Common Fatal Neurodegenerative Diseases Revisited: Beyond Age, Comorbidities, and Devastating Terminal Neuropathology There Is Hope With Prevention

Interplay between oxidative stress, neuroinflammatory cytokines and melatonin in Alzheimer's disease: Insights from cerebrospinal fluid analysis

Background

Among neurodegenerative disorders Alzheimer's disease (AD) displays the highest prevalence and the projected increase in its incidence will require new advances in early diagnosis and treatment, particularly for distinguishing AD from other dementias. While beta-amyloid (Aβ) and tau biomarkers are currently used to discriminate AD from other tauopathies and dementias, additional indicators could enhance patient stratification for specific dementia types. The present study was designed to find potential associations among the classic neurologic markers, Aβ, total and phospho-tau (T-tau and P-tau), with other biomarkers including melatonin and its oxidative-derived metabolite, Formyl-N-acetyl-5-methoxykynurenamine (AFMK) levels, assayed in patients' cerebrospinal fluid (CSF) taken previously for diagnostic purposes. Other factors previously associated with the aetiology of AD, including redox indicators or proinflammatory biomarkers, were also included.

Methods

The cross-sectional study included a cohort of 148 patients showing signs of dementia. A group of age-matched patients without neurological disorders were used as controls. CSF levels of Aβ, T-tau and P-tau were assayed, and patients were further classified according to threshold CSF levels of the three markers protein following the criteria of NIA-AA.

Results

Correlational and group analysis showed a positive association between oxidative stress and neuronal damage. TNF-α negatively correlated with CSF Aβ levels (amyloid plaques) while only RANTES/CCL5 correlated positively with T-tau and P-tau. Qualitative analysis of the proinflammatory cytokines assayed showed a higher detection level in Aβ-positive patients. Regarding melatonin in the CSF, indolamine levels did not correlate with its major oxidative-derived metabolite, i.e., AFMK. However, melatonin CSF levels were significantly reduced in AD patients but not in OT. On the contrary, AFMK showed the opposite pattern, with higher levels in samples from patients displaying high T-tau and P-tau levels. Neuroinflammation was associated with Aβ deposits (low concentration in CSF), while oxidative stress significantly correlated with high T-tau and P-tau levels. Finally, among all the parameters assayed in CSF samples from the cohort studied, P-tau, in combination with antioxidant capacity, offered the best ROC curve for the diagnostic capacity to discriminate between AD and OT, showing an 85 % specificity.

Conclusion

While oxidative stress is instead associated with high T- and P-tau levels, higher neuroinflammatory cytokines correlate with low CSF Aβ levels. An intriguing lack of correlation between neuroinflammation and melatonin found in this study could be as a result of sample size and requires further studies with a larger sample size. Even though indolamine levels in CSF drop significantly in AD, they do not correlate with AFMK, suggesting a different kynurenine synthesis source. None of them appear to discriminate between AD and OT. Finally, among all the parameters assayed in this study, P-tau in combination with antioxidant capacity, offered the best ROC curve for the diagnostic ability capacity to discriminate between AD and OT, showing an 85 % specificity. This study holds the potential to significantly improve patient stratification and contribute to the early diagnosis and treatment of Alzheimer's disease.

Unraveling the Genetic Landscape of Neurological Disorders: Insights into Pathogenesis, Techniques for Variant Identification, and Therapeutic Approaches

Genetic abnormalities play a crucial role in the development of neurodegenerative disorders (NDDs). Genetic exploration has indeed contributed to unraveling the molecular complexities responsible for the etiology and progression of various NDDs. The intricate nature of rare and common variants in NDDs contributes to a limited understanding of the genetic risk factors associated with them. Advancements in next-generation sequencing have made whole-genome sequencing and whole-exome sequencing possible, allowing the identification of rare variants with substantial effects, and improving the understanding of both Mendelian and complex neurological conditions. The resurgence of gene therapy holds the promise of targeting the etiology of diseases and ensuring a sustained correction. This approach is particularly enticing for neurodegenerative diseases, where traditional pharmacological methods have fallen short. In the context of our exploration of the genetic epidemiology of the three most prevalent NDDs-amyotrophic lateral sclerosis, Alzheimer's disease, and Parkinson's disease, our primary goal is to underscore the progress made in the development of next-generation sequencing. This progress aims to enhance our understanding of the disease mechanisms and explore gene-based therapies for NDDs. Throughout this review, we focus on genetic variations, methodologies for their identification, the associated pathophysiology, and the promising potential of gene therapy. Ultimately, our objective is to provide a comprehensive and forward-looking perspective on the emerging research arena of NDDs.

Emerging Potential of the Phosphodiesterase (PDE) Inhibitor Ibudilast for Neurodegenerative Diseases: An Update on Preclinical and Clinical Evidence

Neurodegenerative diseases constitute a broad range of central nervous system disorders, characterized by neuronal degeneration. Alzheimer's disease, Parkinson's disease, amyolotrophic lateral sclerosis (ALS), and progressive forms of multiple sclerosis (MS) are some of the most frequent neurodegenerative diseases. Despite their diversity, these diseases share some common pathophysiological mechanisms: the abnormal aggregation of disease-related misfolded proteins, autophagosome-lysosome pathway dysregulation, impaired ubiquitin-proteasome system, oxidative damage, mitochondrial dysfunction and excessive neuroinflammation. There is still no effective drug that could halt the progression of neurodegenerative diseases, and the current treatments are mainly symptomatic. In this regard, the development of novel multi-target pharmaceutical approaches presents an attractive therapeutic strategy. Ibudilast, an anti-inflammatory drug firstly developed as an asthma treatment, is a cyclic nucleotide phosphodiesterases (PDEs) inhibitor, which mainly acts by increasing the amount of cyclic adenosine monophosphate (cAMP) and cyclic guanosine monophosphate (cGMP), while downregulating the pro-inflammatory factors, such as tumor necrosis factor-α (TNF-α), macrophage migration inhibitory factor (MIF) and Toll-like receptor 4 (TLR-4). The preclinical evidence shows that ibudilast may act neuroprotectively in neurodegenerative diseases, by suppressing neuroinflammation, inhibiting apoptosis, regulating the mitochondrial function and by affecting the ubiquitin-proteasome and autophagosome-lysosome pathways, as well as by attenuating oxidative stress. The clinical trials in ALS and progressive MS also show some promising results. Herein, we aim to provide an update on the emerging preclinical and clinical evidence on the therapeutic potential of ibudilast in these disorders, discuss the potential challenges and suggest the future directions.