-III). Data are the mean ± S.E.M. of 5 to 6 rats in each group. Statistical comparison to control rats is indicated by **P < 0.01.
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Figure 4: Effect of microglia inhibitors administered 3 h earlier on B1R binding sites in the thoracic spinal cord of control and 4-day STZ-diabetic rats. Shown in (A) are autoradiograms of Control (I), Non-specific (II), STZ (III) and STZ + fluorocitrate (IV), and in (B) are the quantification of specific densities of B1R binding sites in spinal dorsal horn (Laminae I-III). Data are the mean ± S.E.M. of 5 to 6 rats in each group. Statistical comparison to control rats is indicated by **P < 0.01.

Mentions: A low density of specific kinin B1R binding sites was detected in the spinal cord dorsal horn (laminae I-III) of control rats (0.637 fmol/mg protein). This value was increased by 4-fold in spinal cord of STZ-treated rats (2.474 fmol/mg protein). Fluorocitrate (1 nmol, i.t.) administered in STZ-diabetic rats, 3 h prior sacrifice, reduced (-38%) the increased density of specific B1R binding sites induced by diabetes to values (1.532 fmol/mg protein) not significantly different from control density (Figure 4).


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 B1R binding sites in the thoracic spinal cord of control and 4-day STZ-diabetic rats. Shown in (A) are autoradiograms of Control (I), Non-specific (II), STZ (III) and STZ + fluorocitrate (IV), and in (B) are the quantification of specific densities of B1R binding sites in spinal dorsal horn (Laminae I-III). Data are the mean ± S.E.M. of 5 to 6 rats in each group. Statistical comparison to control rats is indicated by **P < 0.01.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 4: Effect of microglia inhibitors administered 3 h earlier on B1R binding sites in the thoracic spinal cord of control and 4-day STZ-diabetic rats. Shown in (A) are autoradiograms of Control (I), Non-specific (II), STZ (III) and STZ + fluorocitrate (IV), and in (B) are the quantification of specific densities of B1R binding sites in spinal dorsal horn (Laminae I-III). Data are the mean ± S.E.M. of 5 to 6 rats in each group. Statistical comparison to control rats is indicated by **P < 0.01.
Mentions: A low density of specific kinin B1R binding sites was detected in the spinal cord dorsal horn (laminae I-III) of control rats (0.637 fmol/mg protein). This value was increased by 4-fold in spinal cord of STZ-treated rats (2.474 fmol/mg protein). Fluorocitrate (1 nmol, i.t.) administered in STZ-diabetic rats, 3 h prior sacrifice, reduced (-38%) the increased density of specific B1R binding sites induced by diabetes to values (1.532 fmol/mg protein) not significantly different from control density (Figure 4).

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