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Antiallodynic effects of alpha lipoic acid in an optimized RR-EAE mouse model of MS-neuropathic pain are accompanied by attenuation of upregulated BDNF-TrkB-ERK signaling in the dorsal horn of the spinal cord.

Khan N, Gordon R, Woodruff TM, Smith MT - Pharmacol Res Perspect (2015)

Bottom Line: In an experimental autoimmune encephalomyelitis (EAE)-mouse model of MS, chronic alpha lipoic acid (ALA) treatment reduced clinical disease severity, but MS-neuropathic pain was not assessed.The antiallodynic effect of ALA (10 mg kg(-1) day(-1)) was associated with a marked reduction in the aforementioned spinal dorsal horn markers to match their respective levels in the vehicle-treated sham-mice.Our findings suggest that ALA at 10 mg kg(-1) day(-1) produced its antiallodynic effects in RR-EAE mice by reducing augmented CD3(+) T-cell infiltration and BDNF-TrkB-ERK signaling in the spinal dorsal horn.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrated Preclinical Drug Development, University of Queensland St Lucia Campus, Brisbane, Queensland, 4072, Australia ; School of Pharmacy, University of Queensland, Pharmacy Australia Center of Excellence Woolloongabba, Brisbane, Queensland, 4102, Australia.

ABSTRACT
Neuropathic pain may affect patients with multiple sclerosis (MS) even in early disease. In an experimental autoimmune encephalomyelitis (EAE)-mouse model of MS, chronic alpha lipoic acid (ALA) treatment reduced clinical disease severity, but MS-neuropathic pain was not assessed. Hence, we investigated the pain-relieving efficacy and mode of action of ALA using our optimized relapsing-remitting (RR)-EAE mouse model of MS-associated neuropathic pain. C57BL/6 mice were immunized with MOG35-55 and adjuvants (Quil A and pertussis toxin) to induce RR-EAE; sham-mice received adjuvants only. RR-EAE mice received subcutaneous ALA (3 or 10 mg kg(-1) day(-1)) or vehicle for 21 days (15-35 d.p.i.; [days postimmunization]); sham-mice received vehicle. Hindpaw hypersensitivity was assessed blinded using von Frey filaments. Following euthanasia (day 35 d.p.i.), lumbar spinal cords were removed for immunohistochemical and molecular biological assessments. Fully developed mechanical allodynia in the bilateral hindpaws of vehicle-treated RR-EAE mice was accompanied by marked CD3(+) T-cell infiltration, microglia activation, and increased brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling in the dorsal horn of the lumbar spinal cord. Consequently, phospho-ERK, a marker of central sensitization in neuropathic pain, was upregulated in the spinal dorsal horn. Importantly, hindpaw hypersensitivity was completely attenuated in RR-EAE mice administered ALA at 10 mg kg(-1) day(-1) but not 3 mg kg(-1) day(-1). The antiallodynic effect of ALA (10 mg kg(-1) day(-1)) was associated with a marked reduction in the aforementioned spinal dorsal horn markers to match their respective levels in the vehicle-treated sham-mice. Our findings suggest that ALA at 10 mg kg(-1) day(-1) produced its antiallodynic effects in RR-EAE mice by reducing augmented CD3(+) T-cell infiltration and BDNF-TrkB-ERK signaling in the spinal dorsal horn.

No MeSH data available.


Related in: MedlinePlus

Western blot analyses of microglial activation (Iba-1), as well as expression levels of BDNF, TrkB, pERK, and total ERK in lumbar (L4-L6) spinal cord of RR-EAE mice administered ALA at 10 mg kg−1 day−1 or vehicle, for 3 weeks relative to the respective data for the lumbar spinal cord of vehicle-treated sham-mice. Specifically, for vehicle-treated RR-EAE mice, there was a significant increase in (A) the extent of microglial (Iba-1) activation (approximately threefold; F(2,6) = 29.82; P < 0.05) (B) expression levels of the BDNF isoforms, Pro-BDNF (approximately twofold; F(2,6) = 20.31; P < 0.05) and truncated BDNF (∼2.2-fold; F(2,6) = 24.90; P < 0.05) but not mature BDNF (F(2,6) = 1.79; P > 0.05) (C) expression levels of the TrkB isoforms, truncated TrkB (∼2.3-fold; F(2,6) = 164.7; P < 0.05) and full-length TrkB (approximately fourfold; F(2,6) = 125.2; P < 0.05), as well as (D) expression levels of phospho-ERK (F(2,6) = 16.43; P < 0.05) but not total ERK (F(2,6) = 4.066; P > 0.05) c.f. the respective data for lumbar spinal cord of vehicle-treated sham-mice. For RR-EAE mice treated with ALA (10 mg kg−1 day−1) for 21 days, there were no significant differences (P > 0.05) in expression levels of any of the aforementioned lumbar spinal cord markers from the respective data for the lumbar spinal cord of vehicle-treated sham-mice *P < 0.05 (one-way ANOVA followed by Tukey’s multiple comparison test). EAE, experimental autoimmune encephalomyelitis; FL, full-length; mBDNF, mature-BDNF; Trunc, Truncated; Veh, vehicle; ALA, alpha lipoic acid; BDNF, brain-derived neurotrophic factor; TrkB, tyrosine kinase B.
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fig04: Western blot analyses of microglial activation (Iba-1), as well as expression levels of BDNF, TrkB, pERK, and total ERK in lumbar (L4-L6) spinal cord of RR-EAE mice administered ALA at 10 mg kg−1 day−1 or vehicle, for 3 weeks relative to the respective data for the lumbar spinal cord of vehicle-treated sham-mice. Specifically, for vehicle-treated RR-EAE mice, there was a significant increase in (A) the extent of microglial (Iba-1) activation (approximately threefold; F(2,6) = 29.82; P < 0.05) (B) expression levels of the BDNF isoforms, Pro-BDNF (approximately twofold; F(2,6) = 20.31; P < 0.05) and truncated BDNF (∼2.2-fold; F(2,6) = 24.90; P < 0.05) but not mature BDNF (F(2,6) = 1.79; P > 0.05) (C) expression levels of the TrkB isoforms, truncated TrkB (∼2.3-fold; F(2,6) = 164.7; P < 0.05) and full-length TrkB (approximately fourfold; F(2,6) = 125.2; P < 0.05), as well as (D) expression levels of phospho-ERK (F(2,6) = 16.43; P < 0.05) but not total ERK (F(2,6) = 4.066; P > 0.05) c.f. the respective data for lumbar spinal cord of vehicle-treated sham-mice. For RR-EAE mice treated with ALA (10 mg kg−1 day−1) for 21 days, there were no significant differences (P > 0.05) in expression levels of any of the aforementioned lumbar spinal cord markers from the respective data for the lumbar spinal cord of vehicle-treated sham-mice *P < 0.05 (one-way ANOVA followed by Tukey’s multiple comparison test). EAE, experimental autoimmune encephalomyelitis; FL, full-length; mBDNF, mature-BDNF; Trunc, Truncated; Veh, vehicle; ALA, alpha lipoic acid; BDNF, brain-derived neurotrophic factor; TrkB, tyrosine kinase B.

Mentions: Next, we examined RR-EAE mice for microglial activation, an important player in MS-induced neuropathic pain (Khan and Smith 2014). For vehicle-treated RR-EAE mice at 35 d.p.i., microglial activation, as measured by CD11b or Iba-1 expression, in the lumbar spinal dorsal horn was approximately threefold higher (F(2,33) = 45.57; P < 0.05; Fig.3) c.f. vehicle-treated sham-mice, with a similar difference between the two groups when assessed by western blot (F(2,6) = 29.82; P < 0.05; Fig.4). However, for RR-EAE mice administered ALA at 10 mg kg−1 day−1 for 21 days, levels of microglial expression in the spinal dorsal horn did not differ significantly c.f. vehicle-treated sham-mice when assessed by IHC (F(2,33) = 45.57; P > 0.05) or western blot (F(2,6) = 29.82; P > 0.05).


Antiallodynic effects of alpha lipoic acid in an optimized RR-EAE mouse model of MS-neuropathic pain are accompanied by attenuation of upregulated BDNF-TrkB-ERK signaling in the dorsal horn of the spinal cord.

Khan N, Gordon R, Woodruff TM, Smith MT - Pharmacol Res Perspect (2015)

Western blot analyses of microglial activation (Iba-1), as well as expression levels of BDNF, TrkB, pERK, and total ERK in lumbar (L4-L6) spinal cord of RR-EAE mice administered ALA at 10 mg kg−1 day−1 or vehicle, for 3 weeks relative to the respective data for the lumbar spinal cord of vehicle-treated sham-mice. Specifically, for vehicle-treated RR-EAE mice, there was a significant increase in (A) the extent of microglial (Iba-1) activation (approximately threefold; F(2,6) = 29.82; P < 0.05) (B) expression levels of the BDNF isoforms, Pro-BDNF (approximately twofold; F(2,6) = 20.31; P < 0.05) and truncated BDNF (∼2.2-fold; F(2,6) = 24.90; P < 0.05) but not mature BDNF (F(2,6) = 1.79; P > 0.05) (C) expression levels of the TrkB isoforms, truncated TrkB (∼2.3-fold; F(2,6) = 164.7; P < 0.05) and full-length TrkB (approximately fourfold; F(2,6) = 125.2; P < 0.05), as well as (D) expression levels of phospho-ERK (F(2,6) = 16.43; P < 0.05) but not total ERK (F(2,6) = 4.066; P > 0.05) c.f. the respective data for lumbar spinal cord of vehicle-treated sham-mice. For RR-EAE mice treated with ALA (10 mg kg−1 day−1) for 21 days, there were no significant differences (P > 0.05) in expression levels of any of the aforementioned lumbar spinal cord markers from the respective data for the lumbar spinal cord of vehicle-treated sham-mice *P < 0.05 (one-way ANOVA followed by Tukey’s multiple comparison test). EAE, experimental autoimmune encephalomyelitis; FL, full-length; mBDNF, mature-BDNF; Trunc, Truncated; Veh, vehicle; ALA, alpha lipoic acid; BDNF, brain-derived neurotrophic factor; TrkB, tyrosine kinase B.
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Related In: Results  -  Collection

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fig04: Western blot analyses of microglial activation (Iba-1), as well as expression levels of BDNF, TrkB, pERK, and total ERK in lumbar (L4-L6) spinal cord of RR-EAE mice administered ALA at 10 mg kg−1 day−1 or vehicle, for 3 weeks relative to the respective data for the lumbar spinal cord of vehicle-treated sham-mice. Specifically, for vehicle-treated RR-EAE mice, there was a significant increase in (A) the extent of microglial (Iba-1) activation (approximately threefold; F(2,6) = 29.82; P < 0.05) (B) expression levels of the BDNF isoforms, Pro-BDNF (approximately twofold; F(2,6) = 20.31; P < 0.05) and truncated BDNF (∼2.2-fold; F(2,6) = 24.90; P < 0.05) but not mature BDNF (F(2,6) = 1.79; P > 0.05) (C) expression levels of the TrkB isoforms, truncated TrkB (∼2.3-fold; F(2,6) = 164.7; P < 0.05) and full-length TrkB (approximately fourfold; F(2,6) = 125.2; P < 0.05), as well as (D) expression levels of phospho-ERK (F(2,6) = 16.43; P < 0.05) but not total ERK (F(2,6) = 4.066; P > 0.05) c.f. the respective data for lumbar spinal cord of vehicle-treated sham-mice. For RR-EAE mice treated with ALA (10 mg kg−1 day−1) for 21 days, there were no significant differences (P > 0.05) in expression levels of any of the aforementioned lumbar spinal cord markers from the respective data for the lumbar spinal cord of vehicle-treated sham-mice *P < 0.05 (one-way ANOVA followed by Tukey’s multiple comparison test). EAE, experimental autoimmune encephalomyelitis; FL, full-length; mBDNF, mature-BDNF; Trunc, Truncated; Veh, vehicle; ALA, alpha lipoic acid; BDNF, brain-derived neurotrophic factor; TrkB, tyrosine kinase B.
Mentions: Next, we examined RR-EAE mice for microglial activation, an important player in MS-induced neuropathic pain (Khan and Smith 2014). For vehicle-treated RR-EAE mice at 35 d.p.i., microglial activation, as measured by CD11b or Iba-1 expression, in the lumbar spinal dorsal horn was approximately threefold higher (F(2,33) = 45.57; P < 0.05; Fig.3) c.f. vehicle-treated sham-mice, with a similar difference between the two groups when assessed by western blot (F(2,6) = 29.82; P < 0.05; Fig.4). However, for RR-EAE mice administered ALA at 10 mg kg−1 day−1 for 21 days, levels of microglial expression in the spinal dorsal horn did not differ significantly c.f. vehicle-treated sham-mice when assessed by IHC (F(2,33) = 45.57; P > 0.05) or western blot (F(2,6) = 29.82; P > 0.05).

Bottom Line: In an experimental autoimmune encephalomyelitis (EAE)-mouse model of MS, chronic alpha lipoic acid (ALA) treatment reduced clinical disease severity, but MS-neuropathic pain was not assessed.The antiallodynic effect of ALA (10 mg kg(-1) day(-1)) was associated with a marked reduction in the aforementioned spinal dorsal horn markers to match their respective levels in the vehicle-treated sham-mice.Our findings suggest that ALA at 10 mg kg(-1) day(-1) produced its antiallodynic effects in RR-EAE mice by reducing augmented CD3(+) T-cell infiltration and BDNF-TrkB-ERK signaling in the spinal dorsal horn.

View Article: PubMed Central - PubMed

Affiliation: Center for Integrated Preclinical Drug Development, University of Queensland St Lucia Campus, Brisbane, Queensland, 4072, Australia ; School of Pharmacy, University of Queensland, Pharmacy Australia Center of Excellence Woolloongabba, Brisbane, Queensland, 4102, Australia.

ABSTRACT
Neuropathic pain may affect patients with multiple sclerosis (MS) even in early disease. In an experimental autoimmune encephalomyelitis (EAE)-mouse model of MS, chronic alpha lipoic acid (ALA) treatment reduced clinical disease severity, but MS-neuropathic pain was not assessed. Hence, we investigated the pain-relieving efficacy and mode of action of ALA using our optimized relapsing-remitting (RR)-EAE mouse model of MS-associated neuropathic pain. C57BL/6 mice were immunized with MOG35-55 and adjuvants (Quil A and pertussis toxin) to induce RR-EAE; sham-mice received adjuvants only. RR-EAE mice received subcutaneous ALA (3 or 10 mg kg(-1) day(-1)) or vehicle for 21 days (15-35 d.p.i.; [days postimmunization]); sham-mice received vehicle. Hindpaw hypersensitivity was assessed blinded using von Frey filaments. Following euthanasia (day 35 d.p.i.), lumbar spinal cords were removed for immunohistochemical and molecular biological assessments. Fully developed mechanical allodynia in the bilateral hindpaws of vehicle-treated RR-EAE mice was accompanied by marked CD3(+) T-cell infiltration, microglia activation, and increased brain-derived neurotrophic factor (BDNF)-tyrosine kinase B (TrkB) signaling in the dorsal horn of the lumbar spinal cord. Consequently, phospho-ERK, a marker of central sensitization in neuropathic pain, was upregulated in the spinal dorsal horn. Importantly, hindpaw hypersensitivity was completely attenuated in RR-EAE mice administered ALA at 10 mg kg(-1) day(-1) but not 3 mg kg(-1) day(-1). The antiallodynic effect of ALA (10 mg kg(-1) day(-1)) was associated with a marked reduction in the aforementioned spinal dorsal horn markers to match their respective levels in the vehicle-treated sham-mice. Our findings suggest that ALA at 10 mg kg(-1) day(-1) produced its antiallodynic effects in RR-EAE mice by reducing augmented CD3(+) T-cell infiltration and BDNF-TrkB-ERK signaling in the spinal dorsal horn.

No MeSH data available.


Related in: MedlinePlus