Transglutaminases are a family of Ca2+-dependent enzymes which catalyze post-translational modifications of proteins. The main activity of these enzymes is the cross-linking of glutaminyl residues of a protein/peptide substrate to lysyl residues of a protein/peptide co-substrate. In addition to lysyl residues, other second nucleophilic co-substrates may include monoamines or polyamines (to form mono-or bi-substituted/crosslinked adducts) or -OH groups (to form ester linkages). In absence of co-substrates, the nucleophile may be water, resulting in the net deamidation of the glutaminyl residue. Transglutaminase activity has been suggested to be involved in molecular mechanisms responsible for both physiological and pathological processes. In particular, transglutaminase activity has been shown to be responsible for human autoimmune diseases, and Celiac Disease is just one of them. Interestingly, neurodegenerative diseases, such as Alzheimer’s disease, Parkinson’s disease, supranuclear palsy, Huntington’s disease and other polyglutamine diseases, are characterized in part by aberrant cerebral transglutaminase activity and by increased cross-linked proteins in affected brains. Here we describe the possible molecular mechanisms by which these enzymes could be responsible for such diseases and the possible use of transglutaminase inhibitors for patients with diseases characterized by aberrant transglutaminase activity.

The biological changes caused by oxidative stress (OS) are known to be involved in the etiology of neurodegenerative disorders, including Alzheimer’s disease, amyotrophic lateral sclerosis, Huntington’s disease, and Parkinson’s disease. The brain is particularly vulnerable to OS due to its high lipid content and extensive consumption of oxygen. OS processes, particularly the excessive production of reactive oxygen species (ROS), play a critical role in how neurodegenerative disorders develop. This is evidenced by in vivo studies investigating various biomolecules related to OS, such as products of lipid and DNA oxidation. Accordingly, ROS can also cause oxidative-related damage in neurodegenerative disorders, including dopamine auto-oxidation, mitochondrial dysfunction, glial cell activation, α-synuclein aggregation, excessive free iron, and changes in calcium signaling. Furthermore, excessive levels of cellular oxidants reduce antioxidant defenses, which in turn propagate the cycle of OS. As such, it is increasingly important to determine the linkage between a high intake of antioxidants through dietary interventions and a lower risk of developing neurodegenerative diseases. Indeed, in addition to modulating the immune system, optimal nutritional status is capable of changing various processes of neuroinflammation known to be involved in the pathogenesis of neurodegeneration. Accordingly, a better understanding of the role ROS plays in the etiology of neurodegeneration is needed, along with the identification of dietary interventions that may lead to improved therapeutic strategies for both the treatment and prevention of neurodegenerative disorders. Therefore, this review presents a comprehensive summary of the role of ROS in the pathogenesis of neurodegenerative disorders. In addition, nutrients believed to be useful for mitigating and counteracting ROS are discussed. 

Parkinson’s disease (PD) is thought to be the most common neurodegenerative disease with movement disorder. The key motor symptoms are rigidity, tremor, akinesis/hypokinesia/bradykinesia, and postural instability. However, in our day-to-day clinical practice we tend to see several other symptoms which may be motor or non-motor. Non-motor symptoms (NMS) are quite common and debilitating. The pathological hallmarks of PD are loss of dopaminergic neurons in the substantia nigra pars compacta (SNPc) and accumulation of unfolded or misfolded alpha-synuclein. Diagnosis of PD is difficult in the pre-motor stage. Late diagnosis renders a substantial loss of dopaminergic neurons in SNPc and spread of disease in other parts of the brain. This may manifest as either full blown symptoms requiring multiple medications or may even lead to life threatening condition due to lack of early diagnostic tools and techniques. Biomarkers are required to diagnose PD at a very early stage when prevention is possible. Hence, we see a lot of interest among researchers involved in finding a biomarker specific to the disease. Biomarkers may be clinical, image based, genetic, and biochemical. Cerebrospinal fluid (CSF) and serum markers which may correlate with disease pathophysiology are of great significance. One such molecule which recently gained a lot of attention is neuron-specific enolase (NSE). The main aim of this paper is to highlight the role of NSE in predicting neurodegeneration and neuroinflammation ultimately reflecting damage of brain cells in PD.

Background: The age-dependent sporadic form of PD is characterized by the degeneration of dopaminergic (DA) neurons in the Substantia Nigra (SN), gliosis, and vascular changes. Vascular changes may contribute to the onset of the disease and exacerbate the neurodegenerative process, as some vascular changes occur before the onset of neuronal loss. To demonstrate the anti-neuroinflammatory efficacy of a new compound, a water-soluble form of dihydroquercetin (DHQ-WF), we studied the structural changes of microcirculatory vasculature, astroglial GFAP, and vascular endothelial growth factor –A (VEGF-A) mRNA expression in the SN of young and old rats after unilateral nigral treatment by lipopolysaccharide (LPS) and oral administration of DHQ-WF.Materials and methods: The experiments were performed on 18 young (8 weeks - 10 weeks old; 250 g - 320 g) and 18 old (18 months - 19 months old; 390 g - 450 g) male Vistar rats. Young and adult rats from the experimental groups were stereotactically injected with 2 μL LPS solution (LPS from Escherichia coli; 0,01 μL/mL) into one side of the SN. Control young and old rats were similarly injected with 2 μL sterile saline. Half of the animals in both the control and experimental groups (6 animals in each group) received a 2 ml solution containing DHQ-WF at a concentration of 3 mg/ml orally every day. After 8 weeks, brains were harvested and serial cryostat sections were prepared for histochemical (FITC-labeled tomato lectin), immunohistochemical (anti-GFAP Antibody, Cy3 Conjugate) staining, and real-time PCR (mRNA VEGF-A).Results: Eight weeks after LPS injection into the SN, a significant excess of areas occupied by cell bodies and processes of astroglial cells, the density of microcirculatory vessels, and mRNA VEGF-A expression was observed in old animals compared to control old animals and young LPS-treated rats.  Oral administration of DHQ-WF to LPS-treated rats resulted in a significant reduction of these parameters in old animals.Conclusion: Injection of LPS into rat SN induces neuroinflammation and vascular angiogenesis, maximally expressed in old animals.  Administration of DHQ-WF for 8 weeks significantly reduces these LPS-induced changes. DHQ-WF may be an effective treatment for reducing the effects of neuroinflammation in the aging brain.