Gynura procumbens Root Extract Ameliorates Ischemia-Induced Neuronal Damage in the Hippocampal CA1 Region by Reducing Neuroinflammation

Abstract

Gynura procumbens has been used in Southeast Asia for the treatment of hypertension, hyperglycemia, and skin problems induced by ultraviolet irradiation. Although considerable studies have reported the biological properties of Gynura procumbens root extract (GPE-R), there are no studies on the effects of GPE-R in brain damages, for example following brain ischemia. In the present study, we screened the neuroprotective effects of GPE-R against ischemic damage and neuroinflammation in the hippocampus based on behavioral, morphological, and biological approaches. Gerbils received oral administration of GPE-R (30 and 300 mg/kg) every day for three weeks and 2 h after the last administration, ischemic surgery was done by occlusion of both common carotid arteries for 5 min. Administration of 300 mg/kg GPE-R significantly reduced ischemia-induced locomotor hyperactivity 1 day after ischemia. Significantly more NeuN-positive neurons were observed in the hippocampal CA1 regions of 300 mg/kg GPE-R-treated animals compared to those in the vehicle-treated group 4 days after ischemia. Administration of GPE-R significantly reduced levels of pro-inflammatory cytokines such as interleukin-1β, -6, and tumor necrosis factor-α 6 h after ischemia/reperfusion. In addition, activated microglia were significantly decreased in the 300 mg/kg GPE-R-treated group four days after ischemia/reperfusion compared to the vehicle-treated group. These results suggest that GPE-R may be one of the possible agents to protect neurons from ischemic damage by reducing inflammatory responses.

Keywords: Gynura procumbens root extract; ischemia; microglia; neuroprotection; pro-inflammatory cytokines.

Figure 1

Body weight in the control, vehicle-treated ischemic (Vehicle), 30 mg/kg Gynura procumbens roots (GPE-R)-treated ischemic (GPE30), and 300 mg/kg GPE-R-treated ischemic (GPE300) groups. There are no significant changes in body weight before and after ischemia or GPE-R treatment. Error bars represent standard errors of the means.

Figure 2

Locomotor activity in the control, vehicle-treated ischemic (Vehicle), 30 mg/kg GPE-R-treated ischemic (GPE30), and 300 mg/kg GPE-R-treated ischemic (GPE300) groups. The total distance (meters) traveled in 60 min was observed 1 day before and after ischemia/reperfusion (n = 7 per group, * p < 0.05 vs. the control group; ^$ p < 0.05 vs. the vehicle group; ^§ p < 0.05 vs. the GPE30 group). Error bars represent standard errors of the means.

Figure 3

Immunohistochemistry for NeuN in the CA1 region of the control (A), vehicle-treated ischemic (Vehicle, B), 30 mg/kg GPE-R-treated ischemic (GPE30, C), and 300 mg/kg GPE-R-treated ischemic (GPE300, D) groups. SO, stratum oriens; SP, stratum pyramidale; SR; stratum radiatum. Scale bar = 50 μm. (E) The number of NeuN-immunoreactive neurons per section in the hippocampal CA1 region of each group compared with the control group, is shown (n = 7 per group, * p < 0.05 vs. the control group; ^$ p < 0.05 vs. the vehicle group; ^§ p < 0.05 vs. the GPE30 group). Error bars represent standard errors of the means.

Figure 4

Immunohistochemistry for Iba-1 in the CA1 region of the control (A), vehicle-treated ischemic (Vehicle, B), 30 mg/kg GPE-R-treated ischemic (GPE30, C), and 300 mg/kg GPE-R-treated ischemic (GPE300, D) groups. SO, stratum oriens; SP, stratum pyramidale; SR; stratum radiatum. Scale bar = 50 μm. (E) ROD per section in the SO, SP, and SR of hippocampal CA1 region in each group compared with the control group, is shown (n = 7 per group, * p < 0.05 vs. the control group; ^$ p < 0.05 vs. the vehicle group; ^§ p < 0.05 vs. the GPE30 group). Error bars represent standard errors of the means.

Figure 5

Levels of tumor necrosis factor-α (TNF-α), interleukin (IL)-1β, and IL-6 in the hippocampi of the control, vehicle-treated ischemic (Vehicle), 30 mg/kg GPE-R-treated ischemic (GPE30), and 300 mg/kg GPE-R-treated ischemic (GPE300) groups (n = 7 per group, * p < 0.05 vs. the control group; ^$ p < 0.05 vs. the vehicle group; ^§ p < 0.05 vs. the GPE30 group) are shown. Error bars represent standard errors of the means.