New animal models of progressive neurodegeneration: tools for identifying targets in predictive diagnostics and presymptomatic treatment

Trigeminal nerve stimulation: a current state-of-the-art review

Nearly 5 decades ago, the effect of trigeminal nerve stimulation (TNS) on cerebral blood flow was observed for the first time. This implication directly led to further investigations and TNS' success as a therapeutic intervention. Possessing unique connections with key brain and brainstem regions, TNS has been observed to modulate cerebral vasodilation, brain metabolism, cerebral autoregulation, cerebral and systemic inflammation, and the autonomic nervous system. The unique range of effects make it a prime therapeutic modality and have led to its clinical usage in chronic conditions such as migraine, prolonged disorders of consciousness, and depression. This review aims to present a comprehensive overview of TNS research and its broader therapeutic potentialities. For the purpose of this review, PubMed and Google Scholar were searched from inception to August 28, 2023 to identify a total of 89 relevant studies, both clinical and pre-clinical. TNS harnesses the release of vasoactive neuropeptides, modulation of neurotransmission, and direct action upon the autonomic nervous system to generate a suite of powerful multitarget therapeutic effects. While TNS has been applied clinically to chronic pathological conditions, these powerful effects have recently shown great potential in a number of acute/traumatic pathologies. However, there are still key mechanistic and methodologic knowledge gaps to be solved to make TNS a viable therapeutic option in wider clinical settings. These include bimodal or paradoxical effects and mechanisms, questions regarding its safety in acute/traumatic conditions, the development of more selective stimulation methods to avoid potential maladaptive effects, and its connection to the diving reflex, a trigeminally-mediated protective endogenous reflex. The address of these questions could overcome the current limitations and allow TNS to be applied therapeutically to an innumerable number of pathologies, such that it now stands at the precipice of becoming a ground-breaking therapeutic modality.

Methods to Investigate the Protection Against Neurodegenerative Disorders Provided by Progranulin Gene Transfer in the Brain

Progranulin (PGRN) is a multifunctional protein that is widely expressed throughout the brain, where it has been shown to be a critical regulator of CNS inflammation (Ahmed et al., J Neuroinflammation 4:7, 2007; Yin et al., J Exp Med 207:117-128, 2010; Martens et al., J Clin Investig 122:3955-3959; Inestrosa and Arenas). PGRN functions as an autocrine neuronal growth factor, important for long-term neuronal survival (Ahmed et al., J Neuroinflammation 4:7, 2007; Nat Rev Neurosci 11:77-86, 2009). Together, these critical roles in the CNS suggest that enhancing PGRN expression may provide neuronal support and protection for neurodegenerative disorders, such as Parkinson's disease (PD). Here, we describe the application of PGRN gene transfer using in vivo delivery of lentiviral expression vectors in a rodent model of PD.

Progressive changes in hippocampal cytoarchitecture in a neurodevelopmental rat model of epilepsy: implications for understanding presymptomatic epileptogenesis, predictive diagnosis, and targeted treatments

Epilepsies affect about 4% of the population and are frequently characterized by a prolonged "silent" period before the onset of spontaneous seizures. Most current animal models of epilepsy either involve acute seizure induction or kindling protocols that induce repetitive seizures. We have developed a rat model of epilepsy that is characterized by a slowly progressing series of behavioral abnormalities prior to the onset of behavioral seizures. In the current study, we further describe an accompanying progression of cytoarchitectural changes in the hippocampal formation. Groups of male and female SD rats received serial injections of a low dose of domoic acid (0.020 mg/kg) (or vehicle) throughout the second week of life. Postmortem hippocampal tissue was obtained on postnatal days 29, 64, and 90 and processed for glial fibrillary acidic protein (GFAP), NeuN, and calbindin expression. The data revealed no significant changes on postnatal day (PND) 29 but a significant increase in hilar NeuN-positive cells in some regions on PND 64 and 90 that were identified as ectopic granule cells. Further, an increase in GFAP positive cell counts and evidence of reactive astrogliosis was found on PND 90 but not at earlier time points. We conclude that changes in cellular expression, possibly due to on-going non-convulsive seizures, develop slowly in this model and may contribute to progressive brain dysfunction that culminates in a seizure-prone phenotype.

Small GSK-3 Inhibitor Shows Efficacy in a Motor Neuron Disease Murine Model Modulating Autophagy

Amyotrophic lateral sclerosis (ALS) is a progressive motor neuron degenerative disease that has no effective treatment up to date. Drug discovery tasks have been hampered due to the lack of knowledge in its molecular etiology together with the limited animal models for research. Recently, a motor neuron disease animal model has been developed using β-N-methylamino-L-alanine (L-BMAA), a neurotoxic amino acid related to the appearing of ALS. In the present work, the neuroprotective role of VP2.51, a small heterocyclic GSK-3 inhibitor, is analysed in this novel murine model together with the analysis of autophagy. VP2.51 daily administration for two weeks, starting the first day after L-BMAA treatment, leads to total recovery of neurological symptoms and prevents the activation of autophagic processes in rats. These results show that the L-BMAA murine model can be used to test the efficacy of new drugs. In addition, the results confirm the therapeutic potential of GSK-3 inhibitors, and specially VP2.51, for the disease-modifying future treatment of motor neuron disorders like ALS.

Intervention of mitochondrial dysfunction-oxidative stress-dependent apoptosis as a possible neuroprotective mechanism of α-lipoic acid against rotenone-induced parkinsonism and L-dopa toxicity

The current study evidenced hypothesis that mitochondrial dysfunction-oxidative stress-dependent apoptotic pathways play a critical role in degeneration of dopaminergic neurons in Parkinson's disease. Model of rotenone-induced parkinsonism in rats produced decrease in striatal complex I activity and reduced glutathione with increase in nitrites concentration and caspase-3 activity. This was confirmed by significant correlation of catalepsy score with neurochemical parameters. Moreover, electron microscopic examination of striatal neurons displayed ultrastructure affection as hyperchromatic nuclei and disrupted mitochondria that are typical features of undergoing apoptosis. Administration of L-dopa as replacement therapy, although caused symptomatic improvement in catalepsy score, but further worsening in neurochemical parameters. Therefore, efforts are not only to improve effect of L-dopa, but also to introduce drugs provide antiparkinsonian and neuroprotective effects. In this study, α-lipoic acid exhibited noticeable neuroprotective effects by a mechanism via intervention of mitochondrial dysfunction-oxidative stress-dependent apoptotic pathways. Combination of α-lipoic acid efficiently halting deleterious toxic effects of L-dopa, revealed normalization of catalepsy score in addition to amelioration of neurochemical parameters and apparent preservation of striatal ultrastructure integrity, indicating benefit of both symptomatic and neuroprotective therapy. In conclusion, α-lipoic acid could be recommended as a disease-modifying therapy when given with L-dopa early in course of Parkinson's disease.

Neurodegeneration: accelerated ageing or inadequate healthcare?

Current figures: About 300 million Diabetics frequently affected by Poly-Neuropathy as secondary complication, 18 million patients with Alzheimer’s disease also diagnosed as Diabetes Type 3, neurodegenerative eye diseases with leading causes of blindness—diabetic retinopathy and estimated 67 million glaucoma patients worldwide, millions of patients with Parkinson’s disease, Multiple Sclerosis, Epilepsy, Cerebral Palsy and Dementia in the elderly—altogether dramatically affect life quality, social and economical indexes of populations around the globe. Optimistic versus Pessimistic Prognosis depends much on diagnostic, preventive and treatment approaches which healthcare will preferably adopt in the near future. Without innovation in healthcare, neurodegenerative disorders can reach more than 30% of global disease burden till 2020. In contrast, effective utilisation of advanced early/predictive diagnostics, preventive and personalised medical approaches could enable a significant portion of population to reach the 100-year age limit remaining vibrant in excellent physical and mental health as actively contributing members of society.