Plasticity of immunity in response to eating

Mitochondrial metabolism: a predictive biomarker of radiotherapy efficacy and toxicity

INTRODUCTION

Radiotherapy is a mainstay of cancer treatment. Clinical studies revealed a heterogenous response to radiotherapy, from a complete response to even disease progression. To that end, finding the relative prognostic factors of disease outcomes and predictive factors of treatment efficacy and toxicity is essential. It has been demonstrated that radiation response depends on DNA damage response, cell cycle phase, oxygen concentration, and growth rate. Emerging evidence suggests that altered mitochondrial metabolism is associated with radioresistance.

METHODS

This article provides a comprehensive evaluation of the role of mitochondria in radiotherapy efficacy and toxicity. In addition, it demonstrates how mitochondria might be involved in the famous 6Rs of radiobiology.

RESULTS

In terms of this idea, decreasing the mitochondrial metabolism of cancer cells may increase radiation response, and enhancing the mitochondrial metabolism of normal cells may reduce radiation toxicity. Enhancing the normal cells (including immune cells) mitochondrial metabolism can potentially improve the tumor response by enhancing immune reactivation. Future studies are invited to examine the impacts of mitochondrial metabolism on radiation efficacy and toxicity. Improving radiotherapy response with diminishing cancer cells' mitochondrial metabolism, and reducing radiotherapy toxicity with enhancing normal cells' mitochondrial metabolism.

Targeted Anti-Mitochondrial Therapy: The Future of Oncology

Like living organisms, cancer cells require energy to survive and interact with their environment. Mitochondria are the main organelles for energy production and cellular metabolism. Recently, investigators demonstrated that cancer cells can hijack mitochondria from immune cells. This behavior sheds light on a pivotal piece in the cancer puzzle, the dependence on the normal cells. This article illustrates the benefits of new functional mitochondria for cancer cells that urge them to hijack mitochondria. It describes how functional mitochondria help cancer cells’ survival in the harsh tumor microenvironment, immune evasion, progression, and treatment resistance. Recent evidence has put forward the pivotal role of mitochondria in the metabolism of cancer stem cells (CSCs), the tumor components responsible for cancer recurrence and metastasis. This theory highlights the mitochondria in cancer biology and explains how targeting mitochondria may improve oncological outcomes.

Oxidative damages and antioxidant defences after feeding a single meal in rainbow trout

Feeding and digestion are metabolically demanding causing a rise on metabolic rate called Specific Dynamic Action (SDA). Although SDA has been vastly reported in fish, its potential consequences on the oxidative-antioxidant balance has not been evaluated to date in fish, a model with a long alkaline tide associated with feeding as well. Using rainbow trout (Oncorhynchus mykiss) as a model species, the aims of the present study were to: (1) assess potential oxidative damages and changes in oxidative defences after feeding on a single meal, and (2) identify the timescale of such changes over a 96 h post-feeding period. Oxidative damage in proteins and lipids and the activities of four enzymatic antioxidant defences: superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx) and glutathione-S-transferase (GST) were measured in gill, stomach, intestine and liver. DNA damage was measured in red blood cells. Fish were sampled before and after 1.5, 6, 24, 48, 72 and 96 h of ingestion of a 3% body mass ration. Trends of post-prandial damage were present in all tissues, but only protein oxidation varied significatively during digestion in the stomach. The intestine and stomach presented the highest enzymatic activities, likely due to the high metabolic action that these tissues have during digestion, with peaks during post-feeding: at 24 h of SOD in stomach and at 48 h of CAT in intestine. Observed GPx peaks during post-feeding in gills are likely due to the exacerbated demands for ion fluxes and/or oxygen during feeding. The differential response of the antioxidant system observed in tissues of rainbow trout during digestion indicates a coordinated and tissue-specific antioxidant defence.

Immune and hormonal modulation in the postprandial period of bullfrogs (Lithobates catesbeianus)

Mammals show immune up-regulation and increased plasma and local (gastrointestinal tract) concentrations of some immunoregulatory hormones, such as corticosterone and melatonin, after feeding. However, little is known about the endocrine and immune modulation in the postprandial period of ectothermic animals. This study investigated the effects of feeding on endocrine and immune responses in the bullfrog (Lithobates catesbeianus). Frogs were fasted for 10 days and divided into two groups: fasted and fed with fish feed (5% of body mass). Blood and gastrointestinal tract tissues (stomach and intestine) were collected at 6, 24, 48, 96 and 168 h to measure neutrophil/lymphocyte ratio, plasma bacterial killing ability, phagocytosis of blood leukocytes, plasma corticosterone and melatonin, and stomach and intestine melatonin. Feeding increased plasma corticosterone at 24 h and decreased it at 168 h, and increased neutrophil/lymphocyte ratio at 6, 24 and 96 h. We also observed decreased bacterial killing ability 48 h after feeding. Stomach melatonin increased after 17 days of fasting. We show that feeding activates the hypothalamic-pituitary-interrenal axis and promotes transient immunosuppression, without stimulating an inflammatory response. Increased corticosterone may mobilize energy to support digestive processes and melatonin may protect the stomach during fasting. We conclude that feeding modulates secretion of immunoregulatory hormones, initially increasing plasma corticosterone levels, followed by a decrease at the end of meal digestion, and causes systemic immune cell redistribution, increasing neutrophil/lymphocyte ratio for almost the entire period of meal digestion in bullfrogs. Also, fasting modulates secretion of melatonin in the stomach.

Recovery from discrete wound severities in side-blotched lizards (Uta stansburiana): implications for energy budget, locomotor performance, and oxidative stress

Wounding events (predation attempts, competitive combat) result in injuries and/or infections that induce integrated immune responses for the recovery process. Despite the survival benefits of immunity in this context, the costs incurred may require investment to be diverted from traits contributing to immediate and/or future survival, such as locomotor performance and oxidative status. Yet, whether trait constraints manifest likely depends on wound severity and the implications for energy budget. For this study, food intake, body mass, sprint speed, and oxidative indices (reactive oxygen metabolites, antioxidant capacity) were monitored in male side-blotched lizards (Uta stansburiana) healing from cutaneous wounds of discrete sizes (control, small, large). Results indicate that larger wounds induced faster healing, reduced food consumption, and led to greater oxidative stress over time. Granted wounding did not differentially affect body mass or sprint speed overall, small-wounded lizards with greater wound area healed had faster sprint speeds while large-wounded lizards with greater wound area healed had slower sprint speeds. During recovery from either wound severity, however, healing and sprint performance did not correspond with food consumption, body mass loss, nor oxidative status. These findings provide support that energy budget, locomotor performance, and oxidative status of a reptile are linked to wound recovery to an extent, albeit dependent on wound severity.

Effects of simazine and food deprivation chronic stress on energy allocation among the costly physiological processes of male lizards (Eremias argus)

The residue of simazine herbicide in the environment is known as one of pollutant stress for lizards by crippling its fitness on direct toxic effects and indirect food shortage via the food chain effects. Both stressors were considered in our experiment in the simazine exposure and food availability to lizards (Eremias argus). The results revealed that starvation significantly reduced the lizard's energy reserve and native immune function, while the accumulation of simazine in the liver was significantly increased. Simazine caused oxidative stress in the liver of lizards, but oxidative damage only occurred in the starved lizards. Simazine also changed the energy reserves, native immune function and detoxification of well-fed lizards, while the starved lizards showed different sensitivity to simazine. Simazine or starvation treatment independently activated the lizard HPA axis, but co-treatment caused the HPA axis inhibition. Besides, according to the variations on amino acid neurotransmitters, corticosterone hormone and thermoregulatory behavior, we inferred that lizards in threatens take the appropriate strategy on energy investment and allocation through neural, endocrine and behavioral pathways to maximize benefits in dilemma. Energy allocation was necessary, while suppression on any physiological process comes at a cost that is detrimental to long-term individual fitness.

The reptilian perspective on vertebrate immunity: 10 years of progress

Ten years ago, ‘Understanding the vertebrate immune system: insights from the reptilian perspective’ was published. At the time, our understanding of the reptilian immune system lagged behind that of birds, mammals, fish and amphibians. Since then, great progress has been made in elucidating the mechanisms of reptilian immunity. Here, I review recent discoveries associated with the recognition of pathogens, effector mechanisms and memory responses in reptiles. Moreover, I put forward key questions to drive the next 10 years of research, including how reptiles are able to balance robust innate mechanisms with avoiding self-damage, how B cells and antibodies are used in immune defense and whether innate mechanisms can display the hallmarks of memory. Finally, I briefly discuss the links between our mechanistic understanding of the reptilian immune system and the field of eco-immunology. Overall, the field of reptile immunology is poised to contribute greatly to our understanding of vertebrate immunity in the next 10 years.

The powerful immune system against powerful COVID-19: A hypothesis

On March 11, 2020, the World Health Organization declared the coronavirus outbreak a pandemic. Since December 2019, the world has experienced an outbreak of coronavirus disease 2019 (COVID-19). Epidemiology, risk factors, and clinical characteristics of patients with COVID-19 have been reported but the factors affecting the immune system against COVID-19 have not been well described. In this article, we provide a novel hypothesis to describe how an increase in cellular adenosine triphosphate (c-ATP) can potentially improve the efficiency of innate and adaptive immune systems to either prevent or fight off COVID-19.

Dehydration enhances cellular and humoral immunity in a mesic snake community

The immunocompetence of a community of free-living animals can be affected by seasonality, sex, and parasite burden. However, each of these factors is often examined independently. Recent studies have also found that dehydration can enhance aspects of immunocompetence in drought-adapted species. To explore how all of these factors interact, and their effect on the immune system in mesic-adapted species, we collected blood samples from a community of free-ranging snakes in coastal South Carolina, United States, across 2 years. We specifically examined (a) how sex and seasonality influence humoral and cellular immunocompetence and parasite burden, (b) the dynamics among hydration state, parasite burden, and immunocompetence, and (c) whether mesic-adapted species also show enhanced innate immunity with dehydration. Consistent with previous work on drought-adapted species, we found that dehydration enhances multiple aspects of humoral immunity in mesic species, and we are the first to report that dehydration also enhances aspects of cellular immunocompetence. Contrary to previous results in other squamates, sex and season did not impact immunocompetence or parasite prevalence. Our results also reveal complex interactions among parasite prevalence, immunocompetence, and hydration state demonstrating that hydration state and parasitism are two ubiquitous factors that should continue to be considered in future studies examining ecoimmunological variation.

A tale of two islands: evidence for impaired stress response and altered immune functions in an insular pit viper following ecological disturbance

The frequency and intensity of ecological perturbations affecting wild animal populations is expected to increase in the future with animals facing numerous global threats. Seahorse Key is a continental island off mainland Florida that has historically been a major rookery for several species of waterbirds. As a result of an unknown disturbance, the entire rookery abandoned Seahorse Key in April 2015 and shifted nesting activities to nearby Snake Key, resulting in an influx of food resources in the form of fish carrion to resident Florida cottonmouth snakes (Agkistrodon conanti), while snakes on Seahorse Key experienced a drastic reduction in food resources. Our objective was to assess plasma corticosterone concentrations, corticosterone negative feedback using dexamethasone, blood glucose, body condition, packed cell volume, natural antibody agglutination, white blood cell counts and ratios and erythrocyte sedimentation rate to characterize the long-term effects of differential resource availability in these two snake populations 3 years after this major ecological disturbance. We collected blood samples at three time points from cottonmouths on Seahorse Key (n = 6 individuals) and Snake Key (n = 13 individuals) in fall 2018. In due consideration of the small sample size, our study shows evidence that 3 years after the shift in waterbird nesting Seahorse Key cottonmouths exhibit a dampened acute stress response and presumptive impaired innate immune functions relative to cottonmouths on Snake Key. These results highlight the context-dependent nature of biomarkers and implicate the significant decrease in food resources on Seahorse Key in altering hormonal stress responses and innate immune functions, possibly leading to unknown long-term downstream effects. This study assessed the response of a wild population of pit viper to ecological disturbance in situ with the aim to improve our understanding of how animals cope with such perturbations and improve our capacity to make informed decisions for conservation.

A genetics-based approach confirms immune associations with life history across multiple populations of an aquatic vertebrate (Gasterosteus aculeatus)

Understanding how wild immune variation covaries with other traits can reveal how costs and trade‐offs shape immune evolution in the wild. Divergent life history strategies may increase or alleviate immune costs, helping shape immune variation in a consistent, testable way. Contrasting hypotheses suggest that shorter life histories may alleviate costs by offsetting them against increased mortality, or increase the effect of costs if immune responses are traded off against development or reproduction. We investigated the evolutionary relationship between life history and immune responses within an island radiation of three‐spined stickleback, with discrete populations of varying life histories and parasitism. We sampled two short‐lived, two long‐lived and an anadromous population using qPCR to quantify current immune profile and RAD‐seq data to study the distribution of immune variants within our assay genes and across the genome. Short‐lived populations exhibited significantly increased expression of all assay genes, which was accompanied by a strong association with population‐level variation in local alleles and divergence in a gene that may be involved in complement pathways. In addition, divergence around the eda gene in anadromous fish is likely associated with increased inflammation. A wider analysis of 15 populations across the island revealed that immune genes across the genome show evidence of having diverged alongside life history strategies. Parasitism and reproductive investment were also important sources of variation for expression, highlighting the caution required when assaying immune responses in the wild. These results provide strong, gene‐based support for current hypotheses linking life history and immune variation across multiple populations of a vertebrate model.

Eating increases oxidative damage in a reptile

While eating has substantial benefits in terms of both nutrient and energy acquisition, there are physiological costs associated with digesting and metabolizing a meal. Frequently, these costs have been documented in the context of energy expenditure while other physiological costs have been relatively unexplored. Here, we tested whether the seemingly innocuous act of eating affects either systemic pro-oxidant (reactive oxygen metabolites: ROM) levels or antioxidant capacity of corn snakes (Pantherophis guttatus) by collecting plasma during absorptive (peak increase in metabolic rate due to digestion of a meal) and non-absorptive (baseline) states. When individuals were digesting a meal, there was a minimal increase in antioxidant capacity relative to baseline (4%), but a substantial increase in ROMs (nearly 155%), even when controlling for circulating nutrient levels. We report an oxidative cost of eating that is much greater than that due to long distance flight or mounting an immune response in other taxa. This result demonstrates the importance of investigating non-energetic costs associated with meal processing, and it begs future work to identify the mechanism(s) driving this increase in ROM levels. Because energetic costs associated with eating are taxonomically widespread, identifying the taxonomic breadth of eating-induced ROM increases may provide insights into the interplay between oxidative damage and life history theory.