Benign coxsackievirus damages heart muscle in iron-loaded vitamin E-deficient mice

Ferroptosis, from the virus point of view: opportunities and challenges

Ferroptosis is a new type of cell death, which is mainly dependent on the formation and accumulation of reactive oxygen species and lipid peroxides mediated by iron. It is distinct from other forms of regulation of cell death in morphology, immunology, biochemistry, and molecular biology. Various cell death mechanisms have been observed in many viral infections, and virus-induced cell death has long been considered as a double-edged sword that can inhibit or aggravate viral infections. However, understanding of the role of ferroptosis in various viral infections is limited. Special attention will be paid to the mechanisms of ferroptosis in mediating viral infection and antiviral treatment associated with ferroptosis. In this paper, we outlined the mechanism of ferroptosis. Additionally, this paper also review research on ferroptosis from the perspective of the virus, discussed the research status of ferroptosis in virus infection and classified and summarized research on the interaction between viral infections and ferroptosis.

Selenium, Selenoproteins and Viral Infection

Reactive oxygen species (ROS) are frequently produced during viral infections. Generation of these ROS can be both beneficial and detrimental for many cellular functions. When overwhelming the antioxidant defense system, the excess of ROS induces oxidative stress. Viral infections lead to diseases characterized by a broad spectrum of clinical symptoms, with oxidative stress being one of their hallmarks. In many cases, ROS can, in turn, enhance viral replication leading to an amplification loop. Another important parameter for viral replication and pathogenicity is the nutritional status of the host. Viral infection simultaneously increases the demand for micronutrients and causes their loss, which leads to a deficiency that can be compensated by micronutrient supplementation. Among the nutrients implicated in viral infection, selenium (Se) has an important role in antioxidant defense, redox signaling and redox homeostasis. Most of biological activities of selenium is performed through its incorporation as a rare amino acid selenocysteine in the essential family of selenoproteins. Selenium deficiency, which is the main regulator of selenoprotein expression, has been associated with the pathogenicity of several viruses. In addition, several selenoprotein members, including glutathione peroxidases (GPX), thioredoxin reductases (TXNRD) seemed important in different models of viral replication. Finally, the formal identification of viral selenoproteins in the genome of molluscum contagiosum and fowlpox viruses demonstrated the importance of selenoproteins in viral cycle.

Enterovirus 71 induces mitochondrial reactive oxygen species generation that is required for efficient replication

Redox homeostasis is an important host factor determining the outcome of infectious disease. Enterovirus 71 (EV71) infection has become an important endemic disease in Southeast Asia and China. We have previously shown that oxidative stress promotes viral replication, and progeny virus induces oxidative stress in host cells. The detailed mechanism for reactive oxygen species (ROS) generation in infected cells remains elusive. In the current study, we demonstrate that mitochondria were a major ROS source in EV71-infected cells. Mitochondria in productively infected cells underwent morphologic changes and exhibited functional anomalies, such as a decrease in mitochondrial electrochemical potential ΔΨ_m and an increase in oligomycin-insensitive oxygen consumption. Respiratory control ratio of mitochondria from infected cells was significantly lower than that of normal cells. The total adenine nucleotide pool and ATP content of EV71-infected cells significantly diminished. However, there appeared to be a compensatory increase in mitochondrial mass. Treatment with mito-TEMPO reduced eIF2α phosphorylation and viral replication, suggesting that mitochondrial ROS act to promote viral replication. It is plausible that EV71 infection induces mitochondrial ROS generation, which is essential to viral replication, at the sacrifice of efficient energy production, and that infected cells up-regulate biogenesis of mitochondria to compensate for their functional defect.

Induced susceptibility of host is associated with an impaired antioxidant system following infection with Cryptosporidium parvum in Se-deficient mice

BACKGROUND

Susceptibility or resistance to infection with Cryptosporidium parvum (C.parvum) correlates with Selenium (Se) deficiency in response to infection. Both adult Se-adequate and Se-deficient mouse models of cryptosporidiosis were used to study the cell-mediated immune response during the course of C. parvum infection.

METHODOLOGY/PRINCIPAL FINDINGS

Blood samples from mouse models were used for Se status. The concentration of MDA, SOD, GPx and CAT in blood has revealed that lower Se level exist in Se-deficient mice. Mesenteric lymph node (MLN) lymphocytes from both mouse models were proliferated after ex vivo re-stimulation with C. parvum sporozoite antigen. The study of the cytokine profiles from the supernatant of proliferated MLN cells revealed that Se-adequate mice produced higher levels of Th1 (IFN-gamma and IL-2) and moderate amounts of Th2 (IL-4) cytokines throughout the course of infection. Whereas, MLN cells from Se-deficient mice produced lower levels of IFN-gamma, IL-2 and IL-4 cytokines. The counts of total white cell and CD3, CD4, CD8 cell in Se-adequate were higher than that in Se-deficient mice.

SIGNIFICANCE

These results suggest that Cell immunity is affected by Se status after infection with C. parvum from kinetic changes of different white cells and cytokine. In conclusion, induced susceptibility of host is associated with an impaired antioxidant system following infection with C. parvum in C57BL/6 Selenium deficient mice.

Glucose-6-phosphate dehydrogenase deficiency enhances enterovirus 71 infection

Variations in the cellular microenvironment affect the host's susceptibility to pathogens. Using glucose-6-phosphate dehydrogenase (G6PD)-deficient fibroblasts as a model, this study demonstrated that the cellular redox status affects infectivity as well as the outcome of enterovirus 71 (EV71) infection. Compared with their normal counterparts, G6PD-deficient cells supported EV71 replication more efficiently and showed greater cytopathic effect and loss of viability. Mechanistically, viral infection led to increased oxidative stress, as indicated by increased dichlorofluorescein fluorescence and a diminished ratio of glutathione (GSH) to its disulfide form (GSSG), with the effect being greater in G6PD-deficient cells. Exogenous expression of active G6PD in the deficient cells, which increased the intracellular GSH : GSSG ratio, suppressed the generation of viral progeny. Consistent with this, treatment with N-acetylcysteine offered resistance to EV71 propagation and a cytoprotective effect on the infected cells. These findings support the notion that G6PD status, and thus redox balance, is an important determinant of enteroviral infection.

Viral infection and iron metabolism

Fundamental cellular operations, including DNA synthesis and the generation of ATP, require iron. Viruses hijack cells in order to replicate, and efficient replication needs an iron-replete host. Some viruses selectively infect iron-acquiring cells by binding to transferrin receptor 1 during cell entry. Other viruses alter the expression of proteins involved in iron homeostasis, such as HFE and hepcidin. In HIV-1 and hepatitis C virus infections, iron overload is associated with poor prognosis and could be partly caused by the viruses themselves. Understanding how iron metabolism and viral infection interact might suggest new methods to control disease.

Malnutrition and infection: an update

The original Scrimshaw, Taylor and Gordon conceptual framework for the interaction of nutrition and infection has well served the scientific community for almost half a century. At its core is the notion of synergistic (mutually reinforcing) and antagonistic (mutually nullifying) influences of the malnourished state on infectious conditions and vice versa. Research on a series of advancing fronts, however, has allowed the incorporation of both relevant public health issues (parasitosis, emerging infectious diseases, obesity and overweight, etc.) and advancing science (molecular immunology, oxidation biology, multiple micronutrient deficiencies, etc.). The present review is an interpretative update on close to 50 years of demographic and epidemiological evolution in the field of human nutrition and the implications for the interaction in the context of microbiological and immunological developments on the infectious side of the dialectic.

The immune response to herpes simplex virus encephalitis in mice is modulated by dietary vitamin E

Herpes simplex virus encephalitis (HSE) is the most common fatal sporadic encephalitis in humans. HSE is primarily caused by herpes simplex virus (HSV)-1 infection of the brain. HSE results in increased levels of oxidative stress, including the production of reactive oxygen species, free radicals, and neuroinflammation. The most biologically active form of vitamin E (VE) is alpha-tocopherol (alpha-TOC). In cellular membranes, alpha-TOC prevents lipid peroxidation by scavenging free radicals and functioning as an antioxidant. Supplementation with VE has been shown to decrease immunosenescence, improve immune function, and may be neuroprotective. To determine how VE deficiency and VE supplementation would alter the pathogenesis of HSE, we placed weanling male BALB/cByJ mice on VE-deficient (VE-D), VE-adequate (VE-A), or 10x VE-supplemented diets for 4 wk, and then infected the mice intranasally with HSV-1. VE-D mice had more severe symptoms of encephalitis than VE-A mice, including weight loss, keratitis, hunched posture, and morbidity. VE-D mice had increased cytokine and chemokine expression in the brain and increased viral titers. In contrast, VE supplementation failed to decrease cytokine production and had no effect on viral titer. We demonstrated that adequate levels of VE are important in limiting HSE pathology and that 10x supplementation does not enhance protection.

Nutrition-based health in animal production

Events such as BSE, foot and mouth disease and avian influenza illustrate the importance of animal health on a global basis. The only practical solution to deal with such problems has usually been mass culling of millions of animals at great effort and expense. Serious consideration needs to be given to nutrition as a practical solution for health maintenance and disease avoidance of animals raised for food. Health or disease derives from a triad of interacting factors; diet–disease agent, diet–host and disease agent–host. Various nutrients and other bioactive feed ingredients, nutricines, directly influence health by inhibiting growth of pathogens or by modulating pathogen virulence. It is possible to transform plant-based feed ingredients to produce vaccines against important diseases and these could be fed directly to animals. Nutrients and nutricines contribute to three major factors important in the diet–host interaction; maintenance of gastrointestinal integrity, support of the immune system and the modulation of oxidative stress. Nutrition-based health is the next challenge in modern animal production and will be important to maintain economic viability and also to satisfy consumer demands in terms of food quality, safety and price. This must be accomplished largely through nutritional strategies making optimum use of both nutrients and nutricines.

Antioxidant Therapy for Severe Cardiac Failure Induced by Iron Overload Secondary to Dyserythropoietic Anaemia

We present a case of a patient with longstanding transfusion-dependent congenital dyserythropoietic anaemia (CDA) who developed cardiomyopathy despite iron chelation therapy. She presented with severe heart failure that responded poorly to conventional therapy, recovering only when therapy was augmented with metabolic agents including antioxidants and with increased iron chelation. The present case gives support to the concept of treating oxidatively induced heart failure with metabolic and antioxidant therapy. This therapy may have wider application in refractory heart failure and in the prevention of cardiomyopathy in patients receiving regular red cell transfusions who are at risk of transfusional haemosiderosis.

Selenium and vitamin E status: impact on viral pathogenicity

Selenium (Se), an essential trace element, and vitamin E, a lipid soluble antioxidant, are important mediators for protection against oxidative stress. Recent work has demonstrated that deficiencies in either Se or vitamin E result in increased viral pathogenicity and altered immune responses. Furthermore, deficiencies in either Se or vitamin E results in specific viral mutations, changing relatively benign viruses into virulent ones. Thus, host nutritional status should be considered a driving force for the emergence of new viral strains or newly pathogenic strains of known viruses.

Host nutritional status: the neglected virulence factor

The emergence of new infectious diseases and old diseases with new pathogenic properties is a burgeoning worldwide problem. Severe acute respiratory syndrome (SARS) and acquired immune deficiency syndrome (AIDS) are just two of the most widely reported recent emerging infectious diseases. What are the factors that contribute to the rapid evolution of viral species? Various hypotheses have been proposed, all involving opportunities for virus spread (for example, agricultural practices, climate changes, rainforest clearing or air travel). However, the nutritional status of the host, until recently, has not been considered a contributing factor to the emergence of infectious disease. In this review, we show that host nutritional status can influence not only the host response to the pathogen, but can also influence the genetic make-up of the viral genome. This latter finding markedly changes our concept of host–pathogen interactions and creates a new paradigm for the study of such phenomena.