Transmembrane serine protease 6, a novel target for inhibition of neuronal tumor growth

Transmembrane serine protease 6 (Tmprss6) has been correlated with the occurrence and progression of tumors, but any specific molecular mechanism linking the enzyme to oncogenesis has remained elusive thus far. In the present study, we found that Tmprss6 markedly inhibited mouse neuroblastoma N2a (neuro-2a) cell proliferation and tumor growth in nude mice. Tmprss6 inhibits Smad1/5/8 phosphorylation by cleaving the bone morphogenetic protein (BMP) co-receptor, hemojuvelin (HJV). Ordinarily, phosphorylated Smad1/5/8 binds to Smad4 for nuclear translocation, which stimulates the expression of hepcidin, ultimately decreasing the export of iron through ferroportin 1 (FPN1). The decrease in cellular iron levels in neuro-2a cells with elevated Tmprss6 expression limited the availability of the metal forribo nucleotide reductase activity, thereby arresting the cell cycle prior to S phase. Interestingly, Smad4 promoted nuclear translocation of activating transcription factor 3 (ATF3) to activate the p38 mitogen-activated protein kinases signaling pathway by binding to ATF3, inducing apoptosis of neuro-2a cells and inhibiting tumor growth. Disruption of ATF3 expression significantly decreased apoptosis in Tmprss6 overexpressed neuro-2a cells. Our study describes a mechanism whereby Tmprss6 regulates the cell cycle and apoptosis. Thus, we propose Tmprss6 as a candidate target for inhibiting neuronal tumor growth.

Hepcidin deficiency impairs hippocampal neurogenesis and mediates brain atrophy and memory decline in mice

BACKGROUND

Hepcidin is the master regulator of iron homeostasis. Hepcidin downregulation has been demonstrated in the brains of Alzheimer's disease (AD) patients. However, the mechanism underlying the role of hepcidin downregulation in cognitive impairment has not been elucidated.

METHODS

In the present study, we generated GFAP-Cre-mediated hepcidin conditional knockout mice (HampGFAP cKO) to explore the effect of hepcidin deficiency on hippocampal structure and neurocognition.

RESULTS

We found that the HampGFAP cKO mice developed AD-like brain atrophy and memory deficits. In particular, the weight of the hippocampus and the number of granule neurons in the dentate gyrus were significantly reduced. Further investigation demonstrated that the morphological change in the hippocampus of HampGFAP cKO mice was attributed to impaired neurogenesis caused by decreased proliferation of neural stem cells. Regarding the molecular mechanism, increased iron content after depletion of hepcidin followed by an elevated level of the inflammatory factor tumor necrosis factor-α accounted for the impairment of hippocampal neurogenesis in HampGFAP cKO mice. These observations were further verified in GFAP promoter-driven hepcidin knockdown mice and in Nestin-Cre-mediated hepcidin conditional knockout mice.

CONCLUSIONS

The present findings demonstrated a critical role for hepcidin in hippocampal neurogenesis and validated the importance of iron and associated inflammatory cytokines as key modulators of neurodevelopment, providing insights into the potential pathogenesis of cognitive dysfunction and related treatments.

Brain Iron Homeostasis and Mental Disorders

Iron plays an essential role in various physiological processes. A disruption in iron homeostasis can lead to severe consequences, including impaired neurodevelopment, neurodegenerative disorders, stroke, and cancer. Interestingly, the link between mental health disorders and iron homeostasis has not received significant attention. Therefore, our understanding of iron metabolism in the context of psychological diseases is incomplete. In this review, we aim to discuss the pathologies and potential mechanisms that relate to iron homeostasis in associated mental disorders. We propose the hypothesis that maintaining brain iron homeostasis can support neuronal physiological functions by impacting key enzymatic activities during neurotransmission, redox balance, and myelination. In conclusion, our review highlights the importance of investigating the relationship between trace element nutrition and the pathological process of mental disorders, focusing on iron. This nutritional perspective can offer valuable insights for the clinical treatment of mental disorders.

Ferroptosis-related factors in the substantia nigra are associated with Parkinson's disease

Ferroptosis is an iron-dependent, lipid peroxidation-driven cell death pathway, while Parkinson's disease (PD) patients exhibit iron deposition and lipid peroxidation in the brain. Thus, the features of ferroptosis highly overlap with the pathophysiological features of PD. Despite this superficial connection, the possible role(s) of ferroptosis-related (Fr) proteins in dopaminergic neurons and/or glial cells in the substantia nigra (SN) in PD have not been examined in depth. To explore the correlations between the different SN cell types and ferroptosis at the single-cell level in PD patients, and to explore genes that may affect the sensitivity of dopaminergic neurons to ferroptosis, we performed in silico analysis of a single cell RNA sequence (RNA-seq) set (GSE178265) from the Gene Expression Omnibus (GEO) database. We identified differentially expressed genes (DEGs) in the different cell types in the human SN, and proceeded to perform enrichment analysis, constructing a protein-protein interaction network from the DEGs of dopaminergic neurons with the Metascape database. We examined the intersection of Fr genes present in the FerrDb database with DEGs from the GSE178265 set to identify Fr-DEGs in the different brain cells. Further, we identified Fr-DEGs encoding secreted proteins to implicate cell-cell interactions in the potential stimulation of ferroptosis in PD. The Fr-DEGs we identified were verified using the bulk RNA-seq sets (GSE49036 and GSE20164). The number of dopaminergic neurons decreased in the SN of PD patients. Interestingly, non-dopaminergic neurons possessed the fewest DEGs. Enrichment analysis of dopaminergic neurons' DEGs revealed changes in transmission across chemical synapses and ATP metabolic process in PD. The secreted Fr-DEGs identified were ceruloplasmin (CP), high mobility group box 1 (HMGB1) and transferrin (TF). The bulk RNA-seq set from the GEO database demonstrates that CP expression is increased in the PD brain. In conclusion, our results identify CP as a potential therapeutic target to protect dopaminergic neurons by reducing neurons' sensitivity to ferroptosis.

Iron Metabolism, Redox Balance and Neurological Diseases

Iron is essential for life, and the dysregulation of iron homeostasis can lead to severe pathological changes in the neurological system [...].

Ferrodifferentiation regulates neurodevelopment via ROS generation

Iron is important for life, and iron deficiency impairs development, but whether the iron level regulates neural differentiation remains elusive. In this study, with iron-regulatory proteins (IRPs) knockout embryonic stem cells (ESCs) that showed severe iron deficiency, we found that the Pax6- and Sox2-positive neuronal precursor cells and Tuj1 fibers in IRP1-/-IRP2-/- ESCs were significantly decreased after inducing neural differentiation. Consistently, in vivo study showed that the knockdown of IRP1 in IRP2-/- fetal mice remarkably affected the differentiation of neuronal precursors and the migration of neurons. These findings suggest that low intracellular iron status significantly inhibits neurodifferentiation. When supplementing IRP1-/-IRP2-/- ESCs with iron, these ESCs could differentiate normally. Further investigations revealed that the underlying mechanism was associated with an increase in reactive oxygen species (ROS) production caused by the substantially low level of iron and the down-regulation of iron-sulfur cluster protein ISCU, which, in turn, affected the proliferation and differentiation of stem cells. Thus, the appropriate amount of iron is crucial for maintaining normal neural differentiation that is termed ferrodifferentiation.

Brain Iron Metabolism, Redox Balance and Neurological Diseases

The incidence of neurological diseases, such as Parkinson's disease, Alzheimer's disease and stroke, is increasing. An increasing number of studies have correlated these diseases with brain iron overload and the resulting oxidative damage. Brain iron deficiency has also been closely linked to neurodevelopment. These neurological disorders seriously affect the physical and mental health of patients and bring heavy economic burdens to families and society. Therefore, it is important to maintain brain iron homeostasis and to understand the mechanism of brain iron disorders affecting reactive oxygen species (ROS) balance, resulting in neural damage, cell death and, ultimately, leading to the development of disease. Evidence has shown that many therapies targeting brain iron and ROS imbalances have good preventive and therapeutic effects on neurological diseases. This review highlights the molecular mechanisms, pathogenesis and treatment strategies of brain iron metabolism disorders in neurological diseases.

CHIR99021 Maintenance of the Cell Stemness by Regulating Cellular Iron Metabolism

CHIR99021 is an aminopyrimidine derivative, which can efficiently inhibit the activity of glycogen synthesis kinase 3α (GSK-3α) and GSK-3β. As an essential component of stem cell culture medium, it plays an important role in maintaining cell stemness. However, the mechanism of its role is not fully understood. In the present study, we first found that removal of CHIR99021 from embryonic stem cell culture medium reduced iron storage in mouse embryonic stem cells (mESCs). CHIR99021-treated Neuro-2a cells led to an upregulation of ferritin expression and an increase in intracellular iron levels, along with GSK3β inhibition and Wnt/GSK-3β/β-catenin pathway activation. In addition, iron treatment activated the classical Wnt pathway by affecting the expression of β-catenin in the Neuro-2a cells. Our data link the role of iron in the maintenance of cell stemness via the Wnt/GSK-3β/β-catenin signaling pathway, and identify intermediate molecules, including Steap1, Bola2, and Kdm6bos, which may mediate the upregulation of ferritin expression by CHIR99021. These findings reveal novel mechanisms of the maintenance of cell stemness and differentiation and provide a theoretical basis for the development of new strategies in stem cell treatment in disease.

The divergent effects of astrocyte ceruloplasmin on learning and memory function in young and old mice

Ceruloplasmin (CP) plays an important role in maintaining iron homeostasis. Cp gene knockout (Cp^-/-) mice develop a neurodegenerative disease with aging and show iron accumulation in the brain. However, iron deficiency has also been observed in 3 M Cp^-/- mice. The use of systemic Cp gene knockout is insufficient to reveal specific functions for CP in the central nervous system. Considering recent discoveries that astrocytes synthetize the majority of brain CP, we generated astrocyte conditional Cp knockout (Cp^GfapcKO) mice, and found that iron contents decreased in the cerebral cortex and hippocampus of young (6 M) and old (18 M) Cp^GfapcKO mice. Further experiments revealed that 6 M Cp^GfapcKO mice exhibited impaired learning and memory function, while 18 M Cp^GfapcKO mice exhibited improved learning and memory function. Our study demonstrates that astrocytic Cp deletion blocks brain iron influx through the blood-brain-barrier, with concomitantly increased iron levels in brain microvascular endothelial cells, resulting in brain iron deficiency and down-regulation of ferritin levels in neurons, astrocytes, microglia and oligodendrocytes. At the young age, the synapse density, synapse-related protein levels, 5-hydroxytryptamine and norepinephrine, hippocampal neurogenesis and myelin formation were all decreased in Cp^GfapcKO mice. These changes affected learning and memory impairment in young Cp^GfapcKO mice. In old Cp^GfapcKO mice, iron accumulation with aging was attenuated, and was accompanied by the alleviation of the ROS-MAPK-apoptosis pathway, Tau phosphorylation and β-amyloid aggregation, thus delaying age-related memory decline. Overall, our results demonstrate that astrocytic Cp deletion has divergent effects on learning and memory function via different regulatory mechanisms induced by decreased iron contents in the brain of mice, which may present strategies for the prevention and treatment of dementia.

Mitochondrial ferritin alleviates apoptosis by enhancing mitochondrial bioenergetics and stimulating glucose metabolism in cerebral ischemia reperfusion

Oxidative stress and deficient bioenergetics are key players in the pathological process of cerebral ischemia reperfusion injury (I/R). As a mitochondrial iron storage protein, mitochondrial ferritin (FtMt) plays a pivotal role in protecting neuronal cells from oxidative damage under stress conditions. However, the effects of FtMt in mitochondrial function and activation of apoptosis under cerebral I/R are barely understood. In the present study, we found that FtMt deficiency exacerbates neuronal apoptosis via classical mitochondria-depedent pathway and the endoplasmic reticulum (ER) stress pathway in brains exposed to I/R. Conversely, FtMt overexpression significantly inhibited oxygen and glucose deprivation and reperfusion (OGD/R)-induced apoptosis and the activation of ER stress response. Meanwhile, FtMt overexpression rescued OGD/R-induced mitochondrial iron overload, mitochondrial dysfunction, the generation of reactive oxygen species (ROS) and increased neuronal GSH content. Using the Seahorse and O2K cellular respiration analyser, we demonstrated that FtMt remarkably improved the ATP content and the spare respiratory capacity under I/R conditions. Importantly, we found that glucose consumption was augmented in FtMt overexpressing cells after OGD/R insult; overexpression of FtMt facilitated the activation of glucose 6-phosphate dehydrogenase and the production of NADPH in cells after OGD/R, indicating that the pentose-phosphate pathway is enhanced in FtMt overexpressing cells, thus strengthening the antioxidant capacity of neuronal cells. In summary, our results reveal that FtMt protects against I/R-induced apoptosis through enhancing mitochondrial bioenergetics and regulating glucose metabolism via the pentose-phosphate pathway, thus preventing ROS overproduction, and preserving energy metabolism.

Hepcidin is upregulated and is a potential therapeutic target associated with immunity in glioma

Background

Glioma is the most common primary malignant brain tumor with high mortality and poor prognosis. Hepcidin is a fascinating iron metabolism regulator. However, the prognostic value of hepcidin HAMP in gliomas and its correlation with immune cell infiltration remain unclear. Here, we comprehensively elucidate the prognostic value and potential role of hepcidin in gliomas.

Methods

Hepcidin gene expression and clinical characteristics in glioma were analyzed using the CGGA, TCGA, Rembrandt and Gravendeel glioma databases. A survival analysis was conducted using Kaplan-Meier and Cox regression analyses. A gene set enrichment analysis (GSEA) was conducted to select the pathways significantly enriched for hepcidin associations. The correlations between hepcidin and immune cell infiltration and immunotherapy were analyzed using network platforms such as CIBERSORT and TIMER.

Results

In glioma tissues, the expression of hepcidin was significantly increased. High hepcidin expression is related to grade, age, PRS type, IDH mutation, chemotherapy status and 1p19q codeletion status, which significantly indicates the poor prognosis of glioma patients. Hepcidin can be used as an independent prognostic factor for glioma through the multivariate COX regression analysis. The results of Gene Ontology (GO), Kyoto Encyclopedia of Gene and Genome (KEGG) and gene set enrichment analysis (GSEA) indicated that hepcidin was involved in the immune response. In addition, hepcidin expression was positively correlated with the degree of immune cell infiltration, the expression of various immune cell markers and the efficacy of immunotherapy.

Conclusion

Our results indicate that hepcidin can be used as a candidate biomarker to judge the prognosis and immune cell invasion of gliomas.

A nanomaterial targeting the spike protein captures SARS-CoV-2 variants and promotes viral elimination

The global emergency caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) pandemic can only be solved with effective and widespread preventive and therapeutic strategies, and both are still insufficient. Here, we describe an ultrathin two-dimensional CuInP2S6 (CIPS) nanosheet as a new agent against SARS-CoV-2 infection. CIPS exhibits an extremely high and selective binding capacity (dissociation constant (KD) < 1 pM) for the receptor binding domain of the spike protein of wild-type SARS-CoV-2 and its variants of concern, including Delta and Omicron, inhibiting virus entry and infection in angiotensin converting enzyme 2 (ACE2)-bearing cells, human airway epithelial organoids and human ACE2-transgenic mice. On association with CIPS, the virus is quickly phagocytosed and eliminated by macrophages, suggesting that CIPS could be successfully used to capture and facilitate virus elimination by the host. Thus, we propose CIPS as a promising nanodrug for future safe and effective anti-SARS-CoV-2 therapy, and as a decontamination agent and surface-coating material to reduce SARS-CoV-2 infectivity.

Biocorona modulates the inflammatory response induced by gold nanoparticles in human epidermal keratinocytes

The functional activities of gold nanoparticles (AuNPs) on biological systems depend on their physical-chemical properties and their surface functionalizations. Within a biological environment and depending on their surface characteristics, NPs can adsorb biomolecules (mostly proteins) present in the microenvironment, thereby forming a dynamic biomolecular corona on the surface. The presence of this biocorona changes the physical-chemical and functional properties of the NPs and how it interacts with cells. Here, we show that primary human epidermal keratinocytes (HEK) exposed in culture to branched polyethyleneimine (BPEI)-AuNPs, but not to lipoic acid (LA)-AuNPs, show potent particle uptake, decreased viability and enhanced production of inflammatory factors, while the presence of a human plasma-derived biocorona decreased NPs uptake and rescued cells from BPEI-AuNP-induced cell death. The mechanistic study revealed that the intracellular oxidative level greatly increased after the BPEI-AuNPs treatment, and the transcriptomic analysis showed that the dominant modulated pathways were related to oxidative stress and an antioxidant response. The stress level measured by flow cytometry also showed a significant decrease in the presence of a biocorona. Further anaylsis discovered that nuclear factor erythroid-2 related factor (Nrf2), a major regulator of anti-oxidant and anti-inflammatory gene, as the key factor related to the AuNPs induced oxidative stress and inflammation. This study provides futher understanding into the mechanisms on how NPs-induced cellular stress and reveals the protective effects of a biocorona on inflammatory responses in HEK at the molecular level, which provides important insights into the biological responses of AuNPs and their biocorona.

The emerging role of furin in neurodegenerative and neuropsychiatric diseases

Furin is an important mammalian proprotein convertase that catalyzes the proteolytic maturation of a variety of prohormones and proproteins in the secretory pathway. In the brain, the substrates of furin include the proproteins of growth factors, receptors and enzymes. Emerging evidence, such as reduced FURIN mRNA expression in the brains of Alzheimer's disease patients or schizophrenia patients, has implicated a crucial role of furin in the pathophysiology of neurodegenerative and neuropsychiatric diseases. Currently, compared to cancer and infectious diseases, the aberrant expression of furin and its pharmaceutical potentials in neurological diseases remain poorly understood. In this article, we provide an overview on the physiological roles of furin and its substrates in the brain, summarize the deregulation of furin expression and its effects in neurodegenerative and neuropsychiatric disorders, and discuss the implications and current approaches that target furin for therapeutic interventions. This review may expedite future studies to clarify the molecular mechanisms of furin deregulation and involvement in the pathogenesis of neurodegenerative and neuropsychiatric diseases, and to develop new diagnosis and treatment strategies for these diseases.

Influence of prazosin on systemic iron levels and the associated iron metabolic alterations in spontaneously hypertensive rats

The relationship between cardiovascular diseases and iron disorders has gained increasing attention; however, the effects of hypotensive drugs on iron metabolic alterations in hypertension are not well understood. The purpose of this study was to investigate iron metabolic changes after prazosin treatment of spontaneously hypertensive rats (SHRs) and Wistar–Kyoto (WKY) rats. Our second objective was to examine the effects of hypertension and anti‐hypertensive drugs on bone formation and resorption. SHRs and WKY rats were randomized into either prazosin‐treated groups (WKY + PZ and SHR + PZ) or untreated groups (WKY and SHR). After 7 days of intragastric prazosin administration, the rats were sacrificed for analysis; blood samples and organs (the duodenum, liver, kidneys, spleen, and femur) were collected. Both WKY + PZ and SHR groups exhibited iron deficiency in the serum and liver. Prazosin increased the iron levels in the bone tissue of SHRs. Prazosin stimulated the expression of hepcidin mRNA in the liver of SHRs and inhibited the expression of this iron‐regulatory hormone in WKY rats. FPN1 expression in the duodenum was increased significantly in SHRs, however markedly decreased after prazosin treatment. The expression of TLR4 and Ctsk was enhanced in the bone tissue of SHRs, whereas CLC‐7 expression was inhibited. Both hypotension and hypertension can lead to iron deficiency. Treatment with prazosin restored iron homeostasis in SHRs. The inverse impacts of prazosin on hepatic hepcidin expression in SHRs versus WKY rats indicates differing iron regulatory mechanisms between hypertensive and normal animals. The osteoclast activity was found to be enhanced in SHRs. Further study is needed to address whether the changes in osteoblast and osteoclast activity in SHRs correlates with the effects on iron metabolism.

Overexpression of Mitochondrial Ferritin Enhances Blood–Brain Barrier Integrity Following Ischemic Stroke in Mice by Maintaining Iron Homeostasis in Endothelial Cells

Blood–brain barrier (BBB) breakdown, a characteristic feature of ischemic stroke, contributes to poor patient outcomes. Brain microvascular endothelial cells (BMVECs) are a key component of the BBB and dysfunction or death of these cells following cerebral ischemia reperfusion (I/R) injury can disrupt the BBB, leading to leukocyte infiltration, brain edema and intracerebral hemorrhage. We previously demonstrated that mitochondrial ferritin (FtMt) can alleviate I/R-induced neuronal ferroptosis by inhibiting inflammation-regulated iron deposition. However, whether FtMt is involved in BBB disruption during cerebral I/R is still unknown. In the present study, we found that FtMt expression in BMVECs is upregulated after I/R and overexpression of FtMt attenuates I/R-induced BBB disruption. Mechanistically, we found that FtMt prevents tight junction loss and apoptosis by inhibiting iron dysregulation and reactive oxygen species (ROS) accumulation in I/R-treated BMVECs. Chelating excess iron with deferoxamine alleviates apoptosis in the brain endothelial cell line bEnd.3 under oxygen glucose deprivation followed by reoxygenation (OGD/R) insult. In summary, our data identify a previously unexplored effect for FtMt in the BBB and provide evidence that iron-mediated oxidative stress in BMVECs is an early cause of BMVECs damage and BBB breakdown in ischemic stroke.

Osteoblast Derived Exosomes Alleviate Radiation- Induced Hematopoietic Injury

As hematopoietic stem cells can differentiate into all hematopoietic lineages, mitigating the damage to hematopoietic stem cells is important for recovery from overdose radiation injury. Cells in bone marrow microenvironment are essential for hematopoietic stem cells maintenance and protection, and many of the paracrine mediators have been discovered in shaping hematopoietic function. Several recent reports support exosomes as effective regulators of hematopoietic stem cells, but the role of osteoblast derived exosomes in hematopoietic stem cells protection is less understood. Here, we investigated that osteoblast derived exosomes could alleviate radiation damage to hematopoietic stem cells. We show that intravenous injection of osteoblast derived exosomes promoted WBC, lymphocyte, monocyte and hematopoietic stem cells recovery after irradiation significantly. By sequencing osteoblast derived exosomes derived miRNAs and verified in vitro, we identified miR-21 is involved in hematopoietic stem cells protection via targeting PDCD4. Collectively, our data demonstrate that osteoblast derived exosomes derived miR-21 is a resultful regulator to radio-protection of hematopoietic stem cells and provide a new strategy for reducing radiation induced hematopoietic injury.

Iron promotes neurological function recovery in mice with ischemic stroke through endogenous repair mechanisms

The endogenous repair mechanisms play an important role in the recovery of nerve function after stroke, such as gliosis, synaptic plasticity, remyelination and nerve regeneration. Iron is the most abundant trace metal element in the brain and plays a crucial role in the maintenance of normal cerebral function. It is an important coenzyme factor in the process of cell metabolism, DNA synthesis, purine catabolism and neurotransmitter synthesis and decomposition. However, it is unclear what role iron plays in the long-term recovery of neurological function after stroke. In this study, we first observed that changes in iron metabolism occurred during neurological function recovery in the mice with distal middle cerebral artery occlusion (dMCAO). Our data showed that plasticity changes due to endogenous repair mechanisms resulted in improvements in cerebral cortex function. These changes involved gliosis, synaptic function reconstruction, remyelination, and activation of neural stem cells. In order to examine the potential role of iron, we synthesized liposomal-encapsulated deferoxamine (DFO) nanoparticles to further explore the effect and the mechanism of iron on the recovery of neurological function in dMCAO mice. Our results showed that liposome-DFO decreased iron deposition and reversed plasticity changes in cerebral cortex function after stroke, which delayed neurological function recovery. This experiment shows that the increasing iron level promotes endogenous repair in ischemic stroke. Our finding reveals the change regularity of iron and emphasizes the beneficial role of iron in the recovery process of neurological function, which provides an important basis for the prevention and/or treatment of ischemia-reperfusion and recovery after stroke.

Ckip-1 3′-UTR Attenuates Simulated Microgravity-Induced Cardiac Atrophy

Microgravity prominently affected cardiovascular health, which was the gravity-dependent physical factor. Deep space exploration had been increasing in frequency, but heart function was susceptible to conspicuous damage and cardiac mass declined in weightlessness. Understanding of the etiology of cardiac atrophy exposed to microgravity currently remains limited. The 3′-untranslated region (UTR) of casein kinase-2 interacting protein-1 (Ckip-1) was a pivotal mediator in pressure overload-induced cardiac remodeling. However, the role of Ckip-1 3′-UTR in the heart during microgravity was unknown. We analyzed Ckip-1 mRNA 3′-UTR and coding sequence (CDS) expression levels in ground-based analogs such as mice hindlimb unloading (HU) and rhesus monkey head-down bed rest model. Ckip-1 3′-UTR had transcribed levels in the opposite change trend with cognate CDS expression in the hearts. We then subjected wild-type (WT) mice and cardiac-specific Ckip-1 3′-UTR-overexpressing mice to hindlimb unloading for 28 days. Our results uncovered that Ckip-1 3′-UTR remarkably attenuated cardiac dysfunction and mass loss in simulated microgravity environments. Mechanistically, Ckip-1 3′-UTR inhibited lipid accumulation and elevated fatty acid oxidation-related gene expression in the hearts through targeting calcium/calmodulin-dependent kinase 2 (CaMKK2) and activation of the AMPK-PPARα-CPT1b signaling pathway. These findings demonstrated Ckip-1 3′-UTR was an important regulator in atrophic heart growth after simulated microgravity.

Calcitonin increases hepatic hepcidin expression through the BMP6 of kidney in mice

BACKGROUND

Osteoporosis is frequently accompanied by iron disorders. Calcitonin (CT) was approved as a clinical drug to treat osteoporosis. Hepcidin is a peptide hormone that is secreted by the liver and controls body iron homeostasis. Hepcidin deficiency leads to iron overload diseases. This study was aimed at investigating the effect of CT on hepatic hepcidin and the mechanism by which CT modulates hepatic hepcidin pathways and iron metabolism.

METHOD

RT-PCR, Western blot, ELISA and siRNA were used to detect the effect of CT on iron metabolism in vivo and in vitro. In addition, the regulatory signal molecules of hepcidin were measured to explore the molecular mechanism of its regulation.

RESULTS

The results showed that CT strongly increased hepcidin expression and altered iron homeostasis, after mice were intraperitoneal injection of CT. In response to CT administration, BMP6 level in kidney and the serum BMP6 was increased significantly. The phosphorylation of Smad1/5/8 proteins in liver was increased at 3 h and 6 h. Moreover, the Bmp inhibitor LDN-193,189 pretreatment significantly attenuated the CT-mediated increases in phosphorylated Smad1/5/8 and Hamp1 mRNA levels. Calcitonin receptor (CTR) siRNA transfection significant suppressed the role of CT on BMP6 expression in Caki-1 cells.

CONCLUSION

Our results suggest that CT strongly induces hepcidin expression and affected iron metabolism. It will provide a new strategy for the treatment of calcium iron related diseases.

Vascular smooth muscle cell-specific miRNA-214 knockout inhibits angiotensin II-induced hypertension through upregulation of Smad7

Vascular remodeling is a prominent trait during the development of hypertension, attributable to the phenotypic transition of vascular smooth muscle cells (VSMCs). Increasing studies demonstrate that microRNA plays an important role in this process. Here, we surprisingly found that smooth muscle cell-specific miR-214 knockout (miR-214 cKO) significantly alleviates angiotensin II (Ang II)-induced hypertension, which has the same effect as that of miR-214 global knockout mice in response to Ang II stimulation. Under the treatment of Ang II, miR-214 cKO mice exhibit substantially reduced systolic blood pressure. The vascular medial thickness and area in miR-214 cKO blood vessels were obviously reduced, the expression of collagen I and proinflammatory factors were also inhibited. VSMC-specific deletion of miR-214 blunts the response of blood vessels to the stimulation of endothelium-dependent and -independent vasorelaxation and phenylephrine and 5-HT induced vasocontraction. In vitro, Ang II-induced VSMC proliferation, migration, contraction, hypertrophy, and stiffness were all repressed with miR-214 KO in VSMC. To further explore the mechanism of miR-214 in the regulation of the VSMC function, it is very interesting to find that the TGF-β signaling pathway is mostly enriched in miR-214 KO VSMC. Smad7, the potent negative regulator of the TGF-β/Smad pathway, is identified to be the target of miR-214 in VSMC. By which, miR-214 KO sharply enhances Smad7 levels and decreases the phosphorylation of Smad3, and accordingly alleviates the downstream gene expression. Further, Ang II-induced hypertension and vascular dysfunction were reversed by antagomir-214. These results indicate that miR-214 in VSMC established a crosstalk between Ang II-induced AT1R signaling and TGF-β induced TβRI /Smad signaling, by which it exerts a pivotal role in vascular remodeling and hypertension and imply that miR-214 has the potential as a therapeutic target for the treatment of hypertension.

3' untranslated region of Ckip-1 inhibits cardiac hypertrophy independently of its cognate protein

AIMS

3' untranslated region (3' UTR) of mRNA is more conserved than other non-coding sequences in vertebrate genomes, and its sequence space has substantially expanded during the evolution of higher organisms, which substantiates their significance in biological regulation. However, the independent role of 3' UTR in cardiovascular disease was largely unknown.

METHODS AND RESULTS

Using bioinformatics, RNA fluorescent in situ hybridization and quantitative real-time polymerase chain reaction, we found that 3' UTR and coding sequence regions of Ckip-1 mRNA exhibited diverse expression and localization in cardiomyocytes. We generated cardiac-specific Ckip-1 3' UTR overexpression mice under wild type and casein kinase 2 interacting protein-1 (CKIP-1) knockout background. Cardiac remodelling was assessed by histological, echocardiography, and molecular analyses at 4 weeks after transverse aortic constriction (TAC) surgery. The results showed that cardiac Ckip-1 3' UTR significantly inhibited TAC-induced cardiac hypertrophy independent of CKIP-1 protein. To determine the mechanism of Ckip-1 3' UTR in cardiac hypertrophy, we performed transcriptome and metabolomics analyses, RNA immunoprecipitation, biotin-based RNA pull-down, and reporter gene assays. We found that Ckip-1 3' UTR promoted fatty acid metabolism through AMPK-PPARα-CPT1b axis, leading to its protection against pathological cardiac hypertrophy. Moreover, Ckip-1 3' UTR RNA therapy using adeno-associated virus obviously alleviates cardiac hypertrophy and improves heart function.

CONCLUSIONS

These findings disclose that Ckip-1 3' UTR inhibits cardiac hypertrophy independently of its cognate protein. Ckip-1 3' UTR is an effective RNA-based therapy tool for treating cardiac hypertrophy and heart failure.

Targeting E3 Ubiquitin Ligase WWP1 Prevents Cardiac Hypertrophy Through Destabilizing DVL2 via Inhibition of K27-Linked Ubiquitination

BACKGROUND

Without adequate treatment, pathological cardiac hypertrophy induced by sustained pressure overload eventually leads to heart failure. WWP1 (WW domain-containing E3 ubiquitin protein ligase 1) is an important regulator of aging-related pathologies, including cancer and cardiovascular diseases. However, the role of WWP1 in pressure overload-induced cardiac remodeling and heart failure is yet to be determined.

METHODS

To examine the correlation of WWP1 with hypertrophy, we analyzed WWP1 expression in patients with heart failure and mice subjected to transverse aortic constriction (TAC) by Western blotting and immunohistochemical staining. TAC surgery was performed on WWP1 knockout mice to assess the role of WWP1 in cardiac hypertrophy, heart function was examined by echocardiography, and related cellular and molecular markers were examined. Mass spectrometry and coimmunoprecipitation assays were conducted to identify the proteins that interacted with WWP1. Pulse-chase assay, ubiquitination assay, reporter gene assay, and an in vivo mouse model via AAV9 (adeno-associated virus serotype 9) were used to explore the mechanisms by which WWP1 regulates cardiac remodeling. AAV9 carrying cardiac troponin T (cTnT) promoter-driven small hairpin RNA targeting WWP1 (AAV9-cTnT-shWWP1) was administered to investigate its rescue role in TAC-induced cardiac dysfunction.

RESULTS

The WWP1 level was significantly increased in the hypertrophic hearts from patients with heart failure and mice subjected to TAC. The results of echocardiography and histology demonstrated that WWP1 knockout protected the heart from TAC-induced hypertrophy. There was a direct interaction between WWP1 and DVL2 (disheveled segment polarity protein 2). DVL2 was stabilized by WWP1-mediated K27-linked polyubiquitination. The role of WWP1 in pressure overload-induced cardiac hypertrophy was mediated by the DVL2/CaMKII/HDAC4/MEF2C signaling pathway. Therapeutic targeting WWP1 almost abolished TAC induced heart dysfunction, suggesting WWP1 as a potential target for treating cardiac hypertrophy and failure.

CONCLUSIONS

We identified WWP1 as a key therapeutic target for pressure overload induced cardiac remodeling. We also found a novel mechanism regulated by WWP1. WWP1 promotes atypical K27-linked ubiquitin multichain assembly on DVL2 and exacerbates cardiac hypertrophy by the DVL2/CaMKII/HDAC4/MEF2C pathway.

Casein Kinase-2 Interacting Protein-1 Regulates Physiological Cardiac Hypertrophy via Inhibition of Histone Deacetylase 4 Phosphorylation

Different kinds of mechanical stimuli acting on the heart lead to different myocardial phenotypes. Physiological stress, such as exercise, leads to adaptive cardiac hypertrophy, which is characterized by a normal cardiac structure and improved cardiac function. Pathological stress, such as sustained cardiac pressure overload, causes maladaptive cardiac remodeling and, eventually, heart failure. Casein kinase-2 interacting protein-1 (CKIP-1) is an important regulator of pathological cardiac remodeling. However, the role of CKIP-1 in physiological cardiac hypertrophy is unknown. We subjected wild-type (WT) mice to a swimming exercise program for 21 days, which caused an increase in myocardial CKIP-1 protein and mRNA expression. We then subjected CKIP-1 knockout (KO) mice and myocardial-specific CKIP-1-overexpressing mice to the 21-day swimming exercise program. Histological and echocardiography analyses revealed that CKIP-1 KO mice underwent pathological cardiac remodeling after swimming, whereas the CKIP-1-overexpressing mice had a similar cardiac phenotype to the WT controls. Histone deacetylase 4 (HDAC4) is a key molecule in the signaling cascade associated with pathological hypertrophy; the phosphorylation levels of HDAC4 were markedly higher in CKIP-1 KO mouse hearts after the swimming exercise program. The phosphorylation levels of HDAC4 did not change after swimming in the hearts of CKIP-1-overexpressing or WT mice. Our results indicate that swimming, a mechanical stress that leads to physiological hypertrophy, triggers pathological cardiac remodeling in CKIP-1 KO mice. CKIP-1 is necessary for physiological cardiac hypertrophy in vivo, and for modulating the phosphorylation level of HDAC4 after physiological stress. Genetically engineering CKIP-1 expression affected heart health in response to exercise.

Mitochondrial ferritin attenuates cerebral ischaemia/reperfusion injury by inhibiting ferroptosis

Ischaemic stroke is becoming the most common cerebral disease in aging populations, but the underlying molecular mechanism of the disease has not yet been fully elucidated. Increasing evidence has indicated that an excess of iron contributes to brain damage in cerebral ischaemia/reperfusion (I/R) injury. Although mitochondrial ferritin (FtMt) plays a critical role in iron homeostasis, the molecular function of FtMt in I/R remains unknown. We herein report that FtMt levels are upregulated in the ischaemic brains of mice. Mice lacking FtMt experience more severe brain damage and neurological deficits, accompanied by typical molecular features of ferroptosis, including increased lipid peroxidation and disturbed glutathione (GSH) after cerebral I/R. Conversely, FtMt overexpression reverses these changes. Further investigation shows that Ftmt ablation promotes I/R-induced inflammation and hepcidin-mediated decreases in ferroportin1, thus markedly increasing total and chelatable iron. The elevated iron consequently facilitates ferroptosis in the brain of I/R. In brief, our results provide evidence that FtMt plays a critical role in protecting against cerebral I/R-induced ferroptosis and subsequent brain damage, thus providing a new potential target for the treatment/prevention of ischaemic stroke.

Nrf2 knockout altered brain iron deposition and mitigated age-related motor dysfunction in aging mice

The transcription factor NF-E2-related factor 2 (Nrf2) is a central regulator of cellular antioxidant and detoxification response. The association between Nrf2 activity and iron-related oxidative stress in neurodegenerative diseases has been studied, and Nrf2 was found to transcriptionally regulate the expression of iron transporters and ferroptosis-related factors. However, the role of Nrf2 in age-related motor dysfunction and its link to iron metabolism dysregulation in brain have not been fully elucidated. In this study, with different ages of Nrf2 knockout (KO) and wild type (WT) mice, we investigated the effects of Nrf2 deficiency on brain oxidative stress, iron metabolism and the motor coordination ability of mice. In contrast to the predicted neuroprotective role of Nrf2 in oxidative stress-related diseases, we found that Nrf2 KO remarkably improved the motor coordination of aged mice, which was associated with the reduced ROS level and decreased apoptosis of dopaminergic neurons in substantia nigra (SN) of 18-month-old Nrf2 KO mice. With high-iron and Parkinson's disease (PD) mouse models, we revealed that Nrf2 KO prevented the deposition of brain iron, particularly in SN and striatum, which may subsequently delay motor dysfunction in aged mice. The regulation of Nrf2 KO on brain iron metabolism was likely mediated by decreasing the ferroportin 1 (FPN1) level on brain microvascular endothelial cells, thus hindering the process of iron entry into the brain. Nrf2 may be a potential therapeutic target in age-related motor dysfunction diseases for its role in regulating brain iron homeostasis.

A high-fructose diet in rats induces systemic iron deficiency and hepatic iron overload by an inflammation mechanism

Nonalcoholic fatty liver disease (NAFLD) correlates with the high intake of fructose-rich soft drinks. Both inflammation and dysregulated iron metabolism are pathogenic factors in the development of NAFLD. The present investigation assessed the effects of a high-fructose diet (HF diet) on inflammation and iron metabolism. In this study, rats were fed a control or HF diet for 4, 8, or 12 weeks, after which insulin resistance, transaminases levels, serum and liver lipid profiles, inflammatory factors, and iron metabolism-related molecules were evaluated. The activities of the hepatic inflammation-associated pathways, IKKβ/NF-κB, and JAK2/STAT3, were detected by western blot. Result showed that the HF diet-fed animals developed a time-dependent serum lipid increase and hepatic lipid accumulation as well as insulin resistance. Serum iron (SI), serum ferritin (SF), and transferrin saturation (TS) decreased while total iron-binding capacity (TIBC) and serum transferrin (s-TF) increased at 8 and 12 weeks in the HF diet group. The HF diet led to increased transaminases levels at 8 and 12 weeks, and iron deposition was observed in the liver, accompanied by an upregulation of ferritin light chain (FTL), hepcidin (HEPC), transferrin (TF), transferrin receptor 1 (TfR1), iron regulatory protein 1 (IRP1), hemojuvelin (HJV), and divalent metal transporter 1 (DMT1). Moreover, ferroportin (FPN1) levels were downregulated, as expected from the increased HEPC. A progressive inflammation phenotype was apparent, with increased inflammatory factors, MDA, IL-1β, IL-6, and TNF-α, in the serum and liver tissue. Concomitantly, the hepatic IKKβ/NF-κB and JAK2/STAT3 pathways were activated. In summary, we verified that HF diet induces systemic iron deficiency and hepatic iron accumulation, likely due to the activation of inflammation via the NF-κB and JAK2/STAT3 pathways. PRACTICAL APPLICATIONS: As increasing numbers of individuals consume HF diets, the health implications of this type of over nutrition become globally relevant. Using a high-fructose diet rat model, our present study reveals inflammation as the link between a HF diet and dysregulated iron metabolism. Importantly, both inflammation and disrupted iron metabolism have been shown to be pathogenic factors in nonalcoholic fatty liver disease (NAFLD). The iron regulatory hormone, HEPC, is a link between the liver, inflammation, and iron metabolism. As fructose-rich foods become increasingly abundant and people's fructose intake increases, the impact of high fructose on health requires increased attention. Little research has been conducted on the effects of fructose on iron metabolism. Our study provides useful insights into the prevention and treatment of iron metabolism disorders arising from metabolic syndrome.

Hepcidin overexpression in astrocytes alters brain iron metabolism and protects against amyloid-β induced brain damage in mice

Progressive iron accumulation in the brain and iron-induced oxidative stress are considered to be one of the initial causes of Alzheimer’s disease (AD), and modulation of brain iron level shows promise for its treatment. Hepcidin expressed by astrocytes has been speculated to regulate iron transport across the blood–brain barrier (BBB) and control the whole brain iron load. Whether increasing the expression of astrocyte hepcidin can reduce brain iron level and relieve AD symptoms has yet to be studied. Here, we overexpressed hepcidin in astrocytes of the mouse brain and challenged the mice with amyloid-β_25–35 (Aβ_25–35) by intracerebroventricular injection. Our results revealed that hepcidin overexpression in astrocytes significantly ameliorated Aβ_25–35-induced cell damage in both the cerebral cortex and hippocampus. This protective role was also attested by behavioral tests of the mice. Our data further demonstrated that astrocyte-overexpressed hepcidin could decrease brain iron level, possibly by acting on ferroportin 1 (FPN1) on the brain microvascular endothelial cells (BMVECs), which in turn reduced Aβ_25–35-induced oxidative stress and apoptosis, and ultimately protected cells from damage. This study provided in vivo evidences of the important role of astrocyte hepcidin in the regulation of brain iron metabolism and protection against Aβ-induced cortical and hippocampal damages and implied its potential in the treatment of oxidative stress-related brain disorders.

Astrocyte hepcidin ameliorates neuronal loss through attenuating brain iron deposition and oxidative stress in APP/PS1 mice

Iron overload in the brain and iron-induced oxidative damage have been considered to play key roles in the pathogenesis of Alzheimer's disease (AD). Hepcidin is a peptide that regulates systemic iron metabolism by interacting with iron exporter ferroportin 1 (FPN1). Studies have indicated that the astrocyte hepcidin could regulate brain iron intake at the blood-brain barrier and injection of hepcidin into brain attenuated iron deposition in the brain. However, whether overexpression of hepcidin in astrocytes of APP/PS1 transgenic mice can alleviate AD symptoms by reducing iron deposition has not been evaluated. In this study, we overexpressed hepcidin in astrocytes of APP/PS1 mice and investigated its effects on β-amyloid (Aβ) aggregation, neuronal loss, iron deposition and iron-induced oxidative damages. Our results showed that the elevated expression of astrocyte hepcidin in APP/PS1 mice significantly improved their cognitive decline, and partially alleviated the formation of Aβ plaques in cortex and hippocampus. Further investigations revealed that overexpression of hepcidin in astrocytes significantly reduced iron levels in cortex and hippocampus of APP/PS1 mice, especially iron content in neurons, which led to the reduction of iron accumulation-induced oxidative stress and neuroinflammation, and finally decreased neuronal cell death in the cortex and hippocampus of APP/PS1 mice. This study demonstrated that overexpression of hepcidin in astrocytes of APP/PS1 mice could partially alleviate AD symptoms and delay the pathological process of AD.

Physical exercise: An inducer of positive oxidative stress in skeletal muscle aging

Oxidative stress is the core of most pathological situations, and its attribution toward disease conversion is not yet well established. The adaptive capacity of a cell can overcome ROS-induced pathology. However, when a cell fails to extend its maximum adaptive capacity against oxidative stress, it could lead a cell to misbehave or defunct from its normal functions. Any type of physical activity can increase the cells' maximum adaptive capacity, but aging can limit this. However, whether aging is the initiating point of reducing cells' adaptive capacity against oxidative stress or oxidative stress can induce the aging process is a mystery, and it could be the key to solving several uncured diseases. Paradoxically, minimum ROS is needed for cellular homeostasis. Nevertheless, finding factors that can limit or nullify the production of ROS for cellular homeostasis is a million-dollar question. Regular physical exercise is considered to be one of the factors that can limit the production of ROS and increase the ROS-induced benefits in the cells through inducing minimum oxidative stress and increasing maximum adapting capacity against oxidative stress-induced damages. The type and intensity of exercise that can produce such positive effects in the cells remain unclear. Therefore, this review discusses how physical exercise can help to produce minimal positive oxidative stress in preventing skeletal muscle aging.

Transcriptomic analysis reveals the molecular mechanism of Alzheimer-related neuropathology induced by sevoflurane in mice

Anesthetics could induce cognitive dysfunctions, such as Alzheimer's disease in humans or mice. However, the precise molecular mechanism is unclear. Sevoflurane is a common anesthetic widely used in clinical practice. Here, we demonstrated the induction of cognitive dysfunction induced by Sev in mice to corroborate the signaling pathway and the differentially expressed genes (DEGs) followed by analyzing their functions. The cognitive function of mice was measured by the Morris water maze test. Transcriptomic data were annotated with Illumina HiSeq. 2000. Further, the changes in related proteins or genes were analyzed by western blotting and real-time quantitative polymerase chain reaction. Our results showed that Sev could cause a decline in cognitive competence in mice. The transcriptomic data indicated that adding up to 566 genes were upregulated and 1073 genes were downregulated. The genes of Plin4, Lcn2, Lrg1, Foxf1, and Ctla2a were significantly upregulated, while the genes of Arc, Npas4, Egr2, Hes5, and Cdh9 were downregulated dramatically. The Gene Ontology term with the highest enrichment of DEGs are involved in the regulation of cellular and macromolecule metabolism and cation and nucleic acid binding, respectively. The Kyoto encyclopedia of genes and genomes analysis indicated that the mitogen-activated protein kinases (MAPK) pathway was one of the most important metabolic pathways. In addition, the metabolic pathways related to cognitive function, such as the nervous system and neurodegenerative disease showed significant changes. Furthermore, we found that p38, c-Jun N-terminal kinase, and extracellular signal-regulated kinase of the MAPK signaling pathway played important roles in this process. In conclusion, these results provide the first important clues for identifying the DEGs and signaling pathways in the hippocampus due to a Sev-induced cognitive deficiency in mice.

Overexpression of Dendritic Cell-Specific Intercellular Adhesion Molecule-3-Grabbing Nonintegrin in Dendritic Cells Protecting against Aspergillosis

Background:

Dendritic cells (DCs) play an important role in host defense against pathogen infection. DC-specific intercellular adhesion molecule-3-grabbing nonintegrin (SIGN) is a group II C-type lectin receptor and specifically expressed on the surface of DCs. This study aimed to determine whether DC-SIGN affects intracellular signaling activation, Th1/Th2 imbalance and aspergillus immune evasion in aspergillus infection, and explore the application of DC-SIGN-modified DCs in immunotherapy.

Methods:

DCs were first obtained from the mononuclear cells of peripheral blood. The interferon (IFN)-γ and dexamethasone (Dex) were used to stimulate DCs. The expression of DC-SIGN, Th1 and Th2 cytokines, and the capacity of DCs in stimulating T cells proliferation and phagocytosis, and nuclear factor (NF)-κB activation were analyzed. In addition, adenovirus expression vector Ad-DC-SIGN was generated to transfect DCs. Mannan was used to block DC-SIGN signaling for confirming the involvement of DC-SIGN function in Aspergillus fumigatus (Af)-induced DCs maturation. The unpaired, two-tailed Student's t-test was used in the comparisons between two groups.

Results:

Exogenous IFN-γ could activate Af-induced DCs and promote the Th0 cells toward Th1 profile (interleukin [IL]-12 in IFN-γ/Af group: 50.96 ± 4.38 pg/ml; control/Af group: 29.70 ± 2.00 pg/ml, t = 10.815, P < 0.001). On the other hand, Dex inhibited the secretion of Th2 cytokines (IL-10 in Dex/Af group: 5.27 ± 0.85 pg/ml; control/Af group: 15.14 ± 1.40 pg/ml, t = 14.761, P < 0.001)), and successfully caused immunosuppression. After transfection with Ad-DC-SIGN, DCs have improved phagocytosis (phagocytosis rates in Ad-DC-SIGN group: 74.0% ± 3.4%; control group: 64.7% ± 6.8%, t = 3.104, P = 0.013). There was more Th1 cytokine secreted in the Af-induced DC-SIGN modified DCs (IL-12 in Ad-DC-SIGN/Af group: 471.98 ± 166.31 pg/ml; control/Af group: 33.35 ± 5.98 pg/ml, t = 6.456, P = 0.001), correlated to the enhanced NF-κB activation.

Conclusion:

Overexpressing DC-SIGN in DCs had a protective function on aspergillosis.

Mitochondrial Ferritin Is a Hypoxia-Inducible Factor 1α-Inducible Gene That Protects from Hypoxia-Induced Cell Death in Brain

Aims: Mitochondrial ferritin (protein [FtMt]) is preferentially expressed in cell types of high metabolic activity and oxygen consumption, which is consistent with its role of sequestering iron and preventing oxygen-derived redox damage. As of yet, the mechanisms of FtMt regulation and the protection FtMt affords remain largely unknown. Results: Here, we report that hypoxia-inducible factor 1α (HIF-1α) can upregulate FtMt expression. We verify one functional hypoxia-response element (HRE) in the positive regulatory region and two HREs possessing HIF-1α binding activity in the minimal promoter region of the human FTMT gene. We also demonstrate that FtMt can alleviate hypoxia-induced brain cell death by sequestering uncommitted iron, whose levels increase with hypoxia in these cells. Innovation: In the absence of FtMt, this catalytic metal excess catalyzes the production of cytotoxic reactive oxygen species. Conclusion: Thus, the cell ability to increase expression of FtMt during hypoxia may be a skill to avoid tissue damage derived from oxygen limitation.

Brain Iron Metabolism and Regulation

With the development of research, more and more evidences suggested that mutations in the genes associated with brain iron metabolism induced diseases in the brain. Brain iron metabolism disorders might be one cause of neurodegenerative diseases. This review mainly summarizes the normal process of iron entry into the brain across the blood-brain barrier, and the distribution and transportation of iron among neurons and glial cells, as well as the underlying regulation mechanisms. To understand the mechanisms of iron metabolism in the brain will provide theoretical basis to prevent and cure brain diseases related to iron metabolism disorders.

Brain Iron Metabolism and CNS Diseases

Iron is the most abundant trace element in the human body. It is well known that iron is an important component of hemoglobin involved in the transport of oxygen. As a component of various enzymes, it participates in the tricarboxylic acid cycle and oxidative phosphorylation. Iron in the nervous system is also involved in the metabolism of catecholamine neurotransmitters and is involved in the formation of myelin. Therefore, iron metabolism needs to be strictly regulated. Previous studies have shown that iron deficiency in the brain during infants and young children causes mental retardation, such as delayed development of language and body balance, and psychomotor disorders. However, if the iron is excessively deposited in the aged brain, it is closely related to the occurrence of various neurodegenerative diseases, such as Alzheimer's disease, Parkinson's disease, and Friedreich's ataxia. Therefore, it is important to fully study and understand the mechanism of brain iron metabolism and its regulation. On this basis, exploring the relationship between brain iron regulation and the occurrence of nervous system diseases and discovering new therapeutic targets related to iron metabolism have important significance for breaking through the limitation of prevention and treatment of nervous system diseases. This review discusses the complete research history of iron and its significant role in the pathogenesis of the central nervous system (CNS) diseases.

Hepcidin and iron regulatory proteins coordinately regulate ferroportin 1 expression in the brain of mice

Iron plays an essential role in various cellular metabolic processes of the body. Maintenance of cellular iron homeostasis is particularly important for keeping the normal functions of the cells. Ferroportin 1 (FPN1) is the currently only known iron exporter on the cell membrane. It has been indicated that the regulation of FPN1 in response to the alteration of iron level mainly involves two processes, posttranscriptional repression by iron regulatory proteins (IRPs) and posttranslational degradation by hepcidin, the major iron-sensing hormone. However, whether there is any communication between the two types of regulations or which one plays dominant role has not been reported. In our study with IRP2^-/- mice, we found that knockout of IRP2 increased FPN1 expression in the cerebral cortex of IRP2^-/- mice, whereas the upregulation of FPN1 was more significant in IRP1/IRP2 dual knockdown fibroblasts. Interestingly, we found that the knockout of IRP2 severely affected the regulation effect of hepcidin on FPN1 in mouse brain. FPN1 level decreased dramatically in the brain of wild-type mice injected with hepcidin, but it did not decrease much in IRP2 knockout mice. Further investigation disclosed that the compromised hepcidin-FPN1 regulation in IRP2^-/- cells was directly dependent on the existence of iron-responsive element (IRE) in FPN1 messenger RNA. These results indicate that IRPs and hepcidin coordinately regulate the FPN1 level in mice. This study will provide a more comprehensive understanding of the regulatory mechanisms of FPN1 expression.

Nano-liposomes of lycopene reduces ischemic brain damage in rodents by regulating iron metabolism

In order to discover new drug delivery approaches and to understand the mechanism of iron overload in cerebral ischemia/reperfusion (I/R), we aimed to investigate the effects of lycopene (LYC) in the form of nano-liposomes (L-LYC) on iron-regulating proteins and ischemic brain injury. We found that L-LYC significantly increased the LYC content in serum and the brain. Adult male Sprague-Dawley rats treated with L-LYC for 14 days were subjected to 60 min of ischemia and 7 days of reperfusion. The effects of L-LYC were evaluated by infarction volume, neurological score, neuronal apoptosis, and markers for oxidative stress. Levels of iron-regulating protein such as hepcidin and ferroportin (FPN1) were examined. L-LYC reduced cerebral infarction and improved neurobehavior of the rats more efficiently than "naked" LYC. L-LYC reduced protein levels of oxidases (e.g. nitric oxide synthase and NOX2), increased the level of Bcl-2, lowered caspase-3, and suppressed apoptosis through inhibiting MAPK-JNK. Furthermore, L-LYC suppressed hepcidin-mediated decrease in FPN1, a sole iron exporter, and normalized the levels of iron. We further demonstrated that the effect of L-LYC on hepcidin expression might result from its ability to attenuate the release of the inflammatory factor interleukin 6. The results demonstrated that nano-liposomal encapsulation significantly improved LYC efficacy in providing neuronal protection against I/R injury. The data also revealed a novel mechanism of L-LYC's neuroprotection by regulating iron metabolism in an ischemic brain.

Targeted Brain Delivery of Rabies Virus Glycoprotein 29-Modified Deferoxamine-Loaded Nanoparticles Reverses Functional Deficits in Parkinsonian Mice

Excess iron deposition in the brain often causes oxidative stress-related damage and necrosis of dopaminergic neurons in the substantia nigra and has been reported to be one of the major vulnerability factors in Parkinson's disease (PD). Iron chelation therapy using deferoxamine (DFO) may inhibit this nigrostriatal degeneration and prevent the progress of PD. However, DFO shows very short half-life in vivo and hardly penetrates the blood brain barrier (BBB). Hence, it is of great interest to develop DFO formulations for safe and efficient intracerebral drug delivery. Herein, we report a polymeric nanoparticle system modified with brain-targeting peptide rabies virus glycoprotein (RVG) 29 that can intracerebrally deliver DFO. The nanoparticle system penetrates the BBB possibly through specific receptor-mediated endocytosis triggered by the RVG29 peptide. Administration of these nanoparticles significantly decreased iron content and oxidative stress levels in the substantia nigra and striatum of PD mice and effectively reduced their dopaminergic neuron damage and as reversed their neurobehavioral deficits, without causing any overt adverse effects in the brain or other organs. This DFO-based nanoformulation holds great promise for delivery of DFO into the brain and for realizing iron chelation therapy in PD treatment.

Ceruloplasmin, a Potential Therapeutic Agent for Alzheimer's Disease

AIMS

Ceruloplasmin (CP), a ferrous oxidase enzyme, plays an important role in regulating iron metabolism and redox reactions. Previous studies showed that CP deficiency contributes to Parkinson's disease by increasing iron accumulation and oxidative stress in the substantia nigra. However, the role of CP in Alzheimer's disease (AD) is unclear. We hypothesized that the lack of CP gene expression would affect the pathogenesis and damage of AD by promoting abnormal iron levels and oxidative stress.

RESULTS

AD mouse models were induced in CP knockout mouse either by injection of Aβ_25-35 into the lateral ventricle of the brain or transgenic APP expression. CP levels were decreased significantly in the hippocampus of AD patients, as well as Aβ-CP^+/+ and APP-CP^+/+ mice. Compared to control AD mice, CP gene deletion increased memory impairment and iron accumulation, which could be associated with elevated reactive oxygen species (ROS) levels and lead to cell apoptosis mediated through the Bcl-2/Bax and Erk/p38 signaling pathways in Aβ-CP^-/- and APP-CP^-/- mice. In contrast, the restoration of CP expression to CP^-/- mice through injection of an exogenous expression plasmid into the brain ventricle alleviated Aβ-induced neuronal damage in the hippocampus.

INNOVATION

CP alterations in iron contents were mediated through DMT1(-IRE) and changes in ROS levels, which in turn attenuated the progression of AD through the Erk/p38 and Bcl-2/Bax signaling pathways.

CONCLUSION

Our results show a protective role of CP in AD and suggest that regulating CP expression in the hippocampus may provide a new neuroprotective strategy for AD. Antioxid. Redox Signal. 28, 1323-1337.

The α1-adrenergic receptor is involved in hepcidin upregulation induced by adrenaline and norepinephrine via the STAT3 pathway

Elevated body iron stores are associated with hypertension progression, while hypertension is associated with elevated plasma catecholamine levels in patients. However, there is a gap in our understanding of the connection between catecholamines and iron regulation. Hepcidin is a key iron-regulatory hormone, which maintains body iron balance. In the present study, we investigated the effects of adrenaline (AD) and norepinephrine (NE) on hepatic hepcidin regulation. Mice were treated with AD, NE, phenylephrine (PE, α1-adrenergic receptor agonist), prazosin (PZ, α1-adrenergic receptor antagonist), and/or propranolol (Pro, β-adrenergic receptor antagonist). The levels of hepcidin, as well as signal transducer and activator of transcription 3 (STAT3), ferroportin 1 (FPN1), and ferritin-light (Ft-L) protein in the liver or spleen, were assessed. Six hours after AD, NE, or PE treatment, hepatic hepcidin mRNA levels increased. Pretreatment with PZ, but not Pro, abolished the effects of AD or NE on STAT3 phosphorylation and hepatic hepcidin expression. When mice were treated with AD or NE continuously for 7 days, an increase in hepatic hepcidin mRNA levels and serum hepcidin concentration was also observed. Meanwhile, the expected downstream effects of elevated hepcidin, namely decreased FPN1 expression and increased Ft-L protein and non-heme iron concentrations in the spleen, were observed after the continuous AD or NE treatments. Taken together, we found that AD or NE increase hepatic hepcidin expression via the α1-adrenergic receptor and STAT3 pathways in mice. The elevated hepatic hepcidin decreased FPN1 levels in the spleen, likely causing the increased iron accumulation in the spleen.

Development of real-time recombinase polymerase amplification assay for rapid and sensitive detection of canine parvovirus 2

Background

Canine parvovirus 2, a linear single-stranded DNA virus belonging to the genus Parvovirus within the family Parvoviridae, is a highly contagious pathogen of domestic dogs and several wild canidae species. Early detection of canine parvovirus (CPV-2) is crucial to initiating appropriate outbreak control strategies. Recombinase polymerase amplification (RPA), a novel isothermal gene amplification technique, has been developed for the molecular detection of diverse pathogens. In this study, a real-time RPA assay was developed for the detection of CPV-2 using primers and an exo probe targeting the CPV-2 nucleocapsid protein gene.

Results

The real-time RPA assay was performed successfully at 38 °C, and the results were obtained within 4–12 min for 10⁵–10¹ molecules of template DNA. The assay only detected CPV-2, and did not show cross-detection of other viral pathogens, demonstrating a high level of specificity. The analytical sensitivity of the real-time RPA was 10¹ copies/reaction of a standard DNA template, which was 10 times more sensitive than the common RPA method. The clinical sensitivity of the real-time RPA assay matched 100% (n = 91) to the real-time PCR results.

Conclusion

The real-time RPA assay is a simple, rapid, reliable and affordable method that can potentially be applied for the detection of CPV-2 in the research laboratory and point-of-care diagnosis.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1232-z) contains supplementary material, which is available to authorized users.

Identification of CDAN1, C15ORF41 and SEC23B mutations in Chinese patients affected by congenital dyserythropoietic anemia

Congenital dyserythropoietic anaemias (CDAs) are a group of rare haematological disorders characterized by ineffective erythropoiesis and dyserythropoiesis and reduced numbers of red cells, often with an abnormal morphology. Pathogenic defects in CDAN1, C15ORF41, SEC23B, KIF23, KLF1 and GATA1 genes have been identified in CDAs patients. In this study, we described 13 unrelated Chinese CDAs patients and identified 21 mutations, including 5 novel mutations in CDAN1 gene, and 5 novel mutations in SEC23B gene. Additionally, we predicted the molecular consequence of these missense mutations with Polymorphism Phenotyping v2 (Polyphen), Sorting Intolerant From Tolerant (SIFT), MutPred (http://mutpred1.mutdb.org/) and Protein Variation Effect Analyzer (Provean, http://provean.jcvi.org/seq_submit.php) and analyzed the conservation of the mutated amino acid among proteins from several mammalian species.

Iron Metabolism in Parkinson’s Disease

In the central nervous system, iron is involved in many biologically important processes such as oxygen transport and storage, electron transport, energy metabolism, and antioxidant and DNA synthesis. Parkinson’s disease (PD) is a common neurodegenerative disease characterized by loss of dopaminergic neurons in the substantia nigra. Extensive research has reported that iron is heavily accumulated in the dopaminergic neurons in substantia nigra (SN) of PD patients. Changes in the expression of key iron transporters have also been observed in PD patients. Excessive iron accumulation can induce neuronal damage through reactive oxygen species production, which can cause oxidative stress increased membrane lipid peroxidation, DNA damage and protein oxidation and misfolding. This chapter provides a review about brain iron metabolism in PD, the role of iron transporters expression and function on brain iron homeostasis and distribution of intracellular iron. This knowledge will be of benefit to novel therapeutic targets for PD.

Mitochondrial Ferritin Protects Hydrogen Peroxide-Induced Neuronal Cell Damage

Oxidative stress and iron accumulation are tightly associated with neurodegenerative diseases. Mitochondrial ferritin (FtMt) is identified as an iron-storage protein located in the mitochondria, and its role in regulation of iron hemeostasis in neurodegenerative diseases has been reported. However, the role of FtMt in hydrogen peroxide (H₂O₂)-induced oxidative stress and iron accumulation in neuronal cells has not been studied. Here, we overexpressed FtMt in neuroblastoma SH-SY5Y cells and induced oxidative stress by treating with extracellular H₂O₂. We found that overexpression of FtMt significantly prevented cell death induced by H₂O₂, particularly the apoptosis-dependent cell death. The protective effects involved inhibiting the generation of cellular reactive oxygen species, sustaining mitochondrial membrane potential, maintaining the level of anti-apoptotic protein Bcl-2, and inhibiting the activation of pro-apoptotic protein caspase 3. We further explored the mechanism of these protective effects and found that FtMt expression markedly altered iron homeostasis of the H₂O₂ treated cells as compared to that of controls. The FtMt overexpression significantly reduced cellular labile iron pool (LIP) and protected H₂O₂-induced elevation on LIP. While in H₂O₂ treated SH-SY5Y cells, the increased iron uptake and reduced iron release, in correlation with levels of DMT1(-IRE) and ferroportin 1, resulted in heavy iron accumulation, the FtMt overexpressing cells didn’t show any significant changes in levels of iron transport proteins and in the level of LIP. These results implicate a neuroprotective role of FtMt on H₂O₂-induced oxidative stress, which may provide insights into the treatment of iron accumulation associated neurodegenerative diseases.

Nasal delivery of nanoliposome-encapsulated ferric ammonium citrate can increase the iron content of rat brain

BACKGROUND

Iron deficiency in children can have significant neurological consequences, and iron supplementation is an effective treatment of choice. However, traditional routes of iron supplementation do not allow efficient iron delivery to the brain due to the presence of the blood-brain barrier. So an easily delivered iron formulation with high absorption efficiency potentially could find widespread application in iron deficient infants.

RESULTS

In this study, we have developed and characterized a nanovesicular formulation of ferric ammonium citrate (ferric ammonium citrate nanoliposomes, FAC-LIP) and have shown that it can increase brain iron levels in rats following nasal administration. FAC was incorporated into liposomes with high efficiency (97%) and the liposomes were small (40 nm) and stable. Following intranasal delivery in rats, FAC-LIP significantly increased the iron content in the olfactory bulb, cerebral cortex, striatum, cerebellum and hippocampus, and was more efficient at doing so than FAC alone. No signs of apoptosis or abnormal cell morphology were observed in the brain following FAC-LIP administration, and there were no significant changes in the levels of SOD and MDA, except in the cerebellum and hippocampus. No obvious morphological changes were observed in lung epithelial cells or tracheal mucosa after nasal delivery, suggesting that the formulation was not overtly toxic.

CONCLUSIONS

In this study, nanoscale FAC-LIP proved an effective system delivering iron to the brain, with high encapsulation efficiency and low toxicity in rats. Our studies provide the foundation for more detailed investigations into the applications of niosomal nasal delivery of liposomal formulations of iron as a simple and safe therapy for iron deficiency anemia. Graphical abstract The diagrammatic sketch of "Nasal delivery of nanoliposome-encapsulated ferric ammonium citrate can increase the iron content of rat brain". Nanoliposome-encapsulated ferric ammonium citrate (FAC-LIP) was successfully prepared and intranasal administration of FAC-LIP increased both the total iron contents and iron storage protein (FTL) expression in rat olfactory bulb, cerebral cortex, striatum and hippocampus, compared with those of FAC groups. Moreover, there was not overtly toxic affects to brain, lung epithelial cells and tracheal mucosa.

Astrocyte hepcidin is a key factor in LPS-induced neuronal apoptosis

Inflammatory responses involving microglia and astrocytes contribute to the pathogenesis of neurodegenerative diseases (NDs). In addition, inflammation is tightly linked to iron metabolism dysregulation. However, it is not clear whether the brain inflammation-induced iron metabolism dysregulation contributes to the NDs pathogenesis. Herein, we demonstrate that the expression of the systemic iron regulatory hormone, hepcidin, is induced by lipopolysaccharide (LPS) through the IL-6/STAT3 pathway in the cortex and hippocampus. In this paradigm, activated glial cells are the source of IL-6, which was essential in the iron overload-activated apoptosis of neurons. Disrupting astrocyte hepcidin expression prevented the apoptosis of neurons, which were able to maintain levels of FPN1 adequate to avoid iron accumulation. Together, our data are consistent with a model whereby inflammation initiates an intercellular signaling cascade in which activated microglia, through IL-6 signaling, stimulate astrocytes to release hepcidin which, in turn, signals to neurons, via hepcidin, to prevent their iron release. Such a pathway is relevant to NDs in that it links inflammation, microglia and astrocytes to neuronal damage.