An orally active catalytic metalloporphyrin protects against 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine neurotoxicity in vivo

Abstract

Parkinson's disease (PD) is an age-related neurodegenerative disease in which the role of reactive oxygen species (ROS) is strongly implicated. The presence of oxidative stress has been detected in human and experimental PD using both direct and indirect indices. Scavenging ROS is, therefore, an important therapeutic avenue for the treatment of PD. Manganic porphyrins are catalytic antioxidants that scavenge a wide range of ROS. In this study, we tested the therapeutic effects of a compound [5,15-bis(methoxycarbonyl)-10,20-bis-trifluoromethyl-porphyrinato manganese (III) chloride (AEOL11207)] belonging to a new generation of lipophilic manganic porphyrins for neuroprotection and oral bioavailability in the mouse 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) model of parkinsonism. Groups of adult C57BL/6 mice were administered MPTP with varying subcutaneous or oral dosing regimens of AEOL11207. Neurotoxicity was assessed by measurement of striatal dopamine levels and quantification of tyrosine hydroxylase-positive neurons in the substantial nigra pars compacta one week after the first dose of MPTP. Glutathione depletion, lipid peroxidation, and 3-nitrotyrosine (3-NT) formation were measured as indicators of oxidative stress in the ventral midbrain in vivo. AEOL11207 administered either by subcutaneous or oral routes protected against MPTP-induced dopamine depletion in the striatum as well as dopaminergic neuronal loss, glutathione depletion, lipid peroxidation, and 3-NT formation in the ventral midbrain. Neuroprotection correlated with brain metalloporphyrin concentrations. This is the first demonstration of neuroprotection by an orally active catalytic antioxidant in the MPTP mouse model and suggests its potential clinical utility for the treatment of chronic neurodegenerative diseases such as PD.

Figure 1.

The chemical structure of AEOL11207.

Figure 2.

AEOL11207 penetrates the BBB after subcutaneous or per oral administration. A, B, The concentration of AEOL11207 in the plasma (A) and brains (B) of the C57BL/6 mice at different times points after a single dose of AEOL11207 (15 mg/kg) administered by the subcutaneous or per oral route. Points and error bars represent mean + SEM. Each point is the average of 3–4 animals.

Figure 3.

AELO11207 attenuates MPTP-induced dopamine depletion. A–C, Striatal dopamine levels in C57BL/6 mice 7 d after injection of MPTP (15 mg/kg × 3, s.c., 24 h intervals) alone or in the presence of varying doses (5, 10, 15, or 25 mg/kg, s.c, 1 h before MPTP and daily thereafter for total 3 d) of AEOL11207 (A), after varying injection times (15 mg/kg, s.c., 1 h before MPTP and daily thereafter for a total of 2, 3, or 5 times) of AEOL11207 (B), or after different administration routes (C). Error bars represent mean + SEM. *p < 0.01 versus control; ^#p < 0.05 versus MPTP; one-way ANOVA; n = 6 mice per group.

Figure 4.

Striatal MPP+ levels are not altered by AEOL11207. Striatal MPP⁺ levels 3 and 24 h after MPTP (15 mg/kg, s.c.) alone or in the presence of AEOL11207 (15 mg/kg, s.c.), 1 h before MPTP treatment. Error bars represent mean + SEM. n = 6 mice per group.

Figure 5.

AEOL11207 protects against MPTP-induced loss of TH-positive SNpc cells. A, TH-positive neurons in the SNpc of C57BL/6 mice were counted using stereological analysis 7 d after injection of MPTP (15 mg/kg × 3, s.c., 24 h intervals) alone or in the presence of AEOL11207 (15 mg/kg, p.o. or s.c., 3 times, 24 h intervals). Error bars represent mean + SEM. *p < 0.01 versus control; ^#p < 0.05 versus MPTP; one-way ANOVA; n = 5–6 mice per group. B, Representative TH immunohistochemical staining in brain sections (6 μm thickness) from mice injected with saline (control), MPTP alone, MPTP plus AEOL11207 subcutaneous or MPTP plus AEOL11027 per oral at doses indicated above (A).

Figure 6.

AEOL11207 attenuates MPTP-induced free 3-NT formation and lipid peroxidation. A–E, Levels of 4-HNE (A), 3-NT (B), GSH (C), GSSG (D), and ratio of GSH/GSSG (E) in the ventral midbrain region of C57BL/6 mice 24 h after MPTP (15 mg/kg, 3 times, s.c., 24 h intervals) alone or in the presence of AEOL11207 per oral (15 mg/kg, 3 times, 24 h intervals). Error bars represent mean + SEM. *p < 0.05 versus control; ^#p < 0.01 versus MPTP; one-way ANOVA; n = 6 mice per group.