Effect of a single intrastriatal rotenone injection on oxidative stress and neurodegeneration in the rat brain

Vortioxetine ameliorates motor and cognitive impairments in the rotenone-induced Parkinson's disease via targeting TLR-2 mediated neuroinflammation

Parkinson's disease (PD) is characterized by motor and non-motor symptoms associated with dopaminergic and non-dopaminergic injury. Vortioxetine is a multimodal serotonergic antidepressant with potential procognitive effects. This study aimed to explore the effects of vortioxetine on motor functions, spatial learning and memory, and depression-like behavior in the rotenone-induced rat model of PD. Male Sprague-Dawley rats were daily administered with the rotenone (2 mg·kg^-1, s.c.) and/or vortioxetine (10 mg·kg^-1, s.c.) for 28 days. Motor functions (rotarod, catalepsy, open-field), depression-like behaviors (sucrose preference test), anxiety (elevated plus maze), and spatial learning and memory abilities (novel object recognition and Morris water maze) were evaluated in behavioral tests. Then immunohistochemical, neurochemical, and biochemical analysis on specific brain areas were performed. Vortioxetine treatment markedly reduced rotenone-induced neurodegeneration, improved motor and cognitive dysfunction, decreased depression-like behaviors without affecting anxiety-like parameters. Vortioxetine also restored the impaired inflammatory response and affected neurotransmitter levels in brain tissues. Interestingly, vortioxetine was thought to trigger a sort of dysfunction in basal ganglia as evidenced by increased Toll-like receptor-2 (TLR-2) and decreased TH immunoreactivity only in substantia nigra tissue of PD rats compared to the control group. The present study indicates that vortioxetine has beneficial effects on motor dysfunction as well as cognitive impairment associated with neurodegeneration in the rotenone-induced PD model. Possible mechanisms underlying these beneficial effects cover TLR-2 inhibition and neurochemical restoration of vortioxetine.

Acceleration of protein glycation by oxidative stress and comparative role of antioxidant and protein glycation inhibitor

Hyperglycemia in diabetes causes protein glycation that leads to oxidative stress, release of cytokines, and establishment of secondary complications such as neuropathy, retinopathy, and nephropathy. Several other metabolic disorders, stress, and inflammation generate free radicals and oxidative stress. It is essential to study whether oxidative stress independently enhances protein glycation leading to rapid establishment of secondary complications. Oxidative stress was experimentally induced using rotenone and Fenton reagent for in vivo and in vitro studies, respectively. Results showed significant increase in the rate of modification of BSA in the form of fructosamine and protein-bound carbonyls in the presence of fenton reagent. Circular dichroism studies revealed gross structural changes in the reduction of alpha helix structure and decreased protein surface charge was confirmed by zeta potential studies. Use of rotenone demonstrated enhanced AGE formation, ROS generation, and liver and kidney tissue glycation through fluorescence measurement. Similar findings were also observed in cell culture studies. Use of aminoguanidine, a protein glycation inhibitor, demonstrated reduction in these changes; however, a combination of aminoguanidine along with vitamin E demonstrated better amelioration. Thus, oxidative stress accelerates the process of protein glycation causing gross structural changes and tissue glycation in insulin-independent tissues. Use of antioxidants and protein glycation inhibitors in combination are more effective in preventing such changes and could be an effective therapeutic option for preventing establishment of secondary complications of diabetes.

Gut-brain and brain-gut axis in Parkinson's disease models: Effects of a uridine and fish oil diet

Recent investigations have focused on the potential role of gastrointestinal (GI) abnormalities in the pathogenesis of Parkinson's disease (PD). The 'dual-hit' hypothesis of PD speculates that a putative pathogen enters the brain via two routes: the olfactory system and the GI system. Here, we investigated (1) whether local exposures of the neurotoxin rotenone in the gut or the brain of mice could induce PD-like neurological and GI phenotypes as well as a characteristic neuropathology in accordance with this 'dual-hit hypothesis' and (2) the effects of a diet containing uridine and fish oil providing docosahexaenoic acid (DHA), in both models. Mice were given rotenone either orally or by an injection in the striatum. Dietary interventions were started 1 week before rotenone exposures. We found that (1) both oral and intrastriatal administration of rotenone induced similar PD-like motor deficits, dopaminergic cell loss, delayed intestinal transit, inflammation, and alpha-synuclein accumulation in the colon; (2) the uridine and DHA containing diet prevented rotenone-induced motor and GI dysfunctions in both models. The models suggest possible bidirectional communication between the gut and the brain for the genesis of PD-like phenotype and pathology. The dietary intervention may provide benefits in the prevention of motor and non-motor symptoms in PD.