Tag: NMDA receptors

Treatment of Brain Fog of Long COVID Syndrome: A Hypothesis

Abstract:

The emergence of the SARS-CoV-2 (COVID-19) virus has exacted a significant toll on the global population in terms of fatalities, health consequences, and economics. As of February 2023, there have been almost 800 million confirmed cases of the disorder reported to the WHO [1], although the actual case-positive rate is estimated to be much higher.

While many cases recover, the mortality rate associated with the illness is about 1% (based on the WHO data). Most patients experience the illness as a mild to moderate disorder and recover without significant sequelae. However, as the COVID-19 pandemic has continued, there has emerged a significant group of COVID-19 survivors who experience persistent symptoms beyond the acute course of the illness.

As many as one in eight patients report persistent symptoms 90 to 150 days after the initial infection [2]. These so-called Long COVID or post-COVID syndrome patients are mostly drawn from those who were hospitalised for the disorder, but both non-hospitalised and vaccinated subjects may also experience the syndrome [3]. While an agreed definition of Long COVID is yet to be settled, a multiplicity of symptoms affecting most major organ systems has been reported in patients.

Common Long COVID symptoms include fatigue, dyspnoea, headaches, myalgia, anosmia, dysgeusia, cognitive symptoms, and mental disorders such as depression and anxiety [4]. It is estimated that approximately a third of patients with Long COVID exhibit either fatigue, cognitive impairment, or both up to 12 weeks after a confirmed diagnosis of COVID-19 [5].

Source: Norman TR. Treatment of Brain Fog of Long COVID Syndrome: A Hypothesis. Psychiatry International. 2023; 4(3):242-245. https://doi.org/10.3390/psychiatryint4030024 https://www.mdpi.com/2673-5318/4/3/24 (Full text)

Scientific Rationale for the Treatment of Cognitive Deficits from Long COVID

Abstract:

Sustained cognitive deficits are a common and debilitating feature of “long COVID”, but currently there are no FDA-approved treatments. The cognitive functions of the dorsolateral prefrontal cortex (dlPFC) are the most consistently afflicted by long COVID, including deficits in working memory, motivation, and executive functioning. COVID-19 infection greatly increases kynurenic acid (KYNA) and glutamate carboxypeptidase II (GCPII) in brain, both of which can be particularly deleterious to PFC function.
KYNA blocks both NMDA and nicotinic-alpha-7 receptors, the two receptors required for dlPFC neurotransmission, and GCPII reduces mGluR3 regulation of cAMP-calcium-potassium channel signaling, which weakens dlPFC network connectivity and reduces dlPFC neuronal firing. Two agents approved for other indications may be helpful in restoring dlPFC physiology: the antioxidant N-acetyl cysteine inhibits the production of KYNA, and the α2A-adrenoceptor agonist guanfacine regulates cAMP-calcium-potassium channel signaling in dlPFC and is also anti-inflammatory. Thus, these agents may be helpful in treating the cognitive symptoms of long COVID.
Source: Fesharaki Zadeh A, Arnsten AFT, Wang M. Scientific Rationale for the Treatment of Cognitive Deficits from Long COVID. Neurology International. 2023; 15(2):725-742. https://doi.org/10.3390/neurolint15020045 https://www.mdpi.com/2035-8377/15/2/45 (Full text)

Dissecting the Molecular Mechanisms Surrounding Post-COVID-19 Syndrome and Neurological Features

Abstract:

Many of the survivors of the novel coronavirus disease (COVID-19) are suffering from persistent symptoms, causing significant morbidity and decreasing their quality of life, termed “post-COVID-19 syndrome” or “long COVID”. Understanding the mechanisms surrounding PCS is vital to developing the diagnosis, biomarkers, and possible treatments.

Here, we describe the prevalence and manifestations of PCS, and similarities with previous SARS epidemics. Furthermore, we look at the molecular mechanisms behind the neurological features of PCS, where we highlight important neural mechanisms that may potentially be involved and pharmacologically targeted, such as glutamate reuptake in astrocytes, the role of NMDA receptors and transporters (EAAT2), ROS signaling, astrogliosis triggered by NF-κB signaling, KNDy neurons, and hypothalamic networks involving Kiss1 (a ligand for the G-protein-coupled receptor 54 (GPR54)), among others. We highlight the possible role of reactive gliosis following SARS-CoV-2 CNS injury, as well as the potential role of the hypothalamus network in PCS manifestations.

Source: Mohamed MS, Johansson A, Jonsson J, Schiöth HB. Dissecting the Molecular Mechanisms Surrounding Post-COVID-19 Syndrome and Neurological Features. Int J Mol Sci. 2022 Apr 12;23(8):4275. doi: 10.3390/ijms23084275. PMID: 35457093. https://www.mdpi.com/1422-0067/23/8/4275/htm (Full text)