Complement C5a receptor 1 blockade reverses cognitive deficits following cranial radiation therapy for brain cancer.

Cranial radiation therapy (RT) for brain cancers leads to an irreversible decline in cognitive function without an available remedy. Radiation-induced cognitive deficits (RICD) are particularly a pressing problem for the survivors of pediatric and low grade glioma (LGG) patients who often live long post-RT. Radiation-induced elevated neuroinflammation and gliosis, triggered by the detrimental CNS complement cascade, lead to excessive synaptic and cognitive loss. Using intact and brain cancer-bearing mouse models, we now show that targeting anaphylatoxin complement C5a receptor (C5aR1) is neuroprotective against RICD. We used a genetic knockout, C5aR1 KO mouse, and a pharmacologic approach, employing the orally active, brain penetrant C5aR1 antagonist PMX205, to reverse RICD. Irradiated C5aR1 KO and WT mice receiving PMX205 showed significant neurocognitive improvements in object recognition memory and memory consolidation tasks. C5aR1 inhibition reduced microglial activation, astrogliosis, and synaptic loss in the irradiated brain. Importantly, C5aR1 inhibition in the syngeneic, orthotopic astrocytoma, and glioblastoma-bearing mice protected against RICD without interfering with the therapeutic efficacy of RT to reduce tumor volume in vivo . PMX205 is currently in clinical trials for amyotrophic lateral sclerosis (ALS). Thus, C5aR1 inhibition is a translationally feasible approach to address RICD, an unmet medical need.

Chronic Low Dose Neutron Exposure Results in Altered Neurotransmission Properties of the Hippocampus-Prefrontal Cortex Axis in Both Mice and Rats.

The proposed deep space exploration to the moon and later to Mars will result in astronauts receiving significant chronic exposures to space radiation (SR). SR exposure results in multiple neurocognitive impairments. Recently, our cross-species (mouse/rat) studies reported impaired associative memory formation in both species following a chronic 6-month low dose exposure to a mixed field of neutrons (1 mGy/day for a total dose pf 18 cGy). In the present study, we report neutron exposure induced synaptic plasticity in the medial prefrontal cortex, accompanied by microglial activation and significant synaptic loss in the hippocampus. In a parallel study, neutron exposure was also found to alter fluorescence assisted single synaptosome LTP (FASS-LTP) in the hippocampus of rats, that may be related to a reduced ability to insert AMPAR into the post-synaptic membrane, which may arise from increased phosphorylation of the serine 845 residue of the GluA1 subunit. Thus, we demonstrate for the first time, that low dose chronic neutron irradiation impacts homeostatic synaptic plasticity in the hippocampal-cortical circuit in two rodent species, and that the ability to successfully encode associative recognition memory is a dynamic, multicircuit process, possibly involving compensatory changes in AMPAR density on the synaptic surface.

Human neural stem cell-derived extracellular vesicles mitigate hallmarks of Alzheimer's disease.

BACKGROUND: Regenerative therapies to mitigate Alzheimer's disease (AD) neuropathology have shown very limited success. In the recent era, extracellular vesicles (EVs) derived from multipotent and pluripotent stem cells have shown considerable promise for the treatment of dementia and many neurodegenerative conditions. METHODS: Using the 5xFAD accelerated transgenic mouse model of AD, we now show the regenerative potential of human neural stem cell (hNSC)-derived EVs on the neurocognitive and neuropathologic hallmarks in the AD brain. Two- or 6-month-old 5xFAD mice received single or two intra-venous (retro-orbital vein, RO) injections of hNSC-derived EVs, respectively. RESULTS: RO treatment using hNSC-derived EVs restored fear extinction memory consolidation and reduced anxiety-related behaviors 4-6 weeks post-injection. EV treatment also significantly reduced dense core amyloid-beta plaque accumulation and microglial activation in both age groups. These results correlated with partial restoration of homeostatic levels of circulating pro-inflammatory cytokines in the AD mice. Importantly, EV treatment protected against synaptic loss in the AD brain that paralleled improved cognition. MiRNA analysis of the EV cargo revealed promising candidates targeting neuroinflammation and synaptic function. CONCLUSIONS: Collectively, these data demonstrate the neuroprotective effects of systemic administration of stem cell-derived EVs for remediation of behavioral and molecular AD neuropathologies.

Glia-Selective Deletion of Complement C1q Prevents Radiation-Induced Cognitive Deficits and Neuroinflammation.

The adverse neurocognitive sequelae following clinical radiotherapy (RT) for central nervous system (CNS) malignancies are often long-lasting without any clinical recourse. Despite recent progress, the cellular mechanisms mediating RT-induced cognitive deficits (RICD) are poorly understood. The complement system is an immediate sensor of a disturbed inflammatory environment and a potent mediator of gliosis with a range of nonimmune functions in the CNS, including synaptic pruning, which is detrimental if dysregulated. We hypothesize that complement-mediated changes in glial cell function significantly contribute to RICD. The underlying alterations in CNS complement cascade proteins (C1q, C3), TLR4, and colabeling with glia (IBA1, GFAP) were examined using gene expression, immunofluorescence, and in silico modeling approaches in the adult mouse brain following 9 Gy cranial RT. Three-dimensional volumetric quantification showed elevated molecular signatures of gliosis at short- and long-term post-RT times. We found significant elevations in complement C1q, C3, and TLR4 post-RT accompanied by increased colabeling of astrocytes and microglia. To address the mechanism of RT-induced complement cascade activation, neuroinflammation, and cognitive dysfunction, we used a genetic approach-conditional, microglia-selective C1q (Flox) knockdown mice-to determine whether a glia-specific, upstream complement cascade contributes to RICD. C1q-Flox mice exposed to cranial RT showed no cognitive deficits compared with irradiated WT mice. Further, irradiated C1q-Flox mice were protected from RT-induced microglial activation and synaptic loss, elevation of anaphylatoxin C5a receptor, astrocytic-C3, and microglial-TLR4 expression in the brain. Our findings demonstrate for the first time a microglia-specific mechanism of RICD involving an upstream complement cascade component, C1q. SIGNIFICANCE: Clinically-relevant radiotherapy induces aberrant complement activation, leading to brain injury. Microglia-selective genetic deletion of CNS complement C1q ameliorates radiation-induced cognitive impairments, synaptic loss, and neuroinflammation, highlighting the potential for C1q as a novel therapeutic target.See related commentary by Korimerla and Wahl, p. 1635.

Route of intestinal absorption and tissue distribution of iron contained in the novel phosphate binder ferric citrate.

BACKGROUND: Anemia of chronic kidney disease (CKD) is, in part, caused by hepcidin-mediated impaired iron absorption. However, phosphate binder, ferric citrate (FC) overcomes the CKD-induced impairment of iron absorption and increases serum iron, transferrin saturation, and iron stores and reduces erythropoietin requirements in CKD/ESRD patients. The mechanism and sites of intestinal absorption of iron contained in FC were explored here. METHODS: Eight-week old rats were randomized to sham-operated or 5/6 nephrectomized (CKD) groups and fed either regular rat chow or rat chow containing 4% FC for 6 weeks. They were then euthanized, and tissues were processed for histological and biochemical analysis using Prussian blue staining, Western blot analysis to quantify intestinal epithelial tight junction proteins and real-time PCR to measure Fatty Acid receptors 2 (FFA2) and 3 (FFA3) expressions. RESULTS: CKD rats exhibited hypertension, anemia, azotemia, and hyperphosphatemia. FC-treated CKD rats showed significant reductions in blood pressure, serum urea, phosphate and creatinine levels and higher serum iron and blood hemoglobin levels. This was associated with marked increase in iron content of the epithelial and subepithelial wall of the descending colon and modest iron deposits in the proximal tubular epithelial cells of their remnant kidneys. No significant difference was found in hepatic tissue iron content between untreated and FC-treated CKD or control groups. Distal colon's epithelial tight Junction proteins, Occludin, JAM-1 and ZO-1 were markedly reduced in the CKD groups. The FFA2 expression in the jejunum and FFA3 expression in the distal colon were significantly reduced in the CKD rats and markedly increased with FC administration. CONCLUSION: Iron contained in the phosphate binder, FC, is absorbed by the distal colon of the CKD animals via disrupted colonic epithelial barrier and upregulation of short chain fatty acid transporters.

Sex-Specific Effects of a Wartime-Like Radiation Exposure on Cognitive Function.

Evaluating the risk for central nervous system (CNS) effects after whole-body or partial-body irradiation presents challenges due in part to the varied exposure scenarios in the context of occupational, accidental or wartime releases. Risk estimations are further complicated by the fact that robust changes in brain function are unlikely to manifest until significantly late post exposure times. Collectively, the current data regarding CNS radiation risk are conflicting in humans and a survey of the animal model data shows that it is similarly inconsistent. Due to the sparseness of such data, the current study was conducted using male and female mice to evaluate the brain for the delayed effects of a 2 Gy whole-body exposure to c rays starting six months postirradiation. Behavioral testing indicated sex-specific differences in the induction of anxiety-like behaviors and in the ability to abolish fear memories. Molecular analyses showed alterations in post-synaptic protein levels that might affect synaptic plasticity and increased levels of global DNA methylation, suggesting a potential epigenetic mechanism that might contribute to radiation-induced cognitive dysfunction. These data add to the understanding of the CNS response to whole-body irradiation and may lead to improved risk assessment and provide guidance in the development of effective radiation countermeasures to protect military personnel and civilians alike.

Attenuation of neuroinflammation reverses Adriamycin-induced cognitive impairments.

Numerous clinical studies have established the debilitating neurocognitive side effects of chemotherapy in the treatment of breast cancer, often referred as chemobrain. We hypothesize that cognitive impairments are associated with elevated microglial inflammation in the brain. Thus, either elimination of microglia or restoration of microglial function could ameliorate cognitive dysfunction. Using a rodent model of chronic Adriamycin (ADR) treatment, a commonly used breast cancer chemotherapy, we evaluated two strategies to ameliorate chemobrain: 1) microglia depletion using the colony stimulating factor-1 receptor (CSF1R) inhibitor PLX5622 and 2) human induced pluripotent stem cell-derived microglia (iMG)-derived extracellular vesicle (EV) treatment. In strategy 1 mice received ADR once weekly for 4 weeks and were then administered CSF1R inhibitor (PLX5622) starting 72 h post-ADR treatment. ADR-treated animals given a normal diet exhibited significant behavioral deficits and increased microglial activation 4-6 weeks later. PLX5622-treated mice exhibited no ADR-related cognitive deficits and near complete depletion of IBA-1 and CD68+ microglia in the brain. Cytokine and RNA sequencing analysis for inflammation pathways validated these findings. In strategy 2, 1 week after the last ADR treatment, mice received retro-orbital vein injections of iMG-EV (once weekly for 4 weeks) and 1 week later, mice underwent behavior testing. ADR-treated mice receiving EV showed nearly complete restoration of cognitive function and significant reductions in microglial activation as compared to untreated ADR mice. Our data demonstrate that ADR treatment elevates CNS inflammation that is linked to cognitive dysfunction and that attenuation of neuroinflammation reverses the adverse neurocognitive effects of chemotherapy.

New Concerns for Neurocognitive Function during Deep Space Exposures to Chronic, Low Dose-Rate, Neutron Radiation.

As NASA prepares for a mission to Mars, concerns regarding the health risks associated with deep space radiation exposure have emerged. Until now, the impacts of such exposures have only been studied in animals after acute exposures, using dose rates ∼1.5×105 higher than those actually encountered in space. Using a new, low dose-rate neutron irradiation facility, we have uncovered that realistic, low dose-rate exposures produce serious neurocognitive complications associated with impaired neurotransmission. Chronic (6 month) low-dose (18 cGy) and dose rate (1 mGy/d) exposures of mice to a mixed field of neutrons and photons result in diminished hippocampal neuronal excitability and disrupted hippocampal and cortical long-term potentiation. Furthermore, mice displayed severe impairments in learning and memory, and the emergence of distress behaviors. Behavioral analyses showed an alarming increase in risk associated with these realistic simulations, revealing for the first time, some unexpected potential problems associated with deep space travel on all levels of neurological function.

Long-term neurocognitive benefits of FLASH radiotherapy driven by reduced reactive oxygen species.

Here, we highlight the potential translational benefits of delivering FLASH radiotherapy using ultra-high dose rates (>100 Gy⋅s-1). Compared with conventional dose-rate (CONV; 0.07-0.1 Gy⋅s-1) modalities, we showed that FLASH did not cause radiation-induced deficits in learning and memory in mice. Moreover, 6 months after exposure, CONV caused permanent alterations in neurocognitive end points, whereas FLASH did not induce behaviors characteristic of anxiety and depression and did not impair extinction memory. Mechanistic investigations showed that increasing the oxygen tension in the brain through carbogen breathing reversed the neuroprotective effects of FLASH, while radiochemical studies confirmed that FLASH produced lower levels of the toxic reactive oxygen species hydrogen peroxide. In addition, FLASH did not induce neuroinflammation, a process described as oxidative stress-dependent, and was also associated with a marked preservation of neuronal morphology and dendritic spine density. The remarkable normal tissue sparing afforded by FLASH may someday provide heretofore unrealized opportunities for dose escalation to the tumor bed, capabilities that promise to hasten the translation of this groundbreaking irradiation modality into clinical practice.

Population structure and genotypic variation of Crataegus pontica inferred by molecular markers.

Information about the natural patterns of genetic variability and their evolutionary bases are of fundamental practical importance for sustainable forest management and conservation. In the present study, the genetic diversity of 164 individuals from fourteen natural populations of Crataegus pontica K.Koch was assessed for the first time using three genome-based molecular techniques; inter-retrotransposon amplified polymorphism (IRAP); inter-simple sequence repeats (ISSR) and start codon targeted (SCoT) polymorphism. IRAP, ISSR and SCoT analyses yielded 126, 254 and 199 scorable amplified bands, respectively, of which 90.48, 93.37 and 83.78% were polymorphic. ISSR revealed efficiency over IRAP and SCoT due to high effective multiplex ratio, marker index and resolving power. The dendrograms based on the markers used and combined data divided individuals into three major clusters. The correlation between the coefficient matrices for the IRAP, ISSR and SCoT data was significant. A higher level of genetic variation was observed within populations than among populations based on the markers used. The lower divergence levels depicted among the studied populations could be seen as evidence of gene flow. The promotion of gene exchange will be very beneficial to conserve and utilize the enormous genetic variability.

Genetic variability and structure of Quercus brantii assessed by ISSR, IRAP and SCoT markers.

Persian oak (Quercus brantii Lindl.) is one of the most important woody species of the Zagros forests in Iran. Three molecular marker techniques: start codon targeted (SCoT), inter-simple sequence repeat (ISSR) and inter-retrotransposon amplified polymorphism (IRAP) markers were compared for fingerprinting of 125 individuals of this species collected from different geographical locations of north-west of Iran. A total of 233 bands were amplified by 18 ISSR primers, of which 224 (96.10%) were polymorphic, and 126 polymorphic bands (97.65%) were observed in 129 bands amplified by 10 IRAP primers. Besides, 118 bands were observed for all 10 SCoT primers, of which 113 were polymorphic (95.71%). Average polymorphism information content (PIC) for ISSR, IRAP and SCoT markers was 0.30, 0.32 and 0.38, respectively, and this revealed that SCoT markers were more informative than IRAP and ISSR for the assessment of diversity among individuals. Based on the three different molecular types, cluster analysis revealed that 125 individuals taken for the analysis can be divided into three distinct clusters. The Jaccard's genetic similarity based on the combined data ranged from 0.23 to 0.76. These results suggest that efficiency of SCoT, IRAP and ISSR markers was relatively the same in fingerprinting of individuals. All molecular marker types revealed a low genetic differentiation among populations, indicating the possibility of gene flow between the studied populations. These results have an important implication for Persian oak (Q. brantii) germplasm characterization, improvement, and conservation.