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Adenosine Receptors in Modulation of Central Nervous System Disorders

Choudhury H, Chellappan DK, Sengupta P, Pandey M, Gorain B

Curr Pharm Des, 2019;25(26):2808-2827.
PMID: 31309883 DOI: 10.2174/1381612825666190712181955

The ubiquitous signaling nucleoside molecule, adenosine is found in different cells of the human body to provide its numerous pharmacological role. The associated actions of endogenous adenosine are largely dependent on conformational change of the widely expressed heterodimeric G-protein-coupled A1, A2A, A2B, and A3 adenosine receptors (ARs). These receptors are well conserved on the surface of specific cells, where potent neuromodulatory properties of this bioactive molecule reflected by its easy passage through the rigid blood-brainbarrier, to simultaneously act on the central nervous system (CNS). The minimal concentration of adenosine in body fluids (30-300 nM) is adequate to exert its neuromodulatory action in the CNS, whereas the modulatory effect of adenosine on ARs is the consequence of several neurodegenerative diseases. Modulatory action concerning the activation of such receptors in the CNS could be facilitated towards neuroprotective action against such CNS disorders. Our aim herein is to discuss briefly pathophysiological roles of adenosine on ARs in the modulation of different CNS disorders, which could be focused towards the identification of potential drug targets in recovering accompanying CNS disorders. Researches with active components with AR modulatory action have been extended and already reached to the bedside of the patients through clinical research in the improvement of CNS disorders. Therefore, this review consist of recent findings in literatures concerning the impact of ARs on diverse CNS disease pathways with the possible relevance to neurodegeneration.

Matched MeSH terms: Central Nervous System Diseases/physiopathology*
Fulltext Mechanisms underpinning sympathetic nervous activity and its modulation using transcutaneous vagus nerve stimulation

Deuchars SA, Lall VK, Clancy J, Mahadi M, Murray A, Peers L, et al.

Exp Physiol, 2018 Mar 01;103(3):326-331.
PMID: 29205954 DOI: 10.1113/EP086433

What is the topic of this review? This review briefly considers what modulates sympathetic nerve activity and how it may change as we age or in pathological conditions. It then focuses on transcutaneous vagus nerve stimulation, a method of neuromodulation in autonomic cardiovascular control. What advances does it highlight? The review considers the pathways involved in eliciting the changes in autonomic balance seen with transcutaneous vagus nerve stimulation in relationship to other neuromodulatory techniques. The autonomic nervous system, consisting of the sympathetic and parasympathetic branches, is a major contributor to the maintenance of cardiovascular variables within homeostatic limits. As we age or in certain pathological conditions, the balance between the two branches changes such that sympathetic activity is more dominant, and this change in dominance is negatively correlated with prognosis in conditions such as heart failure. We have shown that non-invasive stimulation of the tragus of the ear increases parasympathetic activity and reduces sympathetic activity and that the extent of this effect is correlated with the baseline cardiovascular parameters of different subjects. The effects could be attributable to activation of the afferent branch of the vagus and, potentially, other sensory nerves in that region. This indicates that tragus stimulation may be a viable treatment in disorders where autonomic activity to the heart is compromised.

Matched MeSH terms: Autonomic Nervous System Diseases/physiopathology*
Large fiber peripheral neuropathy in systemic sclerosis: A prospective study using clinical and electrophysiological definition

Raja J, Balaikerisnan T, Ramanaidu LP, Goh KJ

Int J Rheum Dis, 2021 Mar;24(3):347-354.
PMID: 33432774 DOI: 10.1111/1756-185X.14042

AIM: The reported prevalence of peripheral neuropathy in systemic sclerosis (SSc) is variable between 0.01% to 28%, probably due to differences in sample size, study design and population. Our aim is to determine the prevalence of large fiber peripheral neuropathy in SSc and to identify any contributing factors.
METHOD: A prospective cross-sectional study of 60 SSc patients were evaluated for large fiber neuropathy using the modified clinical Total Neuropathy Score (cTNS) and nerve conduction study (NCS) of the upper and lower limbs. A combination of clinical (cTNS score ≥ 2) and NCS criteria (≥2 abnormal nerves including 1 sural [symmetrical polyneuropathy] and NCS abnormalities consistent with individual nerves/nerve roots [focal neuropathy]) was used to diagnose peripheral neuropathy.
RESULTS: The majority had limited cutaneous subset (75%). Mean age was 55.73 (SD ± 13.04) years and mean disease duration was 8.61 (SD ± 8.09) years. Twenty-two (36.7%) had combined clinical and NCS criteria for peripheral neuropathy, 14 (23.3%) with symmetrical polyneuropathy and 8 (13.3%) with focal neuropathy. Symmetrical polyneuropathy patients had significantly lower hemoglobin levels (11.2 vs. 12.35 g/L; P = .047). Serum vitamin B12 levels were normal, therefore excluding vitamin B12 deficiency. No other associations were found for both polyneuropathy and focal neuropathy with demography, co-morbid diseases and SSc disease factors such as Raynaud's phenomenon and modified Rodnan skin score.
CONCLUSION: Large fiber neuropathy is common in SSc patients, which could contribute to non-lethal burden in SSc with sensory loss and muscle weakness. Apart from lower hemoglobin in polyneuropathy, there were no associations with disease-specific features or co-morbid diseases.

Matched MeSH terms: Peripheral Nervous System Diseases/physiopathology
Fulltext Evidence of Coronavirus (CoV) Pathogenesis and Emerging Pathogen SARS-CoV-2 in the Nervous System: A Review on Neurological Impairments and Manifestations

Jha NK, Ojha S, Jha SK, Dureja H, Singh SK, Shukla SD, et al.

J Mol Neurosci, 2021 Nov;71(11):2192-2209.
PMID: 33464535 DOI: 10.1007/s12031-020-01767-6

The coronavirus disease 2019 (COVID-19) pandemic is an issue of global significance that has taken the lives of many across the world. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is the virus responsible for its pathogenesis. The pulmonary manifestations of COVID-19 have been well described in the literature. Initially, it was thought to be limited to the respiratory system; however, we now recognize that COVID-19 also affects several other organs, including the nervous system. Two similar human coronaviruses (CoV) that cause severe acute respiratory syndrome (SARS-CoV-1) and Middle East respiratory syndrome (MERS-CoV) are also known to cause disease in the nervous system. The neurological manifestations of SARS-CoV-2 infection are growing rapidly, as evidenced by several reports. There are several mechanisms responsible for such manifestations in the nervous system. For instance, post-infectious immune-mediated processes, direct virus infection of the central nervous system (CNS), and virus-induced hyperinflammatory and hypercoagulable states are commonly involved. Guillain-Barré syndrome (GBS) and its variants, dysfunction of taste and smell, and muscle injury are numerous examples of COVID-19 PNS (peripheral nervous system) disease. Likewise, hemorrhagic and ischemic stroke, encephalitis, meningitis, encephalopathy acute disseminated encephalomyelitis, endothelialitis, and venous sinus thrombosis are some instances of COVID-19 CNS disease. Due to multifactorial and complicated pathogenic mechanisms, COVID-19 poses a large-scale threat to the whole nervous system. A complete understanding of SARS-CoV-2 neurological impairments is still lacking, but our knowledge base is rapidly expanding. Therefore, we anticipate that this comprehensive review will provide valuable insights and facilitate the work of neuroscientists in unfolding different neurological dimensions of COVID-19 and other CoV associated abnormalities.

Matched MeSH terms: Nervous System Diseases/physiopathology