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Motor, visual and emotional deficits in mice after closed-head mild traumatic brain injury are alleviated by the novel CB2 inverse agonist SMM-189.

Reiner A, Heldt SA, Presley CS, Guley NH, Elberger AJ, Deng Y, D'Surney L, Rogers JT, Ferrell J, Bu W, Del Mar N, Honig MG, Gurley SN, Moore BM - Int J Mol Sci (2014)

Bottom Line: Because microglial activation can worsen brain damage after a concussive event and because microglia can be modulated by their cannabinoid type 2 receptors (CB2), we evaluated the effectiveness of the novel CB2 receptor inverse agonist SMM-189 in altering microglial activation and mitigating deficits after mild TBI.Our results suggest that treatment with the CB2 inverse agonist SMM-189 after a mild TBI event can reduce its adverse consequences by beneficially modulating microglial activation.These findings recommend further evaluation of CB2 inverse agonists as a novel therapeutic approach for treating mild TBI.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, the University of Tennessee Health Science Center, Memphis, TN 38163, USA. areiner@uthsc.edu.

ABSTRACT
We have developed a focal blast model of closed-head mild traumatic brain injury (TBI) in mice. As true for individuals that have experienced mild TBI, mice subjected to 50-60 psi blast show motor, visual and emotional deficits, diffuse axonal injury and microglial activation, but no overt neuron loss. Because microglial activation can worsen brain damage after a concussive event and because microglia can be modulated by their cannabinoid type 2 receptors (CB2), we evaluated the effectiveness of the novel CB2 receptor inverse agonist SMM-189 in altering microglial activation and mitigating deficits after mild TBI. In vitro analysis indicated that SMM-189 converted human microglia from the pro-inflammatory M1 phenotype to the pro-healing M2 phenotype. Studies in mice showed that daily administration of SMM-189 for two weeks beginning shortly after blast greatly reduced the motor, visual, and emotional deficits otherwise evident after 50-60 psi blasts, and prevented brain injury that may contribute to these deficits. Our results suggest that treatment with the CB2 inverse agonist SMM-189 after a mild TBI event can reduce its adverse consequences by beneficially modulating microglial activation. These findings recommend further evaluation of CB2 inverse agonists as a novel therapeutic approach for treating mild TBI.

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Effect of SMM-189 on cytokines secreted from primary human microglial cells in vitro. Primary human microglia were treated with lipopolysaccharide (LPS) or vehicle, and then SMM-189 or vehicle was added one hour later. Cytokines were then assayed 17 h subsequently. LPS significantly increased cytokine levels above that in control. SMM-189 by itself also significantly elevated interferon-gamma (IFN-γ) and interleukin-12p70 (IL-12p70), but to a lesser extent than LPS. SMM-189 attenuated the effect of LPS on cytokine secretion, significantly reducing IFN-γ, interleukin-6 (IL-6) and interleukin-10 (IL-10) below LPS-only levels and restoring IFN-γ and IL-12p70 to SMM-189-alone levels. SMM-189 also trended toward reducing TNFα. Asterisks above bars spanning the LPS-alone and LPS + SMM-189 columns, or the SMM-189-alone and LPS + SMM-189 columns indicate significance levels for the comparison between these two conditions. Asterisks on a column indicate a significant difference from the control condition. NS—Not significant, *p < 0.05, **p < 0.005, ***p < 0.0005.
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ijms-16-00758-f001: Effect of SMM-189 on cytokines secreted from primary human microglial cells in vitro. Primary human microglia were treated with lipopolysaccharide (LPS) or vehicle, and then SMM-189 or vehicle was added one hour later. Cytokines were then assayed 17 h subsequently. LPS significantly increased cytokine levels above that in control. SMM-189 by itself also significantly elevated interferon-gamma (IFN-γ) and interleukin-12p70 (IL-12p70), but to a lesser extent than LPS. SMM-189 attenuated the effect of LPS on cytokine secretion, significantly reducing IFN-γ, interleukin-6 (IL-6) and interleukin-10 (IL-10) below LPS-only levels and restoring IFN-γ and IL-12p70 to SMM-189-alone levels. SMM-189 also trended toward reducing TNFα. Asterisks above bars spanning the LPS-alone and LPS + SMM-189 columns, or the SMM-189-alone and LPS + SMM-189 columns indicate significance levels for the comparison between these two conditions. Asterisks on a column indicate a significant difference from the control condition. NS—Not significant, *p < 0.05, **p < 0.005, ***p < 0.0005.

Mentions: To evaluate SMM-189 effects, we started by comparing the levels of cytokines released by primary human microglia cultured under control conditions and those activated with lipopolysaccharide (LPS) in the presence and absence of SMM-189. LPS-treatment significantly increased the levels of interferon-gamma (IFN-γ), interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-12p70 (IL-12p70), and tumor necrosis factor-α (TNF-α) (p < 0.002) (Figure 1), but did not increase the levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-2 (IL-2) or interleukin-1β (IL-1β). Addition of SMM-189 reduced the expression of IFN-γ, IL-6, IL-10, and IL-12p70 that occurred in LPS-activated human microglia, so that they were either significantly less (p < 0.015) than in the LPS-alone condition (IFN-γ, IL-6, and IL-10), and/or not significantly different than in the control + SMM-189 condition (IFN-γ and IL-12p70) (Figure 1). Thus, four of the five cytokines whose expression by microglia was increased with LPS treatment showed significantly reduced expression when SMM-189 treatment was combined with LPS-treatment, and the remaining cytokine (TNF-α) trended in that direction. By itself, SMM-189 slightly elevated IFN-γ and IL-12p70, but much less so than did LPS alone.


Motor, visual and emotional deficits in mice after closed-head mild traumatic brain injury are alleviated by the novel CB2 inverse agonist SMM-189.

Reiner A, Heldt SA, Presley CS, Guley NH, Elberger AJ, Deng Y, D'Surney L, Rogers JT, Ferrell J, Bu W, Del Mar N, Honig MG, Gurley SN, Moore BM - Int J Mol Sci (2014)

Effect of SMM-189 on cytokines secreted from primary human microglial cells in vitro. Primary human microglia were treated with lipopolysaccharide (LPS) or vehicle, and then SMM-189 or vehicle was added one hour later. Cytokines were then assayed 17 h subsequently. LPS significantly increased cytokine levels above that in control. SMM-189 by itself also significantly elevated interferon-gamma (IFN-γ) and interleukin-12p70 (IL-12p70), but to a lesser extent than LPS. SMM-189 attenuated the effect of LPS on cytokine secretion, significantly reducing IFN-γ, interleukin-6 (IL-6) and interleukin-10 (IL-10) below LPS-only levels and restoring IFN-γ and IL-12p70 to SMM-189-alone levels. SMM-189 also trended toward reducing TNFα. Asterisks above bars spanning the LPS-alone and LPS + SMM-189 columns, or the SMM-189-alone and LPS + SMM-189 columns indicate significance levels for the comparison between these two conditions. Asterisks on a column indicate a significant difference from the control condition. NS—Not significant, *p < 0.05, **p < 0.005, ***p < 0.0005.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4307274&req=5

ijms-16-00758-f001: Effect of SMM-189 on cytokines secreted from primary human microglial cells in vitro. Primary human microglia were treated with lipopolysaccharide (LPS) or vehicle, and then SMM-189 or vehicle was added one hour later. Cytokines were then assayed 17 h subsequently. LPS significantly increased cytokine levels above that in control. SMM-189 by itself also significantly elevated interferon-gamma (IFN-γ) and interleukin-12p70 (IL-12p70), but to a lesser extent than LPS. SMM-189 attenuated the effect of LPS on cytokine secretion, significantly reducing IFN-γ, interleukin-6 (IL-6) and interleukin-10 (IL-10) below LPS-only levels and restoring IFN-γ and IL-12p70 to SMM-189-alone levels. SMM-189 also trended toward reducing TNFα. Asterisks above bars spanning the LPS-alone and LPS + SMM-189 columns, or the SMM-189-alone and LPS + SMM-189 columns indicate significance levels for the comparison between these two conditions. Asterisks on a column indicate a significant difference from the control condition. NS—Not significant, *p < 0.05, **p < 0.005, ***p < 0.0005.
Mentions: To evaluate SMM-189 effects, we started by comparing the levels of cytokines released by primary human microglia cultured under control conditions and those activated with lipopolysaccharide (LPS) in the presence and absence of SMM-189. LPS-treatment significantly increased the levels of interferon-gamma (IFN-γ), interleukin-6 (IL-6), interleukin-10 (IL-10), interleukin-12p70 (IL-12p70), and tumor necrosis factor-α (TNF-α) (p < 0.002) (Figure 1), but did not increase the levels of granulocyte-macrophage colony-stimulating factor (GM-CSF), interleukin-2 (IL-2) or interleukin-1β (IL-1β). Addition of SMM-189 reduced the expression of IFN-γ, IL-6, IL-10, and IL-12p70 that occurred in LPS-activated human microglia, so that they were either significantly less (p < 0.015) than in the LPS-alone condition (IFN-γ, IL-6, and IL-10), and/or not significantly different than in the control + SMM-189 condition (IFN-γ and IL-12p70) (Figure 1). Thus, four of the five cytokines whose expression by microglia was increased with LPS treatment showed significantly reduced expression when SMM-189 treatment was combined with LPS-treatment, and the remaining cytokine (TNF-α) trended in that direction. By itself, SMM-189 slightly elevated IFN-γ and IL-12p70, but much less so than did LPS alone.

Bottom Line: Because microglial activation can worsen brain damage after a concussive event and because microglia can be modulated by their cannabinoid type 2 receptors (CB2), we evaluated the effectiveness of the novel CB2 receptor inverse agonist SMM-189 in altering microglial activation and mitigating deficits after mild TBI.Our results suggest that treatment with the CB2 inverse agonist SMM-189 after a mild TBI event can reduce its adverse consequences by beneficially modulating microglial activation.These findings recommend further evaluation of CB2 inverse agonists as a novel therapeutic approach for treating mild TBI.

View Article: PubMed Central - PubMed

Affiliation: Department of Anatomy and Neurobiology, the University of Tennessee Health Science Center, Memphis, TN 38163, USA. areiner@uthsc.edu.

ABSTRACT
We have developed a focal blast model of closed-head mild traumatic brain injury (TBI) in mice. As true for individuals that have experienced mild TBI, mice subjected to 50-60 psi blast show motor, visual and emotional deficits, diffuse axonal injury and microglial activation, but no overt neuron loss. Because microglial activation can worsen brain damage after a concussive event and because microglia can be modulated by their cannabinoid type 2 receptors (CB2), we evaluated the effectiveness of the novel CB2 receptor inverse agonist SMM-189 in altering microglial activation and mitigating deficits after mild TBI. In vitro analysis indicated that SMM-189 converted human microglia from the pro-inflammatory M1 phenotype to the pro-healing M2 phenotype. Studies in mice showed that daily administration of SMM-189 for two weeks beginning shortly after blast greatly reduced the motor, visual, and emotional deficits otherwise evident after 50-60 psi blasts, and prevented brain injury that may contribute to these deficits. Our results suggest that treatment with the CB2 inverse agonist SMM-189 after a mild TBI event can reduce its adverse consequences by beneficially modulating microglial activation. These findings recommend further evaluation of CB2 inverse agonists as a novel therapeutic approach for treating mild TBI.

Show MeSH
Related in: MedlinePlus