Paeonol Protection Against Intrastriatal 6-Hydroxydopamine Rat Model of Parkinson's Disease

Abstract

Introduction: Parkinson's Disease (PD) presentations comprise frequent movement disorders in the elderly with various symptoms consisting of motor and non-motor complications. Paeonol is a phenolic chemical agent that has shown antioxidant and anti-inflammatory effects in different disorders and promising effects on metabotropic glutamate receptors (mGluR)- and GABAA-mediated neurotransmission. In this research, we tried to show the neuroprotective potential of paeonol in rat PD model induced by intrastriatal 6-hydroxydopamine (6-OHDA).

Methods: Rats with intrastriatal 6-OHDA lesioning received with paeonol at a dosage of 100 mg/kg/d for one week. In the end, some biomarkers of oxidative stress, apoptosis, and astrogliosis in nigral and striatal tissues were evaluated in addition to behavioral and Tyrosine Hydroxylase (TH) immunohistochemical analysis.

Results: The obtained data showed that paeonol alleviates apomorphine-induced rotations and reduces the delay time to initiate and the total time in the narrow beam test. However, its beneficial behavioral effect vanished after intracerebroventricular administration of mGluR III or GABAA receptor antagonists. Moreover, paeonol significantly restored striatal malondialdehyde, tissue levels of reactive oxygen species, the activity of the protective and vital enzymes consisting of superoxide dismutase and catalase, Glial Fibrillary Acidic Protein (GFAP), DNA fragmentation, phosphor apoptosis signal-regulating kinase 1, and nigral aquaporin 4 with no significant and proper change of nitrite, interleukin-1β, inducible nitric oxide synthase, and angiotensin II. Additionally, paeonol prevented injury and reduced tyrosine hydroxylase-containing neurons in the midbrain nigral tissue.

Conclusion: These obtained findings evidently designate neuroprotective property of paeonol in 6-OHDA murine model of PD that is exerted via easing of oxidative stress, apoptosis, astrogliosis, and its advantageous effect is to some extent mediated via mGluR III/GABAA pathway.

Keywords: 6-hydroxydopamine; Apoptosis; GABA receptor; Metabotropic glutamate receptor; Oxidative stress; Paeonol.

Figure 1.

The effect of paeonol at a dose of 100 mg/kg on the apomorphine-produced rotational bias A: On the latency to start the task and the whole time to perform narrow beam task; B: One week next to intrastriatal microinjection of 6-hydroxydopamine (6-OHDA). MPPG or SR-95531 were ICV administered 30 min before 6-OHDA microinjection as mGluR III/II receptor and GABAA receptor antagonists, respectively. Values are expressed as Means±SEM; n=10–12 for each group. ^**P<0.01, ^***P<0.005; P<0.001 (versus sham); ^# P<0.05, ^## P<0.01 (versus 6-OHDA).

Figure 2.

The effect of paeonol at a dose of 100 mg/kg on nigral and striatal markers of oxidative stress event, including Malondialdehyde (MDA) A: Nitrite; B: Reactive Oxygen Species (ROS); C: Activity of Superoxide Dismutase (SOD); D: Catalase; E: One week after intrastriatal administration of 6-hydroxydopamine (6-OHDA). The measurements for each sample were made in duplicate. Values are expressed as Means±SEM. n=7 for each group. ^* P<0.05; ^** P<0.01 (vs. Sham on the left side); ^#P<0.05 (vs. 6-OHDA on the left side)

Figure 3.

The effect of paeonol at a dose of 100 mg/kg on nigral and striatal quantities of glial fibrillary acidic protein (GFAP) A: DNA fragmentation (as an apoptotic marker); B: Interleukin-1β (IL-1β) 1 week next to intrastriatal administration of 6-hydroxydopamine (6-OHDA). The measurements were made in duplicate for samples. Values are expressed as means±SEM. n=5 for each group. ^* P<0.05; ^** P<0.01 (vs. sham on the left side); ^# P<0.05 (vs. 6-OHDA on the left side).

Figure 4.

The effect of paeonol at a dose of 100 mg/kg on nigral and striatal quantities of iNOS A: Angiotensin II (Ag II); B: Phosphor apoptosis signal-regulating kinase 1 (pASK1); C: Aquaporin 4; D: One week after intrastriatal administration of 6-hydroxydopamine (6-OHDA). The measurements were made in duplicate for samples. Values are expressed as Means±SEM. n=5 for each group; ^* P<0.05; ^**P<0.01; ^*** P<0.005 (vs. sham on left side); ^# P<0.05 (vs. 6-OHDA on left side).

Figure 5.

The effect of paeonol at a dose of 100 mg/kg on the average number of Tyrosine Hydroxylase (TH)-containing neurons of the left side of substantia nigra pars compacta (SNC) A: Photomicrographs obtained from midbrain coronal sections one week after intrastriatal administration of 6-hydroxydopamine (6-OHDA). Arrows indicate an area of remarkable loss of TH-containing neurons. Values are expressed as means±SEM. n=4–5 for each group. (SNR =Substantia nigra pars reticulate); ^* P<0.05; ^** P<0.01 (versus Sham); ^# P<0.05 (versus 6-OHDA).