Control of Neuroinflammation through Radiation-Induced Microglial Changes

Cognitive dysfunction induced by cranial radiotherapy: mechanisms and therapeutic methods

Cranial radiotherapy can damage normal brain tissues, inducing cognitive dysfunction in patients. Radiotherapy-induced cognitive dysfunction is associated with hippocampal injury, white matter damage and microvascular injury. In this study, the mechanisms of cognitive dysfunction induced by cranial radiotherapy and combined chemoradiotherapy are reviewed, and the advances in therapeutic methods for radiotherapy-induced brain injury are summarized. The mechanisms of radiotherapy-induced brain injury include a decline of neurogenesis, impairment of neurons and glial cells, vascular injury, oxidative stress and DNA damage, cell death, and inflammatory response. Disruption of the bloodbrain barrier (BBB) increases the exposure of the brain to chemotherapeutic agents, thus exacerbating radiotherapy-induced brain damage. The current methods used to prevent radiotherapy-induced brain injury mainly include precision radiotherapy, stem cell transplantation, and treatment with neuroprotective drugs. The combined application of precision radiotherapy and neuroprotective drugs, including antioxidants, anti-inflammatory agents and other drugs, might exert better neuroprotective effects. To resolve the issues of neuroprotective drugs, such as difficulty in crossing the BBB, nanoenzymes and drug delivery nano-systems could be applied in the future.

A Synthetic Steroid 5α-Androst-3β, 5, 6β-triol Alleviates Radiation-Induced Brain Injury in Mice via Inhibiting GBP5/NF-κB/NLRP3 Signal Axis

Radiotherapy for head and neck tumors can lead to a severe complication known as radiation-induced brain injury (RIBI). However, the underlying mechanism of RIBI development remains unclear, and limited prevention and treatment options are available. Neuroactive steroids have shown potential in treating neurological disorders. 5α-Androst-3β, 5, 6β-triol (TRIOL), a synthetic neuroprotective steroid, holds promise as a treatment candidate for RIBI patients. However, the neuroprotective effects and underlying mechanism of TRIOL on RIBI treatment are yet to be elucidated. In the present study, our findings demonstrate TRIOL's potential as a neuroprotective agent against RIBI. In gamma knife irradiation mouse model, TRIOL treatment significantly reduced brain necrosis volume, microglial activation, and neuronal loss. RNA-sequencing, immunofluorescence, real-time quantitative polymerase chain reaction, siRNA transfection, and western blotting techniques revealed that TRIOL effectively decreased microglial activation, proinflammatory cytokine release, neuron loss, and guanylate-binding protein 5 (GBP5) expression, along with its downstream signaling pathways NF-κB and NLRP3 activation in vitro. In summary, TRIOL effectively alleviate RIBI by inhibiting the GBP5/NF-κB/NLRP3 signal axis, reducing microglia activation and pro-inflammation cytokines release, rescuing neuron loss. This study highlights the potential of TRIOL as a novel and promising therapy drug for RIBI treatment.

Knockdown of IRF8 alleviates neuroinflammation through regulating microglial activation in Parkinson's disease

Neuroinflammation associated with microglial activation plays a role in the development of Parkinson's disease (PD). The upregulation of interferon regulatory factor 8 (IRF8) in microglia following peripheral nerve injury has been observed to induce microglial activation. This suggests the potential therapeutic significance of IRF8 in PD. This research aims to explore the effects of IRF8 on the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mouse model and lipopolysaccharide (LPS)-induced neuroinflammation, along with its underlying mechanisms. The study examines the differential expression of IRF8 and its effects on neuropathological changes using a PD mouse model and a PD model established from BV2 cells in vitro. IRF8 was found to be prominently expressed in the substantia nigra pars compacta (SNpc) region of PD mice and LPS-stimulated BV2 cells, while the expression of tyrosine hydroxylase (TH) and dopamine (DA) content in the SNpc region of PD mice was notably reduced. MPTP treatment and LPS stimulation intensified microglial activation, inflammation, and activation of the AMPK/mTOR signaling pathway in vivo and in vitro, respectively. Upon IRF8 silencing in the PD mouse and cell models, the knockdown of IRF8 ameliorated MPTP-induced behavioral deficits, increased the counts of TH and Nissl-positive neurons and DA content, reduced the number of Iba-1-positive microglia, and reduced the content of inflammatory factors, possibly by inhibiting the AMPK/mTOR signaling pathway. Similar outcomes were observed in the PD cell model. In conclusion, the suppression of IRF8 alleviates neuroinflammation through regulating microglial activation in PD models in vivo and in vitro by the AMPK/mTOR signaling pathway.

Microglia in radiation-induced brain injury: Cellular and molecular mechanisms and therapeutic potential

BACKGROUND

Radiation-induced brain injury is a neurological condition resulting from radiotherapy for malignant tumors, with its underlying pathogenesis still not fully understood. Current hypotheses suggest that immune cells, particularly the excessive activation of microglia in the central nervous system and the migration of peripheral immune cells into the brain, play a critical role in initiating and progressing the injury. This review aimed to summarize the latest advances in the cellular and molecular mechanisms and the therapeutic potential of microglia in radiation-induced brain injury.

METHODS

This article critically examines recent developments in understanding the role of microglia activation in radiation-induced brain injury. It elucidates associated mechanisms and explores novel research pathways and therapeutic options for managing this condition.

RESULTS

Post-irradiation, activated microglia release numerous inflammatory factors, exacerbating neuroinflammation and facilitating the onset and progression of radiation-induced damage. Therefore, controlling microglial activation and suppressing the secretion of related inflammatory factors is crucial for preventing radiation-induced brain injury. While microglial activation is a primary factor in neuroinflammation, the precise mechanisms by which radiation prompts this activation remain elusive. Multiple signaling pathways likely contribute to microglial activation and the progression of radiation-induced brain injury.

CONCLUSIONS

The intricate microenvironment and molecular mechanisms associated with radiation-induced brain injury underscore the crucial roles of immune cells in its onset and progression. By investigating the interplay among microglia, neurons, astrocytes, and peripheral immune cells, potential strategies emerge to mitigate microglial activation, reduce the release of inflammatory agents, and impede the entry of peripheral immune cells into the brain.

Associations between solar and geomagnetic activity and cognitive function in the Normative Aging study

BACKGROUND

Studies show that changes in solar and geomagnetic activity (SGA) influence melatonin secretion and the autonomic nervous system. We evaluated associations between solar and geomagnetic activity and cognitive function in the Normative Aging Study from 1992 to 2013.

METHODS

We used logistic and linear generalized estimating equations and regressions to evaluate the associations between moving averages of sunspot number (SSN) and Kp index (a measure of geomagnetic activity) and a binary measure for Mini-Mental State Examination (MMSE) scores (≤25 or > 25) and six other cognitive tests as continuous measures, combined into one global composite score and considered separately.

RESULTS

A one-IQR increase in same-day SSN and Kp index were associated with 17% (95% CI: 3%, 34%) and 19% (95% CI: 4%, 36%) increases in the odds of low MMSE score. We observed small increases in the global cognitive score with increasing SSN, although we observed decreases specifically in relation to the backwards digit span test.

CONCLUSIONS

Periods of high SGA were associated with cognitive function. SGA may not equally impact all aspects of cognitive function, as evidenced by differences in associations observed for the MMSE, global cognitive score, and individual cognitive tests. Given that much of the pathology of cognitive decline in the elderly remains unexplained, studies specifically targeting decline and with longer follow-up periods are warranted.

Reduction of acute radiation-induced brain injury in rats by anlotinib

OBJECTIVES

Radiation therapy in the treatment of brain tumors also leads to the occurrence of radiation brain injury (RBI). Anlotinib is a small-molecule inhibitor of multi-receptor tyrosine kinase with high selectivity for vascular endothelial growth factor receptor-2. In this study, we constructed a rat model of RBI and investigated the effect of anlotinib on RBI and its mechanism of action through drug intervention during the acute phase of RBI.

METHODS

Six-week-old male (Sprague-Dawley) rats were used to construct an animal model of RBI to evaluate the protective effect of anlotinib on acute RBI by histopathological staining, brain edema determination, blood-brain barrier integrity evaluation and quick real time-polymerase chain reaction , ELISA detection of inflammation-related indexes, and western-blot detection of related gene protein expression.

RESULTS

Anlotinib reduced the degree of edema in the hippocampal region of rats, improved the pathological morphology of neural cells and vascular endothelial cells, and decreased blood-brain barrier permeability. Anlotinib reduced glial fibrillary acidic protein protein expression in the hippocampal region of rat brain tissue and inhibited astrocyte activation. It inhibited the release of inflammatory factors (interleukin [IL]-6, IL-8 and vascular endothelial growth factor) and down-regulated the expression of janus kinase-2/signal transducer and activator of transcription-3 (JAK2/STAT3) signaling pathway-related proteins.

CONCLUSION

This study found that anlotinib has a protective effect against RBI in rats and anlotinib may be a new candidate for the treatment of RBI.

Low-moderate dose whole-brain γ-ray irradiation modulates the expressions of glial fibrillary acidic protein and intercellular adhesion molecule-1 in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease mouse model

The anti-inflammatory efficacy of radiation therapy (RT) with single fractions below 1.0 Gy has been demonstrated in Alzheimer's disease mouse models. As neuroinflammation is also a major pathological feature of Parkinson's disease (PD), RT may also be effective in PD treatment. Therefore, this study aimed to investigate the anti-inflammatory effect of low-moderate dose RT (LMDRT, 0.6 Gy/single dose, for 5 days) exposure in a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP; 30 mg/kg, intraperitoneally, for 5 consecutive days)-induced PD mouse model. Importantly, LMDRT reduced the levels of glial fibrillary acidic protein and intercellular adhesion molecule-1 (CD54) in the striatum region, which increased following MPTP administration. LMDRT also modulated inflammatory gene expression patterns in the substantia nigra region of the MPTP-treated mice. However, LMDRT had no direct effects on the severe loss of dopaminergic neurons and impaired motor behavior in the rotarod test. These results indicate that LMDRT has anti-inflammatory effects by modulating neuroinflammatory factors, including glial fibrillary acidic protein and intercellular adhesion molecule-1, but showed no behavioral improvements or neuroprotection in the MPTP-induced mouse model of PD.

Mechanisms of action of natural products on type 2 diabetes

Over the past several decades, type 2 diabetes mellitus (T2DM) has been considered a global public health concern. Currently, various therapeutic modalities are available for T2DM management, including dietary modifications, moderate exercise, and use of hypoglycemic agents and lipid-lowering medications. Although the curative effect of most drugs on T2DM is significant, they also exert some adverse side effects. Biologically active substances found in natural medicines are important for T2DM treatment. Several recent studies have reported that active ingredients derived from traditional medicines or foods exert a therapeutic effect on T2DM. This review compiled important articles regarding the therapeutic effects of natural products and their active ingredients on islet β cell function, adipose tissue inflammation, and insulin resistance. Additionally, this review provided an in-depth understanding of the multiple regulatory effects on different targets and signaling pathways of natural medicines in the treatment of T2DM as well as a theoretical basis for clinical effective application.

Behavioral performance and microglial status in mice after moderate dose of proton irradiation

Cognitive impairment is a remote effect of gamma radiation treatment of malignancies. The major part of the studies on the effect of proton irradiation (a promising alternative in the treatment of radio-resistant tumors and tumors located close to critical organs) on the cognitive abilities of laboratory animals and their relation to morphological changes in the brain is rather contradictory. The aim of this study was to investigate cognitive functions and the dynamics of changes in morphological parameters of hippocampal microglial cells after 7.5 Gy of proton irradiation. Two months after the cranial irradiation, 8- to 9-week-old male SHK mice were tested for total activity, spatial learning, as well as long- and short-term hippocampus-dependent memory. To estimate the morphological parameters of microglia, brain slices of control and irradiated animals each with different time after proton irradiation (24 h, 7 days, 1 month) were stained for microglial marker Iba-1. No changes in behavior or deficits in short-term and long-term hippocampus-dependent memory were found, but an impairment of episodic memory was observed. A change in the morphology of hippocampal microglial cells, which is characteristic of the transition of cells to an activated state, was detected. One day after proton exposure in the brain tissue, a slight decrease in cell density was observed, which was restored to the control level by the 30th day after treatment. The results obtained may be promising with regard to the future use of using high doses of protons per fraction in the irradiation of tumors.

A systematic review of pediatric neuropsychological outcomes with proton versus photon radiation therapy: A call for equity in access to treatment

OBJECTIVE

There is increasing interest in the utilization of proton beam radiation therapy (PRT) to treat pediatric brain tumors based upon presumed advantages over traditional photon radiation therapy (XRT). PRT provides more conformal radiation to the tumor with reduced dose to healthy brain parenchyma. Less radiation exposure to brain tissue beyond the tumor is thought to reduce neuropsychological sequelae. This systematic review aimed to provide an overview of published studies comparing neuropsychological outcomes between PRT and XRT.

METHOD

PubMed, PsychINFO, Embase, Web of Science, Scopus, and Cochrane were systematically searched for peer-reviewed published studies that compared neuropsychological outcomes between PRT and XRT in pediatric brain tumor patients.

RESULTS

Eight studies were included. Six of the studies utilized retrospective neuropsychological data; the majority were longitudinal studies (n = 5). XRT was found to result in lower neuropsychological functioning across time. PRT was associated with generally stable neuropsychological functioning across time, with the exception of working memory and processing speed, which showed variable outcomes across studies. However, studies inconsistently included or considered medical and sociodemographic differences between treatment groups, which may have impacted neuropsychological outcomes.

CONCLUSIONS

Despite methodological limitations, including limited baseline neuropsychological evaluations, temporal variability between radiation treatment and first evaluation or initial and follow-up evaluations, and heterogenous samples, there is emerging evidence of sociodemographic inequities in access to PRT. With more institutions dedicating funding towards PRT, there may be the opportunity to objectively evaluate the neuropsychological benefits of patients matched on medical and sociodemographic variables.

A deeper understanding about the role of uranium toxicity in neurodegeneration

Natural deposits and human-caused releases of uranium have led to its contamination in the nature. Toxic environmental contaminants such as uranium that harm cerebral processes specifically target the brain. Numerous experimental researches have shown that occupational and environmental uranium exposure can result in a wide range of health issues. According to the recent experimental research, uranium can enter the brain after exposure and cause neurobehavioral problems such as elevated motion related activity, disruption of the sleep-wake cycle, poor memory, and elevated anxiety. However, the exact mechanism behind the factor for neurotoxicity by uranium is still uncertain. This review primarily aims on a brief overview of uranium, its route of exposure to the central nervous system, and the likely mechanism of uranium in neurological diseases including oxidative stress, epigenetic modification, and neuronal inflammation has been described, which could present the probable state-of-the-art status of uranium in neurotoxicity. Finally, we offer some preventative strategies to workers who are exposed to uranium at work. In closing, this study highlights the knowledge of uranium's health dangers and underlying toxicological mechanisms is still in its infancy, and there is still more to learn about many contentious discoveries.

Advances in the study of the molecular biological mechanisms of radiation-induced brain injury

Radiation therapy is one of the most commonly used treatments for head and neck cancers, but it often leads to radiation-induced brain injury. Patients with radiation-induced brain injury have a poorer quality of life, and no effective treatments are available. The pathogenesis of this condition is unknown. This review summarizes the molecular biological mechanism of radiation-induced brain injury and provides research directions for future studies. The molecular mechanisms of radiation-induced brain injury are diverse and complex. Radiation-induced chronic neuroinflammation, destruction of the blood-brain barrier, oxidative stress, neuronal damage, and physiopathological responses caused by specific exosome secretion lead to radiation-induced brain injury.

Combined Gamma-Rays and Carbon-12 Nuclei Irradiation Modulates Brain Chemokine and Cytokine Production and Improves Spatial Learning in Tau P301S, but not 5xFAD Mouse Line

Earlier we showed the pro-cognitive effect of low doses of combined irradiation (including heavy charged particles) on Wistar rats. In the present work we studied the effect of irradiation (gamma-rays, 0.24 Gy; carbon-12, 0.18 Gy, 400 MeV/nucleon) on the course of neurodegenerative process using Tau P301S and 5xFAD transgenic mice lines, experimental models of Alzheimer's disease. Irradiation led to an increase in pro- and anti-inflammatory cytokines and chemokines (IL-2, IL-6, IL-10, KC) in Tau P301S mice, but not in 5xFAD. At the same time, only the Tau P301S line was found to exhibit radiation-induced improvement in spatial learning.

Skin Wound following Irradiation Aggravates Radiation-Induced Brain Injury in a Mouse Model

Radiation injury- and radiation combined with skin injury-induced inflammatory responses in the mouse brain were evaluated in this study. Female B6D2F1/J mice were subjected to a sham, a skin wound (SW), 9.5 Gy ⁶⁰Co total-body gamma irradiation (RI), or 9.5 Gy RI combined with a skin puncture wound (RCI). Survival, body weight, and wound healing were tracked for 30 days, and mouse brain samples were collected on day 30 after SW, RI, RCI, and the sham control. Our results showed that RCI caused more severe animal death and body weight loss compared with RI, and skin wound healing was significantly delayed by RCI compared to SW. RCI and RI increased the chemokines Eotaxin, IP-10, MIG, 6Ckine/Exodus2, MCP-5, and TIMP-1 in the brain compared to SW and the sham control mice, and the Western blot results showed that IP-10 and p21 were significantly upregulated in brain cells post-RI or -RCI. RI and RCI activated both astrocytes and endothelial cells in the mouse brain, subsequently inducing blood-brain barrier (BBB) leakage, as shown by the increased ICAM1 and GFAP proteins in the brain and GFAP in the serum. The Doublecortin (DCX) protein, the "gold standard" for measuring neurogenesis, was significantly downregulated by RI and RCI compared with the sham group. Furthermore, RI and RCI decreased the expression of the neural stem cell marker E-cadherin, the intermediate progenitor marker MASH1, the immature neuron cell marker NeuroD1, and the mature neuron cell marker NeuN, indicating neural cell damage in all development stages after RI and RCI. Immunohistochemistry (IHC) staining further confirmed the significant loss of neural cells in RCI. Our data demonstrated that RI and RCI induced brain injury through inflammatory pathways, and RCI exacerbated neural cell damage more than RI.

Low-dose radiation therapy suppresses viral pneumonia by enhancing broad-spectrum anti-inflammatory responses via transforming growth factor-β production

Low-dose radiation therapy (LDRT) can suppress intractable inflammation, such as that in rheumatoid arthritis, and is used for treating more than 10,000 rheumatoid arthritis patients annually in Europe. Several recent clinical trials have reported that LDRT can effectively reduce the severity of coronavirus disease (COVID-19) and other cases of viral pneumonia. However, the therapeutic mechanism of LDRT remains unelucidated. Therefore, in the current study, we aimed to investigate the molecular mechanism underlying immunological alterations in influenza pneumonia after LDRT. Mice were irradiated to the whole lung 1 day post-infection. The changes in levels of inflammatory mediators (cytokines and chemokines) and immune cell populations in the bronchoalveolar lavage (BALF), lungs, and serum were examined. LDRT-treated mice displayed markedly increased survival rates and reduced lung edema and airway and vascular inflammation in the lung; however, the viral titers in the lungs were unaffected. Levels of primary inflammatory cytokines were reduced after LDRT, and transforming growth factor-β (TGF-β) levels increased significantly on day 1 following LDRT. Levels of chemokines increased from day 3 following LDRT. Additionally, M2 macrophage polarization or recruitment was increased following LDRT. We found that LDRT-induced TGF-β reduced the levels of cytokines and polarized M2 cells and blocked immune cell infiltration, including neutrophils, in BALF. LDRT-induced early TGF-β production was shown to be a key regulator involved in broad-spectrum anti-inflammatory activity in virus-infected lungs. Therefore, LDRT or TGF-β may be an alternative therapy for viral pneumonia.

Unraveling astrocyte behavior in the space brain: Radiation response of primary astrocytes

Introduction

Exposure to space conditions during crewed long-term exploration missions can cause several health risks for astronauts. Space radiation, isolation and microgravity are major limiting factors. The role of astrocytes in cognitive disturbances by space radiation is unknown. Astrocytes' response toward low linear energy transfer (LET) X-rays and high-LET carbon (12C) and iron (56Fe) ions was compared to reveal possible effects of space-relevant high-LET radiation. Since astronauts are exposed to ionizing radiation and microgravity during space missions, the effect of simulated microgravity on DNA damage induction and repair was investigated.

Methods

Primary murine cortical astrocytes were irradiated with different doses of X-rays, 12C and 56Fe ions at the heavy ion accelerator GSI. DNA damage and repair (γH2AX, 53BP1), cell proliferation (Ki-67), astrocytes' reactivity (GFAP) and NF-κB pathway activation (p65) were analyzed by immunofluorescence microscopy. Cell cycle progression was investigated by flow cytometry of DNA content. Gene expression changes after exposure to X- rays were investigated by mRNA-sequencing. RT-qPCR for several genes of interest was performed with RNA from X-rays- and heavy-ion-irradiated astrocytes: Cdkn1a, Cdkn2a, Gfap, Tnf, Il1β, Il6, and Tgfβ1. Levels of the pro inflammatory cytokine IL-6 were determined using ELISA. DNA damage response was investigated after exposure to X-rays followed by incubation on a 2D clinostat to simulate the conditions of microgravity.

Results

Astrocytes showed distinct responses toward the three different radiation qualities. Induction of radiation-induced DNA double strand breaks (DSBs) and the respective repair was dose-, LET- and time-dependent. Simulated microgravity had no significant influence on DNA DSB repair. Proliferation and cell cycle progression was not affected by radiation qualities examined in this study. Astrocytes expressed IL-6 and GFAP with constitutive NF-κB activity independent of radiation exposure. mRNA sequencing of X-irradiated astrocytes revealed downregulation of 66 genes involved in DNA damage response and repair, mitosis, proliferation and cell cycle regulation.

Discussion

In conclusion, primary murine astrocytes are DNA repair proficient irrespective of radiation quality. Only minor gene expression changes were observed after X-ray exposure and reactivity was not induced. Co-culture of astrocytes with microglial cells, brain organoids or organotypic brain slice culture experiments might reveal whether astrocytes show a more pronounced radiation response in more complex network architectures in the presence of other neuronal cell types.

Radiation-induced neuroinflammation monitoring by the level of peripheral blood monocytes with high expression of translocator protein

PURPOSE

Currently there are no effective diagnostic methods for the control of neuroinflammation before manifestation of cognitive impairment after head irradiation. The translocator protein (TSPO) is highly expressed in glial cells upon brain damage, therefore we compared the changes in the number of cells with high TSPO expression in the brain and peripheral blood during radiation-induced neuroinflammation.

MATERIALS AND METHODS

Hippocampal cytokines mRNA expression and the content of cells with high TSPO expression in the brain and peripheral blood monocytes were analyzed up to eight months after mice head γ-irradiation at a dose of 2 Gy or 8Gy.

RESULTS

Mice irradiation at a dose of 8 Gy causes neuroinflammation, accompanied by an increase of M1 microglia and TSPOhigh cells in the brain, elevated gene expression of pro-inflammatory and decreased of anti-inflammatory cytokines along with an increased number of microglia and astrocytes in the hippocampus. The content of TSPOhigh cells in the brain correlates with the level TSPOhigh monocytes in three days, one month and two months after exposure.

CONCLUSIONS

An increase in the level of the monocytes with high expression of TSPO may be considered as a marker for an early diagnostics of post-radiation brain damage leading to cognitive impairment.

Antifragility and antiinflammaging: Can they play a role for a healthy longevity?

One of the most exciting challenges of the research on aging is to explain how the environmental factors interact with the genetic background to modulate the chances to reach the extreme limit of human life in healthy conditions. The complex epigenetic mechanisms can explain both the interaction between DNA and environmental factors, and the long-distance persistence of lifestyle effects, due to the so called "epigenetic memory". One of the most extensively investigated theories on aging focuses on the inflammatory responses, suggesting that the age-related progression of low-grade and therefore for long time subclinical, chronic, systemic, inflammatory process, named "inflammaging", could be the most relevant risk factor for the development and progression of the most common age-related diseases and ultimately of death. The results of many studies on long-lived people, especially on centenarians, suggested that healthy old people can cope with inflammaging upregulating the antiinflammaging responses. Overall, a genetic make-up coding for a strong antiinflammaging response and an age-related ability to remodel key metabolic pathways to cope with a plethora of antigens and stressors seem to be the best ways for reach the extreme limit of human lifespan in health status. In this scenario, we wondered if the antifragility concept, recently developed in the framework of business and risk analysis, could add some information to disentangle the heterogeneous nature of the aging process in human. The antifragility is the property of the complex systems to increase their performances because of high stress. Based on this theory we were wondering if some subjects could be able to modulate faster than others their epigenome to cope with a plethora of stressors during life, probably modulating the inflammatory and anti-inflammatory responses. In this framework, antifragility could share some common mechanisms with anti-inflammaging, modulating the ability to restrain the inflammatory responses, so that antifragility and antiinflammaging could be viewed as different pieces of the same puzzle, both impinging upon the chances to travel along the healthy aging trajectory.

Anti-neuroinflammatory 3-hydroxycoumaronochromones and isoflavanones enantiomers from the fruits of Ficus altissima Blume

A phytochemical study on the fruits of Ficus altissima Blume (lofty fig) led to the isolation and structural elucidation of three pairs of enantiomeric 3-hydroxycoumaronochromones and two pairs of enantiomeric isoflavanones, including eight undescribed compounds. Their structures were determined based on a comprehensive analysis of NMR and HR-ESI-MS spectroscopic data, calculated ¹³C NMR-DP4 plus analysis and the comparisons of experimental measurements of ECD with calculated ECD spectra by TDDFT or ECD plots in reported protocols. The inhibitory effects of the isolated enantiomers on NO production stimulated by LPS in microglial BV-2 cells were evaluated. Among them, ficusaltin D exhibited the most potent anti-neuroinflammatory activity, which inhibited the production of NO and the expression of iNOS, IL-6 and IL-1β and suppressed the NF-κB nuclear translocation in LPS-induced BV-2 cells, while its enantiomer displayed cytotoxicity.

Development of an Adverse Outcome Pathway for radiation-induced microcephaly via expert consultation and machine learning

BACKGROUND

Brain development during embryogenesis and in early postnatal life is particularly complex and involves the interplay of many cellular processes and molecular mechanisms, making it extremely vulnerable to exogenous insults, including ionizing radiation (IR). Microcephaly is one of the most frequent neurodevelopmental abnormalities that is characterized by small brain size, and is often associated with intellectual deficiency. Decades of research span from epidemiological data on in utero exposure of the A-bomb survivors, to studies on animal and cellular models that allowed deciphering the most prominent molecular mechanisms leading to microcephaly. The Adverse Outcome Pathway (AOP) framework is used to organize, evaluate and portray the scientific knowledge of toxicological effects spanning different biological levels of organizations, from the initial interaction with molecular targets to the occurrence of a disease or adversity. In the present study, the framework was used in an attempt to organize the current scientific knowledge on microcephaly progression in the context of ionizing radiation (IR) exposure. This work was performed by a group of experts formed during a recent workshop organized jointly by the Multidisciplinary European Low Dose Initiative (MELODI) and the European Radioecology Alliance (ALLIANCE) associations to present the AOP approach and tools. Here we report on the development of a putative AOP for congenital microcephaly resulting from IR exposure based on discussions of the working group and we emphasize the use of a novel machine-learning approach to assist in the screening of the available literature to develop AOPs.

CONCLUSION

The expert consultation led to the identification of crucial biological events for the progression of microcephaly upon exposure to IR, and highlighted current knowledge gaps. The machine learning approach was successfully used to screen the existing knowledge and helped to rapidly screen the body of evidence and in particular the epidemiological data. This systematic review approach also ensured that the analysis was sufficiently comprehensive to identify the most relevant data and facilitate rapid and consistent AOP development. We anticipate that as machine learning approaches become more user-friendly through easy-to-use web interface, this would allow AOP development to become more efficient and less time consuming.

Microglia as Therapeutic Target for Radiation-Induced Brain Injury

Radiation-induced brain injury (RIBI) after radiotherapy has become an increasingly important factor affecting the prognosis of patients with head and neck tumor. With the delivery of high doses of radiation to brain tissue, microglia rapidly transit to a pro-inflammatory phenotype, upregulate phagocytic machinery, and reduce the release of neurotrophic factors. Persistently activated microglia mediate the progression of chronic neuroinflammation, which may inhibit brain neurogenesis leading to the occurrence of neurocognitive disorders at the advanced stage of RIBI. Fully understanding the microglial pathophysiology and cellular and molecular mechanisms after irradiation may facilitate the development of novel therapy by targeting microglia to prevent RIBI and subsequent neurological and neuropsychiatric disorders.

Microglia-Mediated Inflammation and Neural Stem Cell Differentiation in Alzheimer's Disease: Possible Therapeutic Role of KV1.3 Channel Blockade

Increase of deposits of amyloid β peptides in the extracellular matrix is landmark during Alzheimer’s Disease (AD) due to the imbalance in the production vs. clearance. This accumulation of amyloid β deposits triggers microglial activation. Microglia plays a dual role in AD, a protective role by clearing the deposits of amyloid β peptides increasing the phagocytic response (CD163, IGF-1 or BDNF) and a cytotoxic role, releasing free radicals (ROS or NO) and proinflammatory cytokines (TNF-α, IL-1β) in response to reactive gliosis activated by the amyloid β aggregates. Microglia activation correlated with an increase K_V1.3 channels expression, protein levels and current density. Several studies highlight the importance of K_V1.3 in the activation of inflammatory response and inhibition of neural progenitor cell proliferation and neuronal differentiation. However, little is known about the pathways of this activation in neural stem cells differentiation and proliferation and the role in amyloid β accumulation. In recent studies using in vitro cells derived from mice models, it has been demonstrated that K_V1.3 blockers inhibit microglia-mediated neurotoxicity in culture reducing the expression and production of the pro-inflammatory cytokines IL-1β and TNF-α through the NF-kB and p38MAPK pathway. Overall, we conclude that K_V1.3 blockers change the course of AD development, reducing microglial cytotoxic activation and increasing neural stem cell differentiation. However, further investigations are needed to establish the specific pathway and to validate the use of this blocker as therapeutic treatment in Alzheimer patients.

The Pivotal Immunoregulatory Functions of Microglia and Macrophages in Glioma Pathogenesis and Therapy

Gliomas are mixed solid tumors composed of both neoplastic and nonneoplastic cells. In glioma microenvironment, the most common nonneoplastic and infiltrating cells are macrophages and microglia. Microglia are the exact phagocytes of the central nervous system, whereas macrophages are myeloid immune cells that are depicted with ardent phagocytosis. Microglia are heterogeneously located in almost all nonoverlapping sections of the brain as well as the spinal cord, while macrophages are derived from circulating monocytes. Microglia and macrophages utilize a variety of receptors for the detection of molecules, particles, and cells that they engulf. Both microglia and peripheral macrophages interact directly with vessels both in the periphery of and within the tumor. In glioma milieu, normal human astrocytes, glioma cells, and microglia all exhibited the ability of phagocytosing glioma cells and precisely apoptotic tumor cells. Also, microglia and macrophages are robustly triggered by the glioma via the expression of chemoattractants such as monocyte chemoattractant protein, stromal-derived factor-1, and macrophage-colony stimulating factor. Glioma-associated microglia and/or macrophages positively correlated with glioma invasiveness, immunosuppression, and patients' poor outcome, making these cells a suitable target for immunotherapeutic schemes.

The roles of microglia and astrocytes in phagocytosis and myelination: Insights from the cuprizone model of multiple sclerosis

In human demyelinating diseases such as multiple sclerosis (MS), an imbalance between demyelination and remyelination can trigger progressive degenerative processes. The clearance of myelin debris (phagocytosis) from the site of demyelination by microglia is critically important to achieve adequate remyelination and to slow the progression of the disease. However, how microglia phagocytose the myelin debris, and why clearance is impaired in MS, is not fully known; likewise, the role of the microglia in remyelination remains unclear. Recent studies using cuprizone (CPZ) as an animal model of central nervous system demyelination revealed that the up‐regulation of signaling proteins in microglia facilitates effective phagocytosis of myelin debris. Moreover, during demyelination, protective mediators are released from activated microglia, resulting in the acceleration of remyelination in the CPZ model. In contrast, inadequate microglial activation or recruitment to the site of demyelination, and the production of toxic mediators, impairs remyelination resulting in progressive demyelination. In addition to the microglia‐mediated phagocytosis, astrocytes play an important role in the phagocytic process by recruiting microglia to the site of demyelination and producing regenerative mediators. The current review is an update of these emerging findings from the CPZ animal model, discussing the roles of microglia and astrocytes in phagocytosis and myelination.

Low-Dose Radiation Therapy Reduces Amyloid Load in Young 3xTg-AD Mice

Background: Low-dose radiation therapy (LD-RT) has been shown to decrease amyloidosis or inflammation in systemic diseases and has recently been proposed as possible treatment of Alzheimer’s disease (AD). A positive effect of LD-RT on tauopathy, the other marker of AD, has also been suggested. These effects have been shown in preclinical studies, but their mechanisms are still not well understood. Objective: This study aimed to evaluate if anti-amyloid and anti-inflammatory effects of LD-RT can be observed at an early stage of the disease. Its impact on tauopathy and behavioral alterations was also investigated. Methods: The whole brain of 12-month-old 3xTg-AD mice was irradiated with 10 Gy in 5 daily fractions of 2 Gy. Mice underwent behavioral tests before and 8 weeks post treatment. Amyloid load, tauopathy, and neuroinflammation were measured using histology and/or ELISA. Results: Compared with wild-type animals, 3xTg-AD mice showed a moderate amyloid and tau pathology restricted to the hippocampus, a glial reactivity restricted to the proximity of amyloid plaques. LD-RT significantly reduced Aβ 42 aggregated forms (–71%) in the hippocampus and tended to reduce other forms in the hippocampus and frontal cortex but did not affect tauopathy or cognitive performance. A trend for neuroinflammation markers reduction was also observed. Conclusion: When applied at an early stage, LD-RT reduced amyloid load and possibly neuroinflammation markers, with no impact on tauopathy. The long-term persistence of these beneficial effects of LD-RT should be evaluated in future studies.

Mitochondrial Translocator Protein (TSPO) Expression in the Brain After Whole Body Gamma Irradiation

The brain's early response to low dose ionizing radiation, as may be encountered during diagnostic procedures and space exploration, is not yet fully characterized. In the brain parenchyma, the mitochondrial translocator protein (TSPO) is constitutively expressed at low levels by endothelial cells, and can therefore be used to assess the integrity of the brain's vasculature. At the same time, the inducible expression of TSPO in activated microglia, the brain's intrinsic immune cells, is a regularly observed early indicator of subtle or incipient brain pathology. Here, we explored the use of TSPO as a biomarker of brain tissue injury following whole body irradiation. Post-radiation responses were measured in C57BL/6 wild type (Tspo +/+) and TSPO knockout (Tspo -/-) mice 48 h after single whole body gamma irradiations with low doses 0, 0.01, and 0.1 Gy and a high dose of 2 Gy. Additionally, post-radiation responses of primary microglial cell cultures were measured at 1, 4, 24, and 48 h at an irradiation dose range of 0 Gy-2 Gy. TSPO mRNA and protein expression in the brain showed a decreased trend after 0.01 Gy relative to sham-irradiated controls, but remained unchanged after higher doses. Immunohistochemistry confirmed subtle decreases in TSPO expression after 0.01 Gy in vascular endothelial cells of the hippocampal region and in ependymal cells, with no detectable changes following higher doses. Cytokine concentrations in plasma after whole body irradiation showed differential changes in IL-6 and IL-10 with some variations between Tspo-/- and Tspo +/+ animals. The in vitro measurements of TSPO in primary microglial cell cultures showed a significant reduction 1 h after low dose irradiation (0.01 Gy). In summary, acute low and high doses of gamma irradiation up to 2 Gy reduced TSPO expression in the brain's vascular compartment without de novo induction of TSPO expression in parenchymal microglia, while TSPO expression in directly irradiated, isolated, and thus highly activated microglia, too, was reduced after low dose irradiation. The potential link between TSPO, its role in mitochondrial energy metabolism and the selective radiation sensitivity, notably of cells with constitutive TSPO expression such as vascular endothelial cells, merits further exploration.