Perinatology.  2016 Sep;27(3):149-157. 10.14734/PN.2016.27.3.149.

Neuroprotective Effects of SYM 2081, Targeting Kainate Receptors in the Neonatal Hypoxic-Ischemic Brain Injury

• Lee JH
• Lee EJ
• Jang YY
• Jeong JE
• Chung HL
• Kim WT

• KMID: 2355572
• DOI: http://doi.org/10.14734/PN.2016.27.3.149

Abstract

PURPOSE
Glutamate induced excitotoxicity has been implicated as a major factor of central neuronal death in neonatal hypoxic-ischemic (HI) injury. Kainate receptors (KARs) are one of glutamatergic receptors involving glutamate toxicity. However, the expression patterns of KARs in the neonatal HI brain injury have not been clearly established. Therefore, this study was designed to investigate the expression pattern of KARs and to determine the potential of SYM 2081 ((2S, 4R)-4-methylglutamic acid) as a neuronal rescue agent after HI brain injury.
METHODS
In an in vivo model, left carotid artery ligation (LCA) was done in Sprague-Dawley (SD) rat pups. The animals were divided into five groups; normoxia (N), hypoxia (8% O2, 92% N2) (H), hypoxia with sham-operation (HS), hypoxia with operation (HO), and HO treated with SYM 2081 before a hypoxic insult (HM). In an in vitro model, the cultured embryonic cortical neuronal cells were divided into three groups: normoxia (95% air, 5% COâ‚‚) (Nc), hypoxia (94% N2, 5% COâ‚‚) (Hc), and Hc treated with SYM2081 (HMc) before a hypoxic insult. The expressions of GluK1-5 were assessed by real-time polymerase chain reaction.
RESULTS
The area of left hemisphere was decreased as compared to contralateral hemisphere in HO group, restored by SYM 2081 treatment. Cell loss observed in the Hc group was decreased in the HMC group. The expressions of all KARs except for GluK2 were decreased in the HO and HC groups, whereas they were increased in HM and HMc groups.
CONCLUSION
This study showed that SYM 2081 had neuroprotective effects on HI brain injury in neonatal rats through modulating KAR expression.

Keyword

(2S,4R)-4-methylglutamic acid; Kainate; Brain-hypoxia-ischemia; Neuroprotection

MeSH Terms

Animals
Anoxia
Brain Injuries*
Brain*
Carotid Arteries
Glutamic Acid
In Vitro Techniques
Kainic Acid*
Ligation
Neurons
Neuroprotection
Neuroprotective Agents*
Rats
Rats, Sprague-Dawley
Real-Time Polymerase Chain Reaction
Receptors, Kainic Acid*
Glutamic Acid
Kainic Acid
Neuroprotective Agents
Receptors, Kainic Acid

Figure

• 

  Fig. 1 Gross morphologic changes revealed in the neonatal hypoxic-ischemic brain injury (in vivo). (A) The image show representative brain. a, normoxia; b, hypoxia without LCA (left carotic artery) ligation operation; c, hypoxia with Sham operation; d, hypoxia with LCA ligation operation; e, d treated with (2S,4R)-4-Methylglutamic Acid (SYM 2081). (B) Data are Percentage of left hemisphere area compared to right hemisphere area (N, 103%±2; H, 111%±8; HS, 105%±5; HO, 96.1%±2; HM, 102%±3). N, normoxisa; H, hypoxia without operation; HS, hypoxia with Sham operation; HO, hypoxia with operation; HM, HO treated with SYM 2081; *P<0.05, statistically significant.

• 

  Fig. 2 Microscopic changes in the embryonic cortical neuronal cell culture of rat (in vitro). The cortical neuronal cells were observed using inverted microscope under high magnification (×200). (A) normoxia, (B) hypoxia, (C) hypoxia treated with (2S,4R)-4-Methylglutamic Acid (SYM 2081).

• 

  Fig. 3 Real-time PCRs of GluK1 (A; N, 100±5.5; H, 118.9±5.9; HS, 64.6±3.2; HO, 70.7±3.5; HM, 26.6±1.3), GluK2 (B; N, 100±5.1; H, 79.3±3.9; HS, 107.2±5.4; HO, 104.9±5.3; HM, 118.1±5.9), GluK3 (C; N, 100±5.4; H, 176.5±8.8; HS, 157.5±7.9; HO, 111.7±5.6; HM, 174.7±8.7), GluK4 (D; N, 100±5.1; H, 188.6±9.4; HS, 125.3±6.3; HO, 75.5±3.8; HM, 200.0±10.0), and GluK5 (E; N, 100±5.4; H, 193.2±9.7; HS, 127.9±6.4; HO, 65.7±3.3; HM, 141.4±7.1) mRNA in the neonatal hypoxic-ischemic brain injury (in vivo) (n=6). The (2S,4R)-4-Methylglutamic Acid (SYM 2081) was administered at 10 mg/kg. N, normoxia; H, hypoxia without operation; HS, hypoxia with Sham operation; HO, hypoxia with operation; HM, HO treated with SYM 2081; *P<0.05, statistically significant. Abbreviation: PCR, polymerase chain reaction.

• 

  Fig. 4 Real-time PCRs of GluK1 (A; Nc, 100±4.2; Hc, 50.2±2.0; HMc, 65.3±2.6), GluK2 (B; Nc, 100±8.1; Hc, 115.3±9.2; HMc, 155.3±12.4), GluK3 (C; Nc, 100±5.2; Hc, 73.5±3.7; HMc, 204.9±10.2), GluK4 (D; Nc, 100±5.2; Hc, 21.8±1.1; HMc, 28.3±1.4), and GluK5 (E; Nc, 100±5.2; Hc, 54.7±2.7; HMc, 88.3±4.4) in the embryonic cortical neuronal cell culture (in vitro) (n=6). The (2S,4R)-4-Methylglutamic Acid (SYM 2081) was administered at 10 µg/mL. Nc, normoxia; Hc, hypoxia; HMc, hypoxia treated with SYM 2081; *P<0.05, statistically significant. Abbreviation: PCR, polymerase chain reaction.

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