1.
Melatonin: Roles in influenza, Covid-19, and other viral infections.
Anderson, G, Reiter, RJ
Reviews in medical virology. 2020;30(3):e2109
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Viruses like influenza and coronaviruses change quickly, making it challenging to develop effective treatments and vaccines in a short time frame. Consequently, the use of generic substances that limit viral effects are of high interest. In this paper, the authors summarize a range of mechanisms in which melatonin can alter the impact of virus infections and infection-associated inflammatory overdrive aka cytokine storm. Melatonin, the sleep hormone, is well known for its potent antioxidant and anti-inflammatory action. It seems highly likely that melatonin can modulate the cellular function of all cells, mostly via mitochondrial function. This is particularly relevant in immune cells. For example, the daytime variance in immune function seems to be closely linked with mitochondrial activity and energy production. Other relevant mechanisms described are the antiviral role of melatonin-induced sirtuins - proteins that regulate cellular health-, the impact of viruses on cell coordinating microRNA, the role of the gut microbiome and gut permeability, as well as sympathetic nervous system activation and the protective effects of parasympathetic activation. Also considered are pre-existing health conditions and conditions that are linked with a decline in melatonin along with ageing, all being groups in which severity of viral infections is felt. This paper may be of interest to those who like to explore in more depth the mechanisms behind melatonin and its ability to influence viral disease progression.
Abstract
There is a growing appreciation that the regulation of the melatonergic pathways, both pineal and systemic, may be an important aspect in how viruses drive the cellular changes that underpin their control of cellular function. We review the melatonergic pathway role in viral infections, emphasizing influenza and covid-19 infections. Viral, or preexistent, suppression of pineal melatonin disinhibits neutrophil attraction, thereby contributing to an initial "cytokine storm", as well as the regulation of other immune cells. Melatonin induces the circadian gene, Bmal1, which disinhibits the pyruvate dehydrogenase complex (PDC), countering viral inhibition of Bmal1/PDC. PDC drives mitochondrial conversion of pyruvate to acetyl-coenzyme A (acetyl-CoA), thereby increasing the tricarboxylic acid cycle, oxidative phosphorylation, and ATP production. Pineal melatonin suppression attenuates this, preventing the circadian "resetting" of mitochondrial metabolism. This is especially relevant in immune cells, where shifting metabolism from glycolytic to oxidative phosphorylation, switches cells from reactive to quiescent phenotypes. Acetyl-CoA is a necessary cosubstrate for arylalkylamine N-acetyltransferase, providing an acetyl group to serotonin, and thereby initiating the melatonergic pathway. Consequently, pineal melatonin regulates mitochondrial melatonin and immune cell phenotype. Virus- and cytokine-storm-driven control of the pineal and mitochondrial melatonergic pathway therefore regulates immune responses. Virus-and cytokine storm-driven changes also increase gut permeability and dysbiosis, thereby suppressing levels of the short-chain fatty acid, butyrate, and increasing circulating lipopolysaccharide (LPS). The alterations in butyrate and LPS can promote viral replication and host symptom severity via impacts on the melatonergic pathway. Focussing on immune regulators has treatment implications for covid-19 and other viral infections.
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Using psychoneuroimmunity against COVID-19.
Kim, SW, Su, KP
Brain, behavior, and immunity. 2020;87:4-5
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This viewpoint article raises awareness of the threat of COVID-19 poses to psychiatric patients who are in mental health hospitals. Those patients appear to have a much elevated mortality rate and are potentially more vulnerable to the effects of panic/anxiety due to the pandemic. Their lifestyle choices, influenced by fears about the virus, may also have a negative effect on their immunity. The article also raises the issue of the effects the pandemic and associated changes to day-to-day life can have on the mental and general health of the rest of the population, and in particular to mental health professionals, whose ability to care for their psychiatric patients may be impaired. The authors also briefly discuss the psychological and immunological mechanisms that connect our mental state to the ability of our immune system to fight infections, and the impact of our lifestyles and environments. To summarise they state that infected patients, uninfected quarantined individuals and medical professionals all require mental health supporting strategies, and that epidemiological studies of potential long-term psychiatric consequences are essential.
Abstract
The worldwide outbreak of coronavirus disease 2019 (COVID-19) raises concerns of widespread panic and anxiety in individuals subjected to the real or perceived threat of the virus. Compared to general populations, patients who are institutionalized in a closed unit are also very vulnerable to COVID-19 infection and complications. This crisis touched on difficult issues of not only psychiatric care and ethics, but also psychological impacts to psychiatric care givers. In this Viewpoint, we address both physical and biopsychosocial aspects of this infection, as well as the psychoneuroimmunity of preventive strategies of healthy lifestyle, regular exercise, balanced nutrition, quality sleep and a strong connection with people. Social distancing and wearing masks might help us from pathogen exposure, yet such these measures also prevent us from expressing compassion and friendliness. Therefore, all forms of psychological support should be routinely implemented not only to consider psychological resilience but also to enhance psychoneuroimmunity against COVID-19.
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Gut dysbiosis: a potential link between increased cancer risk in ageing and inflammaging.
Biragyn, A, Ferrucci, L
The Lancet. Oncology. 2018;19(6):e295-e304
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This study looks at the important role our gut bacterial and commensal microbes play in supporting immunity and potentially reducing the risk of cancer from aging. Cancer risk increases as we age and is one of the main causes of reduced life expectancy. Our gut microbiome changes continually in response to diet, lifestyle, infection, and activation of immune responses. Gut dysbiosis is characterised by a shift towards proinflammatory commensals and a reduction of beneficial microbes, which can cause impairment and leakiness of the intestinal barrier. This is thought to trigger inflammaging or rather aging in a state of continual inflammation, where the immune system is in a heightened state of activation, and the body essentially creates an environment conducive to cancer. The gut is populated by trillions of species of bacteria which work together with our immune cells. As we age the diversity and density of these beneficial bacteria reduce. Therapies which support the balance of our commensal bacteria may prove effective at reducing rates of cancer in the elderly.
Abstract
Cancer incidence substantially increases with ageing in both men and women, although the reason for this increase is unknown. In this Series paper, we propose that age-associated changes in gut commensal microbes, otherwise known as the microbiota, facilitate cancer development and growth by compromising immune fitness. Ageing is associated with a reduction in the beneficial commensal microbes, which control the expansion of pathogenic commensals and maintain the integrity of the intestinal barrier through the production of mucus and lipid metabolites, such as short-chain fatty acids. Expansion of gut dysbiosis and leakage of microbial products contributes to the chronic proinflammatory state (inflammaging), which negatively affects the immune system and impairs the removal of mutant and senescent cells, thereby enabling tumour outgrowth. Studies in animal models and the importance of commensals in cancer immunotherapy suggest that this status can be reversible. Thus, interventions that alter the composition of the gut microbiota might reduce inflammaging and rejuvenate immune functions to provide anticancer benefits in frail elderly people.