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Neuroprotective effect of 6-paradol in focal cerebral ischemia involves the attenuation of neuroinflammatory responses in activated microglia.

Gaire BP, Kwon OW, Park SH, Chun KH, Kim SY, Shin DY, Choi JW - PLoS ONE (2015)

Bottom Line: Through the initial screening for anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated BV2 microglia, 6-paradol was chosen to be the most effective compound without cytotoxicity.Pretreatment with 6-paradol reduced neuroinflammatory responses in LPS-stimulated BV2 microglia by a concentration-dependent manner, which includes reduced NO production by inhibiting iNOS upregulation and lowered secretion of proinflammatory cytokines (IL-6 and TNF-α).Furthermore, as observed in cultured microglia, 6-paradol administration markedly reduced neuroinflammation in M/R-challenged brains by attenuating microglial activation and reducing the number of cells expressing iNOS and TNF-α, both of which are known to be produced in microglia following M/R challenge.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Pharmacology, College of Pharmacy and Gachon Institute of Pharmaceutical Sciences, Gachon University, Incheon, Republic of Korea.

ABSTRACT
Paradols are non-pungent and biotransformed metabolites of shogaols and reduce inflammatory responses as well as oxidative stress as shogaols. Recently, shogaol has been noted to possess therapeutic potential against several central nervous system (CNS) disorders, including cerebral ischemia, by reducing neuroinflammation in microglia. Therefore, paradol could be used to improve neuroinflammation-associated CNS disorders. Here, we synthesized paradol derivatives (2- to 10-paradols). Through the initial screening for anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated BV2 microglia, 6-paradol was chosen to be the most effective compound without cytotoxicity. Pretreatment with 6-paradol reduced neuroinflammatory responses in LPS-stimulated BV2 microglia by a concentration-dependent manner, which includes reduced NO production by inhibiting iNOS upregulation and lowered secretion of proinflammatory cytokines (IL-6 and TNF-α). To pursue whether the beneficial in vitro effects of 6-paradol leads towards in vivo therapeutic effects on transient focal cerebral ischemia characterized by neuroinflammation, we employed middle cerebral artery occlusion (MCAO)/reperfusion (M/R). Administration of 6-paradol immediately after reperfusion significantly reduced brain damage in M/R-challenged mice as assessed by brain infarction, neurological deficit, and neural cell survival and death. Furthermore, as observed in cultured microglia, 6-paradol administration markedly reduced neuroinflammation in M/R-challenged brains by attenuating microglial activation and reducing the number of cells expressing iNOS and TNF-α, both of which are known to be produced in microglia following M/R challenge. Collectively, this study provides evidences that 6-paradol effectively protects brain after cerebral ischemia, likely by attenuating neuroinflammation in microglia, suggesting it as a potential therapeutic agent to treat cerebral ischemia.

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Administration of 6-paradol reduces brain damage in M/R-challenged mice.Mice were challenged with M/R and 6-paradol (1, 5, or 10 mg/kg, p.o.) was administered immediately after reperfusion. Brain damage was assessed 22 h after reperfusion. (A-C) Effects of 6-paradol at different dosages (1 to 10 mg/kg) on infarct volume (A, B) and neurological function (C) were determined. Representative images of TTC-stained brain tissue (A) and quantification of brain infarction (B). Neurological score indicating neurological functions (C). n = 6~7 per group. *p<0.05 and ***p<0.001, versus vehicle-administered M/R mice (M/R+veh). (D, E) Effects of 6-paradol (10 mg/kg) on neural cell survival (D) and death (E) were determined by staining with cresyl violet (Nissl staining) and Fluoro-Jade B, respectively. In both cases, representative images were shown. Dashed lines indicate the lesion site. Diagram boxes display the cerebral area where the images in middle and bottom panels were acquired. Scale bars, 200 μm (top panels) and 50 μm (middle and bottom panels) in D and E.
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pone.0120203.g004: Administration of 6-paradol reduces brain damage in M/R-challenged mice.Mice were challenged with M/R and 6-paradol (1, 5, or 10 mg/kg, p.o.) was administered immediately after reperfusion. Brain damage was assessed 22 h after reperfusion. (A-C) Effects of 6-paradol at different dosages (1 to 10 mg/kg) on infarct volume (A, B) and neurological function (C) were determined. Representative images of TTC-stained brain tissue (A) and quantification of brain infarction (B). Neurological score indicating neurological functions (C). n = 6~7 per group. *p<0.05 and ***p<0.001, versus vehicle-administered M/R mice (M/R+veh). (D, E) Effects of 6-paradol (10 mg/kg) on neural cell survival (D) and death (E) were determined by staining with cresyl violet (Nissl staining) and Fluoro-Jade B, respectively. In both cases, representative images were shown. Dashed lines indicate the lesion site. Diagram boxes display the cerebral area where the images in middle and bottom panels were acquired. Scale bars, 200 μm (top panels) and 50 μm (middle and bottom panels) in D and E.

Mentions: Firstly, the therapeutic potential of 6-paradol on cerebral ischemia was assessed. Oral administration of 6-paradol reduced brain infarction (Fig. 4A, B) and improved the neurological score (Fig. 4C) in a dose-dependent manner. At 10 mg/kg, 6-paradol remarkably reduced brain infarction and improved neurological score by 42.1% (Fig. 4B) and 49.2% (Fig. 4C), respectively, compared to the vehicle-treated M/R group. These neuroprotective effects of 6-paradol (10 mg/kg) were confirmed by determining cell survival or death by staining with Nissl (Fig. 4D) or Fluoro-Jade B (Fig. 4E). In a 6-paradol-administered group, the survival of neural cells was higher than the vehicle-treated group. Similarly, neural cell death was significantly reduced in the 6-paradol group. The observed neuroprotection by 6-paradol administration was similar to that of 6-shogaol (10 mg/kg, p.o.) when the effects were compared at the same dosage (S3 Fig.).


Neuroprotective effect of 6-paradol in focal cerebral ischemia involves the attenuation of neuroinflammatory responses in activated microglia.

Gaire BP, Kwon OW, Park SH, Chun KH, Kim SY, Shin DY, Choi JW - PLoS ONE (2015)

Administration of 6-paradol reduces brain damage in M/R-challenged mice.Mice were challenged with M/R and 6-paradol (1, 5, or 10 mg/kg, p.o.) was administered immediately after reperfusion. Brain damage was assessed 22 h after reperfusion. (A-C) Effects of 6-paradol at different dosages (1 to 10 mg/kg) on infarct volume (A, B) and neurological function (C) were determined. Representative images of TTC-stained brain tissue (A) and quantification of brain infarction (B). Neurological score indicating neurological functions (C). n = 6~7 per group. *p<0.05 and ***p<0.001, versus vehicle-administered M/R mice (M/R+veh). (D, E) Effects of 6-paradol (10 mg/kg) on neural cell survival (D) and death (E) were determined by staining with cresyl violet (Nissl staining) and Fluoro-Jade B, respectively. In both cases, representative images were shown. Dashed lines indicate the lesion site. Diagram boxes display the cerebral area where the images in middle and bottom panels were acquired. Scale bars, 200 μm (top panels) and 50 μm (middle and bottom panels) in D and E.
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pone.0120203.g004: Administration of 6-paradol reduces brain damage in M/R-challenged mice.Mice were challenged with M/R and 6-paradol (1, 5, or 10 mg/kg, p.o.) was administered immediately after reperfusion. Brain damage was assessed 22 h after reperfusion. (A-C) Effects of 6-paradol at different dosages (1 to 10 mg/kg) on infarct volume (A, B) and neurological function (C) were determined. Representative images of TTC-stained brain tissue (A) and quantification of brain infarction (B). Neurological score indicating neurological functions (C). n = 6~7 per group. *p<0.05 and ***p<0.001, versus vehicle-administered M/R mice (M/R+veh). (D, E) Effects of 6-paradol (10 mg/kg) on neural cell survival (D) and death (E) were determined by staining with cresyl violet (Nissl staining) and Fluoro-Jade B, respectively. In both cases, representative images were shown. Dashed lines indicate the lesion site. Diagram boxes display the cerebral area where the images in middle and bottom panels were acquired. Scale bars, 200 μm (top panels) and 50 μm (middle and bottom panels) in D and E.
Mentions: Firstly, the therapeutic potential of 6-paradol on cerebral ischemia was assessed. Oral administration of 6-paradol reduced brain infarction (Fig. 4A, B) and improved the neurological score (Fig. 4C) in a dose-dependent manner. At 10 mg/kg, 6-paradol remarkably reduced brain infarction and improved neurological score by 42.1% (Fig. 4B) and 49.2% (Fig. 4C), respectively, compared to the vehicle-treated M/R group. These neuroprotective effects of 6-paradol (10 mg/kg) were confirmed by determining cell survival or death by staining with Nissl (Fig. 4D) or Fluoro-Jade B (Fig. 4E). In a 6-paradol-administered group, the survival of neural cells was higher than the vehicle-treated group. Similarly, neural cell death was significantly reduced in the 6-paradol group. The observed neuroprotection by 6-paradol administration was similar to that of 6-shogaol (10 mg/kg, p.o.) when the effects were compared at the same dosage (S3 Fig.).

Bottom Line: Through the initial screening for anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated BV2 microglia, 6-paradol was chosen to be the most effective compound without cytotoxicity.Pretreatment with 6-paradol reduced neuroinflammatory responses in LPS-stimulated BV2 microglia by a concentration-dependent manner, which includes reduced NO production by inhibiting iNOS upregulation and lowered secretion of proinflammatory cytokines (IL-6 and TNF-α).Furthermore, as observed in cultured microglia, 6-paradol administration markedly reduced neuroinflammation in M/R-challenged brains by attenuating microglial activation and reducing the number of cells expressing iNOS and TNF-α, both of which are known to be produced in microglia following M/R challenge.

View Article: PubMed Central - PubMed

Affiliation: Laboratory of Pharmacology, College of Pharmacy and Gachon Institute of Pharmaceutical Sciences, Gachon University, Incheon, Republic of Korea.

ABSTRACT
Paradols are non-pungent and biotransformed metabolites of shogaols and reduce inflammatory responses as well as oxidative stress as shogaols. Recently, shogaol has been noted to possess therapeutic potential against several central nervous system (CNS) disorders, including cerebral ischemia, by reducing neuroinflammation in microglia. Therefore, paradol could be used to improve neuroinflammation-associated CNS disorders. Here, we synthesized paradol derivatives (2- to 10-paradols). Through the initial screening for anti-inflammatory activities using lipopolysaccharide (LPS)-stimulated BV2 microglia, 6-paradol was chosen to be the most effective compound without cytotoxicity. Pretreatment with 6-paradol reduced neuroinflammatory responses in LPS-stimulated BV2 microglia by a concentration-dependent manner, which includes reduced NO production by inhibiting iNOS upregulation and lowered secretion of proinflammatory cytokines (IL-6 and TNF-α). To pursue whether the beneficial in vitro effects of 6-paradol leads towards in vivo therapeutic effects on transient focal cerebral ischemia characterized by neuroinflammation, we employed middle cerebral artery occlusion (MCAO)/reperfusion (M/R). Administration of 6-paradol immediately after reperfusion significantly reduced brain damage in M/R-challenged mice as assessed by brain infarction, neurological deficit, and neural cell survival and death. Furthermore, as observed in cultured microglia, 6-paradol administration markedly reduced neuroinflammation in M/R-challenged brains by attenuating microglial activation and reducing the number of cells expressing iNOS and TNF-α, both of which are known to be produced in microglia following M/R challenge. Collectively, this study provides evidences that 6-paradol effectively protects brain after cerebral ischemia, likely by attenuating neuroinflammation in microglia, suggesting it as a potential therapeutic agent to treat cerebral ischemia.

Show MeSH
Related in: MedlinePlus