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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 effect of B1R antagonists administered in the periphery (A) or intrathecally (B) on blood glucose concentration in control and 4-day STZ-diabetic rats. Data are the mean ± S.E.M. of 5 rats in each group. Statistical comparison to control (*) or untreated (0 h) STZ-treated rats (+) is indicated by + P < 0.05, ***P < 0.001.
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Figure 2: Time-course effect of B1R antagonists administered in the periphery (A) or intrathecally (B) on blood glucose concentration in control and 4-day STZ-diabetic rats. Data are the mean ± S.E.M. of 5 rats in each group. Statistical comparison to control (*) or untreated (0 h) STZ-treated rats (+) is indicated by + P < 0.05, ***P < 0.001.

Mentions: As depicted in Figure 1, rats which received STZ (65 mg/kg, i.p.) 4 days earlier displayed a significant increase of blood glucose concentration compared with vehicle-matched control rats. Blood glucose levels in control and STZ-treated rats were not affected by fluorocitrate (1 nmol, i.t.) or minocycline (10 mg/kg, i.p.) injected 3 h earlier (Figure 1). SSR240612 (10 mg/kg, p.o.) reduced significantly hyperglycemia in STZ-treated rats at 3 h post-gavage; the inhibitory effect of the B1R antagonist was not significant at 6 h and was completely resolved at 24 h. A similar pattern of anti-hyperglycemia was seen with R-715 (10 mg/kg, i.p.), yet the inhibitory effect did not reach statistical significance (Figure 2-A). Either antagonist did not affect glycemia in control rats. Intrathecally administered R-715 and SSR240612 (10 μg) failed to alter blood glucose levels in both control and STZ-diabetic rats (Figure 2-B).


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 effect of B1R antagonists administered in the periphery (A) or intrathecally (B) on blood glucose concentration in control and 4-day STZ-diabetic rats. Data are the mean ± S.E.M. of 5 rats in each group. Statistical comparison to control (*) or untreated (0 h) STZ-treated rats (+) is indicated by + P < 0.05, ***P < 0.001.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 2: Time-course effect of B1R antagonists administered in the periphery (A) or intrathecally (B) on blood glucose concentration in control and 4-day STZ-diabetic rats. Data are the mean ± S.E.M. of 5 rats in each group. Statistical comparison to control (*) or untreated (0 h) STZ-treated rats (+) is indicated by + P < 0.05, ***P < 0.001.
Mentions: As depicted in Figure 1, rats which received STZ (65 mg/kg, i.p.) 4 days earlier displayed a significant increase of blood glucose concentration compared with vehicle-matched control rats. Blood glucose levels in control and STZ-treated rats were not affected by fluorocitrate (1 nmol, i.t.) or minocycline (10 mg/kg, i.p.) injected 3 h earlier (Figure 1). SSR240612 (10 mg/kg, p.o.) reduced significantly hyperglycemia in STZ-treated rats at 3 h post-gavage; the inhibitory effect of the B1R antagonist was not significant at 6 h and was completely resolved at 24 h. A similar pattern of anti-hyperglycemia was seen with R-715 (10 mg/kg, i.p.), yet the inhibitory effect did not reach statistical significance (Figure 2-A). Either antagonist did not affect glycemia in control rats. Intrathecally administered R-715 and SSR240612 (10 μg) failed to alter blood glucose levels in both control and STZ-diabetic rats (Figure 2-B).

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