Nigrostriatal damage after systemic rotenone and/or lipopolysaccharide and the effect of cannabis

In this study, we compared the effects of systemic rotenone, lipopolysaccharide (LPS), or both rotenone and LPS on oxidative stress and nigrostriatal cell damage in mice. We further investigated the therapeutic potential of cannabis in these rodent models of Parkinson's disease. Rotenone (1.5 mg/kg, subcutaneously, three times per week), LPS (0.2 mg/kg, intraperitoneally, daily), or LPS plus rotenone was given alone or in combination with cannabis (20 mg/kg, expressed as Δ9-tetrahydrocannabinol, subcutaneously daily) for 2 weeks. Mice were tested for behavioral changes on the 14th day after different treatments. Biochemical markers of oxidative stress such as malondialdehyde (MDA), reduced glutathione (GSH), nitric oxide (nitrite), paraoxonase 1 (PON1) activity as well as monoamine neurotransmitters in the brain were determined. Histopathology, tyrosine hydroxylase immunoreactivity (TH-ir), inducible nitric oxide synthase (iNOS), and caspase-3 immunohistochemistry were also performed. Either rotenone or LPS injection was followed by increased MDA and decreased GSH in the cortex, striatum, and the rest of the brain (subcortex). There was increased nitrite and decreased PON1 activity in the cortex and subcortex. The increase in nitrite by combined LPS–rotenone in the cortex was significantly higher than that caused only LPS. In the subcortex, nitrite was significantly increased compared with either agent alone. The biochemical changes induced by rotenone, LPS, or rotenone + LPS were reduced, but not prevented by cannabis. In the striatum, the administration of only cannabis induced mild degenerative changes with shrunken neurons and pyknotic nuclei, a slight decrease in TH-ir, and mild iNOS and caspase-3 immunoreactivities. LPS injection was followed by pyknotic and apoptotic nuclei and perinuclear cytoplasmic vacuoles and decreased TH-ir with mild iNOS and caspase-3 immunoreactivities. Meanwhile, marked striatal neurodegeneration was observed after rotenone with shrunken and distorted neurons, pericellular haloes, inflammation, and hemorrhage. Markedly decreased TH-ir and increased iNOS and caspase-3 immunoreactivities were observed. The loss of pigmented neurons, the decrease of TH-ir, and the increase in both iNOS and caspase-3 immunoreactivities were markedly increased by administering both rotenone and LPS. The administration of cannabis did not reduce nigrostriatal damage due to rotenone, LPS, or rotenone + LPS, although an improvement in striatal TH-ir was observed. Thus, (1) systemic rotenone or LPS increased oxidative and nitrosative stress in brain and (2) induced nigrostriatal neuronal damage; (3) the effect was not limited to the striatum but involved other areas such as the cerebral cortex and hippocampus; (4) the neuronal damage caused by rotenone was increased in the presence of systemic inflammation; (5) rotenone induced caspase-3-mediated apoptosis; (6) cannabis reduced brain oxidative stress but failed to alleviate nigrostriatal damage due to rotenone, LPS, or rotenone + LPS; and (7) cannabis increased TH immnunostaining in the striatum after rotenone, LPS, or rotenone + LPS. This effect of cannabis does not appear to reflect a neuroprotective effect and might be due to increased striatal dopamine levels by cannabis. © 2013, Springer-Verlag London.