Ferulic acid inhibits nitric oxide-induced apoptosis by enhancing GABA(B1) receptor expression in transient focal cerebral ischemia in rats

Abstract

Aim: Ferulic acid (4-hydroxy-3-methoxycinnamic acid, FA) provides neuroprotection against apoptosis in a transient middle cerebral artery occlusion (MCAo) model. This study was to further investigate the anti-apoptotic effect of FA during reperfusion after cerebral ischemia.

Methods: Rats were subjected to 90 min of cerebral ischemia followed by 3 or 24 h of reperfusion after which they were sacrificed.

Results: Intravenous FA (100 mg/kg) administered immediately after middle cerebral artery occlusion (MCAo) or 2 h after reperfusion effectively abrogated the elevation of postsynaptic density-95 (PSD-95), neuronal nitric oxide synthase (nNOS), inducible nitric oxide synthase (iNOS), nitrotyrosine, and cleaved caspase-3 levels as well as apoptosis in the ischemic cortex at 24 h of reperfusion. FA further inhibited Bax translocation, cytochrome c release, and p38 mitogen-activated protein (MAP) kinase phosphorylation. Moreover, FA enhanced the expression of gamma-aminobutyric acid type B receptor subunit 1 (GABA(B1)) in the ischemic cortex at 3 and 24 h of reperfusion. In addition, nitrotyrosine-positive cells colocalized with cleaved caspase-3-positive cells, and phospho-p38 MAP kinase-positive cells colocalized with nitrotyrosine- and Bax-positive cells, indicating a positive relationship among the expression of nitrotyrosine, phospho-p38 MAP kinase, Bax, and cleaved caspase-3. The mutually exclusive expression of GABA(B1) and nitrotyrosine revealed that there is a negative correlation between GABA(B1) and nitrotyrosine expression profiles. Additionally, pretreatment with saclofen, a GABA(B) receptor antagonist, abolished the neuroprotection of FA against nitric oxide (NO)-induced apoptosis.

Conclusion: FA significantly enhances GABA(B1) receptor expression at early reperfusion and thereby provides neuroprotection against p38 MAP kinase-mediated NO-induced apoptosis at 24 h of reperfusion.

Figure 1

The scheme of ferulic acid (FA) administration.

Figure 2

Effects of FA on PSD-95 (A), nNOS (B), iNOS (C), and nitrotyrosine (D) levels at 24 h of reperfusion. N, negative control of stain. Scale bar=100 μm.

Figure 3

Effects of FA on the expression of cleaved caspase-3 (A, B, and C) and TUNEL-positive cells (D) at 24 h of reperfusion. ^bP<0.05 vs Sham, ^eP<0.05 vs Vehicle.

Figure 4

Effect of FA on nitrotyrosine-cleaved caspase-3 (A), nitrotyrosine-phospho-p38 MAP kinase (B), and nitrotyrosine-GABA_B1 (C) double labeled cells at 24 h of reperfusion.

Figure 5

Effects of FA on the expression of cleaved caspase-8 (A), Bax (B, C) and cytochrome c (D, E) at 24 h of reperfusion. ^bP<0.05 vsSham. ^eP<0.05 vs Vehicle.

Figure 6

Effects of FA on the phosphorylation of ERK, JNK, and p38 MAP kinase (A, B), and phospho-p38 MAP kinase-bax double labeled cells (C) at 24 h of reperfusion. ^bP<0.05 vs Sham, ^eP<0.05 vs Vehicle.

Figure 7

Effects of FA on the expression of GABA_B1 receptors at 3 (A, C) and 24 h (B, D) of reperfusion. ^bP<0.05 vs Sham, ^eP<0.05 vs Vehicle.