Applicability of [18F]FDG/PET for investigating rosmarinic acid preconditioning efficacy in a global stroke model in mice

ABSTRACT Positron emission tomography (PET) is a non-invasive nuclear imaging technique that uses radiotracers to track cell activity. The radiopharmaceutical 18F-fluoro-2-deoxyglucose ([18F] FDG) is most commonly used in nuclear medicine for the diagnosis of various diseases, including stroke. A stroke is a serious condition with high mortality and morbidity rates. Rosmarinic acid (RA) is a promising therapeutic agent that exerts neuroprotective effects against various neurological diseases. Therefore, this study aimed to evaluate the applicability of [18F]FDG/PET for investigating the neuroprotective effects of RA in case of a global stroke model in mice. The [18F]FDG/PET technique facilitates the observation of ischemia and reperfusion injuries in the brain. Moreover, the recovery of glucose metabolism in three specific brain regions, the striatum, superior colliculus, and inferior colliculus, was observed after preconditioning with RA. It was concluded that the [18F]FDG/PET technique may be useful for stroke diagnosis and the assessment of treatment response. In addition, a long-term longitudinal study using biochemical analysis in conjunction with functional imaging may provide further conclusive results regarding the effect of RA on cerebral ischemia.

Neuroprotective effects of sinapic acid involve the iron regulatory role on the rotenone-induced Parkinson's disease model

Abstract In the last decades, ferroptosis and its relationship with Parkinson's disease have gained significant attention. Compounds that affect ferroptosis and iron-dependent pathways in particular, have possible candidates for study in this context.Sinapic acid is an iron-chelator and high antioxidant bioactive phenolic acid. Its neuroprotective action, due to the antioxidant capacity, has been shown in several experimental models.However, the relationship between iron and antioxidant actions is still misunderstood and therefore, in the current study, we tried to investigate the effects of sinapic acid in rotenone-induced Parkinson's disease with the aspect of ferroptosis and iron-dependent alterations.The Parkinson's disease model was induced by a single dose intrastriatal and intrategmental rotenone (5µg/µl) injection.Sinapic acid (30mg/ kg) was orally administered during a 28-day period after the Parkinson's disease model was validated.Our results demonstrated that sinapic acid treatment attenuated rotenone-induced increase of serum transferrin and iron levels.Furthermore, sinapic acid inhibited rotenone-induced heme oxygenase-1(HO-1) increase and decrease of glutathione peroxidase-4 (GPx-4) levels in brain tissue. Also, sinapic acid treatment decreased motor impairment, likely as a result of the ameliorative effects on the tyrosine hydroxylase immunoreactivity loss after the rotenone insult.Our study suggests that the iron regulatory role of sinapic acid possibly plays a role in the protective effect on rotenone-induced neuronal damage.

Neuroprotective effect of PPAR alpha and gamma agonists in a mouse model of amyloidogenesis through modulation of the Wnt/beta catenin pathway via targeting alpha- and beta-secretases.

The present study was conducted to evaluate the efficacy of fenofibrate and pioglitazone in a mouse model of amyloidogenesis induced by amyloidß (ßA) peptide. Mice were injected intracerebroventricularly with ßA1-40 (400 pmol/mouse) once, followed by treatment with fenofibrate (300 mg/kg), pioglitazone (30 mg/kg),or both. After 21 days of daily treatment, memory impairment and cognitive function were evaluated by Morris water maze (MWM), Y-maze and object recognition tests. On the 22nd day, mice were sacrificed, and their hippocampi were dissected to determine the levels of α- and ß-secretase, peroxisome proliferator-activated receptor (PPARα and ß), Wnt and ß-catenin. Significant memory impairment and cognitive dysfunction were observed in the mouse model group. This finding was associated with a significant increase in α- and ß-secretase levels and a significant decrease in Wnt, ß-catenin, and PPARα and ß levels. Neuronal damage was also evident after histopathological examination. Treatment with fenofibrate, pioglitazone and their combination resulted in a significant improvement in the behavioural and neurochemical changes induced by ßA injection. The present findings indicate that the combined administration of fenofibrate and pioglitazone was more effective than monotherapy in ameliorating the behavioural, neurochemical and histopathological changes in amyloidogenesis model mice and provide a promising therapeutic approach in the management of Alzheimer's disease complicated by diabetes and hypercholesterolemia.

GLP-1 receptor agonists show neuroprotective effects in animal models of diabetes.

Enzyme-resistant receptor agonists of the incretin hormone glucagon-like peptide-1 (GLP-1) have shown positive therapeutic effects in people with type 2 diabetes mellitus (T2DM). T2DM has detrimental effects on brain function and impairment of cognition and memory formation has been described. One of the underlying mechanisms is most likely insulin de-sensitization in the brain, as insulin improves cognitive impairments and enhances learning. Treatment with GLP-1 receptor agonists improves memory formation and impairment of synaptic plasticity observed in animal models of diabetes-obesity. Furthermore, it has been shown that diabetes impairs growth factor signalling in the brain and reduces energy utilization in the cortex. Inflammation and apoptotic signalling was also increased. Treatment with GLP-1 receptor agonists improved neuronal growth and repair and reduced inflammation and apoptosis as well as oxidative stress. In comparison with the diabetes drug metformin, GLP-1 receptor agonists were able to improve glycemic control and reverse brain impairments, whereas metformin only normalized blood glucose levels. Clinical studies in non-diabetic patients with neurodegenerative disorders showed neuroprotective effects following administration with GLP-1 receptor agonists, demonstrating that neuroprotective effects are independent of blood glucose levels.

The role of SIGMAR1 gene mutation and mitochondrial dysfunction in amyotrophic lateral sclerosis.

Amyotrophic lateral sclerosis (ALS) patients exhibit diverse pathologies such as endoplasmic reticulum (ER) stress and mitochondrial dysfunction in motor neurons. Five to ten percent of patients have familial ALS, a form of the disease caused by mutations in ALS-related genes, while sporadic forms of the disease occur in 90-95% of patients. Recently, it was reported that familial ALS patients exhibit a missense mutation in SIGMAR1 (c.304G > C), which encodes sigma-1 receptor (Sig-1R), substituting glutamine for glutamic acid at amino acid residue 102 (p.E102Q). Expression of that mutant Sig-1R(E102Q) protein reduces mitochondrial ATP production, inhibits proteasome activity and causes mitochondrial injury, aggravating ER stress-induced neuronal death in neuro2A cells. In this issue, we discuss mechanisms underlying mitochondrial impairment seen in ALS motor neurons and propose that therapies that protect mitochondria might improve the quality of life (QOL) of ALS patients and should be considered for clinical trials.

Lipoic acid protects C6 cells against ammonia exposure through Na⁺-K⁺-Cl⁻ co-transporter and PKC pathway.

Astrocytes play an essential role in the central nervous system (CNS) homeostasis. They providing metabolic support and protecting against oxidative stress and glutamatergic excitotoxicity. Glutamate uptake, an electrogenic function, is driven by cation gradients and the Na⁺-K⁺-Cl⁻ co-transporter (NKCC1) carries these ions into and out of the cell. Elevated concentrations of ammonia in the brain lead to cerebral dysfunction. Ammonia toxicity can be mediated by an excitotoxic mechanism, oxidative stress and ion discharged. Astrocytes also convert excess ammonia and glutamate into glutamine, via glutamine synthetase (GS). Lipoic acid (LA) is a modulator of the cellular redox status potentially beneficial in neurodegenerative diseases. In this study, we investigated the effect of LA on glial parameters, in C6 cells exposed to ammonia. Ammonia increased S100B secretion and decreased glutamate uptake, GS activity and glutathione (GSH) content. LA was able to prevent these effects. LA exerts its protective effect on glutamate uptake and S100B secretion via mechanisms dependent of NKCC1 and PKC. These findings show that LA is able to modulate glial function impairments by ammonia in vitro, indicating a potential therapeutic agent to improve glutamatergic metabolism and oxidative stress against hyperammonemia.

Peroxisome proliferator-activated receptor-γ (PPAR-γ) activation confers functional neuroprotection in global ischemia.

The neuroprotective effect of rosiglitazone, a peroxisome proliferator-activated receptor γ (PPARγ) agonist, has been investigated using both in vivo and in vitro models of global ischemia in CD1 mice. Behavioral tests were carried out prior to and at various times (up to 14 days) subsequent to bilateral common carotid artery occlusion followed by reperfusion. Mice at each time point were euthanized under anesthesia and the brain was removed, serially sliced and stained with 1% triphenyltetrazolium (TTC) to quantify infarct size. Administration of rosiglitazone (5 or 10 mg/kg, i.p.) 10 min prior to occlusion significantly reduced the postsurgical mortality rate (10-11 vs. 36%, P < 0.05). The higher dose of rosiglitazone (10 mg/kg) also significantly reduced the mean area of brain infarct at 1, 3, 7 and 14 days post-ischemia, reduced post-occlusion deficits in limb grasping and forelimb placing at various time points, and reduced total nitrite concentration in serum and brain homogenate at day 7 post-occlusion. To model global ischemia in vitro, coronal brain slices were incubated in oxygenated artificial cerebrospinal fluid (ACSF) in the presence of either glutamate (1 mM) or hydrogen peroxide (H(2)O(2)) (5 µM) for 30 min. Both H(2)O(2) and glutamate caused significant tissue damage, and co-incubation with rosiglitazone (5 µM) significantly reduced H(2)O(2)-induced damage but did not significantly reduce glutamate-induced brain damage in this model. Our observations provide further evidence for a neuroprotective effect of rosiglitazone in rodent models of ischemia.

Block of purinergic P2X(7) receptor is neuroprotective in an animal model of Alzheimer's disease.

Pharmacological antagonism of the ionotropic purinergic P2X7R has been studied for effects on inflammatory reactivity and neuronal viability in amyloid-beta1-42-injected rat hippocampus. Amyloid-beta1-42-injected brains (7-day postinjection) demonstrated marked increases in P2X7R expression, gliosis, leakiness of blood-brain barrier and loss of hippocampal neurons. The P2X7R antagonist, brilliant blue G reduced levels of purinergic receptor expression, attenuated gliosis, diminished leakiness of blood-brain barrier and was neuroprotective in peptide-injected brain. Brilliant blue G also demonstrated neuroprotection and antagonism against inflammatory responses induced by the P2X7R agonist, 2',3'-(benzoyl-4-benzoyl)-ATP. The findings constitute the first report that pharmacological inhibition of P2X7R, possibly by acting to inhibit inflammatory reactivity, confers neuroprotection in an animal model of Alzheimer's disease brain.

Paraxanthine, the primary metabolite of caffeine, provides protection against dopaminergic cell death via stimulation of ryanodine receptor channels.

Epidemiological evidence suggests that caffeine or its metabolites reduce the risk of developing Parkinson's disease, possibly by protecting dopaminergic neurons, but the underlying mechanism is not clearly understood. Here, we show that the primary metabolite of caffeine, paraxanthine (PX; 1, 7-dimethylxanthine), was strongly protective against neurodegeneration and loss of synaptic function in a culture system of selective dopaminergic cell death. In contrast, caffeine itself afforded only marginal protection. The survival effect of PX was highly specific to dopaminergic neurons and independent of glial cell line-derived neurotrophic factor (GDNF). Nevertheless, PX had the potential to rescue dopaminergic neurons that had matured initially with and were then deprived of GDNF. The protective effect of PX was not mediated by blockade of adenosine receptors or by elevation of intracellular cAMP levels, two pharmacological effects typical of methylxanthine derivatives. Instead, it was attributable to a moderate increase in free cytosolic calcium via the activation of reticulum endoplasmic ryanodine receptor (RyR) channels. Consistent with these observations, PX and also ryanodine, the preferential agonist of RyRs, were protective in an unrelated paradigm of mitochondrial toxin-induced dopaminergic cell death. In conclusion, our data suggest that PX has a neuroprotective potential for diseased dopaminergic neurons.

Change of hyperexcitability of hippocampus by cyclosporin A and its modulatory action by fentanyl.

Cyclosporin A is used to treat patients with immune-mediated diseases, chronic diseases requiring organ transplantation, or malignancies. These conditions often require higher cyclosporin A doses, which may be toxic to the central nervous system. Fentanyl is also used in clinical conditions that have a risk of hypoxic neurosusceptibility, which suggests that the drug may be a neuroprotective agonist against brain ischemic injury. Fentanyl is an opioid agonist and appears to play an important role in regulating the excitability of the hippocampus under electroconvulsion. In this study, the effects of fentanyl on modulating cyclosporin A-induced neurotoxicity was investigated. Treatment with 3 micrometer of cyclosporin A was found to reduce the electroconvulsive activity threshold. Fifty ng/mL of fentanyl reduced the electroconvulsive activity, and 1 micrometer of DAGO ([D-Ala2, N-Me-Phe4, Gly-ol]-enkephalin) also decreased the electroconvulsive activity. Fifty ng/mL of fentanyl was also found to reduce cyclosporin A-induced electroconvulsive activity. Although cyclosporin A neurotoxicity may be observed in various conditions, the opioid effect of neuroprotection may be involved in an interrelated mechanism. The exogenous opioid agonist suppressed cyclosporin A-induced electroconvulsive activity. Furthermore, there may be a functional anticonvulsant effect on cyclosporin A-induced neurotoxicity with an increased opioid agonist concentration.

Change of Hyperexcitability of Hippocampus by Cyclosporin A and Its Modulatory Action by Fentanyl

Cyclosporin A is used to treat patients with immune-mediated diseases, chronic diseases requiring organ transplantation, or malignancies. These conditions often require higher cyclosporin A doses, which may be toxic to the central nervous system. Fentanyl is also used in clinical conditions that have a risk of hypoxic neurosusceptiblity, which suggests that the drug may be a neuroprotective agonist against brain ischemic injury. Fentanyl is an opioid agonist and appears to play an important role in regulating the excitability of the hippocampus under electroconvulsion. In this study, the effects of fentanyl on modulating cyclosporin A-induced neurotoxicity was investigated. Treatment with 3 micrometer of cyclosporin A was found to reduce the electroconvulsive activity threshold. Fifty ng/mL of fentanyl reduced the electroconvulsive activity, and 1 micrometer of DAGO ([D-Ala2, N-Me-Phe4, Gly-ol]-enkephalin) also decreased the electroconvulsive activity. Fifty ng/mL of fentanyl was also found to reduce cyclosporin A-induced electroconvulsive activity. Although cyclosporin A neurotoxicity may be observed in various conditions, the opioid effect of neuroprotection may be involved in an interrelated mechanism. The exogenous opioid agonist suppressed cyclosporin A-induced electroconvulsive activity. Furthermore, there may be a functional anticonvulsant effect on cyclosporin A-induced neurotoxicity with an increased opioid agonist concentration.

Effects of trkB and trkC neurotrophin receptor agonists on thermal nociception: a behavioral and electrophysiological study.

Nerve-growth factor (NGF), a member of the neurotrophin family, plays an important role in nociceptor function. Prompted by a previous uinexpected finding that NT-4/5, as well as NGF sensitizes single nociceptors to noxious heat, we have explored the relative potency of all neurotrophins in eliciting thermal hyperalgesia. NGF, brain-derived neurotrophic factor (BDNF), NT-4/5 and NT-3 were injected locally into the hind paw of rats, and the behavioral response to noxious heat was compared with that from the other paw that received an identical injection of vehicle. Like NGF, agonists of tyrosine kinaseB (trkB) receptors (NT-4/5 and BDN F) induced thermal hyperalgesia in the first 5 h after treatment (NT-4/5 > BDNF) but the effect had worn off by 24 h. In contrast, the trkC agonist NT-3 had no effect on the response to noxious heat. Electrophysiological recordings from single C-fibres in the in vitro skin-saphenous nerve preparation revealed sensitization to noxious heat stimuli after direct application of BDNF to the receptive field, as previously noted for NT-4/5, and in parallel with the behavioral findings. NT-3 was ineffective as in the behavioral studies. These results suggest that trkB agonists BDNF and NT-4/5 as well as the trkA agonist NGF can regulate nociceptive responses to noxious heat.